Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States.
Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
J Am Chem Soc. 2020 Mar 25;142(12):5842-5851. doi: 10.1021/jacs.0c01069. Epub 2020 Mar 13.
Herein, the mechanism of catalytic allylic C-H amination reactions promoted by CpRh complexes is reported. Reaction kinetics experiments, stoichiometric studies, and DFT calculations demonstrate that the allylic C-H activation to generate a CpRh(π-allyl) complex is viable under mild reaction conditions. The role of external oxidants in the catalytic cycle is elucidated. Quantum mechanical calculations, stoichiometric reactions, and cyclic voltammetry experiments concomitantly support an oxidatively induced reductive elimination process of the allyl fragment with an acetate ligand proceeding through a Rh(IV) intermediate. Stoichiometric oxidation and bulk electrolysis of the proposed π-allyl intermediate are also reported to support these analyses. Lastly, evidence supporting the amination of an allylic acetate intermediate is presented. We show that Cp*Rh(III) behaves as a Lewis acid catalyst to complete the allylic amination reaction.
本文报道了 CpRh 配合物促进的催化烯丙基 C-H 胺化反应的机理。反应动力学实验、化学计量研究和 DFT 计算表明，在温和的反应条件下，烯丙基 C-H 的活化生成 CpRh(π-烯丙基)配合物是可行的。还阐明了外部氧化剂在催化循环中的作用。量子力学计算、化学计量反应和循环伏安实验共同支持了通过 Rh(IV)中间体进行的带有醋酸盐配体的烯丙基片段的氧化诱导还原消除过程。还报道了所提出的π-烯丙基中间体的化学计量氧化和大规模电解，以支持这些分析。最后，提出了支持烯丙基醋酸盐中间体胺化的证据。我们表明，Cp*Rh(III) 作为路易斯酸催化剂参与反应，完成烯丙基的胺化反应。
