Development of Ferrocene-Based Planar Chiral Imidazopyridinium Salts for Catalysis
Development of Ferrocene-Based Planar Chiral Imidazopyridinium Salts for Catalysis
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DOI：
10.1021/acs.organomet.0c00312
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发表时间：
2020-06
期刊：
影响因子：
2.8
通讯作者：
Keegan P. Fitzpatrick;C. Schwamb;Christopher T. Check;K. Jang;David N. Barsoum;K. Scheidt
中科院分区：
文献类型：
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作者：
Keegan P. Fitzpatrick;C. Schwamb;Christopher T. Check;K. Jang;David N. Barsoum;K. Scheidt
咪唑-2-亚叶烯及其N，N‘-二芳基衍生物是一类重要的N-杂环卡宾(NHCs)，在有机催化和过渡金属催化中具有独特的通用性。然而，这种类型的手性卡宾的例子仍然很少。在这里，我们描述了一类密切相关的基于咪唑并吡啶的NHC的发展，这些NHC的不对称性纯粹是通过结合经典的茂金属骨架而得到的平面手性。对这个家族的77Se络合物的核磁共振分析被用来评估它们的σ亲和性和π酸性的程度，并与更大的NHC家族进行了比较。计算了埋藏体积百分比(%Vbur)来测量这类不同类型的NHC的空间体积。此外，这些NHC还被用于不同的对映选择性转化，以考察它们作为有机催化剂和过渡金属催化过程的配体的用途。
Imidazol-2-ylidenes and their N,N′-diaryl derivatives constitute an important class of N-heterocyclic carbenes (NHCs) which possess a unique level of versatility in both organocatalysis and transition-metal catalysis. However, there remain few examples of carbenes of this type that are chiral. Here we describe the development of a family of closely related imidazopyridine-based NHCs that derive their asymmetry purely from planar chirality through the incorporation of the classic metallocene framework. An NMR analysis of 77Se complexes of this family is used to assess their degrees of σ donicity and π acidity in comparison to a larger family of NHCs. Percent buried volume (%Vbur) calculations were performed to measure the steric bulk of this distinct class of NHCs. Additionally, these NHCs were employed in various enantioselective transformations to survey their use as organocatalysts as well as ligands for transition-metal-catalyzed processes.