The deuteration of α-selenylated-β-silylsulfoxides and α-selenylated-β-tert-butylsulfoxides has been shown to lead, with good levels of diastereocontrols to the formation of syn isomers irrespective of the stereochemistry of the sulfinyl precursors. Our results have been rationalized using transition state models which parallel the Felkin-Anh model.