Synergistic effect from Lewis acid and the Ni–W2C/AC catalyst for highly active and selective hydrogenation of aryl nitro to aryl amine

This work presents a facile approach for clean and chemoselective synthesis of various functionalized arylamines from their corresponding substituted nitroarenes through the unexpected synergistic effect of a Lewis acid and the Ni–W2C/AC catalyst, affording almost 100% arylamine yield. The results challenge the long-held axiom that the combination of Lewis acid and hydrogenation catalyst mainly enhances the transformation of nitrobenzene (NB) to p-aminophenol via Bamberger rearrangement of the formed intermediate phenylhydroxylamine (PHA) under catalytic hydrogenation conditions. X-ray diffraction (XRD) and FT-IR spectroscopy were employed to reveal the relationship between catalyst nature and catalytic performance, and a plausible reaction mechanism is also proposed. Reaction results demonstrate that the FeCl3–Ni–W2C/AC catalytic system shows comparable catalytic performance towards precious metals for chemoselective reduction of various aromatic nitro compounds, affording 100% yield for all substrates involved in this work (99.5% of isolated yield for model substrate). Moreover, it can be found that the catalyst could be easily recovered by filtration and recycled without visible loss of its catalytic activity. Therefore, the developed FeCl3–Ni–W2C/AC catalytic system in this work can be considered as a practical candidate for clean and highly-efficient synthesis of diverse functionalized arylamines. We believe this approach can be extended to the other hydrogenation reactions.