Cyclization of 3-Ethoxycarbonylmethyl-, 3-Cyanomethyl-, and 3-Acetylmethyl-1-amino-2-methylbenzimidazolium Salts Effected by Acetic Anhydride in the Presence of a Base

3-Ethoxycarbonylmethyl- and 3-cyanomethyl-1-amino-2-methylbenzimidazolium chlorides cyclized at treatment with acetic anhydride in the presence of potassium carbonate to afford a mixture of derivatives of pyrazolo[1,5-a]benzimidazole and 4-aminopyrrolo[1,2-a]benzimidazole. Therewith in the first case prevails the process of pyrazole ring fusion, and in the latter pyrrole ring is fused. 3-Aroyl(thenoyl)methyl-1-amino-2-methylbenzimidazolium bromides under the same conditions are converted into 1-aroyl(thenoyl)-2-methyl- and 2-4-acetamido-3-acetylpyrrolo[1,2-a]benzimidazoles.     

Synthesis of 4-alkylpyrazolo[1,5-a]benzimidazoles

2,4-Disubstituted pyrazole[1,5-a]benzimidazoles were obtained by the action of carboxylic acid anhydrides on 1-amino-2-methyl-3-alkylbenzimidazolium salts in the presence of potassium carbonate. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 814–817, June, 1980.     

3-α-Halocarbonyl derivatives of pyrazolo[1,5-a] benzimidazole and their reactions

3-(-haloacyl)-2,4-dialkylpyrazolo[1,5-a]benzimidazoles can be obtained either by brominating 3-acetylpyrazolo[1,5-a]benzimidazoles with bromine in acetic acid, or by acylating the 3-unsubstituted pyrazolobenzimidazoles with haloacetic halides. Halogenation of 3-acetylpyrazolo[1,5-a]benzimidazoles with bromine in acetic acid in the presence of sodium acetate, and bromination with N-bromosuccinimide or 1-chlorobenzotriazole, result in deacylation to give 3,6(7)-dibromo- and 3-chloropyrazolo[1,5-a]benzimidazoles. The mono- and trihaloketones obtained have been used to prepare the corresponding aminoketones, the 3-carboxylic acid, and its derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 43–48, January, 1988.     

Cyclocondensation of n-(prop-2-yn-1-yl)- and n-(penta-2,4-diyn-1-yl)- <Emphasis Type="Italic">o</Emphasis>-phenylenediamines with phenyl isothiocyanate and carbon disulfide

The cyclocondensation of N-(prop-2-yn-1-yl)-o-phenylenediamines with phenyl isothiocyanate leads to the formation of 1-(prop-2-yn-1-yl)-1,3-dihydro-2H-benzimidazole-2-thiones irrespective of the substituent nature at the triple bond. Reactions of both mono- and diacetylenic derivatives of o-phenylenediamine with carbon disulfide in the presence of KOH proceed with the formation of two heterocyclic nuclei simultaneously. From N-(prop-2-yn-1-yl)-o-phenylenediamines containing an aryl substituent at the triple bond, and N-(penta-2,4-diyn-1-yl)-o-phenylenediamines 2-methylidene-2,3-dihydro[1,3]thiazolo[3,2-a]benzimidazoles are formed. The latter are readily isomerized under the action of base giving thiazolo[3,2-a]benzimidazoles. The cyclocondensation of N-(alk-2-yn-1-yl)-o-phenylenediamines with CS₂ leads to [1,3]thiazino[3,2-a]benzimidazoles.     

Quaternary 1-aminobenzimidazolium salts in reactions with β-dicarbonyl compounds. Formation of pyridazino[1,6-a]benzimidazolium cations and 1-arylpyrazoles

Pyridazino[1,6-a]benzimidazolium cations and 1-(o-methylaminoaryl)-4-acetylpyrazoles are formed simultaneously in approximately equal amounts in the reaction of excess acetylacetone with quaternary 1-aminobenzimidazolium salts in aqueous potassium carbonate solution. Mesoionic pyridazinobenzimidazoles and the corresponding 4-ethoxycarbonylpyrazoles were obtained with acetoacetic ester under similar conditions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 256–261, February, 1983.     

