Alkenes from xanthate esters

Radicals formed by fragmentation of xanthate and related thiono esters can also be trapped by reactive alkenes.217 The mechanism of radical generation from thiono esters was discussed in connection with the Barton deoxygenation method in Section 5.4. 

Alkenes from -hydroxy sulfides. This elimination was first observed on attempted reduction of the xanthate ester group of 1 with tri- -butyltin hydride the product, however, was the alkene 2. This is a general reaction of /J-hydroxy and jS-chloro sulfides. It has wide application since -hydroxy sulfides are readily... 

An important group of alkene-forming reactions, some of which are useful in synthesis, are pyrolytic eliminations. Included in this group are the pyrolyses of carboxylic esters and xanthates, of amine oxides, sulfoxides and selenoxides. These reactions take place in a concerted manner, by way of a cyclic transition state and therefore proceed with syn stereochemistry, such that the hydrogen atom and the leaving group depart from the same side of the incipient double bond (in contrast to the eliminations discussed in Section 2.1) (2.14). 

---