Reaction of Perfluorobenzocyclobutene with Excess Pentafluorobenzene in SbF5

Article abstract of DOI:10.1134/S107042801804005X

The reaction of perfluorobenzocyclobutene with excess pentafluorobenzene in SbF₅, followed by hydrolysis, gave a mixture of perfluoro-1,3,3-triphenyl-1,3-dihydro-2-benzofuran-1-ol, perfluoro-1,1,2-triphenylbenzocyclobuten- 5-one, and perfluoro-4-(2,2-diphenylbenzocyclobuten-1-ylidene)cyclohexa-2,5-dien-1- one. When the reaction mixture was treated for a long time with Olah’s reagent (HF–pyridine), isomeric perfluoro-9,10-diphenyl-1,4-, -1,10-, -2,9-, and -9,10-dihydroanthracenes were formed and were converted to perfluoro-9,10-diphenylanthracene by the action of SbF₅.

Full text of DOI:10.1134/S107042801804005X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2018, Vol. 54, No. 4, pp. 545–553. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © T.V. Mezhenkova, V.R. Sinyakov, V.M. Karpov, Ya.V. Zonov, Yu.V. Gatilov, V.E. Platonov, 2018, published in Zhurnal Organicheskoi
Khimii, 2018, Vol. 54, No. 4, pp. 546–553.
Reaction of Perfluorobenzocyclobutene with Excess
Pentafluorobenzene in SbF5
T. V. Mezhenkovaa,* V. R. Sinyakova, V. M. Karpova, Ya. V. Zonova, b,
Yu. V. Gatilova, b, and V. E. Platonova
a Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 9, Novosibirsk, 630090 Russia
*e-mail: mtv@nioch.nsc.ru
b Novosibirsk State University, ul. Pirogova 1, Novosibirsk, 630090 Russia
Received July 5, 2017
Abstract—The reaction of perfluorobenzocyclobutene with excess pentafluorobenzene in SbF5, followed by
hydrolysis, gave a mixture of perfluoro-1,3,3-triphenyl-1,3-dihydro-2-benzofuran-1-ol, perfluoro-1,1,2-tri-
phenylbenzocyclobuten-5-one, and perfluoro-4-(2,2-diphenylbenzocyclobuten-1-ylidene)cyclohexa-2,5-dien-1-
one. When the reaction mixture was treated for a long time with Olah’s reagent (HF–pyridine), isomeric
perfluoro-9,10-diphenyl-1,4-, -1,10-, -2,9-, and -9,10-dihydroanthracenes were formed and were converted to
perfluoro-9,10-diphenylanthracene by the action of SbF5.
DOI: 10.1134/S107042801804005X
Perfluoro-1,2-dialkyl-1-phenylbenzocyclobutenes
in which the perfluoroalkyl groups in positions 1 and 2
are different react with antimony pentafluoride through
opening of the four-membered ring and/or its expan-
sion to five-membered ring, whereas the pentafluoro-
benzene ring remains unchanged [1]. The reaction of
perfluoro-1,2-diethyl-1-phenylbenzocyclobutene with
antimony pentafluoride involves both opening of the
four-membered ring and unusual expansion of the
pentafluorobenzene ring to seven-membered ring
[2, 3]. This is the only example of cationoid expansion
of polyfluorobenzene ring. In order to find out the
possibility of analogous transformations in the series
of perfluoro-1,2-diaryl-1-phenylbenzocyclobutenes it
was necessary to study the behavior of perfluoro-1,1,2-
triphenylbenzocyclobutene under the action of anti-
mony pentafluoride.
For this purpose, perfluorobenzocyclobutene 1 was
treated with excess pentafluorobenzene (3 equiv) in
SbF5 at 50–55°C. The subsequent hydrolysis of the
Scheme 1.
C6F5
C6F5
C6F5
C6F5
6
F
3
C6F5
(1) C6F5H (3 equiv), SbF5, 50–55°C
(2) H2O
O
C6F5
5
4
1
F
F
F
F
+
+
O
2
2'
C6F5
C6F5
3'
HO
F
6'
5'
O
1
2
3
4
O
C6F5
OH
C6F5
C6F5
F
F
+
+
F
F
O
5
6
545

MEZHENKOVA et al.
546
Scheme 2.
C6F5
F
C6F5
(1) C6F5H (3 equiv), SbF5, 50–55°C
(2) HF–Py, 0.5 h
(3) H2O
C6F5
C6F5
3
6'
1'
2'
4
2
1
5'
4'
F
F
F
F
F
F
2
+
+
+
O
F
5
CF2
O
3'
6
C6F5
F
C6F5
C6F5
1
7
8
9
C6F5
C6F5
F
F
F
F
+
5
+
6
+
+
C6F5
10
11
(1) SbF5; (2) H2O
11
6
C6F5
C6F5
F
C6F5
F
(1) C6F5H (3 equiv), SbF5, 50–55°C
(2) HF–Py, 65 h
(3) H2O
F
F
F
F
F
F
F
F
F
8
+
+
+
C6F5
12
C6F5
C6F5
1
13
14
+
2
+
6
+
10
+
11
C6F5
(1) SbF5; (2) H2O
F
F
F
8
+
12
+
13
+
14
C6F5
15
reaction mixture led to the formation of a mixture of
perfluoro-1,3,3-triphenyl-1,3-dihydro-2-benzofuran-1-
ol 2, perfluoro-1,1,2-triphenylbenzocyclobuten-5-one
3, and perfluoro-4-(2,2-diphenylbenzocyclobuten-1-
ylidene)cyclohexa-2,5-dien-1-one 4. In addition, the
reaction mixture contained perfluoro-1-phenylbenzo-
cyclobuten-1-ol 5 and perfluoro[1,2-phenylenebis-
(phenylmethanone)] 6 (Scheme 1).
