Synthesis and reactions of 3-etylnyl-2(triphenyl-phosphoimino)-1-azaazulenes

Article abstract of DOI:10.3987/com-07-s(w)7

3-(Trimethylsilylethynyl)- and 3-(phenylethynyl)-2-(triphenyl-phosphoimino)-1-azaazulenes were synthesized by the Appel reaction of the corresponding 2-amino-3-ethynyl-1-azaazulenes. Reaction of 3-(phenyl-ethynyl)-2-(triphenylphosphoimino)-1-azaazulene (Sb) with Cu(OTf)₂ gave 3-(2-oxophenethyl)-2-(triphenylphosphoimino)-1-azaazulene (11), 3-(1,2-dioxo-phenethyl)-2-(triphenylphosphoimino)-1-azaazulene (12), and 2-amino-3-(1,2-dioxophenethyl)-1-azaazulene (13). The structure of 13 was decided by X-ray structure analysis, and the structure of 12 was discussed by molecular orbital calculation. Reaction of 8b with aryl isocyanate in the presence of benzoyl peroxide gave 1,10-diazabenz[a]azulene derivative.

Full text of DOI:10.3987/com-07-s(w)7

HETEROCYCLES, Vol. 74, 2007
309
HETEROCYCLES, Vol. 74, 2007, pp. 309 - 320. © The Japan Institute of Heterocyclic Chemistry
Received, 1st June, 2007, Accepted, 2nd July, 2007, Published online, 3rd July, 2007. COM-07-S(W)7
SYNTESIS AND REACTIONS OF 3-ETYNYL-2-(TRIPHENYL-
PHOSPHOIMINO)-1-AZAAZULENES†
Noritaka Abe,a* Kentaro Nagamatsu,b Tomoyuki Ariyoshi,a Hiroyuki
Fujii,c Yoshiko Murakami,b Shoji Tagashira,b* and Akikazu Kakehid
a
Applied Molecular Bioscience, Graduate School of Medicine, Yamaguchi
University, Yamaguchi 753-8512, Japan
b Graduate School of Science and Engineering, Yamaguchi University, Yoshida,
Yamaguchi, 753-8512, Japan
c Science Research Center, Yamaguchi University, Yamaguchi 753-8512, Japan
d Department of Chemistry and Material Engineering, Faculty of Engineering,
Shinshu University, Wakasato Nagano 380-8553, Japan
Abstract – 3-(Trimethylsilylethynyl)- and 3-(phenylethynyl)-2-(triphenyl-
phosphoimino)-1-azaazulenes were synthesized by the Appel reaction of the
corresponding 2-amino-3-ethynyl-1-azaazulenes. Reaction of 3-(phenyl-
ethynyl)-2-(triphenylphosphoimino)-1-azaazulene (8b) with Cu(OTf)2 gave
3-(2-oxophenethyl)-2-(triphenylphosphoimino)-1-azaazulene (11), 3-(1,2-dioxo-
phenethyl)-2-(triphenylphosphoimino)-1-azaazulene (12), and 2-amino-3-(1,2-
dioxophenethyl)-1-azaazulene (13). The structure of 13 was decided by X-ray
structure analysis, and the structure of 12 was discussed by molecular orbital
calculation. Reaction of 8b with aryl isocyanate in the presence of benzoyl
peroxide gave 1,10-diazabenz[a]azulene derivative.
INTRODUCTION
It is known that the iminophosphoranes, chemical species having the nitrogen-phosphorus double bond,
reveal synthetic versatility for the construction of fused heterocycles.1-4 We reported the synthesis and
some reactions of phosphoimino-1-azaazulene derivatives (1 and 2), where some types of tandem
aza-Wittig reaction / cyclization and tandem aza-Wittig reaction / heterocumulene-mediated cyclization
underwent and gave a lot of azaazulene-fused heterocycles.5-8 Aryl conjugated acetylene is also an
attractive subject to synthesize a new type of heterocycles. Recently, we reported the synthesis of aryl
conjugated ethynylazaazulenes (3), which afforded thiophene-fused 1-azaazulenes (4) (Scheme 1).9
We also reported that 3-ethynyl-2-(mesylamino)-1-azaazulenes (5) underwent cyclization and gave
1,9-diaza-1H-cyclopent[a]azulene derivatives (6) in the presence of Cu(OAc)2 or Cu(OTf)2 (Scheme
2).10 In the recent studies about heteroaromatics such as carbolines and ellipticine analogues,
benzannulated enyne-carbodiimides and o-ethynylaryliminophosphoranes were used as key
intermediates.11-17 In the line of our studies about 1-azaazulenes,18-20 we investigated the synthesis and
reaction of 3-ethynyl-2-(triphenylphosphoimino)-1-azaazulenes.
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
†Dedicated to Professor Ekkehard Winterfeldt on the occasion of his 75th birthday.

