Transformations of perfluorinated 2-Alkyl- and 2,2- dialkylbenzocyclobutenones in SbF5 and SiO2-SbF 5

Article abstract of DOI:10.1134/S1070428010100131

Perfluorinated 2-methyl- and 2-ethylbenzocyclobutenones on heating in SbF₅ underwent isomerization into perfluoroindan-1-one and perfluoro(2-methylindan-1-one), while their reaction with SiO ₂-SbF₅ gave perfluorinated 3-methyl- and 3-ethylphthalides, respectively. Perfluorinated 2-ethyl-2-methyl- and 2,2-diethylbenzocyclobutenones reacted with SbF₅ to produce perfluorinated 2-(but-2-en-2-yl)- and 2-(pent-2-en-3-yl)-benzoic acids, and their transformations in SbF₅ over SiO₂ afforded 5,6,7,8-tetrafluoro-1-oxo-3-trifluoromethyl-1H-isochromene-4-carboxylic acid and perfluoro(4-ethyl-3-methyl-1H-isochromen-1-one), respectively.

Full text of DOI:10.1134/S1070428010100131

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 10, pp. 1517–1526. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © Ya.V. Zonov, V.M. Karpov, V.E. Platonov, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46, No. 10,
pp. 1512–1520.
Transformations of Perfluorinated 2-Alkyl- and 2,2-Dialkyl-
benzocyclobutenones in SbF5 and SiO2–SbF5
Ya. V. Zonova, b, V. M. Karpova, and V. E. Platonova
a Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 9, Novosibirsk, 630090 Russia
e-mail: karpov@nioch.nsc.ru
b Novosibirsk State University, Novosibirsk, Russia
Received March 16, 2010
Abstract—Perfluorinated 2-methyl- and 2-ethylbenzocyclobutenones on heating in SbF5 underwent isomeriza-
tion into perfluoroindan-1-one and perfluoro(2-methylindan-1-one), while their reaction with SiO2–SbF5 gave
perfluorinated 3-methyl- and 3-ethylphthalides, respectively. Perfluorinated 2-ethyl-2-methyl- and 2,2-diethyl-
benzocyclobutenones reacted with SbF5 to produce perfluorinated 2-(but-2-en-2-yl)- and 2-(pent-2-en-3-yl)-
benzoic acids, and their transformations in SbF5 over SiO2 afforded 5,6,7,8-tetrafluoro-1-oxo-3-trifluoromethyl-
1H-isochromene-4-carboxylic acid and perfluoro(4-ethyl-3-methyl-1H-isochromen-1-one), respectively.
DOI: 10.1134/S1070428010100131
We previously reported on carbocationoid skeletal
transformations of carbonyl derivatives of perfluorinat-
ed tetralin [1], indan [2], 1-methyl- [3] and 1-ethyl-
indanes [4], benzocyclobutene [1], and 1-ethyl-1-
phenyl- and 1,1-diethylbenzocyclobutenes [5], which
were previously unknown for perfluoro ketones. We
found that the behavior of polyfluorinated substrate
depends on the size of the carbonyl-containing ring
and on the nature of perfluoroalkyl groups therein. The
effect of SiO2 on the transformations of perfluoro-
(3-ethylindan-1-one) and perfluoro(3-methylindan-1-
one) in SbF5 was revealed [3, 4]. Cationoid skeletal
rearrangements of other carbonyl derivatives of poly-
fluorobenzocycloalkenes were not reported previously.
relations holding in such transformations of poly-
fluorobenzocycloalkenone derivatives.
Perfluoro(2-methylbenzocyclobuten-1-one) (I) on
heating in SbF5 at 75°C underwent isomerization into
perfluoroindan-1-one (V). Apart from compound V,
the mixture obtained after treatment of the reaction
mixture with water contained small amounts of
2-pentafluoroethyl-3,4,5,6-tetrafluorobenzoic acid
(VI), perfluoro(3-methylphthalide) (VII), 4,5,6,7-tetra-
fluoro-3-hydroxy-3-trifluoromethyl-2-benzofuran-1-
one (VIII), and unreacted compound I (Scheme 1).
Presumably, expansion of the four-membered ring in
ketone I occurs according to Scheme 2. Opening of the
four-membered ring in cation A generated from com-
pound I by abstraction of fluoride ion yields benzoyl
cation B which undergoes intramolecular cyclization to
cation C, and addition of fluoride ion to the latter gives
indanone V.
In the present work we examined the behavior of
perfluorinated 2-methyl-, 2-ethyl-, 2-ethyl-2-methyl-,
and 2,2-diethylbenzocyclobutenones I–IV in SbF5 and
in the system SiO2–SbF5 with a view to reveal general
Scheme 1.
X
CF3
CF3
(1) SbF5, 75°C
(2) H2O
CF2CF3
COOH
F
F
F
F
+
F
+
F
O
O
O
O
I
V
VI
VII, VIII
VII, X = F; VIII, X = OH.
1517

ZONOV et al.
1518
Scheme 2.
