Arylsulfur chlorotetrafluorides as useful fluorinating agents: Deoxo- and dethioxo-fluorinations

Article abstract of DOI:10.1016/j.jfluchem.2012.03.008

Usage of arylsulfur chlorotetrafluorides 1 as versatile deoxo- and dethioxo-fluorinating agents is described. There have been developed two convenient methods for the in situ preparation of reactive arylsulfur trifluorides 2 from 1. The one is reduction of 1 with a reducer such as pyridine to 2, and the other is disproportionation of 1 with a diaryl disulfide to 2 with evolution of chlorine gas. The latter method is a convenient way to get neat 2 from 1. The in situ prepared 2 fluorinates many kinds of substrates such as alcohols, aldehydes, ketones, diketones, and carboxylic acids to give the corresponding CF, CF₂, CF₂CF₂, and CF ₃ compounds in high yields. 2 also fluorinates various sulfur compounds including CS groups to give CF₂, OCF₂, CF ₃, and OCF₃ compounds in high yields. Reactions of 2 with diols or bis(trimethylsilyl) derivatives of diols or amino alcohols provided the corresponding deoxofluoro-arylsulfinylation products in high yields. In addition, it has been found that chlorotetrafluorides 1 directly and effectively react with the sulfur compounds to give the corresponding fluoro compounds in high yields. Since they are the intermediates for the production of industrially useful arylsulfur pentafluorides, arylsulfur chlorotetrafluorides 1, in particular, phenylsulfur chlorotetrafluoride (1a) are expected to find use as inexpensive and versatile deoxo- and dethioxo-fluorinating agents for the preparation of many organofluoro compounds.

Full text of DOI:10.1016/j.jfluchem.2012.03.008

Journal of Fluorine Chemistry 140 (2012) 17–27
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Arylsulfur chlorotetrafluorides as useful fluorinating agents: Deoxo- and
dethioxo-fluorinations§
1
*
Teruo Umemoto , Rajendra P. Singh
IM&T Research, Inc.2, 6860 N. Broadway, Suite B, Denver, CO 80221, USA
A R T I C L E I N F O
A B S T R A C T
Article history:
Usage of arylsulfur chlorotetrafluorides 1 as versatile deoxo- and dethioxo-fluorinating agents is
described. There have been developed two convenient methods for the in situ preparation of reactive
arylsulfur trifluorides 2 from 1. The one is reduction of 1 with a reducer such as pyridine to 2, and the
other is disproportionation of 1 with a diaryl disulfide to 2 with evolution of chlorine gas. The latter
method is a convenient way to get neat 2 from 1. The in situ prepared 2 fluorinates many kinds of
substrates such as alcohols, aldehydes, ketones, diketones, and carboxylic acids to give the
corresponding CF, CF2, CF2CF2, and CF3 compounds in high yields. 2 also fluorinates various sulfur
compounds including C55S groups to give CF2, OCF2, CF3, and OCF3 compounds in high yields. Reactions of
2 with diols or bis(trimethylsilyl) derivatives of diols or amino alcohols provided the corresponding
deoxofluoro-arylsulfinylation products in high yields. In addition, it has been found that chlorotetra-
fluorides 1 directly and effectively react with the sulfur compounds to give the corresponding fluoro
compounds in high yields. Since they are the intermediates for the production of industrially useful
arylsulfur pentafluorides, arylsulfur chlorotetrafluorides 1, in particular, phenylsulfur chlorotetra-
fluoride (1a) are expected to find use as inexpensive and versatile deoxo- and dethioxo-fluorinating
agents for the preparation of many organofluoro compounds.
Received 3 January 2012
Received in revised form 2 March 2012
Accepted 7 March 2012
Available online 5 April 2012
Keywords:
Arylsulfur chloroterafluoride
Arylsulfur trifluoride
Fluorinating agent
Deoxofluorination
Dethioxofluorination
Disproportionation
ß 2012 Elsevier B.V. All rights reserved.
1. Introduction
(m-methylbenzyl)amine [9] have been developed. However, these
reagents have significant drawbacks such as toxic gas, explosive
nature, or limited scope due to narrow reactivity. In response to
these, the authors have recently reported reactive and crystalline
Fluorine has the highest electronegativity and the smallest
atomic radius after the hydrogen atom, and the carbon–fluorine
bond is one of the strongest. Accordingly, introducing fluorine to an
organic molecule brings about remarkable changes in the original
properties of the molecule. Therefore, fluorine has been attracting
many researchers particularly in medicinal, agrochemical, and
new-material chemistries to seek more novel chemicals in their
fields [1]. Among fluorination strategies, deoxo- and dethioxo-
fluorination methods have been chosen as among the most
effective. Therefore, many deoxo- or dethioxo-fluorinating agents
have been developed. Gaseous sulfur tetrafluoride (SF4) [2], liquid
dialkylaminosulfur trifluorides such as Et2NSF3 (DAST) [3] and
4-tert-butyl-2,6-dimethylphenylsulfur
trifluoride
(Fluolead)
which has high thermal stability, ease of handling due to its
relative moisture and water insensitivity, and wide applications
including conversions of COOH and OC(S)SMe to CF3 and OCF3, and
new deoxofluoro-arylsulfinylation [10]. Dialkylamidodifluorosul-
finium tetrafluoroborates such as XtalFluor-E and -M have also
been developed as improved version of DAST recently [11].
We have recently discovered the first practical production
method for arylsulfur pentafluorides (ArSF5) [12], which have long
been desired in academic and industrial fields because ArSF5 has
been considered to be ‘‘super-trifluoromethyl’’ arenes as the SF5
group has the peculiarity of additional fluorine beyond the
trifluoromethyl (CF3) group [13]. The trifluoromethyl arenes have
already grown up into a significant large chemistry and industry
[1,14] since their production method was developed in 1930s–
1940s [15]. The unusual properties of SF5 group have been
attracting many chemists in medicinal, agrochemical, and new
material chemistries [13,16,17]. The practical production method
for the ArSF5 developed by us [12] consists of two steps, (step 1)
treatment of a diaryl disulfide or aryl thiol with chlorine and
potassium fluoride [18], and (step 2) treatment of the resulting
(MeOCH2CH2)2NSF3 (Deoxo-Fluor) [3c,4], a,a-difluoroalkylamines
such as CHFClCF2NEt2 (Yarovenko reagent) [5], CF3CHFCF2NEt2
(Ishikawa reagent) [6], CHF2CF2NMe2 [7], 2,2-difluoro-1,3-
dimethylimidazolidine (DFI) [8], and N,N-diethyl-a,a-difluoro-
§
This was presented at 242nd ACS National Meeting at Denver, Colorado, in
August 28–September 1, 2011.
* Corresponding author. Tel.: +1 303 412 5650.
E-mail address: teruoumemoto@comcast.net (T. Umemoto).
1
Current address: Boulder Ionics Corporation, Colorado, USA.
2
Currently at: Ube America Inc.
0022-1139/$ – see front matter ß 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2012.03.008

18
T. Umemoto, R.P. Singh / Journal of Fluorine Chemistry 140 (2012) 17–27
-
a reducer
-
F
F
S
F
ArSF4Cl
ArSF3
:N
F
+
+
FCl:N
1
Ph
Cl
Ph
2
S
.
.
F
-
-
F
Scheme 1. Reduction of ArSF4Cl 1 to ArSF3 2.
F
3
2a
1a (trans isomer)
arylsulfur chlorotetrafluorides (ArSF4Cl) with ZnF2, HF, or Sb(III/V)
fluorides. By means of this, the ArSF5 can be produced in a
commercially practical scale. This means that the intermediate
ArSF4Cl will be produced in a large amount and at low cost in
industry. This article describes the usefulness of the intermediate
chemicals, ArSF4Cl, as new, inexpensive, and versatile deoxo- and
dethioxo-fluorinating agents.
Scheme 2. Formation of 2a and possible pyridine ClF complex 3 from 1a and
pyridine.
slow without the ammonium iodide. The organics used (runs 2–
4,6,7 Table 1) provided a quantitative yield of benzoyl fluoride,
indicating that 2a was quantitatively formed from 1a by the
reaction with the organics. Actually, 2a was isolated in 88% yield by
treatment of 1a with an equimolar amount of pyridine in
dichloromethane at room temperature for 1.5 h, followed by
careful distillation at reduced pressure in dry atmosphere.
