5 Aliphatic Compounds Part (i)Hydrocarbons By 6. V. SMITH Department of Chemistry King's College London (KQC) Kensington Campus Campden Hill Road London W8 7AH 1 Alkanes Protonolysis of trialkylboranes (RC0,H-diglyme) affords alkanes in variable yields; thus (C6H&B gave C6HI4(91% 2 h) whereas the borane with the hindered 2,4,4-trimethylpentyl structure gave only 5% of alkane.' Since this is a mild method it may be applied safely to sensitive compounds with sulphur halogen or nitrogen functions. Evidence was secured to confirm retention of stereochemistry during protonolysis. Sodium cyanoborohydride -zinc iodide is a unique and selective reducing agent for a range of compounds (aldehydes ketones and benzylic and tertiary alcohols) yielding the corresponding hydrocarbon (and in the former examples some alcohols).' gem-Dialkylation of carbonyl groups (ArCHO ArCOR) by sequential steps (Scheme 1)has been used for synthesis of arylalkane~.~ Tertiary alkyl radicals generated from alcohols via homolytic attack of RS' on (l),formed hydrocarbons in the presence of a thiol; some addition of the radical to an alkene was ob~erved.~ ArCOR' 2ArC(OH)R'R* 5ArC(SeMe)R'R2 iii I ArCR'R2R3 Reagents i RZM-EtzO;ii MeSeH-ZnC1,-CICHzCH,C1; iii BuLi-THF-hexane then R3X -78 "C Scheme 1 The extremely hindered hydrocarbon 2,3-di( l-adamantyl)2,3-dimethylbutanehas been prepared by a Wurtz reaction (0.6%yield in the final stage!).X-Ray diffraction showed deformation arising from torsional strain and lengthening of certain bonds as shown in (2).Theholysis (PhMe-PhSH 180°C 5 h) gave 1-AdCHMe as the major product.A negligible quantity of adamantane (<0.1%)was formed.' Coupling ' H. C. Brown and K. J. Murray Tetrahedron 1986,42 5497. C. K. Lau C. Dufresne P. C. Bilanger S. PiCtri and J. Scheigetz J. Org. Chem. 1986 51 3038. A. Krief M. Clarembeau and P. Barbeaux J. Chem. Soc. Chem. Commun. 1986 457. D. H. R.Barton and D. Crich J. Chem. SOC.,Perkin Trans. I 1986 1603 1613. M. A. Flamm-ter-Meer H.-D. Beckhaus K. Peters H.G. von Schnering H. Fritz and C. Ruchardt Chem. Ber. 1985 118 4665. 77 B. V. Smith of 1-adamantyl-1,l-dibromo-2,2-dimethylpropanewith magnesium gave three diastereoisomeric hydrocarbons (3) separable by crystallization. Structure determi- nation showed that they are a meso-and a d I-pair; it is notable that interconversion of rotamers does not take place at or above room temperature the first reported examples of simple aliphatic compounds which show this property.6 Energy barriers to rotation were measured; e.g.for meso-(3) the barriers for gauche- anti and gauche +gauche interconversions were 217 and 184 kJ mol-' respectively. Ther- molysis of (3) as for (2),gave 2 mols of 1-neopentyladamantane per mol of (3). 163.9 pm ROZC-COZ-N 164.7 pm- Ad S (1) Ad76.4MaLd 40.8 41.2 AdCH( But) CH(But)Ad (Torsional angles) (3) (2) Photolysis of trans-tetra-t-butylazomethane,in C6H6 or C6H5C1 gave a quantita- tive yield of 1,1,2,2-tetra-t-butylethane.' Reports have appeared of the 'Gif' system for functionalizing saturated hydrocar- bons.After some variations in conditions used in earlier experiments,8 the Gif'" system has evolved. It was shown to require an iron-containing catalyst oxygen zinc acetic acid and pyridine. An in-depth study revealed evidence for the role of superoxide (from one-electron reduction of 302). The Gif'" system is not a mimic of cytochrome oxidase (although it was thought that it could be) and does not epoxidize alkenes or oxidize sulphides. Selectivity in the oxidation (of for example adamantane) depends on the partial pressure of oxygen. The proposed mechanism (Scheme 2) is consistent with all observations made so far.' Although this scheme refers to a cyclic hydrocarbon the method will presumably allow of application to acyclic systems.It was shown that zinc could be replaced by an electrochemical cell with improvement in yields." M. A. Flamm-ter-Meer H.-D. Beckhaus K. Peters H.-G. von Schnering H. Fritz and C. Ruchardt Chem. Ber. 1986 119 1492. W. Bernlohr M. A. Flamm-ter-meer J. H. Kaiser M. Schmittel H.-D. Beckhaus and C. Ruchardt Chem. Ber. 1986 119 1911. D. H. R. Barton J. Boivin M. Gastiger J. Morzycki R. S. Hay-Motherwell W. B. Motherwell N. Ozbalik and K. M. Schwartzentruber J. Chem. SOC.,Perkin Trans. I 1986 947. D. H. R. Barton J. Boivin W. B. Motherwell N. Ozbalik K. M. Schwartzentruber and K. Jankowski Now. J. Chim. 1986 10 387. G. Balavoine D. H. R. Barton J. Boivin A. Gref N. Ozbalik and H. Rivibre Tetrahedron Lett.1986 27 2849; J. Chem. SOC.,Chem. Commun. 1986 1727. Aliphatic Compounds -Part (i) Hydrocarbons 79 In the presence of H202 a manganese porphyrin catalyst and imidazole alkanes are oxidized to a mixture of alcohol and ketone." 'Shape-selective hydroxylation' relies on highly hindered iron and manganese porphyrins and unprecedented enhancement of primary hydroxylation was observed in this chemical process.12 Reaction of alkanes with CO-H20 in HF-SbF5 under pressure gave a different product distribution from that obtained by the Koch-Haaf reaction. Thus c5-c6 alkanes with a tertiary hydrogen gave secondary carboxylic acids (from skeletal isomerization) and straight-chain alkanes gave extensive fragmentation judged by the mixtures f~rmed.'~ Activation of alkane C-H bonds by organometallics has been re~iewed.'~ Fe"' eFell ;o2,e-Fe"'OOH H+ =CHR I + ,e",/OH F I -Fe"=O (Major)=Y (Minor) OH Fe"=C / >kH Fen\ / I I 0-0-CH I I I O2 \ \ O=C / C-,CHOOH + ,CH-OH Notes; i n is variable; ii no ligands are shown on Fe atom Scheme 2 2 Alkenes Synthesis.-A stereospecific synthesis of (S)-3-methylpent- 1-ene from L-isoleucine has been achieved (e.e.98.6%).15 Protonolysis of alkenyldialkylboranes forms the basis of a simple stereospecific synthesis of z-alkenes.I6 Some acid catalysis may be needed; the process was applied to preparation of terminal and internal double bonds. In a closely related process lithium(1-alkyny1)tryialkylborates were iodinated to afford an alkyne which was reacted with 9-BBN; the adduct was transformed into a 2-alkene by protonoly~is.'~ Such routes are valuable in synthesis of pheromones or their precursors.A comparative study of stereoselective syntheses of E-trisubstituted alkenes has been published.'* P. Battioni J.-P. Renaud J. F. Bartoli and D. Mansuy J. Chem. SOC.,Chem. Commun. 1986 341. 12 B. R. Cook T. J. Reinert and K. S. Suslick J. Am. Chem. SOC.,1986 108 7281. 13 N. Yoneda Y. Takahashi T. Fukuhara and A. Suzuki Bull. Chem. SOC.Jpn. 1986 59 2819. 14 M. Ephritikhine Nouu. J. Chim. 1986 10 9. V. Schurig U. Leyrer and D. Wistuba J. Org. Chem. 1986 51 242. 16 H. C. Brown and G. A. Molander J. Org. Chem. 1986 51 4512. 17 H. C. Brown and K. K. Wang J.Org. Chem. 1986 51 4514. 18 A. Bernardi W. Cabri G. Poli and L. Prati J. Chem. Res. (S).,1986 52. 80 B. V. Smith E/Z-Selectivity was cu. 1 :1 for the reaction of a-phenylthiosilyl anions with ketones followed by Peterson elimination to form alkenes.” uic-Diols have been converted into alkenes stereospecifically by elimination of C02 AcOH and MeOAc in refluxing Ac,O from the intermediate 2-rnethoxy- 1,3-dioxolanes (4).20Iododesily-R’ lation of vinyl silanes has been used in ‘tuneable’ alkene synthesis with variable stereoselectivity. The intermediate (5) can form Z- or E-vinyl iodide (6) according to the conditions in which control is mediated by a Lewis acid (Scheme 3). Indications from the literature implies retention of stereochemistry in iododesily- ation and hence formation of the Z-vinyl iodide was unexpected.In a further step I I I Scheme 3 the formed vinyl iodide gave an alkene with e.g. RMgBr-Li,CuCl,; wide variation in the E/Z-ratio of the final product is possible by selection of the appropriate Lewis acid in the first step.21 By this approach pheromone synthesis was neatly achieved. Terminal allylic carbonates and acetates afforded terminal alkenes when reacted with formates and a Pd catalyst.22 Elimination from primary alkyl bromides and iodides by a new method gave principally a terminal alkene; the transformation 19 D.J. Ager J. Chem. Soc. Perkin Trans. I 1986 183. 2o M. Ando H. Ohhara and K. Takase Chem. Lett. 1986 879. 21 T. H. Chan and K. Koumaglo Tetrahedron Lett.1986 27 883. 22 J. Tsuji I. Minami and I. Shimizu Synthesis 1986,. 623. Aliphatic Compounds -Part (i) Hydrocarbons 81 was brought about by adding a mixture of RCH2X and 1,8-diazabicyclo[5.4.O]undec-7-ene in THF to C1,(PPh3)2Ni-PPh3-BuLi in THF.23 With HO(CH2),'Br 82% of alk-1-ene was obtained (together with 14% of internal alkene). Elimination of hydrogen bromide or hydrogen chloride from 5-halogeno-4-hydroxypent-1-enes furnished 4,5-epoxypent-l-ene in a short efficient process.24 A regioselective syn- thesis of a terminal alkene is shown in Scheme 4.25 Fe(CO) CP.BF i,ii R~POH +R1p RZ -RIP Reagents i (Pr'0)2POCI;ii Fe(CO)2Cp then HBF,; iii NaI Me2C0 0 "C Scheme 4 Three variations on the Wittig reaction have been reported.A molybdenum metalloazine (8) was generated from (7) and R'R2CN2; reaction of (8) with Ph3P=CR3R4 gave high yields of R'R2C=CR3R4 (Z/E ratio = 1.25 when R' = R3 = H R2 = Ph R4 = Bu).~~ Decomposition of the Wittig-like intermediate gave Ph3P(!) and N2. kine (8) reacted with Bu'NH2 forming an imine. Tungsten alky- 0 :Mo'"(S~CNR,)~ (7) lidene complexes W( =CR'R2)X2Y2 were shown to react with carbonyl groups to form alkenes bearing two three or four substituents. Enol ethers and enamines were also prepared by this method. The tungsten derivatives reacted with esters amides and lac tone^.^^ Carbonyl compounds reacted cleanly with C1CH2Li (from C1CH21-MeLi) forming alkenes.28 The use of mesyltriflone (9) for alkene synthesis has been developed further.29 As shown in Scheme 5 sequential deprotonation -alkylation led to di- tri- and tetra-substitution in the formed alkene.The process is characterized by clean regiospecific reaction and smooth Ramberg-Backlund elimination; it is possible to carry out one-pot operations. Stereospecificity is not controlled since for (lo) a 1:1 mixture of diastereoisomers was formed. Acylation of the sulphone was also examined and shown to be satisfactory; a short convenient synthesis of artemisia ketone (11) was devised (89% yield). 23 S. Jeropoulos and E. H. Smith J. Chem. SOC.,Chem. Commun.,1986 1621. 24 A. De Camp Schuda P. H. Mazzochi G. Fritz,. and T. Morgan Synthesis 1986 309. 25 S. Araki M. Hatano and Y. Butsugan J. Org. Chem. 1986 51 2126.26 J. A. Smegal I. K. Meier and J. Schwartz J. Am. Chem. SOC.,1986 108 1322. 27 A. Agnero J. Kress and J. A. Osborn J. Chem. SOC.,Chem. Commun. 1986 31. 28 J. Barluenga J. L. Fernandez-Simon J. M. Concell6n and M. Yus J. Chem. Soc. Chem. Commun. 1986 1665. 29 J. B. Hendrickson G. J. Boudreaux and P. S. Palumbo J. Am. Chem. Soc. 1986 108 2358. B. V. Smith Tf-S02 TfVS02 2Tf-SO2 TfVSO2 '-2-ii 1 ii 1 I TfYSo2vR2 R' ii li "X TfY TfYso2vR2 R' R4 R' iii 1 I R2 R'I ii ii R' TfXSo2vR2 )= R' R4 R4 iii iii I 1 R' [Tf = CF3S0 -3 )=-R2 RkR2 R4 R4 R3 Reagents i BuLi; ii R'X R2X R3X or R4X; iii KOBUI-THF OT,or K2C03-THF-A or NaOHaq-CH~CI~-BU.,N+HSO; Scheme 5 The addition of lithium to simple cyclic and acyclic alkynes led to formation of ~ic-dilithioalkenes.~~ Thus oct-3-yne by metallation and quenching with MeOD- Et20 gave (12) with isotope distribution of 77%-D2 18%-D1 and 5%-D0.A practical synthesis of methylated alkenes was achieved by quenching the dilithiated oct-3-yne with Me2S04 affording E-3,4-dimethyloct-3-ene (62% ). It was surmised that a cis -* trans isomerization has occurred in such processes since cycloalkynes (and PhCECH) formed cis-lithiated derivatives. An ab initio study of the isomers of 1,2-dilithioethene has a~peared.~' Synthetic applications of tellurium reagents including alkene synthesis and stereomutation of alkenes have been reviewed.32 Reactions.-Multiphoton laser-induced isomerization/fragmentations of alkenes have been 30 A.Maercker T. Grade and V. Girreser Angew. Chem. Int. Edn. Engl. 1986 25 167. 31 P. von R. Schleyer E. Kaufmann A. J. Kos T. Clark and J. A. Pople Angew. Chem. Int. Edn. Engf. 1986 25 169. 32 N. Petragnani and J. V. Comasseto Synthesis 1986 1. 33 F. D. Lewis P. Teng and E. Weitz J. Am. Chem. Soc. 1986 108 2818. Aliphatic Compounds -Part (i) Hydrocarbons 83 Some revision of earlier estimates of regioselectivity of hydroboration has been ~ndertaken.~~ It was recognized that in the addition of the HBBr2.SMe2 reagent to alkenes some addition of HBr may have occurred. Consequently during the alkaline oxidation to form alcohol some alcohol may have been obtained via the bromide. With modified experimental technique such spurious addition is avoided and the true regioselectivity of the reagent can be assessed.Thus 2-methylbut-2-ene and hex-1-ene were shown to form only 1% of Markownikov product. These results now compare with those obtained by the use of ultrasound-promoted hydrobora- ti~n.