8 Alicyclic Chemistry By S. A. MATLIN Chemistry Department The City University. Northampton Square London ECl V OHB 1 General The first quantitative study of the kinetics of SN2 closure of all-carbon 4-to 21-membered rings (Scheme 1) has been published.' The cyclization rates span nine orders of magnitude and show qualitatively the expected trends reflecting a combina- tion of ring-strain and distance factors. However an important feature of the results is that the transition-state strain-energies tend to parallel cycloalkane strain-energies for 7-membered and larger rings but not for the smaller rings. Me,N+ -/CozEt DMSO,25"C Br(CH,)_IC C0,Et Scheme 1 Cyclization of dibromides or ditosylates with methyl thiomethyl sulphoxide anion gives 3-to 6-membered rings in good yields the products with 4-to 6-membered rings being easily converted into ketones by acid hydrolysis.* Alkyl lithium species (1) cyclize efficiently to normal sized rings (2; n = 2-4) but (1 ;n = 5) fails to give the 8-membered ring.3 5-and 6- (but not 4-) membered rings are also formed in high yields by intramolecular cyclization of the Grignard reagents derived from trimethylsilylalkynyl halides (3) and the resulting Grignard reagents (4; n = 0,l) can be further alkylated Me,SiCrC -(CH,) -Br (3) (4) ' M.A. Casadei C. Galli and L. Mandolini J. Am. Chem. Soc. 1984 106 1051. ' K. Ogura M. Yamashita M. Suzuki S. Furukawa and G. Tsuchihashi Bull. Chem. Soc. Jpn. 1984,57 1637. A. R. Chamberlin and S. H. Bloom Tetrahedron Lerr.1984 25 4901. S. Fujikura M. Inoue K. Utimoto and H. Nozaki Tetrahedron Left.,1984,25 1999; see also Y. Okuda Y. Morizawa,K. Oshima and H. Nozaki. ibid. p. 2483. 153 154 S. A. Marlin Whereas the unsaturated diester (5; n = I) undergoes a vinylogous Dieckmann cyclization to (6) by a 6-(enolendo)-exo-trig process (‘favoured’ by the Baldwin Rules) the 5-(enolendo)-exo-trig reaction of (5; n = 0) is ‘disfavoured’ and does not occur. However the corresponding 5-(enolexo) processes from (7) and (8) are ‘favoured’ and proceed in reasonable yields.’ Me0 Me0,C / c+> & & @Me C0,Me C0,Me 6 The importance of stereoelectronic factors is also seen in cyclizations involving intramolecular attack of a carbanion on an oxetane ring that has now been examined for the first time? In the series (9; n = 1-4) only the cyclopropane (10; n = 1) is formed easily under forcing conditions (9; n = 3) will cyclize but even then the 4- and 6-membered rings are not-formed.However in the isomeric series (11; n = 0-3) 3-and 4-membered rings did not form but 5-and 6-membered rings (12; n = 2,3) were obtained in good yields. Catalysed Cope and Claisen reactions used in the synthesis of alicyclic compounds have been reviewed.’ M. Kodpinid and Y. Thebtaranonth Tetrahedron Lett. 1984 25. 2509. M. Yamaguchi and I. Hirao Tetrahedron Lett. 1984 25 4549. ’ R. P. Lutz Chern. Rev. 1984 84. 205. 155 Alicyclic Chemistry (9) 2 Three-membered 5-Bromo- and 5-iodo-pent-2-enes are cyclized in good yields to 1-cyclopropylethyl nitrite by passage through a column of silver nitrate on alumina.* A versatile synthesis of cyclopropyl phosphonates involves treatment of gem-dibromocyclopropanes with triethyl phosphite in the presence of Et,N and a control- led amount of water.' 2-Silyloxycyclopropanecarboxylicesters which are valuable building blocks in synthesis are prepared by diazoacetic ester addition to silyl enol ethers." Silylcyclopropanes (13) and (14) have been synthesized by addition of arsonium ylides to chalcones" and by modified Simmons-Smith cyclopropanation of vinyl-silanes,I2 the silicon function subsequently permitting a variety of functional group modifications to be made.I3 CH,I,-EtZnI ____, 4siMe3 &SiMe A CH,OH \ CHzOH :H,OH The cis-tributylstannylcyclopropyl methanol (15) available by Simmons-Smith rcaction on 3-tributylstannylprop-2-eno1, can be resolved as the 0-methylmandelyl ester.Replacement of the stannyl group by lithium using BuLi then affords the chiral cis-2-substituted cyclopropyl-lithium reagent for use in asymmetric ~yntheses.'~ R. T. Hrubiec and M. B. Smith J. Chem SOC.,Perkin Trans. 1 1984 107. T. Hirao M. Hagihara Y. Ohshiro and T.Agawa Synthesis 1984 60. 10 E. Kunkel I. Reichelt and H.-U. Reissig Annalen 1984,512; I. Reichelt and H.-U. Reissig ibid. p. 531. Y. Shen Z. Gu W. Ding and Y. Huang Tetrahedron Lett. 1984 25 4425. 12 G. J. Wells T.-H. Yan and L.A. Paquette J. Org. Chem 1984,49 3604. l3 L. A. Paquette T.-H. Yan and G.J. Wells J. Org. Chem 1984 49 3610; L. A. Paquette G. J. Wells and G. Wickham ibid. p. 3618; L. A. Paquette C. Blankenship and G. J. Wells J. Am. Chem SOC. 1984 106 6442. 14 E. J. Corey and T. M. Eckrich Tetrahedron Lett. 1984 25 2415. 156 S. A. Math Two new enantiospecific routes to chrysanthemic acid (17) derivatives have been described. One involves a microbiological reduction of the achiral diketone (16)15 and the other utilises the natural chirality of a supv derivative.16 0 0 Halogenovinyl cyclopropanes such as (18) have been synthesized via vinylcar-benoid additions following dehydrohalogenation of 3,3-dihalogenated propene~.'~ Passage of 3-chlorocyclopropene over AgF2-KF results in quantitative conversion into 3-fluoro~yclopropene.'