Expansion of the pentafluorobenzene ring and other skeletal transformations in the reaction of perfluoro(1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene) with antimony pentafluoride

Article abstract of DOI:10.1134/S1070428012040112

The reaction of perfluoro(1-phenyl-1,2-diethyl-1,2-dihydrocuclobutabenzene) with SbF₅ at 20°C, followed by treatment of the reaction mixture with water gave perfluoro{4-[1-(2-propylphenyl)propylidene]- 2,5-cyclohexadien-1-one} together with per

Full text of DOI:10.1134/S1070428012040112

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 4, pp. 529–535. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © T.V. Mezhenkova, V.R. Sinyakov, V.M. Karpov, V.E. Platonov, 2012, published in Zhurnal Organicheskoi Khimii, 2012, Vol. 48,
No. 4, pp. 531–537.
Expansion of the Pentafluorobenzene Ring
and Other Skeletal Transformations in the Reaction
of Perfluoro(1,2-diethyl-1-phenyl-1,2-dihydrocyclobutabenzene)
with Antimony Pentafluoride*
T. V. Mezhenkova, V. R. Sinyakov, 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 August 4, 2011
Abstract—The reaction of perfluoro(1-phenyl-1,2-diethyl-1,2-dihydrocuclobutabenzene) with SbF5 at 20°C,
followed by treatment of the reaction mixture with water gave perfluoro{4-[1-(2-propylphenyl)propylidene]-
2,5-cyclohexadien-1-one} together with perfluoro[4b,10-diethylbenzo[a]azulen-7(4bH)-one] resulting from
unusual expansion of the pentafluorobenzene ring to seven-membered ring. Analogous reaction at 90°C, apart
from the above compounds, afforded perfluorinated 10-ethyl- and 3,10-diethylbenzo[a]azulen-6(10H)-ones via
elimination of C2F5 group from the seven-membered ring or its migration to the benzene ring.
DOI: 10.1134/S1070428012040112
Reactions of perfluorinated 1-alkyl- and 1,1- and
1,2-dialkyl-1,2-dihydrocyclobutabenzenes with SbF5
involve expansion or opening of the four-membered
ring with formation of polyfluorinated indans, o-alkyl-
styrenes, or o-dialkylbenzenes [2]. Perfluorinated
1-(2- or 4-ethylphenyl)-1,2-dihydrocyclobutabenzenes
[3] and 1- or 2-alkyl-1-phenyl-1,2-dihydrocyclobuta-
benzenes [4, 5] in SbF5 undergo opening of the four-
membered ring, and the subsequent cyclization yields
indan, fluorene, and anthracene derivatives. On the
other hand, perfluoro(1-phenyl-1,2-dihydrocyclobuta-
benzene) having no perfluoroalkyl group, did not un-
dergo skeletal transformations under analogous condi-
tions [3]. In the present work we examined the reaction
of perfluoro(1,2-diethyl-1-phenyl-1,2-dihydrocyclo-
butabenzene) (I) with antimony pentafluoride with
a view to elucidate how accumulation of perfluoro-
alkyl and perfluoroaryl groups in the four-membered
ring of 1,2-dihydrocyclobutabenzene affects the direc-
tion of skeletal transformations of polyfluorinated
1,2-dihydrocyclobutabenzenes.
of compound I in excess SbF5 (1:57) with addition of
SO2ClF was kept for 1 month at 20°C a mixture of
salts of perfluorinated 1-(2-propylphenyl)-1-phenyl-
prop-1-yl and 4b,10-diethyl-4b,7-dihydrobenzo[a]-
azulen-7-yl cations III and IV was formed (19F NMR
data), the former considerably prevailing (90:10). The
reaction performed under analogous conditions with
cyclobutabenzene I obtained as a 1:1 mixture with HF
from perfluoro(1,2-diethyl-1,2-dihydrocyclobutaben-
zene) (V) and C6HF5 in SbF5 (1:1:42) gave cations III
and IV at a ratio of 75:25. Reduction of the amount of
SbF5 to 6 mol per mole of the substrate and increase of
the reaction time to two months changed the ratio of
cations III and IV in favor of the latter (20:80). Cation
III is not converted into IV. Hydrolysis of the reaction
mixture containing cations III and IV afforded per-
fluoro{4-[1-(2-propylphenyl)propylidene]cyclohexa-
2,5-dien-1-one} (VI) and perfluoro{4b,10-diethylbenzo-
[a]azulen-7(4bH)-one} (VII), respectively (Scheme 1).
