Opening of the four-membered ring in perfluorinated 1-alkyl-2-phenyl-and 1-aryl-1,2-dihydrocyclobutabenzenes in the system I2-SbF5

Article abstract of DOI:10.1134/S1070428011070104

Reactions of perfluorinated 1-phenyl-, 1-(2-ethylphenyl)-, 1-(4-ethylphenyl)-, 1-methyl-2-phenyl-, and 1-ethyl-2-phenyl-1,2- dihydrocyclobutabenzenes with iodine in antimony pentafluoride at 130°C, followed by hydroysis of the reaction mixture, resulted in the formation of perfluorinated 2-methyl-, 2-ethyl-2′-methyl-, 4-ethyl-2'-methyl-, 2-ethyl-, and 2-propylbenzophenones via opening of the four-membered ring in the initial cyclobutabenzene at the C¹-C² bond. The presence of hydrogen fluoride facilitates the process and promotes profound transformations leading to anthracene derivatives.

Full text of DOI:10.1134/S1070428011070104

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2011, Vol. 47, No. 7, pp. 1026–1034. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © T.V. Mezhenkova, V.M. Karpov, V.E. Platonov, 2011, published in Zhurnal Organicheskoi Khimii, 2011, Vol. 47, No. 7,
pp. 1012–1019.
Opening of the Four-Membered Ring in Perfluorinated
1-Alkyl-2-phenyl- and 1-Aryl-1,2-dihydrocyclobutabenzenes
in the System I2–SbF5
T. V. Mezhenkova, V. M. Karpov, and V. E. Platonov
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 9, Novosibirsk, 630090 Russia
e-mail: mtv@nioch.nsc.ru
Received December 28, 2010
Abstract—Reactions of perfluorinated 1-phenyl-, 1-(2-ethylphenyl)-, 1-(4-ethylphenyl)-, 1-methyl-2-phenyl-,
and 1-ethyl-2-phenyl-1,2-dihydrocyclobutabenzenes with iodine in antimony pentafluoride at 130°C, followed
by hydroysis of the reaction mixture, resulted in the formation of perfluorinated 2-methyl-, 2-ethyl-2′-methyl-,
4-ethyl-2′-methyl-, 2-ethyl-, and 2-propylbenzophenones via opening of the four-membered ring in the initial
cyclobutabenzene at the C1–C2 bond. The presence of hydrogen fluoride facilitates the process and promotes
profound transformations leading to anthracene derivatives.
DOI: 10.1134/S1070428011070104
We previously showed that dimerization of per-
fluoro(1,2-dihydrocyclobutabenzene) (I) in SbF5 and
reactions of compound I, perfluoro(1-methyl-1,2-dihy-
drocyclobutabenzene) (II), and perfluoro(1-ethyl-1,2-
dihydrocyclobutabenzene) (III) with Br2 or HF in the
presence of SbF5 involve opening of the four-mem-
bered ring at the Carom–C2 bond with formation of the
corresponding 2-X-perfluoro(alkylbenzenes) [X = per-
fluoro(1,2-dihydrocyclobutabenzen-1-yl, Br, H] [1–3].
In contrast, opening of the four-membered ring in
compound I in the system I2–SbF5 occurs at both
arom–C2 and C1–C2 bonds, leading to 1,2,3,4-tetra-
C
fluoro-5-iodo-6-(perfluoroethyl)benzene together with
perfluoro(o-xylene) (IV) [4]. However, no iodo deriv-
atives were formed in analogous reactions of cyclo-
butabenzenes II and III, and the major products were
the corresponding perfluoro(1,2-dialkylbenzenes) [5].
With a view to elucidate how the nature of per-
fluorinated substituents in the four-membered ring of
perfluorinated 1,2-dihydrocyclobutabenzenes affects
Scheme 1.
C6F5
OH
(1) I2–SbF5, 130°C
(2) H2O
C6F5
COC6F5
CF3
+
F
F
F
F
F
V
VI
VII
F
F
6
F
3
2'
(1) I2–SbF5, 130°C
(2) H2O
1'
1
5
4
3'
C6HF5, SbF5
1α
2α
V
+
HF
VI
+
+
F
F
F
F
F
F
6'
4'
2
CF3
5'
I
VIII
IX
CF3
+
+
C6F5I
F
CF3
IV
1026

OPENING OF THE FOUR-MEMBERED RING IN PERFLUORINATED
1027
Scheme 2.
O
F
F
F
RF
RF
(1) I2–SbF5, 130°C
(2) H2O
RF
+
F
F
F
F
F
F
CF3
CF3
XIV
X, XI
XII, XIII
X, XII, RF = 2-C2F5; XI, XIII, XIV, RF = 4-C2F5.
the direction of their cationoid skeletal transforma-
tions, in the present work we examined the behavior of
a series of perfluorinated 1-alkyl-2-phenyl- and 1-aryl-
1,2-dihydrocyclobutabenzenes in the system I2–SbF5.
Perfluoro[1-(2-ethylphenyl)-1,2-dihydrocyclobuta-
benzene] (X) reacted with I2–SbF5 at 130°C to give
(after hydrolysis) perfluoro(2-ethyl-2′-methylbenzo-
phenone) (XII), whereas analogous reaction of per-
fluoro[1-(4-ethylphenyl)-1,2-dihydrocyclobutaben-
zene] (XI) afforded perfluoro(4-ethyl-2′-methylbenzo-
phenone) (XIII) and a small amount of perfluoro[1-(4-
ethylbenzyl)-2-methylbenzene] (XIV) (Scheme 2). No
products of four-membered ring opening were ob-
tained from compounds V and XI in SbF5 at 130°C in
the absence of iodine, while compound X was partially
converted into perfluorinated benzophenone XII only
under considerably prolonged heating [7].
