Iron and Palladium(II) Phthalocyanines as Recyclable Catalysts for Reduction of Nitroarenes

Abstract

Iron(II) and palladium(II) phthalocyanines have been established as recyclable heterogeneous catalysts for the reduction of aromatic nitro compounds to corresponding amines using diphenylsilane/sodium borohydride as hydrogen sources in ethanol. Various reducible functional groups, such as acetyl, ester, cyano, amide, sulphonamide and carboxylic acid etc. were well tolerated, and the methods were applicable up to gram scale. Mechanistic studies showed that reduction of nitro group proceed through direct (nitroso) pathway and possibly iron or palladium phthalocyanines activates nitro group for reduction. FePc and PdPc also catalyzed the generation of hydrogen from the combination of diphenylsilane/sodium borohydride and ethanol. Iron and palladium (II) phthalocyanines has been established as an efficient recyclable catalytic systems for reduction of nitroarenes with green solvent system. Various nitro substituted aromatics and heteroaromatics has been successfully reduced to corresponding amines in good to excellent yields. The present methods have also been productively applicable for gram scale reactions.