An improved method for the fluorination of arylsulfur chlorotetrafluorides to arylsulfur pentafluorides

Article abstract of DOI:10.1016/j.jfluchem.2013.10.009

A new method for the fluorination of arylsulfur chlorotetrafluorides to arylsulfur pentafluorides is described. The reaction is promoted by hydrogen fluoride generated from potassium hydrogen fluoride and trifluoroacetic acid which also serves as a solvent. The reaction is performed under mild conditions and uses substochiometric amounts of potassium hydrogen fluorides in certain cases. Recovery and reuse of trifluoroacetic acid was successfully demonstrated which makes this method safe, simple to use, and atom- and cost-effective.

Full text of DOI:10.1016/j.jfluchem.2013.10.009

Accepted Manuscript
Title: An improved method for the fluorination of arylsulfur
chlorotetrafluorides to arylsulfur pentafluorides
Author: Katrin Lummer Maxim V. Ponomarenko
¨
Gerd-Volker Roschenthaler Matthias Bremer Petr Beier
PII:
S0022-1139(13)00336-9
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2013.10.009
FLUOR 8211
To appear in:
FLUOR
Received date:
Revised date:
Accepted date:
29-7-2013
4-10-2013
9-10-2013
¨
Please cite this article as: K. Lummer, M.V. Ponomarenko, G.-V. Roschenthaler,
M. Bremer, P. Beier, An improved method for the fluorination of arylsulfur
chlorotetrafluorides to arylsulfur pentafluorides, Journal of Fluorine Chemistry (2013),
http://dx.doi.org/10.1016/j.jfluchem.2013.10.009
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An improved method for the fluorination of
arylsulfurchlorotetrafluorides to arylsulfurpentafluorides
KatrinLummer,a Maxim V. Ponomarenko,aGerd-Volker Röschenthaler,a Matthias Bremer,bPetrBeier*,c
aSchool of Engineering and Science, Jacobs University of Bremen, Campus Ring 1, 28759 Bremen,
Germany
bMerckKGaA, 250 Frankfurterstr., 64271 Darmstadt, Germany
cInstitute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic,
Flemingovonám. 2, 166 10 Prague, CzechRepublic
beier@uochb.cas.cz
Abstract
A new method for the fluorination of arylsulfurchlorotetrafluorides to arylsulfurpentafluorides is
described. The reaction is promoted by hydrogen fluoride generated from potassium hydrogen fluoride
and trifluoroacetic acid which also serves as a solvent. The reaction is performed under mild conditions
and uses substochiometric amounts of potassium hydrogen fluorides in certain cases. Recovery and
reuse of trifluoroacetic acid was successfully demonstrated which makes this method safe, simple to use,
and atom- and cost-effective.
1. Introduction
The pentafluorosulfanyl group (SF5) is a functionality that has received much attention in recent
years, mainly in material, medicinal, and agrochemical research [1]. The incorporation of strongly
electron-withdrawing pentafluorosulfanyl group into organic molecules can dramatically modify a
variety of properties including lipophilicity, solubility, metabolic, thermal and chemical stability,
bioavailability, bioactivity, or pKa [Error! Bookmark not defined.,2]. This functional group is starting to
appear in compounds in development for various applications including pharmaceuticals,
agrochemicals, energetic materials, liquid crystals, ionic liquids, and others [3]. Recently, the electron-
acceptor and steric properties of the SF5 group were also exploited in catalysis [4].
There is a limited number of commercially available compounds with the SF5 group (compared
to, for example, the CF3-containing compounds), although, in recent years, many new products (mostly
SF5-aromatics) became available. In case of aromatic SF5 compounds, there are two main methods for
their practical synthesis available. The first one was developed in the 1990’s and is based on direct
fluorination of electron-deficient bis(aryl) disulfides (such as bis(m- or p-nitrophenyl) disulfides) with
F2/N2 [5]. Building upon earlier studies of Sharp [6], Shreeve [7] and Janzen [8], the second method by
Page 1 of 13

Umemoto is based on a two-step process of conversion of diaryl disulfides (1) or aryl thiols to aromatic
sulfur chlorotetrafluorides (2) using chlorine in the presence of alkali metal fluorides in acetonitrile [9].
Arylsulfurtrifluorides [10] were identified as intermediates in these reactions. In the second step,
arylsulfurchlorotetrafluorides were fluorinated to arylsulfurpentafluorides (3) using either ZnF2 under
elevated temperature, SbF3/SbF5(SbCl5) in a halocarbon solvent, excess of 70% HF-pyridine complex,
or excess of anhydrous hydrogen fluoride (Scheme 1) [Error! Bookmark not defined.]. A
fluoropolymer reactor or reaction flask is required for all of the methods. These methods havesome
drawbacks: the zinc fluoride method uses high temperature, HF-pyridine and anhydrous hydrogen
fluoride methods use large excess of very toxic and corrosive chemicals. Despite this, the last method
seems to be the most suitable for bigger scale production.
Cl2 (7-27 equiv.)
KF or CsF (16-40 equiv.)
ZnF2 (0.5-2.7 equiv.), 80°-180°,
or SbF3 (1-1.5 equiv.), SbF5 (0.1-1 equiv.),
FC-72 or CH2Cl2, rt,
ArS-SAr
MeCN, 0° to rt
1
ArSF4Cl
or 70% HF-pyridine (10 equiv.), 50°,
or anh. HF (25 equiv.), KHF2 (1.1 equiv.), 15°
Cl2 (5-20 equiv.)
KF or CsF (9-30 equiv.)
2
ArSH
21 examples
52-88% yields
MeCN, 0° to rt
1'
Scheme 1: Umemoto’stwo-step synthesisofarylsulfurpentafluorides [Error! Bookmark not defined.].
Umemoto’s synthesis represents a significant development for economical production of
arylsulfurpentafluorides. Importantly, various substitutions on the phenyl ring are tolerated including
fluoro, chloro, bromo, nitro, alkyl, and methylsulfonyl. A weak point of this process is the second step
which calls for improvements. Safe, inexpensive and atom-economic fluorination method would be
highly desirable.
2. Results and discussion
First, a range of substituted phenylsulfurchlorotetrafluorides (2) were synthesized in good to high
yields using Umemoto’s conditions. The reliability of the method was validated on a multi-gram scale.
Commercial spray-dried potassium fluoride further dried by heating in vacuo for several hours was used,
and the reaction was performed in dry acetonitrile at ambient temperature using excess of chlorine
(Table 1). Compounds 2a-dwere synthesized previously [Error! Bookmark not defined.] while
compounds 2e and 2f are new. Compound 2d could be prepared from p-t-butylthiophenol; however, we
found that this method is not suitable for thiophenols substituted with electron-withdrawing group (4-F,
4-Cl or 2,4-F2), and for these compounds, it was necessary to start from the corresponding diaryl
Page 2 of 13

disulfides. The products were purified either by distillation under reduced pressure (2a-c and 2e) or by
crystallization (2d) and were found to be stable in a perfluoropolymer container but they decomposed
over the course of hours or days on contact with glass.
Table 1: Preparation of arylsulfurchlorotetrafluorides (2).
Cl2 (excess), KF (16 equiv.)
or
1/2 ArS-SAr
ArSH
ArSF4Cl
MeCN, 0° to rt, 20 h
1
2
1'
Entry 1 or 1’ Ar
Product and yield (%)a
1
2
3
4
5
6
Ph
2a, 84
2b, 85
2c, 81
2d, 55
2e, 63
2f, 84
1a
1b
1c
1d’
1e
1f
4-FC6H4
4-ClC6H4
4-t-BuC6H4
2,4-F2C6H3
a Isolated yield.
The fluorine for chlorine exchange in arylsulfurchlorotetrafluorides (2) to
arylsulfurpentafluorides (3) was previously achieved with Lewis acidic fluorides (BF3, SnF4, TiF4 in low
yields, or SbF3/SbF5, CuF2 or ZnF2) in good yields [Error! Bookmark not defined.]. We confirmed that
with alkali metal fluorides (excess spray-dried KF or CsF) in THF under ambient temperature with
ultrasound activation for 1 h, no fluorination of 2a took place. An alternative fluorination reagent to
Lewis acidic fluorides is hydrogen fluoride. Safety hazards associated with anhydrous HF, the necessity
to use special equipment for handling it and cost of disposal of large excess of the reagent prompted us
to think about modification of reaction conditions which would deliver the required minimum amount of
HF in the solution of ArSF4Cl. During the exchange reaction, the side product HCl,which is a more
volatile acid than HF (bp?85 °C HCl; 19.5 °C HF), could react with KHF2 to provide more HF or
partially escape the reaction mixture to drive the reaction to completion.