When the reaction mixture obtained under analo-
gous conditions from compound 1 and 3 equiv of
C6F5H in SbF5 was treated first with a mixture of
pyridine and hydrogen fluoride (Olah’s reagent) over
a period of 0.5 h and then with water, the product was
a mixture of perfluoro-1,1,3-triphenyl-1,3-dihydro-2-
benzofuran 7 and small amounts of perfluoro-9,10-di-
phenyl-9,10-dihydroanthracene 8, perfluoro-4-[(2-ben-
zylphenyl)(phenyl)methylidene]cyclohexa-2,5-dien-1-
one 9, and compounds 2, 5, and 6. In addition, per-
fluoro-1-phenylbenzocyclobutene 10 and perfluoro-
1,2-diphenylbenzocyclobutene 11 were detected
together with unidentified compounds (Scheme 2).
Prolonged treatment (65 h) with Olah’s reagent of
the mixture obtained from 1 and 3 equiv of C6F5H in
SbF5 at 50–55°C and subsequent hydrolysis afforded
perfluoro-9,10-diphenyl-9,10-dihydroanthracene 8,
perfluoro-9,10-diphenyl-1,10-dihydroanthracene 12,
perfluoro-9,10-diphenyl-2,9-dihydroanthracene 13,
perfluoro-9,10-diphenyl-1,4-dihydroanthracene 14,
and compounds 2, 6, 10, and 11. By special experi-
ments we showed that hydrolysis of a mixture of 11
and SbF5 yields diketone 6 and that compound 8 or
a mixture of 8, 12, 13, and 14 is thus converted to
perfluoro-9,10-diphenylanthracene 15 (Scheme 2).
Compound 15 is likely to be formed as a result of
disproportionation of 8, 12, 13, or 14 and/or their de-
fluorination under the given conditions. Dispropor-
tionation of polyfluorinated cyclohexadienes to the
corresponding aromatic compounds and cyclohexenes
by the action of SbF5 was reported in [4, 5]; dispro-
portionation [6, 7] and defluorination of perfluoro-1,2-
dialkylindans with other fluorinated hydrocarbons in
SbF5 [8, 9] are also known.
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REACTION OF PERFLUOROBENZOCYCLOBUTENE
547
Scheme 3.
C6F5
C6F5
C6F5
C6F5
C6F5
SbF5
C6F5H
–H+
10
F
F
F
F
F
–F–
F
A
16
B
C6F5
F
C6F5
C6F5
F–
–F–
F
F
F
C6F5
C
11
C6F5
C6F5
C6F5
C6F5
C6F5H
–H+
SbF5
–F–
H2O
*
B or C
3 + 4
F
F
F
C6F5
C6F5
F
F
F
*
17
D
E
Presumably, the reaction of 1 with excess penta-
fluorobenzene involves initial formation of perfluoro-
1-phenylbenzocyclobutene 10 which generates cation
A by the action of SbF5 [10]; cation A takes up penta-
fluorobenzene molecule to give perfluoro-1,1-di-
phenylbenzocyclobutene 16, and the latter isomerizes
to structure 11 via 1,2-migration of the pentafluoro-
phenyl group in intermediate cation B and subsequent
addition of fluoride ion to cation C (Scheme 3).
sponding perfluoro-1-phenylbenzocycloalken-1-yl
cations [10], which should hamper reaction at the CF2
group. Furthermore, increased dihedral angle between
the pentafluorophenyl substituent and the plane includ-
ing the tetrafluorobenzene ring, cationic center, and
atoms linked thereto reduces steric accessibility of the
cationic center in going from cation A to those derived
from 18 and 19. According to MNDO calculations, this
dihedral angle in cations generated from 10, 18, and 19
is ~23, ~64, and ~85°, respectively [10].
Cations B and C react further with pentafluoro-
benzene to produce perfluoro-1,1,2-triphenylbenzo-
cyclobutene 17 which is likely to be converted in SbF5
to cation D due to elimination of fluoride ion. The
hydrolysis of D leads to compounds 3 and 4 as a result
of nucleophile addition to sterically more accessible
electrophilic centers (marked with an asterisk in struc-
ture D shown in Scheme 3). The possibility of penta-
fluorophenyl group migration to the neighboring cat-
ionic center was considered by us previously [1, 11], in
particular in the isomerization of perfluoro(2-ethyl-1-
methyl-2-phenyl-benzocyclobuten-1-yl) cation to per-
fluoro(1-ethyl-2-methyl-2-phenylbenzocyclobuten-1-
yl) cation [1].
Before proceeding to consider paths of formation of
other compounds given in Schemes 1 and 2, it should
be emphasized that the reaction mixture obtained from
compound 1 and excess C6F5H in SbF5 was a viscous
semi-solid material. Therefore, its hydrolysis occurred
at the phase boundary with water, so that additional
transformations involving both components of the
reaction mixture (SbF5, HF) and water could be
possible in the interface layer. Here, local overheating
cannot be ruled out.
