Synthesis of allylic and propargylic trifluoromethyl thioethers by copper(i)-catalyzed trifluoromethylthiolation of allylic bromides and propargylic chlorides

Article abstract of DOI:10.1002/ejoc.201402480

An efficient method is reported for the copper(I)-catalyzed trifluoromethylthiolation of allylic bromides by using elemental sulfur and CF₃SiMe₃. This rate of this transformation was significantly accelerated in the presence of 18-crown-6, and the reaction afforded the desired products in moderate to excellent yields with high stereo- and regioselectivity. This method can tolerate a number of functional groups and provides facile access to a variety of allylic trifluoromethyl thioethers. The copper(I)-catalyzed trifluoromethylthiolation of propargylic chlorides was also investigated. A plausible mechanism that involves an allylcopper(III) intermediate is proposed.

Full text of DOI:10.1002/ejoc.201402480

FULL PAPER
DOI: 10.1002/ejoc.201402480
Synthesis of Allylic and Propargylic Trifluoromethyl Thioethers by Copper(I)-
Catalyzed Trifluoromethylthiolation of Allylic Bromides and Propargylic
Chlorides
Mingguang Rong,[a] Dongzhe Li,[a] Ronglu Huang,[a] Yangjie Huang,[a] Xiaoyan Han,*[b] and
Zhiqiang Weng*[a]
Keywords: Synthetic methods / Allylic compounds / Alkynes / Regioselectivity / Sulfur / Fluorine
An efficient method is reported for the copper(I)-catalyzed
trifluoromethylthiolation of allylic bromides by using elemen-
tal sulfur and CF3SiMe3. This rate of this transformation was
significantly accelerated in the presence of 18-crown-6, and
the reaction afforded the desired products in moderate to ex-
cellent yields with high stereo- and regioselectivity. This
method can tolerate a number of functional groups and pro-
vides facile access to a variety of allylic trifluoromethyl thio-
ethers. The copper(I)-catalyzed trifluoromethylthiolation of
propargylic chlorides was also investigated. A plausible
mechanism that involves an allylcopper(III) intermediate is
proposed.
cations in agrochemicals and pharmaceuticals as well as in
materials science. Therefore, an efficient synthetic approach
to allylic trifluoromethyl thioethers is highly desirable.
In recent years, tremendous progress has been made in
the direct introduction of the –SCF3 group into organic
molecules.[13] The development of Cu-catalyzed[14] and
transition-metal-free oxidative trifluoromethylthiolation,[15]
related Cu-promoted trifluoromethylthiolation through the
direct functionalization of the C–H bonds of arenes,[16] and
Pd-[17] and Ni-catalyzed processes[18] as well as the use new
trifluoromethylthiolation reagents[19] has provided an at-
tractive approach to the formation of Csp2–SCF3, Csp–
SCF3, and Csp3–SCF3 bonds. Despite these advances, the
development of new methods that catalytically generate
allylic trifluoromethyl thioethers remains an important goal
in synthetic organic chemistry.
Introduction
Fluorinated allylic compounds have emerged as highly
versatile synthons for the preparation of biologically active
products such as drug molecules. These include herbicides,
insecticides, and fungicides as well as fluorinated vitamin D
and prostanoid analogues.[1,2] Additionally, these com-
pounds can serve as an important skeletal motif that allows
for further synthetic manipulations.[3] Accordingly, many
effective methods for the synthesis of allylic fluorides have
been developed such as nucleophilic[4,5] and electrophilic[6]
fluorination reactions as well as the use of a fluorinated
building block approach.[7] In addition, several methods to
synthesize allylic trifluoromethylated compounds have
emerged that rely on the copper-catalyzed electrophilic and
oxidative allylic trifluoromethylation of terminal alkenes by
using Togni’s[8] and Umemoto’s reagents[9] with CF3SiMe3
(Ruppert–Prakash reagent)[10] or the nucleophilic allylic tri-
fluoromethylation of allylic halides.[11] The results of these
investigations further demonstrate the value of these trans-
formations in the synthesis of fluorine-containing allylic de-
rivatives.
Pioneering work by Tyrra and co-workers[20] demon-
strated that allyl trifluoromethyl thioethers could be synthe-
sized from the reaction between an allyl bromide and a sen-
sitive, less-stable reagent such as NMe4(SCF3) or Cs(SCF3)
(see Scheme 1). Inspired by these results, we began to de-
Allylic trifluoromethyl thioethers are of particular signifi-
cance. These species that contain –SCF3 groups have a high
hydrophobicity parameter (πR = 1.44),[12] and this property
makes them increasingly attractive for their potential appli-
[a] Department of Chemistry, Fuzhou University,
Fuzhou 350108, China
E-mail: zweng@fzu.edu.cn
http://chem.fzu.edu.cn/szdw/teacherinfo.aspx?id=99
[b] Testing and Analysis Center, Soochow University,
Suzhou 215123, China
http://fxcs.suda.edu.cn/subnets/zxgk.htm
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201402480.
Scheme 1. Methods for preparation of allylic trifluoromethyl thio-
ethers.
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Synthesis of Allylic and Propargylic Trifluoromethyl Thioethers
velop an expeditious synthetic process for the preparation Table 1. Optimization of the reaction conditions.[a]
of allylic trifluoromethyl thioethers with a broad substrate
scope by using air- and moisture-stable copper reagents.
The reactions of (bpy)Cu(SCF3) (bpy = 2,2Ј-bipyridine) or
(PPh3)2Cu(SCF3) with a wide range of allylic bromides pro-
Entry [Cu]
Ligand
Additive
Solvent T [°C] Yield [%][b]
duced the desired allylic trifluoromethyl thioethers in good
to excellent yields with high stereo- and regioselectivity.[21]
In spite of the utility of these methods, stoichiometric
amounts of copper reagents are required to achieve synthet-
ically useful results.