Raising the temperature to 50°C appreciably accel-
erated the reaction. Hydrolysis of the reaction mixture
gave ketones VI and VII, perfluoro(4b,10-diethyl-
4b,5,6,7-tetrahydrobenzo[a]azulene) (VIII), and per-
fluoro{4b,10-diethyl-5,6-dihydrobenzo[a]azulen-
7(4bH)-one} (IX), compounds VIII and IX being
We previously showed that compound I in SbF5
generates perfluoro(1,2-diethyl-2-phenyl-1,2-dihydro-
cyclobutabenzen-1-yl) cation (II) [6]. When a solution
* For preliminary communication, see [1].
529

MEZHENKOVA et al.
530
Scheme 1.
C2F5
C2F5
C6HF5, SbF5
I
+
HF
F
F
SbF5, SO2ClF
20°C
V
10
11
CF2CF3
CF3CF2
F
C2F5
C6F5
C2F5
C6F5
20°C
4
5
SbF5, SO2ClF
F
6
3
2
SbF5, SO2ClF
+
F
F
F
F
F
9
7
12
CF2
13CF2CF3
C2F5
C2F5
8
1
14
CF2CF3
I
II
III
IV
6
10 11
CF2CF3
O
14 13
5
CF3CF2
7
4
5
4
F
8
6
3
2
3
H2O
+
F
F
F
7
9
9
12
2
10
CF2
O
8
12
1
1
11CF2CF3
13CF21C4F3
VI
VII
Scheme 2.
C2F5
C2F5
C2F5
C2F5
C6HF5, SbF5
F
F
F
F
+
V
I
+
+ HF
C6F5
XI
X
C2F5
CFCF3
C2F5
F
C2F5
C2F5
C2F5
(1) SbF5, 50°C
(2) H2O
O
F
F
F
+
+
+ VI + VII
F
F
O
COC6F5
XV
C6F5
XIII
XIV
6
O
14 13
5
7
8
CF3CF2
CF3CF2
F
4
F
F
3
2
+
+
F
9
10
12
1
11CF2CF3
CF2CF3
IX
VIII
C2F5
C2F5
SbF5
H2O
X
XIII–XV
F
C6F5
XII
formed as a result of fluorination of one double bond
in the seven-membered ring (Scheme 2). The same
reaction was carried out with a mixture of compound I
and perfluoro(1,1-diethyl-2-phenyl-1,2-dihydrocyclo-
butabenzene) (X) which was obtained by reaction of
compound V and perfluoro(1,1-diethyl-1,2-dihydro-
cyclobutabenzene) (XI) with pentafluorobenzene in
the presence SbF5 [6]. Under these conditions, com-
pound X in SbF5 gives rise to stable perfluoro(2,2-
diethyl-1-phenyl-1,2-dihydrocyclobutabenzen-1-yl)
cation (XII) which does not undergo skeletal trans-
formations but is converted (after hydrolysis) into
a mixture of ketones XIII–XV reported previously [6]
(Scheme 2).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 4 2012

EXPANSION OF THE PENTAFLUOROBENZENE RING
531
Scheme 3.
O
(1) SbF5, 90°C
(2) H2O
F
F
C6HF5, SbF5
O
V
I
+
HF
VI–IX
+
F
F
+
F
F
CF2CF3
CF2CF3
XVI
XVII
3'
O
4'
5'
2'
6
7
F
5
HO
F
14 13
CF3CF2
4
7
F
F
6'
F3CF2C
3
1
3
8
6
5
O
+
F
F
+
F
F
+
F
CF3
2
9
2
10
4
1
12
11CF2CF3
CF2CF3
CF2CF3
XX
XVIII
XIX
Scheme 4.
