Synthesis of 2,3-disubstituted derivatives of pyrano-, thiopyrano-, and benzoannelated pyrido[2,3-<Emphasis Type="Italic">b</Emphasis>]thieno[3,2-<Emphasis Type="Italic">d</Emphasis>]pyrimidines

A new methods have been developed for the synthesis of condensed pyrido[2,3-b]thieno[3,2-d]pyrimidines based on cyclic derivatives of 4-cyanopyridine-3-thiones. The presence of two different reactive functional groups NH₂ and CONH gives the possibility of carrying out different conversions of thieno[2,3-b]pyridines. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1245–1252, August, 2008.     

On the Synthesis of Some 2-Arylhydrazono-3-oxothieno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridines by Reaction of Nitrilimines with 2-Mercaptonicotinic Acid

Summary. Nitrilimines prepared from N-arylhydrazono chlorides reacted with 2-mercaptonicotinic acid yielding the corresponding addition products, 2-[(2-oxo-1-arylhydrazonopropan-1-yl)mercapto] nicotinic acids, which were treated with 1,1-carbonyldiimidazole in THF affording by cyclocondensation the corresponding hitherto unknown 2-arylhydrazono-3-oxothieno[2,3-b]pyridines.     

Synthesis and Properties of Substituted Isoxazolo[3',4':4,5]thieno[2,3-b]pyridines

We synthesized derivatives of a novel heterocyclic system, isoxazolo[3',4':4,5]thieno[2,3-b]pyridine by sequential conversions in three steps: isomerization of 2-(2-R-ethylthio-2-oxo)-3-pyridyl cyanides obtained by alkylation from substituted 3-cyano-2(1H)-pyridinethiones by -halomethyl ketones in alkaline medium, to form 3-aminothieno[2,3-b]pyridines; diazotization of the amino group followed by nucleophilic substitution of the diazonium group by an azido group, bypassing the step of isolating the diazonium salts; and thermolysis of the azides formed.     

Synthesis and reactivity of thieno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridine-2,3-diamines

It has been established that the interaction of N¹-(2-hydroxyphenylmethylthieno[2,3-b]pyrid-3-yl)arylamides with hydrazine hydrate leads to thieno[2,3-b]pyridine-2,3-diamines. It was shown that the reaction of the latter with acetylacetone and acetoacetic ester occurs regioselectively at the amino group in position 3 of the thiophene ring. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1400–1408, September, 2007.     

4-Hydroxy-2-quinolones 147. Synthesis and tautomerism of 2-methyl-9H-furo-[2,3-<Emphasis Type="Italic">b</Emphasis>]quinolin-4-one

In the presence of aqueous solutions of alkali, 2-bromomethyl-3,9-dihydro-2H-furo[2,3-b]quinolin-4-one is subjected to dehydrobromination and converted to 2-methyl-9H-furo[2,3-b]quinolin-4-one which exists in acid solution in the 4-oxo-and in base in the 4-hydroxy tautomeric forms. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1039–1043, July, 2008.     

Crystal and molecular structure of new tetrahydrobenzo[<Emphasis Type="Italic">e</Emphasis>]pyrano[4,3-<Emphasis Type="Italic">b</Emphasis>]pyridines

Three tetrahydrobenzo[e]pyrano[4,3-b]pyridines formed in a diethyl 2,4,6-trioxoheptanedicarboxylic ether-substituted salicylic aldehyde-ammonium acetate system were studied by single crystal X-ray diffraction. After the introduction of a methoxy group in the tricyclic system, the tetrahydropyridine and pyrane rings adopted the half-chair conformation, while in the unsubstituted compound, the tetrahydropyridine ring has a distorted boat conformation, and the pyrane ring has a C-envelope conformation. In the compounds, the N-H?O and O-H?O intermolecular hydrogen bonds give rise to the development of chain structures. In two of the three compounds examined, the hydrogen atoms at the chiral centers are in the trans-position, as in the structure of natural tetrahydrocannabinols.     

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.     

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.     

Photochromic Dihetarylethylenes. 21. Synthesis and Photochemical Properties of 1,2-Bis{5-(2-benzothiazolyl)-2-ethylthieno-[2,3-<Emphasis Type="Italic">b</Emphasis>]thiophen-3-yl}Hexafluorocyclopentene

1,2-Bis{5-(2-benzothiazolyl)-2-ethylthieno[2,3-b]thiophen-3-yl}hexafluorocyclopentene has been synthesized for the first time. It was shown that, unlike analogous derivatives of thieno[3,2-b]thiophene, on irradiation with UV light (λ = 313 nm) it did not display photochromic properties, but undergoes an irreversible photoconversion which is accompanied by the display of intense fluorescence. This raises the prospect of using this compound for creating an irreversible photoluminescent recording medium.Dedicated to V. I. Minkin on his 70th birthday.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 360–364, March, 2005.For Part 20 see [1].     

