Selective Synthesis of Benzimidazoles from o-Phenylenediamine and Aldehydes Promoted by Supported Gold Nanoparticles

Abstract

We investigated the catalytic efficacy of supported gold nanoparticles (AuNPs) towards the selective reaction between o-phenylenediamine and aldehydes that yields 2-substituted benzimidazoles. Among several supported gold nanoparticle platforms, the Au/TiO2 provides a series of 2-aryl and 2-alkyl substituted benzimidazoles at ambient conditions, in the absence of additives and in high yields, using the mixture CHCl3:MeOH in ratio 3:1 as the reaction solvent. Among the AuNPs catalysts used herein, the Au/TiO2 containing small-size nanoparticles is found to be the most active towards the present catalytic methodology. The Au/TiO2 can be recovered and reused at least five times without a significant loss of its catalytic efficacy. The present catalytic synthetic protocol applies to a broad substrate scope and represents an efficient method for the formation of a C–N bond under mild reaction conditions. Notably, this catalytic methodology provides the regio-isomer of the anthelmintic drug, Thiabendazole, in a lab-scale showing its applicability in the efficient synthesis of such N-heterocyclic molecules at industrial levels.

UV-visible light-induced photochemical synthesis of benzimidazoles by coomassie brilliant blue coated on W–ZnO@NH2nanoparticles

“…Subsequently, the imine intermediate that is in equilibrium with the corresponding dihydrobenzimidazole (3), can be catalytically dehydrogenated with air to generate the desired final benzimidazole product. Although previous reports 56 strongly commented that conversion of imine intermediate to the corresponding benzimidazole would involve generation of intermediate (3), however, it seems that the protodeauration of imine intermediate (2) should be very fast because we failed to detect it by NMR. In addition, performing this reaction in N 2 atmosphere, led to a significant decrease in the yield% from 95 to 37%.…”

Facile Synthesis of Benzimidazoles via N-Arylamidoxime Cyclization

“…Benzimidazole compounds have attracted great interest of researchers, and many synthetic methods were developed due to their various biological activities and wide applications in the past several decades. Generally, benzimidazole compounds were most often constructed by condensation of o -phenylenediamines with carboxylic acid derivatives − as well as aldehydes, − ketones, primary aliphatic amines, and alcohols , (Scheme A). Additionally, the synthesis of benzamidines from amidines through metal-catalyzed or oxidative cyclization was also explored (Scheme B). − Recently, benzimidazoles were generated from N -phenylamidoxime esters with the iridium photocatalyst …”

Bimetallic CoMoO4@C nanorod catalyzes one‐pot synthesis of benzimidazoles from benzyl alcohol and o‐phenylendiamine without alkali

“…In this case, the coupling of 1,2-diamines with aldehydes or 1,2-diketones was reported for the synthesis of benzimidazoles. [13][14][15][16] However, the availability of the expensive and reactive aldehydes or 1,2-diketones limited these processes for a broader scope.…”