Path a:
C2F5
C6F5
C2F5
C2F5
C6F5
F–
[F]
C6F5
H2O
F
I
III
VI
F
F
F
F
–F–
–F–
CF CFCF3
CF2CF2CF3
CFCF3
A
B
C
Path b:
C2F5
C6F5
C6F5
F
CFCF3
C2F5
H2O
CFCF3
CFCF2CF3
E
I
XX
F
F
F
F
CF3
–F–
C2F5
D
F
Path c:
C2F5
C2F5
C2F5
F
I
F
F
F
F
F
–F–
C2F5
C2F5
C2F5
II
G
H
C2F5
F
H2O
VII
F
C2F5
IV
Hydrolysis of the reaction mixture obtained by
heating compound I in SbF5 in the presence of HF
(1:7:1) at 90°C led to the formation of a complex mix-
ture of products containing compounds VI–IX, per-
fluoro[10-ethylbenzo[a]azulen-6(10H)-one] (XVI),
perfluoro[10-ethylbenzo[a]azulen-8(10H)-one]
(XVII), perfluoro[3,10-diethylbenzo[a]azulen-6(10H)-
one] (XVIII), perfluoro[3,10-diethylbenzo[a]azulen-
8(10H)-one] (XIX), and perfluoro(3-ethyl-2-methyl-1-
phenylindan-1-ol) (XX) (Scheme 3).
Presumably, the four-membered ring in compound I
is opened according to path a with participation of
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 4 2012

MEZHENKOVA et al.
532
Scheme 5.
C2F5
F
F–
–F–
H2O
F–
[F]
VIII
IX
F
C2F5
C2F5
J
F
F
F
F
F
C2F5
F
H2O
[F]
F
XVI + XVII
–[C2F5]+
–F–
F
F
F
F
C2F5
C2F5
K
L
C2F5
F
C2F5
F
C2F5
C2F5
F
F
F
F
F
F
C2F5
C2F5
C2F5
C2F5
IV
F
F
F
C2F5
F
F–
F
F
C2F5
C2F5
F
· · ·
–F–
F
F
F
F
C2F5
C2F5
C2F5
M
N
H2O
XVIII + XIX
cyclobutabenzenylethyl cation A which undergoes
isomerization into diarylalkyl cation B. The latter takes
up fluoride ion, and the subsequent fluorination yields
perfluorinated diarylalkane C. Intermediate C in SbF5
generates cation III whose hydrolysis leads to product
VI (Scheme 4). Expansion of the four-membered ring
in I to five-membered can also follow path b involving
opening of the four-membered ring in cation D. Cy-
clization of benzyl type cation E thus formed yields
phenylindanyl cation F, and hydrolysis of the latter
leads to compound XX. Analogous mechanism was
proposed by us previously for skeletal transformations
of perfluorinated alkyl-, dialkyl-, and alkylphenyl-
cyclobutabenzenes in SbF5 [2–5].
path c. Attack by the cationic center on the phenyl
group gives phenonium ion G which undergoes iso-
merization into ion H and then into ion IV (Scheme 4).
Analogous rearrangements of intermediate carbenium
ions with expansion of the four-membered ring into
five-membered and of the benzene ring into seven-
membered were considered in [7] to rationalize the
formation of 1,2,3-triphenylazulene from (2,3-di-
phenylcycloprop-2-en-1-yl)diphenylmethanol.
Probably, benzoazulene derivatives VIII, IX, and
XVI–XIX are formed via transformations of cation IV.
Addition of a fluoride ion to IV and subsequent
fluorination lead to compound VIII which gives rise to
cation J by the action of SbF5, and hydrolysis of J
yields ketone IX (Scheme 5). Elimination of perfluoro-
ethyl cation from ion IV gives intermediate K which is
converted into cation L via fluorination followed by
abstraction of fluoride ion. Structure L contains two
Unusual expansion of the six-membered aromatic
ring in molecule I to seven-membered with simul-
taneous expansion of the four-membered ring to five-
membered is likely to occur in cation II according to
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 4 2012

EXPANSION OF THE PENTAFLUOROBENZENE RING
533
aromatic fragments, perfluorinated benzene ring and
tropylium ion (generation of perfluorotropylium ion
was reported in [8]). Hydrolysis of L yields ketones
XVI and XVII (Scheme 5).
pounds VII and VIII were measured from solutions in
CDCl3 on a Bruker AV-400 instrument (376.5 MHz).
