16 Aliphatic Compounds Part (i) Unsaturated Aliphatic Compounds By S. R. LANDOR Makerere University College Kampala Uganda Acetylenes.-The synthesis of alkynes from enol esters has been reviewed.' Details of Glaser coupling of the simplest 'skipped' polyacetylene penta-1'4- diyne (now obtained pure for the first time) are reported.2a Dimers and trimers were isolated and small quantities of acyclic and cyclic tetramers detected (1) H-(CrC-CH,-CEC),H TI = 2,3,4 (2) H-C=C(CH,-CFC),H m = 2,4,6 Excess of ethylmagnesium bromide on 1,4dibromobutyne gave octa-l,4.7-triyne (2; m = 2; in up to 29% yield) as well as higher homologues; (2; rn = 2) re-arranged to the conjugated octa-2,4,6-triyne under basic conditions. Hexa-1,5- diyne rearranges to a mixture of cis-and truns-hexa-1,3-dien-5-yne but hepta-1'5- diyne gave only truns-hepta-l,3-dien-5-yne and the previously reported toluene.2b Semihydrogenation of the 'skipped' diacetylenic acid 8,ll-octadecadiynoic acid over a Lindlar or Raney-nickel catalyst is reported to give substantial quantities of isomerised dienes (9-37 %).3 The synthesis by the Chodkiewicz method and identification by gas-chromato- graphy of a number of isomeric alken-diynes and poly-ynes have been described." Simple and convenient procedures for the preparation of bifunctional acetylenic derivatives (3) are reported.Lithium-naphthalene in tetrahydrofuran treated with acetylenic alcohols and then ketones gives (3;X = OH) in good yield;5 similarly halogenopropargyl lithium derivatives prepared from methyl-lithium and 3-halogenopropynes at -20 "C react with carbonyl compounds to give halohydrins (3 ;X = C1) and with carbon dioxide to give 4-halogenobut-2-ynoic R' R3 \ / c-c-c-c R2/I X HA''R4 (3) J.Cymerman-Craig M. D. Bergenthal. I. Fleming and J. Harley-Mason Angew. Chem. Internat. Edn. 1969 8,-429. D. A. Ben-Efraim and F. Sondheimer Tetrahedron 1969 25 (a) 2823 (6)2837. J. Jacob and G. Grimmer Tetrahedron Letters 1969 1633. K. Schulze U. Pfuller F. J. Struber and M. Muhlstadt J. Prakt. Chem. 1969,311. 153. S. Watanabe K. Suga and T. Suzaki Chem. and Ind. 1968 1489. 520 S.R. Landor acids6 Alkynylation of alicyclic epoxides e.g. (4)+(5)with alkynyldiethylalanes proceeds in moderate to excellent yield.' Dehydrohalogenation of vinyl halides to acetylenes has received further attention.An ion-pair mechanism is postulated to explain kinetics which fit a bimolecular mechanism ;no deuterium exchange of the starting material (6)is detected but a marked deuterium isotope effect was noted.* Although it was known that trans-elimination of hydrogen bromide from trans-vinyl halides is considerably faster than cis-elimination of hydrogen bromide from cis-vinyl halides it has now been demonstrated that trans-elimina- tion from vinyl halides is faster than trans-elimination to give allenes which in turn is considerably faster than cis-elimination to give acetylenes (see section on allenes). (4) (5) Br Br Br Br CH ZCBr H. H H HNEt3 Et,NHBr-NEt3 (6) In the light of this a re-interpretation of the bromination4ehydrobromination of cis- and trans-alkenoic acids is possible.The cis-acids (e.g. oleic acid) give threo-dibromo-compounds which by successive trans-eliminations give trans- vinyl bromides and acetylenes. On the other hand trans-acids give erythro- dibromides which by trans-elimination give cis-vinyl bromides and then allenes which partially rearrange to acetylenes but with some triple bond migration.' Evidence for a concerted elimination is reported for the reaction :lo 0 11 p-Me wC-O +Me-C-C-Me nn .. Br Me The cross-conjugated polyacetylenes (7) (8) and (9) have been prepared and all showed similar U.V. spectra with the maximum longest wavelength at ca. 410 nm." 'J. P. Battioni and W.Chodkiewiez Bull. SOC.chim. France 1969 91 I. J. Fried C. Lin and S. H. Ford Tetrahedron Letters 1969 1379. W. K. Kwok W. G. Lee and S. I. Miller J. Amer. Chem. SOC.,1969 91,468. F. D. Gunstone and G. M. Hornby Chem. Phys. Lipids 1969,3 91 lo W. J. LeNoble Tetrahedron Letters 1969 895. " Y. Hori K. Noda S. Kobayoshi and H. Taniguchi Tetrahedron Letters 1969 3563. A liphatic Compounds 52 1 Ph. Ph Ph (7) (8) (9) Some attention has been directed towards synthesis of ‘skipped’ enynes. Up to 70% yield of the ‘skipped’ enyne RC-C-CH,CH=CH, (R = Ph or n-amyl) has been reported from reaction of copper(1) acetylides with ally1 bromide in hexamethylphosphoramide in the presence of potassium carbonate. l2 Cop-per(1) chloride catalysed coupling of the acetylenic Grignard reagent (10)with the allylic bromide (11) followed by hydrolysis gave 46 % of the ‘skipped’ enyne (12) which was semihydrogenated to cis-trans-cisdodeca-3,6,8-trien-l-ol(I 3) the trail-following pheremone for a Southern subterranean termite :’ Thp-0-CH2-CH2-C ECMgBr + Me CH2CH2-C-C-CHACH-CH2Br -+ (10) (1 1) HydrolysisH b Thp-O-CH2CH2-C~C-CH2CH=kH-CrC-CH2CH2 Me Lindlar (12) C C HO-CH2-CH2-CH=CH-CH2-CH=CH-CH=CH-CH2-CH2-Me (13) A trimethylsilyl-protected acetylenic phosphonium salt was the key to a new route to the biogenetically important ‘skipped’ enyne system in the C1 HCrC-CH2-CH20H -I+ Me,SiC-C-CH2CH2-OH -% Me3SiC-C-CH2-CH21 5 Me3SiC-C-CH2CH26Ph3 ,I-11; Me3SiC~C-CH2-CH~CH(CH2),-COOMe % IC=C-CH -CHLCH-(CH2),-COOMe 3 R-CHkH-(C-C)2-CH2-CH~CH(CH2)7COOMe.Reagents i Me,SiCl; ii (PhO),PMe,I-;iii Ph,P,EtOH reflux; iv NaH THF,Me,SO OCH(CH,),COOMe 0 “C; v AgNO ,I2,CH2C12; vi RCH=CH-CGCH Chod-kie wicz. A Wittig reaction on a propargylic aldehyde (14)has given access to a combina- tion of cis-and trans-double bonds in the C9and C, positions of vitamin A.15 l2 M. Bourgain and J. F. Normant Bull. SOC.chim. France 1969 2477. l3 A. Tai F. Matsumura and H. C. Coppel J. Org. Chem. 1969 34 2180. l4 A. G. Fallis Sir Ewart R. H. Jones and V. Thaller Chem. Comm. 1969,924. ’’ J. L. Olive M. Mousseron-Canet and J. Dornand Bull. SOC. chim. France 1969,3247. 522 S. R.Landor Addition of organocopper reagents to acetylenic at low temperature e.g. -78 "C,has provided a further method for the stereospecific synthesis of tri- and tetra-substituted ethylene (see alkenes).Me I + O=CH-C=C-C(OH)-CH=CH Details of the formolysis of homopropargylic toluene-p-sulphonate (15) have been published ;I7 the rate is six times greater than that of its saturated analogue but the rate enhancement is considerably less than for the acetolysis of the homo- allenyl system. OCHO Me OCHO I Me -CrC-C-CH,OTs -+ Me;Z$e -+ Me-C-C-CH,-C-Me I I Me Me (15) Ae 0 Me OCHO Me II I I I Me-CH2-C-CH=C-Me +-Me-CH=C-CH=C-Me Acetylenic radicals generated by the reaction of acetylenic halides (16)with tri- n-butyltin hydride give exclusively the acyclic reduction product (1 7) where n = 2 or 3 but where n = 4 the alkylidene cyclopentane (18) is the sole product ;'* where n = 5 mixtures of cyclic and acyclic products are obtained if the cyclic radical is stabilised by delocalisation (e.g.R = phenyl) but only acyclic products are obtained where this is not possible (e.g.R = n-amyl). l6 (a)E. J. Corey and J. A. Katzenellenbogen J. Amer. Chem. SOC.,1969,91,1851. (b)J.B. Siddall M. Riskuys and J. H. Fried J. Amer. Chem. SOC.,1969 91 1853. I' J. W. Wilson J. Amer. Chem. SOC.,1969 91 3238. J. K. Crandall and D. J. Keyton Tetrahedron Letters 1969 1653. Aliphatic Compounds 523 R-CGC-(CH,),Br -+ R-CrC-(CH,),- CH2 -+ RCZC(-CH,),H (16) (17) Cycloaddition of 2diazopropane to but-2-ynoic ester appears to be sterically rather than electronically controlled giving adducts (19) and (20) in 6:1 ratio.Photolysis of both adducts gave the known cyclopropene (21).19 Me02C. Addition of carbethoxycarbene generated by slow photolysis of ethyl diazo- acetate to acetylenes at 18 "C is reported to- give 15-25 y4 of the cyclopropene (22).2" The addition of nitrene to acetylenes has now been reported ;it is followed by a spontaneous rearrangement of the anti-aromatic IH-azirine (23) to the non- aromatic 2H-azirine (24).21 R-CSCH + N,CH-CO,Et -+ R-y(22) CO,Et A number of new addition reactions of cyanoacetylenes have been described ; these include the Ritter reaction the addition of cyclic secondary aniines acetone and acetaldehyde and thioacetamide.22 l9 A. D. Day and R. N. Inwood J. Chem. SOC.(0,1969 1065.2o M. Vidal F. Massot and P. Arnaud Compt. rend. 1969 268 C 423. D. J. Anderson T. L. Gilchrist and C. W. Rees Chem. Comm. 1969. 147. 22 T. Sasaki S. Eguchi and K. Shoji J. Chem. SOC.(C),1969,406;T. Sasaki T. Yoshioka and K. Shoji J. Chem. SOC.(0,1969 1086; T. Sasaki and K. Shoji Tetrahedron Letters 1969 18 1 1 ;T. Sasaki K. Kanamatsu and K. Shoji Tetrahedron Letters 1969 2371 ;T. Sasaki and A. Kojima Tetrahedron Letters 1969 3639. 524 S. R.Landor H HH H R'-C=C-CN CN \/\/ /\ s s c=c CN /c=c\S/c=c\ CN 'C' I1 (R3),N/\H R' =H H/C'CN R' =H R' =C1 Natural Polyacety1enes.- New and known polyacetylenes have been extracted from carrots23 (25) campanula species ('the clustered bell (26) and lettuce2' (27). The alcohol (25;X =OH Y =H) and a model compound (R2 = Me) gave amongst other products when treated with acid in benzene the phenyl- substituted hydrocarbon (29) presumably via electrophilic attack by an inter- mediate carbonium ion (28) on the solvent.CH,=CH-CHX -(CEC),-CHY -CHACH-(CH2),Me ; R' -(C=C),CH=CH-(26) (25! 