Carbonylative Reduction of Nitrophenols to Aminophenols

Abstract

Two- or three-component catalysts composed of (i) sulfur or sulfur compound (H 2 S, CS 2 , COS, Na 2 S), (ii) basic additive (triethylamine, CH 3 ONa, Na 2 S), and usually (iii) vanadium(V) compounds (e.g. NH 4 VO 3 ) were found to catalyze efficiently the reaction of CO + H 2 O with isomeric nitrophenols to give the corresponding aminophenols. The reaction proceeds smoothly at 398 and 483 K and initial pressure of 7 MPa, and its rate increases from 2- to 4-nitrophenol. The selectivity to aminophenols exceeding 96 per cent was obtained at the water to nitrophenol molar ratio higher than 5. The solvents such as methanol and dioxane ensured better contact of the reactants, which was necessary for achievement of such a high selectivity. The effectiveness of the sulfur components (based on the S content) is expressed by the following sequence: S : CS 2 : Na 2 S : H 2 S : COS = 1 : 1.2 : 2.5 : 10 : 11. The reaction takes place also under the reduced CO pressure to 0.1 - 0.35 MPa. Formation of side products and mechanism of the reaction are discussed.