[2 + 2] Cycloaddition reaction of cycloheptatriene with dichloroketene. A novel and efficient synthetic strategy for the synthesis of 2-hydroxyazulene

Article abstract of DOI:10.1039/b104164a

The reaction of cycloheptatriene with dichloroketene, generated by the treatment of trichloroacetyl chloride with activated zinc in dry diethyl ether, affords 9,9-dichlorobicyclo[5.2.0]nona-2,4-dien-8-one 2 as a major product together with 3′,3′,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-2,4-diene-8, 2′-oxetan)-4′-one 3. Structure 3 is elucidated by the X-ray crystallographic analysis of its partially reduced product. Lactone 3 exhibits [1,5] hydrogen-migration in the seven-membered ring to give 3′,3′,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-3,5-diene-8, 2′-oxetan)-4′-one 7 without any decarbonylation. The reaction of 2 with diazomethane exhibits ring expansion of the four-membered ring to give 1,1-dichloro-3,3a,4,8a-tetrahydroazulen-2(1H)-one 8. 2-Hydroxyazulene 9 is successfully derived by the reaction of 8 with lithium chloride in good yield. The reaction of 8 with triethylamine exhibits dehydrochlorination to give 3-chloro-8,8a-dihydroazulen-2(1H)-one 10 in high yield. N-(Azulen-2-yl)pyrrolidine is also derived from either 9 or 10 in good yield.

Full text of DOI:10.1039/b104164a

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[2 ؉ 2] Cycloaddition reaction of cycloheptatriene with
dichloroketene. A novel and efficient synthetic strategy for the
synthesis of 2-hydroxyazulene
1
Ryuji Yokoyama,a Shunji Ito,a Masataka Watanabe,b Nobuyuki Harada,b Chizuko Kabutoa and
Noboru Morita*a
a Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, 980-8578,
Japan
b Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai,
980-8577, Japan
Received (in Cambridge, UK) 7th May 2001, Accepted 20th July 2001
First published as an Advance Article on the web 29th August 2001
The reaction of cycloheptatriene with dichloroketene, generated by the treatment of trichloroacetyl chloride with
activated zinc in dry diethyl ether, affords 9,9-dichlorobicyclo[5.2.0]nona-2,4-dien-8-one 2 as a major product
together with 3Ј,3Ј,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-2,4-diene-8,2Ј-oxetan)-4Ј-one 3. Structure 3 is elucidated
by the X-ray crystallographic analysis of its partially reduced product. Lactone 3 exhibits [1,5] hydrogen-migration
in the seven-membered ring to give 3Ј,3Ј,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-3,5-diene-8,2Ј-oxetan)-4Ј-one 7
without any decarbonylation. The reaction of 2 with diazomethane exhibits ring expansion of the four-membered
ring to give 1,1-dichloro-3,3a,4,8a-tetrahydroazulen-2(1H)-one 8. 2-Hydroxyazulene 9 is successfully derived by the
reaction of 8 with lithium chloride in good yield. The reaction of 8 with triethylamine exhibits dehydrochlorination
to give 3-chloro-8,8a-dihydroazulen-2(1H)-one 10 in high yield. N-(Azulen-2-yl)pyrrolidine is also derived from
either 9 or 10 in good yield.
Introduction
Results and discussion
Azulene (C10H8) is of great interest to many chemists due to its
special carbon skeleton derived from sesquiterpenes as well as
its beautiful blue color. Synthetic methods for azulenes have
been extensively studied so far.1 Ziegler and Hafner reported
the synthesis of parent azulene using the reaction of Zincke’s
aldehyde with cyclopentadiene in 1955.2 Nozoe et al. found the
reaction of activated troponoids to give 1,2,3-trisubstituted
azulenes.3 Furthermore, Yasunami et al. developed a new syn-
thetic method for various azulene derivatives by the reaction of
2H-cyclohepta[b]furan-2-ones with enamines.4 These methods
are highly efficient for the synthesis of azulenes. However, it
could not be said that azulenes are readily available compounds
even using these methods. If commercially available cyclo-
heptatriene 1 could be utilized as a source for the seven-
membered ring of azulenes, the strategy would become an effi-
cient method for the synthesis of azulenes substituted on the
five-membered ring.
