Acidic Zeolite-Catalyzed Reaction of 2,4-Diaryl-1,1,1-trifluorobut-3-yn-2-ols with Benzene. A New Synthesis of 1,3-Diaryl-1-trifluoromethylindenes

Article abstract of DOI:10.1134/S1070428018120047

Reactions of 2,4-diaryl-1,1,1-trifluorobut-3-yn-2-ols with benzene in the presence of HUSY acidic zeolite (CBV-720) at 100°C in 1 h (glass high-pressure reactor) led to the formation of 1,3-diaryl-1-trifluoromethylindenes in 39–92% yield. A probable react

Full text of DOI:10.1134/S1070428018120047

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2018, Vol. 54, No. 12, pp. 1764–1771. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © S.K. Nursahedova, A.V. Zerov, A.V. Vasilyev, 2018, published in Zhurnal Organicheskoi Khimii, 2018, Vol. 54, No. 12,
pp. 1750–1757.
Acidic Zeolite-Catalyzed Reaction
of 2,4-Diaryl-1,1,1-trifluorobut-3-yn-2-ols with Benzene.
A New Synthesis of 1,3-Diaryl-1-trifluoromethylindenes
S. K. Nursahedovaa, A. V. Zerovb, and A. V. Vasilyeva, b*
a St. Petersburg State Forest Technical University, Institutskii per. 5, St. Petersburg, 194021 Russia
*e-mail: aleksvasil@mail.ru
b St. Petersburg State University, Universitetskii pr. 26, St. Petersburg, 198504 Russia
Received September 24, 2018; revised October 8, 2018; accepted October 15, 2018
Abstract—Reactions of 2,4-diaryl-1,1,1-trifluorobut-3-yn-2-ols with benzene in the presence of HUSY acidic
zeolite (CBV-720) at 100°C in 1 h (glass high-pressure reactor) led to the formation of 1,3-diaryl-1-trifluoro-
methylindenes in 39–92% yield. A probable reaction mechanism was proposed, which involves formation of
the corresponding trifluoromethyl-substituted propargyl cations.
DOI: 10.1134/S1070428018120047
Acetylene derivatives are very important for
chemistry, biology, medicine, materials sciences, and
other fields of science and technology. Fluorinated
acetylenic compounds are valuable building blocks in
organic synthesis, which make it possible to obtain
new compounds and materials possessing practically
useful properties [1–5]. The presence of fluorine atoms
in organic molecules endows them with unique prop-
erties such as high lipophilicity and biological activity,
thermal stability, nonlinear optical and liquid crys-
talline properties, etc. [6–10]. Synthesis of new
organofluorine compounds is a topical problem of
modern organic chemistry.
(CBV-720). It is known that zeolites can be regarded
as “green” catalysts [13].
Initial 2,4-diaryl-1,1,1-trifluorobut-3-yn-2-ols 3a–3i
were synthesized by trifluoromethylation of 1,3-diaryl-
prop-2-yn-1-ones 1a–1i at the carbonyl group by
treatment with trimethyl(trifluoromethyl)silane,
followed by desilylation of trimethylsilyl ethers 2a–2i
(Scheme 1).
Alcohols 3a–3f reacted with benzene in the pres-
ence of CBV-720 in a glass high-pressure reactor at
100°C (1 h) to produce 49–92% of 1,3-diaryl-1-(tri-
fluoromethyl)indenes 4a–4f (Scheme 2). Analogous
reactions of alcohols 3g–3i led to the formation of
mixtures of isomeric indenes 4g′–4h′ and 4g″–4h″
(Scheme 3). The isomer ratios were determined from
the amounts of particular isomers isolated by chro-
matography. The structure of compounds 4 was
In continuation of our studies on electrophilic
activation of unsaturated compounds (alkynes, alkenes,
allenes) by various Lewis and Brønsted acids and
acidic zeolites [11, 12], in this work we examined
reactions of 2,4-diaryl-1,1,1-trifluorobut-3-yn-2-ols
with benzene catalyzed by HUSY acidic zeolite
1
13
determined on the basis of their H and C NMR and
mass spectra (see Experimental). The structure of
Scheme 1.
Me3SiCF3, CsF
MeOCH2CH2OMe
20°C, 4 h
SnCl2, MeCN
or HCl, THF
20°C, 24 h
O
CF3
CF3
Me3SiO
HO
Ar'
Ar'
Ar'
Ar
Ar
Ar
1a–1i
2a–2i
3a–3i
Ar = Ph, Ar′ = Ph (a), 3-MeC6H4 (b), 4-ClC6H4 (c), 2-BrC6H4 (d); Ar′ = Ph, Ar = 4-ClC6H4 (e), 4-BrC6H4 (f),
4-MeC6H4 (g), 3,4-Me2C6H3 (h), 2,4-Me2C6H4 (i).
1764

ACIDIC ZEOLITE-CATALYZED REACTION OF 2,4-DIARYL-1,1,1-TRIFLUOROBUT-...
1765
Scheme 2.
CF3
HUSY zeolite (CBV-720)
glass high-pressure reactor
100°C, 1 h
HO
+
R'
R'
CF3
R
R
3a–3f
4a–4f
R = H, R′ = H (a), 3-Me (b), 4-Cl (c), 2-Br (d); R′ = H, R = Cl (e), Br (f).
Scheme 3.
CF3
CF3
Ph
Ph
HUSY zeolite (CBV-720)
glass high-pressure reactor
100°C, 1 h
HO
Ph
CF3
Me
+
+
Me
Ph
Me
3g
4g'
4g''
Ph
CF3
Ph
Ph
Ph
HUSY zeolite (CBV-720)
glass high-pressure reactor
100°C, 1 h
HO
CF3
CF3
Me
Me
Me
+
+
Me
Ph
Ph
Me
3h
4h'
Ph
4h''
CF3
CF3
Ph
HUSY zeolite (CBV-720)
glass high-pressure reactor
100°C, 1 h
HO
Ph
CF3
Me
Me
+
+
Me
Me
4i''
Ph
Me
4i'
Me
3i
indene derivative 4h′ was unambiguously proved by
X-ray analysis (Fig. 1).
or Ar′ ring yields isomeric indenes 4 and 4E. Alter-
natively, path b implies reaction of benzene at the C4
electrophilic center of A′ with the formation of allene
Synthesis of indenes has attracted particular atten-
tion due to their use as biologically active compounds,
ligands for metal complex catalysts, etc. [14–16].
