1,3-bis(diarylmethylidene)-2-methylidenecyclohexanes in cycloaddition and cyclodimerization reactions. The role of stereoelectronic factors

Article abstract of DOI:10.1039/b210890a

Cycloaddition and cyclodimerization reactions of 1,3-dibenzylidene- and 1,3-bis(p-methoxybenzylidene)-2-methyl-idenecyclohexanes, i.e., the diaryltrienes with fixed S-cis-configurations of exocyclic double bonds are studied. These compounds undergo in situ cyclodimerization of the [4+2]-type upon dehydration of the precursor tertiary alcohols and form endo-adducts in the Diels-Alder reaction with N-phenylmaleimide. In the presence of CF₃COOH, acid-catalyzed cyclodimerization takes place leading to methylidene-substituted spirocylodimers, which undergo intramolecular cyclization upon prolonged contact with CF₃COOH to form a fused carbocyclic system containing a central, 'three-petal' fragment of six-membered rings.

Full text of DOI:10.1039/b210890a

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1,3-Bis(diarylmethylidene)-2-methylidenecyclohexanes in
cycloaddition and cyclodimerization reactions.
The role of stereoelectronic factors
Elena I. Klimova,*a Marcos Martínez García,b Tatiana Klimova,a S. Hernandez Ortegab and
Leon V. Bakinovskyc
a Universidad Nacional Autónoma de México, Facultad de Química, Cd. Universitaria,
Coyoacán, C.P. 04510, México D.F., México. E-mail: klimova@servidor.unam.mx;
Fax: (525) 622-5366; Tel: (525) 622-5366
b Universidad Nacional Autónoma de México, Instituto de Química, Cd. Universitaria,
Coyoacán, C.P. 04510, México D.F., México
c N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 117913 Moscow, Russian Federation
Received 5th November 2002, Accepted 12th February 2003
First published as an Advance Article on the web 12th March 2003
Cycloaddition and cyclodimerization reactions of 1,3-dibenzylidene- and 1,3-bis(p-methoxybenzylidene)-2-methyl-
idenecyclohexanes, i.e., the diaryltrienes with fixed S-cis-configurations of exocyclic double bonds are studied.
These compounds undergo in situ cyclodimerization of the [4ϩ2]-type upon dehydration of the precursor tertiary
alcohols and form endo-adducts in the Diels–Alder reaction with N-phenylmaleimide. In the presence of CF3COOH,
acid-catalyzed cyclodimerization takes place leading to methylidene-substituted spirocyclodimers, which undergo
intramolecular cyclization upon prolonged contact with CF3COOH to form a fused carbocyclic system containing a
central, ‘three-petal’ fragment of six-membered rings.
Introduction
Previously, we have discussed the role of stereoelectronic fac-
tors in the cycloaddition and cyclodimerization reactions of
ferrocenyl-substituted dienes and trienes.1–5 The high regio- and
diastereoselectivities of these processes have been established,
which resulted in exclusive or predominant formation of one of
diastereomers of compounds 1 or 2 (Scheme 1) depending on
the reaction conditions.
Scheme 2
Results and discussion
In the present paper, we describe our approaches to the syn-
thesis of S-cis-diaryltrienes starting from bis(arylmethyl-
idene)cyclohexanones 6a,b8 (Scheme 3).
Scheme 1
Unlike ferrocenyl-1,3-dienes, 1,3-diarylbuta-1,3-dienes6,7
undergo smooth cyclodimerization upon acid-catalyzed
dehydration of 1,3-diarylbut-1-en-3-ols resulting in a ca. 1 : 1
mixture of cyclodimers 3 and 4 (Scheme 2).
The lack of regioselectivity in this reaction and the absence
of the cationic cycloaddition products of the type 5 makes 1,3-
diarylbutadienes essentially different from their ferrocenyl-
containing analogues.
Information on the synthesis and properties of exo-cyclic
cross-conjugated trienes with aryl substituents at the multiple
bonds is almost completely absent. Studies of chemical proper-
ties of this type of compounds, in particular, their behavior in
cycloaddition and cyclodimerization reactions, deserve special
attention, since the peculiarities of their spatial and electronic
structures allow one to expect unusual results which might be
of interest for both their synthetic and theoretical aspects.
Scheme 3
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 1 2 1 0 – 1 2 1 5
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
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The E,E-dienones 6a,b were prepared by the condensation of
cyclohexanone with benzaldehyde and p-anisaldehyde, respect-
ively, in aqueous ethanol in the presence of an alkali.9
POCl3 in pyridine1 or by treatment with Al2O3 (Brockmann
activity I or II)3 (Scheme 4).
The reactions with MeLi1–3 gave ca. 70% of the corre-
sponding alcohols 7a,b. These compounds were isolated as the
single E,E-isomers, which was established by X-ray diffraction
analysis.8 In the presence of traces of oxygen, a side process
takes place, viz., the addition of MeLi in positions 3,4 of the
conjugated heterodiene systems of the dienones giving rise to
substituted 2-hydroxycyclohexanones 8a,b (9–12%). The latter
were isolated in a crystalline state from the mother liquors
following crystallization of the alcohols 7a,b from ethanol.
1H NMR spectrosopic data of compounds 8a,b suggest that
they were formed in single diastereomeric forms.
Scheme 4
In both cases, the Diels–Alder-type cyclodimerization
products, viz., spiro[2,6-bis(arylmethylene)cyclohexane-1,2Ј-(1-
aryl-5-arylmethylene-1,2,3,4,5,6,7,8-octahydronaphthalenes)]
10a,b were isolated (yields ca. 70–73%) (Scheme 5).
The structure of the hydroxyketone 8b was established based
on the X-ray diffraction data of single crystals prepared by
crystallization from methanol. The general view of the
molecule of 2-hydroxy-6-(4-methoxyphenylmethylene)-2-[1-(4-
methoxyphenyl)ethyl]cyclohexanone 8b is shown in Fig. 1; the
main geometrical parameters are given in the caption and
require no further comment. X-ray structural data show that
the arylmethylene fragment has the E configuration for the
double bond as in the alcohols 7a,b.8 The monoclinic crystals of
the racemic form of compound 8b contain two asymmetrical
molecules of the hydroxy ketone corresponding to the R and S
enantiomers in a unit cell. The keto and hydroxy groups of the
enantiomers are bound through hydrogen bonds (Fig. 2).
