Ionic Liquids for Fast and Solvent-Free Nucleophilic Trifluoromethylthiolation of Alkyl Halides and Alcohols

Article abstract of DOI:10.1002/ejoc.201701222

The trifluoromethylthio group is of rising interest in medicinal, agrochemical, and materials chemistry. Although several strategies for the introduction of this functional group have been described, new synthetic methods are needed. A novel ionic liquid, 1-n-butyl-3-methylimidazolium trifluoromethylthiolate, has been developed and is herein reported as an efficient and recyclable in situ generated trifluoromethylthiolating reagent for alkyl halides, sulfonates, and even unactivated alcohols under solvent-free conditions.

Full text of DOI:10.1002/ejoc.201701222

DOI: 10.1002/ejoc.201701222
Full Paper
Trifluoromethylthiolation
Ionic Liquids for Fast and Solvent-Free Nucleophilic
Trifluoromethylthiolation of Alkyl Halides and Alcohols
Elsa Anselmi,[a,b] Cédric Simon,[a] Jérôme Marrot,[a] Patrick Bernardelli,[c] Laurent Schio,[c]
Bruce Pégot,*[a] and Emmanuel Magnier*[a]
Abstract: The trifluoromethylthio group is of rising interest in methylthiolate, has been developed and is herein reported as
medicinal, agrochemical, and materials chemistry. Although an efficient and recyclable in situ generated trifluoromethyl-
several strategies for the introduction of this functional group thiolating reagent for alkyl halides, sulfonates, and even unacti-
have been described, new synthetic methods are needed. A vated alcohols under solvent-free conditions.
novel ionic liquid, 1-n-butyl-3-methylimidazolium trifluoro-
Introduction
partners. Some answers to this issue have been provided with
The late and selective incorporation of fluorine-containing
the help of transition-metal catalysis or radical pathways, in-
cluding, very recently, photocatalysis.[10] The most convincing
preparation of the C(sp3)–SCF3 group nevertheless remains
nucleophilic substitution because of widely available leaving
groups and inexpensive starting materials. This approach in-
volves the use of various nucleophilic SCF3 transfer reagents.
Usually, the trifluoromethanethiolate anion is associated with
either a transition metal (Hg, Ag, or Cu),[9d,11] to stabilize the
CF3S group, or tetramethylammonium or caesium (Me4NSCF3
or CsSCF3),[12,13] as stable salts. Among these, the stable CF3SAg
salt and CF3SCu–phenanthroline complex have been the most
widely used until now.[14] Long reaction times and polar aprotic
solvents (acetonitrile, toluene, and dimethylformamide) are fre-
quently needed for such nucleophilic displacements. Despite
already existing methods, the development of efficient meth-
ods with easy-to-use reagents for late-stage introduction of tri-
fluoromethylthio groups, especially into aliphatic molecules, are
still highly sought after. Recently, as part of our ongoing pro-
gram of development of ecofriendly nucleophilic fluorination
processes, we have shown the potential of the 1-n-butyl-3-
methylimidazolium fluoride ([bmim][F]) ionic liquid (IL) as a
fluorinating agent to provide soft nucleophilic substitution.[15]
This result proved the great potential of ionic liquids,[16] not
only as media for fluorination reactions,[17] but also as a reagent
for the introduction of a perfluorinated group. It also prompted
us to prepare an innovative ionic liquid with a cation designed
to stabilize the trifluoromethylthiolate anion.
groups into organic molecules has become a very important
target in various fields of research (e.g., pharmaceuticals, agro-
chemicals, materials).[1] Among these substituents, the intro-
duction of the trifluoromethylthio moiety (SCF3) has attracted
considerable attention in recent years because of its strong
electron-withdrawing effect and extremely high lipophilicity
(Hansch parameter πR = 1.44).[2]
Indirect strategies for its incorporation into molecules in-
volve the construction of SCF3 by the trifluoromethylation of
sulfur compounds,[3] or recently by an elegant alternative one-
pot thiocyanation/trifluoromethylation reaction.[4] Numerous
methods have also been developed for the direct introduction
of the trifluoromethylthio group into organic compounds.[5] The
recent developments of many efficient novel shelf-stable rea-
gents based on N-SCF3,[6] O-SCF3,[7] or hypervalent iodide[8]
structures, specially designed to substitute toxic CF3SCl,[9] are
very attractive. They are described as electrophilic trifluoro-
methylthiolating entities and they have indeed greatly contrib-
uted to establishing the electrophilic pathway as an essential
methodology. However, although versatile, this pathway suffers
from limitations and is less popular for the synthesis of alkyl
trifluoromethyl thioethers because of the need for nucleophilic
[a] Institut Lavoisier de Versailles, UMR CNRS 8180,
Université de Versailles St-Quentin-Yvelines,
45 avenue des Etats-Unis, 78035 Versailles Cedex, France
E-mail: bruce.pegot@uvsq.fr
emmanuel.magnier@uvsq.fr
[b] Infectiologie et Santé Publique (ISP), UMR INRA 1282,
Université F. Rabelais,
Herein we report the synthesis of a new ionic liquid,
[bmim][SCF3], and its application as a nucleophilic trifluoro-
methylthiolating reagent. The structure, reactivity, and stability
of our reagent were carefully examined. All the reactions de-
scribed in this paper were conducted under microwave irradia-
tion, which is known to be very efficient for the organic synthe-
sis of ionic liquids.[18] Finally, the recyclability of the ionic liquid
was investigated.