To improve the potential of these reactions further, we
set out to develop a metal-catalyzed process for trifluoro-
methylthiolation. We report herein our findings that a cop-
per(I)/1,10-phenanthroline (phen) system[22] in the presence
of 18-crown-6 efficiently catalyzes the trifluoromethyl-
thiolation of allylic bromides with elemental sulfur and
CF3SiMe3.
1
CuI
bpy
phen
Me2phen
phen
phen
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
DMF[c]
CH2Cl2
THF[c]
70
70
70
70
70
70
70
70
70
40
70
70
47
59
41
41
36
30
55
13
36
31
54
32
21
50
21
65
78
76
2
CuI
3
CuI
4
5
6
CuCl
CuBr
CuF2
phen
7
Cu(OTf)2 phen
8
–
phen
phen
phen
phen
phen
phen
phen
phen
phen
phen
phen
9
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
CuI
10
11
12
13
14
15
16
17
18
diglyme
DMSO[c] 70
toluene
DME[c]
dioxane
70
70
70
70
50
Results and Discussion
18-crown-6 dioxane
18-crown-6 dioxane
Initially, the reaction between 3-bromocyclohexene (1a),
CF3SiMe3, and elemental sulfur in the presence of a copper
catalyst was investigated. The trifluoromethylthiolation of
1a in the presence of a catalytic amount of CuI (20 mol-%)/
bpy (20 mol-%) in CH3CN at 70 °C for 16 h afforded the
desired cyclohexenyl(trifluoromethyl)sulfane 2a in 47%
yield (determined by 19F NMR analysis; see Table 1, En-
try 1). Encouraged by this initial result, we proceeded to
optimize the reaction conditions. The use of phen as the
[a] Reagents and conditions: 1a (0.10 mmol), CF3SiMe3
(0.30 mmol, 3 equiv.), S8 (0.30 mmol, 3 equiv.), KF (0.30 mmol,
3 equiv.), [Cu] (0.020 mmol), ligand (0.020 mmol), 18-crown-6
(0.20 mmol, 2 equiv.), solvent (2.0 mL), 16 h, under N2 [b] Yields
were determined by 19F NMR spectroscopic analysis with PhOCF3
as the internal standard. [c] DMF = N,N-dimethylformamide, THF
= tetrahydrofuran, DMSO = dimethyl sulfoxide, DME = 1,2-di-
methoxyethane.
ligand gave an improved yield for 2a of 59%, whereas a of product 2a significantly improved with the addition of
41% yield was achieved by using substrate 1a with Me2phen this cation scavenger (78% yield; see Table 1, Entry 17).
(2,9-dimethyl-1,10-phenanthroline) as the ligand (see Furthermore, the reaction proceeded smoothly even at a
Table 1, Entries 2 and 3). The investigation of various cop- lower temperature (50 °C) in the presence of 2 equiv. of 18-
per salts as the catalyst with phen as the ligand indicated crown-6 to give 2a at 76% yield (see Table 1, Entry 18).
that Cu(OTf)2 (Tf = trifluoromethanesulfonyl) was almost
Subsequently, the established optimal reaction conditions
as efficient a catalyst as CuI (see Table 1, Entry 7). Other (see Table 1, Entry 18) were employed with other allylic
copper salts such as CuCl, CuBr, and CuF2 were less ef- bromides. Various types of substituted cinnamyl bromides
ficient (see Table 1, Entries 4–6). In addition, the yield of were efficiently used in the present catalytic trifluoromethyl-
trifluoromethylthiolated product 2a decreased in the ab- thiolation to produce the linear allylic isomer regioselec-
sence of a copper source (13% yield; see Table 1, Entry 8), tively (see Table 2). The use of cyclic allylic bromide 1a af-
which indicates that copper may be involved in a catalytic forded the desired product 2a in 67% yield. The reaction of
cycle.
cinnamyl bromide 1b furnished the desired product 2b in
After screening various common organic solvents, we the high isolated yield of 94% (see Table 2, Entry 2).
found that the trifluoromethylthiolation proceeded most ef- Furthermore, cinnamyl chloride 1bЈ also underwent trifluo-
ficiently in dioxane, which provided the product in 65% romethylthiolation, although it provided product 2b in 58%
yield (see Table 1, Entry 16). The reactions that were per- yield (see Table 2, Entry 3). The reactions of cinnamyl
formed in CH3CN, THF, and toluene gave diminished bromides 1c–1e with a methyl or isopropyl substituent at
product yields (see Table 1, Entries 2, 11 and 14), whereas the para or meta position of the aromatic ring led to the
other solvents such as DMF, CH2Cl2, diglyme, DMSO, and isolation of products 2c–2e, respectively, in 70–78% yield
DME did not provide desirable results for this reaction (see (see Table 2, Entries 4–6). On the other hand, when p-tert-
Table 1, Entries 9, 10, 12, 13, and 15). Thus, dioxane was butyl- and 2,4,6-trimethyl-substituted cinnamyl bromides 1f
selected as the preferred solvent for the subsequent experi- and 1g were employed in the reaction under the same con-
ments because of its efficiency in the reaction and ease of ditions, relatively moderate yields were attained (58 and
handling during the workup procedure.