~ The unusual reactivity of fluorinated cyclopropanes has been further examined." The first syntheses of methylenecyclopropene (20) leading to direct observation of this unstable species have been reported.20 The diene can be formed by elimination from 2-methylenecyclopropyl chloride bromide or phenylsulphoxide (19; X = C1 Br or SOPh) or by pyrolysis of diazoketone (21) and can be transferred in vacuo and frozen in a liquid nitrogen trap for spectroscopy.The 'Hn.m.r. spectrum at -90 "C displays two apparent triplets (3.60 and 8.18) suggesting a significant contribution from the resonance form (20b). Methylenecyclopropabenzene and methylenecyclopropa[b]naphthalene derivatives have also now been prepared and are stable solids.2' Is D.Buisson R. Azerad G. Revial and J. d'hgelo Tetrahedron Lett. 1984 25 6005. 16 B. F. Fitzsimmons and B. Fraser-Reid Tetrahedron 1984 40,1279. W. Gathling S. Keyaniyan and A. de Meijere Tetrahedron Lett. 1984 25 4101. 18 N. C. Craig K. L. Sloan J. R. Sprague and P. S. Stevens J. Org. Chem. 1984 49 3847. 19 S. F. Sellers W. R. Dolbier jun. H. Koroniak and D. M.Al-Fekri J. Org. Chem. 1984 49 1033. 2o W. E. Billups. L. J. Lin and E. W. Casserly 1. Am. Chem. SOC.,1984 106 3698 S. W. Staley and T. D. Norden ibid p. 3699; G. Maier M. Hoppe K. Lanz and H. P. Reisenauer Tetrahedron Lett. 1984 25 5645. 21 B. Halton C. J. Randall and P. J. Stang J. Am. Chem Soc. 1984 106 6108. Alicyclic Chemistry Unlike propadienone (22),22 which has a kinked ground-state structure (22b) cyclopropylidenemethanone (23) has a quasi-symmetrical structure according to microwave spectroscopy.CH,=C=C=O e* CH,=C- bC=O \+ (22a) (23) On treatment with MeLi gem-dibromocyclopropanes bearing a -C02H group directly attached to the ring undergo a stereospecific debromination leading to trans-2-bromocyclopropanecarboxylic The optically active truns-2,3-dicyanomethylenecyclopropane(24)undergoes an extremely rapid base-catalysed epimerization to the cis-i~omer.~~ A kinetic study" of the thermal stereomutations of deuterated phenylcyclopropanes has revealed unexpectedly large rate constants for the interconversion of the syn- and anti-isomers (25) and (26). The kinetics of reactions of cyclopropyl radicals with olefins have also been reported.26 Bromination of the trans-tetradeuteriocyclopropane(27)gave the dibromides (28) and (29) the latter being formed largely (>85%) as the erythro-product (29a).This is consistent only with corner bromination leading to inversion at both of the substituted carbon atoms.27 Pyridine attack on the spiro-activated cyclopropanes (30; R = H or Ph) is revers- ible and has been the subject of a kinetic study." Cuprates undergo homoallylic addition to the cyclopropylcarbinyl bromides (31 ;R = Bun Pr' or But) giving olefins as E/Z mixtures apparently viu rearrangement of a Cut radical intermediate rather than the previously postulated Cu" radical or Cut cation complex.29 The 22 R. D. Brown P. D. Godfrey B. Kleibomer R.Champion and P. S. Elmes J. Am. Chem. Soc. 1984 106 7715. 23 L. K. Sydnes and S. Skare Can. J. Chem. 1984,62 2073. 24 S. L. Buchwalter J. Org. Chem. 1984 49 4551. 25 J. E. Baldwin T. U. Patapoff and T.C. Barden 1.Am. Chem. Soc. 1984 106 1421. 26 L. J. Johnston J. C. Scaiano and K. U. Ingold J. Am. Chem. Soc. 1984 106 4877. 27 J. B. Lambert W. J. Schulz jun. P. H. Mueller and K. Kobayashi J. Am. Chem. Soc. 1984 106 792. 28 M. A. McKinney K. G. Kremer and T. Aicher Tetrahedron Lett. 1984 25 5477. 29 R. T. Hrubiec and M. B. Smith Tetrahedron 1984 40,1457; see also M. S. Alnajjar G. F. Smith and H. G. Kuivila J. Org. Chem. 1984,49 1271; S. H. Bertz G. Dabbagh J. M. Cook,and V. Honkan ibid. p. 1739. 158 S.A. Matlin R (31)&~ 0 2 ~ 'wMgBr ,CO,Me Me CuI.Me,S (32) Me cuprate-mediated homoconjugate addition of but-3-enylmagnesium bromide to bicyclohexanone (32) has been proved to proceed with inversion of configuration and furnishes a useful intermediate for natural product ~yntheses.~' The thermal ring-opening cycloadditions of cyclopropyl derivatives with activated olefins have been re~iewed.~' Vinylcyclopropanes undergo acid-catalysed ring open- ing uia cations,32 but thermal rearrangement to cyclopentenes uia biradical inter- mediate~.~~ An efficient synthesis of 1-vinylcyclopropanols has been developed and the thermal rearrangements of their silyl ethers provides a versatile route to siloxcyc- lopentenes as illustrated by the spirovetivane synthesis (Scheme 2).34 I +yiox I +& 0 +7ioP 0 d Me3si0& +$io Scheme 2 30 D.F. Taber K. R. Krewson K. Raman and A. L. Rheingold Tetrahedron Lett. 1984 25 5283. 31 T. Tsuji and S. Nishida Acc. Chem. Res. 1984 17 56. 32 Z. Goldschidt B. Crammer and R. Ikan J. Chem. SOC.Perkin Trans. 1 1984 2697; G. Suzukamo M. Fukao and M. Tamura Tetrahedron Lett. 1984 25 1595. 33 J. J. Gajewski and J. M. Warner J. Am. Chem SOC,1984 106 802. 34 J. Ollivier and J. Salaun. Tetrahedron Lett.. 1984. 25. 1269 J. P. Barnier and J. Salaun ibid. p. 1273. Alicyclic Chemistry The cis-1 -methylcyclopropylcarbinylcation has been prepared for the first time and undergoes facile interconversion with the 1-ethylallyl cation.35 The cation (33; R = H or Me) prefers substitution over ring-opening to an ally1 cation as a result of the influence of the ester In protic or strongly ionizing media the cyclopropenylcarbinols (34; R = Me or Et) rearrange to cyclobutenes and low- temperature n.m.r.studies suggest the intermediate to be a homoaromatic cyclo- butenyl cation.37 I C0,Et C0,Et (33) The heat of formation of diphenylcyclopropenone has been estimated38 by photo- acoustic calorimetry as 360 * 17 kJ mol-' indicating a resonance stabilization energy of 46 kJ mol-'. Whereas cyclopropenone ketals react with olefins bearing two electron-withdrawing groups to give cyclopentenes olefins bearing one electron- withdrawing group give cyclopropanes and addition to carbonyl groups leads to products uia butenolide ortho esters (Scheme 3; X = COzMe or CN).39 X Scheme 3 35 C.Falkenberg-Andersen K. Ranganayakulu L. R. Schmitz and T.S. Sorensen J. Am. Chem Soc. 1984 106 178. 