11.8.5 Sonogashira Coupling

The reaction involves the coupling aryl halides with alkynes using the combination of palladium and copper catalysts in the presence of base at moderate temperature (Scheme 13). It is compatible with functional groups such as hydroxo, carbonyl, amino, acyloxy, acetal, esters and amides, and finds extensive applications in organic synthesis.

Scheme 13

Mechanism

Oxidative addition of Pd(0) with aryl halide gives Pd(II) intermediate A that undergoes reaction with in situ generated alkynyl copper to give intermediate B. The latter complete the catalytic cycle by the reductive elimination of the substituted alkyne (Scheme 14).

Scheme 14

Examples: