Diastereoselective oxidation of 2,3-epoxy alcohol-derived thiiranes, and H-1 NMR analysis of the corresponding thiirane S-oxides

Anti-thiirane S-oxides derived from cis-2,3-epoxyhexan-1-ol are prepared to serve as transition state analogs for alkene epoxidation and singlet oxygenation. The P-hydroxyl directing effect commonly exploited in sulfide oxidations is found to be completely ineffective in directing oxidation of cis-epoxy alcohol-derived thiiranes; steric factors alone appear to determine the anti:syn selectivity. Detailed H-1 NMR analysis was performed on both the stable anti- and the unstable syn-thiirane S-oxides. The thiirane S-oxide ring protons are found to possess unusually large vicinal coupling constants (approx. 11 Hz) and their chemical shifts are quite sensitive to the anisotropy of the SO moiety.