Chemodivergent Construction of Seven-Membered Silacycles via Palladium-Catalyzed Ring Expansion from 4- to 7-Membered Rings

Silacycles are fundamental motifs in organosilicon chemistry, yet their structural diversity remains underexplored due to synthetic challenges. Here we report a ligand-controlled, Pd-catalyzed intramolecular silacyclization of allene-functionalized silacyclobutanes that enables modular access to diverse silacycles featuring a seven-membered sila-heterocyclic ring. It was found that tri-<i>o</i>-tolylphosphine promotes Si-C_β bond formation to form allyl-substituted seven-membered silacycles, while tris(perfluorophenyl)phosphine directs β,γ-insertion to yield another type of six/seven-membered silacycles. In addition, the chiral TADDOL-derived phosphoramidite variant as a chiral ligand establishes silicon-stereogenic centers with good enantioselectivity.