9 Aliphatic Compounds Part (ii) Other Aliphatic Compounds By E. W. COLVIN Chemistry Department University of Glasgow Glasgow G12 8QQ 1 Carboxylic Acids The degree of acidity of carboxylic acids has been correlated' with their core- electron ionization potentials; a similar study2 of the proton affinity of esters has been reported. One of the biochemical functions of vitamin BIZ,in the form of its coenzyme is to isomerize acids such as p-methylitaconic (1) and a-methyleneglutaric (2) by reversible conversion of an apparently unactivated methyl group into a methylene group followed by incorporation of the latter into the backbone chain; Dowd3 has succeeded in performing this remarkable process in vitro,in an enzyme-free system (Scheme l),opening the way to a detailed study of the rearrangement mechanism unencumbered by the enzyme.C0,H (2) Scheme 1 Pyrolysis of the doubly labelled chiral ether (3) leads by way of an ene reaction followed by reductive elimination to a product containing a chiral methyl group of predictable configuration thus providing a new route4 to chiral acetic acid (Scheme J. S. Jen and T. D. Thomas J. Amer. Chem. Soc. 1975,97 1265. T. X. Carroll S. R. Smith and T. D. Thomas J. Arner. Gem. Soc. 1975,97,659. P. Dowd M. Shapiro and K. Kang J. Amer. Chem. Soc. 1975,97,4754. C. A. Townsend T. Scholl and D. Arigoni J.C.S. Chem. Comm. 1975,921. 199 200 E. W.Colvin 2). An efficient synthesis' of (R S)-[5-'sO]mevalonolactone' has been described as has an improved route6 to (3R S; 5S)-[5-3H,]mevalonic acid.OCD,OMe heat /D -+ 0 H0 C-C--T \ H Scheme 2 2 Lactones and Macrolides Based on the result of a synthesis7 of optically active avenaciolide from D-glucose the chirality of the naturally occurring enantiomer must be revised to (3aR ; 4R ; 6aR) as shown in (4);consequentially the configurational assignments of this entire series of fungicides are probably incorrect since they have all been related to avenaciolide itself. An efficient synthesis' of (R,S)-4-iso-avenaciolide has been described as have new routes to carolic acid' and the tetronic acids.1° (4) Pig liver esterase hydrolyses the diester (5) to the chiral half-ester (6);differential reduction with LiBH or diborane allows obtentionll of either (R)-or (S)-mevalonolactone (Scheme 3).The electronic rotatory strengths of the n -+ T* transition in saturated chiral y-and &lactones have been measured." Biosynthetic st~dies'~ on some sixteen-membered macrolides have indicated the involvement of butyrate as a four-carbon building block. I3Cn.m.r. spectral4 of J. W. Cornforth and R. T. Gray Tetrahedron 1975,31 1509. J. W. Cornforth F. P. Ross and C. Wakselman J.C.S. Perkin I 1975,429. R. C. Anderson and B. Frazer-Reid J. Amer. Chem. SOC.,1975 97 3870; see also H. Ohrui and S. Emoto Tetrahedron Letters 1975,3657. * R. E. Damon and R. H. Schlessinger Tetrahedron Letters 1975 4551. A. Svendsen and P. M. Boll Acta Chem. Scand. (B),1975,29 197. lo J. V. Greenhill M. Ramli and T.Tomassini J.C.S. Perkin I 1975 588. F.-C. Huang L. F. Hsu Lee R. S. D. Mittal P. R. Ravikumar J. A. Chan C. J. Sih E. Caspi and C. R. Eck J. Amer. Chem. SOC. 1975,9? 