摘要:

5 Photochemistry By A. GILBERT Chemistry Department The University Reading THE Chemical Society has chosen the subject of photochemistry as one of the topics for Specialist Periodical Reports. Two volumes of this annual review have been published covering the literature up to June 1970. Thus it is no longer neces- sary or desirable to present in Annual Reports such a comprehensive review of photochemistry as has appeared in the past. Hence the present report is restricted to some of the publications which in the author’s opinion are of general interest and reflect trends and the most active areas of research. A notable trend is the caution which is now exercised in treating quenching and sensitisation data. Penta-1,3-diene commonly used as a triplet-state detector is now reported to quench the fluorescence of various carbonyl com- pounds at high diene concentrations.’ Such singlet quenching is suggested to explain why Stern-Volmer plots for Norrish type I and I1 reactions have non- zero slopes in the high diene concentration region.Likewise the unambiguous use of triphenylene as a triplet sensitiser appears in doubt as recent work has shown that it may also behave as a singlet sensitiser.2 The triphenylene S state lifetime is sufficiently long (T = 36.3 ns) that energy transfer could occur and this has been ascertained by quenching of its fluorescence by certain enones. The mechanism of intermolecular energy-transfer processes continues to occupy many researchers and the Schenck mechanism for photosensitised cis-trans isomerisa- tion of olefins has again attracted comment.Caldwell has reported inefficiencies in this mechanism for isomerisation of simple olefins and the quenching of ketonic triplet^.^ The same worker has studied the influence of added isoprene on the benzophenone-sensitised isomerisation of stilbene and finds that the only reason- able interpretation of the results is that the isoprene triplets must be capable of transferring energy to the ~tilbene.~ Of the isoprene triplets 12% transfer energy to trans-stilbene and 3% to the cis-isomer. The possibility of both intra- and inter-molecular energy transfer with 1-phenylbut-2-ene has been investigated and each is operative from both singlet and triplet states the intramolecular process is of course favoured at low reactant concentrations and rates for both F.S. Wettack G. D. Renkes M. G. Rockley N. J. Turro and J. C. Dalton J. Amer. Chem. SOC.,1970,92 1793. A. B. Smith and W. C. Agosta Chem. Comm. 1970,466. ’ R. A. Caldwell J. Amer. Chem. SOC.,1970 92 1439. R. A. Caldwell J. Amer. Chem. SOC.,1970 92 3229. 196 A. Gilbert the singlet and triplet processes have been calculated.' Intramolecular energy transfer is also reported for the compounds (la-d) where selective excitation of the carbonyl group results in efficient isomerisation of the olefin moiety.6 A Schenck mechanism for the process is discounted and that advocated is the same as in collisional quenching. In this work it has been demonstrated that the inter- molecular energy transfer cannot compete with the intramolecular process.It is evident from results published within the year that the self-quenching of benzene fluorescence in the vapour phase must be small or non-existent:' this has been confirmed from a study of the effect of pressure upon fluorescence lifetimes.' These results are contrary to previous conclusions which were seemingly based on phenomena believed now to be experimental artefacts. Cundall and Tippett have used the cis-trans but-2-ene isomerisation technique to measure the triplet yields of toluene and benzene.' The importance of charge-transfer phenomena in photophysical and photo- chemical processes is well established and this year the subject has received increased attention in many areas.The high quantum yield of photoreduction of aryl ketones by amines and the low sensitivity of the process to diffusion-controlled quenchers and to amine concentration have led Cohen and co-workers to propose a stepwise mechanism proceeding via rapid charge-transfer interaction of the triplet ketone with amine.lG The process has a high rate- constant and values of this for benzophenone in benzene in various amines and alcohols are reported. Benzophenone is not however reduced by aniline and its reduction by isopropanol is also suppressed in the presence of this amine.' Such suppression of reduction is considered here to be due to triplet-energy transfer from ketone to amine in a diffusion-controlled process there is no evi- dence for complex formation and exciplex participation under the conditions employed is considered to be only nominal.The role of donor-acceptor com-plexes in the photoaddition of unsaturated systems (e.g. maleic anhydride) to aromatic compounds has been much discussed. Trapping of the proposed zwitterionic intermediates resulting from excitation of certain of these complexes has been investigated and a number of new acid-catalysed photoaddition reac- tions of benzene have been discovered.'2 The reactions would seem to proceed C. S. Nakagawa and P. Sigal J. Chem. Phys. 1970,52 3277. D. 0.Cowan and A. A. Baum J. Amer. Chem. SOC.,1970,92 2153. C. S. Burton and H. E. Hunziker J. Chem. Phys. 1970,52 3302. M. Nishikawa and P. K. Ludwig J. Chem. Phys. 1970,52 107. R. B. Cundall and W.Tippett Trans. Faraday SOC.,1970,66 350. lo ' S. G. Cohen and A. D. Litt Tetrahedron Letters 1970 837. M. Santhanam and V. Ramakrishnan Chem. Comm. 1970 344. l2 D. Bryce-Smith R. Deshpande A. Gilbert and J. Grzonka Chem. Comm. 1970 561. Photochemistry by protonation of the zwitterionic intermediates and can be regarded as photo- electrophilic aromatic substitutions yielding Friedel-Crafts-type products (e.g. phenylsuccinic anhydride from maleic anhydride-benzene solutions). Although the pathway for the formation of cyclo-octatetraenes from the photoaddition of acetylenes to benzene may be diverted in the presence of acid in at least one case the excited species has been identified as the a~ety1ene.l~ A full account has appeared of the photoaddition of boron halides to aromatic compounds with the ultimate production of arylboronic acids here again the reaction may involve a loosely-bonded complex.’4 The intermediacy of diradicals and/or zwitterions in the rearrangement of dienones particularly 4,4-diphenylcyclohexa-2,5-dienone, has been under in- vestigation for several years.At present the weight of evidence appears to be in favour of zwitterionic intermediates although attempts to intercept these have met with little success. The cyclohexadienone (2) is light-stable in benzene and 0 OMe (2) t-butanol and no evidence for protonation ofexpected zwitterionic intermediates was obtained in the presence of a good hydrogen donor.” It is proposed that a rapid decay of the dienone triplet or else an orthogonal triplet state is necessary for a ‘type A’ process; the latter is impossible for (2).The phosphorescence excitation spectra of santonin and two derivatives give results which complement earlier evidence that two reactive triplet states (nn*and nn*)are involved in the rearrangement.’ The photochemistry of aromatic systems continues to attract much attention. In comparison with previous years little is reported concerning the valence-bond isomerisation aspects but one interesting account again from the Argonne Laboratories describes the first valence isomer of pyridine 2-azabicyclo[2,2,0]- hexa-2,5-diene (3) ‘Dewar’ pyridine.I7 This isomer has been shown to be the (3) l3 D. Bryce-Smith A. Gilbert and J. Grzonka.Chem. Comm. 1970,498. R. A. Bowie and 0.C. Musgrave J. Chem. SOC.(0,1970,485. ’’ H. E. Zimmerman and G. Jones J. Amer. Chem. SOC., 1970,92,2753. G. Marsh D. R. Kearns and M. Fisch J. Amer. Chem. SOC.,1970,92 2252. ” K. E. Wilzbach and D. J. Rausch J. Amer. Chem. SOC.,1970 92 2178. 198 A. Gilbert intermediate in photohydration of pyridine which yields 5-amino-2,4-pentadienal and also in the formation of (4) from irradiation of pyridine in the presence of sodium borohydride. From preliminary work it appears that other nitrogen heterocycles may show analogous behaviour. The biphotonic photolysis of benzene using an intense 15 ns pulse of 347 nm light from a Q-switched ruby laser is reported to yield the transient absorption spectrum and fluorescence of the excimer of benzene together with a permanent product.18 From its absorp- tion maxima the permanent product is thought to be fulvene but exact identi- fication was not possible.A valence-bond isomerisation is proposed to account for the irreversible transformation of certain 2-substituted thiophens to their 3-derivatives,' but benzvalene type intermediates are discounted in 2,6-di-t- butylphenol rearrangements which are reported to occur via the cyclohexa- dienone tautomers.20 The mechanism of the cycloaddition of acrylonitrile to naphthalene would now seem to be well established and involves the S1 state of the aromaticcompound which probably forms an exciplex with the It is interesting to note that certain difficulties encountered in interpreting the data for this reaction were eventually traced to destruction of the product by a triplet pathway.Contrary to previous reports 9-phenylanthracene has been found to form a photo-dimer but only in the presence of ~iperylene.~~ The dimer is thought from steric considerations to have the anti structure and the unusual role of piperylene here and its relation to singlet-quenching processes are under investigation. Havinga who initiated much of the work in the field of photo- aromatic substitution with charged nucleophiles has investigated similar reac- tions but with uncharged species such as liquid ammonia and reports that aromatic compounds in such a system may be divided into two classes.24 The first class contains rn-methoxynitrobenzenes when the OMe group is replaced by NH ,and the second class includes nitrobenzenes dinitrobenzenes and chloro- nitrobenzenes and here NH substitution occurs at the 0-and p-but not the rn-positions with respect to the nitro-group.The effect of distant substituents on photonucleophilic aromatic substitution has been investigated with compounds Is J. T. Richards and J. K. Thomas Chem. Phys. Letters 1970,5 527. l9 R. M. Kellogg J. K. Dik H. van-Driel and H. Wynberg J. Org. Chem. 1970 35 2737. 2o T. Matsuura Y.Hiromoto A. Okada and K. Ogura Tetrahedron Letters 1970 3727. '' R. M. Bowman and J. J. McCullough Chem. Comm. 1970 948. '' R. M. Bowman T. R. Chamberlain C. W. Huane and J. J. McCullough J. Amer. Chem. SOC.,1970,92,4106. 23 R. 0.Campbell and R.S. H. Liu Chem. Comm. 1970 1191. 24 A. Van-Vliet M. E. Kronenberg J. Corvelisse and E. Havinga Tetrahedron 1970,26 1061. Photochemistry 199 (5) and (6),25and the classical Ciamician-Silber reaction exemplified by the rearrangement of o-nitrobenzaldehyde to o-nitrosobenzoic acid has been shown to occur also with the p-isomer iontrary to previous reports.26 (5) (6) Research on the photocyclisation of stilbenes to dihydrophenanthrenes still provides interesting publications. Two groups working in this area report that for this cyclisation reaction to occur the sum of the free valence indices (CF*)for the first excited state at atoms between which the new bond is formed must be greater than unity and in both papers there are good examples of thi~.~~,~' Discussion of the mechanism of the photo-Fries reaction has continued for several years.However detection of phenol as a major product in the vapour- phase photolysis of phenylacetate and the failure to observe rearrangement products is convincing evidence that the light-induced Fries process is of a radical nature requiring a solvent cage rather than a concerted reaction.29 Since Srinivasan's first observation that furan was photolabile there have been several accounts of both sensitised and unsensitised decomposition of fur an^.^**^ Product mixtures may be quite complex thus eleven characterised products were formed from sensitised photolysis of 2,Sdimethylfuran but only one 2-ethyl-5-methylfuran had a free-radical origin and intermediates for the other products are ~uggested.~' As expected there has again been intense activity in the photochemistry of carbonyl compounds and studies of Norrish type I and I1 processes are still very popular.Knowledge of the chemical reactivity of the radicals produced from C-C cleavage in a type I process has in the past been limited to intra- molecular reactions since such intermediates have not been trapped. However this year it is reported that adducts (7) and (8) are obtained from photolysis of cyclobutanone in butadiene and a-in preference to fi-cleavage is shown by reaction with hexade~teriobutadiene.~~ Formation of (9) from cyclobutanone 0 (7) (8) (9) 25 K. E. Steller and R. L. Letsinger J. Org. Chem. 1970 3S,308. 26 G.W. Wubbels R. R. Hautala and R. L. Letsinger Tetrahedron Letters 1970 1689. '' E. V. Blackburn and C. J. Timmons J. Chem. SOC.(0,1970 172. '' W. H. Laarhoven T.J. H. M. Cuppen and R. J. F. Nivard Tetrahedron 1970,26 1069. " J. W. Meyer and G. S. Hammond J. Amer. Chem. SOC.,1970,92 2187. 3" H. Hiraoka J. Phys. Chem. 1970 74 574. 3' S. Boue and R. Srinivasan J. Amer. Chem. SOC.,1970,92 1824. 32 P. Dowd. A. Gold and K. Sachdev. J. Amer. Chem. Soc. 1970.92. 5724. 200 A. Gilbert and methanol is also suggested to result from or-cleavage giving the 1,4-acyl alkyl biradical which undergoes subsequent or concerted rearrangement and rebonding to the corresponding oxacarbene intermediate.33 Two major processes have been shown to predominate in the photolysis of certain pival~phenones.~~ In benzene solution or-fission occurs giving rise to aldehydes and isobutylene and isobutane whereas in isopropanol both or-fission and predictably reduction processes are evident.The effect of spin multiplicity on the Norrish type I process of cyclo-alkanones has been investigated and it appears that there is a considerable difference of at least two orders of magnitude between the nn* singlet and triplet state^.^ Until this year alkylcycloalkanones had not been examined for a type I1 process but Barltrop and Coyle have now shown with a series of such compounds that such a reaction does occur in some cases although the normal mode is type I.36 The marked difference for the process when the abstract- able hydrogen changes from primary to secondary is thought to reflect the conformational problems previously recognised.Intramolecular hydrogen transfer is also important in photolysis of large ring cycloalkanones (10) when cyclobutanols (1 1) and (12) res~lt.~’ (10) X = CH,CH, or CH (1 1) (12) Much research effort continues to be devoted to oxetan formation even the reaction between acetone and cyclohexene is not it seems fully worked out and three products in addition to the four previously reported have been des- cribed.j8 Turro and co-workers have extended knowledge of the oxetan forma- tion between acetone and electron-rich and electron-deficient ole fin^.^^.^' In the former case in order to explain the results biradical intermediates are suggested and both singlet and triplet states of acetone are involved in the process.On the other hand the addition of acetone to cis-or trans-1,2-dicyanoethyleneis remarkably stereospecific and a singlet mechanism is operative :further details for complex formation in such oxetan-forming reactions have been provided by a study of the fluorescence quenching of cyclohexanones by 1,2-di~yanoethylene.~ 33 D. R. Morton E. Lee-Ruff R. M. Southaam and N. J. Turro J. Amer. Chem. SOC. 1970,92,4349. 34 H. G. Heine Annalen 1970,732 165. 35 J. C. Dalton D. M. Pond D. S. Weiss F. D. Lewis and N. J. Turro J. Amer. Chem. SOC.,1970 92 2564. 36 J. A. Barltrop and J. D. Coyle Chem. Comm. 1970,390. j7 T. Mori K. Matsui and H. Nozaki Tetrahedron Letters 1970 1175. 38 P. Borrell and J.Sedlar Trans. Faraday Soc. 1970 66 1670. ’’ N. J. Turro and P. A. Wriede J. Amer. Chem. SOC.,1970,92 320. 40 J. C. Dalton P. A. Wriede and N. J. Turro J. Amer. Chem. SOC.,1970,92 1318. 4’ J. C. Dalton D. M. Pond and N. J. Turro J. Amer. Chem. SOC.,1970,92 2173. Photochemistry 20 1 Again there have been a vast number of reports dealing with the isomerisation and addition reactions of unsaturated ketones; a few are given here in an attempt to show the breadth of the researches. The photochemical behaviour of ionones has been the subject of many studies but two new isomers (13) and (14) have now Me Me H 6pH Me ko M&:e ,' Me Me been isolated from prolonged irradiation of concentrated solutions of trans-a-ionone in ethanol.42 It is suggested that (13) and (14) are formed by initial a-cleavage in the excited retro-a-ionone.Recombination of the resulting acyl radical with the alternative allylic positions subsequently yields (13) and (14). An example of a .n + ca2(oxa-di-.n-methane) photo-allowed rearrangement has been described for the sensitised rearrangement of the enone (15) to the cyclo- propylketone ( 16).43 In contrast direct irradiation affords only the product (17) of 1.3-acyl migration. The ketone (18) is known to yield its bicyclic isomer (19) on irradiation presumably via (20). Lack of success in trapping (20) or indeed any other intermediate with dienes obviously suggests that (20) is not an inter- mediate or that it isomerises faster than it reacts with dienes even at low tem- perature~.~~ Interest in the dimerisation of ap-unsaturated ketones continues and it has been shown that 3-alkyl substituents do not affect the dimerisation of cyclohe~enones.~~ Last year it was reported that naphthalenone forms only the (18) (19) (20) 42 A.Van-Wageningen and T. J. De-Boer Rec. Trav. chim. 1970,89 797. " W. G. Dauben M. S. Kellogg J. 1. Seeman and W. A. Spitzer J. Amer. Chem. SOC. 1970,92 1786. 44 D. I. Schuster and D. J. Blythin J. Org. Chem. 1970,35 3190. 45 H. Ziffer and B. W. Matthews Chem. Comm. 1970 294. 202 A. Gilbert trans head-to-head dimer ;other workers have now isolated both the cis head-to-head and the trans head-to-tail dimer~,~~ and again there have been many reports concerned with the dimerisation of thymine and related corn pound^.^^ 0 (21) The photoreaction of the cyclohexadienone (21) in cyclohexylamine and water is considered to be a simple process.48 Ketens are reported as the initial products which react with the substrate forming amides and acids.A further study of the photochemistry of eucarvone (22) has been made and reveals that two excited states are involved in the isomerisation to the bicyclic ketone (23) which in turn undergoes conversion to (24).49 A reinvestigation of the photolysis of t-butyl quinones has shown the presence of a thermally unstable intermediate presumed to be the spirocyclopropyldienone (25) this reacts further with the substrate (acetone or acetonitrile) at 30°C in the dark to yield a mixture of products identical with that from photolysis of the quinone in the same re- agents.50 OH (25) 46 T.Mukai T. Oine and H. Sukawa Chem. Comm. 1970 271. " A. G. Szabo W. D. Riddell and R. W. Yip Canad.J. Chem. 1970 48 694; p. J. Wagner and D. J. Bucheck J. Amer. Chem. SOC.,1970,92 181 ;B. H. Jennings S. C. Pastra and J. L. Wellington Photochem. Photobiol. 1970 11,215; N. Camerman and A. Camerman J. Amer. Chem. SOC. 1970 92 2523; E. Ben-Hur and I. Rosenthal Photochem. Photobiol. 1970 11 163. G. Quinkert B. Bronstert P. Michaelis and U. Kriiger Angew. Chem. Znternat. Edn. 1970,9,240; G. Quinkert M. Hintzmann P. Michaelis and P. Juerges Angew. Chem. 1970 82 219; H. H. Perkampus G. Prescher B. Bronstert and G. Quinkert Angew. Chem..1970.82,222. 49 D. I. Schuster and D. H. Sussman Tetrahedron Letters 1970 1657. '' S. Farid Chem. Comm. 1970 303. Photochemistry There have been further observations concerning ‘di-n-methane’ rearrange- ments during the year. Two independent reports have examined the general assumption that acyclic dienes utilise an excited singlet state in such rearrange- ments whereas dienes with steric constraint require a triplet-state reaction for efficient rearrangement.5 9 52 The system examined was 5,5-diphenylcyclohexa- 1,3-diene in benzene under sensitisation from various aromatic ketones. The involvement of such a mechanism in the conversion of the non-conjugated aryl dienes (26) to aryldivinylmethanes and vinyl cyclopropanes is however dis- ~ounted.~ Di-.n-methane rearrangements of non-conjugated dienes still excite (26) R’,R2 R3= H or Me much interest.The diene (27) yields only the cyclopropane (28) and evidence for a singlet-state reaction comes from sensitisation with benzophenone when only isomerisation of the olefin occurs.54 The lack of olefin isomerisation in the un- sensitised reaction may be explained by a Mobius system which prevents free R1 RZ Ph Ph A (27) R’,R2 = H or Me (28) rotation about a diradical centre. Stereochemical aspects of this type of rearrange- ment have been considered as has the effect of unsymmetrical substitution on the direction of the rea~tion.’~ Conversion of C polyenes to semibullvalene (29) is currently of interest and a publication on the mechanism of the light-induced rearrangement of cyclo- octatetraene to (29) discounts the intermediacy of bicyclo[4,2.0]octa-2,4,7-triene since photolysis of the latter yields only benzene.56 In the absence of the suspected di-n-methane mechanism the authors suggest concerted 1,5-and 4,6-bonding as the most likely mode of cyclisation.Both cyclo-octatetraene and (29) have been formed from irradiation of the recently synthesised tricyclo- [3,3,0,02*6]octa-3,7-diene which has a remarkably intense long wavelength (29) 51 J. S. Swenton A. E. Crumrine and T. J. Walker J. Amer. Chem. SOC.,1970,92 1406. 52 H. E. Zimmermann and G. A. Epling J. Amer. Chem. SOC.,1970,92 141 1. 53 E. C. Sanford and G. S. Hammond J. Amer. Chem. SOC.,1970,92 3497. 54 H. E. Zimmerman and A.C. Pratt J. Amer. Chem. SOC.,1970,92,1409. 55 H. E. Zimmerman and A. C. Pratt J. Amer. Chem. Soc. 1970,92 6259 6267. 5h H. E. Zimmerman and H. Iwamura J. Amer. Chem. SOC., 1970,92,2015. 204 A. Gilbert absorption (A,, 300nm E = 190)." Di-n-methane rearrangements are also reported for aza-compounds. * Other interesting publications on olefin photochemistry include the photosensi- tised cyclisation of 2-phenylhexa-1,Sdiene to l-phenylbicyclo[2,1,1]hexane,sg and the photoisomerisation of o-di-isobutenylbenzene.60 Kropp is well known for his work in this area and has demonstrated the synthetic capability of selective light-induced protonation of a cyclo-hexkne or -heptene moiety in a complex molecule with the diene limonene when reaction occurs at the C-1-C-2 position.61 The first example of addition of singlet oxygen to a monocyclic benzenoid ring system is reported and involves formation of the hydroperoxide (30) from the monomethyl ether of di-t-butylresorcinol.62 It is well known that the position 0 Me,C7 'OOH (30) of attack of singlet oxygen on naphthalenes and anthracenes is dependent on the aromatic substituents.Attempts to rationalise this by a Wheland model or an intermediate complex have failed but by using a delocalised transition state model satisfactory results are obtained and the predicted and experimentally observed results tabulated in this report are in complete agreement.63 Two groups of workers report the formation of stable dioxetans by photo-oxygenation of electron-rich olefins at -78 0C.64,65 The stereochemistry of the olefins is preserved in the product and the addition must either involve an antarafacial (2s + 2a) mode or a stepwise mechanism Both reports comment on the possible intermediacy of dioxetans in many chemiluminescence reactions and indeed solutions of the dioxetan in boiling benzene in the presence of a fluorescent hydro- carbon emit luminescence characteristic of the hydrocarbon.From orbital symmetry considerations it has been predicted that the stereo- chemical course of certain reactions will differ according to whether initiation is photochemical or thermal. Examples in support of the predictions are well known but a clear violation is reported in the photo-retro-homo-Diels-Alder reaction of certain azo-compounds [e.g.(31)]."6 The suggested factor for this is 57 J.Meinwald and H. Tsuruta J. Amer. Chem. SOC.,1970,92 2579. 58 L. A. Paquette and R. H. Meisinger Tetrahedron Letters 1970 1479; L. A. Paquette J. R. Malpass and G. R. Krow J. Amer. Chem. Soc. 1970,92 1980. 59 C. Yamada M. J. Pahk and R. S. H. Liu Chem. Comm. 1970 882. 6o L. Ulrich H. J. Hansen and H. Schmid Hefu. Chim. Acta 1970 53 1323. 61 P. J. Kropp J. Org. Chem. 1970,35 2435. 62 I. Saito S. Kato and T. Matsuura Tetrahedron Letters 1970 239. 63 0.Chalvet R. Daudel and T. F. W. McKiIIop Tetrahedron 1970,26 349; 0.Chalvet R. Daudel H. G. Schmid and J. Rigaudy Tetrahedron 1970 26 365. 64 P. D. Bartlett and A. P. Schaap J. Amer. Chem. SOC.,1970,92 3223. 65 S.Mazur and C. S. Foote J. Amer. Chem. SOC.,1970,92 3225. 66 J. A. Berson and S. S. Olin J. Amer. Chem. Suc. 1970 92 1086. Photochemistry that which opposes the trans elimination of nitrogen. There is however danger in application of the Woodward-Hoffman Rules to systems having electronic symmetry characteristics markedly different from those of aliphatic hydro- carbons. Light-induced elimination reactions have found use in synthesis both (31) for the preparation of heterocyclic compounds by the mercury-sensitised loss of carbon monoxide and/or carbon dioxide from cyclic lactones ketones and anhydride^,^^ and for the quantitative removal of the protecting groups 6-nitroveratryloxycarbonyl and 2-nitrobenzy1oxycarbony1,from the amino func- tion in amino-acid derivatives.68 Photonitrosation of hydrocarbons is industrially important and the use of nitrosyl chloride in the process has understandably led workers to search for alternative reagents.A range of hydrocarbons have been studied with t-butyl nitrite with varying degrees of success ;trans-azodioxy-compounds,oximes and monomeric nitroso-compounds have all been encountered as product^.^' The photochemistry of N-nitroso-systems has been studied in some detail in the pres- ence of olefins and diene~.~' Interest in the rearrangements of amine N-oxides continues,'' and the recent observation that pyridinium ylides are photo-labile has occupied several workers and activity is likely to increase in the future." Finally it is encouraging to see that the sociological aspects of photochemistry continue to be examined and work includes the photodegradation of chemicals (e.g.herbicides and pesticides) which are deliberately placed in contact with plant life and hence with sunlight.72 The photochemistry of air pollution is also an area of intense investigation.67 D. R. Arnold and V. Y. Abraitys Tetrahedron Letters 1970 2997. 68 A. Patchornik B. Amit and R. B. Woodward J. Amer. Chem. SOC. 1970 92 6333. 69 A. Makor and T. J. De-Boer Rec. Trau. chim. 1970 89 151 159 164. 70 J. Streith and C. Sigwalt Bull. SOC. chim. France 1970 1157; G. G. Spence E. C. Taylor and 0. Buchardt Chem. Rev. 1970 70 23 1 ;D. M. Jerina D. R. Boyd and J. W. Daly Tetrahedron Letters 1970,457; 0.Simonsen C. Lohse and 0.Buchardt Acta Chem.Scand. 1970 24 268; K. H. Wuensch and H. Bajdala Z. Chem. 1970 10 144. " V. Snieckus and G. Kan Chem. Comm. 1970 172; T. Sasaki K. Kanematsu A. Kakehi I. Ichikama and K. Hayakawa J. Org. Chem. 1970 35 426; A. Balasubra- manian J. M. McIntosh and V. Snieckus J. Org. Chem. 1970,35,433. 72 J. R. Plimmer U. I. Klingebiel and B. E. Hummer Science 1970 167 67; A. S. Hopkins A. Ledwith and M. F. Stam Chem. Comm. 1970,494; L. L. Miller and R. S. Narang Science 1970 169 368.

ISSN:0069-3030    

DOI:10.1039/OC9706700195

出版商:RSC    

年代:1970

数据来源: RSC

摘要:

6 Pulse Radiolysis Studies on Reactive Intermediates in Organic Chemical Processes By G.E. ADAMS and R. L. WILLSON Cancer Research Campaign Research Unit in Radiobiology Mount Vernon Hospital Northwood Middlesex 1 Introduction Application of the pulse radiolysis technique to the study of short-lived organic intermediates continues. Interest has been maintained in organic free-radical equilibria reactions of hydrated electrons hydrogen atoms and hydroxyl radicals in aqueous organic media general properties of organic radicals and in effects of molecular structure.’*’ Although there appears to be a temporary lull in activity in the field concerned with the detection and reactions of excited states there has been a notable increase in interest in the study of short-lived intermediates in biochemical and biological processes.These include reduction and oxidation processes in amino-acids simple peptides enzymes and the nucleic acids mechanisms of protein binding free-radical mechanisms in cellular radiosensitisation and various examples of biochemically-related electron-transport systems. With reference to advances in techniques some early results have been pub- lished on the application of the picosecond pulse radiolysis te~hnique~,~ showing for example that free electrons in both water and alcohols become solvated in times less than lo-“ s. However in the presence of high concentrations of acceptors such as acetone electron capture can occur earlier i.e. before solvation. Future applications of this fast technique to the general study of organic inter- mediates will be valuable.Another interesting advance involves the detection and recording of transient spectra by self-absorption of Cerenkov light produced during nanosecond pulse radiolysis.’ Some spectra of solvated electrons and also a benzene excimer have been confirmed. Relevant review literature published during the year includes a book ‘The Hydrated Electron’ which gives a comprehensive account of the physical chemistry of this important species‘ and a textbook ‘Principles of Radiation ‘ G. E. Adams Ann. Reports (B) 1968 65 223. G. E. Adams Ann. Reports (B) 1969,66,210. R. K. Wolff M. J. Bronskill and J. W. Hunt J. Chem. Phys. 1970,53,4201. M. J. Bronskill R. K. Wolff and J. W. Hunt J.Chem. Phys. 1970,53,4211. D. C. Walker and S. C. Wallace Chem. Phys. Letters 1970 6 11 1. E. J. Hart and M. Anbar ‘The Hydrated Electron’ Wiley New York 1970. G. E. Adams and R. L. Willson Chemi~try'.~Other general articles discuss the nature and reactions of initial species in radioly~is,~,~ electron transfer and protonation,".' ' reactions of excited states in liquids,' and the use of pulse radiolysis in general biochemical and enzyme studies.l3 2 Aqueous Organic Systems Hydroxyl radicals formed in the radiolysis of water add to the double bonds of vinylmethylketone acrolein and crotonaldehyde at diffusion-controlled rates. l4 The respective radicals can disproportionate to form enols of acetoacetaldehyde and malondialdehyde.The hydrated enol of crotonaldehyde a reaction product dehydrates spontaneously in a base-catalysed reaction MeC(OH)=CH-€H(OH) + MeC(OH)=CH<HO + H,O (1) The respective rate constants for the decay of the neutral molecule and its conju- gate base are 54 s-' and lo4s-'. Transient spectra have been obtained on pulse radiolysis of acrylamide in aqueous s~lution.'~ These have been resolved and assigned to the H atom-and OH radical-adducts at the double bond and to the protonated form of the electron adduct. It is proposed that the latter species is of the form CH -CH-C(NH,)OH. The radicals decay rapidly with bimolecular rate con- stants of the order of lo91mol-' s-l although in alkaline solution the unpro- tonated electron-adduct decays unimolecularly to produce the radical CH =CH-CH( 0)NH -.Simultaneous measurements of transient changes in the optical absorption and the electrical conductivity of pulse-irradiated solutions of formic acid and carbon monoxide have provided information on the chemistry of the carboxyl radical.16 As shown previ~usly'~ this radical can be formed either by OH addition to CO,.or by hydrogen abstraction from formic acid or its ion OH + HCOOH -+ H,O + COOH (2) Both COOH and CO (pK = 3.9 k0-3)reduce nitrobenzene by simple electron ' J. H. O'Donnell and D. F. Sangster 'Principles of Radiation Chemistry' Arnold London 1970. B. Cercek E. J. Land and A. J. Swallow 'Large Radiation Sources for Industrial Processes' International Atomic Energy Agency Vienna 1969 p. 51. G.E. Adams in 'Quaderni de La Ricerca Scientifica'. No. 68 Consiglio Nazionale delle Ricerche Rome 1970 p. 27. lo A. J. Swallow Proc. 9th Japan Conference on Radioisotopes Atomic Energy Society of Japan 1970 p. 571. L. M. Dorfman Accounts Chem. Res. 1970,3 224. j2 J. K. Thomas Ann. Rev. Phys. Chem. 1970,21 17. l3 G. E. Adams R. B. Cundall and R. L. Willson 'Chemical Reactivity and Biological Role of Functional Groups in Enzymes' ed. R. M.S. Smellie Academic Press 1970 p. 171. l4 J. Lillie and A. Henglein Ber. Bunsengesellschaft Phys. Chem. 1970 74 388. Is K. W. Chambers E. Collinson and F. S. Dainton Trans. Faraday SOC.,1970,66 142. l6 A. Fojtik G. Czapski and A. Henglein J. Phys. Chem. 1970 74 3204. J. P. Keene J. Raef and A. J. Swallow in 'Pulse Radiolysis' ed.M. Ebert J. P. Keene A. J. Swallow and J. H. Baxendale Academic Press London and New York 1965 p. 99. Pulse Radiolysis Studies on Reactiue Intermediates 209 transfer and CO reacts rapidly with oxygen as shown previously." Other examples of the use of the carboxyl radical as an electron donor are discussed later. Transient absorption spectra have been reported for some hydroxyperoxyl radicals formed from irradiated aqueous solutions of aliphatic alcohols cyclo- hexane and diethylether.' The acid dissociation constants for the methanol ethanol and isopropanol species are respectively 7.1 8.0 and 8.5. or-Hydroxy-peroxyl radicals dimerise to form dibasic acids which decay spontaneously with rates which are pH-dependent. It is suggested that these acid-intermediates are a-hydroxy-hydrotetroxides.The reactivities of the basic form of the hydroxyl radical 0-,with methanol and ethanol have been redetermined by absolute measurement of the rates of formation of the product radical-ions CH20-and C2H,0-.20 Measured rate constants of 5.8 0-8 x lo8 1mol-' s-' and 11.3 f1.7 x lo8 1 mol-'s-' agree reasonably well with earlier indirect deter- minations.2',22 Two reports from Hengelin and c~-workers~~*~~ are concerned with the pulse radiolysis of solutions of poly(ethy1ene oxide) (PEO) poly(vinylpyrrolidone) and dextran. The hydroxyl radical reacts rapidly with these polymers although the rate constants change with chain-length and polymer concentration. Rate constants for bimolecular reaction of PEO radicals decrease with increasing chain-length as expected.The data are compared with theoretical models for polymer kinetics. The large number of papers summarised in the reports for 1968 and 1969 demonstrates the wide interest in reactions involving addition of hydroxyl radicals to aromatic molecules and also in the chemistry of the hydroxycyclo- hexadienyl radicals which result. Michael and Hart have obtained rate con- stants for reaction of OH H and e.& with benzene the 1,3- and 1,4-cyclohexa- dienes and cy~lohexene.~~ The dienes react with OH partly by addition and partly by hydrogen abstraction to form the C6H7.radical. The proportions abstracting were 30 % and 45 % for the 1,3- and 1,4-dienes respectively. Although the rate constants for reaction of OH and H are all in the range 3-10 x lo91 mol-'s-',electron reactivities vary considerably in cyclohexene and the 1,4- diene the rate constants are less than lo61 mol-'s-l whereas for the 1,3- derivative in which conjugation is present the rate constant is much larger (lo91mol-' s-').The trend is reversed in benzene where the rate constant falls to 1.2 x 10' 1 mol-' s-I an effect which is attributed to the large resonance energy of this compound. A similar study has been made of radical reactions in G. E. Adams and R. L. Willson Trans. Furaday Soc. 1969,65,2981. l9 K. Stockhausen A. Fojtik and A. Henglein Ber. Bunsengesellschaft Phys. Chem. 1970 74 34. 2o R. Wander B. L. Gall and L. M. Dorfman J. Phys. Chem. 1970,74 1819.'' G. E. Adams J. W. Boag and B. D. Michael Proc. Roy. Soc. 1966 A289 321. 22 B. L. Gall and L. M. Dorfman J. Amer. Chem. Soc. 1969,91 2199. " U. Borgwardt W. Schnabel and A. Henglein Makromol. Chem. 1969 127 176. 24 A. Behzadi U. Borgwardt A. Henglein E. Schamberg and W. Schnabel Ber. Bun-sengesellschuft Phys. Chem. 1970,74 649. '' B. D. Michael and E. J. Hart J. Phys. Chem. 1970,74,2878. 210 G. E. Adams and R. L. Willson pulse-irradiated aqueous solutions of ben~onitrile.'~ Both H and OH react rapidly by addition (kH = 3.1 x 10' 1 mol-'s-' and k, = 8.5 x lo91 mol-' s-'). The high rate-constant for reaction with e (1.7 x 10'O I mol-' s-l) illustrates the influence on the reaction cross-section of the electronegative CN group.The reaction which is non-dissociative produces the benzonitrile radical-anion which absorbs strongly in alkaline solution with maxima at 315 and 410 nm. Protonation occurs at pH 7.2 as is shown by a shift in the absorption spectrum. Below pH 3 H atoms which are formed by preferential electron scavenging by H,O+ react with the solute to yield a mixture of isomeric adduct-radicals. Nitrobenzene reacts with ea& to form the intensely absorbing anion C6H,N0, an intermediate in the reduction to nitro~obenzene.~' It is now reported" that short-lived hydrates of these nitrose derivatives are formed in the radiation- induced reduction of aromatic nitro-compounds. The mechanism involves the disproportionation of two protonated nitro-radicals e.g. XC6H,N0 H to form the hydrate OH / 2XC6H4NO2H -+ XC6H4N02 + XC6H4N (3) \ OH followed by the unimolecular elimination of water OH / XC,H,N \ -+ XC6H4N0 + HZO (4) OH The reaction proceeds through the protonated form and it was found that the acid equilibrium constant is related to the Hammett constant for the substituent X.Kinetic data from the pulse radiolysis of pyrollidine suggest that OH abstracts hydrogen to form the C,H,NH radical.29 Electron attack which is less efficient occurs at the nitrogen atom. In the presence of the electron scavenger CO, carboxylation occurs presumably by interaction between C4H,NH and the radical COY H The absorption spectrum of the radical intermediate of the ascorbic acid redox couple has been observed.The maximum is at 360nm and the extinction co- efficient 3.7 x lo31 mol-' cm-1.30 26 B. Chutny and A. J. Swallow Trans. Faraday SOC. 1970 66 284. " W. Grunbein and A. Henglein Ber. Bunsengesellschaft Phys. Chem. 1969 73 376. 28 W. Grunbein A. Fojtik and A. Henglein Monatsh. 1970 101 1243. 29 N. Getoff and F. Schworer Radiation Res. 1970 41 1. 30 B. H. J. Bielski and A. 0.Allen J. Amer. Chem. SOC.,1970 92 3793. Pulse Radiolysis Studies on Reactice Intermediates 21 1 3 Non-aqueous Systems Investigations by Sauer and co-workers into reactions of H atoms with organic molecules in the gas phase continues with a paper concerning substituent effects in monosubstituted benzene^.^ ’ Transient spectra and H atom reactivities have been obtained for some benzene and xylene derivatives naphthalene and pyridine.The rate constants for the reactions can be correlated with the Hammett CT values of the substituents and as in aqueous solutions of substituted benzenes,32 the form of the relationship suggests that H atoms are electrophilic in these reactions. This is in contrast with their reaction with olefins processes which have been classified as ele~troneutral.~~ An interesting application of microwave conductivity methods is the study of electron reactivity in pulse-irradiated fluorocarbon gases.34 This paper adequately illustrates the advantage of the technique for studying compounds of low reactivity. An important application of the pulse radiolysis techniques is the determination of free-ion yields in irradiated organic liquids.While this field is central to pro- gress in radiation chemistry much information of general relevance to inter- mediates in organic reactions derives from this work. Large differences can occur in free-ion yields from irradiated organic liquids. This is again illustrated by the values obtained by a pulse conductivity technique35 for neopentane (0-9) and n-hexane (0.13). The difference is attributed to the lower efficiency of electron localisation in the latter liquid a parameter which is a function of the geometry of the hydrocarbon molecule. Galvinoxyl or Coppinger’s radical has been used to measure ion-yields in a range of organic liquids including hydrocarbons alcohols and nitro-com- pounds.36 This stable free radical previously shown to be an efficient electron acceptor,37 absorbs strongly with a maximum near 600 nm.Where available free-ion yields obtained by electrical conductivity methods agree well with the yields of galvinoxyl anion. From the data relative values of the mean charge- separation distance were calculated and found to decrease with increasing polarity of the medium. Lithium aluminium hydride has been used as a positive-ion scavenger in the pulse radiolysis of tetrahydr~furan.~’ In this system the tran- sient spectrum of the solvated electron was observed. In the presence of pyrene or anthracene the anions are formed with yields of 0.66 and 0.70 when measured on microsecond time scales. However on nanosecond time scales yields are much higher.This rapid fall in yield is due to ion-recombination in regions of high local concentration (spurs). LiAlH, by functioning as a cationic scavenger gives increased yields and larger lifetimes of the anions. A primary ion yield of 2.6 ” M. C. Sauer jun. and I. Mani J. Phys. Chem. 1970,74 59. 32 M. Anbar D. Meyerstein and P. Neta Nature 1966 209 1348. 33 R. J. Cvetanovic Adu. Photochem. 1963 1 115. 34 R. W. Fessenden and K. M. Bansal J. Chem. Phys. 1970,53,3468. 35 P. H. Tewari and G. R. Freeman J. Chem. Phys. 1969,51 1276. 36 C. Capellos and A. 0.Allen J. Phys. Chem. 1970,74 840. 37 M. S. Karasch and B. S. Joshi J. Org. Chem. 1957,22 1435. 38 J. H. Baxendale D. Beaumond and M. A. J. Rodgers Trans. Furuduy Soc. 1970 66 1996. 212 G.E. Adams and R. L. Willson was measured and in anthracene solutions. emission due to singlet anthracene was recorded. The low singlet yields (G = 0.1) and also that of the triplet (G = 0.04)are both concentration-invariant in contrast with the behaviour in benzene di~xan,~~ and dimeth~xyethane~' where the excited state yields are much higher. A possible explanation is discussed. Electron-trapping in low-temperature organic glasses have been studied by Richards and Thomas41 using 3-methyl pentane 3-methyl hexane 2-methyl tetrahydrofuran cumene and ethanol. Changes in short-lived transient spectra have been attributed to reorganisation of trapping sites of variable depth. Annealing of pulse-irradiated 3-methyl hexane containing naphthalene revealed the formation of excited states arising from ion-recombination reactions.Fast infra-red detection was used to record the absorption spectra of solvated electrons in ethylene diamine-water and amrn~nia-water.~~ In pure diamine or ammonia the spectra resemble those of the solvated electron in alkali-metal solutions. The dependence of the spectral characteristics on the composition of the two-component systems suggests that the electron is delocalised with proper- ties determined by the aggregate properties of the mixed solvent and not by solvation with a small number of solvent molecules. In pulse-irradiated ethanol43 the free-electron yield derived from the data (G = 1.7) is considerably higher (60%) than that found previously in both stationary-state and pulse experiments.Reasons for this discrepancy are discussed. An unusual series of experiments involved the nanosecond pulse radiolysis of molten napthalene (100 "C)and benzophenone (35 "C)containing 1,2-benz- anthra~ene.~~ Singlet- and triplet-excited solute spectra were formed by excita- tion transfer from the solvent. Ions do not appear to be involved in the transfer. An excited state of all-trans-j3-carotene assumed to be the lowest triplet can be produced by photosen~itisation.~~ The absorption spectrum of this species has now been observed without a sensitiser present in pulse-irradiated hexane solutions.46 The lifetime is rather long (9 ,us) and it is suggested therefore that failure to observe this species in previous flash-spectroscopic studies is due to the very small efficiency for singlet-triplet conversion.Excitation by high- energy radiation in hydrocarbons permits the formation of some triplets inde- pendent of singlet formation. The systematic studies of Dorfman and co-workers on electron- and proton- transfer reactions involving aromatic radical-ions have been extended to include some cationic electron-transfer processes.47 Some aromatic compounds were 39 J. H. Baxendale and M. A. J. Rodgers J. Phys. Chem. 1968,72,3849. 40 T. J. Kemp and P. J. Roberts Trans. Faraday SOC., 1968,64,'2106. 41 J. T. Richards and J. K. Thomas J. Chem. Phys. 1970,53 218. 42 J. L. Dye M. G. DeBacker and L. M. Dorfman J. Chem. Phys. 1970,52,6251. 43 J. W. Fletcher P. J. Richards and W.A. Seddon Canad. J. Chem. 1970,48 1647. 44 R. A. Holroyd L. M. Theard and F. C. Peterson J. Phys. Chem. 1970,74 1895. 45 M. Chessin R. Livingston and T. G. Truscott Trans.Faraday SOC.,1966 62 1519. 4b E. J. Land A. Sykes and T. G. Truscmt Chem. Comm. 1970 p. 332. 47 N. E. Shank and L. M. Dorfman J. Chem. Phys. 1970,52,4441. Pulse Radiolysis Studies on Reactive Intermediates 213 + pulse-irradiated in dichloroethane (DCE) solution. Charged species (DCE ) react with the aromatic solute by electron transfer DCE+ + Ar -+DCE + Ar+ (6) The system was used to investigate cationic electron transfer between pairs of aromatic molecules e.g. to p-terphenyl+ from anthracene and to biphenyl' from p-terphenyl and pyrene. Transfer constants are or are near diffusion- limited values in the range 5.1-9-9 x lo91mol-'s-' at 25 "C.The rate of electron transfer from the aromatic molecules to the solvent cation is so high as to suggest that migration of the solvent cation may involve an electron-jump process in the solvent. Biihler in a recent review,48 has summarised his work on pulse-radiolysis studies of transient charge-transfer complexes with halogen atoms. A current paper reports4' the observation of an absorption band at 560nm formed on pulse radiolysis of deaerated bromobenzene. It is assigned to the charge-transfer complex of a bromine atom with bromobenzene. Alter- native assignment to ions or excited states are ruled out. 4 Systemsof Biological and Biochemical Interest Further work is reported on the reaction of primary-water free-radicals with derivatives of the nucleic acids although owing to the complexity of the systems the assignment of transient spectra has depended principally on the results of product analysis from stationary-state system^.^^^^ Acautionary note has been struck by the observation of transient spectral changes which arise from reaction of pyrimidines with hydroxide ions formed by the radiation pulse.52 The spectral changes associated with this process are not necessarily related to the nature and yield of the final products of the radiolysis.The phenomenon has been observed in solutions of thymine and uracil but not thymidine thymidylic acid or 1,3- dimethyl uracil where the spectra of the tautomeric forms of the solutes are similar.It is well established that in neutral solution the hydroxyl radical adds to the 5,6-double bond in pyrimidine^.'^ It has now been shown that the ionised radical 0-, behaves similarly in alkaline solutions of uracil and cytosine where the pyrimidine structures are i~nised.~~'~ However for thymine and 5-methyl 48 R. E. Buhler in 'Quaderni de La Ricerca Scientifica' No. 68 Consiglio Nazionale delle Ricerche Rome 1970 p. 79. 49 J. M. Bossy R. E. Buhler and M. Ebert J. Amer. Chem. SOC.,1970 92 1099. 50 J. D. Zimbrich J. F. Ward and L. S. Myers jun. Internat. J. Radiation Biol. 1969,16 505. 51 J. D. Zimbrich J. F. Ward and L. S. Myers jun. Internat. J. Radiation Biol. 1969 16 525. 52 E. M. Fielden G. C. Stevens J.M. Phillips G. Scholes and R. L. Willson Nature 1970 225 632. 53 G. Scholes J. F. Ward and J. Weiss J. Mol. Biol. 1960,2 379. 54 L. S. Myers jun. A. Warnick M. L. Hollis J. D. Zimbrich L. M. Theard and F. C. Peterson J. Amer. Chem. SOC.,1970 92 2871. 55 L. S. Myers jun. M. L. Hollis L. M. Theard F. C. Peterson and A. Warnick J.Amer. Chem. SOC.,1970,92,2875. 2 14 G. E. Adam and R.L. Willson cytosine transient spectra were assigned to radicals formed by H-atom abstrac- tion from the methyl group. The H-adduct of thymine is not identical with the protonated electron-adduct. The transient spectrum produced by H-atom abstraction following OH attack on dihydrothymine is almost identical with that formed by H-atom addition to thymine.55 The spectra differ considerably 0 0 0 U Me H H from that observed for thymine after direct electron attachment and protonation thus supporting earlier suggestions that electron addition is probably localised on the carbonyl groups.Although electron adducts of most pyrimidines have low extinction coefficients that for orotic acid 6-carboxypyrimidine (OA) is an exception. At 330 nm the extinction coefficient is 8.5 x lo31mol- 'cm".57 This spectrum is also quite different from that of the H-adduct. The effect of the carboxy-group on the elec- tron affinity of the molecule is illustrated by its ability to oxidise the ethanol radical by simple electron transfer MeCHOH + OA -+ MeCHO + OA-+ H,O+ (8) The suggestion that OA- forms a peroxyl radical with oxygen contrasts with the conclusion that the thymine electron adduct reacts with O2 in a fast electron- transfer reaction,58 (k = 8 x lo91 mol-' s-').This agrees with earlier findings that the reaction of e with thymine in oxygenated solution does not lead to thymine destruction. In general rate constants for reaction of oxygen with OH-adducts of various DNA derivatives tryptophan and histidine appear to be diffusion controlled.60 Data for thymine agree reasonably well with earlier values.6 1,62 Reactivities of nucleotide and nucleoside radicals are about half those of the radicals derived from the corresponding free bases. Radical reactivity studies63 with the cellular radiosensitiser 2,2,6,6-tetramethylpiperidin-4-oneN-oxide (triacetoneamine N-oxyl) have been extended to include various DNA derivatives.In particular the reaction of the OH-adduct of calf thymus DNA has been observed. In general 56 L. S. Myers jun. and L. M. Theard J. Amer. Chem. Soc. 1970,92,2868. '' C. L. Greenstock Trans. Faraday Soc. 1970,66 2541. 58 H. Loman and M. Ebert. Internat. J. Radiation Biol.. 1970 18. 369. 59 G. Scholes and R. L. Willson Trans. Faraday SOC.,1967 63 2983. 6c R. L. Willson Internat. J. Radiation Biol.,1970 17 349. " P. T. Emmerson and R. L. Willson J. Phys. Chem. 1968 72 3669. '' L. M. Theard and F. C. Peterson in 'Radiation Chemistry' ed. R. F. Gould (Advances in Chemistry Series No. 81) 1968 vol. 1 p. 603. 63 R. L. Willson and P. T. Emerson 'Radiation Protection and Sensitisation' ed.H. Moroson and M. Quintiliani Taylor and Francis London 1970 p. 73. Pulse Radiolysis Studies on Reactive Intermediates 215 the reaction rate constants are an order of magnitude lower than the correspond- ing values for oxygen. Several publications have appeared dealing with the reactivities of e, H and OH with substituted amides peptides and enzymes. Hydrogen abstraction by OH from the N-methyl group in N-methyl amides is at least an order of magnitude faster than H-atom abstraction from the a-methyl The marked pH effect on the OH reactivity of the simple peptides glycylglycine and glycylglycylglycine had been previously attributed to the deactivating effect of NH protonation on the rate of electrophilic OH attack.65 This has now been by the demonstration that the pH effect is removed by prior acetyla- tion of both glycine and glycylglycine.The use of narrow band-widths and hence high spectral resolution in the analysis of transient spectra from pulse-irradiated tryptophan solutions has revealed the existence of radical- isomer^.^ The fine structure of the transient absorption band in the 300-350 nm region which is assigned to the OH-adduct shows three subsidiary maxiqa. It was found by comparing OH-adduct spectra from several methyl-substituted tryptophans that the three maxima represent attack at C-2 (A,, = 345 nm) at C-3 (350 nm) and some site on the aromatic ring (310nm). This use of fine resolution indicates obvious future applications for the analysis and identification of isomeric transient species where multiple possibilities exist for the location of the radical centre.Pulse radiolysis studies6* on solutions of glutathione show that H atoms add to the sulphur bond to form a species which is identical to that formed by protona- tion of the electron adduct of disulphide corn pound^.^^ The spectrum of the uncomplexed RS. radical is not observed indicating that dissociation of the RSSR.H radical does not occur. An interesting reaction has been observed in irradiated solutions of ~elenourea.~' A transient absorption similar to that observed previously for thiourea has been assigned to the radical-ion RSeSeR-. It is concluded that the reaction probably involves abstraction of a hydrogen atom from the -SeH group of the enol structure followed by association with another solute molecule.H,N-C=NH H2N-C=NH -I I Se' 1 ] SeH -H+ (9) I H2N-C=NH -[H,N-C=NH " E. Hayon T. Ibata N. N. Lichtin and M. Simic J. Amer. Chem. Soc. 1970,92 3898. h5 G. Scholes P. Shaw R. L. Willson and M. Eberi in 'Pulse Radiolysis' ed. M. Ebert J. P. Keene A. J. Swallow and J. H. Baxendale Academic Press London and New York 1%5 p. 151. 66 M. Simic P. Neta and E. Hayon J. Amer. Chem. Soc. 1970 92 4763. 67 R. C. Armstrong and A. J. Swallow Radiation Res. 1969 40,.563. h8 M. Simic and M. Z. Hoffman J. Amer. Chem. Soc. 1970,92,6096. '* G. E. Adams. G. S. McNaughton and B. D. Michael in 'The Chemistry of Ionization and Excitation' ed. G. R. A. Johnson and G. Scholes Taylor and Francis London 1967 p.28 1. R. Badiello and E. M. Fielden. internat. J. Radiation Biol. 1970 17 I. 216 G. E. Adams and R. L. Willson Spectra similar to the RSSR-ion-complex have now been observed on pulse radiolysis of the enzymes ribonuclease chymotrypsin and papain and the coenzyme lip~ate.'~?~ These have been assigned to electron adducts where the odd-electron is localised on the sulphur bridges. The absorptions are long- lived relative to those from simple disulphides such as cystamine which suggests that the RSSR-radical is stabilised by the overall structure of the macromolecules. Pulse radiolysis continues to provide a kinetic method for the study of protein binding irrespective of whether metachromasia is present or not.7 2-7 Overall reactivities of e,; in solutions of penicillin G in the presence of lysozyme or bovine serum albumen deviate from values calculated from the reactivities of the indi- vidual components.On addition of salt equivalence is restored thus indicating the presence of binding in the salt-free medium. No effect was observed however with pencillin G methyl ester or with lysozyme containing lysine residues which had been chemically modified with 2,4,6-trinitrobenzene sulphonic acid. This suggests that the carboxy-group of penicillin G and the lysine residues in lysozyme participate in the binding process.73 Similar studies are reported on the binding of eosin to protein7' and on the effect of temperature on the electron reactivity of methylene blue and various polyanion~.~~ Attempts were made to estimate thermodynamic parameters for the polyanion-dye reaction.Although to date work on aqueous systems has been concerned principally with the study of reactions of the primary water radicals e,; H and OH the pulse radiolysis technique provides a convenient method for the systematic study of a wide range of free radicals in solution. By the appropriate use of radical scavengers experimental systems can be designed in which a given free radical can be studied in isolation. Some recent investigations of reactions of halide radical-ions e.g. X; illustrate potential applications. In N,O-saturated solu-tions where e,; is effectively replaced by OH ea; + N,O -+ N + OH+OH-(10) the halide radical-ion is formed by subsequent reaction between OH and the halide.It has been shown that the radicals Br; (CNS) react with some enzymes including lysozyme ribonuclease and chymotrypsin.' In addition there is some indication that simple iodine atoms can react with alcohol dei~ydrogenase.~~ There is increasing evidence that some of these reactions are specific for certain amino-acids and when inactivation data are also available are useful for investi- gating enzyme structure. 71 R. L. Willson Chem. Comm. 1970 1425. 72 J. S. Moore G.0.Phillips J. V. Davies and K. S. Dodgson Carbohydrate Res. 1970 12 253. 73 G. 0.Phillips D. M. Power C. Robinson and J. V. Davies Biochim. Biophys. Acta 1970 215 491. J. S. Moore G.0.Phillips D. M. Power and J. V. Davies J. Chem. Sor. (A),1970,1155. '' A.Husain J. Ovadia and L. I. Grossweiner Trans. Faraday Soc. 1970,66 1472. 76 J. V. Davies M. Ebert and M. Quintiliani 'Radiation Protection and Sensitisation' ed. H. L. Moroson and M. Quintiliani Taylor and Francis London 1970 p. 87. Pulse Radiolysis Studies on Reactive Intermediates 217 Chemiluminescence occurring after pulse radiolysis of aqueous solutions of acriflavin can be enhanced three-fold in the presence of halide ions.77 Reaction of e; with the product of reaction between acriflavin and the halide radical is believed to be the cause of the increase in luminescence. The radical-ion Br; also reacts with the coenzyme nicotinamide adenine dinucleotide (NADH) to form the NAD. radical.78 The reaction of NAD. with O2is thought to proceed by simple electron transfer since complementary stationary-state studies show the formation of the oxidised product NAD+.79 The formate radical-ion COY has been used as a one-electron donor in several systems including the reduction of riboflavin and lipoate (RSSR).71 COY + RSSR -+ COz + RSSR-(11) A similar reaction occurs on pulse radiolysis of lysozyme solutions containing formate ion.13 The rate of formation of the RSSR- absorption indicating elec- tron transfer to the disulphide bridges is much slower than the corresponding reaction with e;.Pulse radiolysis studies on quinones continue to be of interest. Reaction of ubiquinone with the methanol radical CH20H yields the semiquinone ion which rapidly protonates in acid solution.80 From pH studies the pK of this equilibrium was found to be 6-45 & 0.15 a value significantly larger than that for the simple benzsemiquinone radical.*’ Following irradiation of an aqueous solution of acetone isopropanol NAD oxygen and benzoquinone sequential electron + transfer along the chain was observed.82 Some fast one-electron oxidation reactions have been observed in pulse-irradiated solutions of simple nucleotides and some cellular radiosensitisers including N-ethylmaleimide (NEM) and 2-methyl naphthaq~inone.~~ Electron transfer from the electron-adducts of the nucleotides was indicated by the formation of the transient spectra of the NEM electron-adduct and the naphthasemiquinone anion.Further information relevant to excitation or electron transfer and to radio-sensitisation mechanisms in organic and biological matrices is provided by measurements of luminescence following pulse radiolysis of solid mixtures.Incorporation of 5-bromodeoxyuridine (5-BUdR) into DNA notably affects the luminescence characteristics of DNA consistent with extensive energy or electron migration to the halogenated base.84 This result is interesting with respect to 77 W. A. Prutz and E. J. Land J. Phys. Chem. 1970,74,2107. 78 E. J. Land and A. J. Swallow Biochem. J. 1969,116 16P. 79 E. J. Land and A. J. Swallow Abstracts of the Fourth International Congress on Radiation Research Evian 1970 p. 127. E. J. Land and A. J. Swallow J. Biol. Chem. 1970,245 1890. G. E. Adams and B. D. Michael Trans. Furuduy SOC.,1967,63 1171.82 R. L. Willson Chem. Comm. 1970 1005. 83 C. L. Greenstock G. E. Adams and R. L. Willson ‘Radiation and Protection and Sensitization’ ed. H. L. Moroson and M. Quintiliani Taylor and Francis London p. 65. 84 E. M. Fielden and S. C. Lilhcrap in ‘Radiation Protection and Sensitisation’ ed. H. L. Moroson and M. Quintiiiani Taylor and Francis London 1970 p. 81. G. E. Adams and R. L. Willson suggested mechanisms for radiosensitisation of organisms in which 5-BUdR is in~orporated.~’.~ General application of pulse radiolysis studies on lumin- escence in the solid state has been reviewed.86 G. E. Adams in ‘Current Topics in Radiation Research’ ed. M. Ebert and A. Howard North-Holland Pub. Co. 1967 p. 35. 86 E. M. Fielden in ‘Quaderni de La Ricerca Scientifical Consiglio Nazionale delle Ricerche Rome 1970 p.63.

