Corey-Fuchs reaction

The Corey-Fuchs reaction is a series of chemical reactions designed to transform an aldehyde into an alkyne. The reaction is named after its discoverers, American chemists Elias James Corey and Philip L. Fuchs.



By suitable choice of base, it is often possible to stop the reaction at the 1-bromoalkyne, a useful functional group for further transformation.

Reaction Mechanism
The Corey-Fuchs reaction is based on a special case of the Wittig Reaction, where the phosphorus ylide is formed from dibromocarbene. This carbene is generated in situ from the reaction of triphenylphosphine and carbon tetrabromide.



Triphenylphosphine then attacks the nascent carbene to form the reactive ylide. This ylide undergoes a Wittig Reaction when exposed to an aldehyde.



The dibromoalkene reacts with butyllithium via lithium-halogen exchange. Next, the resulting species ejects bromide through an alpha-elimination pathway to produce an olefnic carbene. This rapidly undergoes rearrangement to form the more stable alkyne.