Selenides, preparation

The selenides prepared by any of these methods can be converted to selenoxides by such oxidants as hydrogen peroxide, sodium metaperiodate, peroxycarboxylic acids, 1-butyl hydroperoxide, or ozone. 

Cyclohexyldienyl complexes, with Ti(IV), 4, 327 Cyclohexylisocyanides, with gold(I) halides, 2, 281 Cyclohexylphosphine, for semiconductor growth, 12, 9 Cyclohexyl selenides, preparation, 9, 480 Cyclohydrocarbonylation alkenes, 11, 515 alkynes, 11, 522 dienes, 11, 522 overview, 11, 511-555 for ring expansion, 11, 527 Cycloisomerizations, via silver catalysts, 9, 558 Cyclomanganation, product types, 5, 777-778 Cyclometallated azobenzenes, liquid crystals, 12, 251 Cyclometallated complexes for OLEDs... 

Alkenesfrom selenides. Preparation of alkylidenecyclopropanes by selenoxide elimination proceeds in rather low yields. Yields are improved considerably if the selenide is first methylated (CH3OSO2F or CHjI-AgBFi) and the methyl seleno-nium salt is treated with potassium /-butoxide in THF or DMSO (equation I). 

The oxidation of the chiral ferrocenyl vinyl selenides, prepared from the optically active diferrocenyl diselenides and ethyl propiolate derivatives, with 1 molar equivalent of MCPBA under various conditions afforded the corresponding chiral selenoxides. The chiral selenoxides suffered in situ selenoxide elimination to afford the axially chiral allenecarboxyUc esters in moderate chemical yields with high enantioselectivities (Scheme 10). Typical results are shown in Table 5. The reaction temperature had a remarkable effect upon stereoselectivity and the lower temperature gave better results. The addition of molecular sieves (4 A) to the reaction system improved the stereoselectivity. Dichlo-romethane was revealed to be the solvent of choice. In other words, reaction conditions to suppress the racemization of a diastereomeric selenoxide intermediate were required. Asymmetric selenoxide elimination provides a new method for the preparation of the chiral allenecarboxyUc esters which have so far been prepared by optical resolution of the corresponding racemic acids. 

Hydroxy selenides prepared by the reaction of epoxides with selenophenol and methanol are converted to alkenes upon treatment with thionyl chloride/triethylamine in methylene chloride (equations 33... 

Bis[methoxymethyl]-2,S-diphcnylte1lurophene 430 mg (1 mmol) of 3,4-bis[chloromethyl]-2,5-diphenyl-tellurophene are added to a solution of sodium methoxide prepared from 40 ml of absolute methanol and 200 mg (8.7 mmol) of sodium and the mixture is heated under reflux for 10 h. The mixture is then allowed to cool to 20°, poured into water, and extracted several times with diethyl ether. The combined extracts are dried with anhydrous sodium sulfate, filtered, and the filtrate is evaporated. The residue is chromatographed on silica gel with benzene as the mobile phase to give the product as a light yellow oil yield 350 mg (83%). l,3-Diphenyl-4//,6//-selenophene[3,4-c]tellurophene A solution of disodium selenide, prepared from 1.58 g (20 mmol) of selenium and 0.92 g (40 mmol) of sodium in liquid ammonia, in absolute methanol is saturated with nitrogen. 1.28 g (3 mmol) of 3,4-bis[chloromethyl]-2,5-diphenyltellurophene are added and the mixture is refluxed under nitrogen for 15 h. The mixture is then filtered, the filter cake is dissolved in chloroform in the presence of activated charcoal, filtered, and the product is recrystallized from chloroform/methanol yield 0.79 g (60%) m.p. 220°... 

The approach to HTSC electrosynthesis described in this section is entirely analogous to that used for the production of semiconductive films such as CujcInj,S(Se)j [205,206]. The thermal treatment of electrodeposited metallic precursors carried out in an H2S(Se) atmosphere in some cases proved more successful than the cathodic codeposition of sulfur or selenium with the metals [207]. There is also an analogy with other combined methods of selenide preparation the sputtering of copper or indium followed by cathodic deposition of selenium [208], and the chemical reaction of selenium with metals. In this case, as in the deposition of incomplete HTSC precursors [189], the use of the deposition mode is much easier. 

Reaction of acyl or aroyl halides with thallium(I) phenyl selenide, prepared by the reaction of either thallium(I) ethoxide or thdlium(I) phenoxide with benzeneselenol, gave the corresponding phenyl sele-nol esters in yields over 97% (equation 3). ... 

Aldehyde synthesis. a-Bromo selenides, prepared in quantitative yield from vinyl selenides, are converted into aldehydes in about 857o yield when treated with anhydrous DMSO for a brief time. If the reaction is allowed to stand o-seleno aldehydes are obtained by reaction of the aldehyde with the benzeneselenenyl bromide. ... 

Ally Sulphides and Selenides.—Preparative methods described for saturated sulphides may be used for the allyl analogues, and 1,2-phenylthio-shifts can be exploited. Scheme 14 illustrates some of the methods used, and applications for the separate synthesis of 1- and 2-(phenylthio)buta-l,3-dienes. Dehydrochlorination of adducts formed from trisubstituted alkenes and PhSCl yields allyl sulphides. ... 

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