Diselenides, oxidation

Diphenyltellurides, 119-121 molecular modeling, 121 Diselenides, oxidation potentials, 135t... 

Hydrolysis and subsequent oxidation by air of benzoylated selenazolidines gives N.N -diben20vlbis(2-aminoethyl)diselenide (Scheme 73)... 

Diselenides can also be oxidatively fluorinated, as shown in equation 18 [118, 119], Benzene selenyl fluoride is postulated as an intermediate during the fluo-roselenation of alkenes with diphenyl diselenide and xenon difluotide [73, 120]... 

Diphenyl diselenide has been prepared by disproportionation of phenyl selenocyanate in the presence of potassium hydroxide" or ammonia/ and by air oxidation of benzeneselenol. The preparation of benzeneselenol is described in an earlier volume in this series/ In the present procedure phenylselenomagnesium bromide formed from phenylmagnesium bromide and selenium is oxidized directly to diphenyl diselenide with bromine/ Thus the liberation of the malodorous and toxic hydrogen selenide and benzeneselenol is avoided. Benzeneselenenyl chloride has been prepared by thermal elimination of ethyl chloride from ethyl phenyl selenide di-chloride/ by thermal elimination of chlorine from phenylselenium trichloride," and by chlorinolysis of diphenyl diselenide with either sulfuryl chloride " or chlorine. " ... 

It was observed in other works that in sulfide electrolyte, decomposition of ZnSe was still obtained stable PECs could be constructed though from singlecrystal, n-type, Al-doped ZnSe electrodes and aqueous diselenide or ditelluride electrolytes [124]. Long-term experiments in these electrolytes were accompanied by little electrode weight loss, while relatively constant photocurrents and lack of surface damage were obtained, as well as competitive electrolyte oxidation. Photoluminescence and electroluminescence from the n-ZnSe Al electrodes were investigated. 

Another useful reagent for selenenylcyclization is phenylselenenyl triflate. This reagent is capable of cyclizing unsaturated acids101 and alcohols.102 Phenylselenenyl sulfate can be prepared in situ by oxidation of diphenyl diselenide with ammonium peroxy-disulfate.103... 

This reaction depends upon the facile solvolysis of (J-haloselenides and the facile oxidative elimination of a selenoxide, which was discussed in Section 6.6.3. An alternative method, which is experimentally simpler, involves reaction of alkenes with a mixture of diphenyl diselenide and phenylseleninic acid.189 The two selenium reagents generate an electrophilic selenium species, phenylselenenic acid, PhSeOH. 

The formation of silaneselone 57 was evidenced by the trapping reaction with mesitonitrile oxide leading to the corresponding cycloadduct 58 and was also supported by the observation of a remarkably downfield 29Si chemical shift (8Si = 174) indicative of the Si=Se double bond of 57. Although this direct selenation of silylene 55 with an equimolar amount of selenium was not reproducible, the use of excess amount of elemental selenium resulted in the formation of a new cyclic diselenide, diselenasilirane 59, as a stable compound (8Si = -44 and... 

Bloodworth, A. J., et al., J. Chem. Soc., Perkin Trans. 1, 1983, 471-473 Attempted thermal dehydration of benzeneseleninic acid, formed by oxidation of diphenyl diselenide with hydrogen peroxide, gave a solid which exploded at 53-55°C. The solid may have been the complex of the acid with hydrogen peroxide. 

Dry hydrogen or dry nitrogen may be used. The gas must be oxygen-free. Hydrogen tends to decrease the amount of oxidation to diselenide. 

Stable hindered selenoketones222 are easily reduced to give selenolate ions with various reducing agents and oxidized by air to form diselenides (Scheme 39). 

In the case of the most reactive compounds, substitution at the carbon atom of diselenonium and ditelluronium dications is also a possible pathway. For example, formation of diselenide 117 from selenoxide 115 was explained by demethylation of intermediate dication 116 with trifluoroacetate anion.126 Dealkylation of salt 118, which is stable up to —20°C, leads to formation of nitrilium salt 119. The latter is transformed to amide 120 upon hydrolysis.64 Dealkylation of intermediate diselenonium dication 122 was suggested as the key step in the oxidative synthesis of 1,2,4-diselenazolidines 123 from eight-membered heterocycles 121 (Scheme 46).127... 

Diaryl diselenides and benzisoselenazole-3(27/)-ones are used as efficient catalysts in the process of imine oxidation with hydrogen peroxide and tert-butyl-hydroperoxide (25). 

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