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

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