Abstract
Heteroconjugate addition of carbon nucleophile to unsaturated sulfones is known to result in C-C bond formation. This concept was extended to utilize the carbanion intermediate for epoxide opening to end up with the formation of cyclobutane ring with stereochemical control. Study of the vinyl sulfone system indicates that the relative stereochemistry of epoxide (syn-/anti-) to the sulfonyl group is important for the cyclization step. In the limited case of compound 65a, the epoxide situated anti to the sulfone-stabilized carbanion intermediate, which led us to obtain the cyclobutane compound 64 in regio- and stereoselective manner. Not only the Brook rearrangement, in which the silly group migration from carbon to oxygen atom was obtained as the compound 59a, but also Payne rearrangement took place to give compound 59b and 59c. During the course of studies, the spiro-cyclobutene 63 was coincidentally achieved in case of compound 48b, in which the epoxide was situated syn to the sulfone-stabilized carbanion. In addition, the acetylene sulfone (alkynyl sulfone) system was also investigated. Some nucleophile provided the characteristic conjugate addition product, but some nucleophile afforded displacement product at the sulfonyl group to give alkynyl-Nu.