A method for the nucleophilic fluorination of 4-dimethylaminopyridine (DMAP) pyridinium salts

Fluorinated organic compounds have proven to be beneficial in various industries. Recent research has utilized quaternary ammonium salts as precursors for fluorinations using the radioactive isotope 18F. This method was translated into a generic method for the fluorination of pyridinium salts, generated from pyridine derivatives and 4-dimethylaminopyridine (DMAP), using 19F. This translated method affords another fluorination method for the synthesis of fluorinated pyridine derivatives under mild conditions, utilizing starting materials that are easy to isolate and handle. Once optimized conditions were found, a series of reactions with pyridinium salts comprising different functional groups and counter ions were performed. These reactions afforded the fluorinated product in moderate to good yields. Electron withdrawing groups para to the DMAP leaving group were determined to be imperative to the success of this methodology.