40% yield, respectively; see Table 2, Entries 7 and 8). The
To accelerate the reaction, the copper(I)-catalyzed tri- electron-rich o-methoxy-substituted cinnamyl bromide 1h
fluoromethylthiolation was further examined in the pres- worked well (82% yield; see Table 2, Entry 9), but the m-
ence of the additive 18-crown-6.[23] Interestingly, the yield methoxy-substituted and the electron-poor p-trifluoro-
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M. Rong, D. Li, R. Huang, Y. Huang, X. Han, Z. Weng
FULL PAPER
methyl-substituted substrates afforded a lower product yield Table 2. Copper(I)-catalyzed trifluoromethylthiolation of allylic
halides.[a]
(49 and 46% yield, respectively; see Table 2, Entries 10 and
11). Additionally, p-methylthio-substituted cinnamyl brom-
ide 1k enabled the efficient preparation of 2k in excellent
yield (90% yield, see Table 2, Entry 12). It is also worth
noting that halogen functional groups were tolerated well
in the reaction under the current conditions. The fluoro,
chloro, and bromo substituents at the para position of cin-
namyl bromides 1l–1n underwent the reaction smoothly to
give the corresponding products 2l–2n in yields ranging
from 53 to 71% (see Table 2, Entries 13–15). The ability to
incorporate halogen substituents into the products provides
opportunities for further functional manipulations through
cross-coupling reactions. Furthermore, the trifluoromethyl-
thiolation could also be performed with geranyl bromide
(1o), which contained no conjugated aromatic ring, to give
2o in good yield (78% yield, see Table 2, Entry 16) but with
an E/Z ratio of 11:1. Ethyl 4-bromo-3-ethoxy-2-butenoate,
led to the desired product 2p in 60% yield (determined by
19F NMR analysis; see Table 2, Entry 17).
We subsequently proceeded to extend the scope of the
reaction to include propargylic chlorides as electrophiles.
As shown in Table 3, various propargylic chlorides 3 were
examined to give the corresponding propargylic trifluoro-
methylthiolated products 4 in good yields. A larger amount
of CuI (50 mol-%)/phen (50 mol-%) was, however, required.
Interestingly, the process proceeded smoothly even in the
absence of 18-crown-6. For example, the reaction of 3-phen-
ylpropargyl chloride (3a) afforded the desired product 4a in
81% yield (see Table 3, Entry 1). The reactions of 3-aryl-
propargyl chlorides 3b and 3c, which contained methyl- and
n-amyl (nAm) substitutents at the para position of the benz-
ene ring, took place to give the corresponding propargylic
trifluoromethylthiolated products 4b and 4c in 77 and 85%
yields, respectively (see Table 3, Entries 2 and 3). Notably,
useful halogenated arenes were accommodated under the
conditions. Thus, when p-fluoro- or p-chloro-substituted 3-
arylpropargyl chlorides 3d and 3e were subjected to the re-
action conditions, 4d and 4e were obtained in 77 and 75%
yields, respectively (see Table 3, Entries 4 and 5).
To gain better insight into the mechanism of this cop-
per(I)-catalyzed trifluoromethylthiolation of allylic halides,
we performed several experiments as shown in Scheme 2.
To test whether any radical intermediates are involved
in the reaction mechanism, the radical scavenger TEMPO
(2 equiv.) was added to the reaction mixture. An excellent
yield of 2b was obtained (99% yield, determined by 19F
NMR analysis), which was similar to that of the reaction
without TEMPO (94% yield; see Table 2, Entry 2). The tri-
fluoromethylthiolation was unaffected by the addition of
TEMPO, which suggests that no free radical intermediate
was generated during the reaction.
On the basis of the above experimental results and our
previous studies,[21a,24] a possible mechanism for the cata-
[a] Reagents and conditions: CuI (0.050 mmol), phen (0.050 mmol),
lytic trifluoromethylthiolation of the allylic halides is shown
allylic halides (0.25 mmol), CF3SiMe3 (0.75 mmol), S8 (0.75 mmol),
in Scheme 3. The reaction of the copper source with
KF (0.75 mmol), 18-crown-6 (0.50 mmol), dioxane (2.0 mL), 50 °C,
16 h, under N2. [b] Isolated yields. [c] Yield determined by 19F
CF3SiMe3, elemental sulfur, and KF in the presence of the
ligand would easily give copper(I) trifluoromethylthiolate NMR spectroscopic analysis.
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Synthesis of Allylic and Propargylic Trifluoromethyl Thioethers
Table 3. Copper(I)-catalyzed trifluoromethylthiolation of proparg- complex I.[24] Then, the oxidative addition of allylic halide
ylic chlorides.[a]
1 to I would afford allylcopper(III) species II.[11a,25] The
subsequent reductive elimination of II gives the desired
trifluoromethylthiolated product and generates III. Inter-
mediate I is then regenerated by the reaction of III with
CF3SiMe3, S8, and KF.
Conclusions
In summary, an efficient protocol has been developed for
the synthesis of allylic and propargylic trifluoromethyl thio-
ethers through the copper(I)-catalyzed trifluoromethyl-
thiolation of allylic bromides and propargylic chlorides,
respectively, with elemental sulfur and CF3SiMe3. This re-
action is tolerant to a reasonable range of functional groups
and provides facile access to a broad selection of trifluoro-
methylthiolated allylic and propargylic products in moder-
ate to excellent yields with high stereo- and regioselectivity.
The reaction mechanism that has been proposed involves
an allylcopper(III) intermediate. The scope and synthetic
applications of this transformation are under investigation.
Experimental Section
General Methods: The 1H, 19F, and 13C NMR spectroscopic data
[a] Reagents and conditions: CuI (0.25 mmol), phen (0.25 mmol),
1
were recorded with a Bruker AVIII 400 spectrometer. The H and
13C NMR chemical shifts were reported in parts per million (ppm)
downfield from tetramethylsilane. The 19F NMR chemical shifts
were reported relative to CFCl3 as the external standard, and low
field is positive. Coupling constants (J) are reported in Hertz (Hz).
propargylic chloride (0.50 mmol), CF3SiMe3 (2.5 mmol), S8
(2.5 mmol), KF (2.5 mmol), DMF (2.0 mL), 50 °C, 16 h, under N2.