4144. l2 F. 5. Richardson and W. Pitts J.C.S.Perkin 11 1975 1276. I3 S. Omura A. Nakagawa H. Takeshima K. Atsumi J. Miyazawa F. Piriou and G. hkacs J. Amer. Chem. Soc. 1975,97,6600; S. Omura A. Nakagawa H. Takeshima J. Miyazawa C. Kitao F. Piriou and G. Lukacs Tetrahedron Letters 1975,4503 l4 J. G. Nourse and J. D. Roberts J. Amer. Chem. Soc. 1975 97 4584. Aliphatic Compounds-Part (ii) Other Aliphatic Compounds 201 HO bo R-( -1 -* 1 "X ' Hb Me02C C0,Me Me0,C CO,H\ (5) (6) 0 S-(+ 1 Reagents i pig liver esterase; ii LiBH,; iii B2H Scheme 3 some macrolides have been determined as have the conformation and conforma- tional flexibility of inter ah the pikromycin aglyconesl' and erythronolide B.16 Methymycin (7) has yielded to an elegant total synthesis," as has the simpler vermiculine18(8).Data on the complexation reactions between alkali-metal cations and polyether hydroxy-acids such as monen~in'~ and grisorixin2' have been pre- sented; such organic species act as specific sodium- or potassium-ion 'pumps' transporting the ions across the lipid portions of cell membranes. The first synthesis of a macrotetrolide nonactin (9) has been achieved independently by two 0 "0 0 0 (9) Is H. Ogura K. Furuhata H. Kuwano and N. Harada J. Amer. Chem. SOC.,1975,97 1930. Ih R. S. Egan J. R. Martin T.J. Perun and L. A. Mitscher J. Amer. Chem. SOC.,1975,97 4578. S. Masamune H. Yamamoto SXamata and A. Fukuzawa J. Amer. Chem. SOC.,1975 97 3513. E. J. Corey K. C. Nicolaou and T. Tom J. Amer. Chem. SOC.,1975,97 2287. l9 E. M. Choy D. F. Evans and E. L. Cussler J. Amer. Chem. SOC. 1974,96 7085. P. Gachon G. Chaput G.Jeminet J. Juillard and J.-P. Morel J.C.S. Perkin ZZ 1975 907. 202 E. W.Colvin groups.21722 The structures of the polyether hydroxy-acid antibiotic mould metabo- lites alb~rixin,~~ and lonomycinZ5 have been solved by X-ray analysis lyso~ellin,~~ and the structure of antibiotic X-20626has been corrected by the same technique. 3 Functional Derivatives of Carboxylic Acids Spectroscopic evidence27 for the formation of diethylmalonic anhydride (Scheme 4) has been presented; i.r.absorption bands at 1980 and 1900 cm-'were observed the latter being slightly more intense. 0 Reagent :i dicyclohexylcarbodi-imide-CC1 Scheme 4 The E-enol of methyl acetoacetate obtainable in up to 15%yield by distillation of the ester at atmospheric pressure is estimated28 to be 10 kcal mol-' less stable than the H-bonded 2-isomer. A non-polar transition state (10) is proposedz9 for the decarboxylation of P-keto-acids in which the acid proton sits in a stable potential well during cleavage of the C-C bond; low isotope effects are therefore to be expected. An evaluation of kinetic deuterium isotope effects has produced a new transition-state for peracid olefin epoxidation characterized as (11).Ar' I 0-H-0 c=o (1 1) The Qiels-Alder adducts between nitrosocarbonylarenes and 9,lO-dimethylanthracene decompose in the presence of Ph3P to give aryl isocyanates in high yield; kinetic evidence has been presented3l supporting the involvement of free 21 J. Gombos E. Haslinger H. Zak and U. Schmidt Tetrahedron Letters 1975 3391; J. Gombos E. Haslinger A. Nikiforov H. Zak and U. Schmidt Monatsh. 1975,106 1043. 22 H. Gerlach K. Oertle A. Thalmann and S. Servi Helu. Chim. Acta 1975 58 2036. 23 M. Alltaume B. Busetta C. Farges P. Gachon A. Kergomard and T. Staron J.C.S. Chem. Comm. 1972,411. z4 N. Gtake M. Koenuma H. Kinashi S. Sato and Y. Saito J.C.S. Chem. Comm. 1975,92. 25 N. Otake M. Koenuma H. Miyamae S. Sato and Y. Saito Tetrahedron Letters 1975,4147.26 J. F. Blount and J. W. West J.C.S. Chem. Comm. 1975 533. 27 G. Resofszki M. Huhn B. Hegedus P. Dvortsik and K. KB16y Tetrahedron Letters 1975 3091. 