Palladium-Catalyzed Desymmetrization of Silacyclobutanes with Alkynes to Silicon-Stereogenic Silanes: A Density Functional Theory Study

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• 作者：Jin Zhang ; Jin-Zhou Xu ; Dr. Zhan-Jiang Zheng ; Dr. Zheng Xu ; Dr. Yu-Ming Cui ; Dr. Jian Cao and Prof. Dr. Li-Wen Xu
• 刊名：Chemistry – An Asian Journal
• 出版年：2016
• 出版时间：October 20, 2016
• 年：2016
• 卷：11
• 期：20
• 页码：2867-2875
• 全文大小：2012K
• ISSN：1861-471X

文摘

The palladium-catalyzed desymmetrization of silacyclobutanes using electron-deficient alkynes proceeds with high enantioselectivity in the presence of a chiral P ligand; this provides a facile approach for the synthesis of novel silicon-stereogenic silanes. In this work, we used hybrid density functional theory (DFT) to elucidate the mechanism of the palladium-catalyzed desymmetrization of silacyclobutanes with dimethyl acetylenedicarboxylate. Full catalytic cycle including two different initiation modes that were proposed to be a possible initial step to the formation of the 1-pallada-2-silacyclopentane/alkyne intermediate—the oxidative addition of the palladium complex to the silacyclobutane Si−C bond (cycle MA) or coordination of the Pd⁰ complex with the alkyne C≡C bond (cycle MB)—have been studied. It was found that the ring-expansion reaction began with cycle MB is energetically more favorable. The formation of a seven-membered metallocyclic Pd^II intermediate was found to be the rate-determining step, whereas the enantioselectivity-determining step, oxidative addition of silacyclobutane to the three-membered metallocyclic Pd^II intermediate, was found to be quite sensitive to the steric repulsion between the chiral ligand and silacyclobutane.