The chemical shifts were determined relative to C6F6
or SO2ClF (δF 262.8 ppm relative to C6F6) as internal
reference; for atom numbering, see Schemes 1–3. The
elemental compositions of compounds VI–IX and
XVI–XX were determined from the high-resolution
mass spectra which were obtained on a Thermo
Electron Corporation DFS mass spectrometer. Gas–
liquid chromatography was performed on an LKhM-72
chromatograph; oven temperature programming from
50 to 270°C; 4000 × 4-mm column packed with
SKTFT-50 on Chromosorb W (15:100); carrier gas
helium, flow rate 60 ml/min. Initial compounds I and
X were synthesized as described in [6], and com-
pounds V and XI were prepared according to the
procedures reported in [11].
Reaction of perfluoro(1,2-diethyl-1-phenyl-1,2-
dihydrocyclobutabenzene) (I) with SbF5. a. Com-
pound I, 0.05 g (0.08 mmol), was dissolved in 0.99 g
(4.57 mmol) of SbF5, and 0.30 g of SO2ClF was added;
the resulting mixture contained cation II [6]. The mix-
ture was kept for 30 days at 20°C to obtain a mixture
containing cations III and IV at a ratio of 90 :10
(according to the 19F NMR data). The mixture was
poured into ice water and extracted with chloroform,
the extract was dried over MgSO4, and the solvent was
distilled off. The residue, 0.05 g, contained* 81% of
ketone VI and 13% of ketone VII.
b. Compound V, 0.05 g (0.10 mmol), was dissolved
in 0.92 g (4.24 mmol) of SbF5, 0.02 g (0.11 mmol) of
pentafluorobenzene was added, and the mixture was
stirred and kept for 24 h at 20°C; the mixture con-
tained cation II [6] and HF. Sulfuryl chloride fluoride,
0.30 g, was added, and the mixture was kept for
43 days at 20°C; it contained cations III and IV at
a ratio of 75:25 (19F NMR). The mixture was treated
as described above in a to obtain 0.06 g of a mixture
containing 57% of VI and 24% of VII.
c. As described above in b, from 0.21 g (0.47 mmol)
of compound V, 0.08 g (0.48 mmol) of pentafluoro-
benzene, 0.64 g (2.95 mmol) of SbF5, and 0.36 g of
SO2ClF in 40 days at 20°C we obtained a mixture
containing cations III and IV at a ratio of 20 :80
(19F NMR). The mixture was kept for 20 days more at
20°C. According to the 19F NMR data, the ratio of
cations III and IV remained unchanged.
We believe that the driving force for the migration
of C2F5 group to the benzene ring in ion IV is also the
formation of analogous stable cation N. Migration of
the C2F5 group is likely to occur via several successive
1,2-shifts (Scheme 5) leading to cation M. Isomeriza-
tion of the latter into cation N involves addition–
elimination of fluoride ion, and hydrolysis of N gives
a mixture of ketones XVIII and XIX. No C2F5 group
migration in cationic species was observed previously.
However, possible migration of CF3 group via 1,2-shift
was considered by us previously, e.g., in the isomeriza-
tion of perfluoro(1-ethylindan) into perfluoro(1,1-di-
methylindan) by the action of SbF5 [9] and in the
formation of perfluoro(9-ethyl-9-methyl-1,2,3,4-tetra-
hydrofluorene) by reaction of perfluoro(1-ethyl-1-
phenyl-1,2-dihydrocyclobutabenzene) with antimony
pentafluoride [4].
Thus the transformations of compound I in SbF5
revealed previously unknown (for polyfluoroaromatic
compounds) cationoid expansion of pentafluoroben-
zene ring to seven-membered with formation of per-
fluoro(benzo[a]azulene) derivatives. Fluorine-free
benzo[a]azulene compounds were obtained by thermal
reaction of benzene with sodium salts derived from
cyclobutabenzen-1(2H)-one and 2-methylcyclobuta-
benzen-1(2H)-one tosylhydrazones [10].
The structure of cations III and IV was determined
on the basis of their 19F NMR spectra and was con-
firmed by the structure of the corresponding hydrolysis
products. The structure of compounds VI–IX and
XVI–XX was determined by high-resolution mass
spectrometry and 19F NMR spectroscopy. In addition,
the structure of VII and XVI was proved by X-ray
analysis, and specific features of their molecular struc-
tures were discussed in [1]. The 19F NMR spectrum of
VI was analyzed in comparison to the spectrum of
perfluoro{4-[1-(2-methylphenyl)propylidene]cyclo-
hexa-2,5-dien-1-one} whose structure was determined
by X-ray analysis [4].
