Cationoid rearrangements in reactions of perfluoro-1-arylbenzocyclobutenes with antimony pentafluoride

Article abstract of DOI:10.1016/S0022-1139(02)00196-3

In the presence of antimony pentafluoride at 130°C, the four-membered ring of perfluoro-1-(2-ethylphenyl)benzocyclobutene (2) undergoes cleavage, forming perfluoro-2-ethyl-2′-methyldiphenylmethane (5). Compound 5 is converted, under the action of SbF₅ at 170°C, to perfluoro-8,9-dimethyl-1,2,3,4-tetrahydrofluorene (8). Perfluoro-1-(4-ethylphenyl)benzocyclobutene (3) remains unchanged at 130°C, whereas at 170°C it gives a mixture of perfluorinated 4′-ethyl-2-methyldiphenylmethane (9), 6-ethyl-1,2,3,4-tetrahydroanthracene (11) and 2-ethyl-9,10-dihydroanthracene (12). When heated with SbF₅ at 170°C, perfluoro-1-phenylbenzocyclobutene (1) remains unchanged. Solution of compounds 2, 3, 5 and 9 in SbF₅-SO₂ClF generated the perfluorinated 1-(2-ethylphenyl)-1-benzocyclobutenyl (29), 1-(4-ethylphenyl)-1-benzocyclobutenyl (30), 2-ethyl-2′-methyldiphenylmethyl (31) and 4′-ethyl-2-methyldiphenylmethyl (32) cations, respectively.

Full text of DOI:10.1016/S0022-1139(02)00196-3

Journal of Fluorine Chemistry 117 (2002) 73±81
Cationoid rearrangements in reactions of
per¯uoro-1-arylbenzocyclobutenes with antimony penta¯uoride
1
Victor M. Karpov*,Tatyana V. Mezhenkova,Vyacheslav E. Platonov ,
Vladimir R. Sinyakov
N.N. Vorozhtsov Institute of Organic Chemistry, Novosibirsk 630090, Russia
Received 23 May 2002; received in revised form 23 July 2002; accepted 2 August 2002
Dedicated to Prof. em. Dr. mult. Dr. h.c. Alois Haas,on the occasion of 70th birthday
Abstract
In the presence of antimony penta¯uoride at 130 8C,the four-membered ring of per¯uoro-1-(2-ethylphenyl)benzocyclobutene ( 2) undergoes
cleavage,forming per¯uoro-2-ethyl-2 0-methyldiphenylmethane (5). Compound 5 is converted,under the action of SbF 5 at 170 8C,to per¯uoro-
8,9-dimethyl-1,2,3,4-tetrahydro¯uorene (8). Per¯uoro-1-(4-ethylphenyl)benzocyclobutene (3) remains unchanged at 130 8C,whereas at
170 8C it gives a mixture of per¯uorinated 40-ethyl-2-methyldiphenylmethane (9), 6-ethyl-1,2,3,4-tetrahydroanthracene (11) and 2-ethyl-
9,10-dihydroanthracene (12). When heated with SbF5 at 170 8C,per¯uoro-1-phenylbenzocyclobutene ( 1) remains unchanged. Solution of
compounds 2, 3, 5 and 9 in SbF5±SO2ClF generated the per¯uorinated 1-(2-ethylphenyl)-1-benzocyclobutenyl (29),1-(4-ethylphenyl)-1-
0
benzocyclobutenyl (30),2-ethyl-2 -methyldiphenylmethyl (31) and 40-ethyl-2-methyldiphenylmethyl (32) cations,respectively.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Skeletal transformations; Per¯uoroarylbenzocyclobutenes; Antimony penta¯uoride; NMR spectroscopy
1. Introduction
ethylphenyl)benzocyclobutene (2) and per¯uoro-1-(4-ethyl-
phenyl)benzocyclobutene (3) under the action of SbF5 to
study the effect of the per¯uoroaryl group and the size of
alicycle on the route of the skeletal transformations of
poly¯uorobenzocycloalkenes. Product 2 was obtained pre-
viously by dimerization of per¯uorobenzocyclobutene (4) in
SbF5 at 50 8C [2]; product 1 was synthesized by interaction
of compound 4 with penta¯uorobenzene in the presence of
SbF5 [9]; product 3 was prepared by an analogous reaction
from compound 4 and 4-H-per¯uoroethylbenzene in the
present work (Scheme 1).
