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A novel series of 2-(benzimidazol-2-yl)quinoxalines with three types of pharmacophore groups, namely, piperazine, piperidine, and morpholine moieties, which are part of known antitumor drugs, was designed and synthesized. The compounds have been characterized by NMR and IR spectroscopy, high- and low-resolution mass spectrometry, and X-ray crystallography. 2-(Benzimidazol-2-yl)quinoxalines with

A novel and efficient protocol for the synthesis of diversely substituted 2,2′-bibenzimidazoles from the reaction of 3-cyanoquinoxalin-2(1H)-ones with 1,2-diaminobenzenes has been developed, which ...

A facile approach to a range of substituted 7-(benzimidazol-2-yl)thioxolumazines [7-(benzimidazol-2-yl)-2-thioxo-2,3-dihydropteridin-4(1H)-ones] and 7-(benzimidazol-2-yl)lumazines [7-(benzimidazol-2-yl)pteridine-2,4(1H,3H)-diones] is described. These new biheterocyclic systems are obtained via H2SO4-catalyzed rearrangement of quinoxalin-2-ones in the presence of 5,6-diamino-2-mercapto- and 2,5,6-triaminopyrimidin-4-ols. Thus, benzimidazole and pteridine rings are constructed in one synthetic step. A plausible ANRORC (addition of nucleophile, ring opening and ring closure)-type reaction mechanism is proposed. Applying the rearrangement to the aza-analogue of 3-benzoylquinoxalin-2(1H)-one—i.e., 3-benzoylpyrido[2,3-b]pyrazin-2(1H)-one—with 5,6-diamino-2-mercaptopyrimidin-4-ol makes it possible to synthesize inaccessible 7-(1H-imidazo[4,5-b]pyridin-2-yl)-6-phenyl-2-thioxo-2,3-dihydropteridin-4(1H)-one. 7-(Benzimidazol-2-yl)-6-(2-fluorophenyl)-2-thioxo-2,3-dihydropteridin-4(1H)-ones undergoes intramolecular nu...

A new method is proposed for the synthesis of 2-substituted benzimidazole-5(6)-carboxylic acids. The acid-catalyzed rearrangement of 2(3)-aroyl-3(2)-oxo-3,4(1,2)-dihydroquinoxaline-6-carboxylic acids was shown to proceed with the formation of 2-(3-arylquinoxalin-2-yl)-1H-benzimidazole-5(6)-carboxylic acids. NMR studies of the rearrangement reaction product, 2-(3-phenylquinoxalin-2-yl)-1Hbenzimidazole-6-carboxylic acid, indicated that it existed as a mixture of two tautomeric forms due to benzimidazole tautomerism under the NMR conditions. The carboxyl group of the synthesized benzimidazoles was used for the preparation of new derivatives.

A novel and efficient protocol for the synthesis of diversely substituted 2,2'-bibenzimidazoles from the reaction of 3-cyanoquinoxalin-2(1

Interaction of quinoxalin-2(1H)-one-3-carbaldoximes with 1,2-benzenediamine derivatives in AcOH or n-BuOH at reflux in the presence of sulfuric acid as catalyst was found to give 3-(benzimidazol-2-yl)quinoxalin-2(1H)-ones and 2-(benzimidazol-2-yl)quinoxalines in relatively good yields, which formed as a result of the Weidenhagen reaction and Mamedov rearrangement, respectively. The reaction in AcOH afforded 2-(benzimidazol-2-yl)quinoxalines in preference to the 3-(benzimidazol-2-yl)quinoxalin-2(1H)-ones, while the reverse result was obtained in n-BuOH. The synthetic utility of this strategy was illustrated by the concise, one-pot synthesis of 3-(3H-imidazo[4,5-b]pyridin-2-yl)quinoxalin-2(1H)-ones.

A facile approach to a range of substituted 7-(benzimidazol-2-yl)thioxolumazines [7-(benzimidazol-2-yl)-2-thioxo-2,3-dihydropteridin-4(1 H)-ones] and 7-(benzimidazol-2-yl)lumazines [7-(benzimidazol-2-yl)pteridine-2,4(1 H,3 H)-diones] is described. These new biheterocyclic systems are obtained via H

The reaction of 3-benzoylquinoxalin-2(1H)-ones with enamines (generated in situ from ammonium acetate and the corresponding methylaryl(hetaryl)ketones) proceeds smoothly to give the corresponding substituted 1-(pyrrolyl)benzimidazolone derivatives in moderate yields through the novel rearrangement of 3-benzoylquinoxalin-2(1H)-ones involving a dual cleavage of the C3═N4 and C2-C3 bonds under mild conditions.

