Condensed pyridines. 6. Synthesis and strucutre of adamantyl-, cyclopropyl- and alkyl-substituted 3-halomethyl-2,3-dihydro-8-cyanothiazolo[3,2-a]pyridinium salts and their oxazolo and selenazolo derivatives

The reaction of substituted 2-cyanopyridin-2(1H)-ones and their thione and selenone derivatives with allyl bromide gives the corresponding 2-allyloxy-, 2-allylmercapto-, and 2-allylseleno-3-pyridines, which upon treatment with halogens, form intramolecular quaternization products, namely, 3-halomethyl-2,3-dihydro-8-cyanooxazole[3,2-a]pyridinium salts and their thiazolo and selenazolo analogs. X-ray diffraction structural analysis was used to determine the structure of 3-bromomethyl-2,3-dihydro-5,7-dimethyl-8-cyanothiazolo[3,2-a]pyridinium perchlorate.For Communication 5, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 690–700, May, 1987.     

Cyclization reactions of nitrils. 29. Regioselective synthesis of 6-aryl-3-cyano-2(1H)-pyridinethiones and the corresponding selenones and their characteristics

The condensation of cyanothio- and cyanoselenoacetamide with 3-aryl-3-oxo-1-piperidino-1-propene or sodium 3-aryl-3-oxo-1-propen-1-olate takes place regioselectively with the formation of the 6-aryl-3-cyano-2(1H)-pyridinethiones or the corresponding selenones. Thieno[2,3-b]pyridines, thiazolo[3,2-a]pyridinium salts, and other annellated heterocycles were obtained from the 6-aryl-3-cyano-2(1H)-pyridinethiones.For Communication 28, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 805–812, June, 1988.     

New aromatic systems having a fused thiazolium ring

The method developed for the synthesis of thiazolo[3,2-a]pyridinium salts has been extended to the first synthesis of simple thiazolo[3,2-a]pyrimidinium, thiazolo[3,2-a]-pyrazinium and thiazolo[2, 3-b]benzo[d]thiazolium salts. No method could be found for the cyclization of 4′-bromo-2-(2-benzoxazolylthio)acetophenone to the thiazolo[2,3-b]-benzoxazolium system.     

New mesoionic systems of azolopyridine series 2. Synthesis,structures, and biological activity of 2-aminothiazolo[3,2-<Emphasis Type="Italic">a</Emphasis>]pyridinium salts and thiazolo[3,2-<Emphasis Type="Italic">a</Emphasis>]pyridinium 2-imidates

A new procedure was developed for the synthesis of 2-aminothiazolo[3,2-a]pyridinium salts 8 by the reaction of 2-halo-N-phenacylpyridinium salts with KSCN. The anion compositions of salts 8 were studied by ion chromatography. Acylation of salts 8 afforded representatives of the previously unknown bicyclic mesoionic thiazolo[3,2-a]pyridinium 2-imidate system 9. The three-dimensional structures of 2-amino-3-(p-bromobenzoyl)thiazolo[3,2-a]pyridinium thiocyanate and N-trifluoroacetyl-3-(p-nitrobenzoyl)thiazolo[3,2-a]pyridinium 2-imidate were established by X-ray diffraction analysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 226–232, January, 2005.     

New mesoionic systems of the azolopyridine series. 1. Synthesis and structures of thiazolo[3,2-a]pyridinium 2-thiolates

A procedure was developed for the synthesis of representatives of the previously unknown bicyclic mesoionic thiazolo[3,2-a]pyridinium 2-thiolate system by the reaction of 2-X-N-phenacylpyridinium salts (X = Cl, SMe) with CS₂ in the presence of Et₃N. The three-dimensional structure of 3-(p-nitrobenzoyl)thiazolo[3,2-a]pyridinium 2-thiolate was established by X-ray diffraction analysis.     

Interaction of (z)-4-bromo-1,3-di(2-thienyl)- 2-buten-1-one with amines,synthesis of di(2-thienyl)azolo[<Emphasis Type="Italic">a</Emphasis>]pyridines

(Z)-4-Bromo-1,3-di(2-thienyl)-2-buten-1-one was obtained by the bromination of 1,3-di(2-thienyl)-2-buten-1-one by NBS in anhydrous CCl₄. The starting butanone was obtained by the condensation of 1-(2-thienyl)-1-ethanone by the action of SOCl₂. The reaction of (Z)-4-bromo-1,3-di(2-thienyl)-2-buten-1-one with tertiary amines such as Et₃N, pyridine, 1-alkyl-1,3-diazole, 1-alkylbenzimidazole, and 1-alkyl-1,2,4-triazole leads to quaternary salts. The azolium salts cyclize by the action of base to give di(2-thienyl)azolo[a]pyridinium derivatives. 3-Methyl-6,8-di(2-thienyl)[1,3]thiazolo[3,2-a]pyridin-4-ium and 2,4-di(2-thienyl)pyrido[2,1-b]benzothiazol-10-ium bromides were obtained by the same procedure but without separating the intermediate quaternary salts.     