With anthracene (run 4, Table 1), we observed the formation of
9-chloro- and 9,10-dichloroanthracenes by GC–Mass of the
reaction mixture, which resulted from the electrophilic chlorina-
tion of anthracene. This indicates that 1a reacted with anthracene
(C-nucleophile) to give the chlorinated anthracenes and 2a, which
reacted with benzoic acid to give benzoyl fluoride.
With pyridine which is N-nucleophile (run 2, Table 1), it is most
likely that 1a reacted with pyridine to give PyꢀClF complex 3
(Py = pyridine) along with 2a as shown in Scheme 2. It is well known
that interhalogen compounds form complexes with N-nucleophiles
such as pyridine [19]. Recent theoretical studies have revealed the
structure and nature of the PyꢀClF as a stable complex [20].
The reaction of 1a with an equimolar amount of pyridine in
dichloromethane without benzoic acid was traced by 19F NMR. The
NMR measured after 1 h showed two peaks of 2:1 integral ratio at
57.2 and ꢁ39.6 ppm and a broad peak at ꢁ168 ppm. The former
two peaks were assigned to 2a. The latter might be assigned to
complex 3. Benzoic acid was then added to the reaction solution
and the 19F NMR measured after 30 min showed that benzoyl
fluoride was formed and that the broad peak at ꢁ168 ppm
remained intact. Although we did not examine the complex 3
more, it may thus be regarded that extremely reactive ClF [21] is
deactivated by the N-nucleophile.
2. Results and discussion
: R1-5=H
1a
1b
R2
R4
R1
R5
: R3=CH , R1,2,4,5=H
3
: R3=tert-Bu, R1,2,4,5=H
R3
SF4Cl
1c
: R3=F, R1,2,4,5=H
1d
: R3=Cl, R1,2,4,5=H
1e
1f: R2=Br, R1,3-5=H
1g: R3=Br, R1,2,4,5=H
1h: R3=NO2, R1,2,4,5=H
1
2.1. Reduction of arylsulfur chlorotetrafluoride 1 to arylsulfur
trifluoride 2
Phenylsulfur chlorotetrafluoride (1a) did not react with n-
dodecanol, benzaldehyde, or benzoic acid in dichloromethane at
room temperature for 24 h. Thus, we investigated the possibility of
the in situ generation of reactive arylsulfur(IV) trifluorides 2 from
arylsulfur(VI) chlorotetrafluorides 1 by reduction with a reducing
compound (Scheme 1).
As phenylsulfur trifluoride (2a) which is extremely moisture-
sensitive readily reacted with a carboxylic acid to produce a
carbonyl fluoride quantitatively, we sought a suitable reducer by
allowing 1a to react with a reducer in the presence of benzoic acid
in dichloromethane as seen in Table 1. We found that 1a was
readily reduced to 2a under very mild conditions with various
kinds of organic compounds or a combination of metals and a
tetrabutylammonium iodide. The reaction of the metals was very
2.2. Fluorination of various substrates with arylsulfur trifluoride 2 in
situ prepared from arylsulfur chlorotetrafluoride 1 and pyridine
Next, we examined the fluorinations of various substrates using
the arylsulfur trifluorides 2 in situ prepared from 1 with a reducer.
Table 1
Reactions of PhSF4Cl (1a) with reducers in the presence of benzoic acid.
a reducing compound
PhSF Cl (
)
1a
+
PhCOOH
PhCOF
4
Runa
1a (mmol)b
Reducing compound (mmol)c
Reaction conditionsd
Yield (%) of PhCOFe
1
2
3
4
5
6
7
8
9
1.0
1.0
1.1
1.0
1.0
1.0
1.0
2.53
1.75
Non
DCM (2 mL), rt, 1.5 h
DCM (2 mL), rt, 1.5 h
DCM (2 mL), rt, 6 h
DCM (2 mL), rt, 5 h
DCM (2 mL), rt, 5 h
DCM (2 mL), rt, 1.5 h
DCM (2 mL), rt, 1.5 h
THF (4 mL), rt, 3 h
THF (4 mL), rt, 2 h
No reactionf
quant.
quant.
quant.
95
Pyridine (1.0)
Et3N(HF)3 (1.1)
Anthracene (1.0)
Aniline (1.0)
2,3-Dimethyl-2-butene (1.0)
PhSPh (1.0)
quant.
quant.
93 (82)
84
Mg (2.52), TBAI (cat)
Sn (1.75), TBAI (cat)
a
An equimolar amount of benzoic acid to 1a was used except for run 3 in which 0.91 equimolar amounts of benzoic acid to 1a was used.
The amounts (mmol) of 1a used.
b
c
d
e
f
The numbers in parentheses are amounts (mmol) of reducing compounds used. cat = catalytic amount.
DCM = dichloromethane. rt = room temperature. The amounts (mL) of the solvents used are shown in parentheses.
Yields were determined by 19F NMR and calculated based on the amount of benzoic acid used. quant. = quantitative yield. The number in parentheses is an isolated yield.
A small amount of PhCOF was detected, which was formed by the reaction of PhCOOH with a small amount of PhSF3 (2a) containing as an impurity in 1a.

T. Umemoto, R.P. Singh / Journal of Fluorine Chemistry 140 (2012) 17–27
19
Table 2
Fluorinations with ArSF3 in situ prepared from ArSF4Cl and pyridine.
a substrate
pyridine
Fluoro product
ArSF4Cl
1
ArSF3
2
in CH2Cl2
rt, 1.5 h
reaction conditions
Runa
1
1 (mmol)b
Substrate (mmol)c
Reaction conditionsd
DCM (2 mL), rt, 0.5 h
Fluoro product
PhCOF
Yield (%)e
1a
PhCOOH
(1.8)
quant.f
(2.22)
1a
2
n-C12H25OH
(2.6)
DCM (2 mL), rt, 20 h
HF–Py (0.9 mL)
n-C12H25F
86f
(3.84)
1a
3
PhCHO
DCM (2 mL), rt, 2 h
HF–Py (0.7 mL)
PhCF2H
87f
(3.19)
1a
(1.2)
4
PhCOCH3
(1.32)
DCM (3 mL), rt, 20 h
HF–Py (0.8 mL)
PhCF2CH3
75f
(3.30)
1a
5
n-C10H21COCH3
(1.32)
DCM (2 mL), rt, 20 h
HF–Py (0.8 mL)
n-C10H21CF2CH3
1,1-diF-cyclohexane
PhCF2CF2Phh
86f
(4.2)
1a
6
Cyclohexanone
(1.4)
DCM (2 mL), rt, 2 h
HF–Py (0.8 mL)
94f
(3.5)
1a
7
PhCOCOPh
(1.5)
DCM (3 mL), rt, 25 h
HF–Py (1.15 mL)
DCM (6 mL), rt, 2 h
95f
(6.0)
1a
8
(Me3SiOCH2)2
(2.0)
FCH2CH2OS(O)Ph (4)
80g
72g
76g
(2.04)
1b
9
(Me3SiOCH2)2
(5.2)
DCM (6 mL), rt, 2 h
DCM (6 mL), rt, 2 h
FCH2CH2OS(O)Ar (5)
(Ar = 4-tolyl)
(5.27)
1e
10
(Me3SiOCH2)2
(4.3)
FCH2CH2OS(O)Ar (6)
(Ar = 4-chlorophenyl)
(4.44)
a
For runs 1–7, pyridine was used in an equimolar amount to ArSF4Cl. For runs 8–10, pyridine was used in two equimolar amounts to ArSF4Cl.
b
c
d
e
f
The numbers in parentheses are amounts (mmol) of ArSF4Cl used.
The numbers in parentheses are the amounts (mmol) of substrates used.
DCM = dichloromethane. HF–Py = 70 wt% HF–pyridine.
Yields were calculated based on substrates. quant. = quantitative yield.
Determined by 19F NMR.
g
h
Isolated yields.
See Ref. [2].
Among the reducers, pyridine was most suitable for actual
fluoride rearrangement [10a], as shown in Scheme 3. As the Cl+
cation may have two-coordination with N-nucleophile [22], the
latter 7 might be formed by the action of two molecules of pyridine
to 1 or one molecule of pyridine to 3.
fluorination reactions from the viewpoint of its availability and
the easy removal of the reducer-derived product, probably PyꢀClF,
in the post-treatment washing with water. After 1 was treated with
an equivalent amount of pyridine in dichloromethane at room
temperature for 1.5 h, a substrate was added into the dichlor-
omethane solution with an additive if necessary. As shown in Table
2, various substrates were fluorinated in high yields in this manner.
