Mild Copper‐Catalyzed Fluorination of Alkyl Triflates with Potassium Fluoride. Issue 25 (18th May 2014)

• Record Type: Journal Article
• Authors: Dang, Hester; Mailig, Melrose; Lalic, Gojko
• Is Part Of: Angewandte Chemie international edition. Volume 53:Issue 25(2014)
• Page Start: 6473
• Page End: 6476
• Publication Date: 2014-05-18
• Subjects: carbenes -- copper -- fluorine -- isotopic labeling -- phase‐transfer catalysis; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201402238
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: A chemoselective catalytic fluorination of alkyl triflates is described using potassium fluoride as a fluoride source. Excellent yields of the desired alkyl fluorides are obtained after one hour at 45 °C using 2 mol % of the copper catalyst. With 10 mol % of the catalyst, full conversion can be achieved in less than 10 minutes at 45 °C, and thus makes this procedure potentially suited for the preparation of 18 F‐labeled PET probes. As a result of the mild reaction conditions, only the substitution products are observed with no evidence of common side reactions, such as elimination. Reported is a preliminary study of the reaction scope, which demonstrates that the fluorination can be performed in the presence of a wide range of functional groups. Evidence suggests an unusual role of the [IPrCuOTf] catalyst as a phase‐transfer catalyst and points to [IPrCuF] as the active fluorinating reagent (IPr=1, 3‐bis(2, 6‐diisopropylphenyl)imidazol‐2‐ylidene). Abstract : Teacher′s PET : The title reaction delivers excellent yields of the desired alkyl fluorides by using potassium fluoride as a fluoride source in the presence of the copper catalyst [IPrCuOTf]. This procedure is potentially suited for the preparation of 18 F‐labeled PET probes. IPr=1, 3‐bis(2, 6‐diisopropylphenyl)imidazol‐2‐ylidene, Tf=trifluoromethanesulfonyl.