ISSN:0069-3030    

DOI:10.1039/OC9706700207

出版商:RSC    

年代:1970

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7 Electro-organic Chemistry By J. H. P. UTLEY Chemistry Department Queen Mary College Mile End Road London E. ? THISreview is organised as in previous years i.e. anodic and cathodic processes are categorised according to the species believed to be discharged. The bulk of the material is concerned with preparative scale processes although some electro-analytical work which has a direct bearing on mechanistic interpretation is included. 1 Anodic Processes Anodic Reactions of Organic Anions.-Anodic Oxidation of Curboxylates to Radicals (Kobe reaction). A novel hybrid technique polaromicrotribometry has been used to investigate the electrode conditions necessary for Kolbe dimerisation.' In this method a measure of the friction between a glass plate and the platinum electrode is monitored during the construction of a Tafel plot (log current density us.anode potential). For an aqueous solution of acetate ions the coefficient of friction changes markedly at the well-known transition point where oxygen evolution is suppressed and ethane formation begins. At this point the appearance of a film on the electrode was noted and by using electrodes of large surface area sufficient of the pale yellow film was collected for analysis. It is insoluble in water bases and acids (except H2S04)but is soluble in organic solvents. It decomposes at 170°C has the composition 78.2%C 11 %H,and 10x0,and i.r. spectroscopy suggests that it is a polymer containing the unit (CH,) with n > 50. It is tempting to speculate that in aqueous solution such films are necessary for the Kolbe reaction although the Kolbe reaction is often more efficiently performed in organic solution.Oxidation of carboxylates at graphite anodes usually results in carbonium ion formation (Ann. Reports (B),1968 p. 238) but for long-chain alkanoic acids ( >C,) in acetonitrile one-electron oxidation with dimerisation predominates. This is interpreted in terms of the familiar stacking of alkyl chains favouring dimerisation and inhibiting a second electron transfer by slowing diffusion of the radical to the electrode surface after decarboxylation (Scheme 1). A review of the use of the Kolbe reaction for obtaining bifunctional compounds contains useful tables of results and a description of an ingenious cylindrical J.E. Dubois and F. Bruno Compt. rend. 1970 271C 791. D. L. Muck and E. R. Wilson J. Electrochem. Sac. 1970 117 1358. 220 J. H. P. Utley II 02CCH ,CH ,R C CH,CH2R II -+ O,CCH,CH,R 0 A Scheme 1 divided cell.3 The contents are stirred by vibration of the electrodes at 100Hz and the cell is capable of operation at 25 A dm-, thereby allowing large scale reactions to be performed. Good yields of bifunctional compounds whose chemical preparation is difficult have been obtained4 by electrolysis of yy-dimethylalkanoic acids (1) X C(Me),CH,CH,CO,H + XC(Me),(CH,),C(Me),X (1) X = CH,OH CHO C02H CN or NO2 Attempts at cyclisation via Kolbe oxidation are summarised within a general review of electrochemical methods for cyclisation.’ On mechanistic aspects of anodic reactions however the review is badly out of date.Many of the cyclisation reactions attributed to the generation of carboxyl radicals almost certainly proceed by discharge of aromatic portions of the molecules with radical cations thus formed being attacked intramolecularly by carboxylate anions. Anodic Oxidation of Carboxylates to Carbonium Ions. The products of anodic oxidation at graphite of a series of cycloalkane carboxylates have been charac- terised. For alkene and alcohol formation the intermediacy of carbonium ions is supported by the observation6 of mobility of a deuterium label originally at C-1. The extent of deuterium rearrangement is dependent on ring size being at a maximum for electrolysis of [,H ,]cycle-octane carboxylic acid.Thermal decomposition of the corresponding t-butyl peroxyester gives cyclo- octane with no detectable rearrangement of the deuterium label. The major product of anodic oxidation’ of 4-cyano-2,2-dimethylbutanoicacid is NCCH,CH,C(Me):CH (16%) with little of the Saytzeff product NCCH,CH,C CMe (2%). The scheme proposed for anodic acetamidation (Ann. Reports (B),1969,p. 220) has been confirmed and extended by an elegant series of experiments.* Electro- J. Haufe and F. Beck Chem.-Ing.-Tech. 1970 42 170. * G. Cauquis and B. Haemmerle Bull. SOC. chim. France 1970 183. J. D. Anderson J. P. Petrovich and M. M. Baizer Adv. Org. Chem. 1969 6 257. J. G. Traynham E. E. Green and R. L. Frye J. Org. Chem. 1970,35 361 1.’ G. Cauquis and B. Haemmerle Bull. SOC.chim. France 1970 190. J. M. Kornprobst A. Laurent and E. Laurent-Dieuzeide Bull. SOC.chim. France 1970 1490. Electro-organicChemistry 22 1 lysis of 1,l-dimethylbutanoic acid in acetonitrile yields in addition to amides 10% of the acid anhydride. This is rationalised according to Scheme 2. An alternative reaction of intermediates of type (2) is rearrangement to an N-acylamide (3) which may cleave to give amides (4) and (5). The importance of -2e MeCN -+ RCO 5 RCO2-R+ 4R-N=C-CH * R-N=C-CH, -co RNHCOCH + (RC0)ZO R = EtC(Me),-Scheme 2 this route for tertiary acids is confirmed by the results of electrolysis of pivalic acid in the presence of CH3I4CO2H(Scheme 3). The specific radioactivity of the N-t-butylacetamide suggests that 80% of the product is formed via the N-acy lamide.j'?0 ../ COCH RNHCOCH R-N=C-CH 4R-N -c (4) I '14c OR1 RNH 4COR1 R'-l4C (5) \O (3) R = Bu' R' = CH Scheme 3 a-Ketocarboxylic acids are oxidised' to the corresponding acylium ions upon electrolysis although in methanolic solution pyruvic acid affords a small amount of biacetyl the Kolbe product. Anodic bisdecarboxylation has pro- vided" a good route to bicyclo[3,2,2]nona-6,8-diene(6),previously obtainable with some difficulty. ' B. Wladislaw and J. P. Zimmermann J. Chem. SOC.(B) 1970 290. lo A. J. Baker A. M. Chalmers W. W. Flood D. D. MacNicol A. B. Penrose and R. A. Raphael Chem. Comm. 1970 166. J. H. P.Utley Anodic Reactions of Other Organic Anions.An authoritative review of oxidative additions of anions to alkenes has appeared." Anions which may be oxidised anodically to radicals with subsequent addition to alkenes include those of malonic esters aliphatic nitro-compounds and Grignard reagents. Organic azides also may be prepared by oxidative addition of the azide anion. The experimental work connected with anodic oxidation of Grignard reagents is included in an accountI2 of the factors influencing addition dimerisation and polymerisation (Scheme 4)at copper platinum and carbon anodes. In the absence of olefinic trapping agents oxidation' at high current density of di- methylsodiomalonate ethyl sodiomethylacetoacetate and sodiodimedone gives low yields of a confusing variety of products.R-R 6-df ? RMgBr 5R' -+ RH + RH(-H,) RCH,CH(Y)CH(Y)CH,R +- RCH,CHY --+ RCH,CH(Y)CH,CHY1 further oligomerisation Scheme 4 Anodic Reactions of Neutral Organic Molecules.-The report of a two-electron transfer from tetra-p-anisylethylene (TAE) has been qualified (cf Ann. Reports (B) 1969 p. 227). A careful study14 at the rotating disc electrode and cyclic voltammetry in both acetonitrile and methylene chloride solution shows that formation of the dication of TAE is the result of two closely spaced one-electron transfers In methylene chloride solution the separation is visible on the cyclic voltammogram and coulometry supports one-electron transfer at 0.95 V (us. S.C.E.).the second transfer being at 1.2 V. An e.s.r.signal was obtained from the solution electrolysed at 0.95 V. The corresponding dimethylamino-compound (7) is apparently oxidised with a completely reversible two-electron (p-Me N.C6 H,),C=C(C6 H,.NMe,-p) (7) transfer with no detectable separation of the steps. The anodic oxidation of the series of phenyl-substituted ethylenes from PhCH :CH to PhzC:CPh has also been investigated' by cyclic voltammetry. At preparative concentra- tions olefins can be dimerised" anodically (e.g. Scheme 5). Alternatively a ' I H. Schafer Chem.-Ing.- Tech. 1970,42 164. H. Schafer and H. Kiintzel Tetrahedron Letters 1970 3333. '' (a) R. Brettle and D. Seddon J. Chem. Soc. (a, 1970 1153; (h) R. Brettle J. G. Parkin and D. Seddon J. Chem. SOC. (C),1970 1317; (c) R. Brettle and D.Seddon J. Chem. SOC.(C) 1970,2175. l4 A. J. Bard and J. Phelps J. Electroanalyt. Chem. Interfacial Electrochem. 1970 25 2A. I5 B. L. Funt and D. G. Gray J. Electrochem. Soc. 1970 117 1020. Electro-orgunic Chemistry graphireanode 40 % current yield \ MeOH-NaCIO \ / OMe Scheme 5 mixture of two olefins may be oxidised16 at controlled potential and the mixed coupled product obtained (Scheme 6). grdphite anode PhCH :CH + CH :CHOEt M~OH-N~CIO,I PhCH(OMe)CH,CH,C(OMe)OEt 30 "/ current yield Scheme 6 The electrochemical reactions of mercury-olefin complexes have attracted attention. For cyclohexene in acetonitrile the Hg" complex may be formed directly" by using a mercury anode which is self-oxidised to Hgz+.Further oxidation of the complex and reaction between the cation formed and solvent leads to the organo-mercury compound (8) [Scheme 71. The cathodic reactions of (8) are also of some interest (see p. 238). Fleischmann and his co-workers Scheme 7 (8) have investigated the anodic reactions of a number of Hg"-olefin complexes. At high current density efficient oxidation to mixtures of carboxylic acids is achieved. The products are explicable in terms of Scheme 9 noteworthy features EtCH,CHO anode + EtCH,CO,H (33% current yield) f + H$ + EtCH(OH)CH + Et(OH)CHCH,Hg+ H,O. EtCH:CH + Hg2+ L EtCOCH EtC0,H (8 %) + CH,CO,H (44%)+ HC02H(8 %) Scheme 8 of which are the catalytic role of Hg2+ and the suppression of Kolbe oxidation of the acids produced even at +2.4 V (us.Ag/Ag+). In an attempt" to control products by using potential control to select the major electrode reaction mixtures of cyclohexene and chloride ion were oxidised at a series of potentials. The CI-/CI,reaction occurs in acetonitrile at +0.75 V (Ag/Ag+) whereas '' H. Schafer and E. Steckhan Tetrahedron Letters 1970 3835. l7 N. L. Weinberg Tetrahedron Letters 1970 4823. M. Fleischmann D. Pletcher and G. M. Race J. Chern. Snc. (B) 1970 1746. '')G. Faita M. Fleischmann and D. Pletcher J. Electroanalyt. Chern. Interjacial Electro- chern. 1970 25 455. 224 J. H. P. UtIey direct oxidation of cyclohexene demands + 2.05 V. For equimolar mixtures of chloride and cyclohexene electrolysis in acetonitrile at 0.7 V gave with 80 % current efficiency N-(2-chlorocyclohexyl)acetamide,which is also a major pro- duct of the chemical reaction between chlorine and cyclohexene in acetonitrile.At + 2.1 V the only product identified was 3-chlorocyclohexene presumably a result of the deprotonation of the cyclohexene radical ion followed by re- oxidation to the corresponding allylic carbonium ion (cf:Ann. Reports (B),1968 p. 236). Although the products are of trivial importance the results are another encouraging sign that the electrode surface conditions can be manipulated and combined with potential control to select between competing processes. An interesting consequence of a careful cyclic voitammetric study” of the anodic oxidation of 9,lO-diphenylanthracene (DPA) in benzonitrile is the observation of a reduction peak for the dication (9).The smallness of the + Nu = unspecifiednucleophile DPA2+ + Nu -+ \ / Ph (9) Ph Ph Scheme 9 corresponding oxidation peak on the return scan suggests that K in Scheme 9 is very large. Similar studies,” combined with e.s.r. spectroscopy suggest that radical-cations of aromatic hydrocarbons are more stable in methylene chloride solution than in acetonitrile. The stability of 9,lO-disubstituted anthra- cenes is not a simple function of the charge delocalising ability of the substituents. For instance the 9,1O-di-(a-naphthyl)anthraceneradical-cation is less stable than DPA presumably because the naphthyl groups are the more reactive at the para-positions. The anodic oxidation in non-aqueous solution of benzo[a]pyrene gives a mixture of benzo[a]pyrene quinones.Despite the complexity a consistent account” of the major features of the reaction has been constructed. There is compelling evidence for direct discharge of aromatic hydrocarbons prior to nuclear acetoxylation (Ann. Reports (B) 1968 p. 245). Side-chain acetoxylation however is possible by two routes depending on whether the aromatic species or an inorganic anion is discharged (Scheme 10). ’O R. Dietz and B. E. Larcambe J. Chem. SOC. (B) 1970 1369. 21 L. S. Marcoux A. Lornax,and A. J. Bard J. Amer. Chem. SOC.,1970,92 243. 22 L. Jeftic and R. N. Adams J. Amer. Chem. SOC.,1970,92 1332. Electro-0rganic Chemistry x-X’ ArCH,’ [ArCH,] Scheme 10 The difficulty in distinguishing between these processes is ill~strated~~ by the electrochemical oxidation of toluene in acetic acid with potassium acetate tetramet hylammonium nitrate and tetramethylammonium toluene-p-sulphonate as electrolytes.Voltammetric curves show that the relative ease of oxidation of the anions is NO > -0Ac > -0Ts with the tosylate ion oxidising at potentials higher than the discharge potential of toluene. However for each of the anion oxidations added toluene lowers the current suggesting mere adsorption of toluene on the electrode even at high anodic potentials. Addition of the more easily oxidised naphthalene and anthracene causes a large increase in current. Thus the balance of evidence is in favour of route (a)being the major pathway although considerable doubt remains about the relative importance of the two processes.Related on mesitylene and durene compounds the ambiguity as in mixtures hydrocarbons and nitrate ions are oxidised at similar potentials and a current drop is again observed on addition of hydrocarbon at a given potential. In methylene chloride solution the strongest nucleophiles are the electron-rich hydrocarbons themselves. With tetra-n-butylammonium tetra-fluoroborate as electrolyte durene and mesitylene give2 $ upon electro-oxidation the coupled products (10) and (1l),presumably by either of the routes drawn in Scheme 11. coy [H3CArArCH3Izf [ArCH,] f H3CArArCH3 (1 1). A r b [H,CArArCH,] :2$(from mesitylene) ArCH _&*+ ArCH, [ArCHz+] -H+ P ArCH,ArCH (from durene) (10) Scheme 11 A full account26 is available of Eberson’s mechanistic work on anodic aceta- midation of alkylaromatic compounds (cf:Ann.Reports (B) 1969 p. 225). The general conclusion is that most of the results are explained by Scheme 12. In these reactions the yield of acetamidation from hexamethylbenzene is less 23 S. D. Ross M. Finkelstein and R.C. Petersen J. Org. Chem. 1970 35 781. 24 K. Nyberg Acta Chem. Scand. 1970 24 473. 25 K. Nyberg Acta Chem. Scand. 1970 24 1609. 26 L. Eberson and B. Olofsson Acta Chem. Scand. 1969 23 2355. J. H. P.UtIey sensitive to added water than is the yield from toluene. This is interpreted as meaning that the more stable hexamethylbenzene cation is less selective than -' ArCH *[ArCH,]? -H+ ArCH,' /fArCHzCHzAr ArCH,' ArCH,NHCOMe Scheme 12 the benzyl cation thus upsetting the usual relationship between stability reac- tivity and selectivity.Oxidation at +2.0 V (us. S.C.E.)of a mixture of diphenyl- acetylene and sodium cyanide in methanol leads2' to a good and exclusive yield of the 4-cyano-derivative. Breslow and co-workers continue to use electrochemical data to estimate the magnitude of anti-aromatic destabilisation (cf:Ann. Reports (B) 1969 p. 233). They have obtained28 polarographic data for oxidation of the compounds (12) and (13) and of 1,4-naphthohydroquinone (14) [Scheme 131. As compound (13) is oxidised more easily than naphthohydroquinone it is unlikely that strain OH 0 (12) OH 0 OH OH WMe Me @ OH OH (14) Scheme 13 differences involving the bond common to the four- and six-membered rings is reflected in large changes in half-wave potential.This leaves the difference (0.27 V) between the ease of oxidation of (12;R = Ph) and naphthohydroquinone to be explained as an anti-aromatic destabilisation of the cyclobutadiene entity of at least 12 kcal mol- (0.27 x 2 eV). Results from the use of a rotating disc electrode lead29 to the conclusion that hydroquinone is oxidised in acetonitrile by a two-electron process although the method would not distinguish between an EEC and ECE process ifdeprotonation of an intermediate were rapid. An alternative view of this reaction has been 27 K. Yoshida and T. Fueno Chem. Comm. 1970 71 1.28 R. Breslow R. Grubbs and Shun-Ichi Murahashi J. Amer. Chem. Sor. 1970 92 4139. 29 V. D. Parker and L. Eberson Chem. Comm. 1970 1289. Electro-organic Chemistry 227 presented3* and the general problems of hydroquinone electro-oxidation in aprotic solvents ~urveyed.~ Phenols may be coupled anodically and further examples of the application of this technique to phenolic tetrahydroisoquinolines have been described.32 Oxidation of t-butylhydroperoxide at a carbon anode in the presence of tetracyclone leads33 to a lactone which is one of the isomers of (14a). The compound is obtained by electrolysis of a two-layer solution with Ph ( 144 only the peroxide in contact with the electrodes. Oxidation with ceric ammonium sulphate gives the same result and an analogy with the Baeyer-Villiger reaction is drawn.The e.s.r. spectrum of the di-p-anisylamine radical-cation obtained34 by electrolysis of the amine in both neutral (CH3N02) and acidic solution (CF3C02H-CH3N02).is identical with that produced by dissolution of the di-p-anisylnitroxyl radical in the acid mixture. The electrolysis product is further characterised by coulometry and U.V. spectroscopy and it is now doubtful that it was the protonated nitroxide which was prepared in previous experiments (Ann. Reports (B) 1967 p. 317). The stable solid ionic free radical (15) is as a blue-black anodic deposit from the electrolysis of o-tolidine in methylene chloride solution. L (15) The reaction schemes encountered in the electro-oxidation of aromatic amines are now well characterised and during the past year several thorough st~dies~~-~' have been described.In the absence of substituents para to the amino function benzidines are often the major product. However for NN-dimethylaniline 3" B. R. Eggins and J. Q. Chambers J. Electrochem. SOC. 1970 117 186. 3' J. Bessard G. Cauquis and D. Serve Tetrahedron Letters 1970 3103. 32 J. M. Bobbitt K. H. Weisgraber A. S. Steinfeld and S. G. Weiss J. Org. Chem. 1970 35 2884. 33 N. L. Weinberg Canad. J. Chem. 1970 48 1533. 34 G. Cauquis and D. Serve Tetrahedron Letters 1970 17. 35 H. N. Blount and T. Kuwana J. Amer. Chem. SOC. 1970 92 5773. 36 R. Hand and R. F. Nelson J. Electrochem. SOC.,1970 117 1353. " A. G. Hudson A. E.Pedler and J. C. Tatlow Tetrahedron 1970 26 3791. 38 M. Melicharek and R. F. Nelson J. Electroanalyt. Chem. Interfacial Electrochem. 1970 26 201. 39 D. W. Leedy and R. N. Adams J. Amer. Chem. SOC.,1970,92 1646. 228 J. H. P.Utley (ca. lo-' moll-') in acetonitrile or benzonitrile a significant product is (16) with the origin of the extra methylene group being something of a mystery.36 In aqueous acetone at + 1.5 V (us. S.C.E.) pentafluoroaniline is coupled3' at a platinum anode to give decafluoroazobenzene (18 %). Octafluorophenazine (17) is formed as a minor product possibly via formation and oxidation of 2-amino- nonafluorodiphen ylamine. Separate anodic oxidation of the diphenylamine (17) provides an efficient (40%) route to (17). Macroscale anodic oxidation of NN-dimethyl-p-toluidine gives3 mainly the coupled product arising from Scheme 14.+' p-Me,N.C,H,-CH p-Me,NC,H,-CH %p-Me,N-C,H,-CH,' (p-Me NC H,-CH,-) 4 Scheme 14 The scheme is supported by e.s.r. evidence for the radical-cation and coulometric and cyclic voltammetric data for the electrochemical reaction. Dimethylaminoalkenes very readily undergo electrochemical oxidation e.g.(18) is oxidised4' at -0.9 V (us. S.C.E.). Aliphatic tertiary and secondary amines are electrolysed in acetonitrile at ca. 1-OV (Ag/Ag+) resulting41 in smooth de-alkylation. For instance di-n-propylamine is converted into n-propylamine (66%). Controlled potential electrolysis [+ 1-5V (Ag/Ag+)] of NN-diphenylhydrazine in acetonitrile in the presence of perchloric acid yields42 a solution believed to (Me,N),C C(Me)C(Me) :C(NMe,) [Ph,N:NH]+ (18) (19) +-Ph2NNH2+ 2py -2e 2pyH' + Ph,N=N +-2Ph2N-N Ph,N-N=N-NPh, ____+ Scheme 15 40 J.M. Fritsch H. Weingarten and J. D. Wilson J. Amer. Chem. SOC.,1970 92 4038. 41 L. C. Portis V. V. Bhat and C. K. Mann J. Org. Chern. 1970,35 2175. 42 G. Cauquis and M. Genies Tetrahedron Letters 1970 2903. Electro-organic Chemistry 229 contain the diphenyldiazenium cation (19). In the presence of pyridine electro- lysis at 0.3 V yields tetraphenyltetrazine presumed to be formed according to Scheme 15. Cinnoline derivatives may be by two successive oxida- tions of a mixture of NN-diphenylhydrazine and styrene. The possibilities of this method are illustrated by Scheme 16.Ph I -2e Ph,NNH 7[Ph,N=NH]+ -Ph -2e A2H Ph Ph Qf4p-Q I Ph Ph Scheme 16 In practice the cations are obtained as perchlorates and sodium bicarbonate is used to ensure the irreversibility of deprotonation steps. Using 3,6-di-isobutylpiperazine-2,5-dione(20) as a model for dipeptides it has been found44 that 1,3-~ycloaddition of acetonitrile may be induced anodically albeit with low efficiency. Incorporation of CD3CN proves that the solvent is indeed involved the overall reaction being given by Scheme 17. Scheme 17 Alkyl halides may be anodically oxidised to carbonium ions (Ann. Reports (B) 1969 p. 220) and for alkyl iodides in particular several examples of the reaction have been in~estigated.~' In acetonitrile solution the carbonium ions are pro- duced and trapped efficiently to give the range of acetamides familiar from carboxylate oxidations (see p.221) and for cyclohexyl iodide additional pro- duction of an allylic acetamide. Anodic oxidation of cyclohexene in acetonitrile 43 G. Cauquis and M. Genies Tetrahedron Letters 1970 3403. 44 L. A. Simonson and C. K. Mann Tetrahedron Letters 1970 3303. " A. Laurent and R. Tardivel Compt. rend. 1970 271C 324. 230 J. H. P. Utley gives proportions of the saturated (80x)and unsaturated (20x)acetamide similar to those obtained by electrolysis of cyclohexyl iodide thus supporting Scheme 18. 1-. 1MeCN-H,O 0MecN-H,o GOMe MeCONH _II+ Scheme 18 2-Methylthiophen has been oxidised under preparative conditions to give46 in acidic methanol solution ring-opened carbonyl compounds similar to those obtained from furan.At a platinum anode at + 1.0V (us. S.C.E.)or-mercapto-phenylacetic acid oxidises not at the carboxylate group but at sulphur to yield4' the disulphide (21). In methylene chloride with aluminium trichloride electrolyte [PhCH(C02H)S-f2 (21) an aluminium anode is consumed at the rate of 1 g atom per Faraday with the ultimate formation48 of methylenebis(a1uminium dichloride) (22) in Scheme 19. In these insertion reactions an analogy is drawn between the 'AlCl' species and carbene. c1-=% C1' Cl' + A1 -[AICI] [AICI] .tCH,CI -+ CI,AICH,CI [AICI] + CI,AICH2Cl -+ CI,AlCH,AICI (22) Scheme 19 46 J. Sprogl M.Janda and M. Valentova Coll. Czech. Chem. Comm. 1970 35 148. 47 J. Artaud M. Estienne and P. Courbis Compt. rend. 1970 271C 125. 48 E. H. Mottus and M. R. Ort J. Electrochem. Sac. 1970 117 385. Electro-organic Chemistry 231 2 Cathodic Processes Cathodic Reactions of Organic Cations.-Phenyl-substituted cyclopropenyl radicals have been generated4' electrochemically from the corresponding cations. For this system further reduction to the anti-aromatic cyclopropenyl anion is difficult. Some of the key experiments are outlined in Scheme 20. Ph Ph . Ph . Ph' Ph ' Ph Ph ph%Ph H + phm 1% Ph Ph Ph 61 % Ph F H -"@D-. -+ Ph Ph Ph\ Ph 40x Scheme 20 The reviewer's suggestion (Ann.Reports (B),1968,p. 249)for the route by which toluene is formed in the cathodic reduction of the benzyl trimethylammonium ion has been substantiated.Reduction in NN-dimethylformamide solution saturated with carbon dioxide results5' in the formation of phenylacetic acid at the expense of toluene. This is good evidence for the intermediacy of the benzyl anion. A systematic investigation of the electrochemical reduction of quaternary ammonium compounds of the type RNMe,' in hexamethyl-phosphoramide (HMPA) has shown that the competitive rupture of N-C (yR' + NMe R-AMe -%R-NMe3 Ah CH,' + R-NMe (a) R = allyl t-butyl (a)and (h) R = phenyl n-butyl Scheme 21 bonds proceeds5' as in Scheme 21. One unexpected result is the formation of a substantial amount of (23) by electrolysis of PhCH,NMe,+ in HMPA.Catho- 49 T. Shono T. Toda and R. Oda Tetrahedron Letters 1970 369. 50 S. D. Ross M. Finkelstein and R. C. Petersen J. Amer. Chem. SOC., 1970 92 6003. 5' J. E. Dubois A. Monvernay and P. C. Lacaze Electrochim. Acta 1970 15 315. J. H. P.Utley (23) dic cleavage of (1 -propenyI)triphenylphosphonium bromide is very efficient affording triphenylphosphine and pr~pene.’~ Cathodic Reactions of Neutral Organic Compounds.-A romatic Compounds and AIkenes. The use of electroanalytical techniques for the measurement of otherwise inaccessible pK values has been extended (cJ:Ann. Reports (B) 1969 p. 233). Using the data of Voltz and Lotsch (Ann. Reports (B) 1969 p. 231) for polarographic reduction of substituted triarylmethyl cations combined with Deno’s pK,+ values for cation formation from alcohols the pK values for the triarylmethanes have been calculated53 via the cycle shown in Scheme 22.ROH R‘ Scheme 22 The scope of the indirect method of reduction of aromatic systems is still being investigated. Isolated olefinic bonds are less easy to reduce by this method than aromatic species. For instance ally1 benzene can be selectively reduceds4 to 2,5-dihydroallylbenzene by lithium produced electrochemically in methylamine. cT2x CH,’ abstfaction \ dimerisation aldehyde Scheme 23 ’* L. Horner I. Ertel H. D. Ruprecht and 0. Belovsk Chem. Ber. 1970 103 1582. ’’ R. Breslow and W. Chu J. Amer. Chem. SOC.,1970 92 2165. ’‘ R. A. Benkeser and S.J. Mels J. Org.Chem. 1969 34 3970. Electro-organic Chemistry 233 Nitrobenzyl halides readily lose halogen upon electroreduction in aprotic sol- vents. The major products are the corresponding dinitrobibenzyls and nitro- toluenes and in the presence of oxygen aldehydes and esters are also formed.”*56 The results are readily rationalised by Scheme 23 where halide ion loss is rapid for ortho-and para-nitro-substitution but slower for the rneta-isomer. Electrochemical methods seem well suited for the reductions of heteroaro- matic compounds. Recent examples include the reductions of 2-phenylquinoxa-line and 2,3-diphenyl-5,6-dihydropyrazineto (24) and (25) respectively.” The H H H H (24) (25) cathodic reactions of substituted phthalazines demonstrates8 how a variety of reduction products can be obtained depending on cathode potential and pH (Scheme 24).2e high pH 1 Scheme 24 The cyclic voltammogram of 2-methoxyazocine obtained” in DMF solution shows a two-electron reduction peak. The dianion is reoxidised with some difficulty the difference between cathodic and anodic peaks being about one volt. This suggests that the lh-electron dianion (26)is impressively stable. 55 J. G. Lawless D. E. Bartak and M. D. Hawley J. Amer. Chem. SOC. 1969,91,7121. 56 P. Peterson A. K. Carpenter and R. F. Nelson J. Electroanalyt. Chem. Interfacial Electrochem. 1970. 27 1. 57 J. Pinson J. P. Launay and J. Armand Compt. rend. 1970 270C 1881. 58 H. Lund and E. Th. Jensen Acta Chem. Scand. 1970,24 1867. 59 L. A.Paquette J. F. Hansen T. Kakihana and L. B. Anderson Tetrahedron Letters 1970 533. J. H. P. Utley Activated unsaturated functions including olefins are smoothly reduced to radical-anions and anions with subsequent Michael-type coupling. Reductive coupling such as this is covered in a long and comprehensive review.60 Cross- coupling of activated olefins is dependent upon cathode potential in a surprising way the reactivity of the acceptor olefin being enhanced6’ at potentials below those required for discharge. The nature of the supporting electrolyte is also important quaternary ammonium salts favouring hydrodimerisation. Horner has studied62 this dependence by incorporating the reducible species into the ammonium ion in the salts [R,N+CH2CH2.0COCH:CHPh]X-,C1 or I.X = Hydrodimerisation is favoured for the iodides and salts containing long alkyl chains i.e. conditions encouraging ion-pairing in the double layer. In the preparation of 2,3,4,5-tetraphenyl- 1,6-hexanedioic acid (27) it was found63 that the major product from the attempted hydrodimerisation of cc-phenylcinnamo-nitrile was unexpectedly the cyclic compound (28) presumably formed according to Scheme 25. Ph Ph PhCH :C(CN)Ph /” / PhCH :C(CN)Ph 3PhCHCH(CN)Ph Ph e PhC N PhJA:;;Ph i;alkali ii; HNO Ph Ph Ph (27) Scheme 25 The indirect reduction of coumarin provides a good system for asymmetric induction. The conjugate acids of optically active alkaloids are discharged cathodically with production of the chiral radicals (29).Simultaneous discharge of for example 4-methylcoumarin leads to the radical (30) and hydrogen-atom transfer completes the reduction (Scheme 26). In this example the use of sparteine leads to formation64 of (31) with a 17% optical yield. 6o M. M. Baizer and J. P. Petrovich Progress in Physical Organic Chemistry eds. A. Streitweiser and R. W. Taft Interscience London-New York 1970 Vol. 7 p. 189. 61 M. M. Baizer J. P. Petrovich and D. A. Tyszec J. Electrochem. Soc. 1970 117 173. 62 L. Horner and H. D. Ruprecht Tetrahedron Letters 1970 2803. 63 S. Wawzonek A. R. Zigman and G. R. Hansen J. Electrochem. Soc. 1970 117 1351. 64 R. N. Gourley J. Grimshaw and P. G. Millar J. Chem. Soc. (0,1970 2318. Electro-organic Chemistry R1R2R3kH % R'RZR3NH (29) Me Me (30) (31) Scheme 26 Carbonyl Compounds.At a mercury cathode carbon dioxide is reduced to malate ion (Ann. Reports (B),1969 p. 235). Similar electrolysis using a lead elec- trode and quaternary ammonium electrolytes in aqueous solution enables carbon dioxide to be converted65 into glycollate ion. A very high current efficiency (ca. 600%) is associated with both of the processes. Horner reports66 another example of asymmetric induction through the use of chiral supporting electrolytes. Optical yields in the region 5-7% are obtained in the reduction outlined in Scheme 27 with the configuration of the preferred enantiomer depending on that of the chiral salt. Stereoselectivity has also been observed in the reducti01-1~~ of conformationally biased cyclic ketones under carefully controlled conditions.For dihydroisophorone and 4-t-butylcyclohexanone reduction in neutral solution proceeds efficiently at ca. -2.4 V (vs. S.C.E.)to approximately the equilibrium mixture of axial (cu. 10%) and equatorial (ca.90 %) alcohols. However in the presence of acetic acid electroreduction at lead may be achieved at ca. -1.7 V and the epimeric alcohols produced in similar amounts. The result is rationalised in terms of chemisorption of intermediates in certain favoured conformations with protonation of anions by coadsorbed acetic acid before equilibration is reached. PhC(Me):NCH,Ph :;+ P PhCH(Me)NHCH,Ph R*NMe X-R* = (R or S)-PhCH(Me);(R or S)-PhCH(OH)CH(Me) X = I or C1 Scheme 27 65 A.Bewick and G. P. Greener Tetrahedron Letters 1970 391. 66 L. Horner and D. H. Skaletz Tetrahedron Letters 1970 3679. '' J. P. Coleman R.J. Kobylecki and J. H. P. Utley Chem. Cornm. 1971 104. J.H. P.Utley In addition to the secondary alcohol and the meso-and dl-pinacols cathodic reduction68 of o-aminoacetophenone gives rise to both stereoisomers of com- pound (32). Carbonyl reduction with aromatisation to the corresponding tri- hydroxybenzenes is the result6' of electrolysis of humulones of the type (33). (32) (33) A simple indirect electrochemical procedure for the conversion of ketones into either alcohols or N-methylamines is described7' by Benkeser and Mels the reductant being lithium produced by electrolysis of lithium chloride in methylamine.Electrolysis with dropwise addition of the ketone results in alcohol formation whereas electrolysis after the ketone-methylamine-lithium chloride mixture has stood for several hours results in efficient formation of the corresponding N-methylamine. Amides have also been reduced7' by the indirect method and the products are the corresponding alcohols or aldehydes depending on the absence or presence respectively of a proton donor. Direct electroreduction of amides to aldehydes may be achieved for certain heterocyclic systems where in aqueous acid the aldehyde function is hydrated and protected from further reduction. For instance pyridine-2-carboxamide is reduced72 at a mercury cathode to the aldehyde (54 % isolated yield).Trifluoroacetic acid is smoothly reduced73 to l,l,l-trifluoroethane at a platinum cathode at <0.3V (on the hydrogen scale). The smoothness of this reduction contrasts with the irreducibility of acetic acid in this way and points not to a direct electroreduction but to hydrogenation with molecular hydrogen produced at the platinum electrode which can also act as a catalyst. Cathodic electron transfer to the carbonyl function may initiate cleavage reactions. An example of this type of reaction is provided74 by the electrochemical cleavage of carbon-oxygen and carbon-fluorine bonds outlined in Scheme 28. Evidence for the participation of the electroactive substituent (which may also be C t N) includes the desirability of its being ortho or para to the leaving group and the formation of aldehydic and alcoholic products when the reaction is performed in the presence of acetic acid which can efficiently trap the intermediate 68 H.Lund and A. D. Thomsen Acra Chem. Scand. 1969 23 3567. 69 K. L. Schroder Tetrahedron Letters 1970 2479. 70 R. A. Benkeser and S. J. Mels J. Org. Chem. 1970 35 261. 11 R. A. Benkeser H. Watanabe S. J. Mels and M. A. Sabol J. Org. Chem. 1970 35 1210. 72 P. E. Iversen Acta Chem. Scand. 1970 24 2459. 73 R. Woods Electrochim. Acta 1970 15 815. 74 J. P. Coleman H. G. Gilde J. H. P. Utley and B. C. L. Weedon Chem. Comm. 1970 738. Electro-organic Chernis try e I 6" 6' C02 Me IC\ 0 OMe L-(34) -X- -HC\ CO2Me COz Me CO Me '0 OMe R = H;X = OMeorOAc orR = X = F Scheme 28 (34).A similar mechanism might account for the racemisation found7' for reductive cleavage of the atrolactic acid derivative in Scheme 29. Other reac- OCOPh Ph ~ I YoPh/O' -PhCO,-\ /'O Ph-C-C0,Me -% Ph-C-C 1 I t-\ /c=c\ Me Me OMe OMe PhCH(Me)CO,Me PhC(Me)CO,Me -Ph /'='\ Me OMe Scheme 29 tions in this category are the electrored~ction~~ of the ester (35) to 4-methoxy- benzyl cyanide and the preparation of methyl ketone by cathodic cleavage77 of 8-ketosulphones (Scheme 30). (35) RCOCH(R')SO,Ph RCOCHR' fe_ RCOCHR' RCOCH,R' -PhSOZ-R = Ph or PhCH,; R' = H or Me Scheme 30 R. E. Erickson and C. M. Fischer J. Org. Chem. 1970 35 1604. '6 S. Wawzonek and J. D. Fredericksen J.Electrochem. Soc. 1959 106 325. " (a) B. Lamm and B. Samuelsson Acta Chem. Scand. 1970,24 561 ; (b)B. Lamm and B. Samuelsson Chem. Comm. 1970 1010. 238 J. H. P.Utley Reductive Cleavage of Halogens. Despite much experimental work the mechanism by which organic halides may be electroreduced to the hydrocarbon is not clear if indeed there is one mechanism. The full account78 of a careful study of the reduction of the halides (36) leaves the question open. The system was chosen because much is known about the stereochemical behaviour of the PhAMe Ph X (36) relevant radical (racemisation) and carbanion (retention). At the mercury cathode in acetonitrile solution the optically pure bromide of (36) is cleaved with 26% net retention.Use of CD,CN solvent results in a 75% labelling of the cyclo- propane but whether abstraction is by radical or carbanion is not clear. Small ring compounds may be obtained by the electroreduction of dihalides probably through concerted processes (Ann. Reports (B) 1969 p. 240). Further evidence for this saggestion and a useful preparative procedure comes from the macroscale (0.05 mol) electr~lysis~~ described in Scheme 3 1. -Br-Br Br 70 % Scheme 31 The organomercury compound (37) is formeds0 in the reduction at a mercury cathode of either 3-bromo-3-methylbut-1-yne or l-bromo-3-methylbuta-1,2-diene strongly suggesting for this cleavage reaction the intermediacy of the radical (38). Another organomercury derivative obtained cathodically is (39) which is formedI7 at -1.8V (us.S.C.E.)from (8) itself the oxidation product of cyclohexene at a mercury anode an acetonitrile solution (see p. 223). Me,C:C:CH-Hg-CH :C:CMe (37) Me2C:C:CH' (38) I COMe (39) ICOMe A good example of selective electrochemical reaction is provided in the . cathodic removal8' at controlled potential of bromine from p-bromo-y-chloro- butyrophenone (40) a substrate with three electroactive functional groups. p-BrC H,CO(CH,)3 C1 (40) " J. L. Webb C. K. Mann and H. M. Walborsky J. Amer. Chem. Soc. 1970,92,2042. 79 R. Gerdil Helv. Chim. Acta 1970 53 2100. 'O J. Simonet H. Doupeux P. Martinet and D. Bretelle Bull. SOC.chim. France 1970 3930. A. J. Fry M. A. Mitnick and R. G. Reed J. Org. Chem. 1970,35 1232.Electro-organic Chemistry 239 MiscelIaneous Unsaturated Functional Groups. In the presence of suitable adjacent functional groups electroreduction of nitro-groups on aromatic rings initiates cyclisation usually through the corresponding hydro~ylamine.~~-~ A particularly efficient reaction of this type is the near quantitative formationg5 of 3-phenylbenzo- 1,2,4-triazine (Scheme 32). An interesting dimerisation reaction is associated with the reduction" at -1-4V (us. S.C.E.),at mercury of bis-(p-nitropheny1)phosphate.A blue-green solution is obtained upon consumption of 3 Faradays mol-' and e.s.r. spectro- scopy confirms the presence of the 4,4'-dinitrodiphenyl radical anion. There is no evidence from the cyclic voltammogram that the aryl groups are cleaved in a stepwise fashion in the proposed Scheme 33.(ArO),P(0)OH [(ArO) P(O)OH]'-lsolvent SH [Ar-Ar]' Ar-Ar + O:P(OH) + 2s-Ar = p-02N.C6H4-Scheme 33 Intramolecular cyclisation reminiscent of the dihalide reductions (see p. 238) is the basis of a high yield electrochemical method for the preparationa7 of epoxides from ditosyloxyalkanes. For instance ethylene oxide is formed in 85 % yield by electrolysis of TsO(CH,),OTs in dry acetonitrile. The reactions of the superoxide ion 02-with organic compounds have recently attracted attention. Alkali-metal salts of the ion are not very soluble in organic solvents but electrolysis of tetraethylammonium perchlorate in dimethylsul- phoxide saturated with oxygen leadsaa to the formation of a stable solution of the quaternary ammonium superoxide.Under these conditions O2-behaves as a nucleophile. e.g. displacing chloride from alkyl chlorides with the formation of alkylperoxyl radicals. In another it was found that the epoxide (41) resulted from reaction between electrochemically generated superoxide ion and cyclohex-2-enone. 82 M. Jubault Compt. rend. 1970 271C 1671. 83 E. Laviron and T. Lewandowsa Bull. SOC. chim. France 1970 3177. 84 H. Lund and L. G. Feoktistov Actu Chem. Scand. 1969 23 3482. 85 S. Kwee and €3. Lund Actu Chem. Scand. 1969 23,271 1. 86 K. S. V. Santhanam and A. J. Bard J. Electroanalyt. Chem. Interfacial Electrochem. 1970 25 6A. R. Gerdil Helu. Chim. Acta 1970 53 2097. M. V. Merritt and D. T. Sawyer J. Org.Chem. 1970,35,2157. 89 R. Dietz M. E. Peover and P. Rothbaum Chem.-Ing.-Tech. 1970 42 185. 240 J. H. P.Utley (41) Practical Innovations.-Cells Solvents and Reference Electrodes. Details of a versatile cell have been p~blished.’~ One particular feature of the design is that gaseous products can be collected separately from the electrodes. The electroactive range methods of purification and details of suitable reference electrodes are included in an indispensible review” of the use of aprotic solvents in electrochemistry. For propylene carbonate the preparation and stability of salt bridges,92 the useful electroactive range,93 and the properties of a calomel electrode94 have been described. In this solvent between platinum electrodes with potassium hexafluorophosphate a potential range of 6.8 V was obtained before the current density exceeded 1 mA cm-’.As part of a series of reports on amide solvents the standard potential of the Ag/AgCl electrode in N-methylformamide has been rneas~red.~’ The molten salt system aluminium trichloride-sodium chloride-potassium chloride may be used for electrochemistry at 150°C and benzene has been efficiently ~xidised~~ under these conditions albeit to carbon as a ‘coherent deposit on the anode’. 90 G. Cauquis and B. Haemmerle Bull. SOC. chim. France 1970 2000. * C. K. Mann ‘Electroanalytical Chemistry’ ed. A. J. Bard Marcel Dekker Inc. N.Y. 1969 Vol. 3. 92 H. J. McComsey and M. S. Spritzer Analyt. Letters 1970 3 427. 93 J. Courtot-Coupez and M.L’Her Bull. SOC. chim. France 1970 1631. 9A I. Fried and H. Barak J. Electroanalyt. Chem. Interfacial Electrochem. 1970 27 170. 95 M. L. Berardelli G. Pecci and B. Scrosati J. Electrochem. SOC. 1970 117 781. 96 M. Fleischmann and D. Pletcher J. Electroanalyt. Chem. Interfacial Electrochem. 1970 25 449.

ISSN:0069-3030    

DOI:10.1039/OC9706700219

出版商:RSC    

年代:1970

数据来源: RSC

摘要:

8 General Methods By P. G. SAMMES Chemistry Department Imperial College London S.W.7 1 Reduction Catalytic Hydrogenation.4ptimum conditions for the use of homogeneous catalysts are still being thrashed out. Wilkinson’s catalyst chlorotris(tripheny1- phosphine)rhodium(I) has to be activated before it becomes effective. This is achieved by ‘dissociation’ to the active species chlorobis(tripheny1phosphine) rhodium(1). Dissociation occurs in the presence of traces of oxygen when aprotic solvents such as benzene or chloroform are used.’ In alcohol oxygen reacts with the catalyst to give a less active reducing agent which also causes extensive double-bond isomerisation.2 Addition of more triphenylphosphine to the latter system appears to reactivate the catalyst as well as to inhibit the isomer is at ion^.^ The use of homogeneous catalysts in dehydrogenations has also been investi- gated.4 They are more selective than heterogeneous catalysts and less dispropor- tionation of the substrate occurs; again Wilkinson’s catalyst was the most effec- tive.The dimeric species rhodium@) acetate and ruthenium@) acetate function as homogeneous hydrogenation catalysts in a wide range of solvents. The latter rhodium catalyst does not reduce allylic alcohols or trans-oriented double bonds ; the ruthenium catalyst is more a~tive.~ Rhodium catalysts with more basic phosphine ligands (1 ;L = solvent) readily reduce aliphatic ketone^.^ The reduction of ketones is enhanced by traces of water [RhH2(PPhMez)2Lz 3’ PF -(1) in contrast to the reduction of olefins which is inhibited by moisture.A hydride transfer is implied since reduction does not proceed through the enol ;4-t-butyl-cyclohexanone gives 86 % of the trans-alcohol. In complete contrast iridium tetrachloride-phosphorous acid in isopropanol reduces 4-t-butylcyclohexanone to the cis-alcohol with 97 % ~electivity.~ The catalyst prepared from chloro- trispyridinerhodium(1) and sodium borohydride in dimethylformamide is active ’ D. D. Lehman D. F. Shriver and I. Wharf Chem. Comm. 1970 1486. R. L. Augustine and J. F. Van Peppen Chem. Comm. 1970 571. R. L. Augustine and J. F. Van Peppen Chem. Comm.. 1970,497. J. Blum and S. Biger Tetrahedron Letters 1970 1825. B. C. Hin and G. L. Rempel Chem. Comm. 1970 1195. ’ R.R. Schrock and J. A. Osborn Chem. Comm. 1970 567. H. B. Henbest and T. R. B. Mitchell J. Chem. SOC.(C) 1970,785. 242 P.G. Sammes for the reduction with hydrogen of azo-groups to hydrazines imines and nitro- groups to amines and pyridine to piperidines.* The homogeneous hydrogenation of 1,3-dienes to cis-2-enes occurs with aromatic tricarbonylchromium com-plexes.' Full details of the P-1 nickel boride catalyst have appeared."" The reduction of alkynes with these catalysts proceeds in two distinct steps allowing selective partial reduction to the olefin.'" The reduction of substituted aromatic com- pounds has been found to be more specific with osmium and iridium catalysts which give more cis-hydrogenation products.' ' The nature of the support in heterogeneous catalysts has long been known to be important.With a carbon on molecular sieve support platinum preferentially catalysed the reduction of straight-chain rather than branched olefins.I2 Aluminium Hydrides.-The role of steric approach control and product develop- ment control in the reduction of alkylcyclohexanones with lithium aluminium hydride has been studied.' Contrary to earlier work steric approach control is predominant and appears to operate uiaeclipsing in the transition state between the incoming hydride ion and neighbouring substituents. The reduction of salts of alkylated malonic esters to ally1 alcohols was reported several years By reduction of allyl-substituted derivatives [e.g.(2) to (3)] the usefulness of this reaction has been considerably e~tended.'~' CO Me II @ OH (3) Further reductions with the benzene-soluble reductant sodium bis-(2-methoxy- ethoxy)aluminium hydride have been reported.Hydrogenolysis of 0-and p-hydroxy-' and -amino-substituted'sb aryl ketones carbinols and carboxylic acids is possible under forcing conditions. At low temperatures (-70 "C)methyl esters are converted into aldehydes in good yields.' 5c Di-isobutylaluminium hydride is more selective than alane for the reduction of @unsaturated ketones to allylic alcohols.'6 ' I. Jardine and F. J. McQuillin Chem. Comm. 1970 626. E. N. Frankel and R. 0. Butterfield J. Org. Chem. 1969 34 3930. lo (a)C. A. Brown J. Org. Chem. 1970,35 1900; (6) C. A. Brown Chem. Comm. 1970 139.' S. Nishimura F. Mochizuki and S. Kobayakawa Bull. Chem. Soc. Japan 1970 43 1919. * D. L. Trimm and B. J. Cooper Chem. Comm. 1970,477. l3 E. L. Eliel and Y.Senda Tetrahedron 1970 26 241 1. l4 (a)J. A. Marshall N. H. Anderson and A. R. Hochstetler J. Org. Chem. 1967 32 1 13 ; (h) W. Sucrow Tetrahedron Letters 1970 143 1. l5 (a) M. Cerny and J. Malek Coll. Czech. Chem. Comm. 1970 35 2030; (b)M. Cerny and J. Malek ibid. p. 1216; (c) See J. Org. Chem. 1970 35 issue 10 p. 12A. 35 issue 10 p. 12A. K. E. Wilson R. T. Seidner and S. Masamune Chem. Comm. 1970,213. General Methods Boron Hydrides.-The borohydride anion exchanges hydrogens with protic solvents. Thisincludes tritiated water and represents a simple way for the reductive tritiation of compounds.' 'Whereas esters of simple carboxylic acids are normally resistant to sodium borohydride esters of phenols or acidic alcohols such as 2,2,2-trifluoroethanol are reduced allowing selectivity.'* In dimethyl sulphoxide sodium borohydride can reduce alkyl halides and the mechanism has been studied ;I9 in dimethylformamide alkyl bromides and iodides and allylic chlorides are reduced by an S,2 mechanism i.e.with inversion of configuration.20 Sodium borohydride is superior to lithium aluminium hydride for the selective reduc- tion of cyclic anhydrides to lactones.21 Whereas both ketals and toluene-p- sulphonate esters are normally resistant to reduction by sodium borohydride P-ketal esters (e.g.4) reduce with fragmentation. Hydrolysis of the resulting ketal affords an aldehyde and an olefin in this case (5).22 The reduction of oximes to OTs (4) (5) alcohols proceeds smoothly with aqueous alkaline sodium borohydride.The reduction is very selective since conjugated oximes are unaffected but a-oximino- ketones give ~r-glycols.~~ Lithium cyanohydridoborate (LiBH,CN) is a versatile reducing agent stable up until pH 3.24a At these low pH values very rapid exchange of the hydride ions with protic solvents or deuterium oxide occurs the latter permitting reductive deuteriation. At about pH 6 the rate of reduction of imines is much faster than that of carbonyl groups allowing selective reductive amination of ketones. Pyruvic acids give the corresponding a-amino-acids in high yield.24b Sulphurated borohydrides prepared by the addition of hydrogen sulphide to sodium borohydride are more reactive than the parent hydride and are claimed to be useful at or below room temperat~re.~~ A powerful stereo- selective reducing agent is lithium perhydro-9B-boraphenalylhydride ;2-methyl-cyclopentanone gives 94 % of the cis-alcohol with this reagent.26 Synthetic applications of the boranes continue to abound.The reduction of functional groups with diborane has now been summari~ed.~' t-Butyl esters are " R. H. Cornforth Tetrahedron 1970 26 4635. 'I1 S. Takahashi and L. A. Cohen J. Org. Chem. 1970,35 1505. J. Jacobus Chem. Comm. 1970 338. 2o M. Vol'pin M. Dvolaitzky and 1. Levitin Bull. SOC.chim. France 1970 1526. D. M. Bailey and R. E. Johnson J. Org.Chem. 1970,35 3574. 22 W. Kraus and C. Chassin Annalen 1970,735 198. 23 K. H. Bell Austral. J. Chem. 1970 23 1415. (a)R. F. Borch and H. D. Durst J. Amer. Chem. Soc. 1969 91 3996; (6) M. M. Kreevoy and J. E. C. Hutchins ibid. p. 4329. 25 J. M. Lalancette and A. Frecke Canad.J. Chem, 1970,48 2366. 26 H. C. Brown and W. C. Dickason J. Amer. Chem. SOC.,1970,92 709. '' H. C. Brown P. Heim and N. M. Yoon J. Amer. Chem. Soc. 1970,92 1637. 244 P. G. Sammes reduced with the sodium borohydride-boron trifluoride etherate reagent into t-butyl ethers. &Lactones are slowly reduced by one equivalent of diborane into dihydropyrans.28 Terminal olefins can be converted into alkylmercuric salts by reaction of the derived boranes with mercuric acetate.The alkyl mercuric salts thus formed have a variety of uses including ready reduction with sodium borohydride into the corresponding alkane.29 Reduction of azines or hydrazones with diborane stops cleanly at the hydrazine stage.30 The hydroboration of propargyl chlorides is a convenient method for the preparation of terminal allenes [e.g. (6) to (7)].3' Bu-CrC-CH,Cl Bu-CH=C=CH (6) (7) Other Methods.-Diazonium salts are smoothly reduced by a radical mechanism with silyl and stannyl hydride~.~~ Aromatic carboxylic acids can be completely reduced to the corresponding aryl-methane by reduction with trichlorosilane followed by base hydrolysis. Further reduction of the 1-methoxycyclohexa-1,4-diene intermediates from the Birch reduction of anisoles proceeds in the absence of a proton source to give mainly cyclohexenes ;conjugation of the diene is the first step in the further red~ction.~~" In the reductive methylation of naphthalene with sodium in liquid ammonia stereospecific alkylation to cis- 1,4-dimethyl-1,4-dihydronaphthalene(8) With lithium in ammonia H (8) (9) only monoalkylation results.Phenanthrene is also alkylated stereospecifically to the cis-product (9);34'such reductions have been reviewed.34d The reduction of cyclopropyl ketones by lithium in liquid ammonia occurs stereoselectively (Scheme 1)35 and can also be effected with tributyltin hydride on photolysi~.~~ 28 G. R. Pettit and J. R. Dias Chem. Comm. 1970,901. 29 R. C. Larock and H. C. Brown J. Amer. Chem. SOC.,1970,92 2467.30 J. A. Blair and R. J. Gardner J. Chem. SOC.(C),1970 1714. 31 G. Zweifel A. Horng and J. T.Snow J. Amer. Chem. SOC.,1970,92 1427. 32 J. Nakayama M. Yoshida and 0.Simamura Tetrahedron 1970,26,4609. 33 R. A. Benkeser K. M. Foley J. M. Gaul and G. S. H. Li J. Amer. Chem. SOC.,1970 92 3232. 34 (a) A. J. Birch and G. S. R. Subba Rao Austral. J. Chem. 1970 23 1641; (b)P. W. Rabideau and R. G. Harvey Tefrahedron Letters 1970 4139; (c) P. W. Rabideau and R. G. Harvey J. Org. Chem. 1970 35 25; (6) R. G. Harvey Synthesis 1970 2 161. " W. G. Dauben and R. E. Wolf J. Org. Chem. 1970,35,2361. 36 M. Pereyre and J. Godet Tetrahedron Letters 1970 3653. General Methods Reagent i Li-NH,. Scheme 1 During the year under review a variety of new methods for dissolving the alkali metals have been investigated.Cyclohexyl-18-crown-6 (10) dissolves potassium in diethyl ether to give a characteristic blue solution with potential reducing proper tie^.^^ Trimesitylborane and related hindered boranes are electron acceptors and also react with the alkali metals.38 The anion radical formed mediates the transfer of electrons to organic systems in a variety of solvents. The reduction of conjugated enones to ketones was effected in this manner. 2,6-Diphenylpyridine can also be used as an electron transfer agent for the metallation of acidic carbon-hydrogen bonds.39 The combination of sodium in hexamethylphosphoramide containing t-butanol is powerful enough to reduce 01efins.~' The reduction of ap-unsaturated ketones with sodium or lithium in hexamethylphosphoramide has been carefully st~died.~' Amalgamated aluminium in dichloromethane is better than magnesium for the pinacolic reduction of ketones.42 1,3-Diolmonoesters are not reduced by zinc dust but instead undergo fragmentation to give olefins (Scheme 2).43 Chromous chloride is a selective reducing agent and nitro-compounds can be reduced to oximes without further reduction.44 The 0-acetates of oximes how- ever are reduced by chromous salts to give the imine.Mild hydrolysis of the J. L. Dye M. G. De Backer and V. A. Nicely J. Amer. Chem. SOC.,1970,92 5226. 38 S. D. Darling 0.N. Dergan and R. E. Cosgrove J. Amer. Chem. SOC. 1970,92 696. 39 B. Angelo Bull. SOC.chim. France 1969 1710. 40 G. M.Whitesides and W. J. Ehmann J. Org. Chem. 1970 35 3565. 41 K. W. Bowers R. W. Giese J. Grimshaw H. 0. House N. H. Kolodny K. Kron-berger and D. K. Roe J. Amer. Chem. SOC. 1970 92 2783; H. 0. House R. W. Giese K. Kronberger J. P. Kaplan and J. F. Simeone J. Amer. Chem. Soc. 1970 92,2800. 42 A. A. P. Schreibman Tetrahedron Letters 1970 4271. 43 E. Ghera Tetrahedron Letters. 1970 1539. 44 J. R. Hanson and T. D. Organ J. Chem. Sot.(C),1970 1182. 246 P.G. Sammes imine regenerates the ketone and this route has been proposed as a method for the regeneration of carbonyl groups from oximes under mild conditions as required for example in synthetic approaches to the prostaglandin^.^^ Zinc dust in aqueous acetic acid also reduces oximes to the parent ketones in good yields.46 R6 40-*Zn C I R ’R2CCR3 R4CHR ’ HOJ @ AH OCOR6 -+R1R2C=CR3R4 + R6C0,H + R’CHO -+ ~iw;~ R2 R3 R4 Scheme 2 Synthetic applications of the reductive extrusion of sulphur with trivalent phosphorus continue to interest chemists.The N-thioalkylphthalimides (11) react with tris(dimethy1amino)phosphine to give the N-alkylphthalimide thus opening a route from thiols to amine~.~’ Simple t-butylsulphenic esters react with tributylphosphine to produce ethers.48 dNSR \ 0 (1 1) 2 Oxidation Selective N-demethylation of amines is a potentially useful process. This has now been achieved by catalytic oxidation of the corresponding amine salt in aqueous solutions using a platinum catalyst.49 The scope of catalytic oxidations using palladium chloride has been enlarged.An interesting example of its use is oxidation of the sesquiterpene (12) as its palladium complex to give the lactone (13),via allylic attack.” (12) (13) (14) 45 E. J. Corey and J. E. Richman J. Amer. Chem. SOC.,1970,92 5276. ‘‘ M. S. Ahmad and A. H. Siddiqui J. Indian Chem. SOC.,1969 46 44. ” D. N. Harpp and B. A. Orwig Tetrahedron Letters 1970 2691. 48 D. H. R. Barton G. Page and D. A. Widdowson Chem. Comm. 1970 1466. 49 R. D. Birkenmeyer and L. A. Dolak Tetrahedron Letters 1970 5049. 50 H. Yanagawa T. Kato and Y. Kitahara Synthesis 1970 2 257. General Methods 247 The relatively stable phosphite-ozone complex (14)is claimed to be a source of singlet oxygen at temperatures above 0 OC.” However differences are observed in using such complexes as singlet oxygen sources compared to freshly generated material the triphenyl phosphite complex appears to oxidise by at least two different mechanism^.^^" At -90 “C the complex oxidises amines which are stable to singlet oxygen.52b Singlet oxygen generated by a microwave discharge has been efficiently used in the oxidation of organic compounds in the solid state dispersed on cellulose powder or silica gel.53 Ozonolysis of primary organo- mercurials gives the corresponding carboxylic acid ; secondary organomer- curials give the ketone.54 Compelling evidence that the primary step in the oxidation of olefins by chromic acid involves epoxide formation has been pre~ented.~~ By adding lithium chloride the normal course of the oxidation is diverted and chloro- ketones could be isolated.An improved safer method for making the pyridine- chromic oxide complex involves its in situ preparation in dichl~romethane.~~ The monoepoxidation of dienes with t-butyl hydroperoxide catalysed by molyb- denum hexacarbonyl is a useful reaction :57 squalene is oxidised into its epoxides quite effi~iently.~~ Epoxidation of allylic alcohols with t-butyl hydroperoxide is best catalysed with vanadium acetylacetonate. Manganese salts can be used to catalyse the oxidation of lactams to imides with t-butyl hydr~peroxide.~~ Olefins can also be converted into their epoxides by using hydrogen peroxide with isocyanates as co-reactants.60a Use of the hydrogen peroxide adduct of /OOH (CF,),C\ OH (15) hexafluoroacetone (1 5) has been advocated as a powerful electrophilic oxidant.Aniline is oxidised to nitrobenzene and ketones undergo Baeyer-Villiger oxi- dation.60b Bis-(3-nitrobenzenesulphonyl)peroxideis another powerful oxidant and can be employed for the hydroxylation of aromatic compounds by an ionic mechanism in good yield although the reagent is dangerous.61 ” M. E. Brennan Chem. Comm. 1970 956. 52 (a) P. D. Bartlett and G. D. Mendenhall J. Amer. Chem. SOC.,1970 92 210; (6) E. Koch Tetrahedron 1970 26 3503. 53 J. R. Scheffer and M. D. Ouchi Tetrahedron Letters 1970 223. 54 P. E. Pike P. G. Marsh R. E. Erickson and W. L. Waters Tetrahedron Letters 1970 2679. 55 J. Rocek and J.C. Drozd J. Amer. Chem. SOC.,1970,92 6668. 56 R. Ratcliffe and R. Rodehorst J. Org. Chem. 1970 35 4000. ’’ M. N. Sheng and J. G. Zajacek J. Org. Chem. 1970 35 1839. 58 S. A. Matlin and P. G. Sammes unpublished observations. 59 A. R. Doumaux and D. J. Trecker J. Org. Chem. 1970,35 2121. ‘(’ (a)N. Matsumura N. Sonoda and S. Tsutsumi. Tetrahedron Letters 1970 2029; (b) R. D. Chambers and M. Clark ibid. p. 2741. h1 E. M. Levi P. Kovacic and J. F. Gormish Tetrahedron 1970 26 4537. P.G. Sammes The Wessely acetoxylation of phenols with lead tetra-acetate proceeds by a very rapid electrophilic attack at both ortho-and para-positions and is not selec- tive for the ortho-position only.62 The combination of lead tetra-acetate and trimethylsilylazide will oxidise olefins ; 1,2-disubstituted olefins form azido- ketones or allylic a~ides~~" but trisubstituted olefins are cleaved to the keto- nitrile cholesteryl acetate forming the nitrile ( 16).63bThe oxidation of ketone hydrazones with iodine64" is general and chlorine bromine and the pseudo- halogens can also react to give vinyl plus geminal halides.64b The persulphate anion is a useful but underemployed one-electron oxidant.New applications should rectify this situation. It will oxidise the sodium salts of secondary nitroalkanes to vicinal dinitro-compounds in a manner analogous to pinacolic coupling. Allylic nitro-compounds as their nitronate salts are converted into ap-unsaturated ketones [e.g.(17) to (18)].65 Persulphate ions will also decarboxylate aliphatic carboxylic acids the reaction being catalysed by silver ions.66 In the presence of acids the reagent oxidises alcohols to peroxides.The acid then catalyses the cleavage of the peroxide (Scheme 3). The latter reagent is superior to other peracids for Baeyer-Villiger oxidation^.^' Tr + RCH20H -+ R-CHdO-yH2 -+ R-O=CH -+ ROH R'R2CHOH -+ R'R'CHOOH 4 R'R2C=0 + R'CHO + R'CHO Scheme 3 " W. A. Bubb and S. Sternhell Tetrahedron Letters 1970 4499. 63 (a)K. Kischa and E. Zbiral Tetrahedron 1970,26 1417; (b)E. Zbiral and G. Nestler ibid. p. 2945. 64 (a)D. H. R. Barton R. E. O'Brien and S. Sternhell J. Chem. SOC.,1962 470; (6) A. Pross and S. Sternhell Austral. J. Chem. 1970 23 989. 65 A. H. Pagano and H. Schechter J. Org.Chem. 1970,35 295. " J. M. Anderson and J. K. Kochi J. Amer. Chem. SOC.,1970,92 1651. '' N. C. Deno W. E. Billups K. E. Kramer and R. R. Lastoniwsky J. Org. Chem. 1970 35 3080. General Methods lP-Diketones can be prepared by the oxidation of ketones with lead dioxide although in toluene coupling to the solvent occurs.68 Azines (19) as their anions are oxidised by cuprous chloride to a dimer from which the 1,4-diketone (20) can be obtained by hydr~lysis.~’ Fremy’s salt was the reagent of choice for the oxidation of the acid-sensitive enol ether (21) to the quinone (22) many other reagents failing.70 PhR’C=N-N=CR2-CH2R3 R2CO-CHR 3CHR3COR* (19) (20) 0 0 Me0f?J$ Me0 0 0 (21) (22) @-Methylstyrene undergoes an interesting oxidation with 2,3-dichloro-5,6-dicyanobenzoquinone.Initially an unstable bis-aryl ether (23) forms which is solvolysed by alcohols to give predominantly the thermodynamically less favoured unconjugated ether (24).7 Quinone dehydrogenations of steroids have been reviewed.72 Whereas the silver oxide oxidation of a-amino-acids gives mainly the nor-acid silver(I1) picolinate produces the nor-aldehydes almost q~antitatively.’~ The oxidation of secondary alcohols by silver oxide in the presence of bromine has been examined in more detail. The solvent is of the utmost importance. The presence of added ethers such as 2,5-dimethyltetra- hydrofuran dramatically increases the proportion of product tetrahydrofuran f~rrned.’~ 68 R. Brettle Chem. Comm. 1970 342; R.Brettle and D. Seddon J. Chem. SOC.(0 1970 2175. 69 T. Kauffmann and M. Schoenfelder Annalen 1970,731 37. 70 V. H. Powell Tetrahedron Letters 1970 3463. 71 F. E. Lutz and E. F. Kiefer Chern. Comm. 1970 1722. ’’ H. Dannenberg Synthesis 1970 2 74. 73 T. G. Clarke N. A. Hampson J. B. Lee J. R. Morley and B. Scanlon J. Chem. SOC. (C) 1970 815. 74 A. Delazarche A. Maillard P. Rimmelin F. Schue and J. M. Sommer Chem. Comm. 1970 976. P.G. Sammes Thallium(n1) trifluoroacetate readily thallates aromatic Oxi-dation of these metallated intermediates with lead tetra-acetate forms phenolic trifluoroacetates which are readily hydrolysed to the corresponding phen01.~ 5b Reaction of the aromatic thallates with potassium cyanide followed by photo- lysis can give the corresponding aromatic nitrile.Thallium(II1) trifluoroacetate is itself an oxidant and produces quinones from phenols. 75c Thallium(II1) nitrate Reagents i TI"'(NO,),-MeOH; ii H,O+. Scheme 4 in methanol oxidises olefins with rearrangement to aldehydes or ketones via the corresponding ketal (Scheme 4).76 Olefins are also oxidised with cleavage to the ketone or aldehyde by bistriphenylsilylchromate (25).77 0 Oxidations with ruthenium tetroxide are usually performed with catalytic amounts of ruthenium trichloride in the presence of a regenerative oxidant such as sodium periodate. A much cheaper reagent is prepared from the trichloride with sodium hypochlorite. The latter oxidant can also be used in conjunction with osmium tetroxide and rhodium and iridium chloride^.'^ Simple arylalkynes can be prepared in good yields by the oxidation of semi- carbazones with selenium di~xide.'~" This oxidant can also be used to cleave allylic and benzylic ethers producing the alcohol and the conjugated aldehyde.79b An improved preparation of manganese dioxide has been reported.Use of de- colourising charcoal as support during the preparation aids isolation and the product is as active as that prepared by other methods.*' Iodohydrins are readily prepared from olefins by reaction with iodine and water in the presence of an oxidising agent such as iodic acid or oxygen catalysed by nitrous acid." 75 (a) A. McKillop J. S. Fowler M. J. Zelesko J. D. Hunt E. C. Taylor and G. McGillivray Tetrahedron Letrers 1969 2423; (6)E.C. Taylor H. W. Altland R. H. Danforth G. McGillivray and A. McKillop J. Amer. Chem. SOC., 1970 92 3520; (c) A. McKillop B. P. Swann and E. C. Taylor Tetrahedron 1970,26,4031. 76 A. McKillop J. D. Hunt E. C. Taylor and F. Kienzle Tetrahedron Letters 1970 5275. 77 L. M. Baker and W. L. Carrick J. Org. Chem. 1970,35,774. 78 S. Wolfe S. K. Hasan and J. R. Campbell Chem. Comm. 1970,1420. 79 (a) I. Lalizari A. Shafiei and M. Yalpani Angew. Chem. Internat. Edn. 1970 9 464; (b) K. Kariyone and H. Yazawa Tetrahedron Letters 1970 2885. L. A. Carpino J. Org. Chem. 1970 35 3971. *'J. W. Cornforth and D. T. Green J. Chem. SOC.(0,1970 846. General Methods 25 1 3 Olefins Extrusion reactions of sulphur in the preparation of carbon-carbon bonds were highlighted last year.A new general route for the preparation of double bonds from sulphides has now been developed (Scheme 5).8247b This has been success- fully adapted to the preparation of the highly-strained aromatic system (26).82c Reagents i Mel; ii NaH-THF; iii (MeO),CH+BF,-;iv KOBu'. Scheme 5 'Double' extrusion reactions [e.g.(27) to (28)] are also potentially useful especially for the synthesis of highly-substituted olefins. Thus the sulphide (29) gives the olefin (30) on heating with tri~(diethy1amino)phosphine.~~" The thialactone (31) also reacts.83b R' R3 \/ -+ R2/c=c\ R4 oso N=N --+ 00 0' (31) Alkenes can be obtained from epoxides by their reduction with magnesium amalgam in the presence of magnesium bromide.84 Other new methods for the preparation of olefins include the pyrolysis of O-alkyl-N-(toluene-p-sulphony1)-car barn ate^,^^ N-carbalkoxy~ulphamates,~~ the latter and thiono~arbamates,~' 112 (a)V.Boekelheide and J. L. Mondt Terrahedron Lerters 1970. 1203; (6)R. H. Mitchell and V. Boekelheide ibid. p. 1197;(c)V. Boekelheide and R. A. Hollins J. Amer. Chem. Sac. 1970 92 3512. 83 (a)D. H. R. Barton. E. H. Smith and B. J. Willis Chem. Comm.. 1970. 1226;(6)D. H. R. Barton and B. J. Willis ibid. p. 1225. 84 F. Bertini P. Grasselli G. Zubiani and G. Gainelli Chem. Comm. 1970 144. 85 L. C. Roach and W. H. Daly Chem. Comm. 1970 606. 86 E. M. Burgess H. R. Penton and E. A. Taylor J. Amer. Chem. Soc.1970,92,5225. 87 M. S. Newman and F. W. Hetzel J. Org. Chem. 1969 34 3604. 252 P. G. Sammes undergoing smooth cis-elimination at much lower temperatures than do xanthates. The pyrolysis of quaternary ammonium hydroxides occurs much more cleanly and at lower temperatures when very low pressures are employed.88 Thus the base (32) is pyrolysed at 60 "C (0.005 mm Hg pressure) to give cyclo- (32) propene in good yield. The direction of elimination of these quaternary salts (the syn-anti dichotomy) has been explained in terms of steric effects and suitable predictions should now be po~sible.'~ The reaction of some steroidal toluene- p-sulphonylhydrazones with lithium alkyls gave good yields of the olefins but the amount of base used was critical best yields being obtained with three equivalent^.^^ A reinvestigation of the preparation of alkynes via 1,2-dibromides has been made.The eliminations proceed smoothly in dimethyl sulphoxide with sodium hydride or sodamide at room temperature but on heating isomeri- sation of the double bond occurs.91 Steroidal dienes can be prepared from epoxides by their dehydration the reagent of choice being pyridine hydro- chloride.92 The Claisen reaction has been modified in order to yield trisubstituted olefins with high ~tereoselectivity.~~ In related work the use of keten acetals has been strikingly successful (Scheme The product ester can be further modified 0 'R2 Reagents i MeC(OEt),-H +; ii Heat; iii LiAIH,; iv Cr0,-pyridine; v ,)-Li. Scheme 6 D.A. Archer Tetrahedron Letters 1970 1325. 89 D. S. Bailey and W. H. Saunders J. Amer. Chem. SOC.,1970,92,6904. J. E. Hey E. Gonzalez and B. Mardell Austral. J. Chem. 1970,23 857. 91 J. Klein and E. Gurfinkel Tetrahedron 1970 26 2127. 92 I. Morelli and A. Marsili J. Org. Chem. 1970 35 567. 93 W. S. Johnson T. J. Brocksom P. Loew D. H. Rich L. Werthemann R. A. Arnold T. Li and D. J. Faulkner J. Amer. Chem. SOC.,1970 92 4463. 94 W. S. Johnson L. Werthemann W. R. Bartlett T. J. Brocksom T. Li D. J. Faulkner and M. R. Peterson J. Amer. Chem. SOC.,1970 92 741. General Methods for the extension of the chain thus making the method of general synthetic utility in the terpene field. A further stereospecific synthesis of trisubstituted olefins has made use of the pyrolysis of vinyl cyclopropanes [e.g.(33) to (34)].95 H (33) (34) (35) (36) 0 0 1,2-Divinyl-1,2-glycols rearrange.on heating in a Cope reaction to form the diketone. This reaction has been used for an entry into medium ring compounds [e.g.(35) to (36)]96"and the reaction is stereospecific [cf. (37a) to (38a); (37b) to (38b)].96b A further entry into medium ring compounds has also been de- veloped (Scheme 7).97" It is general and has been applied to the synthesis of perhydroa~ulenes,~~~ and heterocyclic systems.97d 0dacyclic 1,5-diene~,~~' OMS 1 4 (MeO)ZB0 HO B(OMe) Reagents i B,H then MeOH; ii NaOMe. Scheme 7 45 E. J. Corey H. Yamamoto D. K. Herron and K. Achiwa J. Amer. Chem. Soc. 1970 92 6635.96 (a)P. Leriverend and J. M. Conia Bull. SOC. chim. France 1970 1040; E. N. Marvell and T. Tao Tetrahedron Lerters 1969 1337; (b) E. N. Marvell and W. Whalley Tetrahedron Letters 1970 509. 97 (a) J. A. Marshall Rec. Chem. Progr. 1969 26 4781; (b) J. A. Marshall and W. E. Hoffman J. Amer. Chem. Soc. 1970 92 6358; (c) J. A. Marshall and J. H. Babler Tetrahedron Letters 1970 3861 ; (6)J. A. Marshall and J. H. Babler J. Org. Chem. 1969.34.4186. 254 P.G.Sammes Dihalogenocarbene adducts of olefins undergo the cyclopropyl-ally1 rearrange- ment under the influence of silver ions;98 these products are useful in the stereo- specific synthesis of trans-hydrindane derivatives (Scheme 8).99 The Simmons- Smith cyclopropane synthesis is improved by dropwise addition of di-iodomethane to a catalyst prepared from zinc dust and cuprous chloride and H Br I -+ 06 Reagents I CBr ii.AgOAc-AcOH ; iii aqueous N-bromosuccinimide Scheme 8 the olefin."' The 1,3-cyclohexadiene system of ergosteryl acetate has been cleverly protected by formation of the adduct (39). The 22-olefin bond of the adduct is preferentially ozonised allowing modification of the side-chain. The diene function was then regenerated by reduction with lithium aluminium hydride. ' NN-Dichlorophosphoramides add across olefins to give after acid hydrolysis the 2-aminoalkylchloride.'02 In the presence of a halogen cyanamide also adds across double bonds,'03 whilst iodonium nitrate adds without the need for a cataly~t."~ Normally olefins are inert to attack by N-chlorocarbamates but the reaction can be promoted by chromous chloride.A radical process is implied 98 C. B. Reese and A. Shaw J. Amer. Chem. SOC.,1970 92 2567; D. Duffin and J. K. Sutherland Chem. Comm. 1970 627. 99 D. Duffin and J. K. Sutherland Chem. Comm. 1970 627. loo R. J. Pawson and I. T. Harrison J. Org. Chem. 1970 35,2057. D. H. R. Barton T. Shiori and D. A. Widdowson Chem. Comm. 1970,939. lo' A. Zwierzak and A. Koziara Tetrahedron 1970 26 3521 3527. lo' K. Ponsold and W. Ihn Tetrahedron Letters 1970 1125. Io4 U. E. Diner and J. W. Lown Chem. Comm. 1970 333. General Methods in the latter reaction as both cis-and trans-addition OCCU~S.'~~~ Enol ethers react and after hydrolysis afford P-carbamidoketones.105b Olefins can be converted into secondary and tertiary amines by prior amino- mercuration followed by reduction with sodium borohydride.lo6 Full de- tails of the Markownikov hydration of olefins by oxymercurationdemercura-tion have appeared. The reaction is general but sensitive to steric effects."' Alkyl bromides can now be made from olefins via their borane derivatives which react with bromine in the presence of base. An anti-Markownikov bro- mination results. log Alternatively the alkylboranes can be converted into the corresponding mercury derivatives and these react smoothly with bromine. 'O9 Terminal acetylenes can be converted into their silyl derivatives (e.g.40) in the presence of a silylating catalyst such as (41).The products behave as protected R'C-CSiRi R,Si-SiR (40) (41) acetylenes since mild acid regenerates the parent function.' lo A new cumulene synthesis albeit of limited use has been devised which proceeds via carbene intermediates (Scheme 9).'l1 R' R2/ I C-CSZCH X \ [::;c=c=c]-b 5 R'R';c=c-C R3 R4 / \ X = leaving group Reagents i Bu'O-Bu'OH; ii R3R4CN Scheme 9 4 Carbonyl Compounds Dihydro-1,3-oxazines are much more versatile than would at first appear.' 12' A novel ketone synthesis is achieved by alkylation of the nitrogen atom to form salts of the type (42). Addition of Grignard reagent gives (43) and subsequent mild hydrolysis liberates the ketone in high yield.' '2b Another useful synthetic intermediate in this area is the isonitrile 1,1,3,3-tetramethylbutyl isocyanide (44).lo5 (a)J. Lessard and J. M. Paton Tetrahedron Letters 1970 4883; (6) J. Lessard H. Driguez and J. P. Vermes Tetrahedron Letters 1970,4887. 'Oh J. J. Perie and A. Lattes Bull. SOC. chim. France 1970 583. H. C. Brown and P. J. Geoghegan J. Org. Chem. 1970,35 1844. '08 H. C. Brown and C. F. Lane J. Amer. Chem. SOC. 1970,92 6660. J. J. Jufarullo and M. M. Hovey J. Amer. Chem. SOC.,1970,92 3221. 'lo R. Calas and P. Bourgeois Compt. rend. 1969,268 C 72. ' ' H. Reimlinger and R. Paulissen Tetrahedron Letters 1970 3 143. ' (a) Ann. Reports (B) 1969 66 259; (b)A. I. Meyers and E. M. Smith J. Amer. Chem. Soc. 1970 92 1084. 256 P.G.Sammes Grignard reagents add on to the carbon atom to give the imine anion (45) which can react in a variety of ways (Scheme 10).'l3 Symmetrical ketones can be easily prepared from alkylboranes via their cyanoborate derivatives (e.g.46). Under the influence of electrophilic reagents (trifluoroacetic anhydride is particularly effective) these rearrange into the adducts e.g. (47) from which the ketone is liberated with alkaline hydrogen peroxide.' l4 RCPO RCOCH(0H)Ph4 9RCOC02H Ti \ (45) R RCOCH,CH(OH)Me )" -%RCOR' RCOSiMe A Reagents i H,O; ii CO,; iii R'X; iv Me,SiCI; v MeCH -CH,; vi PhCHO. Scheme 10 The conjugate addition of alkyl groups from trialkylboranes on to ap-un- saturated carbonyls is a free-radical process and is catalysed by traces of air. Under these conditions reproducible high yields of ketones or aldehydes can be obtained.' ' A new /?-keto-ester synthesis uses the homologation of ketones with diazoacetic esters and is efficiently catalysed by triethyloxonium fluoro- borate.In this way cyclohexanone was converted into the cycloheptanone (48) in over 90% yield."6 Enamines derived from aldehydes react with N-chloro- succinimide to give the appropriate a-chloro-aldehyde. ' ' R,BCN Na' R-B N (46) \// 0-c CF3 (47) H. M. Walborsky W. H. Morrison and G. E. Niznik J. Amer. Chem. SOC.,1970,92 6675. 'I4 A. Pelter M. G. Hutchings and K. Smith Chem. Comm. 1970 1529. I I H. C. Brown and G. W. Kabalka J. Amer. Chem. SOC.,1970,92,712,714. 'Ih W. L. Mock and M. E. Hartman J. Amer. Chem. Soc. 1970 92 5767. 'I' J. J. Riehl and F.Jung Compt. rend. 1970 270 C 2009. General Methods The homologation of aldehydes with enol ethers to give up-unsaturated alde- hydes has been extended ; the method is more adaptable and efficient than the aldol method. It proceeds uiu the ketal(49) which gives the desired product upon 0 CO1Et R' "QR2 OEt 0 mild acid hydrolysis.' y-Hydroxyketones can be dehydrated with carbodi- imides to give cyclopropyl ketones in good yields. The method is general since the starting materials can be obtained from reaction between ketones and epoxides.' Many examples of the thermocyclisation of 68-and &(-unsaturated ketones have recently been recorded and the process can now be considered general occurring with a defined stereochemistry.120" Thus the enone (50) reacts uia its enol (51) to give the bicyclic ketone (52).120b A novel precursor of aldehydes is the Wittig species (53).The vinyl ally1 sulphide produced (e.g. 54) undergoes Claisen rearrangement on heating and in the presence of mercuric oxide generates a new aldehyde (55).' la Vinyl sulphides are produced with ketones and the Wittig reagent precursor (56)l2Iband the products are readily hydrolysed with mercuric chloride in aqueous acetonitrile to give the homologous aldehyde. The acidic nature of sulphides has also been 0 Ph,P=CHSCH,CH=CH / s-(53) 0-MeSCH,-PO(OEt) (54) (55) 'I8 S. Satsumabayashi K. Nakajo R. Soneda and S. Motoki Bull. Chem. SOC.Japan, 1970,43 1586. l9 C. Alexandre and F. Rouessac Terrahedron Lerters 1970 101 1.(a)F. Legendecker G. Mandville and J.-M. Conia Bull. Soc. chim. France 1970,549; (b) F. Legendecker G. Mandville and J.-M. Conia ibid. p. 556. (a)E. J. Corey and J. I. Shulman J. Amer. Chem. Soc. 1970,92 5522; (6) E. J. Corey and J. I. Shulman J. Org. Chem. 1970 35 777. 258 P.G. Sammes exploited in a preparation of ap-unsaturated aldehydes. The lithium salt (57) reacts with epoxides to give the product (58). Mild hydrolysis under the con- ditions mentioned above affords the aldehyde (59).122 Further ramifications of the Wittig reaction have been explored. The betaine adducts (e.g. 60) are known to react with base to form a new ylide (61). These ylides can react in a variety of ways all of which are notably stereoselective (Scheme 11).lz3 Arsonium ylides appear to have properties in between those of H R YR* OH y:*OH T / RHc' + 0-PPh 0-PPh, I1 I1 RCH-CHMe 5R-CH-C-Me (60) / (61) \ 1 H 'HC1 Reagents i PhLi; ii R'CHO; iii paraformaldehyde; iv PhICl,; v N-chlorosuccinimide ; vi I,-H20 ; vii Hg(OAc),-LiI-I .Scheme 11 phosphorus and sulphur ana10gues.l~~ A reaction analogous to the Wittig process is that between ketones and a-silanyl-Grignard reagents. Thus the reagent (62) reacts with cyclohexanone to give after base hydrolysis the corres- ponding methylenated product.' 25 12 E. J. Corey and R. Noyori Tetrahedron Letters 1970 31 1. 123 E. J. Corey J. I. Shulman and H. Yamamoto Tetrahedron Letters 1970 447; E. J. Corey and H. Yamamoto J.Amer. Chem. Soc. 1970 92 226; cf. M. Schlosser and K. F. Christmann Synthesis 1969 1 38. 124 P. Bravo G. Gaudiano P. P. Ponti and M. G. Zubiani Tetrahedron Letters 1970 4535. 125 T. H. Chan E. Chang and E. Vinokur Tetrahedron Letters 1970 11 37. General Methods A simple method for the a-cleavage of ketones involves the process outlined (Scheme 12).126 The trimethylsilyl ethers of enols are readily prepared by the reaction of a ketone and trimethylsilyl chloride using lithium diethylamide as Me,SiCH,MgCl (62) base.I2' Pyridine hydrochloride is the recommended catalyst for the Semmler reaction being superior to the hydrochloric acid-acetic anhydride mixture gen- erally employed.' 28 The decarbonylation of aldehydes ,using chlorotris(tri- phenylphosphine)rhodiurn(~)as catalyst is very stereoselective proceeding with Reagents i ArSO,S(CH,),SSO,Ar ;ii NaOMe-dimethyl sulphoxide.Scheme 12 overall retention of configuration about the adjoining carbon centre. For example the aldehyde (63a) gives the hydrocarbon (63b) virtually quantita- tively.' 29 Finally further reactions of P-keto-esters have been recorded. Derived di-anions from these systems can be made by a two-step procedure. The mono- anion is made first using sodium hydride in tetrahydrofuran followed by genera- tion of the di-anion with butyl-lithium. Selective alkylation occurs at carbon only. no oxygen alkylation being ~bserved.'~' 5 Carboxylic Acids A general method for making a-chloro-nitriles and dialkyl nitriles in preparative yields has been developed by reaction of dichloroacetonitrile with trialkyl- boranes under the influence of a hindered base such as potassium 2,6-di-t- J.A. Marshall and H. Roebke Tetrahedron Letters 1970 1555. 12' H. 0.House L. J. Czuba M. Gall and H. D. Olmstead J. Urg. Chem. 1969,34,2324. ''' R. Royer P. Demerseman and G. Colin Bull. SOC. chim. France 1970 1026. 129 H. M. Walborsky and L. E. Allen Tetrahedron Letters 1970 823. 13* L. Weiler J. Amer. Chem. SOC. 1970,92 6702. 260 P.G. Summes b~tylphenoxide.'~'" This method has also been adapted to alkylate ethyl 4-bromocrotonate when the by-unsaturated ester results.' '' A variety of alter- native methods for preparing nitriles have been introduced. The sulphonyl nitrile (64) is a useful source of 'positive' cyanide.Reaction with Grignard CIC-0 4(3S02CN S I1 reagents produces the corresponding nitrile.I3' Dehydration of primary amides can be effected under almost neutral conditions by heating them in tetrahydro- furan in the presence of carbcn tetrachloride and triphenylph~sphine,'~~ reaction going via the iminochloride. The dehydration of oximes to produce nitriles can be conveniently carried out by reaction at room temperature with chlorothionoformate esters such as (65),in ~yridine.'~~ Ynamines can be pre- pared by conversion of thionamides in one step by reaction with sodamide in xylene the yields being better than those obtained in longer synthetic se-quence~.'~'A rapid simple method for esterifying acids is to use boron tri- fluoride as catalyst.Fewer side-reactions occur compared to the classical Fischer-Speier method.'36 The aminolysis of esters has also been improved. The lithium salts of amines react more cleanly than the corresponding sodium salts. The lithium derivatives are easily prepared using butyl-lithium. '37 Amides are also formed in high yield by reaction between tris(dialky1amino)boranes and carboxylic acids.'38 Conjugated dienoic acids are readily synthesised from the reaction of tertiary acetylenic carbinols with excess malonic acid. Presumably the carbinol is initially isomerised to the ap-unsaturated aldehyde before condensation and decar- boxylation.' 39 The preparative usefulness of the cr-anions of aliphatic carboxylic acids is recorded.These anions (e.g. 66)can be prepared by the reaction of the 13' (a)H. Nambu and H. C. Brown J. Amer. Chem. Soc. 1970,92,5790;(6)H. C. Brown and H. Nambu ibid. p. 176 1 13' A. M. van Leusen and J. C. Jagt Tetrahedron Letters 1970 967. 133 E. Yamato and S. Sugasawa Tetrahedron Letters 1970 4383. 134 D. L. J. Clive Chem. Comm. 1970 1014. 13' A. Halleux H. Reimlinger and H. G. Viehe Tetrahedron Letters 1970 3141. 136 J. L. Marshall K. C. Erickson and T. K. Folsom Tetrahedron Letters 1970 4011. 13' K.-W. Yang J. G. Cannon and J. G. Rose Tetrahedron Letters 1970 1791. 13' A. Pelter and T. E. Levitt Tetrahedron 1970 26 1899. J. Ploquin and L. Sporfel Ann. Chirn. (France),1970 5 143. General Methods 26 1 acid with lithium isopropylamide in tetrahydrofuran containing hexamethyl- phosphoramide.Reaction with ethyl formate followed by decarboxylation gives the corresponding aldehyde. 140a Alkylation and nitrations have also been recorded.14*' 0-and p-Toluic acids can also form dianions (67) capable of similar reactions. An interesting temperature effect in the synthesis of carboxylic acids by the alkylation of anions from dihydro-1,3-oxazines (68; R = alkyl) has been investi- gated. At -78 "C alkylation proceeds cleanly. However at room temperature these anions rearrange to the ketenimines (69)which do not alkylate.14* Whereas the dihydro-oxazines add Grignard reagents across the double bond the corres- ponding oxazolines do not 143a and this system has been used as a protecting group for aromatic carboxylic Thus the derivatives (70) could be converted into their Grignard derivatives caused to react and hydrolysed with release of the carboxylic acid function.The parent system forms anions at the 2-position (71) which can be alkylated to produce mono- and di-alkylated carboxylic acids.143c Ethyl acetate is cleanly transformed into its enolate anion by reaction with lithium bis(trimethylsily1)amide in tetrahydrofuran at -78 "C at which it is stable. The anion readily adds to carbonyl groups to produce P-hydroxy-esters in high yield.144 1-Ethoxyvinyl esters (e.g. 72) rearrange in the presence of zinc salts to give enol-acylated P-keto-esters (73) and this reaction is potentially useful for the preparation of certain P-keto-esters. 14' The Michael addition of Refor- matsky reagents to unsaturated ketones is sensitive to steric effects.1,4-Addition OCOR R (72) (73) I4O (a)P. E. Pfeffer and L. S. Silbert Tetrahedron Letters 1970 699; (b) P. E. Pfeffer and L. S. Silbert J. Org. Chem. 1970 35 262. 14' P. L. Creger J. Amer. Chem. SOC.,1970,92 1396 1397. 142 A. I. Meyers and E. M. Smith Tetrahedron Letters 1970 4355 143 (a) A. I. Meyers and E. W. Collington J. Amer. Chem. SOC.,1970.92 6676; (b)A. I. Meyers and D. L. Temple ibid. P.6646; (c) A. I. Meyers and D. L. Temple ibid. p. 6644. 144 M.W. Rathke J. Amer. Chem. SOC.,1970 92 3222. 145 H. H. Wasserman and S. H. Wentland Chem. Comm. 1970 1. 262 P.G. Sarnrnes is enhanced by using bulky acid groups such as ethyl a-bromomalonate instead of ethyl br0moa~etate.l~~ The a-bromination of acyl halides with N-bromosuccinimide long considered to be a free-radical process is in fact an ionic reaction and is definitely catalysed by acid.14' In concentrated sulphuric acid chlorination of aliphatic acids proceeds via cation radicals the chlorine preferentially entering into the y-position as well as into the terminal methyl group.14' Ethyl P-ketocarboxylates can be decarboxylated at fairly low temperatures (Q 150 "C)by use of boric anhydride as catalyst.'49 Orthoformic acid dimethyl ester dimethylamide (74) is a good dehydrating agent.Epoxides are formed (MeO),CHNMe (74) Ph Ph (75) (76) from 1,2-glycols and it has been found that in cyclic systems only trans-glycols react.15* However in the presence of acetic anhydride a reductive elimination occurs [e.g.(75)to (7611 and in this case cis-glycols react preferentially. lS Orthoesters of the mixed arylalkyl group react with Grignard reagents with preferential displacement of the aryl groups. Thus the orthoester (77) yields the acetal (78).'52 The reduction of carboxylic acids to aldehydes is achieved with PhOCH(OEt) -+ RCH(OEt) (77) (78) lithium in methylamine. The initial product is the imine which can either be hydrolysed to the aldehyde or reduced to the substituted N-methylamine.'53 Dramatically increased yields of the expected products from the Knoevenagel reaction are obtained using titanium tetrachloride and pyridine as catalyst.' 54 6 Alkylations and Couplings Coupling is enhanced between Grignard reagents and alkyl halides if the latter possess neighbouring groups capable of complexation.Thus whereas pentyl bromide does not react with iodomagnesium phenylacetylide ethoxyethyl 14' C. Gandolfi G. Doria M. Amendola and E. Dradi Tetrahedron Letters 1970 3923. L47 J. G. Gleason and D. N. Harpp Tetrahedron Letters 1970 3431. 14* N. C. Deno R. Fishbein and J. C. Wyckoff J. Amer. Chem. Soc. 1970,92 5274. 149 J. M. Lalancette and A. Lachance Tetrahedron Letters 1970 3903. I5O H. Neumann. Chimiu (Switz.) 1969 23 267. 151 F. W. Eastwood K. J. Harrington J. S. Josan and J. L. Pura Tetrahedron Letfers 1970 5223. H. Stetter and E. Reske Chem. Ber. 1970 103 643. 153 A. 0.Bedenbaugh J. H. Bedenbaugh and W.A. Bergin J. Amer. Chem. Soc. 1970 92 5774. 154 W. Lehnert Tetrahedron Letters 1970 4723. General Methods 263 bromide does. The effect is general and allows selectivity in coupling reactions.'55 A similar co-ordination precedes the addition of lithium alkyls to alkenyl ethers.' 56 Reduction often accompanies alkylation by hindered Grignard reagents but reduction can be inhibited in the presence of salts. Tetrabutyl-ammonium bromide is particularly effe~tive.'~' A 'one-step' alternative to the Grignard reaction is to add a 1 1 mixture of the ketone and the alkyl halide to lithium suspended in tetrahydrofuran. Excellent yields of alkylation products are thus obtained.'58 The coupling of allylic Grignard reagents to allylic alcohols is catalysed by magnesium bromide.' 59 The reaction of allylic Grignard reagents with car- bony1 functions is reversible resulting in a non-stereoselective addition.' 6o A good method for the coupling of allylic halides with the propargyl moiety is to make the Grignard derivative followed by trimethylsilylation of the crude product.Subsequent detrimethylsilylation gave better yields ofproduct acetylenes than were obtained previously (Scheme 13.)16' Ally1 ethers are cleaved by mag- nesium in the presence of ethylene dibromide.'62 The coupling of benzyl halides with sodium hydride in hexamethylphosphoramide is activated by the presence SiMez I %Mez Reagents i CH =C=CHMgBr; ii EtMgBr-Me,SiCl; iii alcoholic AgNO,; iv. aqueous NaCN. Scheme 13 of alkoxides.Sodium hydride alone tends to react as a reducing agent.'63"*b Other evidence that sodium hydride can often react as a reducing agent has been acquired in that in dimethylformamide it appears to react as the anion (79).'(j3' A mixture of sodium hydride and a sodium alkoxide formed from a hindered alcohol reacts cleanly with 1,2-dibromides in tetrahydrofuran to give acetylenes.' 64 155 G. W. Cooper and R. P. Houghton Tetrahedron Letters 1970. 3915. L5b A. H. Veefkind F. Bickelhaupt and G. W. Klumpp Rec. Trau. chim. 1969 88 1058. Is' M. Chastrette and R. Anouroux Chem. Comm. 1970,470. 58 P. J. Pearce D. H. Richards and N. F. Scilly Chem. Comm. 1970 1160. H. Felkin and C. Kaeseberg Tetrahedron Letters 1970,4587. Iho P. Miginiac Bull.SOC.ehim. France 1970 1077. 16' R. E. Ireland M. I. Dawson and C. A. Lipinski Tetrahedron Letters 1970 2247. A. Maercker J. Organometallic Chem. 1969 18 249. 163 (a)P. Caubere and J. Moreau Bull. SOC. chim. France 1970 1986; (6)S. Bank and M. C. Prislopski Chem. Comm. 1970 1624; (c)J. M. Z. Gladych and R.Hornby Chem. and Ind. 1970 652. P. Caubere and J. Moreau Tetrahedron 1970 26 2637; cf Ann. Reports (B) 1969 66 260 ref. 122 where aprotic conditions were in fact also employed. 264 P.G. Summes Metallation of alkylbenzenes is readily effected with n-butyl-lithium and N N N' N'-tetramethylethylenediamine.65 Resonance-stabilised organolithium compounds react with secondary halides with inversion of configuration-non-resonance-stabilised lithium compounds are less discriminating.Very high selectivity is observed in the reaction of unsymmetrical epoxides with lithium diethylamide in their isomerisation to allylic alcohols. Thus the epoxide (80) gives virtually only the alcohol (81) probably by ~yn-elimination.'~~ Lithium dialkyl copper complexes react smoothly with epoxides,' 68a as do dialkylmagnesium compounds in the absence of magnesium halides.' 68b The conjugate addition of alkyl groups to unsaturated epoxides has also been recorded and is favoured by use of the lithium dialkyl copper reagents.169 Acid chlorides react with the same alkylating agents to give ketones."' The alkylating properties of a variety of transition metal complexes have been studied and as a result vinyl bromides and iodides were found to couple cleanly with lithium trimethyliron ;I7 allylic bromides also react.95 Another method of coupling two allyl groups used in a synthesis of squalene involved alkylation of an allylphosphonium ylide with another allyl bromide.Reduction of the phosphonium salt was achieved by use of lithium in ethylamine (Scheme 14).'72 R +-CH-~B~ Me + > * L R+R + PBu Br-BrCH -CH=CR1 Me Scheme 14 165 C. D. Broaddus J. Org. Chem. 1970 35 10. L. H. Sommer and W. D. Korte J. Urg. Chem. 1970,35 22. 167 B. Rickborn and R. P. Thummel J. Org. Chem. 1969,34 3583. 168 (a) R. W. Herr D. M. Wieland and C. R. Johnson J. Amer. Chem. SOC.,1970 92 3813; (b)J. D. Morrison R. L. Atkins and J. E. Tomaszewski Tetrahedron Letters 1970,4635.169 R. J. Anderson J. Amer. Chem. SOC.,1970,92 4978; R. W. Herr and C. R. Johnson J. Amer. Chem. SOC., 1970,92 4979. "O G. H. Posner and C. E. Whitten Tetrahedron Letters 1970 4647. E. J. Corey and G. H. Posner Tetrahedron Letters 1970 315. cf. E. J. Corey and 1. Kawazima J. Amer. Chem. SOC.,1970 92 395. '72 E. H. Axelrod G. M. Milne and E. E. van Tamelen J. Amer. Chem. SOC.,1970 92 2139. General Methods The B-methoxydialkylboranes add to olefins in the presence of lithium aluminium hydride to give mixed trialkylboranes thus opening up several variants of the synthetic uses for these compounds.’ 73 Sodium tetracarbonyl- ferrate( -11) homologates alkyl bromides to the corresponding aldehyde.’ 74 Another new class of organometallic compound is exemplified by cis-and tratzs-P-styrylpyridinecobaloximes (82).Both isomers can be isolated and each PhC H =C H.Co(DH)2,py DH = dimethylglyoxime monoanion py = pyridine (82) reacts with halogens stereospecifically with retention of configuration to give P-styrylhalides. This latter reaction should be general for these compounds.’ 75 Thallium(1) bromide catalyses the coupling of aryl magnesium compounds to biaryls probably uia the aryl radical.’ 76 Another novel radical reaction has been developed for substitution at tertiary carbon centres. Thus p-nitrocumyl chloride (83) will accept an electron from isopropyl-2-nitronate anions (84) to form a radical anion. Loss of chloride produces a radical which can couple with more 60-(83) NO2 -P ‘5 N? *o’ ‘0- -b 6/N ’0 0->;NO -‘0/N\ 0-gNo2 + + I )NO2 )-NO2 Scheme 15 I” H.C. Brown E. Negishi and S. K. Gupta J. Amer. Chem. SOC.,1970,92,6648. M. P. Cooke J. Amer. Chem. SOC.,1970,92 6080. ”’ M. D. Johnson and B. S. Meeks Chem. Comm. 1970 1027. ”‘A. McKillop L. F. Elsam and E. C. Taylor Tetrahedron 1970,26,4041. P.G.Sammes of the nitronate anion (84) to produce a new anion radical eventually oxidised to the coupled product. (Scheme 15)' 77a Tertiary nitro-compounds can also be alkylated in this manner since the nitro-group behaves as an excellent leaving group.' Several new sulphur ylides have been prepared. The reagent (85c) inserts carboxymethyl groups into ketones or conjugated olefinic bonds,' 78 whilst the stable ylides (85a)179 and (85b)' similarly transfer methylene groups.N-Cyano- ammonium salts such as (86) behave as potent alkylating agents."l 0 II + Ph-S-CH -Me2kHC0 -Na' I NMe (85b) LiCH,CI R CN (87) The lithium alkyl(87) is superior to the analogous bromide and iodide for the transfer of the methylene group to olefins.lB2 Another method for preparing cyclopropanes is to add di-iodomethane in the presence of diethylzinc.' 83 7 Miscellaneous 1-(2-Carboxyphenyl)triazenes (88) are stable crystalline compounds which give benzyne either on warming or by addition of one equivalent of trichloro- acetic acid.' 84 o-Benzenediazonium carboxylate cannot be used as a benzyne precursor in acetonitrile and related solvents since reaction with the solvent occurs to form (4H)-3,1 -benzoxazin-4-one derivatives (89).18' An improved method for the preparation of methanesulphonate esters has been described.'86 Trifluoromethanesulphonic imidazolide (90) is a convenient reagent for the preparation of 'triflate' esters.'87 Alcohols can be converted into "'(a)N. Kornblum R. T. Swiger G.W. Earl H. W. Pinnick and F. W. Stuchal. J. Amer. Chem. SOC. 1970 92 5513; (6) N. Kornblum S. D. Boyd and F. W. Stuchal ibid. p. 5783. J. Adams L. Hoffman and B. M. Trost J. Org. Chem. 1970 35 1600. C. R. Johnson and G. F. Katcha J. Amer. Chem SOC.,1970,92 5753. I8O C. R. Johnson M. Haake and C. W. Schroeck J. Amer. Chem. SOC.,1970,92 6594. Ia1 J. V. Paukstelis and M. Kim Tetrahedron Letters 1970 4731.la* U. Burger and R. Huisgen Tetrahedron Letters 1970 3049. J. Furukawa N. Kawabata and T. Fujita Tetrahedron 1970 26 243. J. Nakayama 0.Simamura and M. Yoshida Chem. Comm. 1970 1222. R. R. Schmidt and W. Schneider Tetrahedron Letters 1970 5095. R. K. Crossland and K. L. Servis J. Org. Chem. 1970,35 3195. la' F. Effenberger and K. E. Mack Tetrahedron Letters 1970 3947. General Methoh chlorides by reaction with the reagent (91) in the presence of lithium chloride bromides are similarly prepared.’88 Bromides can be converted into chlorides by reaction with the barbiturate derivative (92).18’ aCOzH N=N-NMe (88) Et2NCF2 -CFClH (91) CH,C1 (92) The selective mono-chlorination of phenols and aniline is normally difficult.Use of the mild reagent trichloroisocyanuric acid in the presence of some acid catalyst is now recommended for this transformation.’ 90 The fluorination of aromatic compounds with the mild reagent xenon difluoride is catalysed by hydro- fluoric acid.”’ The fluorination of olefins can be achieved with potassium tetra- fluor~cobaltate.’~~ Iron carbonyl complexes are useful for trapping diene systems. An elegant example is the use of iron(0) pentacarbonyl to trap the Kekule structures (93) and (94) obtained from 3,a-dimethyl~tyrene.’~~ Extrusion of sulphur dioxide from aromatic sulphonyl chlorides is effected with complexes of the platinum group. Good yields of the corresponding chloride are often Iodine in oleum is a powerful iodinating reagent.Even nitro-aromatics are attacked.195 E. J. Bailey H. Fazakerley M. E. Hill C. E. Newall G. H. Phillipps L. Stephenson and A. Tulley Chem. Comm. 1970 106. lS9 J. A. Vida Tetrahedron Letters 1970 3447. 190 E. C. Juenge D. A. Beal and W. P. Duncan J. Org. Chem. 1970,35 719. l9 M. J. Shaw J. A. Weil R. Filler and H. H. Hyman J. Amer. Chem. Soc. 1970,92,5096. IV2 J. C. Tallow. J. Burdon P. L. Coe G.P. 1970 no. 1,925,836 (Chem.Abs. 1970 72 78104). 193 R. Victor R. Ben-Shoshan and S. Sarel Chem. Comm. 1970 1680. 194 J. Blum and G. Scharf J. Org. Chem. 1970,35 1895. J. Arotsky R. Butler and A. C. Darby J. Chem. Soc. (0,1970 1480. 268 P.G. Sammes Primary alkylamines can be prepared by alkylation of the precursor (95). Hydrochloric acid liberates the amine hydr~chloride.'~~ Several methods for the preparation of unsymmetrical disulphides have been reported.Thus sul-phenic esters react with trialkylthioboranes to give unsymmetrical disulphides. 19' Moregeneral is the reaction ofmercaptans with N-(alky1thio)phthalimides (11).19' Active methylene compounds such as 0-keto-esters can also react with the latter derivatives to give the thioalkylated derivative^.'^^ OMe 1 ( Ph S),NLi Ph -C -CO H 1 (95) CF (96) An effective way to demethylate aryl ethers is to react them with lithium200" or sodium200b mercaptides in polar aprotic solvents. Dialkyl ethers can also be rapidly cleaved by aluminium tri-iodide in carbon R' H RZ iii H NH HN+ + H R3 H,N+vco; :\ H R3 Reagents i R3COC0,Me; ii AI-He; iii H,-Pd-C; iv H,O+.Scheme 16 An efficient method for the stereospecific synthesis of a-amino-acids from pyruvic esters has been developed (Scheme 16).202 a-Methoxy-a-trdluoro-methylphenylacetic acid (96) is a good reagent for testing the optical purity of alcohols and amines203" and its preparation has been The use of thallium in organic chemistry has been reviewed204 and a book on modern organic reactions emphasising synthetic methods has been pub- lished. O5 196 T. Mukaiyama and T. Taguchi Tetrahedron Letters 1970 341 1. 191 R. H. Cragg J. P. N. Husband and A. F. Weston Chem. Comm. 1970 1701. 19 8 K. M. Bousfang and A. B. Sullivan Tetrahedron Letters 1970 3547; K. Boustang Chimia (Switz.) 1970,24,396; D.N. Harpp D. K. Ash T. G.Back J. G. Gleason B. A. Orwig and W. F. Van Horn Tetrahedron Letters 1970 1970 3551. 199 T. Mukaiyama S. Kobayashi and T. Kumamoto Tetrahedron Letters 1970 51 15. 200 (a)P. A. Bartlett and W. S. Johnson Tetrahedron Letters 1970,4459; (6) G. I. Feutrill and R. N. Mirrington ibid. p. 1327. 20 I E. Mincione Ricerca sci. 1969 39 424. 20 2 E. J. Corey R. J. McCaully and H. S. Sachdev J. Amer. Chem. Soc. 1970,92,2476. 203 (a)J. A. Dale D. L. Dull and H. S. Mosher. J. Org. Chem. 1969,34 2543; (h)L. Hub and H. S. Mosher ibid. 1970 35,3691. 204 E. C. Taylor and A. McKillop Accounts Chem. Res. 1970 3 338. 20 s 'Modern Reactions in Organic Synthesis' ed. C. J. Timmons Van Nostrand Reinhold Company London 1970.General Methods The ‘crownanes’ (e.g.10) are useful chelating agents and the properties of some of them have been reported.206 A short review on the use of NNN’N’-tetra-methylethylenediamine in organometallic chemistry has appeared.*07 C. J. Pederson J. Amer. Chem. SOC.,1970 92 386 391 207 C. Agami Bull. SOC. chim. France 1970 1619.