Introduction of a trifluoromethyl group into molecules
of indene derivatives (as in structures like 4) could
give rise to new practically important properties of the
resulting compounds.
C16
C17
C18
C15
C14
F2
C10
F3
C13
C1
F1
C9
C8
C12
C2
Scheme 4 outlines a probable mechanism of the
described reaction. The primary intermediate is pro-
pargyl cation A generated from alcohol 3 by the action
of acidic zeolite. The structure of that intermediate can
be represented by propargyl (A) and allenyl (A′)
canonical forms with the electrophilic centers located
on C2 and C4, respectively. The subsequent reaction
with benzene can involve both these centers (paths a
and b in Scheme 4). Path a initially leads to alkyne 5
which is protonated to vinylic cation B. Intramolecular
cyclization of the latter with participation of the phenyl
C4
C7
C6
C3
C20
C19
C24
C5
C21
C11
C23
C22
Fig. 1. Structure of the molecule of 5,6-dimethyl-1,3-di-
phenyl-1-(trifluoromethyl)-1H-indene (4h′) according to the
X-ray diffraction data.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 12 2018

NURSAHEDOVA et al.
1766
Scheme 4.
CF3
HO
Ar'
Ph
Ar
CF3
R'
3
H+
–H2O
Ar
Path a
1CF3
4E
CF3
Ar'
Ph
Ph
H+
2
PhH
–H+
Ar'
Ar'
4
CF3
–H+
Ar
3
Ar' CF3
Ar
Ar
A
5
B
Ar
4
Path b
1CF3
CF3
Ar'
Ar'
CF3
R
2
H+
PhH
–H+
·
Ar'
Ar
·
Ar
CF3
3
–H+
4
Ar
Ph
Ph
Ar'
Ph
A'
6
C
4D
6 whose protonation gives allylic cation C. The
cyclization of C is possible with participation of the
phenyl or Ar ring, leading to structures 4 and 4D,
respectively.
Bruker microTOF (electrospray ionization) and Varian
902-MS (MALDI) instruments. The product mixtures
were analyzed by GC/MS on an Agilent Technologies
6850C GC/MSD instrument (HP-5MS capillary
column, 3 m×0.25 mm, film thickness 0.25 μm). The
X-ray diffraction data for a single crystal of 4h′ were
obtained on an Agilent Technologies Oxford Diffrac-
tion Supernova diffractometer; the structure was
deposited to the Cambridge Crystallographic Data
Centre (CCDC entry no. 1568601). The progress of
reactions was monitored by TLC on Alugram SIL
G/UV254 plates. The products were isolated by
column chromatography on Merck 60 silica gel using
petroleum ether (bp 40–70°C)–ethyl acetate as eluent.
Commercial HUSY zeolite CBV-720 (Zeolyst
International) was activated by heating for 4 h at
550°C in a muffle furnace on exposure to air.
It is not always possible to unambiguously deter-
mine the path of formation of indenes 4a–4i on the
basis of their structure. Nevertheless, it is clear that
compounds 4g′, 4h′, 4h″, and 4i′ are formed along
path b since the last stage is cyclization of cation C at
the Ar fragment (structure 4D). Indenes 4a–4f, 4g″,
and 4i″ can be formed along both path a (4, 4E) and
path b (4). In the case of just these compounds it is
difficult to unambiguously determine the path of their
formation since the Ar and/or Ar′ substituents in the
corresponding initial alcohols 3 are unsubstituted
phenyl ring (Scheme 4).
In summary, we were the first to synthesize tri-
fluoromethyl-substituted indenes by the acidic zeolite-
catalyzed reaction of 2,4-diaryl-1,1,1-trifluorobut-3-
yn-2-ols with benzene.
Initial 1,3-diarylpropynones 1a, 1b, 1f [17], 1c
[18], 1d [19], 1e [20], and 1g–1i [21] were described
previously.
Compounds 2a–2i (general procedure). Trimethyl-
(trifluoromethyl)silane, 167 mg (1.17 mmol), and
cesium fluoride, 7.6 mg (0.05 mmol), were added with
stirring to a solution of 1 mmol of ketone 1a–1i in
0.3 mL of ethylene glycol dimethyl ether. The mixture
was stirred for 4 h at 20°C, poured into 150 mL of
water, and extracted with diethyl ether (3×70 mL).
The combined extracts were washed with water
EXPERIMENTAL
The H, 13C, and 19F NMR spectra were recorded
1
on a Bruker AM-400 spectrometer at 400, 100, and
376 MHz, respectively, using CDCl3 as solvent and
reference (CHCl3, δ 7.26 ppm; CDCl3, δC 77.0 ppm).
The high-resolution mass spectra were measured on
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ACIDIC ZEOLITE-CATALYZED REACTION OF 2,4-DIARYL-1,1,1-TRIFLUOROBUT-...
1767
(50 mL) and dried over Na2SO4, the solvent was
removed under reduced pressure, and the residue was
subjected to chromatographic separation on silica gel.
131.1, 131.8, 135.4, 136.2. 19F NMR spectrum:
δF –78.56 ppm, s (CF3). Mass spectrum (ESI):
m/z 532.9299 [M + Ag]+. C19H18AgBrF3OSi. Calculat-
ed: M + Ag 532.9308.
4,4,4-Trifluoro-1,3-diphenyl-3-(trimethylsilyl-
oxy)but-1-yne (2a). Yield 85%, yellow oily material.
1H NMR spectrum, δ, ppm: 0.25 s (9H, CH3), 7.36–
7.43 m (6H, Harom), 7.54–7.56 m (2H, Harom), 7.79–
7.81 m (2H, Harom). 13C NMR spectrum, δC, ppm:
1.5 (CH3), 74.7 q (C2, JCF = 32.2 Hz), 85.3 (C4), 89.0
(C3), 121.5, 123.5 q (C1, JCF = 286.0 Hz), 127.6 q
(JCF = 0.8 Hz), 128.1, 128.7, 129.3, 129.6, 132.0,
137.7. 19F NMR spectrum: δF –80.63 ppm, s (CF3).
Mass spectrum (ESI): m/z 455.0208 [M + Ag]+.