We initiated investigations in fluorination of 2a using excess 48% aqueous solution of HF and
excess potassium hydrogen fluoride in dichloromethane (Table 2, entry 1). However, no product 3a was
observed. It is known that trifluoroacetic acid (TFA, pKa?0.25) or triflic acid (pKa ~ ?14) react with
KHF2 to form HF. This combination of reagents was used previously for the formation of highly
electrophilic iminium fluorides from enamines [11]. Nevertheless, we did not observe any product 3a
with excess KHF2 and catalytic TFA in dichloromethane (Table 2, entry 2). In acetic acid, hydrolysis to
phenylsulfonylchoride and some phenylsulfonyl fluoride took place (Table 2, entry 3). Application of
strong methanesulfonic acid (pKa?2.6) as the solvent in combination with KHF2 also did not give any
Page 3 of 13

expected product. With even stronger triflic acid, however, small amount of PhSF5 formed in addition to
products of hydrolysis and diphenylsulfone. Similar result was observed using conc. sulfuric acid
(pKa?3). The key to success turned out to be the use of TFA as a solvent. With a two-fold excess of
KHF2, full conversion of 2a to 3a was observed (entry 7). The amount of KHF2 could be reduced down
to 0.6 equivalents (providing 1.2 equivalents of HF in the reaction with TFA) albeit in longer reaction
time. The amount of TFA is critical; under essentially solvent free conditions the reaction mixture
solidified and only low yield of 3a was isolated (entry 11). Application of optimized conditions on
multi-gram scale ? 0.6 equiv. of KHF2 (preferably added in two portions to control the amount of HF
and to release the formed HCl) and 1M solution of 2a in TFA ? provided high isolated yield of 3a (entry
12). All reactions in Table 2 were conducted in a closed fluoropolymer flask under ambient temperature.
Table 2: Optimization of fluorination of phenylsulfurchlorotetrafluride (2a) to phenylsulfurpentafluoride
(3a).
KHF2, additive
PhSF4Cl
2a
PhSF5
rt
3a
Entry
KHF2 (equiv.)
Solvent (mL)
Time Products
(h)
Yields
(%)a
2a
(mmol) + additive
(equiv.)
1
2
3
0.7
0.6
2.8
13 + 48% HF (11) CH2Cl2 (3.5)
16
16
0
0
3a
5 + TFA (0.5)
2 + TFA (2)
CH2Cl2 (2)
AcOH (4.7)
3a
3.5
0
3a
PhSO2Cl
PhSO2F
3a
91
9
4
5
2.2
1.8
1
1
MeSO3H (2.2)
CF3SO3H
(2.25)
1
0
1.5
5
3a
PhSO2Cl
PhSO2F
PhSO2Ph
15
14
9
Page 4 of 13

6
2
2
H2SO4 (3)
0.5
14
44
3a
PhSO2Cl
PhSO2F
PhSO2Ph
3a
36
6
7
6
2
2b
TFA (6)
TFA (2)
TFA (2)
TFA (2)
?
4
1.5
1
100 (59)
100
65
8
1
3a
9
2
0.6
3a
10
11
12
2
0.6
68
16
20
100
(8)
3a
30
19
1 + TFA (1)
0.6b
3a
TFA (19)
3a
(82)
a Determined by GCMS, in brackets isolated yields.
b KHF2 was added in two portions every 15 min.
Our fluorination protocol was applied to substituted phenylsulfurchlorotetrafluorides (2) (Table
3). Compounds 2a-d (entries 1?4) participated in the reaction effectively while 2e showed some
resistance towards fluorination. Excess of potassium hydrogenfluoride and elevated temperature had to
be used; however, under these conditions, considerable hydrolysis to phenylsulfonyl chloride and
fluoride took place and moderate yield of 3e was obtained (entry 5). The 4-
(propylcyclohexyl)benzenesulfurpentafluoride (3f) which was previously synthesized in three steps
from 4-(pentafluorosulfanyl)aniline in overall 6.3% yield and investigated as a novel ionic liquid
material [12] was prepared in good yield from 2f using excess KHF2.
