Episulfide

According to electron diffraction, the and distances in ethylene sulfide are respectively 1.473 and 1.811 Å. The and angles are respectively 66.0 and 48.0°. ==Preparation==

A number of chemists in the early 1900s, including Staudinger and Pfenninger (1916), as well as Delepine (1920) studied episulfides. In 1934 Dachlauer and Jackel devised a general synthesis of episulfides from epoxides using alkali thiocyanates and thiourea. : Episulfides can also be prepared from cyclic carbonates, hydroxyalkylthiols, halohydrins, dihaloalkanes, and chloroalkylthiols. : Base converts monothiocarbonates to episulfides: : The metal-catalyzed reaction of sulfur with alkenes has been demonstrated but is of little preparative value. Tertiary episulfonium ions form when a trinitrophenylsulfonate thioester, or a mercaptonium trimer of the form (RS), attacks an alkene. Note that the products are however still rather unstable. Succinimide- or pthalimide sulfenyl chlorides react with alkenes to form α-chloro sulfenyl amides. Further reaction with lithium aluminum hydride gives the episulfide. ==Reactions==

Episulfides, due to their innate ring strain, often undergo ring-opening reactions, especially with nucleophiles. : Such reactions proceed via episulfonium ions. Episulfonium salts can be prepared using trimethyloxonium tetrafluoroborate: : Episulfide polymerize, especially in the presence of Lewis acids. ==Applications==

, an episulfide-containing drug for the treatment of breast cancer.|left Thiiranes occur rarely in nature but are found in some pharmaceuticals. ==Related compounds==

Dithiiranes consist of three-membered ring containing two sulfur atoms and one carbon. One example was prepared by oxidation of a 1,3-dithietane. File:PIRSAK01(CSDfile).png|thumb|left|122px|Structure of a dithiirane. ==References==