Synthesis, molecular structure, and chemical reactivity of azuleno[1,2-a]acenaphthylene

Article abstract of DOI:10.1016/S0040-4020(02)01614-9

The azuleno[1,2-a]acenaphthylene (1a) was prepared from 1-pyrrolidinylacenaphthylene (5) and 2H-cyclohepta[b]furan-2-one (6) by the method of the Takase-Yasunami azulene synthesis. Its ¹H and ¹³C NMR spectra indicate that 1a comprises azulene and naphthalene rather than acenaphtylene and heptafulvene in accordance with speculation drawn from a previous study of the DEPE calculations. The solid-state structure of 1a was elucidated by X-ray crystallographical analysis, indicating that 1a is nearly planar and exhibits little bond alternation as seen in the optimized structure at the MB3LYP/6-311G* level of theory. All bond lengths observed by the X-ray analysis are in good agreement within 0.024? with those calculated. Under pyrolytic conditions 1a underwent azulene-naphthalene rearrangement to give 9 and 10. The electrophilic substitution of 1a was observed at the 7-position and the second reaction at the 3-position. The cycloaddition reaction of 1a with dimethyl acetylenedicarboxylate (DMAD) yielded the 1:1 cycloadduct with a heptalene skeleton 16a and the 1:2 cycloadduct 19, along with the substitution product 17. The X-ray structural analysis of the cycloadducts 16a and 19 is also described.

Full text of DOI:10.1016/S0040-4020(02)01614-9

Tetrahedron 59 (2003) 801–811
Synthesis, molecular structure, and chemical reactivity of
azuleno[1,2-a]acenaphthylene
*
Masaru Mouri, Shigeyasu Kuroda, Mitsunori Oda, Ryuta Miyatake and Mayumi Kyogoku
Department of Applied Chemistry, Faculty of Engineering, Toyama University, Gofuku 3190, Toyama 930-8555, Japan
Received 17 October 2002; accepted 9 December 2002
Abstract—The azuleno[1,2-a]acenaphthylene (1a) was prepared from 1-pyrrolidinylacenaphthylene (5) and 2H-cyclohepta[b]furan-2-one
(6) by the method of the Takase–Yasunami azulene synthesis. Its 1H and 13C NMR spectra indicate that 1a comprises azulene and
naphthalene rather than acenaphtylene and heptafulvene in accordance with speculation drawn from a previous study of the DEPE
calculations. The solid-state structure of 1a was elucidated by X-ray crystallographical analysis, indicating that 1a is nearly planar and
exhibits little bond alternation as seen in the optimized structure at the MB3LYP/6-311Gp level of theory. All bond lengths observed by the
˚
X-ray analysis are in good agreement within 0.024 A with those calculated. Under pyrolytic conditions 1a underwent azulene–naphthalene
rearrangement to give 9 and 10. The electrophilic substitution of 1a was observed at the 7-position and the second reaction at the 3-position.
The cycloaddition reaction of 1a with dimethyl acetylenedicarboxylate (DMAD) yielded the 1:1 cycloadduct with a heptalene skeleton 16a
and the 1:2 cycloadduct 19, along with the substitution product 17. The X-ray structural analysis of the cycloadducts 16a and 19 is also
described. q 2003 Elsevier Science Ltd. All rights reserved.
1. Introduction
fulvene and acenaphthylene, shown by two broken lines in
Figure 1. DEPEs (Delocalization Energy per p-electron) are
previously calculated to be 0.023 for azulene, 0.055 for
naphthalene, 20.002 for heptafulvene, and 0.039 for
acanaphthylene,6 suggesting that the contribution of the
composition of azulene and naphthalene is preferred for 1a.
In order to clarify structural details of the 1,2-a isomer by
X-ray crystallographical analysis and also its chemical
behavior, we achieved a short-step synthesis of the non-
substituted hydrocarbon 1a. Herein we wish to give a full
account of the synthesis, the X-ray analysis, and some
reactions of 1a.
Fusion of azulene at the 1,2-positions of acenaphthylene
produces three 1,2-a, 4,5-a, and 5,6-a isomers, 1a1, 22, and
3. Among them, the tetrasubstituted derivative of 1,2-a
isomer 1b3, and the non-substituted 4,5-a isomer 2 have
been synthesized. Also, two aza-derivatives of 1,2-a and
5,6-a isomers, acenaphtho[1,2-b]cyclohepta[d]pyrrole4 and
acenaphtho[1,2-b]cyclohepta[e]azepine5, have appeared in
the literature. The 1,2-a isomer 1a can be recognized by two
ways of fusion of two segments of hydrocarbons, i.e. it
consists either of azulene and naphthalene or of hepta
Figure 1.
Keywords: azuleno[12-a]acenaphthylene; delocalization; X-Ray; electrophilic substitution; cycloaddition.
*
Corresponding author. Tel. & Fax: þ81-76-445-6819; e-mail: kuro@eng.toyama-u.ac.jp
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)01614-9

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M. Mouri et al. / Tetrahedron 59 (2003) 801–811
Scheme 1. Synthesis of 1a.
