Selectfluor

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Selectfluor
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Template:Longitem C7H14B2ClF9N2
Molar mass 354.26 g/mol
Appearance colourless solid
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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.[1]

Preparation

F-TEDA-BF4 synthesis

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:[2]

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 C3h symmetry.

Mechanism of fluorination

Electrophilic fluorinating reagents could in principle operate by electron transfer pathways or an SN2 attack at fluorine. This distinction has not been decided.[2] By using a charge-spin separated probe,[3] it was possible to show that the electrophilic fluorination of stilbenes with Selectfluor proceeds through an SET/fluorine atom transfer mechanism.[4]

In certain cases Selectfluor can transfer fluorine to alkyl radicals.[5]

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:[2]

File:SelectfluorRxn.png

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.[6]

Related reagents

Similar to Selectfluor are N-fluorosulfonimides:[7]

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References

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Patents

  • <templatestyles src="Citation/styles.css"/>Template:Citation/make link Script error: No such module "Check for unknown parameters". "1-substituted-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane salts and their application as fluorinating agents"
  • <templatestyles src="Citation/styles.css"/>Template:Citation/make link Script error: No such module "Check for unknown parameters". "Fluorinated Sulfonamide Derivatives"
  • <templatestyles src="Citation/styles.css"/>Template:Citation/make link Script error: No such module "Check for unknown parameters". "Fluorinated Diazabicycloalkane Derivatives"
  • <templatestyles src="Citation/styles.css"/>Template:Citation/make link Script error: No such module "Check for unknown parameters". "Fluorinated Diazabicycloalkane Derivatives"
  • <templatestyles src="Citation/styles.css"/>Template:Citation/make link Script error: No such module "Check for unknown parameters". "Method of Selective Fluorination"

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