Xanthates pyrolysis

Olefin formation (preferentially less substituted) from alcohols via xanthate pyrolysis. 

Xanthates, pyrolysis, 268 X-ray crystallography ethanoate anion, 19 Grignard reagents, 221 Meisenheimer complexes, 171 triphenylmethyl radicals, 311... 

Steps 1-2 Xanthate pyrolysis furnishes the alkene C via syn elimination. 

The lower activation energy for the xanthate pyrolysis means that it occurs at lower temperatures than do the other pyrolyses. As a result, xanthate pyrolysis avoids the necessity of vapor phase pyrolysis that the other eliminations require, and the products are less likely to undergo further reaction at the lower temperature of xanthate pyrolysis. For a discussion, see reference 159. 

Scheme 8.69. The Chugaev reaction. The salt of an alcohol is allowed to react with carbon disulfide, producing the sodium salt of a dithiocarbonate derivative, which, on Sn2 reaction with methyl iodide (CH3I), produces the corresponding xanthate ester. Heating the xanthate (pyrolysis) results in loss of carbon oxysulfide (COS), methane thiol (thiomethane), and the corresponding alkene.

---