EXPERIMENTAL
The 19F NMR spectra of the reaction mixtures
containing cations III and IV in SbF5–SO2ClF and of
solutions of pure compounds VI, IX and XVI–XX in
CDCl3 were recorded on a Bruker AV-300 spectrom-
eter at 282.4 MHz. The 19F NMR spectra of com-
Perfluoro[1-phenyl-1-(2-propylphenyl)prop-1-yl]
cation (III). 19F NMR spectrum (from mixture III/IV),
** Hereinafter the compositions of the reaction mixtures are given
in wt % according to the GLC and 19F NMR data.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 4 2012

MEZHENKOVA et al.
534
δF, ppm: 22.8 (2F, 6-F, 8-F), 23.9 (1F, 3-F), 27.3 (1F,
2-F), 35.0 and 40.2 (1F each, 1-F, 4-F), 40.7 (2F,
13-F), 61.8 (2F, 10-F), 64.5 and 60.8 (1F each, 12-F,
JAB = 290 Hz), 81.8 (1F, 9-F), 83.6 (3F, 14-F), 88.3
24% of VII, 4% of VIII, 4% of IX, 11% of XIII,
3% of XIV, and 24% of XV.
d. A mixture of 1.26 g (2.81 mmol) of compounds
V and XI at a ratio of 55:45 was dissolved in 4.29 g
(19.79 mmol) of SbF5, 0.52 g (3.10 mmol) of penta-
fluorobenzene was added, and the mixture was stirred
for 40 h at 20°C to generate cations II and XII at
a ratio of ~50 :50 [6]. The mixture was stirred for
300 h at 50°C and treated as described above in a to
obtain 1.72 g of a mixture of products containing 18%
of VI, 5% of VII, 15% of VIII, 11% of IX, 11% of
XIII, 3% of XIV, and 25% of XV. By column chro-
matography on silica gel using first hexane and then
carbon tetrachloride as eluents we isolated 0.15 g of
VIII, 0.13 g of IX and 0.22 g of VI.
(3F, 11-F), 92.4 (1F, 5-F), 124.2 (1F, 7-F); J5,7 ≈ J7,9
65, J6,7 ≈ J7,8 ≈ 25 Hz.
≈
Perfluoro(4b,10-diethyl-4b,7-dihydrobenzo[a]-
azulen-7-yl) cation (IV). 19F NMR spectrum (from
mixture III/IV), δF, ppm: 24.9 (1F, 2-F), 30.8 and 31.1
(1F each, 6-F, 8-F), 41.4 (1F, 4-F), 45.1 (1F, 3-F),
~55.3 (1F, 1-F), 57.1 and 56.2 (1F each, 13-F, JAB
=
278 Hz), 58.2 and 57.4 (1F each, 11-F, JAB ≈ 290 Hz),
84.1 (3F, 12-F), 84.9 (3F, 14-F), 117.7 (1F, 5-F), 129.1
(1F, 7-F), 136.3 (1F, 9-F); J4,5 ≈ J5,7 ≈ 60, J7,9 ≈ 80,
J9,10B ≈ 70 Hz.
The mixture was treated as described above in a to
obtain 0.25 g of a mixture containing 14% of ketone
VI and 65% of ketone VII. By column chromatog-
raphy on silica gel using first carbon tetrachloride and
then chloroform as eluents we isolated 0.03 g of ketone
VI and 0.11 g of VII.
Perfluoro(4b,10-diethyl-4b,5,6,7-tetrahydroben-
zo[a]azulene) (VIII). Liquid, purity 98%. 19F NMR
spectrum (at 60°C),*** δF, ppm: 16.4 and 17.1 (1F
each, 2-F, 3-F), 18.1 (1F, 8-F), 32.3 and 33.6 (1F each,
1-F, 4-F), 35.9 (2F, 6-F), 50.9 (1F, 9-F), 51.7 and 47.6
(1F each, 11-F, JAB = 282 Hz), ~55.0 and ~44.5 (1F
each, 7-F), 56.2 and 54.8 (1F each, 5-F, JAB ≈ 280 Hz),
60.5 and 55.8 (1F each, 13-F, JAB ≈ 280 Hz), 80.0 (3F,
12-F), 82.2 (3F, 14-F). Found: m/z 633.9634 [M]+.
