Preparation and Stille cross-coupling reaction of the first organotin reagents of azulenes. Easy access to poly(azulen-6-yl)benzene derivatives

Article abstract of DOI:10.1039/b203836f

The first versatile organometallic reagents derived from azulenes, i.e., 6-(tri-n-butylstannyl)azulene (1a) and its 1,3-diethoxycarbonyl derivative (1b), have been prepared by Pd(0)-catalyzed direct stannylation of 6-bromoazulenes with bis(tri-n-butyltin). We demonstrate the utility of the reagents in the Stille cross-coupling reaction with aryl, acyl and azulenyl halides to afford 6-aryl-, 6-acyl- and bi-azulenes in good yield. Furthermore, the methodology was applied to the synthesis of poly(azulen-6-yl)benzene derivatives. The reaction of 1b with 1,4-di-, 1,3,5-tri-, 1,2,4,5-tetra- and hexabromobenzenes afforded 1,4-di-, 1,3,5-tri-, 1,2,4,5-tetra-, 1,2,4-tri- and 1,2,3,5-tetra(azulen-6-yl)benzene derivatives (18, 20, 22, 24 and 25). The redox behavior of 18 and 22 was examined by cyclic voltammetry (CV) and compared with those of 20 and 24 reported previously. In contrast to the three-step reduction of 20, the compound 18 exhibited a reversible one-step two-electron reduction wave at - 1.30 V upon CV, which revealed the formation of a closed-shell dianion. The four azulen-6-yl substituents on benzene in a 1,2,4,5 relationship increased electron-accepting properties because of the formation of a closed-shell dianion stabilized by four azulen-6-yl groups. As expected, the compound 22 exhibited a color change during the electrochemical reduction. However, the reverse oxidation did not regenerate the spectrum of 22 due to the low stability of the presumed dianionic species under the conditions of the UV-vis measurement.

Full text of DOI:10.1039/b203836f

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Preparation and Stille cross-coupling reaction of the
first organotin reagents of azulenes. Easy access to
poly(azulen-6-yl)benzene derivatives
1
Shunji Ito,* Tetsuo Okujima and Noboru Morita
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578,
Japan. E-mail: ito@funorg.chem.tohoku.ac.jp; Fax: ϩ81(0)222177714
Received (in Cambridge, UK) 19th April 2002, Accepted 25th June 2002
First published as an Advance Article on the web 16th July 2002
The first versatile organometallic reagents derived from azulenes, i.e., 6-(tri-n-butylstannyl)azulene (1a) and its
1,3-diethoxycarbonyl derivative (1b), have been prepared by Pd(0)-catalyzed direct stannylation of 6-bromoazulenes
with bis(tri-n-butyltin). We demonstrate the utility of the reagents in the Stille cross-coupling reaction with aryl, acyl
and azulenyl halides to afford 6-aryl-, 6-acyl- and bi-azulenes in good yield. Furthermore, the methodology was
applied to the synthesis of poly(azulen-6-yl)benzene derivatives. The reaction of 1b with 1,4-di-, 1,3,5-tri-,
1,2,4,5-tetra- and hexabromobenzenes afforded 1,4-di-, 1,3,5-tri-, 1,2,4,5-tetra-, 1,2,4-tri- and 1,2,3,5-tetra(azulen-
6-yl)benzene derivatives (18, 20, 22, 24 and 25). The redox behavior of 18 and 22 was examined by cyclic voltammetry
(CV) and compared with those of 20 and 24 reported previously. In contrast to the three-step reduction of 20, the
compound 18 exhibited a reversible one-step two-electron reduction wave at Ϫ1.30 V upon CV, which revealed the
formation of a closed-shell dianion. The four azulen-6-yl substituents on benzene in a 1,2,4,5 relationship increased
electron-accepting properties because of the formation of a closed-shell dianion stabilized by four azulen-6-yl groups.
As expected, the compound 22 exhibited a color change during the electrochemical reduction. However, the reverse
oxidation did not regenerate the spectrum of 22 due to the low stability of the presumed dianionic species under the
conditions of the UV–vis measurement.
aryl, acyl and/or azulenyl halides to demonstrate the utility of
Introduction
the reagents for carbon–carbon bond formation.10
Palladium-catalyzed cross-coupling reaction has become a
We also demonstrate easy access to poly(azulen-6-yl)benzene
widely used method for carbon–carbon bond formation in
derivatives via the cross-coupling reaction of 1b with aromatic
polybromides promoted by the Pd(0)-catalyzed reaction.
modern organic synthesis.1 Several applications of this
transition-metal catalyzed reaction in the chemistry of azulenes
Recently, Hünig et al. have proposed the concept of violene–
have also appeared in the literature, e.g., palladium-catalyzed
cyanine hybrids as stabilized organic electrochromics.11 The
vinylation,2 arylation,3 ethynylation4 and alkylation5 of azule-
hybrids contain the moiety X᎐C–Y, which represents a
᎐
nyl halides or triflate. However, the lack of a versatile organo-
metallic reagent for the transition-metal catalyzed reaction of
azulene itself imposes restrictions6 because of the synthetic
inaccessibility of such a reagent due to the high reactivity of
azulenes with organolithium and magnesium reagents to pro-
duce dihydroazulene derivatives.7 From the viewpoint of the
general usage of transition-metal catalyzed reactions in the
chemistry of azulenes, we focused on the development of an
organometallic reagent for the transition-metal catalyzed reac-
tion of azulenes. Especially, application of the reagent would be
a great advantage in multiple functionalization with azulenyl
groups because the method does not require the preparation of
troublesome polymetallic species.8
“cyanine”-type structure in fully reduced or oxidized form, as
the end groups of violene. The system provides highly colored
closed-shell systems such as cyanine dyes by an overall two-
electron transfer (Scheme 1). We have recently proposed that the
The Stille cross-coupling of organotin compounds with a
variety of organic electrophiles, catalyzed by palladium, pro-
vides an efficient method for carbon–carbon bond formation.1,9
Functionalization of azulene in the seven membered-ring is
rather difficult so far, although that of the 1,3-positions of the
system can be easily achieved by electrophilic substitution.
Therefore, we examined the stannylation of azulenes in the
seven-membered ring and the potential of the reagents for the
Stille cross-coupling reaction. Herein we report in detail the
preparation of the first versatile organometallic reagents of
azulenes, 6-(tri-n-butylstannyl)azulene (1a) and its 1,3-diethoxy-
carbonyl derivative (1b) and the successful application to the
Pd(0)-catalyzed Stille cross-coupling reaction of 1a and 1b with
Scheme 1
poly(azulen-6-yl)benzene derivatives could be considered as
candidates for such a system.12 Depending on the number
and position of the azulen-6-yl substituents, the system could
1896
J. Chem. Soc., Perkin Trans. 1, 2002, 1896–1905
This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b203836f

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Table 1 Stille cross-coupling reaction of 1b with 4a and 4ba
Yield/%b
Entry
X
Catalyst
Ligand
Additive
Solvent
5
6
7b
8b
1b
1
2
3
4
5
6
7
8
Br
I
Br
Br
I
I
Br
Br
Pd(PPh3)4
Pd(PPh3)4
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Pd2(dba)3
Toluene
Toluene
Dioxane
Dioxane
Dioxane
Dioxane
Dioxane
Dioxane
16
8
52
30
—
—
—
—
17
17
12
25
11
8
4
4
5
2
14
5
6
6
0
11
0
P(t-Bu)3
P(t-Bu)3
P(t-Bu)3
P(t-Bu)3
BINAPc
BINAPc
45
74
11
61
13
35
CsF
CsF
CsF
0
61
22
0
26
5
2
2
0
a Reactions of 1b (0.2 mmol) with 4a or 4b (0.6 mmol) were carried out at reflux temperature for 24 h by using 10 mol% Pd(0)-catalyst, ligand
(Pd : P = 1 : 2), and 2.2 equiv of CsF in 20 ml of the solvent. b All yields are isolated yields. c BINAP: 2,2Ј-bis(diphenylphosphino)-1,1Ј-binaphthyl.
provide a closed-shell cyanine-type structure by the two-
electron reduction. Herein, we also report the redox behavior of
several poly(azulen-6-yl)benzene derivatives prepared by the
cross-coupling reaction of 1b with aromatic polybromides.
Results and discussion
Traditionally, aryltin compounds have been prepared by react-
ing an aryllithium intermediate, generated by deprotonation
or halogen–metal exchange, with trialkyltin compounds that
have good leaving groups.13 However, the azulen-6-yllithium
intermediate was so far unknown and could not be easily gener-
ated by halogen–metal exchange. Therefore, the first 6-stannyl-
azulenes (1a and 1b) were synthesized from 6-bromoazulenes
(2a and 2b)14 via Pd(0)-catalyzed direct stannylation with
bis(tri-n-butyltin) (3).15 The coupling reaction of 2a with 3 in
the presence of a catalytic amount of Pd(PPh3)4 in refluxing
Chart 1
toluene for 1 d provided the desired 6-(tri-n-butylstannyl)-
azulene (1a) in 49% yield. Likewise, diethyl 6-(tri-n-butyl-
Using 4b instead of 4a increased the recovery of 1b (entry 2).
stannyl)azulene-1,3-dicarboxylate (1b) was prepared from 2b
Formation of 6 in considerable yield is attributable to aryl–
with 3 in 69% yield (Scheme 2). These organotin compounds
phenyl exchange with the triphenylphosphine ligand in the
initial intermediate formed by oxidative addition of Pd(0) into
the aryl halide.19 Thus, the choice of the catalytic system was
very important for the success of the reaction of 1b. Substi-
tution of the Pd(PPh3)4 catalyst with Pd2(dba)3–P(t-Bu)3 in
the catalytic protocol resulted in a significant increase of the
desired cross-coupling product 5 (entry 3). A fluoride-activation
strategy,20 which was utilized for the activation of the organotin
compound, was effective for this Stille cross-coupling reaction.
The addition of CsF in the catalytic protocol increased the
desired coupling product 5 up to 74% yield (entry 4). While
good conversions were obtained by using 4a, the use of 4b was
unfavorable under the reaction conditions, which decreased the
conversion ratio of the catalytic reaction significantly (entries 5
and 6). The use of BINAP as a ligand did not afford satisfac-
tory results either in the presence or absence of CsF (entries 7
and 8).
To test the generality, the cross-coupling reaction with several
aryl bromides was conducted under the reaction conditions.
