A simple and effective synthetic approach to pyrido[2,1-<Emphasis Type="Italic">b</Emphasis>]thiazines

The reaction of partially hydrogenated 2-pyridinethiols with 1,3-dibromopropane gives substituted pyrido[2,1-b][1,3]thiazines. The structure of 7,9-dicyano-6-oxo-3,4,6,7-tetrahydro-2H-spirocyclohexane-1′,8-pyrido[2,1-b][1,3]thiazine was solved by X-ray diffraction structural analysis. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1428–1433, September, 2007.     

Pyridyl-substituted [1,3]Dithiolo-[4,5-<Emphasis Type="Italic">b</Emphasis>][1,4]dithiine-2-thiones

We have obtained 5-(2-pyridyl)[1,3]dithiolo[4,5-b][1,4]dithiine-2-thione for the first time by cycloaddition of 2-ethynylpyridine to 4,5-dihydro-1,3-dithioltrithione (isotrithionedithiol). We have studied this thione, 5-(2-pyridyl)- and 5-(4-pyridyl)-5,6-dihydro[1,3]dithiolo[4,5-b][1,4]dithiine-2-thiones by mass spectroscopy and also IR, UV, ¹H and ¹³C NMR spectra. We have determined the crystal and molecular structure of 5-(2-pyridyl)-5,6-dihydro[1,3]dithiolo[4,5-b][1,4]dithiine-2-thione.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 429–434, March, 2005.     

Mannich reaction in the synthesis of N,S-containing heterocycles. 1. Synthesis of novel derivatives of imidazo[2,1-<Emphasis Type="Italic">b</Emphasis>][1,3,5]thiadiazine

Reactions of (Z)-5-benzylidene-2-thiohydantoin with formaldehyde and primary aromatic amines afforded novel derivatives of imidazo[2,1-b][1,3,5]thiadiazine in 50–69% yields. Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2158–2160, September, 2005.     

Reaction of 2-Aryl-5-R-5,6-dihydro-7H-[1,2,4]-triazolo[5,1-<Emphasis Type="Italic">b</Emphasis>][1,3]thiazin-7-ones with Aryl Bromomethyl Ketones and Benzyl Bromide

The products of the reaction of 2-aryl-5-R-5,6-dihydro-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones with aryl bromomethyl ketones are 2-aryl-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones and aryl methyl ketones or 2,5-diaryl[1,3]thiazolo[3,2-b][1,2,4]triazoles and 3-phenyl-2-propenoic acid, depending on the structure of R. The reaction of 2-aryl-5-R-5,6-dihydro-7H-[1,2,4]triazolo[5,1-b][1,3]thiazin-7-ones with benzyl bromide yields 5-aryl-3-benzylthio-4H-1,2,4-triazoles and 3-aryl-2-propenoyl bromide. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 905–909, June, 2005.     

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 3-Aryl[1,2,4]triazolo[3,4-<Emphasis Type="Italic">b</Emphasis>][1,3]benzothiazole-6,7-dicarbonitriles from 5-Aryl-4H-triazole-2-thiols and 5-Bromo-5-nitrophthalonitrile

New 3-aryl-substituted [1,2,4]triazolo][3,4-b][1,3]benzothiazole-6,7-dicarbonitriles have been synthesized by successive interaction of 5-aryl-4H-triazole-2-thiols with 4-bromo-5-nitrophthalonitrile in the presence of K₂CO₃ initially at the bromine atoms and then at the nitro group.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, 270–272, February, 2005.     

Synthesis of Derivatives of 4,6-Dioxo-1,4,6,7,8,9-hexahydropyrimido[4,5-<Emphasis Type="Italic">b</Emphasis>][1,6]naphthyridines

It has been shown that 1-aryl-8-(4-bromophenyl)-4,6-dioxo-2H(phenyl)-7-phenyl-1,4,6,7,8,9-hexahydropyrimido[4,5-b][1,6]naphthyridines are formed on heating anilides of 1-aryl-7-(4-bromostyryl)-4-oxo-1,4-dihydropyrido[2,3-d]pyrimidine-6-carboxylic acids in PPA.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, 597–600, April, 2005.     

11H-isoindolo[2,1-<Emphasis Type="Italic">a</Emphasis>]benzimidazoles (Review)

Data on methods for the synthesis of isoindolo[2,1-a]benzimidazole and its derivatives and their chemical characteristics are reviewed. Data from quantum-chemical calculations of certain structures are presented. Possible practical applications of the compounds are indicated. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 323–351, March, 2007.     

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.     

<Emphasis Type="Italic">N</Emphasis>-bridged heterocycles: regiospecific synthesis of 2-methyl-4H-pyrimido[2,1-<Emphasis Type="Italic">b</Emphasis>]benzothiazol-4-ones

N-bridged heterocycles, 2-methyl-4H-pyrimido[2,1-b]benzothiazol-4-ones, have been synthesized in quantitative yield by the reaction of 2-aminobenzothiazoles with ethylacetoacetate in the presence of polyphosphoric acid involving dehydrative condensation followed by cyclization. The possibility of the formation of 4-methyl-2H-pyrimido[2,1-b]benzothiazol-2-ones has been excluded on the basis of spectral studies.     

Synthesis of Some New Fused and Polyfused [1,2,4]Triazolo-[3,4-<Emphasis Type="Italic">b</Emphasis>][1,3,4]thiadiazepines

7-[1,3-Dithiolan-2-ylidene]-3-phenyl-5,6,7,8-tetrahydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazepine-6,8-dione and 7-[5-oxo-1,3-dithiolan-2-ylidene]-3-phenyl-5,6,7,8-tetrahydro[1,2,4]triazolo[3,4-b][1,3,4]-thiadiazepine-6,8-diones were obtained by treating 3-phenyl-5,6,7,8-tetrahydro[1,2,4]triazolo-[3,4-b][1,3,4]thiadiazepine-6,8-diones with CS₂ and chloroacetyl chloride, respectively. Treatment of the above compounds with mercaptoacetic acid gave 1,2-dibromoethane or the corresponding spiro polyfused heterocycles. Some other triazolothiadiazepine derivatives including spiro polyfused compounds were also synthesized. __________ Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1256–1264, August, 2005.     

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.     

Transformation of 1,2,3,7a-tetrahydroimidazo[1,2-<Emphasis Type="Italic">b</Emphasis>]isoxazole derivatives into isoxazoles

The reactions of 1,2,3,7a-tetrahydroimidazo[1,2-b]isoxazole derivatives with electrophilic reagents, such as protic acids, benzoyl chloride, BF₃, and bromine, produce isoxazole, 2,2,3,3-tetramethylaziridine, and 2,3,3-trimethylpropen-2-ylamine derivatives. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1182–1187, June, 2007.     

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.