Sequential C-F Bond Transformation of the Difluoromethylene Unit in Perfluoroalkyl Groups: A Combination of Fine-Tuned Phenothiazine Photoredox Catalyst and Lewis Acid

Naoki Sugihara; Yoshihiro Nishimoto; Yasuko Osakada; Mamoru Fujitsuka; Manabu Abe; Makoto Yasuda

doi:10.1002/anie.202401117

Sequential C-F Bond Transformation of the Difluoromethylene Unit in Perfluoroalkyl Groups: A Combination of Fine-Tuned Phenothiazine Photoredox Catalyst and Lewis Acid

Angew Chem Int Ed Engl. 2024 Apr 2;63(14):e202401117. doi: 10.1002/anie.202401117. Epub 2024 Mar 5.

Authors

Naoki Sugihara¹, Yoshihiro Nishimoto^{1

2}, Yasuko Osakada^{2

3

4}, Mamoru Fujitsuka^{2

3}, Manabu Abe⁵, Makoto Yasuda^{1

2}

Affiliations

¹ Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
² Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
³ SANKEN (The Institute of Scientific and Industrial Research), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka, 567-0047, Japan.
⁴ Institute for Advanced Co-Creation Studies, Osaka University, Yamadagaoka 1-1, Suita, Osaka, 565-0871, Japan.
⁵ Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima, Hiroshima, 739-8526, Japan.

PMID: 38380969
DOI: 10.1002/anie.202401117

Abstract

A sequential process via photoredox catalysis and Lewis acid mediation for C-F bond transformation of the CF₂ unit in perfluoroalkyl groups has been achieved to transform perfluoroalkylarenes into complex fluoroalkylated compounds. A phenothiazine-based photocatalyst promotes the defluoroaminoxylation of perfluoroalkylarenes with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) under visible light irradiation, affording the corresponding aminoxylated products. These products undergo a further defluorinative transformation with various organosilicon reagents mediated by AlCl₃ to provide highly functionalized perfluoroalkyl alcohols. Our novel phenothiazine catalyst works efficiently in the defluoroaminoxylation. Transient absorption spectroscopy revealed that the catalyst regeneration step is crucial for the photocatalytic aminoxylation.

Keywords: Fluorine; Phenothiazine; Photochemistry; Radical ions; Radical reactions.

Abstract

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