Parc de Grandmont, 37200 Tours, France
[c] Sanofi R&D, Integrated Drug Discovery,
1 avenue Pierre Brossolette, 91385 Chilly-Mazarin, France
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejoc.201701222.
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Results and Discussion
encouraging yield of 25 % in 15 minutes at 120 °C under micro-
wave (MW) irradiation (Table 1, entry 1). An increase in the
amount of IL, silver trifluoromethylthiolate, or reaction time
slightly improved the yield to a maximum of 48 % (entries 2–
4). To our delight, by changing the IL from [bmim][Cl] to
[bmim][I] a very good yield of 90 % was obtained (entry 5).
Importantly, when the reaction was stopped before its comple-
tion, only the 19F NMR signal of [bmim][SCF3] at –17.5 ppm was
detected, with no traces of AgSCF3 being observed. We also
noticed a change of color during the reaction, switching from
orange-red, the color of [bmim][I], to light yellow, the color of
2, and a return to orange-red at the end. This unambiguously
indicated that the real active species was [bmim][SCF3]. The IL
[bmim][I] is not simply a solvent, but also an active player in
this transformation. Other imidazolium halides, [bmim][Br] and
[bmim][F], were also tested. Surprisingly, with these ILs, only
the decomposition of the AgSCF3 was observed (entries 9 and
10).
We first envisioned preparing our target compound
[bmim][SCF3] (2) in one step. We tried to adapt the methodol-
ogy developed by Tyrra et al.[12] for the one-step synthesis of
Me4NSCF3. Unfortunately, the mixture of elemental sulfur S8,
the Ruppert–Prakash reagent, and our IL [bmim][F] as fluorine
source did not lead to the desired IL. This could probably be
explained by the presence of water in our [bmim][F], which is
probably deleterious for this reaction. We then turned our at-
tention to the classic two-step methodology for the preparation
of imidazolium salts. The ionic liquid [bmim][Cl] (1) was first
prepared according to the literature.[19] The second step was
carried out with silver(I) trifluoromethanethiolate in acetonitrile
(Scheme 1).
The fluorinated IL 2 was isolated and the anion exchange
was carefully verified. Detailed examination of the 1H NMR
spectra revealed a slight shift of each signal, especially for the
hydrogen located at the 2-position, that is, between the two
nitrogen atoms, which shifted from 10 to 8.84 ppm. Similarly,
the 19F NMR spectra showed a shift of the SCF3 signal from
–21 to –17.5 ppm. Unfortunately, after a few minutes, the pure
[bmim][SCF3] started to decompose.
This phenomenon was clearly observed by the appearance
of a fluoride signal in the 19F NMR spectrum. This rather poor
stability and the possible generation of a fluoride anion led us
to an in situ preparation of this reagent to enable nucleophilic
substitution.
The trifluoromethylthiolation of 3-phenylpropyl p-toluene-
sulfonate (3a) was investigated as a model reaction (Table 1).
During this study, no particular handling precautions were re-
quired. With only 1 equiv. of [bmim][Cl] and a slight excess of
Finally, the best conditions for the trifluoromethylthiolation
of 3-phenylpropyl p-toluenesulfonate (3a) were 2 equiv. of the
IL [bmim][I] and 1.2 equiv. of AgSCF3 at 110 °C in 15 minutes
(88 % yield, entry 7). Because no additional solvent was added,
even though the reaction was efficient with 1 equiv. of IL, the
use of 2 equiv. was more convenient to avoid a heterogeneous
or very viscous mixture. To demonstrate its practical utility, our
methodology was carried out on a 0.5 g (2.5 mmol) scale with-
out erosion of the yield (86 %, 0.47 g). For comparison, the reac-
tion proceeded more slowly with conventional heating, but was
still very efficient; 1 hour was necessary to obtain a comparable
yield (entry 8).
