OXIDATION OF 2-CHLOROETHYL SULFIDES TO SULFOXIDES BY DIMETHYL-SULFOXIDE

While most organic sulfides were not oxidized by dimethyl sulfoxide (DMSO), the alkyl 2-chloroethyl sulfides and bis (2-chloroethyl) sulfide slowly reacted with DMSO to produce the corresponding sulfoxides at 25–70 °C under nitrogen. The mechanism of the oxidation is proposed to involve nucleophilic substitution by DMSO followed by neighboring sulfur participation to form a transient sulfonium ion with a four-membered ring structure. The sulfonium ion intermediate rapidly reacts with the chloride ion to produce 2-chloroethyl sulfoxides. 2-Hydroxyethyl sulfoxides were also produced, probably due to the presence of a trace amount of water in the DMSO. This reaction demonstrates, for the first time, the unique reactivity of 2-chloroethyl sulfides in DMSO. © 1990, American Chemical Society. All rights reserved.