Phosphine-free palladium-catalyzed direct arylation of imidazo[1,2-a]pyridines with aryl bromides at low catalyst loading.

Ligand-free Pd(OAc)(2) was found to catalyze very efficiently the direct arylation of imidazo[1,2-a]pyridines at C3 under very low catalyst concentration. The reaction can be performed employing as little as 0.1-0.01 mol % catalyst with electron-deficient and some electron-excessive aryl bromides.