A. Three- and Four-membered Rings BY S. A. MATLIN 1 Introduction, Theory, and Structure Since the last Report,’ the number of publications relevant to this chapter has increased by 35%. There have been numerous reviews and articles concerning aspects of the chemistry of three- and four-membered rings.2 Amongst theoretical calculations3 for these systems is included a quantum chemical study of the .n-electron delocalization in triphenylphosphonium ylides, leading to an evaluation of the criteria for reactivity and aromaticity in the Wittig reaction. It was predicted that the as yet unknown ylide (1 ; X = PPh,) will not take part in the Wittig rea~tion.~ Geometry-optimized INDO calculations on substituted cyclopropenyl cations indicate that F and NH, groups conjugate strongly with the ring whereas resonance interaction of a phenyl substituent is weak. Stronger conjugation of all three substitu- ents is seen with the cyclobutadienyl dication. In spite of the strong polarization of the carbonyl group in cyclopropenone (1: X = 0) there was very little indication of charge build-up in the ring or of aromatic character, but protonated cyclopropenone does resemble a 2.r~a romatic ~ysternC.~o mparisons of cyclopropenone with thiiren 1,l-dioxide have also been made.6 S. A. Matlin, in ‘Alicyclic Chemistry’, ed. W. Parker, Specialist Periodical Reports, The Chemical Society, London, 1975, Vol. 3, Chapter 1. D. L. Bunker, Accounts Chem Res., 1974,7, 195; D. Ginsburg, ibid., p. 286; M. Jones, jun, ibid., P. 415; E. H. White, J. D. Miano, C. J. Watkins, and E. J. Breaux Angew. Chem. Internat. Edn., 1974, 23, 22Y; W. Adam, ibid., p. 619; D. Hoppe, ibid, p. 789; W. A. Noyes, jun. and K. E. Al-ani, Chem. Rev., 1974, 74, 29; J. L. Kricka and A. Ledwith, ibid., p. 101; D. E. Pearson and C. A. Buehler, ibid., p. 45; N. L. Holy, ibid., p. 243; W. H. Flygare, ibid., p. 653; J. I. G. Cadogan and R. K. Mackie, Chem. SOC. Rev., 1974, 3, 87; S. R. Hartshorn, ibid., p. 167; J. D. Coyle, ibid., p. 329; R. C. Dougherty, Fortschr. Chem. Forsch., 1974, 45,93; F. D. Mango, ibid., p. 39; L. J. Schaad and B. A. Hess, jun., J. Chem. Educ., 1974, 640; D. Seyferth, J. Organometallic Chem., 1974, 75, 13; H. Suhr, Pure Appl. Chem., 1974, 39, 395; B. M. Mikhailov, ibid., p. 505; A, M. Glatz, Rev. Roumaine Chim., 1974, 19, 455; D. Ginsburg, Tetrahedron, 1974, 30, 1487; K. B. Wiberg and G. B. Ellison, ibid., p. 1573; J. K. Sutherland, ibid., p. 1651: P. CrabbC, ibid., p. 1979: R. M. Moriarty, Topics in Stereochem, 1974, 8, 271; V. I. Labunskaya, A. B. Shebaldova, and M. L. Khidekel, Uspekhi Khim., 1974,43, 3 (Chem. Abs., 1974, 80, 94768); J. D. Coyle, Ed. Chem., 1974, 11, 62; M. Walkowicz, Wiad. Chem., 1974, 28, 87 (Chem. Abs., 1974, 80, 145498). H.-D. Holtje, Arch. Pharm., 1974, 307, 969; S.-S. Sung, Compt. rend., 1974, 278, C, 37; R. J. Buenker and S. D. PeyerimhoK Chem. Rev., 1974,74, 127; D. Lenoir, R. E. Hall, and P. von R. Schleyer, J. Amer. Chem. SOC., 1974,96, 2138; G. A. Russell, P. R. Whittle, C. S. C. Chung, Y. Kosugi, K. Schmitt, and E. Goettert, ibid., p. 7053; J. H. McCreery and G. G. Hall, ibid., p. 7875. H. J. Lindner, Tetrahedron, 1974, 30, 1127; Tetrahedron Letters, 1974, 2479. J. M. F. van Dijk and H. M. Buck, Rec. Pav. chim., 1974.93, 155. C. U. Pittman, jun., A. Kress, T. B. Patterson, P. Walton, and L. D. Kispert, J. Org. Chem., 1974, 39, 373; C. U. Pittrnan, jun., A. Kress, and L. D. Kispert, ibid., p. 378. F. de Jong, A. J. Noorduin, T. Bouwman, and M. J. Janssen, Tetrahedron Letters, 1974, 1209. 