Acid-catalyzed dehydration of hydroxy-substituted perhydroindenyl(perhydronaphthyl)ethanones and perhydroindene(perhydronaphthalene)carboxylates

Article abstract of DOI:10.1007/s11178-008-3003-6

Perhydroindenyl(perhydronaphthyl)ethanones and perhydroindene(naphthalene) carboxylates differing in the size of the fused ring (C₅, C ₆) and in the nature of carbonyl-containing substituent (acetyl, ethoxycarbonyl) undergo dehydration on heating in benzene in the presence of a catalytic amount of p-toluenesulfonic acid. The process is accompanied by complete enolization of the endocyclic oxo group. Depending on the size of the fused ring, individual partially hydrogenated naphthylethanones and naphthalene-carboxylates or mixtures of isomeric partially hydrogenated indenylethanones and indenecarboxylates are formed.

Full text of DOI:10.1007/s11178-008-3003-6

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 3, pp. 331–334. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © A.A. Morozova, A.G. Golikov, A.P. Kriven’ko, 2008, published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 3,
pp. 339–342.
Acid-Catalyzed Dehydration of Hydroxy-Substituted Perhydro-
indenyl(perhydronaphthyl)ethanones and Perhydroindene-
(perhydronaphthalene)carboxylates
A. A. Morozova, A. G. Golikov, and A. P. Kriven’ko
Chernyshevskii Saratov State University, ul. Astrakhanskaya 83, Saratov, 410012 Russia
e-mail: morosova_aa4182@mail.ru
Received April 3, 2007
Abstract—Perhydroindenyl(perhydronaphthyl)ethanones and perhydroindene(naphthalene)carboxylates dif-
fering in the size of the fused ring (C5, C6) and in the nature of carbonyl-containing substituent (acetyl, ethoxy-
carbonyl) undergo dehydration on heating in benzene in the presence of a catalytic amount of p-toluenesul-
fonic acid. The process is accompanied by complete enolization of the endocyclic oxo group. Depending
on the size of the fused ring, individual partially hydrogenated naphthylethanones and naphthalene-carbox-
ylates or mixtures of isomeric partially hydrogenated indenylethanones and indenecarboxylates are formed.
DOI: 10.1134/S1070428008030032
Up to now, the chemistry of monocyclic hydroxy-
cyclohexanones like 3-substituted 2,4-diacetyl[bis-
(ethoxycarbonyl)]-5-hydroxy-5-methylcyclohexanones
has been well documented. These compounds are
available via condensation of aldehydes with CH acids
such as acetylacetone and acetoacetic acid esters [1].
The use of acid catalysts ensures their selective dehy-
dration with formation of α,β-unsaturated enones.
Acetyl-substituted systems were found to undergo
enolization [2, 3].
ethyl acetoacetate. Compounds Ia–Ie were shown to
have the structure with trans-junction of the carbo-
cycles, axial orientation of the hydroxy group, and
equatorial orientation of the other substituents [4].
Diketones Ia and Ic and keto esters Ib, Id, and Ie
underwent dehydration and complete enolization of the
endocyclic carbonyl group on heating in benzene in the
presence of a catalytic amount of p-toluenesulfonic
acid (Scheme 1). Depending on the size of the fused
ring, the products were either isomer mixtures IIa/IIIa
and IIb/IIIb (overall yield 68–74%) with different
positions of the double bond in the bicyclic system or
individual compounds IVc–IVe (70–75%). All the
isolated compounds showed a positive color test for
enolic hydroxy group (violet color) with an alcoholic
solution of iron(III) chloride.
