| Corey–Fuchs reaction | |
|---|---|
| Named after | Elias James Corey Philip L. Fuchs |
| Reaction type | Substitution reaction |
| Identifiers | |
| Organic Chemistry Portal | corey-fuchs-reaction |
| RSC ontology ID | RXNO:0000146 |
TheCorey–Fuchs reaction, also known as theRamirez–Corey–Fuchs reaction, is a series ofchemical reactions designed to transform analdehyde into analkyne.[1][2][3] The formation of the 1,1-dibromoolefins via phosphine-dibromomethylenes was originally discovered by Desai, McKelvie and Ramirez.[4] The phosphine can be partially substituted by zinc dust, which can improve yields and simplify product separation.[1] The second step of the reaction to convert dibromoolefins to alkynes is known asFritsch–Buttenberg–Wiechell rearrangement. The overall combined transformation of an aldehyde to an alkyne by this method is named after its developers, American chemistsElias James Corey andPhilip 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.
The Corey–Fuchs reaction is based on a special case of theWittig reaction, where two equivalents of triphenylphosphine are used withcarbon tetrabromide to produce the triphenylphosphine-dibromomethylene ylide.[2]
This ylide undergoes a Wittig reaction when exposed to an aldehyde. Alternatively, using a ketone generates a gem-dibromoalkene.
The second part of the reaction converts the isolable gem-dibromoalkene intermediate to the alkyne. Deuterium-labelling studies show that this step proceeds through a carbene mechanism. Lithium-Bromide exchange is followed by α-elimination to afford the carbene. 1,2-shift then affords the deuterium-labelled terminal alkyne.[3] The 50% H-incorporation could be explained by deprotonation of the (acidic) terminal deuterium with excess BuLi.
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