Dakin-West trick in the design of novel 2-alkyl(aralkyl) derivatives of oxazolo[3,2-a]pyridines

A series of previously unavailable derivatives of 2-alkyl- and 2-benzylderivatives of oxazolo[3,2-a]pyridines III were obtained via tandem ring opening and ring closure from stable mesoionic 3-acyloxazolo[3,2-a]pyridinium-2-olates I. The key intermediates of this tandem transformation are N-(b-oxoethyl)pyridones-2 II obtained by Dakin-West acylation of (pyridone-2-yl-1)acetic acid. An example of further utilization of this strategy is illustrated by preparation of unknown 2-benzylimidazo[1,2-a]pyridine from the salt I and ammonia.     

1-Amino-3-alkyl-2-(methylthio)benzimidazolium salts: synthesis,reaction with CH-acid anions,and conversion to pyrazolo[1,5-a]benzimidazole derivatives

For the first time, 1-amino-3-alkylbenzimidazolinethiones were obtained by heating 1-amino-3-alkylbenzimidazolium iodides with sulfur in the presence of triethylamine. They were converted to 1-amino-3-alkyl-2-(methylthio)benzimidazolium salts, which, during reaction with CH-acid onions, gave the corresponding 1-amino-3-alkyl-2-methylenebenzimidazoline derivatives. Under conditions of alkaline or acid catalysis, the latter derivatives cyclized to 2-amino- or 2-hydroxy derivatives of pyrazolo[1,5-a]benzimidazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 205–214, February, 1992.     

Synthese von imidazo[1,5-a]- und pyrazino[1,2-a]benzimidazolen

1,2-Dihydro-3H-imidazo[1,5-a]benzimidazoles (6), 1-oxo-1,2-dihydro-3H-imidazo[ 1,5-a] benzimidazoles (8), 3H-imidazo[1,5-a]benzimidazoles (7), 3-oxo-1,2,3,4-tetrahydro-pyrazino[1,2-a] benzimidazoles (12), and 3,4-dioxo-1,2,3,4-tetrahydro-pyrazino[1,2-a]benzinudazoles (13) were synthesized from 2-α-aminobenzyl (benzhydryl)-benzimidazoles (2).     

Reaction of dihalocarbenes with 2-(benzylideneamino)pyridines. Cyclization of 2-(benzylideneamino)pyridinium dihalomethylids to give 2-aryl-3-haloimidazo[1,2-α]pyridines

Pyridinium dichloromethylids, formed in the reaction of dichlorocarbene with 2-(benzylideneamino)pyridines, undergo intramolecular 1,5-cyclization to give 2-aryl-3-chloroimidazo[1,2-a]pyridines, which undergo partial conversion to 2-aryl-3-chloro-4H-pyrido[1,2-a]pyrimidin-4-ones under the reaction conditions. 2-Aryl-3-bromoimidazo[1,2-a]pyridines and 2-[N-(1-aryl-2,2,2-tribromoethyl)amino]pyridines, respectively, are obtained in the reaction of dibromocarbene and the tribromomethyl onion generated in the reaction of bromoform with potassium hydroxide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 810–816, June, 1991.     

Investigations in the imidazole series LXXIII. Synthesis of pyrrolo[1,2-a]benzimidazole derivatives from 2-alkyl(aralkyl)benzimidazoles

The synthesis of 2-alkyl(aryl)- and 2-aryl-3-alkyl(aryl)-4-acylmethyl-substituted pyrrolo-[1,2-a]benzimidazoles was accomplished by the reaction of 2-alkyl(aralkyl)benzimidazoles with -haloketones and subsequent cyclization of the resulting 1,3-(diacylmethyl)-2-alkyl-(aralkyl)benzimidazolium halides.See [1] for communication LXXII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 403–404, March, 1972.     

