The Direct Synthesis of Imines, Benzimidazoles and Quinoxalines from Nitroarenes and Carbonyl Compounds by Selective Nitroarene Hydrogenation Employing a Reusable Iron Catalyst

Abstract

The "replacement" of noble metals by earth abundant metals is a desirable aim in catalysis and a possible way of conserving rare elements. The "replacement" is especially attractive if novel selectivity patterns are observed permitting the development of novel coupling reactions. Herein, we report on a novel, robust and reusable iron catalyst, which permits the selective hydrogenation of nitroarenes in the presence of hydrogenation-sensitive functional groups. Based on the selectivity pattern observed, the direct iron-catalyzed synthesis of imines and benzimidazoles from nitroarenes and aldehydes becomes feasible. In addition, we introduce the direct synthesis of quinoxalines from nitroarenes and diketones applying our catalyst.

A Cobalt Catalyst Permits the Direct Hydrogenative Synthesis of 1H‐Perimidines from a Dinitroarene and an Aldehyde

“…However, the direct use of nitro derivatives in more complex hydrogenative catalytic syntheses has so far been rarely disclosed. Beller and co‐workers introduced the reductive amination of carbonyl compounds with nitroarenes by applying cobalt‐based catalyst systems, whereas the selective synthesis of benzimidazoles and quinoxalines from amino nitroarenes was introduced by our group . We also reported recently on a nickel catalyst formed from a salen complex and a porous alumina support.…”

Cascade Synthesis of Pyrroles from Nitroarenes with Benign Reductants Using a Heterogeneous Cobalt Catalyst

“…[12] This pioneering work sparked the development of other 3d-metal catalysts for the synthesis of various N-heterocycles from nitroarenes. [13] Among the different heterocycles,pyrroles are an important class of compounds with useful biological and physical properties.H ence,avariety of methods for their synthesis exists, [14][15][16][17] including traditional, but still popular, Hantzsch and Paal-Knorr synthesis.S ince its discovery in 1884, [18,19] the latter reaction (1,4-diketones and primary amines) remains ar eliable transformation that continues to be used, for example,i nt he total synthesis of natural products.A sap rominent example,t he pyrrole ring of the drug Lipitor is produced on an industrial scale using Paal-Knorr synthesis. [20] Fort he preparation of N-aryl pyrroles anilines must be used;t hese are typically obtained via hydrogenation of the corresponding nitroarenes.Obviously,the direct use of nitroarenes in Paal-Knorr type reactions has an attractive stepeconomic advantage over anilines.Known synthetic methodologies for this transformation typically involve the use of stoichiometric amounts of areducing agent in the presence of astrong acid (e.g.In/HCl, In/AcOH), [21,22] which is an evident drawback.…”

Low temperaturein situformation of cobalt in silicon nitride toward functional nitride nanocomposites

“…the polymer-derived M/SiCN nanocomposites are attractive as robust and reusable catalysts which can be applied to various catalytic reactions by changing the metal nanoparticle component: dehydrogenation by Pd; 16 hydrogenation and dehydrogenation of N-heterocycles by Pd2Ru; 17 selective hydrocarbon oxidation by Cu; 18,19 dehydrogenative condensation of secondary alcohols and 1,2-amino alcohols by Ir; 20 chemoselective hydrogenation of nitroarenes by Ni, 21 Co 24 and Fe, 25 and hydrolysis of sodium borohydride by Pt. 23 In contrast, the design of metal/Si-based composites in nitride matrix systems (i.e., M/Si3N4) has never been demonstrated and it remains highly challenging while nitrides can be particularly interesting for catalysis as a support and/or as a catalyst itself.…”