Hypervalent iodine(III) catalyzed rapid and efficient access to benzimidazoles,benzothiazoles and quinoxalines: Biological evaluation of some new benzimidazole-imidazo[1,2-a]pyridine conjugates

A rapid, simple and highly efficient method for the synthesis of a variety of 2-aryl-benzimidazoles, 2-aryl-benzothiazoles and quinoxalines has been developed using Koser’s reagent [PhI(OH)OTs] as catalyst. The present work highlights the potential of Koser's reagent ([PhI(OH)OTs]) for the synthesis of benzimidazoles, benzothiazoles and quinoxalines, etc. Short reaction time, high yields, importantly low catalyst loading, broad substrate scope and scalability are the salient features of this methodology. Particularly, this method has been employed successfully to synthesize highly structured indole-benzimidazole and quinoxaline-6-carboxamide derivatives as well as biologically important benzimidazole-imidazo[1,2-a]pyridine conjugates in moderate to good yields. These remarkable features make the present methodology a valid contribution to the existing precedents for the synthesis of benzimidazoles, etc. In the MTT assay, benzimidazole-imidazo[1,2-a]pyridine conjugates 3s, 3t and 3v were found to be active on MCF-7 (IC₅₀ values of 5.10 ± 0.10, 8.23 ± 0.02, and 10.75 ± 0.03 µM, respectively) and MDA-MB-231 cell lines (IC₅₀ values of 10.83 ± 0.13, 7.68 ± 0.05, and 7.87 ± 0.24 µM, respectively). Flow-cytometry analysis revealed that the treatment of MCF-7 cells with compound 3s showed moderate effect on the progression of G0/G1 phase of the cell cycle.