Facile Route to 2‑Fluoropyridines via 2‑Pyridyltrialkylammonium Salts Prepared from Pyridine N‑Oxides and Application to 18F‑Labeling

Among known precursors for 2-[18F]­fluoropyridines, pyridyltrialkylammonium salts have shown excellent reactivity; however, their broader utility has been limited because synthetic methods for their preparation suffer from poor functional group compatibility. In this paper, we demonstrate the regioselective conversion of readily available pyridine N-oxides into 2-pyridyltrialkylammonium salts under mild and metal-free conditions. These isolable intermediates serve as effective precursors to structurally diverse 2-fluoropyridines, including molecules relevant to PET imaging. In addition to providing access to nonradioactive analogues, this method has been successfully applied to 18F-labeling in the radiosynthesis of [18F]­AV-1451 ([18F]­T807), a PET tracer currently under development for imaging tau.