Lewis Acid-Catalyzed Rearrangement of Fluoroalkylated Propargylic Alcohols: An Alternative Approach to β-Fluoroalkyl-α,β-enones

Article abstract of DOI:10.1055/s-0037-1611694

A practical Lewis acid-catalyzed Meyer-Schuster rearrangement of fluoroalkylated propargylic alcohols, leading to a series of β-fluoroalkyl-α,β-enones, is developed. The methodology reported herein features moderate to high yields and high stereoselectivi

Full text of DOI:10.1055/s-0037-1611694

SYNLETT
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
© Georg Thieme Verlag Stuttgart · New York
2019, 30, A–E
letter
A
en
M. Ramasamy et al.
Letter
Synlett
Lewis Acid-Catalyzed Rearrangement of Fluoroalkylated Propar-
gylic Alcohols: An Alternative Approach to β-Fluoroalkyl-α,β-
enones
Manickavasakam Ramasamya
Hui-Chang Lina
Sheng-Chu Kuoa,b,c
Min-Tsang Hsieh*a,b,c,d
O
R1
O
RF R1
2
OH
BF3·OEt2 (0.5 equiv)
DCE, heat
or
2
RF
R1
2
Ar
RF
Ar
OH
Ar
R1 = H, CH3, C2H5, n-C4H9
RF2 = CF3, C2F5, o-ClPhCF2,
o-CF3PhCF2
R1 = Ph, p-ClPh
RF2 = CF3
18 examples
36–86% yield
a School of Pharmacy, China Medical University, Taichung 404,
Taiwan
b Chinese Medicine Research Center, China Medical University,
Taichung 404, Taiwan
c Research Center for Chinese Herbal Medicine, China Medical
University, Taichung 404, Taiwan
d Chinese Medicinal Research and Development Center, China
Medical University Hospital, Taichung 404, Taiwan
T21917@mail.cmu.edu.tw
Received: 07.11.2018
Accepted after revision: 02.12.2018
Published online: 03.01.2019
Meyer–Schuster rearrangement of secondary and tertiary
propargylic alcohols is a straightforward method for the
preparation of α,β-unsaturated carbonyl compounds.12 The
high atom economy, the easily accessible starting materials,
and the high substrate tolerance are features of this meth-
od. However, synthesis of β-trifluoromethyl-α,β-enones di-
rectly from the Meyer–Schuster rearrangement of trifluoro-
methylated propargylic alcohols is rare. Recently, our group
reported a new Lewis acid-catalyzed defluorinative cyc-
loaddition/aromatization cascade reaction,13 in which the
difluorophenylmethylated propargylic alcohols were prone
to cyclizing with nitriles but did not rearrange to α,β-enone
products. Activated benzylic C–F bonds were found to be
necessary for the cascade reaction. During our ongoing ef-
forts toward an efficient methodology for preparing fluori-
nated compounds, we became curious as to whether the
similar Lewis acid-catalyzed conditions, with minor modi-
fications to the fluoroalkylated propargylic alcohols and
solvents, could cause the rearrangement to α,β-enones.
Herein, we report the Lewis acid-catalyzed rearrangement
of fluoroalkylated propargylic alcohols for the synthesis of
β-fluoroalkyl-α,β-enones and β-hydroxy-β-trifluoroalylat-
ed ketones.
The fluoroalkylated propargylic alcohols 1a–s used for
the present study were prepared from the reduction or nu-
cleophilic addition of the corresponding fluorinated alkyl
alkynyl ketones.14 Thus, 1,1,1-trifluoro-4-phenylbut-3-yn-
2-ol 1a was chosen as a model compound and dichlo-
roethane was applied as the solvent to optimize the reac-
tion conditions. AgOTf, InCl3, Sc(OTf)3, and Cu(OTf)2 have
been demonstrated to promote the Meyer–Schuster rear-
rangement in a catalytic manner.15 Initial attempts to uti-
lize these Lewis acids to promote the title reaction were
made. Other rare-earth metal triflates16 were also exam-
ined systematically. The results are compiled in Table 1. As
shown in entries 1–3, the use of one equivalent of Lewis
DOI: 10.1055/s-0037-1611694; Art ID: st-2018-w0724-l
Abstract A practical Lewis acid-catalyzed Meyer–Schuster rearrange-
ment of fluoroalkylated propargylic alcohols, leading to a series of β-flu-
oroalkyl-α,β-enones, is developed. The methodology reported herein
features moderate to high yields and high stereoselectivity in the syn-
thesis of β-alkyl-β-fluoroalkyl-α,β-enones.
