Rhodium-Catalyzed (Asymmetric) Annulation of Silacyclobutanes with Bicyclic Olefins via C–Si Bond Activation

The carbon-to-silicon switch gives rise to silacycles that offer eminent biological and photophysical properties. Access to chiral silacycles, especially midsized ones, via intermolecular coupling remains a considerable challenge due to limited synthetic methods. Herein, rhodium(I)-catalyzed annulations between benzosilacyclobutenes (SCBs) and bicyclic olefins are presented. A series of stable seven-membered chiral silacycles have been accessed in high enantioselectivity via the enantioselective [4 + 3] annulation between SCBs and 7-oxabenzonorbornadienes via a formal [2σ + 2σ] C–C and O–Si coupling. The mechanism of the enantioselective [4 + 3] annulation between SCBs and 7-oxabenzonorbornadienes has been investigated, where C–Si oxidative addition of the SCB has been established as the turnover-limiting step.