Metal halide hydrates as lewis acid catalysts for the conjugated Friedel-Crafts reactions of indoles and activated olefins

Abstract

Metal halide hydrates such as SnCl2·2H2O, MnCl2·4H2O, SrCl2·6H 2O, CrCl2·6H2O, CoCl2· 6H2O e CeCl3·7H2O 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. ©2011 Sociedade Brasileira de Química.