Green Approach for the Domino Reduction/Reductive Amination of Nitroarenes and Chemoselective Reduction of Aldehydes Using Fe/aq. Citric Acid/Montmorillonite K10

Abstract

We have developed a new and mild method for the direct onepot reduction/reductive amination of nitroarenes with arylaldehydes using Fe/aq citric acid/montmorillonite K10 catalytic system under ambient conditions. This catalyst has excellent functional group compatibility and the reaction provides rapid access to a diverse range of secondary amines. Under the conditions, aromatic aldehydes are selectively reduced to benzyl alcohols in the presence of ketones. A concise and efficient approach to the synthesis of diverse range of 1,2disubstituted benzimidazoles has also been accomplished for the first time from 1,2-dinitrobenzene and aromatic aldehydes using the above catalytic system. The method involves the domino nitro reduction/cyclization/reduction cascade.

Multifunctional Catalysis of Nanosheet Defective Molybdenum Sulfide Basal Planes for Tandem Reactions Involving Alcohols and Molecular Hydrogen

“…As one of the most representative oxidized nucleophiles, nitroarenes are inexpensive, stable, and readily available compounds. Since their reduction represents the most convenient methodology to access primary aromatic amines, they are considered essential feedstocks for preparing aniline-derived fine chemicals by means of tandem transformations involving reduction reactions. ,,− ,, Among many others, this is the case of benzimidazoles, a class of N -heterocyclic compounds with industrial interest within the fields of pharmaceuticals, − fertilizers, polymers, , dyes, and so on. , In fact, compared to the common use of o -phenylenediamines as starting reagents, − more shortcut approaches to prepare benzimidazoles have been developed starting from o -nitroanilines, − and even more interestingly, from o -dinitroarenes. ,,− Nevertheless, the use of nitroarene-derived reagents in combination with alcohols as coupling reagents to access benzimidazoles is quite limited. To the best of our knowledge, the synthesis of benzimidazoles has been accomplished from o -nitroanilines through transition metal-catalyzed borrowing hydrogen methodologies, ,− ,− and by means of a synthetic strategy based on redox condensation reactions mediated by a F...…”

Preparation of core–shell catalyst for the tandem reaction of amino compounds with aldehydes

“…In order to drive the tandem reaction, catalysts contain two kinds of sites, the solid acid sites are used to catalyze the condensation of primary amines and aldehydes, and the metal catalytic sites are utilized to catalyze the hydrogenation in required condition. 11,15 Catalysts with both sites are considered as promising alternatives for one-pot tandem reactions due to their relatively low corrosivity, high catalytic activity, high selectivity, and easy separation for subsequent use. 16 In recent years, scholars have favored multifunctional core–shell noble metal-based heterogeneous catalysts.…”

Molecularly Engineering Defective Basal Planes in Molybdenum Sulfide for the Direct Synthesis of Benzimidazoles by Reductive Coupling of Dinitroarenes with Aldehydes

“…However, in spite of the evident potential associated with the more straightforward and step economy route of using dinitroarenes as viable starting reagents to access N-heterocyclic compounds, − the preparation of benzimidazoles from these readily available reactants has so far been scarcely investigated (Scheme ). Synthetic strategies based on the redox condensation of o -dinitroarenes with orthoesters or aldehydes to form 2-subtituted or 1,2-disubstituted benzimidazoles were stablished by using an excess of metal (In or Fe) as reductant and acetic or citric acid as the proton source, respectively. Meanwhile, Cao and co-workers reported the reductive N-formylation of o -dinitroarenes, catalyzed by an Au/TiO 2 (Rutile) heterogeneous catalyst, in which formic acid is used as both a reductant and a C 1 source .…”