C18F22. Calculated: M 633.9643.
Perfluoro{4-[1-(2-propylphenyl)propylidene]-
cyclohexa-2,5-dien-1-one} (VI). Liquid, purity 97%.
19F NMR spectrum, δF, ppm: 15.2 (1F, 2-F), 16.4 and
17.3 (1F each, 6-F, 8-F), 17.3 (1F, 3-F), 29.3 (1F, 4-F),
31.7 (2F, 1-F, 9-F), 34.8 (1F, 5-F), 37.4 (2F, 13-F), 58.7
and 57.7 (1F each, 12-F, JAB = 290 Hz), 62.20 (1F,
10′-F), 62.24 (1F, 10-F), 81.8 (3F, 14-F), 83.7 (3F,
11-F); J1,A = 30, J1,2 = 20, J1,3 = J1,4 = 10, J2,3 = 21,
J2,4 = 7, J3,4 = 22, J4,11 = 12, J5,10 = 62, J5,10′ = 79,
J5,11 = 26, J5,6 = J8,9 = 7, J9,10 = J9,10′ = 11 Hz. Found:
m/z 611.9617 [M]+. C18F20O. Calculated: M 611.9630.
Perfluoro{4b,10-diethyl-5,6-dihydrobenzo[a]-
azulen-7(4bH)-one} (IX). Liquid, purity 98%.
19F NMR spectrum, δF, ppm: 17.3 and 17.7 (1F each,
2-F, 3-F), 23.4 (1F, 8-F), 32.6 (1F, 1-F), 34.1 (1F, 4-F),
45.8 and 38.6 (1F each, 6-F, JAB = 282 Hz), 51.2 and
47.2 (1F each, 11-F, JAB = 284 Hz), 56.3 and 54.2 (1F
each, 5-F, JAB = 279 Hz), 62.7 and 56.6 (1F each, 13-F,
JAB ≈ 280 Hz), 65.9 (1F, 9-F), 79.5 (3F, 12-F), 82.2 (3F,
14-F); J1,11A = 62, J1,11B = 24, J1,12 = 18, J4,5B ≈ 50,
Perfluoro{4b,10-diethylbenzo[a]azulen-7(4bH)-
one} (VII). mp 71–73°C (from hexane–CH2Cl2).
19F NMR spectrum, δF, ppm: 17.0 (2F, 2-F, 3-F), 25.1
(1F, 8-F), 29.3 (1F, 6-F), 32.3 (1F, 1-F), 34.2 (1F, 4-F),
54.3 and 48.6 (1F each, 11-F, JAB = 284 Hz), 54.5 and
51.4 (1F each, 13-F, JAB = 278 Hz), 55.1 (1F, 9-F), 57.4
(1F, 5-F), 80.5 (3F, 12-F), 82.0 (3F, 14-F); J1,11A = 86,
J1,12 = 21, J4,5 = 64, J4,13A = 82, J5,13A = 8, J6,8 = 8,
J8, 9 = 12, J9, 11B = 54, J9, 12 = 21 Hz. Found:
m/z 573.9665 [M]+. C18F18O. Calculated: M 573.9662.
J4,13A ≈ 65, J8,9 = 12, J9,11A = 17, J9,11B = 24, J9,12
=
12 Hz. Found: m/z 611.9635 [M]+. C18F20O. Calculat-
ed: M 611.9630.
f. A mixture of 0.53 g (1.18 mmol) of compound V,
0.2 g (1.19 mmol) of pentafluorobenzene, and 1.79 g
(8.26 mmol) of SbF5 was kept for 40 h at 20°C in
a sealed ampule and was then heated for 15 h at 90°C.
