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The Negishi coupling is a cross coupling reaction in organic chemistry involving an organozinc compound, an organic halide and a nickel or palladium catalyst creating a new carbon-carbon covalent bond  :
Additional recommended knowledge
The active catalyst in this reaction is zerovalent (M0) and the reaction in general proceeds through an oxidative addition step of the organic halide followed by transmetalation with the zinc compound and then reductive elimination:
Both organozinc halides and diorganozinc compounds can be used as starting materials. In one model system it was found that in the transmetalation step the former give the cis-adduct R-Pd-R' resulting in fast reductive elimination to product while the latter gives the trans-adduct which has to go through a slow trans-cis isomerization first .
The Negishi coupling has been applied in the synthesis of a 2,2'-bipyridine from 2-bromopyridine with Tetrakis(triphenylphosphine)palladium(0) , the synthesis of a biphenyl from o-tolylzinc chloride and o-iodotoluene and Tetrakis(triphenylphosphine)palladium(0) , the synthesis of 5,7-Hexadecadiene from 1-decyne and (Z)-1-hexenyl iodide 
The Negishi coupling has been applied in the synthesis of hexaferrocenylbenzene :
In a novel modification palladium is first oxidized by the haloketone 2-chloro-2-phenylacetophenone 1 and the resulting palladium OPdCl complex then accepts both the organozinc compound 2 and the organotin compound 3 in a double transmetalation :
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Negishi_coupling". A list of authors is available in Wikipedia.|