Nickel-Catalyzed Bromide-to-Iodide Aromatic Finkelstein Reaction

Key words

nickel catalysis - aryl iodides - halogen exchange

Significance

In 1978, Takagi, Hayama, and Okamoto disclosed an early example of a halogene exchange reaction using a simple nickel(II) precatalyst, with added Zn or PBu₃, and a nucleophilic source of iodide (KI). As the authors explain, at this time the most common strategy to perform an aromatic Finkelstein reaction was to use copper; however, the ability to go from a bromide to iodide was unattainable. This topic has remained of interest for the last 50 years, with notable contributions from a wide variety of groups.

Review

D. A. Petrone, J. Ye, M. Lautens Chem. Rev. 2016, 116, 8003–8104.

Comment

The addition of Zn was crucial for the reaction to occur at lower temperatures. Moreover, it was found that the addition of a donating phosphine ligand, such as PBu₃, suppressed the formation of the reductive homocoupled side product. At elevated temperatures, only the phosphine additive was necessary for a successful reaction, without the need of the Zn reductant. The reaction did not occur when using various nickel(0) precatalysts.

Publication History

Article published online:
16 February 2022