Generation and reactions of 3-phenyl-7,8-dehydro-1-azaazulene

Article abstract of DOI:10.3987/COM-03-S23

3-Phenyl-7,8-dehydro-1-azaazulenes were generated by the treatment of 8-bromo-3-phenyl-1-azaazulenes with potassium t-butoxide in DMSO or in THF in the presence of 16-crown-8-ether, and trapped with diphenylisobenzofuran as 3,7,12-triphenyl-1-aza-7, 12-ep

Full text of DOI:10.3987/COM-03-S23

HETEROCYCLES, Vol. 61, 2003
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HETEROCYCLES, Vol. 61, 2003, pp. 237 - 245
Received, 6th June, 2003, Accepted, 14th July, 2003, Published online, 15th July, 2003
GENERATION AND REACTIONS OF 3-PHENYL-7,8-DEHYDRO-
1-AZAAZULENE
Noritaka Abe,* Masao Yoshitsugu, Hiroyuki Fujii, and
†
Akikazu Kakehi
Department of Chemistry, Faculty of Science, Yamaguchi University, Yamaguchi
753-8512, Japan
†
Department of Chemistry and Material Engineering, Faculty of Engineering,
Shinshu University, Wakasato Nagano 380-8553, Japan
Abstract – 3-Phenyl-7,8-dehydro-1-azaazulenes were generated by the
treatment of 8-bromo-3-phenyl-1-azaazulenes with potassium t-butoxide in
DMSO or in THF in the presence of 16-crown-8-ether, and trapped with
diphenylisobenzofuran as 3,7,12-triphenyl-1-aza-7,12-epoxynaphth[2,3-
e]azulenes. The structure of the adduct, 2-bromo-3,7,12-triphenyl-1-aza-
7,12-epoxynaphth[2,3-e]azulene, was deduced by X-Ray structure analysis.
Similar treatment of 8-bromo-3-phenyl-1-azaazulene with potassium t-butoxide
in the presence of furan gave 3-phenyl-1-aza-7,12-epoxynaphth[2,3-e]azulene
and
7-phenyl-3H-3a,3c-dihydro-1-aza-3-oxacyclopenta[3,4]cyclobuta[1,2-
e]azulene as cycloadducts.
INTRODUCTION
Arynes were widely investigated from the interest of their high reactivity and synthetic utility.1—3 In spite of
great interests about the non-benzenoid arynes, the studies were observed only few; some reports were about
dehydrotropolone,4 dehydrotropone,5 4,5-dehydrodibenzoheteropins,6,7 5,6-dehydroazulene,8 and 5,6-
dehydro-1,3-diazaazulene.9 Since we succeeded in the generation of azaazulyne in the series of our study
on the reaction of azaazulenes,10,11 we wish to present here the generation and [2 + 4]cycloadducts of 3-
phenyl-7,8-dehydro-1-azaazulene and 2-bromo-3-phenyl-7,8-dehydro-1-azaazulene.
RESULTS AND DISCUSSION
A mixture of 8-bromo-3-phenyl-1-azaazulene (1a) and potassium t-butoxide in the presence of
diphenylisobenzofuran (DPIBF) in DMSO was heated at 100 ℃ for 1.5 h. After worked up, three
products, the cycloadduct (3a) (3%), 8-methylthio-3-phenyl-1-azaazulene (4a) (6%), and 3-phenyl-1-
azaazulen-8(1H)-one (5a)1 2 (11%), were isolated from the reaction mixture (Table 1, Run 1). The

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compound (3a) was analyzed as 1 : 1–adduct (C35H23NO) of 3-phenyl-7,8-dehydro-1-azaazulene (2a) and
DPIBF from its elemental analysis and mass spectrum. In the1H NMR spectrum of 3a, three protons of the
seven-membered ring were observed at d 7.28 (dd, J 10.4, 9.2 Hz), 7.75 (d, J 9.2 Hz), and 8.47 (d, J 10.4 Hz);
this shows that DPIBF reacted at C-7 and C-8 of 1-azaazulene nuclei. From the result, we assigned the
adduct as 3,7,12-triphenyl-1-aza-7,12-epoxynaphth[2,3-e]azulene. Thus we could show the ambiguous
generation of 3-phenyl-7,8-dehydro-1-azaazulene (2a). Its spectroscopic data as well as elemental analysis
assigned the compound (4a). The compound (4a) was consisted with the compound prepared by the
reaction of 1a with sodium methyl sulfide, and the structure was confirmed.