The results of the cross-coupling reaction of 1a and 1b with
aryl bromides are summarized in Table 2. The electron-deficient
aryl bromide, 4-bromonitrobenzene was efficiently reacted with
1b to afford the coupled product 9a in high yield (entry 1).
Under similar conditions, the reaction of 1b with 4-bromo-
acetophenone also afforded the desired coupling product 9b in
good yield (entry 2). In the case of the reaction of 1b with
Scheme 2
are stable and are easily characterized by the usual spectro-
scopic analysis.
To demonstrate the transformations using 1a and 1b, we
conducted the Stille cross-coupling reaction with aryl, acyl and
azulenyl halides to produce 6-aryl-, 6-acyl- and bi-azulenes. The
results of the reaction of 1b with 4-bromo- and 4-iodotoluenes
(4a and 4b) are summarized in Table 1. In our initial experi-
ments, 1b proved to be inefficient in the cross-coupling reaction
under typical conditions for the reaction with aryl halides.16
The reaction of 1b with 4a in the presence of Pd(PPh3)4 catalyst
produced the desired diethyl 6-(4-tolyl)azulene-1,3-dicarb-
oxylate (5) in 16% yield together with a significant amount
of undesired diethyl 6-phenylazulene-1,3-dicarboxylate (6),17
diethyl azulene-1,3-dicarboxylate (7b)18 and tetraethyl 6,6Ј-
biazulene-1,1Ј,3,3Ј-tetracarboxylate (8b) (entry 1) (Chart 1).
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Table
2
Stille cross-coupling reaction of 1a and 1b with aryl
Table 3 Stille cross-coupling reaction of 1b with acyl chloridesa
bromidesa
Entry
R
Time/h
Products (yield(%))b
1
2
3
Ph
n-Hexyl
Me
2
3
3
10a (91)
10b (73)
10c (26)
7b (0)
7b (22)
7b (50)
a Reaction conditions: 1b (0.2 mmol), acyl chlorides (0.6 mmol),
Pd2(dba)3 (10 mol%), P(t-Bu)3 (40 mol%), CsF (2.2 eq), dioxane (20 ml),
refluxed under an Ar atmosphere. b All yields are isolated yields.
Entry
Reagent
R
Time/h
Products (yield(%))b
1
2
3
4
5c
6
7
8
1b
1b
1b
1a
1a
1a
1a
1a
NO2
2
2
2
24
24
2
9a (84)
9b (65)
9c (64)
9d (60)
9d (31)
9e (83)
9f (67)
9g (63)
7b (5)
7b (4)
7b (5)
7a (5)
7a (23)
7a (5)
7a (0)
7a (6)
8b (10)
8b (5)
8b (3)
8a (12)
8a (9)
1a (5)
1a (1)
1a (8)
COMe
OMe
Me
Me
NO2
COMe
OMe
coupling reaction of a mixture of azulenyl halides affords
homo-coupling products in addition to the desired cross-
coupled one. We then applied our new 6-stannylazulene 1b to
the selective synthesis of biazulenes including unsymmetrical
ones. Under conditions analogous to those for the reaction with
aryl bromides, 1b reacted smoothly with 2a and 2b to afford
6,6Ј-biazulenes (11 and 8b) in 46% and 68% yields, respectively.
Similarly, the present method could be applied to the selective
synthesis of 2,6Ј-biazulene. The reaction of 1b with 2-bromo-
azulene (13) under the Pd(0)-catalyzed conditions afforded
2,6Ј-biazulene 12 in 51% yield (Chart 2).
4
6
a Reaction conditions: 1a (0.3 mmol) or 1b (0.2 mmol), aryl bromides
(0.9 and 0.6 mmol, respectively), Pd2(dba)3 (10 mol%), P(t-Bu)3 (40
mol%), CsF (2.2 eq), dioxane (30 and 20 ml, respectively), refluxed
under an Ar atmosphere. b All yields are isolated yields. c The reaction
was carried out without an addition of CsF.
electron-rich bromide, 4-bromoanisole, the reaction also pro-
ceeded smoothly under our reaction conditions to give the
cross-coupling product 9c (entry 3).
The fluoride-activation strategy was also effective for the
catalytic protocol of 1a with 4a. In the presence of CsF the
reaction afforded the desired cross-coupling product 9d3b,21 in
60% yield, although the reaction without CsF did not afford
satisfactory results (entries 4 and 5). On the whole, 1a also
reacted rapidly with a variety of aryl bromides including an
electron-rich one under the Pd(0)-catalyzed conditions and
generally the isolated yields of the cross-coupling product were
above 60% (entries 6–8).
To demonstrate the scope of this procedure, attempts were
made for the preparation of 6-acylazulenes, 6,6Ј- and 2,6Ј-
biazulenes utilizing the cross-coupling reaction of 1b with acyl
chlorides, azulen-6-yl and azulen-2-yl bromides, respectively.
Preparation of 6-actetylazulene 10c has been achieved by multi-
step reaction from a tropolone derivative having an acetyl sub-
stituent.22 However, several 6-acylazulene derivatives 10a–c
could be easily prepared by the cross-coupling reaction of 1b
with acyl chlorides under the Pd(0)-catalyzed reaction condi-
tions. The results of the cross-coupling reaction of 1b with acyl
chlorides are summarized in Table 3. Benzoyl chloride was
efficiently reacted with 1b to afford the coupled product 10a in
high yield (entry 1). Under similar reaction conditions, the reac-
tion of 1b with n-heptanoyl chloride also afforded the desired
coupling product 10b in good yield together with a small
amount of 7b (entry 2). In the case of the reaction of 1b with
acetyl chloride, the reaction also proceeded smoothly under the
reaction conditions, but the reaction did not give the coupled
product 10c in satisfactory yield due to the formation of a
significant amount of 7b (entry 3).
Chart 2
Finally, we demonstrated the use of the new 6-stannylazulene
1b in the synthesis of poly(azulen-6-yl)benzene derivatives.
We have recently reported the preparation of some azulen-6-
ylbenzene derivatives utilizing Diels–Alder reaction of azulen-
6-ylacetylenes with cyclopentadienone4a and Co-catalyzed
cyclotrimerization of the azulen-6-ylacetylenes.12 The reaction
can introduce the azulen-6-yl groups to the aromatic core, but
into limited positions. The scope of this methodology for
multiple substitution was demonstrated utilizing the reaction
of 1b with di-, tri-, tetra- and hexabromobenzenes (14–17).
The reaction of 1b with 14 afforded the desired coupled
product,
1,4-bis[1,3-bis(ethoxycarbonyl)azulen-6-yl]benzene
(18) in 32% yield along with 1-[1,3-bis(ethoxycarbonyl)azulen-
6-yl]-4-butylbenzene (19) in 11% yield (Scheme 3). The reaction
of 1b with 15 also gave the desired tris-adduct 2012 in 28%
yield together with 1,3-bis[1,3-bis(ethoxycarbonyl)azulen-6-yl]-
5-butylbenzene (21) in 13% yield (Scheme 4). Therefore, trans-
fer of an n-butyl group from the organotin reagent 1b was the
side reaction for the multi-functionalization of benzene with
azulen-6-yl substituents. Likewise, the reaction of 1b with 16
afforded the expected tetrakis-adduct 22 in 13% yield together
with5-butyl-1,2,4-tris[1,3-bis(ethoxycarbonyl)azulen-6-yl]benz-
ene (23) and 1,2,4-tris[1,3-bis(ethoxycarbonyl)azulen-6-yl]benz-
Preparation of biazulenes has been achieved by homo-
coupling reaction of azulenyl halides23 or stepwise reaction to
prepare the two azulene rings.24 However, selective synthesis
of unsymmetrical biazulenes has been significantly difficult so
far because of the restriction of the synthetic methods. The
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J. Chem. Soc., Perkin Trans. 1, 2002, 1896–1905

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Scheme 3
Scheme 5
Scheme 4
ene (24)12 in 5% and 6% yields, respectively (Scheme 5). On
increasing the steric hindrance, the reduction of bromide also
took place in addition to the transfer of an n-butyl group. In the
case of the reaction of 1b with 17, the reaction afforded 20 and
a mixture (1.6 : 1) of 22 and 1,2,3,5-tetrakis[1,3-bis(ethoxy-
carbonyl)azulen-6-yl]benzene (25) in 16% and 8% yields,
respectively, instead of the desired hexa(azulen-6-yl)benzene
derivative 26 (Scheme 6). Separation of the products 22 and 25
Scheme 6
was attempted by repeated silica gel preparative TLC, but we
could not separate 22 and 25, completely. The ratio of 22 and
25 could be increased up to 1 : 12 and the characterization of 25
was accomplished by both 1H and 13C NMR spectroscopy.
Formation of the products 20, 22 and 25 indicates that the
transfer of azulen-6-yl groups does not occur at the positions
J. Chem. Soc., Perkin Trans. 1, 2002, 1896–1905
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Scheme 7
Table
4
Reduction potentialsa of the poly(azulen-6-yl)benzene
pointed out by asterisks in Scheme 7, which are interposed
by two azulen-6-yl groups. Since 1,2-disubstitution is unfavor-
able for steric reasons, therefore, a plausible pathway for the
formation of these compounds could be depicted as in Scheme 7.
The methodology was then applied to functionaliaztion at
the 2-position of azulenes. However, the reaction of 2-bromo-
azulene (13) with 3 under similar Pd(0)-catalyzed conditions
afforded the desired 2-stannylazulene (27) in only 11% yield
together with 2,2Ј-biazulene (28) in 48% yield (Scheme 8).25 The
derivatives
Sample
E1red/V
E2red/V
E3red/V
Ref.
