Green Route for the Preparation of p-Aminophenol from Nitrobenzene by Catalytic Hydrogenation in Pressurized CO₂/H₂O System

The preparation of p-aminophenol from nitrobenzene by one-pot catalytic hydrogenation and in situ acid-catalyzed Bamberger rearrangement was first realized in a pressurized CO2/H2O system. By employing Pt–Sn/Al2O3 as catalyst, nitrobenzene could be converted to p-aminophenol with selectivity as high as 85% when the reaction was carried out at 140 °C under 5.5 MPa CO2 and 0.2 MPa H2. This new protocol is environmentally benign because it is fully rid of the use of mineral acid by the application of self-neutralizable carbonic acid.