Modular and Regioselective Synthesis of Eight-Membered Benzosilacycles Enabled by Ring Expansion of Silacyclobutanes with Aryl Halides and Alkynes

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Silacycles are essential structural motifs in silicon-containing functional molecules, which are widely applied in the fields of synthetic chemistry, materials science, and pharmaceuticals. However, the synthesis of silacycles especially medium-sized ones remains a formidable challenge. Herein, we report a general and modular platform technology for the construction of eight-membered benzosilacycles by palladium-catalyzed alkyne insertion/C–H activation/ring expansion cascade. Readily available aryl halides, alkynes, and silacyclobutanes are used as the building blocks, laying the foundation for the diversity-oriented synthesis of these scaffolds (>80 examples). Other features include excellent regioselectivities and chemoselectivities, broad functional group tolerance, good step economy, and scalability. This method is also amenable for the synthesis of fused benzosilacycles and dibenzosilacycles that are otherwise difficult to access. Additionally, the reaction mechanism and the origins of regioselectivity are elucidated by control experiments and density functional theory calculations.