Syntheses of a perfluoroethanesulfonyl fluoride vinyl ether

Article abstract of DOI:10.1021/jo102409s

The target monomer, perfluoroethanesulfonyl fluoride vinyl ether 8, was obtained from the starting material, iodoperfluoroethanesulfonyl fluoride 1, through the intermediate, acyl fluoride 4. Two different synthetic routes were utilized in the conversion of 4 to 8.

Full text of DOI:10.1021/jo102409s

NOTE
pubs.acs.org/joc
Syntheses of a Perfluoroethanesulfonyl Fluoride Vinyl Ether
Changqing Lu, Wanchao Jiang, Tom Hickman, and Darryl D. DesMarteau*
Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
S Supporting Information
b
ABSTRACT: The target monomer, perfluoroethanesulfonyl fluoride vinyl ether
8, was obtained from the starting material, iodoperfluoroethanesulfonyl fluoride
1, through the intermediate, acyl fluoride 4. Two different synthetic routes were
utilized in the conversion of 4 to 8.
erfluoroalkyl trifluorovinyl ethers, such as CF2dCFOCF3,
were initially synthesized through two different synthetic
corresponding acyl chloride 36 using thionyl chloride with DMF
as a catalyst (eq 2).
P
routes. In one route, perfluoroalkyl hypofluorites, such as
CF3OF,1 were added to FClCdCClF to give saturated ether
intermediates. The saturated ether intermediates were dechlori-
nated with zinc to afford the corresponding trifluorovinyl ethers.2
In another route, perfluoroalkyl acyl fluorides, including carbonyl
fluoride, were reacted with hexafluoropropylene oxide (HFPO)
to form perfluoroalkoxy acyl fluorides. The resulting perfluor-
oalkoxy acyl fluorides were then pyrolyzed at high temperatures
in the presence of an inorganic salt to afford dehalocarbonylated
products, perfluoroalkyl trifluorovinyl ethers.3 Pyrolysis could be
carried out in a batch mode3b or in a flow system.3c Through
these two synthetic routes, two important functional monomers,
CF2dCFOCF2CF(CF3)OCF2CF2SO2F and CF2dCFOCF2-
CF2SO2F, have been synthesized.4
The excess SOCl2 could not be completely separated from the
desired acyl chloride 3 at this step. After distillation, the resulting
mixture was converted to the corresponding acyl fluoride 4 and
thionyl fluoride SOF2 using antimony trifluoride in the presence
of chlorine.8 The reaction was carried out in a stainless steel
reactor. Distillation gave 4 in 95% yield based on 2 (eq 3).
Compound 4 was then used to prepare monomer 8. In the first
synthetic route, the acyl fluoride 4 was converted to the hypo-
fluorite 5 by direct fluorination with F2 in the presence of CsF.9
The reaction was carried out on a small scale (ca. 4.00 mmol) at
low temperature in a 150 mL Monel reactor (eq 4).
As part of a program for the development of new fuel cell
membranes, the synthesis of the monomer 8, CF2dCFOCF2C-
F2OCF2CF2SO2F, was of interest. Although monomer 8 was
mentioned in previous ion-exchange membrane5a and recent fuel
cell membrane5b,c applications, no method of preparation for the
compound has been reported.
In this research, iodoperfluoroethanesulfonyl fluoride 1 was
used as the starting material. It was reported that when 1 was
treated with 50% oleum at elevated temperature, the correspond-
ing acyl fluoride 4 was obtained.6 Due to the unavailability of 50%
oleum, 26% oleum was prepared and used with the starting
material 1 (eq 1).
Compound 5 (CAUTION! 5 can undergo explosive decom-
position at 22 °C) was isolated at low temperature in 89% yield
and used immediately in the next step. The decomposition of 5 at
room temperature proceeded as follows (eq 5).
Hypofluorite 5 was combined with 1,2-dichlorodifluoroethy-
lene at low temperature to form the ether intermediate 6 in 73%
yield (eq 6).