Key words Lewis acids, Meyer–Schuster rearrangement, β-trifluoro-
methyl-α,β-enones, metal triflates, fluorinated compounds
Fluorine and fluorinated groups are common function-
alities in the field of organic and medicinal chemistry. In-
troduction of these structural motifs to an organic molecule
significantly alters its physical and biological properties
such as solubility, polarity, lipophilicity, and metabolic sta-
bility.1 Compared with the parent compounds, fluorinated
counterparts are often more suitable for practical uses in
materials science, agrochemistry, and pharmaceutical in-
dustries. β-Trifluoromethyl-α,β-enones are versatile build-
ing blocks in a variety of synthetic transformations such as
asymmetric Diels–Alder reactions,2 Nazarov reactions,3 en-
antioselective conjugate alkynylations,4 phosphine-cata-
lyzed [3+2] cycloadditions,5 and other reactions.6 The
preparation of β-trifluoromethyl-α,β-enones has been
achieved by the aldol condensation of trifluoroacetaldehyde
hemiacetal or hydrate with ketone followed by an acid-me-
diated dehydration process.7 Other methods describing the
preparation of β-trifluoromethyl-α,β-enones include the
base-promoted isomerization of 4,4,4-trifluorinated prop-
argylic alcohols,8 the gold-catalyzed rearrangement of CF3-
substituted propargylic carboxylates,9 the ruthenium-cata-
lyzed isomerization of β-trifluoromethylated secondary al-
lylic alcohols,10 and the Mitsunobu reagent-induced redox
isomerization of CF3-containing propargylic alcohols.11
© Georg Thieme Verlag Stuttgart · New York — Synlett 2019, 30, A–E

B
M. Ramasamy et al.
Letter
Synlett
acids such as AgOTf, InCl3, and Cu(OTf)2 did not promote
the rearrangement even after 12 hours of stirring at 70 °C.
The reaction in the presence of one equivalent of Sc(OTf)3
under identical conditions (entry 4) afforded the desired β-
trifluoromethyl-α,β-enone 2a, but the yield was only 15%.
Additionally, β-hydroxy-β-trifluoromethylated ketone 3a
that could result from the 1,4-addition of H2O to 2a was iso-
lated as a side product with a yield of 13%. Bi(OTf)3 and
Eu(OTf)3 displayed slightly inferior activities to that of
Sc(OTf)3, affording 2a (15–10%) and 3a (18–12%), respec-
tively (entries 5 and 6). Endeavors to use Yb(OTf)3, Zn(OTf)2,
and In(OTf)3 were unsuccessful. In these cases, the starting
material was recovered intact or decomposed (entries 7–9).
It was previously reported that the use of an ionic liquid as
the solvent medium significantly enhances the reaction
rate and selectivity in metal triflate-catalyzed Friedel–
Crafts reactions.17 Inspired by this previous finding, we per-
formed the rearrangement reaction by utilizing [bmim]BF4
or [bmim]PF6 as the solvent. As indicated in entries 10–13,
although [bmim]PF6 enhances the activity of both Sc(OTf)3
and Bi(OTf)3 for the rearrangement reaction, the formation
of 3a could still not be avoided. We then turned our atten-
tion to other Lewis acids. Further screening of the reaction
18
using BF3·OEt2 gave encouraging results. The use of 1.0
equivalent of BF3·OEt2 afforded 2a in good yield (76%, entry
14). The yield remained high upon decreasing the loading of
BF3·OEt2 from 1.0 to 0.8 and 0.5 equivalent (entries 15 and
16). The uses of lower catalyst loading (0.2 equivalents, en-
try 17) or of THF (entry 18) and 1,4-dioxane (entry 19) in-
stead of dichloroethane were examined, but a reduction in
the reaction yield was obtained in all of these cases. There-
fore, the reaction conditions shown in entry 16 were con-
sidered to be optimal.19
Table 1 Optimization of the Reaction Conditions
OH
O
O
OH
2
1
3
Lewis acid
DCE
F
F
F
F
F
2
+
3
4
F
4
F
F
F
1
6
3a
2a
5
1,1,1-trifluoro-4-phenylbut-3-yn-2-ol
Entry
Lewis acid (equiv)
Temp (°C)
Time (h)
Yield (%)a
2a
3a
1
2
InCl3 (1.0)
70
70
12
12
12
12
12
12
12
12
12
7
0
0
0
AgOTf (1.0)
0
0
3
Cu(OTf)2 (1.0)
Sc(OTf)3 (1.0)
Eu(OTf)3 (1.0)
Bi(OTf)3 (1.0)
Yb(OTf)3 (1.0)
Zn(OTf)2 (1.0)
In(OTf)3 (1.0)
Sc(OTf)3 (1.0)b
Sc(OTf)3 (1.0)c
Bi(OTf)3 (1.0)b
Bi(OTf)3 (1.0)c
BF3·OEt2 (1.0)
BF3·OEt2 (0.8)
BF3·OEt2 (0.5)
BF3·OEt2 (0.2)
BF3·OEt2 (0.5)d
BF3·OEt2 (0.5)e
70
0
4
70
15
10
15
0
13
12
18
0
5
70
6
70
7
70
8
70
0
0
9
70
0
0
10
11
12
13
14
15
16
17
18
19
110
110
110
110
70
0
25
22
11
23
4
7
32
0
7
7
24
76
81
80
25
46
39
1.5
2
70
4
70
4
6
70
10
3
22
22
20
70
70
3
a Isolated yields after silica gel chromatography.
