Perfluoroalkylsulfone reactions with nucleophiles

Article abstract of DOI:10.1016/S0022-1139(02)00170-7

Perfluorodialkylsulfones were found to react readily with metal hydroxides in water or alcohol solution and with ammonia to form fluorinated sulfonic acid derivatives.

Full text of DOI:10.1016/S0022-1139(02)00170-7

Journal of Fluorine Chemistry 117 (2002) 13±16
Per¯uoroalkylsulfone reactions with nucleophiles
*
Michael D. Barrera, Yuri Cheburkov , William M. Lamanna
3
M Company, 3M Center, St. Paul, MN 55144, USA
Received 11 June 2002; received in revised form 29 June 2002; accepted 1 July 2002
Abstract
Per¯uorodialkylsulfones were found to react readily with metal hydroxides in water or alcohol solution and with ammonia to form
uorinated sulfonic acid derivatives.
¯
#
2002 Elsevier Science B.V. All rights reserved.
Keywords: Per¯uorodialkylsulfones; Per¯uoroalkylsulfonic acid derivatives
1
. Introduction
preparation of amorphous TFE±HFP copolymers at high
pressures [11].
Totally ¯uorinated sulfones have been known since the
pioneering work of Temple in 1968 [1], who prepared the
sulfones via the reaction of sulfuryl ¯uoride or ¯uorinated
sulfonyl ¯uorides with tetra¯uoroethylene (TFE). Since that
time, some other per¯uorinated sulfones have been reported.
Per¯uorodimethylsulfone was prepared by direct ¯uorina-
tion [2] and by hydrolysis of bis(tri¯uoromethyl)di¯uoro-
sulfoxide [3]. For synthesis of per¯uoromethylethylsulfone,
the addition of per¯uoromethylsulfonyl ¯uoride (PMSF)
to TFE was successfully used [4]. And ®nally, per¯uoro-
sulfolane was prepared by hydrolysis of corresponding
cyclic sulfoxydi¯uoride [5] and also by electro-chemical
2. Results and discussion
We report a new synthesis of per¯uorinated sulfonic acid
derivatives from the reaction of per¯uorodialkylsulfones
with nucleophiles shown below. The reaction mechanism
is probably nucleophilic substitution of the per¯uoroalkyl
group at a sulfonyl sulfur atom:
¯
(
uorination (ECF) from 2,5-dihydrothiophen-1,1-dioxide
sulfolene) [6,7]. ECF is also a known method for prepara-
tion of per¯uorinated diethylsulfone [8] and methylbutyl-
sulfone [9].
For cyclic per¯uorosulfolane and 3,4-dichloroper¯uoro-
sulfolane, the ring opening reaction with base to form
The reaction was not previously reported for per¯uoro-
dialkylsulfones, nor for partially ¯uorinated dialkylsul-
fones with a per¯uoroalkyl group connected to the
sulfonyl groups. For instance, well-known tri¯ones have
considerable value in synthesis because the tri¯uoro-
methanesulfonyl group is one of the strongest electron-
withdrawing group. When attached to carbon the group
activates the adjacent methylene group to proton abstrac-
tion by bases to give the tri¯one a-carbanions rather than
the tri¯uoromethyl carbanion [12]:
¯
uorobutanesulfonates with di¯uoromethyl end group [6]
or tri¯uorovinyl termination [10] has been reported.
Chemical reactions of acyclic per¯uorodialkylsulfones
are practically unknown. Thermal decomposition at
2
75 8C with SO removal is probably the only reaction
2
known for per¯uorodialkylsulfones. The reaction makes
them a good source of per¯uoroethyl radicals. Per¯uoro-
diethylsulfone is reported to be a useful initiator for
À
À
À
CF3SO2CH2ÀR ‡ Nu ! CF3SO2CH ÀR and no CF3
*
On the other hand, nucleophilic displacement of the tri-
¯uoromethyl group has been reported for tri¯uoromethylaryl
Corresponding author. Tel.: ‡1-651-731-1452.
E-mail address: ycheburkov1@mmm.com (Y. Cheburkov).
0022-1139/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 2 ) 0 0 1 7 0 - 7