Scheme 5
These compounds were also obtained under the conditions
of the classical acid-catalyzed cyclodimerization of buta-1,3-
dienes,2,10,11 viz., upon boiling of alcohols 7a,b in acetic acid.
The structures of the cyclodimers 10a,b were established
1
based on the following data. The H NMR spectrum of com-
pounds 10a,b contains (i) multiplets of the protons of four aryl
groups, (ii) three singlets of the olefinic protons of three aryl-
methylidene fragments, (iii) one singlet of the proton of the
ArC(1)H group (δ 3.72 and 3.65, respectively), multiplets of
the protons of eight methylene groups, and (v) four singlets
of the methoxy groups for compound 10b (δ 3.77, 3.80,
3.81, and 3.83). Additional information inferred from the 13C
NMR spectra. These contained, inter alia, four signals for
the C(aromatic)ipso atoms, five signals for the olefinic C᎐ atoms
᎐
bearing no protons, eight signals for the CH2 groups, one
signal for the C(sp3)H atom, and one signal for the C(spiro)
atom. These data altogether point unequivocally to the dimeric
structure of the type 10.
Obviously, the cyclodimers 10a,b originate from the trienes
9a,b, which are formed upon dehydration of the alcohols 7a,b
and underwent the Diels–Alder-type [4ϩ2]-cycloaddition. The
reactions are regioselective and give one diastereomeric
cyclodimer.
Fig. 1 Crystal structure of 8b. Selected bond lengths/Å: O(1)–C(1) =
1.220(3); O(2)–C(2) = 1.417(3); C(1)–C(2) = 1.537(3); C(2)–C(7) =
1.562(3); C(6)–C(8) = 1.341(3).
The results obtained are evidence, in our opinion, of the high
proneness of the trienes 9a,b to enter into the Diels–Alder
cycloaddition reactions. This suggestion was confirmed by
performing dehydration of the alcohols 7a,b with POCl3 in
pyridine at ambient temperature in the presence of N-phenyl-
maleimide. The trienes 9a,b formed in situ give the corre-
sponding Diels–Alder adducts 11a,b (Scheme 6).
Scheme 6
Compounds 11a,b are formed stereospecifically and are iso-
lated as single isomers exclusively, presumably endo isomers.
This assignment is made based on the known3 NMR criteria
for the attribution of the Diels–Alder adducts to exo and endo
isomers. The characteristic feature of the H NMR spectra of
these adducts is that the multiplets of the two protons of the
Fig. 2 Crystal packing of 8b.
The target compounds, viz., 1,3-bis(arylmethylene)-2-
methylenecyclohexanes (9a,b) could not be isolated individually
upon dehydration of the alcohols 7a and 7b under the action of
1
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 1 2 1 0 – 1 2 1 5
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N-phenyl-substituted fragment resonate in higher field (δ 6.43
dienyl cations 13a,b. Presumably, the presence of trifluoroacetic
and 6.52) than the singlets of the olefinic protons of the ArCH᎐
acid is required to suppress this deprotonation.
᎐
groups (δ 6.69 and 6.62, respectively) and the multiplets of
other protons of the aromatic substituents, which is typical of
the endo isomers.
It was also found that the dehydration of the alcohols 7a,b in
a 9 : 1 mixture of acetic and trifluoroacetic acids resulted in the
formation of methylidene-substituted spirocyclodimers 12a,b
(Scheme 7).
Spirocyclodimers 12a,b are formed stereospecifically. Com-
pounds 12a and 12b were isolated as single diastereomers,
which is probably the consequence of favorable effects of both
electronic and steric factors. Thus it is known that the electronic
factor, which manifests itself in a fairly high ability of an aryl
substituent at the carbenium center to stabilize it,14,15 directs the
addition of the cations 13a,b exclusively at the exocyclic ᎐CH
᎐
2
group of the trienes 9a,b, resulting in stabilized dimeric α-aryl-
dienyl cations 14a,b. The E configurations of the double bonds
of arylmethylidene fragments in the trienes 9a,b do not prevent
this direction of the addition (the steric factor). It is also known
that the absence of substantial steric hindrances of the con-
figurational nature in the intermediate linear dimeric allylic
cations16–18 is prerequisite for the intramolecular alkylation and
formation of cyclodimeric cations of the type 15. The configur-
ational features of the cyclohexane moieties in 14a,b seem to
meet these demands and do not create considerable steric
hindrances in the establishment of the conformation most
favorable for the intramolecular cyclization of the cyclic cations
14a,b into the cyclic carbocations 15a,b. In turn, the latter
represent arylallylic cations and seem to be no less stable than
the linear cations 14a,b (electronic factor). These factors
altogether create prerequisites for the cationic cyclodimeriz-
ation resulting in the cyclodimers 12a,b.
Scheme 7
We believe that the cyclodimers 12a,b are the cationic
cyclodimerization products of the trienes 9a,b formed upon
dehydration of the alcohols 7a,b (Scheme 8). This reaction
pathway presumes the presence of both the trienes 9a,b and the
respective dienylcarbenium cations 13a,b.
We have investigated the behavior of the spirocyclodimers
12a,b in reactions promoted by CF3COOH and HBF4 etherate.
Treatment of compounds 12a,b with an excess of HBF4 ether-
ate brings about their fragmentation resulting in the formation
of insoluble tetrafluoroborates of the cations 13a,b in quanti-
tative yield (Scheme 9).
Scheme 9
Scheme 8
The action of trifluoroacetic acid does not bring about com-
plete fragmentation of the dimers 12a,b. Their storage in
CF3COOH at ∼20 ЊC results in slow accumulation of “three-
petal” fused carbocyclic compounds 16a,b representing intra-
molecular ortho-alkylation products of the Ar fragment
(Scheme 10).
The cations 13a,b add to the methylidene groups of the
trienes 9a,b to form dimeric bisdienyl cations 14a,b, which
undergo intramolecular cyclization into the cyclodimeric allylic
cations 15a,b. Subsequent spontaneous deprotonation of the
latter affords the cyclodimers 12a,b.