0 R' =HO(CH2),,or HOCH,CHICH-; Me(C-C),CH(OH)-CH,CH,OH; (27) PhH (25) 5bH2-CH=CH-(C-C),R2 +PhCH,-CHkH-(C=C),R2 (28) (29) Acetylenic aldehydes which have been used as intermediates in synthesis dimerise with elimination of carbon monoxide (30)-(31).26"*b 23 R.K. Bentley D. Bhattacharjee Sir Ewart R.H. Jones and V. Thaller J. Chem. Soc. (0,1969,685. 24 R.K. Bentley J. K. Jenkins Sir Ewart R. H. Jones and V. Thaller J. Chem. Soc. (C) 1969 830.25 R.K. Bentley Sir Ewart R.H. Jones and V. Thaller J. Chem. Soc. (0,1969 1096. 26 (a) R.K. Bentley U. Graf Sir Ewart R.H. Jones R.A. M. Ross V. Thaller and R.A. Vere Hodge J. Chem. SOC.(0, 1969,683; (6) A. Gorgues and E. Levas Compt. rend. 1969 268 C 1905 1968 266,41. A liphat ic Compounds 525 From asters as well as Coreopsis giganter mainly C ,-poly-acetylenic com- pounds have been isolated." Biosynthetic studies have shown that thp_ C ,-poly-acetylenes are derived from oleic acid via P-oxidation2 and dehydrogenation to Cl8-hydroxytriynenoic acids or diynedienoic acids.29 The C14-and C13- polyacetylenes involve /3-and a-oxidation steps of the C ,-triynenoic acids3' Allen-.-A number of new methods for the preparation of allenes have been published which involve SN2(or equivalent radical ilttack) on various derivatives of propargylic alcohols.R' R' R3 \ \ / C-C-C-R3 /c =c=c\\ R2/I 0 R2 Y \ X (32) (33) Details of the previously reported reaction of (32) [X = Ac; R' R2 = (CH2)"; where n = 4,5 or 61 with dimethyl or dibutyl copper lithium have appeared.31 The reaction is not stereoselective and gives a mixture of stereoisomeric allenes from sterically pure starting materials. Optically active (+)and (-) 1,3-di-t-butylallene (33 ;Y = R = H; R2 = R3= Bu') was obtained (together with 1,3-di-t-butylpropyne 44 % and 66 % respec-tively) by the action of lithium aluminium hydride on the resolved diastereomeric d-camphor-10-sulphonatesof 1,3-di-t-butylpropynol (32; R' = H; R2 = R3 = But ; X = CloHl503S).32 Similar optically active allene-acetylene mixtures were also obtained from the reduction [with Li(RO)JlH,; n = 0,1,2; m = 4,3 21 of the toluene-p-sulphonates but the allene was the sole product from the reduction of the propargyl alcohol (32; X = H) in tetrahydrofuran with lithium aluminium hydride in the presence of aluminium chloride.It was shown that hydride attack is trans to the departing sulphonate group but may be cis or trans to the departing hydroxy-group in the presence of aluminium chloride. In the absence of aluminium chloride a tertiary propargylic hydroxy-group will act only as a leaving group under forcing conditions the major product is the expected allylic 27 F. Bohlmann and C. Zdero Chem. Ber. 1969,102,1034,1037,1679,1691;F.Bohlmann C. Zdero and H. Kapteyn Chem. Ber. 1969,102 1682. 28 F. Bohlmann and Burkhardt Chem. Ber. 1969,102 1702. 29 F. BOhlmann and P. Hanel Chem. Ber. 1969,102 3293. 30 F. Bohlmann R. Jente and R. Reinecke Chem. Ber. 1969,102 3283. 31 P. Rona and P. Crabbe J. Amer. Chem. SOC.,1969 91 3289. 32 W. T. Borden and E. J. Corey Tetrahedron Letters 1969 313. 33 L. A. van Dijck K. H. Schonemann and F. J. Zeelen Rec. Trav. chim. 1969 88,254. 526 S. X.Landor Under similar forcing conditions the butyne-diol(34) with one tertiary hpdroxy- group gave the allenic alcohol (X#" which had also been obtained3' from the epoxybutynol(35)by ring opening of epoxide through vigorous treatment with lithium aluniinium hydride in boiling tetrahydrofuran.Oxidation of (36) with manganese dioxide yieided the allenic grasshopper ketone (37) isolated last year from ii secretion of the largc flightless grasshopper Romcllea rnicr~ptera.~~ (35) I H (37) 'The ready elimination of the tetrahydropyranyloxy-groupfrom the monotetra- hydropyranyloxy-derivatives of butynediols (38)provides a mild general method for the preparation of allenic alohols (39),elimination from primary (R' = R2 = H) secondary (R' = H ;R2 = alkyl) or tertiary (R' = R2 = alkyl) carbon being effected in high yield.37 R' \ /' Although it has been known for some time that anti-elimination horn vinyl halides to give acetylenes is much faster than syn-elimination it has now been shown that arzti-elimination of hydrogen bromide to form an allene is also much faster than syn-elimination to give the a~etylene.~~ Thus pure allene was J.Meinwald and L. Hendry Tefrahedron Letters 1969 1657. 