Alcohols, aldehydes, ketones, and diketones were fluorinated with
addition of a small amount of 70 wt% HF–pyridine to give the
corresponding fluorinated compounds in high yields (runs 2–7,
Table 2).
2.3. Preparation of neat arylsulfur trifluoride 2 by disproportionation
of arylsulfur chlorotetrafluoride 1 with 1/6 diaryl disulfide
The in situ preparation mentioned above provides a mixture of
ArSF3 2 and the other product which results from the reducer. The
separation and purification of 2 from the reducer-derived product
is another problem because 2 is extremely moisture-sensitive. Our
studies on the reactivity of 2 have revealed that neat 2 has a strong
fluorination capability including direct conversion of a COOH to a
CF3 group. Therefore, if neat 2 is in situ prepared in a direct manner
from ArSF4Cl 1, its applicability would be greatly expanded. Thus,
according to the following equation (Eq. (1)), we attempted a
disproportionation reaction to get neat 2. As the co-product Cl2 is
gaseous, it can easily be removed from liquid 2.
1,2-Bis(trimethylsiloxy)ethane was readily fluorinated without
any additive to give 2-fluoroethyl arylsulfinates 4–6 in high yields
(runs 8–10), in which ArSF3 was in situ generated from ArSF4Cl
with two equimolar amounts of pyridine. Pure ArSF3 did not react
with the bis(trimethylsiloxy)ethane without a fluoride anion
catalyst. Thus, it is most likely that the bis(trimethylsiloxy)ethane
reacted with ArSF3 by activation of a fluoride anion from the
d
d
complex PyꢀCl +F ꢁ 3 and/or bis(pyridine)chloronium fluoride 7 to
give products 4–6 through a cyclic intermediate followed by
ArSF4Cl 1 þ 1=6 ArSSAr ! 4=3 ArSF3 2 þ 1=2 Cl2 "
(1)
Me3SiO
O
O
2 Py
O
Me3SiO
F- catalysis
ArSF4Cl
ArSF3
+
Ar
2
S
Ar S OCH2CH2F
.
.
4-6
1
F
-
PyCl +F
and/or
3
+
[(Py)2Cl]+F-
2FSiMe3
7
(Py=pyridine)
Scheme 3. Proposed mechanism for the formation of 2-fluoroethyl arylsulfinates 4–6.

20
T. Umemoto, R.P. Singh / Journal of Fluorine Chemistry 140 (2012) 17–27
85 oC, 0.75 h
PhSF4Cl
1a
1/6 (PhS)2
4/3 PhSF3
+
90%
- 1/2 Cl2
2a
95 oC, 0.75 h
- 1/2 Cl2
1/6 (4-tert-Bu-C6H4S)2
+
4-tert-Bu-C6H4SF4Cl
4/3 4-tert-Bu-C6H4SF3
92%
1c
2c
85 oC, 2.3 h
- 1/2 Cl2
4/3 4-Cl-C6H4SF3
2e
89%
C H
4S)2
6
4-Cl-C6H4SF4Cl
+
1/6 (4-Cl-
1e
Scheme 4. Preparation of ArSF3 2 from ArSF4Cl 1 by disproportionation.
Fortunately the expected reaction cleanly took place around
generate neat 2, this disproportionation method has a significant
advantage in that the increased amount (4/3 times mol) of 2 is
obtained. In contrast, the reduction method with a reducer gives an
equimolar amount of 2 to 1.
85 8C to produce ArSF3 2 and chlorine gas. A concentrated solution
of a sixth equimolar amount of diphenyl disulfide in a small
amount of dry dichloromethane was added to neat 1a in a
fluoropolymer reactor heated at 85 8C. The reaction soon occurred
to evolve chlorine gas. The flow of nitrogen served to remove the
chlorine gas and dichloromethane, leaving neat and almost pure 2a
in the reactor.
2.4. Fluorinations with various substrates with neat arylsulfur
trifluoride 2 in situ prepared by disproportionation
As seen in Scheme 4, product 2a was actually isolated after
distillation in 90% yield based on the theoretical amount (4/3 times
mol). 4-tert-Butyl- and 4-chlorophenylsulfur trifluorides 2c and 2e
were also isolated in excellent yields in the same way. The
evolution of chlorine gas was confirmed by passing it through a
solution of stilbene in dichloromethane at ice bath temperature to
give two isomers of 1,2-dichloro-1,2-diphenylethane in 80% yield,
which agreed with an authentic sample produced by reaction of
stilbene with chlorine gas. In addition to this simple process to
The disproportionation method for neat ArSF3 2 was successfully
applied to fluorination reactions of many kinds of substrates as
shown in Table 3. Neat PhSF3 (2a) fluorinated alcohols satisfactorily
in dichloromethane solvent without 70 wt% HF–pyridine (runs 1
and 2)and carbonyl compounds witha catalyticamount ofHFwhich
was generated from the addition of a small amount of ethanol (runs
3 and 4). Aromatic and aliphatic carboxyl groups were converted to
the corresponding CF3 groups in excellent yields by heating a
mixture of neat 2a and 70 wt% HF–pyridine at 50 8C (runs 6 and 10).
Table 3
Fluorinations with ArSF3 in situ prepared from ArSF4Cl and 1/6ArSSAr.
1/6 ArSSAr
85 oC, 0.5 h
a substrate
neat ArSF3
Fluoro product
ArSF4Cl
1
reaction conditions
2
Run
1
1 (mmol)a
Substrate (mmol)b
Reaction conditionsc
DCM (3 mL), rt, 24 h
Fluoro product
n-C12H25
Yield (%)d
80
1a
n-C12H25OH
(2.63)
F
(3.95)
1a
2
n-C10H21CH(OH)CH3
(1.39)
DCM (3 mL), rt, 24 h
n-C10H21CHFCH3
PhCF2H
71
(2.1)
1a
3
PhCHO
DCM (2 mL), rt, 2 h
EtOH (0.04 mL)
90
(2.72)
1a
(1.08)
4
Cyclohexanone
(1.5)
DCM (3 mL), rt, 24 h
EtOH (0.05 mL)
1,1-diF-cyclohexane
PhCOF
80
(3.82)
1a
5
PhCOOH
(1.22)
DCM (3 mL), rt, 2 h
quant.
90
(3.68)
1a
6
PhCOOH
(0.87)
No solvent, 50 8C, 24 h, HF–Py (0.6 mL)
No solvent, 50 8C, 24 h, HF–Py (1.1 mL)
No solvent, 50 8C, 24 h, HF–Py (1.3 mL)
No solvent, 50 8C, 24 h, HF–Py (1.2 mL)
No solvent, 50 8C, 24 h, HF–Py (0.9 mL)
DCM (4 mL), rt, 2 h
PhCF3
(2.63)
1b
7
PhCOOH
(1.54)
PhCF3
77
(4.62)
1e
8
PhCOOH
(1.63)
PhCF3
98
(4.95)
1a
9
PhCOCl
PhCF3
90
(4.65)
1a
(1.55)
10
11
12
13
n-C11H23COOH
(1.30)
n-C11H23CF3
PhCF2H
96
(3.94)
1a
PhCH[–S(CH2)3S–]
(2.25)
99
(3.38)
1a
e
PhC(5S)OCH3
(0.97)
DCM (2 mL), rt, 3 h
PhCF2OCH3
98
(2.43)
1a
f
n-C10H21OC(5S)SCH3
(1.45)
DCM (4 mL), rt, 3 h
n-C10H21OCF3
90
(4.35)
a
The numbers in parentheses are amounts (mmol) of ArSF4Cl used.
The numbers in parentheses are amounts (mmol) of substrates used.
DCM = dichloromethane. EtOH = ethanol. HF–Py = 70 wt% HF–pyridine.
b
c
d
e
f
Yields were calculated based on substrates and determined by 19F NMR. quant. = quantitative yield.
See Ref. [26].
See Ref. [29e].

T. Umemoto, R.P. Singh / Journal of Fluorine Chemistry 140 (2012) 17–27
21
Table 4
Fluorinations of various substrates with PhSF3 (2a).
