Highly enantioselective alpha-chlorination of cyclic beta-ketoesters catalyzed by N,N '-Dioxide using NCS as the chlorine source

A simple and highly efficient N,N'-dioxide organocatalyst system was developed for the asymmetric alpha-chlorination of cyclic beta-ketoesters using easily available NCS as the chlorine source to provide a series of optically active alpha-chloro-beta-ketoesters in excellent yields with 90-98% ee.