When the reaction was performed at rt for 2 d, the yield of 3a slightly increased (7%) and the yield of 4a
decreased (trace) (Run 2). When the base was changed, the results showed almost the same aspects (Runs 3,
4), except for lithium tetramethylpiperidine (LiTMP) (Run 5).
When 8-bromo-3-phenyl-1-azaazulene (1a) was treated with potassium t-butoxide in the presence of 18-
crown-6-ether (CE) and excess DPIBF in dry THF under refluxed for 30 h, the formation of 3a was improved
(Runs 7, 8): the compounds (3a) (15%) and (5a) (20%) were obtained along with small amount of
3-phenyl-1-azaazulene (6a).11,12
Ph
Ph
Ph
Ph
Ph
Ph
base
DPIBF
X
+
X
+
X
X
+
X
X
N
N
N
H
N
N
N
Ph
O
Ph
SMe
O
Br
6a : X = H
1a : X = H
1b : X = Br
2a : X = H
2b : X = Br
3a : X = H
3b : X = Br
5a : X = H
5b : X = Br
4a : X = H
furan
Ph
Ph
+
+
+
+
4a
5a
6a
N
N
O
O
7
8
Scheme 1
Similarly, the reaction of 2,8-dibromo-3-phenyl-1-azaazulene (1b) with potassium t-butoxide in the presence
of CE and DPIBF in dry THF gave 3b (4 %), 5b (13%), and recovered 1b (43%) (Run 9). When the
reaction was performed under elevated temperature and using excess amounts of DPIBF, the yield of 3b was
improved (Runs 10, 11).
Spectroscopic data of 3b were resembled to those of 3a, and this supported the structure. The structure of
the adduct (3b) was finally deduced by X-Ray structure analysis (Figure 1). In the seven-membered ring,

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239
the bond alternation was clearly observed [C(3)-C(4) 1.42(2), C(4)-C(5) 1.37(2), C(5)-C(6) 1.40(2), C(6)-
1
C(7) 1.36(1), C(7)-C(16) 1.42(1), C(16)-C(17) 1.39(1)]. The results agree with the H NMR
spectroscopic results.
Formation of 4a, 5a, and 5b was considered as follows (Scheme 2). Two possible formation mechanisms
for 4a could be considered. When the generated dehydro-1-azaazulene (2a) reacts with DMSO,
intermediate (A) would be produced.
Rearrangement of A affords B, and the successive elimination of
formaldehyde furnishes 4a (path a). Another path is the substitution mechanism (path b). Although
DMAD was purified, methyl sulfide could be produced by decomposition, and reaction of methyl sulfide with
1a gave 4a. Reaction of 1a and 1b with alkoxide gives C. Compound (C) could be easily hydrolyzed to
give 5a and 5b.
