Unusual Tandem Oxidative C-C Bond Cleavage and Acetalization of Chalcone Epoxides in the Presence of Iodine in Methanol

An unusual reaction of chalcone epoxides is observed where chalcone epoxides on heating with iodine in methanol leads to alpha,alpha-dimethoxyacetophenones, through C-C bond cleavage followed by acetalization of the formyl group. The process occurs through ring opening of the chalcone epoxide by methanol to form beta-methoxy alcohol, cleavage of the C-C bond in the latter to form alpha-ketoaldehyde, and acetalization of the formyl group to give the product. The protocol provides direct access to alpha,alpha-dimethoxyacetophenones from chalcone epoxides.