Dithiirane-1 -oxides stereochemistry

The dithiirane 39 is oxidized with w-chloroperbenzoic acid (MCPBA) at 0°C to give a diastereomeric mixure of dithiirane 1-oxides 40 in a 1 1 molar ratio. The stereochemistry of 40a and 40b has been determined by comparison of H NMR spectra with those of known dithiirane 1-oxides 16a and 17a <1997TL1431>. Upon heating the dithiirane 39 in refluxing 1,2-dichloroethane, chloroform, or benzene, a mixture of corresponding bicyclo compound 41 along with diketone 42 and thioketone 43 is obtained. Thermal isomerization of 39 into 41 is a common reaction of 5-oxodithiiranes and competes with desulfurization yielding thioketones. 

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