Mechanistic Study of a Photocatalyzed C-S Bond Formation Involving Alkyl/Aryl Thiosulfate

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Abstract
This study presents thioether construction involving alkyl/aryl thiosulfates and diazonium salt catalyzed by visible‐light‐excited [Ru(bpy)3Cl2] at room temperature in 44–86 % yield. Electron paramagnetic resonance studies found that thiosulfate radical formation was promoted by K2CO3. Conversely, radicals generated from BnSH or BnSSBn (Bn=benzyl) were clearly suppressed, demonstrating the special property of thiosulfate in this system. Transient absorption spectra confirmed the electron‐transfer process between [Ru(bpy)3Cl2] and 4‐MeO‐phenyl diazonium salt, which occurred with a rate constant of 1.69×109 M−1 s−1. The corresponding radical trapping product was confirmed by X‐ray diffraction. The full reaction mechanism was determined together with emission quenching data. Furthermore, this system efficiently avoided the over‐oxidation of sulfide caused by H2O in the photoexcited system containing Ru2+. Both aryl and heteroaryl diazonium salts with various electronic properties were investigated for synthetic compatibility. Both alkyl‐ and aryl‐substituted thiosulfates could be used as substrates. Notably, pharmaceutical derivatives afforded late‐stage sulfuration smoothly under mild conditions.
Funding Information
  • NBRPC (2015CB856600)
  • NSFC (21472050, 21272075)
  • NCET (120178)
  • DFMEC (20130076110023)
  • Fok Ying Tung Education Foundation (141011)
  • program for Shanghai Rising Star (15A1401800)

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