Heating of perfluoro(1-phenyl-1,2-dihydrocyclo-
butabenzene) (V) with iodine in SbF5 at 130°C
resulted in opening of the four-membered ring with
formation (after treatment of the reaction mixture with
water) of perfluoro(2-methylbenzophenone) (VI);
however, the degree of opening of the cyclobutene ring
was not high, and the major product was perfluorinated
1-phenyl-1,2-dihydrocyclobutabenzen-1-ol (VII;
Scheme 1). Analogous reaction with compound V
generated in situ together with 1 equiv of HF by reac-
tion of perfluoro(1,2-dihydrocyclobutabenzene) (I)
with pentafluorobenzene in SbF5 [6] was characterized
by complete conversion of V; apart from products of
opening of the four-membered ring, perfluorinated
benzophenone VI and perfluoro(1-benzyl-2-methyl-
benzene) (VIII), perfluoro(1,2,3,4,5,6,7,8-octahydro-
anthracene) (IX), perfluoroxylene (IV), and penta-
fluoroiodobenzene were formed (Scheme 1).
Cleavage of cyclobutabenzene XI by the action of
I2 in SbF5 in the presence of HF requires milder con-
ditions. Treatment of a mixture of XI and HF {generat-
ed by reaction of compound I with 1,2,4,5-tetrafluoro-
3-(pentafluoroethyl)benzene in SbF5 [7]} with I2 at
100°C and subsequent hydrolysis gave a mixture con-
taining compounds XIII and XIV together with unre-
acted compound XI and perfluoro[1-(4-ethylphenyl)-
1,2-dihydrocyclobutabenzen-1-ol] (XV); in addition,
Scheme 3.
C2F5
, SbF5, 50°C
F
H
I
XI
+
HF
+
C2F5
(1) I2–SbF5, 110°C
(2) H2O
C2F5
CF3
I
OH
F
XI
+
XIII
+
XIV
+
+
F
F
F
F
F3C
XV
XVI
XVII
5
10
4
F
1
(1) I2–SbF5, 130°C
(2) H2O
6
3
2
+
+
XVI
+
XVII
F
F
F
F
F
2α 2β
CF2CF3
7
H
CF2CF3
8
9
XVIII
XIX
(1) SbF5, 130°C
(2) H2O
XV
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011

MEZHENKOVA et al.
1028
Scheme 4.
O
CF3
(1) I2–SbF5, 130°C
(2) H2O
CF3
CF3
C6F5
C6HF5, SbF5
C6F5
+
+ HF
F
F
F
F
F
F
F
CF2CF3
XXII
C6F5
II
XX
XXI
CF3
CF3
F
F
+
+
+
F
F
F
F
F
F
F
F
2α
CF2
2βCF3
O
XXIII
XXIV
XXV
O
(1) I2–SbF5, 130°C
(2) HF
F
F
CF2CF3
CF2CF3
C6F5
C6HF5, SbF5
(3 )H2O
C6F5
CF2CF2CF3
+ HF
+
F
F
F
F
F
F
F
2α
CF22γ
2βCF2CF3
III
XXVI
XXVII
XXVIII
small amounts of perfluoro(4-ethyltoluene) (XVI) and
1,2,3,4-tetrafluoro-5-iodo-6-trifluoromethylbenzene
(XVII) were formed (Scheme 3). Raising the tempera-
ture to 130°C led to the formation of perfluoro(2-ethyl-
3,4,5,6,7,8-hexahydroanthracene) (XVIII) and 2H-per-
fluoro(2-ethyl-1,2,3,4,5,6,7,8-octahydroanthracene)
(XIX), the former prevailing; also, compounds XVI
and XVII were obtained. By special experiment we
showed that no reaction occurred in the absence of I2,
other conditions being equal; treatment of the reaction
mixture with water gave hydroxy derivative XV.
C6F5H in SbF5 [8]} with I2 in SbF5 at 130°C, followed
by hydrolysis, gave perfluoro(2-ethylbenzophenone)
(XXII) and perfluoro(1-benzyl-2-ethylbenzene)
(XXIII) from 1,2-isomer XX and perfluoro(10-methyl-
9,10-dihydroanthracen-9-one) (XXIV) and perfluoro-
(9-methyl-1,2,3,4,5,6,7,8-octahydroanthracene) (XXV)
from 1,1-isomer XXI (Scheme 4). When the reaction
was carried out in the absence of iodine, 1,2-isomer
XX did not undergo skeletal transformations, whereas
only compound XXIV was obtained from 1,1-isomer
XXI [9].
The reaction of a mixture of isomeric perfluorinated
1-methyl-2-phenyl- and 1-methyl-1-phenyl-1,2-dihy-
drocyclobutabenzenes XX/XXI and HF {generated
from perfluorinated methylcyclobutabenzene II and
Perfluoro(1-phenyl-2-ethyl-1,2-dihydrocyclobuta-
benzene) (XXVI) obtained in a mixture with HF from
perfluoro(1-ethyl-1,2-dihydrocyclobutabenzene) (III)
and pentafluorobenzene in SbF5 [10] reacted with I2–
Scheme 5.
F
F
F
F
F
CF2
F–
H+
F
F
F
VIII
IV
H
–C6HF5
CF
CF3
3 F
–F–
A
B
F
F
F–
[F]
IX
F
F
F
F
F
F
F
F
F
F
F
CF2
F
C
D
E
F
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011

OPENING OF THE FOUR-MEMBERED RING IN PERFLUORINATED
1029
SbF5 at 130°C, yielding (after treatment of the reaction
mixture first with anhydrous HF and then with water)
perfluoro(1-benzyl-2-propylbenzene) (XXVII) and per-
fluoro(2-propylbenzophenone) (XXVIII) (Scheme 4).
