Electrochemistry and Reactivity of Chelation‐stabilized Hypervalent Bromine(III) Compounds

Hypervalent bromine(III) reagents possess a higher electrophilicity and a stronger oxidizing power compared to their iodine(III) counterparts. Despite the superior reactivity, bromine(III) reagents have a reputation of hard‐to‐control and difficult‐to‐synthesize compounds. This is partly due to their low stability, and partly because their synthesis typically relies on the use of the toxic and highly reactive BrF3 as a precursor. Recently, we proposed chelation‐stabilized hypervalent bromine(III) compounds as a possible solution to both problems. First, they can be conveniently prepared by electro‐oxidation of the corresponding bromoarenes. Second, the chelation endows bromine(III) species with increased stability while retaining sufficient reactivity, comparable to that of iodine(III) counterparts. Finally, their intrinsic reactivity can be unlocked in the presence of acids. Herein, an in‐depth mechanistic study of both the electrochemical generation and the reactivity of the bromine(III) compounds is disclosed, with implications for known applications and future developments in the field. Despite their promising properties, hypervalent bromine(III) reagents remain underexplored due to their low stability and difficult preparation. A fresh approach involves chelation‐stabilized bromine(III) species which are conveniently prepared by electro‐oxidation of parent bromoarenes. The intrinsic Br(III) reactivity can be unlocked in the presence of acids. In this mechanistic study, electrochemical synthesis, redox properties, and chemical reactivity aspects of chelation‐stabilized hypervalent bromine(III) species are disclosed.