ISSN:0069-3030    

DOI:10.1039/OC9706700241

出版商:RSC    

年代:1970

数据来源: RSC

摘要:

9 Organometallic Compounds Part (i) The Main Group Elements By D. J. CARDIN M. F. LAPPERT J. D. SMITH and D. R. M. WALTON School of Molecular Sciences University of Sussex Brighton BN 7 9QJ THEliterature of organometallic chemistry grows at an alarming rate. The year 1970 has seen the appearance of a new journal.’ The revision of Ingoid’s classic text provides a useful account2 of the mechanism of electrophilic substitution at saturated carbon with particular reference to the Hg-C bond. Books dealing with organometallic chemistry of the Main Group elements include texts on inorganic ring compo~nds,~ organosilicon heteropolymers and carborane~,~ hetero-compounds,’ organometallic compounds of tin‘ and arsenic antimony and bismuth,’” organometallic reaction^,'^ redistribution reaction^,'^ and spectro- scopic methods in organometallic chemistry.8 A commercial journal continues to provide a detailed review of organometallic literature the latest volume covers (except for Si) the year 1969.’ After an interval of six years two further volumes on progress in boron chemistry have appeared including articles on carb-oranes,”“ polymers containing clusters of boron atoms,”’ use of isotopic (’ ‘B and 2H) labels,”‘ oxidation of organic compounds in the presence of boron ’ ‘Organometallics in Chemical Synthesis’ ed.J. G. Noltes and D. Seyferth Elsevier Amsterdam 1970 vol. 1. C. K. Ingold ‘Structure and Mechanism in Organic Chemistry’ Bell London 2nd edn. 1969 Ch. 8. I. Haiduc ‘The Chemistry of Inorganic Ring Systems’ (2 vols.) Wiley New York 1970.R. N. Grimes ‘Carboranes’ Organometallic Chemistry Series (ed. P. M. Maitlis F. G. A. Stone and R. West) Academic Press New York 1970. S. N. Borisov M. G. Voronkov and E. Ya. Lukevits ’Organosilicon Heteropolymers and Heterocompounds’ Plenum Press New York 1970. ‘ W. P. Neumann ‘The Organic Chemistry of Tin’ Wiley London 1970; R. C. Poller ‘The Chemistry of Organotin Compounds’ Logos Press London 1970. (a)G. 0. Doak and L. D. Freedman ‘Organometallic Compounds of Arsenic Anti- mony and Bismuth’ Wiley London 1970; (6) ‘Organometallic Reactions’ ed. E. I. Becker and M. Tsutsui Wiley-Interscience New York 1970 vol. I Ch. 1 by T. Mole (redistribution reactions of organoaluminium compounds) ; Ch. 3 by L. G. Makarova (reactions of organomercury compounds also Ch.3 of vol. 2); vol. 2 Ch. 1 by K. Moedritzer (the redistribution reaction); (c) J. C. Lockhart ‘Redistribution Reactions’ Academic Press New York 1970. ‘Spectroscopic Methods in Organometallic Chemistry’ ed. W. 0. George Butter- worths London 1970. Organometallic Chem. Rec. (B) 1970 vol. 6. lo (a) R. E. Williams Progr. Boron Chem. 1970 2 37; (6) T. L. Heying ibid. p. 119; (c) J. E. Odom and R. Schaeffer ibici. p. 141. 272 D. J. Cardin M. F. Lappert J. D. Smith and D. R. M. Walton compounds,' lUneighbouring-group effects of boron in organoboron chemistry (see also ref. 12),'lb thermochemistry of boron compounds,'" topics in BN chemistry,' Id and organoboronsulphur compounds. ' le Professor E.G. Rochow has contributed an essay entitled 'Of time and carbon- metal bonds.'13 The following specialist topics have been reviewed :n.m.r. spectra of organometallic ally1 compounds ; a-heterodiazoalkanes and the reactions of diazoalkanes with derivatives of metals and metalloids ;l syntheses of organo- metallic compounds by thermal decarboxylation ;' polyfluoro-aromatic,' perfluorovinyl,' 7b chlorocarbon,'8 and bromocarbon derivatives of metals and metalloids ; sulphur dioxide and trioxide insertion reactions into M-C bonds ;I9 some recent results in carbanion chemistry ;20 the thermodynamics of redistribution reactions ;" fast exchange reactions of Group I 11 and I11 organo-metallic compounds ;22 ~rgano-berylliurn~~" and -magnesium23' compounds ; Group 124n and Group I11 organometallic ~hernistry;~~' metal-boron com-pounds ;25 transition-metal-carborane complexes;26 organothallium chem-istry2'" and the use of thallium in organic synthesis;"' isoelectronic species in the organo-aluminium -phosphorus and -silicon series;'* organosilicon ketones;29 platinum metal catalysis in silicon chemistry ;30 n-bonding3 la and radicals3 ' in silicon and Group IVB organometallic chemistry ; non-bonded interactions in organometallic compounds of Group IVB ;32 19Sn Mossbauer I' (a) W.G. Woods and R. J. Brotherton Progr. Boron Chem. 1970 3 1; (b) D. S. Matteson ibid. p. 117; (c) A. Finch and P. J. Gardner ibid. p. 177; (d) H. Noth ibid. p. 21 1 ; (e) B. M. Mikhailov ibid. p. 313. l2 D. S. Matteson Accounts Chem.Res. 1970 3 186. l3 E. G. Rochow Adti. Organometallic Chem. 1970 9 I. '' L. A. Fedorov. Russ. Chem. Rev. 1970,39 655. l5 M. F. Lappert and J. S. Poland Adc. Organometallic Chem. 1970,9 397 l6 G. B. Deacon Organometallic Chem. Rev. (A) 1970 5 355. I' (a)S. C. Cohen and A. G. Massey Adv. Fluorine Chem. 1970,6,185;(b)I. L. Kunyants, R. N. Sterlin and V. L. Isaev Zhi4r. Vsesoyuz. Khim. obshch. im D.I. Mendeleeva 1970 15 25 (Chem. Abs. 1970,72 132825u.). T. Chivers Organometallic Chem. Rev. (A) 1970 6 1. l9 W. Kitching and C. W. Fong Organometallic Chem. Rev. (A) 1970 5 281. 2o U. Schollkopf Angew. Chem. lilternat. Edn. 1970 9 763. 21 A. G. Lee Organometallic Chem. Rev. (A) 1970 6 139. 22 J. P. Oliver Ado. Organometallic Chem. 1970 8 167. 23 (a) G.E. Coates and G. L. Morgan Adv. Organometallic Chem. 1970 9 195; (b) B. Blagoev and D. Ivanov Izvest. Otdel. Khim. Nauk Bulg. Akad. Nauk 1970 2 629 (Chem. Abs. 1970,73 3956). 24 'Methoden der Organischen Chemie' (Houben-Weyl) Thieme Stuttgart 1970 (a) vol. XIII/I ; (6)vol. XIII/4. 25 G. Schmid Angcw. Chem. Internat. Edn. 1970,9 819. 26 L. J. Todd Adv. Organometallic Chem. 1970 8 87. 27 (a)H. Kurosowa and R. Okawara Organometallic Chem. Rev. (A) 1970 6 65; A. G. Lee Quart Rev. 1970,24,310; (6)E. C. Taylor and A. McKillop Accounts Chem. Res. 1970 3 338; Aldrichimica Acta 1970 3 4. H. Schmidbaur Adu. Organomrtullic~ Chrm. 1970 9 260. l9 N. V. Komarov and V. K. Roman Russ. Chem. Rev. 1970,39 578. 30 P. N. Rylander Engelhard Industries Technical Bulletin 1970 10 130.3L (a) C. J. Attridge Organornetallic Chem. Rev. (A) 1970 5 323; (6) R. A. Jackson Chem. SOC. Special Publ. No. 24 1970 p. 295. 32 C. F. Shaw and A. L. Allred Organometallic Chem. Rev. (A) 1970,5,95. Organometallic Compounds-Part (i) The Main Group Elements 273 spectroscopy in organotin chemistry ;33 vibrational spectra of organo-tin and -lead compounds ;34 heterocyclic compounds of phosphorus arsenic antimony and bismuth ;3 fluoroph~sphines;~~~ phosphines arsines stibines and bis- muthines including those containing Si Ge Sn or Pb ;36 organophosphorus compounds with an active methylene group ;37 comprehensive surveys for 1970 of organophosphorus chemistry38 and organobismuth chemistry ;3 and the use of tetramethylethylenediamine (TMEDA) in organometallic ~hemistry.~' Except for the above section this review is necessarily selective.The approach follows last year's pattern ;only compounds containing metal-carbon bonds are considered and more particularly in the context of those of their reactions in which the M-C bond is either made or broken. Structural data are kept to a minimum but readers are referred to appropriate sections in Volume (A) of Annua! Reports. Because of circumstances beyond our control it was not possible for us to consult December issues for the majority of journals for 1970; for the Soviet literature we largely relied on the English translations which cover only about half of 1970. As in recent years compounds of Li Mg B Si Sn and P have received the greatest attention but there appears to be a new impetus in TI organometallic chemi~try.~' Of some general interest are binuclear organometallic compounds containing a Group IVB element bonded via carbon to a transition metal.These compounds frequently appear to have unusual stability' 1342 and com- pounds may be obtained in which the transition metal is either of unusual co-ordination number [e.g. Ni(CPh,SiMe,),]" or in unusual oxidation state [e.g. Cr(CH2SiMe,)4],42 or in which 7r-acceptor ligands are not required [e.g. TiR4" or CrR442 (R = CH,SiMe,)] ;kinetic stabilities of compounds and the absence of j'l-olefin-elimination pathways appear to be important. In com- pounds such as (7c-C,H5)(OC),MoCH,SiMe3,the C-Si bond is cleaved by nucleophiles under exceptionally mild conditions :43 the transition metal neigh- bouring-group effect may be associated with the thermodynamic stability of the delocalised carbanion (n-C,H,)(OC),MoCH; which may thus be regarded as an anionic metal carbene complex.33 P. J. Smith Organometallic Chem. Rev. (A) 1970 5 373; J. J. Zuckerman Adv. Organometallic Chem. 1970 9,22 34 T. Tanaka Organometallic Chem. Rev. (A) 1970,5 I. '* (a)F. G. Mann in 'The Heterocyclic Derivatives of Phosphorus Arsenic Antimony and Bismuth,' Wiley-Interscience London Second Edn. 1970; (b)J. F. Nixon Adc. Inorg. Chem. Radiochem. 1970 13 364. '' J. E. Drake and C. Riddle Quart. Rev. 1970,24,263; E. W. Abel and S. M. Illingworth Organometullic Chem. Rev. (A) 1970 5 143. 3i A.N. Pudovik and G. E. Yastrebova Run. Gem. Rev. (A),1970 655. 3M 'Organophosphorus Chemistry' ed. S. Trippett (Specialist Periodical Reports) The Chemical Society London 1970 vol. 1. 39 P. G. Harrison Organometallic Chem. Rev. (A) 1970 5 183. " C. Agami Bull. Snc. chim. France 1970 1619. " M. R. Collier M. F. Lappert and M. M. Truelock J. Organometallic Chern. 1970 25 C3. 42 G. Yagupsky W. Mowat A. Shortland and G. Wilkinson Chem. Comm. 1970 1369. '' M. R. Collier B. M. Kingston and M. F. Lappert Chem. Comm. 1970 1498. D. J. Curdin,M. F. Luppert J. D. Smith and D. R. M. Walton Group I.-Lithium. The structure of fluorenyl-lithium (and Na or K analogues) complexes with glymes [MeO(CH,CH,O),Me; 1 < n < 61 in ether solvents has been examined spectros~opically.~~ An equilibrium exists between contact and glyme-separated ion pairs which is dependent on n and temperature.Solutions of Bu"Li and 1,3-diphenylbut-l-enyl-lithiumshow associated complexes (Bu"Li),- (DPBLi), also existing in tight and solvent-separated forms but no values of n or were determir~ed.~' An ionic structure [Cl,C=C=CCl]-Li+ is proposed for the new trichloroallenyl-lithium which is stable below -90 0C.46 The unusual stability of tris(trimethylsi1y)methyl-lithium prepared inter ulia by MeLi metallation of (Me,Si),CH in THF-Et,O may be associated with delocalisation of carbanion change into Si d-orbital~.~' The first triarylsilylmethyl metal reagents (-Li and -MgX derivatives) have been prepared; they are best made by Bu"Li metallation of corresponding bromides.48 Metallation with alkyl- lithiums continues to be widely studied.Ethyl acetate is metallated by LiN- (SiMe,) at -78 "C; the lithio-derivative is more stable than previously reported and is useful for preparing P-hydroxy-esters from aldehydes and ketones.49 Allene can be poly-lithiated at -50 "C in THF-hexane the products reacting with Me3SiC1 to give silylated derivative^.^' An a-elimination of LiCl is postu- lated following lithiation of 2-chloronorbornene ; the reaction involves a new type of ring contraction (Scheme l)?' Transmetallations with organolithium Scheme 1 compounds have afforded LiC(=N,)CO,Et (from the bis-mercury compo~nd),~~ which couples normally with e.g. Me3SiC1 or Bu",SnCl affording a-heterodi- azoalkanes; and have afforded Me,NCH,Li (from the SnBun3 c~mpound),'~ using Bu"Li,TMEDA.The TMEDA complex is both more reactive and more selective (than uncomplexed BuLi) in side-chain metallation of o-Me-C,H,-NMe ,s4 although benzyl- and 2- and 4-pyridylmethyl-lithium have been '' Lock Lim Chan K. H. Wong and J. Smid J. Amer. Chem. SOC.,1970 92 1955. 45 J. W. Burley and R. N. Young Chem. Comm. 1970,991. " G. Kobrich and E. Wagner Chem. Ber. 1970 103 2515. 47 M. A. Cook C. Eaborn A. E. Jukes and D. R. M. Walton J. Organornetallic Chem. 1970 24,529. '' A. G. Brook J. M. Duff and D. G. Anderson Canad. J. Chem. 1970,48 561. " M. W. Rathke J. Amer. Chem. SOC.,1970,92 3222. F. Jaffe J. Organometallic Chem. 1970 23 53. " P. G. Gassman and T.J. Atkins J. Amer. Chern. SOC.,1970,92 5810. 52 U. Schollkopf and H. Frasnelli Angew. Chem. Internat. Edn. 1970 9 301. 53 D. J. Peterson J. Organometallic Chem. 1970 21 P63. 54 R. E. Ludt G. P. Crowther and C. R. Hauser J. Org. Chem. 1970 35 1288. Organometallic Compounds-Part (i) The Main Group Elements prepared free of ring substitution using Bu"L~.~~ Many nitroaryl-lithiums have been prepared by metallation.56 A method of obtaining pK values (within a standard deviation of 3.57) of weak carbon acids X-CH,-Y by comparing the 'H n.m.r. shifts of the species X-CH,-Y and X-CHLi-Y has been devised." The formation of carbenes from CC1,Li has been demonstrated by dichlorocyclopropane formation with c5<8 alkenes.s8 Other reactions involv-ing unstable intermediates include the synthesis of two stereoisomers of (1) from (11 MeLi and 6,6-dibromobicyclo[3,l ,O]hexane probably via cyclohexa-1,2-diene;' the preparation of ditolyls from p-tolyl-lithium and p,p'-ditolyl sulphoxide which is shown to involve arynes;59band the reaction of cis-and trans-2-lithio-2-butenes neopentyl-and neophyl-lithium with cobalt(r1) chloride to afford the dimeric organic species with complete retention of stereochemistry and without rearrangement (respectively)uia organo-cobalt intermediates.60 The reaction of ketones with alkyl halides and lithium may proceed via organolithium reagents and provides a one-step synthesis of tertiary alcohols with yields generally better than the two-stage Grignard procedure.6 Treatment of 2-azo-allyl-lithium compounds with unsaturated hydrocarbons susceptible to nucleophilic attack gives heterocycles e.g.,(2),constituting the first example of an anionic [n4+ 7c2] Li+ Phz-C\.N ,;/ -CH + trans-stilbene -+ H Ph Ph 'h -.cycloaddition.62 Thermolysis of o-nitrophenyl-lithium yields no benzene but a dimeric species which can be converted to (O-N02*C6H&.63 An anion-radical 55 C. G. Sereltas J. F. Estham and C. W. Kamienski Chimia (Swifz.),1970 24 109. 56 P. BuckandG. Kobrich Chem. Ber. 1970 103 1412 1420. 57 D. J. Schaeffer Chem. Comm. 1970 1043. 58 G. Kobrich H. Biither and E. Wagner Angew. Chem. Internat. Edn. 1970 9,169. '' (a) W. R. Moore and W. R. Moser J. Amer. Chem. SOC.,1970 92 5469; (b) K. K. Andersen S.A. Yeager and N. B. Peynircioghi Tetrahedron Letters 1970 2485. '' D. B. Denney and W. R. Davis J. Orgcmometallic Chem.. 1970,24 537. '' P. J. Pearce D. H. Richards and N. F. Scelly Chem. Comm. 1970 1160. 62 T. Kauffman H. Berg and E. Koppelmann Angew. Chem. Internat. Edn. 1970 9 380. 63 P. Buck R. Gleiter and G. Kobrich Chem. Ber. 1970 103 1431. D. J. Curdin M. F. Luppert J. D.Smith and D. R. M. Wulton mechanism is postulated. Comparison has been made between polyhalogenoaryl- lithium reagents and polyhalogenoaryl Grignard reagents in their reactions with Me SiC1-benzophenone mixture^.^^ Both organometallics reacted preferentially with Me,SiCl in tetrahydrofuran (except PhMgBr) the reverse being true in ether. With 1,2-epoxybutane Grignards afforded mainly halohydrins whereas alkyl-lithiums (like dialkylmagnesium compounds) gave high yields of the secondary alcohols (product of nucleophilic ring-opening).6 Sodium and the Heavier Alkali-Metals.Crystals of ethylsodium66 and methyl- pota~sium"~ have been obtained from (i) the appropriate R,Hg and either Na or Na-K and (ii) the appropriate RLi and MOBu'. The sodium compound is rhombohedral in which Na+ ions are in trigonal-pyramidal assemblies. Methyl- potassium is the first methyl-metal derivative with isolated Me- ions in the lattice ; MeK has a hexagonal NiAs structure with each Me group co-ordinated by 6K' ions in a trigonal prismatic arrangement. The solvent(Et,O)-separated but not the contact ion pairs M+[PhCH :CHCH(Ph).Me]- fluoresce in certain ethers at low temperature.68 The complex MeSOCH,Na,THF (from DMSO + NaH in THF) is relatively stable decomposing at 120-1 34 0C.69 Trimesitylborane (TMB) was found to be a suitable non-polar aprotic medium for dissolving alkali- metal reductions ;''this allows for the possibility of a much wider range of reaction conditions than had been possible with (Me,N),PO.Group II.-Beryllium. The mass spectra of R,Be (R = Me Et Pr" Pr' Bu' or But) mostly show ions from associated electron-deficient species only at low source temperatures as expected for such weakly-bridged molecules.' lo A bond dissociation energy D(RBe-R)+ -45 kcal mol- ',was obtained from ionisation potential measurements and the unambiguous identification of (Et,Be,)+ and (Et,Be,H)+ provided conclusive evidence for the trimeric ethyl compound Et,Be,.Alkali-metal dialkylberyllium hydrides NaR,BeH (R = Pr Pr' or Bu') and related species have been described; the molecules are associated by h~drogen-bridging.~~~ Pyrolysis (R = Pr' or Bu') affords olefin some R,Be and a residue of sodium beryllium hydrides the composition of which depends upon the pyrolysis conditions. 1.r. studies show that MeBeBH consists of a mixture of monomers and dimers with structures (3) and (4) having linear (3) (4) " R. C. Edmonson A. E. Jukes and H. Gilman J. Organornetallic Chem. 1970,25,273. 65 R. W. Herr and C. R. Johnson J. Amer. Chem. Soc. 1970 92 4979. 66 E. Weiss and G. Sauermann J. Organometallic Chem. 1970 21 1. 67 E. Weiss and G.Sauermann Chem. Ber. 1970 103 265. J. W. Burley and R. N. Young Chem. Comm. 1970 1649. 6q K. R. Martin J. Organometallic Chem. 1970 24 7. 7o S. D. Darling 0.N. Devgan and R. E. Cosgrove J. Amer. Chem. Soc. 1970,92 696. '' (a)D. B. Chambers G. E. Coates and F. Glockling J. Chem. Soc. (A) 1970 741 ;(b) G. E. Coates and R. E. Pendlebury ibid.,p. 156. Organometallic Compounds-Part (i) The Main Group Elements 277 B-Be-(C) skeleton^.^^" The related Be(BH,) is said to have overall CZ0 H /\ symmetry with an equilateral BeB triangle and Be B bridging atoms lying \/ H out of the plane.72b Magnesium. 1.r. and H n.m.r. studies show that the (cryoscopically) monomeric product (5) from EtMgBr and isopropyl mesityl ketone contains three-co- ordinate magnesium.73 Me OMgX,OEt Me Geminal dimagnesium compounds have been reported CH,(MgX) ,which are converted into alkenes in a Wittig-like reaction with ketones.They exhibit no carbenoid Di-Grignards BrMg(CH,),MgBr prepared in THF have been converted by HMPT in dioxan into magnesiacycloalkanes and their reactions have been An interesting development is the preparation of alkyl- and aryl-magnesium fluorides either from RF and Mg using a cataly~t,~” or using dkalkyl- or diaryl-magnesiums and either BF3,OEt, or Et2A1F.756 Stable hydride complexes e.g.KH,2MgPh2 and KMgBu”,H from R,Mg +KH are reported for the first time although Be and Zn analogues are well known.7sc The compound KMgBus2H reacts with hydrogen at 3000 p.s.i. and pyrolyses to give KMgH ;75d reduction by LiAlH4 of dimethylmagnesium affords MgH as the only magnesium-containing product.75‘ The autoxidation of hex-5-enylmagnesium bromide produces 25 %of cyclo- pentylmethanol in the product suggesting the intermediacy of the 5-cyclohexenyl radical; a radical chain process appears to be operating here rather than the usual two-stage ~xidation.~~ Radicals are also produced in the reaction of PhMg- Br with quinones (the e.s.r.spectra of semiquinones from acenaphthenequinone ’’(a) T. H. Cook and G. L. Morgan J. Amer. Chem. SOC. 1970 92 6487; (b) ibid. p. 6493. ”A. G. Pinkus An Bang Wu and J. G. Lindberg Chern. Comm. 1970 859. ’4 (a) F. Bertini P. Graselli G.Zubiani and G. Cainelli Tetrahedron 1970,26 1281 ;(b) B.Denise J. F. Fauvarque and J. Ducom Tetrahedron Letters 1970 335. ’(a)E. C. Ashby S. H. Yu and R. G. Beach J. Amer. Chem. SOC.,1970,92,433; (b)E. C. Ashby and J. A. Lackashi J. Organometallic Chem. 1970 24 C17; (c) E. C. Ashby and R. C. Arnott J. Organometallic Chem. 1970,21 P29; (d)E. C. Ashby R. A. Kovar and R. C. Arnott J. Amer. Chem. SOC. 1970,92,2182;(e)E. C. Ashby and R. G. Beach Inorg. Chem. 1970 9 2300. 7b C. Walling and A. Cioffari J. Amer. Chem. SOC. 1970 92 6609. D.J. Curdin M. F. Luppert J. D. Smith and D. R. M. Wulton and phenanthraquinone having been observed77") and in the reaction of Grignard reagents with conjugated EtMgBr reacts with various polyarenes (A) forming radical anions and carbanions :tetracene affords A-(identified by e.s.r.) and other species e.g.AH-; perylene gives A- A,- and AH,,- whereas naphthalene does not react presumably because its electron affinity is too low. (cJ reaction with sodium). 78 Grignard reactions of the non-enolizable p-hydrogen-free benzophenone have been further examined. Pinacol formation has been eliminated by use of 'super-pure' magnesium but the reaction still does not follow first-order and the production of benzhydrol even in highly purified systems represents a new complication in this system.79b An improved preparation of Bu",Mg,TMEDA utilises the equilibrium below; the product is obtained by distillation as an air- and moisture-sensitive liquid.80 2(RMgX,TMEDA)fR,Mg,TMEDA + MgX ,TMEDA The addition of LiC104 (1.5 mol) to Grignard reagents is reported to increase the yield of addition products with ketones at the expense of reduction from 36% to as much as 70% in one case.81 Reduction at a metal centre Ti" in alkylation with organomagnesium compounds has been prevented by using R,Mg or its pyridine complex in place of RMgX;82 but alkylation of a large number of transition-metal chlorides has been achieved using MeMgI.83 A novel ring contraction of 3-cyclohexenyI-Grignard compounds (compare e.g.homoallylic Grignards which yield cyclopropyl derivatives) involves the inter- mediate bicyclo[3,1 Olhexane species (6) which however could not be detected by n.m.r. spectros~opy.~~ Allylmagnesium halides (in which a rapid exchange of carbons bonded to magnesium is implied by the 'H n.m.r.spectrum) in contrast to methyl ethyl or phenyl Grignard reagents add to l-alkene~.~~ Evidence for RMgBr (R = 9-trypticyl) has been obtained by incorporation of deuterium by treatment of the product from 9-bromotrypticene and magnesium in the presence of 1,2-dibromoethane with heavy water.86 77 (a)C. Blomberg H. H. Grootveld T. H. Gerner and F. Bickelhaupt J. Orgunomerallic Chem. 1970 24 549; (6) J. J. Eisch and R. L. Harrell ihid. 1970 21,21. 78 F. J. Reinders and R. Prins J. Organometallic Chem. 1970 25 C41. 79 (a) E. C. Ashby F. W. Walker and H. M. Neumann Chem. Comm. 1970 330; (b) S. E. Rudolph and S. G. Smith ibid. p. 1428. M. H. Gitlitz and W. J. Considine J. Organometallic Chem. 1970 23 291. " M. Chastrette and R.Amouroux Chem. Comm. 1970,470. 82 G. J. Dubsky K. S. Boustany and A. Jacot-Guillarmod Chimia (Switz.) 1970,24 17. 83 J. R. C. Light and H. H. Zeiss J. Organometallic Chem. 1970 21 517. 84 A. Maercker and R. Geuss Angew. Chem. Internat. Edn. 1970,9 909. 8s H. Lehmkuhl and D. Reinehr J. Organometallic Chem. 1970 25 C47. 86 C. Agami M. Chauvin and J. Levisalles Bull. Soc. chim. France 1970 2712. Organometullic Compounds-Part (ij The Muin Group Elements Zinc and Cadmium. The nature of the Reformatsky reagent from methyl 2-bromo- 3,3-diphenylpropanoate has been studied and products compared with those from the 1,4-addition product of PhMgBr and methyl inna am ate.^^ The results strongly suggest reactive species with the bromozinc enolate structure (7) and the /OR I \c=c,OZnBr -c-c /\ II'OZnBr OR (7) unsymmetrical p-lactone structure (8).Long-chain organozinc halides (R 'CHR2-Znl and R'CHR2ZnBr) have been prepared by the action of R'MgX (R' = octyl Ph or aralkyl) on ICHR2ZnI (R2 =H or Me).88 Dialkyl- and diaryl-zinc hydride complexes have been further in~estigated.~' MHZnR +ZnR S MH(ZnR,) (M =Li or Na) The equilibrium has been demonstrated by n.m.r. for the alkylzinc derivatives ; the hydride resonance is observed at the surprisingly low field value of -7 p.p.m. from TMS. The existence of intermediate a-halogenobenzylzinc halides (PhCHC 1ZnC1) from phenyldiazomethane and zinc chloride has been demon- strated in THF ;the carbenoid (PhcH) which is generated both dimerizes and inserts into the s~lvent.'~ The reaction of RMgX with CdX,(X =C1 Br or I) in molar ratios of 1 :1 and 2 :1 has been studied ;R,Cd is produced in both cases and is co-ordinated with both CdX and MgX via single or double X bridges from the equimolar mixture; the 2 :1 product affords only R,Cd and MgX, which interact.' 'Divinylmercury reacts with dimethylcadmium to give divinyl- cadmium and methylvinylcadmium.Vinyl groups exchange rapidly on an n.m.r. time-scale when bound to cadmium (no '"Cd or 'I3Cd coupling observed) but methyl groups exhibit show exchange." The reaction of carbonyl compounds with organocadmium reagents has been studied :solvent effects are rep~rted,'~' and the rde of metal halides which initiate reaction by virtue of their Lewis acid character,93b the effect of different modes of preparation and the relative re- activities of R,Cd and RCdX93' and reactions with acid chlorides have also been examined.93d Intermetallic compounds are reported ;for Co Fe Cr Mo and W with both zinc and ~admiurn,'~' for Ge and Zn,"' and for Se with Zn Hg and Mg.94c "W.R. Vaughan and H. P. Knoess J. Org. Chem. 1970,35 2394. T. Chaudron A. Sekerra and P. Rumpf Compt. rend. 1970 270 C 559. 89 G. J. Kubas and D. F. Shriver J. Amer. Chem. SOC.,1970,92 1949. L. Y.Goh and S. H. Goh J. Organometallic Chem. 1970 23 5. "J. R. Sanders and E. C. Ashby J. Organometallic Chem. 1970 25 277. 92 H. D. Visser L. P. Stochilski and J. P. Oliver J. Organometallic Chem. 1970 24 563. 93 (a) F. Huet E. Henry-Basch and P.Freon Bull. SOC.chim. France. 1970,1426;(6)ibid. p. 1415;(c)G. Sousson and P. Freon Compr. rend. 1970,271 C 21 1 ;(d)E. K. Euranto and L. Puuponen Acta Chem. Scand. 1970,24 363. "(a)J. M. Burlitch and A. Ferrari fnorg. Chern. 1970,9 563; (6)N. S. Vyazankin V. T. Bychkov 0.V. Linzina and G. A. Razuvaev J. Organometallic Chem. 1970 21 107; (c) 1. A. Vostokov and B. T. Bychkov Zhur. obshchei Khim. 1970,40,319 (Chem. Abs. 1970,72 121659s). D. J. Cardin M. F. Lappert J. D. Smith and D. R. M. Walton Mercury. Halogenomethylmercury compounds as carbene precursors have again been much studied :95-PhHgCC1,Ph + olefins -cyclopropane derivatives (ref. 95b) Despite the previous production of radicals from organomercurials the e.s.r. spectrum of (Me,Si),C.obtained by photolysis of [(Me,Si),C],Hg is the first reported spectrum of a radical produced by Hg-C bond breaking.96 Reductive demercuration of RHgBr (R = bornyl or neophyl) has been shown to involve free radicals ; it occurs without typical carbonium ion rearrangements extensive D-incorporation using NaBD argues against carbanions and the exolendo ratios with norbornane derivatives parallel those for known radical path- way~.~''.~ Mercuration of cyclobutadienyliron tricarbonyl with Hg(OAc) gives all possible acetoxymercury compounds. The polymercury derivatives are the first of this type with more than two mercury atomsg8 P-Mercuration has been observed for the first time in the reaction of Hg(OAc) in alcohols with crp-unsaturated carbonyl compounds bearing only a-sub~tituents.~~ Methoxy-mercuration of bullvalene and bicyclo[4,2,2]deca-2,4,7,9-tetraene affords the novel species (9) and (lo) respectively.loo The reaction between C[B(OMe),] (9) (10) and Hg(OAc) in ethanol affords the new tetrakis derivative C(HgOAc) ,which is a water-stable crystalline material."' Acetylacetone and related P-diketone complexes of mercury have been examined.The reported Hg(acac) (acacH = acetylacetone) does not appear to exist ;the reaction between HgCl and Na(acac) HgCl Me( 0)C ,OHgCl I MeCO-C-COMe I /c=c\ Me HgCl ClHg 95 (a)D. Seyferth S. S. Washburne C. J. Attridge and Keiji Yamamoto J. Amer. Chem. Soc. 1970,92,4405; (b)D. Seyferth and D. C. Mueller J. Organometallic Chem. 1970 25 293; (c) D.Seyferth and S. P. Hopper ibid. 1970 23 99; (d)D. Seyferth E. M. Hanson B. Prokai and R. J. Cross ibid. 1970 24 33; (e) D. Seyferth and K. V. Darragh J. Org. Chem. 1970,35 1297. 96 A. R. Bassindale A. J. Bowles M. A. Cook C. Eaborn A. Hudson R. A. Jackson and A. E. Jukes,.Chem. Comm. 1970 559. 97 (a) G. M. Whitesides and J. San Fillipo J. Amer. Chem. SOC.,1970,92,6611;(b)V.M. A. Chambers W. R. Jackson and G. W. Young Chem. Comm. 1970 1275. 98 G. Amiet K. Nicholas and R. Pettit Chem. Comm. 1970 161. 99 A. J. Bloodworth and R. J. Bunce Chem. Comm. 1970,753. loo H. P. Loffler and G. Schroder Tetrahedron Letters 1970 21 19. '01 D. S. Matteson R. B. Castle and G. L. Larson J. Amer. Chem. Soc. 1970,92 231. Organometallic Compounds-Part (i) The Main Group Elements 28 1 gives a material of uncertain composition and irreproducible analysis while HacacH,O and Co(acac) or Fe(acac) afford (11) and (12) respectively.'OZn The mercury complex of 2,2,6,6-tetramethylhepta-3,5-dienone has also been re-investigated and the structure (13) in which R = But is now proposed on the basis of n.m.r.data.loZ6 Several improved or convenient syntheses are reported. Anions I- NCS- and S203,-have been used to activate mercury enabling alkylmercury halides to be prepared directly from alkyl iodides and mercury in dry ethan01.l'~ RHgX compounds are converted into R,Hg by treatment with polyethyleneimine the other product HgX being held in solution.' O4 cis-j3-Chlorovinylmercury chloride can be obtained conveniently from the trans-isomer by treatment with benzoyl peroxide ;the desired product can be extracted from the mixture with hexane.'05 The first allenylmercury derivatives CH ,=C=CHHgCl and (CH,=C=CH),Hg were prepared from HgCl and Me,SnCH=C=CH .lo6 Alkylmercury salts have been prepared by decarboxylation of appropriate carboxylic acid ~alts.'~''-~ Perfluoroalkylmercury derivatives R,Hg [R = (CF,),CF or (CF,),C] have been obtained from fluoro-olefins and HgC1 with KF in dimethylformamide.The reaction requires less vigorous conditions than previous preparations and is thought to involve perfluoroalkyl carbanions. O8 The 1 1 adduct of chlorotrifluoroethylene and (Me,Si),Hg Me,SiCF,CFCI- HgSiMe, has been isolated. The insertion into the Hg-Si bond is shown to be stereospecific as is the subsequent elimination reaction.' O9 Methylmercuric Io2 (a) F.Bonati and G. Minghetti J. Organometallic Chem. 1970 22 5; (b) K. Flateau and H. Musso Angew. Chem. Internat. Edn.. 1970 9 379. lU3M. E. Volpin E. A. Tevdoradzi and K. Butin Zhur. obshchei Khim. 1970 40 315. (Chem. Abs. 1970 72 12166m). lo' R. C. Wade and D. Seyferth J. Organometallic Chem. 1970,22,265. lo5 A. N. Nesmeyanov A. E. Borisov and N. V. Novikova Izvest. Akad. Nauk S.S.S.R. Ser. khim. 1970 857 (Chem. Abs. 1970,73 35483n). lob A. Jean G. Guillerm and M. Lequan J. Organometallic Chem. 1970,21 PI. lo' (a)Y. A. Ol'dekop N. A. Maier A. A. Erdman and Y. A. Dzhomidava Zhur. obshchei Khim. 1970. 40 300. (Chem. Abs. 1970 72 121662n); (b) ibid. p. 637 (Chem.Abs. 1970 73 35480n); (c) Y. A. Ol'dekop N. A. Maier and Y. D. But'ko ibid. p. 641 (Chem. Abs. 1970,73 14954h); (d)Y. A. Ol'dekop N. A. Maier A. A. Erdman and S. S. Stanoraya ibid. p. 305 (Chem. Abs. 1970 72 121663~). B. L. Dyatkin S. R. Sterlin B. I. Martynov and I. L. Knunyants Tetrahedron Letters 1970 1387. R. Fields R. N. Haszeldine and A. F. Hubbard Chem. Comm. 1970 647. D. J. Cardin M. F. Lappert J. D. Smith and D. R. M. Walton methanesulphonate has been obtained by SO insertion into Me,Mg,' lo" and the phenyl analogue and corresponding sulphinate prepared from Ph,Hg and PhS03H and PhS0,H respectively.' lob The compound reported previously as methylmercuric hydroxide has been shown to be a mixture of (MeHg),O and [(MeHg),O]+OH- but the phenyl analogue has been prepared"'" and some properties of (PhHg),O are reported.' 'lb Mass spectral studies of dialkyl- and diaryl-mercury and alkyl- mercury halide compounds are reported and structural correlations estab- lished.Group 111.-Boron. The B-C bond length in the crystal of Me,NBMe is 1.65 A.1l3 The first ionisation potentials ofa number of simple boron compounds including BEt (9.66eV) and C1,BEt (10.80 eV) have been determined and the results interpreted in MO terms.'I4 Thermochemical data on compounds I -RB-O(CH,);O RB(OEt) ,and RB.OCH(CH,CH,),CH-O have been obtained and ring-strain energies calculated." An e.s.r. study of the decomposition of [Ph,B]-Na+ in dimethoxyethane reveals that the derived Ph radical anion is formed from a single Ph,B radical anion by an intramolecular process.'16 - CPI CPI I+ PhMe + PhBBr ; -50 "CCPKO (Cp = ~c-C~HS) H (i) SnBr (ii) NH,PF,-H,O 1 co .Ph PF,- Ph' 'Br (14) In an interesting ring-expansion reaction the existence of an aromatic C,B ring stabilised by co-ordination to a cobalt atom is proposed;"' crystallo-graphic confirmation for (14) is clearly necessary.Further experiments on pentaphenylborole confirm its instability ;'l8 however a Diels-Alder adduct (15) of a related compound has been well characterised. Compound (16) was obtained from ArB(Cl)CH,Ph and PhCrCH.' 'lo (a) K. A. R. Salib and J. B. Senior Chem. Comm. 1970 1259; (b) G. B. Deacon and P. W. Felder Austral. J. Chem. 1970 23 1275. ''I (a) A. J. Bloodworth J.Organometallic Chem. 1970 23 27; (b) J. Chem. Sor. (a, 1970,2051. 'I2 W. F. Bryant and T. H. Kinstle J. Organometallic Chem. 1970 24 573. 'I3 G. J. Bullen and N. H. Clark J. Chem. SOC. (A) 1970 992. ''' M. F. Lappert M. R. Litzow J. B. Pedley P. N. K. Riley T. R. Spalding and A. Tweedale J. Chem. SOC. (A) 1970,2320. ' A. Finch P. J. Gardner P. M. McNamara and G. R. Wellum J. Chem. SOC. (A),1970 3339. 'I6 J. E. Leffler G. B. Watts T. Tanigaki E. Dolan and D. S. Miller J. Amer. Chem. SOC. 1970,92,6825. 'I7 G. E. Herberich G. Greiss and H. F. Heil Angew. Chem. Internat. Edn. 1970,9 805. 'IB P. J. Grisdale and J. L. R. Williams J. OrganometafficChem. 1970 22 C19. 'I9 P. I. Paetzold and H. G. Smolka Chem. Ber. 1970 103 289. Organometallic Compounds-Part (i) The Main Group Elements L Ph J (15) Lithium perhydro-9b-boraphenalyl hydride (17) obtained from hydroboration of cis,cis,trans-perhydro-9b-boraphenalene and subsequent reaction with LiH in THF is an active reducing agent of unusually high stereoselectivity for cyclic ketones.12' Li+ Further details have appeared of two rather unusual methods of B-C bond-making the ArH-BX (X = Br or I) photolytic conversion to ArBX2,I2' and the ArI-BI reaction to give ArBI,.'22 Ferrocene has been converted to (n-C,H,)Fe(C,H,BCl,-n) by treatment with B2Cl,.' 23 A simple high-yield synthesis of R2BC1 has been published,'24 using a combination of known reactions but without necessity for isolation of intermediates (Scheme 2).An unusual organoboron synthesis has been described (Scheme 3).12 120 H.C. Brown and W. C. Dickason J. Amer. Chem. SOC.,1970,92,709. I*' R. A. Bowie and 0.C. Musgrave J. Chem. Soc. (C),1970,485. W. Siebert Chem. Ber. 1970 103 2308; W. Siebert F. R. Rittig and M. Schmidt J. Organometallic Chem. 1970 25 305; W. Siebert K. J. Schaper and M. Schmidt ibid. p. 315; W. Siebert E. Gast and M. Schmidt ibid. 1970 23 329. J. C. Kotz and E. W. Post Inorg. Chem. 1970,9 1661. 124 L. F. Hohnstedt J. P. Brennan and K. A. Reynard J. Chem. SOC.(A) 1970,2445. Iz5 J. C. McMullen and N. E. Miller Inorg. Chem. 1970 9 2291. 284 D. J. Cardin M. F. Lappert J. D. Smith and D. R. M. Walton ,3(Me3SiCH2BH,) + Me,S -+ Me,SiCHSMe -1 BX 1 complex low temp. *Me,Si(Me)CHBMe, X = Me Scheme 3 Once again there have been upwards of fifty papers on aspects of carborane chemistry; the reader is referred to Volume (A) of Annual Reports.Compounds Me,Ti(R),-, have been obtained from Me,Ti and R,B (R = Ph or PhCH,).' 26 For some years it has been a curiosity that some N-chloroamines cleave a B-C bond in an opposite sense from others the problem has now been resolved by demonstrating that route (a) in Scheme 4 proceeds by a polar mechanism while (b)involves a free-radical pathway;'27 of potential synthetic utility is the suppression of (b)by addition of galvinoxyl. Scheme 4 Other organoboron free-radical systems which have been studied are (i) the CF,'-BMe reaction (efficiency BMe > SnMe >> GeMe xSiMe as radical traps);128 (ii) the kinetics of the RO*-BBu &2 reaction;'29 (iii) the Me2N'-BBu S,2 reaction (the first R2N*-MR reaction to have been studied);',' and (iv) the '9' ag-unsaturated carbonyl compound-BR reaction.' 32 Regarding (iv) the substrate R(Me)CHCH,COMe (ii) H,O R3B\LR(Me)CHCH2CH0 (i) MeCH "C THF cat.O, 25CHCHO (ii) H,O L (i)o,,25mc, cat. MeCOC j CH THF RCH CHCOMe (predominantly cis) (ii) H,O Scheme 5 126 P. Zdunnek and K. H. Thiele J. Organometallic Chem. 1970 22 659. A. G. Davies S.C. W. Hook and B. P. Roberts J. Organometallic Chem. 1970 23 Cll. 128 T. N. Bell and A. E. Platt Chem. Comm. 1970 325. lz9 A. G. Davies D. Griller B. P. Roberts and R. Tudor Chem. Comm. 1970 640. I3O A. G. Davies S. C. W. Hook and B.P. Roberts J. Organometallic Chem. 1970 22 c37. 131 G. W. Kabalka H. C. Brown A. Suzuki S. Henma A. Arase and M. Itoh J. Amer. Chem. Soc. 1970,92,710. L32 H. C. Brown and G. W. Kabalka J. Amer. Chem. SOC. 1970,92 712 714. Organometallic Compounds-Part (i) The Main Group Elements is either 'reactive' such as acrolein or 'inert' such as trans-crotonaldehyde ; in the latter system a radical pathway is promoted by traces of O, hv or other initiation procedures and inhibited by galvinoxyl. The 0,-induced reaction in particular has synthetic utility in combination with hydroboration for the con- version of an olefin into an aldehyde or ketone or an ap-unsaturated ketone (Scheme 5).132 Redistribution reactions have been described which make available some convenient procedures for synthesis of boronic esters,'33 1,2-tetramethylene- diboranes,' 34 and mixed trialkylboranes (which via carbonylation are sources of mixed trialkylcarbinols).' There has been interest in the species [R3BCN]- :136,137 they have been used as sources of ketones (Scheme 6).'37 R hydroboration NaCN 2 MeSO Na + I olefin ,2BR diglyme2[BRJCN] -Na+ ,2R2B-I+ C-NH I RB I 1 - 1 4HI + R,B/L%$IHI +- 2R,BC=NH HN /BR HN ;BR2 C R2 C R Other highlights in hydroboration during 1970 appear to be a convenient four-carbon-homologation (R3B + CH,BrCH CHC0,Et KtOC,H~.BU'Z-2.6 RCH :CHCH2C02Et);'38 a new aldehyde synthesis (R3B + N,CHCHO -P HgO RCH,CHO) an alkyl bromide synthesis via mercurials [R12B-R20H-H2,~ Br R2,Hg3R2Br; R' = s-or t-alkyl; RZ = n-alkyl];'40 another synthesis of prepara-mercurials [R3B Hg(OAC)z ' RHgOAc] ;14' a synthesis of acyclic diene~;'~ tion of terminal allenes (e.g.R,BH li) Bu"C=CCH'C',(ii) NaoH ' Bu"CH=C=CH,);'~~ and routes to cis-enynes 144 a/?-acetylenic ketones and &,cis-dienes (Scheme 7). Aluminium Gallium Indium and Thallium. There seems to be no reason to alter the established view that in solid trimethylaluminium the molecules form '33 H. C. Brown and S. K. Gupta J. Amer. Chem. SOC., 1970,92 6983. 134 H. C. Brown E. Negishi and P. L. Burke J. Amer. Chem. SOC., 1970,92 6649. 135 H. C. Brown E. Negishi and S. K. Gupta J. Amer. Chem. SOC., 1970,92 6648. 136 E. Brehn A. Haag and G. Hesse Annalen 1970 737 8 70.13' A. Pelter M. G. Hutchings and K. Smith Chem. Comm. 1970 1529. ' 38 H. C. Brown and H. Nambu J. Amer. Chem. SOC.,1970,92 1761. 139 J. Hooz and G. F. Morrison Canad. J. Chem. 1970,48 868. 140 J. J. Tufariello and M. H. Hovey Chem. Comm. 1970 372. 14' R. G. Larock and H. C. Brown J. Amer. Chem. SOC.,1970,92 2467. 142 J. A. Marshall and J. H. Babler Tetrahedron Letters 1970 3861. 143 G. Zweifel A. Horng and J. T. Snow J. Amer. Chem. SOC. 1970,92 1427. G. Zweifel and N. L. Polston J. Amer. Chem. SOC., 1970,92 4068. D. J. Curdin M. F. Luppert J. D. Smith und D. R. M. Wulton Bu” C-CBu” \/ H/c=c\D ~ Bu”C iCC .CBu” / (i) BH +Bu”CH,.CO.Ci CBU” \(Ii’ OH-“,O2 H H H’ H Scheme 7 symmetrical dimers (18; X = Y = Me)’45” in spite of a strange that the bonding in the bridge is not symmetrical with respect to the two alumin- ium atoms.Crystallographic studies have shown that in solid dimethylphenyl- aluminium (18; X = Y = Ph) phyl groups form electron-deficient bridges between Ph X I HM~ ,Al~e~ 0 t AIMe (19) aluminium and that in anions of the compound [Na(C,H,O),],- [AlMe2CloH,]2 aluminium atoms link the 1-4’ and 1’4 positions of 1,4-dihydro-1,4-naphthylene skeletons. 14’ Careful thermochemical work has shown that contrary to the usual belief tri-isobutylaluminium is partly associated to dimers at 20 0C.148The enthalpy of association (8.1 kcal(mole[R,Al],)-’>is about half that of triethylaluminium. The compounds MAlBu (M = R4N or alkali metal) are soluble in many organic solvents and have been used to study interactions between ion pairs and solvents.149 Several very reactive allylaluminium compounds have been i~olated.’~’ They undergo self-condensation reactions except at low temperatures. The reactivity 145 (a) F. A. Cotton Znorg. Chem. 1970 9 2804; M. J. S. Dewar and D. B. Patterson Chem. Comm. 1970 544; (b) S. K. Byram J. K. Fawcett S. C. Nyburg and R. J. O’Brien ibid. p. 16. 146 J. F. Malone and W. S. McDonald Chem. Comm. 1970,280. 14’ D. J. Brauer and G. D. Stucky J. Amer. Chem. SOC. 1970 92 3956. 14’ M. B. Smith J. Organometallic Chem. 1970 22 273. 149 J. L. Wuepper and A. I. Popov J. Amer. Chem. SOC. 1970,92 1493; T. D. Westmore- land N. Ahmad and M. C. Day J. Organometallic Chem.1970 25 329; J. F. Ross and J. P. Oliver ibid. 1970 22 503. I5O H. Lehmkuhl and D. Reinehr J. Orgdnometallic Chem. 1970 23 C25. Organometallic Compounds-Part (i) The Main Group Elements 287 of olefins with respect to addition of triphenylaluminium increases in the series Ph,C CH (giving PhCH,CPh,AlPh,) < oct-1-ene (giving C6Hl ,CPhCH,- AlPh,) < exo-5-phenylbicyclo[2,2,l]hept-2-ene< bicyclo[2,2,l]hepta-2,5-di-ene.' 5' Aluminium trialkyls add across the carbonyl group of methyl isopropyl ketone and across the nitrile group of acrylonitrile.' 52 When triethylaluminium reacts with epoxides the products depend on which reagent is in excess :with an excess of triethylaluminium one molecule complexes with the epoxide which is alkylated stereospecifically by a second molecule (Scheme 8)' 53 In the reduction *EtCH MeCH ,OH /O\ Et,Al + Me -CH -CH \(i) MeAH2 uEtCH,CHMeOH (11) HlO Scheme 8 of benzophenone by tri-isobutylaluminium the intramolecular elimination of but-1-ene from the complex Ph,COAlBu' is rate-determining.' 54 The reactions between trimethylaluminium and aldehydes or ketones yield unsymmetrically bridged derivatives (18; X = Me,Y = OCHPhMe OBu' OCPhMe, or OCPh,Me); others have been characterised by n.m.r.spectroscopy.' 55 The stereospecific polymerisation catalyst [Me,Al.OCPh.NPhCMeH.0] formed from acetaldehyde and the compound [Me,Al.OCPh.NPh] reacts with trimethyl- aluminium to give a crystalline derivative (19) which catalyses atactic polymerisa- tion of a~eta1dehyde.l~~ Aluminium alkyls have also been used to alkylate halides e.g to form compounds with quaternary carbon atoms or alkyl-germanium compounds.' 57 The presence of dimeric molecules (18; X = Y = NMe,) has been confirmed in solid dimethyl(dimethylamido)aluminium; trimers with the [AlN] ring in the skew-boat conformation are found in the solid compound [Me,AlN(CH,),] and in one isomer of the methylamido-derivative [Me,AINHMe] .In another isomer [Me,AlNHMe] molecules adopt a chair conformation with all N-methyl groups equatorial.' 58 The compounds [Et,AlNMe,] and [Et,AlSEt] 15' J. J. Eisch and S. J. Y. Liu J. Organometallic Chem. 1970 21 285. 15' A. R. Lyons and E. Catterall J. Organometallic Chem. 1970 25 351; W. Kuran S. Pasynkiewicz and J.Muszynski ibid. p. 23; W. Kuran and S. Pasynkiewicz ibid. 1970 23 343. 153 A. J. Lundeen and A. C. Oehlschlager J. Organometallic Chem. 1970 25 337. E. C. AshbyandS. H. Yu J. Org. Chem. 1970,35 1034. 55 E. A. Jeffery and T. Mole Austral. J. Chem. 1970,23 715; M. Fishwick C. A. Smith and M. G. H. Wallbridge J. Organometallic Chem. 1970 21 P9. 156 Y. Kai N. Yasuoka N. Kasai M. Kakudo H. Yasuda and H. Tani Chem. Comm. 1970 1243. 15' J. P. Kennedy J. Org. Chem. 1970,35 532; L. M. Antipin E. M. Stepina and V. F. Mironov Zhur. obshchei Khim. 1970 40 1 15 ;F. Glockling J. R. C. Light and R. G. Strafford J. Chem. SOC.(A) 1970 426. ' 58 H. Hess H. Hinderer and S. Steinhauser Z. anorg. Chem. 1970,377 I ;J. L. Atwood and G. D. Stucky J. Amer. Chem.SOC. 1970,92,285; K. Gosling G. M. McLaughlin, G. A. Sim and J. D. Smith Chem. Comm. 1970 1617. D.J. Cardin,M. F. Lappert J. D. Smith and D. R. M. Walton react with nitriles with addition across the triple bonds or with lactones with acyl-bond fis~ion.''~ The readily available thallium(II1) trifluoroacetate reacts with arenes to give the arylthallium compounds ArTI(OCOCF,) which may be converted to a variety of other products (Scheme 9)! 6o The formation of arylthallium compounds X- Ar2T10COCF3 -Ar,TIX(X = Hal) Scheme 9 from arenes (ArH) activated to electrophilic substitution needs only mild condi- tions; deactivated arenes must be heated under reflux. An important feature of the reaction compared with mercuration is that there is better control of isomers.Thus at room temperature thallation is mainly at the para-position except when there is an oxygen atom separated from the arene nucleus by less than two carbon atoms then e.g. when Ar = C,H,CO,Me ortho-substitution predominates perhaps through the interaction of thallium and oxygen in the transition state. The formation of iodides nitriles etc. from arylthallium bistrifluoroacetates may involve unstable compounds ArTlX (X = I or CN); the compounds ArTIX (X = F or C1) can however be isolated. Most alkylthallium compounds RTlX are unstable but the neopentyl derivative Me,CCH,TlBr has been made the unusual stability is attributed to the very slow decomposition by bimolecular T. Hirabayashi K. Itoh S. Sakai and Y. Ishii J. Organometallic Chem.1970 21 273; 1970,25,33; J. M. Lalancette Y. Beauregard and M. Bhereur Canad. J. Chem. 1970,48 1092. I6O A. McKillop J. S. Fowler M. J. Zelesko J. D. Hunt E. C. Taylor and G. McGillivray Tetrahedron Letters 1969 2423 2427; A. McKillop R. A. Raphael and E. C. Taylor J. Org. Chem. 1970,35 1670; E. C. Taylor F. Kienzle R. L. Robey and A. McKillop J. Amer. Chem. Soc. 1970 92 2175; E. C. Taylor H. W. Altland R. H. Danforth G. McGillivray and A. McKillop ibid. p. 3520; E. C. Taylor F. Kienzle and A. McKillop ibid. p. 6088; A. McKillop J. D. Hunt and E. C. Taylor J. Organometaffir Chem. 1970,24 77. 16' M. D. Johnson Chem. Comm. 1970 1037. Organometallic Compounds-Part (i) The Main Group Elements attack of halide on neopentyl. Reactions of methylallyl- and bisperfluorophenyl- thallium(I1r) compounds have been described the compound (C,F,),TlOH is a polymer in the cry~ta1.I~~ There are strong intramolecular interactions in solid trimethylthallium so that the carbon atoms round a thallium atom form a distorted trigonal bi~yramid.'~~ Spectral properties of the Me,In+ ion have been interpreted in terms of a linear structure.'650 Dimethylgallium hydroxide seems to show monomeric and dimeric species in solution.There is no evidence for the tetrameric [Me,GaOH] observed in the solid.165b Group1V.-Silicon* and Germanium. The so-called reductive silylation technique for forming carbonsilicon bonds advanced significantly during 1970 notably with the Mg-ZC1-HMPT system developed by Calas and co-workers as examplified in the following equations PhCN -+ PhC(Z)=NZ -+p-ZC6H,CH(Z)NZ2 (ref.166a) A r C 0Bu' -+ Arc( Z) (0Z)Bu' (ref. 166b) Me,C=CHCOCH =CMe -+ Me,C(Z)CH =C(OZ)CH=CMe (ref. 166c) PhOR -+PhCH,Z (R = Z Me or allyl) (ref. 166d) Z (ref. 166e) Buta-1.3-diene -+ ZCH,CH=CHCH,Z (ref. 166f) Ih2 H. Tada and R. Okawara J. Org. Chem. 1970 35 1666; T. Abe H. Kurosawa and R. Okawara J. Organometallic Chem. 1970 25 353; M. Tanaka H. Kurosawa and R. Okawara ibid. 1970 21 41; G. B. Deacon and J. C. Parrott ibid. 1970,22,287. Ih3 H. Luth and M. R. Truter J. Chem. SOC. (A) 1970 1287. Ih4 G. M. Sheldrick and W. S. Sheldrick J. Chem. SOC. (A) 1970 28. Ih5 (a)C. W. Hobbs and R. S. Tobias Inorg. Chem. 1970,9,1998; (b)L. Pellerito and R.S. Tobias ibid. p. 953. (a) C. Biran R. Calas J. Dunogues and N. Duffaut J. Organometallic Chem. 1970 22 557; (b) R. Calas J. Dunogues J-P. Pillot C. Biran and N. Duffaut J. Organo-metallic Chem. 1970,25,43; (c)R. Calas and J. Dunogues Compt. rend. 1970,270 C 855; (4 N. Duffaut C. Biran J. Dunogues and R. Calas J. Organometallic Chem. 1970 24 C5I ; (e) J. Dunogues R. Calas C. Biran N. Duffaut and P.Lapouyade J. Orgunometaflic Chem. 1970 23 (250; (f) J. Dunogues R. Calas J. Dedier and F. Pisciotti J. Organometallic Chem. 1970,25 51 ;(g)R. Calas and J. Dunogues Compr. rend. 1970 270 C 2012; (h)J. Dunogues R. Calas and N. Duffaut Buff. SOC. chim. France 1970,2016. * Z = Me,Si throughout this section. 290 D. J. Cardin M. F. Lappert J. D.Smith and D. R. M. Walton Additional related examples are noteworthy (ref. 166g) Buta-1,3-diene + Me,SiCl -+ GiMe2 (ref. 166f) Stilbene + Me,GeCl-+ PhCH(GeMe,)CH(GeMe,)Ph (ref. 166h) Unexpected products are sometimes encountered as for example in the reductive silylation of bistrimethylsilylacetylene ZCECZ -+ Z,CCH,SiMe,CH,Z + Z,CCH,SiMe,CHZ (ref. 167) Chlorosilanes can usefully be reduced to silicon hydrides by adaptation of the method + Me,SiCl bMe2SiH (75 (ref. 168) M;i:!cl-Further examples of newestablished procedures include MeCN ArC02H + HSiCl Pr,N +ArCH,SiCl (ref. 169) Pyridine + ZC1-Z-N,?Z (ref. 170) w Current interest in carbon compounds possessing geminal lithium and a Group IVB meta117'-'73 has led to improvements in the synthesis of halogenoalkyl derivatives PhHgCBr + R,MH -+R,MCBr,H (R = alkyl; M = Si or Ge) (ref.171) Bu"Li + ClzCHZ -ZCCl,Li AMe,SnCCl,Z (ref. 172) Me SnCl Bu"Li + Cl,CZ +Z,CClLi sZ,CClMe (ref. 172) PhLi ZCI Br,CLi + ZC1 -+ZCBr -ZCBr,Li --+Z,CBr (ref. 173) 167 L. C. Quass R. West and G. R. Husk J. Organometallic Chem. 1970,21 65. 168 R. Calas J. Dunogues and N. Duffaut J. Organometallic Chem. 1970 22 561. 169 R. A. Benkeser and J. M. Gaul J. Amer. Chem. SOC. 1970,92 720. R. A. Sulzbach J. Organometallic Chem. 1970 24 307. D. Seyferth and S. P. Hopper J. Organometallic Chem. 1970 23 99. 172 D. Seyferth E. M. Hanson and F. M. Armbrecht jun. J. Organometallic Chem. 1970 23 361. G. Kobrich and R. v. Nagel Tetrahedron Letters 1970 4693 4697.Organometallic Compounds-Part (i) The Main Group Elements 29 1 The latter reaction sequence is not so straightforward as appears at first sight since the following rapid interconversions occur ZCBr,Li + ZCBr -+Z,CBr + LiCBr (ref. 173) Z,CBrLi + LiCBr -+ 2ZCBr,Li (ref. 173) Useful information regarding isomeric organolithium species in solution can often be gained through couplings with organosilicon halides notably with ZC1 as illustrated by the examples from allene chemistry shown in Scheme 10.Organo-lithium and -magnesium intermediates from perhalogenohydrocarbons may PhC-CCH,Z + PhCH=C=CHZ PhCH=C=CHZ (ref. 174) PhC( Z) =C =CZ Ar,C=C=CBr + 2BuLi( -70 "C) ,clAr,C=C=CZ (ref. 175) Scheme 10 likewise be trapped (Scheme 11)' 76 Organosilyl ketones have attracted attention in recent years in part as a result of interest in their U.V.spectra. a-Silyl ketones c1,c=cclcc12ccl,ccl =CC12 *z,c =c=C(Z)C(Z)=C=CZ2 \Myr 1L-i THF-ZCI Li-THF-ZCI c1ncc12 CI CCI Scheme 11 are particularly difficult to prepare owing to the ease with which they rearrange. Adaptation of the aldimine ketone synthesis' 77 now provides a convenient route to these compounds. EtLi + Bu'CH,CMe,NrC + Bu!CH,CMe,N =C(Et)Li 3Bu'CH ,CMe,N =C( Et)Z ';.:";* ti IdII ZCOEt 174 J. Klein and S. Brenner Tetrahedron 1970 26 2345. G. Kobrich and E. Wagner Angew. Chem. Internat. Edn. 1970,9 524. 176 D. H. Ballard T. Brennan and H. Gilman J. Organometaffic Chem. 1970 22 583. '77 H.M. Walborsky W. H. Morrison and G. G. Niznik J. Amer. Chem. SOC.,1970 92 6675. D. J. Cardin M. F. Luppert J. D.Smith and D.R. M. Wulton Examples of recently synthesised organosilyl ketones include Me' Me Z Br (ref. 178a) (ref. 178b) (ref. 178b) (ref. 178c) The reactions of carbon monoxide with t-butyl- trimethylsilyl- and phenyl- lithium and also of bis-trimethylsilyl and -triethylgermyl ketone with n-butyl- lithium are of interest in the ketone context. Representative carbonsilicon cage ZLi + CO -+ZCOLi -+ LiO OLi zo oz (ref. 179) PhLi + CO -+ Ph,C(Li)COPh %Ph,C(Z)COPh (ref. 180) Bu'Li + CO -+ Bu'COLi ZBu'COZ (ref. 180) HO R,C=C=O + Bun Li -R,C=C(Bu")OLi A R,CHCOBu" lH& RCH=C(Bu")OR (R = Z or GeEt,) (ref.181) structures (carborundanes) (20H22)' 82 have been isolated in small quantities by pyrolysis of tetramethylsilane at 700 "C;however (20)can readily be obtained Me Me Me Me Me (20) (21) (22) 178 (a) W. P. Weber and R. Laine Tetrahedron Letters 1970 4169; (6) H. G. Kuivila and G. L. Grady J. Organometallic Chem. 1970 21 303; (c) R. J. P. Corriu and J. P. Masse ibid. 1970 22 321. 179 P. Jutzi and F-W. Schroder J. Organometallic Chem. 1970 24 C43. 180 P. Jutzi and F-W. Schroder J. Organometallic Chem. 1970 24 1. 181 S. V. Ponomarev and S. A. Lebedev Zhur. obshchei Khim. 1970,40,939. 182 G. Fritz F. Diem H. Koehler D. Kummer and H. Scheer -4ngew. Chem. Internat. Edn. 1970,9 464. Organometallic Compounds-Part (i) The Main Group Elements 293 in 80 % yield by AlBr,-catalysed redistribution within the monocyclic unit (Me,SiCH,)3 Pyrolysis of chlorosilyl compounds gives sila-fluorene and -acenaphthylene derivatives in good yield /\ (ref.184) SiCI3 c1’ ‘c1 FH2SiHC12 (55 %) (ref. 185) -a 600-680°C Synthetically useful reorganisations have been reported in the polysilane series cyclo(Me,Si) %cyclo(Me,Si) + cyclo(Me,Si) (ref. 186) (major product) ZSiMe2H trans-(Et P) PtCI, 90°C. ,8h ’ZH + Z(SiMe2),H(2 < n < 5) (ref. 187) Z.Z + ZC1 AICI,’C~M~~S~S~M~,C~ (ref. 188) (93 x) Z4C + ZC1 A,C, F(ClMe,Si),C (88 %) (ref. 188) Z*(CH2)4.Z+ ZC1 AICI,C~S~M~~(CH,),S~M~,CI (ref. 188) (96 %) Examples of novel syntheses potentially useful for carbon-functional compounds are as follows R SiEt, alkoxide + Et,SiH C,H,-I >=( (R = Me or But) (ref.189) Me H 183 C. L. Frye J. M. Klosowski and D. R. Weyenberg J. Amer. Chem. Soc. 1970 92 6379. E. A. Chernyshev S. A. Shchepinov and T. L. Krasnova Zhur. obshchei Khim. 1970,40 1958. E. A. Chernyshev and N. G. Tolstikova Zhur. obshchei Khim. 1970,40 1052. M. Ishikawa and M. Kumada Chem. Comm. 1970 612. “’ K. Yamamoto H. Okinoshima and M. Kumada J. Organometallic Chem. 1970 23 C7. M. Ishikawa M. Kumada and H. Sakurai J. Organometallic Chem. 1970 23 63. M. S. Newman and C. D. Beard J. Amer. Chem. SOC., 1970,92,4309. D. J. Curdin M. F. Luppert J. D. Smith and D. R. M. Wulton 2,Hg + PhHgCC1,Br +ZCC1,HgZ -+ZCCI2CCl2HgZ 1 ZCIC=CCl + [ZHgCI] (ref.190) R'R2Ge(OMe)H + CH,=CR3CR4=CHR5 -+ (ref. 191) R2 MCl + CH,=C(NMe,) -+C1,MCH2CC1(NMe2) %Cl,MCH=C(NMe,) (M = Si or Ge) (ref. 192) Hydrosilylations of olefins catalysed either by peroxides or by U.V. light have been reported previously. These two methods have now been combined in an attractive low-temperature process. Bu'O'-hv C1,SiH + oct-l-ene ~n-CsH1,SiC13 100%) (ref. 193) (-The range of transition-metal hydrosilylation catalysts has been extended to complexes containing nickel,194a cobalt and rhodium.194b Care must be exercised however when aminosilanes are used as redistribution may precede hydrosilylation. 2Bu"NHSiMe,H SBu"N(SiMe,H) + Bu"NH (ref. 195) Organosilicon rearrangements continue to feature prominently both as regards improvements to and elucidation of existing rearrangements.Several novel processes have been reported. For example allyltrimethylsilane rearranges at 500 "C to trimethylvinylsilane and tetramethylsilane as in Scheme 12.'96 'CH ZCH=CH + :CH ZH4MeZ Scheme 12 Novel examples of silicon and germanium migrations (E +C C +C and C -P N) have been reported. lYoD. Seyferth E. M. Hanson B. Prokai and R. J. Cross J. Organometallic Chem. 1970 24 33. M. Massol P. Riviere J. Barrau and J. Satge Compt. rend. 1970 270 C 237. lYzH. Weingarten and J. S. Wagner Chem. Comm. 1970 854. Ig3 S. W. Bennett C. Eaborn and R. A.Jackson J. Organometallic Chem. 1970 21 79. lg4 (a)M. Kumada Y. Kiso and M. Umeno Chem. Comm. 1970 61 1 ;(b)A. J. Chalk J. Organometallic Chem.1970 21 207. Iy5 W. E. Dennis and J. L. Speier J. Org. Chem. 1970,35 3879. H. Sakurai A. Hosomi and M. Kumada Chem. Comm. 1970,767. Organometallic Compounds-Part (i) The Main Group Elements ether p-Li.C6H4.SMR3 *p-R3M.C6H4.SLi (R3M = Z or Me3Ge) (ref. 197a) 24 h Z,CNC =[Z,CCN] +Z,C=C=NZ (ref. 197b) PhMe,Si(CH,),~H -+ Et,GeCH,CONH Me 140p sooc b MeCON(Me)GeEt (ref. 197d) Chloromethyl(trimethyl)silane,catalysed by SbF rearranges in homogeneous solution (in acetronitrile) to chloro(ethyl)dimethylsilane.'98 Evidence for silacyclopropenium ion intermediates is provided by the following observations ZCD,CH,Br =ZCH2CD2Br (ref. 199a) ZCH,CD,OH PBr,ZCH,CD,Br + ZCD,CH,Br (ref. f99b) The facile acid-catalysed fragmentation of P-hydroxyalkylsilicon compounds provides the basis for a potentially useful olefin synthesis e.g.ZCH,MgCl + R'R2C0 +R'R2C(OH)CH2Z H,O+bR'R2C=CH2 (ref. 200) K'K2C=0 PhCH2Z + BuLi-HMPT +PhCHLiZ -R1R2C=CHPh (ref. 200) Coupling with an acyl halide followed by hydrolysis yields a ketone ZCH,MgCl + RCOCI-+RCOCH,Z +RCOMe (ref. 200) Extensive studies of silacyclobutane ring-opening reactions as a route to organo- metallic sultones have been reported (Scheme 13). Continued interest in novel (ref. 20 1a) (ref. 201b c) Scheme 13 19' (a) A. R. Bassindale and D. R. M. Walton J. Orgunomerallic Chem. 1970 25 389; (b) R. West and G. A. Gornowicz J. Organometallic Chem. 1970 25 385; (c) J. W. Wilt and C. F. Dockus J. Amer. Chem. Soc. 1970,92,5813; (6)Yu. I. Baukov G.S. Burlachenko A. S. Kostyuk and I. F. Lutsenko Zhur. obshchei. Khim. 1970,40 707. 19' T. J. Hairston and D. H. O'Brien J. Organometallic Chem. 1970 23 C41. 199 (a) M. A. Cook C. Eaborn and D. R. M. Walton J. Organometallic Chem. 1970,24 301 ; (6)A. J. Bourne and A. W. P. Jarvie J. Organometallic Chem. 1970,24,335. *O0 T. H. Chan E. Chang and E. Vinokur Tetrahedron Letters 1970 1137. 20' (a)J. Dubac P. M. Mazerolles M. Joly W. Kitching C. W. Fong and W. H. Atwell J. Organometallic Chem. 1970,25 C20;(6)J. Dubac P. Mazerolles and M. Joly ibid. 1970,22 C7; (c)J. Dubac P. Mazerolles M. Lesbre and M. Joly ibid. 1970,25 367. 296 D. J. Cardin M. F. Lappert J. D. Smith and D. R. M. Walton small-ring silicon compounds is typified by synthesis of cyclic silylalkylidene- phosphoranes (Scheme 14).K (i) Me Sic1 Me,P =CH2 + Me2SiC12+ Me2Si %Me2 Me,P=CZ (ii) [Me,P(CH,),]Li K (ref. 203) PMe (ref. 202) Scheme 14 Tin and Lead. In contrast to silicon consolidation of existing methods rather than the opening up of new areas of synthesis characterises organo-lead and -tin chemistry. One radically novel structure has been described however ; thus treatment of the carbollide ion (3)-1,2-B,C,Hl 12-with metal halides MX (M = Ge Sn or Pb) leads to formation of l-rnetalla-2,3-dicarba-cZuso-dode-caboranes (1 l),(23).,04 0BH Intermediates containing tin or lead bonded to lithium or magnesium are used increasingly in the preparation of unsymmetrical derivatives (Scheme 15),205 owing to their capacity to couple with halides rather than to undergo metal-halide exchange.The work with tin has received impetus with the discovery of a novel metallation. Bu3SnH + RMgX Bu3SnD Bu,SnSiMe Bu,SnMgX 145 Bu,Sn(allyl) <=cH >Bu,SnCMe,OH Scheme 15 202 H. Schmidbaur and W. Malisch Chem. Ber. 1970 103 97; H. Schmidbaur and W. Malisch Angew. Chem. Internat. Edn. 1970 9 77. 203 H. Schmidbaur and W. Malisch Chern. Ber. 1970 103 3007 3448. 204 R. W. Rudolph R. L. Voorhees and R. E. Cochoy J. Amer. Chem. SOC.,1970 92 3351. 205 J. C. Lahournere and J. Valade Compt. rend. 1970 270 C 2080; J. C. Lahournere and J. Valade J. Organometallic Chem. 1970 22 C3. Organometallic Compounds-Part (i) The Main Group Elements 297 New species R,PbMgCl (R = Me3SiCH,,206 Me3CCH2,’” Me,”* or EtZo8) have been made from the appropriate Grignard reagent and PbC12 in THF.The intermediates Ar,PbMgCl react with dihalogenomethanes to give hexa-aryldiplumbanes in excellent yield.209 Ar,PbMgCl + CH,X -+Ar,PbPbAr (X = Br or C1) (Ar = Ph; o- m-,p-tolyl; p-anisyl; 1-or 2-naphthyl) Organolithium compounds prepared analogously react cleanly with alkyl halides to give lead-substituted alkanes PhLi + PbC1 iTHF HCCl (Ph3Pb)3CH-Ph,PbLi%(Ph,Pb),C (ref. 210) R,MLI + ClCH=CHCH=CH +R,MCH=CHCH=CH (M = Pb or Sn; R = Et or Ph) (ref. 211) Me,SnLi + CF,COCl -+CF,COSnMe (ref. 212) It is relevant to note that the lead-substituted dichloromethanes react with butyl-lithium at low temperature ( -75 “C)with rupture of only one carbon-lead bond ‘ (Ph3Pb),CC1 Ph,PbCCI,HgPh PhHgCL * Ph PbCCl Li Ph PbCCl SnPh Ph,SnCI (ref.213) Isomeric butadienylmetal compounds may be prepared directly from the Grignard reagent and trialkylmetal halide.’ l1 R MX CH,=C=CHCH,Cl% CH,=CHC(MgCI)=CH 3CH,=CHC(MR,)=CH (M = Pb or Sn; R = Et or Ph) Diazoalkanes insert into tin-hydrogen bonds but not apparently into ger- manes and silanes. (CF,),CN2 + Me,SnH -+ Me,SnC(CFJ,H (ref. 214) Tin (and silicon) also activate B-CH bonds towards carbene-type insertions and a wide range of compounds prepared by this technique have now been de~cribed.”~ ’06 K. C. Williams J. Organometallic Chem. 1970 23 465. ’07 K. C. Williams J. Organometallic Chem. 1970 24 399 ’08 K. C. Williams J.Organometallic Chem. 1970 22 141. 209 L. C. Willemsens and G. J. M. van der Kerk J. Organometallic Chem. 1970,21 123. 2Lo L. C. Willemsens and G. J. M. van der Kerk J. Organometallic Chem. 1970,23 471. 211 E. C. Juenge T. E. Snider and Y-C. Lee J. Organometallic Chem. 1970 22,403. 212 E. Lindner and U. Kunze J. Organometallic Chem. 1970 21 P19. C. M. Warner and J. G. Noltes J. Organometallic Chem. 1970,24 C4; C. M. Warner and J. G. Noltes Chem. Comm. 1970 694. W. R. Cullen and M. C. Waldman Canad. J. Chem. 1970,48 1884. 215 D. Seyferth S. S.Washburne C. J. Attridge and K. Yamamoto J. Amer. Chem. Soc. 1970,92,4405. D. J. Cardin M. F. Lappert J. D. Smith and D. R. M. Walton Me3MCH2CH2Me+ PhHgCC1,Br -+Me,MCH,CH(CCl,H)Me + PhHgBr (M = Sn or Si) Hydrostannylation of o-diethynyl-and o-divinyl-benzene with organotin dihydrides provides a route to novel heterocycles.216 These reactions are of use since subsequent iodinolysis (C-Sn bond rupture) is a stereospecific process.Dibenzostannoles are obtained by heating diphenyltin pentamer with bi- phenylene.2l7 /\ 0;J Ph’ ‘Ph A reaction of considerable potential is the methoxide-catalysed addition of hexa-alkyl-distannanes (and -digermanes) to unsaturated systems.2 ’* HMPT Me,M + PhC-CPh -Ph(MMe,)C=C(MMe,)Ph H MPT Me M ,+ Ph(C -C),Ph NaOMe Ph(M Me,)C =C(M Me,)( M Me,)C=C( MMe,)Ph (M = Ge or Sn) New methods of tin-carbon bond making have been described using R3SnNMe2 and either alkenes or alkynes with electronegative sub~tituents,~ 19a or C6F5H + (R,SnC,F,).’ 19b Additional aids to the synthesis of unsymmetrical organotin compounds are provided by the observation that the well-documented redistribu- tions between alkyl- and alkylhalogeno-stannanes are catalysed by U.V.irradiation at ambient temperatures EtSnC1 (2 moles) + EtSnPh (1 mole) &EtPhSnCl (90%) (ref. 220a) The thermal process requires heating to 140 “C for 1.5 h to achieve a comparable result. Non-volatile organotin halides key intermediates in synthesis are notoriously difficult to obtain pure. A novel method which avoids tedious ’I6 A. J. Leusink A. J. Budding and J. G. Noltes J. Organometallic Chem. 1970,24 375. ’’ J. M. Gaidis J. Org. Chem. 1970 35 281 1. ” E. J. Bulten H. A. Budding and J.G. Noltes J. Organometallic Chem. 1970 22 C5. (a)G. Chandra A. D. Jenkins M. F. Lappert and R. C. Srivastava J. Chem. Soc. (A) 1970 2550; (b)A. D. Jenkins M. F. Lappert and R. C. Srivastava J. Organometalfic Chem. 1970,23 165. ’*’ (a) L. S. Mel’nichenko N. N. Zemlyanskii and K. A. Kocheshkov Doklady Akad. Nauk S.S.S.R. 1970 190 597; (b) G. J. D. Peddle and G. Redl J. Organometallic Chem. 1970,23,461. Organometallic Compounds-Part (i)The Main Group Elements 299 purification involves conversion of the iodide to the sparingly soluble fluoride which can easily be crystallised from methanol followed by generation of the chloride by quantitative halide-halide exchange with chlorotrimethylsilane.220 Further details published regarding the insertion of sulphur dioxide into carbon-lead and -tin bonds depict the reaction as a typical electrophilic insertion process.221b Thus with tetra-alkyl or -aryl metal derivatives insertion of one mole of SO takes place readily at low temperature whereas higher temperatures are required for the reaction of further moles of SO R,Sn + SO =RSO,SnR (R = Me or Et) (ref.221a) Me,Sn + SO2 (MeSO,),Sn (ref. 221b) All products are demonstrated by spectroscopic criteria to possess 0-sulphinate structures with a considerable degree of aggregation in both solid phase and in solution.221bd Carbon-lead are generally more reactive than carbon-tin bonds., Disproportionation and rearrangement may accompany insertion 24 h Ph,MCI + SOz=Ph,M(O,SPh) + Ph,MC12 (M = Sn or Pb) (ref.221e) Me3SnCH=C=CMez *Me3Sn0,SCMe2CZCH (ref. 221f) The Sn-C,H bond is labile:222” thus Me,Sn-C,H oxidatively cleaves bi- nuclear complexes [e.g. Mn(CO), -+ (Z-C,H,)M~(CO)~ + Me,SnMn(CO),]. Carbon disulphide reacts with tetra-alkyl-lead compounds in an autoclave ; however the primary products are unstable and decompose upon warming e.g. Et,Pb + CS -+ Et,PbS,CEt -+ PbS + organosulphur compounds (ref. 222b) Sulphuryl chloride and N-bromosuccinimide serve excellently as mild halo- genodemetallating reagents slow RdPb + SOzClz .-) R3PbCl --+R,PbCl (ref. 223) 0 0 221 (a) G. Vitzthum U. Kunze and E. Lindner J. Organometallic Chem. 1970 21 P38; (b)E. Lindner U. Kunze G. Ritter and A. Haag ibid. 1970,24 119; (c)C. W. Fong and W. Kitching ibid.1970,21 365; (dj C. W. Fong and W. Kitching ibid. 1970 22 95; (e) E. Lindner and U. Kunze ibid. 1970,23 C53;(f)C. W. Fong and W. Kitching, ibid. 1970 22 107. 222 (a) E. W. Abel S. A. Keppie M. F. Lappert and S. Moorhouse J. Organometallic Chem. 1970,22 C31; (6) R. Gelius and E. Kirbach Z. Chem. 1970 10 117. 223 R. Gelius Z. anorg. Chem. 1970 374 297. ”* J. C. Maire R. Prosperini and J. Van Rietschoten J. OrganometafficChem. 1970,21 P41; B. C. Pant ibid. 1970 24 697. D. J. Cardin M. F. Lappert J. D. Smith and D. R. M. Walton An adaptation of the sulphuryl chloride reaction finds use in a novel cyclopropane synthesis e.g. Me,SnH + CH2=CHCRzOH +Me,Sn(CHz)2CR20H + Me,SnCI + wR R (ref. 225) Brominolysis of carbon-tin bonds is usually depicted as proceeding via a mole- cular rather than a radical reaction path.Evidence to the contrary is now inferred from the reaction of bromine with the optically active cyclopropane (Scheme 16),226 where loss of activity accompanies cleavage. An observation of use in Ph Me -phqIe + Br2 4-:MIe Ph MSnMe Ph Scheme 16 carbon-functional organolead chemistry is that p-aminophenyltriphenylplum-bane can be successfully diazotized under aprotic conditions and coupled with /3-naphthol without rupture of the aryl-lead A careful reinvestigation of the only reported resolution of an asymmetric organotin compound228 shows that the original claim was probably based upon erroneous results.229 This finding is compatible with recent n.m.r. studies indicating rapid inversion at tin in asymmetric halides R'R2R3SnX.An observation of considerable importance in mechanistic studies is that H/D isotope product ratios (i.e. X.C6H4*H/X*C6H,*D; X*C6H4.CH2H/X*C6H4 CH,D) in the base-catalyzed cleavage of aryl- and benzyl-tin bonds differ from the solvent isotope ratios (MeOH/MeOD) thus demonstrating that free carban- ions are not involved in these reactions.230a Full details are now available of the synthesis and characterisation of the series (Me,M),CN (M = Ge Sn or Pb) and on the M-C (M = Sn) cleavage re- actions ;230b a corresponding silicon diazoalkane does not form. Group V.-Phosphorus. Established methods for formation of P-C bonds have been used to prepare derivatives with bulky groups e.g. mesityl t-butyl and per~hlorophenyl,~~' and a neat route to the phosphines R'R2R3P has been 225 D.D. Davis R. L. Chambers and H. T. Johnson J. Organometallic Chem. 1970 25 C13. 226 K. Sisido T. Miyanisi T. Isida and S. Kozima J. Organometallic Chem. 1970,23 1 17. 22' D. C. Livingston J. Organometallic Chem. 1970 25 433. 228 W. J. Pope and S. J. Peachey J. Chem. SOC.,1900,42. 229 G. J. D. Peddle and G. Redl. J. Organometallic Chem. 1970 22 139. 230 (a) R. Alexander C. Eaborn and T. G. Traylor J. Organometallic Chem. 1970 21 P65; (b) M. F. Lappert and J. S. Poland J. Chem. SOC. (A) 1970,2954. 23 ' L. K. Il'ina K. V. Karavanov E. N. Karpova A. I. Bokanov and B. I. Stepanov Zhur. obshchei Khim. 1970,40,581;P. C. Crofts and D. M. Parker J. Chem. SOC.(0,1970 332 2529; A. P. Stewart and S. Trippett ibid. p. 1263; Chem. Comm. 1970 1279; 0.J. Scherer and W. Gick Chem. Ber. 1970 103 71; W. Kuchen and G. Hagele, ibid. pp. 21 14 2274; S. S. Dua R. C. Edmondson and H. Gilman J. Organometallic Chem. 1970,24,703. Organometallic Compounds-Part (i) The Main Group Elements 30 1 described.232 (RIP) -LiPR1R2 -!%R1R2R3P a[R1R2R3PMe]+I- LiR' Other methods for making P-C bonds include the photochemical addition of secondary phosphines to alkene~~~~ and the electrochemical reduction of phosphorus in the presence of alkenes or aldehydes.234 This last method at present gives rather low yields. The reaction between calcium carbide and chlorodiphenylphosphine provides new syntheses for tetraphenyldiphosphine and diphenylphosphinic anh~dride.~ CaC,; 15OoC;20h 0 Ph PCI Ph2 PPPh2 Ph,P(O)+P(O)Ph, Ph2PC1 -2c.-CaCI ' Aryl halides have been converted to phosphonates and phosphinates by trialkyl phosphites or dialkyl phosphonites in the presence of nickel salts.236 ArX + RP(OEt) *RArP(O)OEt (R = Ph or OEt) Further light has been shed on the relations between structure and reactions of organophosphorus compounds. Thus ring strain in phosphetans (24; X = C1 or Ph) shown by ready ring-opening and -expansion has been further confirmed by crystallographic studies which show C-C bonds of 1.61 A. The P-C bonds (1.84 A) are comparable with P-C(sp3) bonds in a number of other rnolec~les,~~~~~~~ e.g. (25) and (26). Shorter P-C(sp2) bonds (ca. 1.75A) appear in triphenylphosphine the P'"and Pv phosphorins (27; R = Me) and (28; R = Me or NMe,)241 and in 1-benzylphosphole (29; R' = R2 = H 232 M.Schmidt and W. R. Neeff Angew. Chem. Internat. Edn. 1970,9 807. 233 R. Fields R. N. Haszeldine and J. Kirman J. Chem. SOC. (0,1970 197; R. Fields R. N. Haszeldine and N. F. Wood ibid. pp. 744 1370. 234 L. V. Kaabak N. Ya. Shandrinov and A. P. Tomilov Zhur. obshchei Khim. 1970,40 584. 235 E. J. Spanier and F. E. Caropreso J. Amer. Chem. SOC. 1970,92 3348. 236 P. Tavs Chem. Ber. 1970,103 2428. 237 J. R. Corfield M. J. P. Harger J. R. Shutt and S. Trippett J. Chem. SOC. (0,1970 1855; J. R. Corfield M. J. P. Harger R. K. Oram D. J. H. Smith and S. Trippett, Chem. Comm. 1970 1350; J. R. Corfield and S. Trippett ibid.p. 1267; B. R. Ezzell J. Org. Chem. 1970 35 2426. 238 Mazhar-ul-Haque J. Chem. SOC. (B) 1970 934 938 71 1. 239 J. D. Lee and G. W. Goodacre Actcr Crysr. 1970 B26 506. 240 G. Bandoli G. Bortolozzi D. A. Clemente U. Croatto and C. Panattoni J. Chem. SOC.(A) 1970 2778. 241 J. C. J. Bart and .I..I.Daly J. Chem. So(,.(A) 1970 567; J. J. Daly ibid. p. 1832; U. Thewalt C. E. Bugg and A. Hettche Angew. Chem. Internat. Edn. 1970,8 898. D. J. Cardin M. F. Lappert J. D. Smith and D. R. M. Walton R3= CH2Ph).242A low barrier to pyramidal inversion at phosphorus has been detected in the phosphole (29; R' = Me R2 = Ph R3 = Pr') and this has been OR* R I phbph R2 R3 (28) R' (29) (27) ascribed to delocalisation of the lone pair in the transition state.243 The phos- phorin (27; R = Ph) reacts with hexacarbonylchromium to give (C,H,Ph,P)Cr- (CO),,and thus resembles benzene.244 The rates of pyramidal inversion of acylic phosphines R'R2MeP show activa- tion parameters AGt 29-36 kcal mol-' at 1300C.245 Steric effects are not significant.Inversions in diphosphines MeArPPArMe and in MePhP(S)PMePh are easier than in monophosphines possibly indicating p,-d interactions.246 The free-radical addition of methyl methylphosphinate to alkenes seems to be stereospecific suggesting that phosphinyl radicals RO(Me)PO like corresponding silyl radicals are ~hira1.~~' Menthyl penylphosphinate may be stereospecifically alkylated to give either isomer of the tertiary phosphine oxide (30).248 Me /Pri (i) Pr'l NaH O=P--H /OMenthyl (i) Mel NaH / O=P--Me -FO=P--Pr' \ (ii) MeLi \ (ii) Pr'MgBr \ Ph Ph Ph (304 (30b) It has been suggested that displacements at phosphorus in four-membered rings involve intermediates in which the ring spans apical and equatorial posi- tion~.~~~ However reactions may be faster or slower relative to acyclic phos- phines depending on the electronegativity of the leaving group and in certain cases stereospecificity is lost.Displacements in five-membered rings have also been studied.250 The stereochemistry of the cleavage of benzyl groups from "' P. Coggon J. F. Engel A. T. McPhail and L. D. Quin J.Amer. Chem. SOC.,1970,92 5779. 243 W. Egan R. Tang G. Zon and K. Mislow J. Amer. Chem. SOC., "'J. Deberitz and H.Noth Chem. Ber. 1970,103,2541. 1970,92 1443. 245 R. D. Baechler and K. Mislow J.Amer. Chem. SOC.,1970,92,3090,4758. 246 J. B. Lambert G. F. Jackson and C. D. Mueller J. Amer. Chern. SOC.,1970,92 3093. 247 H. P. Benschop and D. H. J. M. Platenburg Chem. Comm. 1970 1098. 24a W. B. Farnham R. A. Lewis R. K. Murray and K. Mislow J. Amer. Chem. SOC. 1970,92,5808; W. B. Farnham R. K. Murray and K. Mislow ibid. p. 5809. 249 J. R. Corfield N. J. De'ath and S. Trippett Chem. Comm. 1970 1502; P. Haake R. D. Cook T. Koizumi P. S. Ossip W. Schwarz and D. A. Tyssee J. Amer. Chem. Soc. 1970,92 3828. 250 W. Egan G. Chauviere K. Mislow R. T. Clark and K. L. Marsi Chem. Comm. 1970 733. Organometallic Compounds-Part (i) The Main Group Elements phosphonium salts involving six-membered rings has been described ;cleavage from bisphosphonium salts is non-stereospe~ific.~~ 2-Substituted derivatives of 1-phenylphospholan (31)obey the general rule that the group cleaved preferenti- ally is the one forming the most stable anion.252 The stability of cyclic phosphoranes such as (32) or (33) may derive from the ability of the five-co-ordinate phosphorus to accommodate the ring angles.253 An extensive series of ylides has been made from chlorosilanes and trialkyl- phosphines and.migration of the trimethylsilyl group to the ylide carbon has been documented.The silicon atom appears to stabilise the ylide by delocalisation of negative charge.20 29203 R3P + Me,H -,SiCH,CI -+ [R,PCH2SiMe,H3-,]C1 -+ R3P CHSiMe,H,_ Me,P + Me3SiCMe,C1 -+Me,Pr'P CHSiMe There are many examples of reactions between ylides and carbonyl functions.For example a modification of the Wittig olefin synthesis has permitted stereo- specific synthesis of the olefins (34) from the aldehydes RCHO ethylidenetri- phenylphosphorane and paraformaldehyde.* 54 Bisylides and vinylphosphonium salts have been used for the formation of ring The product isolated CH CH, H Me \/ Ph,P4 \PPh Ph2P' \hPh2 c=c \ /I \\ I/ R /\ HC-C C-C C'H,OH /\ /\ Me0,C C0,Me Me0,C C0,Me (34) (35) (36) in the reaction between the bisphosphine (Ph2P),CH2 and the alkyne Me0,C C-C-CO,Me is the diphosph(v)ole (35) formed by a proton shift from the 251 K. L. Marsi and R. T. Clark J. Amer. Chem. SOC.,1970 92 3791 ; G.E. Driver and M. J. Gallagher Chem. Comm. 1970 150. z52 B. R. Ezzell and L. D. Freedman J. Org. Chem. 1970 35 241. 253 E. M. Richards and J. C. Tebby J. Chem. SOC.(0,1970 1425; T. J. Katz and E. W. Turnblom J. Amer. Chem. SOC.,1970 92 6701. 254 E. J. Corey and H. Yamamoto J. Amer. Chem. SOC.,1970,92 226. 255 W. H. Ploderand D. F. Tavares Canad.J. Chem. 1970,48,2446; P. J. Garratt K. P. C. Vollhardt and R. H. Mitchell J. Chem. SOC.(0,1970 2137; E. E. Schweizer C. S. Kim and R. A. Jones Chem. Comm. 1970 39; E. E. Schweizer W. S. Creasy J. G. Liehr M. E. Jenkins and D. L. Dalrymple J. Org. Chem. 1970 35 601. 304 D. J. Cardin M. F. Lappert J. D. Smith and D. R. M. Walton intermediate (36).256 The ylide (Ph,P)2C reacts with pentacarbonylmanganese bromide to give the compound (CO),BrMn :C :C PPh and triphenylphosphine Phosphonates have been used in a number of related ketone syntheses.258 For example the compounds (RO),P(0)CH,CR'=CR20Et con-vert ketones R3R4C0 into derivatives R3R4C=CHCR'=CR20Et which are hydrolysed to R3R4CHCH=CR'COR2.The reactions of ylides with a-halogeno-carboxylic esters give new syntheses of ap-unsaturated acids and reactions with acyl chlorides give a-branched P-ketocarboxylic acids (Scheme R' R' R3 \ \/ 2 ,C=PPh + R3CHXC02R4-+ ,C=C + PPh, \ R2' R2 ' C02R4 + [R'R2HCPPh3]+X-(X = hal) R3 I R'\ C=PPh + R4-C-CO-Cl + / I R202C R5 R3 R' I I c1-electrolysis R~-C-CO-C-H -PPh I R5 C02R2 ' 17).259 The reaction between an ylide from R6R7R8P and an acyl chloride has been developed into a method for the determination of the absolute configuration of carboxylic acids.The reaction between ylides and nitrosyl chloride yields compounds [Ph,PC( :NOH)R]+Cl- and iminophosphoranes have been made from ylides and nitriles or from azido-compounds and triphenylphosphine.260 R'CN + Ph,P:CR2R3+Ph,P=N-C=CR2R3 I R' In the compound Ph,FP NMe the P-N bond is short (1.64 The reaction of phosphorus compounds with 2-iodoalkyl azides provides a convenient route to aziridines (Scheme 18).262 Arsenic Antimony and Bismuth. The ' n.m.r. nuclear quadrupole resonance and mass spectra of compounds Ph,M (M = As Sb or Bi) and I2lSb Mossbauer 256 M. A. Shaw J. C. Tebby R. S. Ward and D. H. Williams J. Chem. SOC.(C),1970,504. '" D. K. Mitchell W. D. Korte and W. C. Kaska Chem. Comm. 1970 1384. 258 G. Lavielle and G. Sturtz Bull. SOC.chim. France 1970 1369; E. J. Corey and J. I. Shulman J. Org. Chem. 1970,35 777. 259 H.-J. Bestmann H. Dornauer and K. Rostock Chem. Ber. 1970 103 685 2011; H.-J. Bestmann G. Graf H. Hartung S. Kolewa and E. Vilsmaier ibid. p. 2794; H.-J. Bestmann H. Scholz and E. Kranz Angew. Chem. Internar. Edn. 1970 9,796. 260 G. Eguchi K. Akiba,andN. Inamoto Bull. Chem.Soc.Japan 1970,43,438; E. Ciganek J. Org. Chem. 1970 35 3631 ;I. N. Zhmurova A. A. Tukhar' and A. V. Kirsanov Zhur. obshchei Khim. 1970,40 986. 261 G. W. Adamson and J. C. J. Bart J. Chem. SOC.(A) 1970 1452. "' A. Hassner and J. E. Galle J. Amer. Chem. SOC.,1970,92,3733.Organometallic Compounds-Part (i) The Main Group Elements N3 PPh3 H I 1 LiAIH, RI<H<H-RZ 3 N I -II R / \.-R2 R1 / \**R2 I-Scheme 18 spectra of a number of organoantimony derivatives have been The weaker proton basicity of triphenylarsine compared with both triphenyl- phosphine and triphenylstibine is attributed to electronic The bond dissociation energy D[Me,As-Me] has been estimated by a kinetic study as 63 kcal mol-1.265 Tricyclopentadienyl compounds have been characterised by spectrosopic methods and a gradation from a diene structure for (C5H=J3 As to one with greater delocalisation of double bonds for (C5H,),Bi has been suggested.266 Barriers to pyramidal inversion of more than 25 kcal mol- ’have been measured in a variety of arsenic compounds fluxional properties of cyclic arsines may be explained without postulating inversion at arsenic.267 Enantiomers of EtMePhAs and [MePhAsCH,] have been separated by crystallisation or chromatography of metal complexes.268 Exchange of alkyl groups between compounds R1 ,,R2 -,,Sb has been studied by n.m.r.269 The chemistry of arsenic ylides has been further explored :compounds stabilised by conjugation undergo normal Wittig reactions with carbonyl compounds but other ylides give mainly ep~xides.~” Reverse Wittig reactions are easier with arsenic than with phosphorus.COR’ FoR2 / Ph,AsO + R1C-CR2 -+ Ph,As=C or Ph,As=C \ \ R’ R2 The mechanism of the reactions between triphenylarsine oxide or sulphide and butyl iodide has been The reaction between R,M(M = Sb or Bi) and benzenethiol involves bimolecular homolytic substitution by PhS.at the metal.,’ 263 0. A. Gansow and B. Y. Kimura Chem. Comm. 1970 1621 T. B. Brill and G. G. Long Inorg. Chem. 1970,9 1980; G.G. Long J. G. Stevens R. J. Tullbane and L. H. Bowen J. Amer. Chem. SOC.,1970,92 4230; A. T. Rake and J. M. Miller J. Chem. SOC.(A) 1970 1881. 264 0.W. Kolling and E. A. Mawdsley Inorg. Chem. 1970,9,408. 265 S. J. W. Price and I. P. Richard Canad. J. Chem. 1970,48 3209. 266 B. Deubzer M. Elian E. 0.Fischer and H. P. Fritz Chem. Ber. 1970,103,799. 267 J. P. Casey and K. Mislow Chem. Comm. 1970,999; P. S. Elmes S. Middleton and B. 0.West Austral. J. Chem. 1970,23 1559. 26a B. Bosnich andS. B. Wild J.Amer. Chem. Soc. 1970 92 459. 269 H. A. Meinema and J. G. Noltes J. Organometallic Chem. 1970,22 653. *’’ A. W. Johnson and H. Schubert J. Org. Chem. 1970 35 2678; E. Ciganek ibid. p. 1725. 271 B. D. Chernokal’skii R. B. Bairamov and G. Kamai Zhur. obshchei Khim. 1970 40 143; B. D. Chernokal’skii A. S. Gel’fond and G. Kamai ibid. p. 151. 272 A. G. Davies and S. C. W. Hook J. Chem. SOC.(B) 1970 735.