18
20
22
24
Ϫ1.30 (2e)
(Ϫ1.38)b
Ϫ1.27 (2e)
Ϫ1.31 (2e)
(Ϫ1.46)b
(Ϫ1.57)b
Ϫ1.63 (1e)
(Ϫ1.55)b
(Ϫ1.62)b
12
12
a The reduction potentials were measured by CV (0.1 M n-Bu4NBF4 in
tetrahydrofuran, Pt electrode, scan rate = 100 mV sϪ1, and Fc/Fcϩ = 0.19
V). In the case of irreversible waves, which, are shown in parentheses,
Ered were calculated as Epc (cathodic peak potential) ϩ 0.03 V. b The
values are peak potentials measured by DPV.
wave for 22 should be due to the one-step two-electron reduc-
Ϫ2
tion to form dianion 22RED and the second one could be
attributed to the stepwise redox reaction of 22REDϪ2 to produce
tetraanion diradical 22RED Ϫ4, by analogy with those of 1,2,4-
ؒؒ
tri(azulen-6-yl)benzene derivative 24.12 Indeed, the second wave
was identified as two waves that were barely separated, at Ϫ1.57
and Ϫ1.62 V, by differential pulse voltammetry (DPV). Thus,
the four azulen-6-yl substituents on benzene in a 1,2,4,5
Scheme 8
relationship increased the electron-accepting properties because
high reactivity of either the desired product 27 with 13 or
homocoupling26 of 27 under the reaction conditions leads to
the formation of 28 in significant amounts. For functionaliz-
ation at the 2-position, use of azulen-2-yl borate, which could
be prepared by the same strategy,27 was more effective for
similar Pd(0)-catalyzed reactions.28
The redox behavior of the benzene derivatives 18 and 22
represented the presumed multi-electron redox properties. The
reduction potentials (V vs. Ag/Agϩ) of 18 and 22, along with
those of 20 and 24, measured by CV are summarized in Table 4.
In contrast to the three-step reduction of the 1,3,5-tri(azulen-6-
yl)benzene 20,12 compound 18 showed a reversible one-step
two-electron reduction wave at Ϫ1.30 V upon CV (Fig. 1a). The
relatively less negative reduction potential of 18 compared with
Ϫ2
of the formation of a closed-shell dianionic structure 22RED
.
Consequently, the redox system of 22 could be illustrated as
a violene–cyanine hybrid and could exhibit a significant
color change with a change to a different oxidation state
(Scheme 10).
Electrochemical reduction of 22 was examined to clarify the
Ϫ2
formation of colored species arising from dianion 22RED by
visible spectroscopy under the electrochemical reduction condi-
tions. When the visible spectra of 22 were measured under the
electrochemical reduction conditions in benzonitrile containing
Et4NClO4 (0.1 M) at room temperature, a new absorption in the
visible region was gradually developed as shown in Fig. 2. The
color of the solution of 22 gradually changed from pink to
brown during the electrochemical reduction. However, the
reverse oxidation of the colored solution did not regenerate the
spectrum of the neutral 22, although good reversibility was
observed upon CV. The color of the solution changed to orange
during the electrochemical oxidation. These results demon-
strate the low stability of the dianionic species under the con-
ditions of the measurement, although the dianions 22REDϪ2 are
stabilized by four azulen-6-yl substituents.
that of 20 is attributable to the stabilization of the dianion by
Ϫ2
the formation of a closed-shell dianionic structure 18RED
.
Therefore, the two azulen-6-yl substituents on the benzene ring
in a 1,4 relationship increased the electron-accepting properties.
Thus, the redox system of 18 can be depicted as illustrated in
Scheme 9.
The voltammogram of 22 was characterized by a reversible
wave at Ϫ1.27 V and the next barely separated irreversible one
centered at Ϫ1.61 V upon CV (Fig. 1b). The first reversible
Conclusion
As stated above, the first organotin reagents of azulenes,
6-stannylazulenes (1a and 1b), were prepared by Pd(0)-catalyzed
direct stannylation of 6-bromoazulenes (2a and 2b) and their
application in Pd(0)-catalyzed Stille cross-coupling reaction
with aryl, acyl and azulenyl halides was investigated. In fact,
our new stannylazulenes were effective in the Stille cross-
Scheme 9
1900
J. Chem. Soc., Perkin Trans. 1, 2002, 1896–1905

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Scheme 10
colored closed-shell dianion of azulene-substituted benzene
derivatives by UV–vis spectroscopy due to the instability of
the species. However, the redox behavior examined by CV
represented the presumed multi-electron redox properties under
the electrochemical conditions used.
Experimental
Fig. 1 Cyclic voltammograms of (a) 18 and (b) 22 in THF containing
n-Bu4NBF4 (0.1 M) as a supporting electrolyte.
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 spectrophoto-
meters, respectively. 1H NMR spectra (13C NMR spectra) were
recorded on a JEOL GSX 400 at 400 MHz (100 MHz) or a
JEOL A500 at 500 MHz (125 MHz). Gel permeation chrom-
atography (GPC) was performed on a TSKgel G2000H6.
Elemental analyses were performed at the Instrumental
Analysis Center of Chemistry, Faculty of Science, Tohoku
University.
6-(Tri-n-butylstannyl)azulene 1a
To a degassed solution of 2a (829 mg, 4.00 mmol) and 3 (4.65 g,
8.02 mmol) in dry toluene (50 cm3) was added Pd(PPh3)4
(239 mg, 0.207 mmol). After the resulting mixture was refluxed
for 24 h under an Ar atmosphere, the solvent was removed
under reduced pressure. The residue was purified by column
chromatography on silica gel and medium-pressure liquid
column chromatography on silica gel with hexane to afford 1a
(817 mg, 49%) as a blue oil (Found: C, 63.3; H, 8.1. Calc. for
C22H34Sn: C, 63.3; H, 8.2%); λmax (CH2Cl2)/nm 238 (log ε 4.16),
286 (4.74), 332 (3.70), 339 (3.67), 347 (3.83), 575 (2.51), 620
(2.44) and 682 (2.01); νmax (neat)/cmϪ1 2960, 2924, 2868, 2852,
1578, 1464, 1446, 1396, 814 and 746; δH (400 MHz, CDCl3) 8.22
(d, J 9.3, 2H, 4,8-H), 7.88 (t, J 3.8, 1H, 2-H), 7.36 (d, J 3.8, 2H,
1,3-H), 7.35 (d, J 9.3, 2H, 5,7-H), 1.57 (m, 6H, 2Ј-H), 1.35 (tq,
J 7.3 and 7.3, 6H, 3Ј-H), 1.14 (m, 6H, 1Ј-H) and 0.89 (t, J 7.3,
9H, 4Ј-H); δC (100 MHz, CDCl3) 159.8 (C-6), 139.7 (C-3a,8a),
Fig. 2 Continuous change in visible spectrum of 22 (2 cm3; 2.0 ×
10Ϫ4 M) in benzonitrile containing Et4NClO4 (0.1 M) upon constant-
current electrochemical reduction (100 uA) at 3 min interval.
coupling reaction to afford 6-aryl-, 6-acyl- and bi-azulenes. This
study shows the potential utility of the new transition-metal
catalyzed reaction for the difficult functionalization of azulenes
in the seven-membered ring. Indeed, the methodology was
applied to the synthesis of several poly(azulen-6-yl)benzene
derivatives (18–25). The redox behavior of 18 and 22 was exam-
ined by cyclic voltammetry (CV) and compared with those
of 20 and 24 reported previously. We could not detect the
J. Chem. Soc., Perkin Trans. 1, 2002, 1896–1905
1901

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137.0 (C-2), 134.5 (C-4,8), 130.6 (C-5,7), 117.4 (C-1,3), 29.0
(C-2Ј), 27.4 (C-3Ј), 13.7 (C-4Ј) and 10.4 (C-1Ј); m/z (EI) 418
(Mϩ, 50%), 361 (Mϩ Ϫ Bu, 86), 305 (Mϩ Ϫ 2BuϩH, 56) and
247 (Mϩ Ϫ 3Bu, 100).
117.3 (C-1,3), 60.3 (t, 1,3-COOEt) and 14.5 (q, 1,3-COOEt);
m/z (EI) 542 (Mϩ, 100%) and 497 (Mϩ Ϫ OEt, 21).
Diethyl 6-(4-nitrophenyl)azulene-1,3-dicarboxylate 9a. The
general procedure was followed by using 1b (111 mg, 0.198
mmol), 4-bromonitrobenzene (120 mg, 0.594 mmol), Pd2(dba)3
(17.6 mg, 0.0192 mmol), P(t-Bu)3 (21.8 mg, 0.108 mmol), CsF
(66.7 mg, 0.439 mmol) and dioxane (20 cm3). Chromatographic
purification afforded 9a (65.7 mg, 84%) as purple crystals, 7b
(2.6 mg, 5%) and 8b (5.4 mg, 10%).
Diethyl 6-(tri-n-butylstannyl)azulene-1,3-dicarboxylate 1b
The same procedure as was used for the preparation of 1a was
adopted. The reaction of 2b (3.49 g, 9.94 mmol) with 3 (11.52 g,
19.86 mmol) in dry toluene (200 cm3) in the presence of
Pd(PPh3)4 (569 mg, 0.492 mmol) followed by chromatographic
purification on silica gel with hexane and CH2Cl2 and medium-
pressure column chromatography on silica gel with 30% ethyl
acetate–hexane afforded 1b (3.86 g, 69%) as a red oil (Found:
C, 59.7; H, 7.45. Calc. for C28H42O4Sn: C, 59.9; H, 7.5%);
λmax (CH2Cl2)/nm 235 (log ε 4.52), 275 (4.44), 311 (4.65), 377
For 9a. Mp 175–175.5 ЊC (Found: C, 67.0; H, 5.0; N, 3.7.
Calc. for C22H19NO6: C, 67.2; H, 4.9; N, 3.6%); λmax (CH2Cl2)/
nm 236 (log ε 4.44), 272 (4.26), 327 (4.72) and 525 (2.78);
νmax (KBr disk)/cmϪ1 1694 (C᎐O), 1522, 1437, 1347, 1206 and
᎐
1048; δH (500 MHz, CDCl3) 9.85 (d, J 11.1, 2H, 4,8-H), 8.87 (s,
1H, 2-H), 8.38 (d, J 8.9, 2H, 3Ј,5Ј-H), 7.89 (d, J 11.1, 2H,
5,7-H), 7.83 (d, J 8.9, 2H, 2Ј,6Ј-H), 4.46 (q, J 7.1, 4H, 1,3-
COOEt) and 1.47 (t, J 7.1, 6H, 1,3-COOEt); δC (125 MHz,
CDCl3) 164.8 (s, 1,3-COOEt), 151.4 (C-6), 149.7 (C-1Ј), 148.0
(C-4Ј), 144.2 (C-2), 142.9 (C-3a,8a), 138.4 (C-4,8), 130.3
(C-5,7), 129.6 (C-2Ј,6Ј), 124.2 (C-3Ј,5Ј), 117.2 (C-1,3), 60.2
(t, 1,3-COOEt) and 14.5 (q, 1,3-COOEt); m/z (EI) 393 (Mϩ,
100%), 348 (Mϩ Ϫ OEt, 41) and 320 (Mϩ Ϫ COOEt, 17).
