Synthesis Of 2-substituted Benzimidazole Derivatives Research Articles

Water extract of onion: chemoselective synthesis of 2-substituted benzimidazole derivatives

Water extract of onion: chemoselective synthesis of 2-substituted benzimidazole derivatives

Synthesis of 2-Substituted Benzimidazole Derivatives as a Platform for the Development of UV Filters and Radical Scavengers in Sunscreens

The modern trend in sunscreen products is towards the development of UV filters with multi-functional properties, to provide a broad shielding against ultraviolet radiation, antioxidant activity, and the prevention of skin cancer. Additionally, they should also be safe for humans as well as the environment. The benzimidazole heterocycle is a suitable platform for the development of such multifunctional molecules with potential application in cosmetic formulations, due to their ability to act as both UV protectors and reactive pharmacophores. This review presents for the first time the progress in the synthesis and optimization of benzimidazole compounds as UV sunscreen filters. The modifications to the substitution pattern of the lead compound and structure–activity relationships are discussed, as well as the synthetic approaches for the preparation of 2-substituted benzimidazoles. These aggregated data will be useful in future in the development of modern benzimidazole-based sunscreen.

Synchronous Proton-Hydride Transfer by a Pyrazole-Functionalized Protic Mn(I) Complex in Catalytic Alcohol Dehydrogenative Coupling.

A series of Mn(I) complexes Mn(L1)(CO)3Br, Mn(L2)(CO)3Br, Mn(L1)(CO)3(OAc) and Mn(L3)(CO)3Br [L1 = 2-(5-tert-butyl-1H-pyrazol-3-yl)-1,8-naphthyridine, L2 = 2-(5-tert-butyl-1H-pyrazol-3-yl)pyridine, L3 = 2-(5-tert-butyl-1-methyl-1H-pyrazol-3-yl)-1,8-naphthyridine] were synthesized and fully characterized. The acid-base equilibrium between the pyrazole and the pyrazolato forms of Mn(L1)(CO)3Br was studied by 1H NMR and UV-vis spectra. These complexes are screened as catalysts for acceptorless dehydrogenative coupling (ADC) of primary alcohols and aromatic diamines for the synthesis of benzimidazole and quinoline derivatives with the release of H2 and H2O as byproducts. The protic complex Mn(L1)(CO)3Br shows the highest catalytic activity for the synthesis of 2-substituted benzimidazole derivatives with broad substrate scope, whereas a related complex [Mn(L3)(CO)3Br], which is devoid of the proton responsive β-NH unit, shows significantly reduced catalytic efficiency validating the crucial role of the β-NH functionality for the alcohol dehydrogenation reactions. Control experiments, kinetic and deuterated studies, and density functional theory (DFT) calculations reveal a synchronous hydride-proton transfer by the metal-ligand construct in the alcohol dehydrogenation step.

Facile one pot synthesis of 2-substituted benzimidazole derivatives under mild conditions by using engineered MgO@DFNS as heterogeneous catalyst.

Benzimidazole derivatives are considered as important heterocyclic motifs that show a wide range of pharmaceutical applications. In view of their wide-ranging bioactivities, it is imperative to direct research on the sustainable catalytic synthesis of benzimidazole. Therefore, herein, we report a novel approach for the synthesis of benzimidazole and its derivatives with engineered MgO supported on dendritic fibrous nano silica (MgO@DFNS) as a sustainable heterogeneous catalyst. The catalyst MgO@DFNS was thoroughly characterized to understand its physio-chemical properties using XRD, FE-SEM, XPS, FT-IR, zeta potential, HR-TEM, TGA, TPR and TPD. The obtained results suggested that the catalyst MgO@DFNS prepared well and have the desired characteristics in it. After the successful characterisation of the prepared catalyst MgO@DFNS, it was applied in the synthesis of benzimidazole derivatives via condensation of o-phenylenediamine, and various aromatic and aliphatic aldehydes under ambient temperature. The catalyst produced a clean reaction profile with excellent yields in a shorter time under the umbrella of green chemistry. The effect of reaction parameters such as the effect of time, catalyst dosage, loading of MgO, effect of solvents and effect of different homo and heterogeneous catalyst were also tested. Furthermore, to understand the scope of the catalyst different substituted diamines and substituted aldehydes were reacted and obtained desired products in good to efficient yield. In addition, a recyclability study was also conducted and it was observed that the catalyst could be recycled for up to six cycles without noticeable changes in the morphology and activity. We believe that the present methodology gave several advantages such as an eco-friendly method, easy work-up, good selectivity, high yields and quick recovery of catalyst. MgO@DFNS is highly stable for several cycles without significant loss of its activity, which possibly demonstrates its applicability at the industrial scale.

