Superelectrophilic activation of 8-hydroxyquinoline in acid media and its reactions with weak nucleophiles

Article abstract of DOI:10.1023/A:1016306814374

According to the ¹H and ¹³C NMR data, 5-azonia-4-hydroxynaphthalen-1-onium cation, generated by protonation of 8-hydroxyquinoline in the system CF₃SO₃H-SbF₅, reacts with cyclohexane to give diprotonated 5,6,7,8-tetrahydroquinolin-8-one. Further reaction of the latter with cyclohexane yields 5,6,7,8-tetrahydroquinolinium ion. The reaction of 8-hydroxyquinoline with benzene in the presence of aluminum bromide or chloride gives 6-phenyl-5,6,7,8-tetrahydroquinolin-8-one and product of its intramolecular cyclization, 11-hydroxy-6,11-dihydro-6,11-methano-5H-benzo[5,6]cyclohepta[1,2-b]pyridine. The effect of the protonated nitrogen atom on the electrophilicity of dications is discussed.

Full text of DOI:10.1023/A:1016306814374

Russian Journal of Organic Chemistry, Vol. 38, No. 3, 2002, pp. 437 442. Translated from Zhurnal Organicheskoi Khimii, Vol. 38, No. 3, 2002,
pp. 457 463.
Original Russian Text Copyright
2002 by Koltunov, Repinskaya.
Superelectrophilic Activation of 8-Hydroxyquinoline
in Acid Media and Its Reactions with Weak Nucleophiles*, **
K. Yu. Koltunov and I. B. Repinskaya
Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090 Russia
e-mail: organic@fen.nsu.ru
Received June 14, 2001
1
Abstract According to the H and 13C NMR data, 5-azonia-4-hydroxynaphthalen-1-onium cation, generated
by protonation of 8-hydroxyquinoline in the system CF3SO3H SbF5, reacts with cyclohexane to give di-
protonated 5,6,7,8-tetrahydroquinolin-8-one. Further reaction of the latter with cyclohexane yields 5,6,7,8-tetra-
hydroquinolinium ion. The reaction of 8-hydroxyquinoline with benzene in the presence of aluminum bromide
or chloride gives 6-phenyl-5,6,7,8-tetrahydroquinolin-8-one and product of its intramolecular cyclization,
11-hydroxy-6,11-dihydro-6,11-methano-5H-benzo[5,6]cyclohepta[1,2-b]pyridine. The effect of the protonated
nitrogen atom on the electrophilicity of dications is discussed.
We previously showed that compounds of the 1-
and 2-naphthol series in the presence of strong protic
or Lewis acids undergo superelectrophilic activation
through formation of C,C-diprotonated species or
structurally similar protonated complexes [2, 3]. Like-
wise, , -unsaturated ketones undergo protonation at
the oxygen and carbon atoms or give rise to the corre-
sponding complexes, depending on the acid system
[4]. As a result, the above substrates can be involved
in reactions with such weak nucleophiles as alkanes
and arenes. The reactions with alkanes gave products
of selective ionic hydrogenation, and with arenes
arylation products were obtained [2, 3, 5 7].
Electrophilic activation of quinoline derivatives
in acid media have not been studied previously. The
present work was aimed at establishing pathways of
electrophilic activation of 8-hydroxyquinoline (I) in
protic acids and in the presence of Lewis acids with
the goal of involving compound I in reactions with
cyclohexane and benzene. The choice of quinoline I
as substrate was dictated by the presence of several
basic centers in its molecule, which provides the
possibility for polyprotonation and formation of inter-
mediates with enhanced electrophilicity.
