Synthesis and redox behavior of 1-azulenyl sulfides and efficient synthesis of 1,1′-biazulenes

Article abstract of DOI:10.1002/ejoc.200700959

The reaction of azulenes with several sulfoxides in the presence of acid anhydrides to afford the corresponding 1-azulenylsulfonium and 1,3-azulenediyldisulfonium ions is reported. The subsequent conversion of these ions in high yields into 1-azulenyl met

Full text of DOI:10.1002/ejoc.200700959

FULL PAPER
DOI: 10.1002/ejoc.200700959
Synthesis and Redox Behavior of 1-Azulenyl Sulfides and Efficient Synthesis of
1,1Ј-Biazulenes
Taku Shoji,*[a] Junya Higashi,[a] Shunji Ito,[b] Kozo Toyota,[a] Toyonobu Asao,[a]
Masafumi Yasunami,[c] Kunihide Fujimori,[d] and Noboru Morita*[a]
Keywords: Azulene / 1,1Ј-Biazulene / Electrophilic substitution / Electrochemistry / Cyclic voltammetry
The reaction of azulenes with several sulfoxides in the pres-
ence of acid anhydrides to afford the corresponding 1-
azulenylsulfonium and 1,3-azulenediyldisulfonium ions is re-
ported. The subsequent conversion of these ions in high
yields into 1-azulenyl methyl and phenyl sulfides and 1,3-
bis(methyl- and phenylthio)azulenes through treatment with
diethylamine is also described. Reaction of the 1-azulenyl
sulfides with MCPBA afforded 1-azulenyl sulfoxides, which
were then efficiently transformed into 1,1Ј-biazulene deriva-
tives under acidic conditions. The redox properties of 1-
azulenyl methyl and phenyl sulfides, 1,3-bis(methyl- and
phenylthio)azulenes, and 1,1Ј-biazulene derivatives bearing
methylthio or phenylthio substituents on each azulene ring
are reported based on the results of cyclic voltammetry ex-
periments.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
however. Recently, we reported the synthesis of several
azulenyl methyl sulfides via azulenethiols, but the method-
ologies require the use of a large number of reaction
steps or tedious separation processes.[4] Balenkova and
co-workers reported that dimethylsulfonium ditriflate
(DMSD), prepared by the reaction of trifluoromethanesul-
fonic anhydride (Tf2O) with dimethyl sulfoxide (DMSO),
can react with nonactivated arenes as a highly reactive elec-
trophile to introduce the sulfur moiety.[5] We, therefore, de-
cided to explore the reaction of azulenes with several sulfox-
ides in the presence of acid anhydrides in detail. In this
paper, we report a facile and efficient synthetic route to sev-
eral 1-azulenyl methyl and phenyl sulfides and 1,3-bis-
(methyl- and phenylthio)azulenes via the formation of 1-
azulenylsulfonium and 1,3-azulenediylsulfonium ions.
