Oxidation of 4-Aryl-1,1,1-trifluorobut-2-en-2-yl Trifluoro?-methanesulfonates by 4-Picoline-N-Oxide: A Novel Approach to β-Trifluoromethyl-α,β-enones

Article abstract of DOI:10.1055/s-0039-1690054

An efficient approach to β-trifluoromethyl-α,β-enones via oxidation of 4-aryl-1,1,1-trifluorobut-2-en-2-yl trifluoromethanesulfonates is described. The reaction proceeds smoothly under mild and metal?-free conditions and tolerates a wide range of functional groups. Various β-trifluoromethyl-α,β-enones were obtained in moderate to good yields.

Full text of DOI:10.1055/s-0039-1690054

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2020, 52, 1203–1210
feature
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en
D. Li et al.
Feature
Synthesis
Oxidation of 4-Aryl-1,1,1-trifluorobut-2-en-2-yl Trifluoro-
methanesulfonates by 4-Picoline-N-Oxide: A Novel Approach
to -Trifluoromethyl-,-enones
Dong Li
Shujun Lv
metal-free
OTf
CF3
O
Jingping Qu
Et3N
+
Yuhan Zhou*
Ar
Ar
CF3
CH2ClCH2Cl, 25 °C, 3–6 h
N
O
18 examples
73–87% yield
State Key Laboratory of Fine Chemicals, School of Chemical
Engineering, Dalian University of Technology, 2 Linggong
Road, Dalian 116024, P. R. of China
mild conditions
zhouyh@dl.cn
Et3N
N
O
Ar
CF3
Received: 28.10.2019
Accepted after revision: 19.01.2020
Published online: 10.02.2020
are more favorable. Therefore, convenient synthetic ap-
proaches to -trifluoromethyl-,-enones are still highly
desired.
DOI: 10.1055/s-0039-1690054; Art ID: ss-2019-z0600-fa
In recent years, our group has focused on the synthesis
of different molecules containing a trifluoromethyl group.
Based on the useful trifluorinated building blocks, -(triflu-
oromethyl)alkenyl trifluoromethanesulfonates, a variety of
methods for the synthesis of trifluoromethyl derivatives
such as alkynes, diarylethylenes, benzofurans, 2H-
chromenes, enynes, allyl azides and -trifluoromethyl ke-
tones have been developed.8 Especially, the double-bond
migration/hydrolysis/isomerization of 4-aryl-1,1,1-tri-
fluorobut-2-en-2-yl trifluoromethanesulfonates has been
documented (Scheme 1, d).8e Thus, we proposed that this
method in combination with an oxidant may result in -tri-
fluoromethyl-,-enone formation. Herein, we report our
progress on the synthesis of -trifluoromethyl-,-enones
via oxidation of 4-aryl-1,1,1-trifluorobut-2-en-2-yl trifluo-
romethanesulfonates under metal-free conditions (Scheme
1, e).
Abstract An efficient approach to -trifluoromethyl-,-enones via
oxidation of 4-aryl-1,1,1-trifluorobut-2-en-2-yl trifluoromethanesulfon-
ates is described. The reaction proceeds smoothly under mild and
metal-free conditions and tolerates a wide range of functional groups.
Various -trifluoromethyl-,-enones were obtained in moderate to
good yields.
Key words fluorine, enones, oxidation, -trifluoromethyl-,-enones,
4-aryl-1,1,1-trifluorobut-2-en-2-yl trifluoromethanesulfonates, pyri-
dine N-oxides
Compounds containing a trifluoromethyl group have re-
ceived great attention because of their application in mate-
rials, pharmaceuticals and agrochemicals.1 -Trifluoro-
methyl-,-enones, as an important series of trifluoro-
methyl building blocks, can be used in a variety of
reactions, such as Michael additions,2 Diels–Alder cyclo-
additions,3 Friedel–Crafts reactions4 and some other novel
reactions.5 So, it is not surprising that the synthesis of -tri-
fluoromethyl-,-enones has been attracting more and
more attention. Trifluoromethylated propargylic alcohols
have been widely used in the synthesis of -trifluorometh-
yl-,-enones (Scheme 1, a).6 However, the high price of tri-
fluoromethylated propargylic alcohols hinders their appli-
cation. Some other synthetic methods, such as the gold-
catalyzed rearrangement of trifluoromethyl-substituted
propargylic carboxylates (Scheme 1, b)3a and Znl2-catalyzed
deamination–elimination of 1,1-bis(dimethylamino)-2,2,2-
trifluoroethane with silyl enol ethers (Scheme 1, c),7 have
been reported but metal catalysts are essential. Because of
the strict restrictions on the residual amount of heavy met-
als in the pharmaceutical industry, metal-free procedures
Initially, (Z)-1,1,1-trifluoro-4-phenylbut-2-en-2-yl tri-
fluoromethanesulfonate (1a) was selected as the represen-
tative substrate for optimization of the oxidant (Table 1).
Due to its oxidizing capacity, pyridine N-oxide9 was first ex-
amined in the presence of Et3N in CH2Cl2 at 25 °C. The de-
sired product 2a was formed in 84% yield with (E)-1,1,1-tri-
fluoro-4-phenylbut-3-en-2-one
(2a′)
as
byproduct
(2a/2a′ = 95:5, Table 1, entry 1). 1H NMR analysis of 2a
showed that the coupling constant of the two hydrogens on
the C=C double bond is 15.5 Hz, which indicates that it is
the E-isomer. Then, different oxidants, such as methyl- (Ta-
ble 1, entries 3, 5 and 7), chloro- (Table 1, entries 2 and 6)
and nitro-substituted (Table 1, entry 4) pyridine N-oxides,
were employed. 4-Picoline N-oxide proved to be the best
oxidant for this reaction (Table 1, entry 5, 81% yield,
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, 1203–1210
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

1204
D. Li et al.
Feature
Synthesis
2a/2a′ = 100:0). When the amount of 4-picoline N-oxide
was decreased to 1.0 equivalent, the yield of 2a decreased to
57% (Table 1, entry 8).
Then, the effect of base was investigated (Table 2). Many
bases, including Et3N, pyrrolidine, DBU and DMAP, can pro-
mote this reaction smoothly. However, some of them gave
low selectivity (Table 2, entries 3–5, 10 and 11). In particu-
lar, 4,4,4-trifluoro-1-phenylbutan-1-one was formed as a
byproduct when DBU was used;8e (E)-1-(1,1,1-trifluoro-4-
phenylbut-3-en-2-yl)pyrrolidine and (E)-1-(4,4,4-trifluoro-
1-phenylbut-2-en-1-yl)pyrrolidine were formed when pyr-
rolidine was used. Finally, Et3N still proved to be the best
base for this reaction (Table 2, entry 1). Reducing the
amount of Et3N to 20 mol% resulted in much lower yield of
2a (Table 2, entry 12), and the reaction cannot occur with-
out a base (Table 2, entry 13).