35 S. W. Russell and B. C. L. Weedon Chem. Comm. 1969 85. 36 J. Meinwald K. Erikson M. €lartshom Y. C. Meinwald and T. Eisner Tetrahedron Letters 1968 2959. 3' J. S. Cowie P. D. Landor and S. R. Landor Cliern. Cornm. 1969. 541. "S. W Staley and R. F. Doherty Chenl. Comm. 1969 288. Aliphatic Compounds obtained in 85"/d yield as the sole product (k2/k = 1500 t300) from c.is-4-bromo-oct -4-ene. Pr" Eir Pr" Pr" The preparation of polyfluoroallenes by dehydroiialogenation of a number of fluorohalogenoallenes has been described.39 Prototropic rearrangement of propynes to allenes have hitherto shown little promise as preparative routes.The t-butoxide-calalysed rearrangement of propargylic ethers to allenic ethers (41;R' = H) in dimethyl sulphouide seems to be an exception ;40 if instead of t-butoxide one equivalent of butyl-lithium is used at -20 "C,the allenic anion (40; R' = Ph) is reported to be sufficiently stable to react subsequently with various halogeno compounds (R"X ;R" = Me ;Me 0 CH2 * ; Et,NCH2 .CH2 CH2 ; Me& -preferably in hexamethylphosphor- a amide. Two equivalents of butyl-lithium at -10 "Capparently give the cunmulene (42). Rase-catalysed 1,3-proton transfer in perdeuteriodimethyl sulphoxide of 3-phenylpropyne to 3-phenylallene is more than 90 "/,intramolecular (i.e. without hydrogen deuterium exchange)." A related cationtropic rearrangement of the Group IVB propyne-metal com-pounds (43; M = Si Ge Sn Pb) to allene-metal compounds (44) has been re- p~rted."~ It is catalysed either by nucleophilic solvents (S)r.g.dimethylsulphoxide (R3 = H) or Lewis acids or the concerted action of both.The action of zinc in hexamethylphosphoramide or magnesium in tetrahydro- furan on dihalogenoacetals (45) gave mixtures of allenes (47) and accbals of cyclopropanones (46) in varying proportion up to 60 % ofallene being reported.43 Iq R.E. Banks M. G.Barlow W. D. Davies R. N. Haszeldine and D. R. Taylor J. Chenz. SOC.(C) 1969,996 1 104. 4v R. Mantione and A. Alves Compt. rend. 1969 268 C 365 997. 41 J. Klein and S. Brenner Cliem. Comm. 1969 1020.'' M. Lequan and Ci. Guillerm Compt. rend. 1969 268 C. 858 1001. J3 G. Giusri C. Morales and C. Feugeas Compt. red.. 1969 269 C 162. 528 S. R.Laltdor R2 H \ c=c=c/ Br Br R' R3 R' I I R3 \ / ,c-c-c= R2 o/ '0I R4 --+ /c=c=c\R4 I II R2 CH,-CHZ H,C-CHZ Details of the synthesis of the allene-rethrins (48; R = chrysanthemoyl or pyrethroyl) accepted in the early literature as the correct structure for some of the pyrethrins have been published.44 Interest in homoallenic participation in solvolytic reactions first reported in 1964 has continued.4548 Adefinitive paper46 which includes kinetic data as well as product analysis from the solvolyses of the toluene-p-sulphonates and bromo- benzene-p-sulphonates clearly shows considerable homoallenic anchimeric assistance in the transition state (49).Bicyclobutonium ions (50) and (51) are the most likely intermediates in these rea~tions.~~,~~ The stability of the intermediate cyclopropylvinyl cations (52) has now been demonstrated by independent syn- thesis and solvolytic st~dies.~~,~~ The intramolecular cyclisation of the homoallenic Grignard compound (53) gave products derived from 1-cyclopropylvinyl magnesium bromide (54).5la 44 L. Crombie P. Hemesley and G. Pattenden J. Chem. SOC.(0,1969 1016. 45 R. S. Bly and S. U. Kook J. Amer. Chem. SOC.,1969,91 3292 3299. 46 T. L. Jacobs and R. S. Macomber J. Arner. Chem. SOC.,1969,91 4824. 47 M. Santelli and M. Bertrand Tetrahedron Letters 1969 251 1 2518 3699. 48 C. Santelli-Rouvier P.Archier and M. Bertrand Compt. rend. 1969 269 C 252. 49 S. A. Sherrod and R. G. Bergman J. Amer. Chem. SOC.,1969 91 21 15. 50 M. Hannack and T. Bassler J. Amer. Chem. Soc. 1969,91 21 17. 51 (a)H. G. Richey and W. C. Kossa Tetrahedron Letters 1969 2313; (b) M. Karila M. Capman and W. Chodkiewiez Compt. rend. 1969,269 C. 342. A lip hatic Compounh c. ‘I ‘OTs (49) yp Y*d ab OH -4 MgBr (53) Stereoselective addition of buta-1,2-dienylmagnesiumchloride to a number of aldehydes gives predominantly threo-l-alkyl-2-methyl-but-3-yn-1-01.5 lb A pre-liminary report of a study of the thermal rearrangement of 1-bromo-2-alkyl-butadiene (55) shows that 2-bromo-3-alkylbuta-1,3-diene(56) is formed.52 The rearrangement appears to be accelerated by polar solvents and Lewis acids but retarded by antioxidants.Both free-radical and polar mechanisms may be operative. The thermal rearrangement of 5-methyl-1,2,4-hexatriene, by a 1-5- hydrogen shift gives 5-methylhex-3-en-l -~ne.