Influences of Phenyl Rings on NHC Ligands with Bicyclic Architectures
Influences of Phenyl Rings on NHC Ligands with Bicyclic Architectures
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苯环对双环结构 NHC 配体的影响
DOI：
10.1021/acs.joc.8b02480
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发表时间：
2019
影响因子：
3.6
通讯作者：
Tadao
中科院分区：
文献类型：
--
作者：
Ando;Shin; Miyata;Ryota; Matsunaga;Hirofumi; Ishizuka;Tadao
除了膦、烯烃、胺和酰胺外，在过去的二十年里，N-杂环卡宾(NHC)已经成为一种有用的替代配体。基于对NHC配体的一系列衍生化研究，咪唑-2-亚甲基和咪唑-2-亚甲基成为标准的杂环形式，并且通常在靠近卡宾碳的氮(S)上引入大量取代基。我们小组之前开发的NHC配备了具有双环结构的非碳化碳，这赋予了它们独特的空间性质，使它们变得笨重但容易接近。在这项研究中，我们合成了一种具有双环[2.2.1]庚烷结构的新型NHC配体，并比较了五种铜催化的烯丙基芳基化衍生物和芳基Grignard试剂。取代的区域选择性明显地表明，当γ-取代是主要途径时，活性中心上的苯环对所得到的铜催化剂具有特征效应。
In addition to phosphanes, olefins, amines, and amides, over the past two decades N-heterocyclic carbene (NHC) has emerged as a useful alternative ligand. Based on a number of derivatization studies on NHC ligands, imidazol-2-ylidene and imidazolin-2-ylidene became the standard heterocyclic form, and bulky substituents have commonly been introduced on the nitrogen(s) adjacent to carbenic carbons. Our group previously developed NHCs equipped with noncarbenic carbons with a bicyclic architecture that gives them unique steric properties that make them bulky but accessible. In this study, we synthesized a novel type of NHC ligand that possesses a bicyclo[2.2.1]heptane architecture, and we compared five derivatives using copper-catalyzed allylic arylations with aryl Grignard reagents. The regioselectivity of the substitution obviously indicates that a phenyl ring over an active site has a characteristic effect on the resultant copper catalysts when γ-substitution is the major pathway.