Ph
Ph
Ph
DMSO
X = H
path a
X
N
N
N
CH2
Br
1a, b
2a
O
A
S
Me
X = H
SMe
path b
Ph
N
OR
Ph
S
path c
Me
CH2
O
N
SMe
B
4a
Ph
Ph
hydrolysis
X
X
N
N
H
OR
O
C
5a, 5b
Scheme 2
The intermediate (2a) could be also trapped by furan. Thus we treated 1a with potassium t-butoxide in the
presence of furan in DMSO and obtained 7 (1%) and 8 (1%) together with 4a and 5a (Run 12). The
products (7 and 8) were 1 : 1–adducts of 2a and furan on the basis of mass spectra (M+ , m/z 271). In the
1H NMR spectrum of 7, three protons of the seven-membered ring appear at d 7.93 (dd, J 11.1 and 9.8, H-
5), 8.53 (d, J 11.1, H-4), 8.65 (d, J 9.8, H-6), two methine protons at d 6.72-6.77 (1H, m) and 7.72-7.74
(1H, m), and two olefinic protons at d 7.51 (1H, dm, J 3.5) and 8.42 (1H, dm, J 3.5), along with phenyl
protons and H-2 proton at d 8.78 (1H, s). The divergence of the coupling shows the existence of bond

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HETEROCYCLES, Vol. 61, 2003
alternation of seven-membered ring of 7. From the results, the compound (7) was assigned as 3-phenyl-
1-aza-7,10-epoxybenz[e]azulene. In the 1H NMR spectrum of 8, three protons of the seven-membered
ring were seen at d 7.29 (1H, dd, J 10.7 and 8.8), 7.70 (1H, d, J 8.8), and 8.45 (1H, d, J 10.7), two
methine protons were seen at d 5.89 (1H, br s), 6.64 (1H, br s), and two olefinic protons were seen at d 7.17
(1H, d, J 5.5 and 1.7) and 7.20 (1H, dd, J 5.5 and 1.8). In the 1 3C NMR spectrum of 8, two methine
carbon signals were seen at d 83.38 and 84.95. Bond alternation of seven-membered ring of 8 was also
seen.
From the results, we assigned the structure as 7-phenyl-3H-3a,9c-dihydro-9a-aza-3-oxa-
cyclopenta[3,4]cyclobuta[1,2-e]azulene.
Interestingly, when the reaction was performed with potassium t-butoxide in the presence of CE under reflux,
7 was obtained; whereas, when the reaction was performed with potassium t-butoxide in the presence of CE
at rt, 8 was obtained (Runs 13, 14). Plausible formation mechanism of 8 is shown in Scheme 3.
Hydrogen abstraction from 1a produces the anion (D). Michel addition of D with furan, and successive
cyclization of E gives F. Debromination of F furnishes 8.
Although the dehydro-1-azaazulene reacts with furan at rt to give [2 + 2] and [2 + 4] cycloadducts, the
dehydro-1-azaazulene with furan underwent preferentially [2 + 4]cycloaddition at elevated temperature (Runs
9, 10, 13, 14).
Table 1. Reactions of 8-bromo- and 2-8-dibromo-3-phenyl-1-azaazulenes (1a,b) with base in the presence
of diphenylisobenzofurane (DPIBF) or furan.
Reaction conditions
Temp. Time
Yield / %
Run Compd Reagent Solvent Base
100℃
1
2
1a
1a
1a
1a
1a
1a
1a
1a
1b
1b
1b
1a
1a
1a
1a
DPIBF DMSO t-BuOK
DPIBF DMSO t-BuOK
DPIBF DMSO MeONa
DPIBF DMSO NaH
1.5 h 3a(3) 4a(6) 5a(11)
rt
2 d
6 h
2 d
2 d
3a(7) 4a(trace) 5a(20)
3a(5) 4a(3) 5a(27)
60 ℃
3
4
rt
rt
3a(5) 4a(trace) 5a(17)
complex mixture
5
DPIBF DMSO LiTMP
6
DPIBF THF
DPIBF THF
DPIBFa) THF
DPIBF THF
DPIBF THF
DPIBFa) THF
t-BuOK
reflux 2 d
3a(1) 5a(24) 6a(5) 1a(5)
7
t-BuOK–CE reflux 30 h 3a(7) 5a(21) 6a(trace) 1a(8)
t-BuOK–CE reflux 30 h 3a(15) 5a(20) 6a(trace)
8
9
t-BuOK–CE rt
10 d 3b(4) 5b(13) 1b(43)
10
11
12
13
14
15
t-BuOK–CE reflux 1 d
t-BuOK–CE reflux 1 d
3b(18) 5b(17) 1b(16)
3b(22) 5b(trace) 1b(36)
7(1) 8(1) 4a(1) 5a(28)
8(1) 5a(27) 1a(4)
furan
furan
furan
furan
DMSO t-BuOK
rt
2 d
6 d
THF
THF
furan
t-BuOK–CE rt
t-BuOK–CE reflux. 12 h 7(4) 5a(9) 6a(5)
t-BuOK rt 7 d 5a(27) 1a(50)
a) 5 eq. of DPIBF was used.

