Copper catalysis Sonogashira reaction

The coupling of terminal alkynes with aryl or vinyl halides under palladium catalysis is known as the Sonogashira reaction. This catalytic process requires the use of a palladium(0) complex, is performed in the presence of base, and generally uses copper iodide as a co-catalyst. One partner, the aryl or vinyl halide, is the same as in the Stille and Suzuki couplings but the other has hydrogen instead of tin or boron as the metal to be exchanged for palladium. 

Oxidative addition of alkenyl halides, triflates, and other esters to zerovalent palladium compounds has been long known as a viable route to palladium(ii)-alkenyl complexes. Stereospecific coupling reactions involving mono- and (E)- or (Z)-dihalo-alkenes with palladium-copper catalysis under modified Sonogashira conditions are quite versatile and useful. These proceed through oxidative addition of the alkenyl halide via palladium(ii) alkenyl complexes, followed by coupling with a nucleophile (usually an alkynylcopper reagent obtained in situ with co-catalytic copper(i) from terminal alkynes in the presence of, in this case, a base like piperidine instead of diethylamine). ... 

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