14
M.D. Barrera et al. / Journal of Fluorine Chemistry 117 (2002) 13±16
sulfones, probably by a haloform-type process [13]:
400 MHz H and 376 MHz 19F NMR spectra were acquired
at room temperature using Varian UNITY plus 400 FT-NMR
spectrometer.
1
See also CF substitution in the reaction of the aryltri¯uor-
3
omethyl sulfone with Grignard reagents [14].
To our surprise, per¯uorodiethylsulfone is easily reacted
with nucleophiles to give penta¯uoroethanesulfonic acid
derivatives and penta¯uoroethane (HFC-125), e.g.:
p-Hexa¯uoroxylene was used as a cross-integration stan-
dard to facilitate the cross-correlation at the various ¯uorine
and proton signal intensities and for quantitative evaluation
of sample purity. GC±MS analysis was performed using an
HP 5890 Series 2 gas chromatograph, with a 105 m Â
C2F5SO2C2F5 ‡ KOH=H O ! C2F5SO3K ‡ C2HF5
2
À
‡
C2F5SO2C2F5 ‡ 2NH3 ! C2F5SO2NH NH4 ‡ C2HF5
0
:32 mm Rtx-5 capillary column to introduce the sample
In these cases, the penta¯uoroethyl group reacts as if it is a
halogen. This rare type of per¯uoroalkyl group reactivity
was previously reviewed by Knunyants and Cheburkov [15].
The reaction of the sulfone with sodium methoxide in
methanol does not stop at methylpenta¯uoroethanesulfo-
nate. The latter alkylates a second methanol molecule to give
dimethylether and the sodium per¯uoroethanesulfonate:
to a Finnigan SSQ-700 mass spectrometer. The samples
were ionized using chemical ionization with methane as the
reagent gas. A gas chromatograph HP 5890 Series 2 with
J&W Scienti®c fused silica capillary column DB 210
(
30 m  0:325 mm) with an FID detector was used for
liquids and a Carbopack C column with thermal conductiv-
ity detector was used for gases. IR spectra were recorded on
a Digilab FTS-40 FT-IR spectrometer.
C F SO C F ‡ CH ONa ‡ CH OH
2
5
2
2
5
3
3
!
C2F5SO3Na ‡ CH3OCH3 ‡ C2HF5
3.1. Perfluorodiethylsulfone purification
Per¯uorodimethylsulfone was reacted in a similar manner
with lithium hydroxide in methanol to give lithium tri¯ate in
high yield. All these reactions involve simple procedures and
give high yields of the sulfonic acid derivatives. For instance,
the reaction of per¯uorodiethylsulfone with sodium methoxide
is exothermic and takes only 10 min to complete at room
temperature. The sodium penta¯uoroethanesulfonate was
obtained quantitatively as a white solid. The procedure in
the reaction of the sulfone with liquid ammonia is more
complex. The product prepared in a stainless steel pressure
reactor was usually contaminated by many by-products of
unknown chemical structure and sometimes deeply colored.
The penta¯uoroethanesulfonylamide was prepared by
extended heating (65 h) of the reactants in a sealed glass tube
at elevated temperature (83 8C) without any solvent. It is
probably possible to shorten the reaction time by increasing
the temperature, but the gaseous reaction product (HFC-125)
has a very low boiling point (À48.5 8C) and does not dissolve
in the primary reaction productÐthe amide salt. Therefore, we
were reluctant to increase the temperature using a sealed glass
tube. Re-crystallization of the salt from benzene or chloroform
and also vacuum sublimation gives known [16] pure per¯uor-
oethansulfonylamide, which is not moisture sensitive and is
soluble in water and acetonitrile. When conducted in a glass
reactor, the yield of the amide was good (isolated 70% on a
A product mixture consisting of 49% per¯uoroethanesulfo-
nyl¯uoride and 49% per¯uorodiethylsulfone was distilled
using a concentric tube ACE Glass Inc. column with condenser
at (À21 8C) to collect pe¯uorodiethylsulfone with bp 63±
63.5 8C and purity 97.1% by GC analysis. The sulfone was
contaminated with per¯uoroethanesulfonyl¯uoride and also
isomeric C F SO F having the same boiling point range.
4
9
2
Agitating the sulfone with concentrated ammonium hydroxide
for 17 h at room temperature, followed by washing, drying and
re-distillation gave the ®nal product with purity >99% by GC
(98.6% by NMR). The main impurity was identi®ed as per-
¯uorobutanesulfonyl¯uoride, which is present at nearly 1%.
3.2. Perfluorodiethylsulfone hydrolysisÐpotassium
perfluoroethylsulfonate and HFC-125
Per¯uorodiethylsulfone (3.0 g, 10 mmol) and 2.5 ml of
52% solution of potassium hydroxide in water (1.3 g KOH,
23 mmol) were heated with stirring at 80 8C with condenser at
À10 8C and end trap at À78 8C until re¯ux ended and initially
two-phase reaction mixture became a clear homogeneous
solution. In the end trap was collected 0.9 g liquid consisting
of (GC): 6% starting sulfone and 94% C HF ; MS (CI): 121
2
5
‡
‡
[85 (M ‡ 1) ], 101 [100 (M À HF) ]. The yield of the
penta¯uoroethane (HFC-125) was 71%. The clear solution
in the reaction ¯ask became solid at room temperature. Water
was added to dissolve the solid material, the solution was
treated by carbon dioxide to remove the excess of KOH and
dried in an oven at 95 8C. Extraction of organics in the solid
residue by methanol gave 2.08 g (yield 98%) of potassium
per¯uoroethanesulfonate. 19F NMR (À) ppm up®eld of inter-
nal CFCl (D O): À79.86 (CF , s), À118.37 (CF , s).
3.0 g sulfone scale) and the product was pure (97%) and did not
require additional puri®cation.
3
. Experimental details
Analytical data was provided by the Specialty Materials
Manufacturing Division analytical group at 3M. The
3
2
3
2

