HUSY zeolite-promoted reactions of trifluoromethylated propargyl alcohols with arenes: Synthesis of CF3-indenes and DFT study of intermediate carbocations

Article abstract of DOI:10.1039/c8ob02887g

The reaction of CF₃-propargyl alcohols [ArCCCH(OH)CF₃] with arenes under the action of acidic HUSY zeolite CBV-720 was investigated. It was found that the reaction at 100 °C for 1 h gave rise to 3-aryl-1-CF₃-indenes in up

Full text of DOI:10.1039/c8ob02887g

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HUSY zeolite-promoted reactions of
trifluoromethylated propargyl alcohols with
arenes: synthesis of CF3-indenes and DFT study
of intermediate carbocations†
Cite this: DOI: 10.1039/c8ob02887g
Selbi K. Nursahedova,a Aleksey V. Zerov,b Irina A. Boyarskaya,b Elena V. Grinenko,a
a,b
Valentine G. Nenajdenko *c and Aleksander V. Vasilyev
*
The reaction of CF3-propargyl alcohols [ArCuCCH(OH)CF3] with arenes under the action of acidic HUSY
zeolite CBV-720 was investigated. It was found that the reaction at 100 °C for 1 h gave rise to 3-aryl-1-
CF3-indenes in up to 83% yield. Electronic characteristics of the reaction key intermediates, mesomeric
CF3-propargyl-allenyl cations [ArCuC−HC+(CF3) ↔ ArC+vCvCH(CF3)], were studied by DFT calcu-
lations. A plausible cationic reaction mechanism is discussed.
Received 19th November 2018,
Accepted 10th January 2019
DOI: 10.1039/c8ob02887g
rsc.li/obc
alcohols under the electrophilic activation conditions have not
been studied to date.
Introduction
Acetylene compounds are of great importance in modern
Based on our previous studies on electrophilic activation of
organic synthesis. Currently alkynes have found broad appli- unsaturated compounds (alkynes, alkenes, allenes), including
cations for the preparation of valuable compounds and fluorinated ones,35–37 we undertook a special study on trans-
materials for chemistry, biology, medicine and materials formation of trifluoromethyl substituted propargyl alcohols.
science.1–12 Among the variety of acetylene derivatives, propar- The main goal of this work was to investigate the reaction of
gyl alcohols have been widely used in the Friedel–Crafts alkyl- 4-aryl-1,1,1-trifluorobut-3-yn-2-oles (CF3-propargyl alcohols)
ation of arenes and heteroarenes. These reactions are pro- with arenes under the action of acidic HUSY zeolite CBV-720,
moted by Brønsted13–18 or Lewis19–29 acids and allow the syn- which are considered as catalysts for various processes of
thesis of new valuable compounds.
“green” chemistry.38
On the other hand, the incorporation of fluorine atoms into
organic molecules leads to the creation of compounds with
unique properties. As a result, many important characteristics
of fluorinated molecules are changed, such as lipophilicity
and biological activity, heat resistance, nonlinear optical and
liquid crystal properties, etc.30–34 Nowadays, around 25% of
drug molecules contain at least one fluorine in the structure.
Therefore, efficient synthesis of new organofluorine derivatives
is an actual goal of organic chemistry. To the best of our
knowledge, reactions of trifluoromethyl substituted propargyl
Results and discussion
Starting 4-aryl-1,1,1-trifluorobut-3-yn-2-oles 1a–e were syn-
thesized from the corresponding acetylenic ketones by chemo-
selective reduction of a carbonyl group with NaBH4 (see
Scheme 1 and the Experimental part). It should be noted that
no reduction of the triple bond was observed most probably
due to the enhanced electrophilicity of starting ynones.
It can be expected that under the action of a Brønsted acid,
protonation of oxygen of the hydroxyl group of 1 (or coordi-
nation of hydroxyl with a Lewis acid) will result in the for-
mation of O-protonated species A (or similar coordinated
species with Lewis acids). Subsequent elimination of water
leads to formation of the corresponding trifluoromethylated
carbocations B ↔ B′ having positive charge delocalized due to
mesomerism of the propargyl-allenyl system (see scheme in
Table 1). These electrophilic species A and B may be formed
under the interaction of starting alcohols 1 with Brønsted or
Lewis acidic sites of zeolites.38
aDepartment of Chemistry, Saint Petersburg State Forest Technical University,
Institutsky per., 5, Saint Petersburg, 194021, Russia. E-mail: aleksvasil@mail.ru,
a.vasilyev@spbu.ru
bDepartment of Organic Chemistry, Institute of Chemistry, Saint Petersburg State
University, Universitetskaya nab., 7/9, Saint Petersburg, 199034, Russia
cDepartment of Chemistry, Lomonosov Moscow State University, Vorobievy Gory, 1,
Moscow, 119899, Russia. E-mail: nenajdenko@org.chem.msu.ru
†Electronic supplementary information (ESI) available: Copies of 1H, 13C, and
19F NMR spectra of compounds, and details of DFT calculations. See DOI:
10.1039/c8ob02887g
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Scheme 1 Synthesis of starting CF3-propargyl alcohols 1a–e.