2. Results and discussions
2.2. Spectroscopic properties
1
2.1. Synthesis
The H- and 13C NMR spectra of 1a in CDCl3 show 12
proton signals and 20 carbon signals sufficient for the
structure of 1a. These signals were completely assigned
based on the H–H COSY, HMQC, HMBC, and NOEDF
spectra. The results are shown in Figures 2 and 3.
Especially, NOE enhancement (7.5%) between H-1 and
H-12, and correlation of the C-3b with any hydrogen in the
HMBC spectrum were important for the assignment. All
proton signals appear in the aromatic region between 7.05
and 8.50 ppm. The average of chemical shifts of all ring
protons of 1a is d7–12 7.61 ppm for the azulene moiety and
Takase and Yasunami developed a useful method for
synthesizing azulenes from enamines and 2H-cyclo-
hepta[b]furan-2-ones.7 We accomplished the synthesis of
1a from 5 according to their method. Although the enamine
5 was previously prepared by the reaction of acenaphthen-1-
one (4) with pyrrolidine in refluxing benzene in high yield, it
required a long reaction time and distillation for isolation.8
We found that 5 can be prepared more conveniently using
Zeolumw as a solid catalyst. After the mixture was stirred at
room temperature for 12 h, filtration to remove the solid
catalyst and evaporation of the filtrate gave a quantitative
yield of enamine 5. The reaction of 5 with 2H-cyclo-
hepta[b]furan-2-one (6) in xylene at reflux for 4 h gave 1a as
dark green needles in 70% yield (Scheme 1). The crystals of
1a are very stable and can be stored at room temperature for
at least a year without any change. However, a solution of
1a in halogenated solvents showed gradual decomposition.
d
1–6 7.70 ppm for the naphthalene moiety. These values are
nearly equal to those of the parent azulene (av. 7.61 ppm)
and naphthalene (av. 7.63 ppm), respectively. The differ-
3
ence in JH–H coupling constants of the azulenyl protons
is small (less than 0.7 Hz), indicating the less bond
alternation in the azulene moiety compared with that of
benz[a]azulene (maximum 2.9 Hz)9 which exhibits clear
bond alternation.
Figure 2. The assigned proton and carbon chemical shifts and coupling constants of 1a.
Figure 3. Correlation in the NOEDF (left) and HMBC (right) spectra of 1a.

M. Mouri et al. / Tetrahedron 59 (2003) 801–811
803
Figure 4. ORTEP drawing and perspective view of the packing of 1a.
2.3. The X-ray crystallographical analysis and
computational studies
of theory. This structure shows complete planarity and the
bond lengths are slightly longer than those of the X-ray
structure except the C3a–C4, C3b–C6a, C7a–C8 and
C12b–C12c bonds (Fig. 6). It is noteworthy that the bond
lengths are in good agreement with those of the structure
revealed by X-ray crystallographical analysis. Although the
largest difference between them (0.024 A) is for the C9–
C10 bond observed at the molecular edge, other differences
˚
are less than 0.016 A.
The solid-state structure of 1a was further elucidated by
X-ray crystallographical analysis. Suitable green mono-
clinic crystals of 1a for the analysis were obtained by
recrystallization from a mixture of hexane and dichloro-
methane. The ORTEP drawing and perspecive view of
packing of 1a are shown in Figure 4. It showed that the
molecule is nearly planar and maximum distance of the
˚
˚
carbon atoms from the mean plane is 0.066 A at the C-4
2.4. Thermal rearrangement
carbon atom (Fig. 5). In a unit cell four molecules of 1a
exist. They are piled in such a way that the dipole of the
azulene moiety of the molecule rules out each other. The
The thermal rearrangement of azulene to naphthalene under
thermolytic conditions has been well studied and is usually
observed at 300–4008C.12 Flash thermolysis of 1a under
nitrogen stream below 4008C gave a quantitative recovery
and the reaction at 6008C provided a mixture of benz[j]-
fluoranthene (9) (28%) and benz[k]fluoranthene (10) (14%),
accompanied with a 58% recovery of 1a. The transform-
ation from 1a into 9 and 10 probably proceeds via the
norcaradiene forms 7a and 7b, as claimed by Wentrup13
(Scheme 2). Reluctance to the rearrangement of 1a
compared with azulenes may be probably attributed to the
acenaphthyl annulation which relatively stabilizes the
azulene moiety mainly by electronic effect and destabilizes
their norcaradiene valence isomers by increasing the
angular strain much more in 7 than in the corresponding
isomer of azulene itself.
˚
minimum non-bonded atomic distance is 3.427 A between
the C-9 atom and the C-12c atom of another molecule. The
difference in the bond lengths of the seven-membered ring is
very small, suggesting that there is little bond alternation in
the azulene moiety. Also, the bond lengths of the azulene
and naphthalene moieties of 1a are nearly equal to those of
the parent azulene,10and naphthalene,11 respectively.
