Acid/base-controlled chemodivergent synthesis of two differently functionalized tetrahydroimidazo[1,2-a]pyridines

Abstract

A new approach for the facile chemodivergent synthesis of tetrahydroimidazo[1,2-a]pyridines from β-ketothioamides, aldehydes and heterocyclic ketene aminals is described. In the presence of a base, an unprecedented ring-opening, tautomerization, recyclization cascade is observed and H₂S eliminated tetrahydroimidazo[1,2-a]pyridines were formed in good yields. With catalytic amounts of acid, another type of different substituted tetrahydroimidazo[1,2-a]pyridines were obtained through dehydration.