Skeletal transformations of XXVI in the absence of
iodine occur under more severe conditions [9].
A probable mechanism of opening of the four-
membered ring in polyfluorinated benzocyclobutenes
by the action of I2–SbF5 was discussed by us previous-
ly [4, 5]. It was presumed that cleavage of the C1–C2
bond occurs with participation of I2 molecule although
iodine in SbF5 exists mainly as I2+ species [11]. The fact
that compounds V and XI react with I2–SbF5 in the
presence of HF more readily (Schemes 1–3) may be
rationalized assuming increase in the concentration of
I2 and reduction in the concentration of I2+ in the system
upon addition of HF [12].
latter to the central ring gives isomer F, and its sub-
sequent fluorination leads to product IX (Scheme 5).
The formation of anthrone XXIV from compound XXI
(Scheme 4) was considered by us previously [9]. Octa-
hydroanthracene XXV is likely to be the product of
fluorination of perfluoro(9-methyl-9,10-dihydroanthra-
cene) in SbF5; obviously, this process is favored by the
presence of iodine, for no compound XXV is formed at
130°C in the absence of iodine [9].
In the reaction of XI with I2–SbF5 in the presence
of HF, compounds XVI–XIX are likely to originate
from diarylmethane XIV, following a scheme analo-
gous to the transformations of VIII. Proton addition to
the methylphenyl group in XIV gives σ-complex G
which decomposes with formation of benzyl cation H
and 1,2,3,4-tetrafluoro-5-trifluoromethylbenzene. The
latter reacts with iodine in SbF5 to give compound
XVII, and cation H takes up fluoride ion to produce
perfluoro(1-ethyl-4-methylbenzene) (XVI) (Scheme 6).
Cyclization of diarylmethane XIV with participation of
benzyl cation J gives tetrahydroanthracene K which
undergoes isomerization into intermediate L, e.g., via
successive elimination–addition of fluoride ion. Ad-
dition of HF at the double bond of tetrahydroanthra-
cene L leads to structure M. Fluorination of the latter
yields compound XIX which loses HF molecule with
formation of hexahydroanthracene XVIII. The trans-
formation sequence XIX → XVIII shown in Scheme 6
is based on experimental data according to which the
reaction mixture obtained at 130°C (Scheme 3) con-
Perfluoroxylene IV and pentafluoroiodobenzene
are likely to be formed in the reaction of compound V
with I2–SbF5 in the presence of HF as a result of attack
by proton on the pentafluorophenyl group in com-
pound VIII. σ-Complex A thus generated decomposes
into C6F5H and benzyl cation B (Scheme 5). The latter
takes up fluoride ion to give xylene IV, while C6F5H
reacts with I2 in SbF5 to produce C6F5I. Presumably,
anthracene derivative IX also results from transforma-
tion of compound VIII. Cation C generated from VIII
by the action of SbF5 undergoes cyclization to cation D
which takes up fluoride ion, yielding tetrahydroan-
thracene E. Migration of double C=C bonds in the
Scheme 6.
I2–SbF5
F
F
F
F
F
H
CF2
F–
H+
F
F
F
F
+
XIV
XVI + XVII
H
C2F5
CF3
C2F5
F3C
G
H
F
F
F–
F
F
F
F
F
F
F
F
–F–
CF2
C2F5
C2F5
C2F5
F
J
K
F–
F–
HF
[F]
XIX
XVIII
F
F
F
F
F
F
–F–
–F–
–HF
H
C2F5
C2F5
L
M
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011

MEZHENKOVA et al.
1030
Scheme 7.
F
O
1α
CF2C6F5
SbF5, SO2ClF
H2O
C6F5
F
F
F
F
RF
RF
2α, 2β, 2γ
RF
VIII, XXIII, XXVII
XXIX, XXX, XXXI
VI, XXII, XXVIII
VI, VIII, XXIX, RF = CF3; XXII, XXIII, XXX, RF = C2F5; XXVII, XXVIII, XXXI, RF = C3F7.
their precursors VIII, XXIII, and XXVII, as well as
increased coupling constants for fluorine atoms in the
positions conjugated with the cationic center, are con-
sistent with the data reported previously for polyfluor-
inated benzyl [13] and diarylalkyl cations [7, 14, 15].
tained after 4 h compounds XIX and XVIII at a ratio
of 60:40; after 10 h, the ratio changed to 31:69 and no
longer changed.
The formation of hydroxy derivatives VII and XV
and ketones XII and XIII in the above reactions
(Schemes 1, 3) may be rationalized assuming that per-
fluorinated cyclobutabenzenes V and XI, perfluoro-
[1-(2-ethylbenzyl)-2-methylbenzene], and diarylmeth-
ane XIV in SbF5 exist as salts of the corresponding
perfluorinated 1-aryl-1,2-dihydrocyclobutabenezen-
1-yl and diarylmethyl cations which were detected by
19F NMR spectroscopy [6, 7]; their hydrolysis yields
compounds VII, XV, XII, and XIII. Presumably,
ketones VI, XXII, and XXVIII (Schemes 1, 4) are
formed in a similar way. In fact, dissolution of com-
pounds VIII, XXIII, and XXVII in SbF5–SO2ClF
generates perfluorinated (2-methylphenyl)-, (2-ethyl-
phenyl)-, and (2-propylphenyl)phenylmethyl cations
XXIX–XXXI, respectively, and their hydrolysis yields
ketones VI, XXII, and XXVIII (Scheme 7).
The structure of compounds VI, VIII, XVI–XIX,
XXII, XXIII, XXVII, and XXVIII was determined on
the basis of their high-resolution mass spectra and
19F NMR spectra. The other compounds were identi-
fied by comparing their 19F NMR spectra with those of
authentic samples (VII [6], IX, XXIV, XXV [16],
XII–XV [7]).