The solubilization capacity of surfactants of different types was quantitatively characterized by spectrophotometry toward 2,2’-bibenzimidazole (BBI), whose derivatives possess a wide range of pharmacological activity. 2,2’-Bibenzimidazole solubilized by sodium dodecyl sulfate micelles is characterized by a high molar absorption coefficient (9400 mol−1 L cm−1) at the absorbance maximum (342 nm at pH 4–10), which may serve as a basis for the development of procedures for analytical monitoring of the BBI content in aqueous solutions and biosystems. The ability of surfactants to enhance the solubility of BBI in water and, as a consequence, to increase its bioavailability in the series sodium dodecyl sulfate < cetyltrimethylammonium bromide < Tween-80.

The reaction of 3-ethoxycarbonylmethylene-3,4-dihydroquinoxalin-2(1H)-one with the Vilsmeier reagent, the treatment of 3-(3,4-dihydroquinoxalin-2(1H)-on-3-yl)-1,2-dihydro-1,5-benzodiazepin-2(1H)-one hydrochloride with 10% sodium hydroxide and 3-benzimidazoylquinoxalin-2(1H)-one with both 1,2-phenylenediamine dihydrochloride, and the reactions of 1,2-phenylenediamine have been reinvestigated and the structures of these reaction products have been revised. It has been shown that in all the three cases other regioisomers of products have been formed as distinct from the literature data. The mechanisms to explain the formation of the products are suggested.

The reaction of 3-ethoxycarbonylmethylene-3,4-dihydroquinoxalin-2(1H)-one with the Vilsmeier reagent, the treatment of 3-(3,4-dihydroquinoxalin-2(1H)-on-3-yl)-1,2-dihydro-1,5-benzodiazepin-2(1H)-one hydrochloride with 10% sodium hydroxide and 3-benzimidazoylquinoxaline-2(1H)-one with both 1,2-phenylenediamine dihydrochloride, and the reactions of 1,2-phenylenediamine have been reinvestigated, and the structures of these reaction products have been revised. The aforementioned reactions have been shown to proceed with the formation of 1-N,N-dimethylaminomethylene-2-oxo-1,2-dihydrofuro[2,3-b]quinoxaline in the first case, the formation of 3-[2-(benzimidazol-2-on-1-yl)vinyl]-1H-quinoxalin-2-one in the second case, and the formation of 2,3-bis-(1H-benzimidazol-2-yl)quinoxaline in the third case and not the formation of 3-(N,N-dimethylaminocarbonyl)furo[2,3-b]quinoxaline hydrochloride , the free base of 3-(3,4-dihydroquinoxalin-2(1H)-on-3-yl)-1,2-dihydro-1,5-benzodiazepin-2(1H)-one , that is, compound and benzodiazepine derivative , as has been described earlier. In the third case, the formation of 2,3-bis-(1H-benzimidazol-2-yl)quinoxaline occurs according to the novel quinoxalin-2(1H)-one benzimidazole rearrangement discovered by us. The potential mechanisms for the investigated reactions are discussed.

A highly efficient and versatile method for the synthesis of quinoxaline derivatives with two benzimidazole fragments have been developed on the basis of the ring contraction of 3-(benzimidazo-2-yl)quinoxalin-2(1H)-one with 1,2-diaminobenzene and its various types of substituted and condensed derivatives. Owing to the inter- and intramolecular processes, involving self association, proton exchange, conformational, and/or tautomeric exchanges between several forms for most of the bis-benzimidazolylquinoxalines signals of bridged and neighboring carbon atoms and the hydrogen atoms of the neighboring carbon atoms of benzimidazole fragments in the NMR spectra are broadened. The conjugation between the benzimidazole fragments and the quinoxaline core of the molecules is increased from the quinoxaline derivative (10c) to its thiadiazol[f]- (17) and pyrrolo[a]-(19) annulated derivatives, resulting in a greater planarity of the molecule as a whole.

An efficient and versatile one-step method for the synthesis of thiazolo[3,4-a]quinoxalines and related new heterocyclic systems have been developed on the basis of a new strategy for the construction of the pyrazine ring system. The key step of the process involves the cascade annulation of the iminothiazolopyrazine system to benzene in the reaction of 4-hydroxy-3,5-diaryl-2-phenyliminothiazolidines with 1,2-diaminobenzenes. The use of selenium analogues instead of thiazolidine derivatives in this reaction, leads to selenazolo[3,4-a]quinoxalines and the use of aza analogues instead of 1,2-diaminobenzenes gives aza analogues of thiazolo[3,4-a]quinoxalines.