Table 3: Fluorination of arylsulfurchlorotetrafluorides (2) to arylsulfurpentafluorides (3).
KHF2
ArSF4Cl
ArSF5
TFA
3
2
Entry 2 (mmol) Ar
KHF2 TFA Temp Time Product
(equiv.) (mL)
(°)
rt
(h)
20
18
12
12
12
18
and yield (%)a
1
2
3
4
5
6
2a, 19
2b, 14
2c, 33
2d, 19
2e, 3.8
2f, 1.9
Ph
0.6b
0.6b
0.66c
0.66c
3d
19
14
3a, 82
4-FC6H4
rt
3b, 69
4-ClC6H4
4-t-BuC6H4
2,4-F2C6H3
30
rt
3c, 75
25
rt
3d, 54
12.7
9
50
rt
3e, 34
3d
3f, 79
7
2f, 6.3
3d
21
rt
18
3f, 71
a Isolated yield.
Page 5 of 13

b KHF2 was added in two portions every 15 min.
c KHF2 was added in two portions every 30 min.
d KHF2 (1 equiv.) was added followed by 2 equiv. after 1 h.
The methodology uses very inexpensive fluorination reagent (KHF2) and even sub-stochiometric
amounts are sufficient for full conversion of certain substrates. The most expensive constituent is the
solvent (TFA) and on multi-gram laboratory and larger scales it might be favorable to recover and reuse
it. A brief study on the recovery of TFA by distillation under normal pressure (in glass apparatus) and its
reuse in the synthesis of 3f showed that the cost of the process and the amount of corrosive waste can be
further reduced (Table 4).
Table 4: Recovery and reuse of trifluoroacetic acid in the synthesis of 3f.
SF4Cl
2f
KHF2 (3 equiv.)
TFA (0.3 M), rt, 18 h
SF5
3f
Entry 2f (mmol) 3f, yield (%)a
1
6.3
2.2
1.7
71
63
70
2b
3b
a Isolated yield.
b Using recovered TFA by distillation from reaction in entry 1.
3. Conclusion
In conclusion, we have described an improved methodology for the fluorination of
arylsulfurchlorotetrafluorides to arylsulfurpentafluorides under mild conditions based on a controlled
release of anhydrous hydrogen fluoride by the reaction of potassium hydrogenfluoride in trifluoroacetic
acid. The process is safe, operationally simple, atom-economic, and high yielding for most tested
substrates.
4. Experimental part
Page 6 of 13

NMR spectra were recorded in CDCl3 at ambient temperature. Chemical shifts (δ) are reported in
ppm relative to Me4Si (0 ppm for 1H NMR), residual CHCl3 (7.26 ppm for 1H NMR), CDCl3 (77.0 ppm
for 13C NMR), and internal CFCl3 (0 ppm for 19F NMR). GCMS spectra were recorded using
quadrupole mass selective electron impact (EI) detector (70 eV). High resolution mass spectra (HRMS)
were recorded on an Agilent 7890A gas chromatograph coupled with a Waters GCT Premier orthogonal
acceleration time-of-flight detector using chemical (CI) ionization. Elemental analyses were performed
using an automatic PE 2400 Series II CHNS/O analyzer. Acetonitrile was dried by distillation from
CaH2 and spray-dried potassium fluoride was dried by heating in vacuofor several hours.
4.1. General procedure for the preparation of compounds 2
Note: The synthesis, distillation or crystallization of compounds 2 was performed in ordinary
borosilicate glassware; however, purified compounds 2 were stored in fluoropolymer containers.To a
solution of 1a-f (21?89 mmol) in dry acetonitrile (7.5-32 mL) spray-dried KF (16 equiv.) was added.
The mixture was cooled with an ice bath and chlorine was introduced into the solution. After several
hours the temperature of the reaction mixture was allowed to reach room temperature and the color of
the mixture changed from yellow to white. After 8 h of passing chlorine the mixture was yellow again.
At this point the chloride bubbling was stopped and the mixture was stirred for another 12 h. The solid
was removed by filtration, washed with hexane, solvent was removed under reduced pressure, and the
product was distilled under reduced pressure (2a-c and 2e), recrystallized form hexane (2d), or used
without further purification (2f), and stored in a fluoropolymer container at 2?8 °C.