The structures of compounds 12a,b were established based
on the analysis of the analysis of the 1H and 13C NMR spectra.
The characteristic features of the 1H NMR spectra of the
dimers 12a,b are as follows: each contained one singlet of the
ArCH group (δ 3.58 and 3.52) and one triplet of the ArCH
group (δ 3.63 and 3.61), two singlets of the ᎐CH fragment
᎐
2
(δ 6.40, 6.50 and 6.25, 6.37), two singlets of the ArCH᎐ substi-
᎐
tuents (δ 6.61, 6.64 and 6.58, 6.65), and multiplets of the pro-
tons of seven methylene groups. The 13C NMR spectroscopic
data corroborate the cyclodimeric structures of compounds
12a,b. The spectra contain, inter alia, four signals for the
C(aromatic)ipso atoms, five signals for the C᎐ atoms bearing no
᎐
protons, one signal for the C(spiro) atom, seven signals for the
Scheme 10
methylene groups, one signal for the methylidene group ᎐CH ,
᎐
2
Presumably, two competing protonation processes of the
and two signals for the olefinic carbon atoms of the ArCH᎐
᎐
᎐CH group occur in the reaction with CF COOH, viz., the
fragments.
᎐
2
3
reversible fast protonation leading to the cations 15a,b and
non-standard (anti-Markovnikov) slow protonation leading to
the cations 17a,b, which alkylate immediately the ortho-position
of the aryl substituent thus shifting the equilibrium towards
compounds 16a,b.
Acid-catalyzed cyclodimerization of the trienes 9a,b occurs
in the presence of trifluoroacetic acid, which suggests, in our
opinion, lower ability of these compounds, compared with the
ferrocenyl analogs,12,13 to undergo cationic cyclodimerization
due apparently to easy deprotonation of the intermediate
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 1 2 1 0 – 1 2 1 5
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The dimers 12a,b gave no fragmentation products upon
treatment with CF3COOH in contrast to the treatment with
HBF4. This may be due to slower cleavage of the spirocarbo-
cations 15a,b into the triene 9a,b and cationic 13a,b com-
ponents (Scheme 10). This retardation of the cleavage process
may be accounted for by the nearly identical stabilities of the
allylic 15a,b and dienyl 13a,b cations.4,5,14,15
As a consequence, conditions are provided for the minor,
unstable primary carbocations 17a,b to alkylate the spatially
proximal phenyl substituent, resulting in compounds 16a,b,
thereby shifting the reaction equilibrium (Scheme 10).
2,6-Bis(arylmethylene)-1-methylcyclohexanols 7a,b.
General procedure
A solution of the dienone 6a,b (50 mmol) in dry benzene
(50 ml) was added with stirring under dry nitrogen to an ether-
eal solution of MeLi (70 mmol). After 30 min the reaction
mixture was quenched with 5% aqueous NaOH, the organic
layer was separated, dried with MgSO4, and the solvent
was evaporated in vacuo. The residue was recrystallized from
ethanol (30 ml). The crystals were filtered off, washed with
ethanol on a filter, and dried in vacuo to give 2,6-dibenzylidene-
1-methylcyclohexanol 7a, yield 1.02 g (70%) and 2,6-bis(4-
methoxybenzylidene)-1-methylcyclohexanol 7b, yield 1.26 g
(72%).
The structures of these compounds 12a,b and 16a,b were
established based on the 1H and 13C NMR spectroscopic data.
Thus the signals for the ᎐CH protons in the 1H NMR spectra
᎐
2
The ethanolic mother liquors were concentrated in vacuo and
the residues were chromatographed on alumina (benzene–ethyl
acetate, 2 : 1) to give 0.15 g (10%) of compound 8a, mp 121–
122 ЊC and 0.17 g (9%) of compound 8b, mp 124–125 ЊC.
Compound 7a, colorless crystals, mp 135–136 ЊC. [Found: C,
86.73; H, 7.78%. Calc. for C21H22O: C, 86.85; H, 7.63%];
νmax(KBr)/cmϪ1: 1140, 1357, 1444, 1491, 1600, 1640, 2932, 3309;
λmax(CHCl3)/nm: 249.5, 205.5; δH (300 MHz, CDCl3): 1.46 (1 H,
m, CH2), 1.66 (3 H, s, CH3), 1.86 (1 H, m, CH2), 1.96 (1 H, s,
OH), 2.28 (2 H, td, J = 4.6, 12.8 Hz, CH2), 2.96 (2 H, td, J = 4.6,
are absent contrary to the spectra of the dimers 12a,b. The
spectra of compounds 16a,b contained each, inter alia, two
doublets of two methylene groups (δ 2.75, 2.87 and 2.64, 2.75),
two triplets and one singlet of three methine protons, and two
singlets of the olefinic protons of the ArCH᎐ fragments.
᎐
The 13C NMR spectra contained five signals for the
C(aromatic)ipso atoms, four signals for the C᎐ atoms bearing no
᎐
protons, one signal for the C(spiro) atom, two signals for the
olefinic C atoms of the ArCH᎐ groups, eight signals for the
᎐
methylene carbon atoms, and three signals for the methine
groups. These data altogether, as well as the presence of reson-
ances of four aryl substituents, confirm unambiguously the
fused structures of compounds 16a,b (Fig. 3).
12.8 Hz, CH ), 6.83 (2 H, s, CH᎐), 7.19–7.40 (10 H, m, C H );
᎐
2
6
5
δC (75 MHz, CDCl3): 27.1 (2 CH2), 27.5 (1 CH2), 28.9 (CH3),
76.50 (C–O), 119.95 (2 CH᎐), 126.2, 128.0, 129.0 (2 C H ),
᎐
6
5
138.1 (2 C), 147.7 (2 Cipso).