DFT calculations were carried out in order to estimate the unlike CF3-cations, species Bf and Bg have positively charged
electronic properties and electrophilicity of cations A and B, carbon C2.
and thermodynamics of their formation (ΔG298 of protonation
Having obtained these theoretical predictions, the reaction
reactions). Electronic characteristics (energies of HOMO/ of alcohols 1 with benzene and some other arenes in the pres-
LUMO, electrophilicity indices ω,39,40 charge distribution, and ence of Brønsted acids H2SO4 and CF3SO3H was studied.
contribution of the atomic orbital into the LUMO) of species However, only the formation of a mixture of oligomeric com-
Aa–d and Ba–d are given in Table 1.
pounds was observed. Nevertheless, the reaction of com-
From the thermodynamic point of view, protonation of the pounds 1a–d with arenes under the action of acidic HUSY
hydroxyl oxygen atom in alcohols 1 is unfavorable, and values zeolite CBV-720 at 100 °C for 1 h in a high pressure glass auto-
of ΔG298 of the formation of cations
A are positive, clave afforded CF3-indenes 2 in good yields (Table 2). This
2.39–6.21 kcal mol−1 (Table 1). However, the next step of water reaction proceeded with various arenes, benzene, o-, m-,
elimination from species A is thermodynamically possible with p-xylenes, and 1,2-dichlorobenzene. Alcohols 1a,c,e in reaction
a negative value of ΔG298 in the range of −15.05 to −5.73 kcal with benzene gave rise to only one type of indene 2a,g,i corre-
mol−1. These data give negative values of ΔG298 for two step spondingly (entries 1, 7 and 9). On the other hand, alcohols
transformation 1 → A → B (Table 1) proving information about 1b and 1d bearing donating methyl and methoxy groups
favorable formation of propargyl cations B. These carbocations afforded mixtures of isomeric indenes 2f1–2 and 2h1–2
have rather high values of electrophilicity indices ω 5.9–6.8 eV, (entries 6 and 8). The same situation was observed for the reac-
which reveal that they should be very reactive electrophiles.41,42 tion of 1a with more electron rich xylenes (entries 2–4) and
In cations B, the carbon atom C4 bears a large positive charge 1,2-dichlorobenzene (entry 5). In the case of o-xylene, four
0.21–0.29e compared to negative charge −0.14 to −007e on the isomers 2d1–d4 were obtained depending on the position of
atom C2 (Table 1). Apart from that, atom C4 gives a rather big primary attack of the electrophile into the o-xylene molecule
contribution into the LUMO, 15.5–26.6%. These data clearly (entry 4). These and other isomeric indenes 2 (Table 2) were
show that, most probably, the carbon C4 is the most reactive obtained as inseparable mixtures after column chromato-
electrophilic center for cations B. According to the calcu- graphy purification, due to their close chromatographic reten-
lations, both charge and orbital control are predicted for this tion parameters on silica gel. The mixtures of isomers were
center. Such properties of species B reveal that allenyl reso- analyzed by means of NMR to identify each isomer by their
nance form B′ has a substantial contribution into the elec- specific signals of groups, C1H, vC2H, CF3, Ar, and the
1
tronic structure of these particular propargyl type cations.
indane core, in H, 13C and 19F spectra, along with the data of
We additionally calculated the characteristics of methyl- GC-MS and HRMS (see the Experimental part and original
(Af, Bf) and phenyl- (Ag, Bg) substituted cations generated spectra in the ESI†). In fact, the formation of mixtures of iso-
from the corresponding propargyl alcohols (1f and 1g) (see meric indenes 2 sheds light on the reaction mechanism (vide
Table 1) in order to compare these species with CF3-propargyl supra).
cation Ba. The thermodynamic data reveal that CH3-propargyl
The difference between Brønsted acids and zeolites in this
cation Bf is easily formed. In contrast to the formation of CF3- reaction can be explained by the high reactivity of CF3-propar-
cation Ba, both alcohol protonation and oxonium ion dehydra- gyl cations B. These species in solution in Brønsted acids may
tion en route to the CH3-substituted carbocation Bf have nega- react with starting alcohols with the formation of oligomeric
tive ΔG298 values (Table 1). The introduction of an additional materials. On the other hand, being more or less isolated in
phenyl group directly at the CF3-substituted propargylic posi- the zeolite cage, cations B react smoothly with arene molecules
tion has a more complex effect. In particular, protonation of leading to the target indenes.
the hydroxyl group in phenyl substituted propargyl alcohol 1g
Despite the reaction in Brønsted acids was unsuccessful
is even more unfavorable, ΔG298 = 5.5 kcal mol−1 (Table 1) (vide infra), the use of Lewis acids, aluminum chloride and
than it is in the case of alcohol 1a. This unexpected finding bromide, led to indenes 2 in moderate yields (Scheme 2). It
suggests that the propargylic Ph group cannot participate in should be noted that the AlCl3-promoted reaction of 1a with
the stabilization of the propargylic oxonium center via hyper- p-xylene at low temperature 0 °C proceeded regioselectively to
conjugation (most likely due to the steric reasons). On the furnish only one type of indene 2b1 (Scheme 3). This result is
other hand, after the dehydration step relieves some of the in contrast to the same reaction under zeolite activation giving
steric congestion, the Ph group is able to stabilize the carbo- a mixture of indenes 2b1 and 2b2 (entry 2, Table 2).
cation (ΔG298 = −6.9 kcal mol−1), albeit not as efficiently as the
aryl group at the alkyne terminus. It should also be noted that moted reactions of alcohols 1 with arenes (Table 2) and elec-
Taking into account all the data obtained on zeolite-pro-
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Table 1 Selected DFT characteristics of 1a–g and carbocations Aa–g and Ba–g
Species
EHOMO, eV
−7.20
ELUMO, eV
−1.34
ωa, eV
q(C2)b, e
−0.01
q(C4)b, e
−0.05
k(C2)LUMOc, %
k(C4)LUMOc, %
ΔG, kcal mol−1
1.6
7.3
3.4
—
−7.70
−2.41
2.4
0.03
0.17
7.8
4.3
4.06
−8.76
−6.96
−5.17
−1.25
6.8
1.5
−0.07
0.29
30.6
7.3
26.6
−5.73
0.01
0.21
3.4
—
−7.41
−2.36
2.4
0.03
0.18
23.6
2.1
2.39
−8.68
−7.12
−4.99
−1.51
6.3
1.7
−0.10
−0.09
0.26
22.0
27.2
15.5
−8.12
0.27
24.0
—
−7.53
−2.48
2.5
0.03
0.17
13.0
4.0
6.21
−8.65
−6.64
−7.00
−5.15
−1.17
−2.30
6.8
1.4
2.3
−0.09
0.01
0.27
0.05
0.18
27.2
10.6
21.9
24.0
2.4
−6.69
—
0.03
2.3
5.02
−8.25
−6.96
−4.70
−1.13
5.9
1.4
−0.14
0.21
25.7
45.3
21.0
−15.05
0.06
−0.01
1.9
—
−7.51
−2.03
2.1
0.10
0.11
24.9
6.5
−4.77
−8.41
−7.21
−4.49
−1.38
5.3
1.6
0.13
0.27
0.04
35.7
5.6
28.1
0.2
−11.46
−0.69
—
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Table 1 (Contd.)