28 R. Matusch Angew. Chem.Internat. Edn. 1975 14 260. 29 M. W. Logue R. M. Pollack and V. P. Vitullo J. Amer. Chem. SOC.,1975,97 6868. 30 R. P. Hanzlik and G. 0.Shearer J. Amer. Chem. Soc. 1975,97,5231. 3l J. E. T. Corrie G. W. Kirby and R. P. Sharma J.C.S. Chem. Comm. 1975,915. Aliphatic Cumpounds-Part (ii) Other Aliphatic Compounds nitrosocarbonylarenes (12) (Scheme 5) N-arylnitrosoimines (13) have now been prepared.32 / HNAr R-C \ ArN=C=O + Ph,PO NO (13) Scheme 5 Aliphatic thioacyl chlorides,33 a -sulphinyl P-oxo-thi~nesters,~~. and acetylene dicarbonyl have been synthesized and their properties studied.An improved liquid-phase to acyloxynitrates biologically deleterious con- stituents of photochemical smog has been described. An ab initio study of acyloxy cations (14) possible intermediates in Kolbe electrolysis has revealed38 that the isomeric dioxiryl cations (15) are the lowest energy species (Scheme 6). 0' [." \ HR-C / Of Rf + CO Scheme 6 The preparation and 'H and l3Cn.m.r. spectra of the acetoacetylium (16) and diacetoa~etylium~~ (17) ions have been reported; halogenoacetylium40 ions and some diacid-derived dications41 have also been studied. + + CH,COCH,CO (CH,CO),CHCO (16) (17) 32 T. L. Gilchrist M. E. Peek and C. W. Rees J.C.S. Chem. Comm. 1975,913 914. 33 G. Seybold Angew.Chem. Internat. Edn. 1975 14,703. 34 J. J. A. van Asten and R. Louw Tetrahedron Letters 1975 671. 35 A. J. Bridges arid G. H. Whitham J.C.S. Perkin I 1975 1603. 36 F. E. Herkes and H. E. Simmons J. Org. Chem. 1975,40,420;F. E. Herkes ibid. p. 423. 37 R. Louw G. J. Sluis and H. P. W. Vermeeren J. Amer. Chem. SOC.,1975,97,4396. 38 W. F. Maier and M. T. Reetz J. Amer. Chem. SOC. 1975,97,3687. 39 G. A. Olah A. Germain H. C. Lin and K. Dunne J. Amer. Chem. SOC.,1975,97 5477. 40 G. A. Olah A. Germain and H. C. Lin J. Amer. Chem. SOC.,1975,97 5481. 41 J. W. Larsen and P. A. Bouis J. Amer. Chem. SOC.,1975,97 6094. 204 E. W.Colvin 4 a-Amino-acids With the increasing natural occurrence of D-amino-acids a rapid method of establishing the absolute configuration of a new amino-acid is of obvious utility; such a method42 is seen in the conversion of the amino-acid into the pyrrolinone derivative (18) (Scheme 7) whose c.d.spectrum shows a negative wavelength extremum for a D-amino-acid and vice versa. * RCHCO + 0 0 Scheme7 Cram43 and continue to develop optically active cyclic polyether hosts which exhibit chiral recognition in complexation in solution with the enantiomers of primary amine and a-amino-acid ester salts as guests; in suitable cases total optical resolution can be achieved by chromatography. A new route45 to chiral a-amino- acids has been described in which a recyclable chiral induction reagent (S)-proline (19) is employed (Scheme 8). co Reagents i dicyclohexylcarbodi-hide ;ii NH Scheme 8 42 V.Toome S. De Bernardo and M. Weigele Tetrahedron 1975,31,2625. 43 G. Dotsevi Y. Sogah and D. J. Cram J. Amer. Chem. Soc. 1975,97,1259; G.W. Gokel J. M. Timko and D. J. Cram J.C.S. Chem. Comrn. 1975,394,444. 44 W. D. Curtis D. A. Laidler J. F. Stoddart and G. H. Jones J.C.S. Chem. Comrn. 1975 833 835. 45 B. W. Bycroft and G. R. Lee J.C.S. Chem. Comm. 1975,988. Aliphutic Compounds-Part (ii) Other Aliphatic Compounds 205 5 Amides and Peptides Tetrahedral Intermediates and Protonation Sites.