Catalyst-Controlled Regiodivergent Oxidative Annulation of 2-Arylimidazo[1,2-a]pyridines with Cinnamaldehyde Derivatives for Construction of Fused N-Heterocyclic Frameworks.

Abstract

Catalyst-dependent regioselective oxidative annulation of 2-arylimidazo[1,2-a]pyridines with cinnamaldehyde derivatives to construct fused N-heterocyclic frameworks has been described. The annulation reaction afforded 5-arylnaphtho[1',2':4,5]imidazo[1,2-a]pyridine-6-carbaldehydes in the presence of [RhCp*Cl2]2 as catalyst while 1,7-diarylimidazo[5,1,2-cd]indolizine-6-carbaldehydes were obtained using Pd(OAc)2 as catalyst. The reaction produced annulated products in good yields and exhibited broad substrate scope and excellent functional group tolerance. The method provides two different isomeric annulated products bearing an aldehyde functionality which can be elaborated into an array of functionalities leading to valuable compounds.