1 B 2 AlicycZic Chemistry Using graph-theoretical technique, Hearndon and Ellzey have identified, within the Huckel MO formalism, a new class of n-structures containing even numbers of n-orbitals of which 2-cyclopropenylallyl is the smallest member. This has a closed shell of electrons according to HMO theory, but is required to have a biradical valence bond structure, and dicationic species should be ~btainable.~ From a graphical study of positional isomers containing bivalent sulphur,8 it was predicted that (2a) should be more stable than (2b). The former has been synthesized, whereas the latter is not a known compound. Following the development of the MIND0/3 method, which is considerably more successful than MIND0/2 in taking account of strain factors, the possibility of collapse of bisdehydrobenzenes (3) to bicyclic structures has been examined. The most striking conclusion was that (3a) should have a stability comparable to that of o- benzyne, and this suggests that m-benzynes may be viable reaction intermediate^.^ MIND0/3 calculations of the cycloreversion of vinylcyclobutane to ethylene and butadiene show a biradical transition state to be involved, and the cycloaddition of cyclobutadiene and acetylene, affording Dewar benzene (4), was also examined.l0 The equilibrium geometry of the latter, predicted by semi-empirical INDO calculations, was in good agreement with experimental results and the calculated dipole moment of < 0.04 D suggests that the likelihood of obtaining a microwave spectrum is marginal at best.' The calculated potential curves for the (CH),CHl system show that the cyclo- propenylcarbinyl, cyclobutenyl, and bicyclobutyl cations are surrounded by relatively low-energy barriers and that they would readily collapse to the most stable conformer, the puckered homocyclopropenyl cation (5).l The iterative maximum overlap approximation (IMOA) method is useful for the semiquantitative prediction of the geometry of hydrocarbons, and has been applied ' W. C. Hearndon and M. L. Ellzey, jun., Tetrahedron Letters, 1974, 1399. J. V. Knop, N. Trinajstic, and T. Zivkovic, Coll. Czech. Chem. Comm.. 1974, 39, 2431. ' M. J. S. Dewar and W.-K. Li, J. Amer. Chem Soc., 1974,%, 5569. lo M. J. S. Dewar, A. C. Griffin, and S. Kirschner, J. Amer. Chem Soc., 1974, 96, 6225. l1 M. D. Newton, J. M. Schulman, and M. M. Manus, J. Amer. Chem. SOC., 1974,%, 17. K. Mori and S. Masamune, Chem. Letters, 1974, 1251. Three- and Four-membered Rings 3 to several cyclopropyl and cyclobutyl derivative^.'^ An intramolecular force field for amides has been derived and used to calculate the crystal structure of cyclopro- panecarboxamide. l4 Several X-ray structure determinations of t hree-mem bered-ring compounds have been reported, including a cyclopropenium salt,’ 7-PO-substituted norcaradienes (6; X = H, C1, or Br),I6 chrysanthemic acid derivative^,'^ and 1,6:8,13-cyclopro- panylidene[ 14)annulene (7).’* The photoelectron spectrum of (7) has also been reported.lg X I Squaric acid and its derivatives continue to be the subject of detailed X-ray examina- tions.” Evidence for strong intramolecular H-bonding has been obtained.21 This is - of two types in the acid, with 0 0 distances of 2.532 and 2.544 & and whilst the acid is planar it is not square but asymmetric.22 Whereas the cyc- l-o butane rings in (8; X = 0 or S)a re planar,23t hat in (9)i s puckered, and two short Br Br distances of 3.55 A are observed in the crystal~.’P~l anarity is also seen in cis-cyclobutene-3,4-dicarboxylica cid25a nd in substituted cyclopentadi- enyl