-In one of the first Tetrahedron Reports Deslong~hamps~~ has given a full account of his stereoelectronic approach to tetrahedral intermediates in ester and amide hydrolysis in which the precise conformation of the intermediate hemi-orthoester or hemi-orthoamide controls the nature of the hydrolysis products the particular mode of breakdown reflecting the orientation of the lone-pair orbitals of the heteroatoms; other have supported and extended these concepts.Further of the A,,2 hydrolysis of benzimidate esters have been described. Acid-catalysed hydrolysis of "0-enriched benzarnide in a small but detectable amount of exchange implying the involvement of tetrahedral intermediates in such hydrolysis; the N+ correlation of nucleophilic reactivities has been shownso to apply to the reactions of nucleophiles with esters when explicit consideration of a tetrahedral intermediate is included. The first direct n.m.r. spectroscopic observationS1 of a potassium alkoxide adduct (20) of an amide has been reported; based on lineshapeanalysis a minimum lifetime of 2.3 s is deduced (Scheme 9).0 OK I CF,C // + EtC(Me),OK CF,-C-NMe, \ I NMe 0 I Me-C-Me I Et An example of arnide hydrolysis proceeding via an N-conjugate acid species has been detected5' in the acid-catalysed decomposition of N-nitroso-2-pyrrolidone; the preference for this particular pathway is ascribed to the cyclic amide structure rather than to the presence of an N-nitroso-group. A of the contribution of N-protonation to the overall acid hydrolysis of NN-dialkylacetamides has indicated not surprisingly that this route will predominate for amides of highly basic amines. While N-ammonioamidates undergo methylation at either 0 or N depending on whether the carbonyl group carries a methyl or a methoxyl substituent n.m.r.spectroscopic evidence54 has indicated that protonation occurs on N; in more acidic media dications are observed. General Properties 8nd Reactions.-The c.d. spectra of a-substituted &lactams may be to determine the configuration of the a-carbon atom. The 46 P. Deslongchamps Tetrahedron 1975 31 2463; see also P. Deslongchamps R. ChCnevert R. J. Taillefer C. Moreau and J. K. Saunders Canad. J. Chem. 1975 53 1601. 47 V. F. Smith and G. L. Schmir J. Amer. Chem. Soc. 1975,97 3171. 48 R. A. McClelland J. Amer. Chem. SOC.,1975,97 3177. 49 R. A. McClelland J. Amer. Chem. SOC. 1975 97 5281. so C. D. Ritchie J. Amer. Chem. SOC.,1975,97 1170. 51 G. Fraenkel and D. Watson J.Amer. Chem. SOC.,1975,97 231. 52 B. C. Challis and S. P. Jones J.C.S. Perkin IZ 1975 153. s3 A. Williams J. Amer. Chem. SOC.,1975 97 6278. 54 M. Liler and D. G. Morris J.C.S. Chem. Comm. 1975 93. ss H. Meguro T. Konno and K. Tuzimura Terruhedron Letters 1975 1309. 206 E. W.Colvin conformational states and biological of cyclic peptides have been reviewed as have rearrangement^^^ of penicillanic acid derivatives. The structure of a highly modified peptide althiomycin (2l),has been established5* by detailed spectral and degradative studies. 0 CH,OH 0 (21) Acid chlorides acylate secondary amides in non-polar solvents at moderate rates in the presence of a neutral scavenger for HCl such as activated molecular sieves.59 Exposure of NN-dichloroamides6' to sodium methoxide produces the correspond- ing methyl esters and nitrogen perhaps uia the sequence shown (Scheme 10).R'C //O + R20-+ R1C0,R2 + NC12 \ NCI I-.'