Electrochemical synthesis and studies of substituted 2-thiopyridines

A series of substituted 2-alkyl(aryl-, hetaryl-)thiopyridines was prepared by cathodic electrolysis of thiols in the presence of 2-chloro-3-cyano-4-methoxymethyl-6-methylpyridine or 4-chloro-6-methyl-3-oxo-1H-furo[3,4-c]pyridine. The reaction of 3-cyano-4-methoxymethyl-6-methyl-2(1H)-thiopyridone with alkyl halides in the presence of KOH is regioselective and leads toS-alkyl derivatives. The advantages of electrosynthesis for the preparation of 2-alkylthiopyridines fused with 2(5H)-furanone and of 3-aminothieno [2,3-b]pyridines is demonstrated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2215–2219, December, 1994.     

Interaction of 3-amino-2-(isoxazol-3-yl)-4-methoxymethyl-6-methyl-thieno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridine with Raney nickel

3-Amino-2-(isoxazol-3-yl)-4-methoxymethyl-6-methylthieno[2,3-b]pyridine was synthesized by the reaction of 2(1H)-thioxopyridine-3-carbonitrile with 3-chloromethylisoxazole in the presence of two equivalents of KOH. Boiling of 3-amino-2-(isoxazol-3-yl)-4-methoxymethyl-6-meth-ylthieno[2,3-b]pyridine with Raney nickel results in 4-aminothieno[2,3-b;4,5-b′]dipyridine or 5-(4-amino-2-pyridyl)pyridine depending on the reaction conditions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 669–670, March, 2008.     

Synthesis and reactions of 3-cyano-6-methoxymethyl-4-methyl-2(1H)-pyridinethione

Nucleophilic substitution of the chlorine atom in 2-chloro-3-cyano-6-methoxymethyl-4-methylpyridine by mercapto group produces the corresponding 2(1H)-pyridinethione, alkylation of which by halogenated compounds in the presence of KOH proceeds regioselectively to form S-alkyl derivatives. Thorpe—Ziegler cyclization of S-alkyl derivatives, which contain an active methylene group, yields new 3-aminothieno[2,3-b]-pyridines.Kuban State Technological University, Krasnodar 350072, Russia, and N. D. Zelinskii Institute of Organic Chemistry of the Russian Academy of Sciences, Moscow 117913; e-mail: stud@issep.rssi.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 337–341, March, 1999.     

Synthesis and properties of (thieno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridin-3-yl)iminotriphenylphosphoranes. Molecular structure of (2-benzoyl-4-methoxymethyl-6-methylthieno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridin-3-yl)iminotriphenylphosphorane

Iminophosphoranes containing a thieno[2,3-b]pyridine fragment were obtained through a sequence of reactions: 1) alkylation of 3-cyano-2(1H)-pyridinethiones in alkaline medium by an -halocarbonyl compound with subsequent Thorpe-Ziegler cyclization of the resultant 2-thioalkylpyridines to give 3-aminothieno[2,3-b]pyridines, 2) diazotization of the amino group and nucleophilic substitution of the diazonium group by an azido group without isolation of the diazonium salts, and 3) reaction of the 3-azidothieno[2,3-b]pyridines with triphenylphosphine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1853–1862, December, 2004.     

Unexpected formation of 4-aryl-3-cyano-6-phenylpyridine-2(1H-thiones from the reaction of arylmethylenecyanothioacetamides with benzoyl-1,1,1-trifluoroacetone

4-Aryl-3-cyano-6-phenylpyridine-2(1H)-thiones, used in the synthesis of substituted 2-alkylthiopyridines, thieno[2,3-b]pyridines, and 1,4-di(pyridin-2-ylthio)butane, have been synthesized by the condensation of arylmethylenecyanothioacetamides with benzoyl-1,1,1-trifluoroacetone. The reaction path includes the formation of the Michael adduct which undergoes loss of the acyl group. The structure of 3-cyano-2-methylthio-4-(1-naphthyl)-6-phenylpyridine has been studied by X-ray crystallography. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, 1821–1828, December 2005.     

Propanal in the Syntheses of Alkyl-substituted 3-Cyano-2-piperidone, 3-Cyano-2,5,6,7-tetrahydropyrindin-2(1H)-one, and 3-Cyanopyridine-2(1H)-thione

Condensation of propanal with cyanothioacetamide and morpholine gave 3-cyano-4-ethyl-5-methyl-6-morpholino-2-piperidone, the structure of which was studied by X-ray analysis. Reaction of propanal with cyanothioacetamides and cycloalkanone enamines gave 3-cyano-4-ethyl-2,5,6,7-tetrahydropyrindin-2(1H)-one and 3-cyano-4-ethyl-5,6-hexamethylenepyridine-2(1H)-thione. The latter was used for the preparation of substituted 2-benzyloxycarbonylmethylthiopyridine and 3-amino-2-benzyloxycarbonylthieno[2,3-b]pyridine. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1053–1059, July, 2005.     