Furthermore, the C6a–C6b and C12b–C12c bonds are
˚
1.457 and 1.463 A long, respectively, which are longer than
of all other C–C bonds. Thus, it is also indicated that 1a
consists of azulene and naphthalene. The Tables of
fractional atomic coordinates and thermal parameters have
been deposited at the Cambridge Crystallographic Data
Center. 12 Union Road, Cambridge CB2 1EZ, United
Kingdom (CCDC 189847). The optimized structure of 1a
was obtained by calculations at the MB3LYP/6-311Gp level
2.5. The electrophilic substitution
The reaction of 1a with bromine in the presence of
triethylamine in dichloromethane exclusively gave the
7-bromo derivative 11 as green needles in 96% yield
(Scheme 3). On the other hand, the reaction of 1a with
triethyl orthoformate in the presence of boron trifluoride
diethyl etherate14 also gave the 7-substituted product 13 as
green needles in 84% yield. When the reaction was carried
out by the typical Vilsmeier method using dimethyforma-
mide (DMF) and phosphorus oxychroride (POCl3), 13 was
obtained in only 3% yield accompanied with a considerable
˚
Figure 5. Distances (A) of the carbon atoms from the mean right plane of
1a.

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M. Mouri et al. / Tetrahedron 59 (2003) 801–811
p
˚
Figure 6. C–C bond distances (A) of 1a, azulene and napthalene by X-ray crystallographical analysis, and 1a optimized by the MB3LYP/6-311G
calculations. Parenthesis are difference between the crystal and calculated structures.
Scheme 2. The thermal rearrangement of 1a.

M. Mouri et al. / Tetrahedron 59 (2003) 801–811
805
Scheme 3. The electrophilic substitution of 1a.
observed in the region of 7.62–8.51 ppm, while those of the
7-fomyl derivative 13 resonate at slightly lower field. The
average (8.23 ppm) of the ring proton shifts of 13 is ca.
0.5 ppm more than those of the others. Their UV–vis
spectra of 1a, 2, 11 and 13 are shown in Chart 1. These
spectra exhibit three similar main bands except for 7-formyl
derivative 13 whose longest absorption (878 nm) shows a
bathochromic shift by ca. 70–100 nm. The longer absorp-
tion maximum and the low field shift of the ring proton of 13
compared to those of others can be attributed to the effect of
the strong electron-withdrawing nature of a formyl group.
The electrophilic substitution of 1a revealed greater
reactivity at the azulene moiety than at the naphthalene
moiety, and that the reaction position of each moiety is the
same as that observed usually in azulene or naphthalene
itself; it is as if two independent molecules of azulene and
naphthalene themselves existed in the molecule of 1a.
Figure 7. Molecular orbital drawings of the HOMOs of 1a and 11
calculated by the PM3 method.
amount of an unidentified complex mixture. The high
reactivity at the 7-position of 1a can be explained by the
highest coefficient at this position except the quaternary
carbons in its HOMO calculated by the PM3 method as we
have already discussed in the protonation of 1a.15
Furthermore, we found that bromination of 11 occurred
exclusively at the 3-position to give 3,7-dibromo derivative
12 in 94% yield (Fig. 7). While the coefficients at 1-, 3-, and
11-positions in the HOMO of 11 are nearly equal, calculated
heats of formation of the protonated species predict that the
11Hþc is the most stable intermediate among them (Fig. 8).
The structures of 11–13 were confirmed by the spectral and
analytical data. The ring protons of 1a, 11 and 12 were
2.6. Cycloaddition reaction
Hafner first reported that the periselective cycloaddition
reactions of the azulenes with dimethyl acethylene-
dicarboxylate (DMAD) gave the heptalene derivatives.16
Later, Hansen studied the reaction in polar media and in the
presence of a Lewis acid catalyst.17 As shown in the
electrophilic reaction, we can expect that cycloaddition of
1a will proceed at the azulene part. Indeed, the reaction of
1a with DMAD in refluxing xylene gave the 1:1 cycloadduct
16a, the 1:2 cycloadduct 19 with two molecules of DMAD
Figure 8. The heats of formation of 11Hþa, 11Hþb, and 11Hþc calculated by the PM3 method.

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M. Mouri et al. / Tetrahedron 59 (2003) 801–811
Chart 1. UV–vis absorption spectra of 1a, 2, 11 and 13 in CH2Cl2.
and the E-isomer of 7-substituted compound 17 in 26, 3, and
6% yields, respectively (Scheme 4). The reaction under
similar conditions in the presence of CF3CO2H16 gave a 1:1
mixture of E- and Z- 7-substituted products 17 and 20 in
60% yield without any cycloadducts.18 The structures of
16a, 17, 19 and 20 were supported by the spectral and
analytical data except the stereochemical configuration of
19. The proton signals of the heptalene moiety of 16a except
those for H-7 (8.19 ppm) appear at the olefinic region
itself and DMAD, reported by Hafner.16 This anomalous
bending of the heptalene ring in 16a may be owing to steric
repulsion between the hydrogens at the 14-position of
heptalene and at the 1-position of the naphthalene. Also,
difference in average bond lengths of the heptalene ring is
˚
observed to be ca. 0.1 A in the crystal molecules, that
indicates the localization of the double bond as shown in the
structure of 16a depicted in Scheme 4. The structure of 19
was also elucidated by X-ray crystallographic analysis. The
ORTEP drawing of 19 is shown in Figure 10. It was
revealed that two DMAD molecules are added to the surface
of the azulene ring with anti stereochemical configuration.