EXPERIMENTAL
The 19F NMR spectra of reaction mixtures and solu-
tions of individual compounds VI, VIII, XVI–XIX,
XXII, XXIII, XXVII, and XXVIII in CDCl3 and
1H NMR spectrum of XIX were recorded on a Bruker
AV-300 spectrometer at 282.4 and 300 MHz, respec-
19
13
tively. The F and C NMR spectra of solutions con-
taining cations XXIX–XXXI (in SbF5–SO2ClF) were
measured on a Bruker AV-400 instrument at 376.5 and
100 MHz, respectively. The chemical shifts are given
relative to C6F6 (19F) and TMS (1H, 13C); C6F6 or
SO2ClF (δF 262.8 ppm relative to C6F6) and CHCl3
(δ 7.24 ppm) were used as internal references, and
acetone-d6 (δC 29.9 ppm) was used as external refer-
ence. The elemental compositions of compounds VI,
VIII, XVIII, XIX, XXII, XXIII, XXVII, and XXVIII
were determined from their high-resolution mass
spectra which were obtained on a Thermo Electron
Corporation DFS instrument. The IR spectra were
recorded on a Bruker Vector 22 spectrometer. Gas
chromatographic–mass spectrometric analysis of a mix-
ture of compounds XVI and XVII was performed on
a Hewlett–Packard G1081A GC–MS system consisting
of an HP 5890 Series II gas chromatograph and
an HP 5971 mass-selective detector (electron impact,
70 eV); HP-5 capillary column (5%-phenyl-95%-
methylpolysiloxane), 30 m×0.25 mm×0.25 μm; car-
rier gas helium, flow rate 1 ml/min. GLC analysis was
The structure of cations XXIX–XXXI was deter-
mined on the basis of their 19F and 13C NMR spectra
and was confirmed by the structure of the hydrolysis
19
products. In the F NMR spectrum of XXIX at 25°C,
the 2′-F and 6′-F atoms in the pentafluorophenyl group
give rise to one broadened signal at δ 60.2 ppm;
lowering the temperature to –30°C makes these atoms
magnetically nonequivalent due to restricted rotation
of the pentafluorophenyl group, and the spectrum dis-
plays two signals at δF 64.0 and 56.5 ppm. The corre-
sponding fluorine signals were not observed in the
19F NMR spectra of XXX and XXXI at 20°C, whereas
signals from the CF2 fragments in the perfluoroethyl
and perfluoropropyl groups were appreciably broad-
ened. In the spectra recorded at reduced temperature
(–10°C for cation XXX or –30°C for XXXI), two
separate signals appeared due to 2′-F and 6′-F, and
fluorine nuclei in the CF2 group became nonequivalent
(AB spin system, JAB ≈ 290–300 Hz). The observed
downfield shifts of signals from fluorine atoms in the
aromatic rings of cations XXIX–XXXI as compared to
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011

OPENING OF THE FOUR-MEMBERED RING IN PERFLUORINATED
1031
performed on an LKhM-72 chromatograph equipped
with a 4000×4-mm column packed with SKTFT-50 on
Chromosorb W (15:100); oven temperature program-
ming from 50 to 270°C; carrier gas helium, flow rate
60 ml/min.
6′-F), 28.7 (1F, 3-F), 29.4 (1F, 6-F), 86.7 (2F, 1α-F),
108.3 (3F, 2α-F); J1α,2 = 17, J1α,6 = 35, J1α,2′(6′) = 15,
J
2α,3 = 32, J3,4 = J4,5 = J5,6 = J4′,3′(5′) = 21, J3,5 = J4,6 = 9,
J3,6 = 10, J4′,2′(6′) = 5 Hz. Found: m/z 433.9774 [M]+.
C14F14. Calculated: M 433.9771.
Reaction of perfluoro(1-phenyl-1,2-dihydro-
cyclobutabenzene) (V) with I2–SbF5. a. A mixture of
4.14 g (19.10 mmol) of SbF5 and 0.35 g (1.38 mmol)
of I2 was heated for 0.5 h at 130°C in a 10-cm3 nickel
high-pressure reactor with intermittent shaking, 0.56 g
(1.41 mmol) of compound V was added to the result-
ing solution, and the mixture was heated for 10 h at
130°C, cooled to 0°C, transferred into ice water, and
extracted with methylene chloride. The extracts were
dried over MgSO4, and the solvent was distilled off to
obtain 0.46 g of a mixture of compounds VI and VII at
a ratio of 17:83 (19F NMR).
Reaction of perfluoro[1-(2-ethylphenyl)-1,2-di-
hydrocyclobutabenzene] (X) with I2–SbF5. A mix-
ture of 0.79 g (3.18 mmol) of compound I and 4.72 g
(21.77 mmol) of SbF5 was heated for 9 h at 90°C to
obtain compound X [1], 0.40 g (1.59 mmol) of iodine
was added, and the mixture was heated for 10 h at
130°C. After appropriate treatment, we obtained 0.74 g
of a mixture containing 85% of compound XII.
Reaction of perfluoro[1-(4-ethylphenyl)-1,2-di-
hydrocyclobutabenzene] (XI) with I2–SbF5. a. The
reaction of 0.8 g (1.61 mmol) of compound XI with
0.41 g (1.61 mmol) of I2 and 4.90 g (22.60 mmol) of
SbF5 (10 h, 130°C) gave 0.73 g of a mixture contain-
ing 69% of XIII and 8% of XIV.
