Recent Developments in Manganese, Iron and Cobalt Homogeneous Catalyzed Synthesis of Primary Amines via Reduction of Nitroarenes, Nitriles and Carboxamides

Abstract

The preparation of primary amines attracts huge attention in the molecular synthetic community. Indeed, amines play a crucial role in chemistry as they are important substructures in a huge amount of drug molecules, agrochemicals, dyes and molecular materials. Compared to stoichiometric reductions using metal hydride based reagents, the catalyzed reduction of nitroarenes, nitriles and carboxamides appears to be an attractive option, mainly when associated to first row transition metals such as manganese, iron, or cobalt. In this short review, we illustrate the progress achieved in homogeneous hydrogenation, hydrogen transfer, hydrogen borrowing and hydrosilylation of nitroarenes, nitriles and carboxamides.

Synergy of redox-activity and hemilability in thioamidato cobalt(iii) complexes for the chemoselective reduction of nitroarenes to anilines: catalytic and mechanistic investigation

“…9 For the above reasons, the quest for novel homogeneous catalytic systems which rely on the low-cost and low-environmental impact, earth-abundant 3d-metals that can mediate the reduction of nitro-compounds to amines selectively and under mild conditions is gaining growing interest. 10 In this context, a method successfully and widely used for this transformation is Béchamp's reduction, which involves the use of Fe powder in concentrated HCl(aq). However, the utilization of harsh reaction conditions and the generation of toxic waste, in combination with the lack of functional group selectivity, suggests the imperative need for more economical and efficient methods.…”

Hydrogenation of amides to amines by heterogeneous catalysis: a review

“…Two key factors in achieving novel homogeneous catalysts for amide hydrogenation were the control of the metal-ligand interaction to enhance the activity at the metal site and the incorporation of specific ligands in combination with appropriate acidic additives. 36 Metal-complexes with diverse ligands, synthesized from a wide range of noble and non-noble metals, such as Ir, 37 Ru, 38,39 Al, 40 Fe, 41 Co, 42 Mn, 31 and Zr, 43,44 as shown in Fig. 4, have been reported as amide hydrogenation homogeneous catalysts.…”

Borrowing hydrogen C-alkylation with secondary saturated heterocyclic alcohols

“…The reaction sequence proceeds as follows: (i) activation of the corresponding alcohol (oxidation to aldehyde or ketone depending on the nature of the alcohol) where a metal catalyst temporarily borrows hydrogens without changing the oxidation state (historically ruthenium, rhodium and iridium metal catalysts were used with recent applications with iron, cobalt and manganese). 7–12 (ii) Condensation or aldolization depending on the nucleophile used, where water is released as the only by-product. (iii) Finally, the hydrogen borrowed from the dehydrogenation step is given back to generate the saturated product (Scheme 1).…”