One of the methyl signals of four methoxycarbony groups in
1H NMR of 19 appears at 2.63 ppm, while the others appear
at 3.59, 3.76 and 3.77 ppm. In the X-ray structure of 19 one
methyl group was found to locate on the naphthalene ring
3
between 5.86 and 6.62 ppm. The JH–H coupling constants
of H10–H11 and H13–H14 are 10.7 and 6.6 Hz, respect-
ively. Thus, the difference between them is large enough to
conclude that clear double bond fixation exists in the
pentalene part of 1a. The structure of 16a is further
confirmed by X-ray crystallographical analysis. The
ORTEP drawing of 16a is shown in Figure 9. There are
two independent molecules in the crystal of 16a with a
slight difference in the bond lengths and torsion angles. It is
noteworthy that one (from C-9a to C-14a via C-12) of the
seven-membered rings in 16a surprisingly bends over the
surface of the acenaphthylene ring with a large interplanar
angle of 65.38 (average of the two molecules in the crystal)
between the least-squares planes of those ring. This
interplanar angle is far greater than that observed at the
corresponding position in the cycloadduct between azulene
˚
with the non-bonded atomic distance of 3.800 A between
this methyl and the C-15 carbons. That accounts for the high
1
field shift of one of the methyl groups in the H NMR
spectrum of 19. The Tables of fractional atomic coordinates
and thermal parameters have been deposited at the
Cambridge Crystallographic Data Center. 12 Union Road,
Cambridge CB2 1EZ, United Kingdom (16a: CCDC
194348, 19: CCDC 194347). The plausible reaction
mechanisms of the formation of the products, 16a, 17 and

M. Mouri et al. / Tetrahedron 59 (2003) 801–811
807
Scheme 4. The reactions of 1a with DMAD.
19, are shown in Scheme 4. As has been pointed out by
Hafner16 and Hansen,17 16a presumably forms via a dipolar
intermediate 14 and the [2þ2] cycloadduct 15 stepwise. The
former intermediate may also account for the formation of
17 by its proton transfer in either inter- or intramolecular
way, though the geometrical selectivity forming only the
E-isomer has not been clarified yet. The 1:2 adduct 19 can
form via either the 1:1 adduct 18 or 21. Calculations at the
PM3 level of theory predict that 21 should be disfavored
relative to 18 by ca. 23 kcal/mol (Fig. 11). Although a
double bond shift of the heptalenes has been reported to
occur with heats of activation enthalpy of 14.7 kJ/mol,19
16a was found to be reluctant to that even in refluxing
decaline. The large bending of the heptalene ring in 16a
Figure 9. ORTEP drawing of one of two independent molecules in the crystal of 16a (left). The drawings of the two in the crystal (right).

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M. Mouri et al. / Tetrahedron 59 (2003) 801–811
MULLIKEN (ver. 2.0.0, 1995, IBM Co.) on an IBM
RS/6000-397 computer.
4.1.1. 1-Pyrrolidinylacenaphthylene (5). To a solution of
1.00 g (5.95 mmol) of acenaphthen-1-one (4) in 10 mL of
dry benzene was added 1.27 g (17.9 mmol) of pyrrolidine in
the presence of 1.00 g of Zeolumw at room temperature.
After being stirred at rt for 12 h the reaction mixture was
filtered, and the solids are washed with 5 mL of dry benzene
three times. The combined filtrate was concentrated to
dryness to give 1.29 g (100%) of dark reddish oil of 5. This
oil was used in the next reaction without further purification.
1H NMR (CDCl3–TMS) d¼2.03 (m, 4H), 3.68 (m, 4H),
5.37 (s, 1H), 7.11 (d, J¼6.8 Hz, 1H), 7.35 (dd, J¼8.1,
6.8 Hz, 1H), 7.36 (d, J¼8.1 Hz, 1H), 7.52 (dd, J¼8.1,
6.8 Hz, 1H), 7.78 (d, J¼8.1 Hz, 1H), 7.81 (d, J¼6.8 Hz,
1H): 13C NMR (CDCl3–TMS) d¼151.9, 143.1, 136.6,
129.6, 129.2, 128.8, 128.7, 127.7, 124.9, 121.3, 117.5, 93.7,
50.9, 26.3.
Figure 10. ORTEP drawing of 19.
4.1.2. Azuleno[1,2-a]acenaphthylne (1a). To a solution of
1.20 g (5.43 mmol) of 5 in 5 mL of dry xylene was added
0.79 g (5.43 mmol) of 2H-cyclohepta[b]furan-2-one (6).
After being refluxed for 4 h, the reaction mixture was cooled
to room temperature. Then, this mixture was directly
chromatographed on silica gel with hexane as eluent to
give 1.26 g (70%) of 1a. Dark green needles, mp 155–
1568C, IR (KBr) nmax 3040w, 1609w, 1563m, 1393m, 830s,
772s, 736m, 716s cm21: H NMR (CDCl3–TMS) d¼7.05
1
Figure 11. The heats of formation of 18 and 21 calculated by the PM3
method.
