A New Approach for the Synthesis of Perfluoroalkanesulfenic Acids

Article abstract of DOI:10.1002/ejoc.202100055

A new and more practical method for the preparation of solution-stable perfluoroalkanesulfenic acids was successfully developed. Starting from perfluoroalkyl iodides, perfluoroalkyl sulfoxides were synthesized by their substitution reaction with alkyl mercaptans and the following oxidation of resulting perfluoroalkyl sulfides with m-CPBA. Subsequent β-H elimination of perfluoroalkyl sulfoxides under heating conditions gave the corresponding perfluoroalkanesulfenic acids in good yields.

Full text of DOI:10.1002/ejoc.202100055

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A New Approach for the Synthesis of
Perfluoroalkanesulfenic Acids
Jia-Hong Xu,[a] Min Jiang,[b] Li-Ping Song,*[a] and Jin-Tao Liu*[b]
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A new and more practical method for the preparation of
solution-stable perfluoroalkanesulfenic acids was successfully
developed. Starting from perfluoroalkyl iodides, perfluoroalkyl
sulfoxides were synthesized by their substitution reaction with
alkyl mercaptans and the following oxidation of resulting
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perfluoroalkyl sulfides with m-CPBA. Subsequent β-H elimina-
tion of perfluoroalkyl sulfoxides under heating conditions gave
the corresponding perfluoroalkanesulfenic acids in good yields.
Introduction
perfluorinated sulfenic acids have good reactivities and could
undergo addition reactions with alkenes, alkynes, or allenes.[11]
In many cases, similar reaction behaviors to those of normal
non-fluorine sulfenic acids were observed with these perfluori-
nated sulfenic acids, indicating that perfluoroalkanesulfenic
acids could provide a simple and stable model to study the
chemistry of sulfenic acids and mimic some life processes
involving sulfenic acids. Previously, perfluoroalkanesulfenic
acids were obtained by Cope-type elimination reaction of the
corresponding perfluoroalkanesulfinimines. As shown in
Scheme 1, the synthesis of perfluoroalkanesulfinimine required
multi-step reactions and made the preparation of perfluoroalka-
nesulfenic acids less efficient and uneconomic. Therefore, it is
very desirable to develop a more convenient synthetic method
for perfluoroalkanesulfenic acids.
Sulfenic acids (RSOH) have been recognized as active sulfur-
containing intermediates which widely exist in organisms and
play important roles in the life process.[1] They are key
intermediates to regulate protein redox and have catalytic or
regulatory functions in many redox-sensitive proteins, which
are related to a variety of signal transduction pathways.[2] These
signal transduction processes are closely related to the patho-
genesis and drug design of many diseases. Sulfenic acids have
both nucleophilic and electrophilic properties[3] and easily
undergo self-condensation to give thiosulfinates in the absence
of suitable trapping agents, which further transform into
thiosulfonates and disulfides through redox conversion.[4] There-
fore, most sulfenic acids are unstable and only exist as active
intermediates in some reactions,[5] and many efforts have been
made to synthesize and isolate stable sulfenic acids.[6] In
general, either a huge steric hindrance[7] or intramolecular
hydrogen bond,[8] or a combination of both,[9] is necessary for a
sulfenic acid to be stable enough for isolation or character-
ization. Although some stable sulfenic acids have been
synthesized so far, most of them are not suitable for directly
studying the chemistry of the sulfenic group (À SOH) due to
difficulties in their preparation, multireactive sites, or huge
steric hindrance. As a result, research on the chemistry of
sulfenic acids is still fragmentary.
During our study on the reaction of polyfluoroalkanesulfenic
acids with alkenes, it was found that the addition of sulfenic
acids to alkenes and the reverse syn-β-H elimination of resulted
sulfoxides could take place at the same time.[11] Inspired by this,
we tried a new synthetic method and found that using β-H
elimination of perfluoroalkyl sulfoxides as a key step, perfluor-
In 2014, we reported a special type of solution-stable
perfluoroalkanesulfenic acids, in which the strong electron-
withdrawing perfluoroalkyl groups played an important role to
stabilize the SOH group.[10] Further studies showed that these
[a] J.-H. Xu, Prof. Dr. L.-P. Song
Department of Chemistry
School of Science, Shanghai University
99 Shangda Road, Shanghai 200436, China
E-mail: lpsong@shu.edu.cn
[b] Dr. M. Jiang, Prof. Dr. J.-T. Liu
Key Laboratory of Organofluorine Chemistry
Shanghai Institute of Organic Chemistry, Chinese Academy of Science
345 Lingling Road, Shanghai 200032, China
E-mail: jtliu@sioc.ac.cn
http://liujintao.sioc.ac.cn
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/ejoc.202100055
Scheme 1. Synthetic methods for perfluoroalkanesulfenic acids.
Eur. J. Org. Chem. 2021, 1919–1923
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°
oalkanesulfenic acids could be easily obtained from perfluor-
oalkyl iodides with high efficiency and good yields (Scheme 1,
eq 2). The results are reported in this paper.
(entries 15–16), and a better result was obtained at À 20 C
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2
3
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°
(entries 17–19). As a comparison, the reaction at À 20 C in the
presence of K3PO4 was also tried and a lower yield was obtained
(44%, entry 20). Therefore, the optimal conditions for the
formation of 2a were set as follows: 1.0 equiv. of alkyl
mercaptan, 1.2 equiv. of perfluoroalkyl iodide, and 1.1 equiv. of
Results and Discussion
°
NaH in DMF at À 20 C.
Initially, we tried to synthesize alkyl perfluoroalkyl sulfides and
embarked on our investigation with the reaction of perfluor-
obutyl iodide with cyclohexanethiol (1a) in the presence of
sodium bisulfite and sodium formate in a mixed solvent of
dimethyl formamide (DMF) and water referring to the
literature.[12] Unfortunately, cyclohexyl perfluorobutyl sulfide
(2a) was only obtained in 10% yield (Table 1, entry 1).
Other bases, such as KH2PO4, NaHCO3, t-BuOK, Na2HPO4,
NaOH, K2CO3, Cs2CO3, K3PO4, and NaH, were also tested
(entries 2–10). It was found that KH2PO4, NaHCO3, t-BuOK,
Na2HPO4, and NaOH could not promote the reaction (entries 2–
6). Gratefully, NaH afforded 2a in 41% yield (entry 10). Solvents
were also screened, and lower yields were obtained in
tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and dichloro-
methane (DCM) (entries 11–13). Changing the addition se-
quence of reactants showed that the yield of 2a could be
improved to 58% when perfluorobutyl iodide was added to the
pre-stirred mixture of cyclohexanethiol and NaH (entry 14).
Further investigation indicated that a slightly higher yield of 2a
could be achieved with a ratio of 1a/C4F9I/NaH=1:1.2:1.1
Next, the oxidation of cyclohexyl perfluorobutyl sulfide was
studied. It was found that 2a could be easily oxidized by 3-
chloroperbenzoic acid (m-CPBA), giving the corresponding
sulfoxide 3a in good yield along with a small amount of sulfone
as a byproduct. Screening the ratio of reactants, reaction
temperature and time showed that the best result was obtained
when 1.0 equivalent of m-CPBA was used and the reaction was
carried out at room temperature (Scheme 2). Other oxidants
such as hydrogen peroxide, oxone, and NaIO4 were also tried
but did not give a better result.
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On the basis of our previous reaction conditions for the
synthesis of perfluoroalkanesulfenic acids via Cope-type elimi-
nation of perfluoroalkanesulfinimines,[10] β-H elimination of 3a
was firstly carried out in toluene at 80 C for 10 h. However, 19F
°
NMR monitoring showed that perfluoro-n-butanesulfenic acid
(4a) was formed in only 14% yield. When the reaction temper-
ature was increased to 110 C, 100% conversion of 3a and 88%
°
yield of 4a were obtained after 8 hours (Scheme 2).
Considering an alkene was also produced in the β-H
elimination reaction of alkyl perfluoroalkyl sulfoxide, and the
alkene with a shorter carbon chain and a lower boiling point
would be easier to remove from the reaction mixture, several
perfluorobutyl sulfoxides (3b–3f) were prepared from different
alkyl mercaptans and their β-H elimination reactions were
studied to find a more practical method for perfluoroalkane-
sulfenic acids. As shown in Scheme 3, perfluoroalkyl sulfoxides
3b–3e with 2-butyl, n-propyl, 2-methyl-1-propyl, or n-butyl
group could not completely convert into sulfenic acid, whether
increasing temperature or prolonging reaction time. Fortu-
nately, 100% conversion was obtained with sulfoxide 3f
containing a shorter iso-propyl group under similar conditions.