We considered that the [2 ϩ 2] cycloadduct of 1 to ketenes
could be easily transformed into azulene derivatives via ring-
expansion reaction of its four-membered ring.5 Therefore, we
focused our attention on [2 ϩ 2] cycloaddition reactions of 1
with ketenes in order to develop a new and efficient synthetic
method for azulene derivatives. Since diphenylketene was syn-
thesized and isolated by Staudinger in 1905,6 reactions of var-
ieties of ketenes with olefins and carbonyl compounds have
appeared in the literature.7 However, there are only two reports
concerning the reaction of 1 with ketenes because of the low
reactivity of their substrates.8,9 We found the reaction condi-
tions in which 1 reacted with dichloroketene to give a [2 ϩ 2]
cycloadduct in good yield. In this paper we report the reaction
of 1 with the ketene and a new strategy for the synthesis of
several azulene derivatives starting from the [2 ϩ 2] cyclo-
adduct.
Dichloroketene is unstable and polymerizes readily.10 However,
it can be easily generated in situ by two methods [equations (1)
and (2)]. The reactivity of 1 with the ketene significantly
(1)
(2)
depended on the preparation method and the solvents used.
The ketene generated by the above two methods did not
react with 1 in either dry hexane or dry benzene. When the
ketene was generated by equation (2) in dry diethyl ether, the
reaction also did not afford satisfactory results. However, we
found that the ketene generated by equation (1) in dry diethyl
ether reacted with 1 to give desired [2 ϩ 2] cycloadduct, 9,9-
dichlorobicyclo[5.2.0]nona-2,4-dien-8-one
2 in 58% yield
together with 3Ј,3Ј,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-2,4-
diene-8,2Ј-oxetan)-4Ј-one 3, (2%) (Scheme 1). GLC analysis
exhibited the recovery of unchanged 1 (17%).The isolated yield
of 3 was increased up to 12% by conducting the reaction at
reflux temperature. Table 1 summarizes isolated and GLC
yields of 2 and 3 under several conditions. Although crude 2
exhibited decomposition even at room temperature, it could be
purified by molecular distillation at 90 ЊC (bath temp)/1.0
mmHg (1 mmHg = 133.322 Pa). Purified 2 was relatively stable
at higher temperature. Even if purified 2 were heated without
any solvent at 100 ЊC for 3 h, it could be recovered almost
quantitatively.
DOI: 10.1039/b104164a
J. Chem. Soc., Perkin Trans. 1, 2001, 2257–2261
This journal is © The Royal Society of Chemistry 2001
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Table 2 Effect of lithium reagent on the dehydrochlorination of 8
Table 1 Reaction of 1 with dichloroketene
Conditions
Reagent
Yield (%)
Conditions
Temp.
Yield (%)a
Entry
Time (t/h)
9
10
CCl3COCl (eq.)
2
3
recovered 1
1
2
3
4
5
18
6
12
12
6
2
73
41
66
46
21
r.t.
Reflux
Reflux
2
2
4
58 (59)
(37)
9 (12)
2 (3)
(13)
12 (14)
(17)
(8)
(0)
LiCl
Li2CO3
LiCl–Li2CO3
LiBr
a Yields of 2 and 3 were calculated on the basis of 1. GLC yields are
shown in parentheses.
Scheme 1
The structure of 3 suggests that it was produced by the
reaction of 2 with another molecule of dichloroketene. Indeed
further reaction of isolated 2 with the ketene generated under
similar reaction conditions afforded 3, although the yield was
poor (4%). The rather low yield of 3 results from the significant
decomposition of 2 under the reaction conditions. Determin-
ation of the stereochemistry of 3 could not be achieved from
the spectroscopic data above; also, suitable crystals for X-ray
crystallographic analysis were not obtained for this compound.
Therefore, compound 3 was partially reduced by zinc in acetic
acid to give (1RS,7SR,2ЈRS,3ЈRS)-3Ј,9,9-trichlorospiro-,(1RS,
7SR,2ЈRS,3ЈSR)-3Ј,9,9-trichlorospiro-, and 9,9-dichlorospiro-
(bicyclo[5.2.0]nona-2,4-diene-8,2Ј-oxetan)-4Ј-ones 4, 5 and 6 in
40, 12 and 14% yield, respectively (Scheme 2). Suitable crystals
Fig. 1 ORTEP drawing of two independent molecules of 4 in the
crystalline state along with the numbering scheme. Thermal ellipsoids
are drawn at the 30% probability level. The two molecules exhibit slight
differences in their conformations.
Scheme 3
Scheme 2
for X-ray crystallographic analysis were obtained from the
major product 4. Thus, the relative structure of 4 was estab-
lished, as shown in Fig. 1. Consequently, the stereochemistry of
3 was elucidated as shown in Scheme 1.