~~ CH2Br / CH2=C=C -+ CH2 =C-C=CH, \ II R Br R (55) (56) The extraordinarily fast solvolysis of the 2-bromo-1,3-diene (57) is explained by postulating the delocalised vinyl-allenyl cation (58) and (59) which with ethanol gives 55% of the allenic ether (60).54 In contrast the conjugated vinyl- allenyl radical (61),formed by abstraction of a hydrogen from the methyl group of the allene gave mainly 3-chloro-3-methylbuta-1,3diene (62).’ ’’S. Combrisson E. Michel and C. Troyanowsky Compt.rend. 1969,269 C 536 555. ’’L. Skattebol Tetrahedron 1969 25 4933. ’‘ C. A. Grob and R. Spaar Tetrahedron Letters 1969 1439. s5 M. Poutsma Tetrahedron Letters 1969 2925. 530 S. R. Lundor R R + \ /Br \+ R /Cm c=c Me /c=c\ /Me -+/ \ /-\ /c=c=c \ EtOH R /c=c\ R C=C ___) /\ R H H Me H Me Further evidence that protonation of allenes usually occurs at the central sp-hybridised carbon atom has a~peared.~~.~’ R’ R3 R’ H R’ H \ /H+\ / R3S \C=C/ R3 /c=c=c \ + /c=c\ / / \/ R2 R4 R2 C R2 C +\ I\ R4 H R4 (63) The 1,3-dimethylalkenyl(63 ;R‘ =R3=H ;R2=R4=Me) and 1,1,3,3-tetra- methylalkenyl (63; R’=R2=R3 =R4=Me) cations are generated quantita- tively at -70 “C in FS0,H-SbF and are unchanged at that temperature after one week.57 Free-radical attack on l-bromoallene also seems to be predom- inantly on the central carbon atom.58 High selectivity in the catalytic hydrogenation of but-3-ynoic buta-2,3dienoic7 and cis-and trans-butenoic acids which are selectively hydrogenated in the order given is described as ‘molecular que~ing’.~’ The allenic acid is second in the queue and gives cis-but-2-enoic acid the latter only being reduced to butanoic acid after all the allenic acid has reacted.Monohydroboration of acyclic allenes with disiamyl borane followed by the alkaline hydrogen peroxide oxidation resulted 56 F. Toda M. Higashi and K. Akagi Bull. Chem. Soc. Japan 1969,42 567. ’’C. U. Pittman Chem. Comm. 1969 122. 58 K. R. Kopecky and S. Grover Canad. J. Chem. 1969,47 3153.5y L. Crombie and P. A. Jenkins Chem. Comm. 1969 394. Aliphatic Compounds 53 1 in attack both on the least substituted and the central carbon atom.60 Mixtures of alk-1-enes alkenols and ketones were isolated. Details of the addition of diazoalkanes to conjugated allenes have been published.61" The addition of diazomethane to terminal allenes in the presence of a dissymmetric copper(u) complex gave optically active methylenecyclopropanes (64) and spiropentanes (65); the optical purity and configuration were not determined.6Ib Ethoxymercuration of cyclononadiene in the presence of boron trifluoride gave up to 85% of 3-etho~ycyclononene~~ with the stereospecificity of the reaction depending on the mercury salt utilised. The enol esters obtained from allenic sulphonium and phosphonium salts by the addition of acids are described as new acylating agents for amines and alcohols.63 + Me2S-CH2 -C( OC0.Ph)=CH2 The diphenyl allenic phosphonium ylide (66)reacted with aromatic aldehydes (but not benzophenone) to give cumulenes (67)in good yield.64 t NEt + PhNH -4'Ph2C=C=CH-PPh3 Ph2C=CBr-CH2-PPh3 ,Br -,= ,Br -Ph2C=C-CH2-PPh3 ,Br -CsHsN I NHPh The epoxidation of allenes with peracids has received considerable atten- ti~n.~ Mono- and di-epoxides initially suggested as unisolatable intermedi- 5,b6 ates in the peracid oxidation oftetramethylallene (68 ;R' = R2R3R4= Me) have now bcen isolated for t-butyl-substituted allenes [(69)isolated for R' = R' = H; R2 = R3= But; (70) isolated for R' = R2= Me; R3= H; R4 = But].The mono-epoxide (69;R' = R4= H; R2= R3= But) isomerises to 2,3-di-t-hutylsyclopropanone (71) on prolonged heating at 100 0C,66but 1,ldi-t-butyl-'' D. S. Sethi Ci. C. Joshi and D. Devaprabhakara Canad. J. Chem. 1969,47 1083. 6' S. D. Andrews A. C. Day and R. N. Inwood J. Chem. SOC.(0,1969 2443; (b) R. Noyori and H. Takaya Y.Nakanisi and H. Nozaki Canad. J. Chem. 1969,47 1242. 62 R. D. Bach J. Amer. Chem. SOC.,1969,91 1771. 63 G. D. Appleyard and C. J. M. Stirling J. Chem. SOC.(C) 1969 1904. 6dK.W. Rattsand R. D. Partos J. Amer. Chem. SOC.,1969,91 6112. "J. K. Craiidail and W. H. Machleder J. Amer. Chem. SOC.,1968,90 7292 7346. 66 R. L. Camp and F. D. Greene J. Amer. Chem. Soc. 1965.90,7349. 532 S.R.Lundor allene gives 2,2-di-t-butylcyclopropanonedirectly as the sole pr~duct.