Studies of the reactions between indole-2,3-diones (isatins) and 2-aminobenzylamine

Reflux of equimolecular amounts 2-aminobenzylamine and isatins in acetic acid produced indolo[3,2-c]quinolin-6-ones in good yields. A proposed mechanism involving initial formation of a spiro compound is given. This isolable intermediate subsequently rearranges via a sequential isocyanate ring opening and a cyclisation process to a urea derivative which finally cyclized to the indolo[3,2-c]quinolin-6-ones. The urea derivative could be prepared separately and cyclized selectively to indolo[3,2-c]quinolin-6-one. Reaction of N-acetylisatin with 2-aminobenzylamine at room temperature yielded the 1,4-benzodiazepinone 3-(2-acetamidophenyl)-1,5-dihydro-1,4-benzodiazepin-2-one whereas its isomer 2(2-acetamidophenyl)-4,5-dihydro-1,4-benzodiazepin-3-one was obtained from 2-(2-acetylaminophenyl)-N-(2-aminobenzyl)-2-oxoacetamide in acetic acid at room temperature.The previously unknown linear isomer of indolo[3,2-c]quinolin-6-one, i.e. indolo[2,3-b]quinolin-11-one, has been prepared by thermal (260°C) cyclization of methyl 2-phenylamino indole-3-carboxylate, which in turn was prepared in two steps from methyl indole-3-carboxylate.     

4-hydroxy-2-quinolones. 169*. synthesis and bromination of 1-allyl-3-(arylamino-methylene)quinoline-2,4-(1h,3h)-diones

Bromination of 1-allyl-substituted 3-(arylaminomethylene)quinoline-2,4-(1H,3H)-diones with one equivalent of molecular bromine in glacial acetic acid and subsequent dilution of the reaction mixture with water is accompanied by halocyclization and hydrolysis to form 2-bromomethyl-5-oxo-1,2 dihydro-5H-oxazolo[3,2-a]quinoline-4-carbaldehyde.     

Synthesis of substituted diazines,diazoles, and condensed thia- and oxadiazoles

The corresponding 2-arylhydrazono-3-oxoimidazo[1,2-a]pyridines, 3-arylhydrazono-2-oxoimidazo [1,2-a]benzothiazoles, 2-oxoimidazolidino[3,2-a]benzimidazoles, 2-oxoimidazo[1,2-a]benzoxazoles, and 2-arylhydrazono-3-oxothiazolo[2,3-a]benzimidazoles were obtained by the condensation of arylazochloroacetyl chlorides with 2-aminopyridine, 2-aminobenzothiazole, 2-aminobenzoxazole, 2-aminobenzimidazole, and 2-mercaptobenzimidazole. 5-Arylhydrazono-1,2-diphenylimidazole-4-ones and 5-arylhydrazono-3,4-diaryl-1,2,4-oxidiazine-6-ones were synthesized by the reaction of arylazochloroacetyl chlorides with N-phenylbenzamidine and N-phenylamidoxime.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 930–936, July, 1971.     

Regioselectivity and stereoselectivity of electrophilic quaternization of substituted 2-allyl(2-cyclohexen-1-yl)thionicotinic acids to thiazolo[3,2-a]pyridinium salts

The electrophilic quaternization of substituted 2-allyl(2-cyclohexen-1-yl)-thionicotinic acids proceeds regioselectively and stereoselectively as a trans process with the formation of salts of 4a,10a-cis-4,4a-trans-1,2,3,4,4a,10a-hexahydrobenzothiazolo-[3,2-a]pyridinium acids. Trihalides of thiazolo[3,2-a]-pyridinium acids exist in equilibrium with their betaine form. The formation of betaines and reactions that proceed with a change in the anionic part of thiazolo[3,2-a]pyridinium salts have virtually no effect on the conformation of the heterocyclic cation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 256–263, February, 1990.     

4-Hydroxy-2-quinolones. 175.*Reaction of -1-allyl-3-[(arylamino)methylene]quinoline-2,4-(1H,3H)-diones with bromine

NMR spectroscopy showed that treatment of 1-allyl-3-[(arylamino)methylene]quinoline-2,4-(1H,3H)-diones with an equivalent amount of dry bromine in anhydrous acetic acid leads to the formation of 4-aryliminomethyl-2-bromomethyl-5-oxo-1,2-dihydro-5H-oxazolo[3,2-a]quinolinium bromides.     