Scheme 4
β-Lactones frequently show decarboxylation, e.g., the [2 ϩ 2]
cycloadduct obtained by the reaction of cyclopentanone with
dichloroketene exhibits decarboxylation even at 120–150 ЊC.11
However, 3 did not show any decarboxylation even on heating
to above 200 ЊC without any solvent. Instead of the decarboxyl-
ation reaction, 3 exhibited intramolecular [1,5] hydrogen-
migration in the seven-membered ring at above 115 ЊC to afford
3Ј,3Ј,9,9-tetrachlorospiro(bicyclo[5.2.0]nona-3,5-diene-8,2Ј-
oxetan)-4Ј-one 7. This rearrangement reached equilibrium in a
ratio of 3 : 7 = 1 : 4.5 at 200 ЊC after 7 h (Scheme 3).
2-Hydroxyazulene 912 was successfully synthesized by the
reaction of 8 with lithium chloride, lithium bromide and/or
lithium carbonate in DMF (Scheme 5). Table 2 displays the
The four-membered cyclobutanone ring of 2 could be
expanded regioselectively to give 1,1-dichloro-3,3a,4,8a-tetra-
hydroazulen-2(1H)-one 8 by the reaction with diazomethane in
85% yield (Scheme 4). The ring-expansion reaction would
become a key step for the synthesis of azulene derivatives using
the adduct 2, although 8 was relatively unstable even at room
temperature.
Scheme 5
results of the reaction of 8 with lithium reagents under several
conditions. Lithium reagents were essential for this reaction.
Heating of 8 alone in DMF for 18 h resulted in the formation
of 9 and 3-chloro-8,8a-dihydroazulen-2(1H)-one 10 in only
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Table 3 Dehydrochlorination of 8 under acidic and basic conditions
Conclusions
We have found that cycloheptatriene 1 reacts with dichloro-
ketene, generated by reaction of trichloroacetyl chloride with
zinc in diethyl ether, to give a [2 ϩ 2] cycloadduct 2, which
is utilized for the synthesis of several azulene derivatives,
i.e., 2-hydroxyazulene 9, 3-chloroazulene-1-carbaldehyde 11,
1-chloro-2-methylazulene 12 and N-(azulen-2-yl)pyrrolidine 13.
This is a new short-step strategy for the synthesis of azulene
derivatives starting from commercially available 1. Synthetic
application using this strategy for the synthesis of other azulene
derivatives is under study in our laboratory.
Entry
Conditions
Yield (%) of 15
1
2
3
4
5
1,4-Dioxane
0a
43
61
86
95
30% H2SO4–1,4-dioxane
5 M HCl–1,4-dioxane
DMSO
Et3N–THF
a Starting material 13 was recovered (41%).
2 and 21% yield, respectively (entry 1). The reaction of 8
with LiCl at 110–120 ЊC for 6 h gave the desired 9 in 73% yield
(entry 2). In the case of the reaction of 8 with LiCl–Li2CO3
or Li2CO3 in DMF, a prolonged reaction time was necessary
to complete the reaction (entries 3 and 4). Lithium bromide
also could serve as a reagent for this reaction (entry 5).
A plausible reaction pathway for the formation of 9 was
assumed to proceed via 10. Indeed the reaction of 10 with
LiCl under similar reaction conditions afforded 9 in 75%
yield. In the present method, 9 can be prepared in 3 steps
starting from the commercially available 1. Using the previously
reported method, 5 steps are necessary for the synthesis of
9 starting from commercially unavailable 2-substituted tropone
derivatives.12
Compound 10 was obtained by the reaction of 8 with tri-
ethylamine in THF at room temperature in almost quantitative
yield. The dehydrochlorination reaction also occurred either
under acidic conditions or in DMSO. The results of the reac-
tion under basic and acidic conditions are summarized in Table
3. Compound 10 was more stable than 8 and could be also
utilized for the synthesis of azulene derivatives. 3-Chloro-
azulene-1-carbaldehyde14 11 was obtained by the Vilsmeier
reaction of 10 in 54% yield. 1-Chloro-2-methylazulene 12 was
obtained by the reaction of 10 with methyllithium followed
by oxidation with p-chloranil in 31% yield. In addition,
N-(azulen-2-yl)pyrrolidine15 13 was obtained by the reaction of
10 with pyrrolidine in refluxing benzene in 47% yield together
with 9 (7%), which could be assumed to be an intermediate
of this reaction (Scheme 6). The reaction of 9 with pyrrol-
idine under similar reaction conditions also afforded 13, in 75%
yield.