M.D. Barrera et al. / Journal of Fluorine Chemistry 117 (2002) 13±16
15
In a separate experiment, per¯uorodiethylsulfone (2.02 g,
0 mmol) and potassium carbonate (2.08 g, 15 mmol) in
.5 ml of water were heated with stirring at 80 8C for 5 h. No
À19 8C and end trap at À78 8C. The exothermic reaction
was completed in 9 min and all gaseous products were
purged by nitrogen from the trap and collected. A total of
1.66 g of liquid consisting of (GC): 60% C HF (calculated
1
2
homogenization of the two-phase reaction mixture, nor gas
evolution, was observed even after addition of a small
amount of phase transfer catalyst tetrabutylammonium bro-
mide. A total of 0.92 g of pure (99.8%) sulfone was recov-
ered (by simple phase separation) and no C HF was
2
5
1.0 g, 83% yield), 36% CH OCH ; MS (CI) 47 [18
3
3
‡
‡
(M ‡ 1) ], 45 [100 (M À H) ] (calculated 0.6 g, 130%
yield) and 4% unconsumed per¯uorodiethylsulfone was
obtained. To the solid residue in the reaction ¯ask was
added 10 ml H O. The solution was treated with CO and
2
5
detected by GC of the gas phase. There is no sulfone
hydrolysis under these conditions.
2
2
dried at 100 8C to give 2.87 g of white solid material.
Methanol (22 ml) extraction of the material, followed by
drying in the open air gave 2.23 g (101% yield) of sodium
per¯uoroethanesulfonate.
3.3. Perfluorodiethylsulfone aminolysisÐ
perfluoroethanesulfonylamide
In a sealed glass tube, a mixture of 3.03 g (10 mmol)
per¯uorodiethylsulfone and 0.52 g (30 mmol) ammonia was
heated at 83 8C for 65 h. Liquid ammonia was not comple-
tely dissolved in the sulfone at room temperature and created
a small upper layer in the tube. The ®nal mixture after
heating contained three layersÐ1:1 clear bottom layer of
penta¯uoroethane and slightly colored middle layer of
penta¯uoroethanesulfonylamide ammonium salt and also
a very small upper layer comprising excess liquid ammonia.
After cooling, the tube was opened and heated to 44 8C to
evaporate volatiles into a cold trap (À78 8C). A total of
3.4.1. Reaction perfluorodimethylsulfone
with lithium hydroxide in methanol
Per¯uorodimethylsulfone with a bp 12.5±17 8C and purity
(NMR) 89.5% (1 g, 4.43 mmol) was gradually added to
solution of 0.25 g (5.95 mmol) LiOHÁH O in 1.5 g methanol
2
at 0 8C. In 30 min, the solution was treated by dry CO ,
2
®ltered and the methanol was evaporated to give 0.667 g of
white solid lithium tri¯ate with a purity (NMR) 92.7%
(3.96 mmol); yield 89%. 19F NMR (À) ppm up®eld of
internal CFCl (D O): À78.4 (CF , s).
3
2
3
1
7
1
.37 g of volatiles were collected in the trap (GC): 6% NH ,
3.4.2. Reaction perfluorodimethylsulfone
with lithium hydroxide in water
Per¯uorodimethylsulfone (1 g, 4.43 mmol), lithium
3
8% C HF and 16% of the sulfone. The yield of C HF was
5
2
5
2
.07 g (89%). After removal of low boilers, the liquid left in
the glass tube contained 0.2 g of pure (99% purity) starting
sulfone as a lower phase and 2.08 g of liquid sulfonylamide
ammonium salt. Another 0.19 g of per¯uorodiethylsulfone
were left in the trap after reventing the trap contents. In
summary, 0.39 g or 13% of the starting sulfone remained
unreacted. After transferring from the glass tube, the 1.68 g
of the liquid sulfonylamide salt quickly solidi®ed in the open
air to give 1.57 g of white crystalline solid with mp 67.5±
hydroxide hydrate (0.276 g, 6.57 mmol) and 3 ml H O were
2
agitated in a sealed glass tube for 4 h at 0 8C. While opening
the tube, 0.36 g of gaseous products escaped. The solution
was ®ltered to remove 0.043 g of white solid, treated with
dry CO to pH 8 (no solid material) and dried to give 0.65 g
2
of solid lithium tri¯ate with purity (NMR) 90.9%
(3.78 mmol); yield 85%.
70 8C. The cross-integration of the proton and ¯uorine NMR
spectral data shows this sample appears to be a mixture of
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2
5
2
2
3
À1
spectrum shows broad absorptions in the 2400±3400 cm
region in addition to sulfonamide NH stretching absorption
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[
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(
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16
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