Chemoselective Transfer Hydrogenation of Nitroarenes Catalyzed By Highly Dispersed, Supported Nickel Nanoparticles

Aromatic amines are useful intermediates in the preparation of dyes, pharmaceuticals, and agricultural chemicals, which can be obtained by the reduction of aromatic nitro compounds. A variety of procedures involving metal catalysts and other reducing agents are available for this purpose; however, the selective reduction of a nitro group in the presence of other reducible functional groups in a molecule is a challenging task. In addition, reduction of aromatic nitro compounds often stops at an intermediate stage, yielding hydroxylamines, hydrazines, azoarenes, or azoxyarenes as byproducts. In this study, a highly active nickel (Ni) nanoparticles catalyst supported on porous silica gel particles was prepared by atomic layer deposition. Chemoselective reduction of nitroarenes was studied using the prepared Ni/SiO₂ as the catalyst and hydrazine hydrate as a hydrogen donor. Different kinds of nitroarenes were converted to the corresponding anilines with high yields. The high activity of the catalysts could be a result of the highly dispersed Ni nanoparticles.