The reaction of singletoxygen with 2-methyl-3-phenylsulfinyl-2-butene (1a) and E2-phenylsulfinyl-2-butene (1b) gives the corresponding allyl alcohols (2a and 2b) after reduction with dimethyl sulfide. α,β-Unsaturated sulfoxides with s-trans conformation failed to proceed the ene-type oxidation but afforded S-oxidation products. On the other hand, 4-methyl-1,2,4-triazoline-3,5-dione (MeTAD) reacted