The mixture was then treated as described above in a
to obtain 0.64 g of a mixture of products containing
23% of VI, 11% of VII, 8% of VIII, 5% of IX, 12% of
XVI, 12% of XVII, 4% of XVIII, 4% of XIX, and 3%
of XX. By column chromatography on silica gel using
first carbon tetrachloride and then chloroform as
d. A mixture of 0.95 g (2.12 mmol) of compounds
V and XI at a ratio of 55:45 was dissolved in 3.23 g
(14.90 mmol) of SbF5, 0.36 g (2.14 mmol) of penta-
fluorobenzene was added, and the mixture was stirred
for 7 h at 25°C to generate cations II and XII at a ratio
of ~50:50 [6]. The mixture was stirred for 200 h at
50°C and treated as described above in a to obtain
1.24 g of a mixture of products containing 17% of VI,
*** In the spectrum recorded at 20°C some signals were not
observed because of considerable broadening.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 4 2012

EXPANSION OF THE PENTAFLUOROBENZENE RING
535
eluents we isolated 0.1 g of VI, 0.06 g of a mixture
containing 27% of XVIII, 27% of XIX, and 30% of
XX, and 0.09 g of an approximately equimolar mixture
of isomers XVI and XVII. Recrystallization of mixture
XVI/XVII from carbon tetrachloride gave 0.02 g of
XVI. The mother liquor was evaporated, and the
residue was recrystallized from hexane with addition
of methylene chloride to obtain 0.03 g of a mixture of
compounds XVI and XVII at a ratio of 20:80 (accord-
ing to the 19F NMR data). Repeated column chroma-
tography of 0.11 g of a mixture containing 28% of
XVIII, 29% of XIX, and 33% of XX (obtained in two
experiments) using first carbon tetrachloride and then
chloroform as eluents gave 0.02 g of XX and 0.04 g of
isomer mixture XVIII/XIX at a ratio of 1:1. The latter
was recrystallized from hexane with addition of meth-
ylene chloride to isolate 0.01 g of compound XVIII.
The mother liquor was evaporated, and the residue was
recrystallized to obtain 0.015 g of a mixture of isomers
XVIII and XIX at a ratio of 25:75 (19F NMR).
XIX), δF, ppm: –12.7 (1F, 10-F), 26.7 (1F, 1-F), 34.8
(1F, 6-F), 40.5 (1F, 2-F), 41.9 (1F, 7-F), 43.8 (2F, 11-F),
50.8 (2F, 13-F), 60.5 (1F, 5-F), 63.1 (1F, 4-F), 68.6 (1F,
9-F), 76.6 (3F, 14-F), 81.7 (3F, 12-F); J4,5 = 156, J5,6
=
J5,7 = J6,7 = 12, J5,9 = 26, J7,9 = 46 Hz. Found:
m/z 573.9644 [M]+. C18F18O. Calculated: M 573.9656.
Perfluoro(3-ethyl-2-methyl-1-phenylindan-1-ol)
(XX). Liquid, purity 97%. 19F NMR spectrum, δF,
ppm: –10.3 (1F, 2-F), –4.2 (1F, 3-F), 2.0 and 2.1 (1F
each, 3′-F, 5′-F), 13.0 (1F, 4′-F), 14.6 (1F, 5-F), 17.5
(1F, 6-F), 21.1 and 25.5 (1F each, 2′-F, 6′-F), 21.5 (1F,
7-F), 26.1 (1F, 4-F), 45.7 and 42.8 (1F each, CF2CF3,
JAB = 294 Hz), 83.0 (3F, CF2CF3), 91.2 (3F, CF3);
J4,5 = J5,6 = J6,7 = 20, J4,7 = 17, J4,6 = 9, J5,7 = 6 Hz.
Found: m/z 593.9716 [M]+. C18HF19O. Calculated:
M 593.9724.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 10-03-00120).
Perfluoro[10-ethylbenzo[a]azulen-6(10H)-one]
(XVI). mp 185–188°C (from hexane–benzene; sealed
capillary). 19F NMR spectrum, δF, ppm: –9.3 (1F,
10-F), 17.9 (1F, 2-F), 19.1 (1F, 3-F), 27.5 (1F, 1-F),
29.6 (1F, 8-F), 40.3 (1F, 4-F), 43.3 (2F, CF2CF3), 44.1
(1F, 7-F), 54.0 (1F, 9-F), 73.4 (1F, 5-F), 81.6 (3F, CF3);
J1,2 = J3,4 = 20, J1,3 = 8, J1,4 = 15, J2,3 = 19, J2,4 = 10,
J4,5 = 150, J5,7 = 46, J5,9 = 27, J7,8 = J7,9 = J8,9 = 14 Hz.
Found: m/z 473.9704 [M]+. C16F14O. Calculated:
M 473.9725.