Species
EHOMO, eV
−7.66
ELUMO, eV
−2.60
ωa, eV
q(C2)b, e
q(C4)b, e
k(C2)LUMOc, %
k(C4)LUMOc, %
ΔG, kcal mol−1
2.6
0.19
0.09
7.9
8.2
5.49
−7.96
−5.08
7.4
0.08
0.26
13.5
11.7
−6.93
a Global electrophilicity index ω = (EHOMO + ELUMO)2/8(ELUMO − EHOMO). b Natural charges. c Contribution of atomic orbital into the molecular
orbital.
Table 2 The reaction of 1 with arenes under the action of HUSY zeolite CBV-720 at 100 °C for 1 h
Starting compounds
Entry
1
Propargyl alcohol, 1
Arene, Ar′H
Reaction products, 2, yield (%)
Benzene
2
para-Xylene
3
meta-Xylene
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Table 2 (Contd.)
Starting compounds
Propargyl alcohol, 1
Entry
4
Arene, Ar′H
ortho-Xylene
Reaction products, 2, yield (%)
5
1,2-Dichloro-benzene
6
Benzene
7
8
Benzene
Benzene
9
Benzene
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the allenyl mesomeric form is responsible for the reactivity of
these species.
Experimental part
The NMR spectra of solutions of compounds in CDCl3 were
recorded on a Bruker AVANCE 500 spectrometer (at 500, 470
1
and 125 MHz for H, 19F and 13C NMR spectra respectively) at
1
25 °C. The solvent residual signals CDCl3 (δ 7.26 ppm) for H
NMR spectra and the carbon signal of CDCl3 (δ 77.0 ppm) for
13C NMR spectra were used as references. 19F NMR spectra
were indirectly referred to the signal of CFCl3 (δ 0.0 ppm).
HRMS was carried out by matrix-assisted laser desorption
ionization (MALDI-MS) using Fourier Transform (ion cyclotron
resonance) mass spectrometer (Varian 902-MS) equipped with
MALDI and 9.4 T magnet (FTMS). Chromato-mass spec-
trometry analysis was done with an Agilent Technologies
machine G 2570A GC/MSD. The preparative reactions were
monitored by thin-layer chromatography carried out on silica
gel plates (Silufol UV-254), using UV light for detection.
Preparative column chromatography was performed on silica
gel, Merck company. HUSY zeolite CBV-720 was purchased
from the company Zeolyst Int., and it was activated at 550 °C
in air for 4 h before reactions.
Scheme 2 Reactions of 1a,c with arenes under activation of AlX3 (X =
Cl, Br).
DFT calculations
All computations were carried out at the DFT/HF hybrid level
of theory using hybrid exchange functional M06 by using
GAUSSIAN 2009 program packages.55 The geometry optimi-
zations were performed using the 6-311+G(2d,2p) basis set
(standard 6-311 basis set added with polarization (d, p) and
diffuse functions). Optimizations were performed on all
degrees of freedom and solvent-phase optimized structures
were verified as true minima with no imaginary frequencies.
The Hessian matrix was calculated analytically for the opti-
mized structures in order to prove the location of correct
minima and to estimate the thermodynamic parameters.
Solvent-phase calculations used the Polarizable Continuum
Model (PCM).
Scheme 3 Plausible reaction mechanism.
tronic properties of intermediate propargyl-allenyl cations B ↔
B′ (Table 1), one may propose a plausible reaction mechanism
(Scheme 3). Since the most electrophilic carbon in the species
B is atom C4 (mesomeric form B′), interaction with arenes pro-
ceeds onto this particular carbon leading to allenes
C
(Scheme 3). Consequent protonation of C gives allyl cation D.
The latter may be cyclized in two different aryl rings Ar and
Ar′, depending on their nucleophilicity and configuration of D
that affords finally mixtures of isomeric indenes 2.
It should be specially emphasized that CF3-indenes are
rather rare and hardly available compounds, and there are just
a few reports on their synthesis.43–50 On the other hand,
indenes have found broad applications in the synthesis of
General procedure for the synthesis of 4-aryl-1,1,1-trifluorobut-
3-yn-2-ols (1a–e) from the corresponding 4-aryl-1,1,1-trifluorobut-
3-yn-2-ones56
sandwich type compounds which are valuable catalysts of NaBH4 (57 mg, 1.51 mmol) was added to a solution of buty-
many industrial processes.51–54
none (0.5 mmol) in methanol (3 mL) at 0 °C with stirring.
