Carbocationic cyclizations: IX. Rearrangement of long-lived 4-(2-biphenylyl)-1,2,3,4-tetramethylcyclobutenyl cation into trans- and cis-4,5,6,6-tetramethyl-4,5,6-trihydrocyclopenta[j,k]phenanthren-5-yl cations

Article abstract of DOI:10.1023/B:RUJO.0000010218.88703.55

According to the ¹H and ¹³C NMR data, long-lived 4-(2-biphenylyl)-1,2,3,4-tetramethylcyclobutenyl cation generated by protonation of 3-(2-biphenylyl)-1,2,3-trimethyl-4-methylenecyclobutene in super-acids undergoes cyclization which l

Full text of DOI:10.1023/B:RUJO.0000010218.88703.55

Russian Journal of Organic Chemistry, Vol. 39, No. 9, 2003, pp. 1301 1308. Translated from Zhurnal Organicheskoi Khimii, Vol. 39, No. 9, 2003,
pp. 1374 1381.
Original Russian Text Copyright
2003 by Bushmelev, Genaev, Osadchii, Shakirov, Shubin.
Carbocationic Cyclizations: IX.* Rearrangement
of Long-Lived 4-(2-Biphenylyl)-1,2,3,4-tetramethylcyclobutenyl
Cation into trans- and cis-4,5,6,6-Tetramethyl-4,5,6-trihydro-
cyclopenta[j,k]phenanthren-5-yl Cations
V. A. Bushmelev, A. M. Genaev, S. A. Osadchii,
M. M. Shakirov, and V. G. Shubin
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 9, Novosibirsk, 630090 Russia
e-mail: bushmelev@nioch.nsc.ru
Received January 8, 2003
Abstract According to the 1H and 13C NMR data, long-lived 4-(2-biphenylyl)-1,2,3,4-tetramethylcyclo-
butenyl cation generated by protonation of 3-(2-biphenylyl)-1,2,3-trimethyl-4-methylenecyclobutene in super-
acids undergoes cyclization which launches further rearrangements finally leading to formation of a mixture
of trans- and cis-4,5,6,6-tetramethyl-4,5,6-trihydrocyclopenta[j,k]phenanthren-5-yl cations.
Carbocationic cyclizations (intramolecular alkyla-
tion) with participation of long-lived carbocations
containing aromatic fragments lie at the interface
between the chemistry of carbocations and aromatic
compounds. Investigation of these reactions by
modern experimental and theoretical methods makes
it possible to get an insight into their mechanism and
and disclose their synthetic potential.
medium undergoes cyclization involving the unsub-
stituted -carbon atom. This reaction gives rise to
subsequent carbocationic rearrangements which even-
tually led to formation of phenalene cation II. Unlike
cation I, 4-phenyl-1,2,3,4-tetramethylcyclobutenyl
cation (III) is not prone to cyclization [2].
With the goal of extending the series of related
carbocations through variation of aromatic fragments
therein, as subject for study we selected 4-(2-bi-
phenylyl)-1,2,3,4-tetramethylcyclobutenyl cation (IV).
We anticipated that more favorable steric factors, as
compared to III (specifically, the possibility for
formation of a six- rather than four-membered ring via
attack by electrophilic carbocationic center on the
aromatic fragment), should make the cyclization of
IV possible. However, one cannot rule out a priori
that the above factor could appear so strong that
carbocation IV could not be generated with a suf-
ficient lifetime because of high rate of its cyclization.
It should be noted that the cyclization of I, which
In the preceding communication of this series [1]
we have reported that 4-(1-naphthyl)-1,2,3,4-tetra-
methylcyclobutenyl cation (I) generated in superacidic
____________
*
For communication VIII, see [1].
1070-4280/03/3909-1301$25.00 2003 MAIK Nauka/Interperiodica

1302
BUSHMELEV et al.
Fig. 1. Conformations of cation IV, calculated by the MINDO/3 method.
(according to Baldwin [3]) is classed with disfavored
A considerable difference in the chemical shifts of
the 1-CH3 and 3-CH3 protons ( 1.36 ppm) in the
5-endo-trig, is nevertheless characterized by a high
1H NMR spectrum of cation IV arises from restricted
rotation about the C4 C2 bond. As a result, protons
of the 1-CH3 group suffer stronger deshielding effect
of the aromatic fragment due to its magnetic aniso-
tropy. Figure 1 shows the structure of cation IV
according to the MINDO/3 calculations.** Conformer
IVA differs from less stable conformer B by morpho-
logy of the four-membered ring: in particular, the C2
atom in IVA appears spatially close to the phenylene
fragment. One methyl group in IVA (1- or 3-CH3)
is located in the area of shielding by the phenyl group
which is turned through an angle of 90 relative to the
o-phenylene moiety, whereas the other methyl group
resides in the area of deshielding by the o-phenylene
fragment. Calculation of the chemical shifts of the
1-CH3 and 3-CH3 protons in conformer IVA by
the IGLO method [6] using the DZ basis set gave
20 C
4
1
rate even at low temperature (k
= 7 10 s ,
G = 77 kJ/mol) [1], whereas the cyclization of IV
is referred to as favored 6-endo-trig process.