Alkylation of 3-cyano-4-methoxymethyl-6-methyl-2(1h)-pyridone by active halomethylene compounds. The molecular structure of 3-amino-2-benzoyl-4-methoxymethyl-6-methylfuro[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridine

The alkylation of 3-cyano-4-methoxymethyl-6-methyl-2(1H)-pyridone by active halomethylene compounds has been studied. It was shown that the reaction of the pyridone with methyl- and ethylchloroacetates and phenacyl and p-bromophenacyl bromides occurs to give N- and O-structural isomers. Only the N-derivatives are separated from the reaction mixture when the pyridone is alkylated with iodoacetamide. It was found that 2-aroylmethyl-3-cyano-4-methoxymethyl-6-methylpyridines cyclize in the presence of KOH to 3-amino-2-aroyl-4-methoxymethyl-6-methylfuro[2,3-b]pyridines. The molecular structure of 3-amino-2-benzoyl-4-methoxymethyl-6-methylfuro[2,3-b]pyridine has been studied using an X-ray analytical method.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1670–1682, November, 2004.     

Reaction of 2-alkylthio-6-amino-pyrimidin-4(3H)-ones with ethyl bromopyruvate. Synthesis of furo-[2,3-<Emphasis Type="Italic">d</Emphasis>]-pyrimidine and furo[3,2-<Emphasis Type="Italic">e</Emphasis>]imidazo-[1,2-<Emphasis Type="Italic">c</Emphasis>]pyrimidine carboxylates

Reaction of 2-alkylthio-6-aminopyrimidin-4(3H)-ones with ethyl bromopyruvate to give ethyl 2-alkyl-thio-4-aminofuro[2,3-d]pyrimidine-5-carboxylates has been shown to proceed under neutral or acidic conditions. The obtained furo[2,3-d]pyrimidines underwent further cyclocondensation reaction with ethyl bromopyruvate to afford diethyl 5-alkylthiofuro[3,2-e]imidazo[1,2-c]pyrimidine-2,9-dicarboxy-lates. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 440–443, March, 2009.     

Synthesis and transformations of 3-(1H-pyrrol-1-yl)thieno[2,3-b]pyridines

Reactions of 2,5-dimethoxytetrahydrofuran with 3-aminothieno[2,3-b]pyridines afford a number of substituted 3-(1H-pyrrol-1-yl)thieno[2,3-b]pyridines. The possibility of the reaction and the yield of the product are determined by the character of a substituent in position 2 of thieno[2,3-b]pyridine. The Curtius rearrangement of 2-acylazido-3(1H-pyrrol-1-yl)thieno[2,3-b]pyridines yields 4,5-dihydropyrido[3",2":4,5]thieno[2,3-e]pyrrolo[1,2-a]pyrazin-4-ones. The molecular and crystal structures of ethyl 4-methoxymethyl-6-methyl-3-(1H-pyrrol-1-yl)thieno[2,3-b]pyridine-2-carboxylate were determined by X-ray diffraction analysis.     

Synthesis of 5-(1H-benzimidazol-2-yl)-1H-pyrazolo-[3,4-<Emphasis Type="Italic">b</Emphasis>]pyridines by the <Emphasis Type="Italic">p</Emphasis>-(dimethylamino)benzaldehyde modification of Hantzsch reaction

The reactions of p-(dimethylamino)benzaldehyde with 5-amino-3-methyl-1-phenylpyrazole and 2-RCOCH₂-1H-benzimidazoles have produced 5-(1H-benzimidazol-2-yl)-1H-pyrazolo[3,4-b]pyridines. The transformation includes the formation of compounds in accordance with a Hantzsch reaction containing a 1,4-dihydropyridine ring, and is completed by the aromatization either by the splitting off of N,N-dimethylanyline or oxidation. The splitting is produced by acetic acid and the oxidation by a nitrocompound. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 578–584, April 2007.     

