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Mechanistic Study of a Photocatalyzed CS Bond Formation Involving Alkyl/Aryl Thiosulfate
Author(s) -
Li Yiming,
Xie Weisi,
Jiang Xuefeng
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201502951
Subject(s) - chemistry , aryl , photochemistry , alkyl , sulfide , thioether , thiosulfate , radical ion , radical , quenching (fluorescence) , electron paramagnetic resonance , medicinal chemistry , polymer chemistry , organic chemistry , sulfur , fluorescence , ion , quantum mechanics , nuclear magnetic resonance , physics
This study presents thioether construction involving alkyl/aryl thiosulfates and diazonium salt catalyzed by visible‐light‐excited [Ru(bpy) 3 Cl 2 ] at room temperature in 44–86 % yield. Electron paramagnetic resonance studies found that thiosulfate radical formation was promoted by K 2 CO 3 . 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) 3 Cl 2 ] and 4‐MeO‐phenyl diazonium salt, which occurred with a rate constant of 1.69×10 9 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 H 2 O in the photoexcited system containing Ru 2+ . 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.