(4.06) and 502 (2.88); νmax (neat)/cmϪ1 2957, 2928, 1694 (C᎐O),
᎐
1431, 1202 and 1048; δH (400 MHz, CDCl3) 9.63 (d, J 10.0, 2H,
4,8-H), 8.83 (s, 1H, 2-H), 7.96 (d, J 10.0, 2H, 5,7-H), 4.44
(q, J 7.1, 4H, 1,3-COOEt), 1.58 (m, 6H, 2Ј-H), 1.46 (t, J 7.1,
6H, 1,3-COOEt), 1.35 (tq, J 7.3 and 7.3, 6H, 3Ј-H), 1.21 (m,
6H, 1Ј-H) and 0.90 (t, J 7.3, 9H, 4Ј-H); δC (100 MHz, CDCl3)
166.6 (C-6), 165.1 (s, 1,3-COOEt), 143.6 (C-3a,8a), 143.5
(C-2), 138.6 (C-5,7), 136.6 (C-4,8), 115.7 (C-1,3), 59.9 (t,
1,3-COOEt), 28.9 (C-2Ј), 27.3 (C-3Ј), 14.6 (q, 1,3-COOEt), 13.6
(C-4Ј) and 10.6 (C-1Ј); m/z (EI) 562 (Mϩ, 40%) and 505
(Mϩ Ϫ Bu, 100).
Diethyl 6-(4-acetylphenyl)azulene-1,3-dicarboxylate 9b. The
general procedure was followed by using 1b (118 mg, 0.210
mmol), 4-bromoacetophenone (123 mg, 0.618 mmol), Pd2(dba)3
(21.6 mg, 0.0236 mmol), P(t-Bu)3 (19.6 mg, 0.0969 mmol), CsF
(75.8 mg, 0.499 mmol) and dioxane (20 cm3). Chromatographic
purification afforded 9b (53.1 mg, 65%) as purple crystals, 7b
(2.3 mg, 4%) and 8b (2.6 mg, 5%).
For 9b. Mp 125–126.5 ЊC (Found: C, 73.65; H, 5.7. Calc. for
C24H22O5: C, 73.8; H, 5.7%); λmax (CH2Cl2)/nm 235 (log ε 4.46),
270 (4.22), 328 (4.79) and 521 (2.86); νmax (KBr disk)/cmϪ1 1686
General procedure for the Stille cross-coupling reaction of 1a
and 1b
To a degassed solution of 1a or 1b and aryl, acyl or azulenyl
halides in dry solvent was added Pd(0)-catalyst, ligand and CsF.
After the resulting mixture was refluxed under an Ar atmos-
phere, the solvent was removed under reduced pressure. The
products were isolated by column chromatography on silica gel
with CH2Cl2 and/or 5–10% ethyl acetate–CH2Cl2, medium-
pressure column chromatography on silica gel with 30% ethyl
acetate–hexane and/or gel permeation chromatography (GPC)
with CHCl3.
(C᎐O), 1437, 1393, 1248, 1208 and 1048; δ (500 MHz, CDCl )
᎐
H
3
9.83 (d, J 11.1, 2H, 4,8-H), 8.85 (s, 1H, 2-H), 8.11 (d, J 8.5, 2H,
3Ј,5Ј-H), 7.93 (d, J 11.1, 2H, 5,7-H), 7.77 (d, J 8.5, 2H, 2Ј,6Ј-H),
4.45 (q, J 7.1, 4H, 1,3-COOEt), 2.68 (s, 3H, 4Ј-COMe) and 1.47
(t, J 7.1, 6H, 1,3-COOEt); δC (125 MHz, CDCl3) 197.4 (s,
4Ј-COMe), 164.9 (s, 1,3-COOEt), 152.9 (C-6), 147.9 (C-1Ј),
143.8 (C-2), 142.9 (C-3a,8a), 138.4 (C-4,8), 137.0 (C-4Ј), 130.5
(C-5,7), 129.0 (C-2Ј,6Ј and C-5Ј,6Ј), 116.8 (C-1,3), 60.1 (t, 1,3-
COOEt), 20.8 (q, 4Ј-COMe) and 14.6 (q, 1,3-COOEt); m/z (EI)
390 (Mϩ, 100%), 345 (Mϩ Ϫ OEt, 36) and 317 (Mϩ Ϫ COOEt,
25).
Diethyl 6-tolylazulene-1,3-dicarboxylate 5. The general
procedure was followed by using 1b (116 mg, 0.207 mmol), 4a
(104 mg, 0.608 mmol), Pd2(dba)3 (18.3 mg, 0.0200 mmol),
P(t-Bu)3 (20.1 mg, 0.0993 mmol), CsF (66.5 mg, 0.438 mmol)
and dioxane (20 cm3). Chromatographic purification afforded 5
(55.4 mg, 74%) as deep red needles, 7b (4.4 mg, 8%) as red
crystals and 8b (2.7 mg, 5%) as a purple powder.
For 5. Mp 171.5–175 ЊC (Found: C, 75.8; H, 6.15. Calc. for
C23H22O4: C, 76.2; H, 6.1%); λmax (CH2Cl2)/nm 235 (log ε 4.57),
271 (4.24), 335 (4.71) and 508 (2.92); νmax (KBr disk)/cmϪ1 1684
Diethyl 6-(4-methoxyphenyl)azulene-1,3-dicarboxylate 9c.
The general procedure was followed by using 1b (114 mg,
0.203 mmol), 4-bromoanisole (128 mg, 0.684 mmol), Pd2(dba)3
(19.6 mg, 0.0214 mmol), P(t-Bu)3 (21.5 mg, 0.106 mmol), CsF
(68.4 mg, 0.450 mmol) and dioxane (20 cm3). Chromatographic
purification afforded 9c (49.5 mg, 64%) as red crystals, 7b
(2.5 mg, 5%) and 8b (1.4 mg, 3%).
For 9c. Mp 149–150 ЊC (Found: C, 72.8; H, 6.0. Calc. for
C23H22O5: C, 73.0; H, 5.9%); λmax (CH2Cl2)/nm 269 (log ε 4.25),
300 (4.21), 349 (4.59) and 505 (2.94); νmax (KBr disk)/cmϪ1 1686
(C᎐O), 1580, 1432, 1426, 1392, 1210, 1194, 1086, 1050 and 814;
᎐
δH (500 MHz, CDCl3) 9.79 (d, J 10.2, 2H, 4,8-H), 8.80 (s, 1H,
2-H), 7.94 (d, J 10.2, 2H, 5,7-H), 7.58 (d, J 8.2, 2H, 2Ј,6Ј-H),
7.34 (d, J 8.2, 2H, 3Ј,5Ј-H), 4.44 (q, J 7.1, 4H, 1,3-COOEt), 2.45
(s, 3H, 4Ј-Me) and 1.46 (t, J 7.1, 6H, 1,3-COOEt); δC (125 MHz,
CDCl3) 165.1 (s, 1,3-COOEt), 154.6 (C-6), 142.9 (C-2), 142.6
(C-3a,8a), 140.6 (C-1Ј), 139.2 (C-4Ј), 138.4 (C-4,8), 130.7
(C-5,7), 129.8 (C-3Ј,5Ј), 128.7 (C-2Ј,6Ј), 116.3 (C-1,3), 60.0 (t,
1,3-COOEt), 21.2 (4Ј-Me) and 14.6 (q, 1,3-COOEt); m/z (EI)
362 (Mϩ, 100%), 317 (Mϩ Ϫ OEt, 41) and 289 (Mϩ Ϫ COOEt,
38).
(C᎐O), 1678 (C᎐O), 1578, 1510, 1429, 1389, 1200, 1183, 1049
᎐
᎐
and 1036; δH (500 MHz, CDCl3) 9.77 (d, J 11.1, 2H,
4,8-H), 8.78 (s, 1H, 2-H), 7.93 (d, J 11.1, 2H, 5,7-H), 7.65 (d,
J 8.9, 2H, 2Ј,6Ј-H), 7.06 (d, J 8.9, 2H, 3Ј,5Ј-H), 4.44 (q, J 7.1,
4H, 1,3-COOEt), 3.90 (s, 3H, 4Ј-OMe) and 1.46 (t, J 7.1, 6H,
1,3-COOEt); δC (125 MHz, CDCl3) 165.1 (s, 1,3-COOEt), 160.6
(C-4Ј), 154.3 (C-6), 142.7 (C-2), 142.4 (C-3a,8a), 138.4 (C-4,8),
135.8 (C-1Ј), 130.4 (C-5,7), 130.1 (C-2Ј,6Ј), 116.3 (C-1,3), 114.6
(C-3Ј,5Ј), 60.0 (t, 1,3-COOEt), 55.5 (4Ј-OMe) and 14.6 (q,
1,3-COOEt); m/z (EI) 378 (Mϩ, 100%), 333 (Mϩ Ϫ OEt, 32) and
305 (Mϩ Ϫ COOEt, 20).
For 7b. Mp 121.5–122.5 ЊC (lit.18 mp 120–121 ЊC).
For 8b. Mp 227.5–230 ЊC (Found: C, 70.8; H, 5.6. Calc. for
C32H30O8: C, 70.8; H, 5.6%); λmax (CH2Cl2)/nm 240 (log ε 4.72),
271 (4.51), 341 (4.79) and 519 (3.17); νmax (KBr disk)/cmϪ1 1705
(C᎐O), 1435, 1213 and 1200; δ (400 MHz, CDCl3) 9.87 (d,
᎐
H
J 11.0, 4H, 4,8-H), 8.90 (s, 2H, 2-H), 7.95 (d, J 11.0, 4H, 5,7-H),
4.47 (q, J 7.2, 8H, 1,3-COOEt) and 1.48 (t, J 7.2, 12H, 1,3-
COOEt); δC (100 MHz, CDCl3) 164.8 (s, 1,3-COOEt), 155.8
(C-6), 144.4 (C-2), 142.9 (C-3a,8a), 138.3 (C-4,8), 131.2 (C-5,7),
6-(4-Tolyl)azulene 9d. The general procedure was followed
by using 1a (134 mg, 0.321 mmol), 4-bromotoluene (176 mg,
1902
J. Chem. Soc., Perkin Trans. 1, 2002, 1896–1905

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1.029 mmol), Pd2(dba)3 (27.4 mg, 0.0299 mmol), P(t-Bu)3
(34.5 mg, 0.171 mmol), CsF (98.4 mg, 0.648 mmol) and dioxane
(30 cm3). Chromatographic purification afforded 9d (42.1 mg,
60%) as blue plates, 7a (2.0 mg, 5%) and 8a (4.8 mg, 12%) as
green crystals.
