Design, Testing and Kinetic Analysis of Bulky Monodentate Phosphorus Ligands in the Mizoroki-Heck Reaction
Design, Testing and Kinetic Analysis of Bulky Monodentate Phosphorus Ligands in the Mizoroki-Heck Reaction
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DOI：
10.1002/ejic.201101271
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发表时间：
2012-04-01
影响因子：
2.3
通讯作者：
Kamer, Paul C. J.
中科院分区：
文献类型：
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作者：
Dodds, Deborah L.;Boele, Maarten D. K.;Kamer, Paul C. J.
一系列新的单齿膦配体2已在Mizoroki-Heck芳基化反应中的碘苯和苯乙烯进行了评估，并与我们以前报道的配体，1，3和4进行了比较。合理的配体设计的概念进行了讨论，我们描述了如何预测这个新的配体家族的性能。采用我们最好的配体，3，3 '-二叔丁基-5，5'-二甲氧基联苯-2，2 '-二基二异丙基亚磷酰胺（3b），我们探索了关于溶剂和底物的反应范围。通过分析反应速率与Hammett常数之间的关系，研究了反应的电子依赖性。需要足够的空间体积来加强催化反应以通过单配位钯物质进行，从而增加其反应性。电子性质从单体二聚体平衡和它们的固有反应性确定活性物种的浓度。环状亚磷酰胺3b在所研究的系统内提供了两种性质的最佳值，导致速率限制迁移插入步骤。
A series of new monodentate phosphane ligands 2 have been evaluated in the MizorokiHeck arylation reaction of iodobenzene and styrene and compared with our previously reported ligands, 1, 3 and 4. The concept of rational ligand design is discussed, and we describe how the performance of this new ligand family could be predicted. Employing our best ligand, 3,3'-di-tert-butyl-5,5'-dimethoxybiphenyl-2,2'-diyl diisopropylphosphoramidite (3b), we explored the scope of the reaction with regards to solvent and the substrate. We also investigated the electronic dependence of the reaction by analysing the relationship between the rate and Hammett constant. Sufficient steric bulk is required to enforce the catalytic reaction to proceed through the mono-coordinated palladium species, thereby increasing its reactivity. The electronic properties determine the concentration of the active species from the monomer dimer equilibrium and their intrinsic reactivity. The cyclic phosphoramidite 3b provides an optimum in both properties within the systems studied, resulting in a rate limiting migratory insertion step.