Compound 7b, colorless crystals, mp 160–161 ЊC. [Found: C,
78.67; H, 7.64. Calc. for C23H26O3: C, 78.82; H, 7.48%];
νmax(KBr)/cmϪ1: 1143, 1250, 1290, 1458, 1509, 1607, 1640, 2930,
3295; λmax(CHCl3)/nm: 260.0, 208.0; δH (300 MHz, CDCl3):
1.39 (1 H, m, CH2), 1.62 (3 H, s, CH3), 1.81 (1 H, m, CH2), 1.90
(1 H, s, OH), 2.23 (2 H, td, J = 4.5, 12.2 Hz, CH2), 2.96 (2 H,
td, J = 4.5, 12.2 Hz, CH2), 3.80 (6 H, s, 2 OCH3), 6.74 (2 H, s,
CH᎐), 6.86 (4 H, d, J = 8.6 Hz, C H ), 7.13 (4 H, d, J = 8.6 Hz,
᎐
6
4
C6H4); m/z 350 [M]ϩ.
Fig. 3 General view of the compound 16a, obtained from MM2
Compound 8a, colorless crystals, mp 121–122 ЊC. [Found: C,
82.49; H, 7.12. Calc. for C21H22O2.: C, 82.32; H, 7.24%];
νmax(KBr)/cmϪ1: 1133, 1412, 1590, 1606, 1631, 1720, 2930, 3319;
δH (300 MHz, CDCl3): 1.15 (3 H, d, J = 5.7 Hz, CH3), 1.94 (4 H,
m, 2 CH2), 2.30 (1 H, s, OH), 2.70 (1 H, m, CH2), 3.15 (1 H, q,
J = 5.7 Hz, CH), 3.28 (1 H, m, CH2), 6.96–7.65 (10 H, m, 2
C6H5); m/z 306 [M]ϩ.
Compound 8b, colorless crystals, mp 124–125 ЊC. [Found: C,
75.17; H, 7.24. Calc. for C23H26O4: C, 75.38; H, 7.15%];
νmax(KBr)/cmϪ1: 1139, 1240, 1271, 1450, 1501, 1603, 1635, 1715,
2929, 3318; δH (300 MHz, CDCl3): 1.10 (3 H, d, J = 6.0, CH3),
1.86 (4 H, m, 2 CH2), 2.19 (1 H, s, OH), 2.61 (1 H, m, CH2), 3.08
(1 H, q, J = 6.0 Hz, CH), 3.23 (1 H, m, CH2), 3.77 (3 H, s,
OCH3), 3.82 (3 H, s, OCH3), 6.82–7.46 (8 H, m, 2 C6H4)); m/z
366 [M]ϩ.
calculations, the hydrogens are omitted for clarity.
Thus, exocyclic diaryltrienes undergo cyclodimerization
according to the [4ϩ2]-cycloaddition and cationic
cycloaddition pathways to yield cyclodimers 10a,b and spiro-
cyclodimers 12a,b, respectively. The intramolecular, acid-
catalyzed alkylation in compounds 12a,b was accomplished for
the first time, this resulted in “three-petal” fused carbocyclic
compounds. Information on this type of processes is lacking in
the chemical literature. Elucidation of the effects of various
factors on the peculiarities of cationic cyclodimerization of
exocyclic cross-conjugated trienes and intramolecular cycliz-
ation in the respective cyclodimers deserve, in our opinion,
further studies.
Dehydration of the alcohols 7a,b with POCl3 in pyridine. General
procedure
Experimental
UV spectra were recorded on a Specord UV-VIS spectro-
photometer. IR spectra were obtained for KBr pellets on a
Specord 75-IR instrument. All 1H and 13C NMR spectra
were recorded on a Unity Inova Varian spectrometer (300 and
75 MHz) for solutions in CDCl3 with Me4Si as the internal
standard. Mass spectra (EI, 70 eV) were obtained on a
Varian-MAT CH-6 mass spectrometer. Column chromato-
graphy was carried out on Al2O3 (Brockmann activity III). 2,6-
Diarylmethylenecyclohexanones 6a,b were synthesized by a
standard procedure9 from cyclohexanone and benzaldehyde
or p-anisaldehyde in aqueous ethanolic alkali. Purification
and isolation of the dienones 6a and 6b were carried out by
column chromatography in a 3 : 1 hexane-chloroform solvent
system. Compound 6a, yield 70%, mp 120–121 ЊC (Lit.9:mp
120 ЊC). Compound 6b, yield 67%, mp 153–154 ЊC (Lit.9:mp
153–154 ЊC).
POCl3 (2 ml, 2.2 mmol) was added dropwise at 5–10 ЊC to a
stirred solution of the alcohol 7a (2.9 g) or the alcohol 7b (3.5 g)
in dry pyridine (120 ml). Stirring was continued for 4 h at
∼20 ЊC and then water (200 ml) was added. The reaction prod-
ucts were extracted with benzene (3 × 50 ml), the combined
extracts were washed with water (2 × 20 ml) and dried with
CaCl2. The solvent was evaporated and the residue was chrom-
atographed on Al2O3 (hexane–benzene, 4:1) to give 1.82 g (67%)
of spiro[2,6-dibenzylidenecyclohexane-1,2Ј-(5-benzylidene-1-
phenyl-1,2,3,4,5,6,7,8-octahydronaphthalene)] 10a and 2.3 g
(72%) of spiro[2,6-bis(4-methoxybenzylidene)cyclohexane-
1,2Ј-(5-(4-methoxybenzylidene)-1-(4-methoxyphenyl)-1,2,3,4,5,
6,7,8-octahydronaphthalene)] 10b.
Compound 10a, colorless powder, mp 235–236 ЊC. [Found:
C, 92.43; H, 7.58. Calc. for C42H40: C, 92.60; H, 7.40%.];
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 1 2 1 0 – 1 2 1 5
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νmax(KBr)/cmϪ1: 1141, 1447, 1492, 1598, 1632, 2855, 2917, 2938;
λmax(CHCl3)/nm: 204.5; δH (300 MHz, CDCl3): 1.50–1.88 (4 H,
m, 2 CH2), 2.0–2.4 (6 H, m, 3 CH2), 2.45–2.78 (6 H, m, 3 CH2),
Dehydration of the alcohols 7a,b on alumina (Brockmann activity
II). General procedure
The alcohols 7a,b (5 mmol) were severally dissolved in dry
benzene (25 ml) and Al2O3 (Brockmann activity II) (50 g) was
added. The suspensions were left at ∼20 ЊC until the solvent
evaporated, the sorbent was applied onto a top of a column
with fresh alumina (30 g) and eluted with a 4 : 1 hexane–
benzene mixture to give 1.02 g (75%) of the cyclodimer 10a,
mp 236 ЊC, and 1.16 g (71%) of the cyclodimer 10b, mp 268–
269 ЊC.