36 R. Amaud A. Dussauge H. Faucher R. Subra M. Vidal and M. Vincens Tetrahedron 1984,40,315. 37 M. Vincens C. Dumont and M. Vidal Bull Soc Chim Fr. ZZ 1984 59. 38 J. J. Grabowski J. D. Simon and K. S. Peters J. Am Chem SOC 1984 106,4615. 39 D. L. Boger and C. E. Brotherton Tetrahedron Lett. 1984,25 5611:D. L. Boger C. E. Brotherton and G.1. Georp. ihid.. p. 5615. 160 S. A. Math Theoretical calculation^^^ predict a non-planar structure for a cyclopropenyl anion in agreement with the expected anti-aromatic character of this species. 3 Four-membered Rings Cyclobutanones have been prepared in high yields by lithiation of l-bromo-l-ethoxycyclopropane addition of an aldehyde or ketone and acid-catalysed rear- rangement of the product (Scheme 4).41A four-step procedure for the synthesis of cyclobutenediones has been described (Scheme 5).42 Reagents i Bu'Li Et20 -78 "C; ii R'R2CO; iii 48% aq.HBF Scheme 4 Reagents i PhSH; ii CI,C=C=O; iii Et3N; iv 3-ClC6H4C03H Scheme 5 Chloro(trimethylsilylmethy1)ketene [2 + 21 cycloaddition to olefins affords sub- stituted cyclobutanones from which methylenecyclobutanones and methylenecyc- lopentanones can be synthesized (Scheme 6).43 'so F-,R2Ra R2 0 Scheme 6 40 B.A. Hess jun. L. J. Schaad and P. Carsky Tetrahedron Lett. 1984 25 4721. 41 R. C. Gadwood Tetrahedron Lett.1984 25 5851. 42 L. S. Liebeskind and S. L. Baysdon Tetrahedron Lett. 1984 25 1747. 43 L. A. Paquette R. S. Valpey and G. D. Annis J. Org. Chem 1984 49 1317; see also G. Mehta and K. S. Rao Tetrahedron Lett. 1984 25 1839. Alicyclic Chemistry Reaction of cyclobutanone with the anion of dialkyl (diazomethy1)phosphonates yields cyclopentyne as an intermediate. This has been trapped by [2 + 21 cycloaddi-tion to cis-1 -methoxyprop-1-ene giving cyclobutene (35). The trapping product (36) with trans-1 -methoxyprop-1-ene cannot be isolated since it undergoes electrocyclic ring opening to diene (37) which has itself been trapped by Diels-Alder reaction.44 The first experimental evidence for a cyclobutyne intermediate has also been 0 II +(RO),PCHN -Beckmann fragmentation of the cyclobutanone oximes (38) has been useda for the stereoselective synthesis of the macrolide intermediates (39)..KH - RCOCl +cN EtO EtO (384 (39a) (61o/o ) RCOCl + +N EtOTo" EtO (38b) (39b) (64%) (9"/0) 44 J. C. Gilbert and M. E. Baze J. Am. Chem. SOC,1984 106 1885. 45 K.-D. Baumgart and G. Szeimies Tetrahedron Lett. 1984 25. 737. 46 G. Frater U. Muller and W. Gunther Terruhedron Lerr. 1984 25 1133. 162 S. A. Matlin A reinvestigation of the cycloaddition of dimethyl acetylenedicarboxylate to enamines has been reported?’ It now transpires that the immediate [2 + 21 cycloaddi-tion products 3-dialkylaminocyclobutenes,are isolable only when the enamine is derived from a 5-membered (or occasionally 6-membered) ring.In all other cases the cyclobutene opens to a cis-truns-cycloalka-1,3-dienewhich may further rearrange under the reaction conditions. 4 Five-membered Rings 3,CDisubstituted pent-2-enals are stereospecificallycyclized by Wilkinson’s catalyst to cis-3,4-disubstituted cyclopentanones which are useful in the preparation of prostaglandin^.^^ The synthesis of the latter from cyclopentane intermediates has been reviewed.49 Cyclopentanone annulation can be achieved by AlCl,-catalysed intramolecular acylation of an allyl~ilane.~~ In two further procedures using intramolecular cycliz-ations of allylsilanes to construct 5-membered rings the epoxy-allylsilane (40) gave mainly cis-l-hydroxymethyl-2-vinylcyclopentane,51 whilst the chiral allylsilane aldehyde (41) cyclized to cyclopentenol (42) in high optical yield.52 TiCI -OH Me,Si T~CI QIl Methylenecyclopentanes have been prepared by a one-pot synthesiss3involving 1,4-bis(bromomagnesio)butane addition to a-chloroesters (43) and by palladium-catalysed additions4 of the ally1 carbonates (44;X = p-MeC6H4S02or CN) to enones and acrylates (45 Y = alkyl or alkoxy).4’ BrMgnMgB, C0,Et + -8 (43) 47 D. N. Reinhoudt W. Verboom G. W. Visser W. P. Trompenaars S. Harkema and G.J. van Hummel J. Am Chem SOC 1984,106 1341. 48 K. Sakai Y. Ishiguro K. Funakoshi K. Ueno and H. Suemune Tetrahedron Lett. 1984 25 961. 49 V. A. Dombrovski D. Y. Fonskii V. A. Mironov and P. M. Kochergin Russ.Chem Rev. 1984,53,401. H. Urabe and I. Kuwajima J. Org. Chem 1984,49 1140. 51 T. S. Tan A. N. Mather G. Procter and A. H. Davidson J. Chem SOC.,Chem Commun 1984 585; see also D. Schinzer Angew. Chem Int. Ed. EngL 1984 23 308. 52 K. Mikami T. Maeda N. Kishi and T. Nakai Tetrahedron Lett. 1984 25 5151. 53 J. Barluenga M. Yus J. M. Concellon P. Bernad and F. Alvarez 1. Chem. Rex (S) 1984 122. 54 1. Shimizu Y. Ohashi and J. Tsuji. Tetrahedron Lett.. 1984. 25. 5183. Alicyclic Chemistry New routes to cyclopentenones include Claisen condensation of crotonates with dimethyl ~xalate,~' acylation of acetylenes with p,y-unsaturated acid chlorides,56 palladium-catalysed cyclization of 1-ethynylprop-2-enyl acetate^,^' the Ramberg- Backlund reaction5* of cyclic sulphones (46) conden~ation'~ of the dithiane anion (47) with methyl thiovinyl phosphonium salt (48) and intramolecular acylation6' of the sulphoxides (49; X = OMe or NMePh).In a modification of the latter method,61 the hydroxy-intermediate (50) is dehydrated alkylated and pyrolysed to give methylenecyclopentenones (Scheme 7). RbSOPh- R1&SOPh PhCH,NMe,+C,-1. Met NaOH R,& R1+ HO SOPh HO + 2. A (50) Scheme 7 55 R. T. Brown W. P. Blackstock and M. Wingfield Tetrahedron Lett. 1984 25 1831. 