(dd, J¼10.0, 9.3 Hz, 1H, H-9),7.08 (t, J¼10.0 Hz, 1H,
H-11), 7.40 (t, J¼10.0 Hz, 1H, H-10), 7.47 (s, 1H, H-7),
7.54 (dd, J¼8.1, 6.8 Hz, 1H, H-5), 7.55 (dd, J¼8.1, 6.8 Hz,
1H, H-2), 7.61 (d, J¼8.1 Hz, 1H, H-3), 7.75 (d, J¼8.1 Hz,
1H, H-4), 7.85 (d, J¼6.8 Hz, 1H, H-1), 7.89 (d, J¼6.8 Hz,
1H, H-6), 8.13 (d, J¼9.3 Hz, 1H, H-8), 8.50 (d, J¼10.0 Hz,
1H, H-12): 13C NMR (CDCl3–TMS) d¼153.8, 148.9,
139.4, 136.4, 136.4, 134.8, 133.9, 133.6, 132.7, 130.9,
130.6, 128.3, 127.8, 127.5, 124.5, 124.1, 123.8, 122.2,
118.9, 109.9: UV–vis (CH2Cl2) lmax 223 (log 1¼4.41)
(nm), 288 (4.33), 310 (4.44), 340 (4.66), 353 (4.62), 404
(3.92), 427sh (3.76), 454sh (3.26), 625 (2.29), 675 (2.78),
740sh (2.41): MS m/z (70 eV) 252 (Mþ, 100), 126 (12.5):
HRMS: found: m/z 252.0943. Calcd for C20H12: 252.0938.
Anal. found: C, 95.26; H, 4.96. Calcd for C20H12: C, 95.21;
H, 4.79.
might be one reason for this reluctance fact. Thus, 16a
behaves as if it comprised vinylheptafulvene and
acenaphthylene rather than heptalene and naphthalene.
3. Conclusion
We have synthesized azuleno[1,2-a]acenaphtylene (1a)
with enamine 5 and 2H-cyclohepta[b]furan-2-one (6) by
method of the Takase–Yasunami azulene synthesis. The
spectral data and X-ray crystallographical analysis
strengthen the conclusion that 1a consists of azulene and
naphthalene rather than acenaphtylene and heptafulvene in
accordance with speculation drawn from the DEPE
calculations. Also, electrophiric reactions of 1a show
reactivities of both azulene and naphthalene. The cyclo-
addition of 1a with DMAD provided the adducts 16a and
19, whose solid-state structures were also elucidated.
4.2. The thermal rearrangement of 1a
A solution of 0.10 g (0.40 mmol) of 1a in 10 mL of benzene
was passed through a hot quarts tube (1.5 mmf£260 mm) at
a rate of 120 mL/min at 6008C and the pyrolysate was
trapped by cold traps at temperature of liquid nitrogen. The
pyrolysate was chromatographed on silica gel with 5%
benzene–hexane as eluent to give 0.028 g (28%) of 9,
0.014 g (14%) of 10, and 0.058 g (58%) of 1a. Compound 9:
pale yellow needles, benz[j]fluoranthene CAS registry
number 205-82-3. Compound 10: pale yellow needles,
benz[k]fluoranthene, CAS registry number 207-08-9.
4. Experimental
4.1. General
Melting points were measured on a Yanako MP-3 and are
uncorrected. IR spectra were recorded on a Perkin–Elmer
Spectrum RX I spectrometer. UV spectra were measured on
1
a Shimadzu UV-1600 spectrometer. H NMR (400 MHz)
and 13C NMR (100 MHz) were recorded with tetramethyl-
silane as an internal standard on a JEOL a400. Mass spectra
were measured on a JEOL GC-Mate mass spectrometer. The
density functional calculations were done by using the
4.2.1. 7-Bromoazuleno[1,2-a]acenaphthylne (11).
A
solution of 0.12 g (0.78 mmol) of Br2 in 5 mL of CH2Cl2
was added dropwise to a solution of 0.20 g (0.79 mmol) of
1a in 20 mL of CH2Cl2 in the presence of 0.08 g

M. Mouri et al. / Tetrahedron 59 (2003) 801–811
809
(0.78 mmol) of triethylamine at 58C in a time period of
10 min. After being stirred at room temperature for 2 h, the
reaction mixture was poured into 20 mL of water and
extracted with CH2Cl2 (10 mL£2). The combined organic
layer was washed with water and brine, and then was dried
with MgSO4. After evaporation of the solvent, the residue
was chromatographed on silica gel with 30% benzene–
hexane as eluent to give 0.26 g (96%) of 11. Dark green
needles, mp 178–1798C, IR (KBr) nmax 3050w, 1570m,
1480m, 1410m, 1380m, 1280m, 800m, 770s, 738m,
mixture was cooled to room temperature. Then, the reaction
mixture was poured into 20 mL of water and extracted with
CH2Cl2 (10 mL£2). The combined organic layer was
washed with aq. NaHCO3 and brine, and then was dried
with MgSO4. After evaporation of the solvent, the residue
was chromatographed on silica gel with CHCl3 as eluent to
give 0.007 g (3%) of 13.
