Cross-Coupling Reactions of Alkenylsilanolates. Investigation of the Mechanism and Identification of Key Intermediates through Kinetic Analysis

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• 作者：Scott E. Denmark and Ramzi F. Sweis
• 刊名：Journal of the American Chemical Society
• 出版年：2004
• 出版时间：April 21, 2004
• 年：2004
• 卷：126
• 期：15
• 页码：4876 - 4882
• 全文大小：128K
• 年卷期：v.126,no.15(April 21, 2004)
• ISSN：1520-5126

文摘

The mechanism of the fluoride-free, palladium-catalyzed cross-coupling reaction of potassium(E)-heptenyldimethylsilanolate, K⁺(E)-1^-, with 2-iodothiophene has been investigated through kineticanalysis. The order of each component was determined by plotting the initial rates of the reaction againstconcentration. These data provided a mechanistic picture which involves a fast and irreversible oxidativeinsertion of palladium into the aryl iodide and a subsequent intramolecular transmetalation step from acomplex containing a silicon-oxygen-palladium linkage. First-order behavior at low concentrations ofsilanolate with excess palladium(0) complex supports the formation of this complex as the turnover-limitingstep. The change to zeroth-order dependence on silanolate at high concentrations is consistent with theintramolecular transmetalation becoming the turnover-limiting step.