Regiocontrolled hydroarylation of (trifluoromethyl)acetylenes in superacids: Synthesis of CF3-substituted 1,1-diarylethenes

Article abstract of DOI:10.1002/ejoc.201201375

The reactions between aryl(trifluoromethyl)-substituted alkynes and arenes in triflic and fluorosulfonic acids were investigated. These reactions proceeded 100 % regioselectively to give 1,1-diaryl-2-trifluoromethylethenes in high yields. Depending on the

Full text of DOI:10.1002/ejoc.201201375

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FULL PAPER
DOI: 10.1002/ejoc.201201375
Regiocontrolled Hydroarylation of (Trifluoromethyl)acetylenes in Superacids:
Synthesis of CF3-Substituted 1,1-Diarylethenes
Haider M. H. Alkhafaji,[a] Dmitry S. Ryabukhin,[a] Vasiliy M. Muzalevskiy,[b]
Aleksander V. Vasilyev,*[a,c] Georgy K. Fukin,[d] Alexey V. Shastin,[b,e] and
Valentine G. Nenajdenko*[b]
Keywords: Superacidic systems / Carbocations / Alkenes / Hydroarylation / Regioselectivity
The reactions between aryl(trifluoromethyl)-substituted
alkynes and arenes in triflic and fluorosulfonic acids were
investigated. These reactions proceeded 100% regioselec-
tively to give 1,1-diaryl-2-trifluoromethylethenes in high
yields. Depending on the workup conditions, 3,3,3-trifluoro-
calculations. The stable 2,2,2-trifluoroethylated carbocation
reaction intermediates were observed by 1H, 13C, and 19F
NMR spectroscopy. Under treatment with aluminium brom-
ide, the reaction of 3,3,3-trifluoro-1-phenylpropyne with
benzene formed 1,3,3-triphenylindene. The hydration of ar-
1,1-diarylpropan-1-ol was also detected in the product mix- yl(trifluoromethyl) alkynes in sulfuric or trifluoroacetic acids
ture. The reaction mechanism was studied by both spectro-
scopic and theoretical methods. The highly reactive nature of
the trifluoromethylated vinyl cations was confirmed by DFT
smoothly produced 2,2,2-trifluoroethyl ketones in high
yields.
sequently protonated by an intramolecular vinylation to
form the corresponding carbo- or heterocycles.[6]
Introduction
Acidic activation of organic compounds with strong
Bronsted and Lewis acids as well as superacids (e.g.,
CF3SO3H, FSO3H) is widely used for the generation and
investigation of active carbocationic species.[1] Despite a
large number of studies in this field[2] only a limited amount
of data is available on the behavior of simple alkyl- and
aryl-substituted acetylenes in superacids. It has been shown
that the superacidic protonation of alkynes leads to the for-
mation of very active vinyl cations, which are capable of
reacting with weak nucleophiles such as fluorosulfate and
trifluoromethanesulfonate anions,[3] aromatic compounds,[4]
and nitroalkanes.[5] Those acetylenes, which have aryl or
heteroaryl groups in the proper position, can be sub-
Vinyl cations are a highly reactive type of carbocation.[7]
In the early 1960s, Grob and co-workers were the first to
detect these intermediates by the solvolysis of vinyl hal-
ides.[8] The structure of the vinyl cations was later con-
firmed by NMR spectroscopic studies conducted at tem-
peratures below –100 °C and even by X-ray analysis.[9,10]
The most important pathways to generate vinyl cations are
by electrophilic addition to alkynes and allenes, solvolysis,
or photolytic solvolysis. As calculations have shown, the
stability of such intermediates depends on the substituents
attached to the double bond. Aryl-substituted derivatives
are one of the most stabilized type of vinyl cations. On the
other hand, electron-withdrawing groups significantly de-
stabilize vinyl cations, and, various quantum chemical cal-
culations have predicted a strong destabilization of vinyl
cations with trifluoromethyl or nitro groups at the carbo-
cationic center.[11] In agreement with this prediction, experi-
mental investigations have shown the dramatic destabilizing
effects of acceptor substituents, neighboring the cationic
center. As a result, rare examples of the superacidic acti-
vation of acetylenes with acceptor groups such as COOR,
CN, and COR can be found in the literature.[12] In addition,
a protonation occurring at a triple bond should proceed
regioselectively with the vinyl cation forming at the β posi-
tion to the destabilizing acceptor group. Calculations and
photochemical studies have also shown the significant de-
stabilizing effect of the trifluoromethyl group in β-CF3-sub-
stituted vinyl cations. However, taking into account the
[a] Saint-Petersburg State Forest Technical University,
Institutsky per., 5, 194021 Saint Petersburg, Russia
E-mail: aleksvasil@mail.ru
Homepage: http://ftacademy.ru/academy/faculties/htf/cafedra/
oh/
[b] Department of Chemistry, Lomonosov Moscow State
University,
119899 Moscow, Russia
Fax: +7-495-9328846
E-mail: nen@acylium.chem.msu.ru
[c] Department of Chemistry, Saint-Petersburg State University,
Petrodvorets, Universitetsky pr., 26, 198504 Saint-Petersburg,
Russia
[d] G. A. Razuvaev Institute of Organometallic Chemistry of
Russian Academy of Sciences,
GSP-445, Tropinina 49, 603950 Nizhny Novgorod, Russia
[e] Institute of Problems of Chemical Physics,
Chernogolovka, Moscow Region 142432, Russia
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201201375.
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A. V. Vasilyev, V. G. Nenajdenko et al.
FULL PAPER
data in the literature, one can expect extremely high reactiv- trimethylsilane (TMSCF3).[18] Other approaches to such
ity from these unusual species. CF3-substituted alkenes based on the application of fluorin-
The trifluoromethyl group is a significant functional ated building blocks, especially trifluoromethylated acetyl-
group because of its ability to change important parameters enes, are frequently used. The hydroalumination, hydro-
of the molecule such as the lipophilicity, metabolic activity, cupration, hydroboration, and carbopalladation reactions
and bioavailability.[13] Another advantage of the trifluoro- of trifluoromethylated alkynes are used as a key step in such
methyl group is its electron-withdrawing nature, which al- sequences.[19] Hence, the development of new methods for
lows control of the selectivity of chemical transformations the synthesis of fluoroalkylated alkenes becomes more and
that use trifluoromethylated compounds as starting materi- more important.
als.
Herein, we investigate the reactions of 1-aryl-2-trifluoro-
Under superacidic conditions, the hydroarylation of tri- methylacetylenes[20] with aromatic compounds in the pres-
fluoromethylated acetylenes could form CF3-substituted ence of strong acids and superacids. The main goal of this
styrene derivatives, which have been widely used for organic work is to determine the synthetic scope of the vinylation
light-emitting diodes (OLEDs) and other material chemis- process and evaluate the regio- and stereoselectivity of the
try applications.[14] However, a more important function is reaction. We propose that β-trifluoromethylated arylvinyl
the application of some stilbene derivatives as a potent anti- cations can be easily generated from CF3-substituted alk-
cancer drugs. For example, combretastatin is a natural stil- ynes by protonation in superacids. One expects total control
bene, which is isolated from the bark of the South African in the regioselectivity of the triple-bond protonation be-
bush willow Combretum caffrum. This alkene exhibits high cause of the polarization of the acetylene fragment by the
anticancer activity. Tamoxifen (Nolvadex) is the well- electron-withdrawing trifluoromethyl moiety as well as the
known triarylethylene-type antiestrogenic drug,[15] which is electron-donating aryl group, which is a very important fea-
used in the therapy of breast cancer and for the treatment ture of this methodology. This is the first example of tri-
of menstrual disorders.[16] Recently, Panamifene, a tri- fluoromethyl-substituted alkynes as reagents for the electro-
fluoromethylated analogue of Tamoxifen, demonstrated philic alkenylation of aromatic compounds to synthesize
higher anticancer activity (see Figure 1).
practical and important trifluoromethylated alkenes (i.e.,
diaryltrifluoromethylethenes). Because of its simplicity and
straightforwardness, this approach could be a useful alter-
native to existing methods.
Results and Discussion
To have insight into the nature of the trifluoromethylated
vinyl cations, we first performed a theoretical study and
compared the parameters of cations A1–A5, which were ob-
tained by protonation of trifluoromethylated acetylenes 1,
with arylvinyl cation A6, which did not contain any fluorine
atoms (see Figure 2 and Scheme 1). We performed a
number of DFT calculations to evaluate the reactivity of
the vinyl cations that were obtained by protonation of the
trifluoromethylated acetylenes. According to the results of
DFT calculations,[21] the distances C-1–C-2 and C-2–C-3 in
Figure 1. Physiologically active arylethenes.
Existing methods for the synthesis of Panamifene[17] and species A1–A6 vary in the range of 1.278–1.286 Å and
other (triaryl-) diaryl-substituted trifluoromethylated alk- 1.338–1.359 Å, respectively. These data differ significantly
enes are not numerous. The CF3 group can be incorporated from analogous details found in the literature from the X-
into the alkene fragment through a palladium-catalyzed tri- ray studies of the vinyl cation tert-butyl(1,1,3,3-tetramethyl-
fluoromethylation of vinyl sulfonates with trifluoromethyl- 1,3-disilacyclohexan-2-ylidene)methylium
7,8,9,10,11,12-
Figure 2. General view of the vinyl cations: (a) R3 = OCH3, R1,2,4,5 = H (for A1), R3 = CH3, R1,2,4,5 = H (for A2), R1–5 = H (for A3),
R3 = Cl, R1,2,4,5 = H (for A4), R1 = NO2, R2–5 = H (for A5); (b) R1–5 = H (for A6).
2
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Regiocontrolled Hydroarylation of (Trifluoromethyl)acetylenes
hexabromo-1-carbadodecaborate (1.221 Å, 1.452 Å).[10] species, and the presence of trifluoromethyl group signifi-
The C-1–C-2–C-3 bond angles are 173.13–179.58°. The C- cantly influences the reactivity of these cations.
1–C-4 distances in A1–A5 (1.523–1.533 Å) exceed the anal-
On the basis of our calculations, we started the experi-
ogous one in A6 (1.512 Å). However, the C-2–C-1–C-4 mental investigation into the protonation of our model
bond angles in A1–A5 (122.20–122.59°) are less than that compound phenyl(trifluoromethyl)acetylene 1a to form the
in A6 (126.66°). Apparently, the difference between the geo- corresponding vinyl cation. Keeping in mind the high reac-
metrical parameters of these fragments is caused by the tivity of the vinyl cation formed, we performed the reaction
electron-withdrawing properties of the CF3 group in A1–A5 in presence of the nucleophile benzene 2a (see Scheme 2 and
compared to the CH3 group in A6. In addition, the dihedral Table 2). In the presence of trifluoroacetic acid (TFA, see
angle between the phenyl and NO2 planes in A5 is 16.89°, Table 2, Entry 1), almost no protonation takes place. In
which demonstrates the conjugation between them.
sulfuric acid, the reaction afforded corresponding ketone 5a
as the major product. This ketone formed as the result of
the hydration of the intermediate vinyl cation (or hydrolysis
of the intermediate vinyl sulfate). In addition, a small
amount of the corresponding alkene 3a was isolated in this
reaction (see Table 2, Entry 2). As we proposed, the proton-
ation proceeded 100% regioselectively to form an interme-
diate with the carbocation conjugated with the phenyl ring.
A much more effective protonation proceeded by treating
the acetylenes with triflic acid (see Table 2, Entries 3–11).
