Atom economical synthesis of oxindoles by metal-catalyzed intramolecular C–C bond formation under solvent-free and aerobic conditions

Diversely substituted oxindoles were obtained from atom economical direct C-C bond formation reactions of various substituted anilides and pyridinylamides with metal salts and oxides. The catalysts include CuO, Cu sub(2)O, FeCl sub(3), Fe sub(2)O sub(3), TiO sub(2), ZnO, and Ag sub(2)O and their nanoparticles. The reaction proceeds under solvent-free and aerobic conditions in excellent yields. The reaction mechanism was proved to be a single electron transfer pathway with oxygen as the re-oxidant of the metal catalysts.