Thus the present study was aimed at elucidating
the possibility for generation of long-lived cation IV
and (provided that the generation is successful)
examining its rearrangements. Analysis of the NMR
spectra of solutions of 3-(2-biphenylyl)-1,2,3-tri-
methyl-4-methylenecyclobutene (V) in the superacidic
system HSO3F/SbF5 SO2ClF CD2Cl2 (1 : 4 : 1, by
volume), prepared at low temperatures, showed that
generation of long-lived cation IV was successful
at 110 to 120 C; 1H NMR spectrum ( 121 C,
200.13 MHz), , ppm: 1.21 br.s (3H, 3-CH3), 1.73 s
(3H, 4-CH3 ), 2.19 s (3H, 2-CH3), 2.57 br.s (3H,
1-CH3), 7.0 8.8 m (9H, Harom). It is characteristic
that the methyl groups in positions 1 and 3 of cation
IV are nonequivalent. The 13C NMR spectrum
( 112 C, 50.323 MHz) contained the following sig-
nals, C, ppm: 10.5 (2-CH3); 11.5 (broadened signal
from two methyl carbon nuclei, 1- and 3-CH3); 19.5
(4-CH3); 73.0 (C4); 126 134, 138.2, 140.8, and 142.1
a
value of 1.10 ppm which approaches that found
experimentally. It would be attractive to anticipate
that, apart from magnetic anisotropy of the aromatic
fragment, some contribution to the difference in the
chemical shifts of the 1-CH3 and 3-CH3 protons is
given by their diastereotopy arising from appearance
of a chiral center as a result of second protonation
at the C2 atom. However, there were no reasons for
____________
(Carom
,
biphenylyl fragment);
165.0 (strongly
broadened and therefore difficult to identify, C1 and
C3); 183.2 (C2). The signals were assigned with
account taken of known spectral data for 4-R-substi-
tuted 1,2,3,4-tetramethylcyclobutenyl cations, where
R = 1-naphthyl [1], Ph [2], PhCH2 [4], and CH3 [2].
**
Among semiempirical methods, the MINDO/3 approxima-
tion is known [5] to reproduce the energy parameters of
carbocations most properly.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 9 2003

CARBOCATIONIC CYCLIZATIONS: IX.
1303
such assumption: according to the 13C NMR data, no
dication was formed (cf. 13C NMR data for arenonium
ions in [7]).
On raising the solution temperature to 103 C the
signals from C1, C3, 1-CH3, and 3-CH3 in the 13C
NMR spectrum become narrower. Simultaneously,
1
the H signals from the 1-CH3 and 3-CH3 groups
initially broaden (at 120 to 100 C) and then merge
together ( 103 C) to give one signal at 1.9 ppm,
which becomes narrower on further raising the tem-
perature. Obviously, this pattern is explained by
resumption of free rotation of the biphenylyl fragment
about the C4 C2 bond. Estimation of the barrier to
rotation by the dynamic NMR procedure gave a G
value of 31 kJ/mol ( 121 C). The barrier calculated
by the MINDO/3 method is 37 kJ/mol (Fig. 2).
1
Analogous H and 13C NMR spectra were obtained
for solutions of compound V in the system HSO3F
SO2ClF CD2Cl2 (1:4:1, by volume).
It should be noted that rotation about the C4 C2
bond in cation IV is not accompanied by overlap of
van der Waals spheres of atoms which are not linked
through covalent bonds. This is consistent with the
very low energy barrier to rotation about analogous
C Ar bond in neutral compound V (precursor of
cation IV; Fig. 2). Both species, IV and V, are charac-
terized by similar geometric parameters. Therefore, we
presume that the main factor responsible for restricted
rotation in the cation is donor acceptor interaction
between its biphenylyl and electron-deficient cyclo-
butane fragments. Comparison of the heats of forma-
tion of conformers IVA and IVB (Fig. 2) shows that
the above donor acceptor interaction is stronger in
the former where, as we already noted, the C2 atom
appears in the vicinity of the phenylene group. This
fact, as well as the other geometric parameters of
structure IVA, led us to conclude that the electron-
donor component is just the o-phenylene moiety of
the biphenyl fragment.
