Metal-Templated Design: Enantioselective Hydrogen-Bond-Driven Catalysis Requiring Only Parts-per-Million Catalyst Loading.
Metal-Templated Design: Enantioselective Hydrogen-Bond-Driven Catalysis Requiring Only Parts-per-Million Catalyst Loading.
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DOI：
10.1021/jacs.6b02769
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发表时间：
2016-07-20
影响因子：
15
通讯作者：
Meggers E
中科院分区：
文献类型：
--
作者：
Xu W;Arieno M;Löw H;Huang K;Xie X;Cruchter T;Ma Q;Xi J;Huang B;Wiest O;Gong L;Meggers E
基于金属模板化方法，以双环金属化八面体铱配合物的形式使用刚性和球形结构支架，开发了一种异常活跃的氢键催化的不对称催化剂，并通过晶体学，核磁共振，计算，动力学实验，与铑同族物的比较以及在竞争性氢键供体和受体存在下的反应来研究其作用模式。仅依靠弱作用力，硝基烯烃的对映选择性共轭还原可以在催化剂负载低至0.004 mol% （40 ppm）的情况下进行，代表周转数高达20 250。测定了2.5 × 105催化剂的加速速率。催化的起源可以追溯到在过渡态中通过精心安排的氢键和催化剂与底物之间的范德华相互作用有效地稳定了发展中的电荷。这项研究表明，仅由氢键和范德华相互作用驱动的不对称催化的熟练程度可以与通过直接过渡金属配合底物的传统活化相媲美。
Based on a metal-templated approach using a rigid and globular structural scaffold in the form of a bis-cyclometalated octahedral iridium complex, an exceptionally active hydrogen-bond-mediated asymmetric catalyst was developed and its mode of action investigated by crystallography, NMR, computation, kinetic experiments, comparison with a rhodium congener, and reactions in the presence of competing H-bond donors and acceptors. Relying exclusively on weak forces, the enantioselective conjugate reduction of nitroalkenes can be executed at catalyst loadings as low as 0.004 mol% (40 ppm), representing turnover numbers of up to 20 250. A rate acceleration by the catalyst of 2.5 × 105 was determined. The origin of the catalysis is traced to an effective stabilization of developing charges in the transition state by carefully orchestrated hydrogen-bonding and van der Waals interactions between catalyst and substrates. This study demonstrates that the proficiency of asymmetric catalysis merely driven by hydrogen-bonding and van der Waals interactions can rival traditional activation through direct transition metal coordination of the substrate.
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