Fluoroalkyl disulfides

Pyrolytic conversion of 6 to 7 with extrusion of sulfur is a slow reaction which apparently involves in the latter stages an unusual attack of thiyl radical on carbon to form the monosulfide structure. Pyrolysis of 8 to 7, also demonstrated separately, is a more direct example of conversion of a fluoroalkyl disulfide to monosulfide by intramolecular attack of thiyl radical on carbon. The dithiane 7, once formed, is stable at 300°C, indicating that the CF2--S bond in these compounds is not subject to homolysis. The related formation of an acyclic monosulfide—e.g., CF3SCF3—from an acyclic disulfide—e.g., CF3SSCF3— requires photochemical activation or temperatures higher than 300°C. 

Numerous S -fluoroaryl or S -fluoroalkyl derivatives of cysteine have been described. Thus, fluorination of S -benzyl cysteine has been performed with XeFa- The photochemical trifluoromethylation of cysteine, or of its disulfide, affords optically pure S -trifluoromethyl cysteine. Some electrophilic halogenated compounds (such as trifluorochloroethylene) are able to achieve the 5-fluoroalkylation of cysteine. 

The present procedure is based on the use of fluoroalkyl alcohols as solvents in oxidation reactions. The method is efficient and versatile, and produces disulfides and sulfoxides under mild conditions. These reactions have also been developed using hexafluoroisopropyl alcohol (HFIP) as solvent with a large variety of substrates (alkyl sulfides, alkyl thiols, vinyl sulfides, fiuorinated vinyl sulfides, thioglucosides) by Begue et al."> Replacement of HFIP with trifluoroethanol, a more common and less expensive solvent, also allows the use of mild conditions and affords high yields of disulfides and sulfoxides without contamination. 30% Aqueous hydrogen peroxide is inexpensive and, since water is the sole byproduct, this method is environmentally friendly. 

Tris- and tetrakis (triphenylphosphine) platinum (0) are the source of many platinum compounds. They react with carbon monoxide, acids/ methyl iodide/ fluoroalkyl derivatives/ carbon disulfide/ oxygen/ chloro/ fluoro/ and activated olefins/ hydrogen sulfide and selenide/ and sulfur dioxide/ yielding many platinum (II) or platinum (0) compounds which cannot be obtained easily by other routes. 

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