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HETEROCYCLES, Vol. 74, 2007
Ph
R
N PPh3
N
N
N
PPh3
1
2
Ph
Ph
NaSH
S
Cl
N
N
3
4
Scheme 1
R
R
Cu(OAc)2 or Cu(OTf)2
NMs
NHMs
N
N
5 : R = H, TMS, Ph
6 : R = H, TMS, Ph
Scheme 2
RESULTS AND DISCUSSION
3-(Trimethylsilylethynyl)- and 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulenes (8) were
synthesized by the Appel reaction of the corresponding 2-amino-3-ethynyl-1-azaazulenes. Thus
treatment of 7a10 with PPh3 and hexachloroethane in the presence of Et3N in benzene under reflux for 1
h gave 8a in 95% yield. Similar treatment of 7b10 gave 8b in 98% yield.
R
R
PPh3, C2Cl6, Et3N
NH2
N PPh3
N
N
8a : R = TMS
8b : R = Ph
7a
7b
: R = TMS
: R = Ph
As 3-ethynyl-2-(mesylamino)-1-azaazulene underwent cyclization in the presence of copper-catalyst,10
we examined the reaction of 8 with copper-catalyst at first.
Reaction of 8a under heating at 90 ℃ for 24 h in the presence of CuI in dry 1,2-dichloroethane in a
sealed tube did not proceed at all. On the other hand, the reaction of 8a with Cu(OTf)2 under same
condition proceeded and gave 3-acetyl-2-(triphenylphosphoimino)-1-azaazulene (9) and
3-acetyl-2-amino-1-azaazulene (10) in 8% and 10% yields, respectively. The reaction in dry benzene
gave 9 and 10 in 18% and 17% yields, respectively. These structures were deduced by spectroscopic

HETEROCYCLES, Vol. 74, 2007
311
data as well as elemental analysis. In the IR spectrum of 9, a carbonyl signal was seen at extremely
low wave number (1603 cm-1). This suggests that appreciable coordinative interaction between
O-atom and P-atom would be existed.
Although it took things simple that hydrolysis of 8a occurred in the reaction, the result of no reaction of
8a with CuI could not be explained. Therefore, we next examined the reaction of 8b with Lewis acids.
TMS
CH3
CH3
O
O
Cu(OTf)2
H
+
PPh3
N
N
N PPh3
H
N
N
N
10
8a
9
Reaction of 8b in the presence of CuI, ZnCl2, or Yb(OTf)3 under heating in a sealed tube did not proceed
at all. Heating of 8b in the presence of Pd(OAc)2 in a sealed tube gave a complex mixture. Only the
reaction of 8b in the presence of Cu(OTf)2 gave distinct results. Thus treatment of 8b with an
equivalent molar of Cu(OTf)2 in dry 1,2-dichloroethane under heating at 90 ℃ for 24 h in a sealed tube
gave 11 (trace), 12 (3%), and 13 (18%).
Ph
Ph
Ph
N
Ph
N
O
O
O
O
O
Cu(OTf)2
+
+
N PPh3
N PPh3
NH2
N PPh3
N
N
11
8b
12
13
The structures of obtained compounds were deduced by the spectroscopic data as well as elemental
1
analysis. In the H NMR spectrum of 11, methylene protons were observed at δ 4.95 together with
phenyl protons and seven-membered ring protons. In its 13C NMR spectrum, a signal at δ 48.68 owing
to a methylene carbon and a signal at δ 196.90 owing to a carbonyl carbon were observed. In its IR
spectrum, carbonyl peak was seen at 1626 cm-1.
1
In the H NMR spectrum of 12, methylene protons were not observed. In its 13C NMR spectrum, two
signals at δ 192.29 and 195.25 owing to carbonyl carbons were observed. In its IR spectrum, two
carbonyl peaks were seen at 1677 and 1600 cm-1. In addition, a sharp signal owing to P-O-C was
appeared at 1111 and 883 cm-1. These suggest that one carbonyl oxygen is free and the other carbonyl
oxygen could have appreciable coordinative interaction with P-atom. Unfortunately, the compound
(12) was unstable on the X-ray analysis conditions and we had not ascertained which carbonyl oxygen
links P-atom. Therefore, to clarify the consideration, we performed the molecular orbital calculation
by Gaussian ’03 using RHF/6-31G*21 (Figure 1).
Two optimized stable structures (12A and 12B)
existed, and 12B was more stable than 12A (about 6.3 kcal/mol). In the calculation of the structure of
12B, the bond distance between O and P was 2.943 Å, and this lies midway between O-P covalent bond
(1.79 Å) and van der Waals radius of O and P (3.30 Å). It is reported that phospa-oxa-azulene (14)
showed the bond lengths 2.00-2.36 Å.22-24 Although the bond distance of 12B is longer than those of

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HETEROCYCLES, Vol. 74, 2007
14, above results suggest that 12 exists as resonance hybrid of 12B. The bond alternation of the
seven-membered ring exists. In addition, one of the bond angles of O-P-C(phenyl) was 178.5 ˚, and
the bond length of the P-C(phenyl) bond (1.380 Å) was slightly longer than those of the other
P-C(phenyl) bonds (1.823 and 1.826 Å). The results supported the consideration.
