Cadiot-Chodkiewicz coupling
The Cadiot-Chodkiewicz coupling is a chemical reaction that is used in organic chemistry for the coupling of two terminal alkynes to form diynes . The reaction is catalyzed by copper salts . A terminal alkyne and a bromoalkyne are required as starting materials :
The Cadiot-Chodkiewicz coupling is a further development of the Glaser coupling and is therefore also related to the Hay coupling and the Eglinton coupling .
Reaction mechanism
The course of the reaction starts from the terminal alkyne. This is first of copper (I) ion by forming a π-complex associated . Due to the considerable lack of electrons in the alkyne, the pKa value is reduced from approx. 30 to below 9. Through this so-called activation , the alkyne can be deprotonated in the next step . Bases such as triethylamine are used for this purpose . At the same time, an organic copper (I) compound is formed, to which the bromoalkyne adds oxidatively . The less stable copper (III) compound thus formed breaks down in a rapid subsequent step by reductive elimination to form the diyne and copper (I) bromide , which is available for association with a new terminal alkyne. In this way the catalyst is restored.
literature
- W. Chodkiewicz: Ann. Chim. 2. Paris 1957, p. 819.
- A. Sevin, W. Chodkiewicz, Paul Cadiot : Bull. Soc. Chim. Fr. 1974, p 913th
- Reinhard Brückner : reaction mechanisms. 3. Edition. Spektrum, Munich 2004, ISBN 3-8274-1579-9 , p. 693.