Copper-catalyzed oxidative heterocyclization by atmospheric oxygen

Abstract

Starting from Schiff bases 1, a wide variety of heterobicycles, which can be applied as pharmaceuticals or as ligands for catalysts, is accessible by copper-catalyzed oxidation with atmospheric oxygen. The scheme shows, for example, the synthesis of imidazo [1,5-a]pyridines 2 (R1 = 2-hydroxy-3-methoxyphenyl, tBu, 2-hydroxyphenyl, 2-aminophenyl; R2 = 2-pyridyl, Me, phenyl).