Mechanism and Origins of Ligand-Controlled Linear Versus Branched Selectivity of Iridium-Catalyzed Hydroarylation of Alkenes
Mechanism and Origins of Ligand-Controlled Linear Versus Branched Selectivity of Iridium-Catalyzed Hydroarylation of Alkenes
复制标题
铱催化烯烃氢芳基化配体控制的线性与支链选择性的机制和起源
DOI：
10.1021/acscatal.5b02201
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发表时间：
2016-02-01
期刊：
影响因子：
12.9
通讯作者：
Liu, Peng
中科院分区：
文献类型：
--
作者：
Huang, Genping;Liu, Peng
铱催化的羰基导向的单取代烯烃的氢化芳基化由Bower和同事开发[Crisenza，G. E. M.; McCremons，N. G.地;鲍尔，J.F. J. Am. Soc.2014，136，10258-10261]提供了用于芳基和烷基取代的烯烃的高度支化选择性加氢芳基化的有效策略。在本研究中的密度泛函理论计算表明，在这个反应中的独特的区域化学控制是由于一个非常规的修改Chalk-Harrod型机制。Ir催化的加氢芳基化反应是通过烯烃迁移插入Ir-芳基键和C-H还原消除而发生的，而不是通常接受的过渡金属催化的加氢芳基化的Chalk-Harrod型机理，该机理涉及C-H氧化加成、烯烃迁移插入Ir-H键和C-C还原消除。实验观察到的配体控制的选择性归因于在选择性确定烯烃迁移插入步骤中的电子和空间效应的组合。配体的空间位阻等高线图表明，在与大咬合角双膦配体（如d（F）ppb）的反应中，底物与配体上芳基取代基之间的空间排斥作用导致完全的支化选择性，而与小咬合角配体的反应中的线性选择性是由于有利于2，1-烯烃迁移插入的电子效应。
The iridium-catalyzed carbonyl-directed hydroarylation of monosubstituted alkenes developed by Bower and co-workers [Crisenza, G. E. M.; McCreanor, N. G.; Bower, J. F. J. Am. Chem. Soc. 2014, 136, 10258-10261] provides an efficient strategy for highly branched-selective hydroarylation of both aryl- and alkyl-substituted alkenes. Density functional theory calculations in the present study revealed that the unique regiochemical control in this reaction is due to an unconventional modified Chalk-Harrod-type mechanism. Instead of the commonly accepted Chalk-Harrod-type mechanism of transition metal-catalyzed hydroarylation that involves C-H oxidative addition, olefin migratory insertion into the Ir-H bond, and C-C reductive elimination, the Ir-catalyzed reaction occurs via migratory insertion of the olefin into the Ir-aryl bond and C-H reductive elimination. The experimentally observed ligand-controlled selectivity is attributed to a combination of electronic and steric effects in the selectivity-determining olefin migratory insertion step. Ligand steric contour maps show that, in reactions with large-bite-angle bisphosphine ligands, such as d(F)ppb, the steric repulsions between the substrate and the aryl substituents on the ligand lead to complete branched selectivity, and the linear selectivity in reactions with small-bite-angle ligands is due to electronic effects that favor 2,1-olefin migratory insertions.