Photoredox-Mediated Deoxygenative Radical Additions of Aromatic Acids to Vinyl Boronic Esters and gem-Diborylalkenes

A new method to access β-keto-gem-diborylalkanes, by direct deoxygenative radical addition of aromatic carboxylic acids to gem-dibortlalkenes, is described. The reaction proceeds under mild photoredox catalysis, and involves a photochemical C–O bond activation of aromatic carboxylic acids in the presence of PPh3 to generate an acyl-radical, which further undergo addition reaction with gem-diborylalkenes to form α-gem-diboryl alkyl radical intermediate, which then reduced to the corresponding anion which after protonation yields the β-keto-gem-diborylalkane product. Moreover, the same scenario has been extended to the vinyl boronic esters e.g., gem-Ar,Bpin-alkenes. Importantly, this protocol provides a general platform for the late-stage functionalization of bio-active and drug molecules containing a carboxylic acid group.