Previously,we have found and investigated the skeletal
transformations of per¯uorobenzocycloalkenes (benzocyclo-
butene,indan and tetralin) and their per¯uoroalkyl deriva-
tives under the action of Lewis acids,changing the alicyclic
fragment of the molecule [1±7]. It was shown that in these
reactions per¯uoroalkylbenzocyclobutenes undergo expan-
sion of the four-membered ring to the ®ve-membered one;
alternatively,the alicycle opens to form poly¯uorostyrenes,
which subsequently undergo cyclization into poly¯uoroin-
dans or ¯uorination [1,4,5]. The skeletal transformations of
per¯uoroarylbenzocycloalkenes were not known. Recently,
we have found that the carbon framework of the molecule in
per¯uoro-1-phenylindan changes under the action of SbF5,
with both alicyclic and aromatic fragments of the substrate
involved in the reaction [8].
2. Results and discussion
In the presence of antimony penta¯uoride,per¯uoro-1-
(ethylphenyl)-benzocyclobutenes 2 and 3 undergo skeletal
transformations,whereas per¯uoro-1-phenylbenzocyclobu-
tene (1) fails to do so under analogous conditions. At 130 8C,
the four-membered ring of 2 opens under the action of SbF5.
Thus,prolonged heating of benzocyclobutene 4 with anti-
mony penta¯uoride at 130 8C with further treatment of the
reaction mixture with anhydrous HF and then with water
leads to per¯uoro-2-ethyl-20-methyldiphenylmethane (5)
The aim of this study is to investigate the behavior of
per¯uoro-1-phenylbenzocyclobutene (1),per¯uoro-1-(2-
* Corresponding author. Fax: ‡7-3832-34-4752.
E-mail addresses: karpov@nioch.nsc.ru (V.M. Karpov),
platonov@nioch.nsc.ru (V.E. Platonov).
1 Tel.: ‡7-3832-34-4437; fax: ‡7-3832-34-4752.
0022-1139/02/$ ± see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 2 ) 0 0 1 9 6 - 3

74
V.M. Karpov et al. / Journal of Fluorine Chemistry 117 (2002) 73±81
Let us consider possible routes of reactions between aryl-
benzocyclobutenes 2 and 3 and antimony penta¯uoride.
Opening of the four-membered cycle in compound 2 seems
to occur as follows (Scheme 4). Reversible elimination of the
¯uoride anion from the di¯uoromethylene fragment of the
ethyl group of benzocyclobutene 2 under the action of SbF5
leads to cation 15. Since the positive charge of the latter is
shared also by the carbon atom bonded to the benzocyclobu-
tenyl fragment,the four-membered cycle of the latter may
undergo ring opening analogous to that in per¯uoro-1-alkyl-
benzocyclobutenes under the action of SbF5 [4] (Scheme 4).
Thisyieldsthebenzylcation16,whichaddsthe¯uorideanion,
giving compound 17. The latter is ¯uorinated to product 5.
A possible route for formation of compound 8 from
diphenylmethane 5 is presented in Scheme 5. The benzyl
cation 18 formed at the ®rst stage undergoes an intramole-
cular rearrangement,as a result of which it isomerizes into
ion 19. The latter is transformed into the diphenylmethyl
cation 20 by addition±elimination of the ¯uoride anion. An
attack of the positively charged carbon atom of one aromatic
ring (resonance structure 20a) at the other ring of cation 20
Scheme 1.
together with per¯uoro-2-ethyl-20-methylbenzophenone (6).
The mixture also contains compound 2 and 1-hydroxyper-
¯uoro-1-(2-ethylphenyl)benzocyclobutene (7) (Scheme 2).
The reaction at 170 8C (7 h) forms per¯uoro-8,9-
dimethyl-1,2,3,4-tetrahydro¯uorene (8) along with products
5 and 6; at increased reaction time,more tetrahydro¯uorene
8 is formed,whereas the proportions of 5 and 6 decrease
(Scheme 2).
In contrast to arylbenzocyclobutene 2,its isomer 3 does
not change in the presence of antimony penta¯uoride at
130 8C; at 170 8C (7 h) it gives,after treatment with anhy-
drous HF and then with water,minor products of alicycle
opening: per¯uoro-40-ethyl-2-methyldiphenylmethane (9)
and per¯uoro-40-ethyl-2-methylbenzophenone (10) together
with per¯uoro-6-ethyl-1,2,3,4-tetrahydroanthracene (11),
per¯uoro-2-ethyl-9,10-dihydroanthracene (12) and per-
¯uoro-2-ethyl-9(10H)anthracenone (13). The reaction mix-
ture also contains unchanged compound 3. Prolonged
reaction time (14 h) and treatment with H2O leads to pro-
ducts 11 and 13 together with per¯uoro-2-ethyl-9,10-anthra-
quinone (14),whereas compounds 3 and 9 are absent
(Scheme 3). At still longer reaction times,the relative
content of tetrahydroanthracene 11 increases,and those of
compounds 12±14 decrease.
