The most synthetically useful ammonium salts are the substituted DABCO bis(ammonium) ions, including Selectfluor.Stavber, S.; Zupan, M.; Poss, A. J.; Shia, G. A. Tetrahedron Lett. 1995, 36, 6769. These can be easily synthesized by alkylation followed by fluorination. The difluoro version, which might at first seem more useful, delivers only a single fluorine atom.