Fig. 2. Barriers to rotation about the C4 C2 bond in
(1) olefin V, (2) conformer IVA, and (3) conformer IVB,
calculated by the MINDO/3 method.
is actually characterized by increased puckering of
the four-membered ring. It is reasonable to believe
that this puckering results from donor acceptor inter-
action in cation IV.
1
According to the H and 13C NMR data, gradual
raising the temperature of a solution containing cation
IV in HSO3F SO2ClF CD2Cl2 above 100 C leads to
irreversible isomerization into a mixture of trans- and
cis-4,5,6,6-tetramethyl-4,5,6-trihydrocyclopenta[j,k]-
phenanthren-5-yl cations VIa and VIb, respectively,
at a ratio of 1:2 ( 35 C). During this process, three
unidentified species successively appear and disap-
pear. We failed to identify these species, for it was
necessary to assign all signals belonging thereto from
a complex set of the observed signals which are over-
lapped in many regions.
The existence of donor acceptor interaction in
A mixture of cations VIa and VIb was also ob-
tained from the product of cyclization of cation IV,
1,2,2a,10b-tetramethyl-2a,10b-dihydrocyclobuta[l]-
phenanthrene (VII), when its solution in CD2Cl2
(1 volume) was added to the acid system HSO3
SO2ClF (1:4, by volume) at 130 C and the resulting
mixture was allowed to warm up to 30 C or when
powdered compound VII was dissolved in HSO3F at
85 C and the solution was allowed to warm up to
50 to 30 C. In the first case, we succeeded in
detecting intermediate species whose spectral param-
eters coincided with those of unidentified species
formed from cation IV. These findings suggest that
cation IV is also supported by its 13C NMR spectrum.
It is known that variation of the angle between the
C2C1C3 and C4C1C3 planes in cyclobutenyl-like
carbocations requires no large energy to be spent but
leads to considerable change in the chemical shifts
of the C1 and C3 atoms. As the above angle decreases,
the C1 and C3 signals shift upfield, the magnitude of
the shift reaching 2.5 ppm per degree [8]. Comparison
of the 13C NMR parameters of cation IV (
=
C1, C3
165 ppm) and 1,2,3,4,4-pentamethylcyclobutenyl
1
3
cation (
= 183.7 ppm), which lacks such donor
acceptor Cin,tCeraction, suggests that the structure of IV
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 9 2003

1304
BUSHMELEV et al.
hydrocarbon VII (which is obtained from diene V
by the action of 85% phosphoric acid) is formed as
intermediate in the rearrangement of IV into a mixture
of cations VIa and VIb. Addition of a solution of VII
(1 volume) to a mixture of CF3SO3H with CDCl3
(2:1, by volume) at room temperature afforded only
trans isomer VIa. Probably, these conditions corre-
spond to equilibrium between isomeric cations VIa
and VIb, where the former (trans) predominates as
more thermodynamically stable isomer.
A solution of VII in HSO3F SO2ClF CH2Cl2
(1:4:1), prepared at 100 C, was neutralized by
adding it in a dropwise manner to a mixture of ether,
sodium carbonate, triethylamine, and a small amount
of methanol, cooled to 100 C. As a result, we
isolated only 9-methyl-9-(cis-1-methyl-1-propenyl)-
10-methylene-9,10-dihydrophenanthrene (VIII) and
4,5,6,6-tetramethyl-4,6-dihydrocyclopenta[j,k]phenan-
threne (IX). The formation of these products suggests
that one more intermediate in the transformation of
IV into VI is 9-(cis-1-methyl-1-propenyl)-9,10-di-
methylphenanthrenium ion E. The fact that olefin
VIII was formed as a single isomer with cis arrange-
ment of the methyl groups indicates stereoselective
character of protonation of tetracyclic olefin VII:
proton adds exclusively from the exo side, for only in
this case allowed disrotatory opening of the four-
membered ring in protonated compound VII could
afford cation E. An analogous pattern in the protona-
tion of olefins containing a cyclobutene fragment
was observed by us previously [1, 4]. As expected,
quenching of a solution of VII in CF3SO3H CDCl3
(1:1, by volume), prepared at 20 C, gave only com-
pound IX. In keeping with the above stated, Scheme 1
shows a plausible mechanism of the isomerization of
cation IV into phenanthrenium ions VIa and VIb
(hereinafter, each chiral structure corresponds in fact
to an equimolar mixture of enantiomers).
