Efficient and "Green" Synthetic Route to Imidazo[1,2- a ]pyridine by Cu(II)-Ascorbate-Catalyzed A 3 -Coupling in Aqueous Micellar Media.

An efficient and environmentally sustainable method for the synthesis of imidazo[1,2-]pyridine derivatives by domino A-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 with sodium ascorbate and aided a facile 5--dig cycloisomerization of alkynes with the condensation products of 2-aminopyridines and aldehydes to afford a variety of imidazo[1,2-]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.