Corey–Fuchs reaction

The Corey-Fuchs reaction is a chemical reaction that is used for displaying of alkynes from aldehydes. It is named after their discoverers, Elias James Corey and Philip L. Fuchs. The following diagram shows an overview of the reaction without the leaving groups.

Mechanism

The Corey-Fuchs reaction is a two-step synthesis. In the first stage a double brominated phosphorus ylid is prepared from carbon tetrabromide, triphenylphosphine and zinc in situ. The ylide reacts with the aldehyde to a Wittig reaction to a 1,1- dibromoalkene.

This is initially set in the second step with one equivalent of n -butyllithium. Thereby a substituted bromo is replaced by lithium. It forms an organolithium compound as a byproduct 1 -bromobutane. The exchange takes place selectively at the sterically more hindered bromine atom instead. For the next step, one finds in the literature two different descriptions:

• The second molecule is n-butyl lithium reacts with the hydrogen atom of the lithium organyl, forming lithium acetylide, lithium bromide and n-butane. The former forms with aqueous workup, the terminal alkyne.

• The organolithium reacts initially in an Umlagerungssreaktion to an alkyne. The resulting alkyne reacts due to its acidity with the remaining equivalent of n -butyl lithium to lithium acetylide. By aqueous work-up, a terminal alkyne.

Swell

• Name reaction