Copper-catalyzed tandem cyclization of 2-(2-iodophenyl)imidazo[1,2-a]pyridine derivatives with selenium: Synthesis of benzo[b]selenophene-fused imidazo[1,2-a]pyridines

Abstract

Cu-catalyzed tandem cyclization of 2-(2-iodophenyl)imidazo[1,2-a]pyridines with selenium for the practical synthesis of the benzo[b]selenophene-fused imidazo[1,2-a]pyridines occurred smoothly via Ullmann-type Se-arylation and Csp2–H selenation. A variety of benzo[b]selenophene-fused imidazo[1,2-a]pyridines were easily obtained in moderate-to-high yields. Single-crystal X-ray analysis of 2a revealed that the benzo[b]selenophene and imidazopyridine rings are almost coplanar. The maximum absorption of tetracyclic compound 2a was red-shifted by 45–47nm from those of imidazo[1,2-a]pyridine and benzo[b]selenophene.