Chemodivergent Construction of Seven-Membered Silacycles via Palladium-Catalyzed Ring Expansion from 4- to 7-Membered
Sui-Fang Peng1, Jia-Wei Si1, Li Li1
1Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Zhejiang Key Laboratory of Organosilicon Material Technology, College of Material, Chemistry and Chemical Engineering Hangzhou Normal University, No. 2318 Yuhangtang Road, Hangzhou, Zhejiang 311121, P. R. China.
Abstract:
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-o-tolylphosphine promotes Si-Cβ 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.
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