4.2.4. Compound 13 with triethyl orthoformate in the
presence of boron trifluoride diethyl etherate. A solution
of 0.12 g (0.79 mmol) of triethyl orthoformate in 5 mL of
CH2Cl2 was added dropwise to a solution of 0.20 g
(0.79 mmol) of 1a in 20 mL of CH2Cl2 in the presence of
0.10 mL (0.79 mmol) of boron trifluoride diethyl etherate at
58C. After being stirred at room temperature for 1 h, the
reaction mixture was poured into 20 mL of water and
extracted with CH2Cl2 (10 mL£2). The combined organic
layer was washed with aq. NaHCO3 and brine, and then was
dried with MgSO4. After evaporation of the solvent, the
residue was chromatographed on silica gel with CHCl3 as
eluent to give 0.22 g (84%) of 13. Dark green needles, mp
179–1808C, IR (KBr) nmax 3040w, 2950w, 1600s, 1420m,
712m cm21
:
1H NMR (CDCl3–TMS) d¼7.16 (t,
J¼9.8 Hz, 1H, H-11), 7.20 (ddm, J¼10.0, 9.8 Hz, 1H,
H-9), 7.50 (t, J¼9.8 Hz, 1H, H-10), 7.60 (dd, J¼8.1, 6.8 Hz,
1H, H-2), 7.65 (dd, J¼8.1, 6.8 Hz, 1H, H-5), 7.69 (d,
J¼8.1 Hz, 1H, H-3), 7.85 (d, J¼8.1 Hz, 1H, H-4), 7.91 (d,
J¼6.8 Hz, 1H, H-1), 8.23 (dd, J¼10.0, 0.7 Hz, 1H, H-8),
8.24 (d, J¼6.8 Hz, 1H, H-6), 8.51 (d, J¼9.8 Hz, 1H, H-12):
13C NMR (CDCl3–TMS) d¼151.4, 143.7, 138.7, 137.8,
136.4, 134.2, 133.9, 132.6, 131.5, 130.7, 130.5, 128.4,
128.2, 128.0, 124.7, 124.6, 124.4, 122.9, 119.4, 97.6:
UV/vis (CH2Cl2) lmax 236 (log 1¼4.39) (nm), 263 (4.31),
342 (4.60), 428sh (3.77), 455sh (3.30), 643 (2.81), 696
(2.82): MS m/z (70 eV) 330, 332 (Mþ, 99.8, 100), 250
(Mþ2HBr, 59.7), 125 (38.0): HRMS: found: m/z 330.0049,
332.0024. Calcd for C20H11Br: 330.0044, 332.0024. Anal.
found: C, 72.27; H, 3.35. Calcd for C20H11Br: C, 72.53; H,
3.35.
1290m, 1080m, 830s, 520s cm21 1H NMR (d-DMSO-
:
TMS) d¼7.70 (dd, J¼10.3, 9.8 Hz, 1H, H-9), 7.73 (dd,
J¼9.8, 9.3 Hz, 1H, H-11), 7.75 (dd, J¼8.1, 6.8 Hz, 1H,
H-2), 7.82 (dd, J¼8.1, 6.8 Hz, 1H, H-5), 7.94 (d, J¼8.1 Hz,
1H, H-3), 7.97 (t, J¼9.8 Hz, 1H, H-10), 8.11 (d, J¼8.1 Hz,
1H, H-4), 8.37 (d, J¼6.8 Hz, 1H, H-1), 8.74 (d, J¼6.8 Hz,
1H, H-6), 9.10 (d, J¼9.3 Hz, 1H, H-12), 9.35 (d,
J¼10.3 Hz, 1H, H-8), 10.85 (s, –CHO): 13C NMR
(d-DMSO-TMS) d¼184.6, 153.5, 148.3, 139.7, 137.4,
136.3, 136.0, 134.4, 132.5, 132.0, 129.8, 129.8, 129.6,
129.6, 128.5, 128.4, 126.8, 125.7, 125.6, 121.3, 118.9:
UV/vis (CH2Cl2) lmax 239 (log 1¼4.51) (nm), 269 (4.31),
352 (4.68), 376 (4.74), 418sh (3.95), 583 (2.74), 624 (2.72),
776 (2.01), 833 (2.03), 866sh (1.64), 878sh (1.31): MS m/z
(70 eV) 280 (Mþ, 100), 250 (47.8): HRMS: found: m/z
280.0881. Calcd for C21H12O: 280.0886. Anal. found: C,
89.97; H, 4.49. Calcd for C21H12O: C, 89.98; H, 4.31.
