988 J. Am. Chem. SOC. zyxwvu 1985, 107, 988-995 Electrophilic Cleavage of Cyclopropanes. Acetolysis of Alkylcyclopropanes Kenneth B. Wiberg* and Steven R. Kass Contribution from the Department zyxwvu of Chemistry, Yale University, New Haven, Connecticut 0651 1. Received June 14, 1984 Abstract: The solvent kinetic hydrogen isotope effect showed that proton transfer is at least partially rate determining for the acetolysis of cyclopropanes which span a range of 1Olo in reactivity. The energies and structures of protonated cyclobutanes were calculated and provide an explanation for the large difference in reactivity between cyclopropanesand cyclobutanes despite their similarity in enthalpies of reaction. The rates and products of acetolysis of a series of alkyl-substituted cyclopropanes were examined. The data, along with the results of ab initio calculations, indicate that for alkyl-substituted cyclopropanes, the protonated species is highly unsymmetrical. Cleavage of the cyclopropanering always occurs so that the nucleophile becomes attached to the most substituted carbon, but the proton may attack either of the remaining carbons. Proton attack may lead to either retention or inversion of configuration depending on the orientation of the attacking proton with respect to the ring. The electrophilic cleavage of cyclopropanes has received con- siderable ~tudy.l-~O The stereochemistry and products of the ring (1) DePuy, C. H. Fortsch. Chem. Forsch. zyxwvutsrq 1973,40, 74; Arc. Chem. Res. 1968, 1, 33. (2) (a) DePuy, C. H.; Breitbeil, F. W.; DeBruin, K. R. J. Am. Chem. SOC. 1966, 88, 3347. (b) DePuy, C. H.; Arney, W. C., Jr.; Gibson, D. H. Ibid. 1968,90, 1830. (c) DeBoer, A,; DePuy, C. H. Ibid. 1970,92, 4008. (d) DePuy, C. H.; McGirk, R. H. Ibid. 1973, 95, 2366. (e) DePuy, C. H.; Andrist, A. H.; Funfschilling, P. C. Ibid. 1974,96, 948. (f) DePuy, C. H.; McGirk, R. H. Ibid. 1974,96, 1121. zyxwvutsrqpo (9) DePuy, C. H.; Klein, R. A,; Clark, J. P. zyxwvutsrqponml J. Org. Chem. 1974,39,483. (h) DePuy, C. H.; Van Lanen, R. T. Ibid. 1974,39, 3360. (i) DePuy, C. H.; Funfschilling, P. C.; Andrist, A. H.; Olson, J. M. J. Am. Chem. SOC. 1977,99, 6297. (3) (a) LaLonde, R T.; Forney, L. S. J. Am. Chem. SOC. 1963,85, 3767. (b) LaLonde, R. T.; Tobais, M. A. Ibid. 1963, 85, 3771. (c) LaLonde, R. T.; Batelka, J . J. Tetrahedron Lett. 1964, 445. (d) LaLonde, R. T.; Tobias, M. A. J. Am. Chem. SOC. 1964,86, 4068. (e) LaLonde, R. T.; Forney, L. S. J. Org. Chem. 1964,29,2911. (f) LaLonde, R. T. J. Am. Chem. zyxwvutsr Soc. 1965, 87, 4217. (g) LaLonde, R. T.; Ding, J.; Tobias, M. A. Ibid. 1967,89, 6651. (h) LaLonde. R. T.: Debboli. A. D.. Jr. J. Ow. Chem. 1970. 35. 2657. (i) LaLonde, R. T.; Ferrara, P.; Debboli, A. Ibid. i972,37, 1094: 0) LaLondk R. T.; Ding, J.-Y. Ibid. 1972,37, 2555. (4) Baird, R. L.; Aboderin, A. A. Tetrahedron Left. 1963,235; J. Am. Chem. SOC. 1964,86, 252, 2300. (5) Boikess. R. S.: MacKav. M. J. Ora. Chem. 1971, 36, 901. (6) Cristol, S. J.; Lim, W. Y.; Dahl, A : R. J. Am. Chem. SOC. 1970,92, (7) Collum, D. C.; Mohamadi, F.; Hallock, J. S. J. Am. Chem. SOC. 1983, (8) Dauben, W. G.; Wipke, W. T. Pure Appl. Chem. 1964,9, 539. (9) Deno, N. C.; Lincoln, D. N. J. Am. Chem. SOC. 1966,88, 5357. Deno, N. C.; LaVietes, D.; Mockus, J.; Scholl, P. C. Ibid. 1968,90, 6457. Deno, N. C.; Billups, W. E.; LaVietes, D.; Scholl, P. C.; Schneider, S. Ibid. 1970, 92, 3700. (10) Gassman, P. G.; Proehl, G. S., J. Am. Chem. SOC. 1980,102,6862. (11) Hammons, J. H.; Probasco, E. K.; Sanders, L. A,; Whalen, E. J. J. (12) Hart, H.; Schlosberg, R. H. J. Am. Chem. SOC. 1966,88,5030; 1968, (13) Hendrickson, J. B.; Boeckman, R. K., Jr. J. Am. Chem. SOC. 1969, (14) Hogeveen, H.; Roobeck, C. F.; Vogler, H. C. Tetrahedron Lett. 