Synthesis of 6′-carbamoylmethylthio-5′-cyano-1′,4′-dihydro-3,4′-bipyridine-3′-carboxylic and 6′-carbamoylmethylthio-5′-cyano-1′,4′-dihydro-4,4′-bipyridine-3′-carboxylic esters and investigation of their stability. 2. Esters of 6′-carbamoylmethyl-thio-5′-cyano-1′,4′-dihydro-4,4′-bipyridine-3-carboxylic acids

The stability of solutions of esters of 6′-carbamoylmethylthio-5′-cyano-2′-methyl-1′,4′-dihydro-4,4′-bipyridine-3′-carboxylic acids was investigated by HPLC. The corresponding esters of 6′-carbamoylmethylthio-5′-cyano-4,4′-bipyridine-3′-carboxylic acids,esters of 8-cyano-5-methyl-3-oxo-7-(4-pyridyl)-2,3-dihydro-7H-thiazolo-[3,2-a]pyridine-6-carboxylic acids, methyl 3-amino-2-carbamoyl-6-methyl-4-(4-pyridyl)-4,7-dihydrothieno[2,3-b]pyridine-5-carboxylate, and methyl 3-amino-2-carbamoyl-6-methyl-4-(4-pyridyl)-thieno[2,3-b]pyridine-5-carboxylate were synthesized as standard compounds (typical impurities). Analysis by HPLC was realized under the conditions of reverse-phase chromatography. It was established that solutions of the investigated compounds (with mixtures of acetonitrile with phosphate buffer, having pH values of not less than 3 and not more than 5, as solvents) are stable for one month when the solutions are stored in a place protected against light. It is also necessary to use chromatographic systems in which the aqueous components have pH 3–5 during determination of the purity of the esters of 6′-carbamoylmethylthio-5′-cyano-2′-methyl-1′,4′-dihydro-4, 4′-bipyridine-3′-carboxylic acid by HPLC in order to separate the analyzed sorbates and their typical impurities more completely. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 841–848, June, 2007.     

Novel Approaches to Synthesis of 4-Alkyl-6-amino-5-cyano-3-methyl(propyl, phenyl)-2H,4H-pyrano[2,3-c]pyrazoles

We have obtained 4-alkyl-6-amino-5-cyano-3-methyl(propyl, phenyl)-2H,4H-pyrano[2,3-c]pyrazoles by reaction of 4-alkylmethylene-3-substituted 5-pyrazolones with malononitrile or cyanothioacetamide. We have used X-ray diffraction to study the structure of 6-amino-5-cyano-4-isopropyl(hexyl)-3-phenyl-2H,4H-pyrano[2,3-c]pyrazoles.     

Synthesis and reactivity of 3-amino-9-methoxymethyl-7-methyl-3,4-dihydropyrido-[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-ones

The reaction of acyl derivatives of ethyl 3-aminothieno[2,3-b]pyridine-2-carboxylate with hydrazine hydrate gives a series of tricyclic 3-amino-3,4-dihydropyrido[3′,2′:4,5]thieno[3,2-d]pyrimidin-4-ones containing aliphatic, aromatic, or heteroaromatic fragments at C₍₂₎. The reactions of 3-aminopyridothieno[3,2-d]pyrimidin-4-ones with aldehydes, formamide, 2,5-dimethoxytetrahydrofuran, acetic anhydride, and Raney nickel were studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1720–1732, November, 2007.     

Reaction of diketene with cyanothioacetamide: A convenient and regioselective method for the preparation of new 4(1H)-pyridone derivatives

The reaction of diketene with cyanothioacetamide in dry dioxane in the presence of triethylamine gives triethylammonium 3-cyano-6-methyl-4-oxo-1,4-dihydro-2-pyridinethiolate. The regioselective S-alkylation of this thiolate is a convenient method for the preparation of substituted 4(1H)-pyridones and also derivatives of thiazolo[3,2-a]pyridine and thieno[2,3-b]pyridine. The action of 2-amino-1,1,3-tricyanopropene on this thiolate leads to its transformation into a new heterocyclic system, namely, 5H-pyrido[2′,3′:4,5]thiopyrano[2,3-b]pyridine; treatment with iodine yields the oxidation product, namely, the corresponding bis(2-pyridyl) disulfide. The structure of isopropyl (3-cyano-6-methyl-4-oxo-1,4-dihydro-2-pyridinyl)thioacetate was confirmed by X-ray diffraction structural analysis. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 716–725, May, 2007.     