An elegant approach for selective synthesis of 2-substituted benzimidazoles at room temperature using Ag nanoparticles as an activator: effect of solvent on the selectivity

An expedient, competent, and green protocol was developed for the selective synthesis of 2-substituted benzimidazole by the condensation of 1,2-diaminobenzene and various aldehydes, including aromatic, heteroaromatic, and aliphatic aldehydes, in methanol and water (1:1) as reaction media in the presence of Ag nanoparticles in a one pot operation at room temperature. The selectivity of the protocol for obtaining 2-substituted benzimidazole is highly dependent on the ratios of methanol and water used, as well as the reaction temperature. The present protocol exhibits several advantages, such as high yield, short reaction time, high selectivity, and no side reaction, and it works at room temperature, which makes this methodology green, providing a practical input to the existing procedures available for the synthesis of 2-substituted benzimidazole derivatives.

The Microwave Assisted and Efficient Synthesis of 2-Substituted Benzimidazole Mono-Condensation of O-Phenylenediamines and Aldehyde

Synthesis of 2-substituted benzimidazole derivatives using reactants aldehyde, o-phenylenediamine, and sodium hypophosphite as a catalyst using microwave irradiation. An efficient and green synthesis carried out using sodium hypophosphite gives high yield in shorts reaction time. This route provides key advantages such as high yield, clean, easy work-up, readily available catalyst, and good yield. Compared with the conventional method, microwave irradiation process has more advantages.

Zinc Sulfamate Catalyzed Efficient Selective Synthesis of Benzimidazole Derivatives under Ambient Conditions

Zinc sulfamate (Zn(NH2SO3)2 is a derivative of sulfamic acid (H3NSO3) which possesses “Lewis acidity” and finds well suited in a number of catalytic applications. The present paper describes an efficient, eco-friendly, and clean synthesis of 2-substituted benzimidazole derivatives by reacting diverse o-phenylenediamine with various substituted aromatic aldehydes using a catalytic amount of zinc sulfamate in ethanol at ambient temperature. As a result, 10 mol.% of Zinc sulfamate catalyst showed 92% of respective product yield with 100% conversion using short reaction period in ethanol. Meanwhile, effect of reaction parameters, such as amount of catalyst, different solvents, and reaction temperature on reaction product, was also studied. In addition, in the optimized reaction condition various substituted biological important benzimidazoles derivatives were prepared by using optimized reaction condition in good to efficient yield. In addition, possible reaction mechanism in the presence of zinc sulfamate for the preparation of benzimidazole derivative was sketched and discussed. The present green approach showed significances with faster reaction rate with inexpensive catalyst, which showed excellent and clean yield of benzimidazole in mild reaction condition with easy work-up procedure.

An efficient NaHSO3-promoted protocol for chemoselective synthesis of 2-substituted benzimidazoles in water

An efficient protocol for chemoselective synthesis of 2-substituted benzimidazoles from a variety of aliphatic/aromatic/heteroaryl aldehydes and o-phenylenediamine derivatives promoted by NaHSO3 in water had been developed. The amount of NaHSO3 had a great effect on the reaction selectivity of 2-substituted benzimidazole and 1,2-disubstituted benzimidazole when the reaction was carried out in water. When the amount of the NaHSO3 was more than 11 equivalents, the 2-substituted benzimidazole could be highly selectively formed as the sole product. NaHSO3 was firstly reacted with aldehyde to form the aldehyde sodium bisulfite, which reacted with o-phenylenediamine to form the 2-substituted benzimidazole and inhibited the formation of 1,2-disubstituted benzimidazole. This protocol solved the poor selectivity problem appearing in traditional method when cyclocondensation between o-phenylenediamine and aldehydes. The method also had advantage of simple work up by filtrating the single 2-substituted benzimidazole precipitates from reaction mixture at the end of the reaction without further purification. In addition, the method was applicable to both electron-rich and electron-poor starting materials, which was successfully used for synthesizing nine novel 2-substituted benzimidazole derivatives containing a 1,2,3-triazole moiety. They were characterized by NMR, IR and HRMS spectrum. Moreover, this method had been applied to a large scale synthesis of 2-substituted benzimidazole derivatives.