Reaction temperature was raised to room temperature and the
mixture was stirred for 2 h. Then the mixture was poured into
water (50 mL) and extracted with CHCl3 (3 × 10 mL). The com-
bined extracts were washed with water (50 mL), saturated
Conclusions
The reaction of trifluoromethyl propargyl alcohols with arenes aqueous solution of Na2CO3 (25 mL), water (50 mL) and dried
under activation of the acidic HUSY zeolite was investigated. with Na2SO4. The solvent was evaporated under vacuum to give
As a result, very rare types of compounds – trifluoromethyl a pure reaction product.
indenes were obtained in good yields. The formation of
1,1,1-Trifluoro-4-phenylbut-3-yn-2-ol (1a). Yield of 70%.
indenes may be explained in terms of the intermediate for- Yellow oil. 1H NMR (CDCl3, 500 MHz) δ, ppm: 2.90 broad s
mation of trifluoromethyl propargyl-allenyl cations, for which (1H, OH), 4.93 q (1H, J = 5.8 Hz), 7.33–7.41 m (3Harom.),
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7.48–7.50 m (2Harom.). 13C NMR (CDCl3, 125 MHz) δ, ppm: General procedure for synthesis of 4-aryl-1-trifluoromethyl-1H-
62.9 q (C2, J = 36.2 Hz), 80.8, 87.7, 121.1, 123.0 q (CF3, J = indenes (2b1,g) from 4-aryl-1,1,1-trifluorobut-3-yn-2-ols (1a,c)
280 Hz), 128.5, 129.5, 132.1. 19F NMR (CDCl3, 470 MHz) δ, and arenes under the action of AlX3 (X = Cl, Br)
ppm: −80.1 d (CF3, J = 5.8 Hz). GCMS (Irel., %): 200 (100) [M+],
279 (10), 396 (13), 236 (35), 202 (55). HRMS: calculated for AlX3 (0.3 mmol) was added to a solution of alcohol (0.15 mol)
C10H8F3O [M + H]+ 201.0522, found 201.0525.
and p-xylene (0.15 mol) in CH2Cl2 (1 mL) (for reaction with
1,1,1-Trifluoro-4-(4-methylphenyl)but-3-yn-2ol (1b). Yield of benzene, 1 mL of it was used as a solvent) with intensive stir-
91%. Yellow oil. 1H NMR (CDCl3, 500 MHz) δ, ppm: 2.36 s ring at 0 °C or room temperature (see Scheme 2). The mixture
(CH3), 2.51 s (OH), 4.90 q (CH, J = 5.6 Hz), 7.15 d (2Harom., J = was stirred for 1 h, then poured into water (50 mL), and
8 Hz), 7.37 d (2Harom., J = 8 Hz). 13C NMR (CDCl3, 125 MHz) δ, extracted with chloroform (3 × 50 mL). The combined extracts
ppm: 21.6 (CH3), 63.2 q (C2, J = 36 Hz), 79.9, 88.4, 117.9, 122.9 were washed with water (30 mL), dried with Na2SO4, the
(CF3, J = 274 Hz), 129.3, 132.0, 140.0. 19F NMR (CDCl3, solvent was evaporated under vacuum, and the residue was
470 MHz) δ, ppm: −79.8 d (CF3, J = 5.6 Hz). HRMS: calculated subjected to column chromatography on silica gel with elution
for C11H10F3O [M + H]+ 215.0678, found 215.0675.
by hexane–ethyl acetate mixtures to purify reaction product 2.
4-(4-Chlorophenyl)-1,1,1-trifluorobut-3-yn-2ol (1c). Yield of
3-Phenyl-1-(trifluoromethyl)-1H-indene (2a). Yield of 77%.
1
1
85%. Yellow solid, m.p. 65–67 °C. H NMR (CDCl3, 500 MHz) Yellow oil. H NMR (CDCl3, 500 MHz) δ, ppm: 4.24 q (1H, J =
δ, ppm: 2.72 s (1H, OH), 4.91 q (CH, J = 5.5 Hz), 7.32 d 9.3 Hz), 6.4 d (1H, J = 2 Hz), 7.33 t (1Harom., J = 7.5 Hz),
(2Harom., J = 8.6 Hz), 7.41 d (2Harom., J = 8.6 Hz). 13C NMR 7.40–7.43 m (2Harom.), 7.45–7.48 m (2Harom.), 7.56–7.60 m
(CDCl3, 125 MHz) δ, ppm: 63.1 q (C2, J = 36.2 Hz), 81.5, 87.0, (3Harom.), 7.6 d (1Harom., J = 7.4 Hz). 13C NMR (CDCl3,
119.4, 122.8 q (CF3, J = 284.2 Hz), 129.0, 133.4, 135.9. 19F NMR 125 MHz) δ, ppm: 52.7 q (C1, J = 29 Hz), 121.3, 124.8 q (J =
(CDCl3, 470 MHz) δ, ppm: −80.0 d (CF3, J = 5.5 Hz). HRMS: cal- 3 Hz), 124.9, 126.2 q (CF3, J = 276.8 Hz), 126.6, 127.8, 128.5,
culated for C10H6ClF3O [M + H]+ 235.0132, found 235.0128.
128.6, 128.8, 134.6, 138.7, 144.2, 149.4. 19F NMR (CDCl3,
1,1,1-Trifluoro-4-(4-methoxyphenyl)but-3-yn-2ol (1d). Yield 470 MHz) δ, ppm: −68.0 d (CF3, J = 9.3 Hz). GCMS (Irel., %):
1
of 79%. Yellow oil. H NMR (CDCl3, 500 MHz) δ, ppm: 2.60 d 260 (100) [M+], 238 (7), 220 (4), 207 (3), 191 (97), 165 (15).
(1H, OH, J = 8.2 Hz), 3.82 s (3H, OMe), 4.89 dq (1H, J = 8, 5.4 HRMS: calculated for C16H12F3 [M + H]+ 261.0886, found
Hz), 6.86 d (2Harom., J = 8.8 Hz), 7.41 d (2Harom, J = 8.8 Hz). 13
C
261.0888.
