Silacyclization through palladium-catalyzed intermolecular silicon-based C(sp)-C(sp) cross-coupling

Silicon-based cross-coupling has been recognized as one of the most reliable alternatives for constructing carbon-carbon bonds. However, the employment of such reaction as an efficient ring expansion strategy for silacycle synthesis is comparatively little known. Herein, we develop the first intermolecular silacyclization strategy involving Pd-catalyzed silicon-based C(sp 2 )-C(sp 3 ) cross-coupling. This method allows the modular assembly of a vast array of structurally novel and interesting sila-benzo[ b ]oxepines with good functional group tolerance. The key to success for this reaction is that silicon atoms have a stronger affinity for oxygen nucleophiles than carbon nucleophiles, and silacyclobutanes (SCBs) have inherent ring-strain-release Lewis acidity. Herein, we develop the first silacyclization between 2-halophenols and SCBs, which allows the modular assembly of sila-benzo[ b ]oxepines with good functional group tolerance and can be applied for the late-stage modification of biologically active molecules.