PhSF3
2a
substrate
+
Fluoro product
reaction conditions
Run
1
2aa (mmol)
Substrate (mmol)b
Reaction conditionsc
Fluoro productd
PhCF3
Yield (%)e
2.7
PhCOOH
No solvent, 100 8C, 2 h (sealed reactor)
90f
(1.08)
2
1.8
PhCOOH
No solvent, 100 8C, 2 h (open reactor)
No solvent, 100 8C, 24 h (open reactor)
No solvent, 100 8C, 2 h (sealed reactor)
No solvent, 100 8C, 2 h (sealed reactor)
No solvent, 100 8C, 2 h (sealed reactor)
DCM (1 mL), rt, 2 h
PhCF3
28f
(0.72)
3
6.4
PhCOOH
PhCF3
49f
(2.1)
4
2.0
PhCOF
PhCF3
ꢂ1f,h
83f
(0.80)
5
1.92
3.19
4.10
2.55
1.59
3.16
2.49
2.98
n-C11H23COOH
(0.77)
n-C11H23CF3
1,3-Ph(CF3)2
PhCF2Ph
n-C7H15CF2OCH3
PhCF3
6
1,3-Ph(COOH)2
(0.70)
93f
7
PhC(5S)Ph
(1.64)
quant.f
80f
i
8
n-C7H15C(5S)OCH3
(1.66)
DCM (3 mL), rt, 20 h
9
PhC(5S)SCH3
(0.31)
No solvent, 70 8C, 22 h (sealed reactor)
No solvent, rt, 24 h
85f
j
10
11
12
2-Py–N(CH3)C(5S)SCH3
(1.26)
2-Py–N(CH3)CF3
98f
HOCH2CH2OH
(2.49)
DCM (5 mL), ꢁ78 8C ! rt, 3 h
FCH2CH2OS(O)Ph (4)
80g
84g
Me3SiOCH2CH2OSiMe3
(2.98)
DCM (4 mL), rt, 2 h, Bu4NF (cat)
4
SiMe3
S(O)Ph
F
Me3SiO
N
13
3.72
3.55
DCM (5 mL), rt, 1 h
DCM (5 mL), rt, 3 h
91g
78g
N
(3.72)
8
OSiMe3
F
k
14
N
N
(3.55)
9
SiMe3
S(O)Ph
a
PhSF3 (2a) which was purified by distillation, was used in these runs. The numbers are amounts (mmol) of PhSF3 used.
The numbers in parentheses are amounts (mmol) of substrates used.
DCM = dichloromethane. cat = catalytic amount.
Py = pyridyl.
b
c
d
e
f
Yields were calculated based on the substrates used. quant. =quantitative yield.
Determined by 19F NMR.
g
h
i
Isolated yields.
95% of PhCOF (a starting material) remained unreacted.
See Ref. [26].
j
Methyl(2-pyridyl)(trifluoromethyl)amine: see Ref. [29c].
Product 9 was assigned a 86:14 mixture of two diastereomers.
k
Neat 4-methyl 2b and 4-chloro 2e generated in situ from 1b and 1e,
The conversion of COOH to CF3 consists of two steps as shown in
Scheme 5. The first reaction readily occurs at room temperature,
giving benzoyl fluoride and HF, and the second reaction requires
elevated temperature. The open reactor at elevated temperature
allowed HF to exit from the reaction solution because of its low
boiling point. Thus, the above results suggested that HF generated
at the first step acts as an important catalyst for the second
fluorination. As shown in run 4, the reaction of benzoyl fluoride
with 2a in which there is no HF did not provide the product, but the
starting material mostly remained unreacted. This clearly demon-
strated that HF is essential for the second fluorination. The sealing
method was thus successfully applied to an alkyl carboxylic acid
and an aryl dicarboxylic acid, and the respective corresponding
trifluoromethyl compounds were obtained in high yields, as seen
in runs 5 and 6, Table 4.
respectively, similarly converted carboxyl groups to CF3 groups in
high yields (runs 7 and 8). A carbonyl chloride was also converted to
a CF3 compound in an excellent yield (run 9). 2a fluorinated various
sulfur compounds in dichloromethane solvent at room temperature
to give the corresponding desulfur fluoro compounds in excellent
yields (runs 11–13). The reaction of 2a with O-alkyl S-methyl
dithiocarbonate proceeded well at room temperature without any
catalyst (run 13), while Fluolead needed SbCl3 as a catalyst for the
smooth reaction [10a].
2.5. Additional examination on reactivity of phenylsulfur trifluoride
(2a)
Table 4 shows the results of our further investigation on the
reactivity of PhSF3 (2a). When a mixture of 2a and benzoic acid was
heated without solvent or additives in a sealed reactor at 100 8C for
2 h, benzotrifluoride was obtained in 90% yield (run 1). However,
when it was conducted in an open reactor, the yield was only 28%
(run 2). The reaction was continued for 24 h, but the yield was still
low (49%, run 3). Thus, the reaction was very slow in the open
reactor for this case.
step 1
step 2
PhCOF
+
HF
PhCF3
PhCOOH
ArSF3
ArSF3
- ArS(O)F
- ArS(O)F
Scheme 5. Stepwise fluorination of carboxylic acids with ArSF3 2.

22
T. Umemoto, R.P. Singh / Journal of Fluorine Chemistry 140 (2012) 17–27
F
PhSF3
OSiMe3
N
S
N
S(O)Ph
N
SiMe3
- 2FSiMe3
O
Ph
F
9
Scheme 6. Proposed mechanism for exclusive formation of product 9.
2a fluorinated thiocarbonyl compounds under mild conditions
All the reported fluorinations of 2-(hydroxymethyl)pyrroli-
dine derivatives were accompanied with the formation of the
ring expansion products, 3-fluoropiperidine derivatives, which
was explained to be formed via an azirinium intermediate [23].
To our knowledge, our reaction with 2a is the first case which
exclusively provided the non-ring expansion product 9. This
to give CF2 compounds in high yields (runs 7 and 8). A C-dithioester
was fluorinated by 2a at 70 8C without solvent to give a CF3
compound in high yield (run 9). A N-dithioester was fluorinated at
room temperature to give a N-CF3 compound in excellent yield
(run 10). 2a reacted with ethylene glycol to give 2-fluoroethyl
benzenesulfinate (4) in high yield (run 11). The reaction of 2a with
1,2-bis(trimethylsiloxy)ethane proceeded in the presence of a
catalytic amount of fluoride anion to give 4 in high yield (run 12).
With bis(trimethylsilyl) derivative of an amino alcohol, the
reaction of 2a readily proceeded without the catalyst to give a
fluoroalkyl benzenesulfinamide derivative 8 in 91% yield (run 13).
Bis(trimethylsilyl) derivative of 2-(hydroxymethyl)pyrrolidine
reacted with 2a to exclusively give 2-fluoromethyl-N-benzene-
sulfinylpyrrolidine (9) in 78% yield (run 14). A 3-fluoropiperidine
derivative was not formed in this reaction. The 19F NMR showed
two triplet-doublet signals corresponding to CH2F at C-2 position
in a 86:14 ratio. We assigned the product 9 as a mixture of two
diastereomers based on two asymmetric centers at C-2 carbon and
the sulfur atom, because our detailed studies have demonstrated
that a mixture of two diastereomers is formed when an arylsulfur
trifluoride reacts with an amino alcohol having an asymmetric
center such as 3-hydroxypyrrolidine [10a].
exclusive formation can clearly be explained by
a cyclic
intermediate [10a] as shown in Scheme 6. Interestingly, Fluolead
did not react with the bis(trimethylsilyl) derivative of 2-
(hydroxymethyl)pyrrolidine under the same reaction conditions,
presumably due to its steric hindrance by the 2,6-dimethyl
groups of Fluolead.
According to the paper reported by Sheppard in 1962 [24], the
fluorination capability of phenylsulfur trifluoride (2a) was poor.
Probably, in addition to the humid climate of the east coast, the
reason was that no solvent or no effective catalyst was used for the
fluorination of aldehydes and ketones and an unsuitable open
reactor probably was used for the fluorination of carboxylic acids
at high temperature. As discussed above, sealing a reactor is a
significant factor to retain HF as a catalyst for the second step
fluorination. Fluorination of alcohols might not be attempted,
probably as it was thought at that time that PhSF3 could not work
well like SF4 [25].