56 M. Karpf Helv. Chim Acta 1984 67 73. 57 V. Rauterstrauch J. Org. Chem. 1984,49,950. 58 H. Matsuyama Y. Miyazawa Y. Takei and M. Kobayashi Chem Lett. 1984 833. 59 A. G. Cameron A. T. Hewson and M. I. Osammor Tetrahedron Lett.1984 25 2267. 60 M. Pohmakotr and P. Phinyocheep Tetrahedron Lett. 1984 25 2249. 61 M. Pohmakotr and S. Chancharunee Tetrahedron Lett. 1984 25 4141. 164 S. A. Matlin Condensation of the dianion of di-isopropyl hex-3-enedioate with ethyl 3- bromopropionate leads to an exo-methylenecyclopentanone (Scheme 8) a con- venient intermediate for the synthesis of prostaglandins and sarkomycin (51).62 Other routes to this type of compound involve addition of ally1 iron complexes to 01efins~~ and cyclization of the allenic ethers (52).& n 1 n Scheme 8 OR 0 5 Six-membered Rings Brominative cyclization of polyenes in acetonitrile at low temperature6’ leads to capture of the intermediate as the ion (53) which eliminates MeCN at room temperature to give the olefin (54).Metal-catalysed cyclization66 of the dienes (55; n = 1;X and Y = H Me C02Et COR) gives mixtures with RhCl( PPh3)3 favouring the 5-em-trig product (56;n = 1) ‘R Br’x 62 A. Misurni K. Furuta and H. Yarnamoto Tetrahedron Lett. 1984 25 671; K. Furuta A. Misumi A. Mon N. Ikeda and H. Yamamoto ibid. p. 669. 63 R. Baker R. B. Keen M. D. Moms and R. W. Turner J. Chem. SOC.,Chem. Commun. 1984 987; J. C. Watkins and M. Rosenblurn Tetrahedron Lett. 1984 25 2097. 64 M. A. Tius and D. P. Astrab Tetrahedron Lett. 1984 25 1539. 6s T. Kato M. Mochizuki T. Hirano S. Fujiwara and T. Uyehara 1.Chem. SOC.,Chem. Commun. 1984 1077. 66 R. Gngg P. Stevenson and T. Worakun J. Chem. SOC.,Chem. Commun..1984. 1073. Alicyclic Chemistry R and Pdo the 6-endo-trig product (57; n = 1; R = H). Pdo-catalysed cyclization of (55; n = 2; X = Y = C02Et) gives mainly (56; n = 2) together with some (57; n = 1; R = Me). In the cyclization of allysilane-substituted ketals the presence of the silicon group provides a very effective means for controlling the final position of the double bond (Scheme 9),67 SiMe, 1 ZnBr SnC'4 CHSiMe -Me0 OMe OMe Me0 OMe OMe Scheme 9 Chiral cyclohexanones have been prepared by the rearrangement of a sugar derivative68 and by the palladium-catalysed cyclization of the sodium salt (58) which proceeds with complete retention at the original chiral centre.69 Na' eMe ee OC0,Me (58) Several new syntheses of shikimic acid (60) and its labelled derivatives7' have been published.Strategies devised include Diels- Alder addition of dimethyl acrylate to f~ran,~' iodolactonization of cyclohex-3-enecarboxylicacid72 and intramolecular Wadsworth-Emmons olefination in the sugar phosphonate (59).73 The cyclohexyne (62) has been observed spectroscopically in a frozen matrix following photolysis of the cyclopropenone (61) and cycloheptyne was similarly generated.74 67 H.-F. Chow and I. Fleming J. Chem. SOC,Perkin Trans. I 1984 1815. 68 F. Chretien and Y. Chapleur J. Chem. SOC.,Chem Commun. 1984 1268. 69 K. Yamamoto R. Deguchi Y. Ogimura and J. Tsuji Chem. Lett. 1984 1657. 70 L. 0.Zamir and C. Luthe Can. J. Chem 1984 62 1169. 71 M.M.Campbell A.D. Kaye M. Sainsbury and R. Yavarzadeh Tetrahedron 1984.49.2461 ;Tetrahedron Lett. 1984 25 1629; D. Rajapaksa B. A. Keay and R. Rodrigo Can. J. Chem. 1984 62 826. 72 P. A. Bartlett and L. A. McQuaid J. Am. Chem SOC,1984 106 7854. 73 G. W. J. Fleet T. K. M. Shing and S. M.Warr J. Chem SOC Perkins Trans. I 1984 905. 74 A. Krebs W. Cholcha M. Miller and T. Eicher Tetrahedron Left. 1984 25 5027. 166 S. A. Matlin CO Bu' I CO Bu' HO' OH (59) (60) A convenient new procedure for Birch reduction of benzenes to cyclohexadienes utilises a calcium-amine-t-butyl alcohol ~ystem.'~ Crystal structures of cis-and truns-cyclohexane-l,2-diolsshow both to be present in chair forms which are held together by pairs of intramolecular H-b~nds.~~ The conformational steric isotope effect for carbon in a methyl group in cis-1,Cdimethyl- cyclohexane (63) has been measured as 1.24 f 0.25J mol-' (13C preferring to be equatorial) a smaller difference than that estimated from force-field calculation^.^^ The 1,3-diaxial interaction of Me and Ph groups on a cyclohexane ring has been determined7' by 13C n.m.r.to be 14.2 * 0.4kJmol-' and the gauche Me-Me interaction in truns-1,2-dimethylcyclohexaneto be 3.1 kJ mol-'. A critical re-examination of Diels- Alder reactions has led Dewar and Pierir~i~~ to conclude that despite their concerted nature a very unsymmetrical transition- state close to a biradical or zwitterion is' involved and that these reactions are neoer synchronous. However Tolbert and AliSo take a different view and have presented evidence that the influence of an adjacent chiral centre in the dienophile on the degree of asymmetric induction observed in the product is in strict accord only with the transition state of a synchronous process.Addition of Lewis acids changes the transition state to a less symmetrical asynchronous one. 75 R. A. Benkeser J. A. Laugal and A. Rappa Tetrahedron Lett. 1984 25 2089. 76 S. Sillapnaa M. Leskela and L. Hiltunen Acta Chem. Scand. Ser. B 1984 38 249. 