Coupling to alkynes: the Sonogashira reaction
المؤلف:
Jonathan Clayden , Nick Greeves , Stuart Warren
المصدر:
ORGANIC CHEMISTRY
الجزء والصفحة:
ص1087-1088
2025-08-09
545
Coupling to alkynes: the Sonogashira reaction
The coupling of terminal alkynes with aryl or vinyl halides under palladium catalysis is known as the Sonogashira reaction and is rather like the Heck reaction. It is a catalytic process, requiring a palladium (0) complex; it 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 alkyne needs no metal to activate it: the reaction works with the alkyne itself.
The mild conditions usually employed, frequently room temperature, mean that the reaction can be used with thermally sensitive substrates. By now, you should not be surprised by the mechanism! Oxidative addition of the organic halide gives a palladium (II) intermediate that undergoes transmetallation with the alkynyl copper (generated from the terminal alkyne, base, and copper iodide). Reductive elimination with coupling of the two organic ligands gives the product and regenerates the palladium (0) catalyst.
It is usually more convenient, as in the Heck reaction, to use a stable and soluble Pd (II) derivative such as bis(triphenylphosphine)palladium (II) chloride instead of Pd (0). This is rap idly reduced in situ to give a coordinatively unsaturated, catalytically active, palladium (0) species. The geometry of the alkene is generally preserved so that cis (Z) and trans (E) dichloro ethylene give the two different geometrical isomers of the enyne below in >99% stereochemical purity as well as excellent yield.
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