‡
with further elimination of CF3 and isomerization of the
resulting compound leads to ¯uorene 21 (cf. formation of
per¯uoro-9-methyl¯uorene from per¯uoro-1-phenylindan
in the presence of SbF5 [8]),which is further ¯uorinated,
giving tetrahydro¯uorene 8 (cf. ¯uorination of poly¯uor-
oarenes in the presence of SbF5 [10±12]).
The skeletal transformations of arylbenzocyclobutene 3
under the action of SbF5 start analogously to the transfor-
mations of its isomer,benzocyclobutene 2. Thus,the benzyl
cation 22 formed from compound 3 is evidently converted to
cation 23. Cyclization of the latter (Scheme 6,route 1) with
further addition of the ¯uoride anion and isomerization of
the intermediate compound 24 gives dihydroanthracene 12,
which is ¯uorinated to give tetrahydroanthracene 11 under
the reaction conditions. Addition of the ¯uoride anion to
cation 23 (route 2) and subsequent ¯uorination of product 25
form compound 9.
It should be noted that,in addition to the formation of
products 11 and 12 according to route 1,an alternative
Scheme 2.

V.M. Karpov et al. / Journal of Fluorine Chemistry 117 (2002) 73±81
75
Scheme 3.
route is possible,which involves generation of cation
26 from diphenylmethane 9 and cyclization of 26 into
compound 27 as a result of an attack of the aromatic ring
by the benzyl carbon atom with further addition of the
¯uoride anion. Isomerization of compound 27 by addition±
elimination of the ¯uoride anion may lead to tetrahydroan-
thracene 11,and de¯uorination and/or disproportionation
form dihydroanthracene 12 (cf. formation of per¯uoro-2,3-
dimethylindene from per¯uoro-1,2-dimethylindan [3,5]
and disproportionation of poly¯uorocyclohexadienes in
SbF5 [13,14]).
Thus,in the framework of the above routes for transfor-
mations of compounds 2 and 3 under the action of antimony
penta¯uoride,it is postulated that cations 15 and 22,respec-
tively,undergo skeletal rearrangements. The latter are not
the most stable cations generated from compounds 2 and 3,
but their concentration is apparently suf®cient for the reac-
tion to occur with an observable rate. The cations formed by
Scheme 4.

76
V.M. Karpov et al. / Journal of Fluorine Chemistry 117 (2002) 73±81
Scheme 5.
elimination of the ¯uoride anion from position 1 of com-
pounds 2 and 3 are more stable.
(32) cations were generated from diphenylmethanes 5 and 9,
respectively (Scheme 7).
Indeed,the reactions of arylbenzocyclobutenes 1, 2 and 3
in SbF5±SO2ClF generate per¯uorinated 1-phenyl-1-benzo-
cyclobutenyl (28) [9],1-(2-ethylphenyl)-1-benzocyclobute-
nyl (29) and 1-(4-ethylphenyl)-1-benzocyclobutenyl (30)
cations. Analogously,per¯uoro-2-ethyl-2 -methyldiphenyl-
methyl (31) and per¯uoro-40-ethyl-2-methyldiphenylmethyl
The treatment of the solutions of the salts of cations 28±30
with water leads to 1-hydroxyper¯uoro-1-phenylbenzocy-
clobutene (33) [9],compound 7 and 1-hydroxyper¯uoro-1-
(4-ethylphenyl)benzocyclobutene (34). Hydrolysis of the
salts of cations 31 and 32 yields ketones 6 and 10,respec-
tively. The structures of the cations were identi®ed by 19F
0
Scheme 6.

V.M. Karpov et al. / Journal of Fluorine Chemistry 117 (2002) 73±81
77
Scheme 7.
NMR spectra. The peculiarities in the spectra of cations 29±
32 (Table 1),which are benzyl type cations,agree with those
for the per¯uoro-1-phenyl-1-benzocycloalkenyl [8,9],poly-
¯uorinated benzyl [15] and diphenylmethyl cations [16],for
which DdF and J are attributed to direct participation of
¯uorine atoms in charge distribution and in conjugation
[15,16].
that the alkylphenyl fragments are orientated by the per-
¯uoroalkyl groups toward the F-a atom.
The structures of compounds were established by spectral
characteristics. Assignment of signals in the 19F NMR
spectra of compounds was made on the basis of chemical
shifts of the signals,their ®ne structure and integral inten-
sities. The 19F NMR spectral data for compounds are given
in Tables 2 and 3.