b [bmim]BF4 was used as the solvent.
c [bmim]PF6 was used as the solvent.
d THF was used as the solvent.
e 1,4-Dioxane was used as the solvent.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2019, 30, A–E

C
M. Ramasamy et al.
Letter
Synlett
Table 2 (continued)
Table 2 BF3·OEt2-Catalyzed Rearrangement of Fluoroalkylated Propar-
gylic Alcohols
Entry
13
Product
Conditions
70 °C, 6 h
Yield (%)a
77
R1
OH
O
O
OH
Ph
O
BF3·OEt2
2
RF
R1
2
Ar
RF
CF3
DCE, heat
Ar
2n
Entry
1
Product
Conditions
70 °C, 12 h
Yield (%)a
78
14
70 °C, 6 h
74
OH
CF3
O
2o
CF3
H3C
2b
Cl
Cl
2
3
4
45 °C, 1 h
70 °C, 14 h
45 °C, 2 h
75
61
73
O
15
16
17
45 °C, 2 h
45 °C, 2 h
70 °C, 3 h
36
43
75
F3C
O
CF3
Ph
2c
MeO
NC
F
F
F
2p
O
Cl
O
CF3
Ph
2d
2q
F
O
O
CF3
C2F5
2e
2r
H3C
F
a Isolated yields after silica gel chromatography.
5
6
70 °C, 17 h
70 °C, 7 h
57
71
O
CF3
2f
The generality of this BF3·OEt2-catalyzed rearrangement
was next examined by using a series of fluoroalkylated
propargylic alcohols. As illustrated in Table 2, the reaction
of secondary alcohols bearing either electron-withdrawing
(–F, –Cl, –CN, and –CO2Et) or electron-donating functional
groups (–CH3 and –OCH3) on the phenyl ring proceeded to
give the thermodynamically more stable (E)-products 2b–g
in moderate to good yields (57–78%, entries 1–6). Notably,
an electron-donating group on the phenyl ring accelerated
the present reaction, whereas an electron-withdrawing
group slowed the reaction down. The electronic effects
were validated again by the reaction of a more electron-de-
ficient substrate 1h. In this case (entry 7), a prolonged reac-
tion time was required to attain full conversion of the start-
ing material. The reaction with use of a substrate bearing a
sterically demanding 1-naphthyl group yielded 2i in 52%
yield (entry 8). For trifluoromethylated tertiary alcohols
with an alkyl group at the tetrasubstituted carbon center,
the reaction provided the desired products 2j–l in high
yield (81–87%, entries 9–11) and stereoselectivity. Excellent
stereoselectivity was also observed in the formation of β-
pentafluoroethyl-α,β-enone 2m (entry 12). We speculated
that the stereocontrol could stem from an intramolecular
interaction between boron and the fluorinated alkyl group
in the boron allenolate intermediate A, facilitating the alle-
nol–enone tautomerism to form (E)-intermediate B, fol-
lowed by protonation to provide the final (E)-product C ex-
clusively (Scheme 1).21
O
CF3
2g
EtO2C
7
8
70 °C, 30 h
70 °C, 3 h
65
52
F
O
CF3
2h
Cl
CO2Me
O
CF3
2i
9
10
11
12
70 °C, 2 h
70 °C, 2 h
70 °C, 2 h
70 °C, 3 h
87
81
86
62
O
CH3
CF3
2j
O
Et
CF3
2k
O
n-Bu
CF3
2l
O
n-Bu
C2F5
2m
© Georg Thieme Verlag Stuttgart · New York — Synlett 2019, 30, A–E

