Selective Reduction of Nitroarenes to Arylamines by the Cooperative Action of Methylhydrazine and a Tris(N-heterocyclic thioamidate) Cobalt(III) Complex

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

Reduction of nitro-compounds to amines is one of the most often employed and challenging catalytic processes in the fine and bulk chemical industry. Herein, we present two series of mononuclear homoleptic and heteroleptic Co(III) complexes, i.e., [Co(LNS)3] and [Co(LNS)2L1L2]x+, respectively (x = 0 or 1, LNS = pyrimidine- or pyridine-thioamidato, L1/L2 = thioamidato, phosphine or pyridine), which successfully catalyze the transformation of nitroarenes to anilines by methylhydrazine. The catalytic reaction can be accomplished for a range of electronically and sterically diverse nitroarenes, using mild experimental conditions and low catalyst loadings, resulting in the corresponding anilines in high yields, with high chemoselectivity, and no side-products. Electronic and steric properties of the ligands play pivotal role in the catalytic efficacy of the respective complexes. In particular, complexes bearing ligands of high hemilability/lability and being capable of stabilizing lower metal oxidation-states exhibit the highest catalytic activity. Mechanistic investigations suggest the participation of the Co(III) complexes in two parallel reaction pathways: (a) coordination-induced activation of methylhydrazine and (b) reduction of nitroarenes to anilines by methylhydrazine, through the formation of Co(I) and Co-hydride intermediates.

Fe3O4@SiO2@KIT-6@2-ATP@CuI as a catalyst for hydration of benzonitriles and reduction of nitroarenes

In this paper, a new type of magnetic mesoporous material (Fe₃O₄@SiO₂@KIT-6@2-ATP@Cu^I) was designed and synthesized and its application in the synthesis of amides and anilines was investigated. The structure of Fe₃O₄@SiO₂@KIT-6@2-ATP@Cu^I was characterized and identified using FTIR, SEM, XRD, TGA, BET, VSM, and ICP techniques. An external magnet can easily remove the synthesized catalyst from the reaction medium, and be reused in several consequence runs.

A Reusable FeCl3∙6H2O/Cationic 2,2′-Bipyridyl Catalytic System for Reduction of Nitroarenes in Water

The association of a commercially-available iron (III) chloride hexahydrate (FeCl3∙6H2O) with cationic 2,2′-bipyridyl in water was proven to be an operationally simple and reusable catalytic system for the highly-selective reduction of nitroarenes to anilines. This procedure was conducted under air using 1–2 mol% of catalyst in the presence of nitroarenes and 4 equiv of hydrazine monohydrate (H2NNH2∙H2O) in neat water at 100 °C for 12 h, and provided high to excellent yields of aniline derivatives. After separation of the aqueous catalytic system from the organic product, the residual aqueous solution could be applied for subsequent reuse, without any catalyst retreatment or regeneration, for several runs with only a slight decrease in activity, proving this process eco-friendly.

Thioamide directed iridium(I)-catalyzed C-H arylation of ferrocenes with aryl boronic acids

The first Ir(I)-catalyzed thioamide-assisted C-H arylation of ferrocenes with aryl boronic acids under base-free mild reaction conditions in the presence of Ag₂CO₃ as an oxidant with eco-friendly 2-MeTHF as a solvent was developed. This reaction has a wide range of substrates (37 examples) and functional group tolerance (18-94% yields), and provides promising access to aryl thioamide-ferrocene compounds with good yields and regioselectivity.