Suzuki reaction

Overview
The Suzuki reaction is the organic reaction of an aryl- or vinyl-boronic acid with an aryl- or vinyl-halide catalyzed by a palladium(0) complex. It is widely used to synthesize poly-olefins, styrenes, and substituted biphenyls. Several reviews have been published.



The reaction also works with pseudohalides, such as triflates (OTf), instead of halides, and also with boron-esters instead of boronic acids.
 * Relative reactivity: R2-I > R2-OTf > R2-Br >> R2-Cl

First published in 1979 by Akira Suzuki, the Suzuki reaction couples boronic acids (containing an organic part) to halides. The reaction relies on a palladium catalyst such as tetrakis(triphenylphosphine)palladium(0) to effect part of the transformation. The palladium catalyst (more strictly a pre-catalyst) is 4-coordinate, and usually involves phosphine supporting groups.

In many publications this reaction also goes by the name Miyaura-Suzuki reaction. It is also often referred to as "Suzuki Coupling".

Reaction mechanism
The mechanism of the Suzuki reaction is best viewed from the perspective of the palladium catalyst. The first step is the oxidative addition of palladium to the halide 2 to form the organo-palladium species 3. Reaction with base gives intermediate 4, which via transmetallation with the boron-ate complex 6 forms the organopalladium species 8. Reductive elimination of the desired product 9 restores the original palladium catalyst 1.



Oxidative addition
Oxidative addition proceeds with retention of stereochemistry with vinyl halides, while giving inversion of stereochemistry with allylic and benzylic halides. The oxidative addition initially forms the cis-palladium complex, which rapidly isomerizes to the trans-complex.

Reductive elimination
Using deuterium-labelling, Ridgeway et al. have shown the reductive elimination proceeds with retention of stereochemistry.