[b] Isolated yields.
1
The solvent peak was used as the internal reference for H NMR
(residual CHCl3 at δ = 7.26 ppm) and 13C NMR (CDCl3 at δ =
77.0 ppm). The abbreviations that were used to describe the multi-
plicity of the signals are s (singlet), d (doublet), t (triplet), q (quar-
tet), m (multiplet), and br. (broad). HRMS was performed with a
Waters GCT-TOF at the Shanghai Institute of Organic Chemistry.
Allylic bromides 1c–1n[26] and propargylic chlorides 3a–3e[27] were
prepared according to published procedures. Other reagents were
received from commercial sources. Solvents were freshly dried and
degassed prior to use according to published procedures.[28] Purifi-
cations were performed by flash column chromatography using
Merck silica gel 60.
Scheme 2. Radical scavenger experiment with 2,2,6,6-tetrameth-
ylpiperidyl-1-oxyl (TEMPO).
General Procedure for Copper(I)-Catalyzed Trifluoromethylthiolation
of Allylic Halides: In a dry glove box, CuI (19.0 mg, 0.10 mmol),
phen (18.0 mg, 0.10 mmol), KF (87.2 mg, 1.5 mmol), S8 (48.0 mg,
1.5 mmol), 18-crown-6 (264.3 mg, 1.0 mmol), CF3SiMe3 (222 μL,
1.5 mmol), and dioxane (2.5 mL) were added to an oven-dried
5 mL test tube that was equipped with a Teflon screw cap. The
mixture was stirred at room temp. for 2 min, and then the allylic
halide (0.50 mmol) was added. The tube was sealed, and the solu-
tion was placed into a preheated 50 °C oil bath for 16 h. The tube
was removed from the oil bath and cooled to room temp. The reac-
tion mixture was filtered through a layer of Celite, which was rinsed
with diethyl ether. Water (5.0 mL) was added to the filtrate at 0 °C.
The resulting mixture was extracted with ethyl ether (3ϫ 10 mL),
and the combined organic layers were washed with water (3ϫ
10 mL) and then dried with magnesium sulfate. The solvent was
removed by rotary evaporation using an ice bath, and the residue
was purified by chromatography on a silica gel column (pentane)
to give the product.
Scheme 3. Proposed reaction mechanism.
Eur. J. Org. Chem. 2014, 5010–5016
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M. Rong, D. Li, R. Huang, Y. Huang, X. Han, Z. Weng
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Cyclohex-2-enyl(trifluoromethyl)sulfane (2a): Colorless oil (61 mg,
67% yield); Rf = 0.83 (pentane). H NMR (400 MHz, CDCl3): δ = orless oil (102 mg, 82% yield). H NMR (400 MHz, CDCl3): δ =
(E)-[3-(2-Methoxyphenyl)allyl](trifluoromethyl)sulfane (2h):[21a] Col-
1
1
5.96–5.91 (m, 1 H), 5.76–5.69 (m, 1 H), 4.01–3.95 (m, 1 H), 2.15–
1.94 (m, 4 H), 1.88–1.77 (m, 1 H), 1.76–1.66 (m, 1 H) ppm. 19F
NMR (376 MHz, CDCl3): δ = –40.1 (s, 3 F) ppm. 13C NMR
(101 MHz, CDCl3): δ = 132.4 (s), 131.0 (q, J = 308.1 Hz), 125.0
7.45 (d, J = 7.6 Hz, 1 H), 7.28 (t, J = 7.8 Hz, 1 H), 7.00–6.93 (m,
2 H), 6.91 (d, J = 8.3 Hz, 1 H), 6.33–6.24 (m, 1 H), 3.89 (s, 3 H),
3.77 (d, J = 7.4 Hz, 2 H) ppm. 19F NMR (376 MHz, CDCl3): δ =
–40.9 (s, 3 F) ppm. 13C NMR (101 MHz, CDCl3): δ = 156.8 (s),
130.9 (q, J = 306.9 Hz), 129.5 (s), 129.2 (s), 127.2 (s), 125.2 (s),
123.5 (s), 120.7 (s), 111.0 (s), 55.5 (s), 33.2 (q, J = 2.3 Hz) ppm.
(s), 41.2 (s), 29.8 (s), 24.6 (s), 18.8 (s) ppm. IR (KBr): ν = 2930,
˜
2358, 2340, 1128, 1035, 748 cm–1. GC–MS: m/z (%) = 182 [M]+, 81
(100) [M – SCF3]+. HRMS (EI): calcd. for C7H9F3S 182.0379;
found 182.0380.
(E)-[3-(3-Methoxyphenyl)allyl](trifluoromethyl)sulfane (2i):[21a] Col-
orless oil (61 mg, 49% yield). 1H NMR (400 MHz, CDCl3): δ =
(E)-Cinnamyl(trifluoromethyl)sulfane (2b):[21a] Colorless oil 7.30–7.27 (m, 1 H), 7.00 (d, J = 7.6 Hz, 1 H), 6.93 (s, 1 H), 6.85
1
(102 mg, 94% yield). H NMR (400 MHz, CDCl3): δ = 7.44–7.29 (dd, J = 8.2, 2.3 Hz, 1 H), 6.60 (d, J = 15.7 Hz, 1 H), 6.30–6.19
(m, 5 H), 6.65 (d, J = 15.7 Hz, 1 H), 6.32–6.22 (m, 1 H), 3.76 (d,
J = 7.4 Hz, 2 H) ppm. 19F NMR (376 MHz, CDCl3): δ = –40.8 (s,
3 F) ppm. 13C NMR (101 MHz, CDCl3): δ = 136.1 (s), 134.4 (s),
130.8 (q, J = 306.9 Hz), 128.7 (s), 128.2 (s), 126.5 (s), 123.0 (s),
32.7 (q, J = 2.2 Hz) ppm.