Table 5
Fluorinations of various thiocarbonyl compounds with ArSF4Cl.
Fluoro product
ArSF4Cl
1
C=S compound
+
reaction conditions
Run
1
1 (mmol)a
C5S compound (mmol)b
Reaction conditionsc
Productd
Yield (%)e
99 (90)
1a
n-C10H21OC(5S)SCH3
(2.0)
DCM (3 mL)
rt, 5 h
n-C10H21OCF3
(2.0)
1b
2
n-C10H21OC(5S)SCH3
(2.96)
DCM (3 mL)
rt, 5 h
n-C10H21OCF3
n-C10H21OCF3
n-C10H21OCF3
n-C10H21OCF3
n-C10H21OCF3
n-C10H21OCF3
n-C10H21OCF3
PhCF2Ph
73
(2.96)
1b
3
n-C10H21OC(5S)SCH3
(2.24)
DCM (3 mL)
rt, 4h
quant. (87)
quant. (89)
quant. (91)
quant. (89)
quant. (90)
quant. (92)
quant. (90)
95 (81)
(3.21)
1d
4
n-C10H21OC(5S)SCH3
(2.77)
DCM (3 mL)
rt, 5 h
(2.77)
1e
5
n-C10H21OC(5S)SCH3
(2.65)
DCM (3 mL)
rt, 5 h
(2.65)
1f
6
n-C10H21OC(5S)SCH3
(2.0)
DCM (3 mL)
rt, 5 h
(2.0)
1g
7
n-C10H21OC(5S)SCH3
(2.93)
DCM (3 mL)
rt, 5 h
(2.93)
1h
8
n-C10H21OC(5S)SCH3
(2.31)
DCM (2 mL)
rt, 5 h
(2.31)
1a
9
PhC(5S)Ph
DCM (10 mL)
rt, 5 h
(7.5)
1a
(5.0)
f
10
11
12
Cyclohexyl-C(5S)OCH3
(10)
DCM (10 mL)
rt, 5 h
Cyclohexyl-CF2OCH3
PhCF3
(15)
1a
PhC(5S)SCH3
(0.53)
DCM (3 mL)
rt, 20 h
99
(1.34)
1a
2-Py–N(CH3)C(5S)SCH3
(5.0)
DCM (10 mL)
rt, 48 h
2-Py–N(CH3)(CF3)g
90 (80)
(7.5)
a
The numbers in parentheses are amounts (mmol) of ArSF4Cl used.
The numbers in parentheses are amounts (mmol) of C5S compounds used.
DCM = dichloromethane.
b
c
d
e
f
Py = pyridyl.
Determined by 19F NMR. The numbers in parentheses are isolated yields. Yields were calculated based on C5S compounds. quant. = quantitative yield.
See Ref. [26].
g
Methyl(2-pyridyl)(trifluoromethyl)amine: see Ref. [29c].

T. Umemoto, R.P. Singh / Journal of Fluorine Chemistry 140 (2012) 17–27
23
As seen in Tables 2–4, our extensive studies on the reactivity of
2a have revealed that 2a has an excellent fluorinating capability for
many kinds of substrates, though 2a is an extremely moisture-
sensitive liquid and has a somewhat unpleasant odor. The in situ
preparation methods reported here work very well as the
corresponding chlorotetrafluoride 1a is much more easily pre-
pared and handled and the moisture-sensitive 2a is not exposed to
air.
compounds in high yields. Since they are the intermediates for the
production of industrially useful arylsulfur pentafluorides (ArSF5),
arylsulfur chlorotetrafluorides 1, in particular, phenylsulfur
chlorotetrafluoride (1a), will be available as inexpensive and
useful deoxo- and dethioxo-fluorinating agents for the commercial
production of many organofluoro compounds as the ArSF5 industry
develops.
4. Experimental
2.6. Fluorinations of various thiocarbonyl compounds with arylsulfur
chlorotetrafluorides 1
4.1. General
Besides DAST [26], Deoxo-fluor [4c], and Fluolead [10a], BrF3
[27], difluoroiodotoluene [28], and N-halo imide/HF–pyridine [29]
have been known as dethioxofluorinating agents for thioketones,
thioesters, or dithiocarbonates. Anodic gem-difluorination of
thioacetals has also been reported [30]. The dethioxofluorination
with DAST or Deoxo-fluor requires a catalyst such as SbCl3.
As seen in Table 5, we have found that arylsulfur chlorotetra-
fluorides 1 themselves are excellent dethioxofluorinating agents
for various thiocarbonyl compounds without any catalyst. A
dithiocarbonate was treated with an equimolar amount of 1a to
give a CF3O compound almost quantitatively (run 1, Table 5). It was
remarkable that the one equimol of 1a was enough to give the
product quantitatively, while PhSF3 (2a) required its 3 equimol for
the high yield fluorination (run 13, Table 3). This is due to higher
sulfur valency (VI) of ArSVIF4Cl than ArSIVF3.
However, with p-methyl derivative 1b, one equimol amount
was not enough and 1.4 equimol was needed to get a quantitative
yield of the product (runs 2 and 3, Table 5). Thus, the electron-
donating methyl substituent of 1b decreases the fluorination
capability compared to unsubstituted 1a. Halogenated derivatives
1d–g and nitro 1h provided quantitative yields with one equimolar
amount of each of them (runs 4–8).
All the fluorination reactions were performed under anhydrous
conditions in an atmosphere of N2 with oven-dried fluoropolymer
vessels. As arylsulfur trifluorides especially are very sensitive to
moisture, their preparation and reactions must be conducted
under very dry atmosphere. It is noted that Denver, Colorado has a
very dry climate, and at the seasons when experiments were
carried out its humidity is less than ca. 20% inside building (the
lowest is ꢂ6% in winter). Dichloromethane as a solvent for the
fluorination reactions was dried over calcium hydride and distilled
before use. THF was dried by distillation over lithium aluminum
hydride. Arylsulfur chlorotetrafluorides (trans-isomers) 1 were
prepared from diaryl disulfides by the method reported by us [12].
The thiocarbonyl compounds were prepared by literature proce-
dures [26,29c–e]. Chemicals were purchased and used without
prior purification unless otherwise noted. 1H, 19F and 13C NMR
spectra were recorded on a JEOL using a deuterium solvent at
300.52, 282.78, and 75.56 MHz, respectively. Chemical shifts are
reported in ppm with TMS as internal standard (
CFCl3 = 0.00). IR spectra were recorded on a Perkin Elmer
d
= 0.00); 19F,
(
d
SpectrumTM RX FT-IR spectrometer. GC–MS analysis was per-
formed on Agilent GC 6890 N and MS 5973 N with SPBTM-1
Capillary Column 60 m ꢃ 0.25 mm ꢃ 0.25 mm film thickness and
column condition: 80 8C. Keep 2 min, then 10 8C/min to 250 8C,
keep 21 min.
1a quantitatively converted a thioketone to the corresponding
CF2 compound (run 9) under mild conditions. A thioester was
similarly converted to the OCF2 compound in high yield (run 10).
1a converted
a
C-dithioester to
a
C-CF3 compound almost
4.2. Treatment of ArSF4Cl 1 with a reducing compound in the presence
quantitatively at room temperature (run 11), while PhSF3 (2a)
needed 70 8C without solvent for the conversion (run 9, Table 4). A
N-dithioester was similarly converted by 1a to a N-CF3 compound
in high yield (run 12). Thus, the successful fluorination reactions of
various thiocarbonyl compounds at mild conditions have demon-
strated the excellent dethioxofluorination capability of ArSF4Cl 1.
However, as 1 has a considerable oxidation power, oxidation
process other than the dethioxofluorination may precede in the
reaction of 1 with a sulfur compound having a more oxidizable
group than the sulfur group.
of benzoic acid
A typical procedure: 79 mg (1 mmol) of pyridine was added to a
stirred solution of 221 mg (1 mmol) of phenylsulfur chlorotetra-
fluoride (1a) and 122 mg (1 mmol) of benzoic acid in 2 mL of dry
dichloromethane (CH2Cl2) in a fluoropolymer (PFA) vessel at room
temperature. The reaction mixture was stirred for 1.5 h at room
temperature and analyzed by 19F NMR. The fluorination with a
different reducing compound was conducted in the same manner.
