Condensed heterocycles. 42. Synthesis and some properties of 3-hydroselenobenzo[b]furan-2-carbaldehyde and 2-hydroselenobenzo[b]furan-3-carbaldehyde

The reactions of 3-chlorobenzo[b]furan-2-carbaldehyde and 2-bromobenzo[b]furan-3-carbaldehyde with sodium hydrogen selenide have yielded isomeric hydroseleno aldehydes which, under the action of atmospheric oxygen, have oxidized to diselenides, while alkylation of the seleno aldehydes with methyl iodide leads to the formation of the corresponding methylseleno derivatives.For communication 41, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1177–1179, September, 1984.     

Mechanism of reaction of n-butane with but-2-enes in the presence of LaCaX faujasites

The reactions of n-butane and an n-butane (80 mol.%)—isobutane (20 mol.%) mixture with but-2-enes in the presence of polycationic PdLaCaX faujasites were studied. Quantum-chemical calculation of the enthalpies of formation of alkanes C₄—C₈ and their cations showed that the reaction [Bnⁿ]⁺ [Buⁱ]⁺ is of crucial importance for the isomeric composition of the products of alkane alkylation. The general scheme of transformations of the hydrocarbons in the alkylation of n- and iso-paraffins was proposed based on the experimental data on the distribution of the C₈ isomers in the catalyzate at different temperatures and duration of the reaction.     

Condensed heterocycles 47. Intramolecular hydrogen bonding in heteroaromatic hydroxy-, mercapto-, and selenolaldimines

Examination of the PMR spectra of benzo[b]furan and benzo[b]thiophene hydroxy-,mercapto-, and selenolaldimines, obtained in different solvents, show the absence of any correlation between the chemical shifts of the NH protons in aldimines and the strength of the intramolecular hydrogen bond (IMHB) NH...X (X = O, S, or Se). Novel condensed thio- and selenopyrans have been obtained from these aldimines and acrylonitrile. The conditions for the reaction are shown to depend on the strength of the IMHB in the aldimines.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 416–422, February, 1990.     

Cyclization reactions of nitriles. 26. Synthesis,structure, and properties of 2-amino-4-methylthio-5-cyano-6(1H)-pyrimidinethione

2-Amino-4-methylthio-5-cyano-6(1H)-pyrimidinethione has been prepared via treatment of N-cyanodimethyldithioimidate or 1,1-di(methylthio)-2-thiocar-bamoyl-2-cyanoethylene with cyanothioacetamide or cyanamide. The structure of the complex formed between 2-amino-4-methylthio-5-cyano-6(1H)-pyrimidinethione and urea has been studied by x-ray structural analysis. Thieno[2,3-d]pyrimidines and thiazolo[3,2-c]pyrimidinium salts have been synthesized based on the 6(1H)-pyrimidinethione.For Communication 25, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1377–1384, October, 1987.     

Polyfunctional zeolite catalysts in the benzene-olefin-hydrogen system

Benzene alkylation by C₂–C₄ olefins in the presence of hydrogen over a steam-treated zeolite catalyst containing lanthanum and nickel, has been studied. The promoting action of hydrogen on benzene alkylation by propylene has been established.

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C₂–C₄ , . .

     

Fluorination of aromatic compounds with xenon difluoride in the presence of boron trifluoride etherate

Fluorination of benzene with the XeF₂—BF₃?Et₂O system in acetonitrile at low temperatures affords fluorobenzene in 18% yield, the conversion of benzene being 92%. The rest products are di-, tri-, tetra-, and polyphenyls with different fluorination pattern. Toluene and chloro- and bromobenzenes are fluorinated predominantly at the ortho and para positions. Fluorination of 4-nitroanisole affords 2-fluoro-4-nitroanisole in 73% yield.