美国威斯康星大学麦迪逊分校的Shannon S. Stahl课题组近日在提高钯催化剂催化C-H活化反应效率的研究中取得重要进展。 2020年11月18日国际知名学术期刊《科学》发表了这一成果。

在该研究中，团队首先探讨了典型的钯催化C-H键氧化芳基化反应的机理，并阐明了破坏催化剂性能的机理特征，包括消耗底物的副反应和猝灭催化剂使其成为非活性物质的反应。基于以上了解，研究人员通过对醌类助催化剂的系统性修饰克服了这些弊端。在反应中，使用2,5-二叔丁基-1,4-苯醌作为助催化剂，可以有效地利用分子氧作为氧化剂，反应收率高，且钯催化剂的循环次数达1900次以上。

据介绍，钯(II)催化的C-H氧化反应可以简化药物、农药和其他复杂有机分子的合成。然而，现有的方法通常表现出较差的催化活性，且存在高钯负载（例如10 mol %）和需要（超过）化学计量比的有毒氧化剂，如苯醌和银(I)盐等缺点。

附：英文原文

Title: Tailored quinones support high-turnover Pd catalysts for oxidative C–H arylation with O2

Author: Chase A. Salazar, Kaylin N. Flesch, Brandon E. Haines, Philip S. Zhou, Djamaladdin G. Musaev, Shannon S. Stahl

Issue&Volume: 2020/11/19

Abstract: Palladium(II)-catalyzed C–H oxidation reactions could streamline the synthesis of pharmaceuticals, agrochemicals, and other complex organic molecules. Existing methods, however, commonly exhibit poor catalyst performance with high Pd loading (e.g., 10 mol %) and a need for (super)stoichiometric quantities of undesirable oxidants, such as benzoquinone and silver(I) salts. The present study probes the mechanism of a representative Pd-catalyzed oxidative C–H arylation reaction and elucidates mechanistic features that undermine catalyst performance, including substrate-consuming side reactions and sequestration of the catalyst as inactive species. Systematic tuning of the quinone co-catalyst overcomes these deleterious features. Use of 2,5-di-tert-butyl-p-benzoquinone enables efficient use of molecular oxygen as the oxidant, high reaction yields, and >1900 turnovers by the palladium catalyst.

DOI: 10.1126/science.abd1085

Source: https://science.sciencemag.org/content/early/2020/11/18/science.abd1085