cobalt complexes of tetraphenylcyclobutadiene, in which each metal atom is sandwiched between parallel, planar f&r- and five-membered rings.26 Crystal structures have been obtained for a variety of polycyclic compounds containing cyclobutane rings.27 Photoelectron spectroscopy is a method of growing importance for structural investigation, particularly for revealing the fine details of bond interactions. Thus, l3 K. Kovacevic and Z. B. Maksic, J. Org. Chem., 1974,39, 539. l4 A. T. Hagler and S. Lifson, J. Amer. Chem. SOC.,1 974, 96, 5327; A. T. Hagler, E. Huler, and S. Lifson, ibid., p. 5319. l5 R. L. Sime and R. J. Sime, J. Amer. Chem. SOC.,1 974,96,892. l6 G. Maas, K. Fischer, and M. Regitz, Acta Cryst., 1974, B30, 1140,2853. l7 J. D. Owen, J.C.S. Chem. Comm., 1974,859; M. J. Begley, L. Crombie, J. D. Simmonds, and D. A. Whiting, J.C.S. Perkin I, 1914, 1230. l8 A. Mugnoli and M. Simonetta, Acta Cryst., 1974, B30, 2896. l9 C. Batich, E. Heilbronner, and E. Vogel, Helu. Chim. Acta, 1974, 57, 2288. 2o H. J. Lindner and B. von Gross, Chem. Ber., 1974, ICn, 598; F. J. Hollander and D. Coucouvanis, J. Amer. Chem SOC.,1 974,%, 5646. Y. Wang and G. D. Stucky, J.C.S. Perkin II, 1974,925. 22 Y. Wang, G. D. Stucky, and J. M. Williams, J.C.S. Perkin 11, 1974, 35. 23 C. D. Shirrell and D. E. Williams, Acta Cryst., 1974, B30, 245, 1974. 24 P. C. Riche, Acta Cryst., 1974, B30, 587. 25 E. Benedetti, M. R. Ciajolo, J. P. Declerq, and G. Germain, Acta Cryst., 1974, B30, 2873. ’26’ A. C. Villa, L. Coghi, A. G. Manfredotti, and C. Guastini, Acta Cryst., 1974, B30,2101. K. Yvon, Acta Cryst., 1974, B30, 1638; J. Bernstein, ibid, p. 1728; F. A. Cotton and B. A. Frenz, ibid., p. 1772; J. V. Silverton, G. W. A. Milne, P. E. Eaton, K. Nyi and G. H. Temme, tert. J. Amer. Chem. SOC., 1974, 96, 7429; Mazher-U1-Haque and D. Rogers, J.C.S. Perkin 11, 1974, 228; J. Iball and J. N. LOW,i bid., p. 1423. 4 Alicyclic Chemistry the technique has been used to demonstrate 0-0 conjugation between the C-Sn bond and cyclopropane orbitals in cyclopropylcarbinyltrimethyltin,28h yperconjuga- tion in unsaturated small rings,29a nd inductive and conjugative interactions in cyclo- prop en one^.^' In contrast to the theoretical calculations outlined above, the photo- electron spectroscopy data suggest that there is indeed some resemblance between cyclopropenone and the aromatic cyclopropenyl cation. Photoelectron spectral data indicate much weaker interactions between a four- membered ring and a n-system than between a three-membered ring and a ~r-system.~~ The photoion spectrum of cyclopropane has been measured, giving appearance potentials in good agreement with those obtained from photoelectron spectroscopy.j2 Conformational aspects of small-ring carbo~yclesh~av~e been reviewed34 and a linear combination of hybrid orbitals treatment has been applied to cyclob~tane.~~ 1.r. and n.m.r. show the gauche conformation (10a; X = H, 4 = 45 & loo) of bicyclopropyl to be more stable than the s-trans (lob) by cu. 150calmol-’~36b ut the rotation angle (4) is considerably increased in rneso-2,2,2’,2’-tetrahalogenobicyclo- propyls (10a; X = C1 or Br, d, = 166°).37 X H 7 ** R. S. Brown, D. F. Eaton, A. Hosomi, T. G. Traylor, and J. M. Wright, J. Orgummetallic Chem., 1974, 66, 249. 29 R. A. Wielesek and T. Koenig, Tetrahedron Letters, 1974, 2429. 30 W. Schafer, A. Schweig G. Maier, T. Syrac, and J. K. Crandall, Tetrahedron Letters, 1974, 1213, 31 R. Bruckmann and M. Klessinger, Chem. Ber., 1974,107,1108 ; H.