Synthesis Of 2-substituted Benzimidazoles Research Articles

Synthesis of benzimidazoles by two methods (C–H functionalization and condensation reaction) catalyzed by α-zirconium hydrogen phosphate-based nanocatalyst

In this report, two heterogeneous nanocatalysts based on α-zirconium hydrogen phosphate were applied. These heterogeneous catalysts have demonstrated the promising catalytic activity for the synthesis of 2-substituted benzimidazoles in two different methods. One of these reactions is the functionalization of the C–H bond and the formation of C–N bond, and the other reaction involves the condensation reaction between aldehydes and 1,2-phenylenediamine. The activity of both catalysts was compared in two methods, and the superior catalyst was introduced. The prepared catalysts are easily separated from the reaction mixture by centrifugation and reused several times without significant loss of activity.

Synthesis of 2-substituted benzimidazole, coumarin, benzo[b][1,4]oxazin and dihydropyrimidinone derivatives using core-shell structured Fe3O4@SiO2-ZnCl2 nanoparticles as an effective catalyst

In this paper, a magnetic nanocatalyst of Fe3O4@SiO2-ZnCl2 has been used which enhances the synthesis of benzimidazoles, coumarins, benzoxazines and dihydropyrimidinones. To begin with, 2-substituted benzimidazoles have been synthesized in proper to high yields from 1,2-phenylenediamine with extensive diversity of aromatic aldehydes in the presence of magnetic nanocatalyst. Then, this magnetic nanocatalyst has been used for the synthesis of coumarin derivatives via Pechmann condensation reaction of phenols with ethyl acetoacetate in good yield under solvent-free conditions. Next, the synthesis of benzo[b][1,4]oxazines has been accomplished efficiently by the multi-component condensation of 2-aminophenol, aromatic aldehyde and isocyanide using magnetic nanocatalyst. Lastly, dihydropyrimidinones were synthesized by a one-pot three-component cyclocondensation using β-keto ester, substituted aromatic aldehyde and urea. The benefits of this method are facile, easy work-up, catalyst reusability and leading to good yields. Theoretical assessments allow us to corroborate the reactions mechanism.

Synthesis, characterization and single crystal X-ray studies of pincer type Ni(II)-Schiff base complexes: Application in synthesis of 2-substituted benzimidazoles

Five new pincer type Ni(II)-Schiff base complexes of the general formula [NiL1(PPh3)] 1, [NiL2(PPh3)] 2, [NiL3(PPh3)] 3, [NiL4(PPh3)] 4 and [NiL4(4-MePy)] 5 [where H2L1 = 2-(2,3-dihydroxybenzylideneamino)phenol, H2L2 = N-(2,3-dihydroxybenzylidene)benzohydrazide, H2L3 = 2-(2,3-dihydroxybenzylidene)hydrazinecarbothioamide, H2L4 = 5-(diethylamino)-2-(2-hydroxybenzylideneamino)phenol, 4-MePy = 4-Methylpyridine] were synthesized by the reaction of the Ni(OAc)2.4H2O with the corresponding Schiff base ligand in methanol as coloured crystalline solids in high yields. All the five complexes were fully characterized by FT-IR, UV–Vis, 1H NMR, 13C{1H} NMR, 31P{1H} NMR, mass spectrometry and single crystal X-ray diffraction studies. The crystal structures of all five new complexes confirmed the tridentate nature of the pincer type Schiff base ligands (ONO and ONS) and distorted square planar geometry around the metal centre in all cases. The monodentate ligand (triphenylphosphine/4-Methylpyridine) occupied the fourth site at nickel. The catalytic potential of the complexes has been demonstrated in the synthesis of a series of 2-substituted benzimidazoles at room temperature using low catalyst loading (0.5 mol %), and without the use of any additives. All organic products were isolated in high yields (85–96%) and fully characterized by 1H and 13C{1H} NMR studies.

P-Toluenesulfonic acid Coated Natural phosphate as an efficient catalyst for the synthesis of 2-substituted benzimidazole

<i>p</i>-Toluenesulfonic acid Coated Natural phosphate as an efficient catalyst for the synthesis of 2-substituted benzimidazole

Sulfonic-acid-functionalized activated carbon made from tea leaves as green catalyst for synthesis of 2-substituted benzimidazole and benzothiazole

A simple and efficient procedure for synthesis of 2-substituted benzimidazole and benzothiazole has been developed by using sulfonic-acid-functionalized activated carbon as heterogeneous catalyst. The activated material was prepared from matured tea leaf in presence of phosphoric acid as activating agent. The final catalyst was prepared by anchoring –SO3H group on the surface of the activated carbon. The catalyst could be easily recovered and reused for more than three catalytic cycles without significant loss in catalytic activity. The catalytic performance of the catalyst was found to be superior to that of a similar catalyst prepared from montmorillonite K10.