C19H19AgF3OSi. Calculated: M + Ag 455.0203.
1-(4-Chlorophenyl)-4,4,4-trifluoro-3-phenyl-3-
(trimethylsilyloxy)but-1-yne (2e). Yield 86%, light
1
yellow oily material. H NMR spectrum, δ, ppm:
0.23 s (9H, CH3), 7.34–7.38 m (2H, Harom), 7.39–
7.43 m (3H, Harom), 7.45–7.49 m (2H, Harom), 7.74–
13
7.78 m (2H, Harom). C NMR spectrum, δC, ppm: 1.5
(CH3), 74.9 q (C2, JCF = 32.5 Hz), 86.3 (C4), 87.8 (C3),
119.9, 123.4 q (C1, JCF = 286.0 Hz), 127.5, 128.2,
19
129.1, 129.4, 133.2, 135.8, 137.4. F NMR spectrum:
δF –80.59 ppm, s (CF3). Mass spectrum (ESI):
m/z 488.9804 [M + Ag]+. C19H18AgClF3OSi. Calculat-
ed: M + Ag 488.9813.
4,4,4-Trifluoro-3-(3-methylphenyl)-1-phenyl-3-
(trimethylsilyloxy)but-1-yne (2b). Yield 91%, yellow
1
oily material. H NMR spectrum, δ, ppm: 0.25 s (9H,
1-(4-Bromophenyl)-4,4,4-trifluoro-3-phenyl-3-
3
SiMe3), 2.42 s (3H, CH3), 7.21 d (1H, Harom, J =
(trimethylsilyloxy)but-1-yne (2f). Yield 75%, orange
3
1
7.5 Hz), 7.30 t (1H, Harom, J = 7.5 Hz), 7.36–7.42 m
oily material. H NMR spectrum, δ, ppm: 0.23 s (9H,
(3H, Harom), 7.53–7.57 m (2H, Harom), 7.58 s (1H,
SiMe3), 7.39–7.43 m (5H, Harom), 7.53 d (2H, Harom
,
H
arom), 7.58–7.60 m (1H, Harom). 13C NMR spectrum,
3J = 8.5 Hz), 7.76–7.77 m (2H, Harom). 13C NMR
δC, ppm: 1.5 (SiMe3), 21.7 (CH3), 74.9 q (C2, JCF
=
spectrum, δC, ppm: 1.5 (SiMe3), 74.9 q (C2, JCF
=
32.9 Hz), 85.5 (C4), 88.9 (C3), 121.6, 123.5 q (C1,
JCF = 285.9 Hz), 124.7, 127.8, 128.2 q (JCF = 0.6 Hz),
128.7, 129.5, 130.0, 132.0, 137.6, 137.8. 19F NMR
spectrum: δF –80.57 ppm, s (CF3). Mass spectrum
(ESI): m/z 469.0371 [M + Ag]+. C20H21AgF3OSi. Cal-
culated: M + Ag 469.0360.
32.6 Hz), 86.5 (C4), 87.9 (C3), 120.4, 123.4 q (C1,
JCF = 285.9 Hz), 124.1, 127.5, 128.2, 129.4, 132.1,
133.4, 137.4. 19F NMR spectrum: δF –80.58 ppm, s
(CF3). Mass spectrum (ESI): m/z 532.9276 [M + Ag]+.
C19H18AgBrF3OSi. Calculated: M + Ag 532.9308.
4,4,4-Trifluoro-1-(4-methylphenyl)-3-phenyl-3-
3-(4-Chlorophenyl)-4,4,4-trifluoro-1-phenyl-3-
(trimethylsilyloxy)but-1-yne (2g). Yield 78%, orange
1
(trimethylsilyloxy)but-1-yne (2c). Yield 93%, yellow
crystals, mp 52°C. H NMR spectrum, δ, ppm: 0.24 s
1
3
oily material. H NMR spectrum, δ, ppm: 0.24 s (9H,
(9H, SiMe3), 2.39 (3H, CH3), 7.19 d (2H, Harom, J =
SiMe3), 7.36–7.43 m (5H, Harom), 7.53–7.55 m (2H,
Harom), 7.72 d (2H, Harom, 3J = 8.5 Hz). 13C NMR spec-
trum, δC, ppm: 1.5 (SiMe3), 74.7 q (C2, JCF = 32.7 Hz),
8.0 Hz), 7.40–7.42 m (3H, Harom), 7.45 d (2H, Harom,
3J = 8.0 Hz), 7.79–7.81 m (2H, Harom). 13C NMR
spectrum, δC, ppm: 1.5 (SiMe3), 21.7 (CH3), 74.9 q
(C2, JCF = 32.4 Hz), 84.7 (C4), 89.2 (C3), 118.5, 123.5 q
(C1, JCF = 285.7 Hz), 127.6, 128.1, 129.2, 129.4, 131.9,
137.8, 139.9. 19F NMR spectrum: δF –80.64 ppm, s
(CF3). Mass spectrum (ESI): m/z 469.0366 [M + Ag]+.
C20H21AgF3OSi. Calculated: M + Ag 469.0360.
84.7 (C4), 89.4 (C3), 121.2, 123.3 q (C1, JCF
=
285.8 Hz), 128.4, 128.7, 129.1 q (JCF = 0.5 Hz),
129.7, 132.0, 135.5, 136.4. 19F NMR spectrum:
δF –80.74 ppm, s (CF3). Mass spectrum (ESI):
m/z 488.9800 [M + Ag]+. C19H18AgClF3OSi. Calculat-
ed: M + Ag 488.9813.