Introduction
Recently, there has been considerable interest in sulfur-
substituted aromatic compounds since there is a wide range
of potential applications for these compounds, for example,
in electroluminescent devices and as organic conductors, li-
quid crystals, and polymer stabilizers.[1] The development
of general synthetic procedures and modification methods
for sulfur-substituted aromatic compounds is, therefore, of
vital importance. The existing methods tend to utilize nucle-
ophilic substitution or a metal-catalyzed coupling reaction
of thiols with aromatic compounds bearing halogen substit-
uents. A major drawback of this sort of approach is that
harsh reaction conditions, such as the use of strong bases,
high reaction temperatures, and long reaction times, are
often required.[1,2]
Recently, a number of transition-metal-mediated aryl–
aryl coupling reactions (including the Stille,[6] Suzuki–
Miyaura,[7] and Ullmann-type[8] coupling reactions) were
developed to provide facile synthetic methodologies for bi-
aryl compounds. In the case of azulene derivatives, Morita
and Takase reported the synthesis of biazulenes using the
Ullmann reaction. The main drawback, however, is that
very high temperatures are required.[9] In 1985, Iyoda et
al. reported a nickel-mediated synthesis of the parent 1,1Ј-
biazulene. Unfortunately, the procedure also afforded
1,1Ј,3Ј,1ЈЈ-ter- and 1,1Ј:3Ј,1ЈЈ:3ЈЈ,1ЈЈЈ-quaterazulenes as by-
products.[10] Razus and co-workers subsequently reported
that reaction of azulene-1-azoarenes[11a,11b] and N-(1-
azulenylmethylene)arylamines[11c] with FeCl3 afforded the
corresponding 1,1Ј-biazulene derivatives under mild condi-
tions. We also recently reported a transition-metal-catalyzed
synthesis of arylazulenes.[12] This approach is highly chal-
The synthesis of various sulfur-substituted compounds
has been reported previously in the context of azulene
chemistry.[3] Comparatively little attention has been paid to
the development of a facile and selective synthetic method,
[a] Department of Chemistry, Graduate School of Science, Tohoku
University Sendai,
980-8578, Japan
Fax: +81-22-795-7714
E-Mail: shoji@funorg.chem.tohoku.ac.jp
morita@funorg.chem.tohoku.ac.jp
[b] Department of Frontier Materials Chemistry, Faculty of Sci-
ence and Technology, Hirosaki University,
Hirosaki 036-8561, Japan
[c] Department of Materials Chemistry and Engineering, College
of Engineering, Nihon University,
Koriyama 963-8642, Japan
[d] Department of Chemistry, Faculty of Science, Shinshu Univer-
sity,
Matsumoto 390-8621, Japan
1242
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Synthesis of 1-Azulenyl Sulfides and 1,1Ј-Biazulenes
lenging in the case of 1,1Ј-biazulenes, however, due to the sulfoxide and methyl phenyl sulfoxide in the presence of
instability of the 1-haloazulenes which form a key part of TFAA or Tf2O to afford the corresponding 1-azulenylsul-
the synthetic pathway. Moreover, preparation of the metal fonium and 1,3-azulenediyldisulfonium ions in high yields
reagents is not straightforward. The most promising rea- (Table 1). We then proceeded to investigate the base-in-
gent, 1-azulenylborane, is unstable due to easy hydrolysis duced conversion of the 1-azulenylsulfonium ions into 1-
to a hydrocarbon derivative.[13] Herein, we report a novel azulenyl methyl and phenyl sulfides (Scheme 2, Scheme 3,
transition-metal-free synthesis of 1,1Ј-biazulenes via 1- and Table 2). Treatment of 2a+ with diethylamine in EtOH
azulenyl methyl and phenyl sulfides[14] which may prove to afforded the desired 1-azulenyl methyl sulfide (8a) in high
have a number of significant advantages over these earlier yield, but the reaction was not efficient when KOH or
approaches.
NaOH was used as base (Table 2). Disulfonium ion 3a2+
was converted into the corresponding 1,3-bis(methylthio)-
azulene (9a) quantitatively by treatment with Et2NH. The
reaction of 4a+ with Et2NH afforded 10a in 24% yield as
part of a complex product mixture, but reaction with KOH
and NaOH resulted in decomposition (Entry 8). In the case
of 4b+, 5a2+, and 5b2+, base-induced conversion to the sul-
fide was also unsuccessful (Entries 9–12). The synthesis of
1-azulenyl phenyl sulfide (10a) via the (1-azulenyl)di-
phenylsulfonium ion (4a+) is clearly quite challenging,
therefore. Reaction of the (1-azulenyl)methylphenylsulfo-
nium ion (6a+) with Et2NH proceeded smoothly to afford
10a, however (Entry 13). The mechanism of these reactions
is an SN2 nucleophilic substitution of the base at the methyl
group on the sulfonium ion with 1-azulenyl sulfide acting
as a leaving group. It should be noted that nucleophilic sub-
stitution is much more efficient when the reaction center is
an aliphatic carbon rather than an aromatic carbon atom.
