Diyne conjugation terminal alkyne coupling

The synthesis of conjugated diynes via the Glaser coupling reaction " is the classical method for homocoupling of terminal alkynes. The coupling reaction is catalyzed by CuCl or Cu(OAc)2 in the presence of an oxidant and ammonium chloride or pyridine to yield symmetrically substituted diynes. " The oxidative dimerization appears to proceed via removal of the acetylenic proton, formation of an alkynyl radical, and its dimerization. 

Cu-catalyzed Glaser coupling Preparation of symmetrical conjugated diynes and polyynes by the oxidative homocoupling of terminal alkynes in the presence of copper salts. 186... 

A Ni/Cu-cocatalyzed oxidative coupling reaction between two different terminal alkynes which provided a variety of unsytnmetrical conjugated diynes under mild... 

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