Selectfluor

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 ((CH₂)₂) group. In fact, these pairs of CH₂ groups are eclipsed so that the cation has idealized C_3h symmetry.

Electrophilic fluorinating reagents could in principle operate by electron transfer pathways or an S_N2 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⁺, 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.

Similar to Selectfluor are N-fluorosulfonimides:

• US 5459267  "1-substituted-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane salts and their application as fluorinating agents"
• US 55227493  "Fluorinated Sulfonamide Derivatives"
• US 5086178  "Fluorinated Diazabicycloalkane Derivatives"
• US 5473065  "Fluorinated Diazabicycloalkane Derivatives"
• US 5442084  "Method of Selective Fluorination"