Alkyl-imidazolium based organosilica supported Fe/porphyrin complex: As novel, highly efficient and reusable catalyst for the unsymmetrical Hantzsch reaction.

A noble alkyl-imidazolium ionic liquid based organosilica supported Fe/meso-tetrakis(4-sulfonatophenyl)porphyrin complex (ILOS@Fe/TSPP) is prepared, characterized and its catalytic efficiency is studied in the unsymmetrical Hantzsch reaction. The ILOS@Fe/TSPP was prepared by hydrolysis and co-condensation of 1,3-bis(3-trimethoxysilylpropyl)imidazolium chloride under acidic conditions followed by treatment with Fe/meso-tetrakis(4-sulfonatophenyl)porphyrin complex at ambient temperature. The material was characterized with TGA, EDX, SEM, TEM, XRD and DRIFT analyses. The ILOS@Fe/TSPP was successfully applied as powerful catalyst in the Hantzsch reaction for the preparation of a set of different derivatives of polyhydroquinolines in high to excellent yields. This catalyst was recovered and reused several times without important decrease in its activity. Furthermore, compared to the classical studies, this study consistently demonstrated the advantages of low catalyst loading, free-solvent media, short reaction times and simple purification of products.