Selectfluor


1-Chloromethyl-4-fluoro-1,4-diazoniabicyclooctane bis 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 nucleophillic base DABCO. This colourless salt was first described in 1992 and has since been commercialized for use in organofluorine chemistry for electrophilic fluorination.

Preparation

Selectfluor is synthesized by the N-alkylation of diazabicyclooctane with dichloromethane, followed by ion exchange with sodium tetrafluoroborate. Finally, this salt is treated with elemental fluorine and sodium tetrafluoroborate:

Mechanism

Electrophilic fluorinating reagents can operate via electron transfer pathways or an SN2 attack at fluorine. 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 addition to these electrophilic fluorinations, it has also been shown that Selectfluor can transfer fluorine to alkyl radicals.

Applications

The conventional source of "electrophilic fluorine", i.e. the equivalent to the superelectrophile F+, is gaseous fluorine, which requires specialised equipment for manipulation. Selectfluor reagent is a salt, the use of which requires only routine procedures. Like F2, the salt delivers the equivalent of F+. It is mainly used in the synthesis of organofluorine compounds:

Specialized applications

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 I–I bond in I2 molecule.

Patents