Ph
Ph
1.495
1.195
1.493
1.196
O
O
1.533
1.20O3
1.528
O
1.213
2.943
1.387
Ph
1.826
1.453
1.414
1.437
1.407
1.437
1.430
1.384
1.387
1.391
1.475
1.343
P
1.361
1.413
1.367
1.472
1.419
1.501
Ph
1.435
1.346
1.823
Ph
N
1.583
N
1.325
1.824
1.319
1.365
1.830
P
Ph
N
1.326
N
1.825
Ph
1.304
1.816
1.380
1.358
Ph
12A
12B
Figure 1. Calculated bond lengths (Å) and the optimized structures of 12A and 12B.
1.360(12)
1.377(11)
1.371(11)
1.381(7)
1.395(7)
1.388(8)
1.473(7)
O
1,213(5)
2.752
1.533(6)
O
H
2.21(3)
1.429(4) 1.239(4)
1.386(4)
1.426(4)
1.379(5)
1.388(6)
1.395(5)
1.471(5)
1.394(4)
H0.86(2)
1.425(5)
N
1.322(5)
1.356(4)
H
0.98(3)
1.346(4)N
1.379(5)
Figure 2. ORTEP drawing with thermal ellipsoids (50% probability) and bond lengths of 13.

HETEROCYCLES, Vol. 74, 2007
313
R
R
R
PPh3
O
PPh3
O
PPh3
O
14 : R = H, CH3, CO2Et, CN
Ph
N
Ph
O
O
O
O
PPh3
PPh3
N
N
12B
12
The structure of 13 was decided by X-ray structure analysis. ORTEP drawing and bond lengths are
shown in Figure 2. Hydrogen bonding between one carbonyl group and NH was observed (2.21 Å).
Another carbonyl group existed at out of 1-azaazulene plane. In the IR spectrum of 13, two carbonyl
signals were seen at 1673 and 1633 cm-1. The latter would be owing to a hydrogen bonding carbonyl
group. Treatment of 13 with PPh3 and hexachloroethane in the presence of Et3N in benzene under
reflux for 5 h gave 12 in 96% yield. This supports the structure of 12.
Ph
Ph
Ph
N
TfO
Tf
Cu
O
OH
N PPh3
H2O
Cu(OTf)2
PPh3
N
N PPh3
N
N
8b
A
B
Ph
N
Ph
Ph
HO
TfOCu
O
O
O
H2O
PPh3
Tf
PPh3
Tf
N PPh3
N
N
N
N
11
C
D
Cu(OTf)2
Cu(OTf)2
H2O
Ph
N
Ph
O
O
O
O
PPh3, C2Cl6, Et3N
NH2
N PPh3
N
13
12
Scheme 3

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HETEROCYCLES, Vol. 74, 2007
In these reactions, oxidation of the ethynyl group with Cu(OTf)2 proceeded. To clarify the reaction
mechanism, we carried out some additional examinations. When 0.1 equivalent molar of Cu(OTf)2
was used on the reaction with 8b, only trace of 12 was obtained along with recovery of 8b (85%).
Therefore, it is considered that stoichiometric reaction was occurred. When the reaction of 8b with an
equivalent molar of Cu(OTf)2 was carried out under heating for 12 h, 11 (25%) and 12 (2%) were
obtained along with 8b (32%). Prolonged reaction resulted in increase of 12 and 13: the reaction for 48
h gave 12 (18%) and 13 (33%), and the reaction for 96 h gave 12 (8%) and 13 (44%). When the
reaction was carried out in benzene for 8 h at 90 ℃ in a sealed tube, 11 (13), 12 (5%), and 13 (41%)
were obtained. Treatment of 11 with Cu(OTf)2 for 20 h gave 12 in 41% yield and formation of 13 was
not observed. Work-up by chromatography of 12 did not give 13 at all. This suggested that 13 would
be formed from the intermediate complex of 8b and Cu(OTf)2. Reaction of 7b with Cu(OTf)2 did not
undergo in the conditions, and 13 was not obtained. From these results, we tentatively suggest the
reaction mechanisms as shown in Scheme 3.25
R
R
ArNCO
N C=N Ar
N PPh3
N
N
8a : R = TMS
8b
: R = Ph
BPO
ArNCO
(Ar = p-Tol)
(R = Ar = Ph)
R
R
Ph
NPh
NH
N
+
N
N
N
N
O
NTol
O
N
Tol
N
Tol
O
17
15a : R = TMS
15b : R = Ph
16a : R = TMS
16b : R = Ph
We previously reported that reaction of 2-(triphenylphosphoimino)-1-azaazulene with aryl isocyanate
proceeded via 2-aryl 1-azaazulen-2-yl carbodiimide intermediate. It is known that
enyne-carbodiimides proceeded cyclization to give heteroaromatics such as carbolines and ellipticine
analogues,11-17 and underwent Pouson-Khand type reaction in the presence of Mo(CO)6.26 Therefore,
we next examined the reaction of 8 with aryl isocyanate. Reaction of 8a with p-tolyl isocyanate in
benzene at rt did no reaction. When the reaction was carried out in xylene under reflux for 48 h, 15a
was obtained in 34% yield. Treatment of 8b with p-tolyl isocyanate in xylene for 9 h at 90 ℃ in a
sealed tube gave 15b (30%) and 16b (12%). In the reaction, ethynyl group was not reacted, and the
reaction was similar to the reported one.8 Next we carried out the reaction in the presence of Lewis
acid. When 8b was treated with p-tolyl isocyanate in the presence of ZnCl2 in xylene under reflux for

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315
0.5 h, 15b was obtained in 82% yield. In this time, reaction rate was accelerated, but the reaction was
same. Reaction of 8b with phenyl isocyanate in the presence of Mo(CO)6 in xylene under reflux for 24
h gave 7b (24%) and 8b (13%), and no distinct cyclization product was isolated. Reaction of 8b in the
presence of Cu(OTf)2 in benzene under reflux for 24 h gave 11 (49%) and 12 (6%). In this reaction,
oxidation of the ethynyl group occurred preferentially, and isocyanate did not take part in.