In the 19F NMR spectra of cations 28 and 30,the F-2 0 and
F-60 atoms are non-equivalent. The larger value of J6;6 156,
0
0
165 Hz (J6;2 < 5 Hz) indicates that the interacting nuclei
are closely spaced,or,in other words,that the per¯uoroaryl
group in cations 28 and 30 is rotated through a small angle.
3. Experimental
The 19F NMR spectra of CHCl3 solutions of the reaction
mixtures,CHCl solutions of the individual compounds
0
In cation 29, J6;6 is 58 Hz,indicating that the per¯uoro-2-
ethylphenyl group is rotated through a larger angle in this
cation compared with the rotation angle of the per¯uoroaryl
group in ions 28 and 30,in which case the per¯uoro-2-
ethylphenyl group is oriented by its F-60 atom toward the
aromatic ring. On passing from cation 28 to 30 and 29, Dd(F-
4) and J4,6 increase,indicating that the positive charge in the
tetra¯uorophenylene part of the ion increases and that
participation of the per¯uoroaryl group in charge delocali-
zation decreases in the series 28 > 30 > 29. In the 19F NMR
3
(<10 mol%),and SbF 5±SO2ClF solutions of the cation salts
were recorded on a WP-200SY (188.3 MHz) instrument.
C6F6 was used as internal standard (SO2ClF in the case of
cations,262.8 ppm from C 6F6). The chemical shifts are
given in d ppm down®eld from C6F6 (À162.9 ppm from
CCl3F). The element compositions of the compounds were
determined by high-resolution mass spectrometry on a
Finnigan Mat 8200 instrument. Yields of products in the
reaction mixtures were determined by GLC and 19F NMR.
0
spectrum of the diarylmethyl cation 32,the F-2 and F-60
atoms give one signal,probably indicating that the 4-ethyl-
phenyl group rotates freely in the ion. In cation 31, Dd(F-4,
6) and J4,6 are larger than the analogous values for the
isomeric cation 32,indicating that the methylphenyl frag-
ment of ion 31 has a larger portion of positive charge
compared to ion 32. Moreover,the larger values of Dd(F-
3.1. Reaction of perfluorobenzocyclobutene (4) with
4-H-perfluoroethylbenzene in the presence of SbF5
A 1:1.1:5 mixture of benzocyclobutene 4 (1.89 g),4- H-
per¯uoroethylbenzene (2.25 g) and SbF5 (8.26 g) was stirred
for 6 h at 50 8C. Then C6F6 (2 ml) was added,and the
mixture was treated with anhydrous HF (14 ml),poured
onto ice,and extracted with CHCl 3. The extract was
dried over MgSO4. CHCl3 and C6F6 were distilled off
to give 3.7 g of the product containing compounds 3 and
34 in the ratio ꢀ4:1. Benzocyclobutene 3 (2.88 g,yield
76%) and compound 34 (0.67 g,18%) were isolated by silica
gel column chromatography (CCl4 and then CH2Cl2 as
eluent).
4,6) and J4,6 compared to Dd(F-40, 60) and J4 ;6 for cation 31
suggest that the methylphenyl fragment takes a greater part
in charge delocalization compared to the ethylphenyl frag-
0
0
0
ment of this ion. The low value of J6;6 in cations 32 (10 Hz)
and 31 (<5 Hz) indicates that the alkylphenyl fragments
deviate from the plane of the cation center and the atoms
bonded to it. The high values of spin±spin coupling con-
stants for F-a interaction (across space) with the ¯uorine
atoms of the per¯uoroalkyl groups in ions 31 and 32 suggest

Table 1
19F NMR spectral data of benzocyclobutenyl and diphenylmethyl cations
Cation dF (DdFa,ppm)
JF,F (Hz)
F-a
F-2
F-3
F-4
F-5
F-6
F-20
F-30
F-40
F-50
F-60
J3,4 J3,5 J3,6 J4,5 J4,6 J5,6 J60
J30
J6;6
0
0
0
;4
;4
(J20
)
(J50
)
(J6;2 )
0
0
0
;4
;4
28 [9]
29c
84.9 (22.0) 35.3 (8.0) 75.3 (55.5)
93.3 (28.7) 38.0 (11.1) 94.0 (75)
82.2 (18.6) 38.7 (11.0) 90.8 (70.3)
35.6 (15.3)
39.0 (19.3)
38.4 (17.6)
67.1 (36.0)
74.6 (46.2)
75.1 (44.1)
59.9 (38.0)
12.4b (10.2) 71.3 (57.0)
12.8b (10.6)
24.3 (7.1)
58.9 (37.0)
58.2 (32.5)
55.5 (32.5)
19
18
18
11
11
11
14
14
12
13
12
<5
<5
19
20
19
19
19
38
49
48
41
39
20
18
19
21
21
31 (31) 21
165 (<5)
58
60.9d (6.3),81.7 (1.9) 45.5 (11.4) 52.4 (36.6)
31
19
e
e
30f
56.4 (32.5)
34.2 (8.7)
52.3d (1.5),79.6 (3.0) 34.2 (8.7)
156 (<5)
<5
31g
32h
242.0 (149.7) 109.5e (0.8) 47.0 (16.9) 69.7 (52.7±54.4) 26.0 (9.0±10.7) 66.7 (36.1±37.4) 62.3d (1.3),82.0 (1.3) 49.0 (14.0) 58.0 (41±42.7)
231.6 (146.9) 109.8e (1.5) 46.2 (17.1) 65.4 (49.6)
26.1 (9.1±10.8) 56.9 (26.3±27.6) 20
36.5 (10.7) 52.4d (1.9),79.8 (3.3) 36.5 (10.7)
51.8 (27.6) 20
32
18±20
e
e
25.7 (9.4)
63.2 (33.5)
51.8 (27.6)
10 (10)
a Changes in chemical shift in going from precursor to ion.
