Efficient Synthesis, Antioxidant Activity Evaluation, and Molecular Docking of Novel Isoxazole Derivatives

A series of previously unknown isoxazole-functionalized imidazopyridine derivatives were synthesized in a few steps, starting from pyridine-2,3-diamine. The synthesis involved the reaction of pyridine-2,3-diamine with lactic acid in PEG-400 to prepare 1-(3H-imidazo[4,5-b]pyridin-2-yl)ethanol which was further reacted with propargyl bromide to form 2-[1-(prop-2-yn-1-yloxy)ethyl]-3H-imidazo[4,5-b]pyridine. Finally, the latter was annulated with substituted benzaldehyde oximes in the presence of a catalytic amount of DBU to obtain the target 3-aryl-5-{[1-(3H-imidazo[4,5-b]pyridin-2-yl)ethoxy]methyl}-isoxazoles. The newly synthesized compounds were characterized by IR and NMR spectroscopy and mass spectrometry and showed excellent DPPH/superoxide/nitric oxide activity in antioxidant assay.