Gem-Disulfoxides

Although perhaps not strictly a conformational study, the structure of the gem-disulfoxide 184 was determined by X-ray crystallography169. A comparison of the structural parameters so measured with 1H and 13C NMR chemical shifts led the authors to conclude that chemical shifts should allow configurational assignments to be made to related sulfoxides. 

The reaction of thioacetals with two equivalents of peroxy acids generally affords epimeric gem-disulfoxides, the ratio of epimers being subject to kinetic and/or equilibrium control (70). However, Poje, Sikirica, Vickovic, and Bruvo (71) have reported the first example of a stereospecific oxidation in the gem-disulfide series. They found that 2,2-bis(methylthio)-l,3-diphe-nylpropane is smoothly oxidized to the corresponding meso-disulfoxide with m-chloroperbenzoic acid. The study of conformational properties in solution by nmr indicated that the meso-disulfoxide exists in conformation 119 which... 

Pot-pourri 323 is the same as that found in the solid state by X-ray analysis. The above authors have suggested that the configuration and conformation of meso-disulfoxide 119 is the result of a stereospecific oxidation of conformation 118 of the gem-disulfide. They have further suggested that this particular stereochemical course cannot be explained by steric effects it must have an electronic origin. 

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