~~ Asymmetric hydroboration of prochiral alkenes has been exploited in a sequence leading to amines R*NH2 with very high (>99%) optical purity.36 Secon- dary deuterium kinetic isotope effects have been analysed in enantioselective hydro- borations; it was concluded that substituents in the allylic position are crucial for enantioselection. Alkenes ( 13)-( 16) were prepared reacted with di-isopinocam- pheylborane and then aqueous Na202 to form the alcohol(s). Analysis of the mixture of e.g.EtCH(OH)CH(D)Et and EtCH,CD(OH)Et [from (13)] was carried out with LIS n.m.r. to enable calculation of k,/ k to be made. The lack of secondary isotope effect with (13) was taken as evidence for absence of steric compression of vinylic hydrogen in the transition state.37 D H -a$%:DHfi: H H n D D n H H H Electrophilic addition of bromine to micelle-associated alkenes has been used as a probe of micelle structure; variation in micellar components reveals a product dependence arising from attack of the counterion on the bromonium ion.38 Regioselectivity in addition of BrCl and the dichlorobromate ion to alkenes has been analysed in terms of contribution from polar and steric effects.39 Fluorine in aqueous MeCN reacts rapidly with alkenes forming epoxides; thus dodec-1-ene gave >go% yield.40 The mechanism is not certain but perhaps HOF is involved; this pathway offers fast selective reaction in high yield and at low temperatures.In the addition of elemental fluorine to alkenes in CHC13-CFC13 mixture addition of a proton donor suppresses radical processes (and tar formation) and encourages ionic addition?l The process appears to take place via syn-addition and it is proposed that rapid collapse of an ion pair involving an a-fluorocarbocation accounts for observed stereochemistry. Yields of difluoro-adducts are 50-55%. 34 H. C. Brown and U. S. Racherla J. Org. Chem. 1986 51 895. 35 H. C. Brown and U. S. Racherla Tetrahedron Lett. 1985 26 2187. 36 H. C. Brown K.-W.Kim T. E. Cole and B. Singaram J. Am. Chem. SOC.,1986 108 6761. 37 B. E. Mann P. W. Cutts J. McKenna J. M. McKenna and C. M. Spencer Angew. Chem. Int. Edn. Engl. 1986 25 577. 38 R. B. Lennox and R. A. McClelland J. Am. Chem. SOC,1986 108 3771. 39 T. Negoro and Y. Ikeda Bull. Chem. SOC.Jpn. 1986 59 2547. 40 S. Rozen and M. Brand Angew. Chem. Int. Edn. Engl. 1986 25 554. 41 S. Rozen and M. Brand J. Org. Chem. 1986 51 3607. 84 B. V. Smith Photoirradiation of a methanolic solution of an alkene (containing EuC13) led to formation of hydroxymethylalkane the dihydrodimer of the alkene hydrogen and HOCH2CH20H. A photo-initiated redox system [Eu"'-Eu"] was impli~ated.~~ Diacylation of alkenes with acid catalysis has been used in synthesis of pyrylium salts and thus of pyridine~.~~ Terminal alkenes add HSiEt, in the presence of Ru,(CO),~ to afford E-RCH=CHSiEt,; for substitution patterns of the type R'R2CH-CH=CH2 some allylic silane and alkane were produced simultaneously.44 Regioselective formation of 1 -or 2-p-toluenesulphonylalk-1-enes was achieved by either iodosulphonylation or sulphonylmer~uration.~~ A synthesis of alk-1-enyl azides from trans- 1,2-epoxy- silanes (18) gave the 2-isomers (17) with Z/E-specificity of 93-95% when R was alkyl; for R = Ph low yield (8%) was reported but the product was a single (Z)-i~omer.~~ A simple route to nitroalkenes (19) is based on an addition-elimination Rt_jN02 f-7 R2 R3 sequence starting with R'R2C=CHR3 and NaN0,-12-EtOAc-H20.Yields were variable (49-82%) in this alternative to the Henry rea~tion.~' Alkenes add Hg(N03)2,forming P-nitrato-alkyl mercury( 11) nitrates (probably by trans-addition) which with bromine formed P-bromoalkylnitrates?* 2-But-2-ene thus formed a single diastereoisomeric mixture differing from that obtained with E-but-2-ene. The complex involved in catalytic hydrocyanation of ethene has been identified as (20); L is a phosphorus-containing ligand.49 An improved procedure for metallation of 2-and E-but-2-enes gave stereochemi- cally pure 2-and E-cr~tylpotassiums.~~ Subsequent boration and reaction with RCHO was employed in a route to erythro-or threo-P-methylhomoallylalcohols with very high diastereo- and enantio-selectivities. Metallation of 2,3-dimethylbut-2- ene leads preferentially to a cross-conjugated dianion agreeing with prediction." The mono- and di-anions were shown to undergo elimination a novel reaction for such systems.Allylic zinc halides react with metallated alkenes (RCH=CHMet; R = C6HI3 Met = Li or MgBr) forming (21) which was transformed further by reaction with electrophiles R'X and R2X to afford (22). In an alternative scheme (21) was transformed into (23) and hence (24) with CH2=CH(R)CH2X.52A wide range of polyfunkional compounds may be prepared by these routes illustrated in the examples cited. 42 A. Ishida S. Yamashita S. Toki and S. Takamuku Bull. Chem. SOC.Jpn. 1986 59 1195. 43 H. G. Rajoharison and C. Roussel Bull. Chem. SOC.Fr. 1986 307. 44 Y. Seki K. Takeshita K.Kawamoto S. Murai and N. Sonoda J. Org. Chem. 1986 51 3890. 45 K. Inomata T. Kobayashi S. Sasaoka H. Kinoshita and H. Kotake Chem. Lett 1986 289. 46 S. Tomoda Y. Matsumoto Y. Takeuchi and Y. Nomura Bull. Chem. SOC.Jpn. 1986 59 3283. 47 S. Jew H. Kim Y. Cho and C. Cook Chem. Lett. 1986 1747. 48 A. J. Bloodworth and P. N. Cooper J. Chem. SOC.,Chem. Commun. 1986 709. 49 R. J. McKinney and D. C. Roe J. Am. Chem. SOC.,1986 108 5167. 50 H. C. Brown and K. S. Bhat J. Am. Chem. SOC.,1986 108 5919. 51 N. S. Mills and A. R. Rusinko 111 J. Org. Chem. 1986 51 2567. 52 P. Knochel and J. F. Normant Tetrahedron Letf. 1986 27 4427. 4431 5727. AIiphatic Compounds -Part (i) Hydrocarbons L-Ni-CN Et RqMet I- ZnBr E2 ZnBr (20) (21) Allylic dimethylphenylsilanes show remarkable regioselectivity in reactions of their carbanions with C02 or MeI.s3 Despite the known tendency for y-selectivity in reaction of CH2=CHCH2SiR3 methylation or carboxylation occurred at the a-position.The a-carboxylated allylic silanes form useful synthetic equivalents for 3-carboxylated ally1 anions. Two general accounts of the Sharpless reaction have appeared.54 Interest in applications and modifications of the process has been maintained. The role of water has been discussed and it was shown that as little as 15 mol% of Ti(OPr') was sufficient to convert geraniol into the epoxide (99'/0 yield 91% optical purity).55 Ally1 alcohols are smoothly converted into epoxides in a process of high regio- and stereo-selectivity which is based on Bu~S~O-BU'OOH.