In these cases, after quenching the reaction mixtures, we
observed the formation of diphenyltrifluoromethylethene 3a
as well as the corresponding alcohol 4a, which resulted
from the hydration of intermediate trifluoroethylated
carbocation B (see Scheme 4). The total yields of these two
products are nearly quantitative. We attempted to find the
optimal conditions for the quenching step and found that a
mixture of alkene 3a and alcohol 4a generally formed (see
Table 2, Entries 3–9). However, using methanol-methoxide
or dry acetonitrile as the quenching system permits for the
selective preparation of alkene 3a (see Table 2, Entries 10
and 11). The reaction proceeded under mild conditions (r.t.,
0.5 h), and pure alkene 3a was directly obtained in 98%
yield (see Table 2, Entry 11).
Scheme 1. Protonation of trifluoromethylated acetylenes.
To gain deeper insight into the electronic structure of
cations A1–A6, we analyzed the charge distribution in the
C-1–C-2–C-3 fragments, the EHOMO/ELUMO values, and the
global electrophilicity index[22] (ω, see Table 1). The charge
analysis showed that the increase of the positive charges on
the C-2 atoms in A1–A3 and A5 is in agreement with the
increase in the electron-withdrawing properties of the sub-
stituent on the aryl ring. This similar trend takes place in
the values for ELUMO and ω for A1–A3 and A5. In cation
series A1–A5, chloro-substituted cation A4 systematically
falls out of the trend. Apparently, a +M (mesomeric) effect
that is provoked by the conjugation between the p orbitals
of the chlorine atom and π system of phenyl ring is taking
place. The same interpretation can be used to understand
the deviation from the trend for the EHOMO values of cat-
ions A4 and A5. As previously described, the reciprocal dis-
position of the phenyl ring and NO2 group in A5 demon-
strates the conjugation between them. The q(C-2), EHOMO
,
ELUMO, and ω values in cation A5 lay between the analo-
gous values for cations A1 and A2. For the reasons given,
we suppose that these cations have similar reactivity. The
significant difference between the ω values of cations A3
and A6 is important. Intermediate A3 with a trifluorome-
thyl group has a much higher global electrophilicity index,
which predicts its higher reactivity compared to nonfluori-
nated cation A6. Evidently, the incorporation of nitro group
into the benzene ring makes cation A5 much more electro-
philic. Thus, the results of calculations predict that the tri-
fluoromethylated vinyl cations should be highly reactive
Scheme 2. Reaction of alkyne 1a with benzene 2a.
To investigate the synthetic scope and limitations of the
reaction, we studied other alkynes 1 and arenes 2 in triflic
acid (see Scheme 3 and Table 3). We found that the reaction
generally gave alkene 3 or, in some cases, a mixture of alk-
ene 3 with alcohol 4 depending on the workup conditions.
Starting acetylenes that have both electron-donating (see
Table 3, Entries 9–18) and electron-withdrawing groups (see
Table 3, Entries 19–24) participated successfully in the reac-
tion. The nature of the substituents did not significantly
influence the course of the reaction or the yields of the final
products. This is also true for the structure of the arene.
Table 1. Selected calculated electronic characteristic of the vinyl
cations.
Cation q(C-1)[a] q(C-2)
q(C-3) EHOMO ELUMO
ω[b]
[e]
[e]
[e]
[eV]
[eV]
[eV]
A1
A2
A3
A4
A5
A6
–0.32
–0.33
–0.33
–0.32
–0.32
–0.22
0.31
0.35
0.37
0.35
0.42
0.34
–0.21
–0.21
–0.21
–0.21
–0.22
–0.22
–11.92
–12.39
–12.57
–12.50
–12.50
–12.13
–7.88
–8.38
–8.75
–8.64
–9.23
–8.14
24.020
26.895
29.747
28.944
36.100
25.744
[a] Natural charges. [b] Global electrophilicity index.
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Table 2. Results of reaction between alkyne 1a and benzene 2a un-
der various conditions.
Entry Acid
Time Quenching
% Yield % Yield
[h]
system
3a
4a
1
2
3
4
5
6
7
8
CF3CO2H[a]
3
1
H2O
H2O
H2O
trace
14[b]
36
91
68
72
73
61
81
trace
–
34
8
19
17
10
27
12
0
H2SO4
TfOH
TfOH
TfOH
TfOH
TfOH
TfOH
TfOH
TfOH
TfOH
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
HClaqueous
HBraqueous
H2SO4
NaHCO3/H2O
NaOH/H2O
MeOH/H2O
MeONa/MeOH
MeCN
Scheme 3. Reactions of alkynes 1 with various arenes 2.
9
10
11
96
98
observed a significant difference in the chemical shift of vin-
yl proton, which indicates that the substituted aryl group
is probably out of plane with respect to the double bond.
The opposite stereoselectivity for nitro-substituted acetyl-
ene 1q can be explained by the electronic repulsion of the
0
[a] Conversion of the alkyne 1a is low (Ͻ5%). [b] The second prod-
uct is ketone 5a (PhCOCH2CF3), obtained in 72% yield.
Apart from the benzene, other alkyl-, methoxy-, and halo- trifluoromethyl group and the nitro fragment, which makes
gen-substituted arenes were involved in this reaction (see the formation of the (E) isomer highly preferable.
Table 3). The nucleophilicity of the substituted arenes were
The E/Z configuration of compounds 3 was determined
over a broad range and varied. The reaction product 3b, by 1H NMR spectroscopy. The E/Z assignments for isomers
1
prepared from anisole, is a straightforward precursor for 3 were made on the basis of our previous H NMR and
the synthesis of panamifene. In the future, we will study the X-ray studies of the stereochemistry of structurally similar
1
possibility of using this alkene in the synthesis of panami- trisubstituted 1,1-diarylethenes.[4b–4f] As a rule, in the H
fene. Our strategy uses vinyl organometallics that are stabi- NMR spectra, the (E) isomers of the ethenes have the vinyl
lized by a trifluoromethyl group as the key compounds.
proton shifted low field compared to the vinyl proton of the
As a rule, mixtures of the (E) and (Z) isomers of alkene (Z) isomers. The chemical shift of the vinyl protons strongly
3 are formed (see Exp. Sect.). However, the products con- depend on the electronic character and position of the sub-
taining an ortho substituent on the aryl ring have a ten- stituents in the aromatic ring.[4b–4f] The (E) isomers of 3
dency to form more selectively to minimize the steric inter- have vinyl proton signals in the region of δ = 5.19–
action of the bulky CF3 group with the ortho substituent. 6.17 ppm. The (Z) isomers have the vinyl proton signals
1
Also, in the H NMR spectra of these diastereomers, we shifted downfield at δ = 6.01–6.26 ppm (see Exp. Sect.). Ad-
Table 3. Synthesis of diaryltrifluoromethylethenes 3 and alcohols 4.
Entry
3/4
Ar1
Ar2
Quenching
% Yield 3 (Z/E)
% Yield 4
Total % yield
1
2
3
4
5
6
7
8
a
b
b
c
c
d
e
f
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
CH3CN
H2O
CH3CN
H2O
CH3CN
H2O
H2O
MeCN
NaOH/H2O
MeOH-MeONa
MeCN
H2O
H2O
H2O
CH3CN
HClaqueous
CH3CN
CH3CN
CH3CN
NaOH/H2O
H2O
H2O
CH3CN
H2O
98 (–)
0
23
0
18
0
0
0
0
25
0
0
0
0
50
0
0
0
0
0
18
28
0
98
68
85
41
75
68
54
81
70
92
85
46
92
63
94
82
73
42
78
82
67
71
94
47
4-MeOC6H4
4-MeOC6H4
3,4-Cl2C6H3
3,4-Cl2C6H3
2,4-Me2C6H3
2,5-Me2C6H3
3,4-(MeO)2C6H3
Ph
45 (75:25)
85 (75:25)
23 (63:37)
75 (63:37)
68 (70:30)
54 (80:20)
81 (61:39)
45 (60:40)
92 (60:40)
85 (61:39)
46 (75:25)
92 (50:50)
13 (–)
9
g
g
g
h
i
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeOC6H4
4-MeOC6H4
4-MeOC6H4
4-MeOC6H4
4-MeOC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
4-ClC6H4
2-NO2C6H4
2-NO2C6H4
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Ph
Ph
2,4-Me2C6H3
3,4-(MeO)2C6H3
4-MeOC6H4
4-MeOC6H4
4-MeOC6H4
2,4-Me2C6H3
2,5-Me2C6H3
Ph
j
j
94 (–)
j
82[a] (–)
k
l
73 (100:0)
42 (92:8)
78 (50:50)
64 (50:50)
49 (50:50)
71 (76:24)
94 (63:37)
47 (0:100)
m
m
n
o
p
q
Ph
4-MeOC6H4
3,4-(MeO)2C6H3
Ph
0
0
4-MeOC6H4
[a] Experiment was performed in HSO3F at –75 °C for 1 h.
4
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Regiocontrolled Hydroarylation of (Trifluoromethyl)acetylenes
ditionally, the stereochemistry of compounds 3 has been center. Again, the electron-withdrawing nature of the CF3
confirmed by NOESY experiments. Compound 3q was iso- group makes the protonation highly selective. Finally, upon
lated as an individual diastereomer, and its NOESY spec- quenching the reaction mixture, cation B is either deproton-
trum was measured. The correlation between the vinyl pro- ated or hydrated to give compounds 3 and 4, respectively.
ton signal (quartet at δ = 5.25 ppm) and the ortho-proton Because of the high steric demand of the trifluoromethyl
signal of the nitro-substituted aryl ring (doublet at δ = moiety, deprotonation is the preferential reaction pathway,
7.36 ppm) was observed, indicating the (E) configuration and the alkene is formed. Moreover, all our attempts to
(see Figure 3). A similar NOESY experiment for the iso- involve other nucleophiles such as MeCN, MeONa, Me2S,
meric mixture of 3c revealed in the case of the (E) isomer and PhSH in the reaction with cation B failed both because
that a correlation exists between the vinyl proton at δ = of the steric explanation and because of the higher acidity
6.11 ppm and the ortho-proton signal of the 3,4-dichlo- of the methylene group connected to the CF3 fragment. We
rophenyl group at δ = 7.07 ppm (doublet of doublets). The also conducted the reaction in fluorosulfonic acid at –75 °C
configuration of the (Z) isomer was assigned by the corre- to confirm the general character of this reaction. In this
lation between the vinyl proton and the ortho-proton signal case, alkene 3j was obtained selectively in 82% yield (see
of the phenyl group (doublet at δ = 7.22 ppm, 2 H, see Table 3, Entry 16).
Figure 3).
Scheme 4. Reaction mechanism.
In addition, by using NMR spectroscopy, we confirmed
Figure 3. NOESY correlations and chemical shifts of compounds
the formation of stable carbocation B, which is an impor-
3c and 3q.
1
tant step of the mechanism. We succeeded to record H,
The proposed reaction mechanism includes the proton- 13C, and 19F NMR spectra of cation B at room tempera-
ation of acetylene to give highly electrophilic and reactive ture. The solutions of the corresponding cations were pre-
vinyl cation A (see Scheme 4). It is significant that the pro- pared directly in the NMR tubes in three different ways,
tonation proceeds 100% regioselectively. The second step that is, by the reaction of alkynes 1 with benzene in triflic
involves the reaction with the arene, which acts as a nucleo- acid, by the protonation of alkenes 3, and by the dehydrox-
phile, to give alkene 3. The alkene is protonated to form ylation of alcohols 4 in triflic acid. The resonance signal for
stable tertiary carbocation B, which contains two aryl the carbocation atom in cation B1 is far downfield at δ =
groups and a 2,2,2-trifluoroethyl group at the carbocation 207.0 ppm (see Figures 4 and 5). The carbocation signals of
Figure 4. Selected NMR spectroscopic data of cations B1–B3.
