Photoinduced Boron-Catalyzed β-Allylation of Carboxylic Acids Enabled by a Mixed Two-Ligand System

A visible light-induced, boron-catalyzed direct β-allylation of carboxylic acids with allylsulfones was developed. The selective promotion of β-allylation over the competing α-allylation was achieved by the combined use of a bulky binaphthol derivative and a N-sulfonyl valine derivative as ligands for the boron catalyst. Photoexcitation of catalytically generated diboron ene-1,1-diolates induces single-electron transfer to the allylsulfones, and ensuing deprotonation of the resulting radical cations generates β-radicals, directing C–C bond formation at the β-position. The versatility of this catalysis was demonstrated through its application to various pharmaceutical compounds. Furthermore, by leveraging the unique features of the carboxy group preserved in the products, subsequent transformations were successfully achieved, showcasing the capability of the boron catalysis in rapidly increasing the molecular complexity of carboxylic acids.