Instead of the desired acyl fluoride 4, the carboxylic acid 27 was
obtained in 88% yield. To obtain 4, 2 was converted to the
Received: December 20, 2010
Published: March 10, 2011
r
2011 American Chemical Society
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into the oleum with stirring. The reaction mixture was stirred at room
temperature overnight and then heated at 70 °C with stirring. The
progress of the reaction was monitored by 19F NMR. After 7 days, the
reaction was complete. The reaction mixture was slowly poured onto ice
to form an aqueous solution which was extracted twice with diethyl
ether. The combined ether layer was washed with sodium bisulfite
(NaHSO3 þ Na2S2O5) aqueous solution and dried with anhydrous
Na2SO4. The solvent was removed by rotary evaporation. Carboxylic
acid 2 (61.3 g, 0.208 mol, 88.5%) was obtained after vacuum distillation:
19F NMR (282 MHz, CDCl3) δ (ppm) 45.1 (m, 1F), -78.3 (m, 2F), -
82.2 (m, 2F), -112.4 (m, 2F).
Compound 6 was then dechlorinated with zinc in NMP10 to
afford the final vinyl ether monomer 8 in 82% yield (eq 7).
Synthesis of 3. Into carboxylic acid 2 (61.3 g, 0.208 mol) was slowly
added SOCl2 (66.1 g, 0.555 mol) with stirring, followed by the addition
of anhydrous DMF (1 mL). The reaction mixture was then stirred at
room temperature under N2 protection for 1 h before it was heated at
65 °C overnight. The completion of the reaction was confirmed by 19F
NMR. The distillation of the reaction mixture under vacuum gave the
desired acyl chloride 3 containing SOCl2 (total 84.7 g): 19F NMR (282
MHz, neat) δ (ppm) 45.3 (m, 1F), -76.6 (m, 2F), -81.8 (m, 2F), -
112.4 (m, 2F).
In the second synthetic route to 8, acyl fluoride 4 was mixed
with hexafluoropropylene oxide (HFPO) in a solvent with CsF as
a catalyst to form acyl fluoride 7. Compound 7 was converted to
the sodium carboxylate with Na2CO3, followed by pyrolysis to
afford the desired vinyl ether 8.
Initially, monoglyme and diglyme were tried as solvents for the
formation of 7. After distillation, 7 (containing some of the
solvent used) was treated with Na2CO3 in the same solvent in a
batch mode. After the sodium carboxylate was formed at 70 °C,
the solvent was removed under reduced pressure. However, the
complete removal of the solvent at this temperature was difficult
to achieve. Therefore, the desired vinyl ether 8 obtained in the
following step by pyrolysis at 200 -220 °C contained small
amounts of the solvent.
Synthesis of 4. Freshly sublimed SbF3 (213 g, 1.19 mol) was added
into a 300 mL stainless steel reactor inside a drybox. The reactor was
evacuated, and Cl2 (11.2 g, 0.158 mol) was condensed into the reactor
cooled with liquid nitrogen. The reactor was then heated at 80 °C for 1 h
before it was cooled with liquid nitrogen again. Acyl chloride 3 containing
SOCl2 (total 84.7 g) was then vacuum transferred into the reactor. The
closed reactor was warmed to room temperature and then heated at 85 °C
for 7 days on a shaker. After the reactor was cooled to 22 °C, the pressure
(SOF2) was released through an oil bubbler, followed by distillation to
remove the residueofSOF2 andtoisolate the acylfluoride4 (58.6 g, 0.198
mol, 95.2% based on carboxylic acid 2): 19F NMR (282 MHz, CDCl3) δ
(ppm) 45.5 (m, 1F), 14.6 (m, 1F), -76.7 (m, 2F), -82.0 (m, 2F), -
112.5 (m, 2F); IR (gas phase, 5 Torr) ν (cm-1) 1895 (s, νCdO), 1474 (s,
νSdO), 1349 (s), 1218 (s), 1157 (s), 1035 (s), 807 (s), 612 (m).