- NCl -+CIN=NCI -''' N2 Scheme 10 The isoimide (22) is remarkably stable,61 possibly due to the nitrogen lone-pair electrons and the acetate function being trans. Further INDO configurational studies6*on the succinimidyl radical have been reported. AcO R2 )=Y' R' 6 Aldehydes and Ketones The inability of the Criegee ozonolysis mechanism to explain the observation that addition of 180-enriched aldehyde to an ozonolysis reaction resulted in some of the label turning up in the peroxide bridge of the ozonide has tended to invalidate this attractively simple mechanism (Scheme 11).It has now been that aldehydes undergo a rapid exchange reaction with ozone resulting in the case of 180-enriched 56 Yu.A. Ovchinnikov and V. T. Ivanov Tetrahedron 1975,31 2177. 57 R. J. Stoodley Tetrahedron 1975,31 2321. 58 B. W. Bycroft and R. Pinchin J.C.S. Chem. Comm. 1975 111. 59 L. M. Weinstock S. Karady F. E. Roberts A.M. Hoinowski G. S. Brenner,T. B. K. Lee W. C. Lumma and M. Sletzinger Tetrahedron Letters 1975 3979. 6o R. E. White and P. Kovacic J. Amer. Chem. SOC.,1975,97 1180. 61 A. F. Hegarty and M. T. McCormack J.C.S. Chern. Comm. 1975 168. T. Koenig and R. A. Wielesek Tetrahedron Letters 1975 2007. 63 G. Klopman and C. M. Joiner J. Amer. Chem. SOC.,1975,97 5287. Aliphatic Compounds-Part (ii) Other Aliphatic Compounds H -4-0 '80 0-0 180-I Scheme 11 aldehydes in equilibration of the label into the ozone thus accounting for peroxide- bridge labelling by the Criegee mechanism.Ab initiio MO-LCAO-SCF calculation^^^ on the enol tautomer of malondial-dehyde have indicated that the energy potential of the intramolecular H-bond is of the double-well type (Scheme 12) with a barrier height of 11kcal mol-I rather than the partially bonded (23) which would have a single potential well. H H H (23) Scheme 12 The formaldehyde cation radical (24) isoelectronic with the well-characterized iminoxyl radical (25),has been detected65 and studied by e.s.r. spectroscopy; it behaves as a strong acid decay occurring by proton transfer (Scheme 13). H\ + H \ 0' + H,SO -+ HCO + H,SO H Scheme 13 64 G.Karlstrom H. Wennerstrom B. Jonsson S. ForsCn J. Almlof and B. Roos J. Amer. Chem. Soc. 1975,97,4188; see also A. D. Isaacson and K. Morokuma ibid. p. 4453. 65 S. P. Mishra and M. C. R. Symons J.C.S. Chem. Comm. 1975,909. 208 E. W.Colvin 13 Cn.m.r. spectra of a variety of conjugated enones have been analysed66 to provide a measure of the relative contributions of the valence-bond canonical structures. has extended his studies on the correlation between conjugate addition to and polarographic reduction of @-unsaturated ketones when radical anions are initially produced. Treatment of dibromide (26) under Reformatsky conditions68 gives the Favorsky rearrangement product (27) via the cyclopropanone (28) and not the oxyallyl zwitterion (29) (Scheme 14) casting some doubt on the necessity of oxyallyl 0 OZnBr 0-ZABr Ph,CHCH,CO,Me PhyA (27) Ph (29) Scheme 14 zwitterions in the Favorsky rearrangement.It has been suggested6’ that both radical and ionic mechanisms can operate simultaneously in the bromination of ketones so that the ratio of brominated products may not be a true measure of the relative proportions of the enols. A ~ynthesis’~ of 2-6-heneicosen-ll-one the principal component of the sex attractant of the Douglas fir tussock moth which is a severe defoliator of firs has been described. The sex pheromone of the German Cockroach 3,l l-dimethyl-2-nonacosanone has been prepared as a diastereoisomeric mixture.” The a! -diketone thioether (30) is the main volatile component72 of the anal scent-gland secretion of 0 both the male and female striped hyena; material was collected daily (from caged animals) with great courage.66 R. H. Levin and L. Weingarten Tetrahedron Letters 1975,611. 