Temperature factor effect on the structure of the separated flow within a supersonic gas stream

The effect of the temperature factor, that is, the ratio of the body temperature to the freestream stagnation temperature, on the structure of the separated flow formed in the presence of a concave corner in a supersonic stream is studied. The strong influence of the temperature factor on the separation zone length and the flow-generated aerodynamic characteristics is established. It is shown that for fairly large deflection angles this flow cannot be described by free interaction, or triple deck, theory.     

Synthesis of N-heteroaromatic onium betaines of indane-1,3-dione

Betaines are formed in good yields in the reaction of N-heteroaromatic compounds with 2-dicyanomethyleneindane-1,3-dione oxide and its 4- and 5-halo derivatives in dioxane. The corresponding oxides were obtained by oxidation of 2-dicyanomethyleneindane-1,3-dione and its 4- and 5-substituted derivatives with hydrogen peroxide in dioxane. Data from the IR spectra of the compounds are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 889–892, July, 1978.     

Conversions of 2-thioxo-1,3-dithiol-4,5-dicarboxylic acid dimethyl ester — The path to a new heterocyclic system, (4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2,5,7-trione and 5,6-dimercaptouracil derivatives

The conversions of 2-thioxo-1,3-dithiol-4,5-dicarboxylic acid methyl ester into anhydride, mono- and diamide, and monoamide methyl ester were demonstrated. The new heterocyclic system, (4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2,5,7-trione, was obtained by oxidative rearrangement-cyclization of 2-oxo-1,3-dithiol-4,5-dicarboxylic acid diamide with phenyliodosyl(hydroxy)tosylate and used to synthesize previously unknown 5,6-dimercaptouracil derivatives, including nickel dithiolene complex.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1270–1275, September, 1992.     

Synthesis of 4- and 6-methyl derivatives of 5,7-dioxo(4h,6h)-1,3-dithiolo[4,5-d]pyrimidine based on methylbarbituric acids,spectroscopic characteristics and acidity constants

We have obtained previously unknown 1-methyl- and 1,3-dimethyl-5-diethylaminothiocarbonylthiobarbituric acids by reaction of sodium diethyldithiocarbamate with 5-phenyliodonium betaines of 1-methyl- and 1,3-dimethylbarbituric acids. Cyclization of these compounds upon heating in conc. H₂SO₄ gives methyl-substituted 5,7-dioxo(4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2-diethylimmonium hydrosulfates; the derivative of 1-methylbarbituric acid forms a mixture of 4-methyl- and 6-methyl-substituted compounds (21). We isolated perchlorates of 4-methyl- and 4,6-dimethyl-substituted derivatives in pure form. By treatment of the immonium salt with sodium sulfide or selenide, we obtained 4-methyl- and 4,6-dimethyl-5,7-dioxo(4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2-thiones and 4-methyl-, 6-methyl-, and 4,6-dimethyl-2-selenones. We characterized the isomeric 4- and 6-methyl-substituted selenones by electronic absorption spectra and ionization constants (7.65 and 4.0). The differences in the pK values and in the electronic absorption spectra makes it possible to distinguish the substitution site in N-mono-substituted derivatives of 5,7-dioxo(4H,6H)-1,3-dithiolo[4,5-d]pyrimidine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1526–1533, November, 1993.     

Synthesis of tetrathiafulvalene derivatives by dimerization of 1,3-dithiolselenones-2 using triphenylphosphine

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1278–1279, September, 1991.     

Synthesis and properties of (4-hydroxy-5-methoxycarbonylthieno)-tetrathiafulvalenes

6-Hydroxy-5-methoxycarbonylthieno[2,3-d]-1,3-dithiol-2-thione, -2-one, and 2-selenone were prepared by intramolecular cyclocondensation of 4-methoxycarbonylmethylthio-1,3-dithiol-2-thione-, 2-one-, and 2-selenone-5-carboxylic acid methyl ester. 2,6(7)-Di(methoxycarbonylmethylthio)-3,7(6)-di(methoxycarbonyl)tetra-thiafulvalene, 2-methoxycarbonylmethylthio-3-methoxycarbonyl-6,7-ethylenedithiotetrathiafulvalene, and the corresponding thieno-condensed tetrafulvalene derivatives were synthesized from them. The electrochemical oxidation potentials of the new tetrafulvalene derivatives were determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 761–768, June, 1993.     

Pyrimidotetrathiafulvalenes. 2. Trimethylsilylation of 5,-dioxo(4H, 6H)-1,3-dithiolo-[4,5-d]pyrimidine-2-selone and the use of the silylated product for the synthesis of 2,4-dioxopyrimidotetrathiafulvalenes

The trimethylsilylation of 5,7-dioxo(4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2-selone with bis(trimethylsilyl) acetamide enables pyrimido-tetrathiafulvalene derivatives to be prepared in benzene solution and increases the yield of the target compounds compared with the reaction of the unsilylated selone in DMF solution. The intermediate 2,4-bis(trimethyl-silyloxy)pyrimidotetrathisfulvalenes were sensitive to hydrolysis. The previously undescribed [2,4-dioxo(1H,3H)pyrimido]di-(methylthio)tetrathifulvalene has been obtained. The redox properties of the compounds obtained have been investigated by cyclic current-potential measurements.Riga Technical University, Riga LV-1658. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1285–1289, September, 1994. Original article submitted July 25, 1994.     

Synthesis of derivatives of 5-amino-7-oxo(6h)-1,3-dithiolo[4,5-d]pyrimidine on the basis of 2-amino-(1h,5h)pyrimidine-4,6-dione

The betaine of 2-amino-5-phenyliodonio(1H,5H)pyrimidine-4,6-dione, upon interaction with sodium diethyldithiocarbamate, forms the previously unknown 2-amino-5-diethylaminothiocarbonylthio (1H,5H)pyrimidine-4,6-dione, the cyclization of which in concentrated sulfuric acid leads to salts of 2-diethylimmonio-5-amino(6H)-1,3-dithiolo[4,5-d]pyrimidin-7-one — a new heterocyclic system. The salts serve as the starting material for obtaining 5-amino-7-oxo(6H)-1,3-dithiolo[4,5-d]pyrimidine-2-selenone and -2-thione.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1117–1121, August, 1992.     

Pyrimidotetrathiafulvalenes. 3.* synthesis and properties of cation-radical salts,cation-radical betaines,and complexes of dimethyl[2,4-dioxo(1H,3H)pyrimido]tetrathiafulvalene and its N-alkyl substituted derivatives with iodine

The reaction of dimethyl[2,4-dioxo(1H,3H) pynmido]tetrathiafulvalene and its N-alkyl derivatives with iodine leads to the formation of complexes with various numbers of iodine atoms. Depending on the conditions, the betaine of the cation-radical of dimethyl[2, 4-dioxo(1 H, 3H)pyrimidojtetrathiafulvalene or a complex of the latter with dimethy1[2,4-dioxo(1H,3H)pyrimidoltetrathiafulvalene is formed by the oxidation of the pyrimidotetrathiafulvalene. The cation-radical perchlorates are formed on carrying out the oxidation of dimethyl[2,4-dioxo(1H,3H)pyrimidojtetrathiafulvalene and its N-methyl derivatives in the presence of perchloric acid. The preparation of the cation-radical salts is usually linked with the reaction of the cation-radical betaine with acids.For part 2 see [1].