Regiodivergent Synthesis of Eight-Membered Benzosilacycles via Palladium-Catalyzed Alkenyl C(sp²)–H Activation

Herein we report a general and efficient method for the regiodivergent synthesis of medium-sized eight-membered aryl- and alkenylsilacycles via a palladium-catalyzed alkenyl C(sp2)-H activation/ring expansion cascade. This protocol features a broad substrate scope regarding o-bromostyrenes and silacyclobutanes, excellent regioselectivities, mild reaction conditions, and scalability. Control experiments revealed that the regioselectivity of this reaction is dictated by the synergistic interplay between the electronic nature of the α-substituent in the substrate and the precisely tuned catalytic system. The synthetic potential of this method is further exemplified by the versatile downstream transformations.