(m, 1 H), 3.85 (s, 3 H), 3.74 (d, J = 7.4 Hz, 2 H) ppm. 19F NMR
(376 MHz, CDCl3): δ = –40.9 (s, 3 F) ppm. 13C NMR (101 MHz,
CDCl3): δ = 159.8 (s), 137.5 (s), 134.2 (s), 130.8 (q, J = 306.9 Hz),
129.7 (s), 123.3 (s), 119.2 (s), 113.7 (s), 111.8 (s), 55.3 (s), 32.7 (q,
J = 2.2 Hz) ppm.
(E)-[3-(p-Tolyl)allyl](trifluoromethyl)sulfane (2c):[21a] Colorless oil (E)-(Trifluoromethyl){3-[4-(trifluoromethyl)phenyl]allyl}sulfane
(85 mg, 73% yield). 1H NMR (400 MHz, CDCl3): δ = 7.31 (d, J = (2j):[21a] Colorless oil (66 mg, 46 % yield). 1H NMR (400 MHz,
8.0 Hz, 2 H), 7.17 (d, J = 8.0 Hz, 2 H), 6.61 (d, J = 15.7 Hz, 1 H), CDCl3): δ = 7.61 (d, J = 8.2 Hz, 2 H), 7.49 (d, J = 8.1 Hz, 2 H),
6.25–6.16 (m, 1 H), 3.75 (d, J = 7.4 Hz, 2 H), 2.38 (s, 3 H) ppm.
19F NMR (376 MHz, CDCl3): δ = –40.9 (s, 3 F) ppm. 13C NMR
(101 MHz, CDCl3): δ = 138.1 (s), 134.3 (s), 133.3 (s), 130.9 (q, J =
6.66 (d, J = 15.7 Hz, 1 H), 6.41–6.31 (m, 1 H), 3.76 (d, J = 7.3 Hz,
2 H) ppm. 19F NMR (376 MHz, CDCl3): δ = –40.8 (s, 3 F), –62.6
(s, 3 F) ppm. 13C NMR (101 MHz, CDCl3): δ = 139.5 (s), 132.8
306.9 Hz), 129.4 (s), 126.4 (s), 121.9 (s), 32.8 (q, J = 2.4 Hz), 21.2 (s), 130.7 (q, J = 307.0 Hz), 129.9 (q, J = 32.5 Hz), 126.7 (s), 126.0
(s) ppm.
(s), 125.6 (q, J = 3.9 Hz), 124.1 (q, J = 271.9 Hz), 32.4 (q, J =
2.4 Hz) ppm.
(E)-[3-(m-Tolyl)allyl](trifluoromethyl)sulfane (2d):[21a] Colorless oil
(90 mg, 78% yield). 1H NMR (400 MHz, CDCl3): δ = 7.29–7.19 (E)-Methyl{4-[3-(trifluoromethylthio)prop-1-enyl]phenyl}sulfane
(m, 3 H), 7.13 (d, J = 7.2 Hz, 1 H), 6.61 (d, J = 15.7 Hz, 1 H),
6.30–6.20 (m, 1 H), 3.75 (d, J = 7.4 Hz, 2 H), 2.39 (s, 3 H) ppm.
19F NMR (376 MHz, CDCl3): δ = –40.9 (s, 3 F) ppm. 13C NMR
(101 MHz, CDCl3): δ = 138.3 (s), 136.1 (s), 134.5 (s), 130.9 (q, J =
306.9 Hz), 128.9 (s), 128.6 (s), 127.2 (s), 123.7 (s), 122.7 (s), 32.7
(q, J = 2.3 Hz), 21.3 (s) ppm.
(2k): White powder (119 mg, 90% yield); m.p. 39–41 °C. Rf = 0.65
(pentane). H NMR (400 MHz, CDCl3): δ = 7.33 (d, J = 8.3 Hz,
1
2 H), 7.24 (d, J = 8.3 Hz, 2 H), 6.58 (d, J = 15.7 Hz, 1 H), 6.27–
6.17 (m, 1 H), 3.74 (d, J = 7.4 Hz, 2 H), 2.52 (s, 3 H) ppm. 19F
NMR (376 MHz, CDCl3): δ = –40.8 (s, 3 F) ppm. 13C NMR
(101 MHz, CDCl3): δ = 138.7 (s), 133.7 (s), 132.9 (s), 130.9 (q, J =
306.9 Hz), 126.9 (s), 126.5 (s), 122.3 (s), 32.8 (q, J = 2.2 Hz), 15.6
(E)-[3-(4-Isopropylphenyl)allyl](trifluoromethyl)sulfane
(2e):[21a]
(s) ppm. IR (KBr): ν = 3021, 2921, 1431, 1404, 1234, 1112, 967,
˜
1
Colorless oil (91 mg, 70% yield). H NMR (400 MHz, CDCl3): δ
= 7.35 (d, J = 8.0 Hz, 2 H), 7.23 (d, J = 8.0 Hz, 2 H), 6.62 (d, J =
15.7 Hz, 1 H), 6.26–6.16 (m, 1 H), 3.75 (d, J = 7.4 Hz, 2 H), 2.94
(hept, J = 6.9 Hz, 1 H), 1.29 (d, J = 6.9 Hz, 6 H) ppm. 19F NMR
824, 801, 518 cm–1. GC–MS: m/z (%) = 264 [M]+, 163 (100) [M –
SCF3]+. HRMS (EI): calcd. for C11H11F3S2 264.0254; found
264.0253.
