Incorporation of CO ₂ Into C(Sp ³ ) Centers: Base‐Driven Carboxylation of Benzylic Boronic Esters

Incorporation of carbon dioxide (CO 2 ) into benzylic boronic esters for carboxylation reactions under mild, transition‐metal‐free conditions remains challenging due to their susceptibility to side reactions such as protodeboronation. In this study, we present a mild and sustainable approach to the direct carboxylation of benzylic boronic esters using CO 2 as a renewable C1 synthon at ambient pressure. This approach employs potassium ethoxide as a highly effective promoter, facilitating the transformation under straightforward operational conditions. A diverse array of electron‐withdrawing and sterically hindered substrates was efficiently converted into the corresponding phenylacetic acids, demonstrating commendable yields. In contrast, electron‐rich and secondary substrates exhibited comparatively diminished reactivity. The practical applicability of this synthetic methodology was further illustrated through the gram‐scale synthesis of pharmaceutically significant nonsteroidal anti‐inflammatory drugs (NSAIDs).