It is reported that the cyclization of N,N’-(o-ethynylphenyl)carbodiimides proceeded in radical
reaction.16 Therefore we treated 8a with phenyl isocyanate in the presence of benzoyl peroxide, and
1
obtained 17 in 5% yield together with unidentified red substance. In the H NMR spectrum of 17, a
vinylic proton was observed at δ 6.32 and broad NH signal was observed at δ 8.5-9.4, together with
phenyl protons and seven-membered ring protons. In its IR spectrum, a peak at 3445 cm-1 attributed
to NH and a peak at 1591 cm-1 attributed to C=N. From these results, we assigned the structure.
CONCLUSION
3-(Phenylethynyl)- and 3-(trimethylsilylethynyl)-2-(triphenyl-phosphoimino)-1-azaazulenes were
synthesized in excellent yields by the Appel reaction of the corresponding 2-amino-3-
ethynyl-1-azaazulenes with PPh3 and hexachloroethane in the presence of Et3N. Oxidation of ethynyl
group underwent by the treatment of 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulene (8b)
with
Cu(OTf)2
to
give
3-(2-oxophenethyl)-2-(triphenylphosphoimino)-1-azaazulene
(11),
3-(1,2-dioxophenethyl)-2-(triphenylphosphoimino)-1-azaazulene
(12), and 2-amino-3-(1,2-
dioxophenethyl)-1-azaazulene (13). The structure of 13 was decided by X-ray structure analysis, and
the structure of 12 was discussed by molecular orbital calculation. Reaction of 8b with aryl isocyanate
in the presence of benzoyl peroxide gave 1,10-diazabenz[a]azulene derivative via
N-(1-azaazulen-2-yl)-N’-phenylcarbodiimide intermediacy.
ACKNOWLEDGEMENTS
This work was partially supported by a Grant-in-Aid for Scientific Research (No.18510075) to S. T.
from the Japan Society for Promotion of Science (JSPS).
EXPERIMENTAL
1
Mps are measured using Yanagimoto micro-melting apparatus and uncorrected. H NMR spectra
(including HH-COSY and CH-COSY NMR) 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; J value are recorded in Hz. IR spectra were
recorded for KBr pellets on a Nicolet FT-IR Avatar 370DTGS. Electronic spectra were recorded with
JASCO V-570 spectrophotometer using chloroform as a solvent. Elemental analyses were taken with a
Perkin Elmer 2400II. Kiselgel 60 was used for column chromatography and Kiselgel 60G was used for
thin-layer chromatography.
Synthesis of 3-(trimethylsilylethynyl)-2-(triphenylphosphoimino)-1-azaazulene
Under argon atmosphere, a mixture of 2-amino-3-(trimethylsilylethynyl)-1-azaazulene (7a)10 (0.1205 g,
0.50 mmol) in dry benzene (30.0 mL) were added consecutively Et3N (4.0 mL, 33.6 mmol), PPh3 (0.170
g, 0.65 mmol) and hexachloroethane (0.1537 g, 0.65 mmol). After refluxed for 1 h, the precipitate was
filtered off. The filtrate was evaporated, and the residue was chromatographed with hexane-AcOEt (4 :

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HETEROCYCLES, Vol. 74, 2007
1) to give 8a (0.2384 g, 95%).
