Visible Light Driven Coupling of 2-aminopyridines and α-Keto Vinyl Azides for the Synthesis of Imidazo[1, 2-a]pyridines and Their Cytotoxicity

α-Keto vinyl azides and 2-aminopyridines were coupled to yield 1-aryl-N-(2-arylimidazo[1, 2-a]pyridin-3-yl)methanimines in the presence of visible light using Ru(bpy)3Cl2.6H2O as a photocatalyst. This synthetic protocol allows the formation of 3 new C−N bonds in the overall transformation at ambient temperature. It is applicable to a wide range of vinyl azides and 2-aminopyridines providing a straightforward access to a variety of highly functionalized imidazo[1, 2-a]pyridines in high yields. The synthesized imidazo[1, 2-a]pyridines were evaluated for their cytotoxic activity against a set of four selected human cancer cell lines i.e, A549 (lung cancer), DU-145 (prostate cancer), MCF-7 (breast cancer) and Hela (cervical cancer). Many compounds of the series (4 e, 4 g, 4 i, 4 j and 4 u) exhibited promising cytotoxicity in these cancer cell lines.