Reactions of epoxides and episulfides with electrophilic halogens

A novel method is described for the conversion of epoxides into β-bromoformates using Ph3PBr2, Ph3P/N-bromosuccinimdes (NBS) and or Ph3P/2,4,4,6-tetrabromo-2,5-cyclohexadiene-1-one (TABCO) in DMF. Epoxides in the presence of Ph3P/I2 were converted into olefins immediately in excellent yields. The application of NBS, NCS, and TABCO as compounds carrying electrophilic halogens for the highly selective alcoholysis of epoxides and dimerization or alcoholysis dimerization of episulfides are also described.