Electrophilic trans quaternization of substituted 2-[2-cyclohexen-1-ylthio(seleno)]pyridines to 4a,10-a-cis-4,4a-trans-l,2,3,4,4a,10a-hexahydrobenzothiazolo(selenazolo)[3,2-a]pyridinium salts

It was established that the electrophilic quaternization of substituted 2-[2-cyclohexen-1-ylthio(seleno)]pyridines is a stereoselective process and proceeds as trans quaternization with the formation of 4a,10a-cis-4,4a-trans-1,2,3,4,4a,10a-hexahydrobenzothiazolo(selenazolo)[3,2-a]pyridinium salts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1506–1514, November, 1988.     

Ring contraction of thia(seleno)diazine rings into pyrazoles in the reaction of 3-aryl-10-methyl-2H-1,3,4-thia(seleno)diazino[3, 2-a]benzimidazolium salts with bases

Reaction of 3-aryl-10-methyl-2H-1,3,4-thiadiazino[3,2-a]benzimidazolium salts with triethylamine led to ring contraction of the thiadiazine ring to a pyrazole ring with the formation of a mixture of derivatives of 3-mercaptopyrazolobenzimidazole and di(pyrazolo[1,5-a]benzimidazolyl-3) disulfide. The disulfides were formed exclusively when these salts react with ethanolic alkali. The reaction with potassium carbonate in acetic anhydridegave3-acetylthiopyrazolo[1,5- a]benzimidazoles. 2-Aryl-4- alkylpyrazolo[1, 5- a]benzimidazoles were formed by heating thiadiazino[3,2-a]benzimidazolium salts in formamide and by treating selenodiazino[3,2-a]benzimidazolium salts with potassium carbonate in acetic anhydride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1698–1705, 1992.     

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.     

Mesoionic compounds with a bridged nitrogen atom. 3. Reactions of 2-[(1-methyl-2-pyridiniathio)acetyl]-thiazolo[3,2-a]pyridinium 3-oxide methylsulfate

The reactions of the product of cyclodehydration of (2-pyridylthio)acetic acid, viz., 2-[(1-methyl-2-pyridylthio)acetyl]thiazolo[3,2-a]pyridinium 3-oxide, were investigated. It is shown that its quaternary salt at the pyridine nitrogen atom in the presence of triethylamine acts as a nucleophile (by reactions at the methylene group with benzothiazolium and quinolinium sulfonatobetaines) and as an electrophile (by reaction with N-phenylrhodanine) with cleavage of both sulfide sulfur bonds with the simultaneous formation of a disulfide. See [1] for communication 2. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 312–314, March, 1980.     

Thiazolo [3,2-a] pyridinium salts

The sulfides formed by the reaction of α-halo ketones or α-halo acetals with 2-mercaptopyridine may be cyclized in good yield to form thiazolo[3, 2-a]pyridinium salts. The presence of chloro or nitro substituents on the pyridine ring does not interfere with the synthesis. Nitration of 3-methylthiazolo[3, 2-a]pyridinium perchlorate has been found to occur at position 8.     

New data on the alkylation of cyclic thioureas with á-halocarboxylic acids and their esters. 2. Alkylation of tetrahydropyrimidine-2(1h)-thione and 5,5-dimethyltetrahydropyrimidine-2(1h)-thione

In the absence of bases all the attempted variations for the alkylation of tetrahydropyrimidine-2(1H)-thione with á-halocarboxylic acids gave only the bicyclic product-2-R-6,7-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidin-3(2H)-one hydrohalide. However the hydrohalide of the “ open” S-ethoxycarbonyl derivative of propyleneisothiourea can be obtained by treatment of tetrahydropyrimidine-2(1H)-thione with ethyl chloro-or bromoacetate in anhydrous acetone at room temperature. Alkylation of 5,5-dimethyltetrahydro-2(1H)-pyrimidinethione with chloro-or bromoacetic acid in anhydrous acetone at room temperature gave the hydrohalide of the “open” S-carboxymethyl derivative of dimethylpropyleneisothiourea. All remaining variations for the alkylation of this substrate with á-halocarboxylic acids or their esters gave only the corresponding bicyclic compounds-the hydrohalide of 2-R-6,6-dimethyl-6,7-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidin-3(2H)-one-independently of the reaction conditions. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, 593–604, April, 2006.     