F
CF3
CF2
F
F
CF2
F–
F
F
F
F
F
F
F
–F–
CO
O
O
O
O
I
A
B
C
V
F
CF2CF3
COF
CF2CF3
COOH
F–
CF2
COF
SbF5
H2O
B
F
F
F
–SbF3
VI
The formation of acyclic intermediate B from
ketone I is confirmed by the presence among the
products of an appreciable amount of acid VI (5–7%)
which is likely to result from addition of fluoride ion to
benzoyl cation B, fluorination of perfluoro(2-vinyl-
benzoyl) fluoride thus obtained, and hydrolysis of the
fluorination product (Scheme 2). By special experi-
ment we showed that acid VI is not formed via trans-
formation of indanone V under analogous conditions
(only traces of VI were detected, ~0.5%). On the other
hand, the presence of phthalides VII and VIII among
the products may be rationalized by transformations of
perfluoro(indan-1,3-dione) generated from indanone V
via disproportionation or reaction with inorganic ox-
ides [2] formed by reaction of antimony pentafluoride
with atmospheric moisture.
Ethylbenzocyclobutenone II underwent isomeriza-
tion into perfluoro(2-methylindan-1-one) (IX) on heat-
ing in SbF5 under more severe conditions as compared
to analogous transformation of methylbenzocyclobute-
none I. Hydrolysis of the reaction mixture obtained by
heating ketone II with SbF5 at 120°C (4.5 h) gave
a mixture of indanone IX, initial compound II, and
small amounts of 3,4,5,6-tetrafluoro-2-heptafluoropro-
pylbenzoic acid (X), perfluoro(3-ethylphthalide) (XI),
and 4,5,6,7-tetrafluoro-3-hydroxy-3-pentafluoroethyl-
2-benzofuran-1-one (XII) (Scheme 3).
Prolonged heating of compound II in SbF5 at
130°C (39 h) resulted in the formation of compounds
IX–XI together with perfluoro(3-methylisochroman-1-
one) (XIII) and perfluoro(2-methylindan) (XIV), the
Scheme 3.
X
C2F5
(1) SbF5, 120°C, 4.5 h
(2) H2O
C3F7
F
F
CF3
+
F
F
+
F
O
COOH
O
O
IX
X
XI, XII
C2F5
F
(1) SbF5, 130°C, 39 h
(2) H2O
CF3
IX
+
X
+
XI
+
F
+
F
F
CF3
F
O
O
II
O
XIII
XIV
F
F
(1) SbF5, 180°C, 63 h
(2) H2O
CF3
X
+
XI
+
XIII
+
F
O
O
XV
XI, X = F; XII, X = OH.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 10 2010

TRANSFORMATIONS OF PERFLUORINATED 2-ALKYL- ...
1519
Scheme 4.
F
C2F5
F
CFCF3
CF3
F
F
F
F
F
F
CF3
–F–
F
CO
O
O
O
II
D
F
O
O
F–
–F–
F
SbF5
F
F
F
F
F
XI, XII
CF3
CF3
+
CF3
O
IX
XIV
E
CF=CFCF3
CF=CFCF2
F–
F
X, XIII, XV
F
F
–F–
COF
COF
H
G
ring in ketone II gives cation F which can also be
generated by reversible opening of the five-membered
ring in indanone IX resulting from the reaction of
ketone II with SbF5. Cation F in SbF5 can undergo
isomerization into cation G through intermediate H.
Possible schemes of further transformations of inter-
mediates G and H, leading to compounds X, XIII, and
XV, were considered previously [1].
conversion of initial ketone II being complete. Raising
the temperature to 180°C led to predominant formation
of acid X; in addition, heterocyclic compounds XI and
XIII and perfluoro(3-methylisochromen-1-one) (XV)
were formed (Scheme 3).
Presumably, the mechanism of isomerization of
pentafluoroethyl-substituted ketone II into methylinda-
none IX (Scheme 4) is analogous to the transformation
of ketone I into indanone V (Scheme 2). More severe
conditions for the reaction with ketone II are likely to
be necessary because of the lower stability of cation D
as compared to A (due to the presence of a trifluoro-
methyl group rather than fluorine atom at the cationic
center in ion D [6]). Analogous reactivity series was
observed previously while studying expansion of the
four-membered ring in perfluorinated 1-methyl- and
1-ethylbenzocyclobutenes [7].
Skeletal transformations of perfluorinated 2,2-di-
alkylbenzocyclobutenones III and IV by the action of
SbF5 require milder conditions than in the reactions
with 2-alkyl-substituted analogs I and II. Perfluoro-
(2-ethyl-2-methylbenzocyclobuten-1-one) (III) was
heated with antimony pentafluoride at 50°C, and hy-
drolysis of the reaction mixture gave perfluoro[2-(but-
2-en-2-yl)benzoic acid] (XVI). When the reaction
temperature was raised to 125°C, a solution containing
perfluorinated 4-ethyl- and 3,4-dimethylisochromenyl
cations XVII and XVIII was obtained, and subsequent
hydrolysis gave a mixture of perfluoro(4-ethylisochro-
men-1-one) (XIX), perfluoro(3,4-dimethylisochromen-
1-one) (XX), and 5,6,7,8-tetrafluoro-3-hydroxy-3,4-bis-
(trifluoromethyl)isochroman-1-one (XXI) (Scheme 5).
