Organic Acid Catalysts in Reactions of Lactones with Silicon Enolates

By choosing the organic acid catalysts, the reaction of lactones with ketene silyl acetals results in selective formation of simple Mukaiyama aldol adducts or olefination products, which are formed by the subsequent elimination of a silanol from the adducts. That is, in the presence of acidic zwitterions, the reaction of lactones with ketene silyl acetals gives simple Mukaiyama aldol adducts in excellent yields. In contrast, the same reaction in the presence of a carbon acid catalyst brings about the formation of olefination products in a Z ‐selective manner.