The presence of geminal methyl groups in the final
rearrangement products (cations VIa and VIb) implies
1,2-migration of methyl group in intermediate phen-
anthrenium ion E (cf. [7]) and subsequent transforma-
tion of allylic cation F (which is more stable than
E by 23 kJ/mol, according to the MINDO/3 calcula-
tions) through cation G and compound IX to cations
VIa and VIb (cf. [9]). The absence of a product which
might be formed from cation F among those obtained
by neutralization of a solution of V in HSO3F
Scheme 1.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 9 2003

CARBOCATIONIC CYCLIZATIONS: IX.
1305
Scheme 2.
SO2ClF SH2Cl2, prepared at 100 C, may be ex-
plained on the assumption that the rate of the 1,2-CH3
shift in cation E is lower than the rate of cyclization
of F. The reason for the much lower rate of 1,2-CH3
shift in E, as compared with analogous process in
9,9,10-trimethylphenanthrenium cation [7], may be
homoallyl interaction in the former. Obviously, the
rearrangement of IV gives a mixture of isomeric
cations VIa and VIb because of the lack of stereo-
selectivity in the protonation of olefinic intermediate
the rate of cyclization of cation I, though the nucleo-
philicity of carbon atom in the biphenylyl fragment
of IV (which is subjected to electrophilic attack by
the carbocationic center at the stage of cyclization)
should be much lower than the nucleophilicity of the
corresponding carbon atom in the -naphthyl group
in cation I (cf. the basicities of biphenyl and naphtha-
lene [10]). The most probable reason is favorable
steric factors, in keeping with the Baldwin rules [3].
Thus, unlike previously examined carbocations
having allyl [11, 12], benzyl [4], and -naphthyl
groups [1], whose rearrangements afforded finally
carbocations with a cyclopropylcarbinyl fragment,
the isomerization of cation IV gives rise to tetracyclic
cations VI of the phenanthrene series. The rearrange-
ment of IV into VIa and VIb attracts certain interest
from the synthetic viewpoint as an example of trans-
formation of a C4 C6 C6 nonfused tricyclic system
into a C5 C6 C6 C6 fused tetracyclic system.
1
IX. According to the H and 13C NMR spectral data,
a mixture of cations VIa and VIb was also formed
by rearrangement of cation IV in the acid system
HSO3F SbF5 SO2ClF CD2Cl2. Apart from signals
belonging to VIa and VIb, the NMR spectra con-
tained signals of an unknown species, other than those
detected in the acid system containing no SbF5. The
relative concentration of this species remained con-
stant on raising the temperature up to 35 C. Taking
into account the higher acidity of the SbF5-containing
system, as compared to HSO3F SO2ClF CD2Cl2, we
presume that in this case the rearrangement of IV into
phenathrenium ions VIa and VIb involves dicationic
intermediates generated from ion E. Here, we cannot
rule out direct formation of dication J from cation E
via anti-Markownikoff proton addition. This pathway
is favored by the lower energy of Coulomb interaction
between positive charges in the resulting dication
(Scheme 2).
The formation of hydrocarbon VII as a result of
acid-catalyzed cyclization of diene V by the action
of 85% phosphoric acid may be interpreted in terms
of insufficient acidity of the medium, which does not
ensure protonation of VII at the endocyclic cyclo-
butene double bond to an extent required for success-
ful further transformations. The rate of cyclization of
cation IV at about 100 C is considerably higher than
EXPERIMENTAL***
1
The H NMR spectra were recorded on Bruker AC-
200, AM-400, and WP-200SY spectrometers. The 13C
NMR spectra were obtained on a Bruker AC-200
instrument (50.323 MHz) with complete decoupling
from protons, with selective decoupling from protons
(off-resonance mode), and without decoupling from
protons. The chemical shifts were measured relative
hexamethyldisiloxane, CHCl3, or CH2Cl2 (1H, 0.04,
7.24, and 5.33 ppm, respectively) and CDCl3 or
CD2Cl2 (13C,
76.9 and 53.3 ppm, respectively) for
C
neutral compounds and relative to CH2Cl2 and
CD2Cl2 or CHCl3 and CDCl3 for cations. The IR
spectra were recorded on a UR-20 spectrometer, and
____________
***
With participation of N.V. Kochubei.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 9 2003

1306
BUSHMELEV et al.
the UV spectra were measured on a Specord UV-Vis
spectrophotometer. The molecular weights and ele-
mental compositions of the newly synthesized com-
pounds were determined from the high-resolution
mass spectra which were obtained on a Finnigan MAT
8200 instrument.
Doubly distilled HSO3F (bp 158 161 C) and tri-
fluoromethanesulfonic acid from Fluka were used for
generation of carbocations. Samples for NMR analysis
were withdrawn according to the procedure described
in [13]. The properties of compounds synthesized by
known methods were consistent with published data.
The heats of formation were calculated by the
MINDO/3 method using MOPAC software [14].