D
M. Ramasamy et al.
Letter
Synlett
Funding Information
BF2
F
OH
F2C
O
BF3
BF2
O
F3C
This research project was funded by Ministry of Science and Technol-
ogy, Taiwan (MOST 105-2113-M-039-004) and “Chinese Medicine Re-
search Center, China Medical University” from The Featured Areas
Research Center Program within the framework of the Higher Educa-
tion Sprout Project by the Ministry of Education (MOE) in Taiwan
F3C
R
C
R
– HF
R
Ph
Ph
A
R = alkyl
Ph
CF3
CF3
O
HF
BF2
R
R
C
(CMRC-CHM-6).
M
i
n
i
stryof
S
c
i
e
n
c
e
a
n
d
T
e
c
h
n
o
l
o
g
y
,
T
a
i
w
a
n
(M
O
S
T
1
0
5-2
1
1
3-M-0
3
9-0
0
4)
O
Ph
Ph
B
Supporting Information
Scheme 1 Proposed mechanism for the exclusive formation of (E)-
product C
Supporting information for this article is available online at
https://doi.org/10.1055/s-0037-1611694.
S
u
p
p
orit
n
gInformati
o
n
S
u
p
p
orit
n
gInformati
o
n
However, in the cases of a tertiary alcohol substituted
with a phenyl (entry 13) or 4-chlorophenyl group (entry
14) at the tetrasubstituted carbon center, the corresponding
β-hydroxy ketones 2n and 2o were produced instead of the
expected enone products. Other structurally diverse sub-
strates, such as diflurophenylmethylated and pentafluoro-
alkylated alcohols (entries 15–17), were subjected to the
BF3·OEt2-catalyzed reaction conditions and furnished the
corresponding α,β-enones 2p–r in moderate to good yields
(36–75%). The inferior yields for 2p and 2q could be as-
cribed to the instability of the benzylic fluoride moiety un-
der the BF3·OEt2-catalyzed conditions. Otherwise, the reac-
tion was limited to aryl-substituted propargylic alcohols
and failure was observed in the case of alcohol 1s that has
an n-butyl group at the acetylenic position.22
References and Notes
(1) (a) Müller, K.; Faeh, C.; Diederich, F. Science 2007, 317, 1881.
(b) O’Hagan, D. Chem. Soc. Rev. 2008, 37, 308. (c) Purser, S.;
Moore, P. R.; Swallow, S.; Gouverneur, V. Chem. Soc. Rev. 2008,
37, 320. (d) Gillis, E. P.; Eastman, K. J.; Hill, M. D.; Donnelly, D. J.;
Meanwell, N. A. J. Med. Chem. 2015, 58, 8315.
(2) (a) Jiang, Q.; Guo, T.; Wu, K.; Yu, Z. Chem. Commun. 2016, 52,
2913. (b) Lin, Y. J.; Du, L. N.; Kang, T. R.; Liu, Q. Z.; Chen, Z. Q.;
He, L. Chem. Eur. J. 2015, 21, 11773.
(3) Congmon, J.; Tius, M. A. Eur. J. Org. Chem. 2003, 68, 2853.
(4) Sanz-Marco, A.; Carcia-Ortiz, A.; Blay, G.; Pedro, J. R. Chem.
Commun. 2014, 50, 2275.
(5) Li, Y.; Wang, H.; Su, Y.; Li, R.; Li, C.; Liu, L.; Zhang, J. Org. Lett.
2018, 20, 6444.
(6) (a) Kawai, H.; Okusu, S.; Yuan, Z.; Tokunaga, E.; Yamano, A.;
Shiro, M.; Shibata, N. Angew. Chem. Int. Ed. 2013, 52, 2221.
(b) Bizet, V.; Pannecoucke, X.; Renaud, J.-L.; Cahard, D. Angew.
Chem. Int. Ed. 2012, 51, 6467. (c) Jiang, Q.; Guo, T.; Wu, K.; Yu, Z.