Taking into account the presence of a hydrogen
atom in both α-positions with respect to the hydroxy
group in molecules Ia–Ie, the dehydration process
could involve abstraction of hydrogen from C7 or C3a
in Ia and Ib or from C4 or C8a in Ic–Ie. By analogy
with hydroxycyclohexanones [2, 3], dehydration with
formation of double bond conjugated with the carbonyl
group might be expected. However, in our case the
dehydration direction depended on the size of the fused
ring. Naphthalene substrates Ic–Ie underwent regio-
selective dehydration involving hydrogen atom in the
bridgehead position (trans-elimination) with formation
In the present article we report on acid-catalyzed
dehydration of related bicyclic systems differing in the
size of the fused carbocycle (five- or six-membered),
nature of the carbonyl-containing substituent (acetyl or
ethoxycarbonyl), and ylidene fragment (benzylidene or
furfurylidene). The initial compounds, 1-(1-benzyli-
dene-7a-hydroxy-6-oxo-4-phenylperhydroinden-5-yl)-
ethan-1-one (Ia), ethyl 1-benzylidene-7a-hydroxy-6-
oxo-4-phenylperhydroindene-5-carboxylate (Ib),
1-(5-benzylidene-4a-hydroxy-3-oxo-1-phenylperhy-
dronaphthalen-2-yl)ethan-1-one (Ic), ethyl 5-benzyli-
dene-4a-hydroxy-3-oxo-1-phenyl-perhydronaphtha-
lene-2-carboxylate (Id), and ethyl 5-furfurylidene-4a-
hydroxy-3-oxo-1-phenyl-perhydronaphthalene-2-car-
boxylate (Ie), were synthesized by us previously by
Michael condensation of diphenylmethylidene-, ben-
zylidene-, and furfurylidene-substituted cyclopenta-
nones and cyclohexanones with acetylacetone and
331

MOROZOVA et al.
332
Scheme 1.
Ph
R'
Ph
R'
4
4
3
3
5
6
5
6
3a
3a
7a
O
O
2
+
2
n = 1
7a
1
R'
Ph
1
OH
R'
OH
7
7
H
R
R
( )n
H
O
p-TsOH, PhH
IIa, IIb
IIIa, IIIb
Ph
1
Ph
R'
O
OH
8
R
8a
2
3
7
6
Ia–Ie
O
O
;
n = 2
4a
4
OH
OH
5
R
R
IVc–IVe
Vc–Ve
I–IV, R = Ph, R′ = Me (a, c), OEt (b, d); R = Fu, R′ = OEt (e); n = 1 (a, b), 2 (c–e).
of exhaustively substituted double bond. Dehydration
of perhydroindene analogs Ia and Ib having a five-
membered fused ring gave rise to formation of both
C3a=C7a and C7=C7a double bond, presumably due to
more planar structure of the fused ring.
4.11 (d, 1H, 4-H, J = 8.5–8.8 Hz), and 12.62
(16.72) ppm (s, 1H, OH). In addition, broadened sig-
nals from olefinic protons in the benzylidene substit-
uent were present at δ 6.12 (IIa/IIIa) and 6.26 ppm
(IIb/IIIb).
The 13C NMR spectra of the products confirmed
formation of isomer mixtures IIa/IIb and IIIa/IIIb
and individual compounds IVc–IVe. In all cases, the
number of signals from sp3-hybridized carbon atoms
in the cyclic fragments was consistent with the enol
structure of these compounds.
Unlike monocyclic analogs [2], both acetyl-, and
ethoxycarbonyl-substituted bicyclic compounds IIa,
IIb, IIIa, IIIb, and IVc–IVe were found to exist in the
enol form. Their IR spectra contained a broad absorp-
tion band at 3065–3568 cm–1 due to enolic hydroxy
group. The C=O stretching vibration band is displaced
to lower frequencies by ~30–80 cm–1 relative to the
corresponding band in the spectra of initial compounds
Ia–Ie (1726–1748 cm–1) due to conjugation [4]. The
C=C absorption is not informative: it appears as
a set of poorly resolved bands in the region 1590–
The dehydration direction and enol structure of the
products were interpreted in terms of heats of forma-
tion of possible intermediates A and B and isomeric
systems II/III and IV/V containing five- and six-
membered fused rings, respectively (Scheme 2). The
calculations were performed in the PM3 approximation
using MOPAC software. The results showed that the
formation of compounds IIa, IIb, and IVc–IVe is
thermodynamically more favorable than the formation
of isomeric structures IIIa, IIIb, and Vc–Ve. The
difference in the ΔHf values for the corresponding
intermediates A and B was 2.3–3.75 kcal/mol for the
perhydronaphthalene derivatives and 1.0–1.1 kcal/mol
for the perhydroindenes. The latter value implies
almost equally probable formation of intermediates A
and B. Enolization of both acetyl- and ethoxycarbonyl-
substituted intermediates to give compounds II–V is
accompanied by a gain in energy of 2.7–6 kcal/mol.