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A. V. Vasilyev, V. G. Nenajdenko et al.
FULL PAPER
cations B2 and B3 with one or two methoxy groups in the
To confirm the general character of this approach to
para position on the aryl rings are shifted upfield shifted at fluorinated ethenes, we also prepared the corresponding
δ = 185.4 and 182.0 ppm, respectively. These data confirm CF2Cl-acetylene 1f. In contrast to the reaction of the tri-
the significant stabilization of the cation as a result of its fluoromethylated alkynes, acetylene 1f produced only tar in
conjugation with the methoxy group(s). For cations B1–B3, the reaction with benzene in triflic acid (0 °C). We were
the same reason explains the similar upfield shifts observed able to overcome this problem by conducting the reaction
for the signals from the CH2 groups in the 1H and 13C in fluorosulfonic acid at a lower temperature of –75 °C. In
NMR spectra and the CF3 group in the 19F NMR spectra. this case, we preserved the CF2Cl fragment and obtained
In these cations, the resonance of the CH2 group is at δ = E/Z-alkenes 6 and alcohol 7 in a total yield of 65% (see
37–39.7 ppm in the 13C NMR spectra and at δ = 4.48– Scheme 5).
1
4.90 ppm in H NMR spectra. The trifluoromethyl group
A complete change in the reaction pattern was observed
has a signal at δ = –58.6 to –60 ppm in the 19F NMR spec- when an excess amount of aluminium bromide was used as
tra (see Figure 4 and Exp. Sect.).
an activator in the reaction between acetylene 1a and benz-
1
Figure 5. H, 13C, 19F NMR spectroscopic data of cation B1.
6
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Regiocontrolled Hydroarylation of (Trifluoromethyl)acetylenes
Scheme 7. The hydration of 1 to form trifluoromethylated ketones
5.
Conclusions
In conclusion, the superacidic generation of vinyl cations
from aryl(trifluoromethyl)acetylenes can be effectively per-
formed by using triflic and fluorosulfonic acids under mild
conditions. The subsequent reaction of the vinyl cations
with various arenes gave the corresponding alkenes and
alcohols in high yields after the appropriate workup. When
acetonitrile was used to quench the reaction mixtures, the
trifluoromethylated alkenes were prepared selectively and in
high yield. The formation of the intermediate trifluoroethyl-
ated carbocations was confirmed by NMR spectroscopy.
Finally, we elaborated a simple and efficient approach to
trifluoromethyl ketones through the hydration of the corre-
sponding aryl(trifluoromethyl)acetylenes in sulfuric acid.
Scheme 5. The reaction of CF2Cl-substituted acetylene 1f with
benzene.
ene. 1,3,3-Triphenylindene (8) was isolated in 58% yield as
the only reaction product. Its formation can be rationalized
by the formation of the difluoropropargylic carbocation,
which is transformed into indene 8 through a multistep de-
fluorination–arylation sequence that is terminated by an in-
tramolecular cyclization (see Scheme 6). In a similar way,
compound 8 was previously obtained from the reactions of
1,3-diphenylpropynone and benzene, 1,1,3-triphenylprop-
yn-2-ol-1 and benzene, and 1,3,3,3-tetraphenylpropyne un-
der the action of AlBr3.[23]
Finally, we studied the transformation of acetylenes 1
into the corresponding ketones 5 in sulfuric acid without
benzene as a competitive nucleophile. The target ketones 5
were easily obtained in almost quantitative yield by mixing
the starting compounds 1 with sulfuric acid at ambient tem-
perature and then following with a water workup (see
Scheme 7). As a result, a convenient and simple route to
Experimental Section
General Methods: The NMR spectroscopic data of the compounds,
which were dissolved in CDCl3, were recorded with a Bruker AM-
1
500 spectrometer at 25 °C (at 500, 470, and 125 MHz for H, 19F,
and 13C NMR spectra, respectively). The residual proton signal for
1
CDCl3 (δ = 7.26 ppm) in the H NMR spectra, the carbon signal
of CDCl3 (δ = 77.0 ppm) in the 13C NMR spectra, and the signal
of CFCl3 (δ = 0.0 ppm) in the 19F NMR spectra were used as refer-
ences. The NMR experiments that were carried out in the superacid
TfOH at 25 °C were performed with the same spectrometer. These
NMR spectra were referenced to the signal of the added CH2Cl2
such fluorinated carbonyl compounds was elaborated. This as the internal standard (δ = 5.32 ppm for 1H NMR, δ = 53.84 ppm
for 13C NMR). IR spectra of compounds, which were dissolved in
one-step protocol avoids the application of toxic mercury
compounds[24] or an expensive ruthenium catalyst[25] to
CHCl3, were recorded with a FSM-1201 spectrometer. CHN analy-
sis was carried out on an elemental analyzer (EA) 300 EuroVektor.
convert trifluoromethylated acetylenes into ketones in pre-
Chromatography–mass spectrometry data were obtained with a
parative yields. Only in the case of nitro-substituted acetyl-
G2570A GC/MSD Agilent Technologies 6850c with a HP-5MS
ene 1e with the most electron-poor triple bond was no pro-
(3 mϫ0.25 mm) column and a stationary phase thickness of
tonation of triple bond observed.[26] On the contrary, even
under treatment with trifluoroacetic acid, the most reactive
0.25 μm. The preparative reactions that were monitored by thin
layer chromatography were carried out on silica gel plates (Silufol
4-methoxy-substituted alkyne 1d with the more easily pro-
tonated electron-rich triple bond gave the corresponding
ketone.
UV-254) using UV light for detection. Column chromatography
was performed on silica gel Chemapol 40/100 (0.04–0.10 mm) with
a mixture of hexanes/ethyl acetate as the eluent. Fluorinated acetyl-
Scheme 6. The transformation of alkyne 1a into indene 8.
Eur. J. Org. Chem. 0000, 0–0
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Date: 07-01-13 16:30:29
Pages: 13
A. V. Vasilyev, V. G. Nenajdenko et al.
FULL PAPER
enes 1 were prepared using our previously published experimental
3,3,3-Trifluoro-1-(2,4-dimethylphenyl)-1-phenylpropene (3d): Yel-
lowish oil (Z/E isomers, 70:30). Data for (Z) isomer: 1H NMR
(500 MHz, CDCl3): δ = 2.00 (s, 3 H, Me), 2.36 (s, 3 H, Me), 6.25
(q, JH,F = 7.8 Hz, 1 H, =CH), 6.82–7.33 (m, 8 H, Ar) ppm. 19F
NMR (470 MHz, CDCl3): δ = –56.78 (d, JH,F = 7.8 Hz, CF3) ppm.
GC–MS (EI): m/z (%) = 276 (20) [M]+, 193 (100), 178 (60). Data
for (E) isomer: 1H NMR (500 MHz, CDCl3): δ = 2.04 (s, 3 H, Me),
2.33 (s, 3 H, Me), 5.78 (q, JH,F = 8.3 Hz, 1 H, =CH), 6.82–7.33
(m, 8 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –56.34 (d,
JH,F = 8.3 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 276 (20) [M]+,
193 (100), 178 (60). Data for Z/E isomers: C17H15F3 (276.30):
calcd. C 73.90, H 5.47; found C 73.84, H 5.43.
protocols.[20c,20d]
General Procedure for Hydroarylation of Alkynes 1a–1f in TfOH or
HSO3F: Alkyne 1 (0.3 mmol) was added (dropwise for liquids, or
in small portions for solids) to a stirred solution of arene 2
(0.45 mmol) in TfOH (1 mL) at room temperature. The reaction
mixture was stirred for 0.5–1 h at room temperature and then
quenched with H2O, MeCN, or other quenching system (see
Tables 2 and 3)]. The products were extracted with CHCl3
(3ϫ30 mL), and the combined extracts were successively washed
with H2O (2ϫ20 mL), a saturated aqueous solution of NaHCO3
(2ϫ20 mL), and H2O (2ϫ20 mL). The organic extracts were then
dried with Na2SO4 and evaporated in vacuo. The resulting residue
was purified by column chromatography on silica gel using the ap-
propriate mixture of hexanes/ethyl acetate as the eluent. In a similar
manner, the reaction was carried out in HSO3F at –75 °C, and the
reaction mixture was quenched with frozen HClaqueous at –75 °C.
The resulting mixture was diluted with water and warmed to room
temperature, and the above-mentioned workup was followed. The
NMR spectroscopic data of compounds 3a,[27] 3b, 3g,[28] 3m, 3n,[29]
5a–5d,[30,31] and 8[23] are in agreement with those in the literature.
3,3,3-Trifluoro-1-(2,5-dimethylphenyl)-1-phenylpropene (3e): Yellow-
ish oil (Z/E isomers, 80:20). Data for (Z) isomer: 1H NMR
(500 MHz, CDCl3): δ = 2.04 (s, 3 H, Me), 2.33 (s, 3 H, Me), 6.26
(q, JH,F = 8.1 Hz, 1 H, =CH), 6.99–7.34 (m, 8 H, Ar) ppm. 19F
NMR (470 MHz, CDCl3): δ = –57.89 (d, JH,F = 8.1 Hz, CF3) ppm.
GC–MS (EI): m/z (%) = 276 (30) [M]+, 193 (100), 178 (80). Data
for (E) isomer: 1H NMR (500 MHz, CDCl3): δ = 2.04 (s, 3 H, Me),
2.33 (s, 3 H, Me), 5.79 (q, JH,F = 8.6 Hz, 1 H, =CH), 6.99–7.34
(m, 8 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –56.37 (d,
JH,F = 8.6 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 276 (30) [M]+,
193 (100), 178 (80). Data for Z/E isomers: 13C NMR (125 MHz,
CDCl3, 25 °C): δ = 19.0, 20.9, 115.4 (q, JC,F = 32.3 Hz), 117.7 (q,
JC,F = 34.1 Hz), 123.1 (q, JC,F = 269.3 Hz), 127.0, 127.9, 128.6,
128.8, 129.0, 129.2, 129.3, 129.6, 129.9, 130.0, 130.6, 132.5, 134.7,
3,3,3-Trifluoro-1,1-diphenylpropene (3a): Yellowish oil. 1H NMR
(500 MHz, CDCl3): δ = 6.14 (q, JH,F = 8.6 Hz, 1 H, =CH), 7.25–
7.26 (m, 4 H, Ph), 7.32–7.36 (m, 3 H, Ph), 7.39–7.40 (m, 3 H,
Ph) ppm. 19F NMR (470 MHz, CDCl3): δ = –55.6 (d, JH,F
=
8.6 Hz, CF3) ppm. 13C NMR (125 MHz, CDCl3, 25 °C): δ = 115.5
(q, JC,F = 33.9 Hz), 123.1 (q, JC,F = 269 Hz), 127.9, 128.0, 128.5,
136.1, 138.5, 151.8 (q, JC,F = 5.4 Hz) ppm. IR: ν = 2953, 1643,
˜
1496, 1272, 1131) cm–1. C17H15F3 (276.30): calcd. C 73.90, H 5.47;
found C 73.94, H 5.46.
129.1, 129.4 ppm. IR: ν = 2930, 1700, 1638, 1601, 1271, 1129 cm–1.