ISSN:0069-3030    

DOI:10.1039/OC9706700271

出版商:RSC    

年代:1970

数据来源: RSC

摘要:

9 Organometallic Compounds Part (ii) Transitional Elements By J. P. CANDLIN A. W. PARKINS and K. A. TAYLOR I.C.I.L td. Petrochemical and Polymer Laboratory Runcorn Cheshire THEtheme of this section is the modification of organic compounds by transition- metal complexes. A brief survey of unusual ligands bonded to transition metals is also included. 1 Reviews This year has seen the appearance of a new journal in this area of chemistry Organometallics in Chemical Synthesis.' An extensive review of olefin complexes has appeared,2 together with two useful reviews on homogeneous ~atalysis.~.~ Accounts have been written of Pd" organosilver7 and organogold' compounds. A useful survey of work from Wilke's group on the use of n-ally1 intermediates in organic synthesis has been published.' Isomerisation," decarbonylation,' 'and hydrogenation' * have also been reviewed.The formation of aryl-metal bonds,' and oxidative addition reaction^'^ have been studied sufficiently for reviews to be written. A useful survey citing many Russian references deals with the structures of n-olefin and n-acetylene complexes. 2 Novel Complexes HydrocarbonComplexes.-Work on transition-metal derivatives of trimethylene-methane (1) has been extended to Cr and Mo,16 and the heptafulvene ligand has Elsevier Publishing Company Amsterdam. H. W. Quinn and J. H. Tsai Adv. Inorg. Chem. Radiochem. 1969 12 217. R. Ugo Chimica e Industria 1969 51 1319. J. P. Candlin K. A. Taylor and D. T. Thompson Ind. chim. belge 1970 35 1085. R. Huttel Brennstoff-Chem.1969 50 281 331. R. Huttel Synthesis 1970 225. ' C. D. M. Beverwijk G. J. M. van der Kerk A. J. Leusink and J. G. Noltes Organo-metallic Chem. Rev. (A) 1970,5,215. ' B. Armer and H. Schmidbaur Angew. Chem. Internat. Edn. 1970 9 161. P. Heimbach P. W. Jolly and G. Wilke Adv. Organometallic Chem. 1970 8 29. lo A. J. Hubert and H. Reimlinger Synthesis 1970 405. J. Tsuji and K. Ohno Synthesis 1970 157. M. E. Vol'pin and I. S. Kolomnikov Russ. Chem. Rev. 1969 38 273. l3 G. W. Parshall Accounts Chem. Res. 1970 3 139. l4 J. Halpern Accounts Chem. Res. 1970 3 386. l5 A. I. Gusevand Yu. T. Struchkov J. Struct. Chem. (U.S.S.R.),1970 11 340. " J. S. Ward and R. Pettit Chem. Comm. 1970 1419. Organometallic Compounds-Part (ii) Transitional Elements been stabilised as its Fe(CO) derivative (2) with a trimethylenemethane system forming an integral part of the ligand.” The X-ray structure of the compound produced in an earlier attempt to stabilise this ligandI8 has shown that it is an (1) (2) (3) alkyl comp~und.’~ A useful method for the preparation of 1,2-disubstituted cyclobutadiene complexes e.g.(1,2-dimethylcyclobutadiene)Fe(CO) has ap- The reaction of 2,3-dichlorobutadiene with Fe,(CO), leads to a C ligand which contains two 71-ally1 groups (3).2 Bis-(butadiene)Fe(CO) has been reported. Carbene Complexes.-This year has seen continued activity in this field. (Phenyl- methoxycarbene)Fe(CO) has been prepared by a photochemical exchange rea~tion.’~ (la-C H ,)Mo(CO)(NO)[C( Ph)OMe] + Fe( CO) 3Fe(CO),[C( Ph)OMe] + (z-C,H~)MO(CO),NO This compound cannot be obtained from the reaction of the acylmetallate salt [Fe(CO),C(Ph)O]-with Me30+ a dimer being f~rmed.~~,~’ Reaction with Ph,CCl also produces a dimer.26 Ph [Fe(CO),C(Ph)O]-+ Ph,CCl -+ \/c-9(CO)3Fe-Fe(CO),\ /c -0 / Ph However using (Ph,P)Fe(CO), CH,Li and Et,O+BF,- a carbene complex can be obtained dire~tly.~’ Last year the reaction of lithium organyls with Mn2(CO), was reported to give carbene complexes.28 Further work29 on the reaction of [Mn(CO),]-D.J. Ehntholt and R. C. Kerber Chem. Comm. 1970 1451. D. J. Ehntholt G. F. Emerson and R. C. Kerber J. Amer. Chem. SOC.,1969,91,7547. l9 M. R. Churchill and J. P. Fennessey Chem. Cornrn. 1970 1056. ‘O R.H. Grubbs J. Amer. Chem. SOC.,1970,92 6693. H. A. Brune W. Schwab and H. P. Wolff Z. Naturforsch. 1970,25b 892. 22 A. Carbonaro and A. Greco J. Orgsnomerallic Chem. 1970 25,477. 23 E. 0.Fischer and H. J. Beck Angew. Chem. Internat. Edn. 1970 9 72. 24 E. 0. Fischer and V. Kiener J. Organometallic Chem. 1970 23,215. 25 E. 0.Fischer V. Kiener and R. D. Fischer J. Organometallic Chem. 1969 16 P60. 26 E. 0. Fischer V. Kiener D. St. P. Bunbury E. Frank P. F. Lindley and 0.S. Mills Chem. Comm. 1968 1378. ’’ D. J. Darensbourg and M. V. Darensbourg Inorg. Chern. 1970,9 1691. 28 E. 0. Fischer and E. Ofiaus Chem. Ber. 1969 102 2449. ’’ C. P. Casey Chem. Comm. 1970 1220. J. P. Candlin A. W. ParkinsandK. A. Taylor with Br(CH2),Br3' has shown that the product is a carbene (4).Reaction of a double Wittig reagent (Ph,P=C=PPh,) with Mn(CO),Br yields a keten derivative (S).31 (4) (5) (6) Several new carbene complexes of chromium have been reported,32 including a bis-carbene derivative obtained by a photolytic exchange reaction,33 Me I N 2R-Cr(CO) !% R,Cr(CO) where R = Q I Me and a chromium carbene complex containing two heteroatoms (6).34The transfer of a carbene ligand to an organic substrate has now been reported for chrorni~rn.,~ -+ Me yo;2Me :,OMe (CO),Cr -2 + _/Co2Me 'Ph Me Ph This reaction recalls similar work with iron,36 although previous attempts led to the dimerisation of the carbene ligand.37 Dimerisation with elimination of a carbonyl group occurs38 with Cr(CO),[C(Ph)NMe,] forming Cr( CO),[ CH( Ph)N Me,] .Several new complexes of the platinum metals have been rep~rted~~-,~ e.g. PhNC-c1 Ph-NHC. 'C1 \-. OEt 30 R. B. King J. Amer. Chem. Soc. 1963,85 1922. 31 D. K. Mitchell W. D. Korte and W. C. Kaska Chem. Comm. 1970 1384. 32 E. 0.Fischer H. J. Kollmeier C. G. Kreiter J. Muller and R. D. Fischer J. Organo-metallic Chem. 1970 22 C39. 33 K. Ofele and M. Herbehold Angew. Chem. Internat. Edn. 1970 9 739. 34 E. 0.Fischer and H. J. Kollmeier Angew. Chem. Internat. Edn. 1970 9 309. Js E. 0. Fischer and K. H. Dotz Chem. Ber. 1970 103 1273. 36 P. W. Jolly and R. Pettit J. Amer. Chem. SOC.,1966 88 5044. 37 E. 0. Fischer B. Heckl K. H. Dotz J. Muller and H. Werner J. Organometaffic Chem. 1969,16 P29.38 J. A. Connor and J. P. Lloyd J. Chem. SOC.(A) 1970 3237. 39 E. M. Badley J. Chatt R. L. Richards and G. A. Sim Chem. Comm. 1969 1322. 'O B. Crociani and T. Boschi J. Organometallic Chem. 1970 24 C1. 41 G. Rouschias and B. L. Shaw Chem. Comm. 1970 183. 42 F. Bonati and G. Minghetti J. Organometallic Chem. 1970 24 251. 43 B. Crociani T. Boschi and U. Belluco Inorg. Chem. 1970,9 2021. Organometallic Compounds-Part (ii) Transitional Elements Sulphur Compounds.-Some interesting reactions of Fe(CO) with sulphur- containing compounds have been reported. Some of these stoicheiometric reactions have synthetic utility for example the formation of RS-SR from RSCl and Fe(CO) ,44and the preparation of(P-naphthyl),S from (P-naphthyl)-SSCN.45 Attack on co-ordinated norbornadiene by Me2S2 yields the tetrasulphur deriva- tive (7),”6 whereas the reaction of co-ordinated cyclo-octene with CS2 probably (7) (8) yields an episulphide (8).47 The first complex containing a thioketo-carbene has been reported.48 Physical Aspects of wComp1exes.-There is still great activity in this field much of it with comprehensive n.m.r.studies of the compounds to establish the fluxional nature of the molecules or homoaromaticity of the ligands. X-Ray work has also continued to give structural information. For example the reac- tion of (9) with (NH,),Cr(CO) yields which has been shown by X-ray” and n.m.r.” analysis to be homoaromatic. Cyclo-o~tatriene~~ complexes of chromium have been reported in which the organic ligand is fluxional.Rearrangement of the bullvalene ligand does not occur on complexation with Group VI metals,’ although it is thought to occur with iron.54 The n.m.r. spectrum of (ethylene),IrCl in the presence of ethylene shows that some exchange between co-ordinated and unco-ordinated ethylene OCCU~S.~ 44 E. Lindner and G. Vitzthum Angew Chem. Internat. Edn. 1969 8 518. 45 J. Roy Z. Naturforsch 1970,25b 1062. 46 R. B. King J. Org. Chem. 1970,35 274. 47 I. S. Butler and A. E. Fenster Chem. Comm. 1970 933. 48 G. N. Schrauzer H. N. Rabinowitz,J. A. K. Frank and I. C. Paul J. Amer. Chem. Suc. 1970 92 212. 49 W. E. Bleck W. Grimme H. Gunther and E. Vogel Angew. Chem. Internat. Edn. 1970 9 303. R. L. Beddoes P. F. Lindley and 0.S.Mills Angew. Chem. Internat. Edn. 1970,9,304. H. Gunther R. Wenzl and H. Klose Chem. Comm. 1970 605. 52 R. Aumann Angew. Chem. Internat. Edn. 1970,9 638. 53 R. Aumann Angew. Chem. Internat. Edn. 1970,9 800. 54 G. N. Schrauzer P. Glockner K. I. G. Reid and I. C. Paul J. Amer. Chem. Soc. 1970,92,4479. ” A. van der Ent and T. C. Van Soest Chem. Comm. 1970,225. 310 J. P. Candlin,A. W.Parkins and K. A. Taylor Work on the temperature dependence of the n.m.r. spectra of substituted arene chromium tricarbonyl complexes has been p~blished.~~-~ a-Complexes.-It was noted several years ago that simple methyl compounds are often more stable than the higher alkyls owing to the absence of P-hydrogen atoms.59 This year has seen the decomposition mechanism of a copper alkyl experimentally established.60 Therefore stable metal alkyls may be formed with hydrocarbyl ligands containing no P-hydrogen atoms.Using this approach stable o-complexes have been prepared using trimethyl~ilylmethyl~~-~~ and benzyl ligands. Some useful synthetic applications of R,CuLi complexes for example the introduction of R into organic compounds have been rep~rted.~~-~~ ‘Grignard’ reagents of ytterbium have been prepared.70 3 Hydrogenation and Hydrogen Exchange Reactions Several new homogeneous catalysts for the hydrogenation of carbon-carbon unsaturation have been discovered during the past year. These include + [RUCl2(C6H,)],,7 [Rh( 1,5-cyclo-octadiene) (MeCN),] and [Ir(l,5-~yclo-octadiene)(MeCN)~]+,~~ IrCl(PPh,) ,73 Rh24+,74Ru2 4+7 74 Rh2(OCOCH3)4,75 [RhH2P’L2]+ 76 [where P‘ = PPh2Me PPhMe, or PMe and L =solvent (e.g.acetone)] COH,(PP~,),,~~ CoH(CO)(PPh,) ,77 and CoH(CO)(PPh,) +AIEt .77 Progress has been made on the homogeneous reduction of other functional groups such as ket~-,’~ azo- imino- and nitro-groups [using Rh(py),Cl,-NaBH as ~atalyst’~]. Thus the homogeneous reduction of pyridine to piperidine has been 56 W. R. Jackson W. B. Jennings S. C. Rennison and R. Spratt J. Chem. SOC.(B) 1969 1214. 57 G. Barbieri and F. Taddei Chem. Comm. 1970 312. 58 W. R. Jackson W. B. Jennings and R. Spratt Chem. Comm. 1970 593. 59 G. Calvin and G. E. Coates J. Chem. SOC.,1960 2008. 60 G. M. Whitesides E. R. Stedronsky C. P. Casey and J. San Filippo J.Amer. Chem. Soc. 1970 92 1426. 61 M. F. Lappert Angew. Chem. Internut. Edn. 1970 9 910. 62 G. Yagupsky. W. Mowat A.Shortland and G. Wilkinson Chem. Comm. 1970 1369. b3 A. Shotani and H. Schimdbaur J. Amer. Chem. SOC.,1970 92 7004. 64 M. R. Collier M. F. Lappert and M. M. Truelock J. Organometaffic Chem. 1970 25 C36. 65 U. Zucchini U. Giannini E. Albizzati and R. D’Angelo Chem. Comm. 1969 1174. 66 G. H. Posner and C. E. Whitten Tetrahedron Letters 1970 4647. 67 N-T Luong Thi and H. Riviere Tetrahedron Letters 1970 1579. 68 E. P. Woo and F. Sondheimer Tetrahedron 1970 26 3933. 69 E. J. Corey and I. Kawajima J. Amer. Chem. SOC.1970 92 395. 70 D. F. Evans G. V. Fazakerley and R. F. Phillips Chem. Comm. 1970 244. 71 I.Ogata R. Iwata and Y. Ikeda Tetrahedron Letters 1970 301 1. 72 M. Green T. A. Kuc and S. H. Taylor Chem. Comm. 1970 1553. 73 H. van Gaal H. G. A. M. Cuppers and A. van der Ent Chem. Comm. 1970 1694. 74 P. Legzdins R. W. Mitchell G. L. Rempel J. D. Ruddick and G. Wilkinson J. Chem. SOC.(A) 1970 3322. 75 B. C. Hui and G. L. Rempel Chem. Cornrn.,1970 1195. 76 R. R. Schrock and J. A.Osborn. Chem. Comm. 1970. 567. 17 M. Hidai T. Kuse T. Htkita Y. Uchida and A. Misono Tetrahedron Letters 1970 1715. 7M I. Jardine and F. J. McQuillin Chem. Comm. 1970 626. Organometallic Compounds-Part (ii) Transitional Elements 31 I a~hieved.’~ The hydrogenation of aromatic systems however can only be performed using heterogeneous catalysts or Ziegler-type systems.79 The latter catalysts have also been used to hydrogenate unsaturated polymers; thus Cr(acety1acetonate),-A1Bu3 hydrogenates polybutadiene polymers,8o and Ni(octoate),-AIEt reduces the unsaturation present in polythene.’ A study of the hydrogenation activity and selectivity of soluble Ziegler-type catalysts has been made.82 The combination Co(acetylacetonate),-AlBu showed the highest activity and it is possible to hydrogenate very selectively hex-1-ene in the presence of cyclohexene and also phenylacetylene in the presence of hex-1-ene.Tris( triphen ylphosphine)chlororhodium(r)’ continues to at tract atten tion. The extent of dissociation in benzene and methylene chloride RhCI(PPh,) * RhCl(PPh,) + PPh which is thought to be a key step in hydrogenation reactions has been shown to be increased by traces of oxygen84 and decreased by the presence of alcohol^.'^ These results explain the conflicting results previously obtained from osmometry and n.m.r.data. In benzene solution traces of oxygen promote hydrogenation but inhibit isomerisation of olefins whereas in the presence of alcohols isomerisa- tion as well as hydrogenation OCCU~S.~~,~~ These results indicate that extreme caution should be taken when handling RhCl(PPh,) in solution with the added complication that different solvents can alter the reactivity pattern. Further mechanistic studies using RhCI(PPh,) include the hydrogenation (in some cases deuteriation or tritiation) of cyclo-olefins,88 substituted exocyclic methylene compounds,90 various olefinic derivatives,” and ap-unsaturated A carbonyl cornpo~nds.~~ comparison of the hydrogenation activity of RhCI(PPh,) and heterogeneous catalyits has been made.92 Rhodium and cobalt carbonyl complexes have catalytic hydrogenation activity.Olefins can be hydrogenated9 and i~omerised~~ by RhH(CO)(PPh,) ,but the activity decreases during the experiment due to the formation of inactive [Rh(CO)2(PPh,),],.g4*95 Deuteriation studiesg6 on the co-ordinated ligand in the ’’ S. J. Lapporte and W. R. Schuett J. Org. Chem. 1963 28 1947. B. I. Tikhomirov I. A. Klopotova and A. I. Yakubchik European Polymer J. (Suppl.) 1969 561. D. R. Witt and J. P. Hogan J. Polymer Sci.(Part A-I) 1970,8 2689. ” W. R. Kroll J. Catalysis 1969 15 281.83 R. S. Coffey Ann. Reports (B) 1969,66 313. D. D. Lehman D. F. Shriver and I. Wharf Chem. Comm. 1970 1486. 85 R. L. Augustine and J. F. Van Peppen Chem. Comm.,1970 497. 86 R. L. Augustine and J. F. Van Peppen Chem. Comm. 1970 571. R. L. Augustine and J. F. Van Peppen Chem. Comm. 1970,495. *’ A. S. Hussey and Y. Takeuchi J. Org. Chem. 1970,35 643. 13’ G. V. Smith and R. J. Shaford Tetrahedron Letters 1970 525. T. R. B. Mitchell J. Chem. SOC.(B) 1970 823. 91 W. Strohmeier and R.Endres 2.Naturforsch 1970 25b 1068. ’’ H. Simon and 0.Berngruber Tetrahedron 1970 26 1401. 93 H.Strohmeier and S. Hohmann 2.Naturforsch 1970 25b,1309. 94 M.Yagupsky and G. Wilkinson J. Chem. SOC.(A) 1970,941. 9s M. Yagupsky C. K. Brown G. Yagupski and G. Wilkinson J.Chem. SOC.(A) 1970,937. 96 G. E. Hartwell and P. W. Clark Chem. Comm. 1970 11 15. J. P. Candlin A. W.Parkins and K. A. Taylor complex [Rh(CO)(Ph,PCH2CH,CH=CH2),]{[Rh(CO)L,]+ f in methanol + show that five- and six-membered ring intermediates (11) and (12) are formed -[(CO)L(H)RhPh2PCH2CH2CHMe]+ [(CO)L(H)RhPh2PCH2CH2CH2kH2]+ This suggests that in the hydrogenation of olefins by similar rhodium complexes e.g. perhaps RhCl(PPh,) ,the two hydrogens are probably transferred in a step- wise manner rather than simultaneously. Hydrosilylation of 0lefins.-Many of the complexes which catalyse the hydro- genation of olefins are also useful catalysts for analogous hydrosilylation reac- tions using silanes e.g. R3SiH. Thus the rhodium complexes RhC1(PPh3), RhCl(CO)(PPh,) and RhH(CO)(PPh,) ,97 Ni(P-P)C1,98 (where P-P is a chelating ditertiary phosphine) and [Pt(substituted ~tyrene)Cl,],~~ catalyse the addition of silanes to olefins.Metal-catalysed Intermolecular Hydrogen Exchange.-Hydride transfer from hydride donors (e.g. secondary alcohols) to reducible groups (e.g. ketones) is catalysed by many transition-metal complexes. Thus RhCl(PPh,) and IrCl,-H,PO catalyse the formation of axial alcohols from ketones in high yields using isopropanol as re duct ant."'^' Mechanistic studies using RhC1,-SnCl mixtures suggest the formation of a rhodium hydride species.lo2 Rhodium complexes e.g. RhCl(C0) (PR3)2 catalyse the formation of aldehydes from aryl chlorides and Et,SiH. A possible mechanism involves hydride trans- fer.'' Homogeneous and heterogeneous hydrogenaeuterium exchange in aromatic compounds has been catalysed by [Pt"C1,I2 -and metallic platinum.7c-Com-plexes are thought to be possible intermediate^.'^^'^^^ Intramolecular Oxidative Addition Reactions.' 3-Thi~ is a relatively new class of reactions in which intramolecular cleavage of a carbon-hydrogen bond by the central metal ion (oxidative state M) results in the formation of a metal- hydride and a metalkarbon bond (oxidation state M2+). In some cases the hydride is lost as H'. 97 A. J. Chalk J. Organometallic Chem. 1970 21 207. 98 M. Kumada Y. Kiso and M. Umeno Chem. Comm. 1970,611. 99 V. 0. Reikhsfel'd M. I. Astrakhanov and E. G. Kagan Zhur. obshchei Khim. 1970 40 699 (Chem.Abs. 1970,73 14324). loo J. C. Orr M. Merserreau and A. Sanford Chem. Comm. 1970 162. lo' H. B. Henbest and T. R. B. Mitchell J. Chem. Soc. (C) 1970 785. H. B. Charman J. Chem. Soc. (B) 1970 584. lo3 S. P. Dent C. Eaborn and A. Pidcock Chem. Comm. 1970 1703. '04 J. L. Garnett and R. S. Kenyon Chem. Comm. 1970 698. K. P. Davis J. L. Garnett and J. H. O'Keefe Chem. Comm. 1970 1672. Organometallic Compounds-Part (ii) Transitional Elements 313 Increase of electron density at the metal centre promotes the oxidative addition reaction. This can be achieved if the complex contains good donor ligands (e.g. PR,) but not ligands having good acceptor properties (e.g.CO). Many aromatic ortho-metallations of P-and N-donor ligands have been rep~rted.'~Recent examples are the formation of Ir1L*HCl[P(OPh)20C,H4] [P(OPh),] ,Io6 Ru"(CO)CI[P(OPh) OC6H4] [P(OPh)312 O ' and [(2-phenylazophenyl)Ru(C0),C1] lo* which contains a Ru-C bond.Intra- molecular cleavage of an aliphatic C-H bond has been found to occur in the compounds [(8-methylquin01ine)PdCl]~'~~ and PtCl(-CH,CH,CH,PBu',)(PPr"Bu~).' lo Bulky substituents on the tertiary phosphine ligands are thought to promote the latter reaction; the expulsion of a C1- ion and the formation of a Pt-C bond results in less steric crowding. The formyl group reacts with Pt(PPh,),; in the case of benzaldehyde the product is Pt(COPh),(PPh,),." ' In a similar manner the formation of [(n-CSH,)(CSH,)TiH] may occur through [(n-C,H,),Ti] followed by hydride abstraction and Ti-C bond formation.''2 The formation and subsequent cleavage of a metal-carbon bond has been used for the specific introduction of a substituent into the aromatic ring."3 Thus chlorination of [(2-phenylazophenyl)PdCI] yields ortho-chlorinated azobenzene.Deuterium exchange in the ortho-positions of aromatic rings in complexes has been shown to occur using D or D20,even in cases where the metal-carbon compound has not been isolated.' 4 Isomerisation Metal-catalysed C=C Isomerisation.-Three mechanisms have been suggested for the isomerisation of olefins ;(i) hydride addition followed by elimination (ii) n-ally1 mechanism (iii) carbene involvement. The possible intermediates in the n-ally1 mechanism have been isolated at low temperatures and the following equilibrium has been observed ;'l4 Me H The intermediate formation of an ally1 chromium hydride is suggested during the conjugation of polyunsaturated materials catalysed by (arene)Cr(CO),.' lS lo6 E.W. Ainsworth and S. D. Robinson Chem. Comm. 1970 863. lo' J. J. Levison and S. D. Robinson J. Chem. SOC.(A) 1970 639. lo' M. I. Bruce M. Z. Iqbal and F. G. A. Stone Chem. Comm. 1970 1325. G. E. Hartwell R. V. Lawrence and M. F. Smais Chem. Comm. 1970,912. lo A. J. Cherry B. E. Mann B. L. Shaw and R. M. Slade Chem. Comm. 1970 1176. " I. Harvie and R. D. W. Kemmitt Chem. Comm. 1970 198. H. H. Brintzinger and J. E. Bercaw J. Amer. Chem. Soc. 1970,92 6182. 'I3 D. R. Fahey Chem. Comm. 1970,417. I l4 H. Bonnemann Angew.Chem. Internat. Edn. 1970,9 736. E. N. Frankel J. Amer. Oil Chemists' SOC.,1970 47 33. J. P. Candlin A. W. Parkins and K. A. Taylor Ru1I1 Rh'" and Pd" have been used as catalysts for the isomerisation of hex-l- ene,' 16,' '' allylbenzene and phenyl butene."* A semiquantitative correlation of their activity in a variety of complexes has been established. The catalysed isomerisation of hex-1-ene by Co(N,)(PPh,) is thought to involve initial replace- ment of N by the olefin.'" As there are many similarities in mechanism between metal-catalysed isomeri- sation and hydrogenation it is not surprising that many complexes perform both transformations simultaneously. Care is therefore required in analysing the data obtained. Thus RhH(CO)(PPh,) (an active hydrogenation catalystg5) causes the isomerisation of cr-~lefins.~~,'Other active rhodium catalysts include 2o RhCl(PPh,) .l2 Interesting examples are the stereochemically-controlled intra-molecular isomerisation of the ligand in RhCl(CO)(PPh,CH,CH,CH =CH2)296 and the formation of PtCl,(MeCOCH,CMe=CH,) from MeCOCH=CMe by a 1,3-hydride shift.', The following 1,5-hydride shift occurs on heating.', Me H Metal-catalysed Carbon Skeletal Isomerisation.-This is a relatively new area of catalysis in which certain thermodynamically unstable organic compounds are transformed into a more stable isomer by metal complexes the process occuring with or without simultaneous hydrogen transfer.An example of the former reaction is the skeletal rearrangement of 1,4-pentadi- ene to 2-methyl-1.3-butadiene using a NiCl,(PR,),-AlBu;CI ~ata1yst.l~~ The conversion is thought to involve a cylopropylcarbinyl organometallic species.If the cyclopropyl group is part of another ring system ring-expansion takes place.' 'I6 H. Hirai H. Sawai E.-I. Ochiai and S. Makishima J. Catalysis 1970 17 119. '' W. H. Clement and T. Speidel Ind. and Eng. Chem. (Product Res. and Development) 1970,9 220. I * J. Blum and Y.Pickholtz Israel J. Chem. 1969 7 723 ;(Chem. Abs. 1970,72,99825). Il9 J. Kovacs G. Speier and L. Marko Inorg. Chim. Acta 1970,4,412. 2o W. Strohmeier and W. Rehder-Stirnwess J. Organometallic Chem. 1970,22 C27. 2' R. L. Augustine and J. F. Van Peppen Chem. Comm. 1970,495. Iz2 R. D. Gillard B. T. Heaton and M.F. Pilbrow J. Chem. SOC.(A) 1970,353. 23 M. 1. Foreman G. R. Knox P. L. Pauson K. H. Todd and W. E. Watts Chem. Comm. 1970 843. 124 R. G. Miller P. A. Pinke and D. J. Baker J. Amer. Chem. SOC.,1970,92,4490. Iz5 C. B. Reese and A. Shaw J. Amer. Chem. SOC.,1970,92,2566. Organometallic Compounds-Part (ii)Transitional Elements 315 Many three- and four-membered rings undergo bond cleavage under the influence of transition-metal complexes. These transformations are frequently thermally forbidden according to the Woodward-Hoffman rules of orbital symmetry conservation,'26-' 29 but catalysis of these reactions by metal com- plexes occurs either by removal of the symmetry constraints by utilising the appropriate &orbitals of the or by an oxidative addition reac- tion involving C< bond breakage.' Thus the Rhl-catalysed conversions of quadricyclene (13) into n~rbornadiene,'~~ cubane (14) into tricy~lo-octadiene,'~~ and cuneane (15) into semibullvalene'35 are considered to proceed via Rh"' intermediates.(15) Ag' and sometimes Pd" compounds catalyse many of these changes usually in a different manner from the Rh' reaction. Thus cubane (14)is isomerised into Agl or Pd"43 126 R. B. Woodward and R. Hoffman Angew. Chem. Internat. Edn. 1969 8 781. 12' G. B. Gill 'Essays in Chemistry' ed. J. N. Bradley R. D. Gillard and R. F. Hudson Academic Press New York 1970. vol. 1 p. 43. 28 J. J. Vollmer and K. L. Servis J. Chem. Educ. 1970,47,491. 129 R. G. Pearson Theor. Chim. Acta 1970 16 107.I3O W. T. A. M. van der Lugt Tetrahedron Letters 1970 2281. 13' J. Manassen J. Catalysis 1970 16 38. 132 G. L. Caldow and R. A. MacGregor Inorg. Nuclear Chem. Letters 1970,6 645. 133 L. Cassar and J. Halpern Chem. Comm. 1970 1082. 134 1970 92 3518. L. Cassar P. E. Eaton and J. Halpern J. Amer. Chem. SOC., ' L. Cassar P. E. Eaton and J. Halpern J. Amer. Chem. SOC.,1970 92 6366. J. P. Candlin A. W.Parkins and K. A. Taylor cuneane (15),13' 1,l'-bishomocubane (16) into a new CloHlo isomer (17),'369'37 and the azo-compound (18) into the rearranged product (19).138 (16) (17) (18) (19) A carbon-carbon bond-making and -breaking reaction that is commanding increasing attention is olefin disproportionation' 39 (also called olefin metathesis or dismutation).The general reaction is R'R2C=CR3R4 + R5R6C=CR7R8 R1R2C=CR5R6 + R3R4C=CR7R8 where R is hydrogen or hydrocarbon groups. Although this general reaction has been known for several years to be heterogeneously cataly~ed,'~~-'~~ it is only in the last three years that homogeneous catalysts of comparable activity have been di~c0vered.l~~ The catalysts in general are Group VI metal halide- aluminium-alkyl-alcohol or carboxylic acid combinations. Thus MoCl,(NO) -(PPh3)2-Me3A12CI disproportionates pent-1-ene at room temperature to its equilibrium mixture of ethylene and oct-4-ene in under 1 h.I4' (ratio of catalyst substrate is 0.1 mmol 10 ml). Various combinations of substrates illustrate the versatile nature of this catalyst system. The kinetics of the disproportionation of pent-2-ene have been The reaction intermediate is a diolefin-molybdenum complex although a carbene 136 W.G. Dauben M. G. Buzzolini C. H. Schallhorn D. L. Whalen and K. J. Palmer Tetrahedron Letters 1970,787 121 8. 13' L. A. Paquette and J. C. Stowell J. Amer. Chem. SOC.,1970,92,2584. R. Askani Tetrahedron Letters 1970 3349. 139 G. C. Bailey Catalysis Rev. 1969 3 37. J. C. Mol F. R. Visser and C. Boelhouwer J. Catalysis 1970 17 114. 14' A. J. Moffat and A. Clark J. Catalysis 1970 17 264. 14' A. Clark and C. Cook J. Catalysis 1969 15 420. 143 V. V. Atlas I. I. Pis'man and A. M. Baksshi-Zade Khim. Prom. (The Soviet Chemical Industry) 1969 10 17. 144 H. R. Menapace J. Org. Chem. 1968,33,2133. 145 E.A. Zuech W. B. Hughes D. €3. Kubieck and E. T. Kittleman J. Amer. Chem. SOC. 1970 92 528. 146 W. B. Hughes J. Amer. Chem. SOC.,1970,92,532. Organometallic Compounds-Part (ii) Transitional Elements intermediate may explain the appearance of odd-numbered carbon alkenes formed in the disproportionation of ~ct-l-ene.'~' The variety of products obtained from the olefin disproportionation reaction appear to be endless. Catenanes are thought to be formed (mass spectral evidence) when large cyclic dienes are used. '48*149 5 Oligomerisa tion of Unsaturated Hydrocarbons Mono-olefins.-The dimerisation of olefins catalysed by nickel complexes in combination with aluminium alkyls has been studied by many groups of workers following the introduction of n-ally1 nickel catalysts by Wilke and co-workers in theearly 1960's.Recent work includes the system R4P+ [NiCl3(PR3)]-Et3Al2C1 which selectively dimerises propylene to 2,3-dimethylbut-l-ene150 and (n-C4Me4)NiC1,-Et3A1,C1 which dimerises ethylene propylene and butene.' 5' The effect of various Lewis acids (LA) in the olefin dimerisation catalyst system Ni(CO),(PPh3),-LA has been studied. 52 Diethyl(bipyridyl)nickel(rI) although inactive for olefin dimerisation becomes an active catalyst for this reaction when treated with aluminium alkyl halides.' 53 The dimerisation and trimerisation of ethylene' 54 and butene' 55 using Ni(oleate),-AlBu\Cl occurs in common with many of these systems at atmospheric pressure and room temperature or below. 1,3-Diphenylbut-l-ene can be obtained in yields approaching 90 % by the dimeri- sation of styrene using n-ally1 nickel halides.' 56 Pd" complexes e.g.(PhCN),PdCI ,dimerise various olefins in high yields e.g.ethylene propylene methyl acrylate styrene ;'57 in general however the rate of reaction is less than the corresponding reaction catalysed by nickel complexes. Co-dimerisation e.g. ethylene-cyclopentene methyl acrylate-styrene ethylene- styrene can also be performed.'57,'58 14' K. Hummel and W. Ast Naturwiss. 1970,57,245. 148 R. Wolovsky J. Amer. Chem. SOC. 1970,92,2132. 149 D. A. Ben-Efraim C. Batich and E. Wasserman J. Amer. Chem. SOC. 1970 92 2133. lS0 G. G. Eberhardt and W. P. Griffen J. Catalysis 1970,16,245. 15' 0-T. Onsager H. Wang and U. Blindheim Helv.Chim. Acta 1969 52 187 196,215 224 230. M. Born Y. Chauvin G. Lefebre and N.-H. Phung Compt. rend. 1969,268 C 1600. IS3 M. Uchino A. Yamamoto and S. Ikeda J. Organometallic Chem. 1970 24 C63. V. S. Fel'dblyum A. I. Leshcheva and N. V. Obeshchalova Zhur. org. Khim. 1970 6,213; (Chem. Ah. 1970,72 121953). 55 V. S. Fel'dblyum A. I. Lechcheva 0.P. Yablonskii and N. M. Pashchenko Perroleurn Chemistry (U.S.S.R)1968 8 176. L. I. Red'kina K. L. Makovetskii E. I. Tinyakova and B. A. Dolgoplosk Doklady Akad. Nauk S.S.S.R. 1969 186 397. (Chem. Ah. 1969,71,60887). M. C. Barlow M. J. Bryant R. N. Haszeldine and A. G. Mackie J. Organometallic Chem. 1970,21 215. 15' K. Kawamoto T. Imanaka and S. Teranishi Bull. Chem. Sac. Japan 1970,43,2512. 318 J.P. Candlin,A. W.Parkins and K. A. Taylor Recently soluble Ziegler catalysts for oligomerisation of ethylene rather than polymerisation have been reported. Thus (EtO),TiCl-AlEtCl ' 59 and (n-CSH5)2TiRC1-R,Al'60 yield a distribution of products from dimers (but-1-ene) up to -C, . Low molecular weight polypropylene (-C40)can also be obtained from similar catalyst systems.' 61 Reviews on the polymerisation of olefins both from theoretical and practical aspects have appeared.'62,163 Acetylenes.-The cyclotrimerisation of acetylenes to aromatic systems has been known for many years and the corresponding transition-metal-catalysed reaction has received attention during the last year. Although several mechanisms have been postulated only the metallocyclic pathway has received positive support.Thus the formation of 1,2,3,6tetramethylnaphthalene from MeCrCMe and Ph3Cr.3THF is thought to proceed through a chromocycle.' 64 Me 2111 C I + CrPh -+ [;$Cr-P] -P I Me Me Me Electron-withdrawing groups (e.g. CF,) tend to favour metallocycle formation and rhodo-and irido-cyclic compounds (20)'65and (21)'66are stable enough to have these structures confirmed by X-ray and n.m.r. analysis respectively. An organopalladium complex formed by the trimerisation of BUT-CH in the presence of (PhCN),PdCl, is thought from n.m.r. and analytical data to have the skeletal structure (22)167-169[the positions of the But groups have not been determined and therefore omitted from (22)]. The intermediate formation of a cyclobutadiene Rh' species (23)is thought to occur during the cyclotrimerisation of substituted acetylenes.' 'O PdCl 2 (22) 159 G.Henrici-Olive and S. Olive Angew. Chem. Internat. Edn. 1970 9 243. G. Henrici-Olive and S. Olive J. Polymer Sci. Part B 1970 8 271. 161 G. Henrici-Olive and S. Olive J. Polymer Sci.,Part B 1970 8 205. 16' G. Henrici-Olive and S. Olive Ado. Polymer Sci. 1969 6 421. 163 M. N. Berger G. Boocock and R. N. Howard Adu. Catalysis 1969 19 211. 164 G. M. Whitesides and W. J. Ehmann J. Amer. Chem. Soc. 1970,92 5625. J. T. Mague Inorg. Chem. 1970,9 1610. 166 B. Clarke M. Green and F. G. A. Stone J. Chem. SOC.(A) 1970,951. '' K. L. Raiser and P. M. Maitlis Chem. Comm. 1970 942. 16* H. Diet] H. Reinheimer J. Moffat and P.M. Maitlis J. Amer. Chem. Soc. 1970 92 2276. 169 H. Reinheimer J. Moffat and P. M. Maitlis J. Amer. Chem. SOC.,1970 92 2285. 'O E. Miiller and E. Langer Tetrahedron Letters 1970,989,993. 319 Organometallic Compounds-Part (ii) Transitional Elements 0 ___) mR RhCI(PPh,) \/ -\/ R 0 0 RhCI(PPh3)2 OR It appears likely that the cyclotrimerisation of substituted acetylenes using Rh,(CO),,,' 71 Ni(C0)4,' 72 and n-allylnickel halides'73 proceeds through metallocyclic intermediates. Reactions of organic substrates with metallocyclic intermediates have yielded interesting results which may have synthetic utility. Thus the reaction of a cobaltocyclic compound (n-C5H5)(PPh3)Co(C4Ph4) with ethylene yields a complex containing the n-bonded ligand tetraphenylcyclohexadiene.74 Dimerisation of acetylene to yield vinylacetylene is known to take place homo- geneously in the presence of Cu' salts.175 Diolefim-The normal thermal dimerisation of butadiene yields a mixture of 4-vinylcyclohex-1-ene (VCH) and 1,5-cyclo-octadiene (COD) the ratio depending on the conditions. It is therefore not surprising that catalytic dimerisation can be arranged to yield either of these dimers sele~tively.'~~ Thus [n-allylFe(NO),],- SnC12 with butadiene yields VCH almost excl~sively'~~ whereas bis(cyc1o- 0ctatetrene)Fe' yields COD'78 (together with a linear C, tetraene). The effect of added CO (4OOpsi) can also alter this ratio and in some cases (e.g. using Ni[P(OPh),] as catalyst} reverse it ~ompletely.'~~ Electrolytic dimerisation in the presence of Ni" salts also yields a mixture of VCH and COD."' Other butadiene dimer isomers (or their derivatives) can be obtained ; Pd(OAc),-HOAc yields linear octatrienes," 'and catalyst systems (Bu,P),NiCl I ' Y.Iwashita and F. Tamura Bull. Chem. SOC. Japan 1970 43 15 17. S. isaoka K. Kogami and J. Kumanotani Makrornol. Chem. 1970. 135 1. " V. 0.Reikhsfel'd B. I. Lein and K. L. Makovetskii Proc. Acad. Sci.(U.S.S.R.) 1970 190 31. ' H. Yamazaki and N. Hagihara J. Organometallic Chem. 1970,21 431. "' ' T. F. Rutledge 'Acetylene Compounds' Reinhold New York 1968 Chapter 6. R. S. Coffey Ann. Reports (B) 1969,66 317. '" P. L. Maxfield Inorg. Nuclear Chem. Letters 1970 6 707. 78 A. Carbonaro A.Greco and G. Dall'asta J. Organometallic Chem. 1969 20 177. 17' J. F. Kohnle L. H. Slaugh and K. L. Nakamaye J. Amer. Chem. SOC.,1969,91 5905. H. Lehmkuhl and W. Lenchte J. Organometallic Chem. 1970 23 C30. ''I W. E. Walker R. M. Maryik K. E. Atkins and M. L. Farmer Tetrahedron Letters 1970 3817. J. P. Candlin A. W.Parkins and K. A. Taylor -RLi (R = o-C,H,CH,NM~,'~~ or o-C6H4Melg3) yield an unusual five-membered cyclic compound l-vinyI-2-methylenecyclopentane,in high yields. The Nio-P(C,H ,),-catalysed dimerisation of butadiene is known to give COD. The corresponding reaction with 1,3-pentadiene gives dimethylcyclo- octadiene.' 84 The potential use of dimerisation catalysts in natural product chemistry is illustrated by the conversion of Cl0 terpenes into C20 terpenes using Pd" and Pdo catalysts.' 85 The catalytic dimerisation of norbornadiene has been studied many times over the last several years.Binor-S (24) is made using a bifunctional transition-metal catalyst e.g. Zn[Co(CO),] or X,Sn[Co(CO),] The list of catalysts for this dimerisation has been extended to include CoBr,(PPh,) and RhCI(PPh,) ,both (24) (25) in combination with BF,-Et,O as co-catalyst.'87 The action of U.V. light on the Cr(CO),-catalysed dimerisation of norbornadiene gives three stereoisomeric cyclobutane derivatives (25)' 88 The polymerisation of diolefins has been reviewed,189 and the effect of various ligands on the polymerisation of isoprene has been studied.'" Co-dimerimtion.-The catalytic co-dimerisation of butadiene and ethylene yields 1,4-hexadiene.This compound has been used comniercially as a termonomer in ethylene-propylene rubbers. Alterations in the ligand R,P(CH,),PR (PP)in the catalyst system CoCI,(PP)-AlEt show that the above co-dimerisation can be made to go exclusively to 1,4-hexadiene."' The co-dimerisation product from norbornadiene and butadiene depends on the catalyst. Co(acac),-AIEt gives (26) exclusively' 92 whereas Fe(cyc1o-octatetraene) gives a mixture of products which includes (27). 93 J. Kiji K. Masui and J. Furukawa Tetrahedron Letters 1970 2561. J. Kiji K. Masui and J. Furukawa Chem. Comm. 1970 1310. P. Heimbach and H. Hey Angew. Chem. Znternat. Edn. 1970,9 528. *" K. Dunne and F. J. McQuillin J. Chem. SOC.(C) 1970,2196,2200 2203.F. P. Boer J. H. Tsai and J. J. Flynn jun. J. Amer. Chem. SOC., 1970,92 6092. G. N. Schrauzer R. K. Y. Ho and G. Schlesinger Tetrahedron Letters 1970 543. W. Jennings and B. Hill J. Amer. Chem. SOC.,1970,92 3199. G. Natta and L. Porri High Polymers 1969,23 (II) 597; R. E. Rinehard ibid.,p. 867. 19* H. E. Swift J. E. Bozik and C. Y. Wa J. Catalysis 1970 17 331. 19' T. Kagawa Y. Inoue and H. Hashimoto Bull. Chem. SOC.Japan 1970,43 1250. 192 A. Takahashi and T. Inukai Chem. Comm. 1970 1473. 193 A Greco A. Carbonaro and G. Dall'asta J. Org. Chem. 1970 35 271. Organometallic Compounds-Part (ii) Transitional Elements 32 1 The reaction between butadiene and aldehydes (RCHO) is as expected catalysed by Pd" complexes. Vinyl substituted pyrans (28)are obtained and this reaction could have synthetic possibilities.'94.'9s 6 Insertion Reactions A large number of insertion reactions have been reported this year but we shall confine our attention to reactions which involve the formation of C-€ bonds since these are most useful synthetically.An interesting carbene insertion reaction is that between (29)and diphenyldi- azomethane to give (30)as one of the products.'96 OMe I (29) (30) A series of reactions of tetrafluoroethylene with low-valent transition-metal complexes has been reported. lg7 It appears that in some cases a three-membered ring containing a nickel atom may undergo an insertion reaction with C2F to form a five-membered ring Et,P (Et,P),Ni +C2F4 + \/ Ni cF2-TF2 /\ I Et,P CF -CF Tetracyanoethylene may be inserted into cyclopentadienylirondicarbonyl-benzyl.* (n-C,HJFe(CO),CH,Ph +C21CN) -+(n-C,H,)Fe(CO),(CN),C(CN),CH,Ph 194 P. Haynes Tetrahedron Letters 1970 3687. 19' R. M. Maryik W. E. Walker K. E. Atkins and E. S. Hammack Tetrahedron Letters 1970,3813. 196 M. M. Bagga G. Ferguson J. A. D. Jeffreys C. M. Mansell P. L. Pauson I. C. Robertson and J. G. Sime Chem. Comm. 1970,672. 19' C. S. Curdy M. Green and F. G. A. Stone J. Chem. SOC.(A) 1970 1647. 19' S. R. Su J. A. Hanner and A. Wojcicki J. Organometallic Chem. 1970 21 P21. 322 J. P. Candlin,A. W. Parkins and K. A. Taylor A curious insertion reaction occurs when the dinuclear Pd" complex (31) is treated with allene to give (32).199 The reactions of dimethyl and diethyl osmium tetracarbonyls with CO show interesting differences.200 Et,Os(CO) +2CO +(EtCO),Os(CO) Me,Os(CO) +CO +C2H +Os(CO) Isonitriles may be inserted into Pd-Me bonds to give successively (33) (34),and (35).201 A similar reaction to the first stage of this sequence is the isonitrile insertion into Pd" compounds202 and [(n-allyl)PdCl] .203 I PPh,Me \/ RNC+ Pd /\ MePh,P Me I PPh,Me \/ Pd MePh,P /\C-C-CH, II I1 / NR NR JRNC (34) RN'1\pd=PPh2Me C=NR $1 where R =C,H c-c II (35) NR 7 Carbonylation Decarbonylation and Carbonyls in Synthesis Carbony1ation.-Several detailed papers have appeared on the catalytic carbony- lation of olefins.Rhodium complexes continue to attract since many of the carbonylation reactions can be performed at atmospheric pressure and are therefore within the reach of synthetic organic chemists.The partial pressure of CO dictates the product distribution in the carbonyla- tion of propylene using Co,(CO),(PBu,) as cataly~t.~" It has also been shown 199 T. Okamoto Chem. Comm. 1970 1126. 'O0 F. L'Eplattenier and C. Ptlichet Helv. Chim. Acta 1970 53 1091. '01 Y. Yamamoto and H. Yamazaki Bull. Chem. SOC.Japan 1970,43 2653. '02 P. M. Treichel and R. W. Hess J. Amer. Chem. SOC.,1970,92,473 1. '03 T. Kajimoto H. Takahashi and J. Tsuji J. Organometallic Chem. 1970 23 275. 204 C. K. Brown and G. Wilkinson J. Chem. SOC.(A) 1970,2753. '05 A. Hershman K. K. Robinson J. H. Craddock and J. F. Roth Ind.and Eng. Chem. (Product Res. and Development) 1969 8 372. '06 M. Takesada and H. Wakamatsu Bull. Chem. SOC.Japan 1970,43 2192. 'O' F. Piacenti M. Bianchi E. Benedetti and P. Frediani J. Organometallic Chem. 1970 23 257. Organometallic Compounds-Part (ii) Transitional Elements 323 that the acidity of the organometallic carbonyl hydride catalyst affects the rate and product distribution in the carbonylation reaction.208 The carbonylation of olefins using Ru3(CO) has been re~iewed.~” Synthetic applications of the carbonylation reaction include the formation of linear acids or esters from olefins (Pt-Sn catalyst),” * formyl nitriles from nitriles (Co catalyst),” formamides from the corresponding secondary amines (several catalysts including Co Ir Rh and Cu complexes),2 l2 and a cyclic C1,-ring keto- compound by the action of CO on the intermediate obtained from three mole- cules of butadiene and Ni(COD) .’I3 Astudy of the mechanism of carbonylation of organochloro-compounds using z-ally1 Pd complexes CH,=CHCH2Cl+ CO -+ CH,=CHCH,COCI suggests that the active intermediate may be a polymeric complex containing three Pd atoms.214 Similar reactions e.g.carbonylation of benzyl chloride are catalysed by [Ni(CO),X]-where X = C1 Br or I.215 Acyl chlorides can also be formed from olefins [Co,(CO) catalyst] by carrying out the carbonylation in the presence of CCI,:216 CCI + CO + CH,=CHR -+ CI,CCH,CHRCOCI Decarbony1ation.-The decarbonylation of carbonyl compounds by organo- metallic complexes has probably reached the stage when it may be considered a synthetic tool.Although it has been known for many years that heterogeneous catalysts (e.g.Pd-C) can perform this reaction,21 recent work has extended this to homogeneous systems. In some cases depending on conditions the reaction can be made to proceed using catalytic amounts of the transition-metal complex. Thus secondary amides can be converted into nitriles [RhCI(PPh,) as cata- ly~t],~~* although the reaction fails when both hydrogen atoms on the nitrogen are replaced by alkyl groups ArCONHCH,R -+ ArCN + RCHzOH Allylic alcohols yield the corresponding hydrocarbon [RhCI(PPh,) as catalyst] :2 l9 RCH=CHCH20H -RCH,Me ’08 N. S. Imjanctov and D. M. Rudkovskij J.prakt. Chem. 1969,311 712.*09 G. Braca G. Sbrana F. Piacenti and P. Pino Chimica e Zndustriu 1970 52 1091. ’lo L. J. Kehoe and R. A. Schell J. Org. Chem. 1970,35,2846. ’I1 Y. Ono Chem. Comm. 1970 1255. ’’ P. Haynes L. H. Slough and J. F. Kohnte Tetrahedron Letters 1970 365. ‘I3 G. Wilke and H. Breil Angew. Chem. Internat. Edn. 1970,9 367. l4 H. C. Volger K. Vrieze J. W. F. M. Lemmers A. P. Praat and P. W. N. M. Leeuwen Inorg. Chim. Acta 1970,4 435. 215 L. Casser and M. Foa Znorg. Nuclear Chem. Letters 1970 6 291. ’I6 T. Susuki and J. Tsuji J. Org. Chem. 1970,35 2982. J. S. Matthews D. C. Ketter and R. F. Hall J. Urg. Chem.,-l970 35 1694. 218 J. Blum and A. Fisher Tetrahedron Letters l.970 1963. A. Emergy A. C. Oehlschlager and A. M. Unran Terrahedron Letters 1970 4401.324 J. P. Candlin,A. W. Parkins and K. A. Taylor The potential of these catalysts is illustrated by the stereoselective decarbonyla- tion of optically active aldehydes to give hydrocarbons with over 90 % retention of optical activity (Rh catalysts).220 The removal of oxygen by carbonyl complexes from many organic compounds containing N_0221*222 and S-0223 linkages may be useful for the preparation of certain organic compounds R,NO + Fe(CO) -+ R,N + C02 + ‘Fe(CO),’ R2S0 + Fe(CO) + R,S + CO + ‘Fe(CO),’ R,C=NOH + Cr(CO),C(OMe) -+R,C=NHCr(CO), I Me A reaction which involves nucleophilic attack by a carbonylmetallate on an alkyl halide can be used to transform RBr into RCH0.224 In a similar manner the nucleophile formed from Ni(C0)4 and PhLi reacts with styrene epoxide to give the lactone (36):22s 0 PhHC 3 Ph-CH-CH + Ph-C-Ni(CO) -+ I 0 I ‘0’ 0-PhHC (34) 8 Nucleophilic Attack onCo-ordinated Ligands This has been an area of great interest since Chatt’s rationalisation226 of Hof- mann and von Narbutt’s original work.Elegant work carried out in Italy has shown that nucleophilic attack on an olefin co-ordinated to platinum occurs by direct attack on the olefin and not via intramolecular attack involving initial co- ordination of the attacking nucleophile to platin~m.~~’*~~* Several groups of ~~rker~~~~-~~~ have studied the mechanistic aspects of nucleophilic attack on dienes co-ordinated to Pd”. An X-ray structure of (C,H,OMe)Pd(py),Br obtained by nucleophilic attack (by OMe-) on co-ordinated norbornadiene shows that it contains a three-membered ring.233 In addition to the work with 220 H.M. Walborsky and L. E. Allen Tetrahedron Letters 1970 823. 221 H. Alper and J. T. Edward Canad. J. Chem. 1970,48 1543. z2z L. Knauss and E. 0.Fischer Chem. Ber. 1970,103 1262 3744. 223 H.Alper and E. C. H. Keung Tetrahedron Lerters 1970 53. 224 M. P. Cooke J. Amer. Chem. SOC.,1970,92,6080. 225 S. Fukuoka M. Ryang and S. Tsutsumi J. Org. Chem. 1970,35 3184. 226 J. Chatt L. M. Vallarino and L. M.Venanzi J. Chem. SOC.,1957 2496. 22’ A. Panunzi A. De Renzi and G. Paiaro J. Amer. Chem. SOC.,1970,92,3488. 228 R. Lazzaroni P. Salvadori and P. Pino Chem. Comm. 1970 1164. 229 J. K. Stille and D. B. Fox J. Amer. Chem. SOC.,1970,92 1274.230 P. Uguagliati B. Crociani and U. Belluco J. Chem. SOC.(A) 1970 363. 231 J. K. Stille and L. F. Hines J. Amer. Chem. SOC.,1970,92 1798. 232 E. Vedejs and M. F. Salomon J. Amer. Chem. SOC.,1970,92,6965. 233 E. Forsellini G. Bombieri B. Crociani and T. Boschi Chem. Comm. 1970 1203. Organometallic Compounds-Part (ii) Transitional Elements 325 co-ordinated dienes studies have also been carried out on chelating ligands in which one of the donor centres is a tertiary phosphorus atom.234,235 Vinylic chlorine atoms are not very susceptible to nucleophilic displacement but this reaction is facilitated when the double bond is co-ordinated to Pd11.236*237 Allylic halogen atoms also show increased reactivity.238 A synthesis of vinyl chloride which may involve intramolecular nucleophilic attack of C1- on ethylene co-ordinated to Pd" has been re~0rted.l~~ 9 Electrophilic Attack on Co-ordinated Ligands This reaction is favoured by a low oxidation state of the central metal ion.In some cases synthetically useful transformations may be carried out by using the metal ion as a blocking group. For example,24o diphenylacetylene may be acetylated under Friedel-Crafts conditions by forming the Co,(CO) adduct and subsequently decomposing the product with Ce". Further work on the electrophilic substitution of (cyclobutadiene)Fe(C0) has been carried When mercuric acetate is used as the electrophile all the possible substituted mercuriacetates may be obtained. Acetylation of co-ordin- ated dimethylbutadiene [(Me2C4H4)Fe(C0)3],242and arenes [x-RC6H5Cr-(CO)3]243 has been performed.234 W. Hewertson and I. C. Taylor Chem. Comm. 1970,428. 235 P. R. Brookes and R. S. Nyholm Chem. Comm. 1970 169. 236 C. F. Kohl1 and R. Van Helden Rec. Trav. chim. 1968,87,471. 237 M. Yamaji Y. Fujiawa I. Imanaka and S. Teranishi Bull. Chem. SOC.Japan 1970 43 2659. 238 D. G. Brady Chem. Comm. 1970,434. 239 H. A. Tayim Chem. and Ind. 1970 1468. 240 D. Seyferth and A. T. Wehmann J. Amer. Chem. SOC.,1970,92 5520. 241 G. Amiet K. Nicholson and R. Pettit Chem. Comm. 1970 161. 242 A. N. Nesmeyanov K. N. Anisimov and G. K. Magomedov Izvest. Akad. Nuuk S.S.S.R. Ser. khirn. 1970,959 (Chem. Abs. 1970 73 56218). 243 W. R. Jackson and W. B. Jennings J. Chem. SOC.(B),1969 1221.