77 S. L. R. Ellison M. S. Fellows M. J. T. Robinson and M. J. Widgery J. Chem SOC.,Chem. Commun. 1984 1069. 78 M. Manoharan and E. L. Eliel J. Am. Chem. SOC.,1984 106 367. 79 M. J. S. Dewar and A. B. Pierini J. Am. Chem SOC.,1984 106 203.8o L. M.Tolbert and M. B. Ali. J. Am. Chem. Soc. 1984. 106 3806. Alicyclic Chemistry 167 The rates of Diels-Alder reactions are dramatically increased by the presence of AlC1 or of the clay Fe"'-doped K10 montmorillonite.81 Regioselectivity in metal- catalysed cycloadditons can be very solvent-dependent.82 New approaches to asymmetric induction in the Diels-Alder reaction include the use of chiral vinyls~lphoxides,~~ and chiral chiral a,P -unsaturated carbo~imides~~ acrylate esters of camphor derivatives8' as dienophiles. The addition of chiral a-chloro-a -nitroso compounds to cyclohexadiene gives a very high enantiomeric excess in the [4 + 21 cycloaddition product.86 6 Seven-membered Rings The cycloaddition of ally1 cations to 1,3-dienes as a general method for the synthesis of 7-membered rings has been re~iewed.~' 3-Methoxycycloheptatrienes are con- veniently prepared88 by the ring expansion of Birch reduction products derived from guaiacol silyl ethers (Scheme 10).OSiEt .,ooMe OSiEt Li-NH, R' R R CH,I IEt,Zn I R R Scheme 10 Substituted homotropylidenes have been synthesized from cycloheptatrienes by Diels- Alder reaction with 1 ,2,4-triazoline-3,5-diones,addition of diazoalkanes and removal of the heterocyclic bridge (Scheme ll) making possible a study of the effects of substituents on the Cope rearrangements of these divinylcyclopropane ana~ogues.'~ " P. Laszlo and J. Lucchetti Tetrahedron Lett. 1984 25 1567; 2147; 4387. 82 J.-L. Metral and P.Vogel Tetrahedron Lett. 1984 25 5387. 83 T. Koizumi I. Hakamada and E. Yoshii Tetrahedron Lett. 1984 25 87; C. Maignan A. Guessous and F. Roessac ibid. p. 1727; S. M. Proust and D. D. Ridley Aust. J. Chem 1984 37 1677. 84 D. A. Evans K. T. Chapman and J. Bisaha J. Am Chem SOC,1984 106,4261. 83 W. Oppolzer C. Chapuis and G. Bernardinelli Tetrahedron Lett. 1984 25 5885; W. Oppolzer and C. Chapuis ibid. p. 5383; W. Oppolzer M. J. Kelly and C. Chapuis ibid. p. 5889. M. Sabuni G. Kresze and H. Braun Tetrahedron Lett. 1984 25 5377; H. Felber G. Kresze H. Braun and A. Vasella ibid. p. 5381. 87 H. M. R. Hoffmann Angew. Chem. tnt. Ed. EngL 1984 23 1. 88 V. A. Roberts M. E. Garst and N. E. Torres J. Org. Chem 1984,49 1136. 89 J. K. Kettering and G.Maas Tetrahedron 1984 40,391. 168 S. A. Matlin Scheme 11 7 Medium and Large Rings Cyclonona- 1,2,3-triene has been synthesized and isolated for the first time by carbenoid ring-expansion of cyclo-octa- 1,2-diene and is calculated to have a bent cumulene structure with angles of around 162” at the allenic carbons.” The 9-membered rings of isocaryophyllene and caryophyllene have been construc- ted9’ by intramolecular acyl transfer reactions of the 13-membered lactam sulphoxide (64a) and its isomer (64b). LDA -.-0 0 (644 (64b) Cyclization by intramolecular alkylation of the a-phenylthio nitrile (65) gives a 10-membered ring and the method has been used in a new germacrene ~ynthesis.’~ Another simple and direct method93 of cyclization leading to a 10-membered ring involves intramolecular alkylation of the di-unsaturated malonates (66; X-X and Y-Y = cis or trans CH=CH or C-C).” R. 0. Angus jun. and R. P. Johnson J. Org. Chem. 1984,49 2880. 91 Y.Ohtsuka S. Niitsuma H. Tadokoro T. Hayashi and T. Oishi J. Org. Chem. 1984 49 2326. 92 T. Kitahara and K. Mori J. Org. Chem. 1984,49 3281. 93 P. Deslongchamps S. Larnothe and H.-S. Lin Con. J. Chem. 1984 62 2395. Alicyclic Chemistry Me0,C C0,Me Me0,C COzMe Y(5 A X II YX w Me0,C C0,Me 0 ph3fi+-Intramolecular Wittig reactions of the aldehydic phosphonium salts (67;n = 5-8) have provided access to macrocyclic die none^.^^ The transannular reactions accompanying electrophilic additions to double bonds in 8-membered rings continue to be ~tudied.~’ Whereas bromination of cyclo-octene gives small amounts of cis-and truns-1,4-dibromides as well as 1,2-dibromides bromination of 1-trimethylsilylcyclo-octene has now been shown96 to give 1-bromocyclo-oct-4-ene in high yield uiu desilylaltion of the lY4-dibromide I68).8 Bicyclic Compounds Ionic bicyclobutane (69)is an intermediate in the reactions of phenylthiolate with 3-halogenobicyclobutanecarbonitrile(70; X = C1 or Br).97 Spiroann~lation~~ of cyclic ketones with 2-chloroethyl dimethylsulphonium iodide occurs readily in the presence of base (Scheme 12; n = 1,2,3,7). The diazoacetic ester (71) cyclizes in high yield in the presence ofa soluble copper catal ys t.99 94 H. J.Bestmann and H. Lutke Tetrahedron Lett. 1984 25 1707. 95 J. E. Norlander K. D. Kotian D. E. Raff F. G. Njoroge and J. J. Winemiller J. Am. Chem. SOC.,1984 106 1427; G. Haufe and M. Muhlstadt Tetrahedron Lett. 1984 25 1777; G. Haufe zbid. p. 4365. 96 D. Dhanak C. B. Reese and D. E. Williams J. Chem. Soc. Chem. Commun. 1984 988. 91 S. Hoz and D. Aurbach J. Org. Chem. 1984,49 3285. 98 S. M. Ruder and R. C. Ronald Tetrahedron Lett. 1984 25 5501. 99 E. J. Corey and A. G. Myers Terrahedron Lett. 1984 25 3559. 