Science of Synthesis

Hopkinson, M. N.; Gouverneur, V., Science of Synthesis Knowledge Updates, (2011) 2, 108.

In order for a coupling reaction to be made catalytic, a method must be found for the reoxidation of the Mn generated upon reductive elimination back to Mn + 2. For palladium and other transition metals, this task is most commonly performed by the oxidative addition of an organic halide or equivalent. This elementary step is particularly challenging for gold as even the most activated organic iodides are generally not sufficiently oxidizing to convert gold(I) into gold(III). Under certain conditions, however, electron-rich alkyl­gold(I) complexes can be oxidized with alkyl iodides although this has not yet been applied in catalytic alkylation reactions (see Section ‌3.6.13.1.1‌). Several examples of gold-catalyzed Suzuki and Sonogashira reactions with aryl iodides have been reported, although the role of the gold catalyst in these processes has been the subject of debate.