Biographical Sketches
Dong Li received his B.S. de-
gree in Chemical Engineering
and Technology from Liaocheng
University (China). After that,
he entered Yunnan University to
undertake his M.S. degree in
Pharmaceutical Engineering un-
der the supervision of Prof. Jun
Lin, from 2013 to 2016. Cur-
rently, he is working towards his
doctor’s degree at Dalian Uni-
versity of Technology under the
supervision of Prof. Yuhan
Zhou.
Shujun Lv participated in an
undergraduate research pro-
gram from January to June 2019
under the supervision of Prof.
Yuhan Zhou. He has now ob-
tained his B.S. degree in Phar-
maceutical Engineering from
Dalian University of Technology.
Jingping Qu was born in Da-
lian (China) in 1960. In 1983, he
received his bachelor’s degree
from Dalian University of Tech-
nology (China) in Basic Organic
Chemical Engineering. He re-
ceived his Ph.D., under the di-
rection of Prof. Masanoubu
Hidai, from The University of
Tokyo (Japan) in 1996. After
working at Mitsubishi Chemical
Corporation (Japan) for seven
years, he returned to Dalian Uni-
versity of Technology as a pro-
fessor in 2004. Currently, he is
the president of East China Uni-
versity of Science and Technolo-
gy (China). His research
interests are organometallics
chemistry and organic synthe-
sis.
Yuhan Zhou was born in Ful-
ing (China) in 1974. In 2003, he
received his Ph.D. in Applied
Chemistry from Dalian Universi-
ty of Technology (China) under
the direction of Prof. Lvbai
Cheng and Prof. Weirong Miao.
Then, he became a teacher at
that university. From February
2009 to January 2010, he
worked with Prof. Laurent Mic-
ouin at Paris Descartes Universi-
ty (France) as a postdoctoral
fellow. Currently, he is a profes-
sor in the School of Chemical
Engineering, Dalian University
of Technology. His research in-
terest is organic synthesis, espe-
cially the synthesis of fluorine-
containing and heterocyclic
compounds.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, 1203–1210

1205
D. Li et al.
Feature
Synthesis
Previous reports on synthesis of b-trifluoromethyl-a,b-enones
Et3N
O
OH
CF3
BF3.Et2O
THF, reflux
OH
Ar
CF3
Mitsunobu reagents
CH2ClCH2Cl, heat
a)
Ar
Ar
PhOH
CF3
OH
Red-Al/toluene
–78 °C, 3 h
2
2
2
reflux, 1 h
Ar
CF3
R2
OAc
R2
O
IPrAuNTf2
b)
c)
Rf
Rf
R1
acetone/H2O, 40 °C
R1
Rf = CF3, CF2CF3, CF2H
O
ZnI2
NMe2
O
OTMS
– HNMe2
CF3CH(NMe2)2
+
Et2O
rt, 2 h
F3C
Ph
F3C
Ph
Ph
Our previous work (synthesis of b-trifluoromethyl ketones)
OTf
CF3
O
H2O, DBU
d)
Ar
DMF
Ar
CF3
–40 °C, 5 h then 80 °C, 3 h
This work
OTf
CF3
O
Et3N
e)
Ar
+
Ar
CF3
CH2ClCH2Cl, 25 °C, 3–6 h
N
O
Scheme 1 Preparation of -trifluoromethyl-,-enones
Moreover, a series of solvents was screened (Table 3, en-
tries 1–7). Upon switching the solvent to DMF or DMSO, as
well as solvent free, the reaction became complicated with
some compounds that could not be characterized (Table 3,
entries 1, 2 and 5). THF, toluene, chloroform and 1,2-dichlo-
roethane were next examined (Table 3, entries 3, 4, 6 and
7): 1,2-dichloroethane provided excellent reactivity with
84% yield of 2a and 100:0 selectivity between 2a/2a′ (Table
3, entry 7). The yield of 2a decreased to 80% when the reac-
tion temperature was reduced to 15 °C (Table 3, entry 8).
With optimal conditions identified (Table 3, entry 7),
the scope of this reaction was next explored (Scheme 2).
Substrates 1 containing a phenyl group or an aryl group
Table 2 Optimization of the Reaction Conditions: Basea
O
O
OTf
CF3
base
CF3
CF3
+
+
CH2Cl2, 25 °C
N
O
2a
2a'
1a
En- Base
try
Conv. (%)b
2a/2a′c
Yield (%) 2ab
Table 1 Optimization of the Reaction Conditions: Oxidanta
1
2
Et3N
pyridine
98
0
100:0
–
81
–
O
O
OTf
CF3
Et3N
R
CF3
CF3
+
+
N
O
CH2Cl2, 25 °C
3
pyrrolidine
DBU
62
95
95
0
100:0
100:0
99:1
–
30
29
47
–
1a
2a
2a'
4
5
DMAP
KF
Entry
R
Conv. (%)b
2a/2a′c
Yield (%) 2ab
6
1
2
3
4
5
6
7
8d
H
98
88
99
80
98
73
95
70
95:5
95:5
84
65
82
55
81
43
71
57
7
(n-Bu)3N
95
98
0
100:0
99:1
–
77
78
–
2-Cl
2-Me
8
Me2NCH2CH2NMe2
PhNMe2
98:2
9
4-NO2
4-Me
97:3
10
11
(i-Pr)2NEt
63
40
17
0
100:0
93:7
100:0
–
26
19
10
–
100:0
80:20
100:0
100:0
BnNMe2
2,6-Cl2
12d Et3N
13
2,6-Me2
4-Me
–
a Reaction conditions: 1a (167 mg, 0.5 mmol), 4-picoline N-oxide (109 mg,
1.0 mmol), base (0.5 mmol), CH2Cl2 (3 mL), argon atmosphere, stirring,
a Reaction conditions: 1a (167 mg, 0.5 mmol), oxidant (1.0 mmol), Et3N (51
mg, 0.5 mmol), CH2Cl2 (3 mL), argon atmosphere, stirring, 25 °C, 3 h.
b Determined by 1H NMR with dimethyl terephthalate as an internal stan-
dard.
25 °C, 3 h.
b Determined by 1H NMR with dimethyl terephthalate as an internal stan-
dard.
c Determined by 1H NMR.
c Determined by 1H NMR.
d Et3N (0.1 mmol, 0.2 equiv) was used.
d 4-Picoline N-oxide (0.5 mmol) was used.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, 1203–1210

1206
D. Li et al.
Feature
Synthesis
Et3N (15 mol%)
NuH (2.0 equiv)
KHCO3 (1.2 equiv)
Nu
Table 3 Optimization of the Reaction Conditions: Solventa
OTf
CF3
CF3
O
O
DME, 65 °C
OTf
94% NuH = H2O
74% NuH = CH3OH
80% NuH = PhOH
Et3N
CF3
CF3
1a
+
CF3
+
solvent, 25 °C
N
O
2a
2a'
Scheme 3 Our previous report on the substitution of 1a8c
1a
Entry
Solvent
Conv. (%)b
2a/2a′c
Yield (%) 2ab
substituted by an electron-withdrawing group or an
electron-donating group can be efficiently transformed into
the corresponding products in moderate to good yields.
Substrates with electron-donating substituents, including
methyl and isopropyl, furnished the desired products in
78–85% yield (2b–2e). Substrates with electron-withdraw-
ing substituents, including chloro, fluoro, trifluoromethyl,
bromo, phenyl and cyano, furnished the desired products in
80–87% yield (2f, 2i–2o). Thus, there is no obvious substitu-
ent effect. The 2′-methyl substrate gave slightly lower yield
than the 3′-methyl and 4′-methyl ones (2b–2d) and the 2′-
chloro substrate also gave slightly lower yield than the 3′-
chloro and 4′-chloro ones (2k–2m), exhibiting a slight steric
effect. In addition, naphthyl derivatives gave moderate
yields (2g and 2h), as did multisubstituted substrates (2p
and 2q). A thienyl-substituted substrate, as a heteroaryl
example, also gave a good yield (2r). (Z)-1,1,1-Trifluoro-
1
2
3
4
5
6
7
8d
DMF
99
100
100
72
76:24
67:33
100:0
95:5
32
48
76
50
47
78
84
80
DMSO
THF
toluene
–
95
85:15
100:0
100:0
100:0
CHCl3
98
CH2ClCH2Cl
CH2ClCH2Cl
100
98
a Reaction conditions: 1a (167 mg, 0.5 mmol), 4-picoline N-oxide (109 mg,
1.0 mmol), Et3N (51 mg, 0.5 mmol), solvent (3 mL), argon atmosphere, stir-
ring, 25 °C, 3 h.
b Determined by 1H NMR with dimethyl terephthalate as an internal stan-
dard.
c Determined by 1H NMR.
d Performed at 15 °C.
OTf
O
Et3N
R1
CF3
+
R1
CF3
CH2ClCH2Cl, 25 °C, 3–6 h
N
O
2
1
O
O
O
O
CF3
CF3
CF3
CF3
2c 82%
2b 84%
2d 78%
2a 81%
O
O
O
O
CF3
CF3
CF3
CF3
Ph
2f 80%
2g 82%
2e 85%
2h 73%
O
O
O
O
Cl
CF3
CF3
CF3
CF3
Br
F
Cl
2i 84%
2j 85%
2k 86%
2l 86%
F
O
O
O
Cl
O
Cl
F3C
CF3
CF3
CF3
CF3
NC
2p 79%
2n 81%
2o 87%
2m 80%
Cl
O
O
O
S
CF3
( )7
CF3
CF3
F
0%
2q 77%
2r 82%
Scheme 2 Preparation of -trifluoromethyl-,-enones. Reagents and conditions: 1 (1.0 mmol), 4-picoline N-oxide (218 mg, 2.0 mmol), Et3N (101 mg,
1.0 mmol), 1,2-dichloroethane (4 mL), argon atmosphere, stirring, 25 °C, 3–6 h. Yield of the isolated product.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, 1203–1210

1207
D. Li et al.
Feature
Synthesis
OTf
CF3
OTf
CF3
OTf
CF3
OTf
Et3N
– H
H
Ar
Ar
Ar
Ar
CF3
1'
1
path I
N2'
N
S
OTf
CF3
O
Ar
path II
SN
1
– OTf
CF3
– OTf
O
N
O
N
Ar
O
Ar
CF3
N
A
Ar
CF3
2
– H
B
Ar
CF3
Ar
CF3
A'
A''
Scheme 4 Possible mechanism for the formation of product 2
tridec-2-en-2-yl trifluoromethanesulfonate was also exam-
ined, as the representative example of an alkyl-substituted
substrate at the 4-position, but the reaction did not occur.
This is attributed to the relatively lower acidity of 4-H in
that molecule.
cial sources and used without further purification. Column chroma-
tography was performed on silica gel (200–300 mesh) using petro-
leum ether/EtOAc as eluent. All 1H NMR (400 MHz), 13C NMR (101
MHz) and 19F NMR (377 MHz or 470 MHz) were recorded on Bruker
AVANCE II-400 or Bruker AVANCE III-500 spectrometers with chemi-
cal shifts reported as ppm (in CDCl3 with TMS as internal standard).
Melting points were recorded on a Novel X-4 spectrometer. IR spectra
were recorded on a Thermo Fisher (6700) spectrophotometer. HRMS
(ESI) were recorded on a Thermo LTQ Orbitrap XL spectrometer.
HRMS (EI) were recorded on a Micromass GCT spectrometer.
Based on the oxidizing capacity of pyridine N-oxides,9
reports on base-promoted isomerization10 and our previ-
ous reports on the substitution of 4-aryl-1,1,1-trifluorobut-
2-en-2-yl trifluoromethanesulfonates (Scheme 3),8c a plau-
sible mechanism for the synthesis of -trifluoromethyl-,-
enones via oxidation of 4-aryl-1,1,1-trifluorobut-2-en-2-yl
trifluoromethanesulfonates is shown in Scheme 4. First,
double-bond isomerization in the presence of Et3N gener-
ates intermediate 1′. Then, intermediate 1′ could be trans-
formed into B by two possible pathways. The first way is
SN2′ substitution, with the OTf group substituted by 4-pico-
line N-oxide directly (path I). In another way, (trifluoro-
methyl)allyl cation A, which has two resonance forms (A′
and A′′), is formed after the OTf group has left. Then, the al-
lyl cation is captured by 4-picoline N-oxide, through reso-
nance form A′, to form intermediate B (path II), because of
the electron-withdrawing character of the trifluoromethyl
group.11 Finally, 4-methylpyridine and proton leave from
intermediate B, resulting in the formation of desired prod-
uct 2.
4-Aryl-1,1,1-trifluorobut-2-en-2-yl Trifluoromethanesulfonates
1; General Procedure
4-Aryl-1,1,1-trifluorobut-2-en-2-yl trifluoromethanesulfonates
1
were prepared according to our previous work.8a To a suspension of
NaH (600 mg, 25.0 mmol) in MTBE (30 mL) was added ethyl trifluoro-
acetate (3.0 mL, 25.0 mmol) at room temperature under an argon at-
mosphere. After about 1 min of stirring, enolizable ketone (12.5
mmol) was added, and the mixture was refluxed for 6–12 h. After the
reaction was complete (monitored by TLC or GC analyses), the reac-
tion solution was cooled to 0 °C. Tf2O (3.56 mL, 25.0 mmol) was added
slowly into the reaction mixture. After the reaction was complete
(monitored by TLC or GC analyses), the reaction was quenched with
ice–water. The aqueous layer was separated and extracted with
EtOAc. The combined organic extracts were washed with brine, dried
over MgSO4, and the solvent was removed under reduced pressure.
The crude product was purified by column chromatography on silica
gel to afford product 1. 1c, 1d and 1g are new compounds. 1a,8a 1b,8a
1e,8c 1f,8c 1h,8b 1i,8c 1j,8b 1k,8b 1l,8a 1m,8b 1n,8c 1o,8b 1p,8c 1q8c and 1r8e
have been reported in our previous work.
In conclusion, an efficient method for the synthesis of -
trifluoromethyl-,-enones has been developed. Oxidized
by 4-picoline N-oxide, 4-aryl-1,1,1-trifluorobut-2-en-2-yl
trifluoromethanesulfonates are transformed into -trifluo-
romethyl-,-enones efficiently, in moderate to good
yields. Both electron-donating groups and electron-
withdrawing groups, such as chloro, fluoro, trifluorometh-
yl, methyl, phenyl and isopropyl, are well tolerated.
(Z)-1,1,1-Trifluoro-4-(m-tolyl)but-2-en-2-yl Trifluoromethane-
sulfonate (1c)
Yield: 3.52 g (81%); light yellow liquid.
IR (KBr): 1695, 1609, 1427, 1329, 1203, 1135, 997, 755, 607 cm–1
.
1H NMR (400 MHz, CDCl3):  = 7.24 (d, J = 7.9 Hz, 1 H), 7.12 (d, J = 7.6
Hz, 1 H), 7.03–7.01 (m, 2 H), 6.51 (t, J = 7.5 Hz, 1 H), 3.66 (d, J = 7.5 Hz,
2 H), 2.37 (s, 3 H).
13C NMR (101 MHz, CDCl3):  = 138.9, 135.6, 133.8 (q, J = 39.4 Hz),
130.1 (q, J = 3.0 Hz), 129.3, 129.0, 128.2, 125.5, 118.7 (q, J = 280.8 Hz),
118.4 (q, J = 314.1 Hz), 32.1, 21.3.
Unless otherwise noted, all reactions were performed under an argon
atmosphere in glassware with magnetic stirring. NaH (60% in mineral
oil) was washed with anhydrous n-hexane to remove mineral oil pri-
or to use. Other reagents and solvents were purchased from commer-
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, 1203–1210

1208
D. Li et al.
Feature
Synthesis
19F NMR (470 MHz, CDCl3):  = –69.72 to –69.89 (m, 3 F), –72.79 to
–72.82 (m, 3 F).
(E)-4,4,4-Trifluoro-1-(p-tolyl)but-2-en-1-one (2b)6d
Yield: 180 mg (84%); light yellow liquid.
IR (KBr): 1685, 1642, 1309, 1135, 974, 815, 726, 654 cm–1
1H NMR (400 MHz, CDCl3):  = 7.88 (d, J = 8.2 Hz, 2 H), 7.55–7.51 (m, 1
H), 7.32 (d, J = 8.0 Hz, 2 H), 6.80 (dq, J = 15.4, 6.7 Hz, 1 H), 2.44 (s, 3 H).
13C NMR (101 MHz, CDCl3):  = 187.5, 145.3, 131.1 (q, J = 6.1 Hz),
130.7, 129.9 (q, J = 35.5 Hz), 129.7, 129.0, 122.6 (q, J = 270.7 Hz), 21.8.
HRMS (EI): m/z calcd for
C
12H10F6O3S [M+•]: 348.0255; found:
.
348.0245.
(Z)-1,1,1-Trifluoro-4-(o-tolyl)but-2-en-2-yl Trifluoromethanesul-
fonate (1d)
Yield: 3.61 g (83%); light yellow liquid.
19F NMR (470 MHz, CDCl3):  = –65.07 (s, 3 F).
HRMS (ESI): m/z calcd for C11H10F3O [M + H]+: 215.0684; found:
IR (KBr): 1691, 1428, 1330, 1202, 1135, 998, 902, 748, 608 cm–1
.
1H NMR (400 MHz, CDCl3):  = 7.26–7.19 (m, 3 H), 7.16 (d, J = 4.7 Hz, 1
H), 6.45 (t, J = 7.4 Hz, 1 H), 3.69 (d, J = 7.4 Hz, 2 H), 2.33 (s, 3 H).
215.0679.
13C NMR (101 MHz, CDCl3):  = 136.3, 134.1, 134.0 (q, J = 39.4 Hz),
130.8, 129.6 (q, J = 3.0 Hz), 129.0, 127.7, 126.7, 118.7 (q, J = 283.8 Hz),
118.4 (q, J = 312.1 Hz), 30.0, 19.3.
19F NMR (470 MHz, CDCl3):  = –69.90 (s, 3 F), –72.82 to –72.95 (m, 3
F).
(E)-4,4,4-Trifluoro-1-(m-tolyl)but-2-en-1-one (2c)5a
Yield: 175 mg (82%); light yellow liquid.
IR (KBr): 1688, 1646, 1307, 1134, 971, 790, 713, 627 cm–1
1H NMR (400 MHz, CDCl3):  = 7.78–7.75 (m, 2 H), 7.55–7.50 (m, 1 H),
7.46–7.39 (m, 2 H), 6.81 (dq, J = 15.5, 6.7 Hz, 1 H), 2.44 (s, 3 H).
13C NMR (101 MHz, CDCl3):  = 188.1, 139.0, 136.2, 134.9, 131.2 (q,
J = 5.1 Hz), 130.1 (q, J = 34.3 Hz), 129.2, 128.8, 126.1, 122.6 (q,
J = 270.7 Hz), 21.3.
.
HRMS (EI): m/z calcd for
C
12H10F6O3S [M+•]: 348.0255; found:
348.0244.
(Z)-1,1,1-Trifluoro-4-(naphthalen-2-yl)but-2-en-2-yl Trifluoro-
methanesulfonate (1g)
19F NMR (470 MHz, CDCl3):  = –65.09 (s, 3 F).
Yield: 4.08 g (85%); light yellow solid; mp 50–51 °C.
HRMS (EI): m/z calcd for C11H9F3O [M+•]: 214.0605; found: 214.0602.
IR (KBr): 1691, 1425, 1328, 1223, 1152, 1081, 1001, 962, 825, 746,
(E)-4,4,4-Trifluoro-1-(o-tolyl)but-2-en-1-one (2d)4c
608 cm–1
.
1H NMR (400 MHz, CDCl3):  = 7.89–7.80 (m, 3 H), 7.67 (s, 1 H), 7.56–
7.47 (m, 2 H), 7.34–7.31 (m, 1 H), 6.64–6.56 (m, 1 H), 3.86 (d, J = 7.5
Hz, 2 H).
13C NMR (101 MHz, CDCl3):  = 134.1 (q, J = 39.4 Hz), 133.6, 133.0,
132.6, 129.9 (q, J = 3.0 Hz), 129.0, 127.8, 127.7, 127.2, 126.6, 126.4,
126.2, 118.7 (q, J = 283.8 Hz), 118.5 (q, J = 312.1 Hz), 32.3.
Yield: 167 mg (78%); light yellow liquid.
IR (KBr): 1689, 1646, 1304, 1134, 970, 769, 729, 628 cm–1
.
1H NMR (400 MHz, CDCl3):  = 7.57 (dd, J = 6.8, 2.2 Hz, 1 H), 7.48–7.42
(m, 1 H), 7.33–7.29 (m, 2 H), 7.28–7.21 (m, 1 H), 6.63 (dq, J = 15.8, 6.6
Hz, 1 H), 2.50 (s, 3 H).
13C NMR (101 MHz, CDCl3):  = 192.0, 138.9, 136.3, 134.5 (q, J = 5.1
Hz), 132.2, 132.1, 130.2 (q, J = 35.3 Hz), 129.2, 125.8, 122.5 (q,
J = 271.7 Hz), 20.8.
19F NMR (470 MHz, CDCl3):  = –69.80 to –69.84 (m, 3 F), –72.72 to
–72.76 (m, 3 F).
C
15H10F6O3S [M+•]: 384.0255; found:
19F NMR (377 MHz, CDCl3):  = –65.06 to –65.11 (m, 3 F).
HRMS (EI): m/z calcd for
384.0244.
HRMS (EI): m/z calcd for C11H9F3O [M+•]: 214.0605; found: 214.0596.
-Trifluoromethyl-,-enones 2; General Procedure
(E)-4,4,4-Trifluoro-1-(4-isopropylphenyl)but-2-en-1-one (2e)
To a solution of (Z)-(trifluoromethyl)alkenyl triflate 1 (1.0 mmol) in
1,2-dichloroethane (4 mL) was added 4-picoline N-oxide (218 mg, 2.0
mmol) and Et3N (101 mg, 1.0 mmol) at room temperature under an
argon atmosphere. Then, the mixture was stirred at 25 °C for 3–6 h.
After the reaction was complete (monitored by TLC), solvent was re-
moved under reduced pressure. The crude product was purified by
column chromatography on silica gel (petroleum ether) to afford
product 2. Compounds 2e, 2l, 2m, 2p and 2q are new.
Yield: 206 mg (85%); light yellow liquid.
IR (KBr): 1686, 1649, 1606, 1307, 1135, 967, 828, 650 cm–1
.
1H NMR (400 MHz, CDCl3):  = 7.92 (d, J = 8.3 Hz, 2 H), 7.57–7.50 (m, 1
H), 7.38 (d, J = 8.3 Hz, 2 H), 6.81 (dq, J = 15.5, 6.7 Hz, 1 H), 3.07–2.93
(m, 1 H), 1.29 (d, J = 6.9 Hz, 6 H).
13C NMR (101 MHz, CDCl3):  = 187.5, 156.0, 134.1, 131.2 (q, J = 5.1
Hz), 129.9 (q, J = 35.4 Hz), 129.1, 127.1, 122.6 (q, J = 271.7 Hz), 34.4,
23.6.
(E)-4,4,4-Trifluoro-1-phenylbut-2-en-1-one (2a)3a
19F NMR (470 MHz, CDCl3):  = –65.06 (s, 3 F).
HRMS (ESI): m/z calcd for C13H14F3O [M + H]+: 243.0977; found:
Yield: 162 mg (81%); light yellow liquid.
IR (KBr): 1688, 1650, 1449, 1307, 1136, 967, 695, 625 cm–1
.
243.0998.
1H NMR (400 MHz, CDCl3):  = 7.98 (d, J = 4.4 Hz, 2 H), 7.64 (t, J = 7.4
Hz, 1 H), 7.57–7.49 (m, 3 H), 6.82 (dq, J = 15.5, 6.6 Hz, 1 H).
13C NMR (101 MHz, CDCl3):  = 188.0, 136.2, 134.1, 131.1 (q, J = 6.1
Hz), 130.3 (q, J = 35.4 Hz), 129.0, 128.8, 122.6 (q, J = 271.7 Hz).
(E)-1-([1,1′-Biphenyl]-4-yl)-4,4,4-trifluorobut-2-en-1-one (2f)3a
Yield: 221 mg (80%); white solid; mp 63–64 °C.
IR (KBr): 1683, 1640, 1603, 1314, 1142, 970, 836, 770, 733, 691, 623
19F NMR (470 MHz, CDCl3):  = –65.13 (s, 3 F).
cm–1
.
HRMS (ESI): m/z calcd for C10H8F3O [M + H]+: 201.0527; found:
201.0522.
1H NMR (400 MHz, CDCl3):  = 8.09 (d, J = 8.4 Hz, 2 H), 7.77 (d, J = 8.4
Hz, 2 H), 7.70–7.65 (m, 2 H), 7.61–7.57 (m, 1 H), 7.54–7.50 (m, 2 H),
7.49–7.42 (m, 1 H), 6.88 (dq, J = 15.5, 6.6 Hz, 1 H).
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, 1203–1210

1209
D. Li et al.
Feature
Synthesis
13C NMR (101 MHz, CDCl3):  = 187.4, 146.9, 139.5, 134.9, 131.0 (q,
J = 6.1 Hz), 130.2 (q, J = 35.4 Hz), 129.5, 129.1, 128.6, 127.6, 127.3,
122.6 (q, J = 271.7 Hz).
1H NMR (400 MHz, CDCl3):  = 7.91 (d, J = 7.9 Hz, 2 H), 7.51–7.48 (m, 3
H), 6.82 (dq, J = 15.5, 6.6 Hz, 1 H).
13C NMR (101 MHz, CDCl3):  = 186.7, 140.8, 134.5, 130.8 (q, J = 35.3
Hz), 130.5 (q, J = 5.1 Hz), 130.2, 129.3, 122.4 (q, J = 271.7 Hz).
19F NMR (470 MHz, CDCl3):  = –65.02 (s, 3 F).
HRMS (EI): m/z calcd for C16H11F3O [M+•]: 276.0762; found: 276.0768.
19F NMR (377 MHz, CDCl3):  = –65.20 (d, J = 5.9 Hz, 3 F).
HRMS (EI): m/z calcd for
234.0052.
C
10H6ClF3O [M+•]: 234.0059; found:
(E)-4,4,4-Trifluoro-1-(naphthalen-2-yl)but-2-en-1-one (2g)4c
Yield: 205 mg (82%); white solid; mp 69–70 °C.
IR (KBr): 1685, 1645, 1621, 1306, 1126, 970, 822, 753, 654 cm–1
.
(E)-1-(3-Chlorophenyl)-4,4,4-trifluorobut-2-en-1-one (2l)
Yield: 201 mg (86%); light yellow liquid.
IR (KBr): 1689, 1646, 1306, 1137, 966, 790, 626 cm–1
1H NMR (400 MHz, CDCl3):  = 8.44 (s, 1 H), 8.02–7.88 (m, 4 H), 7.71–
7.57 (m, 3 H), 6.89 (dq, J = 15.5, 6.6 Hz, 1 H).
.
13C NMR (101 MHz, CDCl3):  = 187.7, 136.0, 133.6, 132.4, 131.05 (q,
J = 5.1 Hz), 131.03, 130.2 (q, J = 35.4 Hz), 129.7, 129.2, 129.1, 127.9,
127.2, 123.9, 122.7 (q, J = 270.7 Hz).
1H NMR (400 MHz, CDCl3):  = 7.95 (t, J = 1.8 Hz, 1 H), 7.87–7.82 (m, 1
H), 7.63–7.60 (m, 1 H), 7.52–7.45 (m, 2 H), 6.84 (dq, J = 15.5, 6.6 Hz, 1
H).
19F NMR (377 MHz, CDCl3):  = –64.93 (d, J = 5.9 Hz, 3 F).
HRMS (EI): m/z calcd for C14H9F3O [M+•]: 250.0605; found: 250.0594.
13C NMR (101 MHz, CDCl3):  = 186.7, 137.6, 135.4, 134.1, 131.0 (q,
J = 35.4 Hz), 130.4 (q, J = 5.1 Hz), 130.3, 128.8, 126.8, 122.4 (q,
J = 270.1 Hz).
19F NMR (470 MHz, CDCl3):  = –65.19 (s, 3 F).
(E)-4,4,4-Trifluoro-1-(naphthalen-1-yl)but-2-en-1-one (2h)6d
HRMS (EI): m/z calcd for
C
10H6ClF3O [M+•]: 234.0059; found:
Yield: 183 mg (73%); white solid; mp 72–73 °C.
234.0067.
IR (KBr): 1684, 1639, 1504, 1303, 1135, 970, 803, 776, 617 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.55 (d, J = 8.5 Hz, 1 H), 8.08 (d, J = 8.2
Hz, 1 H), 7.93 (d, J = 8.0 Hz, 1 H), 7.87 (d, J = 7.2 Hz, 1 H), 7.67–7.54 (m,
3 H), 7.42 (d, J = 15.6 Hz, 1 H), 6.77 (dq, J = 15.6, 6.5 Hz, 1 H).
13C NMR (101 MHz, CDCl3):  = 191.5, 134.7 (q, J = 5.1 Hz), 134.1,
134.0, 133.9, 130.42 (q, J = 35.4 Hz), 130.41, 129.3, 128.7, 128.5,
127.0, 125.5, 124.3, 122.6 (q, J = 271.7 Hz).
(E)-1-(2-Chlorophenyl)-4,4,4-trifluorobut-2-en-1-one (2m)
Yield: 187 mg (80%); light yellow liquid.
IR (KBr): 1686, 1646, 1304, 1137, 970, 764, 623 cm–1
.
1H NMR (400 MHz, CDCl3):  = 7.56–7.51 (m, 1 H), 7.51–7.45 (m, 2 H),
7.42–7.36 (m, 1 H), 7.26–7.19 (m, 1 H), 6.64 (dq, J = 15.8, 6.6 Hz, 1 H).
19F NMR (470 MHz, CDCl3):  = –64.97 (s, 3 F).
HRMS (EI): m/z calcd for C14H9F3O [M+•]: 250.0605; found: 250.0603.
13C NMR (101 MHz, CDCl3):  = 190.6, 137.1, 134.2 (q, J = 5.1 Hz),
133.0, 131.9, 130.7, 130.1, 130.09 (q, J = 35.4 Hz), 127.2, 122.4 (q,
J = 270.1 Hz).
19F NMR (470 MHz, CDCl3):  = –65.21 (s, 3 F).
(E)-1-(4-Bromophenyl)-4,4,4-trifluorobut-2-en-1-one (2i)6a
HRMS (EI): m/z calcd for
C
10H6ClF3O [M+•]: 234.0059; found:
Yield: 234 mg (84%); light yellow liquid.
234.0058.
IR (KBr): 1684, 1650, 1586, 1307, 1130, 1007, 961, 636 cm–1
.
1H NMR (400 MHz, CDCl3):  = 7.87–7.82 (m, 2 H), 7.70–7.65 (m, 2 H),
7.51–7.46 (m, 1 H), 6.83 (dq, J = 15.5, 6.6 Hz, 1 H).
13C NMR (101 MHz, CDCl3):  = 186.9, 134.9, 132.4, 130.7 (q, J = 35.4
Hz), 130.4 (q, J = 5.1 Hz), 130.2, 129.6, 122.4 (q, J = 270.7 Hz).
(E)-4,4,4-Trifluoro-1-(3-(trifluoromethyl)phenyl)but-2-en-1-one
(2n)5a
Yield: 217 mg (81%); light yellow liquid.
IR (KBr): 1692, 1646, 1305, 1132, 967, 693, 628 cm–1
.
19F NMR (470 MHz, CDCl3):  = –65.15 (d, J = 4.7 Hz, 3 F).
1H NMR (400 MHz, CDCl3):  = 8.22 (s, 1 H), 8.16 (d, J = 7.8 Hz, 1 H),
7.91 (d, J = 7.8 Hz, 1 H), 7.69 (t, J = 7.8 Hz, 1 H), 7.53 (d, J = 15.5 Hz, 1
H), 6.88 (dq, J = 15.5, 6.6 Hz, 1 H).
HRMS (EI): m/z calcd for
C
10H6BrF3O [M+•]: 277.9554; found:
277.9547.
13C NMR (101 MHz, CDCl3):  = 186.7, 136.7, 131.8, 131.4 (q, J = 35.4
Hz), 131.2 (q, J = 76.8 Hz), 130.5 (q, J = 4.0 Hz), 130.1 (q, J = 6.1 Hz),
129.7, 125.5 (q, J = 4.0 Hz), 123.5 (q, J = 273.7 Hz), 122.3 (q, J = 271.7
Hz).
(E)-4,4,4-Trifluoro-1-(4-fluorophenyl)but-2-en-1-one (2j)12
Yield: 185 mg (85%); light yellow liquid.
IR (KBr): 1687, 1596, 1307, 1135, 964, 838, 593 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.06–7.98 (m, 2 H), 7.51 (dq, J = 15.5,
1.9 Hz, 1 H), 7.24–7.15 (m, 2 H), 6.82 (dq, J = 15.4, 6.6 Hz, 1 H).
19F NMR (377 MHz, CDCl3):  = –62.94 (s, 3 F), –65.24 (dd, J = 6.5, 1.9
Hz, 3 F).
13C NMR (101 MHz, CDCl3):  = 186.3, 166.4 (d, J = 257.6 Hz), 132.6 (d,
J = 3.0 Hz), 131.6 (d, J = 9.1 Hz), 130.6 (q, J = 5.1 Hz), 130.5 (q, J = 35.4
Hz), 122.5 (q, J = 271.7 Hz), 116.2 (d, J = 22.2 Hz).
HRMS (EI): m/z calcd for C11H6F6O [M+•]: 268.0323; found: 268.0322.
4-((E)-4,4,4-Trifluorobut-2-enoyl)benzonitrile (2o)6d
19F NMR (470 MHz, CDCl3):  = –65.18 (s, 3 F), –102.76 (s, 1 F).
Yield: 196 mg (87%); light yellow liquid.
HRMS (EI): m/z calcd for C10H6F4O [M+•]: 218.0355; found: 218.0354.
IR (KBr): 2234, 1687, 1649, 1309, 1132, 968, 833, 648 cm–1
.
1H NMR (400 MHz, CDCl3):  = 8.07 (d, J = 8.0 Hz, 2 H), 7.84 (d, J = 8.5
Hz, 2 H), 7.52–7.48 (m, 1 H), 6.87 (dq, J = 15.5, 6.5 Hz, 1 H).
(E)-1-(4-Chlorophenyl)-4,4,4-trifluorobut-2-en-1-one (2k)6d
Yield: 201 mg (86%); light yellow liquid.
IR (KBr): 1686, 1650, 1588, 1307, 1140, 970, 827, 641 cm–1
13C NMR (101 MHz, CDCl3):  = 186.9, 139.0, 132.8, 131.6 (q, J = 35.4
Hz), 130.2 (q, J = 5.1 Hz), 129.2, 122.3 (q, J = 270.7 Hz), 117.6, 117.3.
.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, 1203–1210

1210
D. Li et al.
Feature
Synthesis
19F NMR (470 MHz, CDCl3):  = –65.28 (s, 3 F).
HRMS (EI): m/z calcd for C11H6F3NO [M+•]: 225.0401; found: 225.0404.
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0039-1690054.
S
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n
(E)-1-(3-Chloro-2-fluorophenyl)-4,4,4-trifluorobut-2-en-1-one
(2p)
Yield: 199 mg (79%); light yellow liquid.
IR (KBr): 1689, 1601, 1455, 1306, 1137, 970, 640 cm–1
References
.
(1) (a) Müller, K.; Faeh, C.; Diederich, F. Science 2007, 317, 1881.
(b) Hagmann, W. K. J. Med. Chem. 2008, 51, 4359. (c) Shimizu,
M.; Hiyama, T. Angew. Chem. Int. Ed. 2005, 44, 214. (d) Zhou, Y.;
Wang, J.; Gu, Z.; Wang, S.; Zhu, W.; Aceña, J. L.; Soloshonok, V.
A.; Izawa, K.; Liu, H. Chem. Rev. 2016, 116, 422.
(2) (a) Obijalska, E.; Pawelec, M.; Mlostoń, G.; Capperucci, A.;
Tanini, D.; Heimgartner, H. Eur. J. Org. Chem. 2018, 3716.
(b) Huang, B.; Li, C.; Wang, H.; Wang, C.; Liu, L.; Zhang, J. Org.
Lett. 2017, 19, 5102.
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R.; Riant, O.; Gagosz, F. Tetrahedron 2018, 74, 5232. (b) Davies, A.
T.; Taylor, J. E.; Douglas, J.; Collett, C. J.; Morrill, L. C.; Fallan, C.;
Slawin, A. M. Z.; Churchill, G.; Smith, A. D. J. Org. Chem. 2013, 78,
9243.
1H NMR (400 MHz, CDCl3):  = 7.74–7.70 (m, 1 H), 7.69–7.63 (m, 1 H),
7.43–7.35 (m, 1 H), 7.26–7.20 (m, 1 H), 6.83–6.74 (m, 1 H).
13C NMR (101 MHz, CDCl3):  = 185.6, 157.3 (d, J = 257.6 Hz), 135.8,
133.6 (q, J = 5.1 Hz), 130.5 (q, J = 35.4 Hz), 129.3, 126.4 (d, J = 13.1 Hz),
125.2 (d, J = 4.0 Hz), 122.7 (d, J = 19.2 Hz), 122.3 (q, J = 271.7 Hz).
19F NMR (377 MHz, CDCl3):  = –65.27 (dd, J = 6.6, 1.9 Hz, 3 F),
–112.42 to –112.47 (m, 1 F).
HRMS (EI): m/z calcd for
C
10H5ClF4O [M+•]: 251.9965; found:
251.9969.
(E)-1-(2-Chloro-4-fluorophenyl)-4,4,4-trifluorobut-2-en-1-one
(2q)
(4) (a) Wang, W.; Lian, X.; Chen, D.; Liu, X.; Lin, L.; Feng, X. Chem.
Commun. 2011, 47, 7821. (b) Leuger, J.; Blond, G.; Billard, T.;
Haufe, G.; Langlois, B. R. J. Fluorine Chem. 2011, 132, 799.
(c) Blay, G.; Fernández, I.; Muñoz, M. C.; Pedro, J. R.; Vila, C.
Chem. Eur. J. 2010, 16, 9117.
(5) (a) Chai, G.; Sun, A.; Zhai, D.; Wang, J.; Deng, W.; Wong, H. N. C.;
Chang, J. Org. Lett. 2019, 21, 5040. (b) Bai, D.; Wang, X.; Zheng,
G.; Li, X. Angew. Chem. Int. Ed. 2018, 57, 6633. (c) You, Y.; Lu, W.;
Wang, Z.; Chen, Y.; Xu, X.; Zhang, X.; Yuan, W. Org. Lett. 2018,
20, 4453.
(6) (a) Yamazaki, T.; Kawasaki-Takasuka, T.; Furuta, A.; Sakamoto, S.
Tetrahedron 2009, 65, 5945. (b) Watanabe, Y.; Yamazaki, T.
J. Org. Chem. 2011, 76, 1957. (c) Yamazaki, T.; Ichige, T.;
Kitazume, T. Org. Lett. 2004, 6, 4073. (d) Ramasamy, M.; Lin, H.;
Kuo, S.; Hsieh, M. Synlett 2019, 30, 356.
(7) Xu, Y.; Dolbier, W. R. Jr. Tetrahedron Lett. 1998, 39, 9151.
(8) (a) Zhao, Y.; Zhou, Y.; Liu, J.; Yang, D.; Tao, L.; Liu, Y.; Dong, X.;
Liu, J.; Qu, J. J. Org. Chem. 2016, 81, 4797. (b) Zhao, Y.; Zhou, Y.;
Zhang, C.; Wang, H.; Zhao, J.; Jin, K.; Liu, J.; Liu, J.; Qu, J. Org.
Biomol. Chem. 2017, 15, 5693. (c) Zhao, Y.; Zhou, Y.; Zhang, C.;
Li, D.; Sun, P.; Li, J.; Wang, H.; Liu, J.; Qu, J. J. Org. Chem. 2018, 83,
2858. (d) Li, D.; Zhou, Y.; Zhao, Y.; Zhang, C.; Li, J.; Zhao, J.; Qu, J.
J. Fluorine Chem. 2018, 212, 122. (e) Zhou, Y.; Zhang, C.; Zhao, Y.;
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(b) Londregan, A. T.; Jennings, S.; Wei, L. Org. Lett. 2010, 12,
5254.
Yield: 194 mg (77%); light yellow liquid.
IR (KBr): 1698, 1603, 1450, 1310, 1139, 970, 905, 788, 640 cm–1
1H NMR (400 MHz, CDCl3):  = 7.45–7.40 (m, 1 H), 7.28 (d, J = 8.8 Hz, 1
H), 7.11 (t, J = 8.6 Hz, 1 H), 6.99 (d, J = 15.9 Hz, 1 H), 6.58–6.50 (m, 1
.
H).
13C NMR (101 MHz, CDCl3):  = 187.8, 159.8 (d, J = 254.5 Hz), 134.8 (q,
J = 6.1 Hz), 132.6, 132.5, 132.2 (d, J = 5.1 Hz), 131.6 (q, J = 35.4 Hz),
126.1 (q, J = 6.1 Hz), 122.2 (q, J = 271.7 Hz), 114.8 (d, J = 21.2 Hz).
19F NMR (377 MHz, CDCl3):  = –65.37 (d, J = 6.1 Hz, 3 F), –112.22 (dd,
J = 15.1, 7.5 Hz, 1 F).
HRMS (EI): m/z calcd for
C
10H5ClF4O [M+•]: 251.9965; found:
251.9964.
(E)-4,4,4-Trifluoro-1-(thien-2-yl)but-2-en-1-one (2r)4c
Yield: 169 mg (82%); light yellow liquid.
IR (KBr): 1680, 1627, 1305, 1140, 962, 727, 630 cm–1
1H NMR (400 MHz, CDCl3):  = 7.85–7.81 (m, 1 H), 7.79 (dd, J = 4.9, 0.7
Hz, 1 H), 7.40 (dq, J = 15.4, 1.9 Hz, 1 H), 7.24–7.18 (m, 1 H), 6.86 (dq,
J = 15.4, 6.7 Hz, 1 H).
13C NMR (101 MHz, CDCl3):  = 179.7, 143.7, 136.1, 133.6, 130.8 (q,
J = 5.1 Hz), 129.8 (q, J = 35.4 Hz), 128.7, 122.5 (q, J = 271.7 Hz).
.
19F NMR (470 MHz, CDCl3):  = –65.06 (d, J = 9.4 Hz, 3 F).
HRMS (EI): m/z calcd for C8H5F3OS [M+•]: 206.0013; found: 206.0010.
(10) (a) Martinez-Erro, S.; Sanz-Marco, A.; Gómez, A. B.; Vázquez-
Romero, A.; Ahlquist, M. S. G.; Martín-Matute, B. J. Am. Chem.
Soc. 2016, 138, 13408. (b) Hamada, Y.; Kawasaki-Takasuka, T.;
Yamazaki, T. Beilstein J. Org. Chem. 2017, 13, 1507.
(11) Kazakova, A. N.; Iakovenko, R. O.; Boyarskaya, I. A.; Nenajdenko,
V. G.; Vasilyev, A. V. J. Org. Chem. 2015, 80, 9506.
Funding Information
Financial support for this work was provided by the National Natural
Science Foundation of China (No. 21878037).
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(12) Stark, D. G.; Morrill, L. C.; Yeh, P.; Slawin, A. M. Z.; O’Riordan, T. J.
C.; Smith, A. D. Angew. Chem. Int. Ed. 2013, 52, 11642.
Acknowledgment
We acknowledge Prof. Baomin Wang, Dr. Yuming Song and Dr. Ying
Peng (Dalian University of Technology, China) for valuable discus-
sions.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, 1203–1210