Halocyclization of 2-allylthiopyridine

2-Allylthiopyridine reacts with iodine to form 3-iodomethyl-2,3-dihydrothiazolo[3,2-a]pyridinium triiodide, but in reaction with bromine a mixture of 3- and 2-bromomethyl-2,3-dihydrothiazolo[3,2-a]pyridinium bromides is obtained.Chelyabinsk State University, Chelyabinsk 454021; RussiaTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 334–336, March, 1999.     

Thiazolopyridinium salts with an active methyl group and cyanine dyes based on them

5-Methyl- and 7-methylthiazolo[3,2-a]pyridinium salts were synthesized. Condensations leading to the formation of cyanine dyes were carried out at the active methyl groups of these salts.     

Utility of a Pyrimidin-2-Thione Derivative in Synthesis of New Fused Thiazolo[3,2-a]pyrimidines

A pyrimidin-2-thione derivative 2 was prepared and treated with 1,2-dibromoethane, chloroacetic acid and ethyl chloroacetate to give the alkylation products 3,4,9,5, respectively. Furthermore, the reaction of 2 with acrylonitrile and hydrazine hydrate yielded the pyrimidino[2,1-b]thiazine derivative 7, and [1,2,4]-triazolo[4,3-a]pyrimidine 8. Compound 9 was used as the key starting material for synthesis of thiazolo[3,2-a]pyrimidine and pyrano[2′,3′ :4,5]thiazolo[3,2-a]pyrimidine derivatives 10–13, through the reaction with ethyl acetate, malononitrile, hydrazine hydrate, β-aroylacrylic acid, and chalcone, respectively. Treatment of compound 5 with 3,5-dibromo-2-aminobenzoic acid in refluxing butanol gave the 3,1-benzoxazinone derivative 6. The structure assignment of the new compounds is based on chemical and spectroscopic evidence.     

A New Entry to the Thiazolo(3,2-a)Pyridine Ring System: Bromination of 1-Alkenyl-1,2-Dihydropyridine-2-Thiones

Derivatives of the thiazolo(3,2-a)pyridine ring system possess a variety of pharmacological activities like antiinflammatory² hypoglycemic³ and analgesic⁴ activity. Classical methods for the preparation of hydrosoluble thiazolo(3,2-a)pyridinium halides involve reactions of 1H-1,2-dihydropyridine-2-thiones with a-halocarbonyl compounds⁵ I acid-catalyzed dehydration of their 1-phenacyl derivatives6 and halogenation of 2-vinylthiopyridines.⁷     

Mesoionic compounds with a bridged nitrogen atom. 4. Thiazolo[3, 2-a]quinolinium 1-oxide derivatives

It is shown that diverse 2-substituted thiazolo[3,2-a]quinolinium 1-oxides can be obtained from 2-quinolylmercaptoacetic acids. The structures of the synthesized compounds were confirmed by the PMR and mass spectra.See [1] for communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 621–626, May, 1980.     

Studies in the imidazole series

A new synthesis of derivatives of thiazolo[3,2-a]benzimidazoles based on 2-halogenobenzimidazoles has been performed. The reaction of 2-chlorobenzimidazole with -halogeno ketones and the subsequent heating of the resulting 1-acylmethyl-2-chlorobenzimidazoles with thiourea has given 1-acylmethyl-2-mercaptobenzimidazoles. The cyclization of the latter under the action of mineral acids or water-abstracting agents has given a series of 2-alkyl-, 2-aryl-, and 2-heteryl-substituted thiazolo[3,2-a]benzimidazoles.For Communication XLIX, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 6, pp. 827–831, June, 1970.     

An efficient synthesis of novel pyridothieno-fused thiazolo[3,2-a]pyrimidinones via Pictet–Spengler reaction

An efficient method for the synthesis of novel pyrido[3',2':4',5']thieno[3',2':2,3]pyrido [4,5:d][1,3]thiazolo[3,2-a]pyrimidine-4-one derivatives (5) has been developed using a Pictet-Spengler reaction between 2-(3-aminothieno[2,3-b]pyridin-2-yl)thiazolo[3,2-a] pyrimidin-5-one (3), which could be obtained from the condensation of 7-(chloromethyl)-5H-thiazolo[3,2-a]pyrimidin-5-one (1) with 3-cyanopyridine-2-thione (2) via Thorpe-Ziegler isomerization, and aromatic aldehydes under NH₂SO₃H as catalysis in good yields.