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 nucleophillic base DABCO. It is a colourless salt that tolerates air and even water. It has been commercialized for use for electrophilic fluorination.
Selectfluor is synthesized by the N-alkylation of diazabicyclo[2.2.2]octane (DABCO) with dichloromethane in a Menshutkin reaction, followed by ion exchange with sodium tetrafluoroborate (replacing the chloride counterion for the tetrafluoroborate). The resulting salt is treated with elemental fluorine and sodium tetrafluoroborate:
The cation is often depicted with one skewed ethylene ((CH<sub>2</sub>)<sub>2</sub>) group. In fact, these pairs of CH<sub>2</sub> groups are eclipsed so that the cation has idealized C<sub>3h</sub> symmetry.
Electrophilic fluorinating reagents could in principle operate by electron transfer pathways or an S<sub>N</sub>2 attack at fluorine. This distinction has not been decided. By using a charge-spin separated probe, it was possible to show that the electrophilic fluorination of stilbenes with Selectfluor proceeds through an SET/fluorine atom transfer mechanism.
In certain cases Selectfluor can transfer fluorine to alkyl radicals.
The conventional source of "electrophilic fluorine", i.e. the equivalent to the superelectrophile F<sup>+</sup>, is gaseous fluorine, which requires specialised equipment for manipulation. Selectfluor reagent is a salt, the use of which requires only routine procedures. Like F<sub>2</sub>, the salt delivers the equivalent of F<sup>+</sup>. It is mainly used in the synthesis of organofluorine compounds:
Selectfluor reagent also serves as a strong oxidant, a property that is useful in other reactions in organic chemistry. Oxidation of alcohols and phenols. As applied to electrophilic iodination, Selectfluor reagent activates the IâÂÂI bond in I<sub>2</sub> molecule.
Similar to Selectfluor are N-fluorosulfonimides: