Org. Synth. 1977, 57, 50
DOI: 10.15227/orgsyn.057.0050
DIETHYLAMINOSULFUR TRIFLUORIDE
[Sulfur, (diethylaminato)trifluoro-]
Submitted by W. J. Middleton
1 and E. M. Bingham
1.
Checked by Ronald F. Sieloff, Eugene R. Kennedy, and Carl R. Johnson.
1. Procedure
Caution! This procedure should be conducted in a good hood to avoid exposure to sulfur tetrafluoride. Protective gloves should be worn when handling diethylaminosulfur trifluoride since this material can cause severe HF burns.
A dry, 1-l., three-necked, round-bottomed flask is equipped with a thermometer (−100° to 50°), a magnetic stirrer, and two dry-ice condensers (one condenser is capped with a drying tube, the other with a gas-inlet tube). The apparatus is flushed with dry nitrogen, and 300 ml. of trichlorofluoromethane (Note 1) is added to the flask. As the nitrogen atmosphere is maintained, the trichlorofluoromethane is cooled to −70° with an acetone–dry ice bath, and 119 g. (1.10 moles) of sulfur tetrafluoride (Note 2) is added from a cylinder through the gas-inlet tube (Note 3), which is then replaced with a 250-ml., pressure-equalizing dropping funnel charged with a solution of 145 g. (1.00 mole) of N,N-diethylaminotrimethylsilane (Note 4) in 90 ml. of trichlorofluoromethane. This solution is added dropwise, with stirring, to the sulfur tetrafluoride solution at a rate slow enough to keep the temperature of the reaction mixture below −60° (about 40 minutes). The cooling bath is removed, and the reaction mixture is allowed to warm gradually to room temperature. The apparatus is prepared for distillation with a simple distillation head, and the solvent (b.p. 24°) and by-product fluorotrimethylsilane (b.p. 17°) are distilled into a well-cooled receiver by warming the reaction mixture gently to 45° with a heating mantle. The yellow to dark-brown residual liquid is transferred and distilled at reduced pressure through a spinning-band column, yielding 131 g. (81%) of diethylaminosulfur trifluoride as a light yellow liquid, b.p. 46–47° (10 mm.) (Note 5). This product can be stored for several months at room temperature in an inert plastic bottle (such as one made of polypropylene or Teflon FEP), or for short periods of time in a dry, glass bottle.
2. Notes
1.
Trichlorofluoromethane (Freon 11) is available from E. I. duPont de Nemours and Company, Inc., or Matheson Gas Products.
2.
Sulfur tetrafluoride is available from Air Products and Chemicals, Inc., or Matheson Gas Products.
3.
If it is inconvenient to add
sulfur tetrafluoride directly from a cylinder, it may first be condensed in a calibrated
trap containing a boiling chip and cooled in an acetone–dry ice bath. When cooled to −78°,
119 g. of sulfur tetrafluoride has a volume of about 62 ml. The
sulfur tetrafluoride can be added to the cooled flask by allowing it to distil slowly from the trap.
4.
N,N-Diethylaminotrimethylsilane is available from PCR, Inc., or it can be prepared by the following procedure. A solution of
292 g. (413 ml.) of diethylamine in
1000 ml. of diethyl ether is cooled in an
ice bath, and a solution of
216 g. (252 ml.) of chlorotrimethylsilane in
200 ml. of ether is added dropwise with mechanical stirring over a period of 1 hour. The precipitated solid is removed by filtration, thoroughly washed with ether, and the filtrate is fractionally distilled, yielding
175 g. (
60%) of
N,N-diethylaminotrimethylsilane as a colorless liquid, b.p.
124–125°.
5.
The reaction of
diethylaminosulfur trifluoride with water is highly exothermic; clean-up procedures should be carried out with caution.
3. Discussion
Diethylaminosulfur trifluoride is a useful and convenient reagent for replacing primary, secondary, and tertiary hydroxyl and aldehyde and ketone carbonyl oxygen
2,3 with fluorine, even in the presence of other halogens and other functional groups, such as carboxylic esters. In contrast to
sulfur tetrafluoride, this reagent is a liquid easily measured and used in standard glass equipment at moderate temperatures and atmospheric pressure, and can be used on acid-sensitive compounds (such as pivaldehyde) to convert them into the fluorinated derivative. In contrast to other reagents such as SF
4, SeF
4 pyridine HF, HF.pyridine, and (C
2H
5)
2NCF
2CFHCl, this reagent can replace hydroxyl groups with fluorine in primary alcohols such as
2-methyl-1-propanol without causing extensive rearrangement or dehydration.
This preparation of
diethylaminosulfur trifluoride is an adaptation of a procedure first described by von Halasz and Glemser.
4 The same procedure can also be used to prepare other dialkylaminosulfur trifluorides by the substitution of the
diethylaminotrimethylsilane with other dialkylaminotrimethylsilanes.
2This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
Sulfur, (diethylaminato)trifluoro-
Freon 11
ether,
diethyl ether (60-29-7)
nitrogen (7727-37-9)
diethylamine (109-89-7)
2-methyl-1-propanol (78-83-1)
trichlorofluoromethane (75-69-4)
sulfur tetrafluoride (7783-60-0)
CHLOROTRIMETHYLSILANE (75-77-4)
Diethylaminosulfur trifluoride (38078-09-0)
fluorotrimethylsilane (420-56-4)
diethylaminotrimethylsilane,
N,N-diethylaminotrimethylsilane (996-50-9)
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