1-Chloromethyl-4-fluoro-1,4-diazoniabicyclo octane bis(tetrafluoroborate) or Selectfluor® , a trademark of Air Products and Chemicals, is a reagent in chemistry that is used as a fluorine donor. This compound is a derivative of the heterocycle DABCO® . This colourless salt was first described in 1992 and has since been commercialized for use in organofluorine chemistry.Selectfluor® reagent is commercially available. It is synthesized by the alkylation of diazabicyclo octane (DABCO® ) with dichloromethane, followed by ion exchange with sodium tetrafluoroborate (replacing the chloride counterion for the tetrafluoroborate).