Table 1 shows reducing compounds, reaction conditions, and
results. The product, benzoyl fluoride, was identified with an
authentic sample.
3. Conclusion
We have demonstrated the useful deployment of arylsulfur
chlorotetrafluorides 1 as versatile deoxo- and dethioxo-fluorinat-
ing agents. There have been developed two methods to in situ
prepare reactive arylsulfur trifluorides 2 from 1. The one is the
reduction method and the other is the disproportionation method.
The former is a convenient process to generate 2, though the
reducer-derived product is formed together. The latter is a
convenient process to give neat 2 because the side product, Cl2,
is easily removed as a gas. The arylsulfur trifluorides 2 successfully
fluorinated many kinds of oxygen compounds such as alcohols,
aldehydes, ketones, diketones, carboxylic acids, diols, and ami-
noalcohols, and sulfur compounds such as thioacetals, thioketones,
thioesters, dithioesters, and dithiocarbonates. In addition, it has
been shown that the chlorotetrafluorides 1 directly and effectively
react the sulfur compounds to give the corresponding fluoro
4.3. Isolation of PhSF3 (2a) from reaction of PhSF4Cl (1a) with pyridine
Pyridine (0.79 g, 10 mmol) was added to a stirred solution of
2.21 g (10 mmol) of 1a in 5 mL of dry CH2Cl2 in a fluoropolymer
vessel at room temperature. The reaction mixture was stirred at
room temperature for 1.5 h. After that, the reaction solvent was
removed under vacuum and the residue was distilled under
reduced pressure to give 1.46 g (88%) of 2a; bp 70 8C/10 mmHg; 19
NMR (CD3CN)
F
d
57.84 (br.s, 2F), ꢁ41.99 (br.s, 1F). Note: As
arylsulfur trifluorides 2 are extremely moisture-sensitive, the
whole process for the isolation of 2 was conducted with minimum
contact with air using N2 flow in a dry atmosphere (humidity is less
than 20%). Glassware (Pyrex) was used for distillation of 2.
Fluoropolymer grease, not silicon grease, had to be used for sealing
at joints.

24
T. Umemoto, R.P. Singh / Journal of Fluorine Chemistry 140 (2012) 17–27
4.4. Fluorination of substrates with ArSF3 2 in situ prepared from
ArSF4Cl 1 and pyridine
4.1 Hz, 2H), 7.51 (d, J = 8.6 Hz, 2H), 7.81 (d, J = 8.6 Hz, 2H); 19F NMR
(CDCl3)
d
ꢁ224.36 (tt, J = 47.6 Hz, 28.1 Hz); 13C NMR (CDCl3)
d 69.3
(d, J = 20.2 Hz), 80.7 (d, J = 173.0 Hz), 129.2, 129.9, 134.2, 140.9.
A typical procedure: 303 mg (3.84 mmol) of pyridine was added
to a stirred solution of 847 mg (3.84 mmol) of 1a in 2 mL of dry
CH2Cl2 in a fluoropolymer vessel at room temperature. The
reaction mixture was stirred for 1.5 h at room temperature. At this
point, 19F NMR of the reaction mixture showed that 2a was formed.
To the reaction mixture, was added 484 mg (2.6 mmol) of n-
dodecanol and 0.9 mL of 70 wt% HF–pyridine (available from
Sigma–Aldrich). The reaction mixture was then stirred for 20 h at
room temperature and the 19F NMR analysis showed n-dodecyl
fluoride was produced in 86% yield. The product was identified
with an authentic sample. The fluorination of a different substrate
was carried out in a similar way. Table 2 shows substrates, reaction
conditions, and results. The known fluorinated compounds were
identified by spectral analysis or comparison with authentic
samples (runs 1–7).
4.5. Preparation of ArSF3 2 by disproportionation of ArSF4Cl 1 with 1/6
diaryl disulfide
4.5.1. Preparation of PhSF3 (2a) and detection of chlorine (Cl2)
generated
1a (2.18 g, 9.87 mmol) was placed in a fluoropolymer reactor
equipped with a condenser made of fluoropolymer, a gas inlet and
outlet, and a magnetic stirrer. The reactor was heated on an oil bath
of 85 8C, and a solution of 0.359 g (1.64 mmol) of diphenyl disulfide
in 1 mL of dry CH2Cl2 was added dropwise to a stirred liquid of 1a
for 10 min. Evolution of chlorine gas started after about 15 min.
Heating at 85 8C was continued till the evolution of chlorine
ceased. It took 0.75 h. After the reaction, the reaction product was
distilled under reduced pressure to give 1.96 g (11.8 mmol) of 2a;
bp 70 8C/10 mmHg. Yield was 90% based on the theoretical yield
(9.87 ꢃ 4/3 = 13.16 mmol). See Note in Section 4.3.
In run 8, after the reaction, an aq Na2CO3 solution was added to
the reaction mixture. The mixture was then extracted with CH2Cl2
and the organic layer separated was washed with water, dried over
anhydrous MgSO4, and filtered. Removal of solvent at reduced
pressure gave the product, which was further purified by thin-
layered chromatography on silica gel to give pure 4, yield: 80%,
product 4 gradually decomposed on standing at room temperature.
The gas evolved during the reaction was passed with a flow of
N2 through a solution of trans-stilbene (1.44 g, 8 mmol) in 10 mL of
CH2Cl2 at ice water temperature. After that, the reaction solution
was evaporated up to dryness to give a solid (1.72 g). 1H NMR and
GC–Mass analysis of the solid showed that an about 1.5:1 mixture
of two isomers of 1,2-dichloro-1,2-diphenylethane was produced.
The NMR and GC–Mass data agreed with the authentic sample
which was prepared by reaction of trans-stilbene with chlorine gas
in a separate experiment. The weight increase of the product
(1.72 g) from the starting material (trans-stilbene, 1.44 g) was
280 mg (3.94 mmol as Cl2) which corresponded to the amount of
chlorine gas generated. The amount of Cl2 generated was thus
calculated to be at least 80% yield based on the theoretical amount
(9.87 ꢃ ½ = 4.94 mmol). This experiment confirmed that chlorine
(Cl2) was generated from the disproportionation reaction of 1a
with 1/6 equimolar amount of diphenyl disulfide.
2-Fluoroethyl benzenesulfinate (4): oil; 1H NMR (CDCl3)
d 3.5–
3.9 (m, 1H), 4.05–4.30 (m, 1H), 4.3–4.65 (dm, J = 50 Hz, 2H), 7.4–
7.55 (m, 3H), 7.6–7.7 (m, 2H); 19F NMR (CDCl3)
NMR (CDCl3)
d
ꢁ224.33 (m); 13
C
d
63.0 (d, J = 20.0 Hz), 81.9 (d, J = 172.0 Hz), 125.3,
129.2, 132.5, 144.2.
In runs 9 and 10, the post-treatment was carried out in a similar
way as in run 8 to give products 5 and 6. Their spectral data are
shown in the following.
2-Fluoroethyl 4-toluenesulfinate (5): yield 72%; oil; 1H NMR
(CDCl3)d2.38(s, 3H), 3.75(m, 1H), 4.18(m, 1H),4.50(dm, J = 47.5 Hz,
2H), 7.35 (d, J = 8.3 Hz, 2H), 7.56 (d, J = 8.3 Hz, 2H); 19F NMR (CDCl3)
d
ꢁ224.16 (tt, J = 47.6 Hz, 28.1 Hz); 13C NMR (CDCl3)
d 21.6, 62.6 (d,
J = 20.2 Hz), 81.9 (d, J = 171.9 Hz), 125.4, 129.9, 142.2, 143.2.
4.5.2. Preparation of 4-tert-butylphenylsulfur trifluoride (2c)
2-Fluoroethyl 4-chlorobenzenesulfinate (6): yield 76%; oil; 1H
NMR (CDCl3) 3.75 (m, 1H), 4.17 (m, 1H), 4.48 (dm, J = 47.0 Hz,
1c (2.77 g, 10 mmol) was reacted with 0.584 g (1.66 mmol) of
bis(4-tert-butylphenyl) disulfide at 95 8C for 0.75 h in the same
way as for 2a from 1a and diphenyl disulfide as shown above
(Section 4.5.1). Chlorine evolved was removed out of the reactor
with a flow of N2. Evolution of chlorine gas was detected by
checking with a paper soaked with an aq KI solution. After the
reaction, the reaction product was distilled under reduced pressure
d
2H), 7.42 (d, J = 8.6 Hz, 2H), 7.58 (d, J = 8.6 Hz, 2H); 19F NMR (CDCl3)
d
ꢁ224.07 (tt, J = 47.6 Hz, 28.1 Hz); 13C NMR (CDCl3)
d 63.4 (d,
J = 20.2 Hz), 81.8 (d, J = 171.0 Hz), 126.9, 129.5, 138.8, 142.8.
For the final identification, each of the products 4–6 of runs 8–
10 was derivatized to
a known and stable 2-fluoroethyl
arylsulfonate by oxidation. A typical procedure: 3-chloroperben-
zoic acid (77%) (829 mg, 3.7 mmol) was added to a stirred solution
of 684 mg (3.64 mmol) of 4 in 10 mL of CH2Cl2. The mixture was
stirred at room temperature for 3 h. During the reaction, insoluble
3-chlorobenzoic acid was formed. After that, 5 mL of CH2Cl2 was
added to the reaction mixture to dissolve the acid and then a satd
Na2CO3 solution was added. After the mixture was stirred for
20 min, the organic layer was separated, washed with water, dried
over anhydrous MgSO4, and filtered. Removal of solvent under
reduced pressure gave 2-fluoroethyl benzenesulfonate [31] in 87%
to give 2.71 g (12.2 mmol) (92% yield) of 2c; bp 76 8C/1 mmHg. 19
NMR (CDCl3–Et2O)
F
d
55.91 (d, J = 54.5 Hz, 2F), ꢁ37.01 (t,
J = 54.5 Hz, 1F). See Note in Section 4.3.
4.5.3. Preparation of 4-chlorophenylsulfur trifluoride (2e)
1e (2.55 g, 10 mmol) was reacted with 0.477 g (1.67 mmol) of
bis(4-chlorophenyl) disulfide at 85 8C for 2.25 h in the same way as
for 2a from 1a and diphenyl disulfide as shown in Section 4.5.1.
Chlorine evolved was removed out of the reactor with a flow of N2.
Evolution of chlorine gas was detected by checking with a paper
soaked with an aq KI solution. After the reaction, the reaction
product was distilled under reduced pressure to give 2.38 g
(11.9 mmol) (89% yield) of 2e; bp 56 8C/1 mmHg. 19F NMR (CD3CN)
yield. 1H NMR (CDCl3)
d 4.29 (dt, J = 16.0 Hz, 2.4 Hz, 2H), 5.58 (dt,
J = 47.0 Hz, 2.4 Hz, 2H), 7.5–7.75 (m, 3H), 7.85–8.0 (m, 2H); 19F
NMR (CDCl3)
d
ꢁ224.52 (tt, J = 45.0 Hz, 28.0 Hz); 13C NMR (CDCl3)
d
68.8 (d, J = 21.0), 80.6 (d, J = 174.0 Hz), 128.0, 129.4, 134.2, 135.7.
d
55.59 (br.s, 2F), ꢁ40.60 (br.s. 1F). See Note in Section 4.3.
2-Fluoroethyl 4-toluenesulfonate [31]: yield 88%; 1H NMR
(CDCl3)
d
3.36 (s, 3H), 4.18 (dm, 2H), 4.52 (dt, J = 47.1 Hz, 4.1 Hz,
4.6. Fluorination of substrates with neat ArSF3 2 in situ prepared from
ArSF4Cl 1 and 1/6 Ar2S2
2H), 7.30 (d, J = 8.6 Hz, 2H), 7.73 (d, J = 8.3 Hz, 2H); 19F NMR (CDCl3)
d
ꢁ224.49 (tt, J = 47.7 Hz, 28.1 Hz); 13C NMR (CDCl3)
d 21.6, 68.9 (d,
J = 20.2 Hz), 80.7 (d, J = 173.4 Hz), 127.9, 130.1, 132.5, 145.4.
A typical procedure: a solution of 142 mg (0.65 mmol) of
diphenyl disulfide in 0.6 mL of dry CH2Cl2 was added dropwise to a
stirred liquid of 871 mg (3.95 mol) of 1a in a fluoropolymer reactor
2-Fluoroethyl 4-chlorobenzenesulfonate [32]: yield 90%; 1H
NMR (CDCl3) d 4.27 (dt, J = 24.9 Hz, 4.1 Hz, 2H), 4.55 (dt, J = 47.1 Hz,

T. Umemoto, R.P. Singh / Journal of Fluorine Chemistry 140 (2012) 17–27
25
heated on an oil bath of 85 8C. After the addition, the reaction
mixture was stirred for 0.5 h at 85 8C. CH2Cl2 (bp 40 8C) and
chlorine gas (Cl2) evolved were removed out of the reactor with
help of a flow of nitrogen during the reaction. After the reaction,
the reactor was cooled to room temperature. A solution of 489 mg
(2.63 mmol) of n-dodecanol in 3 mL of dry CH2Cl2 was added to the
reactor in which neat 1a left. The reaction mixture was stirred at
room temperature for 24 h. 19F NMR analysis of the reaction
mixture showed that n-dodecyl fluoride was produced in 80%
yield. By means of this, many substrates were fluorinated with the
neat ArSF3. Table 3 shows substrates, reaction conditions, and
results. Products were identified by spectral analysis or compari-
son with authentic samples.
4.7.3) was carried out to give 470 mg (84%) of 4 as an oil. The
spectral data of 4 are shown in Section 4.4.
4.7.5. Fluorination of N-methyl-N-trimethylsilyl-[2-
(trimethylsiloxy)ethyl]amine
N-Methyl-N-trimethylsilyl-[2-(trimethylsiloxy)ethyl]amine
(815 mg, 3.72 mmol) was slowly added to a stirred solution of
618 mg (3.72 mmol) of 2a in 5 mL of dry CH2Cl2 in a fluoropolymer
vessel at room temperature. The reaction mixture was stirred at
room temperature for 1 h, and the reaction mixture was poured
into an aq Na2CO3 solution and extracted with CH2Cl2. The organic
layer separated was washed with water, dried over anhydrous
MgSO4, and filtered. Removal of solvent at reduced pressure gave
680 mg (91%) of pure N-(2-fluoroethyl)-N-methyl-benzenesulfi-
4.7. Fluorination of substrates with PhSF3 (2a) (isolated)
namide (8): oil; 1H NMR (CDCl3)
(dm, J = 44.0 Hz, 2H), 7.2–7.6 (m, 5H); 19F NMR (CDCl3)
(tt, J = 45.0 Hz, 26.0 Hz); 13C NMR (CDCl3)
33.8, 52.8 (d,
d
2.54 (s, 3H), 3.2–3.4 (m, 2H), 4.40
ꢁ220.91
d
4.7.1. Fluorination of carboxylic acids in a sealed reactor
d
A typical procedure: 132 mg (1.08 mmol) of benzoic acid was
added portion by portion to 448 g (2.7 mmol) of 2a in a
fluoropolymer (PTFE or FEP) tube (i.d. 5/1600; o.d. 3/800), the end
of which was sealed, at room temperature. Immediately after
the addition, the other end of the tube was sealed. When the
two reactants were mixed, a mild exothermic reaction occurred.
The sealed tube was heated for 2 h in an oil bath of 100 8C. After
that, the tube was cooled to room temperature and opened. 19F
NMR analysis of the reaction mixture showed that benzotri-
fluoride was produced in 90% yield. n-Dodecanoic acid and
isophthalic acid were reacted with 2a in the same way. Table 4
summarizes substrates, reaction conditions, and results (runs
1,5,6). Products were identified by comparison with authentic
samples.
J = 21.0 Hz), 81.8 (d, J = 170.5 Hz), 126.1, 128.9, 131.0, 143.6.