Synthesis and Crystal Structure of 1-（4-Fluorophenyl）-2-hexylthiobenzo[4,5]-furo[3,2-d]-1,2,4-triazolo[1,5-a]pyrimidin-5（1H）-one

The crystal structure of the title compound 1-(4-fluorophenyl) -2-hexylthio-benzo [4,5]furo[3,2-d]-1,2,4-triazolo[1,5-a]pyrimidin-5(1H) -one(C23H21FN4O2S,Mr = 436.5) has been prepared and determined by single-crystal X-ray diffraction. The crystal is of monoclinic,space group P21/n with a = 13.9854(3) ,b = 17.2678(4) ,c = 18.1828(5) ,β = 99.364(2) °,V = 4332.58(18) 3,Z = 4,Dc = 1.338,F(000) =1824,μ = 0.185 mm-1,MoKa radiation(λ = 0.71073) ,R = 0.0538 and wR = 0.1162 for 4728 observed reflections with I > 2σ(I) . X-ray diffraction analysis reveals the fused rings of benzo[4,5]furo[3,2-d]-1,2,4-triazolo[1,5-a] pyrimidin-5(1H) -one system are nearly coplanar. The crystal packing is mainly stabilized by weak intermolecular C-H···O hydrogen bond and π-π interactions.     

Research on imidazo[1,2-a]benzimidazole derivatives. 22. Synthesis of 2,3-dihydroimidazo[1,2-a]benzimidazoles starting from 2-imino-3-(2-hydroxyethyl)benzimidazolines

A -elimination reaction with the formation of 2-imino-3-vinylbenzimidazolines occurs simultaneously with intramolecular alkylation and the formation of an imidazoline ring in the action of alcoholic alkali on 2-imino-3-(2-chloroethyl) benzimidazolines. The thermolysis of 3-chlorethyl-substituted imines without a solvent or in an inert solvent leads exclusively to 2,3-dihydroimidazo[1,2-a] benzimidazoles. An attempt to obtain the latter directly from 2-imino-3-(2-hydroxyethyl) benzimidazolines by the action of a mixture of thionyl chloride and acetic anhydride on them also leads to ambiguous results.See [1] for communication 21.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 918–925, July, 1986.     

Synthesis of 2-substituted benzylidene-6-b-nitrothiazolo[3,2-α]benzimidazol-3(2H)ones as possible anticonvulsants

Several 2-substituted benzylidene-b-nitrothiazolo[3,2-α]benzimidazol-3(2H)ones were prepared by the condensation of 6-nitrothiazolo[3,2-α]benzimidazol-3(2H)one with suitable aryl aldehydes as possible anticonvulsants. Amongst these benzimidazoles, two compounds possessed anticonvulsant activity and provided 60% protection against pentylene-tetrazol-induced seizures in mice. J. Heterocyclic Chem., 14, 1093 (1977)     

Stereochemistry of electrophilic annelation of 2-allyl- (and 2-cyclohexen-1-yl)thio-1,5-naphthyridines to thiazolo]3,2-a]-1,5-naphthyridinium salts

Methods have been developed for the synthesis of 3-cyano-5,8-ethano-5,6,7,8-tetrahydro-1,5-naphthyridine-2(1H)-thione and 2-allyl- (and 2-cyclohexen-1-yl)thio-1,5-naphthyridines, and their structures have been studied. X-ray diffraction examination has shown that these compounds contain a disordered contact between the free electron pair of the pyridine nitrogen and the -bond of the allyl grouping, so that they react stereoselectively with halogens to give thiazolo[3,2-a]-1,5-naphthyridinium salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 557–563, April, 1989.     

Reactions of 5-mercaptoazoles and pyridine-2-thiones with acetylenic esters. Selectivity of the formation of novel fused thiazin-4-ones and thiazolidin-4-ones

A systematic study of the reactions of dimethyl acetylenedicarboxylate (DMAD) and methyl propynoate with 5-mercaptoazoles and pyridine-2-thiones has been carried out and as a result, a number of novel imidazo[1,5-b]thiazin-4-ones 6a,b, pyrazolo[1,5-b] thiazin-4-ones 15a-f, imidazo[1,5-b]thiazol-4-ones 7a,b and thiazolo[3,2-a]pyridines 21a-c have been prepared. The influence of the size of the ring of the starting "cyclic" thioamides on the size of the fused ring in the reaction products has been established. The preferred formation of a six-membered thiazine ring took place in the reactions of 5-mercaptoazoles. In contrast, the five membered thiazolidine ring is formed in reactions of pyridine-2-thiones. In both cases the product is a five-membered ring fused to a six-membered heterocycle.