The Corey-Fuchs reaction involves the transformation of an aldehyde into an alkene using a combination of carbon tetrabromide and triphenylphosphine as the primary reactants.

Specifically, the reaction utilizes an aldehyde along with a mixture of carbon tetrabromide ($\text{CBr}_4$) and triphenylphosphine ($\text{PPh}_3$). This reaction is classified as a two-step process that ultimately yields an alkene. The Corey-Fuchs reaction is named after the American chemists Elias James Corey and Philip L. Fuchs, who first described it in 1972.

In the initial step of the Corey-Fuchs reaction, the aldehyde reacts with carbon tetrabromide and triphenylphosphine to generate a bromoalkyne intermediate. Here, the aldehyde is transformed into a dibromoolefin through the formation of a phosphonium ylide, which occurs when the aldehyde reacts with triphenylphosphine. The phosphonium ylide subsequently reacts with carbon tetrabromide to yield the dibromoolefin.

The second step involves treating the bromoalkyne intermediate with a strong base, typically butyllithium ($\text{BuLi}$), to produce the final alkene product. The base deprotonates the bromoalkyne, resulting in the formation of a carbanion. This carbanion then undergoes an elimination reaction to generate the alkene.

The Corey-Fuchs reaction is an effective method for synthesizing alkynes from aldehydes, particularly for producing terminal alkynes, which can be challenging to synthesize through alternative methods. Notably, the reaction is stereospecific, producing a single stereoisomer of the alkene product. This property makes the Corey-Fuchs reaction a valuable tool in the synthesis of complex organic molecules.