Cascade Synthesis of Benzimidazole-Linked Pyrroles via Copper Catalyzed Oxidative Cyclization and Ketonization

Abstract

A three-component cascade reaction of 2-aminobenzimidazole, aldehyde, and terminal alkyne has been explored for an efficient synthesis, of benzimidazole-linked tetrasubstituted pyrroles. The reaction sequence involves the formation Of propargylamine, insertion of 4 terminal alkyne, and a ring opening reaction, followed by, an intramolecular carboylative cyclization under aerobic conditions. It represents a novel, strategy to the construction of C=N, C=C, C=0 bonds and a new five-membered 2-ketopyrrole ring. In this process, the reaction conditions are crucial and an attempt to elucidate the novel reaction patway is well, supported by X=ray crystallography.