Phthalides XI and XII and methylindan XIV are
likely to be formed in the reaction of ketone II with
antimony pentafluoride via disproportionation of inda-
none IX into indan XIV and perfluoro(2-methylindan-
1,3-dione) E (Scheme 4). The latter is converted into
phthalides XI and XII by analogy with the transforma-
tion of perfluoroindan-1,3-dione into phthalides VII
and VIII, which was described previously [2]. This
assumption is supported by the fact that compounds XI
and XIV are formed in approximately equal amounts
in the reaction of II with SbF5 at 130°C. The formation
of acid X and six-membered heterocyclic compounds
XIII and XV from benzocyclobutenone II is also illus-
trated by Scheme 4. Opening of the four-membered
Scheme 5 shows a probable path for the formation
of acid XVI in the reaction of ketone III with SbF5.
Initially, abstraction of fluoride ion from molecule III
gives cation J, opening of the four-membered ring in J
generates cation K, and the latter undergoes isomeriza-
tion into unsaturated cation L by the action of SbF5.
Hydrolysis of L yields acid XVI. Isochromenyl cations
XVII and XVIII are formed via heterocyclization of
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 10 2010

ZONOV et al.
1520
Scheme 5.
CF2
CF2CF3
CF3
CFCF3
C2F5
CF2
SbF5
F
F
F
–F–
CO
CO
O
J
K
L
H2O
β
CF3
CFCF3
CF2CF3
CF3
(1) SbF5, 50°C; (2) H2O
α
F
F
COOH
XVI
O
III
X
F
X
H
CF3
CF3
OH
Y
Y
SbF5, 125°C
H2O
+
F
F
F
O
O
O
O
O
XVII, XVIII
XIX, XX
XXI
XVII, XIX, X = C2F5, Y = F; XVIII, XX, X = Y = CF3.
allyl-type cation (which is isomeric to L) generated
from acid XVI fluoride according to the scheme de-
scribed previously [4].
and subsequent hydrolysis of the reaction mixture led
to the formation of methylphthalides VII and VIII and
ethylphthalides XI and XII, respectively (Scheme 7).
These results may be interpreted assuming that the
reaction of methylbenzocyclobutenone I with SiO2–
SbF5 gives indanone V (Scheme 1) which undergoes
further transformations by the action of SiO2–SbF5.
This assumption is confirmed by the fact that ketone V
under analogous conditions gives rise to a mixture of
phthalides VII and VIII (Scheme 7).
On the whole, the behavior of diethylbenzocyclo-
butenone IV in antimony pentafluoride is similar to
that of ketone III, but a longer reaction time and/or
higher temperature are necessary. In the reaction of IV
with SbF5 at 70°C (after treatment of the reaction mix-
ture with water) we obtained perfluoro[2-(pent-2-en-3-
yl)benzoic acid] (XXII), whereas prolonged heating of
ketone IV with SbF5 at 125°C produced a solution
containing perfluoro(4-ethyl-3-methylisochromenyl)
cation (XXIII), and hydrolysis of the latter gave per-
fluoro(4-ethyl-3-methylisochromen-1-one) (XXIV) [5]
(Scheme 6).
On the other hand, the results of the reaction of
ethylbenzocyclobutenone II with SiO2–SbF5 cannot be
rationalized in a similar way. As noted above, the iso-
merization of ketone II into indanone IX by the action
of SbF5 occurs at 120°C, whereas the reaction of II
with SiO2–SbF5 yields phthalides XI and XII at 75°C.
By special experiment we showed that compound II
remains almost unchanged on heating in SbF5 at 75°C
over a comparable period of time. In addition, we
Let us consider now the behavior of perfluorinated
2-alkyl- and 2,2-dialkylbenzocyclobutenones in the
system SiO2–SbF5. Heating of ketones I and II in anti-
mony pentafluoride in the presence of SiO2 at 75°C
Scheme 6.
C2F5
CFCF3
COOH
C2F5
C2F5
C2F5
C2F5
(1) SbF5, 70°C
(2) H2O
CF3
CF3
SbF5, 125°C
H2O
F
F
F
F
O
O
O
F
XXIII
O
XXIV
XXII
IV
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 10 2010

TRANSFORMATIONS OF PERFLUORINATED 2-ALKYL- ...
1521
Scheme 7.
F
OH
RF
RF
RF
(1) SiO2–SbF5, 75°C
(2) H2O
F
+
F
F
O
F
O
O
O
O
I, II
VII, XI
VIII, XII
(1) SiO2–SbF5, 75°C
(2) H2O
VII
+
VIII
F
F
O
V
3'F
COOH
(1) SiO2–SbF5, 75°C
(2) H2O
XI
+
XII
+
F
F
CF3
F
O
O
O
IX
XXV
F
SbF5
CF3
XI
O
–SbF3
F
SiO2–SbF5
SbF5
F
F
F
O
COF
IX
CF3
SiO2–SbF5
H2O
O
O
F
O
XXV
H
M
O
N
I, VII, VIII, RF = CF3; II, XI, XII, RF = C2F5.