˜
GC–MS (EI): m/z (%) = 248 (100) [M]+, 227 (20), 179 (70), 165
3,3,3-Trifluoro-1-(3,4-dimethoxyphenyl)-1-phenylpropene (3f): Yel-
lowish oil (Z/E isomers, 61:39). Data for (Z) isomer: 1H NMR
(500 MHz, CDCl3): δ = 3.80 (s, 3 H, OMe), 3.86 (s, 3 H, OMe),
6.07 (q, JH,F = 8.4 Hz, 1 H, =CH), 6.77–7.38 (m, 8 H, Ar) ppm.
19F NMR (470 MHz, CDCl3): δ = –55.75 (d, JH,F = 8.4 Hz,
CF3) ppm. GC–MS (EI): m/z (%) = 308 (100) [M]+, 261 (10), 233
(65).
3,3,3-Trifluoro-1-(4-methoxyphenyl)-1-phenylpropene (3b): Yellow-
ish oil (Z/E isomers, 75:25). Data for (Z) isomer: 1H NMR
(500 MHz, CDCl3): δ = 3.81 (s, 3 H, OMe), 6.05 (q, JH,F = 8.5 Hz,
1 H, =CH), 6.84–7.39 (m, 9 H, Ar) ppm. 19F NMR (470 MHz,
CDCl3): δ = –55.11 (d, JH,F = 8.5 Hz, CF3) ppm. GC–MS (EI):
m/z (%) = 278 (90) [M]+, 263 (25), 195 (80), 167 (100). Data for
1
(15), 152 (20). Data for (E) isomer: H NMR (500 MHz, CDCl3):
δ = 3.82 (s, 3 H, OMe), 3.90 (s, 3 H, OMe), 6.05 (q, JH,F = 8.4 Hz,
1 H, =CH), 6.77–7.38 (m, 8 H, Ar) ppm. 19F NMR (470 MHz,
CDCl3): δ = –56.06 (d, JH,F = 8.4 Hz, CF3) ppm. GC–MS (EI):
m/z (%) = 308 (100) [M]+, 261 (10), 233 (15), 152 (20). Data for Z/
E isomers: C17H15F3O2 (308.30): calcd. C 66.23, H 4.90; found C
66.28, H 4.86.
1
(E) isomer: H NMR (500 MHz, CDCl3): δ = 3.85 (s, 3 H, OMe),
6.04 (q, JH,F = 8.3 Hz, 1 H, =CH), 6.84–7.39 (m, 9 H, Ar) ppm.
19F NMR (470 MHz, CDCl3): δ = –55.44 (d, JH,F = 8.3 Hz,
CF3) ppm. GC–MS (EI): m/z (%) = 278 (90) [M]+, 263 (25), 195
(80), 167 (100). Data for Z/E isomers: 13C NMR (125 MHz,
CDCl3, 25 °C): δ = 55.3, 55.6, 113.5 (q, JC,F = 32.3 Hz), 114.9 (q,
JC,F = 32.3 Hz), 123.2 (q, JC,F = 281.9 Hz), 127.9, 128.1, 128.2,
128.3, 128.4, 129.0, 129.1, 129.3, 130.6, 130.8, 132.4, 151.8 (q, JC,F
3,3,3-Trifluoro-1-(4-methylphenyl)-1-phenylpropene (3g): Yellowish
oil (Z/E isomers, 60:40). Data for (Z) isomer: 1H NMR (500 MHz,
CDCl3): δ = 2.37 (s, 3 H, Me), 6.10 (q, JH,F = 8.5 Hz, 1 H, =CH),
7.15–7.40 (m, 9 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ =
–57.35 (d, JH,F = 8.5 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 262
(100) [M]+, 247 (30), 227 (15), 193 (20), 179 (55). Data for (E)
= 5.4 Hz), 160.5, 160.6 ppm. IR: ν = 2958, 1639, 1606, 1511, 1271,
˜
1128 cm–1.
1-(3,4-Dichlorophenyl)-3,3,3-trifluoro-1-phenylpropene (3c): Yellow-
ish oil (Z/E isomers, 63:37). Data for (Z) isomer: 1H NMR
(500 MHz, CDCl3): δ = 6.16 (q, JH,F = 7.8 Hz, 1 H, =CH), 7.10
(dd, J = 8.3, J = 1.7 Hz, 1 H, Ar), 7.22 (d, J = 8.0 Hz, 2 H, Ar),
7.34 (d, J = 8.0 Hz, 2 H, Ar), 7.36–7.42 (m, 3 H, Ar) ppm. 19F
NMR (470 MHz, CDCl3): δ = –55.64 (d, JH,F = 7.8 Hz, CF3) ppm.
GC–MS (EI): m/z (%) = 316 (100) [M]+, 281 (50), 261 (40), 246
1
isomer: H NMR (500 MHz, CDCl3): δ = 2.41 (s, 3 H, Me), 6.13
(q, JH,F = 8.4 Hz, 1 H, =CH), 7.15–7.40 (m, 9 H, Ar) ppm. 19F
NMR (470 MHz, CDCl3): δ = –57.48 (d, JH,F = 8.4 Hz, CF3) ppm.
GC–MS (EI): m/z (%) = 262 (100) [M]+, 247 (30), 227 (15), 193
(20), 179 (55). Data for Z/E isomers: 13C NMR (125 MHz, CDCl3,
25 °C): δ = 21.2, 21.3, 114.5 (q, JC,F = 34.1 Hz), 115.1 (q, JC,F
=
33.2 Hz), 123.2 (q, JC,F = 271.1 Hz), 123.3 (q, JC,F = 270.2 Hz),
127.9, 128.0, 128.1, 128.3, 128.4, 128.7, 129.1, 129.2, 129.3, 134.3,
137.2, 137.4, 138.4, 139.6, 140.4, 152.3 (q, JC,F = 5.4 Hz), 152.6 (q,
1
(45), 212 (70). Data for (E) isomer: H NMR (500 MHz, CDCl3):
δ = 6.11 (q, JH,F = 8.2 Hz, 1 H, =CH), 7.07 (dd, J = 8.3, 1.9 Hz,
1 H, Ar), 7.26 (d, J = 8.2 Hz, 2 H, Ar), 7.36–7.42 (m, 3 H, Ar),
7.47 (d, J = 8.2 Hz, 2 H, Ar) ppm. 19F NMR (470 MHz, CDCl3):
δ = –55.92 (d, JH,F = 8.2 Hz, CF3) ppm. GC–MS (EI): m/z (%) =
316 (100) [M]+, 281 (50), 261 (40), 246 (45), 212 (70). Data for Z/
JC,F = 5.4 Hz) ppm. IR: ν = 2925, 1642, 1610, 1511, 1270,
˜
1127 cm–1. C16H13F3 (262.27): calcd. C 73.27, H 5.00; found C
73.32, H 5.06.
E isomers: IR: ν = 2952, 1644, 1471, 1274, 1127 cm–1. C H Cl F
3,3,3-Trifluoro-1-(4-methylphenyl)-1-(2,4-dimethylphenyl)propene
˜
15
9
2
3
(317.14): calcd. C 56.81, H 2.86; found C 56.87, H 2.79.
(3h): Yellowish oil (Z/E isomers, 75:25). Data for (Z) isomer: 1H
8
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Regiocontrolled Hydroarylation of (Trifluoromethyl)acetylenes
NMR (500 MHz, CDCl3): δ = 2.01 (s, 3 H, Me), 2.28 (s, 3 H, Me),
(%) = 306 [M]+. Data for Z/E isomers: C18H17F3O (306.33): calcd.
2.36 (s, 3 H, Me), 6.23 (q, JH,F = 8.0 Hz, 1 H, =CH), 6.82–7.16 C 70.58, H 5.59; found C 70.62, H 5.64.
(m, 7 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –57.57 (d,
1-(4-Chlorophenyl)-3,3,3-trifluoro-1-phenylpropene (3m): Yellowish
JH,F = 8.0 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 290 (30) [M]+,
275 (25), 207 (80), 192 (100), 178 (8). Data for (E) isomer: 1H NMR
(500 MHz, CDCl3): δ = 2.12 (s, 3 H, Me), 2.22 (s, 3 H, Me), 2.32
(s, 3 H, Me), 5.73 (q, JH,F = 8.2 Hz, 1 H, =CH), 6.82–7.16 (m, 7
oil (Z/E isomers, 50:50). Data for (Z) isomer: 1H NMR (500 MHz,
CDCl3): δ = 6.13 (q, JH,F = 8.5 Hz, 1 H, =CH), 7.16–7.40 (m, 9
H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –56.24 (d, JH,F
=
8.5 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 282 (100) [M]+, 247
(70), 227 (42), 199 (33), 178 (92). Data for (E) isomer: 1H NMR
(500 MHz, CDCl3): δ = 6.10 (q, JH,F = 8.5 Hz, 1 H, =CH), 7.16–
7.40 (m, 9 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –56.37
(d, JH,F = 8.5 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 282 (100)
[M]+, 247 (75), 227 (44), 199 (32), 178 (90). Data for Z/E isomers:
13C NMR (125 MHz, CDCl3, 25 °C): δ = 115.7 (q, JC,F = 34.1 Hz),
115.9 (q, JC,F = 34.1 Hz), 122.8 (q, JC,F = 271.1 Hz), 122.9 (q, JC,F
= 271.1 Hz), 127.9, 128.1, 128.4, 128.6, 128.7, 129.0, 129.2, 129.6,
H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –56.27 (d, JH,F
=
8.2 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 290 (30) [M]+, 275 (25),
207 (80), 192 (100), 178 (8). Data for Z/E isomers: IR: ν = 2924,
˜
1641, 1610, 1271, 1130 cm–1. C18H17F3 (290.33): calcd. C 74.47, H
5.90; found C 74.42; H 5.86.
3,3,3-Trifluoro-1-(3,4-dimethoxyphenyl)-1-(4-methylphenyl)propene
(3i): Yellowish oil (Z/E isomers, 50:50). Data for (Z) isomer: 1H
NMR (500 MHz, CDCl3): δ = 2.39 (s, 3 H, Me), 3.82 (s, 3 H,
OMe), 3.91 (s, 3 H, OMe), 6.02 (q, JH,F = 8.2 Hz, 1 H, =CH),
6.75–7.19 (m, 7 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ =
–55.90 (d, JH,F = 8.2 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 322
(100) [M]+, 307 (10), 291 (11), 275 (15), 247 (15). Data for (E)
130.5, 134.7, 135.5, 135.6, 136.8, 138.5, 139.6, 151.3 (q, JC,F
=
5.4 Hz) ppm. IR: ν = 2924, 1642, 1593, 1490, 1272, 1130 cm–1.
˜
1-(4-Chlorophenyl)-3,3,3-trifluoro-1-(4-methoxyphenyl)propene (3n):
1
Yellowish oil (Z/E isomers, 50:50). Data for (Z) isomer: H NMR
1
isomer: H NMR (500 MHz, CDCl3): δ = 2.36 (s, 3 H, Me), 3.81
(500 MHz, CDCl3): δ = 3.68 (s, 3 H, OMe), 6.05 (q, JH,F = 8.3 Hz,
1 H, =CH), 6.84–7.38 (m, 8 H, Ar) ppm. 19F NMR (470 MHz,
CDCl3): δ = –55.85 (d, JH,F = 8.3 Hz, CF3) ppm. GC–MS (EI):
m/z (%) = 312 (60) [M]+, 277 (10), 229 (100), 201 (80), 178 (20),
165 (90). Data for (E) isomer: 1H NMR (500 MHz, CDCl3): δ =
3.65 (s, 3 H, OMe), 6.17 (q, JH,F = 8.3 Hz, 1 H, =CH), 6.84–7.38
(m, 8 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –56.33 (d,
JH,F = 8.3 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 312 (100)
[M]+, 277 (50), 229 (45), 201 (10), 178 (8), 165 (70). Data for Z/E
(s, 3 H, OMe), 3.86 (s, 3 H, OMe), 6.03 (q, JH,F = 8.4 Hz, 1 H,
=CH), 6.75–7.19 (m, 7 H, Ar) ppm. 19F NMR (470 MHz, CDCl3):
δ = –55.73 (d, JH,F = 8.4 Hz, CF3) ppm. GC–MS (EI): m/z (%) =
322 (100) [M]+, 307 (10), 291 (11), 275 (15), 247 (15). Data for
Z/E isomers: C18H17F3O2 (322.33): calcd. C 67.07, H 5.32; found
C 67.13, H 5.36.