b Interchangeable values.
c JF3
ˆ JF2-CF ˆ 25 Hz, JF3
ˆ 18 Hz, J30 ˆ 13 Hz, J50 ˆ 19 Hz.
0 -CF
0 -CF
0
0
;5
;6
2
3
d CF2 gr2oup.
e CF3 group.
f J
ˆ 33 Hz, J
ˆ 7 Hz.
0
0
0
0
ꢁ5 †
-CF
3
ꢁ5
†
3
F
-CF
F
2
3
g JF3-CF ˆ 28 Hz, JF
ˆ JF
ˆ 30 Hz, JF
ˆ JF
ˆ 21 Hz, JF3
0 -CF
2
2
ˆ 35 Hz, J30 ˆ 20 Hz.
0
2
0
0
0
2
2
6
a-CF
a-F
ˆ 61 Hz.
0
†
2
;5
a-CF
a-CF
3
3
2
2
h JF3-CF ˆ 26 Hz, JF
ˆ 28 Hz, 3J
0
ꢁ6
a-F
a-CF
2
F
3
3

Table 2
19F NMR spectral data of benzocyclobutenes and diphenylmethanes
Compound dF (ppm)
JF,F (Hz)
F-20
A0
F-30
F-40
F-50
F-60
J3,4 J3,5 J3,6 J4,5 J4,6 J5,6 J6;6
JA,B
0
F-1 F-2
A
F-3 F-4 F-5 F-6
0
0
(JA ;B )
0
(J6;2
)
B
B0
d
d
d
d
2a,b
3e
35.0 69.2
30.8 68.0
60.0
59.2
26.9 19.0 19.7 28.4
27.7 20.5 20.8 31.0
60.2c,79.8
23.9
49.1c,79.8
34.1 15.8
25.5 50.8c,76.6
35.0 15.8f
25.8 50.4c,76.5
26.2 50.4c,76.6
24.6 50.7c,76.4
17.2
25.5
25.7
23.9
19
19
8
8
24
24
18
18
8
9
19
18
16
205 (285)
d
20 (20) 200
(280)
5a
92.3 108.7d 108.7d 30.1 15.3f 15.8f 30.6 or 29.0 62.5c,80.7
59.4c,80.7
17.0f 30.6 or 29.0
9g
10h
34
84.7 108.3d 108.3d 29.1 15.8 16.3 29.7
106.9d 106.9d 27.5 14.9 16.8 22.2
24.2
23.6
22.4
25.8
26.2
24.6
24.2
23.6
22.4
21
21
20
9
9
8
9
11
24
21
20
18
9
6
8
21
22
19
d
d
d
66.1
56.6
26.9 17.3 19.8 29.2
20 (20) 199
a Chemical shifts (without assignment) of compound 2 (in (CH3)2CO) are reported in [2],compound 5 (in CHCl3) in [17].
b
B
B
-F30
0
A
0
0
0
0
0
0
0
0
0
0
0
0
0
J3 ;4 ˆ J4 ;5 ˆ J5 ;6 ˆ 21 Hz, J4 ;6 ˆ 9 Hz, JF1-F ˆ 18 Hz, JF1-F ˆ 11 Hz, JF1-F ˆ 60 Hz, JF1-CF ˆ 25 Hz, J3 ;5 ˆ J3 ;6 ˆ JF -F ˆ 10 Hz, JF -F ˆ 76 Hz, JF
ˆ 57 Hz, JF3 -CF ˆ 20 Hz.
