Synthesis of 2-substituted 3-ethyl-3H-imidazo[4,5-b]pyridines catalyzed by Al3+-exchanged K10 clay as solid acids

A series of imidazopyridine derivatives have been synthesized efficiently via intramolecular cyclization in excellent yields using Al3+-exchanged on K10 montmorillonite clay (Al3+-K10 clay) as a reusable heterogeneous catalyst. To the best of our knowledge, this is the first report to utilize Al3+-K10 as a catalyst for imidazopyridine synthesis. Many functional groups are tolerated during the synthesis of targeted compounds. The catalyst is reused at least five times with a slight decrease in the yield. This catalyst is environmentally benign, cost-effective, and also provides other advantages such as nontoxicity, operational/experimental simplicity, and mild reaction conditions. (C) 2013 Elsevier Ltd. All rights reserved.