β-Diethoxyphosphorylethyl sulphoxides 4, prepared by selective oxidation of the corresponding sulphides 6 using bromine/potassium hydrogen carbonate as oxidising agent in a two-phase system, undergo the Pummerer rearrangement accompanied by elimination affording E-β-ethylthio-vinylphosphonate 7. The synthesis of Z-α-bromo-β- ethylthiovinylphosphonate 14 is also described.