3.72 (1 H, s, CH), 5.50 (1 H, s, CH᎐), 6.59 (1 H, s, CH᎐), 6.66
᎐
᎐
(1 H, s, CH᎐), 6.68 (2 H, m, Ph), 7.1–7.38 (18 H, m, Ph); δ (75
᎐
C
MHz, CDCl3): 18.5, 18.9, 19.1, 19.7, 20.5, 22.1, 22.9, 27.0
(8CH2); 46.8 (Cspiro); 50.1 (CH); 116.3, 118.9, 120.4 (3 CH᎐);
᎐
120.6, 120.8, 120.9, 121.2, 122.6 (3 C), 122.9 (2 C), 123.1 (2 C),
123.3 (2 C), 123.7 (2 C), 124.3 (2 C), 124.7 (3 C) (4 Ph); 132.6,
133.7, 133.8 (2 C), 134.2 (5 C); 137.8, 141.0 (2 C), 141.4 (4 Cipso);
m/z 544, 546 [M]ϩ
Compound 10b, colorless powder, mp 268–269 ЊC. [Found:
C, 82.95; H, 7.31. Calc. for C46H48O4: C, 83.10; H, 7.28%];
νmax(KBr)/cmϪ1: 1036, 1177, 1250, 1460, 1510, 1607, 1635, 2835,
2933; λmax(CHCl3)/nm: 204.5; δH (300 MHz, CDCl3): 1.52–1.92
(4 H, m, 2CH2), 2.02–2.30 (6 H, m, 3 CH2), 2.52–2.73 (6 H, m,
3 CH2), 3.65 (1H, s, CH), 3.77 ( H, s, OCH3), 3.81 ( H, s, OCH3),
Dehydration of the alcohols 7a,b in acetic acid. General
procedure
A solution of the alcohol 7a (or 7b) (10 mmol) in glacial acetic
acid (100 ml) was refluxed for 30 min and cooled to the ambient
temperature. The finely crystalline colorless precipitate that
sedimented was filtered off, washed with ethanol, and dried in
vacuo. The yields of the cyclodimers 10a and 10b were virtually
quantitative. Following recrystallization from ethanol, 10a had
mp 235–236 ЊC, and 10b, mp 268–269 ЊC.
3.83 (3 H, s, OCH ), 3.85 (3 H, s, OCH ), 5.43 (1 H, s, CH᎐),
᎐
3
3
6.51 (1 H, s, CH᎐), 6.57 (1 H, s, CH᎐), 6.63–6.91 (10 H, m, Ar),
᎐
᎐
7.02–7.29 (6 H, m, Ar); δC (75 MHz, CDCl3): 23.6, 23.9, 24.2,
24.6, 25.5, 27.2, 28.0, 27.0 (8 CH2); 39.6 (Cspiro); 51.8 (CH); 54.1
(OCH ), 55.2 (3 OCH ); 113.0, 113.1, 113.4 (3 CH᎐); 113.6,
᎐
3
3
113.8, 120.6, 123.0, 124.6, 129.4 (2 C), 123.8 (2 C), 130.4 (3 C),
130.5 (3 C), 131.4 (4 Ar); 131.7, 131.8, 134.9, 137.2, 137,3 (5 C);
141.9, 144.6 (2 C), 145.7 (4 Cipso); 157.5, 157.7, 158.0, 158.1
(4 Ar–O); m/z 664 [M]ϩ.
Dehydration of the alcohols 7a,b in a mixture of acetic and tri-
fluoroacetic acids. General procedure
A solution of the alcohol 7a (or 7b) (10 mmol) in a mixture of
glacial acetic acid (90 ml) and anhydrous trifluoroacetic acid
(10 ml) was refluxed for 1 h and cooled to ∼20 ЊC. The reaction
mixture was partitioned between benzene and water (100 ml
each), the organic layer was separated, washed with water
(2 × 20 ml), and dried with CaCl2. The solvent was evaporated
in vacuo and the residue was chromatographed on alumina
(hexane-benzene, 3:1) to give 1.85 g (68%) of spiro[3-benzyl-
idene-2-methylidenecyclohexane-1,2Ј-(5-benzylidene-1,3-di-
phenyl-1,2,3,4,5,6,7,8-octahydronaphthalene)] 12a and 2.22 g
(67%) of spiro[3-(4-methoxybenzylidene)-2-methylidenecyclo-
hexane-1,2Ј-(5-(4-methoxybenzylidene)-1,3-bis(4-methoxy-
phenyl)-1,2,3,4,5,6,7,8-octahydronaphthalene)] 12b.
Compound 12a, white powder, mp 228–229 ЊC. [Found: C,
92.74; H, 7.25. Calc. for C42H40: C, 92.60; H, 7.40%]; νmax (KBr)/
cmϪ1: 841, 898, 1441, 1497, 1597, 1661, 2855, 2919, 3020;
δH (300 MHz, CDCl3): 1.63–1.78 (2 H, m, CH2), 1.88–2.0
(4 H, m, 2 CH2), 2.05–2.18 (4 H, m, 2 CH2), 2.60 (2 H, m,
CH2), 2.77 (2 H, d, J = 5.6 Hz, CH2), 3.58 (1 H, s, CH), 3.63
Dehydration of the alcohols 7a,b with POCl3 in pyridine in the
presence of N-phenylmaleimide. General procedure
POCl3 (0.2 ml) was added dropwise to a solution of the alcohol
7a (or 7b) (1 mmol) and N-phenylmaleimide (0.26 g, 1.5 mmol)
in dry pyridine (30 ml) and the mixture was stirred for 20 h at
∼20 ЊC. Then water (100 ml) was added and the reaction prod-
ucts were extracted with benzene. Subsequent processing and
column chromatography (hexane–benzene, 2 : 1) as described
above gave 0.32 g (73%) of N-phenyl-5-benzylidene-1-phenyl-
1,2,3,4,5,6,7,8-octahydronaphthalene-2,3-dicarboximide 11a
and 0.36 g (70%) of N-phenyl-5-(4-methoxybenzylidene)-1-(4-
methoxyphenyl)-1,2,3,4,5,6,7,8-octahydronaphthalene-2,3-di-
carboximide 11b.