0
0
A
B
0
A
B
3
B
3
c CF2 group.
d CF3 group.
e
0
0
0
0
JF3 -CF ˆ JF5 -CF ˆ 31 Hz, JF3 -CF ˆ JF5 -CF ˆ 14 Hz.
2
2
3
3
f Interchangeable values.
g JF6-CF ˆ 34 Hz, JF3-CF ˆ 32 Hz, JCF
2
1
ˆ JF6 -CF ˆ JF2 -CF ˆ 17 Hz.
0
0
1
2
3
1
1
2
-CF2
3
2
2
h JF3-CF ˆ 18 Hz.
2
3

80
V.M. Karpov et al. / Journal of Fluorine Chemistry 117 (2002) 73±81
Table 3
19F NMR spectral data of compounds 11±14a
Compound
dF (ppm)
F-1 F-3
JF,F (Hz)
F-4
F-5
F-6
F-7
F-8
F-9
F-10
48.6
F-20
F-200
J1,4
J1;2
J1;2
00
J2
J2
J3,4
J4,10
0
0
00
;3
;3
11b
12
13c,d
14c
53.5 32.7 20.4 55.6 or 56.0
51.8 39.0 25.0 26.0 or 25.7
50.8 41.7 24.8 24.9
27.0
27.0
55.6 or 56.0
26.0 or 25.7
24.3
52.2
51.1 76.7
16
18
18
18
34
33
34
34
7
7
8
9
34
33
34
34
7
7
7
6
20
18
19
18
72
18
20
16.2 or 16.5
18.8
16.2 or 16.5
14.7
78.0 or 78.4 78.0 or 78.4 50.5 76.6
79.5
52.6 78.4
52.6 78.4
49.5 41.0 22.6 23.9
18.0 or 17.3
18.0 or 17.3
23.9
a The 19F NMR spectra of perfluorinated 9,10-dihydroanthracene, 9(10H)anthracenone and 9,10-anthraquinone are reported in [18].
b J1;9 ˆ 92 Hz, J5;10 ˆ J8;9 ˆ 23 Hz.
c Spectrum was recorded for (CH3)2CO solution of compound.
d J5;6 ˆ J6;7 ˆ J5;10 ˆ 20 Hz, J7;8 ˆ 19 Hz, J5;7 ˆ 8 Hz, J5;8 ˆ J6;8 ˆ 13 Hz.
Per¯uoro-1-(4-ethylphenyl)benzocyclobutene (3): HRMS
‡
521:9712. 19F NMR spectrum: d 104.6 (ddq,3F,
JF;F ˆ 34,19 and 10 Hz,CF 3-8),89.1 (m,3F,CF 3-9),
m/z,495.97478 ( M ). Calcd. for C16F16 ˆ 495:97444.
1-Hydroxyper¯uoro-1-(4-ethylphenyl)benzocyclobutene
(34): mp 92.5±93.5 8C (from CCl4). HRMS m/z,493.97855
55.9 (m,1F) and 41.7 (m,1F, JA;B ˆ 301 Hz,CF -1),
2
50.8 (m,1F) and 47.3 (m,1F, JA;B ˆ 300 Hz,CF -4),
2
‡
(M ). Calcd. for C16HF15O ˆ 493:97877.
41.2 (m,1F,F-5),39.2 (m,1F,F-7),33.9 (m,1F) and
24.8 (m,1F, JA;B ˆ 277 Hz,CF -2),31.2 (m,1F) and
2
3.2. Reaction of perfluoro-1-phenylbenzocyclobutene (1)
with antimony pentafluoride
22.7 (m,1F, JA;B ˆ 275 Hz,CF -3),15.8 (m,1F,F-6),
2
À20.9 (m,1F,F-9).
3. Analogously to the previous procedure,the reaction of
benzocyclobutene 4 (1.87 g) and SbF5 (5.73 g) (1:3.5)
gave (170 8C,15 h,treatment with 5 ml of HF) 1.51 g of
a mixture containing 18% (yield 13.5%) of 5,5% (4%)
of 6 and 51% (39%) of 8.
Benzocyclobutene 1 (1.24 g) and SbF5 (4.74 g) (1:7) were
heated in a nickel bomb (10 ml) for 7 h at 170 8C. The
mixture was poured onto ice and extracted with CHCl3. The
extract was dried over MgSO4. The solvent was distilled off
to give product 33 (1.1 g,yield 89%). The 19F NMR
spectrum of compound 33 coincides with the spectrum of
the authentic sample [9].