Chem. Commun. 2016, 52, 2913.
(7) Funabiki, K.; Matsunaga, K.; Nojiri, M.; Hashimoto, W.;
Yamamoto, H.; Shibata, K.; Matsui, M. J. Org. Chem. 2003, 68,
2853.
To confirm that the stereoselectivity of our method is
superior to conventional methods,23 we performed the re-
arrangement of 1l–m by using an access amount of concen-
trated H2SO4. As shown in Scheme 2, the reactions provide
the E/Z-isomer and a significant amount of dehydration
product 5.
(8) Yamazaki, T.; Kawasaki-Takasuka, T.; Furuta, A.; Sakamoto, S.
Tetrahedron 2009, 65, 5945.
(9) Boreux, A.; Lambion, A.; Campeau, A.; Sanita, M.; Coronel, R.;
Riant, O.; Gagosz, F. Tetrahedron 2018, 74, 5232.
OH
O
n-Bu
RF
O
RF
conc. H2SO4
(5 equiv)
RF
n-Bu
+
n-Bu
Ph
DCE, 50 °C, 6 h
(10) Bizet, V.; Pannecoucke, X.; Renaud, J.-L.; Cahard, D. J. Fluorine
Chem. 2013, 152, 56.
1l, RF = CF3
1m, RF = C2F5
2l, RF = CF3, 31%
2m, RF = C2F5, 21%
4l, RF = CF3, 15%
4m, RF = C2F5, 9%
(11) Watanabe, Y.; Yamazaki, T. J. Org. Chem. 2011, 76, 1957.
(12) (a) Engel, D. A.; Dudley, G. B. Org. Biomol. Chem. 2009, 7, 4149.
(b) Ramón, R. S.; Marion, N.; Nolan, S. P. Tetrahedron 2009, 65,
1767. (c) Cadierno, V.; Crochet, P.; Carcia-Garrido, S. E.; Gimeno,
J. Dalton Trans. 2010, 39, 4015. (d) Xiong, Y. P.; Wu, M. Y.;
Zhang, X. Y.; Ma, C. L.; Huang, L.; Zhao, L. J.; Tan, B.; Liu, X. Y. Org.
Lett. 2014, 16, 1000. (e) Nikolaev, A.; Orellana, A. Org. Lett. 2015,
17, 5796.
(13) Hsieh, M. T.; Lee, K. H.; Kuo, S. C.; Lin, H. C. Adv. Synth. Catal.
2018, 360, 1605.
(14) For the preparation of fluorinated alkyl alkynyl ketones, see ref-
erence 13 and: Hsieh, M.-T.; Kuo, S.-C.; Lin, H.-C. Adv. Synth.
Catal. 2015, 357, 683.
RF
n-Pr
+
5l, RF = CF3, 18%
5m, RF = C2F5, 24%
Ph
Scheme 2 Sulfuric acid-induced rearrangement reaction of 1l and 1m
In conclusion, we have developed a new and practical
procedure for the synthesis of β-fluoroalkyl-α,β-enones24
by using the BF3·OEt2-catalyzed Meyer–Schuster reaction.
The protocol is highly stereoselective for the conversion of
trifluoroalkylated tertiary allylic alcohols into (E)-β-alkyl-
β-fluoroalkyl-α,β-enones. We envision that the methods
disclosed herein will find practical applications in the syn-
thesis of structurally complex β-fluoroalkyl enones that are
of importance in synthetic chemistry.
(15) Engel, D. A.; Lopez, S. S.; Dudley, G. B. Tetrahedron 2008, 64,
6988.
(16) (a) Okamoto, N.; Sueda, T.; Yanada, R. J. Org. Chem. 2014, 79,
9854. (b) Du, C.; Wang, X.; Jin, S.; Shi, H.; Li, Y.; Pang, Y.; Liu, Y.;
Cheng, M.; Guo, C.; Liu, Y. Asian J. Org. Chem. 2016, 5, 755.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2019, 30, A–E

E
M. Ramasamy et al.
Letter
Synlett
(17) (a) Ross, J.; Xiao, J. Green Chem. 2002, 4, 129. (b) Song, C. E.;
Jung, D.; Choung, S. Y.; Roh, E. J.; Lee, S. Angew. Chem. Int. Ed.
2004, 43, 6183. (c) Tran, P. H.; Hansen, P. E.; Hoang, H. M.; Chau,
D.-K. N.; Le, T. N. Tetrahedron Lett. 2015, 56, 2187.