Diethyl 6-benzoylazulene-1,3-dicarboxylate 10a. The general
procedure was followed by using 1b (131 mg, 0.233 mmol),
benzoyl chloride (84.3 mg, 0.600 mmol), Pd2(dba)3 (20.4 mg,
0.0223 mmol), P(t-Bu)3 (29.9 mg, 0.148 mmol), CsF (69.8 mg,
0.460 mmol) and dioxane (20 cm3). Chromatographic puri-
fication afforded 10a (80.3 mg, 91%) as deep green needles,
mp 153–155 ЊC (Found: C, 73.2; H, 5.5. Calc. for C23H20O5:
C, 73.4; H, 5.4%); λmax (CH2Cl2)/nm 242 (log ε 4.53), 269 (4.34),
313 (4.77), 349 (3.97), 378 (3.95) and 548 (2.73); νmax (KBr disk)/
cmϪ1 1701 (C᎐O), 1663 (C᎐O), 1439, 1235, 1196 and 1042;
For 9d. Mp 202–203 ЊC (lit.3b mp 199–200 ЊC, lit.21 mp
203–205 ЊC).
For 8a. Mp >300 ЊC (lit.24b mp >315 ЊC).
᎐
᎐
6-(4-Nitrophenyl)azulene 9e. The general procedure was
followed by using 1a (130 mg, 0.312 mmol), 4-bromo-
nitrobenzene (183 mg, 0.906 mmol), Pd2(dba)3 (28.2 mg,
0.0308 mmol), P(t-Bu)3 (24.1 mg, 0.119 mmol), CsF (106 mg,
0.698 mmol) and dioxane (30 cm3). Chromatographic puri-
fication afforded 9e (64.4 mg, 83%) as a deep green powder, 7a
(1.8 mg, 5%) and the recovered 1a (5.9 mg, 5%).
For 9e. Mp 205–206 ЊC (Found: C, 76.9; H, 4.7; N, 5.6.
Calc. for C16H11NO2: C, 77.1; H, 4.45; N, 5.6%); λmax (CH2Cl2)/
nm 236 (log ε 4.17), 307 (4.66), 351 (4.01), 373 (4.08) and
604 (2.55); νmax (KBr disk)/cmϪ1 1593, 1574, 1512, 1395, 1339,
839 and 770; δH (500 MHz, CDCl3) 8.43 (d, J 10.5, 2H, 4,8-H),
8.33 (d, J 9.0, 2H, 3Ј,5Ј-H), 7.98 (t, J 3.7, 1H, 2-H), 7.78
(d, J 9.0, 2H, 2Ј,6Ј-H), 7.47 (d, J 3.7, 2H, 1,3-H) and 7.34
δH (500 MHz, CDCl3) 9.82 (d, J 10.9, 2H, 4,8-H), 8.96 (s, 1H,
2-H), 8.02 (d, J 10.9, 2H, 5,7-H), 7.83 (dd, J 8.2 and 1.1, 2H,
2Ј,6Ј-H), 7.66 (tt, J 7.4 and 1.1, 1H, 4Ј-H), 7.52 (dd, J 8.2 and
7.4, 2H, 3Ј,5Ј-H), 4.46 (q, J 7.1, 4H, 1,3-COOEt) and 1.47 (t,
J 7.1, 6H, 1,3-COOEt); δC (100 MHz, CDCl3) 197.5 (CO), 164.7
(s, 1,3-COOEt), 148.2 (C-6), 145.6 (C-2), 144.4 (C-3a,8a), 138.2
(C-4,8), 136.2 (C-1Ј), 133.6 (C-4Ј), 130.6 (C-2Ј,6Ј), 130.1
(C-5,7), 128.6 (C-3Ј,5Ј), 117.4 (C-1,3), 60.3 (t, 1,3-COOEt) and
14.5 (q, 1,3-COOEt); m/z (EI) 376 (Mϩ, 100%), 331 (Mϩ Ϫ OEt,
37) and 303 (Mϩ Ϫ COOEt, 14).
Diethyl 6-(n-heptanoyl)azulene-1,3-dicarboxylate 10b. The
general procedure was followed by using 1b (112 mg,
0.200 mmol), n-heptanoyl chloride (88.6 mg, 0.596 mmol),
Pd2(dba)3 (18.7 mg, 0.0204 mmol), P(t-Bu)3 (35.4 mg, 0.175
mmol), CsF (88.1 mg, 0.580 mmol) and dioxane (20 cm3).
Chromatographic purification afforded 10b (56.3 mg, 73%) as
purple needles and 7b (12.0 mg, 22%).
(d,
J 10.5, 2H, 5,7-H); δC (125 MHz, CDCl3) 151.7
(C-1Ј), 147.9 (C-6), 147.4 (C-4Ј), 139.3 (C-3a,8a), 138.3 (C-2),
135.7 (C-4,8), 129.4 (C-2Ј,6Ј), 123.9 (C-3Ј,5Ј), 122.9 (C-5,7) and
119.2 (C-1,3); m/z (EI) 249 (Mϩ, 100%) and 202 (Mϩ Ϫ NO2,
55).
For 10b. Mp 65–66 ЊC (Found: C, 71.7; H, 7.5. Calc. for
C23H28O5: C, 71.85; H, 7.3%); λmax (CH2Cl2)/nm 245 (log ε 4.50),
272 (4.22), 314 (4.75), 349 (3.90), 377 (3.83) and 559 (2.69);
νmax (KBr disk)/cmϪ1 1698 (C᎐O), 1686 (C᎐O), 1429, 1233, 1210
6-(4-Acetylphenyl)azulene 9f. The general procedure was
followed by using 1a (125 mg, 0.300 mmol), 4-bromo-
acetophenone (181.3 mg, 0.909 mmol), Pd2(dba)3 (30.2 mg,
0.0330 mmol), P(t-Bu)3 (31.7 mg, 0.157 mmol), CsF (119 mg,
0.783 mmol) and dioxane (30 cm3). Chromatographic puri-
fication afford 9f (49.2 mg, 67%) as blue needles and the
recovered 1a (0.9 mg, 1%).
᎐
᎐
and 1032; δH (400 MHz, CDCl3) 9.84 (d, J 11.0, 2H, 4,8-H),
8.91 (s, 1H, 2-H), 8.28 (d, J 11.0, 2H, 5,7-H), 4.45 (q, J 7.1,
4H, 1,3-COOEt), 3.14 (t, J 7.3, 2H, 2Ј-H), 1.80 (tt, J 7.5 and
7.3, 2H, 3Ј-H), 1.47 (t, J 7.1, 6H, 1,3-COOEt), 1.42 (m, 2H,
4Ј-H), 1.38–1.32 (m, 4H, 5Ј,6Ј-H) and 0.91 (m, 3H, 7Ј-H); δC
(100 MHz, CDCl3) 202.1 (C-1Ј), 164.6 (s, 1,3-COOEt), 145.8
(C-2 and C-6), 144.6 (C-3a,8a), 138.1 (C-4,8), 128.7 (C-5,7),
117.2 (C-1,3), 60.3 (t, 1,3-COOEt), 39.6 (C-2Ј), 31.6 (C-5Ј
or C-6Ј), 28.9 (C-4Ј), 24.5 (C-3Ј), 22.5 (C-5Ј or C-6Ј), 14.5
(q, 1,3-COOEt) and 14.0 (C-7Ј); m/z (EI) 384 (Mϩ, 100%), 339
For 9f. Mp 232.5–233.5 ЊC (Found: C, 87.4; H, 5.8. Calc. for
C18H14O: C, 87.8; H, 5.7%); λmax (CH2Cl2)/nm 238 (log ε 4.12),
305 (4.89), 353 (3.95), 371 (4.01) and 598 (2.58); νmax (KBr disk)/
cmϪ1 1682 (C᎐O), 1578, 1402, 1270 and 822; δ (500 MHz,
᎐
H
CDCl3) 8.41 (d, J 10.5, 2H, 4,8-H), 8.06 (d, J 8.5, 2H, 3Ј,5Ј-H),
7.94 (t, J 3.7, 1H, 2-H), 7.72 (d, J 8.5, 2H, 2Ј,6Ј-H), 7.44
(d, J 3.7, 2H, 1,3-H), 7.37 (d, J 10.5, 2H, 5,7-H) and 2.66 (s,
3H, 4Ј-COMe); δC (125 MHz, CDCl3) 197.7 (s, 4Ј-COMe),
149.9 (C-1Ј), 149.3 (C-6), 139.2 (C-3a,8a), 137.7 (C-2),
136.2 (C-4Ј), 135.8 (C-4,8), 128.8 (C-2Ј,6Ј), 128.7 (C-3Ј,5Ј),
123.1 (C-5,7), 118.8 (C-1,3) and 26.7 (q, 4Ј-COMe); m/z (EI) 246
(Mϩ, 100%), 203 (Mϩ Ϫ COMe, 28) and 202 (Mϩ Ϫ COMe Ϫ
H, 30).
(Mϩ Ϫ OEt, 21), 299 (Mϩ Ϫ C6H13, 7) and 271 (Mϩ
Ϫ
COC6H13, 6).
Diethyl 6-acetylazulene-1,3-dicarboxylate 10c. The general
procedure was followed by using 1b (122 mg, 0.217 mmol),
acetyl chloride (57.9 mg, 0.738 mmol), Pd2(dba)3 (20.1 mg,
0.0219 mmol), P(t-Bu)3 (27.0 mg, 0.133 mmol), CsF (79.0 mg,
0.520 mmol) and dioxane (20 cm3). Chromatographic puri-
fication afforded 10c (17.7 mg, 26%) as purple plates and 7b
(29.5 mg, 50%).
6-(4-Methoxyphenyl)azulene 9g. The general procedure was
followed by using 1a (129 mg, 0.309 mmol), 4-bromoanisole
(179 mg, 0.957 mmol), Pd2(dba)3 (31.7 mg, 0.0346 mmol),
P(t-Bu)3 (33.0 mg, 0.163 mmol), CsF (112 mg, 0.737 mmol)
and dioxane (30 cm3). Chromatographic purification afforded
9g (45.4 mg, 63%) as violet crystals, 7a (2.3 mg, 6%) and the
recovered 1a (10.6 mg, 8%).
