Rigidifying Ag(I) Complexes for Selective Nitrene Transfer
Rigidifying Ag(I) Complexes for Selective Nitrene Transfer
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DOI：
10.1002/cctc.202000336
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发表时间：
2020-05-05
期刊：
影响因子：
4.5
通讯作者：
Schomaker, Jennifer M.
中科院分区：
文献类型：
--
作者：
Huang Minxue;Paretsky, Jon;Schomaker, Jennifer M.
通过银催化氮烯转移（NT）实现可调节和可预测的C-H键酰胺化的挑战之一是许多Ag（I）络合物的构象灵活性和动态性质。这种流动行为可能使得难以清楚地了解影响酰胺化事件的位点选择性的因素。对相关系统的机理研究表明，PI…π和Agπ相互作用在改变氮烯转移的偏好方面起着重要的作用，氮烯转移在邻近π系统的位点，包括苄基、烯丙基和炔丙基C-H键。在本文中，我们报道了一种Ag（I）催化剂，旨在提高反应的优先在苄基，烯丙基，和炔丙基的C-H键比更富电子的叔烷基C（sp（3））-H键，通过增强非共价相互作用。通过将sp（3）氮连接到哌啶环中来刚性化柔性三（2-吡啶基甲基）胺配体骨架，加强了底物上的含pi取代基与催化剂的吡啶臂之间的非共价相互作用，并改善了氮宾转移事件的位点选择性。
One of the challenges in achieving tunable and predictable C-H bond amidation via silver-catalyzed nitrene transfer (NT) is the conformational flexibility and dynamic nature of many Ag(I) complexes. This fluxional behavior can make it difficult to obtain a clear understanding of the factors responsible for influencing the site-selectivity of the amidation event. Mechanistic studies on related systems suggest that pi...pi and Ag...pi interactions play important roles in altering the preference for nitrene transfer at sites adjacent to pi systems, including benzylic, allylic, and propargylic C-H bonds. In this paper, we report a Ag(I) catalyst designed to improve the preference for reaction at benzylic, allylic, and propargylic C-H bonds over more electron-rich tertiary alkyl C(sp(3))-H bonds by enhancing non-covalent interactions. Rigidifying a flexible tris(2-pyridylmethyl)amine ligand scaffold by tying back the sp(3) nitrogen into a piperidine ring strengthened non-covalent interactions between the pi-containing substituents on the substrate and the pyridine arm of the catalyst and improved the site-selectivity of the nitrene transfer event.