Mechanism of Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by a Combined System of Ru(π-CH2C(CH3)CH2)2(cod) and the Chiral sp2N/sp3NH Hybrid Linear N4 Ligand Ph-BINAN-H-Py
Mechanism of Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by a Combined System of Ru(π-CH2C(CH3)CH2)2(cod) and the Chiral sp2N/sp3NH Hybrid Linear N4 Ligand Ph-BINAN-H-Py
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DOI：
10.1021/jacs.5b02350
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发表时间：
2015-07-01
影响因子：
15
通讯作者：
Kitamura, Masato
中科院分区：
文献类型：
--
作者：
Nakatsuka, Hiroshi;Yamamura, Tomoya;Kitamura, Masato
GoodwinLions型手性N4配体（R）-Ph-BINAN-H-Py（（R）-3，3 '-二苯基-N-2，N-2'-双（（吡啶-2-基）甲基）-1，1 '-联萘-2，2'-二胺; L），与Ru（pi-CH2C（CH3）CH2）（2）（cod）（A）（cod = 1，5-环辛烷）催化苯乙酮（AP）加氢生成（R）-1-苯基乙醇（PE），对映体比率（er）高。几乎没有Ru络合物形成，A和L在整个反应中保持完整，同时根据[PE] = k（obst）（2）定量生成PE。通过H-2和L的作用，A非常缓慢且不可逆地产生极少量具有C-2-γ-顺式-a立体化学的反应性且不稳定的RuH 2 L（B），其通过Noyoris供体受体双功能机制快速催化AP的加氢。CH-π稳定的Si面选择性过渡态C-Si与中间体Ru酰胺D一起产生（R）-PE，其主要被AP的Ru烯醇化物的形成抑制。决定速率的氢解D完成循环。时间平方项既与周期之前的初始步骤有关，也与周期本身有关，B的产生和周转频率有极不寻常的八阶差异。这一机制是完全支持一系列的实验，包括详细的动力学研究，速率定律分析，模拟t/[PE]曲线拟合的实验观察在初始反应阶段，X-射线晶体学分析的B-相关的八面体金属配合物，和Hammett图分析的电子不同的基板和配体在其对映体选择性。
The combination of a GoodwinLions-type chiral N4 ligand, (R)-Ph-BINAN-H-Py ((R)-3,3'-diphenyl-N-2,N-2'-bis((pyridin-2-yl)methyl)-1,1'-binaphthyl-2,2'-diamine; L), with Ru(pi-CH2C(CH3)CH2)(2)(cod) (A) (cod = 1,5-cyclooctadiene) catalyzes the hydrogenation of acetophenone (AP) to (R)-1-phenylethanol (PE) with a high enantiomer ratio (er). Almost no Ru complex forms, with A and L remaining intact throughout the reaction while generating PE quantitatively according to [PE] = k(obst)(2). An infinitesimal amount of reactive and unstable RuH2L (B) with C-2-gamma-cis-a stereochemistry is very slowly and irreversibly generated from A by the action of H-2 and L, which rapidly catalyzes the hydrogenation of AP via Noyoris donoracceptor bifunctional mechanism. A CH-pi-stabilized Si-face selective transition state, C-Si, gives (R)-PE together with an intermediary Ru amide, D, which is inhibited predominantly by formation of the Ru enolate of AP. The rate-determining hydrogenolysis of D completes the cycle. The time-squared term relates both to the preliminary step before the cycle and to the cycle itself, with a highly unusual eight-order difference in the generation and turnover frequency of B. This mechanism is fully supported by a series of experiments including a detailed kinetic study, rate law analysis, simulation of t/[PE] curves with fitting to the experimental observations at the initial reaction stage, X-ray crystallographic analyses of B-related octahedral metal complexes, and Hammett plot analyses of electronically different substrates and ligands in their enantioselectivities.