For the final identification, product 8 was derivatized to known
and stable N-(2-fluoroethyl)-N-methylbenzenesulfonamide (10)
[33] by oxidation. Oxidation of 8: 3-chloroperbenzoic acid (77%)
(822 mg, 3.67 mmol) was added to a stirred solution of 718 mg
(3.57 mmol) of 8 in 10 mL of CH2Cl2. The mixture was stirred at
room temperature for 3 h. During the reaction, insoluble 3-
chlorobenzoic acid was formed. After the reaction, some CH2Cl2
was added to dissolve the acid. The reaction mixture was mixed
with a satd Na2CO3 solution and stirred for 20 min. The organic
layer was separated, washed with water, dried over anhydrous
MgSO4, and filtered. Removal of solvent at reduced pressure gave
697 mg (90%) of 10: 1H NMR (CDCl3)
J = 25.8 Hz, 24.8 Hz, 2H), 4.45 (dt, J = 47.1 Hz, 4.8 Hz, 2H), 7.30–
7.78 (m, 5H); 19F NMR (CDCl3)
ꢁ220.75 (tt, J = 47.7 Hz, 24 Hz);
13C NMR (CDCl3)
36.3, 50.3 (d, J = 21.0 Hz), 82.6 (d, J = 170.4 Hz),
d 2.74 (s, 3H), 3.25 (dt,
d
4.7.2. Fluorination of thiocarbonyl compounds
d
A typical procedure: 264 mg (1.59 mmol) of 2a and 53.5 mg
(0.31 mmol) of methyl dithiobenzoate were put in a fluoropolymer
tube, an end of which was sealed, at room temperature, and then
the other end of the tube was sealed. The tube was heated in an oil
bath of 70 8C for 22 h. After that, the tube was cooled to room
temperature and opened. 19F NMR analysis of the reaction mixture
showed that benzotrifluoride was produced in 85% yield. Table 4
summarizes substrates, reaction conditions, and results (runs 7–
10). Products were identified by comparison with authentic
samples or spectral analysis.
127.3, 129.3, 132.9, 137.4.
4.7.6. Fluorination of N-trimethylsilyl-2-
(trimethylsiloxymethyl)pyrrolidine
A solution of 858 mg (3.5 mmol) of N-trimethylsilyl-2-(tri-
methylsiloxymethyl)pyrrolidine [34] in 2.5 mL of dry CH2Cl2 was
slowly added to a stirred solution of 590 mg (3.55 mmol) of 2a in
2.5 mL of dry CH2Cl2 in
a fluoropolymer vessel at room
temperature. The reaction mixture was stirred at room tempera-
ture for 3 h and poured into an aq Na2CO3 solution. The mixture
was extracted with CH2Cl2 and the organic layer separated was
washed with water, dried over anhydrous MgSO4, and filtered.
Removal of solvent at reduced pressure gave 2-fluoromethyl-N-
(benzenesulfinyl)pyrrolidine (9) in 78% yield. The product was
assigned a 86:14 mixture of two diastereomers by its 19F NMR in
which two signals were observed at ꢁ224.01 and ꢁ224.81 as
triplet of doublet. The major isomer was isolated in pure form by
thin-layered chromatography on silica gel, but we failed in
isolating the minor isomer in pure form. The major isomer: oil;
4.7.3. Fluorination of ethylene glycol
A solution of 155 mg (2.49 mmol) of ethylene glycol in 2.5 mL of
dry CH2Cl2 was slowly added to a stirred solution of 414 mg
(2.49 mmol) of 2a in 2.5 mL of dry CH2Cl2 cooled at ꢁ78 8C. The
reaction mixture was allowed to warm to room temperature and
stirred at room temperature for 3 h. An aq Na2CO3 solution was
added to the reaction mixture and the mixture was extracted with
CH2Cl2. The organic layer was separated, washed with water, dried
over anhydrous MgSO4, and filtered. Removal of solvent at reduced
pressure gave the product, which was further purified by thin-
layered chromatography on silica gel to give pure 2-fluoroethyl
benzenesulfinate (4) as an oil, yield: 80%. The spectral data of 4 are
shown in Section 4.4.
1H NMR (CDCl3)
3.38 (m, 1H, 5-H), 4.12 (m, 1H, 2-H), 4.44 (dm, J = 47.1 Hz, 2H,
d 1.7–2.2 (m, 4H, 3-H and 4-H), 2.51 (m, 1H, 5-H),
CH2F), 7.35–7.75 (m, 5H, aromatic protons); 19F NMR (CDCl3)
d
ꢁ224.01 (td, J = 47.5 Hz, 17.3 Hz, CH2F); 13C NMR (CDCl3)
d 25.0,
28.4, 42.1, 60.5 (d, J = 20.2 Hz), 84.8 (d, J = 174.1 Hz), 125.8, 128.9,
130.7, 144.4. The minor isomer: 19F NMR (CDCl3)
d
ꢁ224.81 (td,
4.7.4. Fluorination of 1,2-bis(trimethylsiloxy)ethane
J = 47.5 Hz, 19.9 Hz, CH2F).
A typical procedure: 495 mg (2.98 mmol) of 1,2-bis(trimethyl-
siloxy)ethane was added to a solution of 615 mg (2.98 mmol) of 2a
in 6 mL of dry CH2Cl2 at room temperature. Into the solution, was
added 0.1 mL of 1 M solution of 1 M tetrabutylammonium fluoride
in THF (available from Sigma–Aldrich). The reaction mixture was
stirred at room temperature for 2 h. The same post-treatment as
for the reaction of 2a with ethylene glycol as shown above (Section
For the final identification, 9 (major isomer) was derivatized to
stable salt of known 2-(fluoromethyl)pyrrolidine [35] by
a
treatment with CF3COOH/methanol as follows: 4 mL (53 mmol)
of trifluoroacetic acid was added to a stirred solution of 1.50 g
(6.60 mmol) of 9 in 12 mL of methanol and the mixture was stirred
at room temperature for 1 h. After that, all the volatiles were
removed at reduced pressure (by vacuum pump) and the obtained

26
T. Umemoto, R.P. Singh / Journal of Fluorine Chemistry 140 (2012) 17–27
[11] (a) F. Beaulieu, L.-P. Beauregard, G. Courchesne, M. Couturier, F. LaFlamme, A.
L’Heureux, Organic Letters 11 (2009) 5050–5053;
residue was filtered through a short column of silica gel using 30%
ethyl acetate/hexane mixture and finally the product was eluted
with methanol. Removal of methanol gave a residue, which was
then extracted with CH2Cl2 and the extract was filtered to remove
any silica gel which came with methanol from the silica gel
column. Removal of solvent gave 1.26 g (88%) of 2-(fluoromethyl)-
(b) A. L’Heureux, F. Beaulieu, C. Bennett, D.R. Bill, S. Clayton, F. LaFlamme, M.
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[12] (a) T. Umemoto, Presentation at the Joint International Conference of the 19th
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pyrrolidinium trifluoroacetate (12) as an oil. 12: 1H NMR (CDCl3)
1.5–2.2 (m, 4H, 3-H, 4-H), 3.23 (m, 2H, 5-H), 3.79 (m, 1H, 2H), 4.3–
d
3.8 (m, 2H, CH2F), 9.7 (br.s, 2H, NH2+); 19F NMR (CDCl3)
d
ꢁ75.70 (s,
3F, CF3), ꢁ223.47 (dt, J = 22.0 Hz, 44.0 Hz, 1F, CH2F); 13C NMR
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(CDCl3)
d 23.7 (4-C), 25.5 (d, J = 5.8 Hz, 3-C), 45.7 (5-C), 58.9 (d,
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Applications, Springer, Heidelberg, 2000.
J = 18.8 Hz, 2-C), 81.5 (d, J = 176.6 Hz, CH2F), 116.7 (quartet,
J = 292.6 Hz, CF3), 162.1 (quartet, J = 34.7 Hz, CO); IR (neat, KBr)
2987, 2780, 1674, 1430, 1202, 1134, 1034, 837, 799, 722, 614 cmꢁ1
.
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4.8. Fluorination of thiocarbonyl compounds with ArSF4Cl 1
A typical procedure: a solution of 496 mg (2.0 mmol) of O-n-
decyl S-methyl dithiocarbonate in 1 mL of dry CH2Cl2 was added
slowly to a stirred solution of 441 mg (2.0 mmol) of 1a in 2 mL of
dry CH2Cl2 in a fluoropolymer vessel at room temperature. The
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satd Na2CO3 solution. The mixture was extracted with CH2Cl2 and
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residue was distilled at reduced pressure to give 407 mg (90%) of n-
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their reaction conditions and results. Products were identified by
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d
ꢁ60.5. Table 5
´
´
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