Synthesis of 3,9,9,9a-tetramethyl-1,2,3,9a-tetrahydro-9H-imidazo[1,2-<Emphasis Type="Italic">a</Emphasis>]-indol-2-ones by reaction of 2,3,3-trimethyl-3H-indole with 2-bromopropionamides

Alkylation of 2,3,3-trimethyl-3H-indole with 2-bromopropionamide and the subsequent treatment of the formed 1-(1-carbamoylethyl)-2,3,3-trimethyl-3H-indolium bromide with a base afforded 3,9,9,9a-tetramethyl-1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-one. Condensation of the 1-(1-carbamoylethyl)-2,3,3-trimethyl-3H-indolium salt with 2-hydroxy-1-naphthaldehyde gave a mixture of diastereomeric 1-(1-carbamoylethyl)spiro[2H-indole-2,3-[3H]naphtho[2,1-b]pyrans].Published in Khimiya Geterotsiklicheskikh Soedinenii, No 11, pp. 1690–1694, November, 2004.     

Synthesis and reductive reactions of 2,3-dioxo-2,3-dihydrobenzo[<Emphasis Type="Italic">b</Emphasis>]furo[2,3-<Emphasis Type="Italic">f</Emphasis>]-, -[2,3-<Emphasis Type="Italic">g</Emphasis>]-, and -[3,2-<Emphasis Type="Italic">e</Emphasis>]indoles

The Sandmeyer reaction was used to prepare 2,3-dioxo-2,3-dihydrobenzo[b]furoindoles which could be reduced with diborane or with complex hydrides to give the corresponding unsubstituted as well as the 3-hydroxybenzo[b]furoindoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No 11, pp. 1683–1689, November, 2004.     

Reaction of 3-Arylaminobenzofuro-, 3-Arylaminobenzothieno-, and 3-Arylaminoindolo[2,3-<Emphasis Type="Italic">c</Emphasis>]pyrylium Salts with Nucleophilic Reagents

We have studied the reactions of 3-arylaminobenzofuro-, 3-arylaminobenzothieno-, and 3-arylaminoindolo[2,3-c]pyrylium salts with ammonium acetate, primary amines, and hydrazine hydrate. In an alcoholic medium, primary amines and hydrazine hydrate open up the pyrylium ring to form arylamides of 2-(N-benzylmethylketimine)hetaryl-3-acetic acids or the corresponding hydrazones, where further heterocyclization does not occur. Upon treatment with ammonium acetate in acetic acid, 2-aryl-1-methylhetero[2,3-c]pyridin-3-(2H)-ones are formed along with their 2-unsubstituted analogs.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 601–612, April, 2005.     

Synthesis of 1,2,3,4-tetrahydropyrido- [2,3-<Emphasis Type="Italic">b</Emphasis>]pyrazine-2,3-dione derivatives with a chiral substituent at the nitrogen atom

The sequence of steps including nucleophilic substitution of the chlorine atom in 2-chloro-3-nitropyridine by esters of optically active phenylalanine, reduction of the nitro group, acylation with ethyl oxalyl chloride, and intramolecular cyclization, leads to the synthesis of derivatives of 1,2,3,4-tetrahydropyrido[2,3-b]pyrazine-2,3-dione with a chiral substituent at the nitrogen atom. It was established that, depending on the conditions of carrying out the cyclization, the parallel formation of derivatives of imidazo[4,5-b]pyridine is possible. Conditions were found for selectively carrying out the cyclization under with only structures of pyrazines or imidazole condensed with pyridine were formed. Dedicated to Academician J. Stradins in connection with his 75th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 237-243, February, 2009.     

Synthesis of 6-aryl-1,6-dihydrodipyrazolo[3,4-<Emphasis Type="Italic">b</Emphasis>:4,3-<Emphasis Type="Italic">c</Emphasis>]pyridines

6-Azido-1H-pyrazolo[3,4-b]pyridino-5-carbaldehydes react with aromatic amines to give the corresponding N-arylimines which cyclize on heating in boiling toluene to give 6-aryl-1,6-dihydrodipyrazolo[3,4-b:4,3-e]pyridines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, 1717–1722, November, 2004.     

Ecofriendly synthesis of substituted pyridine and pyrido[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidine derivatives

An environmentally benign novel one-pot synthesis of pyridines and pyrido[2,3-d]pyrimidines from chalcones and malononitrile was described. In the reaction under neat conditions using microwave irradiation, enhancement in the reaction rate and high yields were observed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1479–1482, June, 2005.     

Synthesis of pyrano[2,3-<Emphasis Type="Italic">f</Emphasis>]chromen-2,8-diones and pyrano[3,2-<Emphasis Type="Italic">g</Emphasis>]chromen-2,8-diones based on <Emphasis Type="Italic">o</Emphasis>-hydroxyformyl(acyl)neoflavonoids

Novel pyrano[2,3-f]chromen-2,8-diones and pyrano[3,2-g]chromen-2,8-diones were prepared based on modified analogs of natural o-hydroxyformyl(acyl)neoflavonoids. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 15–20, January–February, 2008.