The geometric parameters were optimizes so as to
minimize the heat of formation. The observed stability
of the cyclohexadiene fragment in molecules IIa, IIb,
and IVc–IVe may be rationalized assuming that it
1
1665 cm–1. In the H NMR spectra of IVc–IVe, the
most characteristic are signals from magnetically non-
equivalent methylene protons on C4, δ 3.23–3.40 ppm,
2
d (4-Hax), and δ 3.51–3.54 ppm, d (4-Heq), J = 20.5–
22.2 Hz; the exocyclic C5=CH proton resonated as
a singlet at δ 6.31–6.52 ppm (1H), signal from the
enolic hydroxy proton appeared at δ 12.25–16.01 ppm
(1H), and the chemical shift of 1-H was equal to 4.11–
4.37 ppm.
1
The H NMR spectra of dehydration products
IIa/IIb and IIIa/IIIb obtained from perhydroindene
derivatives contained sets of signals corresponding to
both isomers. Signals at δ 3.07–3.21 (d, 1H, 7-Hax),
3.23–3.36 (d, 1H, 7-Heq; 2J = 19.2–22.2 Hz), 4.04–4.15
(s, 1H, 4-H), and 11.06 (16.51) ppm (s, 1H, OH) were
assigned to isomers IIa and IIb; isomers IIIa and IIIb
displayed signals at δ 6.48–6.79 (s, 1H, 7-H), 4.00–
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 3 2008

ACID-CATALYZED DEHYDRATION OF HYDROXY-SUBSTITUTED
333
Scheme 2.
Ph
R'
O
R'
O
Ph
R'
O
O
( )n
( )n
n = 1
Ph
R'
O
OH
R
R
O
A
IIa, IIb, IVc–IVe
Ph R'
( )n
Ph
OH
Ia–Ie
R
O
O
( )n
( )n
n = 2
OH
R
R
B
IIIa, IIIb, Vc–Ve
n = 1: ΔΔHf(A – B) = 1.0–1.1 kcal/mol; n = 2: ΔΔHf(A – B) = 2.3–3.7 kcal/mol; n = 1, 2: ΔΔHf = 4.2–5.4 kcal/mol.
adopts a boat conformation with pseudoaxial orienta-
tion of the phenyl substituent on C4 (IIa, IIb) or C1
(IVc–IVe), where skewed interaction with the substit-
uent on C5 (C2) is minimized. However, X-ray diffrac-
tion study is necessary to rigorously prove this as-
sumption. The newly synthesized compounds attract
interest from the viewpoint of their subsequent trans-
formation into heterocyclic systems.
ν, cm–1: 3161–3568 (OH); 3024, 3065 (C–Harom); 2924,
2849 (CHaliph); 1664 (C=O); 1593 (C=C–C=O).
1H NMR spectrum (CDCl3), δ, ppm: IIa: 3.21 d and
3.37 d (1H each, 7-H, 2J = 22.2 Hz), 4.15 s (1H, 4-H),
16.51 s (1H, OH); IIIa: 6.48 s (1H, 5-H), 4.00 d (1H,
2-H, J = 8.8 Hz), 16.72 s (1H, OH); IIa/IIIa: 6.12 br.s
(2H, =CH). 13C NMR spectrum (CDCl3), δC, ppm: IIa:
145.70 s (C1), 29.06 t (C2), 31.07 t (C3), 142.98 s (C3a),
45.28 d (C4), 116.98 s (C5), 180.01 s (C6), 33.32 t (C7),
137.92 s (C7a), 200.00 s (C=O), 125.60 d (PhCH=),
27.06 q (CH3); IIIa: 138.90 s (C1), 29.06 t (C2), 29.58 t
(C3), 42.11 d (C3a), 45.10 d (C4), 108.06 s (C5), 159.27 s
(C6), 136.29 d (C7), 142.98 s (C7a), 191.05 s (C=O),
126.54 d (PhCH=), 25.76 q (CH3). Found, %: C 84.84;
H 6.80. C24H22O2. Calculated, %: C 84.82; H 6.43.