1972, (15) Jensen, F. R.; Patterson, D. B.; Dinizo, S. E. Tetrahedron Lett. 1974, (16) Lambert, J. B.; Black, R. D.; Shaw, J. H.; PuPay, J. J. J. Org. Chem. (17) Lawrence, C. D.; Tipper, C. F. H. J. Chem. SOC. 1955, 713. (18) Levina, R. Y.; Kostin, B. N.; Ustynyuk, T. K. Zh. Oschch. Khim. 1960,30, 359. (19) (a) McKinney, M. A,; Smith, S. H.; Hempelman, S.; Gearan, M. M.; Pearson, L. Tetrahedron Lett. 1971, 3657. (b) McKinney, M. A.; So, E. C. J. Org. Chem. 1972,37, 2818. (20) McManus, L. D.; Rogers, W. A. Tetrahedron Lett. 1969, 4735. (21) Moore, W. R.; Taylor, K. G.; Muller, P.; Hail, S. S.; Gaibel, 2. L. F. Tetrahedron Lett. 1970, 2365. (22) Nickon, A,; Lambert, J. L.; Williams, R. zyxwvutsrqp 0.; Werstiuk, N. H. J. Am. Chem. SOC. 1966,88, 3354. Nickon, A.; Frank, J. J.; Covey, D. F.; Lin, Y. J. Am. Chem. SOC. 1974, 96, 7574. Nickon, A,; Covey, D. F.; Pandit, G. D.; Frank, J. J. Tetrahedron Lett. 1975, 3681. Nickon, A,; Frank, J. J. Ibid. 1975, 4335. 4013. 105, 6882. Org. Chem. 1968,33, 4493. 90, 5189. Hart, H.; Levitt, G. J. Org. Chem. 1959,24, 1261. 91, 3269. 221. 1315. 1970,35, 3214. 0002-7863/85/1507-0988$01.50/0 opening of simple cyclopropanes,2~4~9J2J7Jg~24 b i ~ y ~ l i ~ ~ ~ ~ ~ and polycyclic cyclopropanes,10J'~'3~14~20~2s~29~30 cyclopropanols,2s22 and cyclopropyl methyl ethers2have been examined. The cleavages of these compounds by mercuric acetate2s7s15*23 and by halog- e n ~ ~ , ~ * ~ ~ , ~ ~ , ~ ~ , ~ ~ also have been studied. However, relatively few kinetic investigations of the solvolytic cleavage of cyclopropanes have been reported,19*2s,29*32 and questions still remain concerning the structures of the intermediates and the reasons for the variation in stereochemical results. Our interest in the subject has led us to carry out kinetic, tracer, and theoretical investigations of the acetolysis of a variety of cyclopropanes. The results obtained in studying simple alkyl-substituted cyclopropanes are reported herein, and the investigation of bicyclic cyclopropanes will be reported in the following paper. One might think that the enhanced reactivity of cyclopropanes over cyclopentane and similar hydrocarbons should be related to the strain energy which raises the energy of the C-C bonds and may make them more reactive. In this connection, it is interesting to note the difference in reactivity between cyclopropanes and cyclobutanes. The enthalpies of some possible reactions in the gas phase are given below in kilocal~ries/mole:~~ (23) (a) Oulette, R. J.; South, A,, Jr.; Shaw, D. L. J. Am. Chem. SOC. 1965, 87, 2602. (b) Ouellette, R. J.; Robins, R. D.; South, A,, Jr. Ibid. 1968, 90, 1619. (c) Ouellette, R. J.; Miller, A,; South, A., Jr.; Robins, R. D. Ibid. 1969,91, 971. (d) Ouellette, R. J.; Williams, S. J. Org. Chem. 1970,35, 3210. (24) Peterson, P. E.; Thompson, G. J. Org. Chem. 1968,33, 968. (25) Reynolds, R. N. Ph.D. Thesis, University of California at Santa (26) Saba, J. A,; Fry, J. L. J. Am. Chem. SOC. 1983,105, 533. (27) Skell, P. S.; Day, J. C.;Shea, K. J. J. Am. Chem. SOC. 1976,98, 1195. (28) Turnbull, J.; Wallis, E. J. Org. Chem. 1956,21, 663. (29) Warner, P.; LaRose, R.; Schleis, T. Tetrahedron Lett. 1974, 1409. (30) Warnet, R. J.; Wheeler, D. M. S. Chem. Commun. 1971, 547. (31) Wharton, P. S.; Bair, T. I. J. Org. Chem. 1966,31, 2480. (32) Wiberg, K. B.; de Meijere, A. Tetrahedron Lett. 1969, 519. Wiberg, K. B.; Szeimies, G. J. Am. Chem. SOC. 1970,92, 571. Wiberg, K. B.; Bishop, K. C., 111, Davidson, R. B. Tetrahedron Lett. 1973, 3169. (33) Cox, J. D.; Pilcher, G. "Thermochemistry of Organic and Organo- metallic Compounds", Academic Press: London, 1970. Roth, W. R.; Klarner, F-G.; Lennartz, H.-W. Chem. Eer. 1980, 113, 1818. Barbara, 1977. Warner, P.; LaRose, R. Ibid. 1972, 2141. 0 1985 American Chemical Societv I , , -