Palladium N-Heterocyclic Carbene Pre-catalysts Bearing Different Ancillary Ligands for the Buchwald-Hartwig Amination of Cyclic Secondary Amines with Aryl Chlorides

Six novel palladium N-heterocyclic carbene complexes bearing different ancillary ligands such as pyridine, 1-methylimidazole, 4,5-dimethylthiazole and 3-bromoquinoline have been successfully prepared in a one-step process. These complexes were used as pre-catalysts in the Buchwald-Hartwig amination of cyclic secondary amines with aryl chlorides. A range of cyclic secondary amines were tolerated to a wide variety of aryl chlorides in presence of 1 mol% catalyst loading under mild conditions. Under the tested reaction conditions, the expected N-arylamines were obtained in moderate to high yields. The results showed that these novel palladium complexes are effective catalysts for the Buchwald-Hartwig amination.Graphic Abstract

Automated summary

Six novel palladium N-heterocyclic carbene complexes with different ancillary ligands were successfully prepared and used as pre-catalysts in the Buchwald-Hartwig amination reaction. These complexes showed good catalytic activity in the amination of cyclic secondary amines with aryl chlorides, leading to moderate to high yields of N-arylamines under mild reaction conditions.