Synthesis of 5. Dry CsF (15.0 g, 98.7 mmol) was added into a
150 mL Monel reactor inside a drybox. The reactor was then evacuated,
and acyl fluoride 4 (1.18 g, 3.99 mmol) was transferred through the
vacuum line into the reactor cooled to -196 °C. Fluorine (20.0 mmol)
was then transferred into the reactor. The reactor was kept at -60 °C for
36 h. The excess fluorine was then removed at -196 °C through a soda
lime column by pumping under vacuum. The crude product inside the
reactor was then subjected to vacuum fractionation through traps cooled
to -60, -120, and -196 °C. The product from both -60 and -120 °C
trap was vacuum transferred into a 50 mL stainless steel reactor cooled
with liquid nitrogen to give hypofluorite 5 (1.19 g, 3.56 mmol, 89.2%):
19F NMR (282 MHz, CCl4, ca. -20 °C) δ (ppm) 142.5 (m, 1F), 45.1
(m, 1F), -55.5 (m, 2F), -82.8 (m, 1F), -83.5 (m, 1F), -84.8 (m, 1F),
-97.6 (m, 1F), -113.3 (m, 2F); IR (gas phase, 5 Torr) ν (cm-1) 1474
(s, νSdO), 1253 (s), 1221 (s), 1161 (s), 1084 (m), 995 (m), 898 (m, νO-F),
809 (s), 755 (w), 607 (m).
Synthesis of 6. 1,2-Dichlorodifluoroethylene (0.475 g, 3.57 mmol)
was condensed into the 50 mL stainless steel reactor containing
hypofluorite 5 (1.19 g, 3.56 mmol) cooled to -196 °C. The reactor
was warmed and kept at -60 °C for 24 h. Vacuum fractionation through
traps at -60, -120, and -196 °C gave 6 (1.22 g, 2.61 mmol, 73.3%) in
the -60 °C trap: 19F NMR (282 MHz, CDCl3) δ (ppm) 45.3 (m, 1F),
-71.2 (m, 2F), -77.2 (m, 1F), -82.6 (m, 2F), -88.4 (m, 0.5F), -88.9
(m, 2F), -89.9 (m, 1F), -90.4 (m, 0.5F), -112.8 (m, 2F); IR (gas
phase, 5 Torr) ν (cm-1) 1473(s, νSdO), 1252 (s), 1219 (s), 1162 (s),
1139 (s), 1027 (w), 803 (w), 607 (w).
Synthesis of 8 from 6. Activated Zn (0.775 g, 11.8 mmol) was
added into a 100 mL one-piece glass reactor inside a drybox, and dry
NMP (5 mL) was injected into the reactor. The reactor was cooled
to -196 °C and evacuated. The ether intermediate 6 (1.11 g, 2.37
Subsequent use of tetraglyme in the reactions (eq 8) resulted
in pure 7 after distillation in modest yield (74%).
To obtain 8 in higher yield, a flow system for the pyrolysis was
employed. Acyl fluoride 7 was vaporized and carried through
Na2CO3 column by dry nitrogen. Pyrolysis of 7 followed by
distillation gave 8 in a 63% yield (eq 9).
In summary, oleum (26%) converts the iodoperfluoroalkyl
compound 1 into carboxylic acid 2, which requires two additional
steps to obtain the desired acyl fluoride 4. The desired monomer
8 is then obtained by two synthetic routes. In the first route, the
hypofluorite method results in good yields, but is limited in a
batch scale by the instability of the hypofluorite 5. In the second
route, acyl fluoride 4 is converted to acyl fluoride 7 with HFPO in
tetraglyme. The flow pyrolysis of 7 over Na2CO3 gave modest
yields of monomer 8, which could probably be improved by
optimization. However, we believe that the yield is limited by the
-SO2F functional group reacting with Na2CO3.