Electrophilic activation pathways of quinoline I in
protic acids at 25 C were studied by 1H and 13C NMR
spectroscopy. Dissolution of 8-hydroxyquinoline (I)
in CF3COOH (H0 = 2.7 [8]) or CF3SO3H (H0 =
14.1 [9]) leads to formation of 8-hydroxyquinolinium
ion II. A different pattern was observed on dissolution
of hydroxyquinoline I in the system CF3SO3H SbF5
(molar ratio 3.4:1). In this case, 5-azonia-4-hydroxy-
naphthalen-1-onium ion III is generated via protona-
tion of both nitrogen and carbon atoms. Signals in the
1H and 13C NMR spectra of ion III were assigned
1
1
using the H 13C correlation technique. The H NMR
spectrum of III contains a singlet at 5.25 ppm from
the methylene protons and two broadened singlets at
13.7 and 13.8 ppm, which belong to the OH and
NH+ groups. The 13C chemical shifts of dication III
appreciably differ from the corresponding values
found for its closest structural analog, 4-hydroxy-
naphthalen-1-onium ion. This concerns mainly the C2
and C6 atoms (cf. [10, 11]).
Our study of the reactivity of cation II has shown
its inertness toward cyclohexane and benzene. Both
nucleophiles failed to react with II in CF3SO3H at
25 C over a period of 5 and 24 h, respectively. By
contrast, dication III smoothly reacted with cyclo-
hexane (the reaction of III with benzene resulted in
formation of a number of unidentified products).
Addition of cyclohexane to an acid solution of di-
cation III (molar ratio 8-hydroxyquinoline cyclo-
hexane 1:1.4) in 10 min quantitatively yielded the
____________
*
**
For preliminary communication, see [1].
This study was financially supported by the Ministry of
Education of the Russian Federation (project no. 1.20.00)
and by the Integratsiya Federal Special Program (project
no. A0051).
1070-4280/02/3803-0437$27.00 2002 MAIK Nauka/Interperiodica

438
KOLTUNOV, REPINSKAYA
Scheme 1.
corresponding ionic hydrogenation product, O,N-di-
protonated 5,6,7,8-tetrahydroquinolin-8-one (IV)
(Scheme 1).
signals from 7-H and 5-H at 3.68 and 3.93 ppm,
respectively. The spectrum of the mixture (after treat-
ment) contained signals belonging to hydroxyquino-
line I and also a multiplet at 2.2 ppm (6-H) and
two doublets at 2.81 and 3.04 ppm (7-H and 5-H,
respectively), belonging to tetrahydroquinoline V-D.
1
Dication IV shows in the H NMR spectrum
signals in the region
2.7 3.9 ppm, belonging to
three methylene groups, and a singlet at 13.8 ppm
from the NH+ proton. No HO+ signal was observed
due to fast exchange with the medium; however, the
presence of an oxonium moiety in IV can be assumed
taking into account the known [8] ability of ketones
to undergo complete protonation in strongly acidic
media. After appropriate treatment of the reaction
mixture, we isolated 5,6,7,8-tetrahydroquinolin-8-one
(V) (Scheme 1).
The possibility for hydride ion transfer from cyclo-
hexane to dication III was confirmed by studying the
regioselectivity of the process. For this purpose,
quinoline I was brought into reaction with cyclo-
hexane-d12. On the basis of the known data [10] on
charge distribution in naphthalenonium ions, we
expected that dication III will attack cyclohexane
molecule by the C6 atom; as a result, the reduction
product should contain deuterium just at C6. In fact,
addition of cyclohexane-d12 to an acid solution of
III, followed by keeping of the mixture for 50 min at
25 C, resulted in appearance in the 1H NMR spectrum
of signals from O,N-diprotonated 6-deutero derivative
IV-D. After appropriate treatment, we isolated a mix-
ture of compound I and 6-[2H]-5,6,7,8-tetrahydro-
quinolin-8-one (V-D) at a ratio of 1.6:1 (Scheme 2).
In the 1H NMR spectrum of IV-D we observed
a multiplet signal from 6-H at 2.73 ppm and doublet
2
Compound V-D showed in the H NMR spectrum
a multiplet at 2.1 ppm (3-D). The C6 signal of V-D
in the 13C NMR spectrum was split due to coupling
with deuterium.
The above reaction of dication III with cyclo-
hexane is an example of reactions of naphthalenonium
ion with weak nucleophiles. It should be noted that,
according to our earlier data [2, 3], 4-hydroxynaph-
thalen-1-onium ions exhibit no superelectrophilic
properties and do not react with weak nucleophiles
(as was shown using reactions of 1-naphthol deriva-
tives with arenes and alkanes). Our results lead us
to presume that the high electrophilicity of dication
III is determined by participation of the protonated
nitrogen atom in the -electron system.