A practical method, NaOCl-mediated, to prepare thiabendazoles via intramolecular amination reaction

A series of new chlorinated thiabendazoles (6a–m) have been synthesized from readily available anilines and 4-cyanothiazole in moderate to good yields. All synthesized compounds were fully characterized using 1H NMR, 13C NMR, IR, and mass spectrometry. Additionally, the structure of the compound (6f) was confirmed by single-crystal X-ray diffraction. In addition, synthesis of 2-substituted benzimidazoles and 2-phenyl benzothiazole was investigated using our optimized conditions and the outcome is presented herein.

MnO2 Nanoparticles as Efficient Oxidant for Ultrasound-Assisted Synthesis of 2-substituted Benzimidazoles under Mild Conditions

In this article, a novel method for synthesis of 2-substituted benzimidazoles using MnO2 nanoparticles as a convenient oxidant agent in ethanol-water (1:1) as solvent under ultrasound irradiation was demonstrated. In this protocol the desired products were purely obtained in high yields. The main advantages of this research are: mild procedure, simplicity of method, easily work-up, high yields, and short reaction times. The MnO2 nanoparticles were synthesized through a solid-state reaction route using simple strarting materials. Furthermore, their structure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR).

Simple and Efficient One-Pot Synthesis of 2-Substituted Benzimidazoles from θ-Diaminoarene and Aryl Aldehydes

An easy and efficient one-pot condensation method for the synthesis of substituted benzimidazoles from θ-phenylenediamines with aryl aldehydes using urea hydrogen peroxide (UHP) and I2 in dimethylsulfoxide (DMSO) provides wide substrate scope with good to excellent yields and simple and quick isolation of the products.

Facile one-pot clean synthesis of benzimidazole motifs: Exploration on bismuth nitrate accelerated subtle catalysis

Abstract In the present letter, an efficient, clean and one-pot synthesis of 2-substituted benzimidazole and 1,2-disubstituted benzimidazole derivatives has been explored by reacting o -phenylenediamine with aromatic aldehydes using bismuth nitrate as a catalyst in ethanol at ambient temperature. This methodology avails with faster reactions, excellent yield, mild reaction conditions, use of inexpensive and non-toxic catalyst compared to literature reported hitherto.

Iron(III) Tetranitrophthalocyanine Chloride Immobilized on Activated Carbon: Efficient, Excellent Chemoselectivity and Recyclable Catalyst for Synthesis of 2-Substituted Benzimidazoles

Iron(III) Tetranitrophthalocyanine Chloride Immobilized on Activated Carbon: Efficient, Excellent Chemoselectivity and Recyclable Catalyst for Synthesis of 2-Substituted Benzimidazoles

Synthesis of 2-Substituted Benzimidazoles Using 25 % Co/Ce-ZrO2 as a Heterogeneous and Nanocatalyst

25 % Co/Ce-ZrO2 nano fine particles are reported as a new catalyst for the efficient synthesis of 2-arylbenzimidazoles. A simple and convenient procedure, reusable catalyst, easy purification and shorter reaction times are the advantageous features of this method. Also prepared catalyst according to the coprecipitation method was characterized by common techniques such as SEM, XRD, FTIR and so on analysis. The catalyst is reusable and, reusable catalyst was characterized by XRD and FTIR techniques.

One-Pot Synthesis of Benzimidazoles in Water in the Presence of SiO2–OPO3H

Silica-bound phosphoric acid (SiO2–OPO3H), as an eco-friendly, reusable, and heterogeneous catalyst, was applied for synthesis of 2-substituted benzimidazoles in water at 70°C. Very short reaction times, clean work-up, and high yields are among the advantages of this protocol.

Synthesis of 2-Substituted Benzimidazoles in the Presence of Polyaniline Nanoparticles Doped With 12-Tungstophosphoric Acid as Reusable Heterogeneous Catalyst

Polyaniline nanoparticles doped with 12-tungstophosphoric acid was prepared with different loading amounts of 12-tungstophosphoric acid. Doped polyaniline was characterized by XRD, SEM, and FT-IR techniques and the Keggin anion of heteropoly acid was detected on the polymer. Doped polymer was used as heterogeneous solid acid catalyst for the synthesis of 2-substituted benzimidazoles by the reaction of o-phenylenediamine with various types of aldehydes. The activity and reusability of the catalyst were found to be good.