4,7-Dimethyl-3-phenyl-1-(trifluoromethyl)-1H-indene (2b1)
NMR (CDCl3, 125 MHz) δ, ppm: 55.5 (OMe), 63.2 q (C2, J = 36.2
Hz), 79.4, 88.3, 113.0, 114.2, 123.0 q (CF3, J = 280.1 Hz), 133.8, was obtained from alcohol 1a and p-xylene under the action of
1
160.6. 19F NMR (CDCl3, 470 MHz) δ, ppm: −80.2 d (CF3, J = 5.4 AlCl3 in an yield of 48% (see Scheme 2). Yellow oil. H NMR
Hz). HRMS: calculated for C11H10ClF3O2 [M + H]+ 231.0627, (CDCl3, 500 MHz) δ, ppm: 1.93 s (3H, Me), 2.46 s (3H, Me),
found 231.0628.
4.24 qd (1H, C1H, J = 8.0 Hz, J 2.1 Hz), 6.23 d (1H, J = 2.1 Hz),
4-(4-Bromophenyl)-1,1,1-trifluorobut-3-yn-2ol (1e). Yield of 7.03 s (2Harom.), 7.33–7.44 m (5Harom.). 13C NMR (CDCl3,
1
79%. Yellow solid, m.p. 73–75 °C. H NMR (CDCl3, 500 MHz) 125 MHz) δ, ppm: 19.8 q (Me, J = 4.0 Hz), 20.0 (CH3), 52.0 q
δ, ppm: 2.56 d (1H, OH, J = 8 Hz), 4.90 m (1H), 7.34 d (2Harom.
,
(C1, J = 29.0 Hz), 126.7 q (CF3, J = 280.0 Hz), 127.5 q (J =
J = 8.4 Hz), 7.48 d (2Harom, J = 8.4 Hz). 13C NMR (CDCl3, 2.9 Hz), 127.8, 128.2, 128.7, 128.9, 130.0, 132.0, 132.9, 137.0 q
125 MHz) δ, ppm: 63.1 q (C2, J = 36 Hz), 81.6 q (J = 2 Hz), 87.0, (J = 1.8 Hz), 137.9, 143.0, 151.3. 19F NMR (CDCl3, 470 MHz) δ,
119.9, 122.8 q (CF3, J = 279 Hz), 124.2, 131.9, 133.5. 19F NMR ppm: −63.75 dd (CF3, JH–F 8.0, 1.3 Hz). GCMS (Irel., %): 288
(CDCl3, 470 MHz) δ, ppm: −83.2 d (CF3, J = 5.6 Hz). GCMS (100) [M+], 273 (98), 233 (10), 215 (8), 203 (40), 189 (10). HRMS:
(Irel., %): 278 (48) [M+], 261 (4), 209 (100), 182 (7), 170 (3), 152 calculated for C18H16F3 [M + H]+ 289.1199, found 289.1195.
(10), 129 (10), 102 (75). HRMS: calculated for C10H7BrF3O
[M + H]+ 278.9627, found 278.0630.
4,7-Dimethyl-3-phenyl-1-(trifluoromethyl)-1H-indene (2b1)
and 3-(2,5-dimethylphenyl)-1-(trifluoromethyl)-1H-indene (2b2)
were obtained as a mixture of isomers in reaction with zeolite
in a general yield of 82% in a ratio of 1 : 0.6 (see Table 2).
Compound 2b2. H NMR (CDCl3, 500 MHz) δ, ppm (from the
spectrum of a mixture of isomers): 2.19 s (3H, Me), 2.35 s (3H,
General procedure for synthesis of 4-aryl-1-trifluoromethyl-1H-
indenes (2a–i) from 4-aryl-1,1,1-trifluorobut-3-yn-2-ols (1a–e)
and arenes under the action of HUSY zeolite CBV-720
1
The activated zeolite (at 550 °C in air for 4 h) (0.45 g), 4-aryl- Me), 4.19–4.24 m (1H), 6.26 d (1H, J = 2 Hz), 7.2 d (1Harom., J =
1,1,1-trifluorobut-3-yn-2-ol 1 (0.2 mmol) and arene (5 mL for 7.8 Hz), 7.32–7.39 m (4Harom.), 7.6 d (1Harom., J = 8 Hz),
benzene; 3 mL for xylenes and 1,2-dichlorobenzene) were 7.7–7.72 m (1Harom.). 19F NMR (CDCl3, 470 MHz) δ, ppm (from
loaded in a 15 mL high pressure glass tube. The resulting sus- the spectrum of a mixture of isomers): −68.2 d (CF3, J =
pension was magnetically stirred at 100 °C for 1 h. After 9.1 Hz). GCMS (Irel., %) (from the spectrum of a mixture of
cooling, the reaction mixture was filtered off to remove zeolite. isomers): 288 (100) [M+], 273 (30), 233 (5), 219 (53), 203 (22),
Zeolite was refluxed with MeOH (3 × 10 mL) and filtered off. 189 (10). HRMS (MALDI) (for a mixture of isomers): calculated
The combined organic phases were concentrated under for C18H16F3 [M + H]+ 289.1199, found 289.1201.
vacuum to provide a residue, which was subjected to column 4,6-Dimethyl-3-phenyl-1-(trifluoromethyl)-1H-indene (2c1)
chromatography on silica gel with elution by hexane–ethyl and 3-(2,4-dimethylphenyl)-1-(trifluoromethyl)-1H-indene (2c2)
acetate mixtures to purify reaction product 2.