examined the behavior of indanone IX in the system
SiO2–SbF5 at 75°C. In this case, phthalides XI and XII
were formed only as minor products, while the major
product was acid XXV. The transformation of methyl-
indanone IX into acid XXV is likely to follow
Scheme 7. Ketone IX reacts with SiO2–SbF5 to give
indandione H which (like perfluoroindan-1,3-dione
[2, 8]) undergoes isomerization into ethylidene-
phthalide M by the action of SbF5. Compound M is
converted into acid fluoride N via reaction with SiO2–
SbF5, and hydrolysis of N leads to acid XXV. In addi-
tion, fluorination of M with SbF5 gives perfluoro-
phthalide XI which is then hydrolyzed to hydroxy-
phthalide XII [1]. In keeping with the proposed
scheme, the formation of acid XXV, on the one hand,
and phthalides XI and XII, on the other, are concurrent
pathways of the transformation of intermediate M in
SiO2–SbF5. Taking into account that acid XXV was
absent among products of the reaction of ethylbenzo-
cyclobutenone II with SiO2–SbF5 at 75°C and that
compound II did not undergo isomerization into inda-
none IX at the same temperature, we presumed that
phthalides XI and XII are formed in the reaction of II
with SiO2–SbF5 according to a different mechanism,
i.e., the presence of SiO2 radically changes the direc-
tion of skeletal transformations of ketone II in anti-
mony pentafluoride.
The reaction of perfluorinated benzocyclobutenone
III with SbF5–SiO2 at 75°C, followed by hydrolysis of
the reaction mixture, gave perfluoro(3-methyl-1-oxo-
isochromene-4-carboxylic acid) (XXVI). Under analo-
gous conditions, diethylbenzocyclobutenone IV was
converted into isochromenone XXIV containing an
impurity of perfluoro(4-acetyl-3-methylisochromen-1-
one) (XXVII) (Scheme 8). Presumably, acid XXVI is
formed in the reaction of III with SiO2–SbF5 as
a result of initial opening of the four-membered ring in
the initial ketone by the action of SbF5 (Scheme 5) and
subsequent transformations of the ring opening product
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 10 2010

ZONOV et al.
1522
Scheme 8.
COOH
C2F5
CF3
(1) SiO2–SbF5, 75°C
(2) H2O
CF3
F
F
O
O
O
XXVI
III
COCF3
CF2CF3
CF3
C2F5
C2F5
(1) SiO2–SbF5, 75°C
(2) H2O
CF3
+
F
F
F
O
O
O
O
O
IV
XXVII
XXIV
CFCF3
CF2CF3
CFCF3
CFCF3
COF
CFCF3
CF3
SbF5
F–
–F–
SiO2
IV
F
F
F
O
COF
CO
O
P
Q
CFCF3
CF3
F–
XXIV
F
–F–
O
CO
R
in SiO2–SbF5 according to the scheme proposed in [4].
The transformation of ketone IV into compound XXIV
in the reaction with SiO2–SbF5 at 75°C may be illus-
trated by Scheme 8. Opening of the four-membered
ring in IV by the action of SbF5 generates cation O
which undergoes isomerization into cation P via addi-
tion–elimination of fluoride ion. Cation P reacts with
SiO2 to give compound Q whose intramolecular cy-
clization through intermediate benzoyl cation R yields
compound XXIV. An alternative mechanism of the
transformation IV → XXIV in SiO2–SbF5 at 75°C,
involving cyclization of intermediate P to isochro-
menyl cation XXIII and subsequent conversion of the
latter into compound XXIV, seems to be improbable,
for the cyclization P → XXIII requires a higher tem-
perature (125°C; Scheme 6) [5].
Acetylisochromenone XXVII formed in the reac-
tion of IV with SiO2–SbF5 is likely to result from
further transformations of compound XXIV. The latter
can also be converted into XXVII via a series of
hydrolytic reactions. The reaction of XXIV with dilute
hydrochloric acid gave a mixture containing 5,6,7,8-
tetrafluoro-3-hydroxy-4-pentafluoroethyl-3-trifluoro-
methylisochroman-1-one (XXVIII) as the major prod-
uct (Scheme 9). By treatment of that mixture with
NaHCO3 in the two-phase system H2O–CH2Cl2 we
obtained acetylisochromenone XXVII together with a
small amount of 5,6,7,8-tetrafluoro-3-trifluoromethyl-
Scheme 9.
CF2CF3
CF3
COCF3
CF3
H
H
CF2CF3
CF3
OH
H
NaHCO3
H2O–CH2Cl2
CF3
OH
H2O, HCl
+
F
F
F
F
O
O
O
O
O
O
O
O
XXIV
XXVIII
XXVII
XXIX
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 10 2010

TRANSFORMATIONS OF PERFLUORINATED 2-ALKYL- ...
isochroman-1-one (XXIX). The observed hydrolytic
EXPERIMENTAL
1523
transformations of compound XXIV are analogous to
the reactions described in [4] for dimethylisochrome-
none XX.
