Predict the product of the following Negishi coupling reactions.
(a)

Verified step by step guidance

1. Identify the reactants involved in the Negishi coupling reaction. In this case, we have a bromobenzene derivative and an organozinc compound.
2. Understand the role of the catalyst and solvent. The reaction uses a palladium catalyst, Pd(PPh3)4, and is carried out in tetrahydrofuran (THF) at 0°C.
3. Recognize the mechanism of the Negishi coupling reaction. The palladium catalyst facilitates the formation of a carbon-carbon bond between the aryl halide and the organozinc reagent.
4. Predict the product by replacing the bromine atom on the aromatic ring with the alkyl group from the organozinc compound. This results in the formation of a new C-C bond.
5. Draw the structure of the product, which is a combination of the aromatic ring with the methoxy group and the alkyl chain from the organozinc reagent, now attached to the position where the bromine was originally located.

Key Concepts

Negishi Coupling Reaction

Negishi coupling is a cross-coupling reaction that forms carbon-carbon bonds between an organozinc compound and an organic halide, facilitated by a palladium catalyst. This reaction is highly useful in organic synthesis for constructing complex molecules. The presence of a palladium catalyst and a suitable solvent, such as THF, is crucial for the reaction's success.

Role of Palladium Catalyst

Palladium catalysts, such as Pd(PPh3)4, are essential in facilitating the Negishi coupling reaction. They enable the oxidative addition of the organic halide to the palladium, followed by the transmetalation with the organozinc reagent, and finally, reductive elimination to form the desired carbon-carbon bond. The catalyst's efficiency is influenced by its ligands and the reaction conditions.

Transmetalation Process

Transmetalation is a key step in the Negishi coupling where the organozinc reagent transfers its organic group to the palladium complex. This step is crucial for forming the new carbon-carbon bond. The organozinc compound's reactivity and the reaction conditions, such as temperature and solvent, play significant roles in the efficiency of this process.