ISSN:0069-3030    

DOI:10.1039/OC9706700306

出版商:RSC    

年代:1970

数据来源: RSC

摘要:

10 Aromatic Compounds By H. HEANEY Department of Chemistry The University of Technology Loughborough Leicestershire LE11 3TU General.-Predictions that the nuclear polarisation found in cage recombination products from radical pairs will depend upon the multiplicity of the electronic state have been verified for the reaction system benzoyl peroxide in carbon tetrachloride. A warning has been given concerning the interpretation of CIDNP effects as involving major pathways in all cases2 In spite of this these effects are taken as good evidence for the intervention of caged radical species3 The first reported observation of a I9F n.m.r. CIDNP effect was noted in the reaction of p-fluorobenzyl chloride with n-b~tyl-lithium.~’ The detection of hindered rotation and inversion by n.m.r.spectroscopy has been re~iewed.~ Barriers to rotation and nitrogen inversion have been studied for example in the case of tetraben~ylhydrazine.~ Relatively slow inversion at nitrogen has been observed by variable-temperature n.m.r. studies on (1;X = C1 or F).6 The major invertomer is the one shown; this effect may result from Me ON A x N x& X\ X\ X A intramolecular charge-transfer from the lone pair to the halogenated-arene residue. The Report last year’ mentioned the barrier to rotation in p-nitroso- NN-dimethylaniline. Further results have been presented which show that the barrier is markedly dependent on the nature of the para-substituent and a Hammett correlation gives AGS (at 133 K) = 5.1 (k1.0) kcal mol- for rotation ’ R.Kaptein J. A. den Hollander D. Antheunis and L. J. Oosterhoff Chem. Comm. 1970 1687. J. Jacobus Chem. Comm. 1970 709. (a) R. W. Jemison S. Mageswaran W. D. Ollis S. E. Potter A. J. Pretty I. 0. Sutherland and Y. Thebtaranonth Chem. Comm. 1970 1201; (b) J. W. Rakshys ihid. p. 578; (c)G. Ostermann and U. Schollkopf Annalen 1970,737 170. H. Kessler Angew. Chem. Internat. Edn. 1970 9 219. M. J. S. Dewar and W. B. Jennings Tetrahedron Letters 1970 339. ‘ G. W. Gribble N. R. Easton and J. T. Eaton Tetrahedron Letters 1970 1075. ’ Ann. Reports (B) 1969 66 324. 328 H. Heaney in NN-dimethylaniline.8 Good agreement with racemisation data has been observed for the activation parameters for rotation of the phenyl groups in 2,4,2',4-tetra-t-butyl-6,6'-dimethyldiphenylaceticacid by n.m.r.spectros~opy.~ The mechanism of enantiomer and diastereomer interconversion in triaryl- methyl cations has been studied using a m-difluoromethyl group as a diastereo- topic probe. The results obtained support the view that the trityl propeller conformation interconverts via a two-ring flip transition state.' The full paper describing the conformational changes in trisalicylides has appeared.' ' A number of other studies' report the results of variable-temperature n.m.r. studies and these include'2f interconversions between various folded and twisted conformations in bisfluorenylidenes (2). The remarkably low energy barrier to rotation about the formal C=C double bond may well be encouraged by ground-state strain and a transition state of high stability.Large positive nuclear Overhauser effects have been observed between 'H and 19F in a number of fluoro-aromatic compounds for example l-fluoro- naphthalene. l3 Whereas the methyl resonance in 1-fluoro-8-methylbiphenylene is a singlet the methyl resonance in 1-fluoro-8-methylfluorene (3) is a doublet I6JHF)= 8.3 Hz.14 This together with other values has been quoted as further evidence in favour of a through-space mechanism for the transmission of certain spin-spin interactions. Homoaromaticity. The extraction of the hydrocarbon (4) into a superacid medium at ca. -128 "C gave the 1,4-bishomotropylium ion (5).15 The n.m.r. spectrum remained unchanged up to +20 "C,and when the solution was quenched with * R.K. Mackenzie and D. D. MacNicol Chem. Comm. 1970 1299. 0.S. Akkerman Rec. Trau. chim. 1970 89 673. lo J. W. Rakshys S. V. McKinley and H. H. Freedman J. Amer. Chem. SOC. 1970 92 3518. A. P. Downing W. D. Ollis and 1. 0.Sutherland J. Chem. SOC.(B) 1970,24. l2 (a)C. H. Bushweller M. Sharpe and S. J. Weininger Tetrahedron Letters 1970 453; (b)G. Montando S. Caccamese P. Finocchiaro and F. Bottino ibid. p. 877; (c) R. E. Carter and J. Mhrton Actu Chem. Scund. 1970 24 195; (6)H. 0. House. W. J. Campbell and M. Gall J. Org. Chem. 1970 35 1815; (e) M. Nbgradi W. D. Ollis and I. 0. Sutherland Chem. Comm. 1970 158; cf) I. R. Gault W. D. Ollis and I. 0.Sutherland ibid. p. 269. l3 R. A. Bell and J. K. Saunders Chem.Comm. 1970 1078. l4 G. W. Gribble and J. R. Douglas J. Amer. Chem. SOC.,1970,92 5765. Is G. Schroder U. Prange N. S. Bowman and J. F. M. Oth Tetrahedron Letters 1970 3251; M. Roberts H. Hamberger and S. Winstein J. Amer. Chem. SOC. 1970 92 6346. Aromatic Compounds 329 sodium methoxide in methanol the compound (6) was isolated. The n.m.r. spectrum of the monohomotropylium ion (7) determined at 251 MHz has been interpreted in terms of a model in which the planar C(3)-C(4)<(5) segment is 8 (4) (5) (6) (7) slightly tilted (in the direction towards C(*Jwith respect to the plane formed by C(1)-C(2)-H(2).16 An improvement in the synthesis of 2,3-homotropone1' derivatives has been achieved by the reaction of tropone with sulphonium ylides.I8 Thus the ylide (8) affords (9)in 75% yield.The n.m.r. spectrum of (9) in deuterio- sulphuric acid shows the expected chemical shift differences associated with the ion (10). The isolation of homotropylium metal carbonyl salts (12; M = Cr Mo or W) has been reported. 19 The new synthesis involves the abstraction of hydride ion by the triphenylmethyl cation from cyclo-octatriene complexes (1 1 ;M = Cr Mo or W). The existence of a bishomoindenyl anion (14)has been suggested in order to account for the kinetics of deprotonation of (13)." Apparently the fused benzene ring provides about 0-8 times the assistance of a double bond in the carbanion series compared with a value of about 0.5 in the cation series. The protonation of the non-classical anion (15) can be achieved stereoselectively.2 Dimethyl l6 P.Warner D. L. Harris C. H. Bradley and S. Winstein Tetrahedron Letters 1970 4013. Ann. Reports 1963 60,351. l8 Y.Sugimura and N. Soma Tetrahedron Letters 1970 1721. '' R. Aumann and S. Winstein Tetrahedron Letters 1970 903. J. W. Rosenthal and S. Winstein Tetrahedron Letters 1970 2683. I' J. M. Brown and E. N. Cain J. Amer. Chem. SOC.,1970,92 3821. 330 H. Heaney sulphoxide approaches almost exclusively from the exo-face whereas when using methanol approach is from the endo-face. Benzene and Derivatives.-The following topics have been reviewed syntheses of aromatic compounds,22 the methods of synthesis and reactions of benzo-cy~lobutene,~~ n-complexes as intermediates in reaction^,,^ and the distortions of the Ir-electron system in substituted benzene^.,^ The use of the phenacyl group for protecting phenols and acids has been reported.26 Phenacylsulphonylation provides a new method for the protection of amine~.~~ Both of these protecting groups may be removed easily with zinc and acetic acid at room temperature.In the case of the reaction with primary amines the products can be alkylated efficiently and hence this also affords a new approach to the preparation of secondary amines. The cleavage of the aryl-tin bond in aryltrimethylstannanes by nitrosyl chloride provides a new route to aryl-nitroso-compounds.28NN-Dideuterioanilines and 0-deuteriophenols with a high isotopic purity have been prepared by the cleavage of the appropriate trimethylsilyl derivatives with O-deuteri~methanol.~~ Electrophiles attack benzoquinuclidine (16) at position 7to afford for example (17; Y = NO or S02Cl).30 The difference from the normal reactions of NN-dialkylanilines results from the lone pair of electrons on nitrogen in (16) being orthogonal to the n-electron system.Hydrogen bromide acts as a catalyst in the isomerisation and disproportionation of p-bromophenol~.~ No rn-bromo-phenols were detected but the resultant mixtures contained large proportions of o-bromophenols. The analogous chloro-compounds do not undergo this type of reaction under similar conditions. The mechanism of this reaction probably involves slow debromination and concurrent rapid rebromination. The reaction represents a useful method of preparing certain o-bromophenols.The displace- ment of a t-butyl group by an attacking electrophile has been noted on many occasions. However in the reaction of 1,3,5-tri-t-butylbenzenewith phosphorus 22 J. W. Barton in ‘Modern Reactions in Organic Synthesis’ ed. C. J. Timmons Van Nostrand Reinhold London 1970 p. 240. 23 I. L. Klundt Chern. Rev. 1970,70,471. 24 D. V. Banthorpe Chem. Rev. 1970,70,295. 25 A. R. Katritzky and R. D. Topsom Angew. Chem. Internat. Edn. 1970,9 87. 26 J. B. Hendrickson and C. Kandall Tetrahedron Letters 1970 343. 2’ J. B. Hendrickson and R. Bergeron Tetrahedron Letters 1970 345. 28 E. H.Bartlett C. Eaborn and D. R. M. Walton J. Chem. SOC.(C),1970 1717. 29 A. R. Bassindale C. Eaborn and D. R. M.Walton J. Chem. SOC.(C),1970 1577. 30 R. P. Duke R. A. Y. Jones A. R. Katritzky E. E. Mikhlina A. D. Yanina L. M. Alekseeva K. F. Turchin Yu. N. Sheinker and L. N. Yakhontov Tetrahedron Letters 1970 1809. 3’ E. J. O’Bara R. B. Balsley and I. Starer J. Org. Chem. 1970,35 16. Aromatic Compounds 331 trichloride in the presence of aluminium chloride the displaced group is trapped intramolecularly with the formation after hydrolysis of (18).32 The boron- trifluoride-catalysed ethylation of benzene has been studied using [2-'4C]ethyl fluoride.33 The electrophile involved is an ethyl carbonium ion in a non-polar (18) solvent or an unionised complex in a basic organic solvent. The trichloro- methylation of 2-substituted-l,3,5-trimethylbenzenesby carbon tetrachloride in the presence of aluminium chloride followed by methanolysis affords sub- stituted methyl benzoates in high yield.Rearrangement products were obtained in addition to the expected products when the 2-substituent was hal~gen.~" The rearrangement was accounted for in terms of electrophilic attack at the 5-position by the trichloromethyl carbonium ion (or its equivalent) followed by a 1,2-methyl shift. Thus for example (19)gave (20)and (21) in 70 "/ and 30% yield respectively. Evidence has been presented which supports the view that aluminium-chloride-catalysed Diels-Alder reactions proceed via zwitterionic intermediates. Thus the compound (22) gives rise to a mixture of cis-and trans-isomers of both (23) and (24).35 The isolation of stable adducts in the acetoxylation of aromatic hydrocarbons by nitric acid in acetic anhydride36 lends support to the view3' that an addition- (24) (25) (26) 32 M.Yoshifuji I. Fujishirna R. Okazaki and N. Inamoto Chem. andInd. 1970 625. 33 A. Natsubori and R. Nakane J. Org. Chem. 1970 35 3372. '' H. Hart and J. F. Janssen J. Qrg. Chem. 1970 35 3637. 35 H. W. Thompson and D. G. Melillo J. Amer. Chem. SOC.,1970,92 3218. 36 D. J. Blackstock A Fischer K. E. Richards J. Vaughan and G. J. Wright Chem. Comm. 1970 641; D. J. Blackstock J. R. Cretney A. Fischer M. P. Hartshorn K. E. Richards J. Vaughan and G.J. Wright Tetrahedron Letters 1970 2793. 37 P. B. D. de la Mare and R. Koenigsberger J. Chem. Soc. 1964 5327. 332 H. Heaney elimination mechanism operates.p-Xylene affords a pair of cis-(25) and trans-(26)isomers both ofwhich give aryl acetates on decomposition even in propionic acid. This suggests that the breakdown involves an intramolecular 1,2-shift. Some aspects of the use of thallium and its salts in organic synthesis have been reviewed.38 The control over ortho-substitution previously reported in the thallation of benzoic acid by thallium(rI1) trifluoroacetate also operates with methyl benzoate benzyl alcohol and benzyl methyl ether.39 These results indicate the intermediacy of an electrophile-substrate complex. A number of aldehydes have been prepared by the reaction of an olefin with thallium(II1) nitrate in a nucleophilic solvent.40 P-Methylstyrene for example gave phenylace- tone in 81 "/ yield.The oxidation of 4-methoxychalcone (27) with methanolic thallium(m) acetate gives 3,3-dimet hox y-2-p-met hoxyphenyl- 1 -phenylpropan- 1 -one (28).41 I4C-Labelling experiments have shown that the reaction involves a 1,2-aryl migration in contrast to the 1,Zaroyl migration which occurs with chalcone ep~xides.~~ The oxidation of chalcones with thallium(I1r) nitrate in an aqueous acid-glyme system results in the formation of benzil~.~~ Trans-thallation reactions have been studied using phenylthallium(I1r) bis(trifluor0- acetate) and an excess of substituted arene.44 Me Me Ph,Cr 3THF (29) Me (32) The reaction of triphenyltris(tetrahydrofuran)chromium(m) with but-2-yne yields inter alia 1,2,3,4tetramethylnaphthalene.Labelling and kinetic isotope experiments exclude certain mechanisms and suggested the mechanism shown 38 E. C. Taylor and A. McKillop Accounts Chem. Res. 1970,3,338. 39 E. C. Taylor F. Kienzle R. L. Robey and A. McKillop J. Amer. Chem. SOC.,1970 92 2175. 40 A. McKillop J. D. Hunt E. C. Taylor and F. Kienzle Tetrahedron Letters 1970 5275. " W. D. Ollis K. L. Ormand and I. 0.Sutherland J. Chem. SOC.(C),1970 119. 42 Ann. Reports 1956 53 144. 43 A. McKillop B. P. Swann and E. C. Taylor Tetrahedron Letters 1970 5281. 44 A. V. Huygens J. Wolters and E. C. Kooyman Tetrahedron Letters 1970 3341. Aromatic Compounds [(29) +(32)].45 Positional isomers (33) and (34) have been isolated from the product of the irradiation of 3,a-dimethylstyrene in the presence of penta- ~arbonyliron.~~ Intramolecular aromatic substitution in transition-metal com- plexes has been reviewed.47 Me WCO) (co)3Fewe Me (CQ FeDMe (33) (34) Fe(CO) Interest in the reactions of aryl-lithium reagents continues.o-Nitrophenyl-lithium is unstable at temperatures above ca. -100"C and forms an unstable dimer possibly (39 which on oxidation with methyl chloroformate yields 2,2'-dinitr0biphenyl.~' The reaction of pentachlorophenyl-lithium with aromatic nitriles has been shown to be re~ersible.~' Thus the ketimine (36)when converted into its lithio-derivative was shown to give rise to p-tolunitrile and pentachloro- phenyl-lithium. Me (35) a~c1 CI (36) The system ethylene-palladium chloride-silver nitrate has been shown to be very efficient in promoting the oxidative coupling of aromatic compounds to biaryl~.~' The autoxidation of 4-alkyl-2,6-di-t-butylphenols is catalysed by the cobalt complex (37) and results in the formation of cyclohexadienones (38) in (37) (38) 45 G.M. Whitesides and W. J. Ehmann J. Amer. Chem. Soc. 1970,92 5625. 46 R. Victor R. Ben-Shoshan and S. Sarel Chem. Comm. 1970 1680. 47 G. W. Parshall Accounts Chem. Res. 1970 3 139. 48 P. Buck R. Gleiter and G. Kobrich Chem. Ber. 1970 103 1431. 49 D. J. Berry and B. J. Wakefield J. Organometallic Chem. 1970 23 1. Y. Fujiwara I. Moritani K. Ikegami R. Tanaka and S. Teranishi Bull. Chem. Soc. Japan 1970,43 863. 334 H. Heaney high yield via the corresponding hydroperoxides.’ On the other hand the oxidation of 2,4-di-t-butylphenol by the system oxygenxuprous chloride- morpholine gave (39).52 k % 0 0 I‘ 0 0 -N.-Y n 1 U HH‘ u nHH 11 --(40) (41) (42) Reduction of the quinone epoxide (40) with sodium borohydride leads to the naturally occurring dihydroquinone epoxide ( & )-terremutin (41) and its C-4 epimer (42).53 N.m.r. data for both compounds show that the original assign- ment of stereochemistry was incorrect. 2,5-Diazido-3,6-di-t-butyl-1,4-benzo-quinone (43) undergoes very ready thermal cleavage to give the surprisingly stable yet very reactive keten (45),presumably by way of (44).54 Evidence for the intermediacy of p-quinone methides in the oxidation of phenols has involved trapping the reactive species.’ ’ Thus when 2,6-di-t-butyl-p-cresol was oxidised c”’o $c=o N2 -N + N 2-NyJfqvP NC (451 0 CH(0Me) 0 (46) (43) (44) with manganese dioxide in methanol the acetal(46) was is~lated.~’’ The possi- bility that differing acid-catalysed rearrangements of cyclohexa-2,4-dienones proceed through either n-or z-protonated ketones has been suggested in order to account for the large number of reaction types found.56 The dienone (47) rearranges slowly in the presence of acid solely to (48) possibly via the z-pro- tonated species while (49) rearranges more rapidly to (50),possibly uia the n-pro- tonated species.Deuterium-labelling experiments show that the rate-deter- mining step in the dienone-phenol rearrangement of 4,4-dimethylcyclohexa-dienone involves the methyl migration to (51) and not the subsequent deproto- nation.”” The acidity dependence of the activity coefficient ratio fss+/ft 51 T.Matsuura K. Watanabe and A. Nishinaga Chem. Comm. 1970 163. 5z D. G. Hewitt Chem. Comm. 1970,227. 53 G. Read and V. M. Ruiz J. Chem. SOC.(C) 1970 1945. ” H. W. Moore and W. Weyler J. Amer. Chem. SOC.,1970,92,4132. 55 (a)J. W. A. Findlay and A. B. Turner Chem. and Znd. 1970 158; (b) C. M. Orlando J. Org. Chem. 1970 35 3714. ’’ B. Miller J. Amer. Chem. Sac. 1970 92 432 6246 6252. ’’ (a)V. P. Vitullo and N. Grossman Tetrahedron Letters 1970 1559; (b)V. P. Vitullo Chem. Comm. 1970 688. Aromatic Compounds in the rate-determining step suggests that the transition state is less solvated than the ground state by one water molecule.576 N-Alkyl-N-chloroanilines have been shown to be methoxylated in the para-position via silver-ion-assisted ionisation in methanol.58a Evidence for the intermediacy of anilenium ions has now been obtained using N-chloro-4-t-butylaminobiphenyl,which affords the cyclohexadienone (52) in good yield.'*' The dehydration of the dienol (53) results in the formation of the biphenyl derivative (54).59 That the reaction pro- ceeds through the triene (55) was established by trapping the intermediate with tetracyanoethylene which resulted in the formation of (56).6 Me CHCl Me CHCI (CN12 I l lO 1M e 6'.;.HCl2 p h e CH3 Me0 Ph HO Ph Ph CHCI (57) (58) (59) The trans-hexa-2,4-dienyl phenyl ether (57) rearranges in an excess of NN-di-ethylaniline at 186 "Cto the phenols (58) and (59).The latter is the first example of a [5~,5s]sigmatropic rearrangement which has been shown to proceed via a ten-membered transition state.60 [1,7a]Sigmatropic hydrogen shifts are involved in the isomerisation of cis,cis-to cis,trans-o-dipropenylbenzeneand vice versa ; the trans,trans-isomer rearranges at 225 "Cto (60) and this involves a disrotatory cyclisation followed by a [1,5]hydrogen shift.61 The mesitylallene (61) rearranges firstly via an aromatic [1,5s]sigmatropic hydrogen shift to an o-quinodimethane which then gives the dihydronaphthalene (62) or me~itylbuta-1,3-diene.~~ (a) P. G. Gassman G. Campbell and R. Frederick J. Amer. Chem. Soc. 1968 90 7377. (b) P.G. Gassman and G. A. Campbell Chem. Comm. 1970,427. 59 M. S. Newman and W. X. Bajzer J. Org. Chem. 1970. 35,270. 'O Gy. Frater and H. Schmid Hefv. Chim. Acra 1970 53 269. 61 H. Heimgartner H.-J. Hansen and H. Schmid Hefv. Chim. Acta 1970 53,173. " H. Heimgartner J. Zsindely H.-J. Hansen and H. Schmid Heh. Chim. Acta 1970 53. 1212. 336 H. Heaney The thermal rearrangements of the pentenylphenol(63) have been reported.63 A quantitative conversion into the two isomers (65) and (67) was observed which possibly involves the intermediates (64) and (66) respectively MewMe Me Thio-Claisen and thiopropynyl rearrangements of prop-2-ynyl and allenyl phenyl sulphides have been The data are best rationalised as involving a thiopropynylic rearrangement which establishes an equilibrium (68) (69).The compound (68) then leads to (70) and (69) to (71) by thio-Claisen rearrange- ments. p-Tolyl phenyl sulphide undergoes partial disproportionation to diphenyl and di-p-tolyl sulphides when treated with aluminium chloride. 14C-Labelling has shown that the disproportionation occurs by the migration of an arylthio- The reaction of diphenyl disulphide with for example triethyloxonium fluoroborate gives (72) (73) and products derived from (73). That the reactions proceed by an intermolecular mechanism was shown by deuteriation studies and 63 C1. Moreau F. Rouessac and J. M. Conia Tetrahedron Letters 1970,3527. 64 H. Kwart and T. J. George Chem. Comm.. 1970,433. 65 T. Fujisawa N. Ohtsuka and G.Tsuchihashi Bull. Chem. SOC.Jupan 1970,43 1189; S. Oae M. Nakai and N. Furukawa Chem. and Ind. 1970 1438. 337 Aromatic Compounds (78) (79) by the isolation of (74) when the reaction was carried out in anisole.66 2-Nitro- benzenesulphenanilides for example (79 undergo unusual thermal rearrange- ments in the presence of an excess of the corresponding amir~e.~' The compounds (76)--(78) were isolated and include a product of intramolecular transfer of oxygen from the nitro-group to sulphur. Reactions of 2-(alkoxyamino)diaryl sulphones such as (79)with sodium methoxide in methanol result in the loss of the H (801 alkoxy-group and the formation of the diphenylamine (80) and the quinone di-imine (81).68 The evidence available indicates that the products do not arise uia nitrenes.Recent aspects of the chemistry of sulphonyl nitrenes have been re~iewed.~' Thermally generated electrophilic aryl nitrenes have been shown to undergo intermolecular substitution reactions with aromatic substrate^.^' The pyrolysis of oxindole at 850 "Cgave benzonitrile together with a number of other products. I3C- and ''C-Labelling experiments have shown that the nitrile carbon is formed almost exclusively from the benzene ring of the oxindole and that the C-3 of " B. Miller and C.-H. Han Chem. Comm. 1970 623. '' F. A. Davis R. B. Wetzel T. J. Devon and J. F. Stackhouse Chem. Comm. 1970 678. 68 M. F. Grundon R. H. Hall R. McD. Hunter and D. J. Maitland Chem. Comrn. 1970 1280. 69 R. A. Abramovitch and R.G. Sutherland Fortschr. Chem. Forsch. 1970 16(1) 1. '* R. A. Abramovitch and E. F. V. Scriven Chem. Comm. 1970 787. 338 H. Heaney oxindole is incorporated into the ring of ben~onitrile.~ ' o-Tolylnitrene is a likely intermediate. Contrary to the general belief aromatic nitro-compounds are reduced to some extent by sodium borohydride in aqueous or aqueous alcoholic alkali to their radical anions.72 The decomposition of arenediazonium ions in acidic methanol proceeds either by a radical mechanism forming the arene or by an ionic mechanism forming the meth~xyarene.~~ The rates of the two reactions are sufficiently similar to suggest that both proceed via a common intermediate. The formation of spirocyclohexadienyl dimer~'~ from the diazonium salts by reaction with sodium iodide in acetone supports a radical mechanism for the interaction of iodide ions with diazonium salts.The free-radical phenylation of hexafluorobenzene results in the formation of 2,3,4,5,6-pentafluorobiphenyl. The relative yields of the product and residue depend on the temperature used for the distillation of the biaryl from the reaction mixture. It was suggested that this supports the view that the biaryl is formed partly by the defluorination of dimers such as (82) during the isolation.76 FF FF c6c15 a0 c6c15 Fm: Ph FF FF CI c1 (82) (83) The preparations of the remarkably stable perchlorotriphenylmethyl-car-banion7' and -carbonium ions7* have been reported. The perchlorotriphenyl- carbonium hexachloroantimonate may be kept under water for several days without significant decomposition.However when it is dissolved in wet methy- lene chloride it is hydrolysed rapidly to (83). The reactions of 2,4-dinitro-1 -naphthyl ethyl ether with n-butyl- and t-butyl- amine have been studied by the stopped-flow method in dimethyl ~ulphoxide.~~ The kinetics show that the first stage involving the formation of for example the intermediate (84) is not base-catalysed and that (84) is rapidly converted EtO. ,&H,Bu' (84) '' R. F. C. Brown and M. Butcher Tetrahedron Letters 1970 3151. l2 M. G. Swanwick and W. A. Waters Chem. Comm. 1970,63. 73 T. J. Broxton J. F. Bunnett and C. H. Paik Chem. Comm. 1970 1363. 74 Ann. Reports (B) 1969 66 356.75 D. H. Hey G. H. Jones and M. J. Perkins Chem. Comm. 1970 1438. 76 P. H. Oldham G. H. Williams and B. A. Wilson J. Chem. SOC.(B),1970 1346. 77 M. Ballester and G. de la Fuente Tetrahedron Letters 1970 4509. '' M. Ballester J. Riera-Figueras and A. Rodriguez-Siurana Tetrahedron Letters 1970 3615. 79 J. A. Orvik and J. F. Bunnett J. Amer. Chem. SOC.,1970 92 2417. Aromatic Compounds 339 into the relatively stable deprotonated ion. The preparation of Meisenheimer complexes involving the addition of an alkyl anion has been reported." Thus 1,3,5-trinitrobenzene reacts for example with tetramethylammonium tetra-n- butylboride and results in the formation of the complex (85). Similarly the complex (86) was obtained in high yield by the reaction with tetramethylammo- nium borohydride.81 Other Meisenheimer complexes have been studied.82 The formation of bicyclic anions for example (87) which was originally thought only to occur with 1,3,5-trinitrobenzene and certain specific ketones has now been found to be much more general.The reaction occurs between a variety of structurally different ketones and keto-esters and various electron-deficient benzenes.' 0-Benzylvanillin(88) has been found to react with sodamide in liquid ammonia to form (90) in 35 % yield.84 It is probable that the intermediate (89) with the negative charge delocalised by the carbonyl group is involved. In view of the difficulties involved in making amino-arylaldehydes this method is promising. A comparison of the rates of methoxydechlorination of 4-chloro-3,4-dinitro- and 4-chloro-3,3'-dinitro-diphenylmethanessuggests the importance of homo- conjugation involving structures such as (91) in stabilising the intermediate PhCH20 - PhCH,O OCHO OMe OMe (88) (89) (90) R.P. Taylor J. Org. Chem. 1970 35 3578. 81 R. P. Taylor Chem. Comm. 1970 1463. E. J. Fendler J. H. Fendler C. E. Griffin and J. W. Larsen J. Org. Chem. 1970 35 287; M. J. Strauss Chem. Comm. 1970,76; E. Bergman N. R. McFarlane and J. J. K. Boulton ibid. p. 51 1. 83 M. J. Strauss T. C. Jensen H. Schram and K. O'Conner J. Org. Chem. 1970,35,383. 84 D. C. Ayres and R. B. Chater Tetrahedron Letters 1970 171 1. 340 H. Heaney in~olved.~’ Nucleophilic substitution reactions in which a formal expulsion of hydride ion occurs have been reported using phenylacetonitrile derivatives and nitrobenzene.86 Compounds of the type (92) and reduction products were obtained.Benzene Isomers. Hexamethyl-‘Dewar’-benzenereacts with cyanogen azide in a time- and temperature-dependent manner and results in the formation of three distinct products [probably (93)-(95)] of skeletal rearrangement.87 The H NC N (93) (94) (95) product formed when t-butylacetylene reacts8’ in the presence of bis(benzoni-tri1e)palladium chloride has been shown not to be a tri-t-butyl ‘Dewar’ benzene- palladium chloride c~mplex.~’ o-Xylylene has never been isolated but its transient existence has been established by Diels-Alder reactions. The ‘Dewar’ analogue (97) has been prepared at ambient temperatures and isolated at low temperatures by the reaction of potassium t-butoxide with the di-toluene-p- sulphonate (96).” Benzynes.1-(2-Carboxyphenyl)-3,3-dimethyltriazine(98) is a new relatively stable non-explosive precursor for benzyne. When a solution of the triazine was heated under reflux in chlorobenzene in the presence of tetraphenylcyclo-pentadienone 1,2,3,44etraphenylnaphthalene was isolated in 80 % yield.’ N-Nitroso-N-acylanilines isomerise in carbon tetrachloride to form aryldiazo- nium carboxylates several of which have been isolated.” These salts may well serve as benzyne precursors. For example a 46 % yield of 1,2,3,4-tetraphenyl- naphthalene was isolated when benzenediazonium p-chlorobenzoate was heated in carbon tetrachloride in the presence of tetracyclone.Similarly the portion- wise addition of crystalline benzenediazonium fluoroborate to tetracyclone 85 S. Clementi V. Mancini and G. Marino Chem. Comm. 1970 1457. 86 M. Makosza and M. Jawdosiuk Chem. Comm. 1970 648. *’ A. G. Anastassiou and S. W. Eachus Chem. Comm. 1970 429 88 Ann. Reports (B) 1969 66 337. 89 K. L. Kaiser and P. M. Maitlis Chem. Comm. 1970 942. yo F. R. Farr and N. L. Bauld J. Amer. Chem. Soc. 1970,92,6695. 91 J. Nakayama 0. Simamura. and M. Yoshida Chem. Comm. 1970 1222. y2 C. Riichardt and C. C. Tan Chem. Ber. 1970 103 1774. Aromatic Compounds 341 potassium acetate and acetic acid in benzene heated under reflux gave the tetraphenylnaphthalene in very good yield.’j Furthermore competition data for reactions of benzyne with mixtures of a number of dienes gave values which were identical with those obtained in reactions involving N-nitro~oacetanilide.’~ On the other hand the failure to isolate a benzyne adduct from the decomposi- tion of N-nitrosoacetanilide in the presence of furan must place the intermediacy of benzyne in doubt in this case.94 However decomposition of N-nitrosoacetanilides is complex,’ and it has been suggested that the decomposition of the aryldiazonium acetates to aryl radicals competes successfully with the decomposition to an aryne in the presence of an excess of N-nitro~oacetanilide.~~ In accord with this view the isolated yield of 1,2,3,4-tetraphenylnaphthalene became 88 % when a cold solution of N-nitrosoacetanilide was added slowly to a solution of tetracyclone in benzene containing potassium acetate at 60 “C.The reactions of t-butyl-substituted benzynes have been reported in which the aryldiazonium ion was the prec~rsor.’~ The thermal decompositions of 3-carboxy- and 4-carboxy-benzenediazonium chlorides have been studied and products were obtained which were rationalised as involving the 1,3- and 1,4-deh~drobenzenes.’~ 7-QuinoIinyne and a-naphtha- lyne show a much reduced selectivity in reactions with bases when compared with 5-quinolinyne and ben~yne.~* The low-yield dimerisation of p-naphthalyne has been reported,” and the anticipated adducts of both a-and P-naphthalyne with benzene have been prepared’” in order to study the di-n-methane rearrange- ments of these compounds.2-Iodophenylazotriphenylmethanehas been shown to decompose to 2-iodophenyl radicals but not to benzyne. lo’ The unimolecular radical elimination of iodine from 2-iodophenyl radicals must therefore be questioned. The photolysis of 1,2-di-iodotetrafluorobenzenein benzene gives rise to products derived both from the 2-iodotetrafluorophenyl radical’02 and from tetrafluorobenzyne.’02b The aryne product is identical to that produced from other precursors involving non-photochemical methods and thus also suggests that the aryne does not arise by the loss of an iodine atom from the 2-iodotetrafluorophenyl radical. The reaction of benzyne with 1,2-dideuteriocyclohexenewas found to give only the product expected from the concerted ene-rea~ti0n.I’~ This result ” C.Riichardt and C. C. Tan Angew. Chem. Internat. Edn. 1970,9 522. 94 J. I. G. Cadogan J. Cook M. J. P. Harger and J. T. Sharp Chem. Comm. 1970 299. 95 G. R. Chalfont and M. J. Perkins J. Amer. Chem. SOC.,1967,89 3054. 9b R. W. Frank and E. G. Leser J. Org. Chem. 1970,35,3932; and references cited therein. 9’ H. E. Bertorello R. A. Rossi and R. H. de Rossi J. Org. Chem. 1970 35 3332; R. H. de Rossi H. E. Bertorello and R. A. Rossi ibid. p. 3328. y8 T. Kauffmann H. Fischer R. Niirnberg and R. Wirthwein Annalen 1970 731 23. 99 C. F. Wilcox and S. S. Talwar J. Chem. SOC.(0,1970 2162. loo H. E. Zimmerman and C. 0.Bender J. Amer. Chem. SOC.,1970,92,4366. lo‘ G. W. Clark and J. A. Kampmeier Chem.Comm. 1970 996. (a)J. M. Birchall R. N. Haszeldine and J. G. Speight J. Chem. SOC.(0,1970 2187; (b) J. P. N. Brewer I. F. Eckhard H. Heaney M. G. Johnson B. A. Marples and T. J. Ward ibid. p. 2569. lo’ G. Ahlgren and B. Akermark Tetrahedron Letters 1970 3047. 342 H. Heaney should be contrasted with that found using triplet excited maleate.'04 The reaction of benzyne with cyclohepttfg]acenaphthene (99) does not result in the (99) 100) formation of a cycloadduct. Dehydrogenation to cycloheptLfg]acenaphthylene (100) occurs possibly by an orbital-symmetry-allowed electrocyclic dehydro- genation. lo5 The previous suggestion lo6 that benzocyclobutene derivatives arise via an allene in the reaction of benzyne with ethoxypropyne receives support from studies of the reactions of benzyne with a number of allenes.lo7 As well as (2 + 2) cycloaddition products ene-type reactions lead to 1,3-dienes or acety- lenes.Some aspects of the chemistry of highly halogenated arynes have been re- viewed.lo* Reactions of arynes with cinnamaldehyde yield flavenes for example benzyne forms (101) while with benzaldehyde tetrachlorobenzyne affords the 2,4-diphenyl-1,3-benzodioxan (102).'09 The cycloaddition reactions of 3,17p-dimethoxyoestra-l(l0),2,4-triene with tetrafluorobenzyne afford enol ethers which are rapidly hydrolysed to ketones,' lo while reaction between 1,3,5- trimethoxybenzene and tetrafluorobenzyne yields after hydrolysis the phenolic CI Ph (103) ( 104) (105) lo4 G.Ahlgren and B. Akermark Tetrahedron Letters 1970 1885. P. Flowerday M. J. Perkins and A. R. J. Arthur J. Chem. Soc. (0,1970 290. lo6 Ann. Reports (B) 1968 65 356. lo' H. H. Wasserman and L. S. Keller Chem. Comm. 1970 1483. 'OM H. Heaney Fortschr. Chem. Forsch. 1970 16(1) 35. lo9 H. Heaney and C. T. McCarty Chem. Comm.. 1970 123. lo I. F. Eckhard H. Heaney and B. A. Marples J. Chem. Soc. (C) 1970,2493. Aromatic Compounds acid (103).' '' Although benzyne has been found not to form cycloadducts with biphenylene low yields of the expected adducts were isolated from reactions with the tetrahalogenobenzynes (104; X = F or C1).'I2 The addition of benzyne to 5,5-dimethoxytetrachlorocyclopentadienegives the acetal (105) in good yield which on hydrolysis decarbonylates spontaneously to form 1,2,3,4-tetrachloro- naphthalene.'I3 The silver-ion effect on the reaction of benzyne with benzene has been noted previously.Similarly the product ratio in the reaction of ben- zyne with cyclo-octatetraene is dramatically affected by trace amounts of silver ions.'14 In the absence of silver (106)is the major product while in its presence (108) is the major product and probably arises uia (107). (107) (108) The full paper on the generation and reactions of benzynequinone has appeared.' ' The suggestion that tropolonyne intermediates may be involved in certain reactions has been verified.'16 Thus the intermediacy of (109) was implicated by the reaction of 3-bromotropolone with potassium t-butoxide in dimethyl sulphoxide in the presence of 1,3-diphenylisobenzofuran.The adduct (1 10) was isolated in good yield. 8-Cyanoheptafulvene reacts with ben- zyne to form the .8 + .2 cycloadduct (1 11) exclusively.' l7 Deuterium-labelling experiments have been used to demonstrate that the cycloadditions of benzyne (109) (1 10) (111) to cyclopentadienyl- and indenyl-magnesium bromide involve the anions. The absence of possible intermediates from two-step ionic mechanisms has been sug-gested as evidence in favour of a concerted .4 + R2s mechanism. ' Interest in the reactions of aryl-lithium compounds with sulphur compounds' ' continues. The reaction of tri-p-tolylsulphonium bromide with p-tolyl-lithium ' ' B. Hankinson and H. Heaney Tetrahedron Letters 1970 1335.'I2 H. Heaney K. G. Mason and J. M. Sketchley Tetrahedron Letters 1970 485. 'I3 J. W. Wilt and A. Vasilianskas J. Org. Chem. 1970 35 2410. 'I4 E. Vedejs and R. A. Shepherd Tetrahedron Letters 1970 1863. 'I5 C. W. Rees and D. E. West J. Chem. SOC.(C),1970 583. 'I6 T. Yamatani M. Yasunami and K. Takase Tetrahedron Letters 1970 1725. M. Oda and Y. Kitahara Bull. Chem. SOC.Japan 1970,43 1920. 'I8 W. T. Ford R. Radue and J. A. Walker Chem. Comm. 1970,966. 'I9 Ann. Reports (B) 1969 66 329. 344 H. Heaney gave 4,4'-dimethylbiphenyl (71.5%) and 3,4'-dimethylbiphenyl (5.1 %). On the other hand the reaction of p-tolyl-lithium with di-p-tolyl sulphoxide gave 3,4'-dimethylbiphenyl (25.6%) and 4,4'-dimethylbiphenyl (31.4 %).I2* These results were interpreted as involving 4-methylbenzyne in the major pathway of the reaction of the sulphoxide.The decomposition of pentafluorophenylmagnesium bromide in dioxan in the presence of a number of transition-metal complexes has led to the isolation of two complexes which may involve aryne-metal bonds. '21 Benzyne reacts with diaryl diselenides and with diaryl ditellurides to cause metalloid-metalloid bond ~1eavage.I~~ The reactions of arynes with triarylphosphines produce betaines which are stabilised by protonation using for example fluorene or by alkylation using for example methyl iodide.'23 Good yields of tetra-aryl- phosphonium salts may be obtained by this method. Non-benzene Systems.-Three- and Four-membered Rings. The reaction of trichlorocyclopropenium tetrachloroaluminate with phenols or anisole at 30-80 "C yields symmetrical para-substituted triarylcyclopropenium chlor-ide~.'~~ At 0-10 "Cdiarylcyclopropenium ions are formed which give diaryl- cyclopropenones after hydrolysis.Monoarylcyclopropenium salts may also be isolated and hence a route to unsymmetrical diarylcyclopropenones or triaryl- cyclopropenium salts is available. The triarylcycloprapenium ion (112) on treatment with triethylamine in chloroform gave the diarylquinocyclopropene (113).'25 The reversible oxidation of bis(p-hydroxyary1)quinocyclopropenes affords radialenes such as (114). The treatment of tetrachlorocyclopropene with phyph :+ I 8 OH tri-n-butyltin hydride effects successive removal of the chlorine atoms.'26 Hydrolysis of the appropriate dichlorocyclopropenes leads to cycloprope-Th e electrolysis of the triphenylcyclopropenium cation results lZo K.K. Andersen S. A. Yeager and N. B. Peynircioglu Tetrahedron Letters 1970 2485. Iz1 D. M. Roe and A. G. Massey J. Organometallic Chem. 1970 23 547. Iz2 N. Petragnani and V. G. Toscano Chem. Ber. 1970 103 1652. lz3 G. Wittig and H. Matzura Annalen 1970 732 97. lz4 R. West D. C. Zecher and G. Goyert J. Amer. Chem. SOC.,1970,92 149. lZ5 R. West and D. C. Zecher J. Amer. Chem. Soc. 1970,92 155 161. Iz6 R. Breslow G. Ryan and J. T. Groves J. Amer. Chem. Soc. 1970,92,988. lz7 R. Breslow and G. Ryan J. Amer. Chern. SOC.,1967,89 3073. Aromatic Compounds in one-electron reduction to the radical which dimerises to give (115) in good yield.The formation of 1,2,4,5tetraphenylbenzene when the diphenyl-cyclopropenyl cation is reduced by the addition of sodium borohydride was mentioned last year.' 29 Inverse addition results in the formation of diphenyl-cyclopropene in high yield. I3O The previously reported hypothesis for the formation of the benzene derivative has been confirmed and diphenylcyclo- propene forms the adduct (116) with 1,4-diphenylisobenzofuran. The reduction of diphenylcyclopropenone by dissolving metals yields tetraphenylresorcinol as the major product. l3' Since diphenylcyclopropenone is completely protonated in sulphuric acid nitration results in rneta-sub~titution.'~~ The reaction of Me Ph diphenylcyclopropenone with 1,3-diphenylisobenzofuran gives the benzo-tropone derivative (117).'33 This reaction may be regarded as being of the type involving a 1,3-dipolar species with a carbonyl ylide.Reactions of enamines and ynamines with diphenylcyclopropenone result in cleavage of the C(2)-C(3) bond. By contrast the reaction of trans-pyrrolidinepropene with diphenyl- cyclopropenethione results in the cleavage of the C(1)-C(3) bond and the forma- tion of (118).' 34 Michael addition of triphenylphosphine to diphenylcyclopro- penone results in the formation of the ketenphosphorane (119).13' Subsequent addition of 2,6-dimethylphenyl isonitrile gave the iminocyclobutenone (120). The conversion of bromocyclo-octatetraene to P-bromostyrene' 36 has been studied and its mechanism established.13' Valence-tautomerism to (121) is 12' T. Shono T. Toda and R. Oda Tetrahedron Letters 1970 369. 129 Ann. Reports (B) 1969 66 344. I3O D. T. Longone and D. M. Stehouwer Tetrahedron Letters 1970 1017. 13' E. A. Harrison Chem. Comm. 1970 982. '32 C. W. Bird and A.F. Harmer Org. Prep. and Proced. 1970 2 79. 33 J. W. Lown T. W. Maloney and G. Dallas Canad. J. Chem. 1970,48 584. 34 J. W. Lown and T. W. Maloney Chem. and Ind. 1970 870. 135 N. Obata and T. Takizawa Tetrahedron Letters 1970 2231. 13' Ann. Reports 1952 49 176. 13' R. Huisgen and W. E. Konz J. Amer. Chem. Soc. 1970 92 4102; W. E. Konz W. Hechtl and R. Huisgen ibid. p. 4104; R. Huisgen W. E. Konz and G. E. Gream ibid. p. 4105. 346 H. Heaney followed by ionisation to the homocyclopropenium salt (122).Ion recombination then leads to the cyclobutene derivative (123) which on conrotatory ring-opening leads to trans-P-bromostyrene. The naphthoquinone-diphenylacetylenephotoadduct (124) can be converted into the dienolate with sodium hydride but on quenching with water the hydroquinone (125) slowly dime rise^.'^^ A polarographic investigation of (125) shows not only that it is difficult to oxidise the compound to the quinone (126) but also that the quinone is even less stable than (125). Strain and substituent effects are thought to be minimal and it is thought that the major difficulty is associated with the antiaromaticity of the cyclobutadiene ring. The o-quinonoid allene (128) has been generated by pyrolysis of the spirobisulphone (127).13’ A number of products were isolated from the pyrolysate including the 1,l’-spirobi- (benzocyclobutene) (129).The anion (130),which should be antiaromatic has been prepared and an approximate pK for (131) obtained. 14* This latter reveals a strong destabilisation in (130). ‘” R. Breslow R. Grubbs and S.-I. Murahashi J. Amer. Chem. Soc. 1970 92 4139. 139 M. P. Cava and J. A. Kuczkowski J. Amer. Chem. Soc. 1970,92,5800. lQo R. Breslow and W. Washburn J. Amer. Chem. SOC.,1970,92 427. Aromatic Compounds Five- Seven- and Nine-membered Rings. Aspects of the chemistry of conjugated cyclic chlorocarbons have been re~iewed.'~' In spite of a high degree of sym- metry a number of fully chlorinated aromatic compounds for example hexa- chlorofulvene have significant dipole moments when measured in benzene solution.These results indicate further the ability of these chlorocarbons to form charge-transfer complexes with the s01vent.l~~ The pyrolysis of bicyclo[2,2,l]hepta-2,5-diene-2,3-dicarboxylicanhydride at 700"Cmainly gives benzocyclobutenone while at 900"C the pyrolysate consists mainly of the fulveneallene (132).143 Cyclopentadienylsodium reacts with a wide variety of S-methyl isothiuronium iodides (133) to form 6,6-diaminofulvenes (1 34) in good yield. 144 6-Aminofulvene-2-aldimines,for example (135),exhibit very fast (132) (1 33) classical aromaticity due to delocalisation of electrons through the hydrogen bond does not exist.'45 The 1 1-adduct (136)of 6,6-dimethylfulvene and dichloroketen is solvolysed to an unexpected tropolone derivative possibly as shown (136)+(1 39).146 Similarly the adduct formed between dichloro- [2-14C]keten and cyclopentadiene is solvolysed to tropolone in which all of the 14C activity was located at positions 3 and 7 (140).147This result supports the above mechanism. (136) (137) (138) (139) A number of oxazole derivatives for example (141),are quantitatively con- verted into acetamidobenzotropones for example (142),with one mole of selenium dioxide. Hydrolysis then affords the corresponding benzotropolones. 14* 14' R. West Accounts Chem. Res. 1970 3 130. 14' I. Agranat H. Weiler-Feilchenfeld and R. M. J. Loewenstein Chem. Comm. 1970 1153. 143 0. A. Marner F. P. Lossing E.Hedaya and M. E. Kent Canad. J. Chem. 1970 48 3606. 144 K. Hartke and G. Salamon Chem. Ber. 1970,103 133. U. Miiller-Westerhoff J. Amer. Chem. Soc. 1970 92 4849. 146 T. Asao T. Machiguchi T. Kitamura and Y. Kitahara Chem. Comm. 1970 89. 147 T. Asao T. Machiguchi and Y. Kitahara Bull. Chem. SOC.Japan. 1970,43,2662. 14' E. Galantay and W. R. J. Simpson Chem. Comm. 1970 754. 348 H. Heaney Electron transfer from cycloheptatriene and bitropyl to tris-(p-bromopheny1)- amminium salts is a convenient synthetic high yield route to tropylium The reaction of 4-phenyl- 1,2,4-triazoline-3,5-dione with tropone affords the normal .4 + 2,cycloadduct whereas with tropolone the compound (143) was ~btained.''~ The reaction of diphenylnitrile imine (144) with tropone leads to the formation of two adducts.The compound (145) is that predicted for the concerted .4 + .6 1,3-dipolar cy~loaddition.'~' The Claisen re-arrangement of tropolone allyl ethers has been little studied. A comparison with the reactions of mesityl ethers may be drawn from the results obtained with 3,5,7-trimethyltropoloneallyl ether (146). The major (75%) product has been shown to be (147) while two minor products were also ~btaged.''~ P-Chloro- glutaryl dichloride reacts with an excess of diazomethane to form the bis-a- diazoketone. This compound decomposes in the presence of copper acetylace- tonate at high dilution in benzene to afford 6-chlorocyclohept-2-ene-1,4-dione. 0 (146) (1 47) Dehydrochlorination then leads to 4-hydroxytropone in good yield.l5 The reaction of 7-hydroxymethylcycloheptatrienewith di-iron nonacarbonyl gave 149 P.Beresford and A. Ledwith Chem. Comm. 1970 15 so T. Sasaki K. Kanematsu and K. Hayakawa Chem. Comm. 1970,82. K. N. Houk and C. R. Watts Tetrahedron Letters 1970 4025. IS2 M. M. A1 Holly and J. D. Hobson Tetrahedron Letters 1970 3423. Is' J. Font F. Serratosa and J. Valls Chem. Comm. 1970 721. Aromatic Compounds heptafulveneiron tricarbonyl (148). The heptafulvene complex reacted with dimethyl acetylenedicarboxylate and gave after dehydrogenation the azulene (149).lS4 The abstraction of a proton from (150) using sodium hydrogen car- bonate yields (15 l).’ ’’ The reaction of bicyclo[5,4,l]dodecapentaenylium COZ Me NC $J (150) fluoroborate with dimethyl malonate in the presence of triethylamine gave a mixture of (152) and (153).Dehydrogenation with chloranil gave the hende- cafulvenes for example (154).’ 56 (152) Me0,CAC02Me (154) (153) Dibenzo(3,4 :5,6)-cyclononatetraene (155) has been prepared by the reaction of 2,2‘-biphenyldicarboxaldehydewith the 1,3-bis-ylide from 1,3-bis-(triphenyl- phosphonio)propane dibromide. 57 Treatment of (155) with n-butyl-lithium generates a non-planar anion which changes slowly at room temperature to the planar aromatic anion (156).ls7“ When a solution of (156) was quenched with water the phenanthrene derivative (1 57) was ~btained.”~“ The potentially aromatic thionin ring system (158) has been ~repared.”~ However the spectral evidence indicates that the thionin ring is non-planar and hence is non-aromatic.D. J. Ehntholt and R. C. Kerber Chem. Comm. 1970 1451. ls5 K. Takahashi N. Hirata and K. Takase Tetrahedron Letters 1970 1285. 156 L. Knothe D. Forster H. Achenbach H. Friebolin and H. Prinzbach Tetrahedron Letters 1970 3075. 15’ (a) P. J. Garratt and K. A. Knapp Chem. Comm. 1970 1215; (b) M. Rabinovitz A. Gazit and E. D. Bergmann ibid. p. 1430. ls8 P. J. Garratt A. B. Holmes F. Sondheimer and K. P. C. Vollhardt J. Amer. Chern. SOC.,1970 92 4492. 350 H. Heaney Cyclophanes and A~ulenes.-A combination of n.m.r. and optical rotation studies have been used to establish the activation parameters for the barriers to ring rotation in the chiral [2,2]metaparacyclophanes (159; R = C0,H or CHO).15' The optical stability of (159; R = C0,H) indicates that only one of the two rings is flipping and an examination of molecular models suggests that the steric barrier to passing the meta- past the para-ring should be consider- ably less than the alternative process.The full account of the preparation of the multilayered [2,2]paracyclophane (1 60) has appeared. 6o The compound is a mixture of symmetric and dissymmetric isomers. (160) Unusual meta-bridged biphenyls have been isolated from a natural source and shown to have the structures (161; X = H,OH or O).I6' Paracyclopha-diynes for example (162) have been prepared and their electronic spectra show the expected transannular interaction between the benzene ring and the con- jugated diyne unit.162 A number of cyclophanes have been prepared by the extrusion of sulphur di0~ide.I~~ These include the conversion of (163) to ls9 D.T. Hefelfinger and D. J. Cram J.Amer. Chem. SOC.,1970,92 1073. 160 D. T. Longone and H. S. Chow J. Amer. Chem. SOC.,1970,92.994. 16' R. V. M. Campbell L. Crombie B. Tuck and D. A. Whiting Chem. Comm. 1970 1206. 16' T. Matsuoka Y. Sakata and S. Misumi Tetrahedron Letters 1970 2549. Ib3 Ann. Reports (B) 1969 66 337. Ih4M. Haenel and H. A. Staab Tetrahedron Letters 1970 3585. Aromatic Compounds 351 The synthesis of hexahydro[2,2,2]phenanthrenophane and hence [2,2,2]phenan- threnophane has been des~ribed.'~~ A number of reports of the synthesis of aza- oxa- and thia-cyclophanes have appeared.166 HO (163) (164) The chemistry of dihydropyrenes has been re~iewed.'~' A new synthesis of trans-15,16-dimethyldihydropyrenehas been reported starting with the anti-dithia[3,3]metacyclophane (165).Conversion into the bis-sulphonium salt and (165) (166) (167) (168) Stevens rearrangement gave a mixture of the [2,2]metacyclophanes (166) which on re-methylation followed by Hofmann elimination gave the metacyclophane (167) isolated as its valence tautomer (168).' 68 It is ofinterest that conformational inversion does not occur during the sequence. A new route to the dithia[3,3]meta- cyclophanes required in the above synthesis involves the desulphuration of for example (169) with tri~(diethy1amino)phosphine.'~~ The first example of a cis-15,16-dihydropyrene has been reported.''O The synthesis uses the principles outlined above and results in the formation of (170). Molecular models suggest 16' R. Paioni and W. Jenny Hefv. Chim. Acta 1970 53 141. 166 F. Vogtle and P. Neumann Tetrahedron Letters 1970 115; Chem. Comm. 1970 1464; F. Vogtle Annafen 1970 735 193. 167 V. Boekelheide Proc. Welch Foundation 1968 XII 83. R. H. Mitchell and V. Boekelheide Tetrahedron Letters 1970 1197. 169 V. Boekelheide and J. L. Mondt Terrahedron Letters 1970 1203. I7O R. H. Mitchell and V. Boekelheide Chem. Comm. 1970 1555. 352 H. Heaney that the ring portion of the molecule has a shallow saucer-shaped geometry and n.m.r. measurements support this view. Further examples of the new synthesis include (171)171 and (172) the first tris-bridged cyclophane in which only two linking atoms are present.17* S S I I S S The photocyclisation of cis-stilbenes such as (173) results in the formation of tetrahydropyrenes for example (174) which are dehydrogenated by D.D.Q.to the trans-l5,16-dihydr0pyrenes.'~~ The syntheses of a series of trans-15,16-dihydr~pyrene'~~" and trans-15,16-dialkyldihydropyrenes174b have been des- cribed. The n.m.r. spectra of the series methyl ethyl and n-propyl are interesting because they provide a map of the magnetic effects due to the ring current.174b Me L I (173) Me (175) The synthesis of the bridged [16]annulene (175) has been re~0rted.l~~ The n.m.r. data on the mixture of derived dianions indicate that although as expected (175) shows the presence of a paramagnetic ring-current it is nonetheless not a satisfactory model for a neutral rigid [4n]annulene having a planar perimeter.V. Boekelheide and P. H. Anderson Tetrahedron Letters 1970 1207. V. Boekelheide and R. A. Hollins J. Amer. Chem. SOC., 1970 92 3512. H. Blaschke C. E. Ramey I. Calder and V. Boekelheide J. Amer. Chem. Soc. 1970 92 3675. l'' (a) R. H. Mitchell and V. Boekelheide J. Amer. Chem. SOC. 1970 92 3510; (b) V. Boekelheide and T. A. Hylton ibid. p. 3669. R. H. Mitchell and V. Boekelheide Chem. Comm. 1970 1557. Aromatic Compounds The chemistry of bridged annulenes has been reviewed. ’ A particularly interesting series of papers from the group at Koln describe the syntheses and some of the chemistry of new bridged annulenes.The bridged 1071-electron analogue of tropone (177) has been ~ynthesised.”~ The key intermediate (176) was dehydrogenated by DDQ. N.m.r. and chemical data support the polyenone structure. However the n.m.r. spectrum of (177) in deuteriotrifluoroacetic acid indicates that the protonated form (178) is aromatic. Bicyclo[5,4,l]dodeca- pentaenylium fluoroborate (179) has been prepared by the reaction of a bis-ylide derived from 1,3-dibromopropane with cycloheptatriene-1,6-dialdehyde. The abstraction of hydride ion then gave (1 80). 78 0 The synthesis of the aromatic 1,6 :8,13-propandiylidene[l4]annulene (184) the n.m.r. spectrum for which was reported last year,’79 has now appeared.I8* The key intermediates in the synthesis are (181)-(183).The next higher homo- logue (185) has been prepared and its n.m.r. spectrum is very similar to that for E. Vogel Proc. Welch Foundation 1968 XII. 215. W. Grimrne J. Reisdorf W. Tunemann and E. Vogel J. Amer. Chem. SOC.,1970 92 6335. ‘78 E. Vogel R. Feldmann and H. Diiwel Tetrahedron Letters 1970 1941. ’79 Ann. Reports (B) 1969 66 351. E. Vogel A. Vogel H.-K. Kubbeler and W. Sturm Angew. Chem. Internat. Edn. 1970 9 5 14. 354 H. Heaney (184).l8 Hence one concludes that the bridge experiences steric deformation rather than the annulene ring. The synthesis of syn-1,6-methano-8,13-oxido[ 141- annulene (188) has been reported.'82 Surprisingly the tetrabromides derived from (186) and from its anti-isomer both gave (187) on dehydrohalogenation.Dehydrogenation with DDQ then gave (188). The n.m.r. spectrum and reactions for example Friedel-Crafts acylation indicate that (1 88) is aromatic. On the other hand the anti-1,6 :8,13-bismethano[l4]annulene(189) deviates so far from planarity that the delocalisation energy is insufficient to equalise the C-C bond lengths.'83 The hydrocarbon (190) reacts with triamminetricarbonyl- chromium to form a complex which on the basis of n.m.r. evidence was formu- lated as the homoaromatic species (191).'84 Similarly the n8s+ .2 cycloadduct formed by the reaction of tetracyanoethylene with the tetraene (192) exists in the open cycloheptatriene form and not as the norcaradiene form.'85 The hydrocarbon (193) reacts with alkali metals to give eventually the dianion (194) the first analogue of a biphenylene in which one of the o-phenylene rings has been replaced by a l0n-electron system.The dianion is however non- aromatic and is probably associated with a barrier to ring-flattening arising from the antiaromaticity of the cyclobutadienyl ring.'86 The photolysis of (195)- (197) at -100°C results in the formation of the very labile [12]annulene (198) and variable-temperature n.m.r. spectroscopy at temperatures between -170 and + 120 "C shows that a mobile equilibrium exists.'87 Perturbation theory predicts that dibenzo[cd,gh]pentalene should be a particularly good model of a 181 E. Vogel W. Sturm and H.-D. Cremer Angew.Chem. Internat. Edn. 1970 9 516. 182 E. Vogel U. Haberland and J. Ick Angew. Chem. Internat. Ed. 1970 9 517. 183 E. Vogel U. Haberland and H. Giinther Angew. Chem. Internat. Ed. 1970,9 513. 184 W.-E. Bleck W. Grimme H. Gunther and E. Vogel Angew. Chem. Internat. Edn. 1970 9 303. ins G. C. Farrant and R. Feldman Tetrahedron Letters 1970 4979. 186 C. S. Baxter P. J. Garratt and K. P. C. Vollhardt J. Amer. Chem. SOC. 1969 91 7783. 187 J. F. M. Oth H. Rottele and G. Schroder Tetrahedron Letters 1970 61 ;J. F. M. Oth J.-M. Gilles and G. Schroder ibid. p. 67. Aromatic Compounds 355 periphery [12]annulene. The first example to be described is the dianion (199) and the n.m.r. spectrum is in accord with this view.' 88 A number of other papers refer to annulene syntheses,' 89 including a slightly improved synthesis of [181annulene.l90 Electrophilic substitutions have been studied further using [181annulene.l Monodehydro[22]annulene has been synthesised and is aromatic 19* as also is the dianion of an octadehydr0[24]annulene.'~~ b a*-(199) Polycyclic Compounds.-The cycloaddition reactions of dimethyl acetylene- dicarboxylate with 1-methoxy- and 1-(NN-dimethylamino)-indeneresult in the formation of cyclobutene derivatives.'94 The dimethylamino-compound under- goes a particularly ready ring-opening to (200). The thermal reorganisation of (201) to (202) has been studied.'95 Deuterium from the seven-membered ring was scrambled in the benzo-ring in re-isolated (201) and a series of 1,Shydrogen (200) shifts were suggested as possibly accounting for the observed results.The thermolysis of (203)takes an interesting course to give (204).'96 Tertiary amines catalyse the tautomeric conversion of (205; R = H) to (206). The methyl and acetyl derivatives (205; R = Me or Ac) are isomerised to the enol ether (207) "' B. M. Trost and P. L. Kinson J. Amer. Chem. SOC.,1970,92 2591. A. B. Holmes and F. Sondheimer J. Amer. Chem. SOC.,1970 92 5284; K. Endo Y. Sakata and S. Misumi Tetrahedron Letters 1970 2557. 190 H. P. Figeys and M. Gelbcke Tetrahedron Letters 1970 5139. lY1 E. P. Woo and F. Sondheimer Tetrahedron 1970 26 3933. 19' R. M. McQuilkin and F. Sondheimer J. Amer. Chem. SOC.,1970,92 6341. 193 R. M. McQuilkin P. J. Garratt and F.Sondheimer J. Amer. Chem. Suc. 1970 92 6682. IY4 T. W. Doyle Canad. J. Chem. 1970,48 1629; 1633. 195 G. W. Gruber and M. Pomerantz Tetrahedron Letrers 1970 3755. 196 R. Criegee and B. Bastani Chem. Ber. 1970 103 3942; J. Ipaktschi ibid. p. 3944. 356 H. Heaney and the nitronic anhydride (208)re~pectively.'~' The isoindene acetal(210) has been generated from the dibromo-compound (209).lg8 Spiroconjugation with the acetal function was suggested in order to account for the long-wavelength OMe Ph Ph X Ph Ph absorption (A,, 537 nm) and for the instability of (210). In the absence of suit-able trapping agents the dimer (21 1) was isolated. The thermal rearrangements of a number of 2,2-diphenyl-methylenecylopropanes,for example (212) have been re~0rted.l~~ The conversion to (214) almost certainly involves the inter- mediacy of (213).In accord with the conservation of orbital symmetry trans-2- benzylidene- 1 -(diphenylmethylene)indane(2 15) undergoes a thermal disrotatory ring-closure followed by a suprafacial [1,5]-hydrogen shift to give (216).200 The w e @Me Ph \' Ph Me \ Ph (212) (214) 197 J. Skramstad Tetrahedron Letters 1970 955. 198 J. M. Holland and D. W. Jones Chem. Comm. 1970 122. I99 M. Jones M. E. Hendrick J. C. Gilbert and J. R. Butler Tetrahedron Letters 1970 845. 20c H. G. Heller and K. Salisbury J. Chem. SOC.(0,1970 399. Aromatic Compounds 3-methyl derivative only gives one product and this indicates that a steric effect determines which of the two possible disrotatory processes occurs.Ph 'Ph (215) (214) The reaction of 2-bromomethyl-2'-iodobiphenylwith methyl-lithium results in the formation of fluorene,201 Evidence was presented which suggests that the cyclisation involves the lithio-compound (217). Persulphate oxidation of o-phenylphenoxyacetic acids (218 ;R = H or Me) generates o-phenylphenoxy- methyl radicals which cyclise onto the neighbouring benzene ring.202 Li CH,.Br 0-CR2.C02H (217) (218) Thermal rearrangements of dimethylvinylidene benzobicyclo[n,l,O]alkenes (n= 3 or 4) have been studied.203 Thus the indene derivative (219; R = H) gave the naphthalene (220; R = H) while (219; R = Me) gave (221) in refluxing benzene but (221) and (222) at 450 "C.On the other hand (223) gave the acetylene (224) at 450 "C. The reactions appear to proceed via concerted processes involving a %-R \ (222) (223) 'c (224) I Y-hydrogen migration from a carbon atom a-to the cyclopropane ring to one of the carbon atoms in the allene residue. The self oxidation-reduction of 1,2- dihydronaphthalenes in 90 %sulphuric acid has been shown to involve carbonium ion rearrangement^.^'^ Thus the compound (225) gives the corresponding normal tetralin and naphthalene derivatives together with about 25-30 % of the products 201 L. J. Altman and T. R. Erdman J. Org. Chem. 1970,353237. 'OL P. S. Dewar A. R. Forrester and R. H. Thomson Chem. Comm. 1970,850. '03 I. H. Sadler and J. A. G. Stewart Chem. Comm. 1970 1588. *04 H.Tournier R. Longeray and J. Dreux Tetrahedron Letters 1970 21. 358 H. Heaney (225) (226) in which methyl groups have been transposed. A low yield of the tetralin (226) derived from one of the suggested carbonium ions was also isolated. The hydrocarbons (227 ;X = C1 Br I or H) isomerise stereospecifically when heated Me Me Me Me Me Me Me (227) (228) (229) at 150 "C and form the vinylnaphthalenes (228; X = Cl Br I or H).205The reactions probably proceed via a series of valence isomerisations and an allylic rearrangement of (229). Certain 2-substituted or-naphthols for example 2-n-propyl- 1-naphthol have been shown to react with diazomethane to give as the major product the azo- compound derived from the coupling of the naphtholate anion with the methane- diazonium ion for example (230).206 Ph OMe Attempts have again been made to prepare a simple derivative of 2,3-naphtho- q~inone.~~' The oxidation of 2,3-dihydroxy-l,4diphenyInaphthalenewith silver oxide or lead tetra-acetate results in the formation of a trimer.When the oxidation was carried out in butadiene at -40°C the adduct (231) was isolated in good yield. A blue pigment obtained from the wood of Diospyros buxifolia has been shown to have the structure (232),208 while a tetrameric naphthoquinone probably '05 R. Criegee C. Schweickhardt and H. Knoche Chem. Ber. 1970 103 960. '06 J. St. Pyrek and 0.Achmatowicz Tetrahedron Letters 1970 2651. '07 D. W. Jones and R. L. Wife Chem. Comm. 1970 1086. 0.C.Musgrave and D. Skoyles Chem. Comm. 1970 1461. Aromatic Compounds (233) was isolated from D. Dehydrogenation of the hydroxyanthrone (234) by DDQ leads to the unstable quinone (235).2'0 A number of papers have reported the elaboration of quinones using cycloaddition reactions of acetylenes with rhodium complexes.2 The complex (236) reacts for example with diphenylacetylene to form the quinone (237). 0 2-Thianorbiphenylene (238) has been prepared and its n.m.r. chemical shift data show the paramagnetic ring-current shielding effect of the [4n]cyclobuta- dienyl ring."' The primary processes in the ion beams of mass spectrometry and in plasmas are apparently similar and this feature has been used prepara- tively in the decarbonylation of fluorenone to bi~henylene.~'~ The reaction of methylmagnesium iodide with the photodimers of 1,4-naphthoquinone affords tetra-ols the dehydration of which gave a fair conversion to 5,6,11,12-tetramethyl- dibenzo[b,h] bip hen ylene (239).Nucleophilic substitution in polynuclear aro- matic fluorocarbons using the anion [(x-C,H,)Fe(CO),] -occurs in accord with 209 K. Yoshihira M. Tezuka and S. Natori Tetrahedron Letters 1970 7. 'lo P. Boldt and A. Topp Angew. Chem. Internat. Edn. 1970 9 164. 2" E. Miiiier and E. Langer Tetrahedron Letters 1970 989 993; E. Miiller E. Langer H. Jakle and H. Muhm ibid.,p. 5271. 212 P. J. Garratt and K. P. C. Vollhardt Chem. Comm. 1970 109. 2'3 H. Suhr and R.I. Weiss Angew. Chem. Internat. Edn. 1970,9 312. 214 N. P. du Preez P.J. van Vuuren and J. Dekker J. Org. Chem. 1970,35 523. 360 H. Heaney previously established tendencies. The reactivity of octafluorobiphenylene is particularly high in this reactiom2 '' Me Me (239) A number of naturally occurring anthraquinones have been synthesised by making use of the cyclisation of the carbanion (240).2'6 A new method of protecting alcoholic functions consists of the conversion to the 9-anthroxy- derivative via the tosylate. Removal of the protecting group can be achieved by singlet oxygen oxidation to the anthracenyl peroxide (241) followed by yNrOMe OR Me0 0 OMe (240) catalytic hydrogenolysis.2 '' The initial reduction product is presumably the hemi-acetal which decomposes spontaneously to the alcohol and 9-hydroxyan- throne.The n.m.r. spectra of a series ofp-quinodimethanes have been reported.21 * The signal disappearance time was used as a measure of their stabilities and as expected 9,lO-anthraquinodimethaneis more stable than 1,4-naphthoquinodi- methane which is more stable than p-quinodimethane. Nuclear Overhauser enhancements have been used to show that the preferred orientation of 9-alkyl groups is pseudo-axial in a series of 9-alkyl-9,lO-dihydroanthra~enes.~ ' Phenanthrene and its 9-alkyl and 9,lO-dialkyl derivatives are efficiently reduced to the 9,1O-dihydro-compounds by lithium in ammonia in the presence of colloidal iron. The disubstituted compounds undergo stereospecific cis-reduc- tion.220 The reduction of pyrene with lithium in liquid ammonia affords 1,9- dihydropyrene (242) one of five predicted theoretically equivalent structures.22 ' M.I. Bruce J. Organometallic Chem. 1970,21 415. '16 C. H. Hassall and B. A. Morgan Chem. Comm. 1970 1345. W. E. Barnett and L. L. Needham Chem. Comm. 1970 1383. 'I8 D. J. Williams J. M. Pearson and M. Levy J. Amer. Chem. Soc. 1970,92 1436. 219 A. W. Brinckmann M. Gordon R. G. Harvey P. W. Rabideau J. B. Stothers and A. L. Ternay J. Amer. Chem. Soc. 1970,92 5912. 220 P. W. Rabideau and R. G. Harvey J. Org. Chem. 1970,35,25. 221 R. G. Harvey and P. W. Rabideau Tetrahedron Letters 1970,3695. Aromatic Compounds 36 1 The reductive methylation of naphthalene is remarkably dependent on the metal used. Thus lithium in liquid ammonia followed by an excess of methyl bromide gave 1 -methyl- 1,4-dihydronaphthalene in high yield while when using sodium cis-1,4-dimethyl-l,4-dihydronaphthalene was the major product.222 The decomposition of dibenzosemibullvalene-l-carboxaldehydetoluene-p-sulphonyl hydrazone (243) with several bases has been investigated.223 The major product in each case was benzo[c]fluorene (244) together with the allene (245).The unique geometry of the semibullvalene nucleus results in the rearrange- ment of the derived carbene principally by a pathway involving a 1,3-aryl shift CH =N.NH.O.SO,.C,H,.Me-p CH2 II 4 qm \ -(243) (244) (245) to what is formally a trans-disposed carbon atom. The reaction between acenaph- thylene and cyclopentadiene under kinetically controlled conditions gives the endo-and exo-Diels-Alder adducts in the ratio 3 :l.224Despite a number of unsuccessful attempts to prepare 1,2-epoxyacenaphthene this compound can be prepared from acenaphthylene using m-chloroperbenzoic acid.22J The protonation of the stereoisomeric spirocyclopropaneanthrones (246) and (247) in 96% deuteriosulphuric acid leads to stable carbonium ions which retain their stereochemistry upon deprotonation.226 The n.m.r.spectra are consistent with the formation of static bridged ions for example (248). The acetolysis of trans-9,1O-bis(hydroxymethyl)-9,1O-dihydrophenanthrenebisto-luene-p-sulphonate gives the rearranged trans-diol (249) under kinetic control. The stereospecificity was attributed to the involvement of the phenonium ion (250).227 The preparation of homotriptycene has been described via the ring lz2 P.W. Rabideau and R. G. Harvey Tetrahedron Letters 1970,4139. 223 L. A. Paquette and G. V. Meehan J. Amer. Chem. SOC.,1970,92 3039. 224 R. Baker and T. J. Baker J. Chem. SOC.(0,1970 596. 225 T. H. Kinstle and P. J. Ihrig J. Org. Chem. 1970 35 257. 226 J. W. Pavlik and N. Filipescu Chem. Comm. 1970 765. 12’ E. Cioranescu M. Banciu M. Elian A. Bacur and C. D. Nenitzescu Annafen 1970 739 121. 362 H. Heaney expansion of the triptycylcarbinyl cation.228 The reaction of l-aminomethyl- triptycene (251) with nitrous acid gave rise to a mixture (252 ;R = OH or OAc). The degeneracy of the ion (253) was established by deuterium labelling. One of the Diels-Alder adducts obtained from an enol-acetate of isophorone and p-benzoquinone (254) undergoes slow acid hydrolysis to give after acetylation a mixture including (256) which undoubtedly arises by a Grob-fragmentation of (255).229 l-(NN-Dimethy1amino)benzobarrelenederivatives rearrange to 4-(NN-dimethy1amino)biaryls on being heated in protic media.230 Thus (257 ; R = H) gives (258) while (257 ; R = Me) gives the cyclohexadienone (259).F (257) (258) (259) The benzo-(CH), hydrocarbon (260) has been prepared and its thermal isomerisation studied.23 The major product is (261). The precise mechanistic 228 S. J. Cristol and D. K. Pennelle J. Org. Chem. 1970 35 2357. lZy J. Wolinsky and R. B. Login J. Org. Chem. 1970,354 1986. 130 H. Heaney and S. V. Ley Chem.Comm. 1970 1184. 23' L. A. Paquette and J. C. Stowell Tetrahedron Letters 1970 2259; E. Vedejs ibid. 1970 4963. Aromatic Compounds details are in doubt. The acidity of the vinylic protons in dibenzobarrelenes has been utilised in the metallation of for example (262).232The lithio-compound is stable at -70 "C but at higher temperatures dimeric and trimeric products were isolated. The trimer is a tri-triptycene. (260) (261) (262) The acid-catalysed hydrogen-exchange of phenalenone occurs at position 2 to afford (263).23 The reaction of ethoxyphenalenium fluoroborate with lithium 1,3-di-t-butylcyclopentadienideresults in the formation of (265)in Me low yield.234 This could have arisen by the intramolecular nucleophilic attack involving the expected compound (264).Protonation of 3,5,8,10-tetramethylace-heptylene in trifluoroacetic acid at -15°C leads by kinetic control to the &!!: (269) 232 C.F. Huebner R. T. Puckett M. Brzechffa and S. L. Swartz Tetrahedron Letters 1970 359. 233 A. A. El-Anani C. C. Greig and C. D. Johnson Chem. Comm. 1970 1024. 23J I. Murata T. Nakazawa and M. Okazaki Tetrahedron Letters 1970 3269. 364 H. Heaney conjugate acid (266) which is dark At room temperature the thermo- dynamically more stable conjugate acid (267) or (268) which is red is formed. Like acenaphthylene the isomeric compound cyclopent[cd]azulene (269) undergoes 1,2-cycloaddition reactions at the double bond in the five-membered ring with for example dimethyl acetylenedicarboxylate.The stable azulenes (270) and (271) are formed.236 The compound (269) also undergoes cycloaddition reactions with carbenes for example with ethoxy~arbonylcarbene.~~~ Valence isomerisation leads directly to the 2H-benzazulene (272). E. Haselbach Tetrahedron Letters 1970 1543. 23b K. Hafner and R. Fleischer Angew. Chem. Internat. Edn. 1970 9 247. 237 K. Hafner and W. Rieper Angew. Chem. Internat. Edn. 1970 9,248.