1-(3,4-Dimethylphenyl)-4,4,4-trifluoro-2-phenyl-
2-(trimethylsilyloxy)but-1-yne (2h). Yield 94%,
white crystals, mp 92°C. 1H NMR spectrum, δ, ppm:
3-(2-Bromophenyl)-4,4,4-trifluoro-1-phenyl-3-
(trimethylsilyloxy)but-1-yne (2d). Yield 90%, light
1
yellow oily material. H NMR spectrum, δ, ppm:
0.25 s (9H, SiMe3), 2.29 (3H, CH3), 2.30 (3H, CH3),
3
4
3
0.29 s (9H, SiMe3), 7.22 d.t (1H, Harom, J = 7.9, J =
7.15 d (1H, Harom, J = 7.7 Hz), 7.30 d.d (1H, Harom
,
4
1.3 Hz), 7.36–7.42 m (4H, Harom), 7.55–7.57 m (2H,
3J = 7.7, J = 1.3 Hz), 7.33 s (1H, Harom), 7.38–7.46 m
(3H, Harom), 7.77–7.84 m (2H, Harom). C NMR spec-
3
4
13
H
arom), 7.69 d.d (1H, Harom, J = 7.9, J = 1.3 Hz),
3
4
13
7.98 d.d (1H, Harom, J = 7.9, J = 1.3 Hz). C NMR
trum, δC, ppm: 1.5 (SiMe3), 19.7 (CH3), 20.0 (CH3),
74.9 q (C2, JCF = 36.2 Hz), 84.4 (C4), 89.4 (C3), 118.8,
123.5 q (C1, JCF = 285.9 Hz), 127.6, 128.1, 129.2,
129.5, 130.0, 132.9, 137.1, 137.9, 138.7. 19F NMR
spectrum, δC, ppm: 1.6 (SiMe3), 75.1 q (C2, JCF
=
32.9 Hz), 84.5 (C4), 90.8 (C3), 121.6, 122.0, 123.6 q
(C1, JCF = 287.4 Hz), 127.2, 128.7, 129.6, 130.6,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 12 2018

NURSAHEDOVA et al.
1768
4
3
spectrum: δF –80.64 ppm, s (CF3). Mass spectrum
(ESI): m/z 483.0507 [M + Ag]+. C21H23AgF3OSiAg.
Calculated: M + Ag 483.0516.
3J = 8.0, J = 1.3 Hz), 7.96 d (1H, Harom, J = 8.0 Hz).
13C NMR spectrum, δC, ppm: 73.9 q (C2, JCF
=
33.1 Hz), 83.7 (C4), 89.6 (C3), 121.3, 121.7, 123.6 q
(C1, JCF = 287.0 Hz), 127.6, 128.6, 129.7, 130.4 q
(JCF = 1.5 Hz), 130.9, 132.1, 133.7, 135.8. 19F NMR
spectrum: δF –77.56 ppm, s (CF3). Mass spectrum
(ESI): m/z 460.8933 [M + Ag]+. C16H10AgBrF3O. Cal-
culated: M + Ag 460.8913.
1-(2,4-Dimethylphenyl)-4,4,4-trifluoro-2-phenyl-
2-(trimethylsilyloxy)but-1-yne (2i). Yield 81%, yel-
1
low oily material. H NMR spectrum, δ, ppm: 0.23 s
(9H, SiMe3), 2.36 s (3H, CH3), 2.48 s (3H, CH3),
3
7.01 d (1H, Harom, J = 7.8 Hz), 7.09 s (1H, Harom),
7.38–7.44 m (4H, Harom), 7.80–7.82 m (2H, Harom).
13C NMR spectrum, δC, ppm: 1.5 (SiMe3), 20.7 (CH3),
21.6 (CH3), 75.0 q (C2, JCF = 32.3 Hz), 88.3 (C4), 88.5
(C3), 118.3, 123.6 q (C1, JCF 285.9 Hz), 126.7, 127.7,
128.1, 129.2, 130.7, 132.3, 137.9, 139.8, 141.1.
19F NMR spectrum: δF –80.67 ppm, s (CF3). Mass
spectrum (ESI): m/z 483. 0511 [M + Ag ]+.
C21H23AgF3OSi. Calculated: M + Ag 483.0516.
4-(4-Chlorophenyl)-1,1,1-trifluoro-2-phenylbut-
3-yn-2-ol (3e) [25]. Yield 78%, light yellow oily
material. 1H NMR spectrum, δ, ppm: 3.09 s (1H, OH),
3
7.35 d (2H, Harom, J = 8.6 Hz), 7.43–7.48 m (5H,
19
H
arom), 7.79–7.81 m (2H, Harom). F NMR spectrum:
δF –80.20 ppm, s (CF3).
4-(4-Bromophenyl)-1,1,1-trifluoro-2-phenylbut-
3-yn-2-ol (3f) [25]. Yield 92%, orange oily material.
1H NMR spectrum, δ, ppm: 3.00 s (1H, OH), 7.39 d
Compounds 3a–3i (general procedure). Trimethyl-
silyl ether 2a–2i, 1 mmol, was dissolved in 1 mL of
acetonitrile, and 221 mg (1.13 mmol) of SnCl2 or
0.8 mL of 6 N aqueous HCl was added with stirring.
The mixture was stirred for 24 h at 20°C, poured into
water (150 mL), and extracted with diethyl ether
(3×50 mL). The combined extracts were washed with
a 10% aqueous solution of HNO3 (50 mL) and water
(50 mL), dried over Na2SO4, and the solvent was
removed under reduced pressure.
3
(2H, Harom, J = 8.6 Hz), 7.43–7.46 m (3H, Harom),
3
7.51 d (2H, Harom, J = 8.6 Hz), 7.78–7.81 m (2H,
Harom). 19F NMR spectrum: δF –80.20 ppm, s (CF3).
1,1,1-Trifluoro-4-(4-methylphenyl)-2-phenylbut-
3-yn-2-ol (3g) [24]. Yield 79%, orange oily material.
1H NMR spectrum, δ, ppm: 2.38 s (3H, CH3), 3.06 s
(1H, OH), 7.17 d (2H, Harom, 3J = 7.9 Hz), 7.42–7.46 m
(5H, Harom), 7.81–7.7.84 m (2H, Harom). 19F NMR spec-
trum: δF –80.27 ppm, s (CF3).
1,1,1-Trifluoro-2,4-diphenylbut-3-yn-2-ol (3a)
4-(3,4-Dimethylphenyl)-1,1,1-trifluoro-2-phenyl-
but-3-yn-2-ol (3h). Yield 73%, yellow oily material.
1H NMR spectrum, δ, ppm: 2.26 (3H, CH3), 2.29 (3H,
CH3), 3.10 s (1H, OH), 7.12 d (1H, Harom, 3J = 7.8 Hz),
1
[22]. Yield 87%, yellow oily material. H NMR spec-
trum, δ, ppm: 3.11 s (1H, OH), 7.35–7.47 m (6H,
Harom), 7.54–7.56 m (2H, Harom), 7.83–7.85 m (2H,
Harom). 19F NMR spectrum: δF –80.24 ppm, s (CF3).
