A Base Promoted Cyclization of N-Propargylaminopyridines. Synthesis of Imidazo[1,2-a]pyridine Derivatives

A base promoted cyclization of the protected N-propargylaminopyridines was shown to be an efficient method for the preparation of imidazo[1,2-a] pyridine derivatives. The reactions were carried out with a small excess of base, at room temperature or slightly above producing the heterocyclic products in moderate to good yields. The stereoelectronic properties of substituents on the pyridine ring were shown to influence the cyclization process.