Additive- and Oxidant-Free Expedient Synthesis of Benzimidazoles Catalyzed by Cobalt Nanocomposites on N-Doped Carbon

Abstract

A one-pot direct synthesis of a wide range of biologically active benzimidazoles through coupling of phenylenediamines and aldehydes catalyzed by a highly recyclable nonnoble cobalt nanocomposite was developed. A broad set of benzimidazoles can be efficiently synthesized in high yields and with good functional-group tolerance under additive- and oxidant-free mild conditions. The catalyst can be easily recycled for successive uses, and the process permits gram-scale syntheses of benzimidazoles.

Electro-organic synthesis: an environmentally benign alternative for heterocycle synthesis

“…59,60 Over the years, several methods of imidazole synthesis were reported, but most of them suffer several disadvantages like large amounts of waste production, poor regio-selectivity and less efficient conversion. To overcome these issues certain efforts have been made which involve the use of ionic liquids, 61 metal nanocomposites 62 and metal organic frameworks. 63 Despite the numerous advantages associated with these methods, they have not been widely adopted due to their high practical cost.…”

“…Wu et al 82 developed a convenient and multicomponent synthesis of 4-selanylpyrazoles (62). The reaction conditions were optimised using phenyl hydrazine (59a), 2,4-pentanedione (60a) and diphenyl diselenide (61a) as reactants.…”

Recent achievements in the synthesis of benzimidazole derivatives

“…Furthermore, the catalyst could be recycled by a simple procedure and reused for five runs without any significant decrease in reaction yields. 71 The catalyst CoO x @NC-800 catalyzes the dehydrogenation of dihydrobenzimidazole to form the desired benzimidazole with liberation of molecular hydrogen ( Scheme 2 ).…”

The Biological Investigations of a Benzoguanamine-based Nickel Complex and Its Application as a Capable Nano‐catalyst for the Synthesis of Benzimidazoles

“…Due to the biological and industrial importance of benzimidazole compounds, several various methods have been used for their synthesis. For example, from the reaction of aromatic and heteroaromatic 2nitroamines by formic acid, iron powder and NH 4 Cl [29], the use of various o-phenylenediamines and Nsubstituted formamides in the presence of zinc and poly(methylhydrosiloxane) [30], the reaction of oiodoanilines or electron-rich aromatic amines with K 2 S and DMSO [31], the reaction of aryl amines and aldehydes with azides [32], the reaction of anilines, primary alkyl amines with sodium azide in the presence of Cu and t-butyl hydroperoxide [33], the reaction of phenylenediamines and aldehydes by cobalt nano-composite [34], the reaction of aromatic diamine with primary alcohols by Mn(I) complex [35], the condensation reaction of simple o-phenylenediamines and a broad range of aldehydes by molecular iodine under basic conditions [36], the reaction of o-phenylenediamines and primary amines by o-quinone catalyst [37], a solvent-and catalyst-free reaction of alkylamines and ohydroxy/amino/mercaptan anilines in the presence of elemental sulfur as traceless oxidizing agent [38], the reaction of o-nitroanilines with alcohols by sodium sul de and iron(III) chloride hexahydrate [39], a solvent-free cobalt-or iron-catalyzed reaction of 2-nitroanilines with benzylamines In recent years, the use of heterogeneous catalysts and their utility in chemical reactions has been the focus of attention, since they have advantages such as recyclability and reusability, easy separation and environmental friendliness [49][50][51][52][53][54]. That is why the design and preparation of novel heterogeneous catalysts and their use are of particular importance [55,56].…”