3
4
7.28 d.d (1H, Harom, J = 7.8, J = 1.2 Hz), 7.32 s (1H,
1,1,1-Trifluoro-2-(3-methylphenyl)-4-phenylbut-
3-yn-2-ol (3b) [23]. Yield 67%, orange oily material.
1H NMR spectrum, δ, ppm: 2.42 s (3H, CH3), 3.10 s
(1H, OH), 7.25 d (1H, Harom, 3J = 7.9 Hz), 7.31–7.41 m
(4H, Harom), 7.53–7.56 m (2H, Harom), 7.62–7.63 m
(1H, Harom), 7.63 s (1H, Harom). 19F NMR spectrum:
δF –80.18 ppm, s (CF3).
Harom), 7.42–7.46 m (3H, Harom), 7.81–7.83 m (2H,
13
H
arom). C NMR spectrum, δC, ppm: 19.7 (CH3), 20.0
(CH3), 73.5 q (C2, JCF = 32.5 Hz), 83.7 (C4), 88.7 (C3),
118.3, 123.6 q (C1, JCF = 285.4 Hz), 127.4 q (JCF
=
0.8 Hz), 128.4, 129.6, 129.7, 129.9, 133.2, 135.6,
137.1, 138.8. 19F NMR spectrum: δF –80.27 ppm, s
(CF3). Mass spectrum (ESI): m/z 411.0112 [M + Ag]+.
C18H15AgF3O. Calculated: M + Ag 411.0121.
2-(4-Chlorophenyl)-1,1,1-trifluoro-4-phenylbut-
3-yn-2-ol (3c) [24]. Yield 93%, light yellow oily
material. 1H NMR spectrum, δ, ppm: 2.85 s (1H, OH),
7.35–7.44 m (5H, Harom), 7.52–7.55 m (2H, Harom),
4-(2,4-Dimethylphenyl)-1,1,1-trifluoro-2-phenyl-
but-3-yn-2-ol (3i). Yield 81%, yellow oily material.
1H NMR spectrum, δ, ppm: 2.34 s (3H, CH3), 2.45 s
3
7.75 d (2H, Harom, J = 8.4 Hz). 19F NMR spectrum:
3
(3H, CH3), 3.10 s (1H, OH), 7.00 d (1H, Harom, J =
3
δF –80.39 ppm, s (CF3).
7.8 Hz), 7.07 s (1H, Harom), 7.38 d (1H, Harom, J =
2-(2-Bromophenyl)-1,1,1-trifluoro-4-phenylbut-
3-yn-2-ol (3d). Yield 95%, yellow oily material.
1H NMR spectrum, δ, ppm: 3.79 s (1H, OH), 7.26 d.t
7.8 Hz), 7.41–7.46 m (3H, Harom), 7.82–7.85 m (2H,
13
H
arom). C NMR spectrum, δC, ppm: 20.6 (CH3), 21.6
(CH3), 73.7 q (C2, JCF = 32.6 Hz), 87.6 (C4), 87.8 (C3),
117.9, 123.7 q (C1, JCF = 285.8 Hz), 126.6, 127.4 q
(JCF = 0.9 Hz), 128.4, 129.6, 130.7, 132.4, 135.6,
3
4
(1H, Harom, J = 8.0, J = 1.7 Hz), 7.33–7.43 m (4H,
Harom), 7.53–7.56 m (2H, Harom), 7.70 d.d (1H, Harom
,
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ACIDIC ZEOLITE-CATALYZED REACTION OF 2,4-DIARYL-1,1,1-TRIFLUOROBUT-...
1769
140.0, 141.1. 19F NMR spectrum: δF –80.28 ppm, s
(CF3). Mass spectrum (ESI): m/z 411.0123 [M + Ag]+.
C18H15AgF3O. Calculated: M + Ag 411.0121.
27.0 Hz), 122.0, 125.7, 126.6 q (CF3, JCF = 282.4 Hz),
126.9, 127.9, 128.9, 128.9, 128.9, 129.0, 129.4 q
(JCF = 1.8 Hz), 131.6 q (JCF = 1.6 Hz), 133.2, 134.2,
134.3, 143.6, 143.6, 147.8. 19F NMR spectrum:
δF –67.56 ppm, s (CF3). Mass spectrum (MALDI):
m/z 371.0812 [M + H]+. C22H15F3Cl. Calculated:
M + H 371.0809.
Compounds 4a–4i (general procedure). A mixture
of 0.2 mmol of alcohol 3, 0.45 g of activated zeolite
CBV-720, and 5 mL of benzene was stirred for 1 h at
100°C in a glass high-pressure reactor. After cooling,
the catalyst was filtered off, and the products were
extracted therefrom with boiling methanol (3×10 mL),
each time filtering the catalyst off. The extracts were
combined with the organic phase and evaporated under
reduced pressure, and the residue was subjected to
chromatographic separation in a silica gel column.
Given below are the isolated yields.
1-(2-Bromophenyl)-3-phenyl-1-(trifluoro-
methyl)-1H-indene (4d). Yield 83%, light yellow oily
material. 1H NMR spectrum, δ, ppm: 6.42 s (1H, 2-H),
7.17 t.d (1H, Harom, 3J = 7.7, 4J = 1.5 Hz), 7.26–7.31 m
(3H, Harom), 7.41–7.46 m (3H, Harom), 7.48–7.53 m
3
(2H, Harom), 7.56 d (1H, Harom, J = 7.7 Hz), 7.65–
7.67 m (2H, Harom), 7.99–8.02 m (1H, Harom). 13C NMR
spectrum, δC, ppm: 65.9 q (C1, JCF = 25.4 Hz), 121.7,
122.8, 125.0, 126.4 q (CF3, JCF = 284.1 Hz), 126.8,
127.6, 127.8, 128.7, 128.8, 128.9, 129.3, 129.5, 130.7
q (JCF = 4.3 Hz), 133.5, 134.7, 136.4, 144.2, 146.1,
151.1. 19F NMR spectrum: δF –65.17 ppm, s (CF3).
Mass spectrum (MALDI): m/z 415.0308 [M + H]+.
C22H15F3Br. Calculated: M + H 415.0304.
1,3-Diphenyl-1-(trifluoromethyl)-1H-indene (4a).
