title: Copper-mediated C-H activation/C-S cross-coupling of heterocycles with thiols.
abstract: We report the synthesis of a series of aryl- or alkyl-substituted 2-mercaptobenzothiazoles by direct thiolation of benzothiazoles with aryl or alkyl thiols via copper-mediated aerobic C-H bond activation in the presence of stoichiometric CuI, 2,2'-bipyridine and Na(2)CO(3). We also show that the approach can be extended to thiazole, benzimidazole, and indole substrates. In addition, we present detailed mechanistic investigations on the Cu(I)-mediated direct thiolation reactions. Both computational studies and experimental results reveal that the copper-thiolate complex [(L)Cu(SR)] (L: nitrogen-based bidentate ligand such as 2,2'-bipyridine; R: aryl or alkyl group) is the first reactive intermediate responsible for the observed organic transformation. Furthermore, our computational studies suggest a stepwise reaction mechanism based on a hydrogen atom abstraction pathway, which is more energetically feasible than many other possible pathways including β-hydride elimination, single electron transfer, hydrogen atom transfer, oxidative addition/reductive elimination, and σ-bond metathesis.
authors.affiliation: Department of Chemistry, National University of Singapore, Singapore 117543.
authors.forename: Sadananda
authors.initials: S
authors.lastname: Ranjit
authors.forename: Richmond
authors.initials: R
authors.lastname: Lee
authors.forename: Dodi
authors.initials: D
authors.lastname: Heryadi
authors.forename: Chao
authors.initials: C
authors.lastname: Shen
authors.forename: Ji'En
authors.initials: J
authors.lastname: Wu
authors.forename: Pengfei
authors.initials: P
authors.lastname: Zhang
authors.forename: Kuo-Wei
authors.initials: KW
authors.lastname: Huang
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Liu
mesh_terms: D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry*; D006860:Hydrogen Bonding; D008024:Ligands; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D008024:Ligands; D013438:Sulfhydryl Compounds; D003300:Copper