In summary, mechanistic insights into the reaction of alkoxide and benzylic boronate reveal that increasing the amount of alkoxide can convert benzylic boronate into a free carbanion, thereby significantly increasing the nucleophilicity of both secondary and tertiary benzylic boronates. This finding is demonstrated through the mild reaction conditions for the alkoxide-promoted crosscoupling reaction of benzylic boronate with 4-cyanopyridine. Based on these mechanistic findings, a highly efficient and operationally straightforward method has been developed for divergently constructing C-C and C-heteroatom bonds using benzylic boronate derived from the silaboration (or diborylation) reaction of aromatic alkenes. This method can tolerate a broad range of electrophiles, including aryl (pseudo)halides, aromatic heterocycles, carbon dioxide, carbonyl derivatives, etc. Of particular significance is its applicability to aryl electrophiles, allowing for the facile synthesis of valuable 1,1-diaryl frameworks. Moreover, the synthetic value of this strategy is evidenced by its potential for late-stage modification of drug-relevant molecules.