Stereochemical and conformational consequences of the oxidation of 1,4-thiazane-3,5-dicarboxylates

Abstract

The stereoselectivity of the oxidation of 1,4-thiazane-3,5-dicarboxylate derivatives to the corresponding sulfoxides and sulfones was found to be dependent on the type of oxidant used and the conformational preference of the substrate. Direct oxidants, such as sodium periodate, peroxides and peracids, preferentially react with the axial sulfur lone-pair, providing the axial S-oxide. Oxidation with bromine-water yielded the epimeric equatorial S-oxide, presumably as a result of initial attack of the axial sulfur lone pair providing the axial bromosulfonium ion, with subsequent displacement of bromide by water leading to the equatorial S-oxide.