Zirconocene catalyzed synthesis of 2-substituted benzimidazole derivatives

Zirconocene dichloride (Cp2ZrCl2) in the presence of ethanol is found to be a highly efficient catalyst for the one-pot synthesis of structurally diverse 2-substituted benzimidazole derivatives by reaction of o-phenylenediamine and aromatic aldehydes at ambient temperature.

A Mild and Simple One‐pot Synthesis of 2‐Substituted Benzimidazole Derivatives Using DDQ as an Efficient Oxidant at Room Temperature

AbstractA series of 2‐substituted benzimidazoles were prepared through one‐pot reaction of o‐phenylenediamine with various aryl aldehydes in the presence of 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) in acetonitrile as solvent at room temperature. The reactions were smoothly preceded in excellent yields and short reaction times with an easy work‐up. The pure benzimidazoles as products were confirmed and characterized by physical and spectral data.

Facile and Efficient Method for Synthesis of Benzimidazole Derivatives Catalyzed by Zinc Triflate

We report the synthesis of benzimidazole derivatives using zinc triflate as an efficient catalyst. One-pot synthesis of 2-substituted benzimidazole derivatives from o-phynelyenediamine and substituted aldehydes were developed under zinc triflate in ethanol solvent at reflux temperature.

Nanocrystalline magnesium oxide as solid base catalyst in the presence of iodine promoted one-pot synthesis of 2-substituted benzimidazole derivatives under mild conditions

An efficient single-step procedure for the synthesis of 2-substituted benzimidazole derivatives by nanocrystalline magnesium oxide as solid base catalyst under acetonitrile solvent at room temperature has been developed. The worldwide availability, larger scale synthesis, higher yields and shorter reaction times are the advantages of the present method.

Facile and efficient one-pot synthesis of benzimidazoles using lanthanum chloride.

BackgroundWe report the synthesis of benzimidazoles using lanthanum chloride as an efficient catalyst. One-pot synthesis of 2-substituted benzimidazole derivatives from o-phenylenediamine and a variety of aldehydes were developed under mild reaction conditions.ResultsWe have examined the effect of different solvents using the same reaction conditions. The yield of the product varied with the nature of the solvents, and better conversion and easy isolation of products were found with acetonitrile. In a similar manner, the reaction with o-phenylenediamine and 3,4,5-trimethoxybenzaldehyde was carried out without any solvents. The observation shows that the reaction was not brought into completion, even after starting for a period of 9 h, and the reaction mixture showed a number of spots in thin-layer chromatography.ConclusionsIn conclusion, lanthanum chloride has been employed as a novel and efficient catalyst for the synthesis of benzimidazoles in good yields from o-phenylenediamine and a wide variety of aldehydes. All of the reactions were carried out in the presence of lanthanum chloride (10 mol%) in acetonitrile at room temperature.

Chemoenzymatic selective formation of C–N bonds in a benzimidazole heterocycle

A novel and efficient method for the chemoenzymatic selective formation of C–N bonds in the synthesis of a 2-substituted benzimidazole heterocycle, catalyzed by lipase from porcine pancreas (PPL), has been developed. A series of 2-substituted benzimidazole derivatives were synthesized under mild conditions, with high yields (89–96%) and high selectivity. The blank and control experiments reveal that PPL plays an important catalytic role during the selective C–N bond formation process. The results demonstrate that PPL has a broad catalytic tolerance towards different aldehydes containing electron-donating or -withdrawing groups in this reaction. This study provides an efficient tool for the selective formation of C–N bonds in the synthesis of 2-substituted benzimidazole derivatives.

Fast and efficient method for the synthesis of 2-arylbenzimidazoles using MCM-41-SO3H

Abstract Nanosized MCM-41-SO3H material based on ordered mesoporous silica gel with covalently attached sulfonic acid groups was synthesized and used as acid catalyst for green synthesis of 2-substituted benzimidazole derivatives. Echo-friendly protocol, short reaction times, easy and quick isolation of the products, and excellent yields are the main advantages of this procedure.

Ammonium metavanadate: A novel catalyst for synthesis of 2-substituted benzimidazole derivatives

Ammonium metavanadate (10 mol%) was found to be a useful catalyst for the synthesis of various 2-substituted aryl benzimidazoles. It was used as an oxidizing agent for the condensation of o-phenylenediamine with different substituted aryl aldehydes at room temperature in ethanol. The method was proved to be simple, convenient and the product was isolated with good yields (79–91%).