Imidazolium chloride-catalyzed synthesis of benzimidazoles and 2-substituted benzimidazoles from o-phenylenediamines and DMF derivatives

A facile, general, and economical synthesis of diversely functionalized benzimidazoles and 2-substituted benzimidazoles has been realized via the imidazolium chloride-catalyzed cyclization of o-phenylenediamines with DMF derivatives. This protocol shows a broad substrate scope for aliphatic, aromatic, and heteroaromatic amides. A series of benzimidazoles and 2-substituted benzimidazoles have been obtained in moderate to excellent yields.     

Heteroaromatic annulation of 2-methyl/2-cyanomethylbenzimidazole dianions with alpha-oxoketene dithioacetals: a highly regioselective synthetic protocol for 1,2- and 2,3-substituted/annulated pyrido[1,2-a]benzimidazoles

A highly efficient and regioselective annulation protocol for a series of linearly 2,3- and angularly 1,2-substituted and annulated pyrido[1,2-a]benzimidazoles involving [3 + 3] cyclocondensation of the dianions generated from 2-methyl (2A) and 2-cyanomethyl (3A) benzimidazoles with a variety of alpha-oxoketene dithioacetals has been reported. Thus the dianion 2A derived from 2-methylbenzimidazole has been shown to undergo regioselective 1,2-addition with various alpha-oxoketene dithioacetals derived from acyclic (4a-d) and cyclic ketones (13a,b, 20, 29 and 32) to afford various carbinol acetals which on intramolecular cyclocondensation in the presence of phosphoric acid furnish the corresponding 1-methylthio-2,3-substituted (5a-c) and 2,3-fused linear polycyclic (14a,b,21, 30, and 33) pyrido[1,2-a]benzimidazoles in high yields. Similarly the dianion 3A from 2-cyanomethylbenzimidazole undergoes one-pot conjugate addition-elimination and cyclocondensation with these alpha-oxoketene dithioacetals to give 4-cyano-3-(methylthio)-1(or 1,2-)-substituted (6a-d) and the corresponding angularly 1,2-fused (16a,b, 23, 31, and 34) polycylic analogues of pyrido[1,2-a]benzimidazoles in excellent yields.     

Chemistry of 2-substituted benzimidazoles. 1. 5-Amino-2-methyl(aryl, arylalkyl, pyridyl)benzimidazoles

A series of 2-substituted benzimidazoles was synthesized. These products were consecutively converted into 5-nitro- and 5-amino-2-substituted benzimidazoles.Russian People's Friendship University, 117198 Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 493–500, April, 200.     

Transmission of the substituent effects in 2-substituted benzimidazoles studied by 1H and 13C nuclear magnetic resonance

The substituent influence on the ¹H and ¹³C NMR chemical shifts in 2-substituted benzimidazoles and their anions and cations has been investigated. The transmission of the electronic effects of substituents from C-2 to C-5 (6) is approximately 20% less effective than that in the opposite direction. The solvent influence on the chemical shifts of protons and transmission effects in the charged forms of 2-substituted benzimidazoles has been studied.     

A practical synthesis of 2-(N-substituted)-aminobenzimidazoles utilizing CuCl-promoted intramolecular cyclization of N-(2-aminoaryl)thioureas

A practical protocol for synthesis of 2-(N-substituted)-aminobenzimidazoles was developed. N-(2-Aminoaryl)thioureas undergo a CuCl-promoted intramolecular cyclization to give the corresponding 2-(N-substituted amino)benzimidazoles in good to excellent isolated yields.     

Practical application of PhI(OAc)2/I2 combination to synthesize benzimidazoles from 2-aminobenzylamine through ring distortion strategy

In this present work the combination of iodobenzenediacetate (PIDA)/iodine has been established as a promising reagent to promote the construction of 2-substituted benzimidazoles from 2-aminobenzylamine and a variety of easily available aldehydes/arylamines through a ring distortion strategy. The present protocol offers mild, metal free, robust conditions to synthesize 2-substituted benzimidazoles in good to excellent yields. In addition, the oxidation prone functional groups show tolerance during the reaction and after completion of the reaction pure products can be easily obtained applying hassle free filtration of the reaction mixture through silica gel bed.     

The synthesis of some 1-(β-diethylaminoethyl)-2-(p-ethoxybenzyl)-5-substituted benzimidazoles

The syntheses of several 5-substituted benzimidazoles structurally related to the highly active analgesic 1-(β-diethylaminoethyl)-2-(p-ethoxybenzyl)-5-nitrobenzimidazole are presented.     

A Theoretical Study on the Tautomerism of C-Carboxylic and Methoxycarbonyl Substituted Azoles

DFT calculations (B3LYP/6-31+G^**) have been carried out on 106 tautomers and conformers of NH-azoles bearing CO₂H and CO₂CH₃ groups. The following azoles systems have been studied: 2-substituted pyrroles, 2-substituted indoles, 2-substituted imidazoles, 2-substituted benzimidazoles, 4(5)-substituted imidazoles, 3(5)-substituted pyrazoles, 3-substituted indazoles (1H and 2H), 3,4(5)-substituted-1,2,3(5)-triazoles, 2,3(5)-substituted-1,2(3),4-triazoles, 4(5)-1,2,3,4(5)-tetrazoles. In the case of pyrazole, 3,5-disubstituted derivatives have also been computed, including four dimers.Dedicated to our friend Professor Vladimir I. Minkin on his 70th anniversary.     

