Selective reductions of nitroarenes to anilines using metallic zinc in near-critical water

Abstract

A new procedure for the preparation of anilines (2) in good yield by reduction of the corresponding nitroarenes (1) using Zn in H₂O at 250–300 °C is described. The procedure is powerful enough to reduce sterically hindered 2-nitro-m-xylene (1c) and is chemoselective for the NO₂ groups in 1-chloro-2-nitrobenzene (1d) and 1-nitro-3-vinylbenzene (1h). The process involves the reduction of H₂O by Zn to generate H₂ followed by hydrogenation of the NO₂ group catalysed by residual traces of Zn.