Results and Discussion
We initially explored the reaction of azulene (1a) with
several sulfoxides in the presence of acid anhydrides
(Scheme 1 and Table 1). When 1.2 equiv. of Tf2O were used,
the reaction proceeded at room temperature to afford
2a+·TfO– and 3a2+·2TfO– in 55 and 24% yields, respectively.
Compound 3a2+·was obtained in 95% yield as the sole
product when the reaction was carried out with 2.4 equiv.
of Tf2O and excess DMSO (Entries 1 and 2). These results
suggest that the reactivity of the DMSD reagent is too high
with respect to electrophilic substitution of azulene for use
in the selective synthesis of monosubstitution products such
as 2a+. Tf2O was, therefore, replaced with trifluoroacetic
anhydride (TFAA) since the electrophile derived from
TFAA and DMSO should be weaker. As anticipated, 2a+
was successfully prepared in a selective manner (Entry 3).
The reaction of azulene with DMSO in the presence of ace-
tic anhydride did not occur, however (Entry 4).
The reaction of azulene with diphenyl sulfoxide and
methyl phenyl sulfoxide was attempted in the presence of a
wide range of acid anhydrides to determine the applicability
of this method. Azulene was found to react with diphenyl
Scheme 2.
Scheme 1.
Scheme 3.
Table 1. Synthesis of 1-azulenylsulfonium ions.
Entry
Sulfoxide
Acid anhydride, amount (equiv.)
Product, % yield
3a2+·2TfO–, 24
1
2
3
4
5
6
7
8
DMSO
DMSO
DMSO
DMSO
Ph2SO
Ph2SO
PhMeSO
PhMeSO
Tf2O, 1.2
Tf2O, 2.4
TFAA, 1.2
Ac2O, 2.4
TFAA, 1.2
Tf2O, 2.4
TFAA, 1.2
Tf2O, 2.4
2a+·TfO–, 55
2a+·TfO–, 0
3a2+·2TfO–, 95
–
–
2a+·CF3CO2 , 99
3a2+·2CF3CO2 , 0
no reaction
4a+·CF3CO2 , 99
5a2+·2CF3CO2 , 0
–
–
4a+·TfO–, 0
5a2+·2TfO–, 92
–
–
6a+·CF3CO2 , 99
7a2+·2CF3CO2 , 0
6a+·TfO–, 0
7a2+·2TfO–, 89
Eur. J. Org. Chem. 2008, 1242–1252
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T. Shoji, N. Morita et al.
FULL PAPER
The base-induced conversion of the sulfonium ions into sul- 1,1Ј-biazulene (15a) in 89% yield (Entry 1). Similarly, 12a
fides is also more efficient when there are methyl substitu- reacted with 60% HPF6 or HCl to give 15a in 87 and 75%
ents on the sulfonium ions rather than phenyl substituents. yields, respectively (Entries 2 and 3). The reaction of 12a
Isolation of the intermediate sulfonium ions during the re- with trifluoromethanesulfonic acid also afforded 15a, but
action of 6-tert-butylazulene (1b) with sulfoxides in the the yield was relatively low. The presence of sulfuric acid
presence of acid anhydrides is not straightforward and was was found to result in the decomposition of the azulene
not attempted (Entries 4, 6, 14, and 16).
derivative, however, and no reaction was observed with
trichloroacetic acid and acetic acid. Sulfoxides 13a, 12b,
and 13b were found to form the corresponding 1,1Ј-biazu-
lenes under similar acidic conditions. Although details of
the reaction mechanism remain unclear, the radical mecha-
nism reported previously by Razus et al. is probably in-
volved (Scheme 5).[11]
Table 2. Synthesis of 1-azulenyl sulfides.
Entry
Substrate
Base
Product, % yield
1
2
3
4
5
6
7
8
2a+·CF3CO2–
2a+·CF3CO2–
2a+·CF3CO2
2b+·2TfO–
Et2NH
KOH
8a, 99
8a, 58
8a, 35
8b, 96[a]
9a, 99
9b, 95[a]
10a, 24
dec.
dec.
dec.
dec.
dec.