In all subsequent experiments the procedures for
dissolution of I2 in SbF5 and treatment of the reaction
mixtures were similar.
b. A mixture of 0.80 g (3.23 mmol) of compound I,
0.87 g (3.25 mmol) of 1,2,4,5-tetrafluoro-3-perfluoro-
ethylbenzene, and 4.91 g (22.65 mmol) of SbF5 was
heated for 6 h at 50°C to generate compound XI [7],
0.41 g (1.62 mmol) of I2 was added, and the mixture
was heated for 10 h at 110°C. After appropriate treat-
ment, we obtained 1.32 g of a mixture of compounds
XI, XII, and XIV–XVII at a ratio of 6:29:13:42:8:2
(19F NMR).
b. Compound I, 0.89 g (3.59 mmol), and penta-
fluorobenzene, 0.60 g (3.57 mmol), were added to
a solution of 0.46 g (1.81 mmol) of iodine in 5.46 g
(25.18 mmol) of SbF5, and the mixture was kept for
20 h at 20°C. The resulting mixture contained per-
fluoro(1-phenyl-1,2-dihydrocyclobutabenzene) (V)
[6]; it was heated for 7 h at 130°C. After appropriate
treatment, we obtained 1.28 g of a mixture containing*
9% of compound IV, 52% of VI, 10% of VIII, 10% of
IX, and 5% of pentafluoroiodobenzene. The product
mixture was subjected to column chromatography on
silica gel using first hexane and then carbon tetra-
chloride as eluents to isolate 0.09 g of perfluoro-
(1-benzyl-2-methylbenzene) (VIII) and 0.55 g of per-
fluoro(2-methylbenzophenone) (VI).
c. As described above in b, from 0.70 g (2.84 mmol)
of compound I, 0.76 g (2.84 mmol) of 1,2,4,5-tetra-
fluoro-3-perfluoroethylbenzene, 4.31 g (19.88 mmol)
of SbF5, and 0.36 g (1.42 mmol) of I2 (10 h, 130°C) we
obtained 1.34 g of a mixture containing 16% of XVI,
3% of XVII, 43% of XVIII, and 19% of XIX. By
column chromatography on silica gel using hexane as
eluent we isolated 0.1 g of a mixture containing 30%
of perfluoro(4-ethyltoluene) (XVI) and 56% of 2-iodo-
heptafluorotoluene (XVII) (according to the GC–MS
and 19F NMR data), 0.13 g of 1,1,2,2,3,3,4,4,5,5,6,6,-
8,8,9,10-hexadecafluoro-7-(perfluoroethyl)-1,2,3,4,-
5,6,7,8-octahydroanthracene (XIX), and 0.39 g of per-
fluoro(2-ethyl-3,4,5,6,7,8-hexahydroanthracene)
(XVIII).
Compound XVI. 19F NMR spectrum, δF, ppm: 24.8
(2F), 26.1 (2F), 50.4 (2F, CF2CF3), 76.5 (3F, CF2CF3),
104.9 (3F, CF3). GC–MS: m/z 336 [M]+.
Compound XVII. 19F NMR spectrum, δF, ppm:
10.9 (1F, 5-F), 15.4 (1F, 4-F), 28.5 (1F, 6-F), 56.3 (1F,
3-F), 106.1 (3F, CF3); J1, 6 = 34, J3, 4 = 23, J3, 5 = 6,
Compound VI. mp 49–50.5°C (from hexane). IR
spectrum (CCl4), ν, cm–1: 1708 (C=O), 1648, 1525,
1497, 1480 (fluorinated aromatic ring). 19F NMR spec-
trum, δF, ppm: 2.9 (2F, 3′-F, 5′-F), 13.8 (1F, 4-F), 16.3
(1F, 5-F), 19.0 (1F, 4′-F), 21.6 (1F, 6-F), 22.4 (2F, 2′-F,
6′-F), 26.9 (1F, 3-F), 106.8 (3F, 2α-F); J2α,3 = 18, J3,4
J4,5 = 20, J3,5 = 9, J3,6 = 11, J4,6 = 6, J5,6 = 22, J4′,2′(6′)
=
=
7, J4′,3′(5′) = 21 Hz. Found: m/z 411.9750 [M]+. C14F12O.
Calculated: M 411.9752.
Compound VIII, mp 47–48.5°C (from hexane).
19F NMR spectrum, δF, ppm: 2.4 (2F, 3′-F, 5′-F), 14.6
(1F, 4′-F), 15.1 (1F, 4-F), 15.9 (1F, 5-F), 22.2 (2F, 2′-F,
* Hereinafter the compositions of product mixtures (wt %) are
given according to the GLC and 19F NMR data.
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MEZHENKOVA et al.
1032
J3,6 = 10, J4,5 = J5,6 = 19, J4,6 = 9 Hz [17]. GC–MS:
m/z 344 [M]+.
Compound XVIII. Liquid (purity 98%). 19F NMR
spectrum, δF, ppm: 27.3 (4F, 6-F, 7-F), 41.4 (2F, 4-F),
45.2 (2F, 3-F), 49.8 (1F, 10-F), 50.5 (2F, 2α-F), 52.2
(1F, 9-F), 68.7 (1F, 1-F), 54.2 (2F, 8-F), 54.4 (2F, 5-F),
I2 was added, and the mixture was heated for 14 h at
130°C. After appropriate treatment we isolated 1.45 g
of a mixture containing 58% of XXII, 18% of XXIII,
3% of XXIV, and 6% of XXV. The product mixture
was subjected to column chromatography on silica gel
using first hexane and then carbon tetrachloride as
eluents to isolate 0.20 g of perfluoro(1-benzyl-2-ethyl-
benzene) (XXIII) and 0.69 g of perfluoro(2-ethylben-
zophenone) (XXII).
77.2 (3F, 2β-F); J1,9 = 86, J1,2α = 26, J1,2β = 10, J1,3
18, J1,10 = 8, J2α,2β = 3, J2α,3 = 13, J2β,3 = J3,4 = 7, J4,10
=
=
34, J5, 10 = 23, J8, 9 = 24, J9, 10 = 21 Hz. Found:
m/z 571.9670 [M]+. C16F20. Calculated: M 571.9675.