(376 MHz, CDCl3): δ = –40.8 (s, 3 F) ppm. 13C NMR (101 MHz, (E)-[3-(4-Fluorophenyl)allyl](trifluoromethyl)sulfane (2l): Colorless
1
CDCl3): δ = 149.1 (s), 134.3 (s), 133.7 (s), 130.8 (q, J = 306.9 Hz), oil (84 mg, 71% yield); Rf = 0.65 (pentane). H NMR (400 MHz,
126.8 (s), 126.6 (s), 122.0 (s), 33.9 (s), 32.8 (q, J = 2.4 Hz), 23.9
(s) ppm.
CDCl3): δ = 7.39–7.34 (m, 2 H), 7.08–7.01 (m, 2 H), 6.59 (d, J =
15.7 Hz, 1 H), 6.22–6.10 (m, 1 H), 3.73 (d, J = 7.4 Hz, 2 H) ppm.
19F NMR (376 MHz, CDCl3): δ = –40.8 (s, 3 F), –113.5 (m, 1
F) ppm. 13C NMR (101 MHz, CDCl3): δ = 162.6 (d, J = 247.6 Hz),
133.1 (s), 132.3 (d, J = 3.4 Hz), 130.8 (q, J = 306.9 Hz), 128.1 (d,
J = 8.1 Hz), 122.8 (d, J = 2.3 Hz), 115.6 (d, J = 21.7 Hz), 32.6 (q,
(E)-{3-[4-(tert-Butyl)phenyl]allyl}(trifluoromethyl)sulfane (2f):[21a]
1
Colorless oil (79 mg, 58% yield). H NMR (400 MHz, CDCl3): δ
= 7.40 (d, J = 8.3 Hz, 2 H), 7.35 (d, J = 8.3 Hz, 2 H), 6.62 (d, J =
15.6 Hz, 1 H), 6.27–6.17 (m, 1 H), 3.75 (d, J = 7.4 Hz, 2 H), 1.36
(s, 9 H) ppm. 19F NMR (376 MHz, CDCl3): δ = –40.9 (s, 3 F) ppm.
13C NMR (101 MHz, CDCl3): δ = 151.4 (s), 134.2 (s), 133.4 (s),
130.9 (q, J = 304.8 Hz), 126.3 (s), 125.6 (s), 122.1 (s), 34.6 (s), 32.8
(q, J = 2.4 Hz), 31.3 (s) ppm.
J = 2.4 Hz) ppm. IR (KBr): ν = 2360, 1603, 1509, 1233, 1112, 965,
˜
841, 811, 755, 516 cm–1. GC–MS: m/z (%) = 236 [M]+, 135 (100)
[M – SCF3]+. HRMS (EI): calcd. for C10H8F4S1 236.0283; found
236.0281.
(E)-[3-(4-Chlorophenyl)allyl](trifluoromethyl)sulfane (2m):[21a] Col-
orless oil (69 mg, 55% yield). 1H NMR (400 MHz, CDCl3): δ =
7.33 (s, 4 H), 6.58 (d, J = 15.7 Hz, 1 H), 6.29–6.17 (m, 1 H), 3.73
(d, J = 7.3 Hz, 2 H) ppm. 19F NMR (376 MHz, CDCl3): δ = –40.8
(s, 3 F) ppm. 13C NMR (101 MHz, CDCl3): δ = 134.6 (s), 133.8
(s), 133.1 (s), 130.7 (q, J = 307.0 Hz), 128.9 (s), 127.7 (s), 123.8 (s),
32.6 (q, J = 2.4 Hz) ppm.
(E)-(3-Mesitylallyl)(trifluoromethyl)sulfane (2g): Brown oil (52 mg,
40% yield); Rf = 0.77 (pentane). H NMR (400 MHz, CDCl3): δ =
1
6.92 (s, 2 H), 6.64 (d, J = 15.9 Hz, 1 H), 5.84–5.75 (m, 1 H), 3.79
(d, J = 7.2 Hz, 2 H), 2.32 (d, J = 5.6 Hz, 9 H) ppm. 19F NMR
(376 MHz, CDCl3): δ = –40.7 (s, 3 F) ppm. 13C NMR (101 MHz,
CDCl3): δ = 136.7 (s), 136.0 (s), 132.8 (s), 132.2 (s), 130.8 (q, J =
306.9 Hz), 128.7 (s), 128.1 (s), 33.0 (q, J = 2.3 Hz), 21.0 (s), 20.8
(s) ppm. IR (KBr): ν = 2922, 2861, 1612, 1481, 1446, 1241, 1114,
(E)-[3-(4-Bromophenyl)allyl](trifluoromethyl)sulfane (2n):[21a] Color-
˜
1
971, 854, 756 cm–1. GC–MS: m/z (%) = 260 [M]+, 159 (100) [M –
SCF3]+. HRMS (EI): calcd. for C13H15F3S 260.0847; found
260.0848.
less oil (78 mg, 53% yield). H NMR (400 MHz, CDCl3): δ = 7.48
(d, J = 8.3 Hz, 2 H), 7.26 (d, J = 8.3 Hz, 2 H), 6.56 (d, J = 15.7 Hz,
1 H), 6.31–6.16 (m, 1 H), 3.73 (d, J = 7.4 Hz, 2 H) ppm. 19F NMR
5014
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2014, 5010–5016

Synthesis of Allylic and Propargylic Trifluoromethyl Thioethers
(376 MHz, CDCl3): δ = –40.8 (s, 3 F) ppm. 13C NMR (101 MHz, 128.7 (s), 128.4 (s), 122.2 (s), 84.6 (s), 82.2 (s), 19.5 (q, J =
CDCl3): δ = 135.0 (s), 133.1 (s), 131.8 (s), 130.8 (q, J = 307.0 Hz), 3.4 Hz) ppm. IR (KBr): ν = 3059, 2927, 1491, 1443, 1271, 1243,
˜
128.0 (s), 123.9 (s), 122.0 (s), 32.6 (q, J = 2.4 Hz) ppm.