(18) For BF3·OEt2-mediated syn-selective Meyer–Schuster reaction,
see: Puri, S.; Babu, M. H.; Reddy, M. S. Org. Biomol. Chem. 2016,
14, 7001.
ture data.20
White solid; mp = 76.0–77.0 °C; 1H NMR (CDCl3, 500 MHz): δ
7.95–7.93 (m, 2 H), 7.62–7.58 (m, 1 H), 7.49–7.46 (m, 2 H),
4.69–4.65 (m, 1 H), 3.56–3.55 (m, 1 H), 3.39–3.26 (m, 2 H); 13C
NMR (CDCl3, 125 MHz): δ 197.5, 136.0, 134.1, 128.8, 128.4,
124.7 (q, J = 277.0 Hz), 67.0 (q, J = 32.5 Hz), 38.2; 19F NMR
(CDCl3, 470 MHz): δ –79.2.
(19) General Procedure for the Synthesis of Compounds 2a–r
The general procedure is illustrated immediately below with
compound 2a as a specific example.
(20) Xiong, H. Y.; Yang, Z. Y.; Chen, Z.; Zeng, J. L.; Nie, J.; Ma, J. A.
Chem. Eur. J. 2014, 20, 8325.
(21) A similar mechanism in syn-selective Meyer–Schuster rear-
rangement, mediated by BF3·OEt2, was reported. See reference
18.
A stirred solution of compound 1a (100 mg, 0.50 mmol) and
BF3·OEt2 (36 mg, 0.25 mmol) in dichloroethane (2 mL) was
heated at 70 oC under nitrogen for 4 h. Then, water (2 mL) and
saturated Na2CO3 solution (1 mL) were added to quench the
reaction at 0 °C. The aqueous layer was separated and extracted
with CH2Cl2 (3 x 3 mL). The combined organic extracts were
washed with brine, dried with MgSO4, filtered, and concen-
trated to give the crude residue, which was purified by flash
chromatography on silica gel with EtOAc/n-hexane (1:19) to
afford compound 2a (80 mg, 80% yield) as a yellow oil and com-
pound 3a (5 mg, 4% yield) as colorless oil.
(22) As shown below, the BF3·OEt2-catalyzed reaction of 1s did not
proceed and only the starting substrate was recovered.
OH
BF3·OEt (1.0 equiv)
recovery of starting
CF3
material
DCE, 60 °C, 48 h
n-Bu
1s
Scheme 3
(E)-4,4,4-Trifluoro-1-phenylbut-2-en-1-one (2a)
(23) For Brønsted acid-promoted Meyer–Schuster reactions, see
(a) Swaminathan, S.; Narayanan, K. V. Chem. Rev. 1971, 71, 429.
(b) Crich, D.; Natarajan, S.; Crich, J. Z. Tetrahedron 1997, 53,
7139. (c) Park, J.; Yun, J.; Kim, J.; Jang, D.-J.; Park, C. H. Synth.
Commun. 2014, 44, 1924.
(24) All of the synthetic β-fluoroalkyl-α,β-enones were character-
ized according to their 1H NMR, 13C NMR, 19F NMR, and mass
spectra. The stereochemistry of (E)-β-alkyl-β-fluoroalkyl-α,β-
enones was unequivocally determined by comparing their NMR
spectra to those of structurally identical or similar compounds.
The spectroscopic data were in good agreement with the litera-
ture data.12b
Colorless oil; 1H NMR (CDCl3, 500 MHz): δ 8.00 (d, J = 8.5 Hz, 2
H), 7.69–7.65 (m, 1 H), 7.58–7.54 (m, 3 H), 6.85 (dq, J = 15.5, 6.5
Hz, 1 H); 13C NMR (CDCl3, 125 MHz): δ 188.0, 136.1, 134.1,
131.0, 130.3 (q, J = 35.0 Hz), 129.0, 128.3, 122.5 (q, J = 268.7 Hz);
19F NMR (CDCl3, 470 MHz): δ –65.1; HRMS (ESI): m/z [M + H]+
calcd for C10H8F3O: 201.0527; found: 201.0525.
4,4,4-Trifluoro-3-hydroxy-1-phenylbutan-1-one (3a)
The spectroscopic data were in good agreement with the litera-
© Georg Thieme Verlag Stuttgart · New York — Synlett 2019, 30, A–E