Experimental
General
Mps were determined on a Yanagimoto micro melting-point
apparatus MP-S3 and are uncorrected. Mass spectra were
obtained with a JEOL HX-110 or a Hitachi M-2500 instrument
usually at 70 eV. IR and UV spectra were measured on a
Shimadzu FTIR-8100M and
a Hitachi U-3410 spectro-
photometer, respectively. H NMR (13C NMR) spectra were
recorded on a JEOL GSX 400 at 400 MHz (100 MHz), a JEOL
A500 at 500 MHz (125 MHz), a Bruker AM 600, or a JEOL
Lambda 600 spectrometer at 600 MHz (150 MHz). J-Values
are given in Hz. Gel-permeation chromatography (GPC)
was performed on a TSKgel G2000H6. Elemental analyses were
performed at the Instrumental Analysis Center of Chemistry,
Faculty of Science, Tohoku University.
1
9,9-Dichlorobicyclo[5.2.0]nona-2,4-dien-8-one 2. A solution
of trichloroacetyl chloride (22.0 g, 121 mmol) in dry diethyl
ether (200 cm3) was added dropwise at room temperature to a
mixture of activated zinc powder (11.6 g, 177 mg-atom) and 1
(5.54 g, 60.1 mmol) in the same solvent (200 cm3) over a period
of 2 h. After stirring of the mixture at the same temperature for
another 2 h, residual zinc powder was removed by filtration.
The filtrate was washed successively with water and 5% aq.
NaHCO3, dried over MgSO4, and concentrated under reduced
pressure. The residue was purified by molecular distillation at
90 ЊC (bath temp)/1.0 mmHg to afford 2 (7.04 g, 58%) as a pale
yellow oil and 3 (402 mg, 2%) as colorless crystals.
For 2: (Found: C, 53.1; H, 4.2. Calc. for C9H8Cl2O: C, 53.2;
H, 4.0%); λmax (MeOH)/nm 241 (log ε 3.66); νmax (neat)/cmϪ1
1809 (C᎐O); δ (600 MHz; CDCl3) 6.24 (dd, J 11.8 and 3.0,
᎐
H
2-H), 6.01 (m, 4-H and 5-H), 5.94 (ddt, J 11.8, 5.5 and 1.5,
3-H), 4.05 (ddd, J 12.4, 11.4 and 4.0, 7-H), 3.74 (dtd, J 11.4, 3.0
and 1.5, 1-H), 2.64 (dddd, J 13.9, 12.4, 5.9 and 2.2, 6-endo-H)
and 2.55 (ddd, J 13.9, 7.7 and 4.0, 6-exo-H); δC (150 MHz;
CDCl3) 196.0 (C-8), 131.5 (C-4 or C-5), 129.1 (C-2), 128.7
(C-3), 128.6 (C-5 or C-4), 91.2 (C-9), 66.0 (C-7), 51.2 (C-1) and
27.8 (C-6); m/z (EI) 201.9949 (Mϩ. C9H8Cl2O requires M,
201.9952), 139 (98%), 103 (100), 91 (70) and 51 (32).
For 3: mp 101–102 ЊC (Found: C, 42.2; H, 2.6; Cl, 45.2. Calc.
for C11H8Cl4O2: C, 42.1; H, 2.6; Cl, 45.2%); λmax (CH3CN)/nm
245 (log ε 3.65); νmax (KBr disk)/cmϪ1 1864 (C᎐O); δ (600
᎐
H
MHz; CDCl3) 6.27 (dd, J 11.0 and 2.6, 2-H), 6.15 (ddd, J 10.4,
7.9 and 5.5, 5-H), 5.99 (dddd, J 11.0, 4.3, 3.3 and 1.0, 3-H), 5.95
(dddd, J 10.4, 4.3, 2.3 and 0.5, 4-H), 4.23 (ddd, J 12.8, 10.2 and
5.9, 7-H), 3.61 (dddd, J 10.2, 3.3, 2.6 and 0.5, 1-H), 2.68 (tddd,
J 12.8, 5.5, 2.3 and 1.0, 6-endo-H) and 2.03 (ddd, J 12.8, 7.9 and
5.9, 6-exo-H); δC (150 MHz; CDCl3) 159.1 (C-4Ј), 130.8 (C-5),
130.5 (C-4), 129.1 (C-2 and C-3), 94.8 (C-8), 84.1 (C-9), 80.7
(C-3Ј), 54.7 (C-7), 52.9 (C-1) and 22.6 (C-6); m/z (EI) 312 (Mϩ,
6%) and 92 (100).
