Synthesis of tetrahydropyrimidinium salts and their in situ catalytic activities towards the Buchwald-Hartwig amination reaction under microwave irradiation

Abstract

A series of asymmetrical substituted tetrahydropyrimidinium salts and different kinds of bridged bistetrahydropyrimidinium salts were prepared through the quaterization of tetrahydropyrimidine or the dehydrogenation of hexahydropyrimidine. They were characterized and used as NHC precursors in the palladium catalyzed Buchwald-Hartwig amination reaction. The in situ formed catalytic system Pd(OAc)2/tetrahydropyrimidinium and t BuOK catalyzed the amination of heteroaryl halides and heterocyclic amines effectively, producing the heterocyclic amine functionalized heteroaryl derivatives in high yields.