External Oxidant-Free Oxidative Cross-Coupling: A Photoredox Cobalt-Catalyzed Aromatic C-H Thiolation for Constructing C-S Bonds
External Oxidant-Free Oxidative Cross-Coupling: A Photoredox Cobalt-Catalyzed Aromatic C-H Thiolation for Constructing C-S Bonds
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DOI：
10.1021/jacs.5b05665
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发表时间：
2015-07-29
影响因子：
15
通讯作者：
Lei, Aiwen
中科院分区：
文献类型：
--
作者：
Zhang, Guoting;Liu, Chao;Lei, Aiwen
本文报道了一种无外加氧化剂的可见光光催化氧化偶联芳香C-H硫醇化反应。各种底物可以以良好到优异的产率提供苯并噻唑，并且仅产生H2作为副产物。在TBAOH催化下，不仅可以得到2-芳基苯并噻唑，而且可以得到2-烷基苯并噻唑。该方法可以放大并应用于合成具有苯并噻唑结构支架（有效的抗肿瘤剂）的生物活性分子。此外，可以完全避免在硫代苯甲酰苯胺的氧化环化中经常产生的意想不到的氧化副产物酰胺。机理研究表明，H2来源于底物。动力学研究表明，钴催化剂和质子之间的相互作用可能参与了限速过程。
An external oxidant-free oxidative coupling for aromatic C-H thiolation by visible-light photoredox cobalt-catalysis has been developed. Various substrates could afford benzothiazoles in good to excellent yields, and only H2 is generated as a side product. When catalytic TBAOH was used as the base, not only 2-aryl but also 2-alkylbenzothiazoles could be obtained through this novel dehydrogenative coupling reaction. This method could be scaled up and applied to the synthesis of biologically active molecules bearing benzothiazole structural scaffolds (potent antitumor agents). Furthermore, the unexpected oxidation byproduct amides, which are often generated in oxidative cyclization of thiobenzanilides, can be completely avoided. Mechanistic studies showed that the H2 originates from the substrates. The kinetic studies indicate that the interaction between the cobalt catalyst and proton might be involved in the rate-limiting process.