The scope of this transformation was next assessed by using
AgSCF3, the trifluoromethylthiolation of 3a occurred with an the best conditions in the reactions of various substrates to
Scheme 1. Synthesis of [bmim][SCF3] (2).
Table 1. Trifluoromethylthiolation of 3-phenylpropyl p-toluenesulfonate with ILs.
Entry
IL, Amount [equiv.]
AgSCF3 [equiv.]
Time [min]
Temperature [°C]
Yield [%][a]
1
2
3
4
5
6
7
[bmim][Cl], 1
1.2
1.2
2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
15
15
15
45
15
15
15
60
15
15
120
120
120
120
120
120
110
120
110
110
25
35
38
48
90
93
2
2
2
[bmim][I], 1
2
2
2
Quant. (88)[b]
8[c]
9
10
Quant.
0
0
[bmim][Br], 2
[bmim][F], 2
[a] Yield determined by 19F NMR analysis using PhOCF3 as internal reference. [b] Isolated yield. [c] Reaction conducted under conventional heating.
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synthesize previously unreported compounds (Scheme 2). A aromatic ring (4d, 4i, 4j, 4k), and by adjusting the amount of
wide range of electrophiles were converted into the corre- reagent, bis- or tetrakis-substituted compounds were easily ob-
sponding trifluoromethyl sulfides in moderate-to-excellent tained (4t, 4u). This transformation was also compatible with
yields. With iodine and bromine as the leaving group, the yields various other functionalities, such as esters (4c, 4h, 4m), cyano
were excellent, whereas with chlorine lower but still reasonable (4g, 4n), imide (4p), and lactone (4o) groups. The original pyrid-
yields were obtained (4a, 4b). Concerning the benzylic series, ine derivative 4s could also be isolated in good yield without
good yields were obtained irrespective of the nature of the any protection.
Scheme 2. Scope of trifluoromethylthiolation of alkyl halides. [a] Yield determined by 19F NMR analysis using PhOCF3 as internal reference. Isolated yields are
given in parentheses.
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However, with substrates bearing the N–H moiety (4l, 4q,
4r), only medium yields were observed. Nevertheless, none of
them has previously been described in the literature. The reac-
tion seems to be sensitive to steric hindrance, because only
modest yields were observed with secondary bromine deriva-
tives (4x, 4z). With 9-bromofluorene (3y), two compounds were
isolated; in addition to the expected compound 4y, the bis-
trifluoromethylthiolated skeleton 4y′ was obtained in a yield of
29 %. The structure of 4y′ was confirmed by X-ray diffraction
analysis (Figure 1) and the nature of the transformation is cur-
rently under investigation.
Table 2. Recycling of [bmim][I] for the nucleophilic trifluoromethylthiolation
of 1-bromo-3-phenylpropane (3a).[a]
Cycle
1
2
3
4
5
Yield [%][a]
99
95
92
97
96
[a] Reagents and conditions: AgSCF3 (1.2 equiv.), [bmim][I] (2 equiv.), 110 °C,
15 min. Yields determined by 19F NMR analysis using PhOCF3 as internal
reference.
added directly to the crude IL, which afforded the product 4a
in 95 % yield. Further direct reloading of the starting substrates
was not convenient due to the accumulation of salts, which led
to problems with stirring. The IL phase was then dissolved in
CH2Cl2 and the salts were filtered and then recovered as a pure
material after the evaporation of CH2Cl2. The [bmim][I] IL could
then be re-engaged in a new transformation. We were able to
perform five reactions with the same batch without significant
loss of efficiency.
Among the various reagents to have been used for trifluoro-
methylthiolation reactions, trifluoromethanesulfenamides are
perhaps the most versatile. As a result of umpolung activation,
they have shown great efficiency with a large range of alkyl
substrates including alcohols.[20] Despite the wide availability of
alcohols, very few examples of direct dehydroxytrifluoromethyl-
thiolation reactions have been described in the literature.[21] To
extend our methodology even further, the direct dehydroxytri-
fluoromethylthiolation of alcohols without prefunctionalization
could be a pertinent target. Inspired by our previous results,
the reaction conditions were optimized with 3-phenylpropan-
1-ol (5a) with [bmim][I] as the IL (Table 3).
Figure 1. Crystallographic structure of 4y′.
