Negishi coupling

The Negishi coupling is a name reaction of organic chemistry. The cross-coupling is the alkenylation or arylation of arylene. To this end, aryl halides or triflates are reacted in a nickel-or palladium-catalyzed reaction with organozinc compounds. The reaction is related to the Stille, Suzuki and Kumada coupling. The reaction is named after its discoverer, Ei-ichi Negishi, who published it in 1977 and in 2010 it was awarded the Nobel Prize for Chemistry.

As ligands, phosphines such as triphenylphosphine or dppe as well as the chiral chelating ligands such as BINAP or chiraphos are.

Reaction mechanism

In the first step, the aryl halide used oxidative addition to the nickel or palladium catalyst. Here, the oxidation state of the metal changes from 0 to 2. The second step of the cycle consists of a transmetallation, in which the rest of zinc is to be coupled transmetallated to the catalyst metal. After optional isomerization of the trans - to the cis - complex the desired product is reductively eliminated. Here, the catalyst species is re-formed.

Scope

The Negishi coupling is often used because it tolerates a lot of functional groups. This is due to the relative inertness of the organozinc compounds compared to other organometallic compounds, which can be used in coupling reactions.

The zinc organyls needed can usually be obtained from the corresponding organolithium compound.