title: External Oxidant-Free Oxidative Cross-Coupling: A Photoredox Cobalt-Catalyzed Aromatic C-H Thiolation for Constructing C-S Bonds.
abstract: 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.
authors.affiliation: †College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China.
authors.forename: Guoting
authors.initials: G
authors.lastname: Zhang
authors.affiliation: †College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China.
authors.forename: Chao
authors.initials: C
authors.lastname: Liu
authors.affiliation: †College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yi
authors.forename: Qingyuan
authors.initials: Q
authors.lastname: Meng
authors.affiliation: †College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China.
authors.forename: Changliang
authors.initials: C
authors.lastname: Bian
authors.affiliation: †College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.forename: Jing-Xin
authors.initials: JX
authors.lastname: Jian
authors.forename: Li-Zhu
authors.initials: LZ
authors.lastname: Wu
authors.affiliation: †College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, P. R. China.|§Institute for Advanced Studies (IAS) of Wuhan University, Wuhan, Hubei 430071, P. R. China.
authors.forename: Aiwen
authors.initials: A
authors.lastname: Lei