Diselenide, diaryl

Another application concerns the preparation of selenides and tellurides from diaryl diselenides ° or ditellurides. While selenide formation is carried out in refluxing toluene by using a large excess of diselenides, diaryl ditellurides give the best results by utilizing visible irradiation at 35 C. Aryl, benzyl, methyl, and dicyanogen selenides can be prepared in this way. 

Diaryl disulfides and diselenides add to alkynes to afford the (Z)-l, 2-bis(ar-ylthio)alkenes 193 and (Z)-l,2-bis(arylseleno)alkenes 194. Under CO pressure, carbonylative addition takes place to give thio esters and the selenoketones 195[I07], The selenoketones are converted into the /J-seleno-a, 3-unsaturated aldehydes 196 by Pd-catalyzed hydrogenolysis with HSnBu3[108,109],... 

The carbene moieties of methyl diazoacetate 353), dimethyl diazomalonate 3S3) and diazomethane 3541 have been inserted into the Se—Se bond of diaryl diselenides. 

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). 

Introduction of two different chalcogen elements to the C-C unsaturated bond is of particular interest from both synthetic and mechanistic viewpoints. Therefore, extensive studies have been carried out on the development of the (RE)2/(R E )2 binary system without using RE-E R compounds, which are difficult to prepare. (Z)-l-Seleno-2-thio-1-alkenes are produced regio- and stereoselectively when a mixture of diaryl disulfides and diaryl diselenides is subjected to a rhodium-catalyzed reaction with alkynes (Equation (68)).193... 

Reaction of diaryl diselenides with methylenecyclopropanes in the presence of PhI(OAc)2 (2.2equiv.) results in ring expansion to afford 1,2-diselenylcyclobutenes (Scheme 41).206... 

Insertion of carbon monoxide into Csp2—Zr bonds occurs readily at ambient temperatures or below to produce a,(5-unsaturated, reactive acyl zirconocene derivatives [27—29]. Early work by Schwartz demonstrated the potential of such intermediates in synthesis [5d], as they are highly susceptible to further conversions to a variety of carbonyl compounds depending upon manipulation. More recently, Huang has shown that HC1 converts 16 to an enal, that addition of a diaryl diselenide leads to selenoesters, and that exposure to a sulfenyl chloride gives thioesters (Scheme 4.11) [27,28]. All are obtained with (F)-stereochemistry, indicative of CO insertion with the expected retention of alkene geometry. 

D. Crich, X. Hao, M. A. Lucas, Design, Application and Recovery of a Minimally Fluorous Diaryl Diselenide for Catalysis of Stannane-Mediated Radical Chain Reductions , Org Lett 1999,1,1426. 

Aryl trimethylsilylmethyl selenides also yielded the diaryl diselenide as the major product, but possibly through a somewhat different mechanism, due to the increased stability of the initially formed radical cation (Fig. 31) ... 

Diaryl ditellurides, like diaryl disulphides and diselenides, undergo disproportionation into arene tellurolates and tellurinates by alkaline treatment. 

Diaryl diselenide and diaryl disulphide react analogously. 

These results reveal that the a-isomer is thermodynamically more stable than the )3-iso-mer. The radicals so generated are trapped with TEMPO and diaryl diselenides. The addition of alkynes gives rise to vinylic tellurides. 

By the interaction of selenium tetrachloride and benzene in the presence of aluminium chloride. Diaryl selenides and diaryl diselenides are formed as by-products. 

The aryl selenides are crystalline solids or liquids heavier than water. Oxidation by atmospheric oxygen or dilute alkali yields diaryl diselenides. 

The diaryl diselenides are solids of well-defined crystalline form, the benzyl compounds being slowly decomposed by light. The following methods have been used for their preparation, but some are only applicable to special cases ... 

Although examples were not documented, it has been reported that diaryl diselenides undergo oxidative cleavage with BTIB at the Se-Se bond to give are-... 

In a rare example of the use of iodonium salts for heteroatom-heteroatom bond formation, diaryliodonium halides were employed with sodium 0,0-diethyl phosphoroselenolate for a one-pot synthesis of diaryl diselenides (Scheme 9) [27]. These transformations probably occur via arylation of the phosphoroselenolate salt with the diaryliodonium ions, hydrolysis of the resulting aryl phosphoroselenolates with sodium hydroxide, and air oxidation of the arene-selenide ions thus produced. 

An intramolecular Heck-carbonylation/cyclization of the vinyl iodide 881 provides the 5,6-dihydropyran-2-one 882 during a total synthesis of manoalide (Equation 354) <1997CC1139>. The reaction of but-3-yn-l-ol with diaryl sulfides and carbon monoxide in the presence of a palladium(O) catalyst leads to a novel thiolactonization and hence arylthiosubstituted 5,6-dihydropyran-2-one 883 (Equation 355). Similar results are obtained with diaryl diselenides (Equation 355) <1997JOC8361>. Hydrozirconation of O-protected homopropargylic alcohols followed by carbonyla-tion and quenching with iodine provides a simple route to 5,6-dihydropyran-2-ones <1998TA949>. 

Diaryl diselenides were oxidatively cleaved by BTI to form selenenyl tri-fluoroacetates, CF3COOSeAr. This reaction served for the preparation of selenosulphonates which resulted in good yield when BTI was added to a mixture of sodium sulphinate and diaryl diselenide [49] ... 

NiBr2(2,2 -bipyridine) complex44. Aryl halides, such as 4-bromobenzophenone, or 2-bromoquinoline could be transformed into diaryl diselenides 20 or ditellurides 21 elec-trochemically using sacrificial selenium or tellurium cathodes as can be seen in equation 20. 

Various reducing agents have been used for the generation of selenolates from diselenides or selenocyanates. Alkali metals M (M = Li, Na, K)149,150 or alkali hydrides MH (M = Li, Na, K)151,152 can generate the corresponding selenolate anions such as 80 these are more reactive than the borane complexes of type 77 (Scheme 15). Diaryl diselenides are easier reduced than dialkyl diselenides, but the mechanism for the reduction of selenocyanates is complex and can lead to either diselenides or selenolates.153,154... 

Oxidation of alcohols. Alcohols can be oxidized to carbonyl compounds by f-butyl hydroperoxide (slight excess) and a diaryl diselenide (0.1-0.5 equiv.). Diphenyl diselenide is satisfactory, but bis(2,4,6-trimethylphenyl) diselenide is generally more satisfactory. The method is particularly efficient for benzylic and primary allylic alcohols (12 hours, 87-100% yield) oxidation of saturated alcohols, primary and secondary, requires 4-17 hours, but still proceeds in excellent yield. 

The mechanism is not clear. Possibly ArSeOH or ArSeOSeAr is the true catalyst. In any case the diaryl diselenide is recoverable in about 70% yield. 

LiHdiaryl diselenides are more easily reduced than dialkyl diselenides. The reactions are faster in DMF than in THF [7a]. 

Reaction of diphenyl diselenide or dimethyl diselenide with hydrazine hydrate and sodium hydroxide generates the corresponding selenolates smoothly in solvents like DMF or diethyl ether and in the presence of tetrabutylammonium chloride as a phase-transfer catalyst [13]. The selenolates react with organic halides to give various selenides (Scheme 9). Similar conditions have been applied to the synthesis of aryl vinyl selenides from diaryl diselenides and acetylene [14]. 

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