Partial reduction of 3. Zinc powder (660 mg, 10.1 mg-atom)
was added at room temperature to a solution of 3 (320 mg, 1.02
mmol) in acetic acid (10 cm3). After stirring of the mixture for
Scheme 6
J. Chem. Soc., Perkin Trans. 1, 2001, 2257–2261
2259

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1 min at the same temperature, residual zinc powder was
removed by filtration. The filtrate was washed successively with
water and 5% aq. NaHCO3, dried over MgSO4, and concen-
trated under reduced pressure. The residue was purified by
medium-pressure liquid chromatography on silica gel with ethyl
acetate–hexane (1 : 4) to afford 4 (114 mg, 40%) as colorless
prisms, 5 (36 mg, 12%) as colorless crystals, and 6 (36 mg, 14%)
as colorless crystals.
(MeOH)/nm 240 (log ε 3.82); νmax (KBr disk)/cmϪ1 1759 (C᎐O);
᎐
δH (600 MHz; CDCl3) 6.12 (ddd, J 5.9 and 2.5, 7-H), 6.03 (dd,
J 12.1 and 4.1, 8-H), 5.96 (m, 5-H and 6-H), 3.54 (m, 8a-H),
2.98 (m, 3a-H), 2.77 (dd, J 19.7 and 9.0, 3-endo-H), 2.65 (ddd,
J 15.2, 10.8 and 4.8, 4-endo-H), 2.50 (dd, J 19.7 and 6.2, 3-exo-
H) and 2.34 (ddd, J 15.2, 6.8 and 2.5, 4-exo-H); δC (150 MHz;
CDCl3) 201.6 (C-2), 132.5 (C-5), 129.0 (C-7), 127.2 (C-6 and
C-8), 87.0 (C-1), 56.6 (C-8a), 39.2 (C-3a), 38.7 (C-3) and 32.0
(C-4); m/z (EI) 216 (Mϩ, 27%), 180 (93), 152 (35), 138 (54), 117
(100) and 91 (48).
For 4: mp 97–98 ЊC (Found: C, 47.4; H, 3.5. Calc. for C11H9-
Cl3O2: C, 47.3; H, 3.25%); λmax (CH3CN)/nm 242 (log ε 3.72);
νmax (KBr disk)/cmϪ1 1862 (C᎐O); δ (500 MHz; CDCl3) 6.03
᎐
H
(m, 2-H, 3-H and 4-H), 5.91 (m, 5-H), 5.63 (s, 3Ј-H), 3.66 (ddd,
J 13.5, 10.0 and 3.5, 7-H), 3.54 (d, J 10.0, 1-H), 2.88 (tdd,
J 13.5, 4.5 and 2.5, 6-endo-H) and 2.30 (ddd, J 13.5, 8.0 and 3.5,
6-exo-H); δC (150 MHz; CDCl3) 161.5 (C-4Ј), 131.1 (C-4), 128.9
(C-2), 128.4 (C-5), 128.0 (C-3), 89.4 (C-8), 87.6 (C-9), 60.4
(C-3Ј), 52.7 (C-1), 47.1 (C-7) and 25.8 (C-6); m/z (EI) 278 (Mϩ,
13%) and 92 (100).
2-Hydroxyazulene 9. A solution of 8 (435 mg, 2.00 mmol) in
DMF (3 cm3) was added at 110–120 ЊC to a solution of lithium
chloride (856 mg, 20.2 mmol) in DMF (40 cm3). After stirring
of the mixture at the same temperature for 6 h, the reaction
mixture was poured into water. The resulting mixture was acid-
ified with 2 M hydrochloric acid and extracted with toluene.
The organic layer was dried over MgSO4 and concentrated
under reduced pressure. The residue was purified by column
chromatography on silica gel with ethyl acetate–hexane (1 : 4) to
afford 9 (211 mg, 73%) as red plates, mp 115–116 ЊC (lit.,12b
116–117 ЊC).
