Microwave-Assisted Synthesis of Imidazo[1,2-a]Pyridine Derivatives by Three-Component Reaction of Phenyl Glyoxals, 2-Aminopyridines, and Barbituric Acids

A straightforward and facile method for the synthesis of imidazo[1,2-a]pyridine derivatives by one-pot, three-component reaction of phenyl glyoxals, 2-aminopyridines, and barbituric acids has been developed. The synthesis was performed in a microwave reactor and under solvent-free conditions without using any catalyst. The synthesis displayed many other attractive features such as high efficiency, short reaction time, simple product purification, and environmentally benign reaction conditions. Moreover, the synthesis could be applied on a gram scale without any significant decrease in reaction yield. Eleven imidazo[1,2-a]pyridine adducts were provided in high yields (82-96%), and their structures were confirmed by NMR data. A comparison between this method and the literature report was also included. A plausible reaction mechanism involving a Knoevenagel condensation and aza-Michael addition was also suggested. other: None