Organic-Dye-Catalyzed Visible-Light-Mediated Regioselective C-3 Alkoxycarbonylation of Imidazopyridines by Carbazates.

A mild and eco-friendly visible-light-mediated regioselective C-H alkoxycarbonylation of imidazo[1,2- a ]pyridine heterocycles using rose bengal as a photoredox catalyst at room temperature has been developed. Biologically important alkoxycarboxylated imidazo[1,2- a ]pyridines at the C-3 position as well as coumarins and quinoxalin-2(1 H )-ones have been prepared. The present approach has the advantage of having a user- and eco-friendly catalyst, a carbonyl source, as well as extremely mild conditions for direct and regioselective C-H alkoxycarbonylation mediated by visible light as a green energy source.