2-Bromobiphenyl was synthesized by the proce-
dure reported in [15] from 2-aminobiphenyl which
was prepared in quantitative yield by reduction of
2-nitrobiphenyl [16] at 60 C with hydrazine hydrate
in alcohol [17] or with hydrogen (30 atm) over
IKT-3-20 (5% of Pd/C) as catalyst (cf. [17, 18]). The
1H and 13C NMR spectra of the product (2-bromobi-
phenyl) coincided with those given in [19].
preliminarily). The sublimation process was terminat-
ed when first crystals of compound VII (which
sublimes at 100 115 C) appeared on the outer cup
surface. The yield of compound V was 55% on the
1
initial cyclobutene X. H NMR spectrum (10% solu-
tion in CDCl3, 200.13 MHz), , ppm: 1.67 s (3H,
3-CH3), 1.57 (3H) and 1.74 (3H) (1-CH3, 2-CH3;
broadened signals due to quadruplet coupling with
each other; J = 1.2 Hz), 4.57 s (2H, CH2), 7.2 7.8 m
(9H, Harom). 13C NMR spectrum (CDCl3, 10% solu-
tion), C, ppm: 8.6 q and 10.0 q (1-, 2-CH3); 23.6 q
(3-CH3); 56.3 s (C3); 90.7 t ( CH2); 126.2 d and
129.1 d (2C each, C2 , C6 , C3 , C5 ); 125.2 d, 125.9 d,
126.7 d, 128.0 d, 132.0 d (C3 C6 , C4 ); 139.7 s,
140.2 s, 142.1 s, 143.6 s, 153.7 s, 159.5 s (C1, C2 ,
C4, C1 , C2 , C1 ). Found, m/z: [M]+ 260.1565. C20H20.
Calculated: M 260.1565.
1,2,2a,10b-Tetramethyl-2a,10b-dihydrocyclo-
buta[l]phenanthrene (VII) was synthesized by
a procedure analogous to that described in [1] for the
preparation of 6b,7,8,8a-dihydrocyclobut[a]acenaph-
thylene. Yield 61%. mp 153 154 C (from hexane).
1H NMR spectrum (CDCl3, 400.13 MHz), , ppm:
1.51 s (6H) and 1.55 s (6H, CH3), 7.21 7.30 m (4H,
4-H, 5-H, 8-H, 9-H), 7.38 7.42 m (2H, 3-H, 10-H),
7.97 8.01 m (2H, 6-H, 7-H). 13C NMR spectrum
(CDCl3), C, ppm: 8.3 q (1-CH3, 2-CH3); 21.2 q
3-(2-Biphenylyl)-1,2,3-trimethyl-4-methylene-
cyclobuten (V). A solution of 4.06 g (27.06 mmol,
95% purity) of 3-chloro-1,2,3-trimethyl-4-methylene-
cyclobutene (X) [20] in 10 15 ml of ether was added
dropwise over a period of 10 15 min with stirring
at room temperature to a solution of Grignard com-
pound prepared by standard procedure from 0.724 g
of magnesium (activated by iodine vapor) in 20 ml
of ether and a solution of 6.94 g (29.77 mmol) of
2-bromobiphenyl in 15 20 ml of ether. The mixture
was heated for 1 h under reflux (on a water bath) to
complete the reaction, cooled to 0 C, and quenched
by addition of 7 ml of water. The yellow ether layer
was separated by decanting, and the aqueous phase
was extracted with three portions of ether, each time
the ether layer being separated by decanting. The
ether extracts were combined and evaporated at 50 C,
the residue was treated with 30 ml of pentane, the
precipitate was filtered off, and the filtrate was
evaporated at 50 60 C to obtain 7.86 g of a darkish
(2a-CH3, 10b-CH3); 48.9 s (C2a, C10b); 123.0 d,
125.9 d, 127.2 d, 127.4 d (C3 C6, C7 C10); 130.1 s,
140.4 s, 141.5 s (C1, C2, C2b, C10a, C6a, C6b). UV spe-
ctrum (ethanol), max, nm (log ): 218 (4.63), 232
(4.16), 242 (4.01), 272 (4.12), 284 (4.11), 300 (3.70),
1
311 (3.81). IR spectrum (CCl4, 3% solution), , cm :
1040 m, 1060 m, 1375 m, 1380 m, 1440 s, 1450 m,
1495 m, 2915 m, 2940 m, 2970 m, 2995 m, 3070 m.
Found, m/z: [M]+ 260.1567. C20H20. Calculated:
M 260.1565.
