Kinetics of α-chlorination of sulphoxides by N-chlorobenzotriazole

Abstract

The α-chlorination of aryl methyl and aryl isopropyl sulphoxides with N-chlorobenzotriazole in acetonitrile in the presence of pyridine follows second-order kinetics. The reaction is favoured by electron-donating groups and is subject to a noticeable kinetic isotope effect (K_H/K_D). On the basis of the kinetic data a common reaction mechanism is proposed for the two series of sulphoxides, involving formation of an intermediate chloro-oxosulphonium salt which in the rate-determining step collapses on attack by base to give the α-chloro-sulphoxide.