Regioselectivity of heterocyclization of 2-substituted 3,3-bis(methylsulfanyl)acrylo-nitriles with 2-benzimidazoleacetonitrile

Functionalized pyrido[1,2-a]benzimidazoles have been synthesized by the interaction of 2-substituted 2-cyano-3,3-bis(methylsulfanyl)acrylonitriles with 2-benzimidazoleacetonitrile under S _N Vin reaction conditions.     

A convenient synthesis of new heterocycles from benzimidazoles and carbon suboxide

The reaction of carbon suboxide with 2-substituted benzimidazoles was investigated. By this reaction 1,3-diazino- (pyrimido-), 1,3-oxazino- and 1,3-thiazinobenzimidazole-1,3-diones are obtained.     

Synthesis of 2-substituted benzimidazoles and bis-benzimidazoles by microwave in the presence of alumina-methanesulfonic acid

A microwave-assisted method for the synthesis of 2-substituted benzimidazoles in the presence of alumina-methanesulfonic acid (AMA) is reported. In addition, by this method some new bis-benzimidazoles from the direct reaction of phenylenediamine and dicarboxylic acid under microwave irradiation in good to excellent yields are described.     

超声辐射下NH4OAc高效催化合成2-取代苯并咪唑类衍生物（英文）

超声辐射下,以NH4OAc为催化剂,利用芳香醛和邻苯二胺一锅法合成了一系列2-取代苯并咪唑类衍生物,该方法具有反应条件温和、收率高的特点。     

Rapid one-pot preparation of 2-substituted benzimidazoles from 2-nitroanilines using microwave conditions

A high yielding one-pot procedure for the generation of 2-substituted benzimidazoles directly from 2-nitroanilines by in situ reduction and cyclization using a microwave procedure is described.     

Synthesis of 1-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-r-benzimidazoles

Reaction of 2,6-di-tert-butyl-1,4-benzoquinone with o-phenylendiamine gives 2,6-di-tert-butyl-1,4-benzoquinone-4-(N-o-aminophenyl)imine which reacts smoothly with heterocyclic, aromatic and aliphatic aldehydes to form (1-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-substituted benzimidazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 483–485, April, 1990.     

Oxidation and acid-catalyzed cyclization of aldehyde 2-aminophenylhydrazones. Alternative syntheses for 1,2,4-benzotriazines and benzimidazoles

Aldehyde 2-aminophenylhydrazones are easily oxidized by air to 3-substituted 1,2,4-benzotriazines. In two cases the intermediate 3,4-dihydro-1,2,4-benzotriazines were isolated. In the absence of oxygen, acids catalyze the formation of 2-substituted benzimidazoles with loss of ammonia. It is suggested that both reactions proceed via 1,2,3,4-tetrahydro-1,2,4-benzotriazines (III), formed by addition of the amino group on the hydrazone double bond. Such cyclic forms (III) predominate over the open chain structures (II) in the cases of aliphatic and arylalkylaldehyde 2-aminophenylhydrazones, as supported by nmr spectra, while benzaldehyde 2-aminophenylhydrazone exists mainly or exclusively in the open chain form (II).     

Effect of meso substituents on the NH acidities of benzimidazoles

Chemistry of Heterocyclic Compounds - The NH acidities of a systematic series of 2-substituted benzimidazoles in acetonitrile were studied by potentiometric titration. It was found that the...     

Zeolites. Efficient and Eco-friendly Catalysts for the Synthesis of Benzimidazoles

Summary. A superior method of synthesis of 2-substituted benzimidazoles by means of the heterogeneous catalysis of synthetic and natural zeolites in the reaction of 1,2-diaminobenzene with acid chlorides is described.     

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

Ammonium metavanadate (10 tool%) 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-pbenylenediamine 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%).     

DBSA mediated chemoselective synthesis of 2-substituted benzimidazoles in aqueous media

An efficient synthetic method has been developed for the facile synthesis of 2-substituted benzimidazoles in organized aqueous media in the presence of a surfactant (viz. DBSA) as catalyst and I₂ as co-catalyst. The method described has the advantages of operational simplicity, excellent yields, high chemoselectivity, and clean and green reaction profile.     

I2/TBHP promoted oxidative C–N bond formation at room temperature: Divergent access of 2-substituted benzimidazoles involving ring distortion

A new ‘one pot’ tandem synthesis of 2-substituted benzimidazoles has been developed from 2-aminobenzyl alcohol/2-aminobenzamide and different coupling partners (nitriles, aldehydes and 1,3-diketones) via iodine and TBHP promoted oxidative ring contraction. The present strategy involves sequential C–N bond formation, cyclization, subsequent ring contraction and dehydrogenation to afford various medicinally important benzimidazole derivatives in moderate to good yields. This operationally simple synthetic approach proceeds at room temperature under base-free condition, broadly applicable to a wide array of nitriles and aldehydes bearing oxidation prone functional groups and noteworthy to mention that various acyclic 1,3-diketones undergo selective C–C bond cleavage leading to 2-alkyl benzimidazoles under mild condition.