For 5: mp 57–58 ЊC (Found: C, 47.2; H, 3.3. Calc. for C11H9-
Cl3O2: C, 47.3; H, 3.25%); λmax (CH3CN)/nm 242 (log ε 3.80);
νmax (KBr disk)/cmϪ1 1844 (C᎐O); δ (500 MHz; CDCl3) 6.23
᎐
H
(dd, J 11.3 and 2.9, 2-H), 6.09 (ddd, J 10.5, 7.8 and 5.4, 5-H),
5.98 (ddd, J 11.3, 4.6 and 2.9, 3-H), 5.93 (ddd, J 10.5, 4.6 and
2.2, 4-H), 5.05 (s, 3Ј-H), 3.88 (ddd, J 13.5, 10.0 and 5.4, 7-H),
3.66 (d, J 10.0, 1-H), 2.78 (tdd, J 13.5, 5.4 and 2.2, 6-endo-H)
and 2.06 (ddd, J 13.5, 7.8 and 5.4, 6-exo-H); δC (150 MHz;
CDCl3) 162.2 (C-4Ј), 130.7 (C-4), 130.0 (C-2), 129.1 (C-5),
128.7 (C-3), 87.8 (C-8), 86.2 (C-9), 59.7 (C-3Ј), 54.5 (C-1), 54.4
(C-7) and 23.8 (C-6); m/z (EI) 278 (Mϩ, 0.9%) and 92 (100).
For 6: mp 101 ЊC (Found: C, 53.7; H, 4.1; Cl, 28.6. Calc. for
C11H10Cl2O2: C, 53.9; H, 4.1; Cl, 28.9%); λmax (CH3CN)/nm 242
(log ε 3.78); νmax (KBr disk)/cmϪ1 1883 (C᎐O); δ (600 MHz;
3-Chloro-8,8a-dihydroazulen-2(1H)-one 10. A solution of 8
(218 mg, 1.00 mmol) and triethylamine (209 mg, 2.07 mmol) in
THF (30 cm3) was stirred at room temperature for 9 h. The
precipitated ammonium salt was removed by filtration. The fil-
trate was concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel with CH2Cl2
to afford 10 (171 mg, 95%) as pale yellow needles, mp 76 ЊC
(Found: C, 66.3; H, 5.0; Cl, 19.9. Calc. for C10H9ClO: C, 66.5;
H, 5.0; Cl, 19.6%); λmax (MeOH)/nm 231 (log ε 4.00) and 333
᎐
H
CDCl3) 6.05 (dd, J 11.8 and 2.7, 2-H), 6.00 (ddd, J 11.8, 5.3 and
2.5, 3-H), 5.99 (ddd, J 10.2, 5.3 and 4.8, 4-H), 5.88 (m, 5-H),
4.09 (d, J 16.7, 3Ј-endo-H), 3.60 (ddd, J 9.8, 2.7 and 2.5, 1-H),
3.42 (d, J 16.7, 3Ј-exo-H), 3.31 (ddd, J 13.8, 9.8 and 3.6, 7-H),
2.91 (dddd, J 13.8, 13.8, 4.8 and 2.3, 6-endo-H) and 2.38 (ddd,
J 13.8, 8.3 and 3.6, 6-exo-H); δC (150 MHz; CDCl3) 164.6
(C-4Ј), 131.2 (C-2), 128.6 (C-3), 128.2 (C-4 and C-5), 90.8 (C-8),
82.7 (C-9), 52.5 (C-1), 52.0 (C-7), 47.0 (C-3Ј) and 26.5 (C-6);
m/z (EI) 244 (Mϩ, 9%), 139 (40), 103 (38) and 92 (100).
(4.17); νmax (KBr disk)/cmϪ1 1703 (C᎐O); δ (600 MHz; CDCl )
᎐
H
3
6.79 (d, J 11.6, 4-H), 6.42 (dd, J 11.6 and 7.2, 5-H), 6.26 (ddd,
J 11.6, 8.6 and 3.4, 7-H), 6.12 (ddd, J 11.6, 7.2 and 2.8, 6-H),
3.05 (dddd, J 13.5, 6.9, 3.7 and 2.5, 8a-H), 2.93 (dd, J 18.3 and
6.9, 1-endo-H), 2.64 (ddd, J 16.9, 8.6 and 2.5, 8-exo-H), 2.35
(ddd, J 16.9, 13.5 and 3.4, 8-endo-H) and 2.14 (dd, J 18.3 and
3.7, 1-exo-H); δC (150 MHz; CDCl3) 198.8 (C-2), 164.8 (C-3a),
136.6 (C-7), 135.6 (C-5), 129.2 (C-3), 126.9 (C-6), 123.4 (C-4),
40.7 (C-1), 36.9 (C-8a) and 33.4 (C-8); m/z (EI) 180 (Mϩ, 86%),
138 (57) and 117 (100).