3.4. Reaction of perfluoro-1-(4-
ethylphenyl)benzocyclobutene (3) with antimony
pentafluoride
3.3. Reaction of perfluorobenzocyclobutene (4) with
antimony pentafluoride
1. Benzocyclobutene 3 (1.87 g) and SbF5 (5.76 g) (1:7)
were heated in a nickel bomb (10 ml) for 30 h at 130 8C.
The mixture was treated with anhydrous HF (5 ml),
poured onto ice and extracted with CHCl3. The extract
was dried over MgSO4. The solvent was distilled off to
give 1.64 g of a product containing compound 3 and 34
in the ratio ꢀ1:1 (19F NMR spectrum).
1. Benzocyclobutene 4 (0.88 g) and SbF5 (5.37 g) (1:7)
were heated in a nickel bomb (10 ml) for 57.5 h at
130 8C. The mixture was treated with anhydrous HF
(15 ml),poured onto ice and extracted with CHCl . The
3
extract was dried over MgSO4. The solvent was distilled
off to give a product (0.48 g) containing 22% (yield
12%) of 2,44% (22%) of 5,7% (3.7%) of 6 and 13%
(7%) of 7. The 19F NMR spectra of compounds 2 and
5±7 coincide with the spectra of the authentic samples
[2,17].
2. Analogously to the previous experiment,the reaction of
benzocyclobutene 3 (2.03 g) and SbF5 (6.22 g) (1:7)
gave (170 8C,7 h) 1.59 g of a mixture containing 14%
(yield 11%) of 3,6% (4.4%) of 9,2% (1.5%) of 10,26%
(19%) of 11,19% (15%) of 12,10% (8%) of 13 and 4%
(3%) of 34. The individual compounds 9 and 11±13
were isolated by silica gel column chromatography
(CCl4 and then CHCl3 as eluent).
2. Analogously to the previous procedure,the reaction of
benzocyclobutene 4 (1.66 g) and SbF5 (5.09 g) (1:3.5)
gave (170 8C,7 h,treatment with 5 ml of HF) a mixture
(1.37 g) containing 42% (yield 32%) of 5,17% (13.6%)
of 6 and 26% (20%) of 8. The individual compound 8
was isolated using preparative GLC.
3. Benzocyclobutene 3 (1.67 g) and SbF5 (5.12 g) (1:7)
were heated in a nickel bomb (10 ml) for 14 h at 170 8C.
The mixture was poured into an ice±water mixture
(100 ml) and CHCl3 (20 ml) was added. The residue
(0.5 g) containing compounds 13 and 14 in the ratio
Perfluoro-8,9-dimethyl-1,2,3,4-tetrahydrofluorene (8):
‡
HRMS m/z,521.9703 ( M ). Calcd. for C15F18
ˆ

V.M. Karpov et al. / Journal of Fluorine Chemistry 117 (2002) 73±81
81
1:2.7 (19F NMR spectrum) was filtered off. The organic
layer was then separated and dried over MgSO4. CHCl3
was distilled off to give 1.0 g of a mixture containing
47% of 11 and 14% of 13. Yields of compounds 11, 13
and 14 are 26,17.5 and 24%,respectively.
3.8. Perfluoro-40-ethyl-2-methyldiphenylmethyl cation (32)
Cation 32 was generated by the analogous procedure from
diphenylmethane 9 (0.03 g) and SbF5 (1.01 g) (9:SbF5 ˆ
1:83) in SO2ClF (0.28 g). Hydrolysis of the salt of this cation
gave compound 10 (0.02 g,yield 74%),which was addi-
tionally puri®ed on Silufol and then sublimated (90±95 8C,
3 torr).
Perfluoro-4-ethyl-2-methyldiphenylmethane (9):
‡
HRMS m/z,533.97171 ( M ). Calcd. for C16F18
533:97124.
Perfluoro-6-ethyl-1,2,3,4-tetrahydroanthracene (11):
ˆ
Per¯uoro-40-ethyl-2-methylbenzophenone (10): mp 66±
‡
mp 64.5±66 8C (from pentane). HRMS m/z,533.97171
68 8C. HRMS m/z,511.97020 ( M ). Calcd. for C16F16O ˆ
‡
(M ). Calcd. for C16F18 ˆ 533:97124.
511:96935.
Perfluoro-2-ethyl-9,10-dihydroanthracene (12): mp
(in a capillary) 119±120 8C (from hexane). HRMS m/z,
‡
Acknowledgements
495.97330 (M ). Calcd. for C16F16 ˆ 495:97444.
