Читать книгу Organofluorine Chemistry - Группа авторов - Страница 13

The trifluoromethoxy (CF₃O) group is increasingly important in drug development. Although methanol is definitely stable at room temperature, its perfluorinated analog, CF₃OH, is unstable at room temperature and decomposes (eliminating HF to form COF₂) even at −20 °C [25]. Therefore, trifluoromethoxylation with CF₃OH is impractical and the development of new trifluoromethoxylation reagents is highly desired. In 2018, we developed trifluoromethyl benzoate (TFBz) as a new type of shelf‐stable trifluoromethoxylation reagent [10]. TFBz can be readily prepared from triphosgene, KF, and PhCOBr, with COF₂ being an in situ‐generated key intermediate (Scheme 1.9a). Notably, all the fluorine atoms in TFBz come from the cheap fluoride source KF. A variety of other perfluoroalkoxylation reagents can be obtained in a similar manner (Scheme 1.9b). The versatility of TFBz as a trifluoromethoxylation reagent was demonstrated by trifluoromethoxylation‐halogenation of arynes, nucleophilic substitution of alkyl(pseudo)halides, cross‐coupling with aryl stannanes, and asymmetric difunctionalization of alkenes (Scheme 1.9c).