HETEROCYCLES, Vol. 61, 2003
241
Figure 1. An ORTEP drawing of 3b with thermal ellipsoids (50% probability).
Ph
Ph
Ph
N
N
N
O
Br
Br
Br
O
D
E
1a
Ph
Ph
N
N
Br
O
O
8
F
Scheme 3

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HETEROCYCLES, Vol. 61, 2003
CONCLUSION
7,8-Dehydro-1-azaazulenes (2a, 2b) has been generated and trapped with diphenylisobenzofuran to give the
adducts (3a, 3b), and with furan to give 7 and 8. Bond alternation of the adducts were confirmed by
X-Ray structure analysis and 1H NMR spectra.
EXPERIMENTAL
Mps are measured using a Yanagimoto micro-melting apparatus and uncorrected. 1H NMR spectra were
recorded on a Bruker AVANCE 400S (400 MHz) and 13C NMR spectra were recorded on a Bruker
AVANCE 400S (100.6 MHz) using deuteriochloroform as a solvent with tetramethylsilane as an internal
standard unless otherwise stated; J values are recorded in Hz. IR spectra were recorded for KBr pellets
unless otherwise stated on a Nicolet FT-IR Impact 410. Electronic spectra were recorded with Shimadzu
UV-1600PC spectrophotometer. MS spectra were taken with on an LC-MS Waters Integrity System.
Elemental analyses were taken with a Perkin Elmer 2400II. Kieselgel 60 and Alumina Activated 300 were
used for column chromatography and Kieselgel 60G was used for thin-layer chromatography.
Synthesis of 8-bromo-3-phenyl-1-azaazulene (1a)
Under argon atmosphere, a mixture of 3-phenyl-1-azaazulen-8(1H)-one12 (0.234 g, 1.10 mmol), and
phosphorus oxybromide (0.887 g, 3.09 mmol) was heated for 1 h at 110 ℃. To the mixture was added
water,then the solution was neutralized with sodium carbonate. The mixture was extracted with chloroform,
and the solvent was dried over sodium sulfate and evaporated. The residue was chromatographed on
alumina column with benzene to give 8–bromo-3-phenyl-1-azaazulene (1a) (0.226 g, 72%).
1a: Dark violet needles (from hexane-dichloromethane), mp 123-124 ℃; dH 7.43 (1H, d, J 7.4), 7.54 (2H,
dd, J 7.6 and 7.4), 7.59 (2H, d, J 7.6), 7.64 (1H, dd, J 10.2 and 9.7), 7.71 (1H, dd, J 10.8 and 10.2), 8.29
(1H, d, J 10.8), 8.69 (1H, d, J 9.7), 8.94 (1H, s); dC 127.49, 127.88, 129.04, 129.50, 131.08, 133.69,
133.76, 135.28, 136.23, 137.33, 139.95, 155.05, 157.03; nmax / cm-1 729 and 696 (phenyl); lmax(CHCl3) /
cm-1 (log e) 299 (4.49), 369 (3.55, sh) and 515 (2.80); m/z (rel intensity) 285 (M+, 98), 283 (M+, 100), 203
(28). Anal. Calcd for C15H10NBr: C, 63.40; H, 3.55; N, 4.93. Found: C, 63.66; H, 3.45; N, 4.67.