1
Yield 70%, light yellow crystals, mp 95°C. H NMR
spectrum, δ, ppm: 6.68 s (1H, 2-H), 7.32–7.38 m (4H,
H
H
arom), 7.41–7.50 m (4H, Harom), 7.57–7.59 m (3H,
arom), 7.62–7.64 m (2H, Harom), 7.68 d (1H, Harom, 3J =
7.4 Hz). 13C NMR spectrum, δC, ppm: 64.3 q (C1, JCF
27.0 Hz), 121.8 (C2), 125.9, 126.7, 126.8 q (CF3, JCF
=
=
282.5 Hz), 127.9, 128.0, 128.2, 128.7, 128.8, 128.9,
132.2 q (JCF = 1.7 Hz), 134.4, 134.6, 143.7 (C3),
144.0 d (JCF = 0.6 Hz), 147.4. 19F NMR spectrum:
δF –67.45 ppm, s (CF3). Mass spectrum (MALDI):
m/z 337.1208 [M + H]+. C22H16F3. Calculated: M + H
337.1199.
3-(4-Chlorophenyl)-1-phenyl-1-(trifluoro-
methyl)-1H-indene (4e). Yield 49%, light yellow oily
material. 1H NMR spectrum, δ, ppm: 6.67 s (1H, 2-H),
3
7.30–7.37 m (3H, Harom), 7.38 t.d (1H, Harom, J = 7.4,
4J = 1.1 Hz), 7.42–7.47 m (1H, Harom), 7.45 d (2H,
3
3
H
arom, J = 8.5 Hz), 7.51 d (1H, Harom, J = 7.4 Hz),
3
7.55–7.59 m (2H, Harom), 7.56 d (2H, Harom, J =
1-(3-Methylphenyl)-3-phenyl-1-(trifluoro-
methyl)-1H-indene (4b). Yield 72%, light yellow oily
material. 1H NMR spectrum, δ, ppm: 2.34 s (3H, CH3),
6.67 s (1H, 2-H), 7.13 d (1H, Harom, 3J = 7.4 Hz), 7.21–
7.25 m (1H, Harom), 7.34–7.40 m (3H, Harom), 7.41–
8.5 Hz), 7.69 d (1H, Harom, J = 7.4 Hz). 13C NMR
3
spectrum, δC, ppm: 64.4 q (C1, JCF = 26.9 Hz), 121.6,
126.0 q (JCF = 0.8 Hz), 126.7 q (CF3, JCF = 282.6 Hz),
126.9, 128.0 q (JCF = 1.6 Hz), 128.3, 128.8, 128.9,
129.1, 129.2, 132.6 q (JCF = 1.8 Hz), 132.8, 134.4,
3
7.50 m (4H, Harom), 7.57 d (1H, Harom, J = 7.4 Hz),
19
3
134.7, 143.3, 143.8 q (JCF = 0.8 Hz), 146.3. F NMR
7.62–7.65 m (2H, Harom), 7.69 d (1H, Harom, J =
7.5 Hz). 13C NMR spectrum, δC, ppm: 21.8 (CH3),
spectrum: δF –67.46 ppm, s (CF3). Mass spectrum
(MALDI): m/z 371.0798 [M + H]+. C22H15F3Cl. Cal-
culated: M + H 371.0809.
64.2 q (C1, JCF = 26.8 Hz), 121.8, 125.1 q (JCF
=
1.8 Hz), 125.9 q (JCF = 0.7 Hz), 126.7, 126.8 q (CF3,
JCF = 282.6 Hz), 127.9, 128.6, 128.7 q (JCF = 1.9 Hz),
3-(4-Bromophenyl)-1-phenyl-1-(trifluoro-
methyl)-1H-indene (4f). Yield 51%, colorless oily
material. 1H NMR spectrum, δ, ppm: 6.67 s (1H, 2-H),
128.7, 128.7, 128.9, 128.9, 129.0, 132.3 q (JCF
=
1.8 Hz), 134.5, 138.4, 143.6, 144.0 q (JCF = 1.1 Hz),
147.3. 19F NMR spectrum: δF –67.41 ppm, s (CF3).
Mass spectrum (MALDI): m/z 351.1343 [M + H]+.
C23H18F3. Calculated: M + H 351.1356.
3
7.32–7.36 m (3H, Harom), 7.37 t.d (1H, Harom, J = 7.5,
4J = 1.2 Hz), 7.44 t.d (1H, Harom, 3J = 7.5, 4J = 1.2 Hz),
3
7.49 d (2H, Harom, J = 8.5 Hz), 7.50–7.52 m (1H,
1-(4-Chlorophenyl)-3-phenyl-1-(trifluoro-
Harom), 7.54–7.56 m (2H, Harom), 7.61 d (2H, Harom, 3J =
3
methyl)-1H-indene (4c). Yield 92%, light yellow oily
8.5 Hz), 7.68 d (1H, Harom, J = 7.5 Hz). 13C NMR
material. 1H NMR spectrum, δ, ppm: 6.62 s (1H, 2-H),
spectrum, δC, ppm: 64.4 q (C1, JCF = 26.9 Hz), 121.6,
122.8, 126.0, 126.6 q (CF3, JCF = 282.4 Hz), 126.9,
128.0 q (JCF = 1.6 Hz), 128.3, 128.8, 128.9, 129.5,
132.1, 132.6 q (JCF = 1.6 Hz), 133.3, 134.3, 143.2,
143.8, 146.4. 19F NMR spectrum: δF –67.46 ppm, s
3
7.30 d (2H, Harom, J = 8.8 Hz), 7.37 t.d (1H, Harom
,
3J = 7.5, 4J = 1.0 Hz), 7.42–7.51 m (6H, Harom), 7.58 d
3
(1H, Harom, J = 7.5 Hz), 7.60–7.65 m (3H, Harom).
13C NMR spectrum, δC, ppm: 63.8 q (C1, JCF
=
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NURSAHEDOVA et al.
1770
(CF3). Mass spectrum (MALDI): m/z 415.0298
[M + H]+. C22H15F3Br. Calculated: M + H 415.0304.
