The hydroperoxysulfonium ylide. An aberration or a ubiquitous intermediate?

An intramolecular isotope effect has been measured for the reaction of singlet oxygen with 2,2,8,8-tetradeuterio-1,5-dithiacyclooctane, 4d4. The magnitude of the isotope effect, 1.21±0.09, provides verification of removal of an α-hydrogen during the product determining step to form a hydroperoxysulfonium ylide and ultimately the sulfoxide product. The absence of any special structural features in 4d4 to enhance the propensity of hydrogen removal is used to suggest that the hydroperoxysulfonium ylide is a ubiquitous intermediate in the reactions of sulfides with singlet oxygen.