3.5.7 Cadiot-Chodkiewicz Coupling

Monosubstituted alkynes reacts with alkynyl halides in the presence of copper(I) salts to offer unsymmetrical bisacetylenes (Scheme 12).

 

Scheme 12

Mechanism

Proceeds via oxidative addition followed by reductive elimination (Scheme 13).

Scheme 13

3.5.6 Glaser (Oxidative Coupling)

Terminal alkynes can also be coupled by oxidative coupling using copper salts in the presence of molecular oxygen (Scheme 14).

Scheme 14

Scheme 15

Using this method the synthesis of macrocyclic lactone, exaltolide, that is partly responsible for the sweet odour of the angelica root, can be accomplished in high yield (Scheme 15).