3Ј,3Ј,9,9-Tetrachlorospiro(bicyclo[5.2.0]nona-3,5-diene-8,2Ј-
oxetan)-4Ј-one 7. Lactone 3 (238 mg, 0.758 mmol) was heated at
130 ЊC for 12 h under an N2 atmosphere. The reaction mixture
was chromatographed by a short column on Florisil® with
CH2Cl2 and purified by GPC with CHCl3 to afford 7 (153 mg,
64%) as colorless crystals and recovered 3 (24 mg, 10%).
3-Chloroazulene-1-carbaldehyde 11. Phosphoryl trichloride
(468 mg, 3.05 mmol) was added at room temperature to a solu-
tion of 10 (182 mg, 1.01 mmol) in DMF (10 cm3). The resulting
mixture was stirred at 90 ЊC for 3 h. The reaction mixture was
poured into water and extracted with toluene. The organic layer
was washed with water, dried over MgSO4, and concentrated
under reduced pressure. The residue was purified by column
chromatography on silica gel with ethyl acetate–hexane (1 : 4) to
afford 1114 (104 mg, 54%) as purple needles, mp 117–118 ЊC;
λmax (CH2Cl2)/nm 212 (log ε 4.25), 238 (4.28), 271 (4.09), 310
(4.51), 384 (3.92) and 549 (2.69); νmax (KBr disk)/cmϪ1 1655
For 7: mp 57 ЊC (Found: C, 42.1; H, 2.55; Cl, 45.2. Calc. for
C11H8Cl4O2: C, 42.1; H, 2.6; Cl, 45.2%); λmax (CH3CN)/nm 243
(log ε 3.77); νmax (KBr disk)/cmϪ1 1862 (C᎐O); δ (600 MHz;
᎐
H
CDCl3) 6.02 (ddd, J 11.8, 5.7 and 2.7, 5-H), 5.96 (ddd, J 10.6,
8.5 and 4.8, 3-H), 5.88 (ddt, J 10.6, 5.7 and 1.3, 4-H), 5.69 (dd,
J 11.8 and 3.3, 6-H), 4.20 (ddd, J 8.8, 3.3 and 2.7, 7-H), 3.39
(ddd, J 12.7, 8.8 and 3.9, 1-H), 2.58 (dddd, J 14.3, 12.7, 4.8 and
1.3, 2-endo-H) and 2.54 (ddd, J 14.3, 8.5 and 3.9, 2-exo-H);
δC (150 MHz; CDCl3) 159.4 (C-4Ј), 130.2 (C-5), 129.7 (C-3),
128.1 (C-4), 125.3 (C-6), 96.6 (C-8), 84.3 (C-9), 81.0 (C-3Ј), 59.8
(C-1), 44.2 (C-7) and 28.3 (C-2); m/z (EI) 312 (Mϩ, 16%) and 91
(100).
(C᎐O); δ (500 MHz; CDCl3) 10.28 (s, 1-CHO), 9.53 (d, J 9.8,
᎐
H
4-H), 8.57 (d, J 9.9, 8-H), 8.13 (s, 2-H), 7.90 (dd, J 10.1 and 9.6,
6-H), 7.62 (t, J 10.1 and 9.8, 5-H) and 7.59 (t, J 9.9 and 9.6,
7-H); δC (100 MHz; CDCl3) 185.5 (1-CHO), 141.1 (C-6), 139.5
(C-3a), 139.1 (C-2), 138.9 (C-8a), 138.3 (C-4), 136.8 (C-8),
129.9 (C-5), 128.4 (C-7), 123.5 (C-3) and 118.5 (C-1); m/z (EI)
190 (Mϩ, 90%) and 126 (43).
1,1-Dichloro-3,3a,4,8a-tetrahydroazulen-2(1H)-one 8. To a
solution of 2 (938 mg, 4.62 mmol) in methanol (3 cm3) and
diethyl ether (30 cm3) was added a solution of diazomethane
(12 mmol) in the same solvent (12 cm3) at room temperature.
