Au/TiO₂-Catalyzed Selective Hydrogenation of Nitro Compounds

Chemoselective hydrogenation of nitro compounds was achieved by using a Au/TiO2 catalyst with hydrogen. Thus, when the reaction of 3-nitrostyrene was carried out with Au/TiO2 (0.23 mol%) under H2 (9 bar) at 120 °C for 6 h,3-vinylaniline was obtained in 98.5% conversion with 95.9% selectivity. The chemoselective reductions of 4-nitrobenzaldehyde, 4-nitrobenzonitrile and 4-nitrobenzamide were also performed under similar conditions to give the corresponding anilines in high conversion with high selectivity, where formyl, nitrile and amide groups were intact. Cyclohexanone oxime, a precursor of ε-caprolactam, was efficiently prepared from 1-nitro-1-cyclohexene with this catalytic system.