Compound XXII. mp 38–40°C (from hexane). IR
spectrum (CCl4), ν, cm–1: 1709 (C=O), 1648, 1634,
1525, 1499, 1475 (fluorinated aromatic ring). 19F NMR
spectrum, δF, ppm: 2.7 (2F, 3′-F, 5′-F), 13.7 (1F, 4-F),
17.3 (1F, 5-F), 19.0 (1F, 4′-F), 22.2 (1F, 6-F), 22.7 (2F,
2′-F, 6′-F), 30.3 (1F, 3-F), 56.2 (2F, 2α-F), 78.1 (3F,
2β-F); J2α,3 = 21, J2β,3 = 16, J3,4 = J4,5 = 20, J3,5 = 10,
1
Compound XIX. Liquid (purity 98%). H NMR
spectrum (CDCl3): δ 3.78 ppm. 19F NMR spectrum, δF,
ppm: 27.3 (4F, 6-F, 7-F), 43.3 and 36.0 (1F each, 3-F),
50.0 and 48.3 (1F each, 2α-F, JAB = 291 Hz), 50.6 (1F,
10-F), 52.2 (1F, 9-F), 54.5 (4F, 5-F, 8-F), 61.9 and 34.0
(1F each, 4-F), 76.8 and 68.5 (1F each, 1-F), 78.0 (3F,
J
3,6 = 11, J4,6 = 6, J5,6 = 22, J4′,2′(6′) = 7, J4′,3′(5′) = 21 Hz.
2β-F); J1A,1B = 299, J3A,3B = 271, J4A,4B = 291, J4B,10
=
Found: m/z 461.9729 [M]+. C15F14O. Calculated:
M 461.9725.
49 Hz. Found: m/z 591.9735 [M]+. C16HF21. Calculat-
ed: M 591.9737.
Compound XXIII. Liquid (purity 98%). 19F NMR
spectrum, δF, ppm: 2.4 (2F, 3′-F, 5′-F), 14.5 (1F, 4′-F),
15.3 (1F, 4-F), 16.9 (1F, 5-F), 22.3 (2F, 2′-F, 6′-F), 30.6
(1F, 6-F), 32.8 (1F, 3-F), 60.9 (2F, 2α-F), 80.7 (3F,
d. As described above in b, from 0.82 g (3.31 mmol)
of compound I, 0.89 g (3.31 mmol) of 1,2,4,5-tetra-
fluoro-3-perfluoroethylbenzene, 4.77 g (22.0 mmol) of
SbF5, and 0.42 g (1.65 mmol) of I2 (4 h, 130°C) we
obtained 1.74 g of a mixture containing 14% of XVI,
6% of XVII, 21% of XVIII, and 31% of XIX.
2β-F), 87.9 (2F, 1α-F); J1α,2β = 16, J1α,6 = 41, J1α,2′(6′)
=
15, J2α,3 = 32, J2β,3 = 18, J3,4 = J4,5 = J5,6 = J4′,3′(5′) = 21,
J3, 5 = 10, J3, 6 = J4, 6 = 9, J4′, 2′(6′) = 5 Hz. Found:
m/z 483.9752 [M]+. C15F16. Calculated: M 483.9744.
e. As described above in b, from 0.66 g (2.65 mmol)
of compound I, 0.71 g (2.65 mmol) of 1,2,4,5-tetra-
fluoro-3-perfluoroethylbenzene, 4.02 g (18.54 mmol)
of SbF5, and 0.34 g (1.32 mmol) of I2 (15 h, 130°C) we
obtained 1.23 g of a mixture containing 10% of XVI,
3% of XVII, 41% of XVIII, and 19% of XIX.
Reaction of perfluoro(1-ethyl-2-phenyl-1,2-dihy-
drocyclobutabenzene) (XXVI) with I2–SbF5. A mix-
ture of 1.09 g (3.13 mmol) of compound III, 0.53 g
(3.16 mmol) of pentafluorobenzene, and 4.97 g
(22.92 mmol) of SbF5 was kept for 20 h at 20°C to
generate compound XXVI [10], 0.40 g (1.58 mmol) of
iodine was added, and the mixture was heated for 14 h
at 130°C. The mixture was then cooled to 0°C, 6 ml of
anhydrous hydrogen fluoride was added, and the mix-
ture was poured into ice water and extracted with
methylene chloride. The extract was dried over
MgSO4, and the solvent was distilled off to obtain
1.43 g of a mixture containing 59% of XXVII and
19% of XXVIII. The product mixture was subjected to
column chromatography on silica gel using first hex-
ane and then carbon tetrachloride as eluents to isolate
0.75 g of perfluoro(1-benzyl-2-propylbenzene)
(XXVII) and 0.21 g of perfluoro(2-propylbenzophe-
none) (XXVIII).
Reaction of perfluoro[1-(4-ethylphenyl)-1,2-di-
hydrocyclobutabenzene] (XI) with SbF5. A mixture
of 0.68 g (2.74 mmol) of compound I, 0.73 g
(2.72 mmol) of 1,2,4,5-tetrafluoro-3-perfluoroethyl-
benzene, and 4.74 g (21.86 mmol) of SbF5 was heated
for 6 h at 50°C in a nickel high-pressure reactor to
obtain compound XI [7], and the mixture was then
heated for 30 h at 130°C. After appropriate treatment
we isolated 0.86 g of compound XV (according to the
19F NMR data).