Perfluorodihydroanthracenes 8 and 12–14 are likely
to be formed as a result of transformations of per-
fluorotriphenylbenzocyclobutene 17 (Scheme 4). In
keeping with the proposed mechanism, protonation of
17 with HF–SbF5 yields cations F1 and F2 which
undergo isomerization to cations G1 and G2 through
opening of the four-membered ring in a way similar to
that considered previously for polyfluoroalkylbenzo-
cyclobutenes and perfluoro-1-(2-ethylphenyl)- and per-
fluoro-1-(4-ethylphenyl)benzocyclobutenes [7, 8, 12].
The cyclization of G1 and G2 with elimination of
The formation of 11 by reaction of cation E with
C6F5H seems less probable since its concentration in
SbF5 is extremely low as compared to cation A.
Furthermore, neither perfluoro-1-phenylindan 18 nor
perfluoro-1-phenyltetralin 19 takes up pentafluoro-
benzene at any benzylic position. This behavior of 18
and 19 may be rationalized by the fact that these
compounds, as well as 10, in SbF5 exist as the corre-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 4 2018

MEZHENKOVA et al.
548
Scheme 4.
H
C6F5
F
C6F5
F
F
F
F
C6F5
CF
H
C6F5
C6F5
G1
F1
H+
17
F
F
–H+
C6F5
C6F5
C6F5
F
C6F5
C6F5
F
20
F
F
F
F
F
CF
F
CF
F
F
F
H
H
H
F2
G2
≠
C6F5
F
8
12
13 or 14
F
F
F
H
–HF
C6F5
F
HF
TS1
≠
C6F5
13
F
F
–HF
F
F
C6F5
H
F
TS2
proton gives compound 20, and the latter isomerizes to
dihydroanthracenes 8 and 12–14.
generates cation H, and cyclization of H followed by
addition of fluoride ion leads to perfluoro-1,1,3-tri-
phenyl-1,3-dihydro-2-benzofuran 7. Compound 7 is
converted to perfluoro-1,3,3-triphenyl-1,3-dihydro-
2-benzofuran-1-ol 2 via successive reactions with
SbF5 and H2O.
Alternatively, proton elimination from cation G1
produces compound 23 which is fluorinated to 24, and
abstraction of fluoride ion from 24 yields cation I.
Hydrolysis of I gives compound 9 and hydroxy
derivative 25. The latter undergoes cyclization to 7 by
the action of SbF5. Compound 24 can also be con-
verted to cation J whose hydrolysis leads to ketone 22,
and the subsequent steps leading to structure 7 are the
same as those considered above (Scheme 5).
Presumably, compound 20 is converted to isomeric
structure 8 through transition state TS1 with participa-
tion of HF, whereas isomer 13 is formed through
transition state TS2 (Scheme 4). The isomerization of 8
to dihydroanthracene 12 and then to 13 and 14 can be
represented in a similar way. Analogous six-membered
cyclic transition state was presumed previously, e.g.,
for the isomerization of 1,2,3,4,5,6,7-heptafluoro-
indene to 1,1,2,4,5,6,7-heptafluoroindene by the action
of HF [13], as well as for the isomerization of terminal
fluoroolefins into internal ones in the presence of
antimony pentafluoride [14].
The reaction of G1 with water (Scheme 5) gives
compound 21 whose fluorination and subsequent de-
hydrofluorination yields ketone 22. Abstraction of
fluoride ion from the latter by the action of SbF5
Scheme 6 outlines the transformation sequence of
diphenylbenzocyclobutene 11 to diketone 6 on treat-
ment with water of a mixture of 11 and SbF5. Com-
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REACTION OF PERFLUOROBENZOCYCLOBUTENE
549
Scheme 5.
C6F5
CO
C6F5
F
C(C6F5)2
F–
SbF5_H2O
SbF5
–F–
H2O
[2F]
–HF
G1
2
7
F
F
F
F
F
H
CO
CO
C6F5
C6F5
C6F5
H
22
21
–H+
SbF5
–HF
H2O
CF(C6F5)2
CFC6F5
F
SbF5
–F–
J
C6F5
C6F5
OH
CFC6F5
C(C6F5)2
CF2C6F5
C(C6F5)2
SbF5
–F–
[2F]
H2O
F
9
+
F
F
F
F
CF2C6F5
CF2C6F5
F
C6F5
24
23
I
25
Scheme 6.
C6F5
OH
C6F5
OH
C6F5
O
SbF5
–F–
SbF5
–F–
H2O
–H+
11
C
F
F
F
–H+
C6F5
C6F5
C6F5
F
26
K
27
F
F
C6F5
O
C6F5
O
C6F5
SbF5
SbF5
–F–
H2O
–H+
–HF
C6F5
O
F
F
F
F
F
6
O
–SbF3
C6F5
C6F5
C6F5
C6F5
28
29
L
M
for the transformation of perfluoro-1,2-diethylbenzo-
cyclobutene to perfluoro-1,3-diethyl-1,3-dihydro-2-
benzofuran-1,3-diol in the reaction with SiO2‒SbF5.