8a: Red powders (from hexane-benzene), mp 109-111 ℃; δH 0.34 (9H, s), 7.14 (1H, dd, J 10.0, 9.2),
7.27 (1H, dd, J 10.0, 9.6), 7.29 (1H, dd, J 10.0, 9.2), 7.42-7.46 (6H, m), 7.51-7.55 (3H, m), 7.63 (1H, d,
J 9.2), 7.92-7.98 (6H, m), 7.96 (1H, d, J 10.0); δC 0.99, 85.83, 85.56, 101.07 (J 16.0), 125.59, 126.98,
128.70, 128.83, 129.07, 129.23, 129.68, 130.23, 130.91, 132.32, 133.34, 133.73, 133.83, and 149.21;
ν
max / cm-1 2129 (C≡C), 1577 (C=N), and 1472 (P-Ph); λmax nm-1 307 (4.50, sh), 316 (4.58), 333 (4.34,
sh), 350 (4.27, sh), 387 (3.90), 405 (3.90), 433 (3.80), 466 (3.64), 475 (3.64, sh), 510 (3.51, sh), and 552
(3.03, sh). Anal. Calcd for C32H29N2PSi･0.5C6H6: C, 77.89; H, 5.98; N, 5.19. Found: C, 77.64; H,
5.88; N, 5.21.
Synthesis of 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulene
Under argon atmosphere, a mixture of 2-amino-3-(phenylethynyl)-1-azaazulene (7b)10 (0.2106 g, 0.86
mmol) in dry benzene (30.0 mL) were added consecutively Et3N (4.0 mL, 33.6 mmol), PPh3 (0.268 g,
1.03 mmol) and hexachloroethane (0.2415 g, 1.03 mmol). After refluxed for 1 h, the precipitate was
filtered off. The filtrate was evaporated, and the residue was chromatographed with hexane-AcOEt (4 :
1) to give 8b (0.4166 g, 98%).
8b: Red prisms (from hexane-CH2Cl2), mp 164-165 ℃; δH 7.15 (1H, dd, J 9.9, 9.6), 7.28 (1H, dd, J
10.1, 9.4), 7.29 (1H, dd, J 9.9, 9.6), 7.30 (1H, t, J 7.8), 7.35 (2H, dd, J 7.8, 7.1), 7.42-7.47 (6H, m),
7.49-7.55 (3H, m), 7.59 (2H, d, J 7.1), 7.63 (1H, d, J 9.6), 7.93-7.99 (6H, m), 8.05 (1H, d, J 10.1); δC
85.77, 97.45, 102.00 (d, J 21.7), 125.54, 125.63, 126.95, 127.43, 128.53, 128.84 (d, J 16.6), 128.88,
129.35, 129.71, 130.35, 130.85, 131.69, 132.34 (d, J 2.9), 133.79 (d, J 10.0), 148.73, 159.52, 175.09,
and 175.14; νmax / cm-1 2190 (C≡C), 1582 (C=N), and 1451 (P-Ph); λmax nm-1 276 (4.49), 297 (4.49),
322 (4.51), 379 (3.81, sh), 388 (3.80), 448 (3.94), and 506 (3.66, sh). Anal. Calcd for C35H25N2P: C,
83.32; H, 4.99; N, 5.55. Found: C, 83.05; H, 4.94; N, 5.27.
Reaction of 3-(trimethylsilylethynyl)-2-(triphenylphosphoimino)-1-azaazulene in the presence of
Lewis acid
Typical procedure
-
Under argon atmosphere,
a
mixture of 3-(trimethylsilylethynyl)-2-
(triphenylphosphoimino)-1-azaazulene (0.1502 g, 0.30 mmol) and Cu(OTf)2 (0.1085 g, 0.30 mmol) in
dry 1,2-dichloroethane (5 mL) was heated at 90 ℃ for 24 h in a sealed tube. The precipitate was
filtered off, and the filtrate was evaporated. Chromatography of the residue with hexane-AcOEt (1 : 1)
gave 9 (0.0113 g, 8%) and 10 (0.0054 g, 10%).
9: Yellow prisms (from hexane-CH2Cl2), mp 260-262 ℃; δH 3.02 (3H, s), 7.30 (1H, dd, J 10.4, 9.7),
7.48 (1H, dd, J 10.4, 9.8), 7.47-7.49 (6H, m), 7.55 (1H, dd, J 10.2, 9.7), 7.53-7.58 (3H, m), 7.74 (1H, d,
J 9.8), 7.89-7.94 (6H, m), 9.30 (1H, d, J 10.2); δC 48.68, 125.87, 127.59, 127.80, 128.13, 128.47, 128.52,
128.59, 128.78, 129.63, 129.77, 129.88, 131.36, 132.04 (d, J 8.0), 132.70, 133.33, 133.43, 133.53,
196.90; νmax / cm-1 1608 (C=O) and 1491 (P-Ph). Anal. Calcd for C29H25N2OP: C, 78.01; H, 5.19; N,
6.27. Found: C, 78.24; H, 5.20; N, 6.55.
10: Yellow prisms (from hexane-CH2Cl2), mp 198-200 ℃; δH 3.02 (3H, s), 7.30 (1H, dd, J 10.4, 9.7),
7.48 (1H, dd, J 10.4, 9.8), 7.55 (1H, dd, J 10.2, 9.7), 7.74 (1H, d, J 9.8), 9.30 (1H, d, J 10.2); δC 110.93,
127.87, 128.19, 128.29, 128.42, 128.87, 128.96, 129.62, 129.75, 132.01 (d, J 12.0), 132.87, 133.23,
133.33, 134.25, 134.74 (d, J 12.0), 192.29, 195.25; νmax / cm-1 3383 (NH) and 1635 (C=O). Anal.