were obtained as a mixture of isomers with a general yield of
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46% in a ratio of 1 : 0.2. Compound 2c1. 1H NMR (CDCl3, were obtained as a mixture of isomers with a general yield of
500 MHz) δ, ppm (selected signals from the spectrum of a 48% in a ratio of 1 : 0.3. Compound 2e1. 1H NMR (CDCl3,
mixture of isomers): 2.22 s (3H, Me), 2.38 s (3H, Me), 500 MHz) δ, ppm (from the spectrum of a mixture of isomers):
4.24–4.30 m (1H), 6.25 d (1H, J = 1 Hz), 7.07–7.17 m (4Harom.), 4.25 m (1H), 6.44 d (1H, J = 2 Hz), 7.32–7.39 m (1Harom.),
7.28–7.38 m (2Harom.), 7.65 d (1Harom., J = 7 Hz). 13C NMR 7.42–7.46 m (2Harom.), 7.49 d (1Harom., J = 7.5 Hz), 7.53–7.56 m
(CDCl3, 125 MHz) δ, ppm (selected signals from the spectrum (1Harom.), 7.67 d (1Harom., J = 7.5 Hz), 7.69 d (1Harom., J = 2 Hz).
of a mixture of isomers): 52.98 q (J = 27.9 Hz), 126 q (CF3, J = 13C NMR (CDCl3, 125 MHz) δ, ppm (selected signals from the
272 Hz). 19F NMR (CDCl3, 470 MHz) δ, ppm (from the spec- spectrum of a mixture of isomers): 52.93 q (J = 29.5 Hz), 127.7
trum of a mixture of isomers): −67.4 d (CF3, J = 10 Hz). HRMS q (CF3, J = 271.6 Hz). 19F NMR (CDCl3, 470 MHz) δ, ppm (from
(MALDI) (for a mixture of isomers): calculated for C18H16F3 the spectrum of a mixture of isomers): −67.9 d (CF3, J = 9 Hz).
1
[M + H]+ 289.1199, found 289.1196. Compound 2c2. H NMR GCMS (Irel., %) (from the spectrum of a mixture of isomers):
(CDCl3, 500 MHz) δ, ppm (from the spectrum of a mixture of 328 (100) [M+], 308 (4), 293 (18), 273 (11), 259 (56), 238 (20),
isomers): 2.38 s (6H, 2Me), 4.27 m (1H), 6.14 d (1H, J = 1 Hz), 223 (21), 207 (9), 189 (64). HRMS (MALDI) (for a mixture of
7.07–7.17 m (4Harom.), 7.28–7.38 m (2Harom.), 7.65 d (1Harom.
,
isomers): calculated for C16H10Cl2F3 [M + H]+ 329.0106, found
1
J = 7 Hz). 19F NMR (CDCl3, 470 MHz) δ, ppm (from the spec- 329.0110. Compound 2e2. H NMR (CDCl3, 500 MHz) δ, ppm
trum of a mixture of isomers): −67.4 d (CF3, J = 10 Hz).
5,6-Dimethyl-3-phenyl-1-(trifluoromethyl)-1H-indene (2d1), d (1H, J = 2 Hz), 7.32–7.39 m (1Harom.), 7.42–7.46 m (2Harom.),
3-(3,4-dimethylphenyl)-1-(trifluoromethyl)-1H-indene (2d2), 7.49 d (1Harom., J = 7.5 Hz), 7.53–7.56 m (1Harom.), 7.67 d
4,5-dimethyl-3-phenyl-1-(trifluoromethyl)-1H-indene (2d3) and (1Harom., J = 7.5 Hz), 7.69 d (1Harom., J = 2 Hz). 13C NMR
3-(2,3-dimethylphenyl)-1-(trifluoromethyl)-1H-indene (2d4) (CDCl3, 125 MHz) δ, ppm (selected signals from the spectrum
(from the spectrum of a mixture of isomers): 4.32 m (1H), 6.46
were obtained as a mixture of isomers with a general yield of of a mixture of isomers): 52.87 q (J = 29.5 Hz), 127.7 q (CF3, J =
24% in a ratio of 1 : 0.4 : 0.3 : 0.15. Compound 2d1. 1H NMR 271.6 Hz). 19F NMR (CDCl3, 470 MHz) δ, ppm (from the spec-
(CDCl3, 500 MHz) δ, ppm (selected signals from the spectrum trum of a mixture of isomers): −67.9 d (CF3, J = 9 Hz). GCMS
of a mixture of isomers): 2.36 s (3H, Me), 2.39 s (3H, Me), 4.32 (Irel., %) (from the spectrum of a mixture of isomers): 328 (100)
qd (1H, J = 7.8, 2 Hz), 6.35 d (1H, J = 2 Hz). 13C NMR (CDCl3, [M+], 308 (5), 293 (30), 272 (3), 259 (88), 238 (15), 223 (19), 207
125 MHz) δ, ppm (selected signals from the spectrum of a (8), 189 (72).
mixture of isomers): 52.4 q (J = 27 Hz), 126 q (CF3, J = 292 Hz).
3-Methylphenyl-1-(trifluoromethyl)-1H-indene (2f1) and
19F NMR (CDCl3, 470 MHz) δ, ppm (from the spectrum of a 6-methyl-3-phenyl-1-(trifluoromethyl)-1H-indene (2f2) were
mixture of isomers): −64.8 d (CF3, J = 7.8 Hz). GCMS (Irel., %) obtained as a mixture of isomers with a general yield of 78%
(from the spectrum of a mixture of isomers): 288 [M+] (100), in a ratio of 1 : 1. Compound 2f1. 1H NMR (CDCl3, 500 MHz) δ,
273 [M − Me]+ (37), 233 (4), 219 [M − CF3]+ (65), 202 (22), 189 ppm (selected signals from the spectrum of a mixture of
(8). HRMS (MALDI) (for a mixture of isomers): calculated for isomers): 2.44 s (3H, Me), 4.22 m (1H), 6.38 d (1Harom., J =
C18H16F3 [M + H]+ 289.1199, found 289.1197. Compound 2d2. 2.2 Hz). 13C NMR (CDCl3, 125 MHz) δ, ppm (from the spec-
1H NMR (CDCl3, 500 MHz) δ, ppm (selected signals from the trum of a mixture of isomers): 52.6 q (J = 29 Hz), 126 q (CF3,
spectrum of a mixture of isomers): 2.35 s (3H, Me), 2.36 s (3H, J = 290 Hz). 19F NMR (CDCl3, 470 MHz) δ, ppm (from the spec-
Me), 4.19–4.32 m (1H), 6.39 d (1H, J = 2 Hz). 19F NMR (CDCl3, trum of a mixture of isomers): −68.1 d (CF3, J = 10 Hz). GCMS
470 MHz) δ, ppm (from the spectrum of a mixture of isomers): (Irel., %) (from the spectrum of a mixture of isomers): 274 (99)
−68.1 d (CF3, J = 9.3 Hz). GCMS (Irel., %) (from the spectrum of [M+], 259 (19), 238 (8), 221 (98), 205 (96), 191 (27), 178 (35).
