Stereospecific alkyl and alkynyl substitution reactions of epoxy sulfides with organoaluminums with double inversion of the configuration.

A regioselective and stereospecific substitution reaction of 1-(phenylthio)-2,3-epoxyalkanes was achieved by using organoaluminum reagents as a nucleophile. Under the influence of trimethyl- or triethylaluminum, a 1-(phenylthio)-2,3-epoxyalkane underwent substitution at the C2 position to give a product with retention of the configuration. The reaction proceeds through an episulfonium ion intermediate, which gives rise to the C2-substitution products with double inversion of the configuration. Introduction of an alkynyl group was also accomplished by the reaction with dimethyl[2-(trimethylsilyl)ethynyl]aluminum in dichloromethane.