Presumably, compound 29 can also be formed from
diphenylbenzocyclobutene 11 according to a scheme
analogous to Scheme 5 (transformation of 17 to 7).
pound 11 in SbF5 is likely to lose fluoride ion,
generating cation C which reacts with water to form
hydroxy derivative 26. Compound 26 is converted
to cation K by the action of SbF5, and intramolec-
ular attack of the cationic center on the oxygen atom in
K, followed by elimination of proton, yields epoxy
derivative 27. The latter isomerizes to perfluoro-1,3-
diphenyl-2-benzofuran 28 whose fluorination leads to
perfluoro-1,3-diphenyl-1,3-dihydro-2-benzofuran 29
and then (after elimination of fluoride ion) to cation L.
Opening of the five-membered ring in L gives cation
M which is hydrolyzed with water to afford diketone
6. The proposed sequence of formation of diketone 6
from compound 11 is analogous to that given in [15]
The structure of compounds 2–4, 6–9, and 11–15
was determined by elemental analysis, high-resolution
mass spectrometry, and 19F NMR spectroscopy. The
structure of 2 was also confirmed by 13C NMR. In
particular, the 13C NMR spectrum of 2 in CDCl3
contained no signal assignable to carbonyl carbon
atom, and no carbonyl stretching band was observed in
its IR spectrum. These findings ruled out alternative
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 54 No. 4 2018

MEZHENKOVA et al.
550
F10
C16
EXPERIMENTAL
F7
F9
F6
C11
F11
The analytical and spectral data were obtained at
the Joint Chemical Service Center, Siberian Branch,
Russian Academy of Sciences. The IR spectra were
recorded on a Bruker Vector 22 spectrometer. The
19F NMR spectra of cis-8 in (CD3)2CO and of the other
compounds in CDCl3 and the 13C NMR spectrum of 2
in CDCl3 were measured on a Bruker AV-300 spec-
trometer at 282.4 (19F) and 75.5 MHz (13C); the
chemical shifts are given downfield from C6F6 (19F) or
Me4Si; C6F6 and CDCl3 (δC 76.9 ppm) were used as
internal standards. The elemental compositions were
determined from the high-resolution mass spectra
which were obtained on a Thermo Electron Cor-
poration DFS instrument. GLC analysis was performed
with an LKhM-72 chromatograph [4000×4-mm col-
umn packed with SKTFT-50 on Chromosorb W
(15:100), oven temperature 50–270°C; carrier gas
helium, flow rate 60 mL/min]. Compositions of the
reaction mixtures and products were determined by
GLC and 19F NMR. Silica gel Merck (0.063‒
0.200 mm) was used for column chromatography.
C12
C9
F8
C15
C14
C13
C17
C18
F12
F5
C10
C8
C7
F20
C26
C20
C21
C19
F2
F19
C24
F15
C4
C3
C1
C25
C5
F3
F1
C22
C2
F13
F18
F16
C23
C6
F4
F17
O1
Fig. 1. Structure of the molecule of perfluoro-4-[(2-benzyl-
phenyl)(phenyl)methylidene]cyclohexa-2,5-dien-1-one (9)
according to the X-ray diffraction data.
perfluoro[(2-benzoylphenyl)diphenylmethanol] struc-
ture. Compounds 5 and 10 were identified by com-
paring their 19F NMR spectra with those of authentic
samples [10]. The structure of 3 and 4 was determined
by comparing their 19F NMR spectra with those of
perfluoro-1-phenyl-1,2-diethylbenzocyclobuten-5-one
and perfluoro-4-(2,2-diethylbenzocyclobuten-1-
ylidene)cyclohexa-2,5-dien-1-one [16]. In addition,
X-ray analysis of single crystals of 8, 9, and 13–15 was
performed. Figure 1 shows the molecular structure of
compound 9.
The X-ray diffraction data for compound 9 were
obtained on a Bruker Kappa Apex diffractometer
(Mo Kα radiation, 296 K). Monoclinic crystal system,
space group P21/n; unit cell parameters: a =
10.5237(5), b = 13.8880(5), c = 16.2409(7) Å; β =
96.527(2)°; Z = 4; dcalc = 1.995 g/cm3; μ = 0.231 mm–1;
θ ≤ 27.9°. Total of 43786 reflection intensities were
measured, including 5601 independent reflections.
Final divergence factors: R = 0.0534 [for 4545 reflec-
tions with I > 2σ(I)], wR2 = 0.1367 (for all independent
reflections). The positions of non-hydrogen atoms
were refined in anisotropic approximation. All cal-
culations were performed using SHELXTL software
package. The coordinates of atoms and geometric
parameters were deposited to the Cambridge Crystallo-
graphic Data Centre [CCDC entry nos. 1554816 (9)
and 1547527–1547531 (cis-8, trans-8, 13, 14, and 15,
respectively).
The bond lengths in molecule 9 are close to the
corresponding bond lengths in the molecule of 4-(di-
phenylmethylidene)cyclohexa-2,5-dien-1-one [17].
The diphenylmethylidene fragment in structure 9
slightly deviates from coplanarity with the cyclo-
hexadienone fragment (torsion angle C5C4C7C8 16.7°).
