Azek Emna, Khalifa Maroua, Bartholoméüs Johan, Ernzerhof Matthias, Lebel Hélène
Département de Chimie , Université de Montréal , C.P. 6128, Succursale Centre-ville, Montréal , Québec , Canada H3C3J7 . Email:
Chem Sci. 2018 Oct 22;10(3):718-729. doi: 10.1039/c8sc03153c. eCollection 2019 Jan 21.
-Mesyloxycarbamates are practical nitrene precursors that undergo C-H amination reactions in the presence of rhodium dimer catalysts. Under these conditions, both oxazolidinones and chiral amines have been prepared in a highly efficient manner. Given the elevated reactivity of the intermediates involved in the catalytic cycle, mechanistic details have remained hypothetical, relying on indirect experiments. Herein a density functional theory (DFT) study is presented to validate the catalytic cycle of the rhodium-catalyzed C-H amination with -mesyloxycarbamates. A concerted pathway involving Rh-nitrene species that undergoes C-H insertion is found to be favored over a stepwise C-N bond formation manifold. Density functional calculations and kinetic studies suggest that the rate-limiting step is the C-H insertion process rather than the formation of Rh-nitrene species. In addition, these studies provide mechanistic details about competitive by-product formation, resulting from an intermolecular reaction between the Rh-nitrene species and the -mesyloxycarbamate anion.
甲磺酰氧基氨基甲酸酯是实用的氮烯前体，在铑二聚体催化剂存在下会发生C-H胺化反应。在这些条件下，恶唑烷酮和手性胺均已高效制备。鉴于催化循环中涉及的中间体反应活性较高，其机理细节仍基于间接实验而处于假设阶段。本文提出了一项密度泛函理论（DFT）研究，以验证铑催化的与甲磺酰氧基氨基甲酸酯的C-H胺化反应的催化循环。发现涉及Rh-氮烯物种并进行C-H插入的协同途径优于逐步形成C-N键的反应历程。密度泛函计算和动力学研究表明，限速步骤是C-H插入过程，而不是Rh-氮烯物种的形成。此外，这些研究提供了关于竞争性副产物形成的机理细节，该副产物是由Rh-氮烯物种与甲磺酰氧基氨基甲酸酯阴离子之间的分子间反应产生的。
