Cross-coupling reactions of alkenylsilanolates. Investigation of the mechanism and identification of key intermediates through kinetic analysis
Cross-coupling reactions of alkenylsilanolates. Investigation of the mechanism and identification of key intermediates through kinetic analysis
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DOI：
10.1021/ja0372356
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发表时间：
2004-04-21
影响因子：
15
通讯作者：
Sweis, RF
中科院分区：
文献类型：
--
作者：
Denmark, SE;Sweis, RF
通过动力学分析，研究了2-碘噻吩钾(E)-庚烯基二甲基硅烷酸钾(K+(E)-1(-))在钯催化下的无氟交叉偶联反应机理。通过绘制反应的初始速率与浓度的关系图，确定了每一组分的顺序。这些数据提供了一幅机理图，其中包括钯快速和不可逆地插入到芳基碘中，以及随后从包含硅-氧-钯键的络合物中进行的分子内转金属步骤。低浓度硅酸酯与过量钯(0)络合物的一级行为支持该络合物的形成是周转限制步骤。在高浓度下，硅酸盐的零级依赖性的变化与分子内的易位作用成为周转限制步骤是一致的。
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 kinetic analysis. The order of each component was determined by plotting the initial rates of the reaction against concentration. These data provided a mechanistic picture which involves a fast and irreversible oxidative insertion of palladium into the aryl iodide and a subsequent intramolecular transmetalation step from a complex containing a silicon-oxygen-palladium linkage. First-order behavior at low concentrations of silanolate with excess palladium(0) complex supports the formation of this complex as the turnover-limiting step. The change to zeroth-order dependence on silanolate at high concentrations is consistent with the intramolecular transmetalation becoming the turnover-limiting step.