Turkish Journal of Chemistry, Vol.39, No.1, 121-129, 2015
Synthesis of tetrahydropyrimidinium salts and their in situ catalytic activities towards the Buchwald-Hartwig amination reaction under microwave irradiation
A series of asymmetrical substituted tetrahydropyrimidinium salts and different kinds of bridged bis-tetrahydropyrimidinium 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 (BuOK)-Bu-t catalyzed the amination of heteroaryl halides and heterocyclic amines effectively, producing the heterocyclic amine functionalized heteroaryl derivatives in high yields.
Keywords:Tetrahydropyrimidinium salt;Buchwald-Hartwig amination;microwave irradiation;palladium catalysis;N-heterocyclic carbene