Metal Halide Hydrates as Lewis Acid Catalysts for the Conjugated Friedel-Crafts Reactions of Indoles and Activated Olefins

Metal halide hydrates such as SnCl2 center dot 2H(2)O, MnCl2 center dot 4H(2)O, SrCl2 center dot 6H(2)O, CrCl2 center dot 6H(2)O, CoCl2 center dot 6H(2)O e CeCl3 center dot 7H(2)O were investigated as mild Lewis acids catalysts for the conjugate Friedel-Crafts reaction between indoles and activated olefins. The reactions were carried out with aliphatic unsaturated ketones over a period of days at room temperature, while chalcones reacted only under reflux conditions. The reactions with nitrostyrenes were either performed in solvent or under solventless conditions. In all cases reasonable to good yields were obtained.