Visible Light Triggered, Catalyst‐Free Approach for the Click Synthesis of Imidazole‐Fused Nitrogen‐Bridgehead Nucleus in EtOH:H2O Medium

ABSTRACT Here, we have succeeded in developing an eco‐efficient, mild, and metal‐free synthetic protocol for biologically significant scaffolds: imidazopyridines and their derivatives via radical cyclization from a wide variety of simple 2‐aminopyridines and phenacyl bromides as reactants and utilizing visible light as a reaction promoter in the ethanol/water solvent. To the best of our knowledge, the present strategy is the first example of visible light promoted synthesis of imidazo[1,2‐a]pyridine via the formation of C‐N bonds. The proposed methodology has various advantages namely quick reaction time, low cost, simple setup, high atom efficiency, easy‐availability of reactants and non‐involvement of specific glasswares and photo reactor system.