3,3,3-Trifluoro-1,1-bis(4-methoxyphenyl)propene (3j): Yellowish oil.
1H NMR (500 MHz, CDCl3): δ = 3.81 (s, 3 H, OMe), 3.84 (s, 3 H,
OMe), 5.97 (q, JH,F = 8.5 Hz, 1 H, =CH), 6.83 (d, J = 8.8 Hz, 2
H, Ar), 6.90 (d, J = 8.8 Hz, 2 H, Ar), 7.16 (d, J = 8.8 Hz, 2 H, Ar),
7.17 (d, J = 8.8 Hz, 2 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ
= –55.74 (d, JH,F = 8.5 Hz, CF3) ppm. 13C NMR (125 MHz,
CDCl3, 25 °C): δ = 55.2, 55.3, 112.8 (q, JC,F = 33.5 Hz), 113.3,
113.7, 123.3 (q, JC,F = 270 Hz), 128.2, 129.5, 129.7, 130.6, 132.9,
isomers: IR: ν = 2960, 1726, 1639, 1605, 1513, 1273, 1130 cm–1.
˜
1-(4-Chlorophenyl)-3,3,3-trifluoro-1-(3,4-dimethoxyphenyl)propene
(3o): Yellowish oil (Z/E isomers, 76:24). Data for (Z) isomer: 1H
NMR (500 MHz, CDCl3): δ = 3.82 (s, 3 H, OMe), 3.87 (s, 3 H,
OMe), 6.01 (q, JH,F = 8.4 Hz, 1 H, =CH), 6.62–7.37 (m, 7 H,
Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –56.24 (d, JH,F
=
8.4 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 342 (100) [M]+, 327
(5), 295 (8), 277 (4), 264 (8), 249 (15). Data for (E) isomer: 1H
NMR (500 MHz, CDCl3): δ = 3.82 (s, 3 H, OMe), 3.87 (s, 3 H,
OMe), 6.06 (q, JH,F = 8.4 Hz, 1 H, =CH), 6.62–7.37 (m, 7 H,
159.7, 160.6 ppm. IR: ν = 2959, 1714, 1642, 1605, 1513, 1270,
˜
1128 cm–1. GC–MS (EI): m/z (%) = 308 (100) [M]+, 277 (24), 225
(90), 210 (28), 195 (7), 181 (8), 165 (10). C17H15F3O2 (308.30):
calcd. C 66.23, H 4.90; found C 66.28, H 4.94.
Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –55.81 (d, JH,F
=
8.4 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 342 (100) [M]+, 327
(5), 295 (8), 277 (4), 264 (8), 249 (15). Data for Z/E isomers: 13C
NMR (125 MHz, CDCl3, 25 °C): δ = 55.8, 55.9, 110.5, 110.7,
110.9, 111.3, 114.2 (q, JC,F = 34.1 Hz), 115.2 (q, JC,F = 34.1 Hz),
121.5, 123.1 (q, JC,F = 269.3 Hz), 128.3, 128.6, 128.7, 128.8, 129.1,
129.4, 129.8, 130.5, 132.2, 134.5, 135.7, 148.9, 150.4, 150.9 (q, JC,F
= 5.4 Hz) ppm. C17H14ClF3O2 (342.74): calcd. C 59.57, H 4.12;
found C 59.62, H 4.16.
(Z)-3,3,3-Trifluoro-1-(4-methoxyphenyl)-1-(2,4-dimethylphenyl)-
propene (3k): Yellowish oil. H NMR (500 MHz, CDCl3): δ = 2.27
1
(s, 3 H, Me), 2.36 (s, 3 H, Me), 3.79 (s, 3 H, OMe), 6.17 (q, JH,F
= 7.6 Hz, 1 H, =CH), 6.81–6.83 (m, 4 H, Ar), 7.03 (s, 1 H, Ar),
7.18 (d, J = 8.6 Hz, 2 H, Ar) ppm. 19F NMR (470 MHz, CDCl3):
δ = –57.35 (d, JH,F = 7.6 Hz, CF3) ppm. GC–MS (EI): m/z (%) =
306 (20) [M]+, 275 (10), 223 (100), 208 (35), 192 (28), 179 (10).
C18H17F3O (306.33): calcd. C 70.58, H 5.59; found C 70.53, H 5.62.
3,3,3-Trifluoro-1-(2-nitrophenyl)-1-phenylpropene (3p): Yellowish oil
(Z/E isomers, 63:37). Data for (Z) isomer: 1H NMR (500 MHz,
CDCl3): δ = 6.10 (q, JH,F = 7.6 Hz, 1 H, =CH), 6.95–7.45 (m, 9
3,3,3-Trifluoro-1-(4-methoxyphenyl)-1-(2,5-dimethylphenyl)propene
(3l): Yellowish oil (Z/E isomers, 92:8). Data for (Z) isomer: 1H
NMR (500 MHz, CDCl3): δ = 2.02 (s, 3 H, Me), 2.34 (s, 3 H, Me),
3.80 (s, 3 H, OMe), 6.18 (q, JH,F = 8.4 Hz, 1 H, =CH), 6.83–7.20
(m, 7 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –56.31 (d,
JH,F = 8.4 Hz, CF3) ppm. 13C NMR (125 MHz, CDCl3, 25 °C): δ
= 21.2, 21.2, 55.3, 113.5 (q, JC,F = 32.3 Hz), 113.9, 123.4 (q, JC,F
= 269.3 Hz), 126.0, 126.7, 128.4, 130.8, 133.5, 137.8, 137.9, 151.2
(q, JC,F = 5.4 Hz), 160.6 ppm. GC–MS (EI): m/z (%) = 306 [M]+.
H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –57.67 (d, JH,F
=
7.6 Hz, CF3) ppm. GC–MS (EI): m/z (%) = 292 (45) [M]+, 276 (70),
224 (100), 207 (40), 195 (70), 178 (50), 167 (90). Data for (E) iso-
mer: 1H NMR (500 MHz, CDCl3): δ = 5.19 (q, JH,F = 9.5 Hz, 1
H, =CH), 6.95–7.45 (m, 9 H, Ar) ppm. 19F NMR (470 MHz,
CDCl3): δ = –66.70 (d, JH,F = 9.5 Hz, CF3) ppm. GC–MS (EI):
m/z (%) = 292 (45) [M]+, 276 (70), 224 (100), 207 (40), 195 (70),
1
Data for (E) isomer: H NMR (500 MHz, CDCl3): δ = 2.00 (s, 3
178 (50), 167 (90). Data for Z/E isomers: IR: ν = 2955, 1716, 1625,
˜
H, Me), 2.32 (s, 3 H, Me), 3.86 (s, 3 H, OMe), 6.16 (q, JH,F
=
1530, 1267, 1132 cm–1. C15H10F3NO2 (293.24): calcd. C 61.44, H
3.44; found C 61.39, H 3.37.
9.1 Hz, 1 H, =CH), 6.83–7.20 (m, 7 H, Ar) ppm. 19F NMR
(470 MHz, CDCl3): δ = –57.46 (d, JH,F = 9.1 Hz, CF3) ppm. 13C
NMR (125 MHz, CDCl3, 25 °C, only most characteristic signals
given): δ = 21.3, 114.9, 127.6, 129.0, 131.0 ppm. GC–MS (EI): m/z
(E)-3,3,3-Trifluoro-1-(4-methoxyphenyl)-1-(2-nitrophenyl)propene
1
(3q): Yellowish oil. H NMR (500 MHz, CDCl3): δ = 3.79 (s, 3 H,
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. V. Vasilyev, V. G. Nenajdenko et al.
FULL PAPER
OMe), 5.25 (q, JH,F = 9.1 Hz, 1 H, =CH), 6.91 (d, J = 8.6 Hz, 2 137.6 (t, J = 6.2 Hz, Ar), 158.9 (d, J = 5.8 Hz, Ar) ppm. IR: ν =
˜
H, Ar), 6.99 (t, J = 8.6 Hz, 1 H, Ar), 7.28 (t, J = 9.1 Hz, 1 H, Ar), 3486, 2956, 1607, 1511, 1250, 1126 cm–1. GC–MS (EI): m/z (%) =
7.36 (d, J = 9.1 Hz, 1 H, Ar), 7.41 (d, J = 8.6 Hz, 2 H, Ar), 7.57
326 (20) [M]+, 308 (35), 243 (90), 225 (32), 135 (100), 107 (18), 92
(12). C17H17F3O3 (326.31): calcd. C 62.57, H 5.25; found C 62.52,
(d, J = 9.1 Hz, 1 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ =
–70.50 (d, JH,F = 9.1 Hz, CF3) ppm. 13C NMR (125 MHz, CDCl3): H 5.20.
δ = 55.3, 114.5 (q, JC,F = 33.2 Hz), 115.4, 119.2, 122.7, 124.5 (q,
JC,F = 279.28 Hz, CF3), 124.9, 126.4, 128.4, 130.6, 130.8 130.9,
157.3, 160.2 ppm. GC–MS (EI): m/z (%) = 323 (1) [M]+, 307 (70),
292 (5), 278 (8), 264 (7), 248 (4), 238 (100), 210 (20), 189 (35).
C16H12F3NO3 (323.27): calcd. C 59.45, H 3.74; found C 59.39, H
3.69.
1-(4-Chlorophenyl)-3,3,3-trifluoro-1-phenylpropan-1-ol (4m): Yel-
lowish oil. 1H NMR (500 MHz, CDCl3): δ = 2.62 (s, 1 H, OH),
3.17 (q, JH,F = 10.0 Hz, 2 H, CH2), 7.27–7.39 (m, 9 H, Ar) ppm.
19F NMR (470 MHz, CDCl3): δ = –58.88 (t, JH,F = 10.0 Hz,
CF3) ppm. 13C NMR (125 MHz, CDCl3): δ = 29.7, 44.9 (q, JC,F
=
25.4 Hz), 75.3 (q, JC,F = 99.5 Hz), 125.4, 125.6 (q, JH,F = 277 Hz),
3,3,3-Trifluoro-1,1-diphenylpropan-1-ol (4a): Yellowish oil. 1H
127.1, 127.8, 128.5, 128.6, 133.4, 143.5, 144.9 ppm. IR: ν = 3488,
˜
2954, 1510, 1248, 1122 cm–1. GC–MS (EI): m/z (%) = 300 (10)
[M]+, 282 (9), 247 (8), 217 (100), 139 (65), 105 (34), 77 (26).
C15H12ClF3O (300.71): calcd. C 59.91, H 4.02; found C 59.86, H
4.06.