ISSN:0069-3030    

DOI:10.1039/OC9706700327

出版商:RSC    

年代:1970

数据来源: RSC

摘要:

11 Alicyclic Compounds By B. T. GOLDING School of Molecular Sciences University of Warwick Coventry CV4 7AL and A. P.JOHNSON Department of Chemistry Northern Polytechnic Hollowa y Road London N7 8DB 1 Structure and Conformation General.-Application of the MIND0/2 method to the calculation of shapes of molecules and their heats of formation has produced encouraging results for cyclopentane cyclohexane norbornane bicyclo[2,2,2]octane decalins adaman- tane and steroids.’ A new approach for evaluating strain in cyclic systems has been worked out based on addition of ‘single-conformation’ group increments derived from heats of formation for acyclic alkanes in skew-free conformations.2 Strain energies for numerous alicyclic hydrocarbons are calculated by this method and a surprising conclusion is that adamantane is a strained molecule (strain energy 6.48 kcal mol-’).This is thought to arise from across-ring C--C repulsions and angle strain from which the cage structure allows no respite. The former effect is also present in cyclohexane (estimated strain energy 1.35 kcal mol-I !) but can be partly relieved by bond-angle and torsional-angle deformations. The heats of combustion of several bicyclo[n,m,O]alkanes have been measured3 and their strain assessed by essentially the method of Schleyer.2 Heats of formation molecular geometries and gas-phase thermodynamic functions are then calculated using valence force potential functions developed by the authors. Excellent agreement with the experimental values is ~btained.~ Molecular beam electric deflection* shows that cyclopentane cyclohexane cyclohexa-1,4-diene and cyclododecane are non-polar which is expected from their known conformational properties4 Cyclohexane- 1,4-dione is also non- polar which requires that its conformation be the chair (1) or fully extended N.Bodor and M. J. S. Dewar J. Amer. Chem. SOC.,1970,92,4270. P. von R. Schleyer J. E. Williams and K. R. Blanchard J. Amer. Chem. Soc. 1970 92 2377. ’ S. Chang D. McNally S. Shary-Tehrany M. J. Hickey and R. H. Boyd J. Amer. Chem. SOC.,1970,92 3109. P. Dowd T. Dyke R. M. Neumann and W. Klemperer J. Amer. Chem. SOC.,1970 92 6325; P. Dowd T. Dyke and W. Klemperer ibid. p. 6327. * The deflection of a beam of molecules having a polar ground-state in an inhomogeneous electric field.366 B. T. Golding and A. P. Johnson twist-boat (2) form contrary to some previous conclusions. Cyclo-octane is strongly deflected and is therefore a polar molecule which is to be expected if 0H0 O=Ce=O its dominant form is the boat-chair (C,) conformation suggested by previous workers. There have been several impressive applications of newer n.m.r. techniques. Natural abundance I3C n.m.r. spectra have been published5 for several cyclo- alkanols and cycloalkanones particularly with a view to gaining conformational information. Especially interesting is the discovery that an axial hydroxy- group exerts an appreciable influence (ca. 6 p.p.m. upfield shift) on the position of the C-3 resonance in cyclohexanols.This is ascribed to a steric effect operating through space via the oxygen atom and the axial C-3 hydrogen atom. Applica- tions of shift-reagents [e.g. tris(dipivalomethanato)europium]are mushrooming. Interpretation of the H n.m.r. spectra of several adamantyl alcohols was facili- tated using this shift-reagent6 The first application of INDOR spectroscopy to 0 a3Me 0 (3) the solution of a difficult structural problem has shown that the thermal dimerisa- tion product of the propellane (3)is (4)or (9.'Observation of nuclear Overhauser effects confirms the preferred pseudoaxial disposition of the alkyl group in 0 J. D. Roberts F. J. Weigert J. 1. Kroschwitz and H. J. Reich J. Amer. Chem. SOC. 1970 92 1338; F. J. Weigert and J. D.Roberts ibid. p. 1347; D. E. Dorman S. J. Angyal and J. D. Roberts ibid. p. 1351. A. F. Cockerill and D. M. Rackham Tetrahedron Letters 1970 5149 5153; G. H. Wahl and M. R. Peterson Chem. Comm. 1970 1167. ' 0. Sciacovelli W. von Phillipsborn C. Amith and D. Ginsburg Tetrahedron 1970 26. 4589. Alicvclic Compounds 9-alkyl-9,lO-dihydroanthracenes[e.g. (6)].8 The compound (7) shows an ex- traordinary proton-proton spin-spin coupling of 1 Hz over six saturated bondsg (6) (7) (8) [the first such example was reported last year in compound (8)'']. Application of H n.m.r. to the conformational analysis of cyclic compounds (4--6-membered rings) has been comprehensively reviewed.' Photoelectron spectroscopy is the method of choice for detecting homocon- jugation provided certain conditions are met.' A through-space homoconjuga- tive interaction of -0.68 eV is demonstrated in cis,cis,cis-1,4,7-~yclononatriene (9).The effect had previously been concluded to be absent from (9) after con- sidering the magnitude of its bond lengths determined by X-ray study. Photo- electron spectra for bullvalene (10) and homotropilidene (1 1) are inter~reted'~ in (9) (10) (1 1) terms of a large interaction between Walsh orbitals of the cyclopropyl ring with p-orbitals of the double bonds in (lo) but such an effect is negligible for (11). Only the geometry of bullvalene permits the favourable bisected configuration (4.v.)for maximum cyclopropyl-p overlap. Photoelectron spectra for a series of cycloalkenes and cycloalkadienes have been reported and inter~reted.'~ A graphical method has been presented whereby the number and structure of and CZn+ cyclopolyenes (C2,,HZn 1H2,,+2)can be derived.I5 Optically active 3-methylcyclobutene has been synthesised.' Its absolute configuration deduced from the sign of its Cotton effect near 200 nm and using the olefin octant rule" agrees with that assigned on the basis of synthesis and ' A.W. Brinkmann M. Gordon R. G. Harvey P. W. Rabideau J. B. Stothers and A. L. Ternay J. Amer. Chem. Soc. 1970,92 5912. J. E. Baldwin and R. K. Pinschmidt J. Amer. Chem. Soc. 1970,92 5247. lo C. H. M. Adams and K. Mackenzie J. Chem. Soc. (0,1969,480. H. Booth Progr. N. M. R. Specrroscopy 1969 5 149. P. Bischof R. Gleiter and E. Heilbronner Hefu.Chim. Acta 1970 53 1425. l3 P. Bischof R. Gleiter E. Heilbronner V. Hornung and G. Schroder Hefu. Chim. Acta 1970 53 1645. l4 P. Bischof and E. Heilbronner Heh. Chim. Acta 1970 53 1677; D. A. Demeo and A. J. Yendra J. Chern. Phys. 1970,53,4536. A. T. Balaban Rec. Rnumaine Chim. 1070 15 463. I' R. Rossi and P. Diversi Tetrahedron 1970 26 5033. I' A. I. Scott and A. D. Wrixon Tetrahedron 1970 26 3695. 368 B. T. Golding and A. P. Johnson degradation.' An exception to Brewster's rule ( +)-(lR,8R)-trans-bicyclo-[6,l,O]nonane has been firmly established.'* The principles of conformational analysis have been reviewed by Barton. Three-and Four-membered Rings.-The structure of methylenecyclopropane deduced from its microwave spectrum shows the CH,-CH bond to be long (0.1542nm) whilst the double bond has a length (0.1332nm) similar to that in isobutene.,' The extent of cyclopropyl conjugation with a carbonyl group has been evaluated for two possible orientations [(12) and (13)] using chemical shift data obtained from models of fixed geometry [e.g.(14) for (12); (15) for (13)].,' (121 (13) (14) (15) The results support the hypothesis of maximum delocalisation in the bisected conformer (12). Conjugation in (13) is shown not to involve preferential overlap with the o-bond lying over the p-orbital. A complete analysis of the 'Hn.m.r. spectrum of cyclobutane was facilitated using a nematic solvent and gives a value of 27" for the ring-puckering angle.22 A study of conformational equilibria in cis-and trans-3-t-butylcyclobutanol and ethyl 3-t-butylcyclobutanecarboxylate shows the cis-isomers to be enthalpy favoured whilst the trans-isomers are entropy favoured.23 This result is explained by postulating relatively rigid puckered cis-isomers but somewhat flexible trans-isomers.Five- and Six-membered Rings.-Electron diffraction has been used to study pseudorotation in ~yclopentane~~ and to study the structure of 6,6-dimethyl- fulvene2' (planar with bond lengths similar to those in butadiene). The structures of a series of cyclohexane derivatives have been calculated by a 'full relaxation molecular mechanics approach'.26 Agreement with experimentally determined parameters for similar compounds is very good. Of particular interest is a cal- culation for t-butylcyclohexane.The region around C-4 is found to resemble closely a ring position in cyclohexane. However distortions are apparent in the vicinity of the t-butyl group. One consequence is that axial hydrogen atoms at C-2 (C-6) are less hindered than those equatorial which explains the finding Itl T. Aratani Y.Nakanisi and H. Nozaki Tetrahedron 1970,26,4339. l9 D. H. R. Barton Science 1970,169 539. 2o V. W. Laurie and W. M. Stigliani J. Amer. Chem. SOC. 1970,92 1485. 21 S. A. Monti J. Org. Chem. 1970,35 380. 22 K. Wuthrich S. Meiboom and L. C. Snyder,J. Chem.Phys. 1970,52,230;S. Meiboom and L. C. Snyder ibid. p. 3857. 23 G. M. Lampman G. D. Hager and G. L. Couchman J. Org. Chem. 1970,35,2398. 24 W. J. Adams H. J. Geise and L.S. Bartell J. Amer. Chem. SOC. 1970,92 5013. 25 J. F. Chiang and S. H. Bauer J. Amer. Chem. SOC., 1970,92,261. 26 C. Altona and M. Sundaralingam Tetrahedron 1970,26 925. A licyclic Compounds that a hydroxy-group vicinal to t-butyl prefers to be Unusual orders of chemical reactivity are seen in the epimeric 2,5-di-t-butylcyclohexanolsand some of their derivatives and are explained as a consequence of torsional effects and conformational distortions.2 A high inversion barrier (AG!, 17.3 f0-1kcal mol- ') for all-cis-hexamethyl- cyclohexane (1 6) presumably results from torsional interactions and suggests the possibility of resolving certain highly alkylated cyclohexane derivatives2 Alternative pathways for ring inversion of octafluorocyclohexene are discussed in detail.29 Replacing the carbonyl group in 3,3,5,5-tetramethylcyclohexanone by methylene raises the inversion barrier from AG* < 5 kcal mol-' to 7.7 kcal mol- ' 30 (cJ earlier findings for cyclohexanone and methylenecyclo-hexane3').The inversion barrier 10.7 kcal mol- ') for dispiro[2,2,2,2]- decane (17) is very similar to that of cy~lohexane.~~ Me Me An investigation of the magnitude of 1,3-diaxial interactions between sub- stituents in 2,9-disubstituted trans-decalins shows that these bear no simple relationship to the conformational preference of the groups individually. The 1,3-diaxial interactions for CH,--CN CH,--OH and CH3--CO2CH3are 2-66 2.65 and 2.75 kcal mol -' respectively. Equilibria in a variety of substituted cyclopentene and cyclohexene derivatives have been in~estigated.,~ The effect of double-bond substitution can be pre- dicted from the additivity of empirical values for two effects :conjugative stabilisa- tion us.destabilising cis interactions. Some surprising stabilities are observed [e.g. for (18) *(19) dG2gg = -1.2 kcal mol-'I. OMe OMe '' D. J. Pasto and D. R. Rao J. Amer. Chem. SOC.,1970,92 5151. 28 H. Werner G. Mann M. Muhlstadt and H-J. Kohler Terrahedron Lerrers 1970 3563. 29 J. E. Anderson and J. D. Roberts J. Amer. Chem. SOC.,1970,92,97. 30 J. St. Jacques M. Bernard and C. Vaziri Canad. J. Chem. 1970,48,2386. 31 J. T. Gerig and R. A. Rimerman J. Amer. Chem. Soc. 1970,92,1219. 32 J. B. Lambert J. L. Gosnell D. S. Bailey and L.F. Greifenstein Chem. Comm. 1970 1004. 33 M. Tichy A. Orahovats and J. Sicher CON.Czech. Chem. Comm. 1970,35,459. 34 S. J. Rhoads J. K. Chattopadhyay and E. E. Waali J. Org. Chem. 1970 35 3352; S. J. Rhoads and E. E. Waali ibid p. 3358. B. T.Golding and A. P. Johnson The microwave structure of cyclohex-2-en-1-one has been interpreted in terms of a probable structure in which 0,C-1-C-4 and C-6 are coplanar with C-5 deviating from the plane.35 'H n.m.r. studies suggest that the conformation of 1,4-dihydrobenzoic acid36 is a puckered boat (20) with pseudo-equatorial sub- stituent [cf ref. 4 and Ann. Reports (B) 1969 66 p. 3621. The chemical shift of -CHBr in a-bromocyclohexanones is a reliable measure of configuration and conf~rmation.~ ' Complementary information can be obtained from i.r.spectra of such compounds using the integrated intensity of the 1433cm-' band (-CH adjacent to axial halogen) as a measure of the proportion of the axial form.38 A systematic discrepancy is observed between the proportion of axial form in 4-halogenocyclohexanones determined by n.m.r. and that derived from dipole moment measurements (e.g.4-bromocyclohexanone in cyclohexane has 60% axial form by n.m.r. but only 31 "/ as calculated from its dipole moment).39 The differences may arise through failing to take account of deformation in the axial form in the calculation based on dipole moment. Seven-membered and Larger Rings.-A molecular orbital picture using the Walsh representation of cyclopropane qualitatively explains the stabilisation of norcaradienes relative to cycloheptatrienes by electron-accepting substituents at C-7 [e.g.by CN in (2l)]."' Temperature-dependent magnetic non-equivalence in the geminal fluorine atoms of (22) permits its rate of valence tautomerism through (23) to be mea~ured.~' The free-energy change in going from (22) to (22) (23) (23)is estimated to be 6 kcal mol-'.Accepting the estimated difference between cycloheptatriene and norcaradiene to be 11 kcal mol-' leads to an approximate value of 17 kcal mol-' for the change in energy between the two forms brought about by introduction of a di~yano-group.~' Conformational isomers [(24) (24) (25) 35 S. A. Manley and J. K. Tyler Chem. Comm. 1970 382. 36 J. L. Marshall K.C. Erikson and T. K. Folsom J. Org. Chem. 1970 35,2038. 37 A. Baretta J. P. Zahra B. Waegell and C. W. Jefford Tetrahedron 1970,26 15. 38 J. Reisse J. P. Bervelt C. Cuvelier R. Ottinger and P. Peters Tetrahedron 1970 26 2563. 34 F. Loustalot M. Loudet S. Gromb F. Metras and J. Petrissans Teirahedron Letters 1970 4195. 40 R. Hoffman Tetrahedron Letters 1970 2907; cf. H. Gunther ibid p. 5173. 41 H. J. Reich E. Ciganek and J. D. Roberts J. Amer. Chem. Soc.. 1970 92 5166. Alicyclic Compounds 371 (25),AG = -0.78 kcal mol -'3 of 7-cyanocycloheptatriene have been observed by low-temperature n.m.r.42 Electron diffraction reveals a dihedral angle of 37.8" between the olefinic groups of cyclo-octa-1 ,3-diene.43 From a variable-temperature n.m.r.study other physical data and symmetry considerations 4,4,7,7-tetramethylcyclo-nonanone and some of its derivatives are deduced44 to exist almost exclusively in a twist-boat-chair conformation (26) [the form calculated to be most stable for cyclon~nane]~~ in the solid and in solution. In contrast to cyclotetradecane which prefers a diamond-lattice conformation (27) in all phases cyclohexadecane is conformationally heterogeneous in solution although in crystals at -60 "Ca single diamond-lattice conformer (28) is considered to be present.46 Cyclotetra- decane-1,8-dione is conformationally homogeneous ; the carbonyl groups are suggested to prefer the positions shown (29) because gauche interactions with corner hydrogen atoms are thereby eliminated.It is suggested that this effect could be an important factor in determining conformational preferences of some large rings.46 Certain derivatives of cycloeicosane but not 14- 16- 18- 22- and 24-membered rings exhibit remarkable properties in occluding a variety of solvent m01ecules.~' Sublimed 4,4,8,8,14,14,18,18-octamethylcycloeicosane-l,ll-dione rapidly absorbs water from the air ! The hydrated species is suggested to possess conformation (30) with a water molecule bridging two carbonyl groups by hydrogen bonds to their n-bonds. 42 C. H. Bushweller M. Sharpe and S. J Weininger Tetrahedron Letters 1970 453. 43 M. Ttaaetleberg Acta Chem. Scand. 1970,24 2285. 44 G. Borgen and J. Dale Chem. Comm. 1970 1105. 45 J. B. Hendrickson J.Amer. Chem. SOC. 1967 89 7036 7043 7047; M. Bixon and S. Lifson Tetrahedron 1967 23 769. 46 G. Borgen and J. Dale Chem. Comm. 1970 1340. 47 G. Borgen and J. Dale Chem. Comm. 1970 1342. B. T. Golding and A. P. Johnson The 'H n.m.r. spectrum of [12]annulene (4.0.)at -170 "C proves that it then exists as [121-21-annulene (31) sustaining a paramagnetic ring-~urrent.~~ At -80 "Cthe molecule undergoes an isodynamical conformational change uia simultaneous rotation about all single bonds which causes all protons on trans-double-bonds to become equivalent as do all protons on cis-double-bonds. The very low activation barrier for this process (AG; 73 5.5 0.1 kcal mol- ') is expected because severe overcrowding of internal hydrogen atoms in (31) causes the molecule to be non-planar.Explanation of certain reactions of [12]annulene requires the postulate of another conformation (32) in dynamic equilibrium with (31). However this form could not be detected in the 'H n.m.r. ~pectrum.~~ (31) (32) Bicyclic and Tricyclic Systems.-Ab initio SCF calculations lead to a new model for bonding in bicyclo[ l,l,O]butane (33).49 The central bond is described as almost pure p which is also predicted for the unknown propellane (34). An electron diffraction study5' of bicyclo[l,l,l]pentane (35) reaches a similar conclusion in suggesting that C-1 and C-3 are almost sp2 hybridised with consequent overlap of p from C-1 with p from C-3. This is indicated by the C-1-4-3 distance (0.1845 nm the smallest 'non-bonded' C-C distance on record).The C-14-3 interac- tion may be connected with the known long-range H-1-H-3 coupling constant (18 Hz) and the reactivity of the system at the bridgehead. Exact structures have been determined for bicyclo[2,1 ,O]pentane (36) [by electron diffra~tion]~ and bicyclo[2,l,O]pentene (37) [by microwave spectro~copy].~~ The former has two remarkable bond lengths C-1-C-4 (0.1439 nm) is the shortest C-C length observed in any saturated organic system whilst C-24-3 (0.1622 nm) is almost the longest." The structure of (37) is quite different in that C-1-C-4 is long (0.156 nm) whilst C-24-3 is short (0-134 nm).52 Both systems readily undergo 48 J. F. M. Oth H. Rottele and G. Schroder Tetrahedron Letters 1970,61;J. F. M. Oth, J-M.Gilles and G.Schroder ibid p. 67. 4q J. M. Schulman and G. J. Fisanick J. Amer. Chem. SOC.,1970,92,6653. J. F. Chiang and S. H. Bauer J. Amer. Chem. SOC.,1970,92 1614. R.K. Bohn and Y-H. Tai J. Amer. Chem. SOC.,1970,92,6447. s2 S. L. Hsu A. H. Andrist T. D. Gierke R. C. Benson W. H. Flygare and J. E. Baldwin J. Amer. Chem. SOC.,1970 92 5250. A licyclic Compounds cycloadditions at the bridging bond. Electron diffra~tion~~ reveals that hexa- methyl Dewar-benzene has the longest known C-C bond length (C-1-44 0463 nm). This molecule appears to be undergoing twisting motions which it is suggested could facilitate the attainment of a C2structure approximating to two ally1 radicals required for a concerted thermal rearrangement to benzene. In addition to their study of cyclohexanes,26 Altona and S~ndaralingam~~ have carried out similar calculations of geometry in norbornanes particular attention being paid to the size of torsional angles.Some startling distortions from C, symmetry are recognised in one 2-endo-3-exo-disubstitutednorbornane the shape of the five-membered ring carrying the substituents is nearly half way between envelope and half-chair. In derivatives of bicyclo[3,l,l]heptane pinching together C-1 and C-5 by a bridging atom causes an inverse reflex effect55 whereby substituents at C-2 and C-4 lean away from each other and C-3 tends to move into the plane containing C-1 C-2 C-4 and C-5 (Figure). Thus examination of 6,6-dimethylbicycl0[3,1,1]-heptan-2- and -3-01s by ‘H n.m.r.spectroscopy shows them to exist in either a IY6 -1 Figure Inverse refex effect v flattened boat (38) or flattened chair (39) form depending on the configuration of the hydroxy-group and the configuration of a C-2-methyl group (when pre- ~ent).’~,~~ Examples are a-nopinol which prefers a boat (40) and P-nopinol which is a chair (41). A similar study of bicyclo[3,l,l]heptan-2- and -3-ones has also been p~blished.~’ The conclusions are supported by calculations using empirical potential function^.^^ From an electron diffraction study” of bicyclo[2,2,2]octane it was concluded that the molecule possesses a ‘quasi-D,,’ structure since it is undergoing twisting motions through a broad potential well having a hump of ca. 100 cal mol- at D, symmetry. endo-Bicyclo[3,3,l]nonan-3-ol,according to an n.m.r.study,60 ” M. J. Cardillo and S. H. Bauer J. Amer. Chem. SOC. 1970,92 2399. 54 C. Altona and M. Sundaralingam J. Amer. Chem. SOC. 1970,92 1995. 5s C. W. Jefford and U. Burger Chimia (Switr.),1970,24,385;C. W. Jefford A. Baretta J. Fournier and B. Waegell Helv. Chim. Acta 1970,53 1180. 56 A. J. Baretta C. W. Jefford and B. Waegell Bull. SOC. chim. France 1970,3899. 57 A. J. Baretta C. W. Jefford and B. Waegell Bull. SOC.chim. France 1970,3985. 58 J. Fournier and B. Waegell Tetrahedron 1970 26 3195. ’’ A. Yokozeki K. Kuchitsu and Y. Morino Bull. Chem. SOC.Japan 1970,43,2017. 6o M. Fisch S. Smallcombe J. C. Gramain M. A. McKervey and J. E. Anderson J. Org. Chem. 1970 35 1886. 374 B.T. Golding and A. P. Johnson prefers a chair-boat conformation (42). The preference of the parent hydrocarbon for a chair-chair conformation is clearly disturbed by the hydroxy-group. Preliminary studies of conformational equilibria in bicyclo[3,2,2]nona-6,8-diene and some of its derivatives6' and in bicyclo[3,3,3]undecane (manxane)62 have been reported. 2Synthesis General.-The Ziegler-Th~rpe~~ and Dieckmann reactions64 and acyloin condensation^^^ have been reviewed. A general cycloalkanone synthesis utilises the intramolecular alkylation of 2-chl0ro-l-olefins~~ (cf Scheme 1). The chloroalkene unit survives a variety of pc' ____, 9o~~so4Po \ Me0 \ Me0 Scheme 1 other synthetic operations and the cyclisation can be left to a late stage of a synthesis.The intramolecular addition of an organometallic reagent to a car- bony1 group has never been developed to a useful level because of the difficulty encountered in the conversion of a halogeno-carbonyl compound into a reactive organometallic derivative. The use of dialkylcopper lithium reagents overcomes this difficulty with vinyl halides as shown in Scheme 2. For alkyl halides the preferred reagent is the anion (NiTPP2-) prepared by the reaction of nickel tetraphenylporphine with lithium-naphthalene.66 I I Me OH n= lor2 Scheme 2 61 A. J. Baker A. M. Chalmers W. W. Flood D. D. MacNicol A. B. Penrose and R. A. Raphael Chem. Cumm. 1970 166. 62 M. Doyle W. Parker P. A. Gunn J. Martin and D. D. MacNicol Tetrahedron Letters 1970 36 19.63 E. C. Taylor and A.McKillop Adv. Org. Chem. 1970,7 1. 64 H. Kwart and K. King in 'Chemistry of Carboxylic Acids and Esters' ed. S. Patai Interscience New York 1969 p. 341. 65 P. T. Lansbury E. J. Nienhouse D. J. Scharf and F. R. Hilfiker J. Amer. Chem. Soc. 1970,92 5649. 66 E. J. Corey and I. Kuwajima J. Amer. Chem. SOC.,1970 92 395. Alicyclic Compounds 375 Three and Four-membered Rings.-A convenient synthesis of cyclopropyl ketones utilises the reaction of y-hydroxy-ketones with dicyclohexylcarbodi- imide.67 An effective modification of the Simmons-Smith reaction employs a mixture of cuprous salt and zinc in place of pre-formed zinc-copper couple.68 Thermolysis of phenyl(fluorodichloromethy1)mercury is a useful method for generating fluorochlorocarbene.69 Details have appeared of the preparation and synthetic applications of (dimethy1amino)phenyloxosulphoniummethylide (43),an alternative to dimethyloxosulphonium methylide as a methylene transfer reagent.70 Similarly thetin anions such as (44) react with electrophilic olefins to form cyclopropanecarboxylic acids.7 The carbene complex [(CO),CrC(OMe)- Ph] transfers methoxyphenylmethylene to trans-methyl crotonate yielding isomers (45) and (46).72 0 C02Me Ph COzMe OMe + !I -+-Ph -S-C H 2 Me,S-CH-CO; HyOMe HyPh I NMe Me Me (43) (44) (45) (46) Thermolysis of trimethylcyclopropylammonium hydroxide at 60 “C and under reduced pressure gives cyclopropene in 70 % yield.7 Diphenylcylopropenyl fluoroborate is converted to 1,2-diphenylcyclopropeneby reduction with sodium b~rohydride.~~ Previous attempts to effect this reduction led only to 1,2,4,5-tetraphenylbenzene but apparently the key to success is inverse addition to the boro hydride.Photochemical routes to cyclopropane derivatives include the synthesis of a cyclopropanone precursor (47) by irradiation of (48) in t-butyl alcohol75 and the synthesis of cyclopropanyl ethers from ally1 ethers.76 0 OEt (47) (48) Spectroscopic and chemical evidence has been presented for the formation of free alkyl-substituted cyclobutadienes by irradiation of (49) in a tetrahydrofuran matrix at -196 0C.77 The reaction of trans-dibromo-cyclobutene with zinc- ‘’ C. Alexandre and F. Rouessac Tetrahedron Letters 1970 101 1.68 R. J. Rawston and I. T. Harrison J. Org. Chem. 1970,35 2057. b9 D. Seyferth and K. V. Darragh J. Org. Chem. 1970,35 1297. ’O C. R. Johnson M. Haake and C. W. Schroeck J. Amer. Chem. Sac. 1970,92,6594. 71 J. Adams L. Hoffman and B. M. Trost J. Org. Chem. 1970 35 1600. ’’ E. 0.Fischer and K. H. Doetz. Chem. Ber. 1970,103,1273. 73 D. A. Archer Tetrahedron Letters 1970 1325. 74 D. T. Longone and D. M. Stehouwer Tetrahedron Letters 1970 1017. ” T. H. Koch and R. J. Sluski Tetrahedron Letters 1970 2391. 76 J. J. Brophy and G. W. Griffin Tetrahedron Letters 1970 493. 77 G. Maier G. Fritschi and B. Hoppe Angew. Chem. Internat. Edn. 1970,9 539. B. T. Golding and A. P.Johnson DMF or lithium amalgam leads to cyclobutadiene which may be trapped by reactive dienes or dienophiles.' Cyclopropyldiphenyl sulphonium ylide (50) (49) (50) (51) (52) reacts with cyclohexanone to give spiro[3,5]nonan-6-one (5 l) presumably via the spiro-epoxide (52)." Five- and Six-membered Rings.-Derivatives (53) of cyclopentane are available by the reaction of hex-5-enylmercuribromides (54)with iodine.'' Details have appeared of the Claisen rearrangement of 3,4-dihydro-2H-pyranylethylenes, CHgBr :r-JX;. RZ R 0 (53) (54) (55) (56) [(55)-+(%)I a useful method for the synthesis of some cyclohexenes which are not accessible by the Diels-Alder reaction.8 Metal-ammonia reduction of NN-dimethy ladines leads directly to the corresponding cyclohexa- 1,3-diene [(57)-+(58)] which can be alkylated exclusively at the 2-p0sition.*~ G2 6'6 M(JMe Me Me \ C1/"CMe3 CMe3 (57) (58) (59) (60) N-t-Butyl-p-toluidine may be converted in high yield to the Schiff's base of 4-methoxy-4-methylcyclohexa-2,5-dienone (60)by treatment of the corresponding chloramine (59)with silver ions in methanol.83 Medium and Large Rings.-Photosensitised dimerisation of 1,2-dimethylene-cyclobutane gives (61) and other Heating (61)at 330 "Cyields 1,2,5,6- l8 E.K. G. Schmidt L. Brener and R. Pettit J. Amer. Chens. SOC.,1970 92 3240. 79 B. M. Trost R. La Rochelle and M. J. Bogdanowicz Tetrahedron Letters 1970 3449. 8o M. Julia and E. Colomber Compt. rend. 1970 270 C 1305. " G. Buchi and J. E. Powell J. Amer. Chem. Suc. 1970,92 3126. *' A. J. Birch E. G. Hutchinson and G.Subba Rao Chem. Comm. 1970,657. 83 P. G. Gassman and G. A. Campbell Chem. Comm. 1970,427. 84 W. T. Borden L. Sharpe and 1. L. Reich Chem. Comm. 1970,461. A licyclic Compounds tetramethylenecyclo-octane. Following an earlier observation' that solvolysis of exo-8-bromobicyclo[5,l,O]octanegave trans-cyclo-octen-3-01 in accordance with 0 (61) orbital symmetry predictions several trans-cyclo-octenes [e.g. (63) from (62)]86 and trans-cyclononenes have been synthesised by a modification of this route which utilises silver ions to promote the As expected endo-8-bromobicyclo[5,1,0]octane gives cis-cyclo-octen-3-01 on treatment with aqueous silver ions.86 OMe (63) (62) The silver-ion-assisted methanolysis of the dibromocarbene adduct (64) of cyclo-octa- 1,5-diene is stereospecific leading to a single diastereomer -the methyl ether (65),by capture of the intermediate allylic species on the same side as the departing The oxy-Cope rearrangement of 1,2-divinylcyclo-hexanol is the basis of a synthesis of cyclodec-5-en-l-one.89 trans-l,2-Divinyl- Rr cyclohexanol (66) gives exclusively trans-cyclodec-5-en-1 -one (67) but the cis-isomer (68)gives a mixture of (67) and (69) the former predominating.Similarly pyrolysis of cis-1,2-divinyl-1,2-cycloalkanediols (70 n = 6 and 10) gives rise to the corresponding 1,6-cycloalkanediones (7 l).'O (66) (67) (69) 85 G. H. Whitham and M. Wright Chem. Comm. 1967,294. 86 C. B. Reese and A. Shaw J. Amer. Chem. Sac. 1970,92,2566. '' C. B. Reese and A.Shaw Chem. Comm. 1970 1365 1367. 88 D. Duffin and J. K. Sutherland Chem. Comm. 1970,626. 89 E. N. Marvel1 and W. Whalley Tetrahedron Letters 1970 509. P. Leriverend and J. M. Conia Bull. SOC. chim. France 1970 1040. B. T. Golding and A. P.Johnson OH (70) (71) The nickel complex (72)reacts with isonitriles to give 40-70 % of a mixture of cyclic imines (73) and (74) which on treatment with acid afford all-trans-3,7,11- cyclotridecatrien- 1 -one 11-vinyl-trans-3,7-cyclodecadien-1-one and isomers pro- duced in the hydrolysis.” With t-butyl isonitrile the ratio C ,-ring :C,,-ring products is 3 :97 whilst with cyclohexyl isonitrile a ratio of 83 :17 is observed. The peroxide route to macrocyclic rings has been extended to the synthesis of cycloalkanes via triperoxides (Scheme 3).92 Cyclotridecane derivatives (76) are 0 0IQOH 0 6 9-2 1A or hv (C@ + (19 Scheme 3 00 formed by the action ofaqueous base on (79 which is itself made in several steps from the main photoadduct (77) of cyclododecene and dichlorovinylene car-bonate.’ (75) (76) R = H and Me.9’ H. Breil and G. Wilke Angew. Chem. Internat. Edn. 1970 9 367. 92 P. Busch and P. R. Story Synthesis 1970 181. 93 H.-D. Scharf and R. Klar Annalen 1970,739 166. A licyclic Compouna's 379 Bicyclic Systems.-A stable bicyclo[4,2,0]octa-2,4,7-tEiene (78) is the product of the photochemical decarbonylation of (79).94 A useful entry into the bicyclo[3,1,1]- heptane series is the base-induced conversion of 2-methyl-2-dichloromethylcyclo-hexanones such as (80) into derivatives of 1 -methylbicyclo[3,l,l]heptan-6-one (81).95 Details have appeared of the synthesis and chemistry of bicyclo[3,3,1]-n~n-l-ene.~' Even more extreme violators of Bredt's rule are bicyclo[3,2,2]- 397 Me Me non-1-ene (82) and bicyclo[3,2,2]non-l(7)-ene (83) which have been made by the pyrolysis of bicyclo[3,2,2]nonan-l-yltrimethylammoniumhydr~xide.~' They are only stable at -70 "C and dimerise at room temperature.Applications of the Conia thermocyclisation include a synthesis of bicyclo[3,3,1]nonan-9-ones 0 H CH,CH,CH=CH, 6 [(84)from (85)]and bicyclo[3,3,l]nonan-2-ones[(86)from (87)].99 Several hydrin- danes and hydroazulenes have been prepared by stereospecific ring-closures of medium-ring systems (Scheme 4).100-102 94 1.W. McCay and R. N. Warrener Tetrahedron Letters 1970 4779. 95 E. Wenkert P. Bakuzis R. J. Baumgarten D. Doddrell P. W. Jeffs C. L. Leicht R. A. Mueller and A. Yoshikoshi J. Amer. Chem. SOC. 1970 92 1617. 96 J. A. Marshall and H. Faubl J. Amer. Chem. SOC.,1970,92,948. 97 J. R. Wiseman and W. A. Pletcher J. Amer. Chem. SOC.,1970,92,956. 98 J. R. Wiseman and J. A. Chong J. Amer. Chem. SOC. 1969,91,7775. 99 F. Leyendecker G. Mandville and J. M. Conia Bull. SOC. chim. France 1970 549 556. loo D. Duffin and J. K. Sutherland Chem. Comm. 1970 627. lo' G. Nagendrappa and D. Devaprabhakara Tetrahedron Letters 1970,4687. lo' J. A. Marshall and W. F. Huffman J. Amer. Chem. SOC. 1970,92,6358. B.T. Golding and A. P.Johnson Ref N-bromosuccinirnide acetone AcO 0 101 Me ,OH a @ ____* 102 NaHCO H,O-dioxan p -NOZ*C6H,*COO -Scheme 4 A new route to the homotropilidene system involves the Diels-Alder addition of cyclopropenes to the azine (88) followed by photochemical conversion of the adduct (89) to (90).lo3 Addition of dibromocarbene to cyclo-octa-1,3,5-triene followed by reductive removal of bromine leads to bicyclo[6,1 ,O]nona-2,6-diene 70,Me C02Me W. Ditmar G. Heinrichs A Steigel T. Troll and J. Sauer Tetrahedron Letters 1970 1623. A licyclic Compounds 381 (91) an unusually stable cis-divinylcyclopropane system (half-life one day at 25 0C).'04 cis- and trans-Bicyclo[7,1,0]decan-2-one(92) and (93) are formed in good yield by reaction of (94) and (95) respectively with al~mina."~ The latter compounds are prepared from cyclodecane- 1,2-dione.Polycyclic Systems.-The search for tetrahedrane may have ended.'06,'07 The reaction of atomic carbon with cyclopropene leads to acetylene vinylacety- lene and diacetylene. Photolysis of carbon suboxide in the presence of cyclo-propene also yields acetylene and vinylacetylene suggesting the intermediacy of tetrahedrane (96) or the diradical (97).'06 An elegant variation of the same reaction utilises [3,3-2H2]cyclopropene and leads to acetylene products in which C2H2 C2HD and C2D2 are in almost exactly the correct proportions expected from the decomposition of symmetrical dideuteriotetrahedrane (98).'07 Further- more use of [2-'4C]carbon suboxide produced acetylene with half the original specific activity.The distribution of activity between the C2H2 C2HD and C2D2 species was again very close to that expected for tetrahedrane as an intermediate. The authors came to the firm conclusion that tetrahedrane is an intermediate with a finite lifetime.'" One of the products from the irradiation of (97) 1,2,5,6-tetramethylenecyclo-octane(99)84 is the [3,3,2]propellane (100)formed by a transannular photochemical ring-closure.'08 The parent [3,2,2]propellane (101) is readily obtained from (100). The elusive tricyclo[5,3,0,02*'0]deca-3,5,8-triene (99) (102) (103) (102) (isobullvalene) has previously been proposed as a reaction intermediate and has now been isolated from the reaction of the cyclononatetraenide anion with methylene chloride and n-butyl-lithium at low temperatures ( < -30 "C).'09 At higher temperatures (20-35 "C) isobullvalene isomerises to (103) (half-life 35 min at 25 "C).104 M. S. Baird and C. B. Reese Chem. Comm. 1970 1519. 105 J. V. Paukstelis and J-L. Kao Tetrahedron Letters 1970 3691. 106 R. F. Peterson R. T. K. Baker and R. L. Wolfgang Tetrahedron Letters 1969 4749. 107 P. B. Shevlin and A. P. Wolf J. Amer. Chem. SOC.,1970 92 406 3523 5291. I08 W. T. Borden I. L. Reich L. A. Sharpe and H. J. Reich J. Amer. Chem. Soc. 1970 92 3808. 109 K. Hojo,R. T. Seidner and S. Masamune J. Amer. Chem. SOC.,1970,92,6641; T. J. Katz J. J. Cheung and N. Acton ibid p. 6643. B.7'.Golding and A. P. Johnson n-Routes to substituted adamantanes have been reported"0*"' [e.g. (104)+ (105) catalysed by BF,]. Adamantane reacts with dichlorocarbene to form (106) (claimed to be the first successful preparative dichlorocarbene inser- tion into a saturated hydrocarbon).' 'Acid-catalysed hydrolysis and rearrange- ment of (106) yields homoadamantanone (107). An improved preparation of (106) (1 07) (108) diamantane has been reported,' l3 as has the synthesis of hexacyclo[l0,3,1 02~10,03~7,06~15,09~'4]he~ade~ane (log) an ethan~diamantane."~ 3 Miscellaneous Reactions General.-The reactivity of alicyclic compounds with emphasis on strained systems has been reviewed at an introductory level. and Four-membered Rings.-( 109) undergoes a heterolytic cleavage in methanol to give (1 10) and reacts with lithium bromide in dimethylformamide to give (111) via ester cleavage.Racemisation of optically active (109) occurs faster than either of these reactions. Detailed mechanistic arguments involving zwitterionic intermediates [e.g. (112) in which a singlet diradical is also written as a possible contributor to a resonance hybrid] are given for these and related PheCN Ph COzMe Me0 PhPe Ph C02Me (1 12) 'lo M. A. McKervey D. Faulkner and H. Hamill Tetrahedron Letters 1970,1971. ''I D. J. Raber G. J. Kane and P. von R. Schleyer Tetrahedron Letters 1970,4117. 'lZ I. Tabushi Z. Yoshida and N. Takahashi J. Amer. Chem. SOC.,1970,92,6670. 'I3 T. M. Gund V. Z. Williams E. Osawa and P.von R. Schleyer Tetrahedron Letters 1970 3877. S. T. Rao M. Sundaralingam E. Osawa E. Wiskott and P. von R. Schleyer Chem. Comm. 1970,861. 'I5 L. N. Ferguson J. Chem. Educ. 1970,47,46. Alicyclic Compounds Reductive cleavage (Li-NH,) of cis-and trans-2-methylcyclo- propyl methyl ketone is subject to steric and electronic The trans-isomer (113) cleaves preferentially at the C-l-C-3 bond to give (114)through a more stable primary carbanion. In the cis-isomer (1 15) a syn steric interaction raises the activation energy of the corresponding process relative to cleavage of the C-1-C-2 bond which is faster giving rise to (1 16) as the main product. (1 15) The possible synthetic utility of these processes is pointed out.' Substituted cyclopropanols react with mercuric acetate to give P-(acetoxymercuri)-ketones [e.g.(1 17)+(1 18)].' Whereas treatment of the dibromocarbene adducts of mono- di- and tri- substituted alkenes with methyl-lithium gives allenes in high yield the adducts of tetrasubstituted alkenes give bicyclobutanes. However an exception to the &OH -+ AcO HgCH,CH,COPh Ph (1 18) (117) latter rule occurs12o for although (1 19)yields the bicyclobutane (120)exclusively the isomer (121) gives 27 % of l,l-diphenyl-3-methylbuta-1,2-dienein addition Me Ph Ph ph&B% &Me MedByh Me Br Ph Me Br (1191 (120) (121) to 73 % of the expected bicyclobutane. Readers are referred to the paper'20 for an answer to this riddle. 3-Methylcyclopropene and 1,3,3-trimethylcyclopropene l6 E.W. Yankee and D. J. Cram J. Amer. Chem. SOC.,1970,92,6328 6329,6331. '" W. G. Dauben and R. E. Wolf J. Org. Chem. 1970 35 374 (cf. S. W. Staley and J. J. Rocchio J. Amer. Chem. Soc. 1969 91 1565). A. DeBoer and C. H. DePuy J. Amer. Chem. Soc. 1970,92,4008. 'I9 W. R. Moore K. G. Taylor P. Muller S. S. Hall and Z. L. F. Gaibel Tetrahedron Letters 1970 2365. W. R. Moore and J. B. Hill Tetrahedron Letters 1970 4553. B. T. Golding and A. P. Johnson react with Grignard reagents to give after treatment with C02 substituted cyclopropanecarboxylic acids.' 21 (122) R = H or Me Several examples have appeared of base-catalysed rearrangements of sub- stituted cycl~butanols,~~*'~~-'~~ and this reaction can be of synthetic value [e.g.(122) -+(123)]. The stereoelectronics of the reaction [as indicated in (122)] have been discussed.'22 Oxidation (e.g. by Ce") of substituted derivatives of cyclobutanols [e.g. (124)] which are readily available by photoaddition of enol acetates to cyclohexenones gives lP-diketones [e.g. (125)] in high yield.'25 OH (124) (125) This reaction is synthetically useful as it allows the introduction of the synthon CH2COR at C-2 of a cyclohexenone. Five-and Six-membered Rings.-Competitive rate studies have been made for reductions of a series of cyclohexanones with various metal hydrides.'26 The results support the concept of 'steric approach control' and the theory of Cherest and Felkin [see Ann. Reports (B) 1968 65 p. 3811 although the latter is not necessarily regarded as the final answer.Isotope effects have been measured for reduction of several cyclohexanones (with NaBD us. NaBH,) and the results are interpreted'27 in terms of an early transition state in each case in agreement with Eliel's conclusions.'26 A wealth of additional data is provided by an exten- sive kinetic and product study of the borohydride reduction of numerous cyclohexanones.'28 The readily available lithium perhydro-9b-bora henalyl hydride is a reducing agent of high reactivity and stereoselectivityi2' (e.g. 2-methylcyclopentanone -+94 % cis-2-methylcyclopentanol).The stereochemistry of protonation of nitronate anions derived from nitrocyclohexanes shows an interesting contrast to the reduction of structurally similar ketones.Whereas 121 M. Yu. Lukina T. Yu. Rudashevskaya and 0. A. Nesmeyanova Doklady Akad. Nauk. S.S.S.R. 1970 190 1109. 122 P.R. Brook and A. J. Duke Chem. Comm. 1970,652. 123 J. Salaun and J. M. Conia Chem. Comm. 1970 1358. 124 V. R. Fletcher and A. Hassner Tetrahedron Letters 1970 1071. l2 N. R.Hunter G. A. MacAlpine H. J. Liu and Z. Valento Canad. J. Chem. 1970,48 1437. 126 E. L. Eliel and Y. Senda Tetrahedron 1970,26,2411. 12' D. C. Wigfield and D. J. Phelps Chem. Comm. 1970,1152. 12* B. Rickborn and M. T. Wuesthoff J. Amer. Chem. Soc. 1970,92 6894. 129 H. C. Brown and W. C. Dickason J. Amer. Chem. Soc. 1970,92,709. Alicyclic Compounds reduction of 2-methylcyclohexanone with NaBH yields 40% of cis-alcohol,' 28 protonation of the nitronate anion from 2-methyl-1-nitrocyclohexanegives 85 % of the less stable cis-nitro-product.'30 -1000clRR (R = CN or COMe) (main product) Scheme 5 Isophorone can be alkylated at its 4-position as shown (Scheme 5).13' Cyclo-hexa- 12-diene and cyclohexyne are intermediates in the reaction of 1-halogeno-cyclohexenes with K0Bu'-DMSO leading to 1-t-butoxycyclohexene and dimeric products (cf.ref. 135).'32 Bicyclic Systems.-Additions of halogenocarbenes to bridged bicyclic olefins have been reviewed.' 33 In a series of papers,'34 the stereochemical outcome of several additions to norbornene and 7,7-dimethylnorbornene is described. In reactions which involve cyclic transition states (e.g. hydroboration) addition occurs preferentially exo to norbornene but endo to 7,7-dimethylnorbornene (steric effect from gem-dimethyl group).However two-step reactions (e.g. addition of CF3C02H) occur exo in each case because the initial step involving proton-attack at the corner of the system is much less sterically demanding. 6,6-Dibromobicyclo[3,l,0Jhexanereacts with methyl-lithium to give dimers and tetramers which can be rationally derived from cyclohexa-1,2-diene as intermediate13' (cf. ref. 132). The latter can be trapped in styrene giving exo-and endo-7-phenylbicyclo[4,2,0]oct-l-ene.' 36 Treatment of 3-bromobicyclo-I3O F. G. Bordwell and K. C. Yee J. Amer. Chem. SOC.,1970,92 5933 5939. 13' J. C. Leffingwell Tetrahedron Letters 1970 1653. 132 A. T. Bottini F. P. Corson R. Fitzgerald and K. A. Frost Tetrahedron Letters 1970 4753,4757.L33 C. W. Jefford Chimia (Switz.) 1970 24 357. '34 H. C. Brown and J. H. Kawakami J. Amer. Chem. SOC.,1970,92 201 1990; H. C. Brown,J. H. Kawakami and K.-T. Liu ibid. p. 3816; H. C. Brown J. H. Kawakami, and K-T. Liu ibid. p. 5536; H. C. Brown J. H. Kawakami and S. Ikegami ibid. p. 6914. 135 W. R. Moore and W. R. Moser J. Amer. Chem. SOC.,1970,92 5469. '36 W. R. Moore and W. R. Moser J. Org. Chem. 1970 35 908. 3. T. Golding and A. P.Johnson [3,2,l]octa-2,6-diene (126) with K0Bu‘-DMSO gives (127).13’ The homoaro- matic anion (128) is probably an intermediate in this reaction since racemic (126) can be recovered starting with optically active (126). The anion (128) proceeds further to the ‘homoconjugated carbene’ (129) which undergoes cleavage to (127).(126) (127) (128) ( 129) Thermolysis of the tosylhydrazone of bicyclo[3,3,l]non-2-en-9-onegives via the carbene (130) three main products (131) (132) and (133).13* It is suggested ( 134) (135) that formation of the expected products (134) and (135) does not occur because the carbenoid centre in (130) is ‘foiled’ by interaction with the double bond. This causes C-9 to draw closer to the double bond with simultaneous movement of the P-hydrogen at C-4 towards a pseudo-equatorial position which is the wrong stereochemistry for insertion to give (134). This effect may also enhance migration of the C-1-C-2 bond to give (131). Compared with the bicyclo[3,3,l]nonyl system solvolysis of exo-3-bicyclo-[3,2,2]decyl toluene-p-sulphonate is accompanied by a much greater amount (48% us.5%) of transannular hydride shift probably from C-7 to C-3.13’ A remarkable stereoselectivity is observed in hydrolysis of the acetoxonium ion OCOR d0H (136) (137) (136) to give 99.5 % (137).l4’ Several new acid-catalysed rearrangements of possible synthetic value have been described (Scheme 6).14’ 13’ R. G. Bergmann and V. J. Rajadhyaksha J. Amer. Chem. SOC.,1970,92,2163. 138 M. H. Fisch and H. D. Pierce Chem. Comm. 1970 503. 39 M. P. Doyle and W. Parker Chem. Comm. 1970 755. 14* J. F. King and A. D. Allbutt Cunad. J. Chem. 1970,48 1754. l4I R. L. Cargill and J. W. Crawford J. Org. Chem. 1970,35 356; R. L. Cargill D. M. Pond and S. 0. LeGrand ibid. p. 359; R. L. Cargill and A.M. Foster ibid. p. 1971. 387 A licyclic Compounds Scheme 6 ‘0 Polycyclic Systems.-Free-radical cleavage of adaman tan- 1-01 provides a convenient route to (139) which gives tricycl0[4,3,1,0~*~ Jdecan-4-one (1 38) on base treatment.142,’43 A remarkable fragmentation of 1,3-di(bromomethyl)-5,7-dibromo-adamantane occurs with zinc to give 1,3,5,6-tetramethylenecyclo-Br octane which itself undergoes several fascinating reactions [c$ Scheme 7(i)]. 144 Tetracyclo-[4,3,1,14.801~4]undecanereacts with bromine to give l-bromo-3-bromomethyl-adamantane14’[Scheme 7(ii)]. Reactions of bullvalene with acidic methanol,’46 mercuric acetate,’47 and chlorosulphonyl isocyanate148 have been 142 R. M. Black and G. B. Gill Chem. Comm. 1970,972. 143 W.H. Lunn J. Chem. SOC.(c),1970,2124. 144 F. N. Stepanov V. D. Sukhoverkhov V. F. Baklan and A. G.Yurchenko Zhur. org. Khim. 1970,6 884. A. G. Yurchenko A. T. Voroshchenko and F. N. Stepanov Zhur. org. Khim. 1970 6 189. 146 H.-P. Loffler and G. Schroder Chem. Ber. 1970,103,2105. 14’ H.-P. Loffler and G. Schroder Tetrahedron Letters 1970 21 19. 148 L. A. Paquette S. Kirschner and J. R. Malpass J. Amer. Chem. SOC., 1970,92,4330. B. T. Golding and A. P.Johnson reported. Treatment of the bis(dibromocarbene) adduct (140) of cyclo-octa- tetraene with methyl-lithium at -78 "C yields naphthalene via cyclodeca- 1,2,4,6,7,9-hexaene.149 HXZH Me Br (ii)'45 Scheme 7 4 Cycloadditions 2 + 2.-The major product from the thermal dimerisation of cis,trans-cyclo- octa-1,3-diene has the structure (141) which is the expected product from a concerted (x2s+ n2,J cycloaddition.' 50 The stereochemical outcome of the (141) addition of unsymmetrical ketens to cyclopentadiene has been extensively investigated.The reaction is often highly stereoselective [>95 % of endo-product (142) when R1= H R2 = C1 alkyl phenyl or OMe; and R1 = C1 Br or Me R2 = phenyl]. All the investigators interpret these results in terms of a (z2s+ z2a)addition the keten approaches the diene in a crosswise manner with its oxygen atom lying over the ring and the smaller substituent (R') pointing down '49 E. V. Dehmlow and G. C. Ezimora Tetrahedron Letters 1970,4047. I5O C. L. Osborn D. J. Trecker A. Padwa W.Koehn and J. Masaracchia Tetrahedron Letters 1970,4653. ' ' M. Rey S. Roberts A. Dieffenbacher and A. S. Dreiding Helv. Chim. Acta 1970,53 417. 152 P. R. Brook A. J. Duke and J. R. C. Duke Chem. Comm. 1970 574; P. R. Brook J. M. Harrison and A. J. Duke ibid. p. 589. 153 W. T. Brady R. Roe E. F. Hoff and F. H. Parry J. Amer. Chem. Sac. 1970,92,146; W. T. Brady and R. Roe ibid. p. 4618; W. T. Brady F. H. Parry R. Roe and E. F. Hoff Tetrahedron Letters 1970,819;W. T. Brady and E. F. Hoff J. Org. Chem. 1970 35 3733. A licyclic Compounds 389 towards the ring. Closure to the cyclobutanone ring must occur as shown (143) and causes the larger group (R2)to move into the endo-position. The cycloaddi- tion of cis-and trans-1,2-dichloro- 1,2-diAuoroethylene to cyclopentadiene gives (143) in each case 1,2- and 1,4-adduct~.”~ Formation of the latter proceeds with retention of the fluoroalkene configuration and is considered to be concerted whilst the 12-addition involves some loss of configuration and is apparently a diradical process.4 +2.4yclopentadiene reacts with 2,5-dimethyl-3,4-diphenylcyclopentadien-one to give an endo-adduct (144) with greater than 97% selectivity.”’ However (144) when cyclopentene reacts with this dienone an almost equal proportion of exo-and endo-isomers is obtained.”’ These results support the suggestion that steric repulsions with a methylene hydrogen of the diene are responsible for the endo-stereoselectivity of Diels-Alder reactions between cyclopentadiene and mono-olefins.This effect is also invoked to explain the observation that cyclo- propene and furan give a 1:1 ratio of exo-and endo-adducts (N.B.cyclopropene R’ R3 \/ ,c=c R2 ‘x (145) R’ =R2 =R3 =H R’ =R2=H R3 =CH3 R’ =R3 =H R2 =CH R2=R3 =H R’ =CH X =CN C02CH3 etc. ‘54 R. Wheland and P. D. Bartlett J. Amer. Chem. SOC.,1970 92 3822. 155 K.N. Houk Tetrahedron Letters 1970 2621. B. T. Golding and A. P.Johnson and cyclopentadiene yield exclusively endo-product). " In the reaction between cyclopentadiene and methyl-substituted olefins (145) the percentage of endo-X product decreases in the order cis-8-methyl > H > trans-/3-methyl > or-methyl (e.g. a-methylacrylonitrile gives ca. 85 % exo-product !).' 57 Although steric repulsions could account for these results the authors favour strong intermole- cular attractive forces between the methyl group and the diene as an explanation.At 140 "C,the cyclopropene (146) equilibrates with its isomer (147)and the latter reacts with cyclopentadiene giving the endo-adduct (148).158In contrast the ethyleneketal of ( 146) affords the exo-adduct (149) stereospecifically,'58 which is a unique steric course in a Diels-Alder reaction of a cyclopropene. Some light has been shed on the mechanism of Lewis acid catalysis of the Diels-Alder reaction. ' The aluminium-chloride-catalysed reaction of 2-phenylcyclohexenone with butadiene yielded two pairs of epimeric products OAIC13 H Scheme 8 which can be explained by postulating an ionic process as indicated in Scheme 8.However the generality of this mechanism awaits further evidence. Other Types.-The exo-and endo-homofulvenes [(150) and (1 5l)] react with chlorosulphonyl isocyanate to give (1 54) and (155) respectively presumably uia adducts (152) and (153).16* The inversion of C-6 accords with a concerted [(,2 + n4s)+ .2,] pathway. The self-dimerisation of cycloheptatriene to 5b R. W. LaRochelle and B. M. Trost Chem. Comm. 1970 1353. "' Y. Kobuke T. Fueno and J. Furukawa J. Amer. Chem. SOC.,1970,92,6548. H. Monti and M. Bertrand Tetrahedron Letters 1970 2587 2591. H. W. Thompson and D. G. Melillo J. Amer. Chem. Soc. 1970,92,3218. 160 R.Askani Angew. Chem. Internat. Edn. 1970 9 167. Alicyclic Compounds 391 (156) at 170 "C(100 h) probably involves a 6 + 4followed by a 4 + 2 cycloaddi-tion.161 Woodward and Houk'62 have described examples of (n6s+ n4s)and Me (150) X = H,Y = Me (152) X = H,Y = Me (154) X = H,Y = Me (151) X = Me,Y = H (153) X = Me,Y = H (155) X = Me,Y = H (,3lS+ n2s)cycloadditions [e.g.(157) and (158) from tropone and 2,5-dimethyl- 3,4-diphenylcyclopentadienone]. 1,6-Dimethylenecyclohepta-2,4-diene reacts with TCNE or dimethylazidodicarboxylate to give the product [e.g. (159)] expected of a (,JS + n2s)cy~loaddition.'~~ 5 Thermolyses There is evidence' 64 that thermal rearrangements of methylenecyclopropanes proceed via a twisted species such as (160)' rather than a planar trimethylene- methane. A of the stereochemistry of the rearrangement of optically active Feist's ester (161) now provides strong support for this view since it is shown that the configuration at the migrating carbon atom (*) undergoes inver- sion which is to be expected if (162)is an intermediate.A further example of this C02Me C02Me H&== C02Me C02Me 16' K. Takatsuki. I. Murata and Y. Kitahara Bull. Chem. SOC.Japan 1970,43 966. K. N. Houk and R. B. Woodward J. Amer. Chem. Sac. 1970,92,4143 4145; K. N. Houk and C. R. Watts Tetrahedron Letters 1970 4025; K. N. Houk L. J. Luskus and N. S. Bhacca J. Amer. Chem. SOC.,1970,92,6392. 163 G. C. Farrant and R. Feldmann Tetrahedron Letters 1970 4979. J. J. Gajewski J. Amer. Chem. SOC., 1968,90 7178. 165 W. von E. Doering and H. D. Roth Tetrahedron 1970,26 2825.392 B. T. Golding and A. P. Johnson type of rearrangement is the thermolysis of 2,2-diphenyl-l-(dideuteriomethylene)-cyclopropane (163) which sets up an equilibrium between itself and The compound (165) is not obtained although it is expected to be the most stable. As expected the presence of the phenyl groups markedly accelerates the reaction (AH$2522.1 kcal mol-' AS$25 -11.5 cal mol-' deg-' ; cf. data for 2-ethylmethylenecyclopropane -+propylidenecyclopropane AH $25 39.8 kcal mol-I AS$25 3.2 cal mol-'deg-'). At higher temperatures 2,2-diphenyl-methylenecyclopropane rearranges to the indene (166).' 67 D D I I Ph D Ph H H I Ph (163) (1 64) (165) ( 166) At 170-200 "C cis-and trans-2,2,2',2'-tetramethyl-bis-cyclopropylidenesare completely converted to a mixture of (1 67) and (1 68) the former predominating.16* This result again renders unlikely the planar diradical intermediate (169) which would be expected to yield more (168) but supports (170) which could lead to the major product by rotation as shown.Since other cyclopropylidenecycloal-kanes (171 n = 3-5) remain in appreciable amount along with (172) in an Me Me Me Me Me Me Me (170) (171) (172) equilibrium mixture at 220 "C,it is suggested that the methylenespiropentane system possesses extra stabilisation possibly due to cwc ~verlap.'~' Labelling studies rule out the retro-ene mechanism for the thermal isomer- isation of bicyclo[2,1,0]pent-2-ene to cyclopentadiene.' 70 Thermolysis of 166 J. C. Gilbert and J.R. Butler J. Amer. Chem. Soc. 1970,92,2168. 16' M. Jones M. E. Hendrick J. C. Gilbert and J. R. Butler Tetrahedron Letters 1970 845. 168 W. R. Dolbier K.-Y. Akiba M. Bertrand A.Bezaguet and M. Santelli Chem. Comm. 1970,717. 169 W. R. Dolbier J. M. Riemann K.-Y. Akiba M. Bertrand and A. Bezaguet Chem. Comm. 1970,718. J. E. Baldwin R. K. Pinschmidt and A. H. Andrist J. Amer. Chem. SOC.,1970 92 5249. A licyclic Compounds 2-me thy1 bicyclo[2,1 ,O]pent-2-ene gives 1 -met hy lc yclopentadiene as the initial product as shown by its trapping with N-phenylmaleimide.'7' It may arise by a concerted (n2s + ,,2a) reaction (173) rather than the previously assumed diradical pathway which would anyway give 2-methylcyclopentadiene as the primary product.Details have appeared of a study of the thermal rearrangement of isopropenylspiropentane (174).'72 The major products (175) and (176) can both arise from the same diradical intermediate (177) in which case (176) would be formed by a rare example of a 1,2-alkyl shift in a radical species. (173) (175) (176) Heating bicyclo[2,1,0]pentane-5-spirocyclopropane causes an interesting series of changes (see Scheme 9).173 The degenerate rearrangements of the Scheme were detected using deuterium- and/or methyl-substituted materials. The latter were also used to demonstrate the lack of stereoselectivity of the skeletal rearrange- ments. Scheme 9 The synthesis and degenerate Cope rearrangement of 1,3,5,7-tetramethyl-homotropilidene have been reported.'74 An n.m.r.study shows that the more stable conformation of 1,3,5,7-tetramethylhomotropilideneis transoid as in (178) but that the Cope rearrangement proceeds uia the cisoid conformation (179) J. E. Baldwin and A. H. Andrist Chem. Comm. 1970 1561. J. J. Gajewski J. Amer. Chem. SOC.,1970,92 3688. W. R. Roth and K. Enderer Annalen 1970,733,44. "'L. Birladeanu D. L.Harris and S. Winstein J. Amer. Chem. SOC.,1970,92 6387. B. T. Golding and A. P.Johnson and a cis-like bis-homobenzene transition state (180) as predicted by Doering in 1963. (178) (179) (180) Whereas on thermolysis exo-9-hydroxymethylbicyclo[6,l,0]non-2-ene(181; R1 = H R2 = CH,OH) undergoes a 1,5-hydrogen migration to give 2-hydroxy- methyl-cis,cis-nona-1,4-diene(182) the corresponding endo-isomer (181 ; R' = CH,OH R2 = H)is quite ~tab1e.l~' This is attributed to the need for a 'saddle' conformation for the migration which is presumably destabilised by the bulky hydroxymethylene group in the endo-isomer.The very high strain of quadricycl-enes (ca.95 kcal mol- ') has hitherto prevented the preparation of such molecules by ground-state reactions. However heating either (183) or (184) produced the quadricyclene (185) in high yield.'76 It is estimated that the strain energy of (184) is greater than 100 kcal mol-'. Pyrolysis of optically active trans-1,2-di[2H,]methyl-l,2-dimethylcyclobutane (186) yields 2-[2H,]methylpropene with no racemisation or conversion to the cis-isomer observed in recovered starting material.I7 Similarly the cis-isomer does not isomerise to the trans-isomer.This indicates that cleavage of the 3,4- bond in the intermediate diradical (187) must be much faster than the rate of rotation about the 1,4- and 2,3-bonds [contrast cyclopropanes Ann. Reports (B) 1969 66 p. 3751. The major products from the pyrolysis of the isomeric dimethylbicyclo[2,2,O]hexane-2,3-dicarboxylates(Scheme 10) are those expected '" D. L. Garin J. Amer. Chem. SOC.,1970,92 5254. '" L. A. Paquette and L. M. Leichter J. Amer. Chem. SOC.,1970,92 1765. "' J. A. Berson D. C. Tompkins and G. Jones,J. Amer. Chem. SUC.,1970,92 5799. 395 Alicyclic Compounds by a concerted [,2 +.2,] pathway.'78 However the authors favour a radical pathway or a two-step mechanism involving a Cope rearrangement.@ t-cCOzMe COzMe C02Me C02Me cc;;;:e qco2Me * +Q C02Me C02Me C02Me Scheme 10 Berson's observation that the thermal isomerisation of (188 ;R' = D R2 = H) to (189; R' = D R2 = H) proceeded with inversion of configuration at the migrating centre was a remarkable testament to the predictive power of orbital symmetry arguments. A complementary study'79 shows that whereas (188 ; R' = Me RZ = H) behaves similarly to give (189; R' = Me R2 = H) the endo-methyl isomer (188; R' = H R2 = Me) isomerises with retention of con- figuration at the migrating carbon presumably because the transition state for a concerted reaction would involve severe steric interaction between the methyl group and the ring. Steric inhibition of a proper 1,3-sigmatropic shift also occurs with (190) but for a different reason.'80 The bridging CH2-CH unit prevents rotation of the migrating C atom and so thermolytic rearrangement to (191) occurs uia a radical intermediate in contrast to the parent bicyclo[2,l,l]hexene whose rearrangement to bicyclo[3,1,0]hex-2-ene is concerted.These conclusions are supported by the Arrhenius parameters measured for each case. 170 L. A. Paquette and J. A. Schwartz J. Amer. Chem. SOC.,1970,92 3215. 79 J. A. Berson and G. L. Nelson J. Amer. Chem. SOC.,1970,92 1096. H. M. Frey and R. G. Hopkins J. Chem. SOC.(B) 1970 1410. B. T. Golding and A. P. Johnson Gas-phase thermolysis of 1,6-dideuterio-bicyclo[4,2,0]octa-2,7-diene (192) gives cyclo-octatriene (55%) and recovered starting material (45 %) half of which is deuteriated at C-3 and C-8.181 Valence tautomerism through 1,4- dideuterio-cis,trans,cis-cyclo-octatrieneexplains this result.Diels-Alder reac-tions on monosubstituted cyclo-octatetraenes usually trap largely the 7-sub- stituted bicyclo[4,2,0]octatriene because this reacts faster than other valence tautomers. However the very reactive dienophile 4-phenyl-l,2,4-triazoline-3,5-dione reacts with bromocyclo-octatetraene to give products derived from both its 7- and 1-substituted bicyclo-tautomers.'82 The latter compound is the key intermediate in a mechanism (Scheme 1l) deduced mainly from a kinetic study for the thermal conversion of bromocyclo-octatetraene to P-bromostyrene.' Br H e /Hr f-1H I Scheme 11 On heating the bicyclo[4,2,0]octatriene(193) at 65 "C it isomerises to an equili- brium mixture of (194a) and (194b) from which (194a) could be preferentially crystallised.'83 The equilibrium is re-established on dissolving the crystals.Me /Me (193) ( 194a) (194b) Ial J. E. Baldwin and M. S. Kaplan Chem. Comm. 1970 1560. R. Huisgen and W. E. Konz J. Amer. Chem. SOC.,1970 92 4102; W. E. Konz W. Hechtl and R. Huisgen ibid.,p. 4104. I. W. McCay and R. N. Warrener Tetrahedron Lelrers 1970 4783. A licyclic Compounds 397 The relative rates for the opening of the cyclobutene ring in compounds (195)- (198) are 8-7 :954 1 :23 respecti~ely.'~~ These rate differences are attributed to torsional and/or angle strain effects.(195) (196) (1 97) (1 98) Thermal isomerisation of anti-7,8-benzotricyclo[4,2,2,O2~s]deca-3,7,9-triene (199) at 550 "C leads to cis-4b$a-dihydrophenanthrene (200).1857186 Although it has been suggested that (201) might be an intermediate which could be converted to the product via a benzo[lO]annulene,' 85 this has been rejected since at 280 "C both (200) and (201) are formed and the latter is only converted to (200) at much higher temperatures.' 86 (200) syn-Tricyclo[8,2,0,02*g]deca-3,5,7,1 1-tetraene (202) gives 80% [12lannulene (31) on photolysis at -1150C.48 On warming to -40 "C the latter affords (203) probably via (32) [cf discussion on p. 3721. At 20 "C (203) gives (204) which frag- ments to benzene at 130 "C. Sigmatropic shifts around a cyclopentadiene ring continue to be of interest.Thus at 345400 "C spiro[2,4]hepta-4,6-diene(205) yields 6-methylfulvene and three other products (206) (207) and (2O8).lg7 All of these can arise from (209) which can be derived from (205) by a suprafacial 1,5-alkyl shift. In similar (205) (206) (207) (208) (209) H. M. Frey J. Metcalfe and J. M. Brown J. Chem. SOC.(B) 1970 1586. L. A. Paquette and J. C. Stowell Tetrahedron Letters 1970 2259. E. Vedejs Tetrahedron Letters 1970 4963. J. M. E. Krekels J. W. de Haan and H. Kloosterziel Tetrahedron Letters 1970 2751. B. T. Golding and A. P.Johnson fashion thermolysis of (210)gives (211)and double-bond isomers in which the configuration at the migrating carbon atom has been retained.'88 (2101 (211) R1 = R2 = Me R3 = H R1= R3 = Me RZ = H trans-3,6-Dideuteriocyclohexa-1,4-diene and cis-5,6-dideuteriocyclohexa-1,3-diene have been prepared by ingenious routes.'89 The former specifically loses HD on heating but the latter loses H, D, and HD in a non-specific fashion in accordance with orbital symmetry predictions.' 89 Thermolysis of both isomers (212) and (213)gave the same product (214).190 Although (215)is the expected product from (212)by a symmetry-allowed disrota- tory ring-closure its formation may be blocked because of steric repulsion between the methyl groups in the transition state.Me HO Me 0 Me Fluxional isomerism has been studied in bullvalenyl s~lphides,'~' the pre- bullvalene lactone (21 6),'92 and octamethylsemibullvalene.'93 The last named shows an inversion barrier (AG\,,6.4 & 0.2 kcal mol- ') which is lower than those of other homotropilidene systems.Inn M. A. M. Boersma J. W. de Haan H. Kloosterziel and L. J. M. van de Ven Chem. Comm. 1970 1168. I. Fleming and E. Wildsmith Chem. Comm. 1970,223. ''O R. Ramage and A. Sattar Chem. Comm. 1970 173. ''I C. Hoogzand J. Nielsen and J. F. M. Oth Tetrahedron Letters 1970,2287. W. von Phillipsborn J. Altman E. Babad J. J. Bloomfield D. Ginsburg and M. B. Rubin Helv. Chim. Acta 1970 53,725. lg3 F. A. L. Anet and G. E. Schneck Tetrahedron Letters 1970,4237. 399 A licyclic Compounds 6 Reactions with Transition Metals Although an early claim194 which hinted at the promise of this area has been refuted,*'95 significant advances have been realised in the past year.New reactions have led to the discovery of new hydrocarbons and have expedited the synthesis of certain known systems. Homocubane is stable up to 240°C but in deuteriochloroform containing a catalytic amount of AgBF it isomerises at 25 "C to pentacyclo[4,3,0,02~403~*05~7 3-(217) in quantitative yield [Scheme 12 (i)].196 Several related Reg 196 197 @9 C02Me CO2Me C02Me @s@ or Pd" 198 199 200 Scheme 12 194 F. Bonati and G. Wilkinson J. Chrm. SOC.,1964 3156. '95 B. E. North and M.Rosenblum J. Organometallic Chem. 1970,21,467; R. Grigg and J. L. Jackson Tetrahedron Letters 1970. 3493. 196 L. A. Paquette and J. C. Stowell J. Amer. Chem. SOC.,1970,92,2584.* Cycloheptatriene does nor give norbornadiene on heating with (CO),Rh(acetyl-acetonate). B. T. Golding and A. P. Johnson transformations have been described [Scheme 12 (ii)-(~i)].'~~-~~~ Reaction (ii) also proceeds thermally without silver ions but in lower yield and not below 235 0C.197 Reactions (i) and (ii) suggested a brilliant rational synthesis of semi-bullvalene (Scheme 13) which makes this hydrocarbon readily available in gramme R R (R= C0,Et) Scheme 13 quantities.202 The product of reaction (iii) has been named c~neane'~~ and is the second fully saturated (CH) isomer to be synthesised.* It is converted to semi- bullvalene in the presence of [Rh(norbornadiene)Cl] . '' In the absence of metal catalysts the transformations (i)-(iv) are forrnally disallowed (c20+ ,,2a) re-actions while (v) and (vi) are disallowed (n2s+ 02s)cycloreversions.These con- siderations explain the thermal stability of the starting materials of Scheme 12 even though their potential products are much more stable; (217) is estimated'96 to be 45 kcal mol-' more stable than homocubane! Two theories can explain the catalytic r61e of the metal ions in these reactions (a) They are one-step reactions which are symmetry-forbidden for the free hydrocarbon but become allowed by interaction with orbitals of the (b) They are initiated by oxidative addition of the metal ion to a strained C-C bond of the hydrocarbon and proceed via organometallic intermediates for which orbital symmetry may be irrele~ant.~''.~~~ Recent results summarised below support the second proposal at least for reactions catalysed by Rh' complexes.19' W. G. Dauben M. G. Buzzolini C. H. Schallhorn D. L. Whalen and k.J. Palmer Tetrahedron Letters 1970 787. 198 L. Cassar P. E. Eaton and J. Halpern J. Amer. Chem. SOC.,1970,92,6366. L. A. Paquette G. R. Allen and R. P. Henzel J. Amer. Chem. Soc. 1970,92 7002. '0° P. E. Eaton and S. A. Cerefice Chem. Comm. 1970 1494. L. Cassar P. E. Eaton and J. Halpern J. Amer. Chem. Soc. 1970,92 3515. '02 R. Askani Tetrahedron Letters 1970 3349; L. A. Paquette J. Amer. Chem. SOC. 1970,92,5765. '03 F. D. Mango Adv. Catalysis 1969,19,291 ;see W. Th. A. M. van der Lugt Tetrahedron Letters 1970 2281 for a different viewpoint and previous references.'04 L. Cassar and J. Halpern Chem. Comm. 1970 1082 and references therein. * One more awaits discovery; 2,2' 4,4'-bis(bicyclobutyI) which is estimated to be intermediate in stability between cubane and cuneane. 198 Alicyclic Compounds 40 1 In the presence of a stoicheiometric amount of Rh2(CO),C12 cubane gives (218)’01 and quadricyclene gives (219).’04 This is in contrast to their reactions with a catalytic quantity of [Rh(norbornadiene)Cl] where quadricyclene gives norbornadiene’” and cubane reacts as in Scheme 12(vi). The ratio of rate ,Rh-C J? Rh-C I *o oc’& \‘o 1..:/ C1 constants for the reactions of cubane and two derivatives (220) and (221) with stoicheiometric Rh2(CO),C12 is very similar to that for the reaction of the same compounds with catalytic [Rh(n~rbornadiene)Cl],.~~~ Furthermore both reagents react with (220) to give products [cf.Scheme 12(vi) in the case of the catalytic reaction whilst from the stoicheiometric reaction 34% (222) and 66 % (223) are obtained after treatment with triphenylphosphine] which from their similar isomeric distributions imply that intermediates (224) and (225) are involved in each case. R’ gRZ C02Me CO,Me @ @I X (220) R’ = H,R2 = C02CH3 (222) x = co (223) X = CO (221) R’ = RZ = C02CH3 (224) X = Rh (225) X = Rh Evidence for the formation of catenanes by olefin metathesis (WC1,-EtAlC1,- EtOH system) of cyclodecene has been reported.206 Butadiene gives a new dimer (1-methylene-2-vinylcyclopentane) in the presence of arylnickel catalyst^.'^ ’ An 82 yield of methyl 3-methylenecyclopentanecarboxylate is obtained from methylenecyclopropane and methyl acrylate (in excess) on catalysis with bis- (acrylonitrile)nicke1.20*Methyl-substituted derivatives of methylenecyclopro- pane behave similarly and methyl acrylate can be replaced by acrylonitrile or methyl vinyl ketone.A trimethylenemethane complex of nickel is not an inter- mediate as 2,2-dimethylmethylenecyclopropanewith methyl acrylate gave (226) whilst isopropylidenecyclopropane gave (227). In scrupulously clean glassware cyclo-octatetraene and benzyne react to give (199) as the major product. In the presence of silver fluoroborate the reaction is diverted to produce mainly (228).,09 ’05 H. Hogeveen and H.C. Volger J. Amer. Chem. Soc. 1967,89 2486. ’06 R. Wolovsky J. Amer. Chem. Soc. 1970,92,2132; D. A. Ben-Efraim C. Batich and E. Wasserman ibid. p. 2133. 207 J. Kiji K. Masui and J. Furukawa Tetrahedron Letters 1970 2561 ; Chem. Comm. 1970 1310. ’08 R. Noyori T. Odagi and H. Takaya J. Amer. Chem. SOC.,1970,92,5780. ’09 E. Vedejs and R. A. Shepherd Tetrahedron Letters 1970 1863. B. T. Golding and A. P. Johnson Several new catalysts as effective as old ones but more easily made have been developed for the preparation of Binor-S (229) from norbornadiene.210 The 12281 structure of Binor-S has beenconfirmed by an X-ray study.211 A possible inter- mediate in its formation from norbornadiene has been isolated from a catalytic system involving cobalt and tin.” A transannular cyclisation occurs on heating 1,7-or 1,8-~yclotridecadiyne with (~-C,H,)CO(CO)~ or related complexes and novel cyclopentadienylcobalt complexes of a tricyclic cyclobutadiene derivative are obtained [e.g.(230)].” Pyrolysis of the palladium dichloride complex of 1,2-di-t-butyl-3,4-diphenyl-cyclobutadiene gives 23 %ofa derivative(231) of h~motetrahedrane.’~~ Relatively co Me‘ ’Me (231) (233) stable metal complexes of bullvalene have been prepared (232; M = Cr W or Mo).’ l4 The chromium complex rearranges at 80 “C to (233) which liberates bicyclo[4,2,2]decatetraene on treatment with amm~nia.”~ This hydrocarbon can also be obtained from bullvalene by photolysis but not by thermolysis. A new mechanism for the palladium-catalysed isomerisations of alkylnor-bornanes has been proposed and supported by product studies; it involves a substituted nortricyclene intermediate.21 ’lo G.N. Schrauzer R. K. Y. Ho and G. Schlesinger Tetrahedron Letters 1970 543. ”’ F. P. Boer J. H. Tsai and J. J. Flynn J. Amer. Chem. Sac. 1970,92,6092. 21 R. B. King and A. Efraty J. Amer. Chem. SOC.,1970,92 6071. 213 T. Hosokawa and I. Moritani Chem. Comm. 1970,905. ’14 R. Aumann Angew. Chem. Internat. Edn. 1970,9 800. ’’ H. A. Quinn M. A. McKervey W. R. Jackson and J. J. Rooney J. Amer. Chem. SOC. 1970,92,2922 (cf.J. A. Roth ibid. p. 6658).