Calcd for C11H10N2O: C, 70.95; H, 5.41; N, 15.04. Found: C, 70.98; H, 5.54; N, 14.75.

HETEROCYCLES, Vol. 74, 2007
317
Reaction of 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulene in the presence of Lewis
acid
Typical procedure
-
Under argon atmosphere,
a
mixture of 3-(phenylethynyl)-2-
(triphenylphosphoimino)-1-azaazulene (8b) (0.1212 g, 0.24 mmol) and Cu(OTf)2 (0.082 g, 0.24 mmol)
in dry benzene (5 mL) was heated at 90 ℃ for 8 h in a sealed tube. The precipitate was filtered off,
and the filtrate was evaporated. Chromatography of the residue with hexane-AcOEt (1 : 1) gave 8b
(0.0021 g, 2%), 11 (0.0167 g, 13%), 12 (0.0064 g, 5%), and 13 (0.0244 g, 41%).
11: Yellow prisms (from hexane-CH2Cl2), mp 192.5-194 ℃; δH 4.95 (2H, s), 7.17 (1H, t, J 7.2), 7.23
(2H, dd, J 7.4, 7.2), 7.29 (1H, dd, J 10.4, 9.6), 7.38 (2H, d, J 7.4), 7.39 (1H, dd, J 10.2, 9.6), 7.43-7.47
(6H, m), 7.48 (1H, dd, J 10.4, 10.1), 7.53-7.57 (3H, m), 7.71 (1H, d, J 10.1), 7.85-7.90 (6H, m), 9.26
(1H, d, J 10.2); δC 48.68, 125.87, 127.59, 127.80, 128.13, 128.47, 128.52, 128.59, 129.63, 129.77,
129.88, 131.36, 132.03, 132.05, 132.70, 133.33, 133.43, 133.53, 196.90; νmax / cm-1 1626 (C=O) and
1467 (P-Ph); λmax nm-1 276 (4.33), 319 (4.47), 392 (4.04), and 438 (3.89). Anal. Calcd for
C35H27N2OP: C, 80.44; H, 5.21; N, 5.36. Found: C, 79.91; H, 4.97; N, 5.12.
12: Yellow prisms (from MeCN), mp 206.5-208 ℃; δH 7.31 (2H, dd, J 8.4, 7.4), 7.33-7.39 (6H, m),
7.35-7.40 (1H, m), 7.45 (1H, dt, J 7.4, 1.4), 7.46-7.51 (3H, m), 7.54-7.59 (7H, m), 7.62 (1H, dd, J 10.2,
9.8), 7.77 (1H, d, J 10.1), 7.96 (2H, dd, J 8.4, 1.4), 9.28 (1H, d, J 9.8); δC 110.93, 127.87, 128.19,
128.29, 128.42, 128.87, 128.96, 129.62, 129.75, 132.01 (d, J 12.0), 132.87, 133.23, 133.33, 134.25,
134.74 (d, J 12.0), 192.29, 195.25; νmax / cm-1 1677 and 1600 (C=O), and 1492 (P-Ph); λmax nm-1 275
(4.44), 325 (4.58), 396 (4.13), 450 (3.80, sh), and 467 (3.90). Anal. Calcd for C35H27N2O2P: C,
78.35; H, 4.70; N, 5.22. Found: C, 78.24; H, 4.55; N, 5.07.
13: Yellow prisms (from MeCN), mp 209-210.5 ℃; δH 6.8-8.0 (br, 2H, NH2), 7.49-7.52 (2H, dd, J 8.5,
7.4, Ph-m), 7.52-7.55 (2H, m, H-5, H-6), 7.66 (1H, dt, J 7.4, 2.8, Ph-p), 7.46-7.51 (1H, m, H-7), 8.02
(1H, m, H-4), 8.07 (2H, dd, J 8.5, 1.2, Ph-o), 8.05 (1H, d, J 10.2, H-8); δC 103.78, 122.39, 128.09,
129.12, 130.23, 131.36, 133.18, 133.44, 134.47, 134.85, 135.88, 163.83, 189.48, 194.89; νmax / cm-1
3408 (NH), 1673 and 1634 (C=O); λmax nm-1 263 (4.40), 300 (4.56), 359 (3.95, sh), 374 (3.89, sh), and
442 (3.88). Anal. Calcd for C17H12N2O2: C, 73.90; H, 4.38; N, 10.14. Found: C, 73.44; H, 4.55; N,
10.33.
