Imidazo[1,2-a]pyridine A3-Coupling Catalyzed by a Cu/SiO2 Material

In this work, we report the preparation of a copper-silica material (Cu/SiO2) by a sol-gel methodology and its characterization concerning composition and textural properties. The Cu/SiO2 material was successfully applied as a Lewis acid heterogeneous catalyst for the A3-coupling from 2-aminopyridine, aldehydes and alkynes to imidazo[1,2-a]pyridines (45-82%), which are relevant pharmacological scaffolds. The synthesis shows a number of advantages, such as easy separation from the reaction media and the minimal formation of metal aqueous wastes. Investigation of the mechanism supports the involvement of the formation of reaction intermediates inside the pores of the mesoporous material prior to 5-exo-dig cyclization.