-D. Martin, S. Kagabu, and R. Schwes- inger; ibid., p. 3130; P. Bischof, R. Gleiter, A. de Meijere, and L.-U. Meyer, Helv. Chim. Actu, 1974, 57 1519 32 R. Kraessig D. Reinke, and H. Baumgaertel, Ber. Bunsengesellschajt phys. Chem., 1974,78, 425. 33 L. Radom. J. Paviot, J. A. Pople, and P. von R. Schleyer, J.C.S. Chem. Comm., 1974, 58; R. L. Cook and T. B. Malloy. iun., J. Amer. Chem SOC., 1974, 96. 1703; B. A. Arbuzov, G. G. Butenko, A. N. Vereshchagn, and N. A. Shishkina, Izvest. Akad. Nauk. S.S.S.R., Ser. khim., 1974, 313 (Chem. Abs., 1974, 81, 37 151). 34 F. A. Cotton and B. A. Frenz, Tetrahedron, 1974, 30, 1587. J. A. Pople, ihid., p. 1605. 35 A. Y. Meyer and R. Pasternak, Theor. Chim. Acta, 1974,33, 215. 36 A. de Meijere, W. Luttke, and F. Heinrich, Annalen, 1974, 306. 37 M. J. Aroney, K. E. Calderbank, and H. J. Stootman, Austral. J. Chem., 1974, 27, 1563. Three- and Four-membered Rings 5 Optical activity in high-symmetry chiral molecules has been di~cussed*, ~an d the importance of the role of conformational dissymmetry emphasized by comparison of allenes md spir0[3,3]heptanes.~’ Baboulhe and Sturtz have discussed the relation- ship between stereochemistry and pharmacological activity in l-aminomethyl-2- benzoylcyc lopropanes. 40 Included in reports of thermochemical studies4’ are estimates of the heats of forma- tion and strain energies of the azoalkenes (11) and (12)42 and hydrocarbon (13).43 The conversion of the azoalkenes into bicyclo[n, 2, Ofalkanes is now suggested to be much less exothermic than previously estimated. 2 Synthesis of Three-membered Rings Condensation Reactions.-Trost44 has reviewed the preparation and synthetic uses of cyclopropyldiphenylsulphonium ylides. The regioselectivity and chemospecificity of the cyclopentane and cyclopentenone annelation reactions have been examined.45 Whereas diphenylsulphonium methylide does not cyclopropanate simple, un- activated olefins such as tetramethylethylene, transfer of a methylene group from the ylide can be effected stereospecifically in the presence of a copper catalyst46 and this reaction may provide a model for biological cyclopropanations by the ylide derived from S-adenosyl-methionine. Attempts to catalyse a similar transfer to unactivated olefins using PdCl, were not su~cessful.~~ The ylide (14), stabilized by both sulphonium and phosphinyl substituents, has been prepared48 and reacts with Michael acceptors to give phosphonocyclopropanes. The same cyclopropane (15 ) results from addition to both maleate and fumarate, implicating the betaine (16) as a common intermediate. As reported earlier by Trost, racemization of chiral sulphonium ylides inhibits their utility for asymmetric cyclopropanations. The rates of racemization of a series of sulphonium acylylide derivatives have now been measured and their ease of racemiza- 38 M. Farina and C. Morandi, Tetrahedron, 1974,30,1819. 39 H. Wynberg and L. A. Hulshof, Tetrahedron, 1974,30, 1775. 40 M. Baboulhe and G. Sturtz, Bull. SOC.c him. France, 1974,2929. 41 S. M. Pimenova, L. Fogel, M. P. Kozina, and G. L. Gal’chenko, Zhwr. obshchei Khim., 1974,44,1383 (Chem. Abs., 1974, 81, 62983); R. M. Varushchenko, A. I. Druzhinina, 0. Y. Kovner, E. M. Mil’vitskaya, A. A. Bobyleve, N. A. Belinkova, and G. L. Galchenko, Zhur. fiz. Khim., 1974, 48, 1886 (Chem. Abs., 1974, 81, 119 646). 42 P. S. Engel, J. L. Wood, J. A. Sweet, and J. L. Margrave, J. Amer. Chem. SOC., 1974, 96, 2381. 43 E. Osawa, P. von R. Schleyer, L. W. K. Chang, and V. V. Kane, Tetrahedron Letters, 1974, 4189. 44 B. M. Trost, Accounts Chem. Res., 1974, 7, 85. 