4-(2-Biphenylyl)-1,2,3,4-tetramethylcyclobutenyl
cation (IV). A mixture of 0.1 ml of superacid (HSO3F
or an equimolar mixture of HSO3F and SbF5, diluted
with three volumes of HSO3F) and two volumes of
SO2ClF as diluent was placed in an NMR ampule,
thoroughly stirred, and cooled to 130 C, a layer of
SO2ClF (1 2 volumes) was condensed thereonto, and
then a suspension of precursor V (45 75 mg) in one
volume of SO2ClF and/or one volume of CD2Cl2
was layered on the top (after layering, the mixture
remained colorless). The mixture was stirred with
a glass rod cooled with liquid nitrogen to obtain
a red solution with a purple crimson shade. The
mixture was filtered (by breaking the bottom of the
ampule) at 130 C through a small layer of mineral
1
liquid which, according to the H NMR data, was the
target compound containing some impurities. The
pure product was isolated by sublimation from several
portions of the liquid under reduced pressure (1 mm)
in a sublimator equipped with a finger condenser to
which a small cup (empty hemisphere) was attached
through a short arm to collect cyclobutene V. The
latter condensed onto the condenser and fell into the
cup at a temperature exceeding by 10 25 C the tem-
perature of sublimation of biphenyl under the given
residual pressure (72 74 C; biphenyl was separated
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 9 2003

CARBOCATIONIC CYCLIZATIONS: IX.
1307
wool into another NMR ampule which was prelimi-
narily connected to the first one.
phenanthrenylium ions; see references in [7]). 1H
NMR spectrum (20 C, 200.13 MHz), , ppm: 1.60 d
(3H, 4-CH3, J 7 = Hz), 1.85 d (3H, 5-CH3, J = 7 Hz),
1.89 s (3H) and 1.96 s (3H) (6-CH3), 3.49 q (1H, 4-H,
J = 7 Hz), 3.62 q (1H, 5-H, J = 7 Hz), 7.66 t (1H,
9-H), 7.76 d (1H, 3-H), 7.78 t (1H, 8-H, J = 8 Hz),
7.93 d (1H, 7-H, J = 8 Hz), 8.33 d (1H, 1-H, J =
7 Hz), 8.41 d (1H, 10-H, J = 8 Hz), 8.60 t (1H, 2-H,
trans- and cis-4,5,6,6-Tetramethyl-4,5,6-tri-
hydrocyclopenta[j,k]phenanthren-5-yl cations VIa
and VIb. a. A mixture of cations VIa and VIb was
initially generated by adding powdered compound VII
(2 3 mmol), cooled to 85 C, to 70 80 mmol of
HSO3F cooled to 85 C. The mixture was stirred and
kept for 5 min at 50 C, and a small amount of
CD2Cl2 was added to stabilize conditions for record-
J = 7 Hz). 13C NMR spectrum (20 C), C, ppm:
1
3
16.0 q.q (4-CH3, J = 130, J = 5 Hz); 16.6 q.q
1
1
3
ing NMR spectra. According to the H NMR spec-
(5-CH3, J = 130, J = 5 Hz); 27.1 q.d.d (1J = 130,
2J = 6, J = 3 Hz) and 28.2 q.d.d (1J = 130, J = 6,
3
2
trum ( 40 C, 200.13 MHz), the ratio of VIa and VIb
was 1:2. The spectrum contained the following non-
overlapped signals, , ppm: cation VI: 3.60 q (1H,
4-H, J = 7 Hz), 3.73 q (1H, 5-H, J = 7 Hz); cation
VIb: 4.05 q.d (1H, 4-H, J = 7, 3 Hz), 4.32 q.d (1H,
5-H, J = 7, 3 Hz); partially overlapped signals: VIa:
1.71 d (4-CH3, J = 7 Hz), 1.98 s and 2.07 s (6-CH3);
VIb: 1.64 d (4-CH3, J = 7 Hz), 1.79 d (5-CH3, J =
7 Hz), 1.99 s and 2.05 s (6-CH3); the spectrum also
contained unresolved multiplets from aromatic
3J = 3 Hz) (6-CH3); 49.9 d.m (C4, J = 130 Hz);
1
59.2 d.m (C5, J = 125 Hz); 50.3 s (C6); 122.9 (C1),
1
125.3 (C3), 126.6 (C10), 127.2 (C7), 129.0 (C9), and
134.1 (C8) (d.d each, J = 163, J = 8 Hz); 126.2 s
1
3
(C10a); 138.3 s (C10c); 145.8 s (C10b); 150.4 s (C6a);
172.7 s (C3a); 155.6 d (C2, J = 163 Hz); 239.2 s
1
(C5a) (13C H coupling constants are given).