~ The major product from the epoxidation of allenenes (72) with p-nitroperbenzoic acid is the cyclopent-2-enone (73); allenyl epoxide (74) is obtained as a minor product in some cases.67 R2 I 0 R2 -R'-CH=C=C-CH=CH-R3 -R1*R3 (72) R' I I Details of some of the nucleophilic reactions of 1,4-dibromobuta-1,2-diene reported earlier have been published.6 * Thio-Claisen rearrangements under unusually mild conditions (30 "C in hexane) gave the allenic dithioester (76)from the propargyl vinyl sulphide (75)and the acetylenic dithioester (78) from the allenyl vinyl sulphide (77).69 CH-C-CH \I CH2=C -+ CH=C=CH,1 2 CH2-C \ SEt \ SEt (75) (76) 67 J. Grimaldi and M.Bertrand Tetrahedron Letters 1969 3269. 68 M. V. Mavrov E. S. Vakanyan and V. F. Kurcherov Tetrahedron 1969,25 3277 69 P. J. W. Schuijl and L. Brandsma Rec. Trav. chim. 1969 597 1201. Aliphatic Compounds S 2-1 / CH2=C CH2-C \ \ SEt SEt The stereochemistry and mechanism of allene dimerisation may be rationalised by postulating a diradical mechanism and disrotatory ring c10sure.~ Dipole moment evidence suggests that trans-substituted cyclobutanes are perhaps more common than cis-substituted cycl~butanes.~ The four cyclobutane (2 + 2) adducts from R-(-)-173-dimethylallene and acrylonitrile are all optically active requiring a dissymmetric diradical (79) which gives the observed products by symmetry-allowed rotation round C-2.72 Only one (2 + 2) adduct is obtained from dimethylketen and cyclononadiene and this has been utilised in a synthesis of 5,6-dihydronor~aryophyllene.~ CN' Me XY J I CN Me CN Me (79) X = H;Y = CN X=CN;Y=H CH2 Dimerisation of allene in the vapour phase over phosphine-modified nickel carbonyl catalysts gave predominantly 1,3-dimethylenecyclobutaneand little 1,2-dimethylenecyclobutane,which is the major product in liquid phase dimerisa- ti~n.~~ Interesting new monocyclic allene pentamers (80) or (81) were obtained 0.J.Muscio and T. L. Jacobs Tetrahedron Letters 1969 2867. 71 E. V. Dehmlow Tetrahedron Letters 1969 4283. "J. E. Baldwin and U. V. Roy,Chem. Comm. 1969 1225. l3 J. L. Gras R. Maurin and M. Bertrand Tetrahedron Letters 1969 3533.534 S. R.Lundor with a polymeric nickel carbonylphosphine and pentamers (82) and (83) with bis-( 1,5-cyclo-octadiene)nickeland RhCI(C2H4) as cataly~t.~ A o-bonded cobalt allene complex7' and various n-bonded rhodium-allene complexes77 have been described. A1kenes.-The search for convenient better and more stereospecific methods for the synthesis of di- and tri-substituted alkenes has continued. Details have been published of the P-hydroxyphosphonamide methodT8 first reported in 1967 ; preferential cis-elimination has been demonstrated and the reaction has been extended to the synthesis of conjugated dienes. Stereospecific dimethylacylphos- phonate and Wittig syntheses were used respectively to produce the truns-13,14-and cis-5,6-double bonds in stereocontrolled syntheses of prostaglandins F2 and E2 (84).79 A stereospecific Wittig reaction was also the key step in the syntheses of (a)the insecticidal N-isobutylamide of dodeca-2,6,8,10-tetraenoicacid,80 and (b)the racemic form of the hydrocarbon dictyopterene A (85 ;trans-trans) isolated from an algae (Dictyopteris) and possessing the characteristic 'odour of the sea.'81 A trigonal-bipyramidal co-ordination complex of ylide and aldehyde is suggested to explain the stereochemistry of the Wittig reaction.82 A combination of the phosphonate and Wittig reactions was used for the synthesis of asperenone and isomers which proved the structure of this pigment to be (86).'' F. W. Hoover and R. V. Luisey J. Org. Chem. 1969,34 3051.75 S. Dtsuka A. Nakumara K. rani and S. Neda Tetrahedron Letters 1969 297. 76 M. D. Johnson and C. Mayle Chem. Comm. 1969 192. 77 T. Kashiwagi N. Yasnoka N. Kasai and M. Kakudo Chem. Comm. 1969 317. 78 E. J. Corey and D. E. Cane J. Org. Chem. 1969,34 3053. 79 E. J. Corey N. M. Weinshenker T. K. Schaaf and W. Huber J. Amer. Chem. SOC. 1969,91 5675. P. A. Sonnet J. Org. Chem. 1969,34 1147. K. C. Das and B. Weinstein Tetrahedron Letters 1969 3459. "W. P. Schneider Chem. Comm. 1969 785. Aliphatic Compounds Application of the Claisen-type rearrangement to the stereospecific synthesis of trans-trisubstituted double bonds provides an excellent method for the synthesis of isoprenoid systems under relatively mild condition^.^^ Similarly the pyrolysis of allylacetoacetates (Carroll reaction) gave mainly trans-trisubstituted enes but as expected the more extreme conditions result in less ~tereospecificity.~~ A new route to Insect Juvenile Hormone makes use of a Claisen rearrangement as the first step.* OH Me0 0 100% trans J5 steps 83 D. J. Faulkner and M. R. Petersen Tetrahedron Letters 1969,3243. 