Approximately similar torsion angle (14.5°) was
observed in 4-(diphenylmethylidene)cyclohexa-2,5-
dien-1-one. However, the corresponding angle in
perchloro-4-(diphenylmethyliden)cyclohexa-2,5-dien-
1-one [18] is increased to 34.9°, presumably for steric
reasons. Mutual orientation of the tetrafluorobenzene
and pentafluorobenzene rings in molecule 9 is
characterized by the torsion angle C4C7C8C13 61.7 and
C4C7C14C19 56.1°. Molecules 9 in crystal form centro-
symmetric dimers with short contacts between the
carbonyl groups (O···C 3.11 Å); also, a number of
C–F···π interactions are observed with the fluorine–
centroid distances ranging from 3.46 to 3.73 Å. The
molecular and crystal structures of cis-8, trans-8, and
13–15 were discussed in [19].
Reaction of perfluorobenzocyclobutene 1 with
pentafluorobenzene in antimony pentafluoride.
a. A mixture of 1.77 g (7.14 mmol) of compound 1,
3.6 g (21.43 mmol) of pentafluorobenzene, and 9.29 g
(42.85 mmol) of SbF5 was heated for 50 h at 50–55°C
in a sealed glass ampule. The ampule was cooled to
0°C and opened, the reaction mixture was transferred
into an ice–water mixture (200 mL) with stirring,
30 mL of concentrated aqueous HCl was added, and
the mixture was extracted with methylene chloride
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REACTION OF PERFLUOROBENZOCYCLOBUTENE
551
(3×20 mL). The extract was dried over MgSO4, and
the solvent was distilled off. The residue was 4.8 g of
a mixture containing (according to the GLC and
19F NMR data), compounds 2 (50%), 3 (10.5%), 4
(3%), 5 (6%), and 6 (11%). By silica gel column
chromatography (eluent chloroform) we isolated 0.1 g
(14%) of 6, 0.5 g (48%) of 2, and 0.2 g of isomer
mixture 3/4 (91:9). In addition, fractions containing
compounds 6 and 2, 2 and 3, and others were isolated.
ν, cm–1: 1699, 1685 (C=O), 1524, 1505 (C=Carom).
19F NMR spectrum, δF, ppm: 2.6 m (4F, m-F), 16.2 m
(2F, 4-F, 5-F), 17.1 t.t (2F, p-F, J = 21, 6 Hz), 21.7 m
(4F, o-F), 24.4 m (2F, 3-F, 6-F). Found: [M]+ 537.9666.
C20F14O2. Calculated: M 537.9675.
b. A mixture of 0.43 g (1.74 mmol) of compound 1,
0.87 g (5.21 mmol) of pentafluorobenzene, and 3.01 g
(13.88 mmol) of SbF5 was heated for 30 h at 50–55°C
in a sealed ampule. The ampule was cooled to 0°C and
opened, and the mixture was added to 10 mL of HF–
pyridine at 0–20°C. The mixture was stirred for 0.5 h
at 25°C, cooled to 0°C, and transferred into an ice–
water mixture (100 mL) with stirring. The mixture was
then treated with 10 mL of concentrated aqueous HCl
and extracted with methylene chloride (3×10 mL), the
extract was dried over MgSO4, and the solvent was
distilled off. The residue was 1.06 g of a mixture
containing (GLC, 19F NMR) compounds 2 (4%), 5
(7%), 6 (5%), 7 (22%), cis-8 (4%), 9 (4%), and 10
(10%) and isomers 11a (16%) and 11b (10%). By
column chromatography on silica gel using first carbon
tetrachloride and then chloroform as eluents we
isolated 0.46 g of a mixture of 7, cis-8, 10, 11a, and
11b at a ratio of 28:5:23:27:17 (19F NMR) and 0.02 g
(3.5%) of 9. Repeated chromatography with hexane as
eluent afforded 0.09 g of a mixture of 10 and 11a
(60:40; 19F NMR), 0.06 g of 7, and 0.12 g of a mixture
of 7 and 11b (45:55) (19F NMR).
Perfluoro-1,3,3-triphenyl-1,3-dihydro-2-benzo-
furan-1-ol (2). mp 128–129.5°C (from hexane). IR
spectrum (KBr), ν, cm–1: 3604 (O‒H), 1529, 1499
(C=Carom). 13C NMR spectrum, δC, ppm: 83.2 s (C3),
2
105.1 s (C1), 112.7 t (Ci, JCF ≈12 Hz), 113.0 t (Ci,
2
2JCF ≈ 12 Hz), 115.5 t (Ci, JCF ≈ 10 Hz), 122.9 d (C3a
2
2
or C7a, JCF ≈ 14 Hz), 123.6 d (C7a or C3a, JCF
≈
1
16 Hz), 138–145 d.m (19C, C–F, JCF ≈ 250–260 Hz).
19F NMR spectrum, δF, ppm: 1.5 m (2F, m-F), 1.8 m
(2F, m-F), 2.1 m (2F, m-F), 10.8 t.t (1F, p-F, J = 21,
4 Hz), 11.2 t.t (1F, p-F, J = 21, 4 Hz), 11.3 t.t (1F, p-F,
J = 21, 4 Hz), 11.8 d.d.d (1F, 5-F or 6-F, J = 20, 19,
5 Hz), 12.5 d.d.d (1F, 6-F or 5-F, J = 20, 19, 5 Hz),
20.3 m (1F, 4-F or 7-F), 20.3 m (2F, o-F), 21.0 m
(1F, 7-F or 4-F), 21.4 m (2F, o-F), 22.1 m (2F, o-F).