The IR spectra were recorded on a Bruker Vector
22 spectrometer. The UV spectra were measured on
a Hewlett–Packard 8453 spectrophotometer. The H
1
Thus we have shown that perfluorinated 2-alkyl-
benzocyclobutenones I and II in antimony penta-
fluoride undergo isomerization to perfluoroindanones
V and IX. The process is likely to follow a path
involving cleavage of the four-membered ring in the
initial ketone, which is consistent with the formation of
perfluorinated 2-alkenylbenzoic acids XVI and XXII
from 2,2-dialkylbenzocyclobutenones III and IV under
analogous conditions. The transformations of perfluor-
inated 2,2-dialkylbenzocyclobutenones III and IV in
the system SiO2–SbF5, leading to isochromenones
XXVI and XXVII, also begin with opening of the car-
bonyl-containing ring by the action of SbF5. Presum-
ably, the transformations of four-membered ring in
ethylbenzocyclobutenone II and probably in methyl-
benzocyclobutenone I occurring in SbF5 in the pres-
ence of SiO2 and leading to phthalides XI and VII
follow a different path where SiO2 plays the key role,
but the mechanism of participation of SiO2 still re-
mains unclear.
and 19F NMR spectra were obtained on a Bruker AV-
300 instrument at 300 and 282.4 MHz, respectively,
using the residual solvent signal (1H, acetone-d5,
δ 2.04 ppm) or C6F6 (19F) as reference. The elemental
compositions were determined from the high-resolu-
tion mass spectra which were recorded on a Thermo
Electron Corporation DFS instrument. The reactions
were carried out in glass vessels or a nickel bomb
(V = 10 ml). The reaction mixtures were analyzed by
19F NMR spectroscopy.
Initial compounds I, II, IV, V, and IX were syn-
thesized according to the procedure reported in [12].
Previously unknown ketone III was prepared in a simi-
lar way.
Perfluoro(2-ethyl-2-methylbenzocyclobuten-1-
one) (III). A mixture of perfluorinated 1-ethyl-1-meth-
ylbenzocyclobutene and 2-ethyl-1-methylbenzocyclo-
butene (XXX) at a ratio of 55:45, 6.14 g (15.43 mmol),
was added to a solution of 1.25 g (10.95 mmol) of tri-
fluoroacetic acid in 5.02 g (23.13 mmol) of antimony
pentafluoride, and the mixture was vigorously stirred
for 5 h at 20°C. The upper layer (1.01 g, compound
XXX) was separated, 5% hydrochloric acid was added
to the residue, and the organic phase (4.78 g) contain-
ing 63% of ketone III (yield 93%) and 37% of com-
pound XXX was separated. A 1.00-g portion of that
mixture was separated by column chromatography on
silica gel using first hexane and then chloroform as
eluent to isolate 0.23 g of compound XXX and 0.50 g
of ketone III, bp 67–68°C (17 mm). UV spectrum
(hexane), λmax, nm (logε): 203 (4.31), 242 (3.98), 249
(3.94), 276 (3.11). IR spectrum (CCl4), ν, cm–1: 1831
(C=O), 1523, 1484 (fluorinated aromatic ring).
19F NMR spectrum (CDCl3), δF, ppm: 97.3 (3F, α-CF3),
80.5 (3F, β-CF3), 49.5 and 48.7 (1F each, CFAFB), 37.5
(1F, 6-F), 29.9 (1F, 4-F), 28.4 (1F, 3-F), 19.6 (1F, 5-F);
The structure of compounds III, XXV, and XXVII
was confirmed by high-resolution mass spectrometry
and other spectral methods. Compound XXV dis-
played in the 19F NMR spectrum a large spin–spin
coupling constant (JFF = 93 Hz) between the fluorine
atom at the exocyclic double bond (3′-F) and 4-F,
indicating E configuration of the double bond (the 3′-F
and 4-F atoms appear spatially close) [9]. The J3′, 4
value is similar to analogous coupling constants for
perfluorinated 1-ethylideneindane [10] and 3-ethyli-
deneindan-1-one [11]. Compound XXVIII was formed
as a mixture of stereoisomers, and its structure was
1
assigned by comparing its H and 19F NMR spectra
with those of perfluoroisochroman-1-one XXI reported
previously [4]. The configuration of particular isomers
of XXVIII was determined on the basis of the 19F–19F
coupling constants for the 3-CF3 and 4-CF2 groups.
The JFF values for isomer XXVIIIa with cis orienta-
tion of the fluoroalkyl groups were equal to 5.5 and
29.5 Hz, and the corresponding values for trans isomer
XXVIIIb were less than 2 Hz.
JFF, Hz: JAB = 290, Jα,β = 5, Jα,A = 9, Jα,B = 9.5, Jα,3
2.5, Jβ,A = 1, Jβ,B = 1, Jβ,3 = 7, JA,3 = 3, JB,3 = 2.5, J3,4
19, J3,5 = 8, J3,6 = 23.5, J4,5 = 17.5, J4,6 = 12.5, J5,6
=
=
=
20. Found: m/z 375.9752 [M]+. C11F12O. Calculated:
M 375.9758.
Compounds VI–VIII [2], X–XIII, XV [1], XIV
[7], XVI–XXI, XXVI, XXIX [4], and XXII–XXIV
[5] were described previously; they were identified by
comparing their 19F NMR spectra with the spectra of
authentic samples.
Reaction of perfluoro(2-methylbenzocyclobuten-
1-one) (I) with SbF5. a. A solution of 0.24 g
(0.87 mmol) of compound I in 1.84 g (8.48 mmol) of
SbF5 was heated for 8 h at 75°C. The mixture was
treated with 5% hydrochloric acid and extracted with
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ZONOV et al.
