Synthesis of Catalyst Using Bio-benign Precursors and Its Application in One-Pot Catalytic Synthesis of Imidazo[1,2-a]pyridines

Development of catalysts using natural feedstock is the need of the current era, and accordingly, we have developed a new ligand N-(2-hydroxynapthylidene)-L-leucienyl-4,6-O-ethylidene-beta-D-glucopyranosylamine using natural occurring D-glucose and L-amino acid. It interacts with several bio-relevant metal ions like iron, copper, zinc, etc., but its association with cupric ions is immune to pH (4.2-9.1) change. In-situ copper-catalyzed reactions have been proven to be pivotal in many important organic syntheses, including imidazo[1,2-a]pyridines, which is one of the important precursors of many drug molecules. Catalytic synthesis of imidazo[1,2-a]pyridines requires high catalyst loading, hazardous solvent, high temperature, and long reaction time, which are major drawbacks towards green synthetic methodology. Interestingly, our glycoconjugate-derived cupric complex catalyzes the reactions among aldehydes, 2-aminopyridines, and terminal alkynes under the solvent-free condition to afford one-pot synthesis of imidazo[1,2-a]pyridines and 23 derivatives have been reported in good to excellent yields (53-93 %) using lower reaction time, temperature, and catalyst loading compared to other reports on similar reactions. Hence, our approach enhances the green methodology towards the catalytic synthesis of imidazo[1,2-a]pyridine derivatives.