Found, %: C 44.49; H 0.22; F 51.13. [M]+ 705.9726.
C26HF19O2. Calculated, %: C 44.22; H 0.14; F 51.11.
M 705.9673.
Perfluoro-1,1,2-triphenylbenzocyclobuten-5-one
(3) and perfluoro-4-(2,2-diphenylbenzocyclobuten-
1-ylidene)cyclohexa-2,5-dien-1-one (4) (mixture of
isomers at a ratio of 91:9). mp 186–192°C (from
hexane–CH2Cl2). IR spectrum (KBr), ν, cm–1: 1659
(C=O), 1526, 1493 (C=Carom). 19F NMR spectrum, δF,
ppm: isomer 3: 2.4 m (4F, m-F, 1-C6F5), 3.4 m (2F,
m-F, 2‑C6F5), 11.6 t.t (2F, p-F, 1‑C6F5, J = 21, 4 Hz),
18.2 t.t (1F, p-F, 2‑C6F5, J = 21, 5 Hz), 22.7 m (4F,
o-F, 1‑C6F5), 26.9 d.d (1F, 4-F, J3,4 = J4,6 = 8 Hz),
27.3 m (2F, o-F, 2‑C6F5), 28.0 t.d.d (1F, 3-F, J3,o-F = 38,
Perfluoro-1,1,3-triphenyl-1,3-dihydro-2-benzo-
furan (7). mp 168–171°C (from hexane). 19F NMR
spectrum, δF, ppm: 1.8 m (4F, m-F, C6F5), 2.4 m (2F,
m-F), 12.0 t.t (1F, p-F, J = 21, 4 Hz), 12.1 t.t (1F, p-F,
J = 22, 4 Hz), 12.9 t.t (1F, p-F, J = 21, 5 Hz), 13.9 t.d
(1F, 5-F, J = 19, 4 Hz), 14.3 t.t (1F, 6-F, J = 19, 5 Hz),
21.5 m (2F, o-F), 21.8 m (1F, 4-F or 7-F), 22.2 m (3F,
7-F or 4-F, o-F), 22.9 m (2F, o-F), 88.9 t (1F, 3-F, J =
27 Hz). Found: [M]+ 707.9623. C26F20O. Calculated:
M 707.9624.
J3,6 = J3,4 = 8 Hz), 28.7 quint.d.d (1F, 6-F, J = 14, J3,6
=
Perfluoro-4-[(2-benzylphenyl)(phenyl)methyli-
dene]cyclohexa-2,5-dien-1-one (9). mp 189–192°C
(from hexane–CHCl3). 19F NMR spectrum, δ, ppm:
1.9 m (1F, m-F, C6F5), 2.0 m (1F, m-F, C6F5), 2.7 m
(2F, m-F, CF2C6F5), 13.5 d (1F, 2-F, J = 9 Hz), 13.6 d
(1F, 2-F, J = 10 Hz), 14.2 d.d.d and 14.6 d.d.d (1F
each, 4′-F, 5′-F, J = 21, 21, 6 Hz), 14.9 t (1F, p-F,
CF2C6F5, J = 21 Hz), 15.8 t.t (1F, p-F, C6F5, J = 21,
5 Hz), 21.8 m (2F, o-F, CF2C6F5), 23.2 m (1F, o-F,
C6F5), 24.7 m (1F, 6′-F), 25.5 d.d (1F, 5-F, J = 9, 6 Hz),
26.6 m (1F, o-F, C6F5), 27.8 m (2F, 3-F, 3′-F), 86.1 m
J4,6 = 8 Hz); isomer 4: 2.7 m (4F, m-F, C6F5), 11.0 d
(1F, 3′-F, J2′,3′ = 11 Hz), 11.9 t.t (2F, p-F, C6F5, J = 21,
4 Hz), 12.0 d (1F, 5′-F, J5′,6′ = 11 Hz), 15.6 d.d.d (1F,
4-F, J3,4 = 19, J4,5 = 18, J4,6 = 5 Hz), 23.9 m (1F, 6-F),
24.1 m (4F, o-F, C6F5), 25.6 d.d.d (1F, 6′-F, J3,6′ = 163,
J5′,6′ = 11, J2′,6′ = 6 Hz), 25.8 m (1F, 5-F), 25.8 m (1F,
2′-F), 39.0 d.d.d.d (1F, 3-F, J3,6′ = 163, J3,4 = J3,6 = 19,
J3,5 = 12 Hz). Found, %: C 46.44; F 51.05.
[M]+ 669.9647. C26F18O. Calculated, %: C 46.59;
F 51.02. M 669.9662.
2
Perfluoro[1,2-phenylenebis(phenylmethanone)]
(6). mp 124–126°C (from hexane). IR spectrum (KBr),
and 80.2 m (1F each, CF2, J = 287 Hz). Found:
[M]+ 707.9621. C26F20O. Calculated: M 707.9624.
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MEZHENKOVA et al.
552
Perfluoro-cis(or trans)-1,2-diphenylbenzocyclo-
[M]+ 691.9673. C26F20. Calculated, %: C 45.11.