4.2.2. 3,7-Dibromoazuleno[1,2-a]acenaphthylne (12). A
solution of 0.07 g (0.44 mmol) of Br2 in 5 mL of CH2Cl2
was added dropwise to a solution of 0.15 g (0.45 mmol) of
11 in 20 mL of CH2Cl2 in the presence of 0.04 g
(0.44 mmol) of triethylamine at 58C in a time period of
10 min. After being stirred at room temperature for 2 h, the
reaction mixture was poured into 20 mL of water and
extracted with CH2Cl2 (10 mL£2). The combined organic
layer was washed with water and brine, and then was dried
with MgSO4. After evaporation of the solvent, the residue
was chromatographed on silica gel with 30% benzene–
hexane as eluent to give 0.19 g (94%) of 12. Dark green
needles, mp 228–2298C, IR (KBr) nmax 3016w, 1571m,
4.2.5. The reaction of 1a with DMAD. A solution of 0.30 g
(1.19 mmol) of 1a and 0.27 g (1.19 mmol) of DMAD in
5 mL of dry xylene was refluxed for 4 h. The reaction
mixture was cooled to room temperature and then was
directly chromatographed on silica gel with 20% AcOEt–
hexane as eluent to give 0.12 g (26%) of 16a and 0.03 g
(6%) of 17, with 50% AcOEt–hexane as eluent to give
0.02 g (3%) of 19. Compound 16a: dark red needles, mp
217–2188C, IR (KBr) nmax 3030w, 2940w, 1720s, 1580m,
1430s, 1320m, 1280m, 1240m, 1120m, 1080m, 820m, 768s,
1
1414m, 1381s, 1349m, 815s, 768m, 736s, 712m cm21: H
NMR (CDCl3–TMS) d¼7.13 (t, J¼9.8 Hz, 1H, H-11), 7.18
(dd, J¼9.8, 9.3 Hz, 1H, H-9), 7.48 (t, J¼9.8 Hz, 1H, H-10),
7.62 (d, J¼7.3 Hz, 1H, H-1), 7.67 (dd, J¼8.3, 6.8 Hz, 1H,
H-5), 7.74 (d, J¼7.3 Hz, 1H, H-2), 7.98 (d, J¼8.3 Hz, 1H,
H-4), 8.18 (d, J¼6.8 Hz, 1H, H-6), 8.19 (d, J¼9.3 Hz, 1H,
H-8), 8.36 (d, J¼9.8 Hz, 1H, H-12): 13C NMR (CDCl3–
TMS) d¼151.1, 144.2, 140.2, 138.1, 135.8, 134.3, 134.0,
133.3, 131.7, 131.3, 130.7, 130.5, 129.1, 127.5, 125.1,
124.8, 123.6, 119.8, 119.5, 98.2: UV/vis (CH2Cl2) lmax 228
(log 1¼4.51) (nm), 298 (4.35), 317 (4.45), 346 (4.67), 364
(4.59), 414sh (3.98), 439sh (3.92), 465sh (3.67), 647 (2.94),
696 (2.96), 762 (2.62): MS m/z (70 eV) 408, 410, 412 (Mþ,
52.3, 100, 53.2), 330, 332 (Mþ2Br, 12.3, 10.9), 250
(Mþ2Br2, 58.7): Anal. found: C, 58.78; H, 2.55. Calcd for
C20H10Br2: C, 58.57; H, 2.46.
1
720m cm21: H NMR (CDCl3–TMS) d¼3.67 (s, –OMe),
3.80 (s, –OMe), 5.86 (d, J¼10.7 Hz, 1H, H-10), 6.21 (d,
J¼6.6 Hz, 1H, H-14), 6.34 (dd, J¼10.7, 6.6 Hz, 1H, H-11),
6.53 (dd, J¼11.1, 6.6 Hz, 1H, H-12), 6.62 (dd, J¼11.1,
6.6 Hz, 1H, H-13), 7.57 (dd, J¼8.2, 6.9 Hz, 1H, H-2), 7.64
(dd, J¼8.2, 6.9 Hz, 1H, H-5), 7.75 (d, J¼6.9 Hz, 1H, H-1),
7.83 (d, J¼6.9 Hz, 1H, H-6), 7.90 (d, J¼8.2 Hz, 1H, H-4),
7.91 (d, J¼8.2 Hz, 1H, H-3), 8.19 (bs, 1H, H-7): 13C NMR
(CDCl3–TMS) d¼167.6, 167.5, 143.4, 142.7, 137.9, 137.8,
137.1, 136.3, 135.0, 132.8, 132.0, 131.4, 130.5, 130.2,
129.2, 128.8, 128.6, 128.4, 128.1, 128.0, 125.5, 124.9,
123.4, 122.8, 52.3, 51.8: UV/vis (CH2Cl2) lmax 212
(log 1¼4.26) (nm), 228 (4.48), 336 (4.31), 515 (3.06): MS
4.2.3. Azuleno[1,2-a]acenaphthylene-7-carboaldehyde
(13) with POCl3-DMF. To
a solution of 0.20 g
(0.79 mmol) of 1a in 20 mL of dimethylformamide at 58C
was added dropwise 0.12 g (0.79 mmol) of POCl3 in a time
period of 10 min. After being refluxed for 2 h, the reaction

810
M. Mouri et al. / Tetrahedron 59 (2003) 801–811
m/z (70 eV) 394 (Mþ, 100), 379 (27.9), 363 (12.6): HRMS:
found: m/z 394.1206. Calcd for C26H18O4: 394.1205. Anal.
found: C, 79.10; H, 4.76. Calcd for C26H18O4: C, 79.18; H,
4.60. 17: dark brown needles, mp 163–1648C, IR (KBr)
130.4, 128.3, 128.1, 128.0, 126.1, 125.5, 124.9, 124.2,
122.7, 119.6, 116.5, 52.7, 52.1: UV/vis (CH2Cl2) lmax 239
(log 1¼4.46) (nm), 267 (4.32), 365 (4.72), 404 (4.05), 425
(3.98), 627 (2.81), 674 (2.81), 736 (2.46): MS m/z (70 eV)
394 (Mþ, 100), 335 (31.7), 320 (18.3), 276 (56.2): Anal.