Dication IV formed by ionic hydrogenation and
subsequent protonation also shows superelectrophilic
properties and is capable of abstracting hydride ion
from alkane. After addition of excess cyclohexane to
an acid solution of dication IV and keeping of the
1
reaction mixture for 80 min at 25 C, the H NMR
data indicated quantitative formation of 5,6,7,8-tetra-
hydroquinolinium ion (VI). By appropriate treatment
of the mixture we isolated 5,6,7,8-tetrahydroquinoline
(VII) (Scheme 3).
Scheme 2.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 3 2002

SUPERELECTROPHILIC ACTIVATION OF 8-HYDROXYQUINOLINE
439
Scheme 3.
Obviously, the formation of cation VI is preceded
by reduction in acid medium of the carbonyl group to
hydroxy to give dication A. The latter or product of
its dehydration (dication B) abstracts hydride ion from
cyclohexane, affording the final reduction product,
cation VI. However, we failed to detect dications
A and B by NMR spectroscopy. Some notes should
be given on participation of dications A and B in
the hydride transfer process. According to published
data [12], neither ketones nor alcohols react with
alkanes under conditions ensuring their complete
protonation with formation of oxonium ions [12]. In
particular, tetrahydronaphthalenones do not react with
arenes and alkanes in fairly acidic media [2, 3, 5].
Ionic hydrogenation of ketones with alkanes occurs
only in media with increased acidity, where additional
protonation (protosolvation) is assumed to be possible.
The reaction stops at the stage of formation of alcohol
[13]. The subsequent ionic hydrogenation of alcohol
was reported only for methanol by the action of
sodium tetrahydridoborate in trifluoromethanesulfonic
acid [14]. These findings prompted the researchers to
postulate additional protonation (protosolvation) of
oxonium cations formed initially from alcohols [12].
Presumably, superelectrophilic activation of di-
cations IV and A, which is required for the reaction
with alkane to occur, is achieved due to the presence
of nearby protonated nitrogen atom rather than due to
additional protonation of oxonium ion. Activating
effect of protonated nitrogen was recently reported
for the reactions of 3-formylpyridinium ion and oxo-
piperidine derivatives with arenes in trifluoromethane-
sulfonic acid [15]. An analogous activation of cationic
center with respect to arenes was achieved through
assistance by other charged or neutral electron-
acceptor groups, e.g., CCl3 or CF3 [16].
With the goal of estimating electrophilic properties
of dications III and IV and also of the assumed short-
lived intermediates A and B on a quantitative level,
we performed MNDO quantum-chemical calculations
of some their parameters (the complete results of
MNDO and 3-21G calculations of dications III, IV,
A, and B will be reported elsewhere). The calculated
energies of the lowest unoccupied molecular orbitals
(
LUMO) of dications III, IV, A, and B turned out to
be fairly low: 10.83, 11.04, 9.57, and 11.79 eV,
respectively. These values approach those found for
C,C-diprotonated 1- and 2-naphthol derivatives which
showed superelectrophilic properties toward alkanes
and arenes [2, 3, 5]. Taking into account the above
data and also the inertness of the corresponding
carbon analogs with respect to benzene and alkanes,
we can conclude that just the presence of protonated
nitrogen atom is reponsible for superelectrophilic
properties of dications III, IV, A, and B.
Superelectrophilic activation of quinoline I toward
another weak nucleophile, benzene, was achieved by
the action of Lewis acids. The reaction of quinoline I
with benzene occurred in the presence of excess
aluminum chloride or bromide. By stirring a mixture
of 8-hydroxyquinoline (I), benzene, and aluminum
bromide at a molar ratio of 1:10:5 for 24 h at 20 C
(the mixture was preliminarily saturated with hydro-
gen bromide) we obtained 6-phenyl-5,6,7,8-tetra-
hydroquinolin-8-one (VIII) in 68% yield (Scheme 4).