4.1.1. Phenylsulfurchlorotetrafluoride (2a)[Error! Bookmark not defined.]
Pale yellow liquid (84% yield, 29.9 g from 17.6 g of 1a).1H NMR (400 MHz) δH 7.75?7.72 (m,
2H), 7.49?7.42 (m, 3H); 19F NMR (376 MHz) δF 137.3 (s).
4.1.2. 4-Fluorophenylsulfur chlorotetrafluoride (2b)[Error! Bookmark not defined.]
Pale yellow liquid (85% yield, 14.87 g from 9.27 g of 1b).1H NMR (400 MHz) δH 7.74 (m, 2H),
7.11 (m, 2H); 19F NMR (376 MHz) δF 138.3 (s, 4F), ?107.0 (s, 1F).
4.1.3. 4-Chlorophenylsulfur chlorotetrafluoride (2c)[Error! Bookmark not defined.]
Pale yellow liquid (81% yield, 14.31 g from 10.0 g of 1c).1H NMR (400 MHz) δH 7.67 (dm, 2H,
J = 9.2 Hz), 7.42 (d, 2H, J = 9.2 Hz); 19F NMR (376 MHz) δF 137.4 (s).
4.1.4. 4-(tert-Butyl)phenylsulfurchlorotetrafluoride (2d)[Error! Bookmark not defined.]
Blue solid (55% yield, 13.62 g from 14.84 g of 1d’). 1H NMR (400 MHz) δH 7.65 (dm, 2H, J =
8.7 Hz), 7.43 (d, 2H, J = 8.7 Hz), 1.32 (s, 9H); 19F NMR (376 MHz) δF 138.3 (s).
4.1.5. 2,4-Difluorophenylsulfur chlorotetrafluoride (2e)
Pale yellow liquid (63% yield, 14.0 g from 12.6 g of 1e). 1H NMR (400 MHz) δH 7.78?7.70 (m,
1H), 6.97?6.87 (m, 2H); 19F NMR (376 MHz) δF 141.4 (m, 4F), ?102.1 to ?102.5 (m, 1F), ?102.5 to
13
?102.7 (m, 1F); C NMR (100 MHz)δC164.4 (dd, J = 258.8, 12.5 Hz), 156.8 (dd, J = 263.6, 12.5 Hz),
137.8 (quintdd, J = 11.5, 4.2 Hz), 130.0 (m), 111.4 (d, J = 22.0 Hz), 105.7 (t, J = 26.8 Hz); Anal. Calcd
for C6H3ClF6S: C, 28.08; H, 1.18. Found: C, 28.17; H, 1.35.
Page 7 of 13

4.1.6. 4-(4-Propylcyclohexyl)phenylsulfurchlorotetrafluoride (2f)
Colorless viscous oil (84% yield, 12.41 g from 10.0 g of 1f).1H NMR (400 MHz) δH7.64 (d, 2H,
J = 8.2 Hz), 7.26 (d, 2H, J = 8.2 Hz), 2.52 (tm, 1H, J = 11.9 Hz), 1.88 (d, 4H, J = 11.0 Hz), 1.51?1.19
(m, 7H), 1.11?1.01 (m, 2H), 0.91 (t, 3H, J = 7.3 Hz); 19F NMR (376 MHz) δF 138.4 (s); 13C NMR (100
MHz) δC 153.3 (quint, J = 17.3 Hz), 152.0, 127.1, 125.7, 44.4, 39.7, 37.1, 34.0, 33.4, 20.1, 14.5; Anal.
Calcd for C15H21ClF4S: C, 52.24; H, 6.15. Found: C, 52.43; H, 6.28.
4.2. General procedure for the preparation of compounds 3
To a stirred solution of 2a?f (1.9?33 mmol, 0.21?1.1 M in TFA) in a fluoropolymer screw-cap
flask, KHF2 was added (0.6 equiv. in two portions every 15 min for 2a and 2b; 0.66 equiv. in two
portions every 30 min for 2c and 2d; 1 equiv. followed by 2 equiv. after 1 h for 2e and 2f). The reaction
mixture was stirred at room temperature (or at 50 °C for 2e) for 12?20 h, and then poured into water.
Extraction into dichloromethane, drying (Na2SO4), and solvent removal provided the crude product
which was purified by chromatography on silica gel using hexane or pentane as eluent giving pure 3.