REFERENCES
1. Mezhenkova, T.V., Sinyakov, V.R., Karpov, V.M.,
Platonov, V.E., Rybalova, T.V., and Gatilov, Yu.V.,
J. Fluorine Chem., 2008, vol. 129, p. 64.
2. Karpov, V.M., Mezhenkova, T.V., Platonov, V.E., and
Yakobson, G.G., J. Fluorine Chem., 1985, vol. 28,
p. 115; Karpov, V.M., Mezhenkova, T.V., Platonov, V.E.,
and Yakobson, G.G., Izv. Akad. Nauk SSSR, Ser. Khim.,
1990, p. 1114; Karpov, V.M., Mezhenkova, T.V., and
Platonov, V.E., Izv. Ross. Akad. Nauk, Ser. Khim., 1992,
p. 1419.
Perfluoro[10-ethylbenzo[a]azulen-8(10H)-one]
(XVII). 19F NMR spectrum (from mixture XVI/XVII),
δF, ppm: –11.2 (1F, 10-F), 16.9 (1F, 2-F), 18.7 (1F,
3-F), 27.6 (1F, 1-F), 34.2 (1F, 6-F), 37.8 (1F, 4-F), 41.2
(1F, 7-F), 43.8 (2F, CF2CF3), 58.7 (1F, 5-F), 68.5 (1F,
3. Karpov, V.M., Mezhenkova, T.V., Platonov, V.E., and
Sinyakov, V.R., J. Fluorine Chem., 2002, vol. 117, p. 73.
4. Mezhenkova, T.V., Sinyakov, V.R., Karpov, V.M., Plato-
nov, V.E., and Gatilov, Yu.V., J. Fluorine Chem., 2009,
vol. 130, p. 951.
9-F), 81.7 (3F, CF3); J1,2 ≈ J2,3 ≈ J3,4 ≈ 20, J1,3 ≈ J2,4
≈
5. Mezhenkova, T.V., Karpov, V.M., and Platonov, V.E.,
8, J1,4 ≈ 15, J4,5 = 146, J5,6 ≈ J5,7 ≈ J6,7 ≈ 12, J5,9 = 27,
J7,9 = 46 Hz. Found: m/z 473.9724 [M]+. C16F14O.
Calculated: M 473.9725.
Russ. J. Org. Chem., 2011, vol. 47, p. 1018.
6. Sinyakov, V.R., Mezhenkova, T.V., Karpov, V.M., and
Platonov, V.E., Russ. J. Org. Chem., 2007, vol. 43,
p. 1677.
7. Breslow, R. and Battiste, M., J. Am. Chem. Soc., 1960,
vol. 82, p. 3626.
8. Dailey, W.P. and Lemal, D.M., J. Am. Chem. Soc., 1984,
vol. 106, p. 1169.
9. Karpov, V.M., Mezhenkova, T.V., and Platonov, V.E.,
Izv. Akad. Nauk SSSR, Ser. Khim., 1990, p. 645.
10. O’Leary, M.A., Richardson, G.W., and Wege, D., Tetra-
hedron, 1981, vol. 37, p. 813.
Perfluoro[3,10-diethylbenzo[a]azulen-6(10H)-
one] (XVIII). mp 164–166°C (from hexane–CH2Cl2;
sealed capillary). 19F NMR spectrum, δF, ppm: –10.6
(1F, 10-F), 26.6 (1F, 1-F), 29.5 (1F, 8-F), 41.5 (1F,
2-F), 43.4 (2F, 11-F), 44.6 (1F, 7-F), 50.8 (2F, 13-F),
54.1 (1F, 9-F), 65.5 (1F, 4-F), 75.2 (1F, 5-F), 76.6 (3F,
14-F), 81.6 (3F, 12-F); J4,5 = 156, J5,7 = 46, J5,9 = 26,
J7,8 = J7,9 = J8,9 = 14 Hz. Found: m/z 573.9649 [M]+.
C18F18O. Calculated: M 573.9656.
Perfluoro[3,10-diethylbenzo[a]azulen-8(10H)-
one] (XIX). 19F NMR spectrum (from mixture XVIII/
11. Karpov, V.M., Mezhenkova, T.V., Platonov, V.E., and
Yakobson, G.G., J. Fluorine Chem., 1985, vol. 28, p. 121.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 48 No. 4 2012