Synthesis of substituted 2-alkyl(aryl)thio-3-cyanopyridines and 3-aminothieno[2,3-b]pyridines

The alkylation of 6-methyl-4-methoxymethyl-3-cyano-2-(1H)pyridinethione by halogen derivatives in the presence of KOH proceeds regioselectively with the formation of S-alkyl derivatives. By cathodic electrolysis of the thiols in the presence of 6-methyl-4-methoxymethyl-2-chloro-3-cyanopyridine, 2-arylthiopyridines are obtained. By Thorpe-Ziegler cyclization of 2-alkylthiopyridines having an ctive methylene group, 2-aminothieno[2,3-b]pyridines have been synthesized.Kuban State Technological University, Krasnodar, 350072. N. D. Zelinskii Institute of Organic Chemistry, Moscow 117913. Southern Branch of Association Rosvuznauka, Krasnodar, 350072. Translated from Khimiya Geterotsiklicheskikh Soedinenii, NO. 10, pp. 1432–1437, October, 1996. Original article submitted April 2, 1996; revision submitted August 20, 1996.     

Synthesis of 6-amino-4-aryl-5-cyano-3-(3-cyanopyridin-2-ylthiomethyl)-2,4-dihydropyrano[2,3-c]pyrazoles and their hydrogenated analogs. Molecular structure of 6-amino-5-cyano-3-(3-cyano-4,6-dimethylpyridin-2-ylthiomethyl)-4-(2-nitrophenyl)-2,4-dihydropyrano[2,3-c]pyrazole

Substituted 3-hydroxypyrazoles, which were prepared based on ethyl esters of substituted 4-(pyridin-2-ylthio)- or 4-(1,4-dihydropyridin-2-ylthio)acetoacetic acids and hydrazine hydrate, were used in the synthesis of 6-amino-4-aryl-5-cyano-3-(pyridin-2-ylthiomethyl)-2,4-dihydropyrano[2,3-c]pyrazoles. The molecular and crystal structure of 6-amino-5-cyano-3-(3-cyano-4,6-dimethylpyridin-2-ylthiomethyl)-4-(2-nitrophenyl)-2,4-dihydropyrano[2,3-c]pyrazole was established by X-ray diffraction analysis.     

Heterocyclic analogs of 5,12-naphthacenequinone 6. Synthesis of 4,11-dimethoxy derivatives of anthra-[2,3-<Emphasis Type="Italic">b</Emphasis>]thiophene-5,10-dione and anthra[2,3-<Emphasis Type="Italic">d</Emphasis>]isothiazole-5,10-dione

Condensation of 2-formyl-or 2-cyano-3-chloro-1,4-dimethoxyanthraquinone with methyl thioglycolate in the presence of base gave methyl 4,11-dimethoxyanthra[2,3-b]thiophene-5,10-dione-2-carboxylate and its 3-amino derivative respectively. Hydrolysis of the ester group in methyl 4,11-dimethoxyanthra[2,3-b]thiophene-5,10-dione-2-carboxylate and subsequent decarboxylation of the carboxylic acid formed gave 4,11-dimethoxyanthra[2,3-b]thiophene-5,10-dione. Condensation of 3-chloro-2-formyl-1,4-dimethoxyanthraquinone with ammonia in the presence of sulfur gave 4,11-dimethoxyanthra[2,3-d]isothiazole-5,10-dione __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 538–543, April, 2007.     

Synthesis of 6-substituted 3-cyano-5-nitropyridine-2(1H)-thiones

The reactions of 1-substituted 2-nitro-3-phenylaminoprop-2-en-1-ones with cyanothioacetamide afforded the corresponding 6-substituted 3-cyano-5-nitropyridine-2(1H)-thiones, which were used for the synthesis of 6-substituted 3-cyano-2-methylthio-5-nitropyridines and 7-substituted 4-hydroxy-8-nitropyrido[2",3":4,5]thieno[2,3-b]pyridin-2(1H)-ones.     

Synthesis of 3-amino-4-methyl-6-trifluoromethylthieno[2,3-b]pyridine-2-carboxanilide and its crystal and molecular structure

4-Methoxy-1,1,1-trifluoropent-3-en-2-one reacts with cyanothioacetamide to give 3-cyano-4-methyl-6-trifluoromethylpyridine-2(1H)-thione, which was transformed into 3-amino-4-methyl-6-trifluoromethylthieno[2,3-b]pyridine-2-carboxanilide by the reaction with chloroacetanilide. The crystal and molecular structure of the amide obtained was studied by X-ray analysis. Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 4, pp. 701–703, April, 1998.     

