Metal-Templated Design: Enantioselective Hydrogen-Bond-Driven Catalysis Requiring Only Parts-per-Million Catalyst Loading

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• 作者：Weici Xu ; Marcus Arieno ; Henrik Löw ; Kaifang Huang ; Xiulan Xie ; Thomas Cruchter ; Qiao Ma ; Jianwei Xi ; Biao Huang ; Olaf Wiest ; Lei Gong ; Eric Meggers
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：July 20, 2016
• 年：2016
• 卷：138
• 期：28
• 页码：8774-8780
• 全文大小：569K
• 年卷期：0
• ISSN：1520-5126

文摘

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.