45 B. M. Trost and S. Kurozumi, Tetrahedron Letters, 1974, 1929. 46 T. Cohen, G. Herman, T. M. Chapman, and D. Kuhn, J. Amer. Chem. SOC., 1974,96, 5627. 47 P. Bravo, G. Fronza, C. Ticozzi, and G. Gaudiano, J. Organometallic Chem., 1974,74, 143. ‘’ K. Kondo, Y. Liu, and D. Tunemoto, J.C.S. Perkin I, 1974, 1279. 6 Alicyclic Chemistry H C0,Me 0 2 b y Me 0 0 Me’ \+S -CH- -P(OTE t), Me MMee’ \ g-CHI- P t (OEt), (14) CH-C0,Me I P (0E t j2 J- -CH-C0,Me 0 (16) (15) tion and reduced nucleophilicity compared with simple sulphonium ylides noted. It seems that chiral sulphonium ylides will serve as useful asymmetric transfer reagents only when significant free-energy differences exist between diastereomeric transition states.49 Condensation of the enol ethers of P-dicarbonyl compounds with dimethylsul- phonium methylide generally takes place by attack on the carbonyl group, leading to furans. However, enol ethers derived from P-keto-aldehydes are attacked first at the double bond to give cyclopr~panesT.~he~s e further react at the carbonyl group, the resulting cyclopropyl epoxides rearranging to dihydropyrans (Scheme 1). Scheme 1 Tropone is cyclopropanated in good yield at the 2,3-double bond with phenacyl dimethylsulphonium ~lide.~ A number of cyclopropyl ketones have been prepared by reaction of ap-unsaturated ketones with dimethylsulphoxonium methylide. With the aid of kinetic results, the principal factors governing the reactivity and stereochemistry of the cyclopropanes were analysed. From both cis and trans acyclic enones, only E-cyclopropyl ketones were isolated, the trans-isomer reacting much faster than the cis and the products being formed via conformationally equilibrating zwitterionic intermediates. It was noted that much less stereoselectivity was observed when the acyl group of the enone was replaced by a CN function. With conjugated cyclohexenones, the conformational changes in the intermediates are suppressed so that epimerizations are not observed. The stereochemistries of the cyclopropyl ketones formed then reflect the direction of attack of the ylide on the ring, with axial attack at C-3 of the enone being favoured in the absence of steric effects.52 The condensation of dimethylsulphoxonium methylide with ethylenic ketones53 49 S. J. Campbell and D. Darwish, Canad. J. Chem., 1974,52,2953. 50 C. M. Harris, J. J. Cleary, and T. M. Harris, J. Org. Chem., 1974,39, 72. 51 N. Soma, H. Takagi, and M. Sugimura, Japan P. 7343737 (Chem. Abs., 1974,81,13 181). 52 F. Roquet and A. Sevin, Bull. SOC.c him. France, 1974,881,888. 53 J. A. Donnelly, S. O’Brien, and J. OGrady, J.C.S. Perkin I, 1974, 1674; E. J. Cragoe jun. and 0. W. Wolters- dorf, Ger. Offen., 2351411 (Chem Abs., 1974, 81, 13323). Three- and Four-membered Rings 7 may be successful when other methods, such as the Simmons-Smith procedure, fail, as for example in the reaction with pyridyl styryl ketones which gives trans-cyclo- propanes in moderate to good yields.54 Attack occurs exclusively at the least substituted double bond of the seven-membered ring in the cyclohepta[clthiophens (17; R = H or Me), and similar specificity is seen with the cyclohepta[b]thiophens (18a) and (18b). Compound (19) affords a mixture of two products. P Me,S=CH, 1 0 f Me, S=CH Phenalenone (20; R = H) did not give the expected cyclopropylketone (21; R = H) on reaction56w ith dimethylsulphoxonium methylide, attack at the 9-position instead generating the betaine (22), which collapsed to 9-methylphenalenone (20; R = Me). However, treatment of the latter gave the cyclopropane (21 ; R = Me). Steric effects on the formation of 6,7-methano-steroids from steroidal 4,6-dien-3- ones have been examined.57T he results (Scheme 2) show that the reaction is governed by steric approach control, as axial attack from the least hindered side would give 54 M. Coussac, A. Boucherle, and J.