Using cyclohexyl or iso-propyl as the counterpart alkyl
group, a series of alkyl perfluoroalkyl sulfoxides were synthe-
sized from different perfluoroalkyl iodides and their β-H
elimination reactions were studied to prepare the correspond-
Table 1. Optimization of reaction conditions for the formation of sulfide 2a.
Entry[a]
Base
C4F9I
(equiv.)
Solvent
Temp
Yield
[%][b]
°
[ C]
1
2
3
4
5
6
7
8
Na2SO3/HCOONa
KH2PO4
NaHCO3
tBuOK
Na2HPO4
NaOH
K2CO3
Cs2CO3
K3PO4
NaH
NaH
NaH
NaH
NaH
NaH
NaH
NaH
NaH
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.2
1.5
1.2
1.2
1.2
1.2
DMF/H2O
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
THF
DMSO
DCM
DMF
DMF
DMF
DMF
DMF
DMF
DMF
RT
RT
RT
RT
RT
RT
RT
RT
RT
RT
RT
RT
RT
RT
RT
RT
0
10
trace
trace
trace
trace
trace
20
13
30
41
10
34
trace
58
63
54
55
85
80
44
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10
11
12
13
14[c]
15[c]
16[c]
17[c]
18[c]
19[c]
20
À 20
À 40
À 20
NaH
K3PO4
[a] Reaction conditions: 1 a (1.0 mmol), C4F9I (1.0–1.5 mmol), base
(1.1 mmol) for 1 h. [b] Determined by 19F NMR spectroscopy using PhCF3
as internal standard. [c] After stirring the mixture of 1a and NaH for 1 h at
room temperature, perfluorobutyl iodide was added at the specified
temperature.
Scheme 2. Synthesis of perfluoro-n-butanesulfenic acid.
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acids. With advantages such as high efficiency, easy-to-handle,
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2
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and mild conditions, this new method would find applications
in organic syntheses and researches on the chemistry of
sulfonic acids.
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Experimental Section
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General information
Unless otherwise mentioned, solvents and reagents were purchased
from commercial sources and used as received. Solvents were
freshly distilled by standard procedure prior to use. Melting points
were measured on a RY-I apparatus and uncorrected. 1H NMR
spectra were recorded in CDCl3 on a Bruker AM 400 spectrometer
(400 MHz) with TMS as an internal standard. 19F NMR spectra were
taken on a Bruker AM 400 (376 MHz) spectrometer with CFCl3 as an
external standard. 13C NMR spectra were recorded in CDCl3 on a
Varian AM-400 spectrometer (100 MHz) or Agilent AM-400
(100 MHz) spectrometer with TMS as an internal standard. For
compounds 3a–3f and 3i–3l, the peaks for fluorine-possessing
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Scheme 3. β-H elimination of various perfluorobutyl sulfoxides.
ing perfluoroalkanesulfenic acids. As shown in Table 2, trifluor-
omethanesulfenic acid (4b), perfluoroethanesulfenic acid (4c),
perfluoro-n-hexanesulfenic acid (4d), and perfluoro-n-octane-
sulfenic acid (4e) were successfully prepared in good yields
under the optimized conditions, and similar results were
obtained with isopropyl and cyclohexyl. It is worth mentioning
that crude products 2 could be used directly in this process
without purification.
carbon atoms in perfluoroalkyl groups are difficult to find out in 13
C
NMR spectra because of their multiplicity. High-resolution mass
spectra (HRMS) were recorded on an IonSpec FT-ICR mass
spectrometer with FI or ESI resource.
Typical procedure for the prepartion of compound 2: In a 50 mL
three-necked flask, the solution of sodium hydride (11 mmol) and
alkyl mercaptan (10 mmol) in DMF (15 mL) was stirred at room
Conclusions
°
temperature for 1 hour. Then the mixture was cooled to À 20 C and
perfluoroalkyl iodide (12 mmol) was quickly added. After 1 hour,
the reaction mixture was warmed to room temperature and
quenched with water. The resulting solution was extracted with
DCM for three times (3×10 mL). The organic layers were combined,
dried over MgSO4, and concentrated to give crude product 2.
In summary, we have developed a convenient and more
practical method for the synthesis of perfluoroalkanesulfenic
acids. Using perfluoroalkyl iodides as starting materials, the
corresponding perfluoroalkyl sulfides could be easily prepared
by the substitution reaction with alkyl mercaptans. Subsequent
oxidation with m-CPBA and β-H elimination reaction of resulted
perfluoroalkyl sulfoxides gave desired perfluoroalkanesulfonic
Typical procedure for the prepartion of compound 3: To a
solution of m-CPBA (1.0 equiv) in DCM (20 mL) was added dropwise
the solution of above crude product 2 in DCM (10 mL) in 5 minutes.
The mixture was stirred overnight at room temperature. The
resulting mixture was quenched with aqueous NaHCO3 solution.
The resulting solution was extracted with DCM for three times (3×
20 mL). The combined organic solution was washed with brine,
dried over MgSO4, and concentrated under reduced pressure. The
residue was purified by column chromatography on silica gel (PE:
DCM=5:1) to give product 3.
Table 2. Synthesis of perfluoroalkanesulfenic acids.
Typical procedure for the preparation of compound 4: A solution
°
of sulfoxide 3 in dry toluene (0.2 M) was stirred at 100–160 C in a
sealed tube. After the completion of the reaction, the mixture was
cooled to room temperature and the yield of 4 was determined by
19F NMR spectroscopy.
Compound 3a: light yellow liquid; 2.10 g, 60% yield; IR (neat, cmÀ 1):
1
v 2939, 2862, 1454, 1235, 1138, 1047, 862, 746; H NMR (400 MHz,
CDCl3) δ 3.09–3.19 (m, 1H), 1.97–2.01 (m, 1H), 1.82–1.92 (m, 3H),
1.51–1.69 (m, 3H), 1.30–1.43 (m, 2H), 1.17–1.27 (m, 1H) ppm; 19F
NMR (376 MHz, CDCl3) δ À 81.31~À 81.41 (m, 3F), À 116.82 (AB, J=
248.1 Hz, 2F), À 122.27 (AB, J=300.8 Hz, 2F), À 126.45 (AB, J=
293.3 Hz, 2F) ppm; 13C NMR (101 MHz, CDCl3) δ 56.95, 27.08, 25.26,
24.94, 24.80, 23.90 ppm; MS (FI) (m/z, %): 351 (3) [M+H]+; HRMS
(FI) calcd for C10H12F9OS [M+H]+ requires 351.0456, found
351.0460.
Entry
R/Rf
3
Elimination
4
Yield [%][a]
Yield [%][b]
°
1
2
3
4
5
6
7
8
Cy/C4F9
i-Pr/C4F9
Cy/CF3
Cy/C2F5
Cy/C6F13
i-Pr/C6F13
Cy/C8F17
i-Pr/C8F17
3a, 60
3f, 61
3g, 23
3h, 48
3i, 51
3j, 55
3k, 55
3l, 56
110 C, 8 h
4a, 86
4a, 88
4b, 70
4c, 86
4d, 84
4d, 86
4e, 87
4e, 85
°
100 C, 3 h
°
160 C, 10 min
°
110 C, 8 h
°
110 C, 8 h
°
100 C, 3 h
°
110 C, 8 h
Compound 3b: light yellow liquid; 1.40 g, 43% yield; IR (neat,
cmÀ 1): v 2968, 2937, 1468, 1351, 1237, 1139, 866, 725; 1H NMR
(400 MHz, CDCl3) δ 3.02–3.08 (m, 1H), 2.51–2.58 (m, 1H), 2.24–2.31
°
100 C, 3 h
[a] Overall isolated yields for two steps. [b] Determined by 19F NMR
spectroscopy using PhCF3 as internal standard.
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(m, 1H), 1.08–1.12 (m, 6H) ppm; 19F NMR (376 MHz, CDCl3) δ
NMR (400 MHz, CDCl3) δ 3.13–3.21 (m, 1H), 2.00–2.04 (m, 1H), 1.84–
1.96 (m, 3H), 1.22–1.76 (m, 3H), 1.34–1.46 (m, 2H), 1.21–1.31 (m, 1H)
ppm; 19F NMR (376 MHz, CDCl3) δ À 81.14 (t, J=10.0 Hz, 3F),
À 116.44 (AB, J=244.4 Hz, 2F), À 121.17 (AB, J=304.6 Hz, 2F),
À 122.02~À 122.17 (m, 2F), À 122.93~À 123.08 (m, 2F), À 126.34~
À 126.47 (m, 2F) ppm; 13C NMR (101 MHz, CDCl3) δ 57.01 (t, J=
3.6 Hz), 27.11, 25.31, 24.98, 24.84, 23.93 ppm; MS (EI) (m/z, %): 368
(1) [MÀ C6H11]+, 169 (6), 131 (13), 119 (12), 100 (9), 83 (100), 69 (21),
55 (80); HRMS (ESI) calcd for C12H11F13OS [M+Na]+ requires
473.0214, found 473.0215.
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2
3
4
5
6
7
8
9
À 81.20~À 81.35 (m, 3F), À 119.26 (AB, J=248.2 Hz, 2F), À 121.83
(AB, J=308.3 Hz, 2F), À 126.48 (AB, J=304.6 Hz, 2F) ppm; 13C NMR
(101 MHz, CDCl3) δ 56.12 (t, J=17.0 Hz), 23.23, 22.60, 20.98 ppm;
MS (FI) (m/z, %): 324 (34) [M]+; HRMS (FI) calcd for C8H9F9OS [M]+
requires 324.0218, found 324.0225.
Compound 3c: light yellow liquid; 0.91 g, 29% yield; IR (neat, cmÀ 1):
1
v 2975, 2942, 1465, 1351, 1236, 1013, 865, 725; H NMR (400 MHz,
CDCl3) δ 3.04–3.11 (m, 1H), 2.72–2.80 (m, 1H), 1.79–1.98 (m, 2H),
1.09 (t, J=7.4 Hz, 3H) ppm; 19F NMR (376 MHz, CDCl3) δ À 81.30~
À 81.35 (m, 3F), À 119.25 (AB, J=248.2 Hz, 2F), À 122.03 (AB, J=
304.6 Hz, 2F), À 126.57 (AB, J=293.3 Hz, 2F) ppm; 13C NMR
(101 MHz, CDCl3) δ 49.50, 15.61, 12.87 ppm; MS (EI) (m/z, %): 311 (3)
[M+H]+, 219 (19), 131 (50), 119 (28), 100 (38), 91 (54), 69 (100), 63
(18); HRMS (ESI) calcd for C7H7F9OS [M+H]+ requires 311.0145,
found 311.0147.
°
Compound 3j: white solid; m.p. 36–38 C; 2.26 g, 55% yield; IR
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13
14
15
16
17
18
19
20
21
22
23
24
25
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27
28
29
30
31
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41
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1
(neat, cmÀ 1): v 2934, 2859, 1453, 1241, 1203, 1145, 1076, 666; H
NMR (400 MHz, CDCl3) δ 3.32–3.39 (m, 1H), 1.38–1.41 (m, 6H) ppm;
19F NMR (376 MHz, CDCl3) δ À 80.95~À 81.01 (m, 3F), À 116.73 (AB,
J=244.4 Hz, 2F), À 120.99~À 121.08 (m, 1F), À 121.16~À 121.27 (m,
1F), À 121.90~À 122.07 (m, 2F), À 122.82~À 123.01 (m, 2F),
À 126.21~À 126.35 (m, 2F) ppm; 13C NMR (101 MHz, CDCl3) δ 49.39
(t, J=3.5 Hz), 17.34, 13.9 ppm; MS (FI) (m/z, %): 411 (1) [M+H]+;
HRMS (FI) calcd for C9H8F13OS [M+H]+ requires 411.0086, found
411.0081.
Compound 3d: light yellow liquid; 0.94 g, 29% yield; IR (neat,
cmÀ 1): v 2968, 2937, 1468, 1350, 1237, 1099, 866, 725; 1H NMR
(400 MHz, CDCl3) δ 3.04–3.09 (m, 1H), 2.52–2.59 (m, 1H), 2.26–2.33
(m, 1H), 1.11–1.14 (m, 6H) ppm; 19F NMR (376 MHz, CDCl3) δ
À 81.10~À 81.18 (m, 3F), À 118.65 (AB, J=251.9 Hz, 2F), À 121.73
(AB, J=293.3 Hz, 2F), À 126.39 (AB, J=293.3 Hz, 2F) ppm; 13C NMR
(101 MHz, CDCl3) δ 56.19 (t, J=4.1 Hz), 23.25, 22.70, 21.07 ppm; MS
(FI) (m/z, %): 324 (30) [M]+; HRMS (FI) calcd for C8H9F9OS [M]+
requires 324.0222, found 324.0225.