170 S. A. Matlin PhsVcN xTN Scheme 12 The cyclization of y-stannyl alcohols to cyclopropanes has been further developed and extended to the synthesis of gem-substituted bicyclo[n.l.O]alkanes (Scheme 13 ; n = 1-3).'0° Whereas cis-1,2-diethylcyclopropaneis 4.6kJ mol-' less stable than the trans-isomer cis-and trans-bicyclo[6.1 .O]nonanes have the same enthalpies of formation.'" PhLi SOCI ___ (cza ___ (PPh SnBu3 SnBu Scheme 13 Bicyclic compounds with various ring-sizes can be obtained by the transmetalla- tion-cyclizations of the trimethylstannyl olefins (72) lo' and lanthanide-induced cyc- lizations of the iodo-ketones (73).'03 Copper( I)-catalysed intramolecular [2 + 21 photo-cyclization'@' of myrcene (74) afforded the bicyclo[3.1 .O]heptane (75) as well as the cyclobutene (76).Enantioselec-tion in [2 + 21 photo-cyclizations has not been extensively studied hitherto but it is now rep~rted"~ that the product (78) of addition of the (S)-enantiomer of the 100 J.F. Kadow and C. R. Johnson Tetrahedron Lett. 1984 25 5255. LO1 K. B. Wiberg E. C. Lupton jun. D. J. Wasserman A. de Meijere and S. R. Kass J. Am. Chem. Soc. 1984 106 1740. lo' E. Piers and H. L. A. Tse,Tetrahedron Lett. 1984 25 3155. 103 G. A. Molander and J. B. Etter Tetrahedron Lett. 1984 25 3281. 104 K. Avasthi S. R. Raychoudhun and R. G. Salomon J. 0%.Chem. 1984,49 4322. 105 K. Bruneel D. De Keukeleire and M.Vandewalle J. Chem. Soc. Perkin Trans. I 1984 1697. Alicyclic Chemistry SnMeJ H (73) ketene acetal (77) to cyclopentenone is formed with high intrinsic asymmetric induction. The regioselectivity of the ene reactionlM is affected by the presence of a TMS group,lo7 the diene (79; R = H) cyclizing to a mixture of (80; R = H) and (81) whereas the diene (79; R = SiMe,) cyclizes exclusively to (80; R = SiMe,).Several strategies have been reported for the synthesis of hydrindanes including the use of 9,10-dibromocamphor to construct the intermediate (82) from which methylenehydrindane (83) was obtained,'08 intramolecular acylations of the '06 F. E. Ziegler and J. J. Mencel Tetrahedron Lett. 1984 25 123. I07 F. E. Ziegler and K. Mikami Tetrahedron Lett. 1984 25 127. 108 J. H. Hutchinson T. Money and S. E. Piper 1. Chem. SOC.,Chem. Commun. 1984 455. 172 S. A. Matlin vinylsilane (84) and related intramolecular Diels- Alder reactions' lo such as the HF-catalysed cyclization of the chiral trienic ester (85) which furnishes the alcohol (86) after reduction but without asymmetric induction,"' and the Me,AlCl-catalysed intramolecular Diels- Alder reaction of (87 ; X = chiral oxazolidone) which affords hydrindane (88) with a high degree of asymmetric induction.ll2 Whilst these methods give trans-hydrindanes construction of the cis-hydrindane system is required for the synthesis of a number of classes of natural Br H (87) (88) 109 S.E. Denmark and J. P. Germanas Tetrahedron Lett. 1984,25 1231; K. Fukuzaki E. Nakamura and I. Kuwajima ibid. p. 3591. 110 M. Yoshioka H. Nakai and M. Ohno J. Am. Chem. SOC.,1984 106 1133; P. G. Gassman and D. A. Singleton ibid p. 6085; M. J. Kurth D. H. Bums,and M.J. OBrien J. Org. Chem. 1984,49,731; D. D. Sternbach D. M.Rossana and K.D.Onan ibid. p. 3427; S. D. Burke D. R. Magnin J. A. Oplinger J. P.Baker and A. Abdelmagid Tetrahedron Lett. 1984 25 19. 111 W. R. Roush H. R.Gillis and A. P.Essenfeld 1. Org. Chem 1984,49 4674. 112 D. A. Evans K. T. Chapman and J. Bisaha Tetrahedron Lett. 1984 25 4071. I13 S. Ohira Bull. Chem. SOC.Jpn. 1984 57 1902; H. Niwa K. Wakamatsu T. Hida K. Niiyama H. Kigoshi M. Yamada H. Nagase M.Suzuki and K. Ya'mada J. Am Chem SOC 1984 106,4547; M. E. Jung and L. A. Light ibid. p. 7614. Alicyclic Chemistry 173 Reagents i H2,Pd-C or Li-NH,-Bu'OH; ii LiAIH,; iii MeCOSH; iv; 3-CIC6H4C03H Scheme 14 and a strategy has been de~eloped"~ for the stereospecific conversion of hydrin- denones such as (89) into either type of product (Scheme 14).Approaches to the stereocontrolled synthesis of cis-and truns-bicyclo[6.3.0] and [5.3.01 systems are illustrated by the Al-catalysed cyclization"' of the keto-olefin (90) Ru04 oxidation116 of the triquinane olefin (91) to the diketone (92) use of boron hydride as a template for the carbonylation-cyclization"7 of the diene (93) to ketone (94) and conjugate addition-enolate trapping' '' to generate the intermedi- ate (95) which was cyclized to lactone (96; X = "Me or OCH2CH20) and this was converted by Claisen rearrangement of the silyl enolate of the ester into trans-hydrazulene (97). 6 0 1C12Me MeAICI H 114 E. J. Corey and T. A. Engler Tetrahedron Lett. 1984 25 149. B. B. Snider and C. P. Cartaya-Marin J. Org. Chem. 1984 49 153.116 G. Mehta and A. N. Murty J. Chem. Soc. Chem. Commun. 1984 1058. 117 J. W. S. Stevenson and T. A. Bryson Chem. Lett. 1984 5. 118 M. J. Begley A. G. Cameron and D. W. Knight 1. Chem. SOC.,Chem. Commun.,1984 827. + 9 '"> 1.BuLi S. A. Matlin 2. BrCH,CO,Et 0 OTHP OTHP (95) n I n I. LDA Bu'SiMe,CI t 2. A CO,Si+ I (97) (96) Silicon-directed N-acyliminium ion cycli~ation"~ of the ethoxylactam (98; R = H or CH2Ph) provides access to the trans-fused compound (99). Titanium-catalysed cyclization of the allylsilane (100; R = H Me) affords a cis- and trans-mixture (101) which is converted entirely into the trans-isomer with base.12* SiMe3 -0 0 Many additional strategies for obtaining the decalin system have been reported12' and some are depicted in Scheme 15.119 H. Hiemstra W. J. Klaver M. J. Moolenaar and W. N. Speckamp Tetrahedron Lett. 1984 25 5453. I2O T. Tokoroyama M. Tsukamoto and H. Iio Tetrahedron Lett. 1984 25 5067. 