Catalysis with a Skip: Dynamically Coupled Addition, Proton Transfer, and Elimination during Au- and Pd-Catalyzed Diol Cyclizations
Catalysis with a Skip: Dynamically Coupled Addition, Proton Transfer, and Elimination during Au- and Pd-Catalyzed Diol Cyclizations
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跳过催化：金和钯催化二醇环化过程中的动态耦合加成、质子转移和消除
DOI：
10.1021/acscatal.1c02408
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发表时间：
2021
期刊：
影响因子：
12.9
通讯作者：
Ess, Daniel H.
中科院分区：
文献类型：
--
作者：
Teynor, Matthew S.;Scott, Windsor;Ess, Daniel H.
Au、Pd络合物已成为构筑杂环的高效π键环催化剂。这些环化反应通常被认为是通过涉及Au-或Pd-烷基中间体的多步加成-消除机理进行的。对于Au和Pd催化的烯丙基二醇环化反应，虽然密度泛函理论势能面景观显示了烷氧基化π加成、质子转移和水消除的逐步顺序，但准经典直接动力学模拟揭示了依赖于金属中心的动力学机理。对于Au，轨迹显示在π加成后，Au-烷基中间体总是被跳过，因为加成与质子转移和水消除是动态耦合的。相比之下，对于Pd催化，由于势能景观形状的不同，只有大约一半的轨迹显示Pd-烷基中间体跳跃。轨迹的另一半显示了带有Pd-烷基中间体的传统两步反应机理。总体而言，这项工作揭示了对DFT势能格局的解释可能不足以理解催化中间体和机理，需要通过动力学模拟来确定中间体是否真的是催化循环的一部分。
Au and Pd complexes have emerged as highly effective π-bond cyclization catalysts to construct heterocycles. These cyclization reactions are generally proposed to proceed through multistep addition–elimination mechanisms involving Au– or Pd–alkyl intermediates. For Au- and Pd-catalyzed allylic diol cyclizations, while the density functional theory (DFT) potential energy surface landscapes show a stepwise sequence of alkoxylation π-addition, proton transfer, and water elimination, quasiclassical direct dynamics simulations reveal dynamical mechanisms that depend on the metal center. For Au, trajectories reveal that after π-addition the Au–alkyl intermediate is always skipped because addition is dynamically coupled with proton transfer and water elimination. In contrast, for Pd catalysis, due to differences in the potential energy landscape shape, only about half of trajectories show Pd–alkyl intermediate skipping. The other half of the trajectories show the traditional two-step mechanism with the intervening Pd–alkyl intermediate. Overall, this work reveals that interpretation of a DFT potential energy landscape can be insufficient to understand catalytic intermediates and mechanisms and that atomic momenta through dynamics simulations are needed to determine if an intermediate is genuinely part of a catalytic cycle.