ISSN:0069-3030    

DOI:10.1039/OC9706700365

出版商:RSC    

年代:1970

数据来源: RSC

摘要:

12 Terpenoids and Steroids By B. A. MARPLES Department of Chemistry The University of Technology Loughborough THIStopic is the subject of one of the Chemical Society’s series of Specialist Periodical Reports the first volume of which has been published covering the literature up to August 1970. Hence this report is very selective. A review on photochemical reactions in natural product synthesis has appeared,’ and a book on the relatively recently explored cyclopentanoid terpene derivatives is now available.2 1 Monoterpenes The chemistry of a-terpineol has been re~iewed.~ The structure of yomogi alcohol (1) has been established by synthe~is,~ and the previously reported unreactive 2-p-anisylnorbornene-2,3-exo-oxide has been shown to be the dimer (2).5The unusual trans-fused structure (3) is proposed for n-camphanic acid.6 Evidence of hydrogen bonding between the cyclopropane ring and the hydroxy- group in thujanol suggests that a chair conformation (4) for the bicyclohexane ring is more likely than the often preferred boat conf~rmation.~ (1) (2) (3) (4) An = p-anisyl Transformation of the pinane to the oxapentalane skeleton is demonstrated by the rearrangement of ( -)-2-hydroxypinocamphane (5) to ( -)-dihydro-/I-’ P.G. Sammes Quart. Rev. 1970,24 37. ‘Cyclopentanoid Terpene Derivatives,’ ed. W. I. Taylor and A. R. Battersby Marcel Dekker New York 1969. J. Verghese Flavour Znd. 1970 1 545. (a)Ann. Reports (B) 1968,65,412; (b)B. Willhalm and A. F. Thomas Chem. Comm. 1969 1380; (c) W.Sucrow and W. Richter Chem. Ber. 1970,103 3771 ;(d)K. Yano S. Hayashi T. Matsuura and A. W. Burgstahler Experientia 1970,25 8. C. Anselmi P. L. Barili G. Berti B. Macchia F. Macchia and L. Monti Tetrahedron Letters 1970 1743. M.-J. Brienne and J. Jacques Tetrahedron 1970 26 5087. ’ V. Hach R. F. Raimonds D. M. Cartlidge and E. C. McDonald Tetrahedron Letters 1970 3175. 404 B. A. Marples campholeno-lactone (6).* Acid-catalysed rearrangement of the 7-hydroxy- norbornenyl derivative (7) gives compound (9) via C(l)-C(6)-cleavage while the isomer (8) gives compounds (10) and (1 1) via C( 1)-C(7) cleavage.' The presence (9) R2 (10) (7) R' = Me R2 = H (11) (8) R' = H R2 = Me of the 7-hydroxy-group appears to be necessary for the unique C(lW(6)- cleavage.Exclusive C(ti)-C(7)-cleavage is observed in the rearrangement of car-3-ene-2,5-dione (12) to compound (1 3)." Camphene-8-carboxylic acid (14) rearranged in formic acid to the lactones (15) (initial product) (16) and (17).'' An earlier suggestion that the product was a p-lactone is thus incorrect. Reduc- tion of o-nitrocamphene (18) with chromous chloride leads to the ring-expanded ketol (19).12The artemisiyl skeleton of epoxide (20) is rearranged by acid to the santolinyl skeleton of the oxetan (21). The 1,Zshift of the vinyl group lends some support to the suggestion that the santolinyl monoterpenes are derived biogenetically from the artemisia group.' Racemic sabina ketone (23) has been synthesised from compound (22) by the now commonly used intramolecular carbene-olefin additi~n.'~ New syntheses f-p-'o^ qH.$ 0 OAc COzH (12) (13) (14) (15) * (a) T.Suga T. Hirata M. Noda and T. Matsuura Experientia 1970 26 1192; (b) T. Hirata T. Suga and T. Matsuura Bull. Chem. SOC.Japan 1970,43 2588. V. K. Jones and L. B. Jones Tetrahedron Letters 1970 3 171. lo I. W. J. Still and G. W. Nathan Canad. J. Chem. 1970,48 1013. W. R. Vaughan J. Wolinsky R. R. Dueltgen S.Grey and F. S. Seichter J. Org. Chem. 1970,35,400. S. Ranganathan and B. B. Singh Chem. Comm. 1970 218. l3 A. F. Thomas Chem. Comm. 1970 1054. l4 K. Mori M. Ohki and M. Matsui Tetrahedron 1970,26 2821. Terpenoids and Steroids of ( -)-cis-car-4-eneI5 and rosoxidesI6 are also reported and the structure of (2)-karahana ether (24) is confirmed by its synthesis from geraniol.17 0 0 A new procedure for alkylation of isophorone at C(4) is reported.18 The dienol-acetate mixture from isophorone is allowed to react with acrylonitrile or ethyl methyl ketone and retro-aldolisation of the resultant adducts (25) gives compounds (26).The previously reported bromination product of iso-phorone is now shown to be the unusually stable hydrobromide salt (27).19 The R (25) R = CN COMe (26) reaction of car-3-ene with formaldehyde in acetic acid gives the ether (28) (inter alia) while in the presence of strong acid the ether (29) is obtained.” Pyrolyses Is M. S. Carson W. Cocker and P. B. Kulkarni Tetrahedron Letters 1970 669. l6 E. H. Eschinasi J. Org.Chem. 1970 35 1097. R. M. Coates and L. S. Melvin jun. J. Org. Chem. 1970,35 865. J. C. Leffingwell Tetrahedron Letters 1970 1653. l9 J. N. Marx Tetrahedron Letters 1970 3517. *’ J. Chlebicki and B. Burczyk Tetrahedron Letters 1970 4775. 406 B. A. Murples of nopinol,21 nopinone,22 and cis-pinocarveol (30)23are reported The latter compound gives (inter ah) the extensively rearranged aldehyde (31). -THO A non-natural terpene (33) is obtained by acid-catalysed isomerisation of the spiropentylcarbinol (32).24 Several new monoterpene alcohols25 and iridoid- glucosides26 have been isolated and the absolute configuration of loganin (34) has been e~tablished.~~ Studies on the biosynthesis of camphor,28 thujane derivative^,^' gerani01,~' and the iridoidgluc~sides~~ are reported.Hoeo 4 OH 0 Glucose 21 J. M. Coxon R. P. Garland and M.P. Hartshorn Chem. Comm. 1970 1709. 22 C. F. Mayer and J. K. Crandall J. Org. Chem. 1970,35,2688. 23 J. M. Coxon R. P. Garland and M. P. Hartshorn Chem. Comm. 1970 542. 24 R. Maurin and M. Bertrand Tetrahedron Letters 1970 1307. 25 (a) Y. Fujita S. Fujita and H. Yoshikawa Bull. Chem. SOC.Japan 1970 43 1599; (b) Y. Fujita S. Fujita and Y. Hayama ibid. p. 2637. 26 (a) H. Inoye S. Saito and T. Shingu Tetrahedron Letters 1970 3581 ;(6) 0.Sticher Helv. Chim. Acta 1970 53 2010; (c) Y. Asaka T. Kamikawa T. Tokoroyama and T. Kubota Tetrahedron 1970,26,2365. 27 H. Inoye T. Yoshida S. Tobita and M. Okigawa Tetrahedron 1970 26 3905. 28 D. V.Banthorpe and D.Baxendale J. Chem. SOC.(0,1970,2695. 29 D. V. Banthorpe J. Mann and K. W. Turnbuil J. Chem. SOC.(C),1970,2689. 30 M. J. 0.Francis D. V.Banthorpe and G. N. J. Le Patourel Nature 1970,228 1005. 31 (a)R. Guarnaccia L. Botta and C. J. Coscia J. Amer. Chem. SOC.,1970 92 6098; (6) S. Escher P. Loew and D. Arigoni Chem. Comm. 1970 823; (c) H. Inouye, S.Ueda and Y. Takeda Tetrahedron Letters 1970 3351. Terpenoidsand Steroids 407 2 Sesquiterpenes Reviews have appeared on some aspects of the sesquiterpenoid lac tone^,^^ the sesquiterpenes containing a five-membered ether ring,33 and the insect juvenile hormone and some analogues.34 The observation that hydrolysed germacrano- lides bearing a C(6) or a C(8) a-hydroxy-group preferentially re-lactonise at C(8) allows the assignment of structure (35) to ~alonitenolide.~~ The previously assigned structure (36) is that of artemisiifolin which is isolated from Ambrosia artemiszif~lia.~~ Revised structures are presented for (+)-nardostachone (37),36 nordrimenone (38),3 and valencene (39).38 The full details of microbiological oxidations and structural derivations of guaioxide and liguloxide are now a~ailable.~' Full stereochemical details are reported for the structures of ~ericenine,~' (-))-t~rreyol,~' isocollybolide,43 co~tunolide,4~ chilo~cyphone,~~ and pulchellin (40).45 Pulchellins B C E and F which were isolated with 32 (a)J.Romo Pure Appl. Chem. 1970 21 123; (b) T. A. Geissman and M. A. Irwin ibid.,p. 167; (c) S. M. Kupchan ibid.,p.227; (d) F. SBrm ibid. p. 263; (e) s. c. Bhattacharyya J. Indian Chem. Soc. 1970,41 299. 33 K. Takeda Pure Appl. Chem. 1970 21 181. 34 (a)B. M. Trost Accounts Chem. Res. 1970,3 120; (b)Y. S. Ysizin and A. A. Drabkina Russ. Chem. Rev. 1970 39 498. 35 H. Yoshioka W. Renold and T. J. Mabry Chem. Comm. 1970 148. 36 A. R. Pinder Tetrahedron Letters 1970 413. 37 C. J. W. Brooks G. Lindsay and K. H. Overton J. Chem. Soc. (0,1970 203. 38 (a)T. Ishida M. Nishimura S. Hayashi T. Matsuura and M. Araki Chem. and Ind. 1970,312; (b) R. M. Coates and J. E. Shaw J. Org. Chem. 1970,35,2597. 39 (n) H. Ishii I. Tozyo M. Nakamura and H. Minato Tetrahedron 1970 26 2751 ; (h) E. Funke T. Tozyo H. Ishii and K. Takeda J. Chem. Soc. (0,1970 2548. 40 K. Takeda K. Tori I.Horibe H. Minato N. Hayashi S. Hayashi and T. Matsuura J. Chem. Soc. (C),1970,985. 4' L. Westfelt Acta Chem. Scand. 1970 24 1618. 42 A. Matsuo and S. Hayashi Tetrahedron Letters 1970 1289. 43 C. Pascard-Billy Chem. Comm. 1970 1722. 44 F. SBrm M. Suchy M. Holub A. Linek I. Hadinec and C. Novak Tetrahedron Letters 1970 1893. " K. Aota C. N. Caughlin M. T. Emerson W. Herz S.Inayama and Mazhar-ul-Haque J. Org. Chem. 1970 35 1448. 408 B. A. Marples (40) pulchellin from Gaillurdia pulchella have been shown to possess the isolanto- lactone structure [e.g.pulchellin B is (4S)].46 Reaction of santonic acid (42) with sodium amalgam gives dihydrosantonic acid (43) by an intramolecular pinacol reduction.47 The previously proposed structure for dihydrosantonic acid is incorrect and it seems likely that previous samples were contaminated with dihydrometasantonic acid.The aluminium-alkoxide-catalysedrearrangement of isolongifolene epoxide (44)48to the alcohol (45) suggests the epoxide has the endo-rather than the exo-stru~ture.~~ Buffered peracetic acid oxidation of longifolene gives a mixture of products derived by rearrangement of the epoxide (44).50 It seems possible that 1,2-humulene epoxide (46) is involved in the biosynthesis of tricyclohumula- diol(47) and caryophyllene since the epoxide (46)is converted to tricyclohumula- diol (47) by treatment with acid.51 The alcohol (49) is the major product from the treatment of longifolene (48) successively with trifluoroacetic acid and 0.H 46 H.Yoshioka T. J. Mabry N. Dennis and W. Herz J. Org. Chem. 1970 35 627. 47 A. G. Hortman and D. S. Daniel Tetrahedron Letters 1970 2599. 48 E. H. Eschinasi G. W. Shaffer and A. P. Bartels Tetrahedron Letters 1970 3523. 49 T. S. Santhanakrishnan R. R. Sobti U. R. Nayak and Sukh Dev Tetrahedron 1970 26 657. L. K. Lala and J. B. Hall J. Org. Chem. 1970 35 1172. 51 M. A. McKervey and J. R. Wright Chem. Comm. 1970 117. Terpenoids and Steroids (48) (49) lithium aluminium h~dride.~’ The rearrangement appears to involve a trans- annular hydride ion migration in the longibornyl cation. The keto-ester (50) of the longifolene series rearranges with boron trifluoride etherate to the keto- ester (51) which can be converted to the unusual tricyclic compound (52).’3 Solv01ysis~~ of longicamphenyl tosylate (53) gives norlongicyclene and the unusual olefins (54) and (55).Olefin (54) is probably formed via intramolecular hydride migration from C(10) to C(8) followed by methylene migration from C(9) to C(10). C02Me oqQ 41t COzMe C0,Me The Cope rearrangement of the germacrane- to the elemane-type skeleton is rever~ible,~~ and the stereochemistry of the product is related to the conforma- tion of the ten-membered ring of the germa~rane.~~ The structures of two conformational isomers of neolinderalactone were determir~ed,~’ and two conformational isomers of the germacranolide (56) (relative configuration) were isolated.” This new germacranolide aldehyde (56) was isolated from Uro-spermum dalechampii.The novel cyclisation of the elemane-type skeleton of 52 G. Mehta. Chem. and Ind. 1970 1264. ’’ J. Lhomme and G. Ourisson Bull. SOC. chim. France 1970 3935. 54 R. M. Coates and J. P. Chen Chem. Comm. 1970 1481. ” T. C. Jain C. M. Banks and J. E. McCloskey Tetrahedron Letters 1970 841. 56 (a)K. Takeda I. Horibe and H. Minato J. Chem. SOC.(0,1970 1142; (b)K. Takeda K. Tori I. Horibe M. Ohtsru and H. Minato J. Chem. SOC.(C) 1970 2697. 5’ K. Tori I. Horibe K. Kuriyama and K. Takeda Chem. Comm. 1970,957. R. K. Bentley J. G. St. C. Buchanan T. G. Halsall and V. Thaller Chem. Comm. 1970,435. 410 B. A. Marples dehydrosaussurea lactone (57)to the bicyclic compounds (58)and (59)is achieved by treat men t with N-bromosuccinimide.5 q0 0 &o Torreyal (61) has been synthesised by use of the double Claisen-Cope re-arrangement of the ether (60)60and a study of this reaction on (-)-cis-carveol 2-methyl-butadienyl ether (62)shows that below 150"C two sigmatropic processes are involved.61 Full details are available of the application of intramolecular carbene-olefin addition reactions to the synthesis of sirenin.62 Further examples of this process have been applied to the syntheses of sire1-1111,~~ sesq~icarene,~~ (62) 59 T.C. Jain C. M. Banks and J. E. McCloskey Tetrahedron Letters 1970 2387. " A. F. Thomas and M. Ozainne J. Chem. SOC.(C) 1970,220. '' A. F. Thomas and G. Ohloff Helv. Chim. Acta 1970 1145. 62 (a) K. Mori and M. Matsui. Tetrahedron.1970 26 2801 ; (b) U. T. Bhalerao J. J. Plattner and H. Rapoport J. Amer. Chem. SOC.,1970 92 3429. '' E. J. Corey and K. Achiwa Tetrahedron Letters 1970 2245. 64 (a) R. M. Coates and R. M. Friedinger Tetrahedron 1970 26 3487; (b) 0. P. Vig, 0. P. Chugh R. C. Anand and M. S. Bhatia J. Indian Chem. SOC.,1970,47 506. Terpenoids and Steroids 41 1 p-c~bebene,~~ and thujopsene.66 The syntheses of juvabione are reported in full.67 A modified Wittig reaction allows the stereospecific syntheses of a-santalol (63),68 farne~ol,~’ and the juvenile hormone.70 The process involves the stereospecific formation of the betaine (65) from the P-oxidophosphonium ylide (64) and elimination to give the olefin (66). A second stereospecific syn- 0 0 $Ph R ‘CH-C=PPh CH *O -I H,R2R’HwR2 I H‘ CH,OH R2 R’ CH20 thesis of or-santalol is also reported.Alternative syntheses are reported for ~eychellene,~~ and b~lnesol.~~ juvenile hormone,73 illudin M,74 n~otkatone,~~ Syntheses are reported for (+)-davanone (67) and the ra~emate,~~ calameon &Q= H 65 0.P. Vig M. S. Bhatia A. K. Verma and K. L. Matta J. indian Chem. Soc. 1970 41. 277. 66 K. Mori M. Ohki A. Kobayashi and M. Matsui Tetrahedron 1970 26 2815. 67 (a) A. J. Birch P. L. Macdonald and V. H. Powell J. Chem. SOC.(C),1970 1469; (b)B. A. Pawson H.-C. Cheung S. Gurbaxani and G. Saucy J. Amer. Chem. Suc. 1970 92 336. 68 E. J. Corey and H. Yamamato J. Amer. Chem. SOC.,1970,92,226 3523. 69 E. J. Corey and H. Yamamato J. Amer.Chem. Soc. 1970,92 6637. 70 E. J. Corey and H. Yamamato J. Amer. Chem. Soc. 1970 92,6636. 71 E. J. Corey H. A. Kirst and J. A. Katzenellenbogen J. Amer. Chem. SOC.,1970 92 63 14. 72 K. J. Schmalzl and R. N. Mirrington Tetrahedron Letters 1970 3219. 73 E. E. van Tamelen and J. P. McCormick J. Amer. Chem. Soc. 1970.92 737. 74 T. Matsumoto H. Shirahama A. Ichihara H. Shin S. Kagawa and F. Sakan Tetra-hedron Letters 1970 1 171. 75 J. A. Marshall and R. A. Ruden Tetrahedron Letters 1970 1239. 76 M. Kato H. Kosugi and A. Yoshikoshi Chem. Comm. 1970 185. 77 (a)G. Ohloff and W. Giersch Helv. Chim. Acta 1970,53 841 ; (h)A. J. Birch T. E. T. Corrie and G. S. Subba Rao Austral. J. Chem. 1970 23 1811; (c) P. Naegeli and G. Weber Tetrahedron Letters 1970 959.412 B. A. Marples (68),78 (+ )-&-cadinene (69),79 isoishwarane (70),80 p-santalol (71),81 and dama- scenone (72),82 thus confirming their respective structures. The methylene group of conjugated a-methylene-lactones may be protected by a reversible thiol addition reaction. Thus vernolepin (73) may be converted to 1,2-dihydrovernolepin (74).83 The stereochemistry of the ring junctions in the (73) (74) a-methylene-lactones may be determined by a study of the allylic coupling constants in the n.m.r. spectra.84 Artemone (75) has been isolated with the isomeric davanone (67)from Arternisia pall en^.^ A number of sesquiterpenoid compounds with novel carbon skeletons have been reported. Worthy of special mention are cyclonerodiol (76),86 spiro- laurenone (77),87 and occidenol (previously occidiol) (78).88 A unique terpenoid antibiotic LL-Z1271a with a 16-carbon skeleton (79) has been isolated from an Acrostalagrnus species of f~ngus.~ Methanolysis of compound (79) gives the 78 M.Iguchi A. Nishiyama M. Nirva J. Yamamura and Y. Hirata Chem. Comm. 1970 1323. l9 M. D. Soffer and L. A. Burk Tetrahedron Letters 1970 21 1. 'O R. B. Kelly and I. Zamecnik Chem. Comm. 1970 1102. 81 H. C. Kretschmar and W. F. Erman Tetrahedron Letters 1970 41. " E. Demole P. Enggist U. Sauberli M. Stoll and E. Sz. Kovats Helu. Chim. Acta 1970 53 541. '' S. M. Kupchan T. J. Giacobbe and I. S. Krull Tetrahedron Letters 1970 2859. 84 Z. Samek Tetrahedron Letters 1970 671. 85 P.Naegeli J. KlimeS and G. Weber Tetrahedron Letters 1970 5021. '6 S. Nozoe M. Goi and N. Morisaki Tetrahedron Letters 1970 1293. 87 M. Suzuki E. Kurosawa and T. Irie Tetrahedron Letters 1970 4995. " B. Tomita and Y. Hirose Tetrahedron Letters 1970 235. 89 G. A. Ellestad R. H. Evans jun. M. P. Kuntsmann J. E. Lancaster and G. 0. Morton J. Amer. Chem. SOC.,1970,92 5483. Terpenoids and Steroids isomeric compound (80) by Michael addition at C(7)followed by elimination of methoxide ion from C(14). The long-sought thermally and chromatographically -* q/$l $.oMe H -' H 'OMe 0 0 (79) 0 O (80) labile germacrene-A (81) has been isolated from Eunicea mammosa by use of chromatography at 5 "C on a sucrose-florisil adsorbent." Trichodiene (82)91 and trichodiol (83)92 have been isolated from Tricotheseum roseurn.These compounds may be biogenetic precursors of the physiologically active tricothe- cane sesquiterpenoids. CHZOH p....f -075 . ow (81) (82) (83) 3 Diterpenoids A review on the synthesis of diterpenes has been published.93 The diterpenoid lactone amarolide which was previously isolated from Ailanthus glandulosa has now been isolated from Castela nicholsoni and on the basis of 100MHz (84) (85) (86) n.m.r. data the structure has been amended to (84).94 Rosein 111has been shown to be 1lp-hydroxyrosenonolactone(85),95 and final details of the structure of abbeokutone (86) have been el~cidated.~~ 90 A. J. Weinheimer W. W. Youngblood P. H. Washecheck T. K. B. Karns and L.S. Cieresko Tetrahedron Letters 1970,497. 91 S. Nozoe and Y. Machida Tetrahedron Letters 1970 2671. 92 S. Nozoe and Y. Machida Tetrahedron Letters 1970 1177. q3 E. Wenkert Rec. Chem. Progr. 1970,31 1. 94 W. Stocklin M. Stefanovic and T. A. Geissman Tetrahedron Letters 1970 2399. q5 R. Guttormson P. Main A. J. Allison and K. H. Overton Chem. Comm. 1970 719. 96 J. R. Hanson and A. F. White Tetrahedron 1970 26 4839. 414 B. A. Marples The acid-catalysed rearrangement of solidagenone (87) (from Solidago canadensis) to the tetracyclic compound (89) is notable. The reaction probably involves an initial dehydration and 1,2-methyl shift to the intermediate (88) l1 0 0 which cyclises to the pr~duct.'~ Deamination of the 8-aminogibberellin (90) leads via ring D inversion to the 7-deoxy-compound (91) and suggests a plausible synthetic route from gibberic acid to 7-deo~ygibberellins.~~ Chromic acid oxidation of erythroxylol A (92) and related compounds leads to cleavage of the H H \ Me CH20H OH CH,OH (92) R = Me (99) R = CHzOH C(4)-C(18) bond." The extent of this cleavage is dependent in part upon the substitution in ring D which controls the steric interaction between the 4a- substituent and the lowmethyl group.A number of novel approaches to the construction of the bicyclo[3,2,l]octane system have been made. Steviol(94) was prepared by an acyloin-like condensa- tion of the keto-ester (93). loo Treatment of the diketone (95) with zinc amalgam and hydrochloric acid gave the ketol(96) which was also converted into steviol.lo' This key step was similarly employed in the synthesis of epiallogibberic acid.lo2 Reaction of the ketobromide (97) with di-n-butylcopper lithium gave the tetra- cyclic compound (98).'03 The synthesis of erythroxydiol A (99) employed the rearrangement of the expoxide (100) to the ketol (101).'04 97 T. Anthonsen P. H. McCabe R. McCrindle R. D. H. Murray and G. A. R. Young, Tetrahedron 1970 26 309 1. 98 J. C. Brown and B. E. Cross J. Chem. SOC.(0,1970 71. 99 A. Martin and R. D. H. Murray J. Chem. SOC.(0,1970,2023. loo I. F. Cook and J. R. Knox Tetrahedron Letters 1970 4091. lo' K. Mori Y. Nakahara and M. Matsui Tetrahedron Letters 1970 241 1. lo* K. Mori M. Matsui and Y. Sumiki Tetrahedron Letters 1970 429.E. J. Corey M. Narisada T. Hiraoka and R. A. Ellison J. Amer. Chem. SOC.,1970 92 396. lo4 K. Mori and M. Matsui Tetrahedron Letters 1970 3287. Terpenoids and Steroids pJo C0,Me & '% H '-H COZH I (93k! C02Me Biogenetic-type syntheses are reported for a-and /I-levantenolides (102) and (103) respectively from acyclic and monocyclic precursors. Nitrodeiso-propylation of the 12-acetyl-abietic acid derivative (104) gives the 13-nitro- compound (105) and thus provides a useful route to the 13-hydroxy-compound (106).lo' Podocarpic acid has been synthesised employing the stereospecific 4a-methylation of a 4a-cyano-3-ketone."' Full details of the synthesis of ( -)-sandaracopimaric acid involving the more usual stereoselective 4P-methyla- (104) R' = Ac R2 = i-C,H (105) R' = Ac RZ = NO (106) R' = H,R2 = OH lD5(a) M.Tanemura T. Suzuki T. Kato and Y. Kitahara Tetrahedron Letters 1970 1463; (b)T. Kato M. Tanernura T. Suzuki and Y. Kitahara Chem. Comm. 1970 28. '06 R. C. Cambie and R. A. Franich Chem. Cumm.. 1970 845. lo' M. E. Kuehne and J. A. Nelson J. Org. Chem. 1970. 35 161. 416 B. A Murples tion of a 4cr-methoxycarbonyl-3-ketone are also reported. O8 Methyl sandara- copimarate (107) is converted directly with rn-chloroperoxybenzoic acid to the allylic alcohol (108) which gives dihydroisopimaric acid (109).'09 This use of the high reactivity of the 8,14-a-epoxides in this series provides the first total ( 107) (108) (109) synthesis of a A'-diterpenoid.The formally total synthesis of taxodione (1 10) from podocarpic acid is reported."' A partial synthesis of gibberellin A, norketone (1 13) from 7-hydroxykaurenolide (1 11) confirms the structure of gibberellin A, (114).'" A key step in this synthesis is the functionalisation of the angular methyl group of the amide (112) by its reaction with lead tetra- acetate and iodine. A total synthesis of gibberellin Al ,uiu the previously prepared enone (1 15) is reported. '* H oc-0 0- H (113) R = 0 (114) R = CH H R COzH (115) Trachyloban-19-oic acid (116) a new pentacyclic diterpene was isolated from Heliunthus annus along with the biogenetically related (-)-kaur-16-en-19-oic acid.' Other interesting new diterpenes are the quinone miltirone (1 17) (from lo8 A.Afonso J. Org. Chem. 1970,35 1949. lo9 J. W. ApSimon Chem. Comm. 1970,83. llo K. Mori and M. Matsui Tetrahedron 1970 26 3467. I B. E. Gross and I. L. Gatfield Chem. Comm.. 1970 33. 'I2 W. Nagata T. Wakabayashi Y. Hayase M. Narisada and S. Kamata J. Arner. Chem. SOC.,1970 92 3202. 113 J. St. Pyrek Tetrahedron 1970 26 5029. Terpenoids and Steroids 417 Saluia miltiorrhiza),' l4 baccatin V (118)(from Taxus baccata),' ' and the macro- cyclic tumour inhibitor jatrophone (119) (from Jatropha gossypiifolia).' ' Jatrophone (119) forms a dihydrobromide by two novel transannular conjugate addition reactions. 6,20-Epoxylathyrol (120) was isolated from Euphorbia lathyris,"' and the related bertyadionol (121) was found in Bertya sp.~OU.''~ It was suggested that compounds (120) and (121) may be related biogenetically with phorbol. Oxidative studies on phorbol' l9 and the isolation of 4a-phorbol are reported. '** Further examples of grayanotoxins have been isolated.' ' Two new norditerpenoids podolactones A (122) and B (123) which are related to inumakilactone are shown to strongly inhibit expansion and mitosis of plant I I4 T. Hayashi H. Kakisawa Hong-Yen Hsu and Yuh Pan Chen Chem. Comm. 1970 299. 115 D. P. Della Casa de Marcano T. G. Halsall E. Castellano and 0. J. R. Hodder Chem. Comm. 1970 1382. 1 I6 S. M. Kupchan C. W. Sigel M. J. Matz J. A. S. Renauld R. C. Haltiwanger and R. F. Bryan J. Amer. Chem. SOC.,1970,92,4476. 117 (a) W.Adolf E. Hecker A. Balmain M. F. Lhomme Y. Nakatani G. Ourisson. G. Ponsinet R. J. Pryce T. S. Santhanakrishnan L. G. Matyukhina and I. A. Salti- kova Tetrahedron Letters 1970 2241; (6) K. Zechmeister M. Rohrl F. Brandl S. Hechtfischer W. Hoppe E. Hecker W. Adolf and H. Kubinyi Tefrahedron Letters 1970 307 1. 1 in E. L. Ghisalberti P. R. Jeffries T. J. Payne and G. K. Worth Tetrahedron Letters 1970,4599. 119 H. W. Thielmann and H. Hecker Annalen 1970,735 113. 120 P. Jacobi E. Harle H. U. Schairer and E. Hecker Annalen 1970 741 13. I21 (a) T. Okuno N. Hamanaka H. Miyakoshi and T. Matsumoto Tetrahedron 1970 26 4765; (b) S. von Kurten P. Pachaly F. Zymalkowski and G. Snatzke Annalen 1970,741 142. 418 B. A. Marples cells.'22 Chettaphanin-I (124)123 and 88-hydroxymarubiin (125)'24 are new furanoditerpenoids.The relative stereochemistry of the rx,p and 6-caesalpins at @..6zOH R. (122) R = H (123) R = OH 0 all but positions 9 and 14 has been assigned.'25 The prefuranoid compound nepetaefolin (126) was isolated from Leonotis nepetaefolia' 26 and the novel cis-clerodanes cistodiol (127) and cistodioic acid (128) were isolated from Cistus rnonspeliensis.'27 Incubation of dehydroabietic acid with Flavobacterium vesinovorurn leads to monocyclic and acyclic metabolites.' 28 w-FR f 1 R (127) R = CH,OH 122 M. N. Galbraith D. H. S. Horn J. M. Sasse and D. Adamson Chem. Comm. 1970 170. 123 A. Sato M. Kurabayashi H. Nagahori A. Ogiso and H. Mishima Tetrahedron Letters.1970. 1095. 124 E. R. Kaplan K. Naidu and D. E. A. Rivett J. Chem. SOC.(C) 1970 1656. 125 A. Balmain J. D. Connolly M. Ferrari E. L. Ghisalberti U. M. Pagoni and F. Pelizzoni Chem. Comm. 1970 1244. 126 J. D. White and P. S. Manchand J. Amer. Chern. SOC.,1970,92 5527. 127 G. Berti 0.Livi and D. Segnini Tetrahedron Letters 1970 1401. 128 J. F. Biellmann R. Wennig Ph. Daste and M. Faure-Raynaud Chem. Comm. 1970 346. Terpenoids and Steroids 419 4 Sesterterpenoids The monocyclic and optically active lipids diumycinol(129) isodiumycinol(l30) and diumycene (13I) which have been isolated from the phosphorus-containing antibiotic di~mycin,'~~ are new members of this class. (129) R = H2C-OH (130) R = H C Y HO (131)R = H2C 5 Triterpenes The position of the double bond in fissinolide which may be obtained by suc- cessive borohydride reduction and acetylation of mexicanolide has been dis- puted.' 30 Double irradiation n.m.r.data favour the A8(14)-structure (132). 130a Oxidation of A20(29)-1~pene derivatives (133) with mercuric acetate gives the 18,20(29)-dienes (1 34) and not the 13( 18),20(29)-dienes as previously suggested. OAc R = Me CH,OAc C0,Me The absence of U.V. spectra in these products is due to the strong steric interaction between the 12P-H and the isopropenyl group which results in a twisted con- formation for the dienes. Similar oxidation of a 28-hydro~y-A~~(~~)-lupene gives the 19,28-0xide.'~~ Further work on helvolic acid which was originally formu- lated as a 6-oxo-7-acetoxy-compound indicates that the structure should be W.A. Slusarchyk J. A. Osband and F. L. Weisenborn J. Amer. Chem. SOC.,1970 92,4486. lJO (a)D. A. H. Taylor Tetrahedron Letters 1970,2797;(6)D. Lavie E. C. Levy C. Rosito and R. Zelnik Tetrahedron 1970 26 219. 13' (a) G. V. Baddeley J. J. H. Simes and T. G. Watson Tetrahedron 1970 26 3799; (6)S. P. Adhikary W. Lawrie and J. McLean J. Chem. SOC.(0,1970 1030. 13' A. VystrEil and Z. Blecha Coll. Czech. Chem. Comm. 1970,35 3309. 420 B. A. Marples amended to (135)' 33 Accordingly the structures of helvolinic acid 7-deacetoxy- helvolic acid and 7-oxofusidic acid should all be amended.' 33 A detailed study of OAc (135) the n.m.r. data of the two cis-2,3-diols obtained by oxidation of methyl olean-2,12- dien-28-oate (1 36) reveals that the original structural assignments should be interchanged.' 34 The cis-2cr,3cc-diol (1 37) occurs in Shorea acurninata resin.' 34 'O.*Q} (136) R = H HO" (136) R = Me (137) Aromatisation of barrera-7,9( ll)-dienyl acetate (138) with sulphuric acid in acetic acid leads to the A-nor-compound (139) presumably by the indicated (139) '33 S.Iwasaki M. I. Sair H. Igarashi and S. Okuda Chem. Comm. 1970 11 19. ' 34 H. T. Cheung and T. C. Yan Chem. Comm. 1970 369. Terpenoids and Steroids 42 1 mechanism.'35 Previously it was suggested that the product was of the anthra- steroid type. Pyridinium chloride appears to be a useful reagent for the conversion of triterpene oxides to unrearranged dienes.' 36 Oxidation of 7-hydrazones with lead tetra-acetate provides a useful route to 7a-acetoxy-triterpenes.'37 New routes to 4-demethyl- and 4,4-bisdemethyl-triterpenoids are described,' 38 and improved degradations of the side-chain of lanosterol derivatives to 4,4,14- trimethylpregn-8-en-20-onesare reported.' 39 Degradation of the side-chain of cucurbitacins leads to novel 9P-methyl-steroids.140 Meliacins of the general structure (140; R = H,OAc; 0)are generally stable to acid. However the 7-hydroxy-compounds (140 ;R = a-OH,H ;P-OH,H) re- arrange with boron trifluoride etherate in benzene.I4'. Thus 7-deacetylkhivorin (141) gives the ketone (142) and the diene (143).14' Full details have appeared c. co 0 0 (140) (141) R = a-OH H (1 42) (143) of the biogenetically significant conversion of turraeanthin to a simple meliacin.142 Acid-catalysed backbone-rearrangement of the 11-0x0-onocerin (144) proceeds in a non-concerted fashion to the 18a-fernane derivative (146).'43 An inter- n 'I(145) I,(146) '" M. Fukuoka and S. Natori Tetrahedron Letters 1970,4867. 136 I. Morelli and A. Marsili J. Org. Chem. 1970 35,367. 13' D.H. R. Barton J. F. McGhie and P. L. Batten J. Chem. SOC.(C) 1970 1033. 13' (a)C. W. Shoppee N. W. Hughes R. E. Lack and J. T. Pinhey J. Chem. SOC.(C) 1970 1443; (6) D. H. R. Barton and D. Kumari Annalen 1970 737,108. 139 (a) G. Habermehl and G. Volkein Annalen 1970 742 145; (b) L. H. Briggs J. P. Bartley and P. S. Rutiedge Tetrahedron Letters 1970 1237.I4O J. R. Bull and K. B. Norton J. Chem. SOC.(0,1970 1593. D. E. U. Ekongand M. D. Selema Chem. Comm. 1970,733. (a)J. G. St. C. Buchanan and T. G. Halsall J. Chem. SOC.(C) 1970 2280; (b)G. P. Cotterrell T. G. Halsall and M. J. Wriglesworth J. Chem. SOC.(0,1970 1503; cf. Ann. Reports (B) 1967 64 360. 143 H. Kakisawa and K. Iguchi Chem. Comm. 1970 1488. 422 B. A. Marples mediate such as (145) would explain the epimerisation at C(18). Hopa-9(11),21- diene is converted by a backbone rearrangement to ferna-7,9( 1 1)-diene which is reduced to fern-8-ene.'44 Use of the Barton reaction with the nitrite ester of 13-hydroxyoleanane (derived from P-amyrin) led to oleanolic The Barton reaction with the nitrite ester of 1 1P-hydroxylanostanes is reported to give only C(19)-functionalised compounds.However the hypoiodite reaction (147) with 3P-acetoxy-1 lp-hydroxylanostane gave the iodo-ether (147).14(j The forma- tion of 11,19-ethers in the triterpenes thus appears to be unfavourable and attack at C(18) occurs after initial formation of the 19-iodo-compound. A partial synthesis of methyl angolensate (148) from 7-0x0-7-deacetoxykhivorin established that the relative configuration of the ether oxygen at C(l) is A 31-step total synthesis of (-t The epoxy-diol(l49) )-germanicol is re~0rted.I~~ C02Me (148) -+ I HO K. Iguchi and H. Kakisawa Chem. Comm. 1970 1487. 145 R. B. Boar D. C. Knight J. F. McGhie and D. H. R. Barton J. Chem. SOC.(0 1970 679.P. Roller and C. Djerassi J. Chem. Soc. (0,1970 1089. J. D. Connolly I. M. S. Thornton and D. A. H. Taylor Chem. Comm. 1970 1205. R. E. Ireland S. W. Baldwin D. J. Dawson M. I. Dawson J. E. Dolfini and J. New-bould J. Amer. Chem. SOC..1970 92 5743. 14' Terpenoids and Steroids 423 gives( +)-malabaricanediol(l50) on treatment with picric acid in nitr~methane.'~~ This is the first natural product derived from squalene in a non-enzymic process. Among the novel triterpenoids reported are 31 -norcycloartenol (from Car-negiea gigantea),' s' the 5,10-seco-compound baccharis oxide (151) (from Baccharis halimifolia),' 'and sapelins A (152) and B (153)(from Entandrophragma cylindricurn).'s2 Clavatol (154) the first natural bisnorenocerane was isolated OH HO" HO-from Lycopodium clavatum.' 53 Lycoclavanin is a 16-oxoserrat-14-ene' s4 and two further members of this class have been is01ated.l'~ Cucurbitacins 0,P and Q which have significant activity against human carcinoma of the nasopharynx were isolated from Brandegea bigelovii.'s6 Hexanorcucurbitacin D was isolated from Begonia tuberhydrida. lS7 Examination of several Khaya species' 58 and 14' (a) K. B. Sharpless J. Amer. Chem. Soc. 1970 92 6999; (6) Chem. Comm. 1970 1450. I5O M. Derys A. Alcaide F. Pinte and M. Barbier Tetrahedron Letters 1970,4621. lJ1 T. Anthonsen T. Bruun E. Hemmer D. Holme A. Lamvik E. Sunde and N. A. Serensen Actu Chem. Scund. 1970,24,2479. 15' W. R. Chan D. R. Taylor and T. Yee J. Chem. SOC.(0,1970 31 1.153 T. Sano T. Fujimoto and Y. Tsuda Chem. Comm. 1970 1274. 154 Y. Tsuda and T. Fujimoto Chem. Comm. 1970 260. Y. Tsuda T. Fujimoto and K. Kimpara Chem. Comm. 1970 261. 156 S. M. Kupchan R. M. Smith Y. Aynehchi and M. Maruyama J. Org. Chem. 1970 35,2891. R. W. Doskotch and C. D. Hufford Canad. J. Chem. 1970,48 1787. (a)E. K. Adesogan D. A. Okorie and D. A. H. Taylor J. Chem. SOC.(C),1970,205; (6) E. K. Adesogan and D. A. H. Taylor ibid. p. 1711; (c) D. A. H. Taylor ibid. p. 336. 424 B. A. Marples Xylocarpus granatum' 59 has produced several new limonoids. Interestingly the West African Khaya anthotheca lacks the characteristic lactones of this species.' 580 A study of the variation of the 7-substituent on the rearrangement of havanensin is reported.' 6 Steroids The I.U.P.A.C.revised rules for steroid nomenclature have been published. 160 Reviews have appeared on the applications of mass spectrometry'61 and photo- chemical transformations'62 in the steroid field. Recent advances in the chemistry of the plant steroids,' 63 the synthesis pf cardenolides,' 64 specific fluorination,' 65 vitamin D chemistry,'66 the contraceptive proge~togens,'~~ and other physio- logically active steroids' 68 have been reviewed. Application of the Barton reaction'69 and an X-ray structure determination'" have shown that the A-ring in 4,4-dimethyl steroids is in a flattened chair con- formation owing to rotation around the C(4)-C(S)-bond. Photolysis of the nitrite (155) gives the cyanoketone (156) thus supporting the initially proposed OH 7s.0 4 >*ij (156) mechanism for the oxidative cyanohydrin-cyanoketone rearrangement. l7' In the normal examples of this rearrangement the hydroxy-group of the cyanohydrin functions to remove a hydrogen atom from C(18) and to stabilise an intermediate radical during the cyanide group migration. Oxidation of remote centres in the steroid nucleus is achieved by irradiation of suitable steroidal benzophenone derivatives.'72 Thus irradiation of 3cr-cholestanyl-5-(4-benzoylphenyl) valerate leads through the benzophenone triplet primarily to the A' 4-compound 54 D. A. Okorie and D. A. H. Taylor J. Chem. SOC. (0,1970,210. Iho I.U.P.A.C. J. Steroid Biochem. 1970 1 143. l6 ' C. Djerassi Pure Appl.Chem. 1970 21 205. Ih2 0.Jeger and K. Schaffner Pure Appl. Chem. 1970 21 247. lb3 K. Schreiber Pure Appl. Chem. 1970 21 131. Ib4 R. Deghenghi Pure Appl. Chem. 1970,21 153. 65 D. H. R. Barton Pure Appl. Chem. 1970 21 285. Ib6 G. M. Sanders J. Pot and E. Havinga Fortschr. Chem. org. Naturstoffe 1969 27 131. 167 V. Petrow Chem. Rev. 1970 70 713. Ih8 R. Wiechert Angew. Chem. Internat. Edn. 1970,9 321. lh9 J. M. Midgley J. E. Parkin and W. B. Whalley Chem. Comm. 1970 789. 170 G. Ferguson E. W. Macaulay J. M. Midgley J. M. Robertson and W. B. Whalley Chem. Comm. 1970,954. 17' J. Kalvoda Chem. Comm. 1970 1002. 17' (a)R. Breslow and S. W. Baldwin J. Amer. Chem. Soc. 1970,92,733; (b) J. E. Baldwin A. K. Bhatnagar and R. W. Harper Chem.Comm. 1970 659. Terpenoids and Steroids (157).'72b The site of oxidation and the type of product (macrocyclic hydroxy- lactone or unsaturated ester) depends upon the size of the starting ester carbon chain. (1 57) Further studies on microbiological reactions are reported. Hydroxylation of some pregnanes with Aspergillus ochraceus leads to 1&1la-dihydroxy-com-pounds,' 73 and progesterone is hydroxylated (mono- di- and tri-) at C(6) C(1l) C(17),and C(21) with Aspergillus niger 100 and Rhizopus nigricans REF 129.'74 Micro biological reduction of 3-alkoxy-l 9-nor-A2p5(' ')-steroids and the 3-keto- A5(")-steroids to 3-hydroxy (preferentially P)-A5('0)-compounds is achieved with Pichia fermantans NCYC 246.' 75 Studies on backbone rearrangements continue.An unusually extensive hydrogen-fluoride-catalysed rearrangement of cholesterol to the D-homo-compound (158) is reported. '' The 20(S)-epimer of the normal 20(R)-A' 3(17)-' compound was detected in the backbone rearrangement of cholesterol.' Rearrangement of the des-A-steroid (159) in deuterium fluoride to the mono- deuterio-ketone (160) (after base-catalysed removal of deuterium a-to the carbonyl) indicates that protonation and deprotonation of possibly intermediate olefins or cyclopropanes is not inv01ved.l~~ Backbone rearrangement of 17a-deuterio-3P,17j?-dihydroxyandrost-5-eneto the corresponding 13-deuterio-17- ketone shows that a 13,17-enol is not intermediate in the formation of the HO (158) A. S. Clegg Sir E. R. H. Jones G.D. Meakins and T. J. Pinhey Chem. Comm. 1970 1029. '74 L. Sallam A.-M. El-Refai and I. El-Kady Bull. Chem. SOC.Japan 1970 43 1239. (a)K. Kieslich and H.-J. Koch Chem. Ber. 1970 103 610; (6)H.-J. Koch G. Schulz and K. Kieslich ibid. p. 603. 176 P. Bourguignon J.-C. Jacquesy R. Jacquesy J. Levisalles and J. Wagnon Chem. Comm. 1970 349. D. N. Kirk and P. M. Shaw Chem. Comm. 1970 806. J. P. Bertholet and J. Levisalles Chem. Comm. 1970 1162. 426 B. A. Marples ( 159) ( 140) 8o ketone." Rearrangement is inhibited by 7-hydroxy-s~bstituents.~ Evidence for the non-concertedness of backbone-type rearrangements is presented from a study of an epoxy-decalin.18' Unlike the 3P-acetoxy-5,6-epoxides the 3P-hydroxy-and 3~-methoxy-compounds react predominantly uia C(5)-0-cleavage.' 82 The 6P-phenyl-Sa,6a-epoxide (161) rearranges via the A-homo-B- nor-ketone to the thermodynamically more stable 4(5-+6)aheo-ketone (162).'83 Whereas lanostane 9a,l la-epoxides are unreactive towards boron trifluoride a 4,4-dimethyl-A5-9a 1 la-oxide rearranges to the 9P-methyl derivative due to stabilisation of the developing cationic centre by the 5,6-double bond.Ig4 1 Ph (161) ( 162) Acid-catalysed dehydration of 4,4-dimethyl-5cr-hydroxy-6~-acetoxy-, -6a-acetoxy- and -6-0x0-steroids leads to normal Westphalen-type rearrangement suggesting the polar and steric factors required for rearrangement may be separated.' Similar 6a- and 6P-hydroxy-compounds did not rearrange in this way.Ig6 The increased rate of rearrangement of a 10-ethyl-5a-hydroxy-compound (5.3 x) over that for the equivalent 10-methyl compound may indicate a concerted C(5)-0-cleavage and methyl migrati~n.'~' Although other hydroxy-steroids appear to rearrange under similar conditions via discrete carbonium ions,' 88 the differences in product types or reactants make correla- tion difficult.* Formulae (161)-(164) (168) (169) (172) and (173) are cholestane derivatives. J.-C. Jacquesy J. Levisalles and J. Wagnon Bull. SOC. chim. France 1970 670; cf. Ann. Reports (B) 1967 64 367. J.-C. Jacquesy R. Jacquesy and M. Petit Tetrahedron Letters 1970 2595. H. W. Whitlock jun. and A. H. Olsen J. Amer. Chem. SOC. 1970 92 5383. ls2 I. G. Guest and B. A. Marples J. Chem. SOC. (C) 1970 1626; cf. Ann. Reports (B) 1969.66 416. J. M. Coxon M. P. Hartshorn and W. J. Rae Tetrahedron 1970 26 1091. J. W. ApSimon and J. M. Rosenfeld Chem. Comm. 1970 1271. ''' J. G. L1. Jones and B. A. Marples J. Chem. Soc. (C) 1970 2273. IR6 M. Fetizon and P. Foy Cull. Czech. Chem. Comm. 1970 35,440. J. G. L1. Jones and B. A. Marples Chem. Comm. 1970 126. (a)J. M. Coxon M. P. Hartshorn and C. N. Muir Chem. Comm. 1970 1591 ;(6) C. Monneret C. Tchernatinsky and Q. Khuong-Huu Bull. SOC.chim. France 1970 1520. Terpenoids and Steroids The products of buffered solvolysis of the epimeric A-nor-tosylates (163) and (164) are the same as those of the 4a- and 4/?-methyl-A5-3P-tosylatesrespectively OTs (163) R' = H R2 = Me (164) R' = Me R2 = H showing that homoallylic participation of the double bond occurs in each case.It is suggested that an unstable unsymmetrical non-classical ion is formed from (164) (and the 4/?-methyl-compound); this collapses to a classical ion and thence to the 4-methyl-3,5-diene. Solvolysis of 19-mesylates gave ~-homo-steroids,'~~ and lithium in biphenyl treatment of a A'-3-oxo-19-mesylate gave a 3-0x0-1,19-~yclosteroid. The course of the deaminations of 16-amino-o-nor-steroids is stereo-electronically controlled thus the migrating groups are antiparallel to the departing nitrogen. 192 Treatment of the 3/?-hydroxy-A5-steroids with NN-dibromo-5,5-dimethyl-hydantoin gives 4-methyl-~-ring aromatic compounds through a dienol-benzene rearrangement. 93 The dienone-phenol rearrangement of the 6p-bromo-androstane (165) gives the 1 -methyl-androstane ( 167)Ig4 and the 6cr-phenyl- cholestane (166) gives the 4-methyl-cholestane (168) and some l-methyl-(165) R = P-Br (167) (168) R' = OH R2 = Me (166) R = a-Ph (169) R' = Me R2 = OH cholestane (169).'"' This latter compound arises from the migration of the C(SW(6) bond in the spiran intermediate.Aromatisation of the c-ring in a phenolic steroid'96 and in a cholic acid deri~ative'~' is reported. R. M. Moriarty and K. Bhamidipaty J. Org. Chem. 1970 35,2297. lYoF. Kohen W. Van Bever and R. E. Counsell J. Org. Chem. 1970,35 2272. P. Wieland and G. Anner Helv. Chim. Acta 1970 53,116. IQ2 J. Meinwald and T. N. Wheeler J. Amer. Chem. SOL-.,1970 92 1009. (a) J. R. Hanson and T. D. Organ Chem.Comm. 1970 1052; (6)J. Chem. SOC.(C) 1970 51 3. IQ4 T. Wolff and H. Dannenberg Chem. Ber. 1970 103,917. IY5 H.Dannenberg and T. Wolff 2.Nuturforsch 1970 25b 823. M. Kimura K. Akiyama K. Harita T. Miura and M. Kawata Tetrahedron Letters 1970 377. lY7T. Meney Y.-H. Kim R. Stevenson and T. N. Margulis Chem. Comm. 1970 1706. 428 B. A. Marples The introduction of a 7,8-double bond into the SP-3-keto-steroids reverses the usually preferred direction of enolisation. Thus en~l-acetylation'~~ and methyla- tion'" give products derived from enolisation towards C(2). This conforma- tional transmission does not affect the position of formylation [C(2)I2Oo but is significant in the solvolysis of 5~-A7-3-tosylates.201 Conformational effects are discussed in the reactions of some 5,10-seco-steroids.202 Diastereoisomeric selenoxides have been isolated and found to have similar pyrolytic and chiroptic properties to those of the sulpho~ides.~~~ Neighbouring group effects of the oxygen atom of 2,19- and 16,18-epoxides are reported.204 The stereochemistry of enolate alkylations of decalones is determined largely by the angular substit~ents.~~~ Alkylation of 2-cyano-3-ketones leads stereo- specifically to the a-alkyl compounds.206 cf '07 Chlorofluorocarbene reacts stereoselectively with steroid analogues to give a S-endo-F-add~ct.~'~ This would be predicted from the low reactivity of dichlorocarbene and the P-addition of difluorocarbene in these systems.The steroidal bicyclobutane (170) is uniquely hydrogenolised to the dihydro-compound (171).208 Other bicyclobutanes react with hexafluoroa~etone.~~~ Dichloroketen reacts regioselectively with steroidal olefins to give dichlorocyclobutanones.210The dichlorocyclobutanone (172) rearranges with sodium methoxide to the cyclopropanes (173).210a An empirical relationship between the magnitude of the geminal coupling constant and a dihedral angle of a P-bromine substituent is useful in conforma- n 198 A.J. Liston P. Toft P. Morand and H. Stollar J. Chem. SOC.(C) 1970 2121. 199 P. Morand J. M. Lyall and H. Stollar J. Chem. SOC.(C) 1970 21 17. 200 A. T. de B. Andrews A. D. Boul G. D. Meakins and M. J. Sledge J. Chem. SOC.(0 1970 1052. 201 R. Baker J. Hudec and K. L. Rabone J. Chem. SOC.(B) 1970 1446.202 (a) M. Lj. Mihailovid Lj. Lorenc J. Fordk H. NeSoviC G. Snatzke and P. TrSka Tetrahedron 1970 26 557; (6) M. Lj. Mihailovic M. Dabovic Lj. Lorenz and M. GaSiC Tetrahedron Letters 1970 4245. 203 D. Neville Jones D. Mundy and R. D. Whitehouse Chem. Comm. 1970 86. 204 (a)H.-P. Husson J. de Rostolan Y. Pepin P. Potier and J. Le Men. Tetrahedron 1970 26 147; (6) F. Kohen G. Adelstein and R. E. Counsell Chem. Comm. 1970 770. 205 (a)R. S. Matthews S. J. Girgenti and E. A. Folkers Chem. Comm. 1970,708;(6)R. S. Matthews P. H. Hyer and E. A. Folkers ibid. p. 38. 206 P. Beak and T. L. Chaffin J. Org. Chem. 1970,35 2275. 201 R. A. Moss R. W. Kleinman and K. L. Williamson Chem. Comm. 1970 927. 208 E. Galanty N. Paolella S. Barcza. R. Coombs and H.P. Weber J. Amer. Chem. SOC.,1970,92 5771. 209 E. Lee-Ruff and G. Just Tetrahedron Letters 1970 4017. 210 (a) V. R. Fletcher and A. Hassner Tetrahedron Letters 1970 1071; (6) A. Hassner and V. R. Fletcher ibid. p. 5053; (c) G. M. L. Cragg J. Chem. SOC.(C),1970 1829. Terpenoids and Steroids (172) (173) aandp tional analysis.2 Apiezon-potassium hydroxide columns are suitable for g.1.c. deuteriation of steroid ketones and may be used in conjunction with mass spectrometry for characterisation.2 The reaction of 2-lithio-1,3-dithian with epoxides provides a useful route to the construction of corticoid C(17)side-chains.213 Selective reduction of steroid ketones to the axial alcohols with homogeneous catalysts and an improved catalyst [(Ph,P),RhCl] are reported.2 '' 1 l~-Hydroxy-19-nor-steroids are converted satisfactorily to the 1l-fluoro-compounds using N-(2-chloro- 1,1,2-trifluoroethyl)diethylamine(cfi 1Op-Me steroids).215 In the presence of lithium bromide or chloride the lla-bromo- or chloro-compounds are obtained.The reaction of epoxides with hydrogen cyanide and triethylaluminium gives high yields of the diaxial cyanohydrins.21 Selective oxidation of spiro-ethers to the lactones is achieved with t-butyl chromate.21' Two new synthetic approaches to 18-nor-steroids are reported.218 Reductive fragmentation of the mesylate of 12a-hydroxyconanine with AIClzH \0 N I ''I J. Hudec Chem. Comm. 1970 242. G. M. Anthony and C. J. W. Brooks Chem. Comm. 1970,200. 'I3 J. B. Jones and R.Grayshan Chem. Comm. 1970 141 741. J. C. Orr M. Mersereau and A. Sanford Chem. Comm. 1970 162. "' E. J. Bailey H. Fazakerley H. E. Hill C. E. Newall G. H. Phillips L. Stephenson and A. Tulley Chem. Comm. 1970 106. *I6 W. Nagata M. Yoshioka and T. Okumura J. Chem. SOC.(C) 1970 2365; cf. Ann. Reports 1966 63 455. 'I7 G. F. Reynolds G. H. Rasmusson L. Birladeanu and G. E. Arth Tetrahedron Letters 1970 5057. 'I8 (a) G. Lukacs L. Cloarec and X. Lusinchi Tetrahedron Letters 1970 89; (h) Y. Shimizu Experientia 1970 26 588. 430 B. A. Marples gave the 18-nor-compound (174).218aHypoiodite reaction of the 20-hydroxy-12- oxopregnane (175) directly gave the lactone (176) which was readily decarboxyl- ated to the 18-nor-compound (177).218b The use of i-steroid intermediates considerably abbreviates the synthesis of ecdysones.2 Such intermediates allow the simultaneous introduction of appropriate functional groups at C(3) and C(6).A non-photochemical total synthesis of precalciferol is reported.220 Specific introduction of the 8,9-double bond was achieved viu a 8-hydroxy-9-chloro-compound. A new total synthesis of bufalin from digitoxigenin represents the first chemical transformation of a cardenolide to a bufadienolide.221 Cholanic acid is converted into the novel 5&14cc-bufa-20(22)-dienolide(178).222 A key step is the toluene-p-sulphonic 0 acid-catalysed D.D.Q. dehydrogenation of a P,y-unsaturated-S-lactone to the appropriate a-pyrone. The use of anhydrous hydrogen chloride in this reaction yields different products.The phytoecdysone ponasterone C has the structure (179) and not the 2a,3a- diol structure as previously suggested.224 The new phytoecdysone precyasterone (180),225 and the important ecdysterol metabolite poststerone (181),226 have been isolated from Cyathula capitata. The 20-ketone (181) is an important link in the catabolism of the ecdysterols to the 17-0x0-compounds. Bufadienolides and cardenolides have been isolated from Ch'an Sutoad venom.227 This appears * (a)D. H. R. Barton P. G. Feakins J. P. Poyser and P. G. Sammes J. Chem. SOC.(0 1970 1585; (6) W. Van Bever F. Kohen V. V. Ranade and R. E. Counsell Chem. Comm. 1970 758. 220 J. Dixon P. S. Littlewood B. Lythgoe and A. K. Saksena Chem. Comm. 1970 993.22' (a) G. R. Pettit L. E. Houghton J. C. Knight and F. Bruschweiler Chem. Comm. 1970 93; (6)J. Org.Chem. 1970 35 2895. 222 S. Sarel Y. Shalon and Y. Yanuka Chem. Comm. 1970 80. 223 S. Sarel Y. Shalon and Y. Yanuka Chem. Comm. 1970 81. 224 M. Koreeda and K. Nakanishi Chem. Comm. 1970 351. 225 H. Hikino K. Nomoto R. Ino and T. Takemoto Chem. and Pharm. Bull. (Japan) 1970,18 1078. 226 H. Hikino K. Nomoto and T. Takemoto Steroids 1970 16 393. 227 (a)N. Horiger D. Zivanov. H. H. A. Linde and K. Meyer Hefv. Chim. Acta 1970 53,1993 205 1 ;(6)N. Horiger H. H. A. Linde and K. Meyer ibid. p. 1503. Terpenoids and Steroids 43 1 to be the first report of the natural co-occurrence of these types. The originally assigned structure of bufotalin has been confirmed.228 The two very unusual OH marine sterols gorgosterol (182)y9 and 23-demethylgorgosterol (183),230are reported.It is conceivable that side-chain-alkylated sterols could be biogeneti-cally derived from such cyclopropyl derivatives. Messel shale extracts yield a number of 4-methyl-sterols (inter The major component of the sterol fraction from the seed oil of Vernonia anthehintica is vernosterol (184) which is HO (183) R = H (184) 228 G. R. Pettit P. Brown F. Bruschweiler and L. E. Houghton Chem. Comm. 1970 1566. ”’) (a)R. L. Hale J. Leclercq B. Tursch C. Djerassi R. A. Gross,jun. A. J. Weinheimer K. Gupta and P. J. Scheuer 1.Amer. Chem. SOC.,1970 92 2179; (b) N. C. Ling R. L. Hale and C. Djerassi J. Amer. Chem. SOC.,1970 92 5281.230 F. J. Schmitz and T. Pattabhiraman J. Amer. Chem. SOC.,1970,92 6073. 23’ G. Mattern P. Albrecht and G. Ourisson Chem. Comm. 1970 1570. 432 B. A. Marples related to the previously isolated A’-avena~terol.~~~ A number of new withano- lides are reported.233 Full details of the structures of physalins A and B are available.234 Physalin C another bitter principle of the winter cherry is shown to be 7-deoxyphysalin A.235 232 J. A. Fioriti M. G. Kolor and R. P. McNaught Tetrahedron Letters 1970 2971. 233 (a) I. Kirson E. Glotter A. Abraham and D. Lavie Tetrahedron 1970 26 2209; (6) I. Kirson D. Lavie S. M. Albonico and H. R. Juliani ibid. p. 5063. 234 T. Matsuura M. Kawai R. Nakashima and Y. Butsugan J. Chem. SOC.(0,1970 665; cf. Ann.Reports (B) 1969,66,422. 235 M. Kawai and T. Matsuura Tetrahedron 1970 26 1743.

