Efficient, Safe, and Scalable One-Pot Telescopic Synthesis of 2-Arylimidazo[1,2-a]pyridines

A one-pot telescopic approach has been developed for the safe, scalable, and efficient synthesis of substituted 2-arylimidazo[1,2-a]pyridines starting from commercially available and inexpensive substituted acetophenones and 2-aminopyridine. The procedure involves the in situ formation of phenacyl bromides via chemoselective bromination of acetophenones with N-bromosuccinimide, followed by nucleophilic substitution and heterocyclization with 2-aminopyridine to yield 2-arylimidazo[1,2-a]pyridines. This streamlined telescopic method avoids handling and isolation of hazardous and lachrymatory phenacyl bromides. Moreover, this synthetic protocol eliminates unit operations such as solvent extraction, solvent evaporation/distillation, and final product purification. Notably, the practical utility of this telescopic approach has been demonstrated on a gram scale, affording the product in good yields.