General Method for the Preparation of Electron-Deficient Imidazo[1,2-<i>a</i>]pyridines and Related Heterocycles
作者:Ivar M. McDonald、Kevin M. Peese
DOI:10.1021/acs.orglett.5b02966
日期:2015.12.18
A new annulation method for the preparation of the imidazo[1,2-a]pyridine ring system under mild conditions is presented. Treatment of a 2-aminopyridine with a dimethylketal tosylate in acetonitrile at elevated temperature (80–140 °C) in the presence of catalytic Sc(OTf)3 provides the imidazo[1,2-a]pyridine product in good yield. The annulation method is broadly applicable to electron-poor 2-aminopyridines
提出了一种在温和条件下制备咪唑并[1,2- a ]吡啶环体系的新方法。在催化的Sc(OTf)3存在下,在高温(80–140°C)下,在乙腈中用甲苯磺酸二甲基缩酮酯处理2-氨基吡啶,可得到高产率的咪唑并[1,2- a ]吡啶产物。该成环方法广泛适用于电子贫乏的2-氨基吡啶,并通过溴代酮与富电子和中性底物的反应,与经典的咪唑并[1,2- a ]吡啶环体系制备显示出互补性。讨论了过程的范围和机械方面的考虑。