67 H. 0.House and P. D. Weeks J. Amer. Chem. SOC.,1975,97 2770 2778,2785. 6s H. M. R. Hoffmann and T. A. Now J.C.S. Chem. Comm. 1975,37. 69 V. CaIb and L. Lopez J.C.S. Chem. Comm. 1975,212. 70 R. G. Smith and G. D. Daves and G. E. Daterman J. Org. Chem. 1975,40 1593. 71 M. Schwartz J. E. Oliver and P. E. Sonnet J. Org. Chem. 1975,40 2410; A. W. Burgstahler L. 0. Weigel W. J. Bell and M. K. Rust ibid.,p. 3456. 72 J. W. Wheeler D. W. von Endt and C. Wemmer J. Amer. Chem. SOC.,1975,97,441.Aliphatic Compounds-Part (ii) Other Aliphatic Compounds 209 Reviews have appeared on the chemistry of of halogenomalondial- dehyde~,~~ and of the reactions of Grignard reagents with of vicinal polyketone~,~~ thiocarbonyl 7 Alcohols Full details have been given of the appli~ation~~ of the exciton chirality method7* for the determination of absolute configuration of vicinal glycols and amino-alcohols. Vicinal diesters show a preference for gauche oxygen functions with respect to the ethane backbone nearly as large as that shown by the parent diols; this conforma- tional preference is ascribed,79 at least in the case of erythro diesters to some intrinsic attraction related to electronegativity. A quantum-mechanical study" of the effects of alkyl substituents on the acidity or basicity of alcohols or amines has been described.Preferential complexation of one component of a binary alcohol mixture with calcium chloride or manganese chloride offers'' an attractive purification method; the alcohol with the longer chain is clearly favoured the degree of selectivity increasing with the difference in chain length between the competing components. Protonated chloromethyl alcohol (3l),a suggested intermediate in chloromethyla- tion with formaldehyde and HCl has now been observed8* by low-temperature n.m.r. spectroscopy (Scheme 15). + -CH,O + 2HC1 + ZnC1 + ClCH,OH ZnC1 (31) Scheme 15 8 Amines The absolute configurations of chiral sterically non-hindered primary and secondary amines can be determined by direct inspections3 of the sign of the longer-wavelength c.d.spectral bands of their neutral complexes with copper(I1). Chiral polyether host molecules capable of resolving racemic amine salts by specific molecular complexa- tion have been des~ribed.~~,~~ 'H Dynamic n.m.r. spectroscopy has provideds4 a general picture of the rotation-inversion dichotomy in alkyl-amines. If the barrier to nitrogen inversion is greater than that for isolated rotation about the C-N bond then the process having the lowest barrier that is available for equilibrating the '3 F. I. Luknitskii Chem. Rev. 1975,75 259. 74 C. Reichardt and K. Halbritter Angew. Chem. Internat. Edn. 1975 14 86. 75 M. B. Rubin Chem. Rev. 1975,75 177. 76 D.Paquer Bull. SOC.chim. France 1975 1439; see also R. Couturier D. Paquer and A. Vibet ibid. p. 1670. 77 J. Dillon and K. Nakanishi J. Amer. Chem. Soc. 1975,97 5409 5417. 78 N. Harada S. L. Chen and K. Nakanishi J. Amer. Chem. Soc. 1975,97,5345. 7y C. A. Kingsbury and C. R. Cowles J. Org. Chem. 1975,40 1302. 8o R. F. Hudson 0.Eisenstein and N. T. Anh Tetrahedron 1975,31 751. K. B. Sharpless A. 0.Chong and J. A. Scott J. Org. Chem. 1975,40 1252. 82 G. A. Olah and S. H. Yu J. Amer. Chem. SOC.,1975,97 2293. 