~~ A new approach to structure-selectivity relationships in epoxidation has explored the use of a novel family of peracids chosen in order to magnify steric effects at the expense of electronic effects." Since selectivity arising from the transition state in the Prilaschajew reaction [written as (25)J is low for cisltrans-pairs of alkenes an attempt was made to prepare a peracid (U-shaped) in which steric bulk could modify the ease of approach of the alkene to the site of oxygen transfer.Such an acid (26) R I showed low selectivity and even when the bridge across the cyclohexane ring contained a naphthalene residue there was negligible selectivity. The C-shaped peracid (27) showed greater selectivity; thus for (27b) Bu'CH=CHEt gave kcis/kfrans = 7.8.These results are consistent with a transition state in which the C=C bond is parallel to the 0-H bond of the peracid. Chiral sulphamyloxaziridines have been used in the asymmetric oxidation of non-functionalized alkenes. Thus (R,R)-(28)with PhCH=CHPh gave syn-stereo- specific epoxidation. Reaction was fastest in MeCN but some selectivity was lost.'* 53 H. Uno Bull. Chem. SOC.Jpn. 1986 59 2471. 54 K. B. Sharpless Chem. Brit. 1986 38; A. Pfenninger Synthesis 1986 89. 55 R. M. Hanson and K. B. Sharpless J. Org. Chem. 1986 51 1922. 56 S. Kanemoto T. Nonaka K. Oshima K. Ultimoto and H. Nozaki Tetrahedron Lett. 1986 27 3387. 51 J. Rebek jun. L. Marshall J. McManis and R. Wolak J. Org. Chem. 1986 51 1649.F. A. Davis and S. Chattopadhyay Tetrahedron Lett. 1986 27 5079. B. V. Smith Me 0 '. / 0 \ CsF5 (27a) R = Me (27b) R = Et [a = (S)-( -)-N-benzyl-1-phenylethylamine] A dinuclear iron peroxide complex has been described which can epoxidize e.g. 2-stilbene; the yield is very low (2.5%) but the product was claimed to have a cis/ trans-ratio of 5 :95.59 Dinuclear copper complexes do not epoxidize terminal alkenes and give modest yields with di-or tetra-substituted alkenes; thus Me,C=CMe gave 41% and PhCH=CHPh 23% (E) and 8% (2)of epoxide. In the latter example some PhCHO was also formed.60 Novel vanadium( v) complexes epoxidize alk-1-enes in addition to other types e.g. oct-1-ene gave 40% and Me2C=CMe2 yielded 98% of product.61 A system based on mimicking mono- oxygenase action which used Mn"'-NaOC1 has been the subject of a study of rates and products of reaction.62 A theoretical analysis of epoxidation by v2-peroxo- complexes of Group VI transition metals has analysed the interactions in terms of frontier orbitals.62 The unusual alkene (29) prepared from reductive coupling of (30) (TiCl3-LiA1H4-THF) is very easily oxidized (Eo= 0.7V) and yet forms a normal ep~xide.~~ The chiral ligand ( -)-(&R)-N,N,N',N'-tetramethylcyclohexane-1,2-truns-diamine allows high levels of asymmetric hydroxylation of alkenes by OSO~.~~ Thus hept-1-ene gave (R)-heptan-1,2-diol (75% 86% e.e.) in 2 h at room temperature.With PhCH=CH2 reaction was slower and the e.e. was much lower (34%).Chalcone did not react in three days. A review of allylic oxidation brought about by stoicheiometric or catalytic quantities of metal complexes has been published.65 Amongst+other work on additions to alkenes reports have appeared of addition of Ar-CEN-0 to (3R)-but-l-ene in which addition seems to occur from attack 59 B. P. Murch F. C. Bradley and L. Que jun. J. Am. Chem. SOC.,1986 108 5027. 60 A. F. Tai L. D. Margerum and J. S. Valentine J. Am. Chem. Soc. 1986 108 5006. 61 H. Mimoun M. Mignard P. Brechot and L. Saussine J. Am. Chem. SOC.,1986 108 3711. 62 J. A. S. J. Razenberg R. J. M. Nolte and W. Dreuth J. Chem. SOC.,Chem. Commun. 1986 277; K. A. J~rgensen and R. Hoffman Acra Chem. Scand. (B) 1986,40 411. 63 H. Wenck A. de Meijere F. Gerson and R.Gleiter Angew. Chern. Znr. Edn. Engl. 1986 25 335. 64 M. Tokles and J. K. Snyder Tetrahedron Lett. 1986 27 3951. 65 J. Muzart Bull. Chem. SOC.Fr. 1986. 65. Aliphatic Compounds -Part (i) Hydrocarbons 87 on the more hindered face of the preferred conformation of the alkene,66 addition of SO3-PhIO forming cyclic ~ulphates,~~ and halogenocyclopropanation via MeLi- CH2C12-LiBr.68 In the latter reaction allylic alcohols containing a methyl group cis to the hydroxyl gave rise to an unexpected syn-stereoselection which was attributed to a synergic interaction between the groups. Thus (31) gave only trans-(32) (X = Cl or Br; Cl/Br = 77/23) whereas (33) gave (34) (X = C1 c/t = 76/24 X = Br c/t = 97/3; Cl/Br = 75/25). .r PT' Me ..OH OH X Me Alkanes add to alkenes in a thermally initiated process with characteristics of a radical chain.69 Addition of carbocations of the type Ar2CH+ to alkenes R'R2C=CR3R4 was the subject of analysis of rates and products. A conclusion which was drawn from the data suggests that the transition state is scarcely bridged. A second paper refers to reaction with diene~.~' It is believed that the nickel-promoted addition of a perfluoroalkyl iodide to an alkene proceeds via single-electron transfer since scavenging experiments gave positive results.71 The complex Cl,(MeOCH,OMe)( WECCMe,) with alkenes gave disproportion- ation and dimerization; thus oct-1-ene gave ethene and tetradec-7-ene. In this way 40% conversion of oct-1-ene was realized in 30 minutes at room ternperat~re.~' Cationic nickel complexes containing dithio-P-diketonate and chelating diphos- phine ligands serve as effective catalysts for oligomerization and double-bond migration of olefins.The product mix is rich in dimers with a high proportion of linear or near-linear isomers; e.g. propene gave ca. 75% methylpentenes and 16% hexene~.~~ A substantial review of transition metal-catalysed dimerization of small alkenes has appeared.74 Stereoregulation of ionic polymerization of alkenes has been reviewed.75 It has been observed that the cyclization of 1-methylhex-5-enyl halides (Na or Na-C$8 in THF or DME) is suppressed by Bu'NH2. Cyclization of the radical is unaffected however and this method is shown to be a valid probe for the radical and to distinguish between radical and polar pathways.76 Double-bond migration in alk-1-en-3-yl acetates can be effected by N~OH-ACOH.