Selective Hydrogenation of Aromatic Nitro Compounds Using Unsupported Nickel Catalysts

Hydrogenation of nitroarenes has attracted renewed attention since it was discovered that non-noble metal catalysts could selectively reduce nitroarenes with sensitive reducible groups. Here, we report the results of the chemoselective catalytic hydrogenation of nitroarenes with unsupported Ni NPs. Initial catalytic assessments showed high activity and selectivity, reaching conversions up to 99 % and 100 % selectivity towards the substituted anilines containing reducible groups such as halogens and nitrile. The recyclability test showed impressive stability of the catalyst up to the fifth run for the target product. Preliminary studies on the catalytic mechanism of the Ni NPs indicate that the nitrosobenzene might not participate as an intermediate in this reaction. Instead, a hydroxylamino adsorbed on the Ni surface is proposed. This work displays an accessible approach for synthesizing an active and selective catalyst for reducing nitroarenes in the presence of facile reducible substituents.