Cu(OAc)2-Et3N mediated oxidative coupling of α-azido ketones with pyridinium ylides: utilizing in situ generated imines for regioselective synthesis of imidazo[1,2-a]pyridines.

Phenacyl azides were reacted with pyridinium ylides in the presence of Cu(OAc)2 (2 mol%) and Et3N utilizing molecular oxygen as a green oxidant to yield imidazo[1,2-a]pyridines in exclusive regioselectivity. Following the optimized protocol, 28 different fused heterocycles were synthesized in high yields (71-92%). In order to get mechanistic insight into the reaction, a few control experiments were carried out and the role of the copper salt was discussed.