LEADING QUESTION

Kumada Coupling is a type of cross-coupling reaction, a reaction in which two hydrocarbon fragments are coupled with the aid of a metal catalyst. Kumada Coupling therefore generates new carbon-carbon bonds from the reaction between a grignard reagent and an organic halide, and this procedure specifically requires a transition metal, palladium or nickel, catalyst to occur.

In the example below, a Kumada Coupling reaction occurs between an organohalide, R₁-X, and a grignard reagent, RMgBr using a palladium catalyst. This reaction begins with an oxidative addition between the Pd⁽⁰⁾ and R₁-X to form a Pd^(II) complex.

Next, the R group of the grignard reagent replaces the halide anion on the palladium complex while a magnesium(II) halide salt is made as a by product.

Finally, the electrons bonding the R group and Pd attack the R₁ group, to form the final coupled product, while the Pd leaves and becomes regenerated allowing the catalytic cycle to continue.

¹ Kumada Cross-Coupling. http://name-reaction.com (accessed April 5, 2018).
² Oxidative Addition: General Ideas. http://chem.libretexts.org (accessed April 5, 2018).