Stereoselective free-radical addition of secondary phosphine selenides to aromatic acetylenes

Free-radical addition (AIBN, 65-70 °C, 5-7 h) of secondary phosphine selenides to arylacetylenes proceeds stereoselectively to give anti-Markovnikov adducts of predominantly Z-configuration (up to 97%) in 60-80% isolated yields, thus representing a rare example of stereoselective free-radical addition to the triple bond. Microwave irradiation (600 W) of the reactants with the same content of AIBN reduces the reaction time to 8 min though compromises the stereoselectivity. Under UV-initiation the reaction loses its stereoselectivity due to isomerization of the primary Z-adducts. In this reaction, a specific facilitating and Z-configuration-controlling effect of aromatic substituents at the triple bond has been revealed.     

Analysis of rare earth sulfides, selenides and tellurides

The rare earth content of sulfides, selenides and tellurides is determined by titration with EDTA using Xylenol Orange as indicator. Sulfur is measured by titration of sulfate with lead nitrate solution after removal of rare earths on a cation exchanger. Selenium metal is precipitated from hydrochloric-sulfurous acid solution. Metallic tellurium is deposited from strongly acidic solutions containing sulfurous acid and hydrazine sulfate. An evaluation of the accuracy and precision of these methods is made.     

Nucleophilic addition of secondary phosphine sulfides to divinyl sulfoxide and divinyl sulfone

Secondary phosphine sulfides readily undergo addition to divinyl sulfoxide and divinyl sulfone in the presence of KOH (THF, 20–22°C, 1 h) with regiospecific formation of bis[2-(diorganylthiophosphoryl)-ethyl] sulfoxides and sulfones. A dramatic increase in the electrophilicity of the double bond in the monoadduct suggests transfer of the electron-acceptor effect of the thiophosphoryl group directly though space, due to its donor-acceptor interaction with the polarized S-O bond. It was demonstrated by the example of divinyl sulfoxide that, when performed with equimolar amounts of reactants and a weaker base (LiOH), the reaction can be stopped at the stage of formation of the monoadduct.     

Lanthanum-catalyzed stereoselective synthesis of vinyl sulfides and selenides

Lanthanum oxide/TMEDA-catalyzed cross-coupling of vinyl halides with thiols/diphenyl diselenide in anhydrous DMSO and KOH is reported. Utilizing this protocol various vinyl sulfides and selenides were synthesized in excellent yields with retention of the stereochemistry. The catalyst was recyclable.     

A simple and general preparation of vinylic sulfides, selenides and tellurides

A general method for the synthesis of vinylic chalcogenides by nucleophilic and Ni-catalyzed vinylic substitution on vinylic halides by phenyl chalcogenolates is described. The reactions were regio and stereoselective for the nickel catalyzed substitution, and mixture of isomers was observed for some examples in the thermal process in DMF.     

Comparative crystal-chemical analysis of d-metal sulfides, selenides, and tellurides and binary compounds

The structures of d-metal sulfides, selenides, and tellurides containing a tetrahedral complex anion have been compared to 1573 representatives of the topological types of binary compounds with the use of the TOPOS structural topological program package. The cases of similarity between these classes of compounds are found and discussed. Based on the results of topological analysis of ionic matrices, the rules are formulated that allow one to predict specific features of the structures of salts with complex chalcogen-containing anions.     

Short and efficient preparation of alkynyl selenides, sulfides and tellurides from terminal alkynes

Diphenyl diselenide reacts with terminal alkynes at room temperature in DMSO in the presence of catalytic amounts of copper iodide to give good to excellent yields of alkynyl phenyl selenides. The reaction occurs under neutral conditions and the solvent acts as the oxidant. Diphenyl disulfide and ditelluride undergo the analogous reaction, but require the presence of a weak inorganic base.     

Radical addition to vinyl sulphones and vinyl phosphonium salts

Alkyl radicals, derived from decarboxylation of carboxylic acids, add readily to phenyl vinyl sulphone and vinyl phosphonium bromide. The adducts may be further converted into a variety of useful synthetic intermediates.     

Radical addition of secondary phosphine chalcogenides to allylamine: Atom-economic synthesis of aminopropylphosphine chalcogenides

Secondary phosphine sulfides and phosphine selenides react with allylamine under the conditions of radical initiation (UV or AIBN) to form the anti-Markovnikov adducts in up to 93 % yield.     

Nucleophilic diaddition of secondary phosphine sulfides to acetylene and methylacetylene

Secondary phosphine sulfides react with acetylene and methylacetylene in the system KOH—DMSO (50 °C, 2—3 h) to form the corresponding tertiary bis-phosphine sulfides in high yield (up to 97%). Specific features of the NMR spectra (¹H, ¹³C, and ³¹P) of compounds obtained are discussed.     

Radical addition of methyldichlorosilane to vinyl acetate

The GC-MS method was used to identify the addition products of methyldichlorosilane to vinyl acetate. Radiation-induced addition of methyldichlorosilane to vinyl acetate produces 2-methyldichlorosilylethyl ethyl ether. The reaction follows a radical-chain mechanism. The ratio of the rate constants of methyldichlorosilyl radical addition to C=C and C=O to vinyl acetate amounts to 0.4±0.1 (303 K).

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- . , - 2- . , C=C C=O 0,4±0,1.

     

Catalyst-free addition of secondary phosphine chalcogenides to pyrazolecarbaldehydes

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