The regioselectivity of this reaction may be ex-
plained on the assumption that quinoline I is activated
through formation of intermediate C, a structural
Scheme 4.
X = AlmBr3m, AlmCl3m, H.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 3 2002

440
KOLTUNOV, REPINSKAYA
Scheme 5.
X = AlmBr3m, AlmCl3m, H.
analog of dication III. The reaction of C with benzene
leads to formation of another intermediate D, and
subsequent treatment of the reaction mixture yields
final product VIII.
We previously studied reactions of 1-naphthol
derivatives with benzene and found that aluminum
halide complexes with the corresponding keto forms
are not active intermediates therein [2, 3, 17]. There-
fore, superelectrophilic properties of intermediate C
may be attributed to its dicationic nature.
preparative viewpoint, the reaction of 8-hydroxy-
quinoline (I) with benzene provides a convenient
procedure for synthesizing aryl-substituted tetrahydro-
quinolinones and compounds like IX. Its advantage is
accessibility of initial compounds. Known tetrahydro-
quinolinones are few in number because of the lack
of general procedures for their synthesis. We have
found no analogs of compound IX in the literature.
EXPERIMENTAL
When the reaction of hydroxyquinoline I with
benzene in the presence of aluminum bromide was
performed for 75 h with subsequent heating for 5 h
under reflux, we isolated 85% of 11-hydroxy-6,11-di-
hydro-6,11-methano-5H-benzo[5,6]cyclohepta[1,2-b]-
pyridine (IX) (Scheme 5). The same product was
obtained when the reaction mixture was perliminarily
saturated with hydrogen bromide. In this case the
reaction was complete in 300 h at 20 C or in 20 h
under reflux (yield 63 and 54%, respectively). The
reaction of I with benzene in the presence of excess
aluminum chloride instead of bromide required 40 h
under reflux, and the yield of IX was 43%.
As shown in Scheme 5, primary intermediate D
undergoes intramolecular cyclization to give complex
E. The possibility of such cyclization in acid medium
(X = H) was proved by special experiment. Tetra-
hydroquinoline VIII was dissolved in CF3SO3H, and
the solution was kept for 45 min at 25 C to obtain
cation E (X = H); after appropriate treatment, we
isolated compound IX in quantitative yield.
The ability of oxonium ions to react with benzene
(either inter- or intramolecularly) was reported in
[12, 15]. These reactions usually require strongly
acidic media which ensure additional protonation
(protosolvation). The intramolecular reaction in inter-
mediate D is likely to be facilitated by complex
formation (protonation) at the nitrogen atom.
Thus, the results of our study allowed us to extend
the number of stable carbocations exhibiting super-
electrophilic properties due to additional activation
by the second cationic center [2 5, 12, 15]. From the
1
The H and 13C NMR spectra were recorded on
a Bruker DPX-250 spectrometer operating at 250.13
and 62.9 MHz, respectively. The H NMR spectrum
was obtained on a Bruker AM-400 instrument
(61.42 MHz). The chemical shifts of cationic species
were measured relative to (CH3)4N+ BF4 ( 3.2 ppm
2
and
54 ppm), and those of neutral compounds,
76.9 ppm).
relativCe to CDCl3 ( 7.28 ppm and
C
The IR spectra were recorded on a Vector-22 spectro-
photometer in KBr. The molecular weights were
determined by high-resolution mass spectrometry
using a Finnigan MAT MS 8200 mass spectrometer.
The progress of reactions was monitored by TLC on
DC-Alufolien Kieselgel 60 F254 plates (Merck) with
benzene acetone as eluent.
We used trifluoromethanesulfonic acid, AlCl3, and
8-hydroxyquinoline from Merck, chemically pure tri-
fluoroacetic acid, and AlBr3 and benzene of analytical
grade. Cyclohexane-d12 (from Izotop) contained
99.5% of deuterium. Technical-grade SbF5 was
purified by distillation. The reactions in CF3SO3H and
in the system CF3SO3H SbF5 were carried out in
NMR ampules. MNDO quantum-chemical calcula-
tions with full geometry optimization were performed
using MOPAC-7 software [18].
