Copper-Catalyzed Functionalization of Benzylic C–H Bonds with N‑Fluorobenzenesulfonimide: Switch from C–N to C–F Bond Formation Promoted by a Redox Buffer and Brønsted Base

A copper catalyst in combination with N-fluorobenzenesulfonimide (NFSI) has been reported to functionalize benzylic C–H bonds to the corresponding benzylic sulfonimides via C–N coupling. Here, we reported a closely related Cu-catalyzed method with NFSI that instead leads to C–F coupling. This switch...

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Bibliographic Details
Published in:Organic letters 2020-08, Vol.22 (15), p.5749-5752
Main Authors: Buss, Joshua A, Vasilopoulos, Aristidis, Golden, Dung L, Stahl, Shannon S
Format: Article
Language:English
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Summary:A copper catalyst in combination with N-fluorobenzenesulfonimide (NFSI) has been reported to functionalize benzylic C–H bonds to the corresponding benzylic sulfonimides via C–N coupling. Here, we reported a closely related Cu-catalyzed method with NFSI that instead leads to C–F coupling. This switch in selectivity arises from changes to the reaction conditions (Cu/ligand ratio, temperature, addition of base) and further benefits from inclusion of MeB­(OH)2 in the reaction. MeB­(OH)2 is shown to serve as a “redox buffer” in the reaction, responsible for rescuing inactive Cu­(II) for continued promotion of fluorination reactivity.
ISSN:1523-7060
1523-7052
DOI:10.1021/acs.orglett.0c02239