~~ 66 K.N. Houk H.-Y. Duh Y.-D. Wu and S. R. Moses J. Am. Chem. SOC.,1986 108 2754. 67 N. S. Zefirov V. D. Sorokin V. V.Zhdankin and A. S. Koz'min J. Org. Chem U.S.S.R,1986,22,398. 6a R. Barlet R. Baharmast and M. Vidal C. R Hebd. Seances Acad. Sci Ser. C 1986 303,289. 69 J. Hartmanns K. Klenke and J. 0.Metzger Chem. Ber. 1986,119,488; J. Hartmanns and J. 0.Metzger ibid. 1986 119 500; J. Hartmanns J. 0. Metzger and D. Eisermann ibid. 1986 119 508. 70 H. Mayr and R. Pock Chem. Ber. 1986 119 2473. 71 Q.-Y. Chen and Z.-Y. Yang J. Chem. SOC.,Chem. Commun. 1986 498. 72 K. Weiss Angew. Chem Int. Edn.Engl. 1986 25 359. 73 K. J. Cavell and A. F. Masters Aust. J Chem 1986 39 1129. 74 S. M. Pillai M. Ravindranathan and S. Sivaram Chem. Rev. 1986 86 353. 75 K. S. Minsker M. M. Kapasas and G. E. Zaikov Russ. Chem. Rev. 1986 55 17. 76 J. F. Garst J. B. Hines jun. and J. D. Bruhnke Tetrahedron Lerr. 1986 27 1963. I7 A. G. Martinez M. 0. Ruiz and J. L. Contelles Synthesis 1986 125. B. V. Smith New applications of tetracyanoethene have been reviewed.78 3 Polyenes Synthesis.-A practical stereoselective synthesis of 1,3-dienes is shown in Scheme 6.79Carbocupration of ethyne by lithium dialkylcuprates leads to 12,3Z-dienyl cuprates intermediates in the synthesis of Z,Z-dienes; this methodology was used to synthesize llZ,13Z-hexadecadienal the pheromone of the navel orange worm.8o r 1 SiPh3 -R& SiPh3 I I OH \ I 1 vi vii x\ 4 \ Reagents i BuLi-THF; ii Ti(OPr'), -78 "C; iii RCHO -78 "C;iv -78 "C lh -P 30 "C,3h; v HCI-H20; vi H,SO,-THF; vii KOBU' Scheme 6 Cu' iodide-catalysed cross-coupling of 2-( 1-trimethylsily1)alk- 1 -enyl dicyclohexyl boranes with ally1 bromide (or 1-bromohex-1-yne) gave rise stereoselectively to 2-1,4-dienes (or conjugated 2-enynes) having the trimethylsilyl group on the internal position of the double bond.Thus BuC-CSiMe gave via the above steps Z-BuCH=C(SiMe3)CH2CH=CH2 stereospecifically.81 A route to E,Z-1,3-dienes is outlined in Scheme 7; the product was obtained in modest yield (51%) but was 97% pure.82 A regiospecific free radical addition of a-halogenoalkanesulphonyl bromides (RCHBrS02Br or ICH2S02Br) to alkenes e.g.oct-1-ene gave a single adduct which copld be transformed into a bromoalkenyl sulphone or a diene. In this latter pathway nona-1,3-diene (59%) was formed with 83 :17 Z/E-rati~.~~ In a similar way hex-3-yne gave oct- 1 -ene-3-yne. An improved method for preparation of 2,Z-1-bromo-l,3-dienes shown in Scheme 8 is efficient and E-and 2-1 -hydroxybuta-1,3-diene have been obtained from the retro-Diels-Alder reaction of the corresponding 3-exovinyl-78 A. J. Fatiadi Synthesis 1986 249. 79 Y. Ikeda and H. Yamamoto Bull. Chem. SOC. Jpn. 1986 59 657. 8o M. Furber R. J.K. Taylor and S. C. Burford J. Chem. SOC.,Perkin Trans. 1 1986 1809. 81 M. Hoshi Y. Masuda and A.Arase Bull. Chem. SOC.Jpn. 1986 59 659. 82 S. Hyuga S. Takinami S. Hara and A. Suzuki Tetrahedron Lett. 1986 27 977. 83 E. Block M. Aslam V. Eswarakrishnan K. Gebreyes J. Hutchinson R. Iyer J.-A. Lafitte and A. Wall J Am. Chem. SOC.,1986 108 4568. 84 S. Hyuga S. Takinami S. Hara and A. Suzuki Chem. Lett. 1986 459. Aliphatic Compounds -Part (i) Hydrocarbons 89 R2 R' R2 R'C=CR 2R' -w A 7 H BBr Br-BUBr A H R3 I iv H R3 H R3 U R? c-v R-Br -7 HA R2 R2 Reagents i HBBr,.SMe2; ii BBr,; iii HCFCR3; iv I, KOAc; v Bu'Li MeOH Scheme 7 R / UH BrmR2 Reagents i BBr, ii R'C-CR' iii I, KOAc Scheme 8 OTMS / R-. P=C ,OTMS P=C Bu' .=+But (35) Bu' (36) bicycl0[2,2,l]hept-5-en-2-01(35) by FVP (750"C t~rr).~~ 2-2-Hydroxy-2,4-dienes (2-dienols) were implicated in photoenolization of P-alkyl-a$-unsaturated ketones since trapping by a silylating reagent was achieved.86 The first stable open-chain 1,3-diphosphabutadiene (36) has been synthesized." 85 F.TureEek Z. Havlas F. Maquin N. Hill and T. Gaumann J. Org. Chem. 1986 51 4061. 86 C. S. K. Wan A. C. Weedon and D. F. Wong J. Org. Chem. 1986,51 3335. 87 R. Appel P. Folling W. Schuhn and F. Knoch Tetrahedron Lett. 1986 27 1661. B. V. Smith Allene formation from propargyl ethers has been intensively investigated. Scheme 9 sets out the details of this transformation a valuable route to chiral allenes.88 l-Bromo-3-methylpenta-l,2-diene with Bu'M( M = Al Zn Mg) gave reduction Bu I p BuMgBr L.--3 I Bu +I ii Tv Bu Cu u B'uMgX -y Bu Bu Me0 Me0 Reagents i 5% CuBr ligand [l or 2 eq.PR3 P(OR), or P(NMe,),] and HCZC-C' ; ii CuBr I 'Bu ,H Me0 Me,S Et,O then H-CEC-C' ; iii I,; iv Bu"Li Et20 -78 "C then MgX, Et,O -78 "C; Me0I \Bu V -78 + +5 "C X = I anti-elimination 68% opt. yield X = CI syn-elimination 35% opt. yield Scheme 9 elimination or alkylation with chemo- and regio-selectivity governed by the organometallic reagent used.89 So,it was noted that BuiM and Et(Me)C=C=CHBr gave mainly Et(Me)C=C=CHBu' whereas BuiZn gave less allene and MeCH=C( Me)CrCH in slightly greater yield. 1H-Allene-l,3-dicarboxylicacid monoesters have been prepared from Ph3P=C(R)C02Me (R = Me,Ph) and AcCl; the formed H2C=C=C(R)C02Me was lithiated and treated with C02 to form the product.By reacting R'CH(C02R2)COC1 and Ph3P=CHC02R3 the desired half ester was also available provided R3 was But (cleaved by acid) or CH2CC13 (cleaved by zinc) and that R2 was unreactive under these conditions. This alternative method extends the scope of reaction since the lithiation-carboxylation sequence only works for H2C=C=C( Ph)C02Me.90 Porcine liver esterase-catalysed hydrolysis of racemic allenic esters showed moderate-high selectivity; thus Ph( Me)C=C=C( Me)CO,Me gave modest yield (33%) of the ( -)-acid but the e.e. was 90% .91 The bis-phosphaal- lene (37)has been synthesized and reactions of phosphorus (e.g.oxidation thiation methylation) take place normally.92 1.Marek P. Mangeney A. Alexakis and J. F. Normant Tetrahedron Lett. 1986 27 5499. 89 A. M. Caporusso L. Lardicci and F. Da Settimo Gazz. Chim. Ital. 1986 116 599. 90 F. W. Nader A. Brecht and S. Kreisz Chem. Ber. 1986 119 1196. 91 S. Ramaswamy R. A. H. F. Hui and J. B. Jones J. Chem. SOC,Chem. Commun. 1986 1545. 92 M. Schmidbaur and T. Pollok Angew. Chem. Inf. Edn. EngL 1986 25 348. Aliphatic Compounds -Part (i) Hydrocarbons But Ph ,c=c=c=c=c/ 4 (Ph,P),C=C=C( PPh,) EtO2C 'C02H (37) (38) 1H-Allene-l,3-dicarboxylic acid monoester acid chlorides are precursors of buta- 1,2,3-trienone which by Wittig olefination can be transformed into l-t-butyl-5- phenylpenta-l,2,3,4-tetraene- 1,5-diesters. Cleavage of the t-butyl ester group in the above type of compound gave the first synthesized derivative of the tetraene acid ( 38).93 Reactions.