Denmark Scott E, Sweis Ramzi F
Roger Adams Laboratory, Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA.
J Am Chem Soc. 2004 Apr 21;126(15):4876-82. doi: 10.1021/ja0372356.
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.
通过动力学分析研究了无氟、钯催化的（E）-庚烯基二甲基硅醇钾（K(+)(E)-1(-)）与2-碘噻吩的交叉偶联反应机理。通过将反应的初始速率对浓度作图来确定各组分的反应级数。这些数据提供了一个机理图，该机理涉及钯快速且不可逆地氧化插入芳基碘中，以及随后从含有硅-氧-钯键的配合物进行分子内金属转移步骤。在低浓度硅醇盐与过量钯（0）配合物的情况下呈一级反应行为，支持了该配合物的形成是周转限制步骤。在高浓度下对硅醇盐的零级依赖性变化与分子内金属转移成为周转限制步骤一致。