1113, 756, 690 cm–1. GC–MS: m/z (%) = 216 [M]+, 115 (100) [M –
SCF3]+. HRMS (EI): calcd. for C10H7F3S 216.0221; found
216.0218.
(E)-(3,7-Dimethylocta-2,6-dienyl)(trifluoromethyl)sulfane (2o):[21a]
1
Colorless oil (93 mg, 78% yield). H NMR (400 MHz, CDCl3): δ
= 5.30 (t, J = 7.8 Hz, 1 H), 5.09 (t, J = 6.7 Hz, 1 H), 3.59 (d, J =
7.9 Hz, 2 H), 2.09 (dt, J = 12.8, 5.9 Hz, 4 H), 1.72 (s, 6 H), 1.63 (s,
3 H) ppm. 19F NMR (376 MHz, CDCl3): δ = –41.4 (s, 3 F) ppm.
13C NMR (101 MHz, CDCl3): δ = 142.1 (s), 132.0 (s), 131.0 (q, J
= 306.7 Hz), 123.6 (s), 117.0 (s), 39.5 (s), 28.0 (q, J = 2.3 Hz), 26.2
(s), 25.7 (s), 17.7 (s), 16.0 (s) ppm.
(3-p-Tolylprop-2-ynyl)(trifluoromethyl)sulfane (4b): Brown oil
(89 mg, 77% yield); Rf = 0.73 (pentane). 1H NMR (400 MHz,
CDCl3): δ = 7.38 (m, 2 H), 7.17 (m, 2 H), 3.94 (s, 2 H), 2.40 (s, 3
H) ppm. 19F NMR (376 MHz, CDCl3): δ = –41.8 (s, 3 F) ppm. 13
C
NMR (101 MHz, CDCl3): δ = 138.9 (s), 131.6 (s), 130.4 (q, J =
307.5 Hz), 129.1 (s), 119.2 (s), 84.8 (s), 81.4 (s), 21.4 (s), 19.5 (q, J
= 3.3 Hz) ppm. IR (KBr): ν = 3031, 2924, 2360, 2342, 1510, 1457,
˜
(Z)-Ethyl 3-Ethoxy-4-(trifluoromethylthio)but-2-enoate (2p): Color-
less oil (60% yield by 19F NMR analysis; 18 mg, 14% yield); Rf =
0.45 (pentane). 1H NMR (400 MHz, CDCl3): δ = 5.10 (s, 1 H),
4.17 (dd, J = 8.0, 6.2 Hz, 2 H), 4.15 (s, 2 H), 3.89 (q, J = 7.0 Hz,
2 H), 1.37 (t, J = 7.0 Hz, 3 H), 1.28 (t, J = 8.1, 6.3 Hz, 3 H) ppm.
19F NMR (376 MHz, CDCl3): δ = –41.6 (s, 3 F) ppm. 13C NMR
(101 MHz, CDCl3): δ = 169.1 (s), 167.0 (s), 130.8 (q, J = 306.7 Hz),
92.8 (s), 64.7 (s), 59.9 (s), 29.8 (q, J = 2.3 Hz), 14.2 (s), 13.8 (s) ppm.
1409, 1275, 1245, 1114, 1021, 816, 756, 693 cm–1. GC–MS: m/z (%)
= 230 [M]+, 129 (100) [M – SCF3]+. HRMS (EI): calcd. for
C11H9F3S 230.0377; found 230.0373.
[3-(4-Pentylphenyl)prop-2-ynyl](trifluoromethyl)sulfane (4c): Brown
1
oil (126 mg, 85% yield); Rf = 0.68 (pentane). H NMR (400 MHz,
CDCl3): δ = 7.37 (d, J = 8.1 Hz, 2 H), 7.16 (d, J = 8.1 Hz, 2 H),
3.92 (s, 2 H), 2.71–2.46 (m, 2 H), 1.69–1.57 (m, 4 H), 1.39–1.28 (m,
3 H), 0.92 (t, J = 6.9 Hz, 2 H) ppm. 19F NMR (376 MHz, CDCl3):
δ = –41.9 (s, 3 F) ppm. 13C NMR (101 MHz, CDCl3): δ = 143.9
(s), 131.7 (s), 130.4 (q, J = 307.5 Hz), 128.5 (s), 119.4 (s), 84.8 (s),
81.4 (s), 35.9 (s), 31.4 (s), 30.9 (s), 22.5 (s), 19.6 (q, J = 3.4 Hz),
IR (KBr): ν = 2924, 1701, 1624, 1395, 1373, 1350, 1303, 1257, 1114,
˜
1053, 816, 756 cm–1. GC–MS: m/z (%) = 258 [M]+, 157 (100) [M –
SCF3]+. HRMS (EI): calcd. for C9H13F3O3S 258.0538; found
258.0536.
Procedure for Copper(I)-Catalyzed Trifluoromethylthiolation of
Cinnamyl Bromide (1b) in the Presence of TEMPO: In a dry glove
box, CuI (3.8 mg, 0.020 mmol), phen (3.6 mg, 0.020 mmol), KF
(17.4 mg, 0.30 mmol), S8 (9.6 mg, 0.30 mmol), 18-crown-6
(52.9 mg, 0.20 mmol), TEMPO (31.3 mg, 0.20 mmol), and dioxane
(1.0 mL) were added to a oven-dried 5 mL test tube that was
equipped with a Teflon screw cap. CF3SiMe3 (45 μL, 0.30 mmol)
was then added by syringe to the mixture. The reaction was stirred
at room temp. for 2 min, and then cinnamyl bromide (1b, 19.7 mg,
0.10 mmol) was added. The tube was sealed, and the solution was
placed into a preheated 50 °C oil bath for 16 h. The tube was re-
moved from the oil bath and then cooled to room temp. (Trifluoro-
methoxy)benzene (10 μL) was then added as an internal standard.