NMR (500 MHz, CDCl3): δ = 2.65 (s, 1 H, OH), 3.21 (q, JH,F
=
10 Hz, 2 H, CH2), 7.26 (t, J = 7.6 Hz, 2 H, Ph), 7.34 (t, J = 7.6 Hz,
4 H, Ph), 7.42 (d, J = 7.6 Hz, 4 H, Ph) ppm. 19F NMR (470 MHz,
CDCl3): δ = –62.14 (t, JH,F = 10 Hz, CF3) ppm. 13C NMR
(125 MHz, CDCl3): δ = 45.0 (q, JC,F = 25.4 Hz), 76.2 (q, JC,F
=
1-(4-Chlorophenyl)-3,3,3-trifluoro-1-(4-methoxyphenyl)propan-1-ol
(4n): Yellowish oil. H NMR (500 MHz, CDCl3): δ = 2.60 (s, 1 H,
OH), 3.14 (q, JH,F = 10.4 Hz, 2 H, CH2), 6.84–7.26 (m, 8 H,
99.5 Hz), 125.7 (q, JC,F = 277 Hz), 125.6, 127.5, 128.4, 145.25 ppm.
1
IR: ν = 3472, 3030, 1449, 1262, 1124 cm–1. GC–MS (EI): m/z (%)
˜
= 266 (10) [M]+, 248 (5), 183 (100), 105 (80), 77 (30). C15H13F3O
(266.26): calcd. C 67.66, H 4.92; found C 67.61, H 4.86.
Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –58.97 (t, JH,F
=
10.4 Hz, CF3) ppm. 13C NMR (125 MHz, CDCl3): δ = 29.7, 45.0
(q, JC,F = 25.4 Hz), 55.3, 75.1 (q, JC,F = 99.5 Hz), 113.8, 125.6 (q,
JH,F = 277 Hz), 126.8, 127.1, 128.4, 133.3, 137.1, 143.7, 159.0 ppm.
3,3,3-Trifluoro-1-(4-methoxyphenyl)-1-phenylpropan-1-ol (4b): Yel-
lowish oil. 1H NMR (500 MHz, CDCl3): δ = 2.57 (s, 1 H, OH),
3.17 (q, JH,F = 10.2 Hz, 2 H, CH2), 3.78 (s, 3 H, OMe), 6.85 (d, J
= 8.8 Hz, 2 H, Ar), 7.26 (t, J = 7.7 Hz, 1 H, Ar), 7.30–7.34 (m, 4
H, Ar), 7.40 (d, J = 7.7 Hz, 2 H, Ar) ppm. 19F NMR (470 MHz,
IR: ν = 3484, 2954, 1512, 1254, 1118 cm–1. GC–MS (EI): m/z (%)
˜
= 330 (12) [M]+, 312 (10), 277 (5), 247 (100), 139 (85), 111 (34), 77
(18). C16H14ClF3O2 (330.73): calcd. C 58.11, H 4.27; found C
58.16, H 4.32.
CDCl3): δ = –62.44 (t, JH,F = 10.4 Hz, CF ) ppm. IR: ν = 3438,
˜
3
2960, 1463, 1273, 1124 cm–1. GC–MS (EI): m/z (%) = 296 (20)
[M]+, 213 (100), 135 (90), 105 (30). C16H15F3O2 (296.29): calcd. C
64.86, H 5.10; found C 64.81, H 5.04.
3-Chloro-1-(4-chlorophenyl)-3,3-difluoro-1-phenylpropene (6): Yel-
lowish oil (Z/E isomers, 45:55). Data for (Z) isomer: 1H NMR
(500 MHz, CDCl3): δ = 6.30 (t, JH,F = 11.7 Hz, 1 H, =CH), 7.16–
7.40 (m, 9 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –41.24
(d, JH,F = 11.7 Hz, CF2) ppm. GC–MS (EI): m/z (%) = 298 (10)
[M]+, 263 (100), 243 (12), 227 (10), 207 (14), 161 (30). Data for (E)
isomer: 1H NMR (500 MHz, CDCl3): δ = 36.33 (t, JH,F = 11.7 Hz,
1 H, =CH), 7.16–7.40 (m, 9 H, Ar) ppm. 19F NMR (470 MHz,
CDCl3): δ = –41.13 (d, JH,F = 11.7 Hz, CF2) ppm. GC–MS (EI):
m/z (%) = 298 (10) [M]+, 263 (100), 243 (12), 227 (9), 207 (11), 161
(31). Data for Z/E isomers: C15H10Cl2F2 (299.15): calcd. C 60.23,
H 3.37; found C 60.18, H 3.32.
1-(3,4-Dichlorophenyl)-3,3,3-trifluoro-1-phenylpropan-1-ol (4c): Yel-
lowish oil. 1H NMR (500 MHz, CDCl3): δ = 2.71 (s, 1 H, OH),
3.17 (q, JH,F = 10.2 Hz, 2 H, CH2), 7.21–7.57 (m, 8 H, Ar) ppm.
19F NMR (470 MHz, CDCl3): δ = –62.18 (t, JH,F = 10.2 Hz,
CF3) ppm. 13C NMR (125 MHz, CDCl3): δ = 29.7, 44.7 (q, JC,F
=
25.4 Hz), 75.0 (q, JC,F = 99.5 Hz), 125.4 (q, JH,F = 277 Hz), 125.2,
125.3, 127.8, 128.1 128.3, 128.7, 129.0, 130.2, 144.3, 145.2,
167.8 ppm. IR: ν = 3472, 3063, 1715, 1470, 1380, 1271, 1127 cm–1.
˜
GC–MS (EI): m/z (%) = 334 (10) [M]+, 251 (100), 173 (55), 145
(45). C15H11Cl2F3O (335.15): calcd. C 53.76, H 3.31; found C
53.72, H 3.35.
3-Chloro-1-(4-chlorophenyl)-3,3-difluoro-1-phenylpropan-1-ol (7):
Yellowish oil. 1H NMR (500 MHz, CDCl3): δ = 1.26 (s, 1 H, OH),
3.45 (t, JH,F = 13.6 Hz, 2 H, CH2), 7.16–7.40 (m, 9 H, Ar) ppm.
19F NMR (470 MHz, CDCl3): δ = –47.89 (t, JH,F = 13.6 Hz,
CF2) ppm. GC–MS (EI): m/z (%) = 316 (8) [M]+, 263 (10), 217
(100), 139 (50), 105 (36), 77 (21). C15H12Cl2F2O (317.16): calcd. C
56.80, H 3.81; found C 56.84, H 3.86.
3,3,3-Trifluoro-1-(4-methylphenyl)-1-phenylpropan-1-ol (4g): Oily
1
compound. H NMR (500 MHz, CDCl3): δ = 2.32 (s, 3 H, CH3),
2.64 (s, 1 H, OH), 3.18 (q, JH,F = 10.3 Hz, 2 H, CH2), 7.14 (d, J =
7.6 Hz, 2 H, Ar), 7.25 (t, J = 7.6 Hz, 1 H, Ar), 7.29–7.34 (m, 4 H,
Ar), 7.41 (d, J = 7.6 Hz, 2 H, Ar) ppm. 19F NMR (470 MHz,
CDCl3): δ = –62.15 (t, JH,F = 10.3 Hz, CF3) ppm. 13C NMR
(125 MHz, CDCl3): δ = 29.7, 44.9 (q, JC,F = 25.4 Hz), 75.5 (q, JC,F
= 99.5 Hz), 125.4, 125.5, 125.7 (q, JH,F = 277 Hz), 127.4, 128.3,
General Procedure for Hydration of Alkynes 1a–1c in H2SO4: A
solution of trifluoromethyl alkyne 1 (0.3 mmol) in H2SO4 (2 mL)
was stirred at room temperature for 1 h. The mixture was then
quenched with H2O (20 mL), and the resulting solution was ex-
tracted with CHCl3 (3ϫ30 mL). The combined extracts were suc-
cessively washed with H2O (2ϫ20 mL), a saturated aqueous solu-
tion of NaHCO3 (2ϫ20 mL), and H2O (2ϫ20 mL), dried with
Na2SO4, and then evaporated in vacuo to give the pure reaction
product.
129.1, 132.5, 137.2, 142.3, 145.3 ppm. IR: ν = 3491, 3060, 1723,
˜
1461, 1370, 1264, 1120 cm–1. GC–MS (EI): m/z (%) = 280 (10)
[M]+, 262 (8), 197 (100), 189 (5). C16H15F3O (280.29): calcd. C
68.56, H 5.39; found C 68.51, H 5.44.
3,3,3-Trifluoro-1,1-bis(4-methoxyphenyl)propan-1-ol (4j): Yellowish
1
oil. H NMR (500 MHz, CDCl3): δ = 2.52 (s, 1 H, OH), 3.12 (q,
JH,F = 10.4 Hz, 2 H, CH2), 3.78 (s, 6 H, 2 MeO), 6.84 (d, J =
8.8 Hz, 4 H, Ar), 7.29 (d, J = 8.8 Hz, 4 H, Ar) ppm. 19F NMR
(470 MHz, CDCl3): δ = –59.00 (t, JH,F = 10.4 Hz, CF3) ppm. 13C
NMR (125 MHz, CDCl3, C-H coupled): δ = 45.2 (tq, J =
1
3,3,3-Trifluoro-1-phenylpropan-1-one (5a): Yellowish oil. H NMR
(500 MHz, CDCl3): δ = 3.79 (q, JH,F = 9.8 Hz, 2 H, CH2), 7.50 (t,
J = 7.6 Hz, 2 H, Ar), 7.63 (t, J = 7.6 Hz, 1 H, Ar), 7.92 (d, J =
129.37 Hz, JC,F = 25.4 Hz, CH2), 55.2 (q, J = 142.90 Hz, OCH3), 7.6 Hz, 1 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –65.64
75.2 (t, J = 4.46 Hz, COH), 113.7 (dd, J = 158.81, 4.9 Hz, Ar),
125.8 (q, JH,F = 281.3 Hz, CF3), 130.0 (dd, J = 156.59, 7.1 Hz, Ar),
(t, JH,F = 9.8 Hz, CF3) ppm. 13C NMR (125 MHz, CDCl3): δ =
42.0 (q, JC,F = 28.1 Hz, CH2), 124.0 (q, JC,F = 275.2 Hz, CF3),
10
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Job/Unit: O21375
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Regiocontrolled Hydroarylation of (Trifluoromethyl)acetylenes
128.3, 128.9, 134.1, 135.8, 189.7 (q, J = 1.8 Hz, C=O) ppm. IR: ν
= 8.0 Hz, 2 H, Ar), 8.67 (br. t, J = 7.0 Hz, 1 H, Ph) ppm. 19F NMR
(470 MHz, TfOH): δ = –59.64 (t, JH,F = 8.5 Hz, CF3) ppm. 13C
NMR (125 MHz, TfOH): δ = 37.9 (q, JC,F = 31 Hz, CH2), 55.6
(MeO), 119.7 (q, JC,F = 277 Hz, CF3), 126.1, 126.6, 131.8, 131.9,
134.5, 134.7, 135.1, 178.8, 185.4 (C+) ppm.
˜
= 1690 (C=O) cm–1. GC–MS (EI): m/z (%) = 188 (20) [M]+, 105
(100), 77 (70), 51 (20). C9H7F3O3 (220.15): calcd. C 57.45, H 3.75;
found C 57.51; H 3.69.
3,3,3-Trifluoro-1-(4-methylphenyl)propan-1-one (5b): Yellowish oil.
1H NMR (500 MHz, CDCl3): δ = 2.42 (s, 3 H, Me), 3.75 (q, JH,F
= 10.6 Hz, 2 H, CH2), 7.29 (d, J = 7.8 Hz, 2 H, Ar), 7.82 (d, J =
7.8 Hz, 2 H, Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –62.69
(t, JH,F = 10.6 Hz, CF3) ppm. 13C NMR (125 MHz, CDCl3): δ =
21.7, 42.0 (q, JC,F = 28.1 Hz, CH2), 124.0 (q, JC,F = 275.2 Hz,
CF3), 128.5, 129.6, 133.5, 145.3, 189.3 (q, J = 1.8 Hz, C=O) ppm.