8-Hydroxyquinolinium ion (II). Compound I,
40 mg (0.26 mmol), was dissolved at 25 C in 0.7 g
(4.7 mmol) of trifluoroacetic acid. A solution con-
1
taining cation II was thus obtained. H NMR spec-
trum, , ppm: 7.57 d.d (1H, 7-H, J = 7.11, 1.9 Hz),
7.77 m (2H, 5-H, 6-H), 7.99 d.d (1H, 3-H, J = 8.53,
5.69 Hz), 8.94 d.d (1H, 2-H, J = 7.58, 5.69 Hz),
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 3 2002

SUPERELECTROPHILIC ACTIVATION OF 8-HYDROXYQUINOLINE
441
9.00 d (1H, 4-H, J = 8.53 Hz), 13.6 br.s (1H, NH).
13C NMR spectrum, C, ppm: 115.76 (C7), 118.6 (C5),
120.01 (C3), 127.42 (C9), 128.97 (C10), 130.1 (C6),
140.62 (C2), 144.72 (C8), 146.46 (C4).
(2H, 7-H, J = 6.54 Hz), 3.04 d (2H, 5-H, J = 5.81 Hz).
2D NMR spectrum, , ppm: 2.1 m (6-D). 13C NMR
spectrum, C, ppm: 22.14 (C6, JC, D = 20.23 Hz),
28.87 (C5), 39.37 (C7).
5-Azonia-4-hydroxy-1H +-naphthalenium ion
(III). A 0.27-g (1.25-mmol) portion of SbF5 was
added at 25 C to a solution of 19 mg (0.13 mmol) of
hydroxyquinoline I in 0.63 g (4.2 mmol) of trifluoro-
methanesulfonic acid. Quantitative formation of ion
5,6,7,8-Tetrahydroquinoline (VII). To the solu-
tion of dication IV, prepared by the above procedure,
we added an additional 50-mg (0.6-mmol) portion of
cyclohexane. The mixture was kept for 80 min at
25 C with occasional shaking. The transformation of
dication IV into tetrahydroquinolinium ion VI was
1
III was observed. H NMR spectrum, , ppm: 5.25 s
1
observed. H NMR spectrum, , ppm: 2.05 m (4H,
(2H, 1-H), 8.05 d (1H, 3-H, J = 8.53 Hz), 8.78 br.s
(1H, 7-H), 9.28 d (1H, 2-H, J = 8.53 Hz), 9.35 br.s
(1H, 6-H), 9.48 br.s (1H, 8-H), 13.66 br.s and
6-H, 7-H), 3.05 t (1H, 5-H, J = 5 Hz), 3.17 t (1H,
8-H, J = 6 Hz), 7.79 t (1H, 3-H, J = 8 Hz), 8.34 m
(2H, 2-H, 4-H), 11.71 br.s (1H, NH). The mixture
was treated as described above to isolate 16 mg (90%)
13.8 br.s (1H each, OH and NH). 13C NMR spectrum,
C, ppm: 37.95 (C1), 123.69 (C3), 130.79 (C9), 132.54
(C7), 146.29 (C8), 147.88 (C2), 148.61 (C10), 181.54
(C4), 183.71 (C6).
1
of tetrahydroquinoline (VII). H NMR spectrum, ,
ppm: 1.85 m (4H, 6-H, 7-H), 2.78 t (2H, 5-H, J =
5.81 Hz), 2.94 t (2H, 8-H, J = 5.45 Hz), 7.04 d.d (1H,
3-H, J = 8.7, 5 Hz), 7.36 d (1H, 4-H, J = 8.7 Hz),
O,N-Diprotonated 5,6,7,8-tetrahydroquinolin-8-
one (IV). Cyclohexane, 15 mg (0.18 mmol), was
added at 25 C to a solution of ion III, prepared by
the above procedure. After 10 min, dication III was
8.36 d (1H, 2-H, J = 5 Hz) (cf. [20]). 13C NMR spec-
trum, , ppm: 22.52 (C6), 22.9 (C7), 28.6 (C5), 32.29
(C8), 120.72 (C3), 132.17 (C10), 136.66 (C4), 146.53
(C2), 157.20 (C9) (cf. [20]).