’ EXPERIMENTAL SECTION
Synthesis of 2. Into a three-necked round-bottom flask (1 L) was
added 20% fuming sulfuric acid (500 g). SO3 (40 g) was then slowly
added into the flask with stirring to form an oleum (25.9%). A water-
cooled condenser with a balloon on the top, a pressure-equalizing
addition funnel, and a glass stopper were fitted to the flask. Iodide 1
(100 g, 0.235 mol) was added dropwise through the additional funnel
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mmol) was vacuum transferred into the reactor, and the mixture was
heated at 60 °C overnight. After being cooled to 22 °C, the reaction
mixture was vacuum fractionated through traps at -75, -115, and -
196 °C. 8 (0.779 g, 1.96 mmol, 82.7%) was obtained in the -75 °C trap:
19F NMR (282 MHz, CDCl3) δ (ppm) 45.3 (m, 1F), -82.5 (m, 2F), -
88.1 (m, 2F), -90.6 (2d, 5J = 4.7 Hz, 5J = 4.7 Hz, 2F), -112.7 (m, 2F),
-113.5 (dd, 3J = 83.4 Hz, 3J = 66.7 Hz, F), -121.7 (ddt, 2J = 112.0 Hz, 3J
= 83.4 Hz, 5J = 4.7 Hz, F), -135.7 (ddt, 2J = 112.0 Hz, 3J = 66.7 Hz, 5J =
4.7 Hz, F); IR (gas phase, 5 Torr) ν (cm-1) 1841 (w, νCdC), 1474 (s,
νSdO), 1344 (s), 1293 (s), 1251 (s), 1219 (s), 1177 (s), 1158 (s), 1097
(m), 994 (m), 808 (m), 757 (w), 609 (m).
’ REFERENCES
(1) Kellogg, K. B.; Cady, G. H. J. Am. Chem. Soc. 1948, 70, 3986.
(2) (a) Durrell, W. S.; Stump, E. C., Jr.; Westmoreland, G.; Padgett,
C. D. J. Polym. Sci. Part A 1965, 3, 4065. (b) Marchionni, G.; De Patto,
U.; Spataro, G.; Tortelli, V. J. Fluorine Chem. 2003, 119, 83. (c)
Navarrini, W.; Corti, S. J. Fluorine Chem. 2004, 125, 189.
(3) (a) Fritz, C. G.; Moore, E. P., Jr.; Selman, S. U.S. Patent 3 114
778, 1963. (b) Morita, S.; Iwasaki, Y. U.S. Patent 5 902 908, 1999. (c)
Harris, J. F., Jr.; McCane, D. I. U.S. Patent 3 132 123, 1964.
(4) (a) Harris, J. F., Jr.; McCane, D. I. U.S. Patent 3 180 895, 1965.
(b) Ezzell, B. R.; Carl, W. P.; Mod, W. A. U.S. Patent 4 358 412, 1982. (c)
Arcella, V.; Ghielmi, A.; Tommasi, G. Ann. N.Y. Acad. Sci. 2003, 984, 226.
(5) (a) Kaneko, I.; Kanba, M.; Watakabe, A.; Miyake, H. Jpn. Kokai
Tokkyo Koho, JP 63083138 A, 1988. (b) Tayanagi, J.; Watakabe, A.;
Saito, S.; Ueno, K. PCT Int. Appl., WO 2004066426 A1, 2004. (c)
Tayanagi, J.; Watakabe, A.; Saito, M.; Ueno, K. Jpn. Kokai Tokkyo Koho,
JP 2006032157 A, 2006.
Synthesis of 7. Dry CsF (10.0 g, 65.8 mmol) was added into a 1 L
Ace thread flask inside a drybox. Tetraglyme (120 mL, sodium dried) was
then added. Theflaskwas cooledto-196 °C and evacuated. Acylfluoride
4 (55.8 g, 0.188 mol) was vacuum transferred into the flask. The flask was
then maintained at -10 to -20 °C, and hexafluoropropylene oxide
(HFPO) (97%, 33.9 g, 0.198 mol, 1.05 equiv) was slowly introduced into
the flask with stirring at pressures ranging from 400 to 700 Torr over 3 h.