1524
methylene chloride, the extract was dried over MgSO4,
and the solvent was distilled off under reduced pres-
sure to obtain 0.20 g of a mixture containing 12% of
compound I, 72% (yield 61%) of ketone V, 8% (7%)
of acid VI, 3% (3%) of phthalide VII, and 5% (4%) of
phthalide VIII.
b. A mixture of 0.44 g (1.16 mmol) of compound
III and 2.51 g (11.58 mmol) of SbF5 was heated for
7 h at 125°C (nickel bomb). The 19F NMR spectrum of
the resulting solution contained signals assignable to
cations XVII and XVIII and perfluoro(4-fluorocar-
bonyl-3-methylisochromenyl) cation [4] at a ratio of
13:75:12. The mixture was treated with 5% hydro-
chloric acid and extracted with methylene chloride, the
extract was dried over MgSO4, and the solvent was
distilled off under reduced pressure to obtain 0.38 g of
a mixture containing compounds XIX–XXI and XXVI
at a ratio of 11:64:9:16 (overall yield 93%).
b. Following an analogous procedure, from 0.42 g
(1.52 mmol) of compound I and 3.04 g (14.02 mmol)
of SbF5 (75°C, 17 h) we obtained 0.37 g of a mixture
containing 6% of compound I, 79% (yield 70%) of
ketone V, 5% (5%) of acid VI, 7% (6%) of phthalide
VII, and 3% (3%) of phthalide VIII.
Reaction of perfluoro(2-methylbenzocyclobuten-
1-one) (I) with SiO2–SbF5. A mixture of 0.27 g
(0.98 mmol) of compound I, 0.06 g (1.00 mmol) of
SiO2 (silica gel calcined at 400–450°C), and 2.07 g
(9.55 mmol) of SbF5 was stirred for 8 h at 75°C. The
mixture was treated with 5% hydrochloric acid and
extracted with methylene chloride, the extract was
dried over MgSO4, and the solvent was distilled off
under reduced pressure to obtain 0.18 g of a mixture
containing 38% of phthalide VII and 62% of phthalide
VIII (overall yield 64%).
Reaction of perfluoroindan-1-one (V) with SbF5.
Likewise, the reaction of 0.48 g (1.74 mmol) of ketone
V with 3.42 g (15.77 mmol) of SbF5 (75°C, 17 h,
nickel bomb) gave 0.43 g of a mixture containing 93%
of ketone V, 0.5% of acid VI, 4% of phthalide VII,
and 2% of phthalide VIII.
Reaction of perfluoro(2-ethylbenzocyclobuten-
1-one) (II) with SbF5. a. A mixture of 0.17 g
(0.52 mmol) of compound II and 1.10 g (5.07 mmol)
of SbF5 was heated for 4.5 h at 120°C. The mixture
was treated with 5% hydrochloric acid and extracted
with methylene chloride, the extract was dried over
MgSO4, and the solvent was distilled off under reduced
pressure to obtain 0.15 g of a mixture containing 58%
of compound II, 37% (yield 33%) of ketone IX, 1% of
phthalide XI, 1% of phthalide XII, and 3% of acid X.
Reaction of perfluoroindan-1-one (V) with SiO2–
SbF5. Following an analogous procedure, from 0.53 g
(1.92 mmol) of ketone V, 0.11 g (1.85 mmol) of SiO2,
and 4.02 g (18.55 mmol) of SbF5 (75°C, 8 h) we ob-
tained 0.48 g of a mixture containing 25% of phthalide
VII and 75% of phthalide VIII (overall yield 86%).
b. Following an analogous procedure, from 0.57 g
(1.74 mmol) of ketone II and 3.07 g (14.16 mmol) of
SbF5 (130°C, 39 h, nickel bomb) we obtained 0.54 g of
a mixture containing compounds IX–XI, XIII, and
XIV at a ratio of 17:27:11:33:12 (overall yield 94%).
Reaction of perfluoro(2-ethylbenzocyclobuten-
1-one) (II) with SiO2–SbF5. A mixture of 0.34 g
(1.03 mmol) of compound II, 0.06 g (1.00 mmol) of
SiO2, and 2.21 g (10.18 mmol) of SbF5 was stirred for
10 h at 75°C. The mixture was then treated with 5%
hydrochloric acid and extracted with diethyl ether,
the extract was dried over MgSO4, the solvent was
distilled off, and vacuum sublimation of the residue
(130°C, 30 to 2 mm) gave 0.32 g of a mixture con-
taining 10% of phthalide XI and 90% of phthalide XII
(overall yield 90%).
c. As described above in a, the reaction of 1.09 g
(3.34 mmol) of ketone II with 5.81 g (26.80 mmol) of
SbF5 (180°C, 63 h, nickel bomb) gave 0.94 g of a mix-
ture containing compounds X, XI, XIII, and XV at
a ratio of 70:6:10:14 (overall yield 81%).
Reaction of perfluoro(2-ethyl-2-methylbenzo-
cyclobuten-1-one) (III) with SbF5. a. A mixture of
0.37 g (0.98 mmol) of compound III and 2.15 g
(9.90 mmol) of SbF5 was heated for 11 h at 50°C. The
mixture was diluted with 1.63 g of hexafluorobenzene,
treated with 5% hydrochloric acid, and extracted with
methylene chloride, and the extract was dried over
MgSO4. The extract contained hexafluorobenzene and
acid XVI as a mixture of E and Z isomers at a ratio of
~25:75. The solvent and C6F6 were distilled off under
reduced pressure, and vacuum sublimation of the resi-
due (100°C, 3 mm) gave 0.27 g (74%) of acid XVI.
