Visible-Light-Induced Regioselective Cyanomethylation of Imidazopyridines and Its Application in Drug Synthesis.

3-Cyanomethylated imidazopyridines were synthesized via a visible light-promoted reaction of imidazopyridines with bromoacetonitrile or iodoacetonitrile catalyzed by fac-Ir(ppy)3 under mild conditions. For the substrates with various substituents on benzene or pyridine ring, the reaction proceeded smoothly to give the corresponding products in moderate to good yields. The synthetic utility of this visible-light-induced reaction has been illustrated in the efficient synthesis of zolpidem and alpidem.