Yb(OTf)3-catalyzed Mannich reaction of imidazo[1,2-a]pyridine and pyrazolo[1,5-a]pyrimidines

Abstract

An efficient one-pot condensation reaction of imidazo[1,2-a]pyridine/pyrazolo[1,5-a] pyrimidines, aldehydes and acetamide has been investigated using Yb(OTf)3 as a catalyst in 1,4-dioxane. The reaction furnishes good to excellent yield of 1-amidomethyl-imidazo[1,2-a]pyridines and 1-amidomethyl-pyrazolo[1,5-a]pyrimidines along with small quantities of bis(imidazo[1,2-a]pyridyl)methanes and bis(pyrazolo[1,5-a]pyrimidinyl)methanes. The product distribution is found to be dependent on the nature of imidazo[1,2-a]pyridine/pyrazolo[1,5-a]pyrimidines and aldehydes.