Alkynylcopper derivatives

Coupling is an important reaction of alkynes that leads to di-ynes. It occurs under a variety of condi-tions,32 but is particularly important when alkynylcopper derivatives are involved. Two classical alkyne coupling reactions involve copper derivatives. In the Glaser reaction,33 where an alkyne such as phenylacetylene reacts with basic cupric chloride (CuCl2), subsequent air oxidation gives a diyne (in this case 26 in 90% yield). 

Alkynylstannanes react with copper(II) nitrate to give, via the alkynylcopper(II) derivatives, the corresponding 1,3-dialkynes108 and they show a high reactivity in Stille-type palladium-catalysed coupling reactions (Section 22.2).109... 

Scheme 18 CuAAC reactions of azides and alkynes using alkynylcopper(I) derivatives as a precatalyst and ascorbate as ligand...

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