Reaction of perfluoro(2-methylindan-1-one) (IX)
with SiO2–SbF5. A mixture of 0.30 g (0.91 mmol) of
compound IX, 0.06 g (1.00 mmol) of SiO2, and 2.09 g
(9.65 mmol) of SbF5 was stirred for 9 h at 75°C. The
mixture was treated with 5% hydrochloric acid and
extracted with methylene chloride–diethyl ether (2:1,
by volume), and the extract was dried over MgSO4. It
contained compounds XI and XII, fluoro[(3E)-4,5,6,7-
tetrafluoro-1-oxo-2-benzofuran-3-ylidene]acetic acid
(XXV) and tetrafluorophthalic acid at a ratio of
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TRANSFORMATIONS OF PERFLUORINATED 2-ALKYL- ...
1525
9:8:65:18. The solvent was distilled off, and vacuum
sublimation (100–150°C, 2 mm) of the residue gave
0.14 g of a mixture of compounds XI, XII, and XXV
and tetrafluorophthalic acid at a ratio of 19:25:12:44;
further sublimation at 200°C (2 mm) afforded 0.11 g
(43%) of acid XXV. By repeated vacuum sublimation
(180°C, 2 mm) and washing of the sublimed crystal-
line material with diethyl ether (4 ml) we obtained
an analytically pure sample (0.06 g) of compound
XXV with mp 245.5–246°C. IR spectrum (KBr), ν,
cm–1: ~2800 br (O–H), 1828, 1803, 1695 (C=O), 1524,
(XXVIIIb), 8% of perfluoro(4-acetyl-3-methyliso-
chromen-1-one) (XXVII), 4% of compound XXIX,
and two unidentified compounds (4 and 6%). The
product mixture was dissolved in 4 ml of methylene
chloride with addition of 0.2 ml of diethyl ether, the
solution was stirred with a saturated aqueous solution
of NaHCO3 over a period of 1 min, the organic layer
was separated and dried over MgSO4, and the solvent
was distilled off under reduced pressure to isolate
0.11 g (67%) of compound XXVII. The aqueous phase
was acidified with hydrochloric acid and extracted
with diethyl ether, the extract was dried over MgSO4,
and removal of the solvent gave 0.03 g of XXIX.
1
1498 (fluorinated aromatic ring). H NMR spectrum
(acetone-d6): δ 6.5 ppm, br.s (OH). 19F NMR spectrum
(acetone-d6), δF, ppm: 33.9 (1F, 4-F), 24.2 (1F, 7-F),
20.9 (1F, 5-F), 20.2 (1F, 3′-F), 15.6 (1F, 6-F); JFF,
Hz: J3′,4 = 93, J3′,5 = 3, J3′,6 = 6, J3′,7 = 2, J4,5 = 19,
J4,6 = 7, J4,7 = 18, J5,6 = 18, J5,7 = 10, J6,7 = 20.
Found: m/z 279.9780 [M]+. C10HF5O4. Calculated:
M 279.9795.
Compound XXVII. mp 66.5–67°C (from hexane).
UV spectrum (hexane), λmax, nm (logε): 226 (4.38),
267 (3.75), 310 (3.63). IR spectrum (CCl4), ν, cm–1:
1798, 1766 (C=O), 1518, 1491 (fluorinated aromatic
ring). 19F NMR spectrum (CH2Cl2), δ, ppm: 95.6 (3F,
3-CF3), 85.9 (3F, 4-CF3 ), 34.0 (1F, 8-F), 28.9 (1F,
5-F), 23.3 (1F, 6-F), 16.8 (1F, 7-F); JFF, Hz: J3,4 = 4.5,
J4,5 = 12, J5,6 = 20, J5,7 = 5.5, J5,8 = 13, J6,7 = 20.5,
J6, 8 = 13.5, J7, 8 = 20. Found: m/z 381.9693 [M]+.
C12F10O3. Calculated: M 381.9688.
Compound XXVIII. 1H NMR spectrum (CDCl3), δ,
ppm: isomer XXVIIIa: 4.82 br.s (1H, OH), 4.41 d.d
(1H, 4-H); J(4-H, FB) = 22, J(4-H, FA) = 4 Hz; isomer
XXVIIIb: 5.28 br.s (1H, OH), 4.53 d.d (1H, 4-H);
J(4-H, FB) = 17.5, J(4-H, FA) = 7 Hz. 19F NMR spec-
trum (CDCl3), δF, ppm: XXVIIIa: 80.8 (3F, 3-CF3),
79.4 (3F, 4-CF3), 51.9 (1F, FA) and 38.6 (1F, FB) (CF2),
30.2 (1F, 8-F), 23.8 (1F, 5-F), 19.9 (1F, 6-F), 12.9 (1F,
7-F); JFF, Hz: J(3-CF3, FA) = 29.5, J(3-CF3, FB) = 5.5,
J(4-CF3, 5-F) = 12.5, JAB = 277, JA,5 = 4, J5,6 = 21,
J5,7 = 5.5, J5,8 = 13.5, J6,7 = 20, J6,8 = 12, J7,8 = 20.5,
J(FA, 4-H) = 4, J(FB, 4-H) = 22; XXVIIIb: 82.1 (3F,
4-CF3), 79.6 s (3F, 3-CF3), 55.1 (1F, FA) and 46.8
(1F, FB) (CF2), 30.3 (1F, 8-F), 24.4 (1F, 5-F), 20.6 (1F,
Reaction of perfluoro(2-ethyl-2-methylbenzo-
cyclobuten-1-one) (III) with SiO2–SbF5. A mixture
of 0.42 g (1.11 mmol) of compound III, 0.07 g
(1.20 mmol) of SiO2, and 2.39 g (11.01 mmol) of SbF5
was stirred for 10 h at 75°C. The mixture was treated
with 5% hydrochloric acid and extracted with diethyl
ether, the extract was dried over MgSO4, the solvent
was distilled off, and the residue was subjected to
vacuum sublimation (170°C, 2 mm) to isolate 0.33 g
(90%) of acid XXVI.