83 F. Kerek and G. Snatzke Angew. Chem. Internat. Edn. 1975 14 109. 84 C. H. Bushweller,W. G. Anderson P. E. Stevenson and J. W. O'Neil J. Amer. Chem. Soc. 1975,97 4338. 210 E. W.Colvin environments of the alkyl substituents on carbon is simple rotation with no inversion; if on the other hand the barrier to inversion is lower than that for isolated C-N bond rotation the lowest-barrier process available for equilibrating such environ- ments involves concomitant C-N bond rotation and inversion at nitrogen.A general methodg5 for the conformational analysis of aliphatic hydrazines has been presented based on a direct correlation of the dihedral angle between the two electron lone-pairs with the split As of the n-orbitals obtained from photoelectron spectra. ‘H N.m.r. spectroscopic evidence has indicateds6 that the monoprotonated forms of 1,3-and 174-diamines exist largely as cyclic H-bonded species in which the added proton is attached to both amino-groups simultaneously. 173-Diaminopropane reacts with KH to give a new ‘superbase’ highly soluble in and stable towards excess amine which can accordingly be used as solvent for a variety of prototropic processes .87 N-Nitrosamines are biologically important owing to their extreme carcinogenic- ity.The solution chemistry of methyl(aceroxymethy1)nitrosamine (32) the acetate of the presumed carcinogenic metabolite cf dimethylnitrosamine has been studied;” the parent alcohol is highly unstable in aqueous solution transferring a methyl group to any suitable nucleophile thus mimicking its proposed metabolism. SeebachS9 has minimized handling procedures in his method for the a-alkylation of amines via nitrosamines by making the process ‘one-pot’. The energetic ordering of the molecular orbitals of nitrosamines has been determined” by photoelectron spectroscopy and quantum chemical analysis.9 Diazoalkanes Ab initio generalized V.B. and configurational interaction calculations have indi- cated” that the ground state of diazomethane is better represented as a singlet biradical (33) than as a zwitterion (34). H \ H \. + /C-N=N:H H/C-N=N 8s P. Rademacher Chem. Ber. 1975,108 1548; P. Rademacher and H. Koopman ibid. p. 1557. eb J. Hine and W. S. Li J. Org. Chem. 1975,40 1795. 87 C. A. Brown J.C.S. Chem. Comm. 1975 222. 8H P. Roller D. R. Shimp and L. K. Keefer Tetrahedron Letters 1975 2065. 89 D. Seebach andD. Enders Angew. Chem. Internat. Edn. 1975,14,15; Chem. Ber. 1975,108,1293. 90 D. R. Battiste L. P. Davis and R. V. Nauman J.Amer. Chem. Soc. 1975,97 5071. 91 S. P. Walch and W. A. Goddard J. Amer. Chem. SOC. 1975,97 5319. Aliphatic Cbmpounds-Part (ii) Other Aliphatic Compounds The syntheses and reactivities of a-diazo-y-butyr~lactone~~ (35) and of a@-epoxydiazomethyl ketones93 (36) have been investigated and the chemistry of phosphoryldiazoalkanesy4(37) has been reviewed. 0 RACOCHN, R2P-CR II RR II 0 N2 The first example of a reversible photochromic valence between diazo-compounds- and diazirines has been described (Scheme 16). hv d -do R heat R Scheme 16 10 Alkyl Halides An n.m.r. spectroscopic inve~tigation~~ of the role of solvent in acyclic carbonium ion-cyclic halonium ion equilibria (Scheme 17) has indicated that cyclic halonium ions become relatively more stable as the solvent becomes less capable of nucleo-philic solvation.The numerous literature reports of increased stereoselectivity in electrophilic alkene halogenations in non-polar solvents and at low temperatures serve as qualitative examples of this effect. Scheme 17 Olah" has detected both alkyl and aryl hydridohalonium ions (38) and methyl methylene halonium ylides (39)by n.m.r. spectroscopy; he has also written a booky8 on cyclic and acyclic halonium ions. + +-RXH Me-X-CH (38) (39) y2 A. Schmitz U. Kraatz and F. Korte Chem. Ber. 1975,108 1010. 