-Reactions of E,E- E,Z- and Z,Z-1,4-di-t-butoxybuta-1,3-diene with singlet oxygen have been st~died.9~ 1,3-Dienes with NH4N03-(CF3C0)20-HBF4 gave nitrotrifluoroacetate adducts which via elimination gave l-nitr0-1,3-dienes.~' With NOZBF, in MeCN conjugated dienes gave nitroacetamidation in a process showing 1,2- and 1,Caddition.The products could be transformed into dihy- droirnidaz~les.~~ 1,3-Butadiene will add ketones ( Me2C0 PrCOMe Pr'COMe) under catalysis by ceric ammonium nitrate; 1,2- and 1,4-adducts were obtained. A free-radical pathway for reaction was propo~ed.~' Coupling of C02 and butadiene has been achieved by using the complex (39); the products (see Scheme 10) are L3Fe 0 0Iiii \ ./-=CC02H HO2CnCO?H \ + + -P-CO2H HozcL Reagents i CO,; ii H30+;iii COz H,O; iv FeCI, H,O+ Scheme 10 dependent on the conditions used.98 Buta-1,3-diene forms a zirconacycle (40) on reaction with the product from C1,ZrCp2 and 2 eq. RM (containing Li or Mg).99 The structure of an allenyl sodium derivative has been discussed in terms of competition between carbanion resonance delocalization and gegenion charge 93 F. W. Nader A. Brecht and S. Kreisz Chem. Ber. 1986 119 1208. 94 E. L. Clennan R. P. L'Esperance and K. K. Lewis J. Org. Chem. 1986 51 1440. 95 A. J. Bloom and J. M. Mellor Tetrahedron Lett. 1986 27 873. 96 A. J. Bloom M. Fleischmann and J. M. Mellor J.Chem. SOC.,Perkin Trans. I 1986 79. 97 E. Baciocchi and R. Ruzziconi J. Org. Chem. 1986 51 1645. 98 H. Hoberg K. Jenni C. Kriiger and E. Raabe Angew. Chem. Int. Edn. Engl. 1986 25 810. 99 E. Negishi F. E. Cederbaum and T. Takahoshi Tetrahedron Lett 1986 27 2829. B. V. Smith Na+( tmeda) I\ -119 -144 -\ Me [Bond lengths/pm] I-localization.'00 For Bu'C=C-(Me)C-C-CBu' a localized charge depiction is favoured with the Na(tmeda)2 counter-ion; when the Li derivative was examined it was extensively dimerized. The structure shown (41) reflects the localization. Reduction of allenes [HMn(CO)5 or HCO(CO)~] was monitored by CIDNP which supports the mechanism shown in Scheme 11."' Allenes and phenyl-substituted Me +HM 7 Meb.4 -1 Me*Me M.1 Me* / \ Me Me Me bde + HM Me Me Me Me Scheme 11 allenes add (PhMe,Si),CuLi in THF at -78 "C to form an E-vinylsilane.lo2 Di- and tri-alkylallenes gave a 3 :1 mixture of (allyl-/vinyl-silane; reaction at -78 "C gave only allylsilane whereas warming to 0°C for one hour before quenching gave a mixture of vinylsilane and allylsilane.Allenes add Me,SiCN in the presence of palladium or nickel catalyst; C6H13CH=C=CH2 gave mostly E-C6H13CH=C(SiMe3)CH2CN(95%) together with 5% of Z-isomer (66% overall yield).lo3 Ally1 azides can undergo [3,3] sigmatropic rearrangement. However with IN3 allene itself formed a bis-adduct with a gem-diazide structure.'o4 Bromine azide behaved similarly. A novel allene-ene reaction was observed with e.g.2,5,5-trimethylocta-l,6,7-triene-4-one which gave products of [2 + 21 thermal addition. Two other examples were noted for substituted n~natrienones."~ The cycloaddition of chloro- cyano- methoxy- and phenylthio-allenes with 1,l-dichloro-2,2-difluoroethene has been investigated.'06 Other (dienophile) addends were also used. 100 C. Shade P. von R. Schleyer M. Geissler and E. Weiss Angew. Chem. Znt. Edn. Engl. 1986 25 902. 101 J. F. Garst T. M. Bockman and R. Batlaw J. Am. Chem. Soc. 1986 108 1689. 102 I. Fleming and F. J. Pulido J. Chem. SOC.,Chem. Commun.. 1986 1010. 103 N. Chatani T. Takeyasu and T. Hanafusa Tetrahedron Lett. 1986 27 1841. 104 A. Hassner and J. Keogh J. Org. Chem. 1986 51 2767. 105 L. Skattebcil Y. Stenstram and E.Uggerud Acta Chern. Scand. Ser. (B) 1986,40 363. 106 D. J. Pasto and S. N. Yang J. Org. Chem. 1986 51 1676 3611. Aliphatic Compounds -Part (i) Hydrocarbons Shifts in 'H n.m.r. of chiral allenes induced by chiral silver and ytterbium complexes have been measured and this approach is recommended for 1,3-disub- stituted allenes. Results for ( -)-trideca-6,7-diene and ( -)-2,2-dimethyldeca-3,4-diene are the first application of an absolute method via this technique.'" It was concluded that butatrienone does not have a 'kink' in the structure.'08 Pentatetraenes show some lengthening of the terminal double bonds with respect to 'central' bonds whereas cumulenes with an odd number of double bonds differ in structure from those with an even number.Representative examples are shown in (42) (43) and (44).'09 Ph Ph 1.327 1.27A (42) 4 Alkynes Synthesis. Lithium acetylides react smoothly with organoboranes in THF to form lithium( 1-a1kynyl)organoborates;iodination of the latter compounds at low tem- perature gives an alkyne with good yields in some instances. By this method hex-1-yne afforded dec-5-yne in high yield. The lithium acetylide-ethylenediamine complex was found to give superior results in some cases. The method is versatile and allows of preparation of a wide range of alkynes with or without functional groups."' An improvement in the synthesis of unsymmetrical alkynes was secured by iodination of the 'ate' complexes formed from thexylalkylborinates. It was shown that whilst compounds such as (45) gave BuC_CC8H, and MeC=CC,H, by an iodination/oxidation sequence the use of (46) gave an improved yield of the desired product (47)."' It was further shown that this route was compatible with the presence Me -,Bu CaH17-/ -B-C=CBuH\OMe H,,C,CrCBu &ccnH'7(45) (46) (47) of other functional groups as shown by the synthesis of CI(CH,),CFCBu in 53% yield.An enantioselective synthesis of disubstituted alkynes is possible uia the same route but with the use of the 'ate' complex from diisopinocampheyl s-butyl borane [from 2-but-2-ene and (ip~)~BH)l. Optical activity of 95% was preserved in the 107 A. Mannschreck W. Munninger T. Burgemeister J. Gore and B. Cazes Tetrahedron 1986 42 399. 108 R. D. Brown P.D. Godfrey M. J. Ball S. Godfrey D. McNaughton M. Rodler B. Kleibomer and R. Champion J. Am. Chem. SOC.,1986 108 6534. I09 H. lrngartinger and W. Gotzmann Angew. Chem. Int. Edn. Engl. 1986 25 340. I10 A. Suzuki N. Miyaura S. Abiko M. Itoh M. M. Midland J. A. Sinclair and H. C. Brown J. Org. Chem. 1986 51 4507. Ill J. A. Sikorski N. G. Bhat T. E. Cole K. K. Wang and H. C. Brown J. Org. Chern.. 