For 9g. Mp 212.5–214 ЊC (Found: C, 86.85; H, 5.8. Calc. for
C17H14O: C, 87.15; H, 6.0%); λmax (CH2Cl2)/nm 234 (log ε 4.19),
286 (4.49), 315 (4.61), 377 (4.11) and 581 (2.58); νmax (KBr
disk)/cmϪ1 1582, 1404, 1296, 1252, 1178, 826, 816 and 752;
δH (500 MHz, CDCl3) 8.38 (d, J 10.4, 2H, 4,8-H), 7.87 (br,
1H, 2-H), 7.61 (d, J 8.8, 2H, 2Ј,6Ј-H), 7.40 (br, 2H, 1,3-H), 7.39
(d, J 10.4, 2H, 5,7-H), 7.02 (d, J 8.8, 2H, 3Ј,5Ј-H) and 3.89
(s, 3H, 4Ј-OMe); δC (125 MHz, CDCl3) 159.8 (C-4Ј), 150.6
(C-6), 138.7 (C-3a,8a), 137.8 (C-1Ј), 136.4 (C-2), 135.8 (C-4,8),
129.7 (C-2Ј,6Ј), 123.1 (C-5,7), 118.2 (C-1,3), 114.2 (C-3Ј,5Ј)
and 55.4 (4Ј-OMe); m/z (EI) 234 (Mϩ, 100%) and 219
(Mϩ Ϫ Me, 12).
For 10c. Mp 120.5–123 ЊC (lit.22 mp 129–130 ЊC).
Tetraethyl 6,6Ј-biazulene-1,1Ј,3,3Ј-tetracarboxylate 8b. Fol-
lowing the general procedure, the reaction of 1b (113 mg,
0.201 mmol) with 2b (79.8 mg, 0.227 mmol) in refluxing
dioxane (20 cm3) for 2 h in the presence of Pd2(dba)3 (19.5 mg,
0.0213 mmol), P(t-Bu)3 (26.7 mg, 0.132 mmol) and CsF
(75.5 mg, 0.497 mmol) afforded 8b (73.9 mg, 68%).
Diethyl 6,6Ј-biazulene-1,3-dicarboxylate 11. Following the
general procedure, the reaction of 1b (113 mg, 0.201 mmol)
with 2a (50.0 mg, 0.241 mmol) in refluxing dioxane (20 cm3) for
2 h in the presence of Pd2(dba)3 (18.8 mg, 0.0205 mmol),
P(t-Bu)3 (24.3 mg, 0.120 mmol) and CsF (69.8 mg, 0.460 mmol)
afforded 11 (36.7 mg, 46%) as deep purple crystals, mp 190–
191 ЊC (Found: C, 78.2; H, 5.7. Calc. for C26H22O4: C, 78.4; H,
5.6%); λmax (CH2Cl2)/nm 241 (log ε 4.61), 273 (4.54), 328 (4.88),
376 (4.53), 448 (3.06) and 520 (3.03); νmax (KBr disk)/cmϪ1 1686
J. Chem. Soc., Perkin Trans. 1, 2002, 1896–1905
1903

View Article Online
(C᎐O), 1678 (C᎐O), 1433, 1391, 1198 and 1044; δ (500 MHz,
1,3,5-Tris[1,3-bis(ethoxycarbonyl)azulen-6-yl]benzene
20.
Following the general procedure, the reaction of 1b (391 mg,
0.697 mmol) with 15 (61.3 mg, 0.195 mmol) in refluxing
dioxane (20 cm3) for 18 h in the presence of Pd2(dba)3 (53.8 mg,
0.0588 mmol), P(t-Bu)3 (48.2 mg, 0.238 mmol) and CsF
(235 mg, 1.55 mmol) afforded 20 (47.9 mg, 28%) as a purple
powder, 21 (16.5 mg, 13%) as red needles and the recovered 1b
(76.3 mg, 20%).
᎐
᎐
H
CDCl3) 9.84 (d, J 11.1, 2H, 4,8-H), 8.86 (s, 1H, 2-H), 8.45 (d,
J 10.5, 2H, 4Ј,8Ј-H), 8.00 (t, J 3.8, 1H, 2Ј-H), 7.98 (d, J 11.1,
2H, 5,7-H), 7.50 (d, J 3.8, 2H, 1Ј,3Ј-H), 7.39 (d, J 10.5, 2H,
5Ј,7Ј-H), 4.46 (q, J 7.1, 4H, 1,3-COOEt) and 1.47 (t, J 7.1, 6H,
1,3-COOEt); δC (125 MHz, CDCl3) 165.0 (s, 1,3-COOEt), 158.1
(C-6), 152.4 (C-6Ј), 143.7 (C-2), 142.9 (C-3a,8a), 139.3
(C-3Јa,8Јa), 138.5 (C-2Ј), 138.3 (C-4,8), 135.6 (C-4Ј,8Ј), 131.6
(C-5,7), 124.0 (C-5Ј,7Ј), 119.4 (C-1Ј,3Ј), 116.8 (C-1,3), 60.1
(t, 1,3-COOEt) and 14.6 (q, 1,3-COOEt); m/z (EI) 398 (Mϩ,
100%), 353 (Mϩ Ϫ OEt, 18) and 325 (Mϩ Ϫ COOEt, 12).
For 20. Mp >300 ЊC. (lit.12 mp >300 ЊC).
For 21. Mp 240–241 ЊC (Found: C, 73.8; H, 6.4. Calc. for
C42H42O8ؒ½H2O: C, 73.8; H, 6.3%); λmax (CH2Cl2)/nm 236 (log ε
4.76), 272 (4.49), 336 (4.91) and 513 (3.18); νmax (KBr disk)/cmϪ1
Diethyl 2,6Ј-biazulene-1Ј,3Ј-dicarboxylate 12. Following the
general procedure, the reaction of 1b (113 mg, 0.201 mmol)
with 13 (50.7 mg, 0.245 mmol) in refluxing dioxane (20 cm3) in
the presence of Pd2(dba)3 (18.4 mg, 0.0201 mmol), P(t-Bu)3
(22.5 mg, 0.111 mmol) and CsF (73.7 mg, 0.485 mmol) afforded
12 (41.3 mg, 51%) as green needles, mp 193–195 ЊC (Found:
C, 78.2; H, 5.7. Calc. for C26H22O4: C, 78.4; H, 5.6%);
λmax (CH2Cl2)/nm 244 (log ε 4.63), 279 (4.25), 326 (4.69), 336
(4.71), 364 (4.62), 380 (4.64), 415 (4.61) and 540 (3.20);
1694 (C᎐O), 1435, 1393, 1202 and 1040; δH (500 MHz, CDCl3)
᎐
9.85 (d, J 11.1, 4H, 4Ј,8Ј-H), 8.85 (s, 2H, 2Ј-H), 8.01 (d, J 11.1,
4H, 5Ј,7Ј-H), 7.78 (t, J 1.7, 1H, 2-H), 7.61 (d, J 1.7, 2H, 4,6-H),
4.46 (q, J 7.1, 8H, 1Ј,3Ј-COOEt), 2.85 (t, J 7.8, 2H, 1Љ-H), 1.77
(tt, J 7.8 and 7.5, 2H, 2Љ-H), 1.48 (qt, J 7.5 and 7.3, 2H, 3Љ-H),
1.47 (t, J 7.1, 12H, 1Ј,3Ј-COOEt) and 1.00 (t, J 7.3, 3H, 4Љ-H);
δC (125 MHz, CDCl3) 165.0 (s, 1Ј,3Ј-COOEt), 154.0 (C-6Ј),
144.9 (C-5), 144.6 (C-1,3), 143.5 (C-2Ј), 142.8 (C-3Јa,8Јa), 138.5
(C-4Ј,8Ј), 130.8 (C-5Ј,7Ј), 129.4 (C-4,6), 126.6 (C-2), 116.7
(C-1Ј,3Ј), 60.1 (t, 1Ј,3Ј-COOEt), 35.8 (C-1Љ), 33.7 (C-2Љ), 22.5
(C-3Љ), 14.6 (q, 1Ј,3Ј-COOEt) and 13.9 (C-4Љ); m/z (FAB) 675
(Mϩ ϩ H), 674 (Mϩ) and 629 (Mϩ Ϫ OEt).
νmax (KBr disk)/cmϪ1 1692 (C᎐O), 1440, 1394, 1208, 1184 and
᎐
800; δH (500 MHz, CDCl3) 9.78 (d, J 11.1, 2H, 4Ј,8Ј-H), 8.76 (s,
1H, 2Ј-H), 8.37 (d, J 11.1, 2H, 5Ј,7Ј-H), 8.36 (d, J 9.8, 2H, 4,8-
H), 7.77 (s, 2H, 1,3-H), 7.60 (t, J 9.9, 1H, 6-H), 7.21 (dd, J 9.9
and 9.8, 2H, 5,7-H), 4.45 (q, J 7.1, 4H, 1Ј,3Ј-COOEt) and 1.47
(t, J 7.1, 6H, 1Ј,3Ј-COOEt); δC (125 MHz, CDCl3) 165.1 (s,
1Ј,3Ј-COOEt), 150.7 (C-2), 149.2 (C-6Ј), 143.2 (C-2Ј), 142.9
(C-3Јa,8Јa), 141.4 (C-3a,8a), 138.7 (C-6), 138.3 (C-4,8), 138.2
(C-4Ј,8Ј), 130.6 (C-5Ј,7Ј), 124.5 (C-5,7), 116.5 (C-1,3), 116.4
(C-1Ј,3Ј), 60.0 (t, 1Ј,3Ј-COOEt) and 14.6 (q, 1Ј,3Ј-COOEt);
m/z (EI) 398 (Mϩ, 100%), 353 (Mϩ Ϫ OEt, 27) and 325 (Mϩ Ϫ
COOEt, 17).
1,2,4,5-Tetrakis[1,3-bis(ethoxycarbonyl)azulen-6-yl]benzene
22. Following the general procedure, the reaction of 1b (575 mg,
1.02 mmol) with 16 (78.0 mg, 0.198 mmol) in refluxing dioxane
(20 cm3) for 18 h in the presence of Pd2(dba)3 (73.2 mg, 0.0799
mmol), P(t-Bu)3 (82.5 mg, 0.408 mmol) and CsF (329 mg, 2.17
mmol) afforded 22 (30.7 mg, 13%) as red crystals, 23 (9.8 mg,
5%) as a deep red powder, 24 (10.0 mg, 6%) as a brown powder
and the recovered 1b (70.1 mg, 12%).