a mixture of isomers): 288 [M+] (100), 273 [M − Me]+ (28), 219 HRMS (MALDI) (for a mixture of isomers): calculated for
[M − CF3]+ (70), 202 (20), 189 (9). Compound 2d3. 1H NMR C17H14F3 [M + H]+ 275.1042, found 275.1040. Compound 2f2.
(CDCl3, 500 MHz) δ, ppm (selected signals from the spectrum 1H NMR (CDCl3, 500 MHz) δ, ppm (selected signals from the
of a mixture of isomers): 2.32 s (3H, Me), 2.34 s (3H, Me), spectrum of a mixture of isomers): 2.42 s (3H, Me), 4.22 m
4.19–4.32 m (1H), 6.34 d (1H, J = 2 Hz). 19F NMR (CDCl3, (1H), 6.35 d (1Harom., J = 2.2 Hz). 13C NMR (CDCl3, 125 MHz) δ,
470 MHz) δ, ppm (from the spectrum of a mixture of isomers): ppm (obtained from the spectrum of a mixture of isomers):
−68.1 d (CF3, J = 9.4 Hz). GCMS (Irel., %) (obtained from 52.7 q (J = 29.3 Hz), 126 q (CF3, J = 290 Hz). 19F NMR (CDCl3,
the spectrum of a mixture of isomers): 288 [M+] (100), 273 470 MHz) δ, ppm (from the spectrum of a mixture of isomers):
[M − Me]+ (38), 233 (4), 219 [M − CF3]+ (49), 202 (20), 189 (7). −68.1 d (CF3, J = 10 Hz). GCMS (Irel., %) (from the spectrum of
Compound 2d4. 1H NMR (CDCl3, 500 MHz) δ, ppm (selected a mixture of isomers): 274 (84) [M+], 259 (9), 238 (5), 221 (6),
signals from the spectrum of a mixture of isomers): 2.26 s (3H, 205 (99), 189 (23), 178 (11).
Me), 2.27 s (3H, Me), 3.95 m (1H), 6.41 m (1H). 19F NMR
3-(4-Chlorophenyl)-1-(trifluoromethyl)-1H-indene (2g). Yield
(CDCl3, 470 MHz) δ, ppm (from the spectrum of a mixture of of 76%. Yellow solid, m.p. 49–51 °C. 1H NMR (CDCl3,
isomers): −69.6 d (CF3, J = 8.8 Hz). GCMS (Irel., %) (from the 500 MHz) δ, ppm: 4.24 m (1H), 6.4 d (1H, J = 2 Hz), 7.4 t (1H,
spectrum of a mixture of isomers): 288 [M+] (1), 224 (50), 209 J = 7.5 Hz), 7.41–7.50 m (3Harom.), 7.50–7.54 m (3Harom.), 7.7 d
(100), 194 (20), 179 (21), 165 (6).
(1Harom., J = 7 Hz). 13C NMR (CDCl3, 125 MHz) δ, ppm: 52.8 q
3-(3,4-Dichlorophenyl)-1-(trifluoromethyl)-1H-indene (2e1) (C1, J = 29 Hz), 121.1, 125.1, 125.3 q (J = 2.6 Hz), 126.7, 127.2,
and 5,6-dichloro-3-phenyl-1-(trifluoromethyl)-1H-indene (2e2) 127.8, 128.67, 129.2, 133.1, 134.6, 138.7 q (J = 1.9 Hz), 143.9,
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148.4. 19F NMR (CDCl3, 470 MHz) δ, ppm: −68.0 d (CF3, J = 9.1
Hz). GCMS (Irel., %): 294 (100) [M+], 274 (5), 259 (32), 238 (13),
225 (84), 207 (5), 189 (51). HRMS: calculated for C16H11ClF3
[M + H]+ 295.0496, found 295.0496.
4 E. A. Zakharova, O. I. Shmatova and V. G. Nenajdenko,
Russ. Chem. Rev., 2018, 87, 619–635.
5 I. V. Alabugin and B. Gold, J. Org. Chem., 2013, 78, 7777–
7784.
3-(4-Methoxyphenyl)-1-(trifluoromethyl)-1H-indene
(2h1)
6 V. V. Voronin, M. S. Ledovskaya, A. S. Bogachenkov,
K. S. Rodygin and V. P. Ananikov, Molecules, 2018, 23, 2442.
7 G. L. Larson, Synthesis, 2018, 50, 2433–2462.
8 I. V. Alabugin and E. Gonzalez-Rodriguez, Acc. Chem. Res.,
2018, 51, 1206–1219.
and 6-methoxy-3-phenyl-1-(trifluoromethyl)-1H-indene (2h2)
were obtained as a mixture of isomers with a general yield of
71% in a ratio of 1 : 0.6. Compound 2h1. 1H NMR (CDCl3,
500 MHz) δ, ppm (selected signals from the spectrum of a
mixture of isomers): 3.87 s (3H, Me), 4.22 m (1H), 6.35 d (1H,
J = 2.2 Hz). 19F NMR (CDCl3, 470 MHz) δ, ppm (from the spec-
9 D. S. Ryabukhin and A. V. Vasilyev, Russ. Chem. Rev., 2016,
85, 637–665.
trum of a mixture of isomers): −68.1 d (CF3, J = 9.8 Hz). GCMS 10 A. M. Asiri and A. S. K. Hashmi, Chem. Soc. Rev., 2016, 45,
(Irel., %) (from the spectrum of a mixture of isomers): 290 (100) 4471–4503.
