Carboranes as Aryl Mimetics in Catalysis: A Highly Active Zwitterionic NHC-Precatalyst.
Carboranes as Aryl Mimetics in Catalysis: A Highly Active Zwitterionic NHC-Precatalyst.
复制标题
DOI：
10.1002/chem.201700209
复制
发表时间：
2017-06
期刊：
影响因子：
--
通讯作者：
Christoph Selg;W. Neumann;P. Lönnecke;E. Hey‐Hawkins;K. Zeitler
中科院分区：
文献类型：
--
作者：
Christoph Selg;W. Neumann;P. Lönnecke;E. Hey‐Hawkins;K. Zeitler
现代催化利用基于芳基的相互作用来调节和控制反应。在N-杂环-卡宾催化剂的设计中，氮取代基的电子性质和空间性质都起着至关重要的作用。尽管基于碳氢化合物的体系，特别是芳基残基在克服多方面的催化挑战方面做出了很大贡献，但碳硼烷部分的独特性质，包括离域电荷、潜在的平面手性和众所周知的热力学稳定性，为开发新的催化剂提供了前所未有的机会，同时被用作芳基模拟物。我们报道了一种新型的两性离子三唑基氮杂环卡宾(NHC)预催化剂的直接合成路线。该催化剂的优良活性和广泛的适用性在广泛的有机催化转化中得到了展示。通过与已知的N-芳基NHC催化剂的性能比较，可以初步了解这种Nido-Carboranyl取代基的立体电子性质。
Modern catalysis takes advantage of aryl-based interactions to tune and control reactions. In the design of N-heterocyclic-carbene catalysts, both the electronic and steric nature of the nitrogen substituents play a crucial role. Although hydrocarbon-based systems and especially aryl residues have contributed considerably to overcome multifaceted catalytic challenges, the unique properties of carborane moieties, including delocalized charge, potential planar chirality, and well-known thermodynamic stability, offer unprecedented opportunities to develop new catalysts while being employed as aryl mimetics. We report a straightforward synthetic route to a novel zwitterionic triazolium-based N-heterocyclic carbene (NHC) precatalyst bearing a 7,8-dicarba-nido-undecaboranyl substituent. The catalyst's excellent activity and its broad applicability are demonstrated in a wide range of organocatalytic transformations. Comparison of the performance with known N-aryl NHC catalysts offers preliminary insights into the stereoelectronic nature of this nido-carboranyl substituent.