After the desired amount of HFPO had been added (total pressure drop
3631 Torr in 1.01 L of volume), the reaction mixture was stirred for
another 8 h at 22 °C. The crude product was distilled out of the flask
under dynamic vacuum and collected in a two-necked flask cooled with
liquid nitrogen. Upon slow warming to room temperature, the crude
product was transferred into a 100 mL flask and subjected to further
distillation at atmospheric pressure. Acyl fluoride (7) (64.4 g, 0.139 mol,
73.9%) was obtained: bp 118 °C; 19F NMR (282 MHz, CDCl3) δ (ppm)
45.2 (m, 1F), 26.4 (m, 1F), -82.3 (m, 3F), -82.6 (m, 2F), -84.3 (dd,
2J = 145.3 Hz, 4J = 19.7 Hz, 1F), -88.4 (m, 2F), -91.4 (dt, 2J = 145.3 Hz,
5J = 6.5 Hz, 1F), -112.8 (m, 2F), -131.2 (d, 4J = 19.7 Hz, 1F).
Synthesis of 8 from 7. Granular Na2CO3 (160 g, predried at
160 °C under vacuum) and glass beads (160 g) were well mixed and
packed into a column (50 cm long, 2.5 cm inner diameter) inside a
drybox. The column was fitted with a pressure-equalizing addition funnel
at the top and a two-necked 250 mL flask at the bottom. A flow of dry
nitrogen (90 mL/min) was maintained down through the column. The
column was heated at 260 °C for 1 h and then kept between 200 and
210 °C. Acyl fluoride 7 (22.5 g, 48.7 mmol) was added dropwise into the
column through the finely controlled addition funnel over 3 h. The crude
product was collected in the flask cooled to -10 to -20 °C. The final
product 8 (12.2 g, 30.8 mmol, 63.2%) was obtained after distillation at
atmospheric pressure: bp 107 °C; HRMS of hydrolyzed 8 m/z [M - F þ
ONa þ Na]þ 438.9077, calcd (C6O5F11SNa2) 438.9081; 19F NMR (282
MHz, CDCl3) δ (ppm) 45.3 (m, 1F), -82.5 (m, 2F), -88.1 (m, 2F), -
90.6 (2d, 5J = 5.6 Hz, 5J = 5.6 Hz, 2F), -112.7 (m, 2F), -113.6 (dd, 3J =
83.3 Hz, 3J = 66.4 Hz, 1F), -121.8 (ddt, 2J = 112.2 Hz, 3J = 83.7 Hz, 5J =
5.2 Hz, 1F), -135.7 (ddt, 2J = 112.2 Hz, 3J = 65.6 Hz, 5J = 5.2 Hz, 1F).
(6) Su, D.-B.; Chen, Q.-Y.; Zhu, R.-X.; Hu, H.-P. Acta Chim. Sinica
1983, 41, 946.
(7) Long, Z.-Y.; Duan, J.-X.; Lin, Y.-B.; Guo, C.-Y.; Chen, Q.-Y.
J. Fluorine Chem. 1996, 78, 177.
(8) Sharts, C. M. J. Chem. Educ. 1968, 45, 185.
(9) (a) Prager, J. H.; Thompson, P. G. J. Am. Chem. Soc. 1965,
87, 230. (b) Storzer, W.; DesMarteau, D. D. Inorg. Chem. 1991, 30, 4122.
(c) Lu, C.; Kim, J.-H.; DesMarteau, D. D. J. Fluorine Chem. 2010,
131, 17.
(10) Resnik, P. R. Jpn. Kokai Tokkyo Koho, JP 11228474 A, 1999.
’ ASSOCIATED CONTENT
Supporting Information. IR and 19F NMR spectra for
S
b
selected compounds and LCMS analysis for the final product.
This material is available free of charge via the Internet at http://
pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: fluorin@clemson.edu.
’ ACKNOWLEDGMENT
We thank Solvay Solexis for partial financial support of
this work.
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