After stirring of the mixture for 30 min, the solvent was
removed under reduced pressure. The residue was purified by
column chromatography on silica gel with CH2Cl2 to afford 8
(856 mg, 85%) as colorless crystals, mp 49–50 ЊC (Found: C,
55.4; H, 4.5. Calc. for C10H10Cl2O: C, 55.3; H, 4.6%); λmax
1-Chloro-2-methylazulene 12. A solution of methyllithium in
diethyl ether (2.0 cm3, 2.2 mmol) was added at Ϫ78 ЊC under an
N2 atmosphere to a solution of 10 (182 mg, 1.01 mmol) in THF
(30 cm3) over a period of 5 min. After stirring of the mixture at
the same temperature for 4 h, the mixture was warmed to room
temperature and stirred for another 30 min. The reaction mix-
ture was poured into water and extracted with diethyl ether. The
organic layer was washed with water, dried over MgSO4, and
2260
J. Chem. Soc., Perkin Trans. 1, 2001, 2257–2261

View Article Online
concentrated under reduced pressure. p-Chloranil (748 mg, 3.04
mmol) and CH2Cl2 (30 cm3) were added to the residue, and the
mixture was refluxed for 3 h. The solvent was removed under
reduced pressure, and the residue was purified by column
chromatography on silica gel with CH2Cl2 to afford 12 (55 mg,
31%) as blue needles, mp 61 ЊC (Found: C, 74.6; H, 5.3; Cl, 20.2.
Calc. for C11H9Cl: C, 74.8; H, 5.1; Cl, 20.1%); λmax (CH2Cl2)/nm
284 (log ε 4.60), 290 (4.62), 352 (3.57) and 588 (2.25); νmax (KBr
disk)/cmϪ1 1576, 1495, 1401, 1051, 871 and 731; δ (400 MHz;
CDCl3) 8.23 (d, J 9.8, 8-H), 8.21 (d, J 9.3, 4-H), 7.54 (dd, J 10.2
and 9.3, 6-H), 7.19 (dd, J 9.8 and 9.3, 7-H), 7.17 (s, 3-H), 7.14
(dd, J 10.2 and 9.3, 5-H) and 2.62 (s, 2-Me); δC (100 MHz;
CDCl3) 145.9 (C-2), 138.5 (C-3a), 136.9 (C-6), 135.2 (C-4),
133.7 (C-8a), 132.3 (C-8), 123.5 (C-5), 123.0 (C-7), 116.4 (C-1),
115.9 (C-3) and 14.6 (2-Me); m/z (EI) 176 (Mϩ, 100%) and 141
(45).
tions = 5258 (Rint = 0.028). Final R = 0.041, Rw = 0.042 for 2442
observed reflections [I0 > 2σ(I0)]. Parameters = 289. GOF =
0.94. ∆ρmax and ∆ρmin are 0.21 and Ϫ0.22 e ÅϪ3, respectively.
Refinement method: full-matrix least-squares. All calculations
were performed using software package of Molecular Structure
Corporation (Crystal Structure Analysis Package, Molecular
Structure Corporation, 1985 and 1999).
References
1 K.-P. Zeller, in Houben-Weyl, Methoden der Organischen Chemie,
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N-(Azulen-2-yl)pyrrolidine 13. A solution of 9 (76 mg, 0.53
mmol) and pyrrolidine (80 mg, 1.1 mmol) in benzene (30 cm3)
was refluxed for 12 h. The solvent was removed under reduced
pressure, and the residue was purified by column chromato-
graphy on silica gel with CH2Cl2 to afford 13 (77 mg, 75%) as an
orange powder, mp 117–118 ЊC (lit.,15 114–115 ЊC).
X-Ray crystallographic data for 4†. Data and diffraction
parameters were obtained for a crystal with dimension 0.05 ×
0.10 × 0.20 mm using a Rigaku/MSC mercury CCD diffract-
ometer with Mo-Kα radiation (λ = 0.710 69 Å) at 20 ЊC. Crystal
system: monoclinic. Space group: P21/a. Unit-cell dimensions:
a = 9.751(1), b = 18.486(1), c = 14.7287(6) Å, β = 115.7591(4)Њ,
V = 2391.1(3) Å3, Z = 8. Dcalc = 1.553 g cmϪ3; µ (Mo-Kα) = 7.45
cmϪ1; F (000) = 1136. 2θ-Range for data collection = 0.0–55.0Њ.
Number of measured reflections = 20 686. Independent reflec-
12 (a) T. Nozoe, K. Takase and N. Shimazaki, Bull. Chem. Soc. Jpn.,
1964, 37, 1644; (b) K. Takase, T. Asao and T. Nozoe, Chem.
Commun., 1968, 368.
13 N. Morita, M. Kudo, R. Yokoyama and S. Ito, Heterocycles, 2001,
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14 V. A. Nefedov, Zh. Org. Khim., 1973, 9, 783 (Chem. Abstr., 1973, 79,
418486).
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† CCDC reference number(s) 164081. See http://www.rsc.org/suppdata/
p1/b1/b104164a/ for crystallographic files in .cif or other electronic
format.
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