Vanadyl Acetylacetonate Catalyzed Methylenation of Imidazo[1,2-a]pyridines by Using Dimethylacetamide as a Methylene Source: Direct Access to Bis(imidazo[1,2-a]pyridin-3-yl)methanes

摘要

An efficient protocol has been developed for the methylenation of imidazo[1,2-a]pyridines using dimethylacetamide (DMA) as methylene source in the presence of vanadyl acetylacetonate [VO(acac)(2)] as the catalyst and iodobenzene diacetate as the oxidant. The reaction involves coupling of sp(3)- and sp(2)-hybridized carbons and proceeds through the formation of an iminium ion. A wide variety of imidazo[1,2-a]pyridines were converted to bis(imidazo[1,2-a]pyridin-3-yl)methanes in good to excellent yields. A gram-scale reaction demonstrated the potential for the scale-up processes.