Based on the mechanism proposed in the literature,[19,20] we
initially employed 2 equiv. of AgSCF3. One equiv. collapses into
difluorothiophosgene to form carbonofluoridothiolate as leav-
ing group and the second equiv. enables the nucleophilic sub-
stitution to provide the expected trifluoromethylthiolated prod-
uct. Under these conditions, the trifluoromethylthiolated prod-
In previous studies, and despite the use of excess reagents,
additives, activators, and ligands, recycling of the ionic liquid
has never been mentioned. We therefore turned our attention
to the recovery of the IL. 1-Bromo-3-phenylpropane (3a) was
chosen for this study (Table 2).
After completion of the trifluoromethylthiolation process, uct was produced in moderate yield and was accompanied by
simple extraction of the crude mixture with diethyl ether af- the formation of alkyl fluoride 6a in a ratio of 1:1 (Table 3,
forded product 4a along with traces of unreacted starting ma- entry 1). This was in accord with our previous work, which dem-
terial. After extraction of the product 4a from the first run, onstrated that nucleophilic fluorination proceeded extremely
1-bromo-3-phenylpropane (3a) and 1.2 equiv. of AgSCF3 were well under these conditions.[15] Decreasing the temperature re-
Table 3. Trifluoromethylthiolation of 3-phenylpropan-1-ol with [bmim][I].
Entry
IL [equiv.]
AgSCF3 [equiv.]
Time [min]
T [°C]
Yield [%][a]
4a
6a
1
2
3
4
2
2
2
4
4
6
6
2.2
2.2
2.2
2.2
2.2
3
30
15
60
30
30
110
100
90
110
100
100
100
44
39
30
52
70
45
30
15
18
9
5
6
30
120
88 (74 %)[b]
68
2
–
7[c]
3
[a] Yields determined by 19F NMR analysis using PhOCF3 as internal reference. [b] Isolated yield. [c] Reaction conducted under conventional heating.
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Scheme 3. Scope of the dehydroxytrifluoromethylthioation of alcohols. [a] Yields determined by 19F NMR analysis using PhOCF3 as internal reference. Isolated
yields are given in parentheses.
duced the monofluorination, but also the yield of compound showed that the reaction could be carried out with the same
4a, even with a longer reaction time (entries 1–3). We then IL batch for at least three turns.
changed the [bmim][I]/AgSCF3 ratio to 2:1, as used in the reac-
Table 4. Recycling of [bmim][I] for the nucleophilic trifluoromethylthiolation
of 3-phenylpropan-1-ol (5a).
tions of the alkyl halides. The positive consequences were an
increase in the yield of 4a to 70 % and a decrease in the yield
Cycle
1
2
3
of the monofluorinated compound 6a to below 10 % (entry 5).
Finally, with 6 equiv. of IL and 3 equiv. of AgSCF3 at 100 °C, the
desired compound was obtained in a good yield of 88 % in
only 30 minutes (entry 6). Under conventional heating, the reac-
tion was less effective; after 2 hours, only 68 % yield of trifluoro-
methylthiolated compound 4a was obtained (entry 7).
Yield [%][a]
82
69
72
[a] Reagents and conditions: AgSCF3 (3 equiv.), [bmim][I] (6 equiv.), 100 °C,
30 min. Yields determined by 19F NMR analysis using PhOCF3 as internal
reference.
The scope of this reaction was successfully explored with
various alcohols (Scheme 3). Primary benzyl, alkyl, and allylic
alcohols gave rise to the corresponding trifluoromethylthiolated
molecules in good yields. Long-chain aliphatic alcohols deliv-
ered moderate yields (4aa, 4w) because of the poor solubility
of the starting materials in the reaction media. A furan deriva-
tive was also compatible with this methodology, but the result-
ing compound 4af was too volatile to be isolated in pure form.
A secondary alcohol reacted smoothly to form the product 4ae
in 64 % yield, and tertiary and secondary cyclic alcohols were
also suitable substrates, albeit the corresponding products (4ah
and 4ai) were isolated in poor yields.