4.2.1. Phenylsulfurpentafluoride (3a)[Error! Bookmark not defined.]
1
Colorless liquid (82% yield, 3.18 g, from 4.19 g of 2a). H NMR (400 MHz) δH 7.78?7.74 (m,
2H), 7.53?7.44 (m, 3H); 19F NMR (376 MHz) δF 85.5?83.8 (m, 1F), 62.7 (d, 4F, J = 150.3 Hz).
4.2.2. 4-Fluorophenylsulfur pentafluoride (3b)[Error! Bookmark not defined.]
1
Colorless liquid (69% yield, 2.14 g, from 3.34 g of 2b). H NMR (400 MHz) δH 7.76 (m, 2H),
7.13 (t, 2H, J = 8.4 Hz); 19F NMR (376 MHz) δF 85.1?83.5 (m, 1F), 63.8 (d, 4F, J = 150.3 Hz), ?107.1
(m).
4.2.3. 4-Chlorophenylsulfur pentafluoride (3c)[Error! Bookmark not defined.]
Colorless liquid (75% yield, 5.91 g, from 8.42 g of 2c). 1H NMR (400 MHz) δH 7.69 (dm, 2H, J
= 8.8 Hz), 7.43 (d, 2H,J = 8.8 Hz); 19F NMR (376 MHz) δF 84.5?82.9 (m, 1F), 63.3 (d, 4F, J = 150.3
Hz).
4.2.4. 4-(tert-Butyl)phenylsulfurpentafluoride (3d)
Colorless liquid (54% yield, 2.67 g, from 5.26 g of 2d). 1H NMR (400 MHz) δH 7.70 (dm, 2H, J
= 8.7 Hz), 7.48 (dm, 2H, J = 8.7 Hz), 1.34 (s, 9H); 19F NMR (376 MHz) δF 86.3?84.7 (m, 1F), 63.3 (d,
4F, J = 150.3 Hz).13C NMR (100 MHz) δC 155.1, 151.5 (quint, J = 16.3 Hz), 125.7, 35.0, 31.1; HRMS
(CI) m/zcalcd for C10H13F5S [M]+ 260.0658, found 260.0650.
4.2.5. 2,4-Difluorophenylsulfur pentafluoride (3e)
Colorless liquid (34% yield, 319 mg, from 990 mg of 2e). 1H NMR (400 MHz) δH 7.77 (ddd, 1H,
J = 9.2, 7.8, 5.7 Hz), 7.01?6.97 (m, 1H), 6.97?6.93 (m, 1H); 19F NMR (376 MHz) δF 81.9?80.3 (m, 1F),
68.6 (dd, 4F, J = 151.4, 25.3 Hz),?102.8 to ?102.9 (m, 1F), ?102.9 to ?103.2 (m, 1F); 13C NMR (100
MHz) δC 164.4 (dd, J = 244.5, 13.6 Hz), 157.1 (ddquint, J = 262.5, 11.7, 1.6 Hz), 136.5 (quintdd, J =
15.9, 4.5, 1.2 Hz), 130.2 (m), 111.6 (dd, J = 22.5, 3.7 Hz), 105.8 (t, J = 26.5 Hz). HRMS (CI) m/zcalcd
for C6H3F7S [M]+ 239.9844, found 239.9842.
4.2.6. 4-(4-Propylcyclohexyl)phenylsulfurpentafluoride (3f)[Error! Bookmark not defined.]
Page 8 of 13

Colorless liquid (79% yield, 493 mg, from 655 mg of 2f). 1H NMR (400 MHz) δH 7.64 (dm, 2H,
J = 8.7 Hz), 7.26 (dm, 2H, J = 8.7 Hz), 2.51 (t, 1H, J = 12.3 Hz), 1.87 (m, 4H), 1.48?1.16 (m, 7H),
1.10?0.98 (m, 2H), 0.89 (t, 3H, J = 7.3 Hz); 19F NMR (376 MHz) δF 86.4?84.8 (m, 1F), 63.0 (d, 4F, J =
150.3 Hz).
4.3.