Synthesis of 2,8-dibromo-3-phenyl-1-azaazulene (1b)
Under argon atmosphere, a mixture of 2-chloro-3-phenyl-1-azaazulen-8(1H)-one12 (1.67 g, 6.52 mmol), and
phosphorus oxybromide (5.71 g, 19.90 mmol) was heated for 1 h at 110 ℃. To the mixture was added
water, then the solution was neutralized with sodium carbonate. The mixture was extracted with chloroform,
and the solvent was dried over sodium sulfate and evaporated. The residue was chromatographed on
alumina column with benzene to give 2,8–dibromo-3-phenyl-1-azaazulene (1b) (1.82 g, 77%).
1b: Red scales (from hexane-dichloromethane), mp 164-166 ℃; dH 7.45 -7.56 (5H, m), 7.64 (1H, dd, J
10.4 and 9.5), 7.69 (1H, dd, J 10.8 and 10.4), 8.27 (1H, d, J 10.8), 8.37 (1H, d, J 9.5); dC 128.13, 128.70,
129.02, 129.81, 130.66, 132.26, 134.33, 135.07, 135.64, 136.10, 140.83, 148.78, 153.30; nmax / cm- 1
731 and 700 (phenyl); lmax(CHCl3) / cm-1 (log e) 254 (4.52), 306 (4.64), 377 (3.21, sh) and 498 (3.12); m/z
(rel intensity) 365 (M+ , 44), 363 (M+, 81), 361 (M+, 43), 203 (100). Anal. Calcd for C15 H9NBr2 : C,

HETEROCYCLES, Vol. 61, 2003
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49.62; H, 2.50; N, 3.86. Found: C, 49.9; H, 2.41; N, 3.74.
Generation and trapping of 7,8-dehydro-1-azzaazulenes with diphenylisobenzofuran
Typical procedure A -Under argon atmosphere, a mixture of 8-bromo-3-phenyl-1-azaazulene (1a) (0.291 g,
1.02 mmol), potassium t-butoxide (0.141 g, 1.26 mmol), and diphenylisobenzofuran (0.325 g, 1.20 mmol)
in dry DMSO (35 mL) was stirred for 2 d at rt. To the mixture was added water, and the mixture was
extracted with chloroform. The extract was washed with water, dried over sodium sulfate, and evaporated.
The residue was chromatographed on silica gel column (benzene then hexane-ethyl acetate (2 : 1)) to give 3a
(0.035 g, 7%), 4a (0.001 g, 0.4%), and 5a12 (0.045 g, 20%).
Typical procedure B -Under argon atmosphere, a mixture of 8-bromo-3-phenyl-1-azaazulene (1a) (0.145 g,
0.51 mmol), potassium t-butoxide (0.069 g, 0.61 mmol), diphenylisobenzofuran (0.675 g, 2.50 mmol) ,
and 18-crown-6-ether (0.164 g, 0.62 mmol) in dry THF (30 mL) was refluxed for 30 h. To the mixture
was added water, and the mixture was extracted with chloroform. The extract was dried over sodium sulfate,
and evaporated. The residue was chromatographed on silica gel column (benzene then hexane-ethyl
acetate (2 : 1)) to give 3a (0.036 g, 15%), 5a (0.023 g, 20%), and 6a (0.0004 g, 0.4%).
In a similar manner, the reactions of 1a and 1b were performed under some variety of conditions. The
results were listed in Table 1.