found: C, 79.11; H, 4.72. Calcd for C26H18O4: C, 79.18; H,
4.60.
n
1433s, 1418m, 1386m, 1317m, 1287m, 1252s, 1202m,
max 3031w, 2952w, 1734s, 1721s, 1625m, 1568m, 1482m,
1
1177m, 1021m, 881m, 819m, 766s, 711m cm21: H NMR
(CDCl3–TMS) d¼3.40 (s, –OMe), 3.74 (s, –OMe), 7.11
(ddm, J¼9.8, 9.5 Hz, 1H, H-9), 7.18 (t, J¼9.8 Hz, 1H,
H-11), 7.39 (s, 1H), 7.47 (t, J¼9.8 Hz, 1H, H-10), 7.53 (dd,
J¼8.3, 6.8 Hz, 1H, H-2), 7.57 (dd, J¼8.3, 6.8 Hz, 1H, H-5),
7.65 (d, J¼8.3 Hz, 2H, H-3, -4), 7.78 (d, J¼6.8 Hz, 1H,
H-1), 7.90 (dd, J¼9.5, 0.7 Hz, 1H, H-8), 7.93 (d, J¼6.8 Hz,
1H, H-6), 8.58 (d, J¼9.8 Hz, 1H, H-12): 13C NMR (CDCl3–
TMS) d¼167.4, 165.5, 152.7, 145.7, 139.3, 139.1, 137.2,
134.4, 134.4, 134.3, 133.6, 132.0, 131.7, 130.5, 130.1,
128.3, 127.9, 127.9, 125.2, 124.9, 124.5, 122.8, 119.4,
115.5, 53.0, 51.9: UV/vis (CH2Cl2) lmax 228 (log 1¼4.49)
(nm), 343 (4.59), 364 (4.62), 406 (3.95), 427 (3.87), 454
(3.51), 630 (2.79), 681 (2.78), 744sh (2.41): MS m/z (70 eV)
394 (Mþ, 100), 335 (36.9), 323 (41.9), 276 (69.8): Anal.
found: C, 79.33; H, 4.81. Calcd for C26H18O4: C, 79.18; H,
4.60. Compound 19: orange needles, mp 242–2438C, IR
(KBr) nmax 3038w, 2997w, 2950w, 1726s, 1714s, 1619m,
1432m, 1271s, 1259s, 1210m, 1102m, 1056m, 820m, 773m,
4.3. Computations
Ab initio molecular orbital calculations were performed
using the MULLIKEN (ver. 2.0.0, 1995, IBM Co.) on an
IBM RS/6000-397 computer on 1a. The MB3LYP
(Mbecke3LYP) functional in MULLIKEN uses the local
correlation function of Perdew and Wang20 instead of the
Vosko, Wilk, and Nusair functional,21 and is very similar to
the Becke3LYP density by Stephens et al.22 Semiempirical
molecular orbital calculations were performed using the
CAChe MOPAC program with the PM3 method23 on 1a, 11,
11Hþa, 11Hþb, 11Hþc, 18, and 21.
Acknowledgements
1
751m cm21: H NMR (CDCl3–TMS) d¼2.63 (s, –OMe),
This work was financially supported by a Grant-in-Aid for
Scientific research (No. 13640528 to M. O.) from the
Ministry of Education, Science, Technology, Culture and
Sports, Japan.
3.59 (s, –OMe), 3.76 (s, –OMe), 3.77 (s, –OMe), 3.78
(t-like, J¼6.8 Hz, 1H, H-4), 4.90 (s, 1H, H-10), 6.13 (d,
J¼10.5 Hz, 1H, H-6), 6.44 (d, J¼7.9 Hz, 1H, H-11), 6.46
(dd, J¼10.5, 6.8 Hz, 1H, H-5), 6.65 (dd, J¼7.9, 6.8 Hz, 1H,
H-12), 7.46 (dd, J¼8.3, 6.8 Hz, 1H, H-16), 7.48 (dd, J¼8.3,
6.8 Hz, 1H, H-19), 7.54 (d, J¼6.8 Hz, 1H, H-15), 7.65 (d,
J¼6.8 Hz, 1H, H-20), 7.70 (d, J¼8.3 Hz, 1H, H-17), 7.73
(d, J¼8.3 Hz, 1H, H-18): 13C NMR (CDCl3–TMS)
d¼166.6, 165.2, 164.9, 164.2, 156.4, 155.6, 153.3, 147.0,
143.8, 142.5, 138.5, 134.0, 133.7, 132.5, 132.3, 130.6,
128.5, 128.0, 127.7, 127.5, 127.1, 123.5, 123.1, 123.0, 92.8,
64.5, 54.1, 52.3, 52.2, 52.1, 51.1, 37.2: UV/vis (CH2Cl2)
lmax 228 (log 1¼4.57) (nm), 293 (3.84), 333 (4.13), 435
(2.49): MS m/z (70 eV) 536 (Mþ, 11.6), 477 (30.9), 445
(33.5), 415 (75.7), 300 (32.9): Anal. found: C, 71.59; H,
4.53. Calcd for C32H24O8: C, 71.64; H, 4.51.
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