1986. 51. 4521. B.V. Smith formed alkyne.' l2 Iodination/oxidation of complexes formed analogously from 1-alkynyl lithiums and B-alkoxyborinanes gave alkynols with 1-iodoalk-1-ynes; increase of the steric bulk of the alkoxy-group gave more alkynol at the expense of the iodo-compound. The best result from this point of view was obtained with the triphenylmethoxy-group leading to alk-6-yn-1-01 (85% ).Modifications to the method led to alk-7-yn- 1-01s and by using complexes from dialkylmethylboranes unsymmetrical alkynes could be obtained.' l3 In the equilibrium set up between RC-CM and MeSOMe competition existed between regeneration of RCECH and alkylation of RCrCM by added R'X; the presence of inductively stabilizing groups favoured alkylation.' l4 The products from such reactions are useful intermediates especially when R = -CH,OTHP or -CH(OEt) . Thexylalkenylalkynylboraneswith I,-KOMe form E-1,3-enynes in acceptable yields and good stereochemical purity (295%).l15 The route was used to prepare Z-E-dodeca-5,7-diene-l-ol, a caterpillar pheromone. The palladium-catalysed cross- coupling shown in Scheme 12 showed a preference for reaction of E-isomers.'16 R Br i R Br :+ + mw-:+* + m\"=/ Br SiMe Reagents i n CIZnC=CSiMe, (PPh,),Pd THF Scheme 12 Fluorinated alkenyl iodides couple with RCECZnCl in a palladium-promoted reaction to yield fluoro-substituted enynes.'" Peracid oxidation of (48)gave 1,3- diynes in good yield (R = Ph R' = Et or Ph) but failed when R = Bu and R' = Ph.'18 During attempted alkylation of PhCECH in a two-phase system oxidative dimerization to 1,4-diphenylbuta-l,3-diyneand 1,4-diphenylbut-l-en-3- yny was noted.Products of alkylation with cg. ally1 bromide were unconjugated and conjugated phenyl-substituted pentenynes.' l9 Oligomerization of ethyne (Cu' NH4C1) forms E-and Z-o~ta-1,3,7-trien-5-yne.*~~ A phosphaalkyne (P-CR R = 1-adamantyl) has been obtained by elimination from (49) of Me,SiOSiMe .12' The product shows intense absorption at 1520 cm-' OSi Me Me,Si -P = C,/ C.A. Brown M. C. Desai and.P. K.Jadhav J. Org. Chem. 51 162. '13 H. C. Brown D. Basavaiah and N. G. Bhat J. Org. Chem. 1986 51 4518. J. M. Chong and S. Wong Tetrahedron Lett. 1986 27 5445. H. C. Brown N. G. Bhat and D. Basavaiah Synthesis 1986 674. B. P. Andreini A. Carpita and R.Rossi Tetrahedron Lett. 1986 27 5533. F. Tellier R. Sauvetre and J.-F. Normant Tetrahedron Lett. 1986 27 3147. I18 J. V. Comasseto V. Catani J. T. B. Ferreira and A. L. Braga J. Chem. Soc. Chem. Commun. 1986,1067. 119 S. L. Paravyan G. D. Torosyan and A. T. Babayan J. Org. Chem. USSR. 1986 22 631.H. Hopf L. Eisenhuth V. Lehne and L. Emst Chem. Ber. 1986 119 1105. 121 T. Allspach M. Regitz G. Becker and W. Becker Synthesis. 1986 31. Aliphatic Compounds -Part (i) Hydrocarbons 95 ( vpSc) and readily undergoes [3 + 21 cycloaddition with a nitrile oxide to give a 1,2,4-0xazaphosphole. Aminoacetylene was identified as the product of decarbonyla- tion of HCECCONH in a mass spectrometer.'22 Alkyne-forming eliminations have been studied from a theoretical aspect.123 Reactions.-Rates of base-catalysed hydrogen exchange of 13 terminal alkynes have been reported and ana1y~ed.l~~ The effect of added triphenylphosphine and metal loading and/ or dispersion on product distribution from reduction of hex-3-yne and di-t-butylacetylene by palladized alumina has been studied.'25 Some enhanced cis-selectivity was found when dispersion increased.Addition of dichlorobromate and bromine monochloride to alkynes shows anti-stereospecificity (but non-regios- pecificity except for PhCECH).126 Iodine fluoride and bromine fluoride add to alkynes forming adducts CF2CX2 (X = 1,Br). Reaction is rapid at low temperature (<5 min at -75 "C) and yields are good (e.g. but-2-yne gave 85% MeCF2C12Me). Aryl alkynes also react; thus PhCECH gave PhC(F)=CHX (1 eq. of FX; E/Z-ratio = 1:1) and with an excess of reagent PhCF2CHX2. Triple bonds which are a,P-related to ester functions also react.12' Alkynes react with bis-pyridine-iodine( I) tetrafluoroborate in the presence of nucleophiles (Hal- SCN OAc etc.) to yield R'C( Nu)=C( I)R2.'28Chlorosulphamation of alkynes (R2NC1-S03) gives a mixture of adducts of the form R'C(Cl)=C(OS02NR2)R2.'29 An account of hydrocyanation of alkynes has appeared.13' Addition of thiocyanic acid to alkynes is a two-step process; in the first Hg(SCN)2 and the alkyne generate an adduct which in a second step undergoes acid-promoted demercuration thus forming a vinylic is~thiocyanate.'~' The Hg"-promoted hydration of oct-4-yne in methanol afforded octan-4-one as major product with small amounts of 4- methoxyoct-4-ene and the dimethyl ketal of the 0ctan0ne.l~~ Addition of H~(OAC)~ in AcOH which gave vinylic acetoxymercuric acetates has been studied for a range of a1k~nes.l~~ Phenol (and thiophenol) add to PhC_CCF3 under base catalysis and with thermodynamic control; with PhOH the principal adduct was Z-Ph( PhO)C_CHCF,;-with PhSH the E-adduct was formed.The differing pathways were rati0na1ized.l~~ An expedient route to either E-or 2-alkenyl bromides is shown in Scheme 13.13' The selectivity associated with formation of hexa-l,5-dien-3-ols has been attributed to chemodiff erentiation in reaction between R'CECBR and (50).136 122 B. van Baar W. Koch C. Lebrilla J. K. Terlouw T. Weiske and H. Schwarz Angew. Chem Int. Edn. Engl. 1986 25 827. 123 R. D. Bach and J. C. Evans J. Am. Chem SOC. 1986 108 1374. 124 A. J. Kresge and M. F. Powell J. Org. Chem. 1986 51 819 822. 125 S. Siege1 and J. A. Hawkins J. Org. Chem. 1986 51 1639. 126 T. Negoro and Y.Ikeda Bull. Chem. SOC.Jpn.1986 59 3515. 127 S. Rozen and M. Brand J. Org. Chem. 1986 51 222. 128 J. Barluenga M. A. Rodriguez J. M. Gonzllez and P. J. Campos Tetrahedron Lett. 1986 27 3303. 129 N. S. Zefirov N. V. Zyk S. I. Kolbasenko and E. M. Itkin J. Org. Chem. USSR 1986 22 397. 130 W. R. Jackson and P. Perlmutter Chem. Brit. 1986 338. 131 M. Giffard J. Cousseau L. Gouin and M.-R. Crahe Tetrahedron 1986 42 2243. 132 M. Bassetti and B. Floris Gazz. Chirn. Ital. 1986 116 595. 133 M. Bassetti and B. Floris J. Org. Chem. 1986 51 4140. 134 C. L. Bumgardner J. E. Bunch and M.-H. Whangbo Tetrahedron Lett. 1986 27 1883. 135 H. C. Brown N. G.Bhat and S. Rajogopalan Synthesis 1986 480. J.-M. Mas J. Gore and M. Malacria Tetrahedron Lett. 1986 27 3133. 