3,3,3-Trifluoro-1,1-di(4-methoxyphenyl)prop-1-ylium (B3): 1H
NMR (500 MHz, TfOH): δ = 4.28 (s, 6 H, 2 MeO), 4.48 (q, JH,F
= 8.5 Hz, 2 H, CH2), 7.46 (d, J = 8.0 Hz, 4 H, Ar), 8.06 (d, J =
8.0 Hz, 4 H, Ar) ppm. 19F NMR (470 MHz, TfOH): δ = –60.02 (t,
JH,F = 8.5 Hz, CF3) ppm. 13C NMR (125 MHz, TfOH): δ = 37.1
(q, JC,F = 31 Hz, CH2), 53.8 (MeO), 119.8 (q, JC,F = 276 Hz, CF3),
114.2, 130.1, 139.7, 170.9, 182.0 (C+) ppm.
IR: ν = 1685 (C=O) cm–1. GC–MS (EI): m/z (%) = 202 (25) [M]+,
˜
119 (100), 91 (60), 65 (17). C10H9F3O (202.17): calcd. C 59.41, H
4.49; found C 59.37, H 4.43.
Preparation of 1,3,3-Triphenylindene (8): (Trifluoromethyl)alkyne
1a (0.1 g, 0.6 mmol) was added dropwise to a stirred solution of
aluminium bromide (800 mg, 3 mmol) in benzene (4 mL) at room
temperature. The reaction mixture was stirred at room temperature
for 1 h and then quenched with H2O (50 mL). The product was
extracted with CHCl3 (3ϫ30 mL), and the combined extracts were
successively washed with H2O (2ϫ20 mL), a saturated aqueous
solution of NaHCO3 (2ϫ20 mL), and H2O (2ϫ20 mL), dried with
Na2SO4, and then evaporated in vacuo. The residue was purified
by column chromatography on silica gel (hexanes/ethyl acetate) to
give compound 8 in 58% yield. The spectral data of 8 are in agree-
ment with those previously reported.[23]
1-(4-Chlorophenyl)-3,3,3-trifluoropropan-1-one (5c): Yellowish oil.
1H NMR (500 MHz, CDCl3): δ = 3.76 (q, JH,F = 9.9 Hz, 2 H,
CH2), 7.47 (d, J = 8.4 Hz, 2 H, Ar), 7.87 (d, J = 8.4 Hz, 2 H,
Ar) ppm. 19F NMR (470 MHz, CDCl3): δ = –62.68 (t, JH,F
=
9.9 Hz, CF3) ppm. 13C NMR (125 MHz, CDCl3): δ = 42.2 (q, JC,F
= 28.1 Hz, CH2), 123.8 (q, JC,F = 275.7 Hz, CF3), 129.3, 129.8,
134.1, 140.9, 188.5 (q, J = 2.2 Hz, C=O) ppm. IR: ν = 1684
˜
(C=O) cm–1. GC–MS (EI): m/z (%) = 222 (20) [M]+, 139 (100), 111
(55), 75 (22). C9H6ClF3O (222.59): calcd. C 48.56, H 2.72; found
C 48.61, H 2.77.
Supporting Information (see footnote on the first page of this arti-
cle): Copies of the 1H and 13C NMR spectra for all key intermedi-
ates and final products.
Hydration of Alkyne 1d in CF3SO3H: A solution of the alkyne 1d
(0.25 mmol) in CH2Cl2 (1 mL) and CF3SO3H (0.09 mL) was stirred
at room temperature for 1 h. The mixture was then diluted with
CHCl3 (50 mL), and the resulting solution was washed successively
with H2O (10 mL), a saturated aqueous solution of NaHCO3
(2ϫ20 mL), and H2O (10 mL), dried with Na2SO4, and then evap-
orated in vacuo to give 3,3,3-Trifluoro-1-(4-methoxyphenyl)pro-
Acknowledgments
This project was supported by the Russian Foundation for Basic
Research (grant numbers 12-03-90822 and 12-03-90834) and the
Federal Grant-in-Aid Program “Human Capital for Science and
Education in Innovative Russia” for 2009–2013 (agreement number
14.B37.21.0794).
1
pan-1-one (5d); m.p. 44–46 °C. H NMR (500 MHz, CDCl3): δ =
3.74 (q, JH,F = 10.0 Hz, 2 H, CH2), 3.88 (s, 3 H, OMe), 6.96 (d, J
= 8.3 Hz, 2 H, Ar), 7.91 (d, J = 8.3 Hz, 2 H, Ar) ppm. 19F NMR
(470 MHz, CDCl3): δ = –62.62 (t, JH,F = 10.0 Hz, CF3) ppm. 13C
NMR (125 MHz, CDCl3, C-H coupled): δ = 41.8 (qt, J = 128.5,
28.1 Hz, CH2), 55.5 (q, J = 143.9 Hz, OMe), 114.1 (dd, J = 161.0,
4.4 Hz), 124.1 (qt, J = 275.3, 8.0 Hz, CF3), 129.0 (t, J = 7.1 Hz),
130.8 (dd, J = 159.7, 6.9 Hz), 164.4 (d, J = 8.0 Hz), 188.1 (q, J =
[1] a) G. A. Olah, G. K. S. Prakash, A. Molnar, J. Sommer, Su-
peracid Chemistry, 2nd ed., Wiley, New York, 2009; b) G. A.
Olah, D. A. Klumpp, Superelectrophiles and their Chemistry,
John Wiley & Sons, New York, 2008; c) G. A. Olah, P.
v. R. Schleyer, Carbonium Ions, John Wiley & Sons Inc., New
York, 1968–1976, vol. 1–5; d) V. A. Koptyug, Arenonium Ions:
Structure and Reactivity (in Russian), Nauka, Novosibirsk,
1983.
2.2 Hz, C=O) ppm. IR: ν = 1686 (C=O) cm–1. GC–MS (EI): m/z
˜
(%) = 218 (36) [M]+, 135 (100), 107 (11), 92 (14), 77 (19).
C10H9F3O2 (218.17): calcd. C 55.05, H 4.16; found C 55.01, H 4.11.
General Procedure for Generation of the Cations B1–B3 in TfOH:
A solution of alkyne 1 (20 mg) in benzene (0.05 mL, method a),
neat alkene 3 (20 mg, method b), or neat alcohol 4 (20 mg, method
c) was added to TfOH (1 mL) in a NMR tube at room temperature.
The internal standard CH2Cl2 was added, and the NMR tube was
gently shaken. 1H, 13C, 19F NMR spectra of the cations B1–B3
were recorded at room temperature.
[2] G. K. S. Prakash, P. R. Schleyer, Stable Carbocation Chemistry,
John Wiley & Sons Inc., New York, 1997.
[3] a) P. J. Stang, R. Summerville, J. Am. Chem. Soc. 1969, 91,
4600–4604; b) G. A. Olah, R. J. Spear, J. Am. Chem. Soc. 1975,
97, 1845–1849; c) S. Walspurger, A. V. Vasilyev, J. Sommer, P.
Pale, P. Yu. Savechenkov, A. P. Rudenko, Russ. J. Org. Chem.
2005, 41, 1485–1492; d) A. V. Vasilyev, S. Walspurger, S. Chas-
saing, P. Pale, J. Sommer, Eur. J. Org. Chem. 2007, 34, 5740–
5748.
[4] a) V. D. Nefedov, E. N. Sinotova, V. P. Lebedev, Russ. Chem.
Rev. 1992, 61, 283–296; b) P. Yu. Savechenkov, A. P. Rudenko,
A. V. Vasilyev, G. K. Fukin, Russ. J. Org. Chem. 2005, 41,
1316–1328; c) S. A. Aristov, A. V. Vasilyev, G. K. Fukin, A. P.
Rudenko, Russ. J. Org. Chem. 2007, 43, 691–705; d) A. O.
Shchukin, A. V. Vasilyev, Appl. Catal. A 2008, 336, 140–147; e)
A. O. Shchukin, A. V. Vasilyev, Tetrahedron 2008, 64, 6334–
6340; f) A. O. Shchukin, A. V. Vasilyev, S. A. Aristov, G. K.
Fukin, A. P. Rudenko, Russ. J. Org. Chem. 2008, 44, 965–979;
g) D. A. Klumpp, R. Rendy, Y. Zhang, A. McElrea, A. Gomez,
H. Dang, J. Org. Chem. 2004, 69, 8108–8110; h) Y. Zhang,
3,3,3-Trifluoro-1,1-diphenylprop-1-ylium (B1): 1H NMR (500 MHz,
TfOH): δ = 4.90 (q, JH,F = 8.5 Hz, 2 H, CH2), 8.07 (t, J = 7.5 Hz,
4 H, Ph), 8.20 (d, J = 7.5 Hz, 4 H, Ph), 8.54 (t, J = 7.5 Hz, 2 H,
Ph) ppm. 19F NMR (470 MHz, TfOH): δ = –58.56 (t, JH,F
=
8.5 Hz, CF3) ppm. 13C NMR (125 MHz, TfOH): δ = 39.8 (q, JC,F
= 32 Hz, CH2), 119.1 (q, JC,F = 278 Hz, CF3), 128.0 (Cmeta, Ph),
137.9 (Cipso, Ph), 137.8 (Cortho, Ph), 145.3 (Cpara, Ph), 207.0
(C+) ppm.
3,3,3-Trifluoro-1-(4-methoxyphenyl)-1-phenylprop-1-ylium (B2): 1H
NMR (500 MHz, TfOH): δ = 4.46 (s, 3 H, MeO), 4.53 (q, JH,F
=
8.5 Hz, 2 H, CH2), 7.53 (br. d, J = 8.0 Hz, 2 H, Ar), 7.76 (br. d, J
= 7.0 Hz, 2 H, Ph), 7.83 (br. t, J = 7.0 Hz, 2 H, Ph), 8.04 (br. d, J
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. V. Vasilyev, V. G. Nenajdenko et al.
FULL PAPER
Tetrahedron 2006, 62, 3917–3927; i) R. Rendy, Y. Zhang, A.
McElrea, A. Gomez, D. A. Klumpp, J. Org. Chem. 2004, 69,
2340–2347.
[15] G. Nemeth, R. Kapiller-Dezsofi, G. Lax, G. Simig, Tetrahedron
1996, 52, 12821–12826.
[16] a) R. A. Magarian, L. B. Overacre, S. Singh, K. L. Meyer, Curr.
Med. Chem. 1994, 1, 61–74; b) V. C. Jordan, J. Med. Chem.
2003, 46, 883–908; c) V. C. Jordan, J. Med. Chem. 2003, 46,
1081–1090.
[5] G. V. Roitburd, V. A. Smit, A. V. Semenovskii, V. F. Kucherov,
O. S. Chizhov, Izv. Akad. Nauk SSSR, Ser. Khim. 1972, 10,
2225–2231.
[6] a) X. Zeng, R. Kinjo, B. Donnadieu, G. Bertrand, Angew.
Chem. 2010, 122, 954; Angew. Chem. Int. Ed. 2010, 49, 942–
[17] X. Liu, M. Shimizu, T. Hiyama, Angew. Chem. 2004, 116, 897;
Angew. Chem. Int. Ed. 2004, 43, 879–879.
945; b) N. Asao, Y. S. Salprima, T. Nogami, Y. Yamamoto, [18] E. J. Cho, S. L. Buchwald, Org. Lett. 2011, 13, 6552–6555.