°
Compound 3k: white solid; m.p. 72–74 C; 3.03 g, 55% yield; IR
1
(neat, cmÀ 1): v 2931, 2859, 1371, 1204, 1148, 1120, 1076, 652; H
NMR (400 MHz, CDCl3) δ 3.15–3.22 (m, 1H), 2.02–2.06 (m, 1H), 1.85–
1.98 (m, 3H), 1.56–1.74 (m, 3H), 1.35–1.48 (m, 2H), 1.22–1.33 (m, 1H)
ppm; 19F NMR (376 MHz, CDCl3) δ À 80.98~À 81.04 (m, 3F), À 116.3
(AB, J=248.2, 2F), À 121.01 (AB, J=300.8 Hz, 2F), À 121.64~À 122.15
(m, 6H), À 122.80~À 122.96 (m, 2F), À 126.23~À 126.37 (m, 2F) ppm;
13C NMR (101 MHz, CDCl3) δ 57.04 (t, J=3.1 Hz), 27.16 (d, J=2.8 Hz),
25.36, 25.01, 24.89, 23.96 ppm; HRMS (ESI) calcd for C14H11F17OS [M
+Na]+ requires 573.0149, found 573.0151.
Compound 3e: light yellow liquid; 1.33 g, 41% yield; IR (neat, cmÀ 1):
1
v 2967, 2939, 1468, 1350, 1236, 1139, 864, 724; H NMR (400 MHz,
CDCl3) δ 3.00–3.07 (m, 1H), 2.73–2.82 (m, 1H), 1.74–1.85 (m, 2H),
1.40–1.53 (m, 2H), 0.86–0.94 (m, 3H) ppm; 19F NMR (376 MHz, CDCl3)
δ À 81.43~À 81.67 (m, 3F), À 119.93 (AB, J=248.2 Hz, 2F), À 122.11
(AB, J=312.1 Hz, 2F), À 126.70 (AB, J=293.3 Hz, 2F) ppm; 13C NMR
(101 MHz, CDCl3) δ 47.42 (t, J=4.4 Hz), 23.74, 21.69, 13.11 ppm;
HRMS (ESI) calcd for C8H9F9OS [M+H]+ requires 325.0301, found
325.0303.
°
Compound 3l: white solid; m.p. 70–72 C; 2.86 g, 56% yield; IR
(neat, cmÀ 1): v 2929, 1371, 1331, 1203, 1150, 1121, 928, 654; 1H NMR
(400 MHz, CDCl3) δ 3.31–3.42 (m, 1H), 1.39–1.42 (m, 6H) ppm; 19F
NMR (376 MHz, CDCl3) δ À 80.93~À 80.99 (m, 3F), À 116.68 (AB, J=
244.4, 2F), À 120.92~À 121.01 (m, 1F), À 121.08~À 121.18 (m, 1F),
À 121.71~À 122.07 (m, 6F), À 122.77~À 122.93 (m, 2F), À 126.23~
À 126.32 (m, 2F) ppm; 13C NMR (101 MHz, CDCl3) δ 49.42 (t, J=
10.2 Hz), 17.36, 14.01 ppm; MS (FI) (m/z, %): 511 (17) [M+H]+;
HRMS (FI) calcd for C11H8F17OS [M+H]+ requires 511.0013, found
511.0019.
Compound 3f: light yellow liquid; 1.89 g, 61% yield; IR (neat, cmÀ 1):
1
v 2925, 1353, 1275, 1248, 1137, 1079, 749, 724; H NMR (400 MHz,
CDCl3) δ 3.30–3.41 (m, 1H), 1.38–1.41 (m, 6H) ppm; 19F NMR
(376 MHz, CDCl3) δ À 81.42~À 81.62 (m, 3F), À 117.39 (AB, J=
247.9 Hz, 2F), À 122.43 (AB, J=304.6 Hz, 2F), À 126.60 (AB, J=
293.3 Hz, 2F) ppm; 13C NMR (101 MHz, CDCl3) δ 49.36, 17.31,
13.99 ppm; MS (FI) (m/z, %): 311 (9) [M+H]+; HRMS (FI) calcd for
C7H8F9OS [M+H]+ requires 311.0145, found 311.0147.
