Hydroxyphosphine Ligand for Nickel-Catalyzed Cross-Coupling through Nickel/Magnesium Bimetallic Cooperation
Hydroxyphosphine Ligand for Nickel-Catalyzed Cross-Coupling through Nickel/Magnesium Bimetallic Cooperation
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DOI：
10.1021/ja903091g
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发表时间：
2009-07-15
影响因子：
15
通讯作者：
Nakamura, Eiichi
中科院分区：
文献类型：
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作者：
Yoshikai, Naohiko;Matsuda, Hirokazu;Nakamura, Eiichi
我们报道了羟基膦配体(PO配体)显著地加速了镍催化的未反应的芳基亲电试剂和格氏试剂的交叉偶联反应。基于镍-PO-格氏组合的新催化体系可以方便地活化氟化物、氯化物、多氟化物和多氯化物等非活性芳基卤化物以及氨基甲酸酯和磷酸盐等苯酚衍生物，从而以良好到极佳的产率获得相应的交叉偶联产品。我们将高催化活性归因于由镍预催化剂、PO配体和格氏试剂形成的镍膦/醇镁双金属物种，它通过亲核镍和Lewis酸性镁中心的协同推拉作用激活了芳基-X键。动力学、同位素效应实验和密度泛函理论计算证实了这一机理猜想。与传统的三中心氧化加成机理不同，C-X键的活化机理为交叉偶联反应的设计以及涉及亲电底物活化的其他均相催化剂的设计提供了一个新的概念。
We report here that hydroxyphosphine ligands (PO ligands) significantly accelerate nickel-catalyzed cross-coupling reactions of unreactive aryl electrophiles and Grignard reagents. The new catalytic system based on the nickel-PO-Grignard combination allows facile activation of unreactive aryl halides such as fluorides, chlorides, polyfluorides, and polychlorides as well as phenol derivatives such as carbamates and phosphates to give the corresponding cross-coupling products in good to excellent yields. We ascribe the high catalytic activity to a nickel phosphine/magnesium alkoxide bimetallic species that forms from the nickel precatalyst, the PO ligand, and the Grignard reagent and undergoes activation of the aryl-X bond by a cooperative push-pull action of the nucleophilic nickel and Lewis acidic magnesium centers. This mechanistic conjecture was corroborated by kinetic, isotope effect experiments and density functional theory calculations. Being distinct from the conventional three-centered mechanism for oxidative addition, the proposed mechanism for the C-X bond activation offers a new concept for the design of cross-coupling reactions as well as other homogeneous catalyses involving activation of electrophilic substrates.