Catalytic performance of SiO2-supported Fe(ClO4)3. 6H2O in synthesis of 2-substituted benzimidazoles

Benzimidazole derivatives have been synthesized using a catalytic amount of Fe(ClO 4 ) 3 /SiO 2 at room temperature with excellent yields under solvent-free conditions. The solid phase conditions and use of a heterogeneous, and inexpensive catalyst are attractive features of this method.

Efficient, Rapid and One Pot Synthesis of 2-substituted Benzimidazoles Using the NaOH/I2 System as an Oxidant Under Mild Conditions

A one-pot efficient synthesis of benzimidazole derivatives has been achieved from aryl aldehydes and o-phenylenediamine in the presence of the NaOH/I2 system at room temperature in acetonitrile. The simplicity of the procedure and work-up, larger scale synthesis, high yields and short reaction times are the advantages of this method.

Eco-Friendly Synthesis of 2-Substituted Benzimidazoles Using Air as the Oxidant

A simple, environmentally friendly procedure for the synthesis of 2-substituted benzimidazoles by the one-pot condensation of o-phenylenediamines with aromatic aldehydes using continuous bubbling of air in absolute ethanol at room temperature is described. The simplicity of the system, mild conditions, involvement of a non-toxic and practically inexhaustible oxidant, easy and quick isolation of the products, and moderate to good yields are the main advantages of this procedure.

Nanosized sulfated zirconia as solid acid catalyst for the synthesis of 2-substituted benzimidazoles

AbstractThe condensation reaction of o-phenylenediamine and arylaldehydes was investigated in the presence of nanosized sulfated zirconia (SO42−-ZrO2) as the solid acid catalyst. Nanosized SO42−-ZrO2 was prepared and characterized by the XRD, FT-IR, and SEM techniques. The results confirm good stabilization of the tetragonal phase of zirconia in the presence of sulfate. Reusability experiments showed partial deactivation of the catalyst after each run; good reusability can be achieved after calcinations of the recovered catalyst before its reuse.

Synthesis of 2-Substituted Benzimidazoles and 1,5-Disubstituted Benzodiazepines on Alumina and Zirconia Catalysts

In this study, alumina, zirconia, manganese oxide/alumina, and manganese oxide/zirconia have been investigated for their catalytic activity in the condensation reaction between o -phenylenediamine and an aldehyde or a ketone to synthesise 2-substituted benzimidazoles and 1,5-disubstituted benzodiazepines respectively. Surface area, surface acidity, and morphology of the catalysts have been analysed and correlated with their catalytic activity. The isolated yields of 2-substituted benzimidazoles and 1,5-disubstituted benzodiazepines are in the range of 30% to 95%. A good correlation between the amount of surface acid sites as well as the surface morphology of the catalysts and the catalytic activity has been observed. This method has been found to be simple and economical. The solid supports could be regenerated and reused without much loss in their activity. Further, the solid supports have been also found to be effective as general catalysts in the condensation of o -phenylenediamine with other substituted aldehydes and ketones. The presence of amount of surface acid sites, morphology of the catalyst, and presence of manganese oxide on the surface of the catalyst plays a synergistic role in the synthesis of benzimidazoles and benzodiazepines.

A Combined-Redox Synthesis of 2-Alkylbenzimidazoles from 2-Nitroanilines by Semiconductor Photocatalysis

One-pot photocatalytic synthesis of 2-substituted benzimidazoles from 2-nitroanilines with different alcohols by combined redox cyclization reaction using TiO2-P25 is reported. The reaction, when performed with ethanol, gives 2-methylbenzimidazole as a single product. However, in a mixture of ethanol and water (1:1), it gives both 2-methylbenzimidazole and 1-ethyl-2-methylbenzimidazole. The products have been characterized by Fourier transorm–infrared, 1H NMR, 13CNMR, and gas chromatography–mass spectrometry analysis. TiO2-P25 behaves as a combined redox photocatalyst by reducing 2-nitroaniline and oxidizing alcohols simultaneously under ultraviolet light. Easy product isolation under mild conditions and good yield make this one-pot synthesis ecofriendly.

Synthesis of 2-Substituted Benzimidazoles Catalyzed by Cyclic Phosphoric Acid

In the presence of cyclic phosphoric acid, a series of 2-substituted benzimidazoles were synthesized by the reaction of o-phenylenediamine and aldehyde in tetrahydrofuran at room temperature. The influence of different catalysts, catalyst amount and solvent were investigated, the optimal reaction conditions were obtained and a possible mechanism was proposed. The reaction has the virtue of simple operation, mild reaction condition, high yield and environment friendliness.