On the mechanism of the direct acid catalyzed formation of 2,3-disubstituted imidazo[1,2-a]pyridines from 2-aminopyridines and acetophenones. Concurrence between ketimine and Ortoleva–King type reaction intermediated transformations

Abstract

Direct acid catalyzed formation of 2,3-disubstituted imidazo[1,2-a]pyridines from 2-aminopyridines and acetophenones was studied in order to gain insight into the reaction mechanism. The formation of differently substituted products was explained by a concurrent ketimine and Ortoleva–King type reaction intermediated transformations. The dependence of the reaction output on the catalyst used and on acetophenone and pyridine substituents was discussed.