Reaction of perfluoro(1-methyl-2-phenyl-1,2-di-
hydrocyclobutabenzene) (XX) and perfluoro-
(1-methyl-1-phenyl-1,2-dihydrocyclobutabenzene)
(XXI) with I2–SbF5. A mixture of 1.01 g (3.37 mmol)
of compound II, 0.57 g (3.37 mmol) of pentafluoro-
benzene, and 5.11 g (23.57 mmol) of SbF5 was kept for
20 h at 20°C to obtain a mixture of compounds XX
and XXI at a ratio of 89:11 [8], 0.43 g (1.69 mmol) of
19
Compound XXVII. Liquid (purity 98%). F NMR
spectrum, δF, ppm: 2.4 (2F, 3′-F, 5′-F), 14.6 (1F, 4′-F),
15.4 (1F, 4-F), 17.0 (1F, 5-F), 22.2 (2F, 2′-F, 6′-F), 30.7
(1F, 6-F), 32.8 (1F, 3-F), 40.5 (2F, 2β-F), 63.9 (2F,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011

OPENING OF THE FOUR-MEMBERED RING IN PERFLUORINATED
1033
2α-F), 81.2 (3F, 2γ-F), 87.5 (2F, 1α-F); J1α,2α = J1α,2β
=
cation XXX, while compound XXIII was absent
23, J1α, 6 = 39, J1α, 2′(6′) = 15, J2α, 2γ = 10, J2α, 3 = 33,
J2β, 3 = 24, J3, 4 = J4, 5 = J5, 6 = J4, 3′(5′) = 21, J3, 5 = 10,
J3,6 = J4,6 = 9, J4′,2′(6′) = 5 Hz. Found: m/z 533.9706
[M]+. C16F18. Calculated: M 533.9712.
(according to the 19F and 13C NMR data). 13C NMR
1
spectrum, δC, ppm (J, Hz): 109. 8 t.q (C2α, JCF = 262,
2JCF = 43), 110.1 (C1, C1′), 114.2 (C2), 116.1 q.t (C2β,
2
1
1JCF = 286, JCF = 35), 138.7 d (C3′, C5′, JCF = 271),
142.1 d (C5, 1JCF = 273), 148.3 d (C3 or C6, 1JCF = 272),
148.7 d (C4, 1JCF = 284), 149.0 d (C6 or C3, 1JCF = 271),
153.0 d (C2′, C6′, 1JCF = 301), 163.4 d (C4′, 1JCF = 311),
Compound XXVIII. mp 40–41°C (from hexane).
IR spectrum (CCl4), ν, cm–1: 1709 (C=O), 1648, 1634,
1524, 1497, 1475 (fluorinated aromatic ring). 19F NMR
spectrum, δF, ppm: 2.7 (2F, 3′-F, 5′-F), 13.7 (1F, 4-F),
17.5 (1F, 5-F), 19.0 (1F, 4′-F), 22.2 (1F, 6-F), 22.5 (2F,
2′-F, 6′-F), 30.5 (1F, 3-F), 37.1 (2F, 2β-F), 59.0 (2F,
195.1 d (C1α, JCF = 359). F NMR spectrum at 25°C,
δF (∆δF), ppm: 16.5 (14.1) (2F, 3′-F, 5′-F), 24.6 (7.7)
(1F, 5-F), 41.7 (26.4) (1F, 4-F), 43.4 (10.6) (1F, 3-F),
44.1 (13.5) (1F, 6-F), 61.5 (0.6) (2F, 2α-F), 81.3 (0.6)
(3F, 2β-F), 85.6 (71.1) (1F, 4′-F), 221.1 (133.2) (1F,
1α-F); J1α,2′(6′) ≈ 85, J1α,4′ = 23, J1α,2β = 24, J2α,3 = 18,
J3,4 ≈ J4,5 ≈ J4,6 ≈ J5,6 ≈ 20, J3,5 ≈ 15, J4′,2′(6′) ≈ 40 Hz.
19F NMR spectrum at –10°C, δF (∆δF), ppm: 16.1 and
17.0 (2F, 3′-F, 5′-F), 25.0 (1F, 5-F), 42.6 (1F, 4-F), 43.9
(1F, 3-F), 44.8 (1F, 6-F), 58.2 (35.9) (1F, 6′-F), 63.1
and 60.7 (1F, each, 2α-F), 66.3 (44.0) (1F, 2′-F), 81.6
1
19
2α-F), 81.7 (3F, 2γ-F); J2α,2γ = 10, J2α,3 = J2β,3 = J5,6
=
22, J3, 4 = J4, 5 = 20, J3, 5 = 10, J3, 6 = 11, J4, 6 = 6,
J4′,2′(6′) = 7, J4,3′(5′) = 21 Hz. Found: m/z 511.9689 [M]+.
C16F16O. Calculated: M 511.9694.
Perfluoro[(2-methylphenyl)(phenyl)methyl]
cation (XXIX). Compound VIII, 0.14 g (0.32 mmol),
was dissolved in 0.99 g (4.57 mmol) of SbF5, and
0.22 g of SO2ClF was added. The resulting solution
contained cation XXIX, while compound VIII was
absent (according to the 19F and 13C NMR data).
13C NMR spectrum, δC, ppm (J, Hz): 108.9 and 109.4
(3F, 2β-F), 85.3 (1F, 4′-F), 220.7 (1F, 1α-F); JAB
≈
300 Hz.
The solution was poured into ice water, the mixture
was extracted with chloroform, and the extract was
dried over MgSO4 and evaporated to isolate 0.09 g of
ketone XXII.