The reaction mixture was filtered through a layer of Celite, and the
filtrate was analyzed by 19F NMR spectoscopy. The yield of 2b was
calculated to be 99%.
14.0 (s) ppm. IR (KBr): ν = 3030, 2959, 2930, 2858, 2359, 2341,
˜
2225, 1511, 1466, 1275, 1243, 1114, 837, 756 cm–1. GC–MS: m/z
(%) = 285 [M – H]+, 185 (100) [M – SCF3]+. HRMS (EI): calcd.
for C15H17F3S 286.1003; found 286.0999.
[3-(4-Fluorophenyl)prop-2-ynyl](trifluoromethyl)sulfane (4d): Yellow
1
oil (90 mg, 77% yield); Rf = 0.68 (pentane). H NMR (400 MHz,
CDCl3): δ = 7.44 (dd, J = 8.7, 5.4 Hz, 2 H), 7.03 (t, J = 8.7 Hz, 2
H), 3.90 (s, 2 H) ppm. 19F NMR (376 MHz, CDCl3): δ = –41.9 (s,
3 F), –110.2 (m, 1 F) ppm. 13C NMR (101 MHz, CDCl3): δ = 162.8
(d, J = 250.1 Hz), 133.7 (d, J = 8.4 Hz), 130.4 (q, J = 307.5 Hz),
118.4 (d, J = 3.5 Hz), 115.6 (d, J = 22.1 Hz), 83.5 (s), 82.0 (s), 19.3
(q, J = 3.4 Hz) ppm. IR (KBr): ν = 3059, 2927, 2225, 1491, 1443,
˜
1271, 1243, 1113, 756, 690 cm–1. GC–MS: m/z (%) = 233 [M –
H]+, 133 (100) [M – SCF3]+. HRMS (EI): calcd. for C10H6F4S
234.0126; found 234.0125.
[3-(4-Chlorophenyl)prop-2-ynyl](trifluoromethyl)sulfane (4e): Yellow
oil (94 mg, 75% yield); Rf = 0.76 (pentane). H NMR (400 MHz,
CDCl3): δ = 7.38 (d, J = 8.0 Hz, 2 H), 7.32 (d, J = 8.0 Hz, 2 H),
3.90 (s, 2 H) ppm. 19F NMR (376 MHz, CDCl3): δ = –41.8 (s, 3
F) ppm. 13C NMR (101 MHz, CDCl3): δ = 134.8 (s), 133.0 (s),
130.3 (q, J = 307.5 Hz), 128.7 (s), 120.7 (s), 83.4 (s), 83.3 (s), 19.4
General Procedure for Copper(I)-Catalyzed Trifluoromethylthiolation
of Propargylic Chlorides: In a dry glove box, CuI (48.0 mg,
0.25 mmol), phen (45.0 mg, 0.25 mmol), KF (145.0 mg, 2.5 mmol),
S8 (80.0 mg, 2.5 mmol), CF3SiMe3 (370 μL, 2.5 mmol), and DMF
(2.5 mL) were added to an oven-dried 5 mL test tube that was
equipped with a Teflon screw cap. The mixture was stirred at room
temp. for 2 min, and then the propargylic chloride (0.50 mmol) was
added. The tube was sealed, and the solution was placed into a
preheated 50 °C oil bath for 16 h. The tube was removed from the
oil bath and cooled to room temp. The reaction mixture was fil-
tered through a layer of Celite, which was rinsed with diethyl ether.
Water (5.0 mL) was added to the filtrate at 0 °C. The resulting mix-
ture was extracted with ethyl ether (3ϫ 10 mL), and the combined
organic layers were washed with water (3ϫ 10 mL) and then dried
with magnesium sulfate. The solvent was removed by rotary evapo-
ration using an ice bath, and the residue was purified by
chromatography on a silica gel column (pentane) to give the prod-
uct.
1
(q, J = 3.4 Hz) ppm. IR (KBr): ν = 2962, 2360, 2341, 1490, 1275,
˜
1243, 1112, 1015, 827, 757 cm–1. GC–MS: m/z (%) = 249 [M –
H]+, 149 (100) [M – SCF3]+. HRMS (EI): calcd. for C10H6ClF3S
249.9831; found 249.9833.
Supporting Information (see footnote on the first page of this arti-
1
cle): Copies of the H, 19F, and 13C NMR spectra of all products.
Acknowledgments
Financial support from the National Natural Science Foundation
of China (NSFC) (grant number 21372044), the Research Fund for
the Doctoral Program of Higher Education of China (grant
number 20123514110003), the Scientific Research Foundation for
the Returned Overseas Chinese Scholars, State Education Ministry,
P. R. China (grant number 2012-1707), the Science Foundation of
the Fujian Province, China (grant number 2013J01040), and
(3-Phenylprop-2-ynyl)(trifluoromethyl)sulfane (4a): Brown oil
(88 mg, 81% yield); Rf = 0.73 (pentane). 1H NMR (400 MHz,
CDCl3): δ = 7.49–7.41 (m, 2 H), 7.39–7.29 (m, 3 H), 3.92 (s, 2
H) ppm. 19F NMR (376 MHz, CDCl3): δ = –41.8 (s, 3 F) ppm. 13
C
NMR (101 MHz, CDCl3): δ = 131.8 (s), 130.4 (q, J = 307.5 Hz),
Eur. J. Org. Chem. 2014, 5010–5016
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5015

M. Rong, D. Li, R. Huang, Y. Huang, X. Han, Z. Weng
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Received: April 24, 2014
Published Online: July 10, 2014
5016
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