Thioetherification of Chloroheteroarenes: A Binuclear Catalyst Promotes Wide Scope and High Functional-Group Tolerance

• Published in: Chemistry : a European journal 2014-09, Vol.20 (39), p.12584-12594
• Main Authors: Platon, Mélanie, Wijaya, Novi, Rampazzi, Vincent, Cui, Luchao, Rousselin, Yoann, Saeys, Mark, Hierso, Jean-Cyrille
• Format: Article
• Language: English
• Subjects: Activation; binuclear catalyst; Catalysis; Catalysts; Chemistry; Constraints; density-functional calculations; Furans - chemistry; Halogenation; Joining; Ligands; Models, Molecular; Palladium; Palladium - chemistry; Phenols - chemistry; phosphane ligands; Phosphines - chemistry; Pyrazines - chemistry; Pyridines; Pyridines - chemistry; Quinolines - chemistry; Stability; Sulfhydryl Compounds - chemistry; Sulfides - chemistry; tetradentate ligands; Thiazoles - chemistry; thioetherification; Thiophenol
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201403337

A constrained binuclear palladium catalyst system affords selective thioetherification of a wide range of functionalized arenethiols with chloroheteroaromatic partners with the highest turnover numbers (TONs) reported to date and tolerates a large variety of reactive functions. The scope of this system includes the coupling of thiophenols with six‐ and five‐membered 2‐chloroheteroarenes (i.e., functionalized pyridine, pyrazine, quinoline, pyrimidine, furane, and thiazole) and 3‐bromoheteroarenes (i.e., pyridine and furane). Electron‐rich congested thiophenols and fluorinated thiophenols are also suitable partners. The coupling of unprotected amino‐2‐chloropyridines with thiophenol and the successful employment of synthetically valuable chlorothiophenols are described with the same catalyst system. DFT studies attribute the high performance of this binuclear palladium catalyst to the decreased stability of thiolate‐containing resting states. Palladium loading was as low as 0.2 mol %, which is important for industrial application and is a step forward in solving catalyst activation/deactivation problems. A constrained binuclear palladium catalyst system affords selective coupling of a wide range of functionalized arenethiols to six‐ and five‐membered chloroheteroarenes at the highest turnover numbers (TONs) reported to date (see picture; DPPF=1,1′‐bis(diphenylphosphano)ferrocene). DFT calculations support the ligand‐screening efforts and attribute the high performance of this binuclear catalyst, which incorporates a “super‐DPPF”, to the decreased stability of thiolate‐containing resting states.