Reaction of 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulene in the presence of Lewis
acid
Under argon atmosphere, a mixture of 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulene (11)
(0.0242 g, 0.046 mmol) and Cu(OTf)2 (0.0166 g, 0.046 mmol) in dry benzene (5 mL) was heated at
90 ℃ for 20 h in a sealed tube. The precipitate was filtered off, and the filtrate was evaporated.
Chromatography of the residue with hexane-AcOEt (1 : 1) gave 12 (0.0102 g, 41%).
Appel reaction of 13
Under argon atmosphere, a mixture of 2-amino-3-(1,2-dioxo-phenethyl-1-azaazulene (13) (0.0055 g,
0.02 mmol) in dry benzene (20.0 mL) were added consecutively Et3N (4.0 mL, 33.6 mmol), PPh3
(0.0053 g, 0.02 mmol) and hexachloroethane (0.0047 g, 0.02 mmol). After refluxed for 5 h, the
precipitate was filtered off. The filtrate was evaporated, and the residue was chromatographed with
hexane-AcOEt (5 : 1) to give 12 (0.0103 g, 96%).

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Reaction of 3-(trimethylsilylethynyl)-2-(triphenylphosphoimino)-1-azaazulene with aryl isocyanate
Under argon atmosphere, a mixture of 3-(trimethylsilylethynyl)-2-(triphenylphosphoimino)-1-
azaazulene (a) (0.2504 g, 0.50 mmol) and p-tolyl isocyanate (0.073 g, 0.50 mmol) in dry xylene (20 mL)
was heated under reflux for 48 h, and the solvent was evaporated. Chromatography of the residue with
hexane-AcOEt (1 : 1) gave 15a (0.0817 g, 34%).
15a: Dark green micro needles (from MeCN), mp 179.5-181 ℃; δH 0.23 (9H, s), 2.27 (3H, s), 2.41 (3H,
s), 6.92 (1H, dd, J 11.2, 9.2), 7.00 (2H, d, J 8.3), 7.06 (1H, dd, J 11.1, 9.2), 7.07 (1H, dd, J 11.2, 9.4),
7.12 (2H, d, J 8.3), 7.23 (2H, d, J 8.3), 7.31 (2H, d, J 8.3), 7.64 (1H, d, J 11.1), 8.59 (1H, d, J 9.4); δC
21.06, 21.46, 93.81, 101.02, 106.95, 121.98, 124.07, 126.70, 124.06, 128.51, 128.65, 130.34, 132.26,
132.73, 133.58, 134.40, 135.02, 135.52, 142.89, 148.41, 148.87, and 155.84; νmax / cm-1 2145 (C≡C)
and 1716 (C=O); λmax nm-1 298 (4.46), 481 (4.33), 560 (3.82, sh), and 630 (3.03, sh). Anal. Calcd for
C30H28N4OSi: C, 73.74; H, 5.78; N, 11.47. Found: C, 73.54; H, 5.60; N, 11.03.
Reaction of 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulene with aryl isocyanate
Under argon atmosphere, a mixture of 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulene (8b)
(0.2018 g, 0.40 mmol) and p-tolyl isocyanate (0.158 g, 1.20 mmol) in dry xylene (20 mL) was heated at
90 ℃ for 9 h, and the solvent was evaporated. Chromatography of the residue with hexane-AcOEt
(4 : 1) gave 15b (0.0594 g, 30%) and 16b (0.0194 g, 12%).
15b: Dark green micro needles (from MeCN), mp >300 ℃; δH 2.32 (3H, s), 2.43 (3H, s), 6.92 (1H, dd,
J 11.2, 9.8), 7.04 (1H, dd, J 11.2, 9.3), 7.09 (2H, d, J 8.3), 7.10 (1H, ddd, J 11.2, 9.8, 1.0), 7.14 (2H, d, J
8.3), 7.27 (2H, d, J 8.3), 7.33 (2H, d, J 8.3), 7.35-7.36 (3H, m), 7.48-7.50 (2H, m), 7.71 (1H, d, J 11.2),
8.58 (1H, d, J 9.3); δC 21.03, 21.37, 85.03, 100.44, 101.04, 118.56, 120.27, 122.81, 123.93, 128.37,
128.49, 128.67, 128.71, 128.91, 130.26, 130.55, 131.66, 132.83, 135.16, 137.58, 142.91, 147.88, and
155.75; νmax / cm-1 2194 (C≡C), 1714 (C=O); λmax nm-1 283 (4.50), 310 (4.40), 485 (4.29), 600 (3.42,
sh), and 655 2.76 (sh). Anal. Calcd for C33H24N4O: C, 80.47; H, 4.91; N, 11.37. Found: C, 80.32;
H, 4.76; N, 11.70.