ISSN:0069-3030    

DOI:10.1039/OC9706700403

出版商:RSC    

年代:1970

数据来源: RSC

摘要:

13 Heterocyclic Chemistry ~~~~~~~~ ~ By B. C. UFF Department of Chemistry Loughborough University of Technology. Leicestershire Threemembered Rings.-Mare examples of slow nitrogen inversion in hetero- cycles have appeared. In general there is a marked increase in inversion barrier caused by the presence of electronegative substituents (Cl Br N 0)on nitrogen and by the inclusion of nitrogen in a strained cyclic system.’,’ For example N-alkoxyaziridines (l),formed from alkoxynitrene insertion into olefins reveal the expected slow inversion at the nitrogen atom.3 ff N Thermal C-C cleavage of the 3-aroylaziridine system to permit [2 + 3]cyclo-addition reactions has been put to further good use in synthesis4 For example addition of (2) to activated imino-compounds provides a new general route to imidazolidines (4),uia the intermediate ylide (3).’ Addition of activated aromatic aldehydes to aroylaziridines gives 4-aroyloxazolidines in good yield.6 ’ Ann.Reports (B) 1969,66,423; 1968,65 441. E.g. J. M. Lehn and J. Wagner Tetrahedron 1970 26 4227; H. Kessler and D. Leib-fritz Tetrahedron Letters 1970 4289 4293 4297; G. W. Gribble N. R. Easton and J. T. Eaton ihid. 1970 1075; P. Rademacher and W. Luttke Angew. Chem. inrernat. Edn. 1970,9,245; J. M. Lehn and J. Wagner Chem. Comm. 1970,414. ’ S. J. Brois J. Amer. Chem. SOC.,1970 92 1079. Ann. Reports (B) 1969 66 423; 1968,65 443. J. W. Lown J. P. Moser and R. Westwood Canad. J. Chem. 1969 47 4335; 1970 48 1682. ti G. Dallas J. W. Lown and J. P.Moser Chem. Comm. 1970,278; J. Chem. SOC.(C) 1970 2383. 434 %. c. ug Treatment of 2,3-diaryl-1-azirine-3-carboxamides (5) with hydrazine results in ring expansion to give 172,4-triazin-6-onederivatives (6):' reactions of aziridines involving ring expansion have been reviewed.* N-Cyanoaziridines (8) have been prepared by treatment of olefins with cyanamide and a source H CONH Ar Ar N Ar Ar H tf X-C-C-NHCN -+ N X-L-A-NHCN -+ I II CN (7) (8) of positive halogen via a vicinal halogenocyanoamine (7).9 The stereochemistry of the oxidation of cis-and trans-1-amino-2,3-diphenylaziridines has been studied," as also has the solvolysis of 3-phenyl-l-azabicyclo[l,l,0]butane.' Good support for the existence of the azepine-benzeneimine equilibrium (9 S10) has been provided by the isolation of adduct (11 R = tosyl) from N-R + Me0,C N (9) (10) addition of diazomethane to (9).The observed orientation of addition rules out direct attack on (9) and subsequent isomerisation. Adducts from attack on (9) were however also isolated.I2 PhyHC0.NH-CMe3-+ N I I CF3 CMe (12) (13) ' T. Nishiwaki and T. Saito Chem. Comm. 1970 1479. F. N. Gladysheva A. P. Sineokov and V. S. Etlis Russ. Chem. Rev. 1970 39 118; and see J. W. Lown and K. Matsumoto Chem. Comm. 1970 692. K. Ponsold and W. Ihn Tetrahedron Letters 1970 1125. lo L. A. Carpino and R. K. Kirkley J. Amer. Chem. Sue. 1970 92 1784. I ' J. L. Kurtz J. Arner. Chem. SOC.,1970,92 5008. '' H. Prinzbach D.Stusche and R. Kitzing Angew. Chem. Internat. Edn. 1970 9 377. Heterocyclic Chemist r.y 435 An unusually stable trisubstituted a-lactam (13)has been reported formed from (12)by treatment with t-butyl hypochlorite and potassium t-butoxide.I3 Although a-lactams have been known for some years attempts to prepare the correspond- ing aziridine imines have been less successful. Now however they have been prepared from 1,3-elimination of a-bromo-amidines. For example (14) yields about equal amounts of (15) and (16). Valence isomerisation between (15) and Me,CCH-C=NCMe -+ CMe3 N + Me N $r AHMe Me3C -I(NMe Me3C AN CMe (14) (15) (16) (16) has not been detected. l4 The related three-membered ring amidine system 2-arnino-l-azirine has also been reported for the first time.Treatment of a-chloroenamine (17) with sodium azide yields ( 18)presumably via an a-azido-ena- mine.’’ (17) (18) (19) A high-yield route to the formation of epoxides is reported using the novel reagent peroxyacetyl nitrate (19) of potential value as a non-acidic epoxidising agent. The iodohydrination of double bonds followed by base treatment has also been shown to provide an efficient route to the oxiran ring.I7 The novel epoxyketen ketal(21) has been synthesised from (20). As can be anticipated the epoxy ortho-ester readily breaks down in acid but proves very inert to basic Me2CBrCO2CH2C(Me),CH20H% Meq>Me Me Me (20) CMe CMe 0 I’ E. R. Talaty and C. M. Utermoehlen Tetrahedron Letters 1970 3321 l4 H.Quast and E. Schmitt Angew. Chem. Internat. Edn. 1970,9 381. ‘’ M. Rens and L. Ghosez Tetrahedron Letters 1970 3765. l6 K. R. Darnall and J. N. Pitts Chem. Comm. 1970 130. ” J. W. Cornforth and D. T. Green J. Chem. SOC.,(0,1970 846. 436 B. C. Ufl reagents.18 Addition of excess diazomethane to diepoxide (22) results in an unusual rearrangement to give ketone (23) together with the anticipated tetra- epoxide.' A review has appeared on cyclisation reactions involving participation of epoxy-compounds.20 Persuasive evidence exists that a-lactones occur as intermediates in certain displacement and free-radical reactions.21 Now an a-lactone (24) has been prepared in solution by ozonolysis of di-t-butylketen at -78 "C on warming to -20 "C it begins to polymerise presumably by participation of the dipolar form (25).The analogous reaction with diphenylketen did not give a stable Me3Cy~~ 0 + (Me3C),C-C!/* -Me3C \ 0 (24) (25) a-lactone polyester being formed immediately at -78 0C.22A cyclobutadiene epoxide (28; R = alkyl X = halogen) is claimed to have been isolated from treatment of (26) by alkoxide possibly via the anion (27).23 The preparation of 1,2-naphthalene oxide (29) was reported previously24 and no isomeric benzoxepin could be detected spectroscopically. In such cir- cumstances (29) should be isolable in optically active forms and use of an optically active precursor has now resulted in production of (29) with an optical purity of ca. Isolation of the epoxide (30) of acenaphthylene is reported as resulting from treatment of acenaphthylene with rn-chloroperbenzoic acid.The M. S. Newmann and E. Kilbourn J. Org. Chem. 1970,35 3186. l9 H. W. Moore and M. W. Grayston J. Org. Chem. 1970,35 2832. 2o V. N. Yandovskii V. S. Karavan and T. I. Temnikova Run. Chem. Rev. 1970 39 265. 21 E.g. J. E. Leffler and R. G. Zepp J. Amer. Chem. SOC.,1970 92 3713. 22 R. Wheland and P. D. Bartlett J. Amer. Chem. SOC.,1970 92 6057. 23 F. Toda and K. Akagi Chem. Comm. 1970 764. 24 Ann. Reports (B) 1968 65 371. 25 D. R. Boyd D. M. Jerina and J. W. Daly J. Org. Chem. 1970 35. 3171. Heterocyclic Chemistry product (30) is readily converted to acenaphthenone which probably accounts for previous difficulties in isolating this compound.26 The I9F n.m.r.shielding parameters have been determined for a series of trans-p-fluor0-m’- and $-substituted stilbene epoxides and show that the oxiran ring transmits conjugation to the same extent as does the cyclopropane ring i.e. ca. 26% as effective as a double bond.” An example of cis-opening of an oxiran ring is provided by the conversion of (31)into the diacetate (32). Rearward c1 approach of acetate is hindered and possibly o-participation is involved.28 The epoxide-allylic alcohol rearrangement of cis-and trans-4-t-butylcyclo-hexene oxide by lithium diethylamide is shown through appropriate deuterium substitution to occur by a syn-elimination process.29 The mechanism of oxida- tion ofSchiff bases to oxaziranes by peroxy-acids reported last year3’ has been further studied in aprotic solvent^.^ Four-membered Rings.-Pyrolysis of the p-lactams (33) and (35) gives the olefins (34)and (36)stereospecifically.The process involved is a reverse [,2 + x2a]cyclo-addition in which the cyanuric acid acts as the ,2 component. The high tempera- ture necessary is considered an indication of a high energy of activation asso- ciated with the severe ring distortion required for adoption of the antarafacial mode.32 (33) (34) (35) (36) The conditions for the C-6epimerisation of the penicillin nucleus by a p-elimina- tion mechanism have been di~cussed,~ and a new non-basic reversible method of epimerising penicillin sulphoxides at C-6 by exposure to NO-bis(trimethy1- sily1)acetamide is reported.The equilibrium occurs regardless of the nature of the amide ~ide-chain.~~ The trans-p-lactam (37) is epimerised on heating with 26 T. H. Kinstle and P. J. Ihrig J. Org. Chem. 1970,35,257. ” R. G. Pews and N. D. Ojha Chem. Comm. 1970 1033. 28 A. S. Y.Chua and W. P. Cochrane Chem. and Ind. 1970 1569. ’’ R. P. Thummel and B. Rickborn J. Amer. Chem. SOC.,1970,92 2064. 30 Ann. Reports (B) 1969 66 425. V. Madan and L. B. Clapp J. Amer. Chem. SOC.,1970,92,4902. 32 L. A. Paquette M. J. Wyvratt and G. R. Allen J. Amer. Chem. Sac. 1970 92 1763. 33 S. Wolfe W. S. Lee and R. Misra Chem. Comm. 1970 1067. 34 G. E. Gutowski Tetrahedron Letters 1970 1779. 438 B. C. Uf the base 1,5-diazabicyclo[4,3,0]non-5-eneto give an equilibrium mixture con- taining 30% of the cis-isomer.No reaction occurred when the weaker base HH Br -_{-f Ph triethylamine was An efficient non-enzymic conversion of benzyl-penicillin (38)to 6-aminopenicillanic acid (39)has been accomplished by treating (38) (39) the silyl ester of benzylpenicillin consecutively with phosphorus pentachloride n-butanol and water at low temperature^.^^ The chemical conversion of penicillin to the cephalosporin system was dis- cussed last year37 and a further report involving a double sulphoxide rearrange- ment has appeared.38 Two other novel rearrangements of penicillin derivatives p-NO,. C,H4C H =N t> 'CO,CH,OMe p-NO,.C,H,CH=N zc3 /. 0 'C02CH ,OMe (42) ~-No,.c,H,cH=N% 'NKCO,Me (4)MeAMe 35 A. K. Bose C. S.Narayanan and M. S. Manhas Chem. Comm. 1970,975. " H. W. 0.Weissenberger and M. G.van der Hoeven Rec. Trau. chim. 1970,89 1081 3' Ann. Reports (B) 1969 66 429. '' D. 0.Spry J. Amer. Chem. SOC.,1970,92 5006. Heterocyclic Chemistry 439 have appeared. The penicillin sulphoxide ester (40) on treatment with trimethyl phosphite rearranged to (41) probably via a sulphenic acid inte~mediate.~' Secondly the 6-P-aminopenicillanic acid derivative (42) on treatment with base followed by diazomethane has been shown to give the 1,3-thiazine (44).40 The rearrangement is considered to proceed via the 1,4-thiazepine (43) an analogue of which was formed in competition with the epimerisation of methyl 64-phthalimidopenicilliate on treatment with base.41 Relatively few azetines are known and the formation of the 1-azetine (48) is now reported it results from nucleophilic addition of trichloromethyl-lithium Me I to azirine (45) followed by treatment with base via (46) and presumably the azabicyclobutane (47) as intermediate.42 PhCH,CH2C0.Me -+ PhCH (49) (50) (51) 3-Thietanones have been prepared by reaction of ketones with thionyl chloride [e.g.(49)+(SO)].An a-chloro-a-sulphenyl chloride is considered a likely inter- mediate.43 The parent compound (51)of a new skeleton in the strained sulphur- bridged polycyclics series has been prepared by base treatment of 3-chloro- cyclopentyl thi~acetate.~~ The previously unknown 2-thiabicyclo[2,2,0]hexane system has been formed by cycloaddition of the reactive thiete 1,l-dioxide with enamines and ynamines [e.g.to give (53)]."' 39 R.D. G. Cooper and F. L. Jose J. Amer. Chem. Soc. 1970,92,2575 and see R. D G. Cooper ibid. p. 5010. 40 J. R. Jackson and R. J. Stoodley Chem. Comm. 1970 14. 41 0.K'. J. Kovacs B. Ekstom and B. Sjoberg Tetrahedron Letters 1969 1863. 42 A. Hassner J. 0.Currie A. S. Steinfeld and R. F. Atkinson Angew. Chem. Internat. Edn. 1970 9 731. 43 A. J. Krubsack,T. Higa and W. E. Slack J. Amer. Chem. SOC.,1970,92,5258. 44 I. Tabushi Y. Tamura and Z. Yoshida Tetrahedron Letters 1970 2931. 45 L. A. Paquette R. W. Houser and M. Rosen J. Org. Chem. 1970,35 905. 440 B. C.U’ The first preparations of 1,2-dioxetans by photo-oxygenation are For example cis-and trans-diethoxyethylenes on reaction with singlet oxygen give stereospecifically cis-and trans-diethoxy-l,2-dioxetansrespectively [e.g.OEt EtO OEt (54) (54)]. If the process is concerted then the singlet oxygen must undergo antara- facial addition to the alkene. Five-membered Rings with One Hetero-atom.-Reviews have appeared on the physicochemical properties of pyrr~les,~’ the reduction of in dole^,^^ the elec- trolysis of N-hetero~ycles,~~ and on the reactions and properties of cyclic mono- hides particularly of the succinimide and phthalimide type.50 A new synthesis of substituted pyrroles is reported resulting from the rearrangement of O-vinyl-oximes. For example on heating (55)(the adduct from acetophenone oxime and dimethyl acetylenedicarboxylate) the pyrrole (57)is produced probably via the CO Me CO,Me PhyMro2Me NLO C0,Me H (55) (56) (57) OS02R Et 0 Et 9-Meff&Me CHO CHO dH ,CI -(58) (59) (60) iminoketone (56)? Also reported is a synthesis of 7-azabicyclo[2,2,l]heptane (59) by treatment of the sulphonate (58) with aqueous base.52 Recent chemistry and biochemistry of the bile pigments have been reviewed,53 as has the structure of porphyrins and metall~porphyrins~~ and the synthesis55 46 P.D. Bartlett and A. P. Schaaf J. Amer. Chem. Soc. 1970 92 3223; S. Mazur and C. S. Foote ibid. 1970 92 3225. 47 R. A. Jones Adv. Heterocyclic Chem. 1970 11 383. 48 B. Robinson Chem. Rev. 1969,69 785. 49 H. Lund Adu. Heterocyclic Chem. 1970 12 213. ’O M. K. Hargreaves J.G. Pritchard and H. R. Dave Chem. Rev. 970 70 439. T. Sheradsky Tetrahedron Letters 1970 25. 52 R. R. Fraser and R. B. Swingle Canad. J. Chem. 1970 48 2065. ” W. Rudiger Angew. Chem. Internat. Edn. 1970 9 473. ” E. B. Fleischer Accounts Chem. Res. 1970 3 105. ” A. Eschenmoser Quart. Rev. 1969 24 366. Heterocyclic Chemistry 441 and chemistry56 of the corrin system. An improved route to 5,S-diformyl- dipyrrylketones [e.g. (60)] is reported by oxidation of 5,S-diformyldipyrryl- methanes with bromine followed by sulphuryl chloride:57 a range of oxypor-phyrins were then synthesised by condensation with appropriate dipyrryl- me thane^.^^ A methyl group has been introduced into the 1-position of the octaethyl- porphin derivative (61) via a chloroform adduct to give (62).59The synthesis of some NN’-dimethylporphyrins has been reported by direct methylation of the Et ?+ Et Et Et 20H-i CHCI,-AICI A ii NaBH iii HCl Et Et .Et Et (62) parent porphyrins.60 The reaction of benzoyl peroxide with octaethylpor- phyrin leads to side-chain and meso-substituted benzoyloxy-derivatives.61 Electrophilic substitution reactions of a wide range of metalloporphins have been examined and contrasted with the behaviour of metal-free porphins.62 The conformation of a number of metalloporphyrins in solution has been calculated by use of the high-field shift of the co-ordinated extra-planar ligand in the H n.m.r. spectrum.63 An appraisal of bond strain in the porphin skeleton r Ph 12+ Ph + 2c104 --Ph -B Ph -,Ph CIO -Ph 2 56 T.A. Melent’eva N. D. Pekel’ and V. M. Berezovskii Russ. Chem. Rev. 1969 38 926. ’’ P. S. Clezy A. J. Liepa A. W. Nichol and G. A. Srnythe AustruI. J. Chem. 1970,23 589. 58 P. S. Clezy A. J. Liepa and G. A. Smythe AustraI. J. Chem. 1970,23,603. ’’ J.-H. Fuhrhop T. Lumbantobing and J. Ullrich Tetrahedron Letters 1970 3771. 6o G. R. Dearden and A. H. Jackson Chem. Comm. 1970 205; M. J. Broadhurst R. Grigg and G. Shelton ibid. 1970 231; R. Grigg A. Sweeney G. R. Dearden A. H. Jackson and A. W. Johnson ibid. 1970 1273. 6‘ R. Bonnett and A. F. McDonagh Chem. Comm. 1970 337. 62 R. Grigg A. Sweeney and A. W. Johnson Chem. Comm. 1970 1237. ‘’ C. B. Storm J. Amer. Chem. Soc. 1970,92 1423. 442 B.C. UJY. has also appeared.64 A metalloisoporphyrin (64) has been synthesised by nucleophilic addition of methanol to dication (63).65 The disruption of the aro- matic system and consequent loss of ring current is reflected in the n.m.r. spectrum of (64).66 The part structure of heme A of cytochrome c oxidase has been shown to be (65) in which the group X is a labile substituent lost during the isolation.67 xo A new potentially general method for the synthesis of semicorrins has been described based on the use of isoxazoles as intermediates. The latter result from a nitrile oxide-alkyne cycloaddition. Reduction of (66)and treatment with Ncfl 3-OCj HN N-O (66) (67) base gives (67) as a mixture of double-bond isomers.68 Methylation of nickel(rr) corrole was formerly thought to occur at the metal atom.69 However an X-ray structure determination of the methylation product of copper 8,12-diethyl- 2,3,7,13,17,18-hexamethylcorrole has shown that substitution takes place on the nitrogen atom of ring A giving (68)." Nickel 1-substituted octa-p-alkyltetrade- hydrocorrins (69)on heating rearrange to nickel corroles (70)containing geminal 64 D.M. Collins and J. L. Hoard J. Amer. Chem. Soc. 1970,92 3761. 65 D. Dolphin R. H. Felton D. C. Borg and J. Fajer J. Amer. Chem. Soc. 1970 92 743. " J. Fajer D. C. Borg A. Forman D. Dolphin and R. H. Felton J. Amer. Chem. SOC. 1970 92 345 1. 6' G. A. Smythe and W. S. Caughey Chem. Comm. 1970 809. " R. V. Stevens L. E. DuPree and M. P. Wentland Chem.Comm. 1970 821. 69 Ann. Reports (B) 1968 65 453. '' R. Grigg T. J. King and G. Shelton Chem. Comm. 1970 56. Heterocyclic Chemistry substituents at C-3 rather than at C-2 as previously thought. The rearrangement proceeds in a two-stage process involving C-2 and probably occurs by a sigma- tropic mechani~m.~ ' Me Me Me Me I Me Me Et Me Et Me (69) (70) 3H-Indol-3-01s [e.g. (7111 result from a novel ring-contraction of 4H-3,l-benzoxazines on treatment with potassium amide in liquid ammonia. In methanolic sodium hydroxide (71) rearranged further to the indoxyl (72).'' The structure (73) which incorporates a cyc1[4,2,2]azine system is one of the cyclazines which has been obtained starting from 3H-pyrrolizine. It represents a 14 r-electron analogue of a~ulene.~~ " R.Grigg A. W. Johnson K. Richardson and M. J. Smith J. Chem. SOC.(C),1970 1289; R. Grigg A. W. Johnson and K. W. Shelton ibid. 1968 1291. 72 D. Lednicer and D. E. Emmert J. Heterocyclic Chem. 1970 7 575. 73 M. A. Jessop and D. Leaver Chem. Comm. 1970 791. 444 B. c. u-Tetrachlorobenzyne has been shown to react with simple carbonyl compounds to form benzo-1,3-dioxan derivatives [e.g.(74)from acetone and butane-2,3-dione]. These rearrange on cleavage with sulphuric acid in acetic anhydride to give CI CI (74) (75) Me02C@ C02Me Me02C -+ & C0,Me (76) (77) benzofurans of type (75).74The oxygen-bridged system (77) a potential precursor of fully unsaturated C ,-hydrocarbons has been synthesised from photoproduct (76) by reduction dehydration and oxidative decarboxylation of the correspond- ing A review of macrocycles involving the thiophen ring system has appeared76 and one of recent advances in the chemistry of benzo[b]thiophen~.~~ A further route to thiophens utilising 2-thiocarbonylenamines and a-bromocarbonyl compounds is reported.78 The ring system has also been synthesised from base condensation of a-bromocarbonyl compounds with (a-thiobenzoy1)acetophe-none.79 Thiophens have been shown to react with singlet oxygen forming sulphines as oxidation products or intermediates.80 The non-symmetrical N MeOyJJJ -+ Me0ds Me0 Me0 (78) (79) 74 H.Heaney and C. T. McCarty Chem. Comm. 1970 123. 7s N. E. Rowland F. Sondheimer G.A. Bullock E. LeGoff and K. Graham Tetrahe-dron Letters 1970 4769. 76 0.Meth-Cohn Quart. Reports Sulfur Chem. 1970 5 129. 77 B. Iddon and R. M. Scrowston Adv. Heterocyclic Chem. 1970,11 178. 78 S. Rajappa and B. G. Advani Tetrahedron Letters 1969 5067; cf. Ann. Reports (B) 1969 66 438. 79 M. Takaku Y. Hayasi and H. Nozaki Bull. Chem. SOC. Japan 1970,43 1917. ao C. N. Skold and R. H. Schlessinger Tetrahedron Letters 1970 791 ;H. H. Wasserman and W. Strehlow ibid. 1970 795. Heterocyclic Chemistry 445 isothianaphthene (79) results from pyrolysis of the isothiachromanone enamine (78) possibly through the intermediacy of a thiiranium ion.* Condensation reactions of 1,3-dimethyl-6H-cyclohepta[c]thiophen-6-one(80) have been carried out to yield potentially 6n-10n:dipolar systems for example with (81) the heterosesquifulvalene (82) is obtained.Examination of the electronic CI CI qcl c1 0 A Ac,O Me Q+ + s Me spectra however indicates a high occupancy of the apolar limiting formula in the ground state.82 The first example of a heterocyclic analogue of biphenylene is reported. 1,2-Benzocyclobutadienoquinone(83) with (84)gave 2-thianorbi- phenylene (85). Comparison of the n.m.r. spectra of (85) and the corresponding Ph,P-\ S-W -t Ph,P=/ /' (83) (84) (85) 2,2-dioxide clearly demonstrates the presence of a paramagnetic ring-current shielding effect of the 4n cyclobutadienyl ring in (85).83 The synthesis of a hepta- heterohelicene was reported last year.84 Now the heptaheterohelicene has been employed in the formation of the optically active undecaheterohelicene (86).85 " F.H. M. Deckers W. N. Speckamp and H. 0.Huisman Chem. Comm. 1970 1521. 82 G. Seitz and H. Monnighoff Angew. Chem.Internat. Edn. 1970,9,907;cf. G. V. Boyd, A. W. Ellis and M. D. Harms J. Chem. SOC.(C),1970 800; G. V. Boyd and M. D. Harms ibid. 1970 807. 83 P. J. Garratt and K. P. C. Vollhardt Chem. Comm. 1970 109. 84 Ann. Reports (B) 1969 66 438. 85 H. Wynberg and M. B. Groen J. Amer. Chem. SOC.,1970,92,6664. 446 B. C. Ufl Five-membered Rings with Two or More Hetero-atoms.-Advances in imidazole chemistry have been reviewed.86 The utility of dipolar cycloaddition reactions for the synthesis of five-membered ring heterocycles continue^.^' For example intramolecular nitrone-allene cycloaddition has resulted in the formation of bicyclic isoxazolidines.88 The novel diazatetracycloundecane system (88) results from a double 1,3-cycloaddition of sydnone (87) with cis,cis-cyclo-octa- l,5-diene.89 The use of 1$dipolar cycloaddition in heterocyclic synthesis has R' (87) been discussed.g0 For example u-triazoles (90) are obtained from vinyl azides (89) in strongly basic media whereas thermolysis in neutral or protic solvents leads to azirine formation (91).9 Examples of syntheses of condensed s-triazoles are also pre~ented.'~ Protonation of the mesoionic 3-phenylsydnone and 1,l-disydnonylethylene in FS03H-SbF solution has been shown to occur on the carbonyl oxygen atom by analogy with protonation of regular carbonyl groups.93 Oxidation of the bis(benzoy1hydrazone) (92) with potassium hexacyanoferrate(rI1) has been N -COPh / Me N-NH*CO.Ph Me + x$.-..Ph x Me N-NH-CO-Ph Me (92) (93) 8b M.G. Grimmett Ado. Heterocyclic Chem. 1970 12 104. '' Ann. Reports (B) 1969 66 439. " N. A. LeBel and E. Banucci J. Amer. Chem. SOC.,1970,92 5278. 89 P. M. Weintraub Chem. Comm. 1970 760. 'O H. Reimlinger Chem. Ber. 1970 103 1900. 9' F. P. Woerner and H. Reimlinger. Chem. Ber. 1970,103. 1908; also see H. Reimlinger. J. J. M. Vandewalle G. S. D. King W. R. F. Lingier and R. Merenyi ibid. p. 1918; A. J. Hubert and H. Reimlinger ibid. p. 381 I. pz H. Reimlinger. J. J. M. Vandewalle and W. R. F. Lingier Chem. Ber.. 1970.103. 1960; H. Reimlinger and M. A. Peiren ibid. p. 3266; H. Reimlinger ibid. p. 3278; H. Reimlinger Chem. and Ind, 1970 1082. 9J G.A. Olah D. P. Kelly and N. Suciu J. Amer. Chem. Soc. 1970,92 3133. Heterocyclic Chemistry 447 shown to give the mesoionic triazole (93) and not a dihydrotetrazine as previously The water-soluble 5-tetrazolyl ylide (94) has been obtained from reaction of 5-dimethylaminotetrazole with benzyl chloride in base together with the expected 1- and 2-benzyl derivative^.^^ NMe PhCH,NMe2 (94) Benz[cd]indazole 1-oxide (95) and 1,2-dioxide (96)have been prepared and the latter is considered to have the structure shown (96)rather than that of l,&dinitro- ~onaphthalene.~~ Reduction of the 1-oxide bypasses the unknown benz[cd]inda- (95) (96) (97) zole itself giving di- and tetra-hydro-derivatives two of which were reported last year.97 4-Phenyl- 1,2,4-triazoline-3,5-dione is well known as a very powerful dienophile :98 now the parent compound (97) has been prepared though not isolated and trapped by a series of dienes.” 0-and N-Acylated derivatives of 3-hydroxy-1,2-benzisoxazole(98) and (99) have been shown to undergo a thermal rearrangement to the isomeric acylated benzoxazol-2-ones (100).With the N-acyl derivatives (99) the rearrangement can also be achieved photochemically. It is thought to proceed by initial cleavage Rx *q:-0Jo \ / \ CO R OCO R 0 I CO R (98) (99) (100) II R R’ Ph-C-CH-CH-NR Me1 -+ Ph*R N N ‘0 H 1 (101) OH (102) 94 S.Peterson and H. Heitzer Angew. Chem. Internat. Edn. 1970,9 67. 95 L. Huff D. M. Forkey D. W. Moore and R. A. Henry J. Org. Chem. 1970,35,2074. 96 R. W. Alder G. A. Niazi and M. C. Whiting J. Chem.SOC.(C),1970 1693. 9’ Ann. Reports (B) 1969 66 441. z Ann. Reports 1962 59 331; 1967 (B)64 205. M. G. de Amezua M. Lora-Tamayo and J. L. Soto Tetrahedron Letters 1970 2407. 448 B. C. Ufl of the 0-N bond in (99).loo The stereochemical consequences of the known'" involvement of the oximate anion as a powerful neighbouring group in the synthesis of A2-isoxazolines (102) by base-induced cyclisation of (101) has been used to provide the first synthesis of optically active A2-isoxazolines.'02 A number of mechanistic pathways have been reported for the thermal decomposition of cyclic azo-compounds.'03 Now the first example of a car- bonium ion mechanism is provided in the acetolyses of azo-p-bromobenzene- sulphonates (103; R' = H R2= OBs and R' = OBs R2= H).Evidence for neighbouring-group participation by the -N=N-group is also presented.lo4 The novel bridged heterocyclic system (104) has been isolated from the pyrolysis of N-(2-hydroxyethyl)trifluoroacetamide.'05 A review has appeared on five-membered cyclic disulphides,'06 on thiadiazole and thiadiazine 5-oxides,'07 and on 5-aryl-1,2,4-dithiazole-3-thiones. The thermal reaction of carbon disulphide with acetylenes having at least one elec- tron-attracting substituent has been shown to generate 1,3-dithiolium carbenes (e.g.105) which have been captured by electrophilic reagents and have effected c1 alkylations and acylations. Chlorinated benzothiazoles (e.g. 106) have been formed by thermal cyclisation of o-chloroaryl isothiocyanates. 'lo Unsubstituted thiazolo[5,4-d]thiazole (107) has been obtained from an acid derivative the loo H. Boshagen and W. Geiger Chem. Ber. 1970,103 123. lo' Ann. Reports 1963 60 259. Ioz R. J. MacConaill and F. L. Scott Tetrahedron Letters 1970 2993. lo3 Ann. Reports (B) 1969 66 455. Io4 E. L. Allred and C. R. Flynn J. Amer. Chem. Soc. 1970,92 1064. Io5 G. M. J. Shusarczuk and M. M. Joullie Chem. Comm. 1970 469. A. Hordvik Quart. Reports Sulfur Chem. 1970 5 21. lo' A. Lawson and R. B. Tinkler Chem. Rev. 1970 70 593.J. Vialle Quart. Reports Sulfur Chem. 1970 5 15 1. Io9 H. D. Hartzler J. Amer. Chem. SOC.,1970 92 1412 1413. 'lo E. Degener G. Beck and H. Holtschmidt Angew. Chem. Infernat. Edn. 1970,9,65. Heterocyclic Chemistry compound proves remarkably stable and does not undergo electrophilic sub- stitution. ''' Further studies' l2 on the thiathiophthene' l3 no-bond resonance system and related structures have appeared.'I4 The first X-ray structure of an extended Ph &CMe2 s-s s-s no-bond resonance system uiz. (108) has shown the row of five sulphur atoms to be linear. Bond distances suggest there probably exists partial bonding between all the sulphur atoms.' ' Six-membered Rings with One Hetero-atom.-Nitrogen derivatives. The synthesis of pyridines via Diels-Alder addition of oxazoles has been reviewed,' l6 as also has the chemistry of lactim ethers"' and 3-piperideines."' A synthesis of the pyridine system is provided by reaction of unsaturated y-cyanocarbox- ylic acid chlorides with hydrogen chloride in an ether (e.g.109-llO).'I9 Me Ph (109) (110) (111) 4-Amino-2-pyridones have been formed from cycloaddition of ynamines to styrylisocyanates.' 2o The acetylation product of 4-pyridone formerly thought to be 4-acetoxypyridine has been shown to be wholly N-acetyl-Spyridone in the solid state although an equilibrium exists in The first example in the heteroaromatic series of a stable aroxyl radical (111) has been generated 'I1 J. R. Johnson D. H. Rotenberg and R. Ketcham J. Amer.Chem. Soc. 1970 92 4047. Ann. Reports (B) 1969 66 443. 'I3 L. K. Hansen and A. Hordvik Acta Chem. Scand.. 1970 24 2246; A. Hordvik and L. J. Saethre ibid. p. 2261. '14 E.g. D. Festal and Y. Mollier Tetrahedron Letters 1970 1259; K. I. G. Reid and I. C. Paul Chem. Comm. 1970 329; F. Leung and S. C. Nyburg ibid. 1970 707; R. J. S. Beer D. Frew P. L. Johnson and I. C. Paul ibid. 1970 154. ' J. Sletten Acta Chem. Scand. 1970 24 1464. M. Ya. Karpeiskii and V. L. Florent'ev Russ. Chem. Rev. 1969,38 540. l'' R. G. Glushkov and V. G. Granik Adv. Heterocyclic Chem. 1970 12 185; Russ. Chem. Rev. 1969 38 91 3. 'I' M. Ferles and J. Pliml Ado. Heterocyclic Chem. 1970,12,43. ' l9 G. Simchen Chem. Ber. 1970 103 389. R. Fuks Tetrahedron 1970 26 2161. I.Fleming and D. Philippides J. Chem. SOC. (0,1970 2426; F. Arndt and A. Kalischek Ber. 1930 63 587. 450 B. C. Ufl by dehydrogenation of 3-hydroxy-2,4,6-triphenylpyridine.The pyridoxyl proves stable towards oxygen and reacts preferentially as a dehydrogenating agent. 22 A new heterocyclic system 2H-thiapyrano[2,3-b]pyridine (1 12) has been prepared from ethyl 2-thioethylnicotinate as shown. 123 By a similar procedure (1 12) (113) (114) the 2H-pyrano[2,3-b]pyridine system (1 13) has been formed from 2-ethoxy-3- (1',3'-dihydroxypropy1)pyridine. 24 Synthesis of the new furo[2,3-b]pyridine structure (114) has resulted from a route commencing with 3-bromoacetyl- pyridone. ' 3-Azabicyclo[3,3 llnonanes have been synthesised for example (115; R' = CO,Et R2R3= 0)from the pyrrolidine enamine of N-toluene-p-sulphonylpiperidone and or-bromomethylacrylate.The diol (I 15;R' = CH,OH, 95 H R' OH (1 15) (116) RZ = OH R3 = H) underwent smooth detosylation to give 4hydroxyaza- adamantane (1 16).' 26 A number of syntheses of the 1-azatwistane system (119) H have been rep~rted.'~' For example on heating the mesylate (1 17)the salt (1 18) was obtained which formed (1 19)in quantitative yield on hydr~genolysis.'~~' Interest in some branches of heterocyclic chemistry has now risen to the level of duplicate publication. Reviews concerning the naphthyridine~'~' and the benzoisoquinolines and azafluorenes' 30 have appeared. Most syntheses of tetra- or di-hydroisoquinolines require an activating substituent in the carbo- lZ2 H.-J.Teuber G. Schutz and H.-J. Gross Angew. Chem. Internat. Edn. 1970 9 519. H. Sliwa Bull. SOC. chim. France 1970 642. '14 H. Sliwa Bull. SOC. chim. France 1970 631. 25 H. Sliwa Bull. Sac. chim. France 1970 646. W. N. Speckamp J. Dijkink and H. 0.Huisman Chem. Comm. 1970 196 197. (a)K. Heusler Tetrahedron Letters 1970,97; (b)D. Perelman S. Sicsic and Z. Welvart ibid. 1970 103; (c) S. Dube and P. Deslongchamps ibid. 1970 101. E.g. Tetrahedron Letters 1969 5143 5287. 12' W. W. Paudler and T. J. Kress Adu. Heterocyclic Chem. 1970,11 124. I3O N. S. Prostakov Russ. Chem. Rev. 1969 38 774. Heterocyclic Chemistry 45 1 cyclic ring. A general synthesis of 4-aryltetrahydroisoquinolinesis reported in which this condition is not necessary involving the cyclisation of 2-vinylbenzyl-amines under basic conditions.' ' Base-catalysed elimination of hydrogen chloride from the isoquinoline Reissert compound chlorohydrin (120) results in rearrangement probably via (121) to an isochromene (122).This product can be further attacked by ethoxide to ring-open again and re-form a new isoquinoline (123).132 A two-carbon ring-expansion of heterocycles can be achieved by NC NHCOPh]+wo @:h-[a NC EtOe NCOPh CHO (123) OEt ynamine addition to a cyclic imine. For example 3,4-dihydroisoquinoline with (124) gives the 3-benzazocine (126). The primary cycloadduct (125) can be isolated as its hydrolysis product (127) without ring opening. By a similar proce- dure indolenines can be expanded to benzazepines.l3 1,2,3,4-Tetrahydroiso-quinolines of the type (1 28) have been prepared by a-aminoalkylation of styrenes -NMe + PhC =CNMel-+ (124) ' ' Ph Ph Ph Ph Ph G ,CHR' H+ PhCH=CH /CH,O -9 Ph R=R'=H 'NH O' R' R (129) 13' K. Freter E. Dubois and A. Thomas J. Heterocyclic Chem. 1970,7 159. '32 G. W. Kirby S. L. Tan and B. C. Uff,Chem. Comm. 1970 1 138. 133 R. Fuks and H. G. Viehe Chem. Ber. 1970 103 573. 452 B. C. Ufl with an aldehyde and aromatic amine. If formaldehyde is used with primary amines 1H,SH-benzo[ij]quinolizines are the principal products (e.g. 129).'34 Oxygen and Sulphur Derivatiues. Reviews have appeared on unsaturated sugars ' nitro-sugars,' 36 branched-chain amino-sugars,' 1,6-anhydroaldo-hexopyranoses,' 38 mutarotation of sugars in solution,' 39 mechanistic aspects of carbohydrate ~hemistry,'~' sulphonic esters of carbohydrate^,'^' the synthesis of O-glyc~sides,'~~ gums and mucilages '43 and the formation of polysaccharide gels and net~0rks.I~~ A simple procedure has been developed for the stereo- specific synthesis of some 2-chloro-2-deoxypentoses.For example treatment of H #H -.OR% OR OR H ci H (130) (131) (130; R = S0,CI) with aluminium chloride resulted in (131) via anomeric chlorine migration to the extent of almost loO%.145A high-yield synthesis of 2,3-isopropylidene-~-~-ribofuranosylamine is reported from reaction of D-ribo- pyranosylamine with acetone 2,2-dimethoxypropane and toluene-p-sulphonic acid.The product is of value as an intermediate in nucleoside ~yntheses.'~~ The synthesis of two tetra-amino-sugars has been reported 2,3,4,6-tetra- tetrahydr~chloride'~~ amino-2,3,4,6-tetradeoxy-~-galactose and the glucose analogue.'48 The route to the latter compound for example is from the galacto- dimesylate derivative (1 32) which on conversion to the diazide (1 33) gives (1 34) 134 K.-D. Hesse Annalen. 1970,741 117. 135 R. J. Ferrier Adv. Carbohydrate Chem. 1969 24 199. 136 H. H. Baer Adv. Carbohydrate Chem. 1969,24 67. 13' F. W. Lichtenthaler Fortschr. Chem. Forsch. 1970 14 556. 138 M. Cerny and J. Stangk Fortschr. Chem. Forsch. 1970 14 526. 139 H. S. Isbell and W. Pigman Adv. Carbohydrate Chem. 1969 24 14. J. S. Brimacombe Fortschr.Chem. Forsch. 1970 14 367; H. Simon and A. Kraus ibid. p. 430; H. Paulsen H. Behre and C.-P. Herold ibid. p. 472. 141 D. H:Ball and F. W. Parrish Adu. Carbohydrate Chem. 1969 24 139. 142 R. J. Ferrier Fortschr. Chem. Forsch. 1970 14 389. G. 0.Aspinall Adv. Carbohydrate Chem. 1969 24 333. 144 D. A. Rees Adv. Carbohydrate Chem. 1969,24 267. 145 H. J. Jennings Canad. J. Chem. 1970,48 1834. 146 N. J. Cusack and G. Shaw Chem. Comm. 1970 11 14. 14' W. Meyer zu Reckendorf Chimia (Switz) 1970,24 16. W. Meyer zu Reckendorf Tetrahedron Letters 1970 287. Heterocyclic Chemistry 453 in good yield by hydrogenation and hydrolysis. A one-step procedure for protecting trans-diequatorial amino- and hydroxy-groups in amino-sugars is reported utilising p-nitrophenoxycarbonyl chloride.For example methyl CH,OH "Ox+) \fH OMe 0 (135) 2-amino-2-deoxy-a-~-glucopyranoside gives the 2,3-carbamate derivative (135) in good yield.'49 Glycosides have been obtained in good yields by the use of silver salts of 2- 3- or 4-hydroxyalkanoic acids or of 1,3- or 1,4-dicarboxylic acids with alcohols and 2,3,4,6-tetra-0-acetyl-a-~-ghcopyranosy1bromide in ether the method proves simple and mild.' so A crystal structure of a seven-membered-ring sugar 1,2 :3,4-d~-O-isopropylidene-5-O-chloroacetyl-or-~-glucoheptanose,shown has the heptanose ring to adopt a conformation which lies between the chair and twist-chair forms.' s1 A new route to or-pyrones (137) is reported from P-diketones and the phos- phorane (1 36).52 Pyrolytic decarboxylation of 5-methyl-6-carboxy-2-pyrone affords 3-methyl-2-pyrone. The rearrangement occurs for other similar pyrones PO HZC + k-O R and it is suggested that following decarboxylation a 1,5-sigmatropic hydrogen shift is involved accompanying reversible electrocyclic ring opening (138) +(1 39)' 2-Alkoxy-3,4-dihydro-2H-pyrans (140) have been found to undergo an oxidative rearrangement to substituted tetrahydrofuran derivatives (141) in the presence of peracid possibly via ring-opening of the intermediate epoxide.' s4 fixGcqX= flX e nx OOH IIH 0 0 H II HOO (138) 0 0 (139) lQ9 S. Umezawa T. Tsuchiya and Y.Takagi Bull. Chem. SOC. Japan 1970,43 1602. 150 G. Wulff G. Rohle and W. Kruger Angew. Chem.Internat. Edn. 1970,9,455. 51 J. Jackobs and M. Sandaralingam Chem. Comm. 1970 157. A. K. Sorensen and N. A. Klitgaard Acta Chem. Scand. 1970,24 343. W. H. Pirkle H. Seto and W. V. Turner J. Amer. Chem. SOC. 1970,92,6984. 154 S. S. Hall and H. C. Chernoff Chem. andfnd. 1970 896. 454 B. C.U! A number of syntheses of 2-oxabicyclo[2,2,2]octane(143) have been reported ; the most efficient involves a l&transannular elimination from the cis-tosylate (142) proceeding in over 95 yield. " The 2,7-dioxaisotwistane (145 ;R = H) and 2,7-dioxatwistane (146; R = H) ring systems have been obtained via the acetoxy-compounds (145 and 146; R = OAc). The twistane skeleton results from a molecular rearrangement of the iodoisotwistane compounds (144) on treatment with silver acetate.156 The first synthesis of loganin (150),the key iridoid glucoside involved in indole alkaloid biogenesis has been achieved involving as main step the formation of (149) by photocycloaddition of the P-tricarbonyl compound (147) to the protected lS5 T. A. Giudici and T. C. Bruice J. Org. Chem. 1970 35 2386; W. Schneider and K. Lehman Tetrahedron Letters 1970 428 I. C. Ganter and K. Wicker Helv. Chim.Acta 1970 53,1693. Heterocyclic Chemistry 455 olefin (148).lS7 A useful route to azachromones is reported employing hetero- cyclic enamines. Treatment of (151) with diketen gives (152) which on dehydro- genation gives (153).' '* Me Halfordinin (154) a linear furanocoumarin has been isolated from the bark of Ha2fordia kendak and shown to possess the novel feature of an aa-dimethylallyl side-chain joined to the ring through an ether linkage.'" A review has appeared on the chemistry of the aflatoxins,16' and a book on flavanoid identification.16' Two optically active flavans (155 R = H and Me) have been isolated from two Me0 OMe 0 Me 9 (154) (1 55) species of Dianellinae and have an uncommon feature of no oxygen atom attached to the heterocyclic ring.162 Eight new members of the small family of homoiso-flavones' 63 have been isolated e.g.punctatin (1 56). 164 Treatment of flavylium OMe salts with hydroxylamine has been shown to give A3-isoxazolines [e.g. (157)+ (158)]'65 and not a chalcone oxime as thought earlier although the latter may be an intermediate.15' G. Buchi J. A. Carlson J. E. Powell and L.-F. Tietze J. Amer. Chem. SOC.,1970,92 2165. I 58 I. Belskey Tetrahedron Letters 1970 4597. I 5y J. K. MacLeod Tetrahedron Letters 1970 361 1. I6O C. P. Mathew Chem. andInd. 1970 913. 16' T. J. Mabry K. R. Markham and M. B. Thomas 'The Systematic Identification of Flavanoids' Springer-Verlag New York 1970. 162 R. G. Cooke and J. G. Down Tetrahedron Letters 1970 1037. Ann. Reports (B) 1967 64 414. 164 W. T. L. Sidwell and Ch. Tamm Tetrahedron Letters. 1970. 475; R. E. Finckh and Ch. Tamm Experientia 1970 26 472. L. Jurd Chem. and Ind. 1970 624. 456 B. C. Ufl MW / O -Me \ woMe \ 0-NH (157) (158) Interest in quadrivalent-type sulphur heterocycles continues.' For example thiabenzene (160) has been generated from the fluoroborate (159) with base. The spectral and chemical properties of (160) are consistent with an ylide-type C 1 CH (161) Me (162) 1 1 Me (163) bonding description for thiabenzenes. ' ' Thermolysis of prop-2-ynyl phenyl sulphide (161) can produce (162) (163) and (164) the first being the result of a thiopropynylic rearrangement (by analogy with the thioallylic shift in ally1 phenyl sulphides). Both (161) and (162) then undergo a thio-Claisen rearrange- ment followed by cyclisation to give the 2H-thiachromene (163)and benzo[b]thio- phen (1 64).'68 Six-membered Rings Containing Two or More Hetero-atoms.-The conforma-tional analysis of saturated heterocylic compounds containing two hetero-atoms has been re~iewed.'~' A book has appeared on the pyrirnidine~'~' and a review 166 Ann.Reports (B) 1969 66 455; 1968 65 476. 167 A. G. Hortmann and R. L. Harris J. Amer. Chem. Soc. 1970,92 1803. 16' H. Kwart and T. J. George Chem. Comm. 1970,433. 16' E. Eliel Accounts Chem. Res. 1970 3 1 ; Bull. SOC. chim. France 1970 517. I7O D. J. Brown 'The Pyrimidines' Supplement 1 of 'Chemistry of Heterocyclic Com- pounds' Volume 16 Wiley-Interscience New York 1970. Heterocyclic Chemistry on progress in 1,3,4-thiadiazine chemistry has been published. l7 The synthesis of adenine from formamide and phosphorus oxychloride was reported pre- viou~ly.'~~ The method has now been modified by addition of other amides to give a one-step route to pyrimidines (165) and condensed pyrimidine^.'^^ (165) The isomerisation of 2-pyridylcarbene to phenylnitrene was discussed last year' 74 and the work has been extended to a study of nitrene~diazines.'~~ Whereas displacement with potassium amide in liquid ammonia of 6-bromo-4-t-butyl-pyrimidine (1 66) gives the 6-amino-derivative probably via a 56-heteroaryne CMe3 N5 _____) C,HIoNLi IkHCN d Br H,,C,N H ( 166) (1 67) intermediate,17' treatment of the system with a different nucleophile lithium piperidide in ether causes ring-opening.The product (167) is considered to arise by addition of the nucleophile to the azomethine bond in (166) followed by opening of the 1,Zdihydro-compound. N H H. Beyer Quart. Reports Sulfur Chem.1970 5 177. Ann. Reports (B) 1968 65 479. K. Morita S. Kobayashi H. Shimadzu and M. Ochiai Tetrahedron Letters 1970 861. 'l4 Ann. Reports (B). 1969. 66. 444. 175 C. Wentrup and W. D. Crow Tetrahedron 1970,26,4915; C. Wentrup ibid. p. 4969. 176 Ann. Reports (B) 1968 65 480. H. C. van der Plas and A. Koudijs Rec. Trav. chim. 1970 89 129. 458 B. c. ufl An unusual rearrangement of a pyrimidine derivative (168) is reported on' treatment with aqueous hydrazine or water alone at 210 "Cthe 1,2,4-triazole (169) is produced. A possible mechanism initiated by nucleophilic attack at position 2 with ultimate loss of the C6-N1 fragment is indicated."' A new synthesis of the quinazoline system results from cyclisation of o-cyano-phenyl isocyanates (170) in the presence of hydrogen halide giving 4-halogeno-2- quinazolones (171).17' The triazolo[4,3-a]pyrazines (172) have been shown to ,aCN sRelo N=C=O H R' R2$TNH R3 NH2 R3 Nf 0 R1 (172) (173) rearrange in acid to the hitherto unreported 1H-imidazo[2,l-c]-s-triazoles (173)"' and not to triazolo[2,3-a]pyrazinesas reported previously.l8 The dihydro-1,3-oxazine system (1 74) was reported last yearLs2 as a building block for the synthesis of aldehydes ketones and carboxylic acids. Other aspects 0 (178) 178 H. C. van der Plas and H. Jongejan Rec. Trau. chim. 1970,89,680. 179 G. Simchen G. Entenmann and R. Zondler Angew. Chem. Internat. Edn. 1970 9 523. I80 F. L. Rose G. J. Stacey P. J. Taylor and T. W. Thompson Chem.Comm. 1970 1524. I81 Ann Reports 1966 63 479. 182 Ann Reports (B),1969,66 458. Heterocyclic Chemistry of the aldehyde synthesis sequence have been e~amined,'~~.'~~ and a further route to ketones (177) is now recorded via Grignard or alkyl-lithium addition to the cation (175 ;R = alkyl or aryl) followed by acid-catalysed ring-cleavage of (176).18' The synthetic utility of the oxazine approach has also been comple- mented by use of the 2-oxazoline ring system in application to the synthesis and alkylation of acids,' 86 and the formylation of Grignard reagents. ' The structure of mitiromycin has been elucidated as (178) and represents the first mitomycin antibiotic to contain an oxazinone ring in place of the usual open-chain carbamate ester grouping.88 A new synthesis of the 1,2,4-oxadiazine system is provided by condensation of chloroacetylisocyanate (179) with N-monosubstituted hydroxylamines. The intermediate (180) cyclises in base to give (181).'89 A poisonous compound (1821 found in the Daphne genus has the structure (182) daphnetoxin. The structure is similar in its high degree of oxygen-bridging to a number of other toxic nitro- genous and non-nitrogenous compounds. ''' An attempted Bischler-Napieralski reaction on the thioketal (183) gave instead of the expected isoquinoline the 183 A. I. Meyers G. R. Malone and H. W. Adickes Tetrahedron Letters 1970. 3715. A. I. Meyers and E. M. Smith Tetrahedron Letters 1970,4355. A. I. Meyers and E. M. Smith J. Amer. Chem. SOC.,1970,92 1084.A. I. Meyers and D. L. Temple J. Amer. Chem. Soc. 1970,92,6644 6646. 18' A. I. Meyers and E. W. Collington J. Amer. Chem. SOC.,1970 92 6676. G. 0. Morton G. E. Van Lear and W. Fulmor J. Amer. ChCm. SOC.,1970,92,2588. P. Rajagopalan and B. G. Advani Chem. Comm. 1970 167. I9O G. H. Stout W. G. Balkenhol M. Poling and G. L. Hickernell J. Amer. Chem. SOC. 1970 92 1070. 460 B. C. Ufl dihydro-p-dithiin structure (184) with loss of the amide group. Other dihydro-p- dithiins have been prepared similarly and the method extended to give a dihydro- dithiepin from a propylene thioketal.lgl Seven-membered and Larger Rings.-A novel transannular ring contraction is reported as resulting from the attempted Wolff-Kishner reduction of 2,7-di-phenylhexahydro-4-azepinone (185) the product being the pyrrole (186).Several (1851 (186) mechanisms for the transformation have been suggested which must involve cleavage of the W,bond of the intermediate hydrazone.Ig2 Although cis-azo- dienophiles were found to add in a (4 + 2)n manner to N-ethoxycarbonylazepine [e.g. to give (187)] reaction of diethyl azodicarboxylate (trans-configuration) 0 proceeded very slowly to give the (6 + 2)n product (188) suggesting steric factors are inhibiting concerted attack in this case.Ig3 Compound (190) an aza- analogue of homocyclohexadienone is afforded by the thermal [3,3)sigmatropic (189) (190) (191) (192) rearrangement (the Cope rearrangement) of the cyclopropylisocyanate (189) the process is reversed photo~hemically.'~~ Ring-expansion of the azahomo- adamantane (191) to the diaza-homologue (192) is reported via Beckmann rearrangement of the corresponding oxime.95 19* J. L. Massingill M. G. Reinecke and J. E. Hodgkins J. Org. Chem. 1970,35 823. 192 C. G. Overberger J. Reichenthal and J.-P. Anselme J. Org. Chem. 1970 35 138. 193 W. S. Murphy and J. P. McCarthy Chem. Comm. 1970 1129. 19' T. Sasaki S. Eguchi and M. Ohno J. Amer. Chem. Soc. 1970,92 3192. 19s V. G. Keizer J. Q. Korsloot F. W. v. Deursen and M. E. v. d. Heeden Tetrahedron Letters 1970 2059. Heterocyclic Chemistry 46 1 An example of the 4-am-azulene system viz. (194) results from treatment of (193) with pyrrolidine in the presence of an acid cata1y~t.l’~ Whereas azulene (193) (194) does not appear to undergo cycloaddition reactions the 5-aza-azulene system is reported to add to alkynes.6-Phenyl-5-am-azulene (195) gives products (196) (197) and (198) derived from the two initial adducts as sh~wn.’’~ Ph Ph RC sCR (€95) (198) The activity of annulated thiepins towards dienophiles was reported last year.’98 The adducts normally reveal loss of sulphur but by use of bulky sub- stituents a stable 8n-electron thiepin system (199) has been prepared.lgg This is of particular interest since calculations have predicted the thiepin system to be antiaromatic.200 Thermal decomposition of the azide (200)leads to the thiazepin (201) via a rearrangement involving nitrene participation.201 In the case of the 0 OH M&OH (199) 196 M.K. Conner and E. LeGoff Tetrahedron Letters 1970 2687. 19’ K. Hafner J. Haring and W. Jakel Angew. Chem. Internat. Edn. 1970 9 159. 19’ Ann. Reports (B) 1969 66 462. 199 J. M. Hoffmann and R. H. Schlessinger J. Amer. Chem. Soc. 1970,92,5263. M. J. S. Dewar and N. Trinajstic J. Amer. Chem. Soc. 1970,92 1453. 201 J. I. G. Cadogan and S. Kulik Chem. Comm. 1970 233. 462 B. C. Ufl dimethoxy-analogue a nitrene-induced 1,4-rnethoxy shift occurs to give (202) as one product.202 A compound (203) in which a triple bond is present in a seven-membered ring has been isolated for the first time from the bis-hydrazone shown.203 Me -? H Me Me A new route to azocines [e.g. (204)] is reported using a sequence of cyclo-addition/retro-Diels-Alder reactions as indicated.204 It is known that the four double bonds in simple azocines lack appreciable conjugative interaction due Ph N+N C02Me Ph'N~ C02R C02Me C02Me I (204) COzMe to the preferred tub conformation of these heterocycles.205 However it has now been shown that the azocine ring readily undergoes two-electron reductions to give like cyclo-octatetraene,z06 a planar 1%-electron dianion [e.g.(ZOS)] (206) J. 1. G. Cadogan and S. Kulik Chem. Comm. 1970,792. '03 A. Krebs and H. Kimling Tetrahedron Letters 1970 761. lo4 J. A. Elix W. S. Wilson and R. N. Warrener Tetrahedron Letters 1970 1837. Ann. Reports (B) 1968 65 485. 'Ob Ann. Reports 1960 57 230. Heterocyclic Chemistry with a high degree of n-electron delo~alisation.'~~ l-Azabicyclo[3,3,3]undecane (207) has been prepared by sodium in liquid ammonia treatment of the tricyclic salt (206) synthesis of the carbocyclic analogue is also described.208 We reported last year the synthesis of N-ethoxycarbonylazonine.209Brief low-temperature contact with potassium t-butoxide has now been shown to lead to the parent 1H-azonine (208) itself."' There has been disagreement over the (208) interpretation of the temperature-dependent n.m.r.spectra of N-ethoxycar- bonylazonine.21 l2 A c omparative study of oxonin and N-substituted azonines 'p2 indicates there is a gradual transition from polyenic to aromatic character on increasing the availability of the electron pair on the heter~atom.~'~ There is good evidence supporting the concertedness of the majority of 1,3-dipolar cycloaddition reactions,' l4 thus addition of 1,3-dipoles to trienes is a symmetry- allowed [,6 + .4,] thermal process and some reactions of this type have been pr0vided.l s*21h For example the bridged dihydrodiazonine (209) results from generation of diphenylnitrileimine in the presence of tropone.2 ' Thermal cycloaddition of 4-phenyl- 1,2,4-triazoline-3,5-dioneto oxonin gives adduct (210) which could result from a direct [2 + 2 + 21 cycloaddition or a two-step process involving initial [2 + 81 intera~tion.~'~ Two isomers (211) and (212) of an analogue of biphenylene in which one of the benzene rings has been Ph Ph I -N O O + + ;I -C 1 Ph '07 L.A.Paquette T. Kakihana and J. F. Hansen Tetrahedron Letters 1970 529; L. A. Paquette J. F. Hansen T. Kakihana and L. B. Anderson Tetrahedron Letters 1970 533. N. J. Leonard and J. C. Coll J. Amer. Chem. Soc. 1970,92 6685. '09 Ann. Reports (B) 1969 66 465. 'lo A. G. Anastassiou and J. H. Gebrian Tetrahedron Letters 1970 825. A. G. Anastassiou R. P. Cellura and J. H. Gebrian Chem. Comm. 1970,375. ''' K. Hojo and S. Masamune J. Amer. Chem. SOC.,1970,92,6690. 'I3 A. G. Anastassiou S. W. Eachus R. P. Cellura and J. H. Gebrian Chem. Comm. 1970 1133. Ann. Reports (B),1968,65 457. K. N. Houk and C. R. Watts Tetrahedron Letters 1970 4025. 'I6 K. N. Houk and L. J. Luskus Tetrahedron Letters 1970 4029. 'I7 A. G. Anastassiou and R. P. Cellura Chem. Comm.1970 485. 464 B. c. ufl replaced by an alkylated potentially aromatic thionin ring are reported. Isomer (212) represents the first isolated case of a fully unsaturated nine-membered ring containing a trans-double bond.’ l8 Formation of NN’-dimethyl[2,2] (2,5)pyrrolophane (213) has been achieved from the corresponding difurano-cyclophane.2 l9 The nitrogen-bridged [12]- annulene derivative (214) has been synthesised :n.m.r. studies suggest it is not in pJ \I equilibrium with the diaza-annulene structure (215) although no definite con- clusion has yet been drawn.220 In interesting juxtaposition to this however is the report of the synthesis of [2,2](2,6)pyridinophane-1,9-diene(216).22 (216) (217) The product contrary to earlier predictions,’22 does not undergo spontaneous valence tautomerisation to 15,16-dihydro-15,16-diazapyrene (217).221 The synthesis of some fully unsaturated 11- 12- and 13-membered sulphur heterocycles has been reported including the trans,trans 13-membered ring *18 P.J. Garratt A. B. Holmes F. Sondheimer and K. P. C. Vollhardt J. Amer. Chem. Soc. 1970 92,4492. 219 H. H. Wasserman and D. T. Bailey Chem. Comm. 1970 107. 120 W. W. Paudler and E. A. Stephan J. Amer. Chem. SOC., 1970,92,4468. 221 V. Boekelheide and J. A. Lawson Chem. Comm. 1970 1558; cf. V. Boekelheide and W. Pepperdine J. Amer. Chem. SOC.,1970,92 3684. 222 Ann. Reports 1958 55 268. Heterocyclic Chemistry structure (218). The n.m.r. spectra of the macrocycles indicate no appreciable ring-current effects and they are presumably non-planar molecules.223 The Me Me Me I I I N-NH N-N=N-N 1 (N-NH2 -+( N-N=N-N I I I Me Me Me (219) (220) cyclic bis-2-tetrazene (220) has been formed by potassium bromate oxidation of (219)224 and a number of dihydro-octa-aza[l4]annulenes(221 n =0 1 2) have been prepared from the corresponding bishydrazones as (223) (224) Further hetero-bridged cyclophanes have appeared.226 For example the triaza-cyclophanes (222; X = NS02C6H,Me)227 and (222; X = S and X = have been synthesised.Interest continues229 in heteromacrocycles and their use as complexing agents for metal ions.230 The macrocycle (223) has been used to solubilize potassium metal in ether solvents231 and to give the familiar deep blue solution and the thioether macrocycle (224) is able to complex two nickel ions at 223 A.B. Holmes and F. Sondheimer J. Amer. Chem. SOC.,1970,92 5284. 224 M. Iwamura P. J. Hintz and S. F. Nelson J. Amer. Chem. Soc. 1970,92,3496. 225 H. Neunhoeffer and L. Motitschke Tetrahedron Letters 1970 655. 226 Ann. Reports (B) 1969 66 466. 227 F. Vogtle and P. Neumann Chem. Comm. 1970 1464; and see F. Vogtle and P. Neu- mann Tetrahedron Letters 1970 115. 228 F. Vogtle Annafen 1970 735 193. 229 C. J. Pedersen J.Amer. Chem. Sac. 1970,92,386,391;J. M. Lehn J. P. Sauvage and B. Dietrich ibid. p. 2916. "O Ann. Reports (B) 1969 66 467. 231 J. L. Dye M. G. DeBacker and V. A. Nicely J. Amer. Chem. Soc.. 1970,92. 5226. 232 K. Travis and D.H. Busch Chem. Comm. 1970 1041.

ISSN:0069-3030    

DOI:10.1039/OC9706700433

出版商:RSC    

年代:1970

数据来源: RSC