[M+], 275 (8), 221 (91), 206 (8), 178 (23), 152 (10). HRMS 11 B. A. Trofimov and E. Yu. Schmidt, Russ. Chem. Rev., 2014,
(MALDI) (for a mixture of isomers): calculated for C17H14F3O
83, 600–619.
1
[M + H]+ 291.0991, found 291.0994. Compound 2h2. H NMR 12 A. V. Vasilyev, Russ. Chem. Rev., 2013, 82, 187–204.
(CDCl3, 500 MHz) δ, ppm (selected signals from the spectrum 13 G. G. K. S. N. Kumar and K. K. Laali, Tetrahedron Lett.,
of a mixture of isomers): 3.86 s (3H, Me), 4.22 m (1H), 6.29 d
(1H, J = 2.2 Hz). 19F NMR (CDCl3, 470 MHz) δ, ppm (from the 14 R. Sanz, A. Martinez, J. M. Alvarez-Gutierrez and
spectrum of a mixture of isomers): −68.3 d (CF3, J = 9.8 Hz). F. Rodriguez, Eur. J. Org. Chem., 2006, 1383–1386.
2013, 54, 965–969.
GCMS (Irel., %) (from the spectrum of a mixture of isomers): 15 R. Sanz, D. Miguel, A. Martinez, M. Gohain, P. Garcia-
290 (100) [M+], 275 (18), 221 (53), 206 (6), 178 (33), 152 (5).
Garcia, M. A. Fernandez-Rodriguez, E. Alvarez and
3-(4-Bromophenyl)-1-(trifluoromethyl)-1H-indene (2i). Yield
of 83%. Yellow oil. H NMR (CDCl3, 500 MHz) δ, ppm: 4.24 dq 16 S. A. Savarimuthu, D. G. L. Prakash and S. A. Thomas,
F. Rodriguez, Eur. J. Org. Chem., 2010, 7027–7039.
1
(1H, J = 9.3, 1.7 Hz), 6.4 d (1H, J = 2 Hz), 7.35 td (1Harom., J =
7.4 Hz, J = 1 Hz), 7.43 t (1Harom., J = 7.4 Hz), 7.47 d (2Harom., J = 17 S. Gujarathi, H. P. Hendrickson and G. Zheng, Tetrahedron
8.4 Hz), 7.5 t (1Harom., J = 7.4 Hz), 7.61 d (2Harom., J = 8.4 Hz), Lett., 2013, 54, 3550–3553.
7.67 d (1Harom., J = 7.4 Hz). 13C NMR (CDCl3, 125 MHz) δ, 18 P. Srihari, J. S. S. Reddy, S. S. Mandal, K. Satyanarayana and
ppm: 52.8 q (C1, J = 29 Hz), 121.1, 125.0, 125.3 q (J = 3 Hz),
J. S. Yadan, Synthesis, 2008, 1853–1860.
Tetrahedron Lett., 2014, 55, 3213–3217.
126.1 q (CF3, J = 281 Hz), 126.7, 128.3, 128.7, 132.1, 133.6, 19 Z.-P. Zhan, J.-L. Yu, H.-J. Liu, Y.-Y. Cui, R.-F. Yang,
138.7, 143.8, 148.4, 160.9. 19F NMR (CDCl3, 470 MHz) δ, ppm:
68.0 q (CF3, J = 9.3 Hz). HRMS: calculated for C16H11BrF3
[M + H]+ 338.9991, found 338.9994.
W.-Z. Yang and J.-P. Li, J. Org. Chem., 2006, 71, 8298–
8301.
20 J. Liu, E. Muth, U. Florke, G. Henkel, K. Merz, J. Sauvageau,
E. Schwake and G. Dyker, Adv. Synth. Catal., 2006, 348,
456–462.
Conflicts of interest
21 M. Georgy, V. Boucard and J.-M. Campagne, J. Am. Chem.
Soc., 2005, 127, 14180–14181.
22 J. S. Yadan, B. V. S. Reddy, K. V. R. Rao and
G. G. K. S. N. Kumar, Synthesis, 2007, 3205–3210.
23 Y. Masuyama, M. Hayashi and N. Suzuki, Eur. J. Org.
Chem., 2013, 2914–2921.
There are no conflicts to declare.
Acknowledgements
24 Z.-P. Zhan, W.-F. Yang, J.-L. Yu, J.-P. Li and H.-J. Liu, Chem.
Commun., 2006, 3352–3354.
25 M. Gohain, C. Marais and B. C. B. Bezuidenhoudt,
Tetrahedron Lett., 2012, 53, 1048–1050.
26 M. Gohain, C. Marais and B. C. B. Bezuidenhoudt,
Tetrahedron Lett., 2012, 53, 4704–4707.
This work was supported by the Russian Scientific
Foundation: grant no. 18-13-00008 – study on electrophilic
reactions of CF3-propargyl alcohols, and 18-13-00136 – part of
discussion (VGN).
27 J. S. Yadav, B. V. S. Reddy, K. V. R. Rao and
G. G. K. S. N. Kumar, Tetrahedron Lett., 2007, 48, 5573–
5576.
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