Solvent and catalyst-free synthesis of imidazo[1,2-a]pyridines by grindstone chemistry

The present work describes the solvent and catalyst-free synthesis of imidazo[1,2-a]pyridines in excellent to nearly quantitative yields from 2-aminopyridines and a wide variety of omega-bromomethylketones using a grindstone procedure at 25 degrees C to 30 degrees C for 3 to 5 minutes. The absolute structure of the compound, 2-(3-bromophenyl)-7-methylimidazo[1,2-a]pyridine is determined by X-ray crystallography. This green strategy has several noteworthy advantages such as wide spread substrate scope, short reaction times, water work up and the products do not require any chromatographic purification. Moreover, the method does not require any specialized equipment and is highly economical, environmentally benign and easy to carry out in any laboratory. Hence, the developed method meets the concept of benign by design and is greener alternative to the reported procedures for the synthesis of imidazo[1,2-a]pyridines.

Automated summary

This study presents a solvent and catalyst-free method for the synthesis of imidazo[1,2-a]pyridines, which is green, economical, and environmentally friendly. The method has a wide substrate scope, short reaction times, and eliminates the need for chromatographic purification.