Unbalanced-Ion-Pair-Catalyzed Nucleophilic Fluorination Using Potassium Fluoride.

An unbalanced ion pair promoter (e.g., tetrabutylammonium sulfate), consisting of a bulky and charge-delocalized cation and a small and charge-localized anion, greatly accelerates nucleophilic fluorinations using easy handling KF. We also successfully converted an inexpensive and commercially available ion-exchange resin to the polymer-supported ion pair promoter (A26-SO42-), which could be reused after filtration. Moreover, A26-SO42- can be used in continuous flow conditions. In our conditions, water is well-tolerated.