Single crystals of 4h′ suitable for X-ray analysis
were obtained by slow evaporation of a solution of
isomer mixture 4h′/4h″ in a mixture of petroleum
ether (bp 40–70°C) with ethyl acetate. Triclinic crystal
system, space group P-1; unit cell parameters: a =
10.3000(8), b = 10.5159(6), c = 17.5695(11) Å; α =
91.086(5), β = 103.868(6), γ = 103.835(6)°; V =
1788.1(2) Å3; Z = 4; dcalc = 1.354 g/cm3; μ(MoKα) =
0.099 mm–1; total of 24400 reflection intensities were
measured in the range 5.244° ≤ 2θ ≤ 54.998°,
including 8212 independent reflections (Rint = 0.0335);
R1 = 0.0429 [reflections with I >2σ(I)], wR2 = 0.1110
(all independent reflections).
6-Methyl-1,3-diphenyl-1-(trifluoromethyl)-1H-
indene (4g′) and 3-(4-methylphenyl)-1-phenyl-1-
(trifluoromethyl)-1H-indene (4g″) were isolated as
an oily mixture of isomers at a ratio of 3:1 in an over-
all yield of 43%.
1
Compound 4g′. H NMR spectrum, δ, ppm: 2.45 s
3
(3H, CH3), 6.61 s (1H, 2-H), 7.24 d (1H, Harom, J =
7.9 Hz), 7.31–7.38 m (3H, Harom), 7.40–7.49 m (5H,
H
H
arom), 7.56–7.58 m (2H, Harom), 7.62–7.65 m (2H,
arom). 13C NMR spectrum, δC, ppm: 21.8 (CH3),
64.1 q (C1, JCF = 26.9 Hz), 121.5, 126.7 q (JCF
=
1
0.8 Hz), 126.8 q (CF3, JCF = 282.5 Hz), 127.9, 127.9 q
(JCF = 1.8 Hz), 128.1, 128.6, 128.8, 128.8, 129.4,
131.3 q (JCF = 1.8 Hz), 134.6, 135.0, 136.7, 141.0,
144.3 (JCF = 1.0 Hz), 147.3. 19F NMR spectrum:
δF –67.33 ppm, s (CF3). Mass spectrum (MALDI):
m/z 351.1361 [M + H]+. C23H18F3. Calculated:
M + H 351.1356.
Compound 4h″. Colorless oily material. H NMR
spectrum, δ, ppm: 1.99 s (3H, CH3), 2.29 s (3H, CH3),
6.36 s (1H, 2-H), 7.24 d (1H, Harom, 3J = 7.9 Hz), 7.27–
7.33 m (6H, Harom), 7.39–7.47 m (3H, Harom), 7.57–
7.60 m (2H, Harom). 13C NMR spectrum, δC, ppm:
16.5 q (CH3, JCF = 3.6 Hz), 20.4 (CH3), 65.7 q (C1,
JCF = 26.3 Hz), 118.9, 124.4 q (CF3, JCF = 295.5 Hz),
127.0 q (JCF = 1.8 Hz), 127.6, 128.0, 128.5, 128.8,
128.9, 130.5, 133.9 q (JCF = 2.0 Hz), 134.7, 134.8,
Compound 4g″. 1H NMR spectrum, δ, ppm: 2.43 s
3
(3H, CH3), 6.64 s (1H, 2-H), 7.29 d (2H, Harom, J =
19
134.9, 136.7, 142.9, 143.6, 146.2. F NMR spectrum:
7.9 Hz), 7.31–7.38 m (5H, Harom), 7.40–7.42 m (1H,
3
H
arom), 7.53 d (2H, Harom, J = 7.9 Hz), 7.56–7.58 m
δF –62.71 ppm, s (CF3). Mass spectrum (MALDI):
m/z 365.1520 [M + H]+. C24H20F3. Calculated:
M + H 365.1512.
3
13
(2H, Harom), 7.68 d (1H, Harom, J = 7.4 Hz). C NMR
spectrum, δC, ppm: 21.5 (CH3), 64.2 q (C1, JCF
26.3 Hz), 121.8, 125.8, 126.6, 126.8 q (CF3, JCF
=
=
4,6-Dimethyl-1,3-diphenyl-1-(trifluoromethyl)-
1H-indene (4i′) and 3-(2,4-dimethylphenyl)-1-
phenyl-1-(trifluoromethyl)-1H-indene (4i″) were
isolated as an oily mixture of isomers at a ratio of 6:1
in an overall yield of 39%.
282.5 Hz), 127.8, 127.9, 128.0 q (JCF = 2.0 Hz), 128.1,
129.5, 129.5, 131.5, 131.6 q (JCF = 1.7 Hz), 134.8,
19
138.6, 143.8, 144.0 q (JCF = 1.1 Hz), 147.3. F NMR
spectrum: δF –67.45 ppm, s (CF3). Mass spectrum
(MALDI): m/z 351.136 [M + H]+. C23H18F3. Calculat-
ed: M + H 351.1356.
1
Compound 4i′. H NMR spectrum, δ, ppm: 1.97 s
(3H, CH3), 2.39 (3H, CH3), 6.39 s (1H, 2-H), 6.95 d
5,6-Dimethyl-1,3-diphenyl-1-(trifluoromethyl)-
1H-indene (4h′) and 6,7-dimethyl-1,3-diphenyl-1-
(trifluoromethyl)-1H-indene (4h″) were isolated as
an amorphous mixture of isomers at a ratio of 1.5:1 in
an overall yield of 70%.
4
(1H, 5-H, J = 0.6 Hz), 7.30 s (1H, 7-H), 7.32–7.43 m
3
13
(8H, Harom), 7.57 d (2H, Harom, J = 7.5 Hz). C NMR
spectrum, δC, ppm: 20.2 (CH3), 21.5 (CH3), 63.7 q
(C1, JCF = 26.6 Hz), 124.3 q (JCF = 0.7 Hz), 126.9 q
(CF3, JCF = 282.5 Hz), 127.9 q (JCF = 1.8 Hz),
127.9, 128.0, 128.2, 128.6, 128.7, 132.5, 132.6,
133.2 q (JCF = 1.8 Hz), 135.2, 136.6, 137.5, 139.2,
144.5 q (JCF = 0.9 Hz), 149.3. 19F NMR spectrum:
δF –67.36 ppm, s (CF3).
Compound 4h′. Colorless crystals, mp 120°C.
