Ei-ichi Negishi discoverer of Negishi coupling process

Ei-ichi Negishi – discoverer of Negishi coupling process

Category : Personalities
Published by : Data Research Analyst, Worldofchemicals.com

Biography & contributions

Ei-ichi Negishi, Japanese chemist and Nobel laureate is born on July 14, 1935. Negishi is famous for his notable discovery of Negishi coupling process.

He also worked on palladium catalyzed cross couplings in organic synthesis.

Negishi was the receiver of many awards and medals like Sir Edward Frankland Prize Lectureship from Royal Society of Chemistry in the year of 2000, Nobel Prize in chemistry for palladium catalyzed cross couplings in organic synthesis in the year of 2011.

Facts about palladium

Palladium was named after the asteroid Pallas. William Hyde Wollaston, an English chemist, discovered palladium in 1803. Palladium is a transition metal.It is silvery white and does not tarnish in air. It has the lowest density and lowest melting point of any member of the platinum group. It can be attacked by nitric and sulfuric acid. It is soft and ductile when annealed.

Palladium has the unusual property of absorbing up to 900 times its own volume of hydrogen when at room temperatures. It can then possibly form the compound palladium hydride (Pd2H).

Palladium as a catalyst is often used for hydrogenation and dehydrogenation reactions because hydrogen readily diffuses through heated palladium.

Coupling reactions/ Cross coupling reactions

A coupling reaction in organic chemistry is a catch-all term for a variety of reactions where two hydrocarbon fragments are coupled with the aid of a metal catalyst. In one important reaction type a main group organometallic compound of the type RM.

Negishi coupling/ Negishi cross-coupling reaction


The Negishi cross-coupling reaction is the organic reaction of an organohalide with an organozinc compound to give the coupled product using a palladium or nickel catalyst. The palladium catalyzed mechanism is occurred through three different types of reactions

  • Oxidative addition of organohalide
  • Transmetalation by organozinc
  • Reductive elimination

Firstly the oxidative addition of the organohalide to the Pd(0) to form a Pd(II) complex.Transmetalation with the organozinc then follows where the R group of the organozinc reagent replaces the halide anion on the palladium complex and makes a zinc(II) halide salt. Reductive elimination then gives the final coupled product, regenerates the catalyst, and the catalytic cycle can begin again.

Reference

[1] © From, http://www.name-reaction.com/negishi-cross-coupling

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