Decarboxylative Bromination of Aliphatic Carboxylic Acids via Visible Light-Driven Proton-Coupled Electron Transfer

An efficient method for the decarboxylative bromination of aliphatic carboxylic acids has been developed via a tether-tunable distonic radical anion-mediated proton-coupled electron transfer process. Under blue light irradiation, the combination of a cyclic diacyl peroxide and tetrabutylammonium bromide generates such a reactive intermediate that facilitates the direct homolytic cleavage of carboxylic O-H bonds, enabling decarboxylation and subsequent bromination. This strategy exhibits a broad substrate scope, including challenging primary, secondary, and tertiary carboxylic acids, as well as complex three-dimensional scaffolds and biologically relevant molecules without the involvement of heavy metals or prefunctionalization, and demonstrates excellent functional group tolerance and scalability. Mechanistic studies support a radical chain process initiated by visible light. This method provides a practical and versatile route to alkyl bromides from readily available carboxylic acids.