3a: Red purple needles (from ethanol), mp 192-194 ℃; dH 7.01 (1H, dd, J 7.5 and 7.4), 7.21 (1H, dd, J 7.5
and 7.4), 7.28 (1H, dd, J 10.4 and 9.2), 7.36 (1H, dd, J 7.3 and 7.2), 7.46-7.55 (8H, m), 7.59 (2H, d, J
7.4), 7.63 (1H, d, J 7.3), 7.75 (1H, d, J 9.2), 7.92-8.00 (5H, m), 8.47 (1H, d, J 10.4), 8.73 (1H, s); dC
91.46, 94.20, 121.00, 123.75, 126.32, 126.61, 126.88, 127.05, 127.67, 128.02, 128.66, 128.71, 128.85, 128.88,
129.10, 1 29.12, 12 9.92, 13 0.28, 132 .16, 134 .23, 135. 17, 142.8 7, 146.3 0, 150.41 , 150.48 ,
150.79, 155.63, 158.89; nm ax / cm-1 1658 (C=O), 758 and 703 (phenyl); lmax (CHCl3) / cm-1 (log e) 303
(4.40), 374 (3.76), 519 (2.95); m/z (rel intensity) 473 (M+, 92), 368 (94), 105 (100) and 77 (60). Anal.
Calcd for C35H23NO: C, 88.77; H, 4.90; N, 2.96. Found: C, 88.83; H, 5.01; N, 3.32.
4a: Orange prisms (from hexane-dichloromethane), mp 135-136 ℃; dH 2.73 (3H, s), 7.37 (1H, d, J 7.4),
7.41 (1H, dd, J 9.8 and 9.6), 7.50 (1H, dd, J 7.4 and 7.2), 7.57 (2H, d, J 7.2), 7.61 (1H, d, J 11.0), 7.76
(1H, dd, J 11.0 and 9.6), 8.57 (1H, d, J 9.8), 8.63 (1H, s); dC 15.54, 123.72, 125.20, 126.91, 128.86,
129.31, 129.47, 134.47, 135.48, 135.88, 138.02, 151.96, 152.64, 154.77; nmax / cm-1 769 and 703
(phenyl); lmax(CHCl3) / cm-1 (log e) 273 (4.70), 339 (4.62), 495 (3.03); m/z (rel intensity) 251 (M+ , 100),
204 (97), 177 (75). Anal. Calcd for C16H13 NS: C, 76.45; H, 5.21; N, 5.57. Found: C, 76.94; H,
5.19; N, 5.69.
6a12,13: Red violet oil; dH 7.34 (1H, t-like, J 7.4), 7.53 (2H, t-like, J 7.7), 7.62-7.67 (3H, m), 7.76 (1H, t-
like, J 9.9), 7.91 81H, t-like, J 9.9), 8.76 (2H, t-like, J 9.2), 8.91 (1H, s); m/z (rel intensity) 205 (M+, 100),

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HETEROCYCLES, Vol. 61, 2003
176 (30), 76 (32).
Synthesis of 4a
A mixture of 8-bromo-3-phenyl-1-azaazulene (1a) (0.293 g, 1.03 mmol) and sodium methyl sulfide (0.088 g,
1.25 mmol) in dry THF (20 mL) was refluxed for 2 h. To the mixture was added water, and the mixture
was extracted with chloroform. The extract was washed with water, dried over sodium sulfate, and
evaporated. The residue was chromatographed on silica gel column (benzene then hexane-ethyl acetate (3 :
1)) to give 4a (0.242 g, 93%).
Generation and trapping of 7,8-dehydro-1-azzaazulenes with furan
Typical procedure A -Under argon atmosphere, a mixture of 8-bromo-3-phenyl-1-azaazulene (1a) (0.581 g,
2.04 mmol), potassium t-butoxide (0.367 g, 1.26 mmol), and furan (1.1 mL) in dry DMSO (15 mL) was
stirred for 2 d at rt. To the mixture was added water, and the mixture was extracted with chloroform. The
extract was washed with water, dried over sodium sulfate, and evaporated. The residue was
chromatographed on silica gel column (benzene then hexane-ethyl acetate (2 : 1)) to give 7 (0.006 g, 1%), 8
(0.007 g, 1%), 4a (0.005 g, 1%), and 5a (0.163 g, 28%).
