As we have discovered and reported herein, the reaction between benzylic organoboronates and alkoxide bases can be fine-tuned to achieve irreversible cleavage of the C-B bond and generate free carbanions by increasing the amount of base used (Fig. ). This results in enhanced nucleophilicity of both secondary and tertiary benzylic organoboronates. By integrating the alkoxide-mediated silaboration (or diborylation) reaction of aromatic alkenes with the nucleophilic-type reaction, we have developed a versatile platform for constructing C-C and C-X bonds under mild reaction conditions. This bond-making approach is mechanistically unique from existing protocols achieved through transition-metal catalysis or radical processes. It has a broad reaction scope, as demonstrated by successful reactions with up to 12 different classes of nucleophiles, including the challenging substitution of aromatic heterocycles and nucleophilic addition of carbon dioxide.