Strongly Reducing (Diarylamino)anthracene Catalyst for Metal-Free Visible-Light Photocatalytic Fluoroalkylation

Well-defined 9,10-bis­(di­(p-tert-butylphenyl)­amino)­anthracene serves as a photocatalyst for radical fluoroalkylation under visible light irradiation. The diarylamine (Donor)–anthracene (π conjugated system)–diarylamine (Donor) scaffolds are easily accessed by typical palladium-catalyzed cross-cou...

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Veröffentlicht in:ACS catalysis 2018-10, Vol.8 (10), p.9408-9419
Hauptverfasser: Noto, Naoki, Tanaka, Yuya, Koike, Takashi, Akita, Munetaka
Format: Artikel
Sprache:eng
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Zusammenfassung:Well-defined 9,10-bis­(di­(p-tert-butylphenyl)­amino)­anthracene serves as a photocatalyst for radical fluoroalkylation under visible light irradiation. The diarylamine (Donor)–anthracene (π conjugated system)–diarylamine (Donor) scaffolds are easily accessed by typical palladium-catalyzed cross-coupling protocols of the corresponding halogenated anthracenes with various lithium diarylamides. The anthracene-based photocatalyst exhibits high reducing power, leading to generation of versatile fluoroalkyl radicals such as tri- and difluoroethyl and tri- and difluoromethyl radicals from the corresponding electron-accepting precursors. Catalyst design strongly influences the absorption capability of visible light and stability toward redox stimuli. The detailed mechanistic studies on the metal-free photocatalytic amino-trifluoroethylation of styrene with diphenyl­(2,2,2-trifluoroethyl)­sulfonium trifluoromethanesulfonate suggest that the reaction proceeds via catalytic radical processes rather than radical chain processes. In addition, the static quenching process is involved in the first single-electron-transfer (SET) process from the photocatalyst to the fluoroalkylating reagent. Furthermore, the 1e-oxidized cationic radical species of 9,10-bis­(di­(p-tert-butylphenyl)­amino)­anthracene, a key active catalytic species with long lifetime and a characteristic IVCT (Intervalence Charge Transfer) band in the near IR (NIR) region, is detected. From the viewpoint of elemental strategy initiative and green chemistry, the present noble metal-free organic photocatalytic system provides a pivotal technology to replace ruthenium- and iridium-based metal photocatalysis.
ISSN:2155-5435
2155-5435
DOI:10.1021/acscatal.8b02885