Zinc Redox Catalysis in the Photochemical Borylation of Fluorocarbons

Zinc compounds are ubiquitous in synthesis and materials. They find applications as reagents, catalysts, porous materials and as metalloenzymes — all of which rely on the properties of redox stable and electrophilic zinc(II) centres. In this paper we report the first clear example of redox catalysis involving reversible changes between zinc(I) and zinc(II) oxidation states. Under photochemical conditions a zinc(I) compound was shown to react with fluoroarenes. Turnover was achieved through addition of a diborane reagent, resulting in a catalytic borylation of the C(sp2)–F bonds of fluoroarenes. Mechanistic studies and DFT calculations support a key role of a zinc(II) boryl intermediate in the reductive step from zinc(II) to zinc(I). These findings were further exploited in a small array of photocatalytic approaches to the borylation and reductive coupling of C(sp3)–F, C(sp2)–O and C(sp3)–O bonds.