Perfluoro-2-ethyl-9(10H)anthracenone (13): mp (in a
capillary) 200±202 8C (after sublimation at 1208C,
5 torr). HRMS m/z,473.97322 ( M ). Calcd. for
We gratefully acknowledge the Russian Foundation for
Basic Researches (project no. 99-03-32876a) and Siberian
Branch of RAS (IG SB RAS-00-N47) for ®nancial support.
‡
C16F14O ˆ 473:97254.
Perfluoro-2-ethyl-9,10-anthraquinone (14): mp (in a
capillary) 292±293.5 8C (from acetone). HRMS m/z,
‡
References
451.97043 (M ). Calcd. for C16F12O2 ˆ 451:97065.
4. Analogously to the experiment 1,the reaction of ben-
zocyclobutene 3 (1.05 g) and SbF5 (3.21 g) (1:7) gave
(170 8C,30 h) 0.97 g of mixture containing 40% (yield
34%) of 11,20% (18%) of 12 and 11% (11%) of 13.
[1] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,G.G. Yakobson,J.
Fluorine Chem. 28 (1985) 115.
[2] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,G.G. Yakobson,Bull.
Soc. Chim. Fr. (1986) 980.
[3] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,Izv. Akad. Nauk
SSSR Ser. Khim. (1990) 645.
3.5. Perfluoro-1-(2-ethylphenyl)-1-benzocyclobutenyl
cation (29)
[4] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,G.G. Yakobson,Izv.
Akad. Nauk SSSR Ser. Khim. (1990) 1114.
[5] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,Izv. Akad. Nauk Ser.
Khim. (1992) 1419.
Benzocyclobutene 2 (0.15 g) was added to a solution of
SbF5 (1.14 g) in SO2ClF (0.24 g) (2:SbF5 ˆ 1:17.4) at
À10 8C. The mixture was stirred. The 19F NMR spectrum
was measured at ‡20 8C. The solution contained the salt of
cation 29,and precursor 2 was not found. The solution was
poured into water and extracted with CHCl3. The extract was
[6] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,J. Fluorine Chem. 77
(1996) 101.
[7] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,Zh. Org. Khim. 33
(1997) 755.
[8] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,V.R. Sinyakov,J.
Fluorine Chem. 107 (2001) 53.
[9] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,V.R. Sinyakov,L.N.
Shchegoleva,Zh. Org. Khim.,in press.
dried over MgSO4,and CHCl was distilled off to give
3
compound 7 (0.11 g,yield 73%).
[10] Yu.V. Pozdnyakovich,V.D. Shteingarts,Zh. Org. Khim. 14 (1978)
2237.
3.6. Perfluoro-1-(4-ethylphenyl)-1-benzocyclobutenyl
cation (30)
[11] V.V. Bardin,G.G. Furin,G.G. Yakobson,Izv. Sib. Otd. Akad. Nauk
SSSR Ser. Khim. Nauk 6 (1978) 142.
[12] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,Zh. Org. Khim. 35
(1999) 1204.
An analogous procedure was used to generate cation 30
from benzocyclobutene 3 (0.23 g) and SbF5 (1.17 g)
(3:SbF5 ˆ 1:11.6) in SO2ClF (0.19 g). Hydrolysis of the
salt of cation 30 yielded compound 34 (0.17 g,yield 74%).
[13] V.D. Shteingarts,Yu.V. Pozdnyakovich,G.G. Yakobson,Zh. Org.
Khim. 7 (1971) 2002.
[14] Yu.V. Pozdnyakovich,T.V. Chuikova,V.D. Shteingarts,Zh. Org.
Khim. 11 (1975) 1689.
[15] Yu.V. Pozdnyakovich,V.D. Shteingarts,J. Fluorine Chem. 4 (1974)
283.
3.7. Perfluoro-2-ethyl-20-methyldiphenylmethyl cation (31)
[16] Yu.V. Pozdnyakovich,V.D. Shteingarts,J. Fluorine Chem. 4 (1974)
297.
Cation 31 was generated by the analogous procedure from
diphenylmethane 5 (0.2 g) and SbF5 (1.01 g) (5:SbF5 ˆ
1:12.4) in SO2ClF (0.2 g). Hydrolysis of the salt of cation
31 gave compound 6 (0.16 g,yield 84%).
[17] V.M. Karpov,T.V. Mezhenkova,V.E. Platonov,Mendeleev Commun.
(1997) 71.
[18] B.G. Oksenenko,V.D. Shteingarts,G.G. Yakobson,Zh. Org. Khim. 7
(1971) 745.