For 22. Mp 225 ЊC (decomp.) (Found: C, 71.95; H, 5.4. Calc.
for C70H62O16ؒ½H2O: C, 72.0; H, 5.4%); λmax (CH2Cl2)/nm 238
(log ε 5.06), 271 (4.85), 331 (5.14) and 519 (3.44); νmax (KBr
disk)/cmϪ1 1694 (C᎐O), 1433, 1210 and 1049; δ (500 MHz,
CDCl3) 9.61 (d, J 11.0, 8H, 4Ј,8Ј-H), 8.80 (s, 4H, 2Ј-H), 7.85 (s,
2H, 3,6-H), 7.74 (d, J 11.0, 8H, 5Ј,7Ј-H), 4.39 (q, J 7.1, 16H,
1Ј,3Ј-COOEt) and 1.42 (t, J 7.1, 24H, 1Ј,3Ј-COOEt); δC (125
MHz, CDCl3) 164.8 (s, 1Ј,3Ј-COOEt), 151.8 (C-6Ј), 144.2
(C-2Ј), 143.2 (C-1,2,4,5), 142.8 (C-3Јa,8Јa), 138.0 (C-4Ј,8Ј),
134.0 (C-3,6), 132.4 (C-5Ј,7Ј), 117.2 (C-1Ј,3Ј), 60.1 (t, 1Ј,3Ј-
COOEt) and 14.5 (q, 1Ј,3Ј-COOEt); m/z (FAB) 1159 (Mϩ ϩ H),
1158 (Mϩ), 1113 (Mϩ Ϫ OEt) and 1085 (Mϩ Ϫ COOEt).
1,4-Bis[1,3-bis(ethoxycarbonyl)azulen-6-yl]benzene 18. Fol-
lowing the general procedure, the reaction of 1b (283 mg,
0.504 mmol) with 14 (46.1 mg, 0.195 mmol) in refluxing
dioxane (20 cm3) for 18 h in the presence of Pd2(dba)3 (36.3 mg,
0.0396 mmol), P(t-Bu)3 (56.1 mg, 0.277 mmol) and CsF
(177 mg, 1.17 mmol) afforded 18 (38.3 mg, 32%) as a pink
powder, 19 (8.6 mg, 11%) as reddish purple prisms and the
recovered 1b (80.1 mg, 28%).
᎐
H
For 18. Mp >300 ЊC (Found: C, 72.8; H, 5.7. Calc. for
C38H34O8ؒ½H2O: C, 72.7; H, 5.6%); λmax (CH2Cl2)/nm 237 (log ε
4.78), 269 (4.51), 358 (4.88), 376 (4.89) and 515 (3.26); νmax (KBr
disk)/cmϪ1 1690 (C᎐O), 1431, 1391, 1204 and 1046; δ (500
For 23. Mp 280–285 ЊC (Found: C, 72.8; H, 6.0. Calc. for
C58H56O12ؒ½H2O: C, 73.0; H, 6.0%); λmax (CH2Cl2)/nm 237 (log ε
4.95), 271 (4.75), 326 (4.97) and 511 (3.32); νmax (KBr disk)/cmϪ1
᎐
H
MHz, CDCl3) 9.87 (d, J 11.1, 4H, 4Ј,8Ј-H), 8.86 (s, 2H, 2Ј-H),
8.02 (d, J 11.1, 4H, 5Ј,7Ј-H), 7.87 (s, 4H, 2,3,5,6-H), 4.47 (q,
J 7.1, 8H, 1Ј,3Ј-COOEt) and 1.48 (t, J 7.1, 12H, 1Ј,3Ј-COOEt);
δC (125 MHz, CDCl3) 165.0 (s, 1Ј,3Ј-COOEt), 153.3 (C-6Ј),
144.1 (C-1,4), 143.6 (C-2Ј), 142.9 (C-3Јa,8Јa), 138.5 (C-4Ј,8Ј),
130.6 (C-5Ј,7Ј), 129.5 (C-2,3,5,6), 116.8 (C-1Ј,3Ј), 60.1 (t, 1Ј,3Ј-
COOEt) and 14.6 (q, 1Ј,3Ј-COOEt); m/z (EI) 618 (Mϩ, 100%)
and 573 (Mϩ Ϫ OEt, 15).
1694 (C᎐O), 1433, 1206 and 1044; δ (500 MHz, CDCl3) 9.86
᎐
H
(d, J 10.8, 2H, 4ٞ,8ٞ-H), 9.59 (d, J 11.1, 2H, 4Љ,8Љ-H), 9.54 (d,
J 11.0, 2H, 4Ј,8Ј-H), 8.89 (s, 1H, 2ٞ-H), 8.79 (s, 1H, 2Ј-H or
2Љ-H), 8.76 (s, 1H, 2Ј-H or 2Љ-H), 7.85 (d, J 10.8, 2H, 5ٞ,7ٞ-H),
7.70 (d, J 11.1, 2H, 5Љ,7Љ-H), 7.67 (d, J 11.0, 2H, 5Ј,7Ј-H), 7.58
(s, 1H, 6-H), 7.52 (s, 1H, 3-H), 4.47 (q, J 7.1, 4H, COOEt), 4.40
(q, J 7.1, 4H, COOEt), 4.37 (q, J 7.2, 4H, COOEt), 2.73 (t,
J 7.9, 2H, 1ЉЉ-H), 1.57 (tt, J 7.9 and 7.5, 2H, 2ЉЉ-H), 1.48 (t, J 7.1,
6H, COOEt), 1.42 (t, J 7.1, 6H, COOEt), 1.40 (t, J 7.2, 6H,
COOEt), 1.26 (qt, J 7.5 and 7.3, 2H, 3ЉЉ-H) and 0.80 (t, J 7.3,
3H, 4ЉЉ-H); δC (125 MHz, CDCl3) 165.0 (s, COOEt), 164.9 (s,
COOEt), 164.8 (s, COOEt), 153.5 (C-6ٞ), 153.1 (C-6Љ), 152.8
(C-6Ј), 144.3 (C-4), 143.8 (C-2Ј, C-2Љ and C-2ٞ), 143.1
(C-3ٞa,8ٞa), 142.8 (C-3Јa,8Јa or C-3Љa,8Љa), 142.7 (C-1 and
C-3Јa,8Јa or C-3Љa,8Љa), 141.1 (C-5), 140.3 (C-2), 138.2 (C-4ٞ,8ٞ),
138.0 (C-4Љ,8Љ), 137.9 (C-4Ј,8Ј), 132.8 (C-5Ј,7Ј or C-5Љ,7Љ), 132.7
(C-6 and C-5Ј,7Ј or C-5Љ,7Љ), 132.3 (C-3), 131.9 (C-5ٞ,7ٞ), 116.9
(C-1Ј,3Ј, C-1Љ,3Љ and C-1ٞ,3ٞ), 60.2 (t, COOEt), 60.1 (t,
COOEt), 60.0 (t, COOEt), 33.3 (C-2ЉЉ), 32.6 (C-1ЉЉ), 22.5
(C-3ЉЉ), 14.6 (q, COOEt), 14.5 (q, 2C, COOEt) and 13.8 (C-4ЉЉ);
m/z (FAB) 944 (Mϩ), 899 (Mϩ Ϫ OEt) and 871 (Mϩ Ϫ COOEt).
For 24. Mp 151.5–153 ЊC (lit.12 mp 150–153 ЊC).
For 19. Mp 111–113 ЊC (Found: C, 75.5; H, 6.9. Calc. for
C26H28O4ؒ½H2O: C, 75.5; H, 7.1%); λmax (CH2Cl2)/nm 236 (log ε
4.54), 271 (4.20), 336 (4.70) and 507 (2.92); νmax (KBr disk)/cmϪ1
1688 (C᎐O), 1431, 1391, 1204 and 1046; δH (500 MHz, CDCl3)
᎐
9.80 (d, J 11.1, 2H, 4Ј,8Ј-H), 8.80 (s, 1H, 2Ј-H), 7.96 (d, J 11.1,
2H, 5Ј,7Ј-H), 7.61 (d, J 8.3, 2H, 2,6-H), 7.35 (d, J 8.3, 2H,
3,5-H), 4.44 (q, J 7.1, 4H, 1Ј,3Ј-COOEt), 2.71 (t, J 7.7, 2H,
1Љ-H), 1.67 (tt, J 7.7 and 7.6, 2H, 2Љ-H), 1.46 (t, J 7.1, 6H, 1Ј,3Ј-
COOEt), 1.41 (qt, J 7.6 and 7.3, 2H, 3Љ-H) and 0.97 (t, J 7.3,
3H, 4Љ-H); δC (125 MHz, CDCl3) 165.1 (s, 1Ј,3Ј-COOEt), 154.7
(C-6Ј), 144.3 (C-3Јa,8Јa), 142.9 (C-2Ј), 142.7 (C-4), 140.9
(C-1), 138.5 (C-4Ј,8Ј), 130.8 (C-5Ј,7Ј), 129.2 (C-3,5), 128.7
(C-2,6), 116.3 (C-1Ј,3Ј), 60.0 (t, 1Ј,3Ј-COOEt), 35.3 (C-1Љ), 33.5
(C-2Љ), 22.4 (C-3Љ), 14.6 (q, 1Ј,3Ј-COOEt) and 13.9 (C-4Љ);
m/z (EI) 404 (Mϩ, 100%), 359 (Mϩ Ϫ OEt, 24) and 331 (Mϩ Ϫ
COOEt, 12).
1904
J. Chem. Soc., Perkin Trans. 1, 2002, 1896–1905

View Article Online
3 (a) G. Dyker, S. Borowski, J. Heiermann, J. Körning, K. Opwis,
Reaction of 1b with 17. Following the general procedure, the
reaction of 1b (804 mg, 1.43 mmol) with 17 (104 mg,
0.189 mmol) in refluxing dioxane (20 cm3) in the presence
of Pd2(dba)3 (105 mg, 0.115 mmol), P(t-Bu)3 (121 mg,
0.598 mmol) and CsF (497 mg, 3.27 mmol) afforded 20
(27.5 mg, 16%), a mixture (1.6 : 1) of 22 and 25 (16.8 mg, 8%)
and the recovered 1b (119.2 mg, 15%).