Compound 11a, white finely crystalline powder, mp 244–245
ЊC. [Found: C, 83.69; H, 6.28; N,2.92. Calc. for C31H27NO2: C,
83.57; H, 6.11; N, 3.14%]; νmax(KBr)/cmϪ1: 1145, 1365, 1412,
1600, 1622, 1665, 1720, 2912; δH (300 MHz, CDCl3): 1.74
(1 H, m, CH2), 2.0 (1 H, m, CH2), 2.23 (1 H, m, CH2), 2.53 (2 H,
m, CH2), 2.86 (1 H, m, CH2), 3.14 (2 H, m, CH2), 3.47 (2 H,
(1 H, t, J = 5.6 Hz, CH), 6.40 (1 H, s, CH ᎐), 6.51 (1 H,
᎐
2
s, CH ᎐), 6.61 (1 H, s, CH᎐), 6.64 (1 H, s, CH᎐), 7.1–7.43
᎐
᎐
᎐
2
(20 H, m, 4 Ph); δC (75 MHz, CDCl3):18.4, 21.2, 23.3,
m, 2 CH), 3.54 (1 H, d, J = 6.9 Hz, CH), 6.69 (1 H, s, CH᎐),
6.43 (2 H, m, Ph), 7.14–7.39 (13 H, m, Ph); δC (75 MHz,
28.0, 28.1, 31.1, 32.9 (7 CH2); 41.7 (Cspiro); 46.2, 58.2 (2 CH);
121.2 (CH ᎐); 125.2, 125.3 (2 CH᎐); 125.9, 126.2, 126.5,
᎐ ᎐
2
᎐
CDCl3):21.2, 23.2, 27.4, 31.2 (4 CH2), 37.9, 44.1, 47.2 (3 CH);
126.6, 126.7, 127.9 (3 C), 128.1 ( 3C), 128.1 (2 C), 128.4, 128.5,
129.3 (3 C), 129.7 (2 C) (4 Ph); 129.1, 129.5, 132.8, 135.9,
137.7 (5 C); 138.0, 138.5 (2 C), 141.4, 144.1 (4 Cipso); m/z 544,
546 [M]ϩ.
Compound 12b, white powder, mp 265–266 ЊC. [Found: C,
83.23; H, 7.09. Calc. for C46H48O4: C, 83.10; H, 7.28%]; νmax
(KBr)/cmϪ1: 838, 1021, 1165, 1220, 1441, 1500, 1601, 1670,
2848, 2924, 3033; δH (300 MHz, CDCl3): 1.58–1.80 (2 H, m,
CH2), 1.90–2.05 (4 H, m, 2 CH2), 2.11–2.18 (4 H, m, 2 CH2),
2.68 (2 H, m, CH2), 2.74 (2 H, d, J = 6.1, CH2), 3.52 (1 H, s,
CH), 3.61 (1 H, t, J = 6.1 Hz, CH), 3.75 (3 H, s, OCH3), 3.82
(3 H, s, OCH3), 3.85 (3 H, s, OCH3), 3.87 (3 H, s, OCH3), 6.25
123.0 (CH᎐); 126.3 (3 C), 127.8, 128.1 (2 C), 128.4, 128.8
᎐
(2 C), 128.9 (2 C), 129.3 (2 C), 129.5 (2 C) (3 Ph) 131.4, 136.7,
137.7 (3 C); 136.8, 136.9 (2 Cipso); 169.8 (C–N) 178.5 (2 C᎐O);
᎐
m/z 445 [M]ϩ.
Compound 11b, white powder, mp 273–274 ЊC. [Found: C,
78.52; H, 6.04; N,2.58. Calc. for C33H31NO4: C, 78.39; H, 6.18;
N, 2.77%]; νmax(KBr)/cmϪ1: 1138, 1257, 1345, 1437, 1597, 1623,
1670, 1728, 2903; δH (300 MHz, CDCl3): 1.51 (1 H, m, CH2),
1.76 (1 H, m, CH2), 2.03 (1 H, m, CH2), 2.25 (1 H, m, CH2), 2.47
(1 H, m, CH2), 2.85 (1 H, m, CH2), 3.10 (2 H, m, CH2), 3.43
(2 H, dm, 2 CH), 3.75 (3 H, s, OCH3), 3.83 (3 H, s, OCH3), 3.88
(1 H, d, J = 6.2 Hz, CH), 6.62 (1 H, s, CH᎐), 6.52 (2 H, m, Ph),
(1H, s, CH ᎐), 6.37 (1 H, s, CH ᎐), 6.59 (1 H, s, CH᎐), 6.65 (1 H,
᎐ ᎐ ᎐
2 2
s, CH᎐), 7.00–7.31 (16 H, m, 4 An); δ (75 MHz, CDCl ): 23.4,
᎐
C 3
᎐
6.80 (2 H, d, J = 9.0 Hz, An), 6.91 (2 H, d, J = 8.7 Hz, An), 7.06
(2 H, d, J = 8.7 Hz, An), 7.27 (2 H, d, J = 9.0 Hz, An), 7.29 (3 H,
m, Ph); δC (75 MHz, CDCl3): 21.1, 22.3, 27.5, 31.1 (4 CH2);
23.8, 24.3, 24.4, 25.6, 27.3, 31.5 (7 CH2); 30.6 (Cspiro); 44.9,
52.9 (2 CH); 54.4, 54.5, 54.7, 55.0 (4 OCH ); 118.1 (CH ᎐);
᎐
2
3
37.9, 44.3, 46.4 (3 CH); 55.2, 55.3 (OCH ), 113.5 (CH᎐) 114.1
121.1, 122.0 (2 CH᎐); 123.2, 123.6, 124.6, 124.8, 125.1, 126.1
᎐
᎐
3
(2 C), 122.4, 126.3 (2 C), 128.4, 128.8, 130.4 (2 C), 130.5 (2 C),
129.5 (2 C) (3 Ar); 127.9, 129.5, 130.6 (3 C); 136.3, 136.4
(2 C), 126.5 (2 C), 126.8 (2 C), 127.0 (2 C), 127.8 (2 C), 128.0
(4 An); 127.9, 128.2, 128.9, 130.2, 131.34 (5 C); 134.9, 135.9,
137.2, 139.9 (4 Cipso); 152.9, 153.8, 155.7, 156.1 (4 Ar–O); m/z
664 [M]ϩ.