Reaction of perfluoro(2,2-diethylbenzocyclo-
buten-1-one) (IV) with SiO2–SbF5. A mixture of
0.70 g (1.64 mmol) of compound IV, 0.11 g
(1.76 mmol) of SiO2, and 3.59 g (16.54 mmol) of SbF5
was stirred for 30 h at 75°C. The mixture was treated
with 5% hydrochloric acid and extracted with methyl-
ene chloride, the extract was dried over MgSO4, the
solvent was distilled off, and vacuum sublimation of
the residue (100°C, 2 mm) gave 0.50 g of a mixture of
compounds XXIV and XXVII at a ratio of 80:20
(overall yield 77%).
6-F), 14.1 (1F, 7-F); JFF, Hz: J(4-CF3, 5-F) = 3, JAB
=
283, JA,5 = 10, JB,5 = 6, J5,6 = 21, J5,7 = 6, J5,8 = 13.5,
J6, 7 = 20, J6, 8 = 12, J7, 8 = 20.5, J(FA, 4-H) = 7,
J(FB, 4-H) = 17.5.
Hydrolytic transformations of perfluoro(4-ethyl-
3-methylisochromen-1-one) (XXIV). Compound
XXIV, 0.18 g (0.44 mmol), was dissolved in 2 ml of
diethyl ether, 5 ml of 5% hydrochloric acid was added,
and the mixture was stirred for 25 h. The organic phase
was separated, dried over MgSO4, and evaporated on
a watch glass to obtain 0.16 g of a mixture containing
35% of 5,6,7,8-tetrafluoro-r-3-hydroxy-t-4-penta-
fluoroethyl-3-trifluoromethylisochroman-1-one
(XXVIIIa), 44% of 5,6,7,8-tetrafluoro-r-3-hydroxy-c-
4-pentafluoroethyl-3-trifluoromethylisochroman-1-one
This study was performed under financial support
by the Russian Foundation for Basic Research (project
nos. 06-03-32170, 10-03-00120).
REFERENCES
1. Zonov, Ya.V., Karpov, V.M., Platonov, V.E., and Gati-
lov, Yu.V., Russ. J. Org. Chem., 2008, vol. 44, p. 202.
2. Zonov, Ya.V., Karpov, V.M., and Platonov, V.E.,
J. Fluorine Chem., 2005, vol. 126, p. 437.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 10 2010

ZONOV et al.
1526
3. Zonov, Ya.V., Mezhenkova, T.V., Karpov, V.M., and Pla-
tonov, V.E., Russ. J. Org. Chem., 2008, vol. 44, p. 1652.
4. Zonov, Ya.V., Karpov, V.M., and Platonov, V.E.,
8. Zonov, Ya.V., Karpov, V.M., Platonov, V.E., Rybalo-
va, T.V., and Gatilov, Yu.V., J. Fluorine Chem., 2006,
vol. 127, p. 1574.
9. Ng, S. and Sederholm, C.H., J. Chem. Phys., 1964,
J. Fluorine Chem., 2007, vol. 128, p. 1065.
vol. 40, p. 2090.
5. Zonov, Ya.V., Mezhenkova, T.V., Karpov, V.M., and Pla-
10. Chuikov, I.P., Karpov, V.M., Platonov, V.E., and Yakob-
son, G.G., Izv. Akad. Nauk SSSR, Ser. Khim., 1988,
p. 1652.
tonov, V.E., J. Fluorine Chem., 2008, vol. 129, p. 1206.
6. Olah, G.A. and Pittman, C.U., J. Am. Chem. Soc., 1966,
vol. 88, p. 3310; Pozdnyakovich, Yu.V. and Shtein-
garts, V.D., J. Fluorine Chem., 1974, vol. 4, p. 283; ibid.,
p. 297.
11. Karpov, V.M., Platonov, V.E., Chuikov, I.P., and Shche-
goleva, L.N., Russ. J. Org. Chem., 1999, vol. 35, p. 80.
7. Karpov, V.M., Mezhenkova, T.V., Platonov, V.E., and
12. Zonov, Ya.V., Karpov, V.M., and Platonov, V.E.,
Yakobson, G.G., J. Fluorine Chem., 1985, vol. 28, p. 115.
J. Fluorine Chem., 2007, vol. 128, p. 1058.
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