Thioether-Assisted Cu-Catalyzed C5-H Arylation of Imidazo[1,5- a ]pyridines.

A Cu-catalyzed regioselective C5-H arylation of imidazo[1,5- a ]pyridines with aryl iodides was achieved with the assistance of an ethylthio group at the C3 position. This directing group could be easily removed to furnish a range of 5-(hetero)arylimidazo[1,5- a ]pyridine derivatives. The reaction tolerates a variety of functionalities and is compatible with sterically hindered substrates.