Selective Hydrogenation of Aromatic Chloronitro Compounds

Many effective strategies have been developed in order to inhibit the hydrodechlorination in the selective hydrogenation of chloronitrobenzenes to chloroanilines which are important intermediates in the chemistry and industry of dyes, herbicides, pesticides and medicines. However, hydrogenolysis of the carbon-halogen bond as a defect of the hydrogenation process could not be avoided completely over the metal catalysts reported previously, especially at complete conversion of the substrates. Recently we overcame this problem by the invention of nanocomposite catalysts composed of noble metal nanoclusters and inorganic semiconductor nanoparticles. Over these nanocomposite catalysts, the hydrodechlorination of ortho-chloroaniline was completely suppressed even at 100% conversion of ortho-chloronitrobenzene. In this review, we deal with the great efforts and remarkable contributions of different authors during the long exploration for the solutions of this hard obstacle. Stress is placed on supported metal catalysts and polymer-protected metal nanoclusters or colloid catalysts.