Conclusions
We have shown that the IL 1-n-butyl-3-methylimidazolium tri-
fluoromethylthiolate (2) could be prepared from 1-n-butyl-3-
methylimidazolium chloride (1) by anion exchange with
AgSCF3. Prepared in situ, this compound demonstrated its po-
tential as a trifluoromethylthiolating reagent to enable the soft
nucleophilic substitution of various alkyl halides and even
alcohols. Except for the work-up procedures and recycling
processes, no solvent, special precautions, or complex or haz-
ardous additives were necessary for this transformation. The use
Finally, the recyclability of the ionic liquid in this reaction of microwave irradiation allowed a short reaction time. The IL
was investigated by using 3-phenylpropan-1-ol (5a; Table 4). could be reused for several cycles with high efficiency, thereby
Despite a slight decrease in the yield in the second run, we contributing to a decrease in reaction waste. Further develop-
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tert-Butyl {3-[(Trifluoromethyl)thio]propyl}carbamate (4l): Yield:
18 mg, 23 % %; colorless liquid. Eluent for the preparative TLC chro-
matography: Et2O/petroleum ether (1:9). 1H NMR (300 MHz, CDCl3):
δ = 4.58 (br. s, NH), 3.27–3.20 (m, 2 H), 2.91 (t, J = 6.9 Hz, 2 H), 1.89
(quint., J = 6.9 Hz, 2 H), 1.44 (s, 9 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 156.1, 131.1 (q, J = 305.6 Hz), 28.4, 27.2 (d, J = 2.2 Hz) ppm.
19F NMR (188 MHz, CDCl3): δ = –41.72 (s) ppm. HRMS: calcd. for
C9H16F3NO2SNa 282.0752; found 282.0748 [M + Na]+ (δ = –1.4).
ments of this new reagent and other applications are under
study in our laboratory.
Experimental Section
General: Chemicals were purchased from commercial sources un-
less otherwise stated in the Supporting Information. Reactions were
monitored by 19F NMR spectroscopy. Yields refer to materials puri-
fied by preparative TLC chromatography. NMR spectra were col-
lected with a Bruker AC-200 or AC-300 spectrometer. The reported
coupling constants and chemicals shifts are based on first-order
analysis. The residual peak of CHCl3 (δ = 7.26 ppm) for 1H NMR (200
or 300 MHz), the central peak of CDCl3 (δ = 77.16 ppm) for 13C NMR
(75 or 50 MHz), and CFCl3 (δ =0.00 ppm) for 19F NMR (188 MHz)
were used as internal references. HRMS was performed with a
XEVO-QTOF Mass Spectrometer at the Institute Lavoisier of Versail-
les – University of Versailles Saint Quentin. The compounds de-
scribed in this section are limited to new products. The analytical
data for molecules that have previously been reported can be found
in the Supporting Information. X-ray Diffraction: Data collection:
Bruker APEX2; cell refinement: Bruker SAINT; data reduction: Bruker
SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick,
1990); program(s) used to refine structure: SHELXL97 (Sheldrick,
1997); molecular graphics: Bruker SHELXTL; software used to pre-
pare material for publication: Bruker SHELXTL.
Ethyl 5-[(Trifluoromethyl)thio]pentanoate (4m): Yield: 51 mg,
74 %; pale-yellow liquid. Eluent for the preparative TLC chromatog-
raphy: Et2O/petroleum ether (1:9). 1H NMR (300 MHz, CDCl3): δ =
4.12 (q, J = 7.1 Hz, 2 H), 2.91–2.83 (m, 2 H), 2.36–2.28 (m, 2 H), 1.76–
1.68 (m, 4 H), 1.25 (t, J = 6.9 Hz, 3 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 173.1, 131.2 (q, J = 305.8 Hz), 60.5, 33.6, 29.6 (q, J = 2.0 Hz),
29.0, 23.8, 14.3 ppm. 19F NMR (188 MHz, CDCl3): δ = –41.69 (s) ppm.
HRMS: calcd. for C8H13F3O2S 231.06611; found 231.06592 [M + H]+
(δ = –0.8).
3-[(Trifluoromethyl)thio]dihydrofuran-2(3H)-one (4o): Yield:
30 mg, 53 %; pale-yellow liquid. Eluent for the preparative TLC chro-
1
matography: Et2O. H NMR (300 MHz, CDCl3): δ = 4.48 (td, J = 8.6,
3.1 Hz, 1 H), 4.34 (td, J = 9.1, 6.7 Hz, 1 H), 4.18 (t, J = 9.1 Hz, 1 H),
2.91–2.79 (m, 1 H), 2.50 (dq, J = 13.1, 9.0 Hz, 1 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 172.4, 130.0 (q, J = 306.7 Hz), 66.9, 41.2 (d, J =
2.2 Hz), 31.9 ppm. 19F NMR (188 MHz, CDCl3): δ = –40.64 (s) ppm.
HRMS: calcd. for C5H5F3O2S 187.00351; found 187.00346 [M + H]+
(δ = –0.2).