-L.P ierre, Buil. SOC.c him. France, 1974, 1442. 55 R. Guilard and B. Hanquet, Compt. rend., 1974,278, C, 295. 56 R. M. Pagni and C. R. Watson, jun., J.C.S. Chem. Comm., 1974,224. 5’ G. E. Arth, G. F. Reynolds, and G. H. Rasmusson, Tetrahedron Letters, 1974. 291 6 8 Alicycli”c Chemistry &R &R \ CH,, SM+ e2 ‘\ / ‘\ / / / a-cyclopropanation. Van der Waals attractive forces of the lop methyl group are probably not involved, as the rates are A, B > C, D, F > E, indicating a rate-retarding effect of the lop and llp substituents. The most likely explanation is that the initial step of ylide addition to the dienone is reversible and axial (a) attack is preferred. However, the second step is subject to secondary steric interactions caused by tor- sional changes in forming the final ring system, and it appears that ring-closure to form ct-methylene adducts with a lop methyl substituent is inhibited by diaxial inter- actions involving the functions at Sp, lop, and 11 p. In the case of the 19-nor-dienes A and B these interactions are minimized,. and .product formation is governed by the concentration of the most rapidly formed a-intermediate. Both cis- and trans-1,2-diphenylcyclopropanes, on treatment with DMSO-, afford exclusively the trans-cyclopropane after work-up, which is taken as evidence that cyclopropanes are not intermediates in the alkylation of activated double bonds with DMSO-.’* Y R X Y c1 :p A H H P-OAC 90: 10 B H H CH,O(CH2)3 90: 10 C Me H P-OAC 40: 60 D Me H CHzO(CHJ3 40: 60 E Me P-OH CH20(CH2), < 5:95 F Me 0 CHz0(CH2)3 50: 50 Scheme 2 Further details have appeared of the condensation of the dimethylsulphoxonium ylide (23; R = H or Me) with ap-unsaturated carbonyl cornp~unds,~w’h ich were discussed in an earlier Report.’ In the attempted alkylation of the ylide (24) with phenacyl bromide the ylide functions solely as a base, trans-1,2,3-tribenzoylcyclo- propane being the sole product formed in high yield.60 58 B. G. James and G. Pattenden, J.C.S. Perkin I, 1974, 1204. s9 Y. Tamura, T. Miyamoto, H. Kiyokawa, and Y. Kita, J.C.S. Perkin I, 1974, 1125. B. Koutek, L. Pavlickova. and M. Soucek, CoIl. Czech. Chem. Comm., 1974,39, 192. Three- and Four-membered Rings 9 II CCOOPPhh MeS0,-C 'R k ! M e02 \ Cyclopropanes are formed in the condensation of epoxides with ylides derived from phosphonates.6' Attempts to carrj' out similar reactions with phosphonium ylides were generally unsuccessful, an exception being the reaction of the phosphonium halide (25)w ith oxiran.62 The bis-ylide (26) is alkylated by dibromoacetone and in the presence of excess ylide the initial product cyclizes, providing a route to cyclopropyl ketones.63 - A0 0 0 Ar,P -A P A r 3 + Ar3P'Ar3 cpAr;261 Br Br (26) PAr, Br BF The condensation of stabilized carbanions with epoxide~a,c~t~iv ated ole fin^,^^ or alkanes bearing a good leaving group to a second good leaving group,66 or a carbanion-stabilizing f~nction,~pr'o vides a general series of routes to cyclopropanes. In the reaction of the phosphonate (27) with methacrylate in the presence of sodium hydride, a mixture of cis- and trans-isomers of the phosphonate-substituted cyclo- propane (28) was obtained in all solvents examined. A plot of the logarithm of the translcis ratio against the Kirkwood-Onsager term for solvent polarity gave a straight 61 M. Baboulhe and G. Sturtz, Bull. Sac. chim. France, 1974,1585; Fr. Demande, 2 168 947 (Chem. Abs., 1974, 80,47 531). 