Compound 4a: 19F NMR (376 MHz, CDCl3) δ À 81.18 (t, J=10.0 Hz,
3F), À 102.72 (t, J=12.7 Hz, 2F), À 122.28~À 122.37 (m, 2F),
À 126.13~À 126.20 (m, 2F) ppm.
Compound 3g: light yellow liquid; 0.46 g, 23%; IR (neat, cmÀ 1): v
1
2937, 2860, 1453, 1169, 1139, 1076, 1046, 745; H NMR (400 MHz,
Compound 4b: 19F NMR (376 MHz, CDCl3) δ À 56.03 (s, 3F) ppm.
CDCl3) δ 3.04–3.11 (m, 1H), 2.04–2.11 (m, 1H), 1.82–1.96 (m, 3H),
1.51–1.71 (m, 3H), 1.21–1.49 (m, 3H) ppm; 19F NMR (376 MHz, CDCl3)
δ À 70.09 (s, 3F) ppm; 13C NMR (101 MHz, CDCl3) δ 123.93 (q, J=
336.3 Hz), 57.46, 26.17, 25.08, 25.04, 24.77, 24.40 ppm; MS (FI) (m/z,
%): 201 (1) [M+H]+; HRMS (FI) calcd for C7H12F3OS [M+H]+ requires
201.0551, found 201.0555.
Compound 4c: 19F NMR (376 MHz, CDCl3) δ À 82.64~À 82.62 (m,
3F), À 107.61~À 107.73 (m, 2F) ppm.
Compound 4d: 19F NMR (376 MHz, CDCl3) δ À 81.13 (t, J=10.3 Hz,
3F), À 102.51 (t, J=13.7 Hz, 2F), À 121.40~À 121.48 (m, 2F),
À 121.92~À 121.99 (m, 2F), À 122.81~À 122.90 (m, 2F), À 126.21~
À 126.31 (m, 2F) ppm.
Compound 3h: light yellow liquid; 1.21 g, 48% yield; IR (neat,
cmÀ 1): v 2938, 2861,1454, 1331,1216, 1122, 949, 747; 1H NMR
(400 MHz, CDCl3) δ 3.17–3.24 (m, 1H), 2.03–2.10 (m, 1H), 1.84–1.98
(m, 3H), 1.67–1.74 (m, 2H), 1.56–1.67 (m, 1H), 1.35–1.48 (m, 2H),
1.21–1.33 (m, 1H) ppm; 19F NMR (376 MHz, CDCl3) δ À 80.42 (s, 3F),
À 120.03 (AB, J=244.4 Hz, 2F) ppm; 13C NMR (101 MHz, CDCl3) δ
118.01 (qt, J=288.3, 32.1 Hz), 117.03 (ddq, J=314.5, 304.2, 39.1 Hz),
56.75 (t, J=3.0 Hz), 26.88 (d, J=2.9 Hz), 25.15, 24.98, 24.79,
24.10 ppm; HRMS (ESI) calcd for C8H12F5OS [M+H]+ requires
251.0522, found 251.0524.
Compound 4e: 19F NMR (376 MHz, CDCl3) δ À 81.11~À 81.22 (m,
3F), À 102.41~À 102.50 (m, 2F), À 121.36~À 121.41 (m, 2F),
À 121.74~À 121.95 (m, 6F), À 122.78 (s, 2F), À 126.21~À 126.32 (m,
2F) ppm.
Acknowledgements
Financial support from the National Natural Science Foundation
of China (No. 21572257) is gratefully acknowledged.
°
Compound 3i: white solid; m.p. 44–46 C; 2.31 g, 51% yield; IR
1
(neat, cmÀ 1): v 2934, 2859, 1453, 1241, 1203, 1145, 1076, 666; H
Eur. J. Org. Chem. 2021, 1919–1923
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Full Papers
doi.org/10.1002/ejoc.202100055
Chem. 2000, 611, 146–157; g) T. Saiki, K. Goto, N. Tokitoh, R. Okazaki, J.
Conflict of Interest
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Keywords: β-H Elimination
Oxidation · Synthetic methods
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Fluorinated compounds
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Manuscript received: January 19, 2021
Revised manuscript received: March 4, 2021
Accepted manuscript online: March 15, 2021
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