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.     

Palladium-catalyzed N-heteroannulation of N-allyl- or N-benzyl-2-nitrobenzenamines: synthesis of 2-substituted benzimidazoles

A palladium-catalyzed reductive N-heteroannulation of N-allyl- or N-benzyl-2-nitrobenzenamines, using carbon monoxide as the ultimate reducing agent, affording 2-substituted benzimidazoles has been developed.     

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.     

An efficient method to access 2-substituted benzimidazoles under solvent-free conditions

An expeditious method to access 2-substituted benzimidazoles was developed. Both aromatic (phenols, anilines, and thiophenols) and alkyl nucleophiles (amines and thiols) react with 2-methylsulfonyl benzimidazole under solvent-free conditions to generate a variety of 2-substituted benzimidazoles.     

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.     

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.     

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.     

Synthesis of benzimidazoles from 1,1-dibromoethenes

A mild and efficient method for the preparation of substituted benzimidazoles from 1,1-dibromoethenes and o-diaminobenzenes is described. The reaction employs DABCO as the base and NMP as the solvent. A variety of substitutions on both 2-aryl-1,1-dibromoethenes and o-diaminobenzenes are tolerated. This new procedure is carried out under mildly basic conditions, which may provide a complementary route to the existing preparations of benzimidazoles.     

PEG-mediated catalyst-free expeditious synthesis of 2-substituted benzimidazoles and bis-benzimidazoles under solvent-less conditions

A wide variety of 2-substituted benzimidazoles and bis-benzimidazoles were synthesized in high yields by PEG-mediated catalyst-free synthesis under solvent-less conditions. The products were directly recrystallized from hot methanol. The reaction occurred giving excellent yields with low as well as high molecular weight PEGs.     

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。     

Chiral benzimidazoles and their applications in stereodiscrimination processes

Chiral aspects of benzimidazoles have been over-shadowed for a long time due to the large number of reports on benzimidazoles in the medical field in numerous categories of therapeutic agents. The vigorous research activity in chiral applications of benzimidazole derivatives started after bifunctional benzimidazoles made their appearance especially in the last 2–3 decades. Thus, chiral benzimidazoles form a comparatively young branch of chiral chemistry. The presence of pyridine and pyrrole type of nitrogens along with the fused benzene ring confer on this class of molecules, special properties including useful nucleophilicity, hydrogen bonding ability and a rigid backbone, all of which play decisive roles in proven chiral applications. The present review aims to cover the synthetic routes to access chiral benzimidazoles and their applications in a plethora of chiral fields including enantioselective organocatalysis, metal-based catalysis, asymmetric transformations involving benzimidazole-N-heterocyclic carbenes, kinetic resolution, benzimidazole-based macrocyclic hosts in chiral supramolecular chemistry and other miscellaneous chiral applications.     

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.     

Copper-doped silica cuprous sulfate: A highly efficient heterogeneous nano-catalyst for one-pot three-component synthesis of 1-H-2-substituted benzimidazoles from 2-bromoanilines,aldehydes, and [bmim]N3

A facile and highly efficient one-pot three-component synthesis of 1-H-2-substituted benzimidazole derivatives from readily available substrates catalyzed by copper-doped silica cuprous sulfate (CDSCS) is described. In this method, treatment of diverse 2-bromoanilines, aldehydes, and [bmim]N₃ in DMF at 110 °C in the presence of CDSCS as a highly efficient heterogeneous nano-catalyst affords the corresponding 1-H-2-substituted benzimidazoles in good to excellent yields. The CDSCS is an inexpensive and stable nano-catalyst that could be simply prepared, recovered and reused for many consecutive reaction runs without significant loss of its activity.     

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.     

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.     

The study of benzimidazoles

The nature of the first two long-wave bands in the UV spectra of 2-substituted benzimidazoles has been analyzed on the basis of photoelectron spectra (PES). Three basic types of spectroscopic situations are typical of these compounds: 1) a change in the sequence of the occupied MO of the ground state does not influence the order of the excited energy levels; 2) when the π-levels are in the same order, inversion of the excited states occurs; 3) reversal of the occupied π-MO of the ground state causes the inversion of the excited states. For communication 7 see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1761–1766, October, 1993.     

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...     

A mild, one-pot synthesis of disubstituted benzimidazoles from 2-nitroanilines

A one-pot synthesis of disubstituted benzimidazoles from 2-nitroanilines is described. Hydrogenation of N-substituted 2-nitroanilines with palladium on carbon as catalyst in the presence of trimethyl orthoformate and catalytic pyridinium p-toluenesulfonate (PPTS) at room temperature provided good to excellent yields of the corresponding disubstituted benzimidazoles.     

Synthese et polymerisation du diamino-3,4 styrene: Application a une methode generale de preparation de polyvinyl-5(6) benzimidazoles

We describe a new method for preparation of 2-substituted poly-5(6) vinyl benzimidazoles starting from a new polymer, poly3,4-diaminostyrene. The monomer (3,4-diamino-styrene) is synthesized by an original 6-step process with an improved overall yield using p-aminoacetophenone. The radically induced polymerization affords the best results under emulsion conditions. The one-step transformation into poly-5(6) vinyl benzimidazole is achieved with a high degree of conversion.     

CN bond formation and cyclization: A straightforward and metal-free synthesis of N-1-alkyl-2-unsubstituted benzimidazoles

A straightforward and metal-free synthesis of N-1-alkyl-2-unsubstituted benzimidazoles from the corresponding o-fluoro aryl formamidines and primary amines using microwave irradiation is described. The displacement of -F by the primary amine and cyclization to form the corresponding benzimidazoles took place in one pot.