Conversions of polyfunctional 3-amino-1(2H)iso quinolines

The acylation of 3-amino-4-cyano-1(2H)isoquinolines with benzoyl chloride leading to the formation of 1,3 oxazino[4,5-clisoquinoline-6-ones has been studied. Previously undescribed 1-aminopyrimido[4,5-cJisoquinolirt 6-ones have been obtained by the reaction of the appopriate 3-amino-](2H)isoginolones with formamide. Nucleophilic replacement has been carried out with 3-amino-1-chloroisoquinoline by the action of sodium hydroxide, primary alcohols, hydrazine hydrate, and various amines. 1,2,4-Triazino[2,3-b]isoginolone has been synthesized by condensing 2,3-diamino-1 (2H)isoquinolone with mesoxalic acid ethyl ester.     

Synthesis and Properties of 7-Acetyl-8-aryl-9-cyano-3-hydroxy-6-methyl-3,4-dihydro-2H,8H-pyrido[2,1-<Emphasis Type="Italic">b</Emphasis>][1,3]thiazines

7-Acetyl-8-aryl-2-(1-chloro-2-hydroxy-3-propyl)thio-9-cyano-6-methyl-1,4-dihydropyridines were obtained by treatment of 1,4-dihydropyridine-2(3H)-thiones with epichlorohydrin in the presence of sodium bicarbonate. When treated with NaOMe, these compounds are readily intramolecularly alkylated with formation of 7-acetyl-8-aryl-3-hydroxy-9-cyano-6-methyl-3,4-dihydro-2H,8H-pyrido[2,1-b]-[1,3]thiazines. We have studied amination of 2-(1-chloro-2-hydroxy-3-propyl)thio-1,4-dihydropyridines and acylation of 3-hydroxy-3,4-dihydro-2H,8H-pyrido[2,1-b][1,3]thiazines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1394–1399, September, 2005.     

Synthesis of 6-methylfuro[2,3-b]pyridine

The Claisen condensation of ethyl 2-ethoxy-6-methylpyridine-3-carboxylate with ethyl acetate gave ethyl 2-ethoxy-6-methylnicotinoylacetate, which was converted to 3-bromo-acetyl-6-niethyl-2-pyridone by heating with bromine in 48% hydrobromic acid. The cyclization of the bromoacetylpyridone by the action of silver oxide in methanol gave 3-oxo-6-methyl-2,3-dihydrofuro[2,3-b]pyridine, which was reduced to 3-hydroxy-6-methyl-2,3-dihydrofuro[2,3-b]pyridine with lithium aluminum hydride in dimethoxyethane. Acetylation of the latter gave its acetate, the pyrolysis of which in vacuo gave 6-methylfuro[2,3-b]-pyridine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1544–1546, November, 1972.     

Regioselective synthesis and properties of 3-cyano-6-methyl-4-trifluoromethylpyridine-2(1H)-thione. Molecular and crystal structure of 3-cyano-2-ethylthio-6-methyl-4-trifluoromethylpyridine

The reaction of trifluoroacetylacetone with cyanothioacetamide proceeded regioselectively to form 3-cyano-6-methyl-4-trifluoromethylpyridine-2(1H)-thione from which the corresponding 2-alkylthiopyridines and 3-aminothieno[2,3-b]pyridines were obtained. The crystal and molecular structure of 3-cyano-2-ethylthio-6-methyl-4-trifluoromethylpyridine was established by X-ray diffraction analysis.     

Studies on the Synthesis of New 3-(3,5-Diamino-1-substituted-pyrazol-4-yl)azo-thieno[2,3-b]pyridines and 3-(2-Amino-5,7-disubstituted-pyrazolo[1,5-a]pyrimidine-3-yl)azothieno[2,3-b]pyridines

Coupling the diazonium salt of 3-amino-2-cyano-4,6-dimethylthieno[2,3-b]pyridine 1 with malononitrile 2 gave 2-cyano-3-(hydrazonomalononitrile)-4,6-dimethylthieno[2,3-b]pyridine 3 which then reacted with hydrazine compounds 4a-4h to yield corresponding 2-cyano-3-(3,5-diamino-1-substituted-pyrazol-4-yl)azo-4,6-dimethylthieno[2,3-b]pyridines 5a-5h. The 2-cyano-3-(2-amino-5,7-disubstituted-pyrazolo-[1,5-a]pyrimidine-3-yl)azo-4,6-dimethylthieno[2,3-b]pyridines 7a-7f were obtained in good yield by the cyclocondensation reaction of 2-cyano-3-(3,5-diamino-pyrazol-4-yl)azo-4,6-dimethylthieno[2,3-b]pyridine 5a with the appropriate 1,3-diketones 6a-6f under acidic condition.