Selectfluor

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]

Selectfluor
Names
IUPAC name
1-(Chloromethyl)-4-fluoro-1,4-diazabicyclo[2.2.2]octane-1,4-diium ditetrafluoroborate
Other names
F-TEDA, N-Chloromethyl-N-fluorotriethylenediammonium bis(tetrafluoroborate)
1-Chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.101.349
EC Number
  • 414-380-4
UNII
  • InChI=1S/C7H14ClFN2.2BF4/c8-7-10-1-4-11(9,5-2-10)6-3-10;2*2-1(3,4)5/h1-7H2;;/q+2;2*-1 ☒N
    Key: TXRPHPUGYLSHCX-UHFFFAOYSA-N ☒N
  • InChI=1/C7H14ClFN2.2BF4/c8-7-10-1-4-11(9,5-2-10)6-3-10;2*2-1(3,4)5/h1-7H2;;/q+2;2*-1
    Key: TXRPHPUGYLSHCX-UHFFFAOYAI
  • [B-](F)(F)(F)F.[B-](F)(F)(F)F.C1C[N+]2(CC[N+]1(CC2)CCl)F
Properties
C7H14B2ClF9N2
Molar mass 354.26 g/mol
Appearance colourless solid
Melting point 190 °C (374 °F; 463 K) decomposes >80 °C, exact m.p. is uncertain[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation

Selectfluor is synthesized by the N-alkylation of diazabicyclo[2.2.2]octane (DABCO) with dichloromethane, 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]

F-TEDA-BF4 synthesis

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]

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]

References
  1. Banks, R. Eric; Murtagh, Vincent; An, Ilhwan; Maleczka, Robert E. (2007). "1-(Chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane Bis(tetrafluoroborate)". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rc116.pub2. ISBN 978-0471936237.
  2. Nyffeler, Paul T.; Durón, Sergio Gonzalez; Burkart, Michael D.; Vincent, Stéphane P.; Wong, Chi-Huey (2005). "Selectfluor: Mechanistic Insight and Applications". Angewandte Chemie International Edition. 44 (2): 192–212. doi:10.1002/anie.200400648. PMID 15578736.
  3. Tojo, Sachiko; Morishima, Kazuhiro; Ishida, Akito; Majima, Tetsuro; Takamuku, Setsuo (1995). "Remarkable Enhancements of Isomerization and Oxidation of Radical Cations of Stilbene Derivatives Induced by Charge-Spin Separation". The Journal of Organic Chemistry. 60 (15): 4684–4685. doi:10.1021/jo00120a004. ISSN 0022-3263.
  4. Brandt, Jochen R.; Lee, Eunsung; Boursalian, Gregory B.; Ritter, Tobias (2014). "Mechanism of electrophilic fluorination with Pd(iv): fluoride capture and subsequent oxidative fluoride transfer". Chem. Sci. 5 (1): 169–179. doi:10.1039/C3SC52367E. ISSN 2041-6520. PMC 3870902. PMID 24376910.
  5. Paquin, J.-F.; Sammis, G.; Chatalova-Sazepin, C.; Hemelaere, R. (2015). "Recent advances in radical fluorination". Synthesis. 47 (17): 2554–2569. doi:10.1055/s-0034-1378824.
  6. Stavber, Stojan; Kralj, Petra; Zupan, Marko (2002-08-01). "Progressive Direct Iodination of Sterically Hindered Alkyl Substituted Benzenes". Synthesis. 2002 (11): 1513–1518. doi:10.1055/s-2002-33339. ISSN 0039-7881.

Patents
  • 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"
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