Somerville Rosie J, Hale Lillian V A, Gómez-Bengoa Enrique, Burés Jordi, Martin Ruben
Institute of Chemical Research of Catalonia (ICIQ) , The Barcelona Institute of Science and Technology , Av. Països Catalans 16 , 43007 Tarragona , Spain.
Department of Chemistry , University of Michigan , Ann Arbor , Michigan 48109 , United States.
J Am Chem Soc. 2018 Jul 18;140(28):8771-8780. doi: 10.1021/jacs.8b04479. Epub 2018 Jul 2.
Monodentate phosphine ligands are frequently employed in the Ni-catalyzed C-O functionalization of aryl esters. However, the extensive body of preparative work on such reactions contrasts with the lack of information concerning the structure and reactivity of the relevant nickel intermediates. In fact, experimental evidence for a seemingly trivial oxidative addition into the C-O bond of aryl esters with monodentate phosphines and low-valent nickel complexes still remains elusive. Herein, we report a combined experimental and theoretical study on the Ni(0)/PCy-catalyzed silylation of aryl pivalates with CuF/CsF additives that reveals the involvement of unorthodox dinickel oxidative addition complexes in C-O bond cleavage and their relevance in C-Si bond formation. We have obtained a mechanistic picture that clarifies the role of the additives and demonstrates that dinickel complexes act as reservoirs of the propagating monomeric nickel complexes by disproportionation. We believe this study will serve as a useful entry point to unravelling the mechanistic underpinnings of other related Ni-catalyzed C-O functionalization reactions employing monodentate phosphines.
单齿膦配体常用于镍催化的芳基酯的碳-氧官能化反应。然而，关于此类反应的大量制备工作与相关镍中间体的结构和反应性信息匮乏形成了鲜明对比。事实上，对于单齿膦和低价镍配合物对芳基酯的碳-氧键进行看似简单的氧化加成反应，实验证据仍然难以捉摸。在此，我们报道了一项关于Ni(0)/PCy催化的芳基新戊酸酯与CuF/CsF添加剂的硅烷化反应的实验与理论相结合的研究，该研究揭示了非传统的二镍氧化加成配合物参与碳-氧键断裂及其在碳-硅键形成中的相关性。我们获得了一个机理图景，阐明了添加剂的作用，并证明二镍配合物通过歧化作用作为传播的单体镍配合物的储存库。我们相信这项研究将成为解开其他相关的使用单齿膦的镍催化碳-氧官能化反应机理基础的有用切入点。
