Corey-Winter olefin synthesis

The Corey-Winter olefin synthesis is a series of chemical reactions for converting 1,2-diols into olefins. It is named for the American chemist and Nobelist Elias James Corey and the American-Estonian chemist Roland Arthur Edwin Winter.



Often, thiocarbonyldiimidazole is used instead of thiophosgene as shown above.

Mechanism
The reaction mechanism involves the formation of a cyclic thio-carbonate from the diol and thiophosgene. The second step involves treatment with trimethyl phosphite, which attacks the sulphur atom, producing S=P(OMe)3 (driven by the formation of a strong P=S double bond) and leaving a carbene. This carbene collapses with loss of carbon dioxide to give the olefin.