13' B.V. Smith R1 R2 R'-CeC-R2 2R' R2 iiw n n H BBr2.SMe2 H 1B(OMe)2 iv 1 (R2=Br) iii R' Br R' Br u W n H BBr2.SMe2 I I R2 ii (E) Reagents i BHBr2.SMe2,CH2C12;ii MeOH; iii Br2 CH2C12 -40°C; iv R2BHBr.SMe2 Scheme 13 R' R2 n H SiMe2 J-u 0 I PhMe,SiZnR:Li Ph (51) (52) R' R2 u n Me2Si H I PhMe,SiZnBu; Li Ph (53) (54) Addition of (51) to an alkyne (silylzincation) gave with C,,H,,C~CH exclusive formation of vinylsilane (52). Silylalumination gave a similar result. However (53) gave principally (99 :1)the adduct (54).'37 Terminal alkynes react with silylstannanes in the presence of catalytic amounts of Pd( PPh3)4 to give regio- and stereo-selective cis-addition (55) in which the tin atom is attached at the 'internal' po~ition.'~' Further reaction with e.g.MeCOCl-AICI leaves the tin in place; thus PhCECH gave Ph(SnBu,)C=CHCOMe in 30-50% yield. However iodination of (55) gave (56) (83% ).Reaction between bis-(trimethylsily1)acetyleneand NOlBF gave 70% of the nitroalkyne 02NC~CSiMe3.'39 Nitryl fluoride at low temperature gave a low yield of the above product together with the product of addition of NOzF to 137 K. Wakamatsu T. Nonaka Y. Okuda W. Tuckmantel K. Oshima K. Ultimoto and H. Nozaki Tetrahedron 1986 42 4427. 138 B. L. Chenard and C. M. Van Zyl J. Org. Chem. 1986 51 3561. 139 R. J. Schmitt and C. D. Bedford Synthesis. 1986 132. Aliphatic Compounds -Part (i) Hydrocarbons the 7-system. Acetylenic ketones with Me,SiI gave iodovinyl ketones and hence alkenyliodides.140 Disilenes add to alkynes with formation of disilacy~lobutenes.'~' Trimethylsilyl acetylenes with Os04-B~'OOH-R'OH gave a-ketoesters RCOC02R1.142 Stannylated aminoalkynes R'R2NC=CSnRi react with a triarylmethyl halide Ar3CCl to form triarylmethylynamines R'R2NC=C -CAr3 which by hydration form tertiary amides R' R2NCOCH2CAr3 .143 Stannylated alkynes RC_CSnMe3 with Pb(OAc) in chloroform generate the species RC_CPb(OAc) an alkynyl lead triacetate.In the presence of 2-ethoxycarbonylcyclopentanone,alkylation occurs; the lead derivative may thus be considered to function as an equivalent for an alk-1-ynyl carbocation.'44 In the presence of a palladium catalyst the alkynyl zinc RC-CZnCl reacts preferentially with E-1,2-dibromoethene (even in the pres- ence of the 2-isomer).The formed endiyne (57) is obtained in a high state of purity.'45 R / Vanadium derivatives of alkynes have been obtained from reaction of RCECM (M = Li or MgBr) and VC13 in CH2C12 at -78 "C; they react with RCHO to afford an acetylenic ketone.'46 Phenylacetylene with MtI-CO-Mn( CO)5Br under phase- transfer catalysis (CH2Cl2-H20-Na0H-PhCH2NEt3C1-) gave a mixture of 4- methyl-2-phenylbutyrolactone(47% trans- 31O/O cis-isomer). Such a simple novel approach seems a promising method for synthesis of this class of compound. With other alkynes yields were variable (17-78% ).147 With saturated or unsaturated acids in the presence of RuC13 or ruthenium complexes phenylacetylene gave regioselective enol ester f~rmation.'~~ Diphenylacetylene has been shown to form a triphenylazulene derivative by a process of photo-oxidation rearrangement and dimeri~ati0n.l~~ 140 S.H. Cheou W. J. Christ L. D. Hawkins H. Jin Y. Kishi and M. Taniguchi Tetrahedron Lett. 1986 27 4759. 141 D. J. De Young and R. West Chem. Lett. 1986 883. 142 P. C. B. Page and S. Rosenthal Tetrahedron Lett. 1986 27 1947. 143 G. Himbert and R. Giesa Liebigs Ann. Chem. 1986 292. 144 M. G. Moloney J. T. Pinhey and E. G. Roche Tetrahedron Lett. 1986 27 5025. 145 A. Carpita and R. Rossi Tetrahedron Lett. 1986 27 4351. 146 T. Hirao D. Misu and T. Agawa Tetrahedron Lett. 1986 27 933. 147 J.-X. Wang and H. Alper J. Org.Chem. 1986,51 273.148 C. Ruppin and P. H. Dixneuf Tetrahedron Lett 1986 27 6323. 149 C. J. Cooksey J. L. Courtneidge A. G. Davies J. C. Evans P. S. Gregory and C. C. Rowlands J. Chem. SOC.,Chem. Commun. 1986 549. B. V. Smith In the process of reductive ester homologation,'50 it has now been shown that lithium hydride adds to an ynolate anion in the key Cyclohexadiene used in the earlier experiments is thus not needed and its role would seem to be to generate LiH from BuLi. The prediction of Houk that LiH should add to the ynolate is thus justified. A dianion is invoked as the intermediate in such additions with support from deuterium incorporation experiments. It was judged that Z-PhCH=CHOLi did not form the E-isomer. Quenching the ynolate with R3SiCl gave RC=C-OSiR (-78 "C); warming to room temperature gave R3Si(R)C=C=0.'52 Alkynyl tosylates RCGC-OTs react with two equivalents of MeLi forming an ynolate (and Ts2CH2); as before trapping gave an expected (and an unexpected) result.whilst R,MCl (R = Et M = Ge; R =.Bu,M = Sn) gave R3M( R)C=C=O only with Bu'Me2SiC1 0-trapping was observed with forma- tion of RCEC-OS~M~~BU'.'~~ This is the first recorded example of 0-trapping in such a system. Palladium-mediated alkylation of lithium alkynoates with ally1 chloride has been re~0rted.l~~ Addition of organolithiums to 1-thiomethyl (or l-thiophenyl)-3-methylbut-3-en-l-yne gives rise to a-lithiated allenic sulphides which could be transformed into a$-unsaturated aldehydes; alkylation prior to protonolysis gave corresponding ketones.'55 But-1-en-3-yne with CO-H2-Rh,(C0)12 under pressure gave formyl dienes cyclopentenones and unsaturated lactones.The 1,4-diphenyl analogue gave 91% conversion into products in this way.'56 Chiral alkynyl acetals have been used to generate optically pure propargyl alcohols by reaction with organoaluminium compo~nds.'~' Regioselective reduction of pro- pargyl acetates. (Sm12-Pdo-THF) gives rise to allene and alkene. Thus CH3(CH2)17C-CCH20Ac gave 85% of allene and in the presence of an alcohol as a proton source the allene alkyne ratio was as high as 20 1.'58 150 C. J. Kowalski and M. S. Haque J. Am. Chem. SOC.,1986 108 1325. C. J. Kowalski and G. S. Lal J. Am. Chem. SOC.,1986 108 5356. I52 C. J. Kowalski G. S. Lal and M.S. Haque J. Am. Chem. SOC.,1986 108 7127. 153 P. J. Stang and K. A. Roberts J. Am. Chem. SOC.,1986 108 7125. 154 N. Yanagihara C. Lambert K. Iritani and H. Nozaki J. Am. Chem. SOC.,1986 108 2753. 155 E. Guittet C. B. Ekogha and S. A. Julia Bull. SOC.Chim. Fr. 1986 325. 156 K. Doyama T. Joh and S. Takahashi Tetrahedron Lett. 1986 27,4497. 157 K. Isihara A. Mori I. Irai and H. Yamamoto Tetrahedron Lett. 1986 27,983. 158 T. Tabuchi J. Inanaga and M. Yamaguchi Tetrahedron Lett. 1986 27,5237.