1H NMR spectrum, δ, ppm: 2.32 s (3H, CH3), 2.35 s
(3H, CH3), 6.58 s (1H, 2-H), 7.30–7.35 m (4H, Harom),
7.40–7.43 m (2H, Harom), 7.46–7.50 m (2H, Harom),
7.55–7.57 m (2H, Harom), 7.60–7.63 m (2H, Harom).
13C NMR spectrum, δC, ppm: 20.3 (CH3), 20.3 (CH3),
Compound 4i″. 1H NMR spectrum, δ, ppm: 2.25 s
(3H, CH3), 2.40 (3H, CH3), 6.52 s (1H, 2-H), 7.08–
7.13 m (2H, Harom), 7.15 m (1H, Harom), 7.21 d (1H,
64.0 q (C1, JCF = 27.2 Hz), 123.0, 127.0 q (CF3, JCF
=
282.1 Hz), 127.1, 128.0, 128.0, 128.0, 128.6, 128.7,
128.8, 131.4, 134.7, 135.1, 135.2, 137.1, 141.4, 141.7,
147.4. 19F NMR spectrum: δF –67.50 ppm, s (CF3).
Mass spectrum (MALDI): m/z 365.1520 [M + H]+.
C24H20F3. Calculated: M + H 365.1512.
3
Harom, J = 7.5 Hz), 7.30–7.43 m (5H, Harom), 7.56–
3
7.61 m (2H, Harom), 7.67 d (1H, Harom, J = 7.5 Hz).
13C NMR spectrum, δC, ppm: 20.1 (CH3), 21.3 (CH3),
64.6 q (C1, JCF = 26.9 Hz), 121.9, 125.5 q (JCF
=
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 12 2018

ACIDIC ZEOLITE-CATALYZED REACTION OF 2,4-DIARYL-1,1,1-TRIFLUOROBUT-...
1771
8. Fluorinated Heterocyclic Compounds: Synthesis, Chem-
istry, and Applications, Petrov, V.A., Ed., Hoboken:
Wiley, 2009.
0.6 Hz), 126.5, 126.6, 126.8 q (CF3, JCF = 284.1 Hz),
127.9, 128.1, 128.8, 129.2, 129.2, 131.0, 131.1,
133.2 q (JCF = 1.7 Hz), 134.8, 136.3, 138.1, 143.4 q
(JCF = 1.1 Hz), 145.1, 147.7. 19F NMR spectrum:
δF –67.50 ppm, s (CF3). Mass spectrum (MALDI;
isomer mixture): m/z 365.1497 [M + H]+. C24H20F3.
Calculated: M + H 365.1512.
9. Fluorine in Heterocyclic Chemistry, Nenajdenko, V.G.,
Ed., Berlin: Springer, 2014.
10. Prakash Reddy, V., Organofluorine Compounds in
Biology and Medicine, Amsterdam: Elsevier, 2015.
11. Vasilyev, A.V., Adv. Org. Synth., 2018, vol. 8, p. 81.
This study was performed under financial support
by the Russian Science Foundation (project no. 18-13-
00008). The spectral studies were performed at the
Magnetic Resonance Research Center, Chemical
Analysis and Materials Research Center, and Center
for X-Ray Diffraction Studies of the St. Petersburg
State University.
12. Kazakova, A.N. and Vasilyev, A.V., Russ. J. Org.
Chem., 2017, vol. 53, p. 485.
13. Chassaing, S., Bénéteaua, V., Louis, B., and Pale, P.,
Curr. Org. Chem., 2016, vol. 20, p. 1.
14. Gabriele, B., Mancuso, R., and Veltri, L., Chem. Eur. J.,
2016, vol. 22, p. 5056.
15. Ivchenko, N.B., Ivchenko, P.V., and Nifant’ev, I.E.,
Russ. J. Org. Chem., 2000, vol. 36, p. 609.
16. Kuck, D., Chem. Rev., 2006, vol. 106, p. 4885.
REFERENCES
17. Chen, L. and Li, C.-J., Org. Lett., 2004, vol. 6, p. 3151.
18. Wang, Y., Liu, J., and Xia, C., Tetrahedron Lett., 2011,
1. Modern Alkyne Chemistry: Catalytic and Atom-Economic
Transformations, Trost, B.M. and Li, C.-J., Eds., New
York: Wiley, 2014.
vol. 52, p. 1587.
19. Zhao, T. and Xu, B., Org. Lett., 2010, vol. 12, p. 212.
2. Modern Acetylene Chemistry, Stang, P.J. and
20. Chen, J.-Y., Lin, T.-C., Chen, S.-C., Chen, A.-J.,
Mou, C.-Y., and Tsai, F.-Y., Tetrahedron, 2009, vol. 65,
p. 10134.
Diederich, F., Eds., New York: Wiley, 2008.
3. Acetylene Chemistry, Diederich, F., Stang, P.J., and
Tykwinski, R.R., New York: Wiley, 2005.
21. Shchukin, A.O., Vasil’ev, A.V., and Grinenko, E.V.,
4. Ledovskaya, M.S., Voronin, V.V., and Rodygin, K.S.,
Russ. J. Org. Chem., 2010, vol. 46, p. 82.
Russ. Chem. Rev., 2018, vol. 87, p. 167.
22. Correia, C.A., McQuade, D.T., and Seeberger, P.H., Adv.
Synth. Catal., 2013, vol. 355, p. 3517.
23. Motoki, R., Kanai, M., and Shibasaki, M., Org. Lett.,
5. Voronin, V.V., Ledovskaya, M.S., Bogachenkov, A.S.,
Rodygin, K.S., and Ananikov, V.P., Molecules, 2018,
vol. 23, no. 10, article no. 2442.
2007, vol. 9, p. 2997.
6. Bégué, J.P. and Bonnet-Delpon, D., Bioorganic
and Medicinal Chemistry of Fluorine, Hoboken: Wiley,
2008.
7. Fluorine and Health: Molecular Imaging, Biomedical
Materials, and Pharmaceuticals, Tressaud, A. and
Haufe, G., Eds., Amsterdam: Elsevier, 2008.
24. Zhang, G.-W., Meng, W., Ma, H., Nie, J., Zhang, W.-Q.,
and Ma, J.-A., Angew. Chem., Int. Ed., 2011, vol. 50,
p. 3538.
25. Wang, L., Liu, N., Dai, B., Ma, X., and Shi, L., RSC
Adv., 2015, vol. 5, p. 10089.
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