Typical procedure B -Under argon atmosphere, a mixture of 8-bromo-3-phenyl-1-azaazulene (1a) (0.286 g,
0.51 mmol), potassium t-butoxide (0.069 g, 0.61 mmol), furan (1.0 mL), and 18-crown-6-ether (0.164 g,
0.62 mmol) in dry THF (30 mL), was refluxed for 12 h. To the mixture was added water, and the mixture
was extracted with chloroform. The extract was dried over sodium sulfate, and evaporated. The residue
was chromatographed on silica gel column (benzene then hexane-ethyl acetate (2 : 1)) to give 7 (0.011 g, 4%),
5a (0.019 g, 9%), and 6a (0.011 g, 5%).
7: Red violet oil; dH 6.72-6.77 (1H, m), 7.40 (1H, t-like, J 7.4), 7.51 (1H, dm, J 3.5), 7.52 (2H, tm, J 7.6),
7.63 (2H, dm, J 7.8), 7.72-7.74 (1H, m), 7.93 (1H, dd, J 11.1 and 9.8), 8.42 (1H, dm, J 3.5), 8.53 (1H,
d, J 11.1), 8.65 (1H, d, J 9.8), 8.78 (1H, s); m/z (rel intensity) 271 (M+ , 100), 245 (25), 243 (54), 241 (39),
213 (13).
8: Orange needles (from hexane-dichloromethane), mp 133-134 ℃; dH 5.89 (1H, br s), 6.64 (1H, br s),
7.17 (1H, d, J 5.5 and 1.7), 7.20 (1H, dd, J 5.5 and 1.8), 7.29 (1H, dd, J 10.7 and 8.8), 7.39 (1H, d, J
7.4), 7.51 (2H, dd, J 7.7 and 7.5), 7.59 (2H, d, J 7.7), 7.70 (1H, d, J 8.8), 8.45 (1H, d, J 10.7), 8.85 (1H,
s); dC 83.38, 84.95, 126.44, 127.20, 128.54, 128.83, 128.97, 131.42, 134.03, 140.03, 141.90, 143.48,
147.40, 150.55, 155.38, 159.39; nmax / cm-1 (CHCl3) 1629 (C=C), 769 and 703 (phenyl); m/z (rel intensity)
271 (M+, 100), 243 (71), 215 (17). Anal. Calcd for C19H13NO: C, 84.11; H, 4.83; N, 5.16. Found: C,
84.36; H, 4.42; N, 4.98.
X-Ray structure determination
Crystal data of 3b: Red prism, C35H22NOBr, M=552.47, monoclinic, space group P21/c, a=10.48(1),

HETEROCYCLES, Vol. 61, 2003
245
b=17.638(4), c=14.321(4) Å, V=2632(2) Å3, Z=4, Dcalcd=1.394 g/cm3, crystal dimensions 0.46 x 0.38 x
0.07 mm. Data were measured on a Rigaku AFC 5S radiation diffractometer with graphite-monochromated
Mo-Ka radiation. Total 4852 (4581 unique) reflections were collected using w-2q scan technique with in a
2q range of 50.0°. The structure was solved by direct methods and refined by a full-matrix least-squares
method using 343 variables refined with 1357 reflections [I > 2s(I)]. The weighting scheme w =
4Fo2/s2(Fo2) gave satisfactory agreement analyses. The final refinement converged to R = 0.066 and Rw
= 0.048.
Selected bond lengths (azaazulene ring) of 3b (Å): N(1)-C(1) 1.34(1), C(1)-C(2) 1.41(1), C(2)-C(3) 1.38(1),
C(3)-C(4) 1.42(2), C(4)-C(5) 1.37(2), C(5)-C(6) 1.40(2), C(6)-C(7) 1.36(1), C(7)-C(16) 1.42(1), C(16)-
C(17) 1.39(1), C(17)-N(1) 1.39(1), C(3)-C(17) 1.45(1).
ACKNOWLEDGEMENTS
This work was partially supported by a Grand-in Aid for Scientific Research on Priority Areas (A) of
Exploitation of Multi-Element Cyclic Molecules (Nos. 13029083 and 14044074) from the Ministry of
Education, Culture, Sports, Science and Technology, Japan.
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