General Procedure for the Trifluoromethylthiolation of Halide
and Tosylate Substrates: A microwave tube with a magnetic stir-
ring bar was charged with a halide or tosylate (1.0 equiv., 0.3 mmol)
and [bmim][I] (2.0 equiv., 0.6 mmol, 0.16 g). After stirring the mix-
ture, AgSCF3 (1.2 equiv., 0.36 mmol, 75 mg) was added in one por-
tion and the mixture was subjected to microwave irradiation at
110 °C during 15 min. The mixture was then cooled to room tem-
perature, diluted with acetonitrile, and the conversion was verified
by 19F NMR analysis with PhOCF3 as internal reference. The crude
was directly purified by preparative TLC chromatography on silica
gel to give the desired product.
3-{2-[(Trifluoromethyl)thio]ethyl}-1H-indole (4q): Yield: 20 mg,
27 %; brown paste. Eluent for the preparative TLC chromatography:
1
Et2O/petroleum ether (2:8). H NMR (300 MHz, CDCl3): δ = 8.02 (br.
s, NH), 7.59 (d, J = 7.8 Hz, 1 H), 7.39 (d, J = 7.8 Hz, 1 H), 7.24–7.07
(m, 2 H), 3.20 (m, 4 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 137.5,
131.4 (q, J = 307.1 Hz), 127.0, 122.4, 122.2, 119.8, 118.5, 113.6, 111.4,
30.7 (d, J = 2.2 Hz), 26.0 ppm. 19F NMR (188 MHz, CDCl3): δ = –41.40
(s) ppm. HRMS: calcd. for C11H11F3NS 246.0564; found 246.0571 [M
+ H]+ (δ = 2.8 ppm).
3-[(Trifluoromethyl)thio]-1,3,4,5-tetrahydro-2H-benzo[b]azepin-
2-one (4r): Yield: 31 mg, 39 %; brown solid. M.p. 138 °C. Eluent for
the preparative TLC chromatography: Et2O. 1H NMR (300 MHz,
CDCl3): δ = 8.16 (br. s, NH), 7.34–7.19 (m, 4 H), 7.07 (d, J = 7.8 Hz, 1
H), 4.07 (dd, J = 11.3, 7.5 Hz, 1 H), 3.07–2.95 (m, 1 H), 2.80–2.65 (m,
2 H), 2.54–2.42 (m, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 170.6,
136.4, 133.4, 130.6 (q, J = 306.6 Hz), 130.1, 128.3, 127.0, 122.6, 46.4,
38.3, 29.9 (d, J = 2.2 Hz) ppm. 19F NMR (188 MHz, CDCl3): δ = –40.56
(s) ppm. HRMS: calcd. for C11H11F3NOS 262.0513; found 262.0517
[M + H]+ (δ = 1.5 ppm).
Methyl 4-{2-[(Trifluoromethyl)thio]ethyl}benzoate (4h): Yield:
47 mg, 59 %; colorless liquid. Eluent for the preparative TLC chroma-
tography: Et2O/petroleum ether (2:8). 1H NMR (200 MHz, CDCl3): δ =
8.00 (d, J = 8.7 Hz, 2 H), 7.28 (d, J = 8.4 Hz, 2 H), 3.91 (s, 3 H), 3.11
(m, 4 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 166.9, 144.1, 131.1 (q,
J = 306.6 Hz), 130.1, 129.0, 128.7, 52.2, 36.1, 30.8 (q, J = 2.1 Hz) ppm.
19F NMR (188 MHz, CDCl3): δ = –41.49 (s) ppm. HRMS: calcd. for
C11H12F3O2S 265.0516; found 265.0516 [M + H]+ (δ = 2.3 ppm).
(4-Fluorobenzyl)(trifluoromethyl)sulfane (4i): Yield: 45 mg, 72 %;
2,6-Bis{[(trifluoromethyl)thio]methyl}pyridine (4s): Yield: 77 mg,
84 %; pale-yellow liquid. Eluent for the preparative TLC chromatog-
raphy: Et2O/petroleum ether (1:9). 1H NMR (300 MHz, CDCl3): δ =
7.68 (t, J = 7.7 Hz, 1 H), 7.29 (d, J = 7.7 Hz, 2 H), 4.23 (s, 4 H) ppm.