04 N. Wakabayashi R. M. Waters and J. P. Church Tetrahedron Letters 1969 3253. 85 J. A. Findlay and W. D. Mackay Chem. Comm. 1969 733. 536 S. R. Lundor Two stereospecific syntheses of the terpenoid sesquicarene (88) from acyclic polyenes have been described,86 the cyclisation being effected through the diazo- ketone (87) or the diazo-compound (89) obtained from the hydrazone of farnesal.The diazoketone cyclisation method was also used in four different synthe~is~~-~' of dl-sirenin (90) the sperm attractant produced by the female gametes of the water mold Allomyces. Allylic halides have been prepared by the reaction of the alcohol in ether-hexamethylphosphoramide with methyl-lithium followed by toluene-p-sulphonyl chloride and lithium chloride and these were coupled without rearrangement with allylic Grignard reagents in hexamethylphosphoramide to give 1,5-dienes in 95 % yield."" The allylic alcohols were obtained by controlled ozonolysis of the terminal isopropylidene group of neryl and geranyl acetates.' lb The addition of dialkyl copper lithium complexes to gp-acetylenic esters has provided a further method for the stereospecific synthesis of tri- and tetra- substituted enes.92,93 The reaction is temperature dependent but at -78 "C 99 % of cis-ester (91) is formed whereas at 0 "C (91) and (92) are formed in a ratio of 39:61.The utility of this reaction was demonstrated by the synthesis of methyl trans-3,7-dimethylocta-2,6-dienoate(93) from 4-methylpent-3-enyl bromide and but-2-ynoic acid in the presence of the copper complex (94).93 Enol phosphates like the previously reported phenyl phosphate^,'^ are reductively deoxygenated by lithium-ammonia-t-butanol or lithium-thylamine-t-butanol to give good 86 E. J. Corey and K. Achiwa Tetrahedron Letters 1969 1837 3257. "E. J. Corey K. Achiwa and J. A. Katzenellenbogen J. Amer. Chem. SOC.,1969 91 43 18. 88 J.J. Plattner N. T. Bhalerao and H. Rapoport J. Amer. Chem. SOC.,1969 91 4933. 89 P. A. Grieco J. Amer. Chem. SOC.,1969,91 5660. 90 K. Mori and M. Matsui Tetrahedron Letters 1969 4435. 91 (a)G. Stork P. A. Grieco and M. Gregson Tetrahedron Letters 1969 1393; (b)ibid. p. 1391. 92 E. J. Corey and J. A. Katzenellenbogen J. Amer. Chem. SOC.,1969 91 1851. 93 J. B. Siddall M. Biskup and J. H. Fried J. Amer. Chem. Soc. 1969,91 1853. 94 G. W. Kenner and N. R. Williams J. Chem. Soc. 1955 522. A liphatic Compounds 537 yields of cycl~alkenes.~~*~~ The enol phosphates were prepared either by the Perkov reaction from or-bromoketonesg5 or directly from the action of the enolate anion on diethyl-phosph~chloridate.~~ R' C02Me R' R'-CrC-COOMe + R2,CuLi -* L/ R2nH R2 AC02Me (91) (92) The synthesis of squalene (96 ;R=H) involving allylic sulphonium ylide inter- mediates has been shown to be a possible model for its biosynthe~is.~' Orbital symmetry control in such sulphonium ylide rearrangements has been suggested.98 (95) i X = C1; ii X = SC(NH2)2+,C1-R (96; R = SPh; R = H) Allylic carbanions derived from phenylthioethers are stereochemically unusu- ally stable and have been used in a stereospecific synthesis of squalene and the lO-~is-isomer.~~ Nucleophilic substitution of the anion of (95; X = SPh) on farnesyl bromide (95 ;X = Br) gave (96 ;R = SPh) which is desulphurated with lithium in ethylamine to (96; R = H).The 'ene' reaction (97a)+(98)'*' and the chemistry of enol ethers (vinyl ethers)"' has been reviewed.95 M. Fetizon M. Jurion and N. T. Anh Chem. Comm. 1969 112. 96 R. E. Ireland and G. Pfister Tetrahedron Letters 1969 2145. 97 G. M. Blackburn W. D. Ollis C. Smith and I. 0.Sutherland Chem. Comm. 1969,99. 98 R. W. C. Cose A. M. Davies W. D. Ollis C. Smith and I. 0.Sutherland Chem. Comm. 1969 293. 99 J. F. Biellmann and J. P. Ducep Tetrahedron Letters 1969 3707. loo H. M. R. Hoffmann Angew. Chem. Internat. Edn. 1969 8 556. lo' F. Effenberger Angew. Chem. Internat. Edn. 1969,8 295. 