Efficient and “Green” Synthetic Route to Imidazo[1,2-a]pyridine by Cu(II)–Ascorbate-Catalyzed A3-Coupling in Aqueous Micellar Media

An efficient and environmentally sustainable method for the synthesis of imidazo[1,2- a ]pyridine derivatives by domino A 3 -coupling reaction catalyzed by Cu(II)-ascorbate was developed in aqueous micellar media in the presence of sodium dodecyl sulfate (SDS). The catalyst, a dynamic combination of Cu(II)/Cu(I), was generated in situ in the reaction mixture by mixing CuSO 4 with sodium ascorbate and aided a facile 5- exo -dig cycloisomerization of alkynes with the condensation products of 2-aminopyridines and aldehydes to afford a variety of imidazo[1,2- a ]pyridines in good overall yields. A simple experimental setup, water as the "green" medium, and inexpensive catalyst and auxiliary are some of the merits of this protocol.