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 the photochemical C−O bond activation of aromatic carboxylic acids in the presence of PPh(3). It generates an acyl radical, which further undergoes an additional reaction with gem‐diborylalkenes to form an α‐gem‐diboryl alkyl radical intermediate, which then reduces to the corresponding anion, which after protonation, affords the β‐keto‐gem‐diborylalkane product. Moreover, the same scenario has been extended to the vinyl boronic esters, for example, gem‐(Ar, Bpin)‐alkenes, and gem‐(Alkyl, 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.