Reusable Cobalt(III)‐Salen Complex Supported on Activated Carbon as an Efficient Heterogeneous Catalyst for Synthesis of 2‐Arylbenzimidazole Derivatives

Abstract

Various 2-arylbenzimidazoles were synthesized from phenylenediamines and aromatic aldehydes via a one-step process in the presence of a catalytic amount of a cobalt-salen complex supported on activated carbon [CoxO-CoA C H T U N G T R E N N U N G (salen) 11] at room temperature. The salient features of this method include mild conditions, short reaction times, high yields, easy purification, recyclable catalyst, largescale synthesis and simple procedure. The reactions were performed in ethanol and the catalyst could be reused for several cycles without a decrease in activity. The heterogeneous catalyst was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic forced microscopy (AFM), thermogravimetric (TG) methods for analysis of nitrogen adsorption and FT-IR spectroscopy. Leaching experiments showed that the catalyst is most strongly anchored to the activated support after 10 cycles of reuse.

Catalytic role of sodium dodecyl sulfate: Selective synthesis of 1, 2-disubstituted benzimidazoles in water

“…As a large body of protocols have been established for synthesizing benzimidazoles of type 4 [21][22][23][24][25][26][27], relatively rare methods have been reported to directly prepare 1, 2-disubstituted benzimidazole 3 with ideal selectivity [28][29][30][31][32]. Recently, several elegant catalyst systems have been developed to prepare 3 in excellent chemoselectivity by employing some organic solvents and water as the medium in the presence of costly organometallic catalysts [27,29,31,32].…”

“…have also been developed to prepare functionalized benzimidazoles. However, directly employing the condensation-aromatisation reaction of ophenylenediamines and aldehydes under oxidative condition turned out to be the most facile and effective method to synthesize 2-substituted benzimidazole 4 [21][22][23][24][25][26][27] and 1, 2-disubstituted benzimidazole 3 from readily available cheap starting materials [28][29][30][31][32].…”

Simple, Efficient, and Applicable Route for Synthesis of 2-Aryl(Heteroaryl)-Benzimidazoles at Room Temperature Using Copper Nanoparticles on Activated Carbon as a Reusable Heterogeneous Catalyst

“…Albeit several reports [25][26][27][28][29][30][31][32][33], the direct condensation of o-aryldiamines and aromatic aldehydes at room temperature is less developed because as previously reported [36] this superficially simple reaction is a complex sequence of competing reactions and leads to the formation of a complex mixture of products containing 1,2-disubstituted benzimidazoles and 1,2-disubstituted benzimidazolines as main byproducts. Moreover, most of the catalysts have been used for this purpose are not recoverable and destroyed in the work-up procedure.…”

Benzoimidazole Derivatives Containing Indole Unit: Activated Carbon/Air Promoted Synthesis and Spectral Properties

“…空气是一种资源丰富、 环境友好的天然氧化剂, 以其直接参与反应, 不仅可避 免其它氧化剂带来的环境污染问题, 同时又增加经济效 益, 符合现代绿色化学理念. 活性炭是一种价廉的多孔 物质, 比表面积大, 热化学稳定性高, 在反应中可增大 原料之间的接触，而且对环境基本无污染 [34] . 本文介绍…”