What is Negishi Coupling reaction?

The Negishi coupling is a widely employed transition metal catalyzed cross-coupling reaction. The reaction couples organic halides or triflates with organozinc compounds, forming carbon-carbon bonds (c-c) in the process. The organic residue R = alkenyl, aryl, allyl, alkynyl or propargyl.

What does Negishi mean?

Negishi (根岸) is a Japanese surname and place name. It may refer to: Ei-ichi Negishi, a Japanese chemist who was awarded the 2010 Nobel Prize in Chemistry. Negishi coupling, a chemical reaction discovered by Ei-ichi Negishi in 1977.

What is Negishi reagent?

The Negishi reaction is the palladium-catalyzed cross-coupling between organozinc reagents and aryl- or alkenyl halides or triflates. It is compatible with some functional groups that can tolerate the presence of the organozincs, including ketones, esters, amines and cyano groups.

How do Suzuki reactions prevent dehalogenation?

This dehalogenation can be suppressed by protection of the pyrrole nitrogen. Using a BOC protecting group, not only is dehalogenation suppressed, but the protecting group is also removed under the reaction conditions.

Which base is used in Suzuki coupling?

The general scheme for the Suzuki reaction is shown below, where a carbon-carbon single bond is formed by coupling an organoboron species (R1-BY2) with a halide (R2-X) using a palladium catalyst and a base….

Why is a base necessary for Suzuki coupling?

Hence, the main role of the base in the reaction mechanism is to increase the reactivity of the boronic acid toward the Pd–halide complex by converting it into the respective organoborate.

What is Negishi coupling?

The Negishi Coupling, published in 1977, was the first reaction that allowed the preparation of unsymmetrical biaryls in good yields. The versatile nickel- or palladium-catalyzed coupling of organozinc compounds with various halides (aryl, vinyl, benzyl, or allyl) has broad scope, and is not restricted to the formation of biaryls.

What are the limitations of the Negishi coupling for organozincs?

Organozincs are moisture and air sensitive, so the Negishi coupling must be performed in an oxygen and water free environment, a fact that has hindered its use relative to other cross-coupling reactions that require less robust conditions (i.e. Suzuki reaction).

What are the advantages of the Negishi coupling in palladium catalysts?

Palladium catalysts in general have higher chemical yields and higher functional group tolerance. The Negishi coupling finds common use in the field of total synthesis as a method for selectively forming C-C bonds between complex synthetic intermediates.

Can negnegishi coupling be used in the synthesis of hexaferrocenylbenzene?

Negishi coupling has been applied in the synthesis of hexaferrocenylbenzene: with hexaiodidobenzene, diferrocenylzinc and tris (dibenzylideneacetone)dipalladium (0) in tetrahydrofuran. The yield is only 4% signifying substantial crowding around the aryl core.