(S)-Dimethylsulfonium(p-tolylsulfinyl)methylide: A New Chiral Sulfonium Ylide and its Use in Asymmetric Epoxidation

The title optically active sulfonium ylide was prepared by methylation of easily available (-)-(S)-p-tolylmethylthiomethylsulfoxide and subsequent deprotonation. Its reaction with aldehydes gave (alpha),(beta)-epoxy sulfoxides with full enantioselectivity and moderate diastereoselectivity. The steric course of acid-catalyzed rearrangement of sulfinyl oxiranes is briefly discussed.