1
9-Methyl-9-(cis-1-methyl-1-propenyl)-10-me-
thylene-9,10-dihydrophenanthrene (VIII). A solu-
tion of 0.5 g (1.9 mmol) of olefin VII in 2 ml of
CH2Cl2 was added dropwise over a period of 20 min
to a solution of 1.0 ml (17.4 mmol) of HSO3F in 5 ml
of SO2ClF, stirred at 100 C under argon. The result-
ing dark crimson solution was added dropwise over
a period of 30 min to a suspension of 5.4 g (51 mmol)
of Na2CO3 in a mixture of 7.4 ml (5.3 mmol) of tri-
ethylamine, 5 ml of methanol, and 70 ml of dry ether
under vigorous stirring at 100 C. The mixture was
stirred for 2 h, allowing it to gradually warm up to
room temperature. The liquid part was separated by
decanting, filtered through a small layer of Al2O3,
washed with a 10% solution of Na2CO3, dried over
K2CO3, and evaporated under reduced pressure to
obtain 0.46 g of an oily substance which, according
to the NMR spectra, was a mixture of approximately
equal amounts of compounds VIII and IX. Pure
product VIII was isolated by column chromatography
protons of both isomers at
7.7 8.7 ppm and the
5-CH3 signals of isomer VIa at 1.9 2.0 ppm. The
13C NMR spectrum of the same solution ( 40 C) con-
tained the following signals, C, ppm: VIb: 15.3 q
(4-CH3), 15.6 q (5-CH3), 25.9 q and 28.8 q (6-CH3),
45.9 d (C4), 54.7 d (C5), 50.6 s (C6), 122.8 d (C1),
125.8 d (C3), 126.5 d (C10), 127.3 d (C7), 128.7 d
(C9), 133.6 d (C8), 126.6 s (C10a), 138.1 s (C10c),
145.1 s (C10b), 149.8 s (C6a), 174.4 s (C3a), 155.1 d
(C2), 241.5 s (C5a); VIa: 15.2 q (4-CH3), 15.9 q
(5-CH3), 27.0 q and 27.1 q (6-CH3), 49.7 d (C4),
59.4 d (C5), 50.0 s (C6), 125.4 d, 127.5 d, 138.4 s,
145.4 s, 150.5 s, 173.1 s, 155.6 d (C2), 239.8 s (C5a);
the other singlet and doublet signals from sp2-carbon
atoms were obviously overlapped with those of VIb.
b. A similar mixture containing cations VIa and
VIb was obtained (according to the NMR data) by
heating solutions of IV from 130 to 36 C, as well
as by heating from 130 to 36 C of a sample pre-
pared by dissolution at 130 C of a mixture of 45 mg
of compound VII with two volumes of SO2ClF and
one volume of CD2Cl2 in HSO3F (0.1 ml) diluted
with two volumes of SO2ClF.
1
on Al2O3 using hexane as eluent. H NMR spectrum
(CDCl3, 400.13 MHz), , ppm: 1.43 quint (3H,
1-CH3, J = 1.2 Hz), 1.49 s (3H, 9-CH3), 1.58 d.q (3H,
CH3C , J = 6.7, 1.1 Hz), 5.38 q.q (1H, CH3CH , J =
6.7, 1.2 Hz), 5.15 s (1H, CH2), 5.49 s (1H, CH2),
7.19 7.35 m (5H, 2-H, 3-H, 6-H, 7-H, 8-H), 7.56 d.d
(1H, 1-H, J = 7.6, 1.7 Hz), 7.74 7.82 m (2H, 4-H,
5-H); the cis configuration of the 1-methyl-1-propenyl
trans-4,5,6,6-Tetramethyl-4,5,6-trihydrocyclo-
penta[j,k]phenanthren-5-yl cation (VIa). A solution
of 0.063 g of compound VII in 0.3 ml of CDCl3 was
added with stirring at room temperature to a mixture
of 0.5 ml of trifluoromethanesulfonic acid and 0.3 ml
5
fragment follows from the value of JHH equal to
1.2 Hz [21]. 13C NMR spectrum (CDCl3), C, ppm:
13.6 q, 15.6 q, 26.4 q, 51.4 s, 111.2 t, 120.9 d,
122.9 d, 123.4 d, 125.8 d, 126.5 d, 127.0 d, 127.6 d,
127.7 d, 128.2 d, 132.1 s, 132.8 s, 134.9 s, 139.3 s,
1
of CDCl3. According to the H and 13C NMR spectra,
the resulting dark violet solution contained cation
VIa (cf. the spectral data for known 9,10-disubstituted
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 9 2003

1308
BUSHMELEV et al.
142.5 s, 149.8 s (cf. [22]). Found, m/z: [M]+ 260.1557.
C20H20. Calculated: M 260.1565.