M 691.9675.
butene (11a). 19F NMR spectrum (from a mixture with
10), δF, ppm: 1.8 m (4F, m-F), 13.4 t (2F, p-F, J =
21 Hz), 18.2 m (2F, 4-F, 5-F), 22.9 m (4F, o-F), 26.3 m
(2F, 3-F, 6-F), 30.6 m (2F, 1-F, 2-F). Found:
[M]+ 543.9742. C20F16. Calculated: M 543.9739.
Perfluoro-trans-9,10-diphenyl-9,10-dihydroan-
thracene (trans-8). mp 355–360°C (decomp., from
acetone; sealed capillary). 19F NMR spectrum, δF,
ppm: 0.9 m (4F, m-F), 9.8 t (2F, p-F, J = 21 Hz),
13.3 m (4F, 2-F, 3-F, 6-F, 7-F), 21.3 m (4F, o-F),
24.7 m (2F, 9-F, 10-F), 26.0 m (4F, 1-F, 4-F, 5-F, 8-F).
Found, %: C 45.21. [M]+ 691.9670. C26F20. Calculated,
%: C 45.11. M 691.9675.
Perfluoro-trans(or cis)-1,2-diphenylbenzocyclo-
butene (11b). 19F NMR spectrum (from a mixture with
7), δF, ppm: 3.0 m (4F, m-F), 14.8 t (2F, p-F, J =
21 Hz), 18.2 m (2F, 4-F, 5-F), 23.3 m (4F, o-F), 25.6 m
(2F, 1-F, 2-F), 26.3 m (2F, 3-F, 6-F). Found:
[M]+ 543.9740. C20F16. Calculated: M 543.9739.
Perfluoro-9,10-diphenyl-1,10-dihydroanthracene
(12). NMR spectrum19F (from a mixture with cis-8 and
13), δF, ppm: –0.3 m (2F, m-F, 9-C6F5), 1.6 m (2F, m-F,
10-C6F5), 7.9 m (1F, 3-F), 10.6 t (1F, p-F, 9- or
10-C6F5, J = 21 Hz), 10.6 m (1F, 2-F), 10.8 t (1F, p-F,
10- or 9-C6F5, J = 21 Hz), 13.5 d.d.d.d (1F, 7-F, J = 20,
20, 7, 5 Hz), 15.5 d.d.d (1F, 6-F, J = 20, 20, 7 Hz),
21.7 m (2F, o-F, 10-C6F5), 23.1 m (1F, o-F, 9-C6F5),
24.0 m (1F, o-F, 9-C6F5), 25.0 m (1F, 5-F), 27.3 m (1F,
10-F), 34.6 m (1F, 8-F), 47.2 m (1F, 4-F), 80.6 m and
76.4 m (1F each, 1-F, 2J = 302 Hz).
c. A mixture of 0.75 g (3.02 mmol) of compound 1,
1.52 g (9.05 mmol) of pentafluorobenzene, and 5.22 g
(24.08 mmol) of SbF5 was heated for 30 h at 50–55°C
in a sealed glass ampule. The ampule was cooled to
0°C and opened, and the mixture was transferred into
15 mL of HF–pyridine at 0–20°C. The mixture was
stirred for 65 h at 25°C, cooled to 0°C, and transferred
into an ice–water mixture (250 mL) with stirring,
30 mL of concentrated aqueous HCl was added, and
the mixture was extracted with methylene chloride
(3×20 mL). The extract was dried over MgSO4, the
solvent was distilled off, the residue was treated with
5 mL of chloroform, and the precipitate, 0.2 g (9.6%)
of trans-8 was filtered off. The filtrate was evaporated,
and the residue, 1.79 g, was a mixture containing
(according to the GLC and 19F NMR data) compounds
2 (27%), 6 (4%), cis-8 (11%), 10 (2%), 11a (9%), 11b
(2%), 12 (10%), 13 (12%), and 14 (2%). By column
chromatography on silica gel using carbon tetra-
chloride as eluent we isolated from that mixture 0.51 g
of a solid consisting of cis-8, 12, 13, and 14 at a ratio
of 30:30 :35:5 (19F NMR). Recrystallization from
chloroform gave 0.09 g (9.4%) of cis-8. The mother
liquor was evaporated to leave 0.42 g of product mix-
ture which was subjected to repeated chromatography
with hexane as eluent. We thus isolated 0.011 g (1.7%)
of 14, 0.09 g of a mixture of cis-8, 12, 13, and 14 at
a ratio of 6:6:68:20 (19F NMR) and 0.08 g of a mix-
ture of cis-8, 12, and 13 at a ratio of 29:42:29
(19F NMR). Found, %: C 45.12; F 54.73. Found:
[M]+ 691.9680. C26F20. Calculated, %: C 45.11;
F 54.89. M 691.9675.
Perfluoro-9,10-diphenyl-2,9-dihydroanthracene
(13). 19F NMR spectrum (from a mixture with cis-8,
12, and 14), δF, ppm: 1.1 m (2F, m-F), 1.8 m (2F, m-F),
8.6 m (1F, 3-F), 11.0 t (1F, p-F, J = 21 Hz), 11.2 t (1F,
p-F, J = 21 Hz), 14.0 d.d.d.d (1F, 6-F, J = 20, 20, 7,
6 Hz), 15.6 d.d.d (1F, 7-F, J = 20, 20, 7 Hz), 20.6 m
(1F, o-F, 10-C6F5), 21.0 m (1F, 4-F), 21.2 m (1F, o-F,
10‑C6F5), 21.6 m (2F, o-F, 9-C6F5), 25.6 m (2F, 5-F,
8-F), 27.6 m (1F, 9-F), 45.1 m (1F, 1-F), 57.4 m and
56.4 m (1F each, 2-F, 2J = 302 Hz).