(2 Cipso); 158.0, 159.3 (2 Ar–O) 177.1 (C–N); 179.0 (2 C᎐O);
᎐
m/z 505 [M]ϩ.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 1 2 1 0 – 1 2 1 5
1214

View Online
The action of CF3COOH on the cyclodimers 12a,b.
General procedure
7.21 (4 H, d, J = 8.8 Hz, C6H4), 8.02 (4 H, d, J = 8.8 Hz, C6H4),
8.55 (2 H, s, CH᎐).
᎐
A solution of compound 12a or 12b (1 mmol) in anhydrous
trifluoroacetic acid (50 ml) was kept for 7–10 d at ambient tem-
perature. Then the mixture was partitioned between benzene
and water (50 ml each) and the organic layer was processed as
described above to give after column chromatography (hexane-
benzene, 3:1) 0.07 g (12%) of the starting 12a, mp. 235 ЊC, or
0.05 g (8%) of the starting 12b, mp. 268 ЊC, and 0.33 g (60%) of
4,10-dibenzylidene-6-phenyl-1,2,3,4,5,6,6a,7,8,9,10,10a,11,15b-
tetradecahydronaphtho[1,2-f]-anthracene 16a and 0.44 g (65%)
of 4,10-bis(4-methoxybenzylidene)-13-methoxy-6-(4-methoxy-
phenyl)-1,2,3,4,5,6,6a,7,8,9,10,10a, 11, 15b-tetradecahydro-
naphtho[1,2-f]-anthracene 16b, respectively.
Compound 16a, white powder, mp 248–249 ЊC.[ Found: C,
92.74; H, 7.21. Calc. for C42H40: C, 92.60; H, 7.40%]; νmax (KBr)/
cmϪ1: 1368, 1441, 1502, 1603, 2904, 2938; λmax(CHCl3)/nm:
206.5; δH (300 MHz, CDCl3): 1.69 (4 H, m, 2 CH2), 1.88 (4 H,
m, 2 CH2), 2.04 (2 H, m, CH2), 2.28 (2 H, m, CH2), 2.75 (2 H, d,
J = 6.8 Hz, CH2), 2.87 (2 H, d, J = 7.1 Hz, CH2), 3.62 (1 H, t,
J = 6.8 Hz, CH), 3.99 (1 H, t, J = 7.1 Hz, CH), 4.06 (1 H, s, CH),
Crystal structure determination
The unit cell parameters and the X-ray diffraction intensities
were recorded on a Siemens P4/PC diffractometer. The struc-
ture of compound 8b was solved by the direct method
(SHELXS) and refined using full-matrix least-squares on F 2.
Crystal data for C23H26O4, Mr = 366.44 g molϪ1, colorless prism,
size 0.40 × 0.24 × 0.08, monoclinic P2(1)/c, a = 12.915(2) Å,
b = 5.694(2) Å, c = 27.080(3) Å, β = 98.69Њ, V = 1968.5(8) Å3,
T = 293ЊK, Z = 4, ρ = 1.26 g cmϪ3, λ(Cu Kα) = 1.54178 Å,
F(000) = 784, index ranges Ϫ1 ≤ h ≤ 13, Ϫ1 ≤ k ≤ 6, Ϫ28 ≤ l ≤
28,scan range 3.30 ≤ 2θ ≤ 56.7Њ, 2626 independent reflections,
Rint = 0.0281, 2187 reflections with Fo > 3.0 σ(F), 248 param-
eters, Final R indices [I > 2σ(I )] R1 = 0.0423, wR2 =0.1037, R
indices (all data) R1 = 0.0533, wR2 = 0.1124, Largest difference
peak and hole 0.137/Ϫ0.149 e ÅϪ3.†
† CCDC reference number 169688. See http://www.rsc.org/suppdata/
ob/b2/b210890a/ for crystallographic data in .cif or other electronic
format.
5.75 (1 H, s, CH᎐), 6.27 (1 H, s, CH᎐), 6.93–7.74 (19 H, m,
᎐
᎐
3 C6H5, C6H4); δC (75 MHz, CDCl3): 21.0, 21.95, 22.7, 23.25,
28.9, 30.35, 34.4, 40.7 (8 CH2); 45.3 (CH); 55.6 (Cspiro); 65.1,
Acknowledgements
65.6 (2 ArCH); 119.2 (2 PhCH᎐), 121.0, 121.3, 121.7, 121.9,
᎐
122.2, 122.4, 122.65 (3 C), 122.9 (3 C), 123.1, 123.2, 123.5, 124.0
(3 C), 124.6 (3 Ph, 1C6H4); 125.0, 129.9, 135.2, 134.1 (4 C);
136.0, 138.1, 140.2, 141.0, 142.15 (5 Cipso); m/z 546 [M]ϩ.
This work was supported by the grant DGAPA–UNAM
(IN 207102–3). Thanks are due to M. L. Velasco, J. Perez,
H. Rios, E .R. Patiño, and O. S. Yañez Muñoz for their tech-
nical assistance.