16b: Yellow needles (from MeCN), mp >300 ℃; δH 2.42 (3H, s), 7.23 (2H, d, J 8.5), 7.27-7.36 (2H,
m), 7.34 (2H, d, J 8.3), 7.37-7.40 (3H, m), 7.41 (1H, ddd, J 11.0, 8.8, 1.4), 7.63-7.65 (2H, m), 8.08 (1H,
d, J 11.0), 9.04 (1H, dd, J 8.9, 1.4); δC 21.29, 88.23, 100.48, 102.60, 122.59, 123.72, 127.90, 128.40,
128.91, 130.29, 131.90, 131.99, 133.23, 134.64, 135.67, 136.21, 139.04, 142.03, 148.49, 148.73, and
159.18; νmax / cm-1 2112 (C≡C), 1740, 1685 (C=O); λmax nm-1 302 (4.52), 454 (4.23, sh), 466 (4.26),
and 522 (3.56, sh). Anal. Calcd for C26H17N3O2: C, 77.41; H, 4.25; N, 10.42. Found: C, 77.95; H,
3.95; N, 10.36.
Reaction of 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulene with aryl isocyanate in the
presence of Lewis acid
Under argon atmosphere, a mixture of 8b (0.011 g, 0.020 mmol), p-tolyl isocyanate (0.008 g, 0.060
mmol), and ZnCl2 (0.0027 g, 0.020 mmol) in dry xylene (20 mL) was heated under reflux for 0.5 h, and
the solvent was evaporated. Chromatography of the residue with hexane-AcOEt (1 : 1) gave 15b
(0.0081 g, 82%).
Reaction of 3-(phenylethynyl)-2-(triphenylphosphoimino)-1-azaazulene with aryl isocyanate in the

HETEROCYCLES, Vol. 74, 2007
319
presence of benzoyl peroxide
Under argon atmosphere, a mixture of 8b (0.101 g, 0.20 mmol), p-tolyl isocyanate (0.050 mL, 0.22
mmol), and benzoyl peroxide (0.003 g) in dry xylene (20 mL) was stirred at rt for 1 h, and after the
heating the mixture at 90 ℃ for 9 h, the temperature was elevated to 150 ℃ and reaction was
continued 48 h. The precipitate was filtered off, and the filtrate was evaporated. Then the solvent
was evaporated, and chromatography of the residue with hexane-CHCl3 (1 : 1) gave 17 (0.0032 g, 5%),
unidentified red needles (0.0146 g), and recovered (8b) (0.030 g, 30%).
17: Green powders (from hexane), mp 179-183 ℃; δH 6.32 (1H, s), 7.31 (1H, t, J 7.6), 7.47 (2H, t, J
7.6), 7.54 (2H, dd, J 7.6, 7.2), 7.63 (1H, t, J 7.2), 7.76 (1H, dd, J 10.8, 10.0, H-5), 7.78-7.82 (1H, m,
H-6), 7.80 (2H, d, J 7.6), 7.83-7.85 (1H, m, H-7), 8.43 (2H, d, J 7.6), 8.59 (1H, d, J 10.0, H-4), 8.76 (1H,
m, H-8); δC 107.57, 122.63, 127.56, 128.03, 128.81, 128.87, 129.09, 130.19, 130.54, 133.00, 134.54,
135.16, 135.77, 136.27, 136.56, 137.58, 142.17, 144.92, 150.52, and, 152.81; νmax / cm-1 3445 (N-H),
1591 (C=N ; λmax nm-1 286 (4.27, sh), 296 (4.31), 354 (4.40, sh), 363 (4.43), 420 (3.52), 450 (3.61), 472
(3.57, sh), 563 (3.18, sh), 592 (3.21), and 664 (2.97, sh). Anal. Calcd for C24H17N3: C, 82.97; H,
4.93; N, 12.10. Found: C, 82.88; H, 4.75; N, 12.37.
X-Ray structure determination
Crystal data of 13: Yellow needle, C17H12N2O2, M = 276.29, monoclinic, space group P21/c, a =
14.484(8) Å, b = 6.996(15) Å, c = 15.310(10) Å, β = 117.72(4)°, V = 1373.3(32) Å3, Z = 4, Dcalc = 1.336
g/cm3, crystal dimension 0.88 x 0.32 x 0.12 mm. Data were measured on a Rigaku AFC 5S radiation
diffractmeter with graphite-monochromated Mo-Kα radiation. Total 3254 reflections (3133 unique)
were collected using ω-2θ scan technique with in a 2θ range of 55.0°. The structure was solved by
direct methods (SIR92),27 and expanded using Fourier techniques (DIRDIF99),28 and refined by a
full-matrix least-squares method using 208 variables refined with 1265 reflections [I > 2σ(I)]. The
non-hydrogen atoms were anisotropically. The final refinement converged to R = 0.0491 and Rw =
0.0307. All calculations were performed using the CrystalStructure29,30 crystallographic software
package.
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