1
completely converted into dication IV. H NMR spec-
trum, , ppm: 2.73 m (2H, 6-H), 3.68 t (2H, 7-H, J =
6.5 Hz), 3.93 t (2H, 5-H, J = 5.8 Hz), 8.72 d.d (1H,
3-H, J = 9, 7 Hz), 9.01 d (1H, 4-H, J = 9 Hz), 9.18 d
(1H, 2-H, J = 7 Hz), 13.4 s (1H, NH). The mixture
was poured onto ice and washed with diethyl ether,
and the aqueous phase was neutralized with NaHCO3.
The product was extracted into diethyl ether, the
extract was dried over MgSO4, and the solvent was
removed to obtain 13 mg (65%) of tetrahydroquino-
6-Phenyl-5,6,7,8-tetrahydroquinolin-8-one
(VIII). 8-Hydroxyquinoline (I), 2 g (14 mmol), was
added to a solution of 20 g (75 mmol) of aluminum
bromide in 18 g (230 mmol) of benzene, and the solu-
tion was saturated with hydrogen bromide [the weight
of the mixture increased by 2.5 g (31 mmol of HBr)].
The mixture was kept for 24 h at 20 C and poured
onto ice, 40 ml of concentrated hydrochloric acid was
added, the aqueous phase was separated and washed
with diethyl ether, and a 10% solution of NaOH was
added to make it strongly alkaline. The precipitate
was filtered off and dissolved in benzene, and the
solution was filtered through a layer of Al2O3 and
evaporated. The residue was recrystallized from a 1:2
mixture of benzene with petroleum ether (bp 70
100 C) to obtain 2.1 g (68%) of compound VIII with
1
linone V. IR spectrum: (C O) 1702 cm (cf. [19]).
1H NMR spectrum, , ppm: 2.21 m (2H, 6-H), 2.82 t
(2H, 7-H, J = 6.54 Hz), 3.05 t (2H, 5-H, J = 5.81 Hz),
7.39 d.d (1H, 3-H, J = 7.27, 3.28 Hz), 7.67 d (1H,
4-H, J = 7.27 Hz), 8.72 d (1H, 2-H, J = 3.28 Hz)
(cf. [19]). 13C NMR spectrum, C, ppm: 22.49 (C6),
28.97 (C5), 39.49 (C7), 126.86 (C3), 137.5 (C4),
140.62 (C4a), 147.99 (C8a), 148.96 (C2), 196.7 (C8).
1
mp 138 139 C. IR spectrum: (C O) 1697 cm .
1H NMR spectrum, , ppm: 2.8 3.3 m (4H, 5-H,
7-H), 3.4 3.6 m (1H, 6-H), 7.22 7.35 m (6H, 3-H,
Harom), 7.65 d (1H, 4-H, J = 7.8 Hz), 8.69 d (1H, 2-H,
J = 4.5 Hz). 13C NMR spectrum, , ppm: 36.64 (C5);
Reaction of dication III with cyclohexane-d12.
Cyclohexane-d12, 16 mg (0.17 mmol), was added to
a solution of 19 mg (0.13 mmol) of compound I and
0.27 g (1.25 mmol) of SbF5 in 0.63 g (4.2 mmol) of
1
CF3SO3H. After 50 min, the H NMR spectrum of
40.11 (C6); 46.07 (C7); 126.27, 126.88, 126.91,
128.55 (C6, Co, Cm, Cp); 137.37 (C4); 139.23, 142.27,
the resulting solution contained signals of dications
1
III and IV-D. H NMR spectrum of IV-D, , ppm:
147.55 (Ci, C4a, C8a); 149.03 (C2); 195.57 (C8).
Found: [M]+ 223.09948. C15H13NO. Calculated:
M 223.09971.