Perfluoro-9,10-diphenyl-1,4-dihydroanthracene
(14). mp 232–237°C (decomp., from hexane–CHCl3;
sealed capillary). 19F NMR spectrum, δF, ppm: –0.1 m
(4F, m-F), 8.2 m (2F, 2-F, 3-F), 11.2 t (2F, p-F, J =
21 Hz), 15.4 m (2F, 6-F, 7-F), 22.7 m (2F, 5-F, 8-F),
24.1 m (4F, o-F), 68.4 m (4F, 1-F, 4-F). Found:
[M]+ 691.9684. C26F20. Calculated: M 691.9675.
Reaction of perfluoro-1,2-diphenylbenzocyclo-
butene (11) with SbF5. A mixture of compounds 10
(0.11 mmol) and 11a (0.09 mmol), 0.094 g, was
dissolved in 0.57 g (2.63 mmol) of SbF5, and the
mixture was kept for 5 h at 25°C. It was then treated
with water at 0–20°C and extracted with methylene
chloride (3×2 mL), the extract was dried over MgSO4,
and the solvent was distilled off. The residue was
0.078 g of a mixture of compounds 5, 6, 10, and 11a at
a ratio of 50:40:5:5 (19F NMR).
Perfluoro-cis-9,10-diphenyl-9,10-dihydroanthra-
cene (cis-8). mp 267–268°C (from CHCl3; sealed
capillary). 19F NMR spectrum, δF, ppm: 0.8 m (4F, m-
F), 10.6 t (2F, p-F, J = 21 Hz), 14.5 m (4F, 2-F, 3-F,
6-F, 7-F), 23.4 m (4F, o-F), 26.8 m (4F, 1-F, 4-F, 5-F,
8-F), 38.6 m (2F, 9-F, 10-F). Found, %: C 44.95.
Perfluoro-9,10-diphenylanthracene (15). a. A so-
lution of 0.08 g (0.12 mmol) of trans-8 in 1.02 g
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REACTION OF PERFLUOROBENZOCYCLOBUTENE
553
6. Karpov, V.M., Mezhenkova, T.V., and Platonov, V.E.,
Bull. Acad. Sci. USSR, Div. Chem. Sci., 1990, vol. 39,
p. 566.
7. Karpov, V.M., Mezhenkova, T.V., and Platonov, V.E.,
Bull. Acad. Sci. USSR, Div. Chem. Sci., 1990, vol. 39,
p. 1000.
8. Karpov, V.M., Mezhenkova, T.V., and Platonov, V.E.,
Bull. Russ. Acad. Sci., Div. Chem. Sci., 1992, vol. 41,
p. 1110.
9. Mezhenkova, T.V., Karpov, V.M., Platonov, V.E., and
Gatilov, Yu.V., J. Fluorine Chem., 2009, vol. 130,
p. 951.
(4.70 mmol) of SbF5 was stirred for 50 h at 25°C. The
mixture was treated with water at 0–20°C and
extracted with methylene chloride (3 ×2 mL), the
extract was dried over MgSO4, and the solvent was
distilled off. The residue was 0.07 g of a dark material
which was subjected to column chromatography on
silica gel using chloroform as eluent to isolate 0.05 g
(66%) of 15. mp 220–221°C (from hexane–CH2Cl2).
19F NMR spectrum, δF, ppm: –0.2 m (4F, m-F), 9.8 t
(2F, p-F, J = 21 Hz), 11.6 m (4F, 2-F, 3-F, 6-F, 7-F),
20.9 m (4F, 1-F, 4-F, 5-F, 8-F), 21.1 m (4F, o-F).
Found: [M]+ 653.9704. C26F18. Calculated:
M 653.9707.
10. Karpov, V.M., Mezhenkova, T.V., Platonov, V.E., Sinya-
kov, V.R., and Shchegoleva, L.N., Russ. J. Org. Chem.,
2002, vol. 38, p. 1158.
b. As described above in a, 0.057 g of 15 was
obtained from 0.12 g (0.17 mmol) of a mixture of
cis-8, 12, 13, and 14 at a ratio of 30:30 :35:5 and
1.88 g (8.67 mmol) of SbF5.
11. Zonov, Ya.V., Karpov, V.M., and Platonov, V.E.,
J. Fluorine Chem., 2012, vol. 135, p. 159.
12. Karpov, V.M., Mezhenkova, T.V., Platonov, V.E., and
Sinyakov, V.R., J. Fluorine Chem., 2002, vol. 117,
p. 73.
13. Karpov, V.M., Platonov, V.E., and Yakobson, Bull. Acad.
Sci. USSR, Div. Chem. Sci., 1976, vol. 25, p. 355.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 16-03-00348).
14. Belen’kii, G.G., Savicheva, G.I., Lur’e, E.P., and
German, L.S., Bull. Acad. Sci. USSR, Div. Chem. Sci.,
1978, vol. 27, p. 1432.
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