The reaction of singlet oxygen 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 with α, β-unsaturated sulfoxides (1a ...