In recent investigations1 we have had the objective determining whether the rate of azomethine ylide formation from aziridines could be increased to a level that it would be compatible with the mild conditions demanded by click chemistry. A comprehensive computational study of the effect of substituents at the MP2(Full)/6-311++G(d,p)// MP2(Full)/6-31+G(d) was undertaken. Integral to this research effort has been the a study of the torquoselectivity1 when diminished symmetry of the substituted aziridine gives rise to two possible modes of conrotatory rotation; i.e., the substituent or a specified substituent rotates either inward or outward. In virtually all cases a preference for outward rotation was determined with certain substituents exhibiting a preference that exceeded 10 kcal mol-1. The effects of charge development in the dipolar transition state as well as the importance of frontier molecular orbital considerations have been considered in rationalizing the findings.(1) Banks, H.D. Abstracts of Papers, 237th ACS National Meeting, Salt Lake City, UT, March 23, 2009.(2) Torquoselectivity has been studied by Houk and coworkers for the related isoelectronic cyclobutenes and 1,2-dihydroazete. See, for example (a) Rondan, N.G.; Houk, K.N. J. Am. Chem. Soc. 1985, 107, 2099. (b) Dolbier, Jr., W.R.; Koroniak, H.; Houk, K.N.; Shue, C. Acc. Chem. Res. 1996, 29, 471. (c) Walker, M.J.; Wietbrink, B.N.; Thomas IV, B.E.; Nakamura, K.; Kallel, E.A.; Houk, K.N., J. Org. Chem. 2001, 66, 6669.

Torquoselectivity in the thermal conrotatory cleavage of substituted aziridines

239th National Meeting (2010)

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