Komp’yuternaya khimiya. Prakticheskoe rukovodstvo
po raschetam struktury i energii molekuly, Moscow:
Mir, 1990, p. 178.
4,5,6,6-Tetramethyl-4,6-dihydrocyclopenta[j,k]-
phenanthrene (IX). A solution of 0.19 g (0.73 mmol)
of olefin VII in 0.9 ml of CHCl3 was added dropwise
over a period of 10 min to an emulsion formed by
1.5 ml (17 mmol) of CF3SO3H and 0.9 ml of CHCl3,
which was stirred at room temperature under argon.
The resulting dark crimson solution was added drop-
wise over a period of 30 min under vigorous stirring
to a suspension of 3.6 g (34 mmol) of Na2CO3 in
a mixture of 5 ml of triethylamine and 70 ml of
hexane. The mixture was stirred for 30 min and fil-
tered through a small layer of Al2O3, the precipitate
was washed with 40 ml of ether, and the filtrate was
evaporated under reduced pressure to obtain 0.19 g of
an oily substance which was almost pure olefin IX.
1H NMR spectrum (CDCl3, 400.13 MHz), , ppm:
1.55 (4-CH3), 1.94 (6-CH3), 1.95 (6-CH3), 1.94
(6-CH3), 2.44 (5-CH3), 3.46 (4-H), 7.42 (2-H), 7.47
(3-H), 7.48 (9-H), 7.50 (8-H), 7.76 (7-H), 7.93 (1-H),
8.15 (10-H); JHH, Hz: 4-CH3 4-H 7.5, 5-CH3 4-H
0.9, 1-H 2-H 7.8, 1-H 3-H 0.7, 1-H 10-H 0.5,
2-H 3-H 7.4, 3-H 4-H 0.9, 7-H 8-H 8.0, 7-H 9-H
1.3, 7-H 10-H 0.5, 8-H 9-H 7.3, 8-H 10-H 1.5,
9-H 10-H 7.8. 13C NMR spectrum (CDCl3), C, ppm:
13.7 q, 15.6 q, 30.8 q, 30.8 q, 37.0 s, 48.5 d, 118.6 d,
121.2 d, 121.8 d, 124.7 d, 125.5 s, 126.0 d, 127.3 d,
127.4 d, 130.3 s, 138.3 s, 140.1 s, 141.2 s, 145.7 s,
146.4 s. Found, m/z: [M]+ 260.1562. C20H20. Cal-
culated: M 260.1565.
6. Kutzelnigg, W., Fleischer, U., and Schingler, M.,
NMR Basic Principles and Progress, Diehl, P.,
Fluck, E., Gunter, H., Kosfeld, R., and Seelig, J.,
Eds., Berlin: Springer, 1991, p. 165.
7. Koptyug, V.A., Arenonievye iony. Stroenie i reaktsi-
onnaya sposobnost’ (Arenonium Ions. Structure and
Reactivity), Novosibirsk: Nauka, 1983, pp. 45, 97,
98, 183.
8. Salnikov, G.E., Genaev, A.M., and Mamatyuk, V.I.,
Mendeleev Commun., 2003, p. 48.
9. Pittman, C.U., Jr. and Miller, W.G., J. Am. Chem.
Soc., 1973, vol. 95, p. 2947.
10. Shatenshtein, A.I., Izotopnyi obmen i zameshchenie
vodoroda v organicheskikh soedineniyakh (Isotope
Exchange and Substitution of Hydrogen in Organic
Compounds), Moscow: Akad. Nauk SSSR, 1960,
p. 218.
11. Osadchii, S.A. and Shubin, V.G., Zh. Org. Khim.,
1989, vol. 25, p. 2349.
12. Osadchii, S.A., Drobysh, V.A., Shakirov, M.M.,
Mamatyuk, V.I., and Shubin, V.G., Zh. Org. Khim.,
1988, vol. 24, p. 267.
13. Osadchii, S.A., Polovinka, M.P., Korchagina, D.V.,
Pankrushina, N.V., Dubovenko, Zh.V., Bar-
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1981, vol. 17, p. 1211.
14. MOPAC Program. Version 6.00. QCPE
455.
15. Itoh, K., Miyake, A., Nada, N., Hirata, M., and
This study was financially supported by the Rus-
sian Foundation for Basic Research (project nos. 02-
03-32881 and 00-03-40135).
Oka, Y., Chem. Pharm. Bull., 1984, vol. 32, p. 130.
16. Ger. Patent no. 602698, 1932; Frdl., vol. 21, p. 272.
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Berlin: Wissenschaften, 1976, 15th ed. Translated
under the title Organikum. Praktikum po organiche-
skoi khimii, Moscow: Mir, 1979, vol. 2, p. 224.
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