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Nanoscale Fe2O3-Based Catalysts for Selective Hydrogenation of Nitroarenes to Anilines

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Science  29 Nov 2013:
Vol. 342, Issue 6162, pp. 1073-1076
DOI: 10.1126/science.1242005

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Lighter Hydrogenation Catalysts

Enzymes have evolved to use abundant metals such as iron, cobalt, and nickel for redox catalysis. However, synthetic catalysis has generally relied on the rarer, heavier relatives of these elements: ruthenium, rhodium, iridium, palladium, and platinum (see the Perspective by Bullock). Friedfeld et al. (p. 1076) used high-throughput screening to show that the right cobalt precursor can be activated for asymmetric hydrogenation catalysis by using the traditional ligands developed for the precious metals. Zuo et al. (p. 1080) focused on iron, demonstrating a highly effective asymmetric transfer hydrogenation catalyst that uses a ligand rationally designed after careful mechanistic study. Jagadeesh et al. (p. 1073) prepared supported iron catalysts that selectively reduce nitro substituents on aromatic rings to amines, thereby facilitating the preparation of a wide range of aniline derivatives.

Abstract

Production of anilines—key intermediates for the fine chemical, agrochemical, and pharmaceutical industries—relies on precious metal catalysts that selectively hydrogenate aryl nitro groups in the presence of other easily reducible functionalities. Herein, we report convenient and stable iron oxide (Fe2O3)–based catalysts as a more earth-abundant alternative for this transformation. Pyrolysis of iron-phenanthroline complexes on carbon furnishes a unique structure in which the active Fe2O3 particles are surrounded by a nitrogen-doped carbon layer. Highly selective hydrogenation of numerous structurally diverse nitroarenes (more than 80 examples) proceeded in good to excellent yield under industrially viable conditions.

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