62 J. Buddrus, Chem. Ber., 1974,107,2050. 63 A. Hercouet and M. Le Corre, Tetrahedron Letters, 1974,2491. 64 S. Nogami, K. Waki, and K. Toymoto, Japan Kokai, 74 11867 (Chem. Abs., 1974,81, 49338); H. Cousse and G. Mouzin, Ger. Offen., 2351 729 (Chem. Abs., 1974, 81, 13 173). 6s C. F. Hobbs and H. Weingarten, J. Org. Chem., 1974,39,918; J. Villieras, J.-R. Disnar, and J.-F. Normant, J. Organometallic Chem., 1974,81,295; T. Oishi, H. Takechi, and Y. Ban, Tetrahedron Letters, 1974,3757; J. D. Bacha and C. M. Selwitz, U.S.P. 3769356 (Chem. Ah., 1974,80, 3 160); L. H. Shepherd jun., U.S.P. 3770840 (Chem. Abs., 1974, SO, 14640); R. H. Rynbrandt, U.S.P. 3770747 (Chem. Abs., 1974, SO, 59557); W. I. Fanta and J. I. Shulman, U.S.P. 3823177 (Chem. Abs., 1974,81, 77562). 66 J. D. Bacha and C. M. Selwitz, U.S.P. 3769357 (Chem. Abs., 1974,80,3163). 10 Alicyclic Chemistry line, with the slope being the inverse of that found in nearly all similar cases pre- viously reported, i.e. the cis-isomer predominates in polar solvents and the trans in non-polar media. This inversion of the solvcnt-isomer ratio relationship was seen as a consequence of the presence of the polar, activating phosphonate group68a nd the result is consistent with the general concept of sterochemical control by transition- state dipole-solvent interactions proposed by Inouye. It should be noted, however, that the assignment of configuration to the cyclopropanes was based essentially on n.m.r. evidence, and a rigorous examination of product geometries is clearly important in a case of this type. - 0 t + C0,Me ClCH,---P(OMe), (27) The kinetically controlled product of condensation of t-butyl isocyanide with acetylene dicarboxylic ester has been shown to have the bicyclobutane structure (29).69 C0,Me C0,Me C0,Me Me0co,2C& C. // NB u‘ Intramolecular Cyc1izations.-Theoretical calculations have been reported for the conversion of 1,3-disubstituted propanes into cyclopr~panes.M~~et al-promoted eliminations in 1,3-dihaIogenoalkanes afford cyclopropanes, generally in good yields. The trans- 1,2-dipropylcyclopropane formed in the Li(Hg)-induced debromination of R,R-4,7-dibromononane is generated with inversion of configuration at both centres. This stereochemical result rules out the possibility that the popular ‘.rc-cyclo- propane’ takes part as an intermediate, and suggests a process in which metal- halogen exchange is followed by an internal displacement of the second halide The stereoconvergence observed in such cyclization reactions73( i.e.f ormation of the 67 Z. Csuros, R. Soos, E. Fogassy, J. Palinkas, and G. Hernandi, Hung. Teljes, 8014 (Chem. Abs., 1974, 81, 37 316). 68 E. W. Hellmuth, J. A. Kaczynski J. Low, and L. I. McCoy, J. Org. Chem., 1974,39, 3125. 69 H. J. Dillinger, G. Fengler, D. Schumann, and E. Winterfeld, Tetrahedron, 1974,30,2553; see also p. 2561. ’O 0. S. Tee, J. A. Altmann, and K Yates, J. Amer. Chem. SOC., 1974,%, 3141. 71 Y. Ito, K. Nakayama, K. Yonezawa, and T. Saegusa, J. Org. Chem., 1974,39,3273;A . A. Kamyshova, E. T. Chukovskaya, and R. K. Friedlina, Izuest. Akad. Nauk, S.S.S.R., Ser. khim., 1974,896 (Chem Abs., 1974,81, 37279); S. Takahashi, Y. Suzuki, and N. Hagihara, Chem. Letters, 1974, 1363. 72 M. Schlosser and G. Fouquet, Chem. Ber., 1974, 107, 1162. 73 M. Schlosser and G. Fouquet, Chem. Ber., 1974, 107, 1171.