Pd-Catalyzed Regioselective Oxidative C–H Functionalization of Substituted Imidazo[1,2-a]quinoline: Structural Characterization of Binuclear Cyclometalated Intermediates

Reaction of 4-phenylimidazo[1,2-a]quinoline with one and more than two equivalents of PhI(OAc)2 afforded regioselective mono- and bis-acetoxylated products respectively in presence of catalytic amount of Pd(OAc)2. Stoichiometric reaction between imidazo–quinoline ligand and Pd(OAc)2 gave an acetate bridged binuclear cyclometalated complex 1. X-ray structure confirmed selective cyclometalation at ortho position of the phenyl ring. Furthermore, a formamidinate analogue, 2 is obtained by replacing the bridging acetates in 1.