Enhancing the nucleophilicity of benzylic boronates enables the divergent formation of C−C and C−X bonds

Tetracoordinated boron species generated from the complexation of organoboron compounds with bases are highly important intermediates in molecular fragments coupling. The type of base significantly impacts both the reaction activity and mechanism of organoboron compounds. Herein, our structural and mechanistic insights show that the full heterolytic cleavage of the C−B bond in benzylic boronates, leading to the formation of benzyl potassium species, can be achieved by increasing the amount of alkoxides. This, in turn, significantly enhances the nucleophilicity of both secondary and tertiary benzylic boronates. This mechanistic insight has proven valuable in the divergent construction of C(sp3)−C(sp3 or sp2) and other C−X bonds (X = Si, Ge, Sn, S, Se), as demonstrated through the integration of base-catalyzed silylboration/diborylation reactions. Through machine-learning-assisted screening of approximately 104 substrate combinations, we have expanded the scope of electrophiles for this transformation to include challenging aromatic heterocycles. Moreover, the synthetic potential of this protocol was demonstrated through the construction of drug-relevant molecules that contain 1,1-diaryl pharmacophores.