Substd aminobenzenes from nitrobenzenes - carrying halogen, haloalkyl or aliphatic sulphonyl groups, by hydrogenation at pH 6-7.5 controlled by buffer system

摘要

Title cpds are prepared by hydrogenating the corresp. nitrobenzenes in aq. phase, using Ni catalysts, and adjusting the pH to 6-7.5 by addn. of oxyacids of 3-or 5-valent P, or of B, CO2 or low-mol. carboxylic acids and strong bases, or the corresp. salts; the additives are metered in such a way that the pH does not fall below the above limit. Nitrobenzenes carrying the above substits. cannot be hydrogenated by previous methods. Only 0.01-10 wt. % Ni catalyst is needed. Lower temps., e.g. 20-120 degrees C, can be used. Aminoacids have esp. strong stabilising effect on the pH.