EXPERIMENTAL
1
The H NMR spectra were recorded on a Bruker
AC-200 spectrometer at 200 MHz using tetramethyl-
silane as internal reference. The IR spectra were meas-
ured on an FSM-1201 spectrophotometer with Fourier
transform. The progress of reactions and the purity of
products were monitored by TLC on Silufol UV-254
plates using hexane–diisopropyl ether–acetone (3:1:1)
as eluent; spots were detected by treatment with iodine
vapor or water.
Ethyl 1-benzylidene-6-hydroxy-4-phenyl-2,3,4,7-
tetrahydro-1H-indene-5-carboxylate (IIb) and ethyl
1-benzylidene-6-hydroxy-4-phenyl-2,3,3a,4-tetra-
hydro-1H-indene-5-carboxylate (IIIb) were synthe-
sized in a similar way from 1 g (2.56 mmol) of com-
pound Ib. Yield 0.71 g (74%), a mixture of yellow and
orange crystals; Rf 0.356, 0.420; mp 130–136°C. IR
spectrum, ν, cm–1: 3065–3568 (OH); 3025, 3065
(C–Harom); 2926, 2854 (C–Haliph); 1712 (C=O); 1653
Initial perhydroindenyl(perhydronaphthyl)etha-
nones and perhydroindene(perhydronaphthalene)car-
boxylates Ia–Ie were synthesized as described in [4].
1-(1-Benzylidene-6-hydroxy-4-phenyl-2,3,4,7-
tetrahydro-1H-inden-5-yl)ethan-1-one (IIa) and
1-(1-benzylidene-6-hydroxy-4-phenyl-2,3,3a,4-tetra-
hydro-1H-inden-5-yl)ethan-1-one (IIIa). p-Toluene-
sulfonic acid, 0.01 g (0.07 mmol), was added to a solu-
tion of 1 g (2.77 mmol) of compound Ia in 25 ml of
benzene, the mixture was heated for 30 min under
reflux and cooled, and the precipitate was filtered off,
washed with benzene, and recrystallized from hexane.
Yield 0.65 g (68%), a mixture of yellow and orange
crystals; Rf 0.324, 0.405; mp 179–185°C. IR spectrum,
1
(C=C–C=O). H NMR spectrum (DMSO-d6), δ, ppm:
2
IIb: 3.07 d and 3.23 d (1H each, 7-H, J = 19.2 Hz),
4.14 s (1H, 4-H), 11.06 s (1H, OH); IIIb: 6.79 s (1H,
7-H), 3.98 d (1H, 2-H, J = 8.5 Hz), 12.62 s (1H, OH);
IIb/IIIb: 6.26 s (2H, =CH). 13C NMR spectrum
(DMSO-d6), δC, ppm: IIb: 141.13 s (C1), 30.27 t (C2),
32.16 t (C3), 141.16 s (C3a), 47.03 d (C4), 110.03 s
(C5), 154.96 s (C6), 32.13 t (C7), 139.96 s (C7a), 168.00 s
(C=O), 126.83 d (PhCH=), 60.83 t (OCH2), 14.32 q
(CH3); IIIb: 139.92 s (C1), 30.27 t (C2), 30.15 t (C3),
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 3 2008

MOROZOVA et al.
334
41.43 d (C3a), 47.15 t (C4), 111.27 s (C5), 150.53 s
(C6), 137.21 d (C7), 141.08 s (C7a), 168.69 s (C=O),
127.92 d (PhCH=), 60.83 t (OCH2), 14.32 q (CH3).
Found, %: C 80.48; H 6.63. C25H24O3. Calculated, %:
C 80.64; H 6.45.
60.81 t (OCH2), 14.42 q (CH3). Found, %: C 80.68;
H 6.90. C26H26O3. Calculated, %: C 80.83; H 6.79.
Ethyl 5-furfurylidene-3-hydroxy-1-phenyl-
1,4,5,6,7,8-hexahydronaphthalene-2-carboxylate
(IVe) was synthesized in a similar way from 0.7 g
(1.78 mmol) of compound Ie. Yield 0.47 g (71%),
yellow crystals, Rf 0.70, mp 179–180°C. IR spectrum,
ν, cm–1: 3102–3568 (OH); 3064, 3028 (C–Harom); 2952,
2875 (C–Haliph); 1702 (C=O); 1618 (C=C–C=O).