Aroylquinoxalin-2(1H)-ones were found to be hetero analogues of a-diketones for the efficient, one- pot, three component synthesis of 2,4,5-trisubstituted imidazoles and imidazo(1,5-a)quinoxalin-4(5H)- ones in boiling methanol. The key advantages of this process are high yields, ready availability and low cost of 3-aroylquinoxalin-2(1H)-ones and easy work-up and separation of the products by non- chromatographic methods. Furthermore, the presence of an ortho-iminoanilide fragment at position 4 of the imidazoles obtained has made it possible to produce 2-(imidazol-4-yl)benzimidazoles in almost quantitative yields.

Condensation of methyl phenyl(alkyl)halopyrotartrates with N,N′-diphenylselenourea leads to the formation of methyl 4-hydroxy-3-phenyl-5-phenyl(alkyl)-2-phenyliminoselenazolidine-4-carboxylates, which undergo reaction with 1,2-phenylenediamines to give selenazolo-[3,4-a]quinoxalin-4(5H)-ones.

The condensation of 4-hydroxy-3,5-diphenyl-2-phenyliminothiazolidine with 5-fluoro-4-morpholino- and 5-fluoro-4-(4-methylpiperazino)-1,2-phenylenediamines leads to region-isomeric thiazolo[3,4-a]quinoxalines differing in substituents in positions 7 and 8 of the benzene ring. From the ratio of isomers formed it follows that the mesomeric effect of a fluorine atom in 1,2-phenylenediamines is comparable with the influence of an aminosubstituent.

The reaction of 3-benzoylquinoxalin-2(1H)-ones with enamines (generated in situ from ammonium acetate and the corresponding methylaryl(hetaryl)ketones) proceeds smoothly to give the corresponding substituted 1-(pyrrolyl)benzimidazolone derivatives in moderate yields through the novel rearrangement of 3-benzoylquinoxalin-2(1H)-ones involving a dual cleavage of the C3═N4 and C2-C3 bonds under mild conditions.

The reaction of (I) with Vilsmeier reagent to give (III), the reaction of (V) with aqueous NaOH to give (VI), and the reaction of (X) with o-phenylenediamine to give (XI) are studied and earlier reports are revised.

The rearrangement process includes a novel ring contraction as the key step to produce various benzimidazole structures bearing a pyrrole part at one of the nitrogens.

The reactions depicted in the scheme are reinvestigated and the structures of the reaction products (III), (VI), and (VIII) are revised.

A synthetically useful protocol has been developed for the preparation of highly functionalized N-pyrrolylbenzimidazol-2-ones. The reaction of variously substituted 3-aroyl- and 3-alkanoylquinoxalin-2(1H)-ones with commercially available enamines in acetic acid results in a rapid rearrangement and formation of N-pyrrolylbenzimidazol-2-ones in modest to excellent yields. The key step of the rearrangement involves the novel ring contraction of 3-aroyl- and 3-alkanoylquinoxalin-2(1H)-ones with enamines. In this case, the atom of carbon which is displaced from the pyrazine ring of quinoxalin-2(1H)-one becomes the fourth carbon atom of the newly formed pyrrole ring. The method is applicable for the aza analogues of quinoxalin-2(1H)-ones.

A highly efficient, one-step, versatile method for the synthesis of tetrahydroindoles has been developed on the basis of new ring formation in the reactions of 1-(1-pyrrolidino)cyclohexene with chloropyruvates.

An interesting synthesis of title compounds is achieved by acid-promoted rearrangement of intermediates (III) or (VI), readily prepared by reaction of acyl- substituted quinoxalinones with diaminomalononitrile.

Benzoylquinoxalinone (I) is used as an hetero analogue of α-diketones in the three-component reaction.

Recyclization of quinoxalines and aza-analogues (I) in the presence of o-phenylenediamines (II) or (V) proceeds smoothly in acidic solution to give 2-quinoxalinylbenzimidazoles and aza-analogues (III) and (VI)/(VII), respectively.

A highly efficient, one-step, versatile method for the synthesis of tetrahydroindoles has been developed on the basis of new ring formation in the reactions of 1-(1-pyrrolidino)cyclohexene with chloropyruvates.

Three-component condensation of pyridin-2-one, bis(2-chloroethyl)amine hydrochloride, and K2CO3 in DMF unexpectedly gave N-and O-oxazolidinylethylation products of pyridin-2-one in the ratio 3: 2.

Three-component condensation of pyridin-2-one, bis(2-chloroethyl)amine hydrochloride, and K2CO3 in DMF unexpectedly gave N-and O-oxazolidinylethylation products of pyridin-2-one in the ratio 3: 2.