93 P. M. M. van Haard L. Thijs and B. Zwanenburg Tetrahedron Letters 1975 803; A. C. Brouwer L. Thijs and B. Zwanenburg ibrd.,p. 807. 94 M. Regitz Angew.Chem. Internat. Edn. 1975 14 222. 95 E. Voigt and H. Meier Chem. Ber. 1975,108 3326. y6 S. P. McManus and P. E. Peterson Tetrahedron Letters 1975 2753. 97 G. A. Olah Y.Yamada and R. J. Spear J. Amer. Chem.SOC.,1975,97,680. 98 G. A. Olah 'Halonium Ions' John Wiley and Sons New York 1975. 212 E. W.Cblvin The precise structure and anchimeric intermediacy of halogeno-alkyl radicals continue to generate considerable controversy. Absolute rate constants99 for the reaction of the t-butylperoxyl radical with 1-bromo- and 1-chloro-2-methylpropane have provided kinetic evidence for anchimeric assistance in the abstraction of a hydrogen atom from these substrates. a-Bromo- and a! -iodo-carboxylate deriva- tives can apparently'" give rise to either a -halogenocarboxylate radicals (40) or rearranged P-halogeno-radicals (41); a -chloro-carboxylates form only the radicals (40) (Scheme 18).Hal = 1 or B y HalCH,COX H,CCOX + Hal- HalCHCOX (40) Scheme 18 It has been suggested'" that the species detected by e.s.r. spectroscopy on X-irradiation of isobutyl chloride or bromide in a [2Hl,]adamantane matrix at 77 K was not a P-halogeno-t-butyl radical (42) but was the t-butyl radical itself; the original authors in a full account'02 of their work do detect the disproportionation reaction shown in Scheme 19 but only at temperatures above 209 K. > 209 K BrCH,kMe -DCH,CMe + Me,C C,oD, (42) Scheme 19 The force-field method of conformational analysis has been successfully applied103 to alkyl halides.An alkyl perbromate (43) has been preparedlo4 (Scheme 20). AgBrO + Pr'Br -200c R Pr'OBrO 20"c MeCOMe (43) Scheme 20 11 Miscellaneous Force-field calculations105 on alkanethiols and thioethers have been described as have generalized V.B. descriptions of formaldehyde and formarnide.'O6 Synthese~"~ yy J. H. B. Chenier J. P.-A. Tremblay and J. A. Howard J. Amer. Chem. SOC.,1975,97 1618. loo R. J. Booth S. P. Mishra G. W. Neilson and M. C. R. Symons Tetrahedron Letters 1975 2949. Io1 D. Nelson and M. C. R. Symons Tetrahedron Letters 1975 2953. lo* R. V. Lloyd and D. E. Wood J. Amer. Chem. SOC.,1975,97 5986. Io3 A. Y.Meyer and N. L. Allinger Tetrahedron 1975,31 1971. Io4 K. Baum C. D. Beard and V. Grakauskas J. Amer. Chem. Soc.1975,97 267. *05 N. L. Allinger and M. J. Hickey J. Amer. Chem. SOC.,1975,97 5167. 106 L. B. Harding and W. A. Goddard J. Amer. Gem. SOC.,1975,97,6293,6300. lo7 B. W. Christensen and A. Kjaer J.C.S. Chem. Comm. 1975,784. Aliphatic Compounds-Part (ii) Other Aliphatic Compounds of the chiral sulphimide (44) and sulphodi-imide (45) have been reported and the stability of NN-dialkylthiohydroxylamineshas been explored. log (44) (45) The relevance of the hard-soft acid-base theory to organic chemistry has been the subject of a review.lo9 log D. H. R. Barton S. V. Ley and P. D. Magnus J.C.S. Chem. Comm. 1975 855. Io9 T.-L. Ho Chem. Rev. 1975,75 1.