121 Y. L. Yang S. Manna and J. R. Falck J Am Chem SOC.,1984,106,3811; E. R. Koft and A. B. Smith ibid. p. 2115; W. G. Dauben and G. Shapiro J. Org. Chem. 1984 49 4252; C. Agami F. Maynier C. Puchot. J. Guilhem and C. Pascard Tetrahedron 1984 40,1031. Alicyclic Chemistry &:. (Ref 122) ~ wC02Et 0-O \ ( Ref 123) u- H H (Ref 124) Scheme 15 A new approach'*' to spirovetivanes is based on the fragmentation and recycliz- ation of Diels-Alder adducts (Scheme 16). An alternative route involves intramolecular cyclization of substituted cyclopentadienes.'26 $3 0 / Scheme 16 122 E.Piers and B. W. A. Yeung .I.Org. Chem. 1984 49 4567. P. R. Jenkins K. A. Menear P. Barraclough and M. S. Nobbs J. Chem SOC.,Chem. Commun. 1984 1423. 124 K. Mori and M. Waku Tetrahedron 1984,40 305. 125 A. Murai S. Sato and T. Masamune BulL Chem SOC.Jpn. 1984,57 2276; 2282; 2286; 2291. 126 K. Annak J. F. Kingston and A. G. Fallis Can. J. Chem. 1984 62 2451; see also K. Annak J. F. Kingston S. J. Alward and A. G. Fallis ibid. p. 829. 176 S. A. Matlin Ally1 cation cycloaddition to cyclopentadiene provides entry to the bicyclo[3.2.l]octane ~keleton,”~ whilst the bicyclo[4.1 .O] system is available by [6 + 21 cycloadditions of cycloheptatrienes.’28 The [6 + 41 cycloadditions of unsym-metrical tropolones with dienes have been shown’29 to proceed with ‘even’ selectivity faveunng the 1,6-product (Scheme 17).oo+& Q-) B Scheme 17 Bicyclic compounds with unusual geometries for which syntheses have been reported include the in,out-bicyclo[4.4.4]tetradecane (lO2),l3’ the bicyclo[5.3.2]- dodecane derivative (103) which contains a doubly orthogonal 1,3,5-triene unit,”’ and the chiral [10.10]- and [22.10]-betweenanes (104; n = 10 or 221 of (R)-configur-ation.13’ Analysis of c.d. spectra indicates that the bis-dienes (105; R = D Me) have eclipsed conformations whereas the structure of the alcohol (105; R = OH) is twisted.’33 2 (1 02) (1 03) TH(104))I0 (1 05) BH A a&.,.fi 9 Polycyclic Compounds A theoretical study’34 of the C(l)-C(3) bond in [l.l.l]propellanes in which the two bridgehead carbons have inverted configurations suggests a novel non-axial orbital arrangement termed ‘a-bridged T’.One-electron oxidation of tetra-t-butyltetrahedrane gives tetra-t-butylcyclo- butadiene radical cation.135 A one-step synthesis of tricyclo[3.2.1 .02*’]octan-6-ones has been developed’36 which involves vinylsulphone addition to a cyclohexenone anion by a combination of inter- and intra-molecular Michael reactions (Scheme 18). This type of combina-127 H. M. R. Hoffmann,A. Weber and R. J. Giguere Chem. Ber. 1984 117 3325. 128 K. Mach H.Antropiusova L. Petrusova V. Hanus and F. Turecek Tetrahedron 1984 40,3295.129 M. E. Garst and V. A. Roberts J. Am. Chem SOC 1984 106 3882. J. E. McMurry and C. N. Hodge J. Am. Chem. SOC.,1984 106 6450. 131 W. von E. Doering and J. C. Schmidhauser J. Am Chem SOC 1984 106 5025. 132 J. A. Marshall and K. E. Flynn J. Am Chem SOC.,1984,106,723; see also J. A. Marshall,J. C. Peterson and L. Lebioda ibid. p. 6006. 133 R Gabioud and P. Vogel Tetrahedron Lett. 1984 25 1729. 134 J. E. Jackson and L. C. Allen J. Am Chem. SOC.,1984 106 591. 135 H. Bock B. Roth and G. Maier Chem Ber. 1984 117 172. R. M. Cory and R. M. Renneboog J. Org. Chern. 1984,49 3898. 136 Alicyclic Chemistry SO,R Scheme 18 + w .m+ Scheme 19 tion has also been in a new strategy for the synthesis of cedrene (Scheme 19).The isomeric hydrocarbon clovene has been prepared'38 by application of the a-alkynone cyclization reaction (Scheme 20). The highly strained (247 kJ mol-' calculated) 1,7-cyclobutanonorbornanesystem has been synthesized for the first time by rearrangement of the propellane (106) followed by ring contraction. As expected the ketone (107) shows extreme reluctance to enolize towards the 2-position and undergoes acid-catalysed H-D exchange only slowly at the 4-po~ition.l~~ 137 M. Horton and G. Pattenden J. Chem. SOC.,Perkin Trans. I 1984 811. 138 J. Ackroyd M. Karpf and A. S. Dreiding Helv. Chim. Acta 1984 67 1963. 139 P. E. Eaton P. G. Jobe and I. D. Reingold J. Am. Chem. SOC., 1984 106 6437. 178 S. A. Matlin X-Ray studies have established that the double bond in norbornenes is not planar but bent towards the endo-face.Ia Two propellatrienones (109) and (1lo) have been prepared in nine steps from the diester (108) and their ring inversion dynamics studied by n.m.r.These studies led to the conclusion that energy barriers are not high enough to provide for the possibility of optical resol~tions.'~~ Conformational equilibria in perhydrophenalene isomers142 and in polyspirane (111)143 have also been examined and cascade rearrangements of the polyspiranes continue to be studied.14 0 C0,Me 140 A. A. Pinkerton D. Schwarzenbach J.-L. Birbaurn P.-A. Carrupt L. Schwager and P. Vogel Helv. Chim Actu 1984,67 1136. 141 H. Jendralla C. W. Doecke and L. A.Paquette J. Chem SOC Chem Commun 1984,942. 142 J. L. M. Dillen J. Org. Chem 1984,49 3800. 143 L. J. Fitjer U. Klages W. Kuhn D. S. Stephenson G. Binsch M. Noltemeyer E. Egert and G. M. Sheldrick Tetrahedron 1984 40,4337. 144 L. J. Fitjer D. Wehle M. Noltemeyer E. Egert and G. M. Sheldrick Chem Ber. 1984 117 203; L. J. Fitjer W. Kuhn U. Klages E. Egert W. Clcgg N. Schormann and G. M. Sheldrick ibid p. 3075. Alicyclic Chemistry 179 Dimerization of the strained olefin (1 12) takes place at room temperature in DMF and furnishes the 'superphane' (1 13).14' The homologous polyene (1 14) has also been prepared.'& All-cis-[5.5.5.5]fenestrane,containing a planoid tetraco-ordinate carbon atom has been ~ynthesized'~~ by two routes (Scheme 21) as well as the first derivative (115) of [4.4.4.5]fene~trane.'