1H NMR spectrum (DMSO-d6), δ, ppm: 3.23 d and
3.52 d (1H each, 4-H, 2J = 21.4 Hz), 4.27 s (1H, 1-H),
12.25 s (1H, OH), 6.31 s (1H, =CH), 2.17 m (2H,
6-H), 1.55 m (2H, 7-H), 2.52 m (2H, 8-H), 7.18 m
(5H, Harom), 7.72 m (1H, 5′-H), 6.41 m (2H, 3′-H,
4′-H), 4.29 t (2H, CH2, J = 8.2 Hz), 1.07 t (3H, CH3,
1-(5-Benzylidene-3-hydroxy-1-phenyl-1,4,5,6,7,8-
hexahydronaphthalen-2-yl)ethan-1-one (IVc) was
synthesized in a similar way from 1 g (2.67 mmol) of
compound Ic. Yield 0.67 g (70%), yellow crystals,
Rf 0.624, mp 157–158°C. IR spectrum, ν, cm–1: 3078–
3568 (OH); 3044, 3078 (C–Harom); 2947, 2855
1
(C–Haliph); 1645 (C=O); 1596 (C=C–C=O). H NMR
spectrum (CDCl3), δ, ppm: 3.40 d and 3.54 d (1H each,
2
4-H, J = 20.5 Hz), 4.37 s (1H, 1-H), 16.01 s (1H,
OH), 6.52 s (1H, =CH), 2.15 m (2H, 6-H), 1.50 m
(2H, 7-H), 2.52 (2H, 8-H), 7.30 m (10H, Harom), 1.07 s
(3H, CH3). 13C NMR spectrum (DMSO-d6), δC, ppm:
49.17 d (C1), 110.35 s (C2), 178.78 s (C3), 32.70 t (C4),
130.03 s (C4a), 138.49 s (C5), 27.60 t (C6), 26.91 t (C7),
29.46 t (C8), 137.27 s (C8a), 200.90 s (C=O), 123.44 d
(PhCH=), 26.32 q (CH3). Found, %: C 84.55; H 6.57.
C25H24O2. Calculated, %: C 84.23; H 6.74.
13
J = 8.2 Hz). C NMR spectrum (DMSO-d6), δC, ppm:
48.59 d (C1), 100.72 s (C2), 169.95 s (C3), 31.04 t (C4),
128.91 s (C4a), 138.98 s (C5), 27.79 t (C6), 22.59 t (C7),
29.21 t (C8), 135.37 s (C8a), 171.58 s (C=O), 112.72 d
(C5=CH), 61.11 t (OCH2), 14.59 q (CH3). Found, %:
C 76.02; H 6.52. C24H24O4. Calculated, %: C 76.59;
H 6.38.
Ethyl 5-benzylidene-3-hydroxy-1-phenyl-
1,4,5,6,7,8-hexahydronaphthalene-2-carboxylate
(IVd) was synthesized in a similar way from 1 g
(2.47 mmol) of compound Id. Yield 0.72 g (75%),
yellow crystals, Rf 0.605, mp 149°C. IR spectrum, ν,
cm–1: 3159–3568 (OH); 3078, 3026 (C–Harom); 2962,
2866 (C–Haliph); 1665 (C=O); 1618 (C=C–C=O).
1H NMR spectrum (CDCl3), δ, ppm: 3.38 d and 3.51 d
(1H each, 4-H, 2J = 22.0 Hz), 4.11 s (1H, 1-H), 12.29 s
(1H, OH), 6.43 s (1H, =CH), 2.01 m (2H, 6-H), 1.54 m
(2H, 7-H), 2.56 m (2H, 8-H), 7.28 m (10H, Harom),
4.09 t (2H, CH2, J = 8.0 Hz), 1.15 t (3H, CH3, J =
8.0 Hz). 13C NMR spectrum (CDCl3), δC, ppm: 48.75 d
(C1), 100.88 s (C2), 169.84 s (C3), 31.50 t (C4), 124.73 s
(C4a), 138.57 s (C5), 27.72 t (C6), 23.29 t (C7), 29.73 t
(C8), 137.78 s (C8a), 171.82 s (C=O), 122.93 d (PhCH=),
This study was performed under financial support
by the Federal Science and Innovation Agency (project
no. 02.513.11.3028).
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