2
(C1, C1′), 114.8 q.d (C2, JCF = 38, 11), 117.4 q (C2α,
1
2
1JCF = 276), 138.0 d.t (C3′, C5′, JCF = 270, JCF = 12),
141.2 d.t (C5, JCF = 274, JCF = 13), 147.2 d.d (C3,
1
2
Perfluoro[(phenyl)(2-propylphenyl)methyl]
cation (XXXI). Compound XXVII, 0.12 g
(0.22 mmol), was dissolved in 1.04 g (4.80 mmol) of
SbF5, and 0.22 g of SO2ClF was added to obtain a so-
lution containing cation XXXI, while compound
XXVII was absent (according to the 19F and 13C NMR
1JCF = 275, 2JCF = 12), 149.4 d (C4, 1JCF = 283), 149.4 d
(C6, JCF ≈ 280), 152.1d (C2′, C6′, JCF = 294), 162.1 d
1
1
1
1
19
(C4′, JCF = 307), 193.2 d (C1α, JCF = 359). F NMR
spectrum at 25°C, δF (∆δF),** ppm: 16.0 (13.6) (2F,
3′-F, 5′-F), 23.7 (7.8) (1F, 5-F), 40.3 (11.6) (1F, 3-F),
46.0 (30.9) (1F, 4-F), 47.2 (17.8) (1F, 6-F), ~60.2
(38.0) (2F, 2′-F, 6′-F), 82.3 (67.7) (1F, 4′-F), 109.4
(1.1) (3F, 2α-F), 217.8 (131.1) (1F, 1α-F); J1α,2′(6′) ≈ 80,
13
data). C NMR spectrum, δC, ppm (J, Hz): 106.5 t.t.q
1
2
(C2β, JCF = 267, JCF = 38, 38), 110.0 (C1, C1′),
112.2 t.t (C2α, JCF = 264, JCF = 36), 114.2 (C2),
1
2
115.4 q.t (C2γ, 1JCF = 287, 2JCF = 33), 138.5 d.t (C3′, C5′,
J1α,4′ ≈ J3,4 ≈ J4,5 ≈ J4,6 ≈ J5,6 ≈ J4′,3′(5′) ≈ 20, J1α,2α
≈
J2α,3 ≈ 21, J3,5 ≈ 14, J4′,2′(6′) ≈ 40 Hz; 19F NMR spec-
trum at –30°C, δF, ppm: 16.4 and 16.1 (2F, 3′-F, 5′-F),
24.2 (1F, 5-F), 40.8 (1F, 3-F), 47.1 (1F, 4-F), 48.3 (1F,
6-F), 56.5 (1F, 6′-F), 64.0 (1F, 2′-F), 82.0 (1F, 4′-F),
109.9 (3F, 2α-F), 217.3 (1F, 1α-F).
1JCF = 271, 2JCF = 12), 142.0 d.t (C5, 1JCF = 274, 2JCF
=
=
13), 148.2 d (C3 or C6, 1JCF = 271), 148.5 d (C4, 1JCF
284), 148.9 d (C6 or C6, JCF = 272), 152.8 d (C2′, C6′,
1
1JCF = 299), 163.6 d (C4′, JCF = 311), 194.9 d (C1α,
1
1JCF = 364). 19F NMR spectrum at 25°C, δF (∆δF), ppm:
16.5 (14.1) (2F, 3′-F, 5′-F), 24.8 (7.8) (1F, 5-F), 41.0
(0.5) (2F, 2β-F), 41.8 (26.4) (1F, 4-F), 43.9 (11.1) (1F,
3-F), 44.1 (13.4) (1F, 6-F), 64.9 (1.0) (2F, 2α-F), 83.6
(2.4) (3F, 2γ-F), 85.6 (71.9) (1F, 4′-F), 220.8 (133.3)
(1F, 1α-F). 19F NMR spectrum at –30°C, δF (∆δF),
ppm: 16.4 and 17.1 (2F, 3′-F, 5′-F), 25.3 (1F, 5-F), 42.4
and 39.9 (1F each, 2β-F, JAB = 291 Hz), 43.1 (1F, 4-F),
44.6 (1F, 3-F), 45.3 (1F, 6-F), 58.1 (35.9) (1F, 6′-F),
66.2 (44.0) (1F, 2′-F), 66.3 and 64.2 (1F each, 2α-F2,
JAB = 300 Hz), 84.1 (3F, 2γ-F), 85.1 (1F, 4′-F), 220.1
(1F, 1α-F).
The solution was poured into ice water, the mixture
was extracted with chloroform, and the extract was
dried over MgSO4 and evaporated to isolate 0.12 g of
ketone VI.
Perfluoro[(2-ethylphenyl)(phenyl)methyl] cation
(XXX). Compound XXIII, 0.10 g (0.21 mmol), was
dissolved in 0.60 g (2.77 mmol) of SbF5, and 0.27 g of
SO2ClF was added. The resulting solution contained
** Change of the chemical shift relative to the corresponding
value for the precursor.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 47 No. 7 2011

MEZHENKOVA et al.
1034
8. Sinyakov, V.R., Mezhenkova, T.V., Karpov, V.M., Plato-
The solution was poured into ice water, the mixture
nov, V.E., Rybalova, T.V., and Gatilov, Yu.V., Russ. J.
Org. Chem., 2003, vol. 39, p. 837.
was extracted with chloroform, and the extract was
dried over MgSO4 and evaporated to isolate 0.11 g of
ketone XXVIII.
9. Mezhenkova, T.V., Karpov, V.M., and Platonov, V.E.,
Russ. J. Org. Chem., 2011, vol. 47, p. 1018.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 06-03-32170).
10. Sinyakov, V.R., Mezhenkova, T.V., Karpov, V.M., and
Platonov, V.E., Russ. J. Org. Chem., 2007, vol. 43,
p. 1677.
11. Kemmitt, R.D.W., Murray, M., McRae, V.M.,
Peacock, R.D., Symons, M.C.R., and O’Donnell, T.A.,
J. Chem. Soc. A, 1968, p. 862; Davies, C.G., Gil-
lespie, R.J., Ireland, P.R., and Sowa, J.M., Can. J.
Chem., 1974, vol. 52, p. 2048.
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