Facile synthesis and antioxidant activity of lignin-related imidazo[1, 2-a]pyridine derivatives

Abstract

A convenient protocol is described for the preparation of lignin related imidazo[1, 2-a] pyridine derivatives via three-component reactions among 2-aminopyridines, isocyanides and aromatic aldehydes obtained from lignin with excellent yields. Their in vitro antioxidant effects were evaluated by scavenging effect on 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical. The structure activity relationship (SAR) studies presented that the introduction of electron-donating group in imidazo[1, 2-a]pyridine could increase the radical scavenging activity; On the contrary, the presence of electron-withdrawing might decrease the radical scavenging activity. In addition, cyclopentyl and cyclohexyl groups almost had the same influence on the antioxidant activity. Furthermore, the methoxy moiety had a significant impact on antioxidant capability, and hence syringyl imidazo[1, 2-a]pyridines a, d, g, j and m exhibited excellent antioxidant properties.