13C NMR (75 MHz, CDCl3): δ = 135.2, 130.7 (q, J = 306.7 Hz), 129.5,
35.8 (q, J = 2.0 Hz) ppm. 19F NMR (188 MHz, CDCl3): δ = –41.99
(s) ppm. HRMS: calcd. for C9H7F6NS2 308.0002; found 307.9999 [M
+ H]+ (δ = –1.0).
yellow liquid. Eluent for the preparative TLC chromatography: Et2O/
petroleum ether (1:9). H NMR (300 MHz, CDCl3): δ = 7.32 (m, 2 H),
1
7.05 (t, J = 8.5 Hz, 2 H), 4.11 (s, 2 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 162.5 (d, J = 247.0 Hz), 131.0 (d, J = 3.3 Hz), 130.7 (d, J = 8.1 Hz),
130.6 (q, J = 306.1 Hz), 115.9 (d, J = 22.0 Hz), 33.7 (q, J =
2.2 Hz) ppm. 19F NMR (188 MHz, CDCl3): δ = –42.08 (s, 3 F), –114.40
(m, 1 F) ppm.
[(Perfluorophenyl)methyl](trifluoromethyl)sulfane (4k): Yield:
47 mg, 56 %; pale-yellow liquid. Eluent for the preparative TLC chro- 1,2,4,5-Tetrakis{[(trifluoromethyl)thio]methyl}benzene
(4u):
matography: Et2O/petroleum ether (1:9). 1H NMR (300 MHz, CDCl3):
δ = 4.15 (s, 2 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 145.2 (dm, J =
250.1 Hz), 141.5 (dm, J = 255.0 Hz), 137.8 (dm, J = 251.7 Hz), 130.3
(q, J = 307.6 Hz), 110.8 (td, J = 17.0, 4.2 Hz), 20.9 (m) ppm. 19F NMR
(188 MHz, CDCl3): δ = –42.59 (t, J = 3.5 Hz, 3 F), –142.56 (m, 2 F),
–154.02 (t, J = 2.0 Hz, 1 F), –161.90 (m, 2 F) ppm. HRMS: calcd. for
C8HF8S 280.9671; found 280.9678 [M – H]– (δ = –0.7).
Yield: 130 mg, 81 %; pale-orange solid. M.p. 39 °C. Eluent for the
preparative TLC chromatography: Et2O/petroleum ether (1:9). 1H
NMR (300 MHz, CDCl3): δ = 7.37 (s, 2 H), 4.23 (s, 8 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 134.4, 133.9, 130.3 (q, J = 307.4 Hz), 30.9 (q,
J = 2.0 Hz) ppm. 19F NMR (188 MHz, CDCl3): δ = –42.13 (s) ppm.
HRMS: calcd. for C14H10F12S4 532.9396; found 532.9388 [M – H]+
(δ = –1.5).
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(7-Phenylhept-6-yn-1-yl)(trifluoromethyl)sulfane (4v): Yield:
CCDC 1571218 (for 4y′) contains the supplementary crystallo-
38 mg, 46 %; colorless liquid. Eluent for the preparative TLC chroma- graphic data for this paper. These data can be obtained free of
tography: petroleum ether. 1H NMR (300 MHz, CDCl3): δ = 7.46–7.43 charge from The Cambridge Crystallographic Data Centre
(m, 2 H), 7.35–7.30 (m, 3 H), 2.96 (t, J = 7.0 Hz, 2 H), 2.48 (t, J =
Supporting Information (see footnote on the first page of this
6.5 Hz, 2 H), 1.83–1.61 (m, 6 H) ppm. 13C NMR (75 MHz, CDCl3): δ =
article): Materials and apparatus, general experimental procedures,
131.6, 131.3 (q, J = 305.6 Hz), 128.3, 127.7, 124.0, 89.7, 81.1, 29.9 (d,
1
and H and 13C NMR spectra of all the synthesized compounds.
J = 2.2 Hz), 29.1, 28.1, 27.8, 19.3 ppm. 19F NMR (188 MHz, CDCl3):
δ = –41.68 (s) ppm. HRMS: calcd. for C11H16F3S 237.09303; found
237.09123 [M – H]+ (δ = –2.9).
Acknowledgments
Decyl(trifluoromethyl)sulfane (4w): Yield: 22 mg, 30 %; colorless
C. S. thanks Sanofi for a postdoctoral fellowship. We gratefully
thank the Centre National de la Recherche Scientifique (CNRS)
and the French Fluorine Network (GIS fluor). Flavien Bourdreux
is acknowledged for recording the mass spectra.
liquid. Eluent for the preparative TLC chromatography: Et2O/petro-
1
leum ether (1:9). H NMR (300 MHz, CDCl3): δ = 2.87 (t, J = 7.5 Hz,
2 H), 1.67 (q, J = 7.6 Hz, 2 H), 1.43–1.27 (m, 14 H), 0.88 (t, J = 6.7 Hz,
3 H) ppm. 13C NMR (75 MHz, CDCl3): δ = 131.4 (q, J = 306.4 Hz),
32.0, 30.0 (q, J = 1.5 Hz), 29.6, 29.5 (2 C), 29.4, 29.1, 28.6, 22.8,
14.2 ppm. 19F NMR (188 MHz, CDCl3): δ = –41.77 (s) ppm.