Compound 16b, white powder, mp 276–277 ЊC. [Found: C,
82.88; H, 7.41. Calc. for C46H48O4: C, 83.10; H, 7.28%]; νmax
(KBr)/cmϪ1: 1050, 1180, 1247, 1453, 1508, 1603, 1620, 2830,
2954; λmax(CHCl3)/nm: 205.5; δH (300 MHz, CDCl3): 1.69 (4 H,
m, 2 CH2), 1.93 (4 H, m, 2 CH2), 2.01 (2 H, m, CH2), 2.19 (2 H,
m, CH2), 2.64 (2 H, d, J = 6.4 Hz, CH2), 2.75 (2 H, d, J = 6.8 Hz,
CH2), 3.59 (1 H, t, CH, J = 6.4 Hz), 3.75 (3 H, s, OCH3), 3.78
(3 H, s, OCH3), 3.83 (3 H, s, OCH3), 3.87 (3 H, s, OCH3), 3.96
References
1 E. G. Perevalova, E. I. Klimova, V. V. Kryuchkova and A. N. Pushin,
Zh. Obsch. Khim., 1989, 59, 873 (J. Gen. Chem. USSR (Engl.
Transl.), 1989, 59, 873).
2 E. I. Klimova, A. N. Pushin and V. A. Sazonova, J. Organomet.
Chem., 1984, 270, 319.
3 A. N. Pushin, E. I. Klimova and V. A. Sazonova, Zh. Obsch. Khim.,
1987, 57, 1102.
4 E. G. Perevalova, A. N. Pushin, E. I. Klimova, Yu. L. Slovokhotov
and Yu. T. Struchkov, Metalloorg. Khim., 1989, 2, 1405.
5 V. N. Postnov, E. I. Klimova, A. N. Pushin and N. N. Meleshonkova,
Metalloorg. Khim., 1991, 4, 116.
6 W. W. Herz and E. Liwis, J. Org. Chem., 1958, 23, 1640.
7 T. Jakobs and R. H. Yoodrow, J. Org. Chem., 1958, 23, 1653.
8 E. I. Klimova, G. M. Martinez, B. T. Klimova, Z. C. Damian,
S. Ortega, I. D. Mendez, P. R. Gutierrez and G. R. A. Vazquez,
Synthesis, 2002(13), 1891.
9 Gy. Oszbach and D. Szabo, Acta Chim. Acad. Sci. Hung., 1975, 86,
449.
10 H. M. R. Hoffmann and H. V. Ernst, Chem. Ber., 1981, 114, 1182.
11 H. V. Ernst and H. M. R. Hoffmann, Angew. Chem., 1980, 92,
861.
12 V. N. Postnov, E. I. Klimova, M. Martinez Garcia and N. N.
Meleshonkova, J. Organomet. Chem., 1994, 476, 189.
13 V. N. Postnov, E. I. Klimova, N. N. Meleshonkova and M. Martinez
Garcia, Dokl. Akad. Nauk, 1992, 326, 113.
14 V. F. Lavrushin, L. M. Kutchenko and L. M. Grin, Zh. Org. Khim.,
1967, 3, 72.
15 V. X. Grif, V. M. Nikitchenko and V. F. Lavrushin, Zh. Org. Khim.,
1978, 14, 1293.
16 R. J. Giguere, G. Ilsemann and H. M. R. Hoffmann, J. Org. Chem.,
1982, 47, 4948.
17 E. I. Klimova, L. Ruiz Ramirez, M. Martinez Garcia and N. N.
Meleshonkova, J. Organomet. Chem., 1997, 532, 181.
18 V. N. Postnov, E. I. Klimova, M. Martinez Garcia, N. N.
Meleshonkova, V. B. Rybakov and L. A. Aslanov, Zh. Obsch. Khim.,
1996, 66, 99.
(1 H, t, J = 6.8 Hz, CH), 4.07 (1 H, s, CH), 5.72 (1 H, s, CH᎐),
᎐
6.22 (1 H, s, CH᎐), 7.00–7.65 (15 H, m, 3 C H , C H ) δ (75
᎐
6
4
6
3
C
MHz, CDCl3): 21.4, 22.9, 23.6, 23.9, 28.1, 30.9, 36.0, 39.9
(8 CH2); 44.1 (CH); 53.1 (Cspiro); 54.0, 54.1, 55.2, 55.4 (4 OCH3);
63.9, 65.4 (2 ArCH); 117.95, 119.0 (2 ArCH᎐); 120.6, 122.9,
᎐
124.0, 124.2, 124.4 (3 C), 126.5 (3 C), 127.2, 127.5, 127.6, 127.9,
128.1 (3 C6H4, C6H3); 125.8, 127.9, 132.9, 134.0 (4 C); 135.9,
137.1, 138.3, 139.8, 141.1 (5 Cipso); 156.7, 157.4, 157.95, 158.0
(4 Ar–O); m/z 664 [M]ϩ.
Fragmentation of the cyclodimers 12a,b. General procedure
Tetrafluoroboric acid etherate (3 ml) was added dropwise with
stirring in an atmosphere of dry nitrogen to a solution of com-
pound 12a (or 12b) (1.5 mmol) in dry ether (100 ml) and the
mixture was stirred for 1 h at ∼20 ЊC. A dark violet precipitate
was filtered off, washed with several portions of dry ether and
dry hexane, and dried in vacuo. The yield of the salt 13a was
0.94 g (87%); the yield of the salt 13b was 1.03 g (82%).
Compound 13a, decomposes at ∼300 ЊC. [Found: C,69.93; H,
6.01; F, 20.99. Calc. for C21H21BF4: C, 70.02; H, 5.88; F,
21.10%]; δH (300 MHz, CD2Cl2): 2.16 (2 H, m, CH2), 3.07 (3 H,
s, CH3), 3.13 (4 H, t, J= 5.7 Hz, 2 CH2), 7.21–7.43 (6 H, m,
C H ), 7.64–8.10 (4 H, m, C H ), 8.81 (2 H, s, 2 CH᎐).
᎐
6
5
6
5
Compound 13b, decomposes at ∼312 ЊC. [Found: C,65.49; H,
6.18; F, 17.87. Calc. for C23H25BF4O2: C, 65.73; H, 6.00; F,
18.08%]; δH (300 MHz, CD2Cl2): 2.06 (2 H, m, CH2), 2.95 (3 H,
s, CH3), 3.08 (4 H, t, J = 6.0 Hz, 2 CH2), 4.08 (6 H, s, 2 OCH3),
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 1 2 1 0 – 1 2 1 5
1215