Regioselective Base‐controlled Pd‐catalyzed Arylation of Imidazo[1,2‐a]pyridines: leading selectivity at C8 position by N‐chelation over O‐chelation.

A base controlled operationally simple catalytic system for the regioselective arylation of 2‐aryl‐imidazo[1,2‐a]pyridine by Pd catalyzed C−H activation has been developed. Herein, we report Pd/Ag2CO3 promoted C8 arylation of the heterocycles by overriding the N‐chelation on O‐chelation. In this way, various examples have been synthesized in good to excellent yield. Furthermore, Pd/t‐BuOK system has been developed for the novel deformylative C3 arylation of 2‐aryl‐imidazo[1,2‐a]pyridine. The choice of the catalytic system is also demonstrated for heteroarylation. Both standardized protocols have been explored with broad substrate scope and good functional group tolerance. [ABSTRACT FROM AUTHOR]