538 S. R.Landor The cyclisation of polyenes has received further attention. The key step in the synthesis of the sesquiterpenoid alcohol elemol (100) was the cyclisation of the dibromide (99) with excess of nickel carbonyl in N-methylpyrrolidone.lo2 ___) MeMgUr NHCO) ___) Br C02Me COzMe OH BrTa (99) ( 100) Enzymic cyclisation of cis-and trans-1 -methylsqualene 2,3-oxide has been shown to be selective only the cis cyclising to the ster01.l'~ Acid-catalysed cyclisation of the tetraenol (101) gave a mixture of stereoisomeric alcohols (102) of the podocarpane series.lo4 Kinetic and thermodynamic data for the conrotary ring closure of trans-cis-cis-trans-decatetraene (103)at 171 "Con a g.1.c. column show the specificity of this reaction to be 0.9999967. During the 10.5 min on the column each molecule ring closes and opens 1028 times.'05 Neighbouring-group orbital interaction has been used to explain the inhibition of the Diels-Alder reaction of certain trans-trans-dienes (104).'06 Vinyl bromides were found to give methylesters stereospecifically with nickel carbonyl in the presence of methoxide.' O7 The same reagent catalyses the cyclo-dimerisation of bis-allylic bromides (105) at 50 "C in polar solvents.n-Ally1 nickel bromide dimerises allyl bromide in ether or dimethylformamide and allylates allyl or aryl halides.''* Oxymercuration in the presence of pure alcohols followed by treat- ment with alkaline sodium borohydride provides a simple method for Markovni- kov addition of alcohols to alkenes giving ethers in excellent yield (except from E. J. Corey and E. A. Broger Tetrahedron Letters 1969 1779. '03 L. 0.Crosby E. E. van Tamelen and R. B. Clayton Cliem. Cumm.. 1969 532. Io4 W. S. Johnson and T. K. Schaaf Chem.Comm. 1969,61 I. Io5 A. Dahmen and R. Huisgen Tetrahedron Letters 1969 1461 1465. lo6 A. T. Austin and B. Pearson Nature 1969,221 950. lo' E. J. Corey and L. S. Hededys J. Amer. Chem. Soc. 1969,91 1223. E. J. Corey Angew. Chem. Internat. Edn. 1969 8 149. Aliphatic Compounds t-alcoh~ls)'~~ and the same procedure with the t-butylhydroperoxide gives the corresponding t-butylperoxides. lo L 7 o$:e Me Br Br-CH2-CH=CH-(CH2)6-CH=CH-CH2 (105) At 0°C the addition of bromine in methylene dichloride to asymmetrically disubstituted double bonds has now been shown to give a mixture of 1,2- and 2,3-dibromides as well as monobromides (by allylic substitution) and tribromides but bromine in dimethylformamide gives only the normal 1,2-bromide.' ' ' Saturated aldehydes are converted smoothly to a,/?-unsaturated aldehydes through the enol acetates 8-bromination with N-bromosuccinimide and dehydrohalogenation.l2 An Octant Rule has been proposed for chiral olefins.' ' R-CHZ-CH2-CHO -+ R-CH~-CH=CH-OAC + R-CH(Br)-CH=CH-OAc + R-CH=CH-CHO Alkanes.-Evidence for a radical mechanism in the reaction between alkyl-lithium and alkyl halides has been obtained by e.s.r. studies'l4 and a re-examination of the substitution with racemisation at a chiral centre."5 It was confirmed how- ever that allyl-lithium gave 99-100% inversion typical for an S,2 attack by a stabilised ally1 anion. A detailed study of the reaction of dialkyl (normal second- ary and tertiary) and diary1 lithium copper reagents with alkyl halides and aryl iodides has further demonstrated its usefulness in synthesis.' ' lo9 H.C. Brown and J. T. Kurek J. Amer. Chem. SOC.,1969,91 5646. 'lo D. H. Ballard A. J. Bloodworth and R. J. Bunce Chem. Comm. 1969 815. 'I1 J. Wolinsky R. W. Novak and K. L. Erickson J. Org. Chem. 1969,34,490. 'I2 J. J. Riehl and F. Jung Tetrahedron Letters 1969 3139. A. F. Scott and A. D. Wrixon Chem. Comm. 1969 1182. G. A. Russell and D. W. Lamson J. Amer. Chem. SOC.,1969,91 3967. J. Sauer and W. Braig Tetrahedron Letters 1969 4275. G. M. Whitesides W. F. Fischer J. S.Filippo R. W. Baske and H. 0.House J. Amer. Chem. SOC.,1969,91,4871. 540 S. R.Landor The oxidation of unactivated and remote methylene groups has received further attention.Apart from oxidation with lead tetra-acetate previously reported,' l7 6-methylene groups in primary and secondary alcohols can be converted to tetrahydrofurans in 6&70 % yield with silver oxide and bromine in pentane or with mercuric oxideiodine in carbon tetrachloride.' Ceric ammonium nitrate effects the same oxidation in lower yield."' Attack at the C9 to CI7 methylene groups of a long-chain alkyl p-benzoyl- benzoate (106) was effected by the photochemically generated benzophenone triplet.'20 H I Me-(CH,) -CH Me-(CH,),-C-(CH,),-CH \ \ II -IIP-I Ph-COC Ph-LGC' \'O 0 0 OH Me -(CH,) -C-(CH2) -Cy2 Me -(CH,) -C-(CH,) -CH I1 p 0 e3 Ph-:oC II II -0-0 \'0 Methyl fluoride-antimony pentafluoride has been shown to be an extraordin- arily powerful methylating agent which will even methylate alkanes.l2 RH + MeF-SbF -+ RMe + HF + SbF 'I7 M. Lj. Mihailovic M. Jakovljivic and Z. Cekovic Tetrahedron 1969 25 2269. 'I8 M. Lj. Mihailovic Z. Cekovic and J. Stankovic Chem. Comm. 1969 981. '19 W. S. Trahanovsky M. G. Young and P. M. Nave Tetrahedron Letters 1969 2501. R. Breslow and M. A. Winnik J. Amer. Chem. SOC.,1969,91 3083. 12' G. A. Olah J. R. DeMember and R. H. Schlosberg J. Amer. Chem. SOC.,1969 91 21 12.