Recovery and reuse of TFA in the synthesis of 3f
KHF2 (492 mg, 6.3 mmol) was added to a solution of 2f (2.17 g, 6.3 mmol) in TFA (21 mL) in a
fluoropolymer flask. The mixture was stirred at room temperature and after 1 h, KHF2 (984 mg, 12.6
mmol) was added. The mixture was stirred for further 17 h and then transferred to a glass round bottom
flask. The solvent was distilled under normal pressure (90 °C bath temperature). Water was added to the
residue and the product was worked-up as described in section 4.2. giving 3f (71% yield, 1.47 g). To a
solution of 2f (0.76 g, 2.2 mmol) in recovered TFA (7.4 mL), KHF2 (172 mg, 2.2 mmol) was added. The
mixture was stirred at room temperature for 1 h followed by addition of KHF2 (343 mg, 4.4 mmol). The
mixture was stirred for further 17 h, followed by addition of water and work-up as described in section
4.2. giving 3f (63% yield, 455 mg). To a solution of 2f (0.59 g, 1.7 mmol) in recovered TFA (5.8 mL),
KHF2 (134 mg, 1.7 mmol) was added. The mixture was stirred at room temperature for 1 h followed by
addition of KHF2 (268 mg, 3.4 mmol). The mixture was stirred for further 17 h, followed by addition of
water and work-up as described in section 4.2. giving 3f (70% yield, 391 mg).
Acknowledgments
The authors wish to thank Deutsche Forschungsgemeinschaft for financial support through the
Initiation and Enhancement of International Cooperation Grant number RO 362/54-1. Support from the
Academy of Sciences of the Czech Republic (RVO: 61388963) is also acknowledged.
References[1]
(a) S. Altomonte, M. Zanda, J. FluorineChem. 143 (2012)57–93;
[2] B. Stump, C. Eberle, W.B.Schweizer, M. Kaiser, R. Brun, R.L.Krauth-Siegel, D. Lentz, F.
Diederich, ChemBioChem 10 (2009) 79?83.
[3] (a) P. Kirsch, ModernFluoroorganicChemistry, Wiley-VCH, Weinheim, 2004, pp.
[4] (a) Y.-D.Yang, X. Lu, E. Tokunaga, N. Shibata, JournalofFluorineChem. 143 (2012) 204?209;
[5] (a) R.D.Bowden, M.P.Greenhall, J.S. Moilliet, J. Thomson, WO 9705106 (1997);
[6] J.I.Darragh, D.W.A.Sharp, J. Chem. Soc. Chem. Commun. (1969) 864?865.
[7] T. Abe, J.M. Shreeve, J. Fluorine Chem. 3 (1973) 187?196.
[8] X. Ou, G.M. Bernard, A.F.Janzen, Can. J. Chem. 75 (1997) 1878?1884.
[9] T. Umemoto, L.M.Garrick, N.Saito, Beilstein J. Org. Chem. 8 (2012) 461–471 and patents by T.
Umemotocitedtherein.
[10] T. Umemoto, R.P.Singh, Y. Xu, N. Saito, J. Am. Chem. Soc. 132 (2010) 18199?18205.
[11] (a) V.V.Levin, A.D. Dilman, P.A Belyakov, M.I. Struchkova, V.A.Tartakovsky, Eur. J. Org.
Chem. (2008) 5226?5230;
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[12] P. Kirsch, M. Bremer, M. Heckmeier, K. Tarumi, Angew. Chem. Int. Ed. 38 (1999) 1989?1992.
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Graphical Abstract - pictogram
SF4Cl
SF5
KHF2, CF3CO2H
25-50 °C
R
R
34-82% yield
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Graphical Abstract – synopsis
An improved method for the fluorination of arylsulfur chlorotetrafluorides to arylsulfur pentafluorides
Katrin Lummer, Maxim V. Ponomaranko, Gerd-Volker Röschenthaler, Matthias Bremer, Petr Beier
School of Engineering and Science, Jacobs University of Bremen, Campus Ring 1, 28759 Bremen, Germany
Merck KGaA, 250 Frankfurterstr., 64271 Darmstadt, Germany
Institute of Organic Chemistry and Biochemistry, Academy of Science of the Czech Republic, Prague, Czech Republic
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Highlights
Fluorination ArSF4Cl to ArSF5 takes place with KHF2 in trifluoroacetic acid.
The solvent (trifluoroacetic acid) could be recovered by distillation and reused.
The reaction is performed under mild conditions.
The reaction does not require handling anhydrous HF
2
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