Menthylamine synthesis via gold-catalyzed hydrogenation of menthone oxime

In the current work gold nanoparticles supported on oxides (MgO, Al₂O₃, ZrO₂, TiO₂) were used for menthylamine synthesis via menthone oxime hydrogenation. An increase of the gold nanoparticles size and application of metal oxides with a strong basic character such as magnesia favored deoximation to menthone. Au/Al₂O₃ catalyst with the gold nanoparticles size of 2.0 nm afforded high catalytic activity and selectivity to menthylamine. The reaction kinetics including stereoselectivity to the reaction products and recyclability of the catalyst was studied using Au/Al₂O₃ in the temperature range 90−110 °C under hydrogen pressure of 5.5–7.5 bar. The catalytic behavior was influenced by the solvent nature, with higher selectivity to desired amine achieved using methanol. The reaction rate was pressure independent, while has first order with respect to menthone oxime concentration. Stereoselectivity to menthylamines and menthones was independent on the reaction temperature and the hydrogen pressure.