Corey–Winter olefin synthesis

The Corey - Winter elimination, also known as Corey - Winter fragmentation, is a response from the field of organic chemistry. It is used for synthesis of alkenes from 1,2- diols. To this end, in addition to the diol thiophosgene and trimethyl phosphite are required. The reaction is named after its discoverers, the Nobel laureate Elias James Corey Jr. and the Estonian- American chemist Roland Arthur Edwin winter. In the following overview, the leaving groups are not listed.

Mechanism

The two Diolsauerstoffatome stepwise nucleophilic attack on the Thiocarbonylkohlenstoff. With elimination of hydrogen chloride thus forming a cyclic thiocarbonate. Trimethyl phosphite takes the next step is nucleophilic at sulfur to form a carbanion on. The cleavage of the thiophosphoric provides a cyclic carbene. This breaks down now under CO2 capture to the desired alkene.

The elimination is selectively syn in this reaction. This means that a rotation must be made to the carbon- carbon bond in the starting material during the first reaction step to form the five-membered ring, until the two OH groups are eclipsed or syn to each other. The substituents R1 to R4 ( see figure) are then according to their arrangement in the starting material either on the same side or on opposite sides of the five-membered ring. Whether an (E ) - or ( Z)- alkene, then must be determined according to the known rules. For example, the reaction of trans -1 ,2- cyclooctanediol ( e ) cyclooctene. In place of thiophosgene, which are easier to handle thiocarbonyl imidazole is often used, but wherein the atom economy is deteriorated.