~~ Semi-empirical calculations predict orthogonene (1 16) to be an olefin with an orthogonal ground-state structure having singlet and triplet states close in energy.'49 0 Scheme 21 (1 17) The first synthesis of homoiceane (117) uses a homo-Diels-Alder reaction to assemble the frarnew~rk.'~' The intramolecular Diels- Alder reaction has been reviewed'" and applications demonstrated in the synthesis of a variety of polycyclic including anthra~yclines'~~ and atisane.lS4 145 K.B. Wiberg M. G. Matturro P.J. Okarma and M. E. Jason J. Am. Chem. SOC.,1984 106 2194; K. B. Wiberg R.D. Adams P. J. Okarma M. G. Matturro and B. Segmuller ibid. p. 2200. 146 J. E. McMurry G.J. Haley J. R.Matz J. C. Clardy G. Van Duyne R. Gleiter W. Schafer and D. H. White J. Am. Chem. SOC.,1984 106 5018. 147 M. Luyten and R.Keese Angew. Chem. Int. End. EngL 1984,23,390; Helv. Chin Actq 1984,67 2242. 148 V. B. Rao S. Wolff and W. C. Agosta J. Chem. SOC Chem. Commun. 1984 293. 149 D. A. Jeffrey and W. F. Maier Tetrahedron 1984 40,2799. 150 R. Yamaguchi M. Ban and M. Kawanisi J. Chem. SOC.,Chem. Commun. 1984 826. 151 A. G. Fallis Can. J. Chem. 1984 62 183. 152 G. Gallacher A. S. Ng S. K. Attah-Poku K. Antczak S. J. Alward 3. F. Kingston and A. G. Fallis Can. J. Chem. 1984 62 1709; B. M. Trost M. Lautens M.-H. Hung and C. S. Carmichael J. Am. Chem. SOC.,1984 106 7641. 153 J. Tamariz and P. Vogel Angew. Chem. Int. Ed. Engl.1984 23 74. 154 M. Ihara M. Toyota. K. Fukumoto T. Kametani and T. Honda J. Chem. Res. (S) 1984 252. 180 S. A. Matlin New approaches to the taxane carbon skeleton have been devel~ped'~~ and two are shown in Scheme 22. (Ref156) OH (Ref 157) Scheme 22 A polyene cyclization route to the androstane skeleton has been as well as intramolecular Diels- Alder routes to steroid^"^ and multi-step syntheses of gibberellic acid'60 and quassinoids161 have been developed. Antitumour sesquiter- penes such as quadrone (1 18) and coriolin16* continue to excite interest following 155 H. Nagaoka K. Ohsawa T. Takata and Y. Yamada Tetrahedron Letr. 1984 25 5389. 156 P. A. Brown P. R. Jenkins J. Fawcett and D. R. Russell J. Chem. SOC.,Chem.Commun.. 1984 253; see also K. Sakan and D. A. Smith Tetrahedron Lett. 1984 25 2081. 157 H. Neh S. Blechert W. Schnick and M. Jansen Angew. Chem. Znt. Ed. Engl. 1984 23 905. 158 J. R. Hwu and E. J. Leopold J. Chem. SOC.,Chem Commun. 1984 721. 159 M. E. Jung and K. M. Halweg Tetrahedron Lett. 1984 25 2121; G. Stork G. Clark and T. Waller ibid. p. 5367. 160 J. M. Hook,L. N. Mander. and R. Urech J. Org. Chem.. 1984 49 3250. 161 P.A. Grieco H. L. Sham J. Inanaga H. Kim and P. A. Tuthill J. Chem. SOC.,Chem. Commun. 1984 1345; D. G. Batt N. Takamura and B. Ganem J. Am. Chem. SOC.,1984,106,3353; G. Vidari. S. Femno and P.A. Grieco ibid. p. 3539. 162 M. Demuth P. Ritterskamp and K. Schaffner Helu. Chim Acra 1984,67,2023; S. Knapp A. F. Trope, M.S. Theodore N. Hirata and J. J. Barchi J. Org. Chem. 1984 49 608; T. Ito N. Tomiyoshi K. Nakamura S. Azuma M. Izawa F. Maruyama M.Yanagiya H.Shirahama and T. Matsumoto Tetrahedron 1984 40 241; P. F. Schuda and M. R. Heimann ibid. p. 2365. Alicyclic Chemistry 181 on from last year's reports of synthetic strategie~,'~~ new details of synthetic approaches to both compounds have appeared and the absolute configuration of the natural (-)-quadrone is now established as (1 18).'@ Among numerous reports dealing with routes to triq~inanes,'~' two groups'66 have independently described the transannular cyclization of a bicyclo[6.3.0]un- decane derivative as a method for constructing the ring system of pentalenene (120; Scheme 23).The related pentalenolactones have been appr~ached'~' through intramolecular carbenoid insertion in the diazoester (121). ' BF JU H' & OCOH Scheme 23 0 (121) The heat of formation of dodecahedrane is predicted'68 to be -20.9 kJ mol-' by ab initio MO calculations. A better synthesis of peristylane and as yet unsuccessful attempts to roof it to form dodecahedrane have been de~cribed.'~~ I63 S. A. Math Annu. Rep. hog. Chem. Sect. B 1983 83 189. 164 S. D. Burke C. W. Murtiashaw J. 0. Saunders J. A. Oplinger and M. S. Dike J. Am. Chem. Soc. 1984 106 4558; K. Cooper and G. Pattenden J. Chem. SOC.,Perkin Trans. 1 1984 799; A. B. Smith and J. P. Konopelski J. Org. Chem. 1984 49 4094; K. Kon K. Ito and S. Isoe Tetrahedron Lett. 1984 25 3739.I65 M. Dorsch V. Jager and W. Sponlein Angew. Chem. Int. Ed. Engl. 1984 23 798; S. J. Alward and A. G. Fallis Can. J. Chem. 1984 62 121; H. A. Patel and J. B. Stothers ibid. p. 1926; L. A. Paquette and K. E. Stevens ibid. p. 2415; B. A. Dawson A. K. Ghosh J. L. Jurlina A. J. Ragauskas and J. B. Stothers ibid. p. 2521; E.Carceller M.L. Garcia A. Moyano and F. Serratosa J. Chem. Soc. Chem. Commun. 1984 825; Y. Tobe S. Yamashita T. Yamashita K. Kakiuchi and Y. Odaira ibid. p. 1259; G. Mehta D. S. Reddy and A. V. Reddy Tetrahedron Lett. 1984,25,2275; D. Wilkening and B. P. Mundy ibid. p. 4619. 166 G. Pattenden and S. J. Teague Tetrahedron Lett. 1984 25 3021; G. Mehta and K. S. Rao' ibid. p. 3481; see also J. L. Jurlina H. A. Patel and J.B. Stothers Can. J. Chem. 1984 62 1159; E. Piers and V. Karunaratne J. Chem. SOC., Chem. Commun. 1984 959. 167 D. E. Cane and P. J. Thomas. J. Am. Chem SOC..1984. 106. 5295. 168 J. M. Schulrnan and R. L. Disch J. Am. Chem. SOC.,1984 106 1202. 169 P. E. Eaton A. Srikrishna and F. Uggeri J. Org. Chem. 1984,49 1728; P. E. Eaton W. H Bunnelle and P. Engel Can. J. Chem. 1984 62 2612.