The reduction of nitro compounds to the corresponding amines is one of the most utilized catalytic processes in the fine and bulk chemical industry. The latest development of catalysts with cheap metals like Fe, Co, Ni, and Cu has led to their tremendous achievements over the last years prompting their greater application as “standard” catalysts. In this review, we will comprehensively discuss the use of homogeneous and heterogeneous catalysts based on non-noble 3d-metals for the reduction of nitro compounds using various reductants. The different systems will be revised considering both the catalytic performances and synthetic aspects highlighting also their advantages and disadvantages.

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Reduction of Nitro Compounds Using 3d-Non-Noble Metal Catalysts

Selective catalytic hydrogenation of nitroarenes is of great importance for dyestuff and pharmaceutical industry. A critical step toward the rational design of targeted catalysts is to determine their electronic structures and related reaction mechanism. In this review, we summarize the breakthroughs on the development of multiple catalytic technologies in the past decade, including direct hydrogenation using high-pressure hydrogen; transfer hydrogenation using reductive compounds; photocatalytic hydrogenation using hole scavenger; electrocatalytic hydrogenation accompanied with water oxidation. We focus on how to understand the two key element steps including hydrogen dissociation and the activation of nitro group in the process of hydrogenation, and design and fabricate nanostructured catalysts with desired activity and selectivity. For direct catalytic hydrogenation, representative catalysts include metal, metal oxide/sulfide/carbides/nitrides/boride, and functional carbon material, and the crucial factors to tune their activity and selectivity are discussed such as metal-support interaction, size effect, alloy effect, defect engineering, and so on. Catalytic transfer hydrogenation, photocatalytic and electrocatalytic hydrogenation, in which these catalysts abstracts hydrogen species from the hydrogen donor and stabilizes it on the catalyst surface, restricting active H* recombination, and then the active hydrogen species can be promptly transferred to nitroarenes for the hydrogenation. It is worth mentioning that the light harvesting and charge separation of photocatalyst and the conductivity of electrocatalyst should also be considered together for the overall performance. All these experiences lay the foundation for large scale production of anilines and guide the rational design of catalysts for other organic transformation reactions.

Review on selective hydrogenation of nitroarene by catalytic, photocatalytic and electrocatalytic reactions

Cellulosic protic ionic liquids hydrogel: A green and efficient catalyst carrier for Pd nanoparticles in reduction of 4-nitrophenol in water

Cobalt nanoparticles supported on N-doped mesoporous carbon as a highly efficient catalyst for the synthesis of aromatic amines

The synthesis of aromatic amines from nitroarenes through hydrogenation is an industrially and academically important reaction. In addition, the employment of base metal catalysts in reactions that are preferentially mediated by rare noble metals is a desirable aim in catalysis and an attractive element-conservation strategy. Especially appealing is the observation of novel selectivity patterns with such inexpensive metal catalysts. Herein, we report a novel mesostructured Ni nanocomposite catalyst. It is the first example of a reusable Ni catalyst that is able to hydrogenate nitroarenes selectively to anilines in the presence of highly sensitive functional groups such as C=C bonds and nitrile, aldehyde, and iodo substituents.

Yongzheng Wang

Papers

Nickel embedded in N-doped porous carbon for the hydrogenation of nitrobenzene to p-aminophenol in sulphuric acid