Kumada clutch

The Kumada coupling is a name reaction in organic chemistry . It is used for the alkenylation and arylation of alkenyl or aryl halides or triflates . It is a metal- catalyzed reaction; as catalysts are nickel used compounds. The reaction is named after Makoto Kumada (1920–2007), who published one of the first publications on this reaction. The reaction is of preparative interest because, in contrast to similar reactions such as the Suzuki or Stille coupling, sp ³ - hybridized residues can be used.

Reaction mechanism

Nickel complexes with phosphine ligands , for example dppe or dppp, are used as the catalyst . In the first step , the bromide or triflate used adds oxidatively to the nickel complex. The Grignard reagent used is then transmetallated from magnesium to nickel, with magnesium bromide being formed. After the subsequent cis - trans isomerization , the reductive elimination takes place between the organic residues, as a result of which the product is released and the catalyst is reformed.

Catalytic cycle of the Kumada coupling. L = ligand , Ar = aryl , R = organic radical

In addition to nickel catalysts, more expensive palladium complexes can also be used.

swell

• Reinhard Brückner : reaction mechanisms . 3rd edition, Spektrum Akademischer Verlag, Munich 2004, ISBN 3-8274-1579-9 , pp. 693-696.

Individual evidence

1. ↑ K. Tamao, K. Sumitani, M. Kumada: Selective carbon-carbon bond formation by cross-coupling of Grignard reagents with organic halides. Catalysis by nickel-phosphine complexes . In: J. Am. Chem. Soc. 94, 1972, pp. 4374-4376, doi : 10.1021 / ja00767a075 .
2. ↑ M. Yamamura, I. Moritani, S.-I. Murahashi: The reaction of σ-vinylpalladium complexes with alkyllithiums. Stereospecific syntheses of olefins from vinyl halides and alkyllithiums . In: J. Organomet. Chem. 91, 1975, C39-C42, doi : 10.1016 / S0022-328X (00) 89636-9 .