Keywords: Fluorinated compounds · Ionic liquids ·
Fluorine · Sulfur · Trifluoromethylthiolation · Nucleophilic
substitution
(9H-Fluoren-9-yl)(trifluoromethyl)sulfane (4y): Yield: 20 mg,
25 %; waxy solid. Eluent for the preparative TLC chromatography:
Et2O/petroleum ether (2:8). 1H NMR (300 MHz, CDCl3): δ = 7.75–7.71
(m, 4 H), 7.47–7.35 (m, 4 H), 5.32 (s, 1 H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 142.6, 140.6, 131.2 (q, J = 307.6 Hz), 129.0, 128.0, 125.9,
120.3, 47.8 ppm. 19F NMR (188 MHz, CDCl3): δ = –39.51 (s) ppm.
HRMS: calcd. for C14H9F3S 265.0299; found 265.0298 [M – H]+ (δ =
–0.4).
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(9H-Fluorene-9,9-diyl)bis[(trifluoromethyl)sulfane] (4y′): Yield:
32 mg, 29 %; pale-yellow solid. M.p. 73 °C. Eluent for the preparative
TLC chromatography: Et2O/petroleum ether (2:8). 1H NMR (300 MHz,
CDCl3): δ = 7.81–7.74 (m, 4 H), 7.54–7.38 (m, 4 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 143.0, 138.7, 130.6, 128.4, 128.3 (q, J =
310.8 Hz), 125.8, 120.9, 63.3 ppm. 19F NMR (188 MHz, CDCl3): δ =
–38.68 (s) ppm. HRMS: calcd. for C15H7F6S2 364.9893; found
364.9885 [M – H]+ (δ = –2.2).
General Procedure for the Trifluoromethylthiolation of Alcohol
Substrates: A microwave tube with a magnetic stirring bar was
charged with the alcohol compound (1.0 equiv., 0.3 mmol) and
[bmim][I] (6.0 equiv., 1.8 mmol, 0.47 g). After stirring the mixture,
AgSCF3 (3 equiv., 0.9 mmol, 188 mg) was added in one portion and
the mixture subjected to microwave irradiation at 100 °C during
30 min. The mixture was then cooled to room temperature, diluted
with acetonitrile, and the conversion was determined by 19F NMR
with PhOCF3 as internal standard. The crude was directly purified
by preparative TLC chromatography on silica gel to give the desired
product.
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(Z)-(3,7-Dimethylocta-2,6-dien-1-yl)(trifluoromethyl)sulfane
(4ab): Yield: 48 mg, 67 %; pale-yellow liquid. Eluent for the prepara-
tive TLC chromatography: Et2O/petroleum ether (1:9). 1H NMR
(300 MHz, CD3CN): δ = 5.31 (t, J = 7.7 Hz, 1 H), 5.13 (m, 1 H), 3.64
(d, J = 7.8 Hz, 2 H), 2.05–2.19 (m, 4 H), 1.76 (s, 3 H), 1.69 (s, 3 H),
1.62 (s, 3 H) ppm. 13C NMR (75 MHz, CD3CN): δ = 143.2, 133.0, 132.3
(q, J = 305.7 Hz), 124.6, 118.8, 32.3, 28.6 (q, J = 2.2 Hz), 27.1, 25.8,
23.5, 17.7 ppm. 19F NMR (188 MHz, CD3CN): δ = –42.09 (s) ppm.
HRMS: calcd. for C14H14F3S 271.07738; found 271.07561 [M + H]+
(δ = 2.4 ppm).
(4-Isopropylbenzyl)(trifluoromethyl)sulfane (4ad): Yield: 54 mg,
77 %; yellow liquid. Eluent for the preparative TLC chromatography:
Et2O/petroleum ether (1:9). 1H NMR (300 MHz, CD3CN): δ = 7.31–
7.20 (m, 4 H), 4.13 (s, 2 H), 2.93 (sept., J = 6.7 Hz, 1 H), 1.26 (d, J =
6.9 Hz, 6 H) ppm. 13C NMR (75 MHz, CD3CN): δ = 149.8, 132.0 (q,
J = 306.8 Hz), 129.9, 129.4, 127.8, 118.2, 70.1, 34.5 (q, J = 2.2 Hz),
24.2 ppm. 19F NMR (188 MHz, CD3CN): δ = –42.24 (s) ppm.
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Received: August 31, 2017
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