Angew. Chem. 2005, 117, 5662; Angew. Chem. Int. Ed. 2005,
44, 5526–5528; c) A. Matsnev, S. Noritake, Y. Nomura, E. To-
kunaga, S. Nakamura, N. Shibata, Angew. Chem. 2010, 122,
582; Angew. Chem. Int. Ed. 2010, 3, 572–576; d) K. Yu. Koltu-
nov, S. Walspurger, J. Sommer, Eur. J. Org. Chem. 2004, 19,
4039–4047; e) A. V. Vasilyev, S. Walspurger, M. Haouas, J.
Sommer, P. Pale, A. P. Rudenko, Org. Biomol. Chem. 2004, 2,
3483–3489; f) A. V. Vasilyev, S. Walspurger, P. Pale, J. Sommer,
M. Haouas, A. P. Rudenko, Russ. J. Org. Chem. 2004, 40,
1769–1778; g) D. S. Ryabukhin, A. V. Vasilyev, Russ. J. Org.
Chem. 2008, 44, 1849–1851; h) D. S. Ryabukhin, G. K. Fukin,
A. V. Cherkasov, A. V. Vasilyev, Russ. J. Org. Chem. 2009, 45,
1252–1254; i) D. S. Ryabukhin, A. V. Vasilyev, E. V. Grinenko,
Russ. J. Org. Chem. 2011, 47, 619–621.
[19] a) T. Konno, J. Chae, T. Tanaka, T. Ishihara, H. Yamanaka, J.
Fluorine Chem. 2006, 127, 36–43; b) T. Konno, J. Chae, T.
Tanaka, T. Ishihara, H. Yamanaka, Chem. Commun. 2004,
690–691; c) T. Konno, K. Taku, T. Ishihara, J. Fluorine Chem.
2006, 127, 966–972; d) T. Konno, T. Daitoh, A. Noiri, J. Chae,
T. Ishihara, H. Yamanaka, Org. Lett. 2004, 6, 933–936.
[20] a) K. Zhang, Y. Huang, F.-L. Qing, X.-L. Qiu, Eur. J. Org.
Chem. 2012, 1, 58–61; b) A. Yu. Rulev, I. A. Ushakov, E. V.
Kondrashov, V. M. Muzalevskiy, V. G. Nenajdenko, A. V. Shas-
tin, J. Fluorine Chem. 2011, 132, 945–950; c) V. G. Nenajdenko,
V. M. Muzalevskiy, E. S. Balenkova, A. V. Shastin, E. V. Kond-
rashov, I. A. Ushakov, A. Yu. Rulev, J. Org. Chem. 2010, 75,
5679–5688; d) V. M. Muzalevskiy, V. G. Nenajdenko, E. S. Ba-
lenkova, A. V. Shastin, G. Haufe, Synthesis 2009, 13, 2249–
2259; e) A. Yu. Rulev, V. M. Muzalevskiy, E. V. Kondrashov,
I. A. Ushakov, A. V. Shastin, E. S. Balenkova, G. Haufe, V. G.
Nenajdenko, Eur. J. Org. Chem. 2010, 300–310; f) A. A. Gold-
berg, V. M. Muzalevskiy, A. V. Shastin, E. S. Balenkova, V. G.
Nenajdenko, J. Fluorine Chem. 2010, 131, 384–388; g) V. G.
Nenajdenko, V. M. Muzalevskiy, A. V. Shastin, E. S. Balen-
kova, G. Haufe, J. Fluorine Chem. 2007, 128, 818–826; h) V. G.
Nenaidenko, V. N. Korotchenko, A. V. Shastin, D. A. Tyurin,
E. S. Balenkova, Russ. Chem. Bull. 2003, 52, 1835–1840; i)
V. M. Muzalevskiy, A. V. Shastin, E. S. Balenkova, V. G.
Nenajdenko, Russ. Chem. Bull. 2007, 56, 1526–1533.
[7] For a recent monograph on vinyl cations, see: Z. Rappoport,
P. J. Stang (Eds.), Dicoordinated Carbocations, Wiley, New
York, 1997.
[8] C. A. Grob, J. Csapilla, G. Cseh, Helv. Chim. Acta 1964, 47,
1590–1600.
[9] a) F.-P. Kaufmann, H.-U. Siehl, J. Am. Chem. Soc. 1992, 114,
4937–4944; b) H.-U. Siehl, F.-P. Kaufmann, K. Hori, J. Am.
Chem. Soc. 1992, 114, 9343–9352; c) H.-U. Siehl, Pure Appl.
Chem. 1995, 67, 769–776; d) H.-U. Siehl in Stable Carbocation
Chemistry (Eds.: G. K. S. Prakash, P. v. R. Schleyer), Wiley,
New York, 1997, pp. 165–197; e) H.-U. Siehl, F.-P. Kaufmann,
Y. Apeloig, V. Braude, D. Danovich, A. Berndt, N. Stamatis,
Angew. Chem. 1991, 103, 1546; Angew. Chem. Int. Ed. Engl.
1991, 30, 1479–1483; f) H.-U. Siehl, T. Müller, J. Gauss, P. Bu-
zek, P. v. R. Schleyer, J. Am. Chem. Soc. 1994, 116, 6384–6391;
g) T. Okuyama, Acc. Chem. Res. 2002, 35, 12–18.
[21] DFT calculations were performed using the program PC-
Gamess
(A. A.
Granovsky,
Firefly,
v. 7.1c,
2009).
᭿᭿((Ͻ=Author: is Granovsky the programmer? is there a ci-
tation or URL available for a more informative citation?))᭿᭿
The hybrid B3LYP functionals with 6-311(2p,2d) basis set were
used. The absence of imaginary frequencies shows that the mo-
lecules are at minimum potential energy.
[10] T. Müller, M. Juhasz, C. A. Reed, Angew. Chem. 2004, 116,
1569; Angew. Chem. Int. Ed. 2004, 43, 1543–1546.
[11] a) K. v. Alem, G. Belder, G. Lodder, H. Zuilhof, J. Org. Chem.
2005, 70, 179–190; b) M. McAllister, T. T. Tidwell, M. R. Pe-
terson, G. I. Csizmadia, J. Org. Chem. 1991, 56, 575–580; c)
K. v. Alem, G. Lodder, H. Zuilhof, J. Phys. Chem. A 2002, 106,
10681–10690.
[12] For a review and the references cited therein, see: A. V. Vasi-
lyev, Russ. J. Org. Chem. 2009, 45, 1–17.
[22] a) P. K. Chattaraj, S. Giri, S. Duley, Chem. Rev. 2011, 111, 43–
75; b) V. G. Nenajdenko, A. M. Moissev, E. S. Balenkova, Russ.
Chem. Bull. 2004, 53, 2241–2265; c) V. G. Nenajdenko, V. N.
Korotchenko, A. V. Shastin, D. A. Tyurin, E. S. Balenkova,
Russ. J. Org. Chem. 2004, 40, 1750–1758.
[23] a) A. O. Shchukin, A. V. Vasilyev, E. V. Grinenko, Russ. J. Org.
Chem. 2010, 46, 82–97; b) A. V. Vasilyev, A. O. Shchukin, Russ.
J. Org. Chem. 2006, 42, 1239–1241.
[24] N. Yoneda, S. Matsuoka, N. Miyaura, T. Fukuhara, A. Suzuki,
Bull. Chem. Soc. Jpn. 1990, 63, 2124–2126.
[25] M. Kawatsura, J. Namioka, K. Kajita, M. Yamamoto, H.
Tsuji, T. Itoh, Org. Lett. 2011, 13, 3285–3287.
[26] a) A. D. Allen, G. Angelini, C. Paradisi, A. Stevenson, T. T.
Tidwell, Tetrahedron Lett. 1989, 30, 1315–1318; b) R. A. Cox,
E. Grant, T. Whitaker, T. T. Tidwell, Can. J. Chem. 1990, 68,
1876–1881.
[27] E. J. Cho, S. L. Buchwald, Org. Lett. 2011, 13, 6552–6555.
[28] T. Konno, J. Chae, T. Tanaka, T. Ishihara, H. Yamanaka, J.
Fluorine Chem. 2006, 127, 36–43.
[29] T. Konno, T. Daitoh, A. Noiri, J. Chae, T. Ishihara, H. Yam-
anaka, Org. Lett. 2004, 6, 933–936.
[30] P. V. Pham, D. A. Nagib, D. W. C. MacMillan, Angew. Chem.
2011, 123, 6243; Angew. Chem. Int. Ed. 2011, 50, 6119–6122.
[31] Ch.-P. Zhang, Z.-L. Wang, Q.-Y. Chen, J.-C. Xiao, C.-T.
Zhang, Y.-C. Gu, Chem. Commun. 2011, 47, 6632–6634.
Received: October 16, 2012
[13] a) T. Hiyama, Organofluorine Compounds: Chemistry and Ap-
plications, Springer, Berlin, 2000; b) R. D. Chambers, Fluorine
in Organic Chemistry, Blackwell, Oxford, 2004; c) P. Kirsch,
Modern Fluoroorganic Chemistry: Synthesis Reactivity, Applica-
tions, Wiley-VCH, Weinheim, 2004; d) K. Uneyama, Organ-
ofluorine Chemistry, Blackwell, Oxford, 2006; e) G. Theodor-
idis, Fluorine-Containing Agrochemicals: An Overview of Recent
Developments in: Advances in Fluorine Science (Ed.: A. Tres-
saud), Elsevier, Amsterdam, 2006, vol. 2, pp. 121–175; f) J. P.
Bégué, D. Bonnet-Delpon, Bioorganic and Medicinal Chemistry
of Fluorine, John Wiley & Sons, Hoboken, 2008; g) A. Tres-
saud, G. Haufe (Eds.), Fluorine and Health. Molecular Imaging,
Biomedical Materials and Pharmaceuticals, Elsevier, Amster-
dam, 2008, pp. 553–778; h) A. Gakh, K. L. Kirk (Eds.), Fluori-
nated Heterocycles, Oxford University Press, Oxford, UK,
2008; i) V. A. Petrov (Ed.), Fluorinated Heterocyclic Com-
pounds: Synthesis Chemistry, and Applications, John Wiley &
Sons, Hoboken, 2009.
[14] M. Shimizu, Y. Takeda, M. Higashi, T. Hiyama, Angew. Chem.
2009, 121, 3707; Angew. Chem. Int. Ed. 2009, 48, 3653–3656.
Published Online: ᭿
12
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Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O21375
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Date: 07-01-13 16:30:29
Pages: 13
Regiocontrolled Hydroarylation of (Trifluoromethyl)acetylenes
Vinyl Cations
The superacidic generation of vinyl cations
from aryl(trifluoromethyl)acetylenes was
effectively performed using triflic and
fluorosulfonic acids under mild conditions.
H. M. H. Alkhafaji, D. S. Ryabukhin,
V. M. Muzalevskiy, A. V. Vasilyev,*
G. K. Fukin, A. V. Shastin,
V. G. Nenajdenko* .......................... 1–13
These vinyl cations underwent
a sub-
sequent reaction with various arenes to
give the corresponding alkenes and al-
cohols in high yields. The formation of
these trifluoroethylated carbocations was
confirmed by NMR spectroscopy.
Regiocontrolled Hydroarylation of (Tri-
fluoromethyl)acetylenes in Superacids: Syn-
thesis of CF3-Substituted 1,1-Diarylethenes
Keywords: Superacidic systems / Carbo-
cations / Alkenes / Hydroarylation / Regio-
selectivity
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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