2.73 m (1H, 6-H), 3.68 d (2H, 7-H, J = 5.21 Hz),
3.93 d (2H, 5-H, J = 7.81 Hz). The mixture was
poured onto ice and treated as described above to
obtain 15 mg of a mixture of quinoline I and tetra-
11-Hydroxy-6,11-dihydro-6,11-methano-5H-ben-
zo[5,6]cyclohepta[1,2-b]pyridine (IX). a. Hydroxy-
quinoline I, 2.3 g (16 mmol), was added to a solution
1
hydroquinolinone V-D at a ratio of 1.6:1. H NMR
spectrum of V-D, , ppm: 2.2 m (1H, 6-H), 2.81 d
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 3 2002

442
KOLTUNOV, REPINSKAYA
of 20 g (75 mmol) of aluminum bromide in 18 g
(23 mmol) of benzene, and the resulting solution was
saturated with hydrogen bromide until a gain in
weight of 2.5 g (31 mmol of HBr) was attained. The
mixture was kept for 75 h at 20 C, heated for 5 h
under reflux, poured onto ice, and treated as described
above in the synthesis of compound VIII. Recrystal-
lization from ethanol gave 3 g (85%) of compound
IX with mp 135 137 C. IR spectrum: (O H)
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and Shchegoleva, L.N., Zh. Org. Khim., 1994,
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1
1
3416 cm . H NMR spectrum, , ppm: 2.28 d (1H,
12-H, J = 10.2 Hz), 2.7 2.9 m (2H, 5-H, 12-H),
3.34 d.d (1H, 5-H, J = 17.1, 5.1 Hz), 3.58 3.65 m
(1H, 6-H), 5.73 s (1H, OH), 7.0 7.4 m (6H, 3-H, 4-H,
7-H, 8-H, 9-H, 10-H), 8.28 d (1H, 2-H, J = 4.5 Hz)
(the signals were assigned using 1H COSY technique).
13C NMR spectrum, C, ppm: 33.99 (C5); 37.63 (C6);
46.76 (C10); 79.42 (C11); 119.71 (C3); 122.76, 123.02
(C8, C9); 126.86, 127.37 (C7, C10); 128.29 (C14);
136 (C4); 143.07 (C15); 144.64 (C2); 149.9 (C16);
160.42 (C13). Found: [M]+ 223.10014. C15H13NO.
Calculated: M 223.09971.
b. Hydroxyquinoline I, 2 g (14 mmol), was added
to a solution of 20 g (75 mmol) of aluminum bromide
in 15.6 g (200 mmol) of benzene, and the mixture was
kept for 300 h at 20 C. It was then treated by the
procedure described above for compound VIII to
obtain 1.95 g (63%) of product IX.
c. Compound I, 3 g (20 mmol), was added to
a solution of 26 g (100 mmol) of aluminum bromide
in 26 g (330 mmol) of benzene, and the resulting dis-
persion was stirred for 20 h on heating under reflux.
After appropriate treatment, 2.5 g (54%) of compound
IX was isolated.
d. A mixture of 0.5 g (3.5 mmol) of compound
I, 5 g (38 mmol) of aluminum chloride, and 9 g
(120 mmol) of benzene was stirred for 40 h on heating
under reflux. After appropriate treatment, 0.33 g
(43%) of compound IX was isolated.
e. Tetrahydroquinoline VIII, 15 mg (0.07 mmol),
was added to 0.7 g (4.7 mmol) of trifluoromethane-
sulfonic acid. The solution was kept for 45 min at
25 C and poured onto ice. The aqueous phase was
neutralized with a 10% aqueous solution of NaOH,
and the precipitate was filtered off. Yield of com-
pound IX 14 mg (93%).
9. Superacids, Olah, G.A., Prakash, G.K.S., and
Sommer, J., Eds., New York: Wiley, 1985.
10. Koptyug, V.A., Arenonievye iony. Stroenie i reak-
tsionnaya sposobnost’ (Arenium Ions. Structure and
Reactivity), Novosibirsk: Nauka, 1983.
11. Koptyug, V.A., Kamshii, L.P., and Mamatyuk, V.I.,
Zh. Org. Khim., 1975, vol. 11, no. 1, pp. 128 129.
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 3 2002