G. Henkel and M. Köckerling, J. Organomet. Chem., 2000, 606,
108–111; (b) D. Balschukat and E. V. Dehmlow, Chem. Ber., 1986,
119, 2272–2288; (c) H. Otani and Y. Tsunoda, presented at 79th CSJ
National Meeting, Kobe, Mar. 31, 2001, Abstr. No. 4B2 10.
4 (a) S. Ito, H. Inabe, T. Okujima, N. Morita, M. Watanabe and
K. Imafuku, Tetrahedron Lett., 2000, 41, 8343–8347; (b) K. H. H.
Fabin, A. H. M. Elwahy and K. Hafner, Tetrahedron Lett., 2000, 41,
2855–2858.
For 25. δH (500 MHz, CDCl3) 9.89 (d, J 11.1, 2H, 4ЉЉ,8ЉЉ-H),
9.55 (d, J 11.1, 4H, 4Ј,8Ј-H and 4ٞ,8ٞ-H), 9.31 (d, J 11.1, 2H,
4Љ,8Љ-H), 8.88 (s, 1H, 2ЉЉ-H), 8.78 (s, 2H, 2Ј-H and 2ٞ-H), 8.68
(s, 1H, 2Љ-H), 8.08 (d, J 11.1, 2H, 5ЉЉ,7ЉЉ-H), 7.96 (s, 2H, 4,6-H),
7.68 (d, J 11.1, 4H, 5Ј,7Ј-H and 5ٞ,7ٞ-H), 7.50 (d, J 11.1, 2H,
5Љ,7Љ-H), 4.45 (q, J 7.1, 4H, 1Љ,3Љ- or 1ЉЉ,3ЉЉ-COOEt), 4.38 (q,
J 7.1, 8H, 1Ј,3Ј- and 1ٞ,3ٞ-COOEt), 4.32 (q, J 7.1, 4H, 1Љ,3Љ- or
1ЉЉ,3ЉЉ-COOEt), 1.47 (t, J 7.1, 6H, 1Љ,3Љ- or 1ЉЉ,3ЉЉ-COOEt),
1.41 (t, J 7.1, 12H, 1Ј,3Ј- and 1ٞ,3ٞ-COOEt) and 1.36 (t, J 7.1,
6H, 1Љ,3Љ- or 1ЉЉ,3ЉЉ-COOEt); δC (125 MHz, CDCl3) 164.9 (s,
1ЉЉ,3ЉЉ-COOEt), 164.7 (s, 1Ј,3Ј- and 1ٞ,3ٞ-COOEt), 164.6 (s,
1Љ,3Љ-COOEt), 152.4 (C-6Ј and C-6ٞ), 151.8 (C-6ЉЉ), 150.0
(C-6Љ), 144.9 (C-1,3), 144.4 (C-2ЉЉ), 144.2 (C-5), 144.1 (C-2Ј,
C-2Љ and C-2ٞ), 142.9 (C-3Љa,8Љa), 142.8 (C-3Јa,8Јa and
C-3ٞa,8ٞa), 142.6 (C-3ЉЉa,8ЉЉa), 140.8 (C-2), 138.6 (C-4ЉЉ,8ЉЉ),
137.8 (C-4Ј,8Ј and C-4ٞ,8ٞ), 137.2 (C-4Љ,8Љ), 133.7 (C-5Љ,7Љ),
132.2 (C-5Ј,7Ј and C-5ٞ,7ٞ), 131.0 (C-4,6), 130.4 (C-5ЉЉ,7ЉЉ),
117.4 (C-1Љ,3Љ), 117.2 (C-1Ј,3Ј, C-1ٞ,3ٞ and C-1ЉЉ,3ЉЉ), 60.2 (t,
1Љ,3Љ- or 1ЉЉ,3ЉЉ-COOEt), 60.1 (t, 1Ј,3Ј-, 1ٞ,3ٞ- and 1Љ,3Љ- or
1ЉЉ,3ЉЉ-COOEt), 14.6 (q, 1Љ,3Љ- or 1ЉЉ,3ЉЉ-COOEt), 14.5 (q, 1Ј,3Ј-
and 1ٞ,3ٞ-COOEt) and 14.5 (q, 1Љ,3Љ- or 1ЉЉ,3ЉЉ-COOEt).
5 J. L. Kane, K. M. Shea, A. L. Crombie and R. L. Danheiser, Org.
Lett., 2001, 3, 1081–1084.
6 Generation of azulen-2-yllithium was recently reported by Fujimori
et al. using the reaction of 2-iodoazulene with n-butyllithium:
H. Shimoyama, A. Ito, K. Takeda, H. Hamazaki, A. Ohta and
K. Fujimori, presented at 29th Symposium on Structural Organic
Chemistry, Urawa, 1999, Abstr. p 310.
7 K.-P. Zeller, ‘Azulene’, in Houben-Weyl; Methoden der Organischen
Chemie; 4th edn.; Georg Thieme, Stuttgart, 1985; Vol. V, Part 2C,
pp 127–418.
8 M. Fujita, H. Oka and K. Ogura, Tetrahedron Lett., 1995, 36,
5247–5250.
9 (a) A. M. Echavarren and J. K. Stille, J. Am. Chem. Soc., 1987, 109,
5478–5486; (b) I. P. Beletskaya, J. Organomet. Chem., 1983, 250,
551–564.
10 The preliminary communication of this work has been published:
T. Okujima, S. Ito and N. Morita, Tetrahedron Lett., 2002, 43,
1261–1264.
11 (a) S. Hünig, M. Kemmer, H. Wenner, I. F. Perepichka, P. Bäuerle,
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13 See e.g.: (a) M. Pereyre, J.-P. Quintard and A. Rahm, Tin in Organic
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14 R. N. McDonald, J. M. Richmond, J. R. Curtis, H. E. Petty and
T. L. Hoskins, J. Org. Chem., 1976, 41, 1811–1821.
2-(Tri-n-butylstannyl)azulene 27
The same procedure as was used for the preparation of 1a was
adopted. The reaction of 13 (106 mg, 0.512 mmol) with 3
(583 mg, 1.01 mmol) in dry toluene (20 cm3) in the presence of
Pd(PPh3)4 (28.7 mg, 0.0248 mmol) followed by chromato-
graphic purification on silica gel with hexane and CH2Cl2
afforded 28 (31.1 mg, 48%) as a green powder. Further puri-
fication of the hexane eluate by medium-pressure column
chromatography on silica gel with hexane afforded 27 (23.1 mg,
11%) as a blue oil.
15 H. Azizian, C. Eaborn and A. Pidcock, J. Organomet. Chem., 1981,
215, 49–58.
16 M. Kosugi, T. Ishikawa, T. Nagami and T. Migita, Nippon Kagaku
Kaishi, 1985, 520–526.
For 27. (Found: C, 63.3; H, 8.2. Calc. for C22H34Sn: C, 63.3;
H, 8.2%); λmax (CH2Cl2)/nm 242 (log ε 4.25), 288 (4.74), 336
(3.78), 351 (3.82), 364 (3.48), 589 (2.52) and 632 (2.46);
νmax (neat)/cmϪ1 2957, 2926, 2870, 2853, 1458, 1393, 803, 727
and 573; δH (500 MHz, CDCl3) 8.27 (d, J 9.7, 2H, 4,8-H), 7.53
(t, J 9.9, 1H, 6-H), 7.53 (s, 2H, 1,3-H), 7.13 (dd, J 9.9 and 9.7,
2H, 5,7-H), 1.60 (m, 2H, 2Ј-H), 1.36 (qt, J 7.4 and 7.3, 2H,
3Ј-H), 1.14 (m, 2H, 1Ј-H) and 0.90 (t, J 7.4, 3H, 4Ј-H);
δC (125 MHz, CDCl3) 153.9 (C-2), 140.0 (C-3a,8a), 136.9 (C-6),
134.9 (C-4,8), 126.5 (C-1,3), 122.5 (C-5,7), 29.3 (C-2Ј), 27.4
(C-3Ј), 13.7 (C-4Ј) and 10.0 (C-1Ј); m/z (EI) 418 (Mϩ, 15%), 361
(100), 360 (50), 359 (77), 357 (40), 305 (45), 249 (72), 247 (92),
245 (62) and 129 (43).
17 T. Morita, T. Abe and K. Takase, J. Chem. Soc., Perkin Trans. 1,
2000, 3063–3070.
18 T. Nozoe, S. Seto, S. Matsumura and Y. Murase, Bull. Chem. Soc.
Jpn., 1962, 35, 1179–1188.
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20 A. F. Littke and G. C. Fu, Angew. Chem., Int. Ed., 1999, 38,
2411–2413.
21 V. A. Nefedov, N. A. German, A. I. Lutsenko and G. I. Nikishin,
J. Org. Chem. U.S.S.R., 1987, 23, 154–162.
22 T. Nozoe, K. Takase and T. Tada, Bull. Chem. Soc. Jpn., 1963, 36,
1010–1016.
23 (a) T. Morita and K. Takase, Bull. Chem. Soc. Jpn., 1982, 54, 1144–
1152; (b) S. Hünig and B. Ort, Liebigs Ann. Chem., 1984, 1905–1935;
(c) M. Iyoda, K. Sato and M. Oda, Tetrahedron Lett., 1985, 26,
3829–3832.
24 (a) M. Hanke and C. Jutz, Angew. Chem., Int. Ed. Engl., 1979, 18,
214–215; (b) M. Hanke and C. Jutz, Synthesis, 1980, 31–32.
25 After this manuscript was submitted, Professor Klaus Hafner
of Techische Universität Darmstadt informed us of his inde-
pendent synthesis of 2-(tri-n-butylstannyl)azulene (27) and its
6-methyl derivative by the reaction of bis(tri-n-butylstannyl)-
cyclopentadiene with [5-(dimethylamino)penta-2,4-dienylidene]-
dimethylammonium perchlorate or its 3-methyl derivative in 5%
and 11% yields, respectively. T. R. Schäfer, Diploma Thesis,
Techische Hochschule Darmstadt, 1991; and K. Hafner, personal
communication.
For 28. Mp >300 ЊC (lit.23a mp >320 ЊC).
Acknowledgements
We are grateful to Professor Klaus Hafner of Techische
Universität Darmstadt for helpful discussions.
References
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28 Details will be reported elsewhere.
J. Chem. Soc., Perkin Trans. 1, 2002, 1896–1905
1905