–
NaOH
Et2NH
Et2NH
Et2NH
Et2NH
KOH
NaOH
KOH
KOH
3a2+·2TfO–
3b2+·2TfO–
4a+·CF3CO2–
–
4a+·CF3CO2–
4a+·CF3CO2–
4b+·CF3CO2
5a2+·2TfO–
9
10
11
12
13
14
15
16
5b2+·2TfO–
KOH
–
6a+·CF3CO2–
Et2NH
Et2NH
Et2NH
Et2NH
10a, 98
10b, 94[a]
11a, 95
11b, 92[a]
6b+·CF3CO2
7a2+·2TfO–
7b2+·2TfO–
[a] Yield from 6-tert-butylazulene (1b).
In the next set of experiments, we investigated the synthe-
sis of bis(1-azulenyl)sulfonium ions. Recently, we reported
the synthesis and properties of tris(1-azulenyl)methyl cat-
ions[15] and bis(1-azulenyl)-p-tolylamines.[16] As part of
these studies, we attempted the preparation of bis(1-
azulenyl)sulfonium ions. The preparation of these ions had
been reported previously based on the reaction of diphenyl
sulfoxide and benzene derivatives in the presence of
TFAA.[17] We carefully examined the synthesis of bis(1-
azulenyl)methylsulfonium ion (14a) using reaction condi-
tions similar to those described previously. Previously, the
1-azulenyl methyl sulfoxide (12a) starting material was pre-
pared by the reaction of 8a with NaIO4, using a relatively
long reaction time.[3] We found that treatment of 8a with
MCPBA in CH2Cl2 at 0 °C readily afforded 12a in 96%
yield. Therefore, 1-azulenyl methyl and phenyl sulfides 8b,
10a, and 10b were treated with MCPBA under the same
conditions to afford the corresponding sulfoxides 12b, 13a,
and 13b in 98, 95, and 97% yields, respectively.
Scheme 4.
Table 3. Synthesis of 1,1Ј-biazulene derivatives.
Entry
Substrate
Acid
Product, % yield
1
2
3
4
5
6
7
8
12a
12a
12a
12a
12a
12a
12a
12b
12b
13a
13a
13b
13b
CF3CO2H
HPF6
HCl
TfOH
H2SO4
CCl3CO2H
CH3CO2H
CF3CO2H
HPF6
CF3CO2H
HPF6
15a, 89
15a, 87
15a, 75
15a, 39
dec.
no reaction
no reaction
15b, 80
15b, 81
16a, 51
16a, 71
16b, 56
16b, 77
9
10
11
12
13
The reaction of 1-azulenyl sulfoxides 12a and 13a with
acid anhydride, such as Tf2O, TFAA, and Ac2O, was then
investigated. Initially, we anticipated the formation of bis(1-
azulenyl)sulfonium ions 14a and 14b. The reaction of 12a
and 13a with azulene in the presence of Tf2O or TFAA did
CF3CO2H
HPF6
There have been several reports of the preparation of
not afford 14a and 14b, however. Decomposition of 12a and 1,1Ј-biazulenes, but the methods used involved high tem-
13a was observed instead. Sulfoxide 12a also failed to react peratures or metal reagents. The method described above
with azulene in the presence of Ac2O. We eventually discov- proceeds under much milder conditions with very short re-
ered that 1,1Ј-biazulene derivatives 15a and 16a, could be action times and does not require tedious modification of
obtained by replacing the acid anhydrides with the corre- the azulene prior to reaction, such as halogenation, bo-
sponding acids (Scheme 4, Table 3). Reaction of 12a with rylation, or stannylation. This synthetic strategy may, there-
trifluoroacetic acid at 0 °C afforded 3,3Ј-bis(methylthio)- fore, prove to have considerable advantages.
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Synthesis of 1-Azulenyl Sulfides and 1,1Ј-Biazulenes
Scheme 5.
To further evaluate this new methodology, we attempted
the conversion of 15a, 15b, 16a, and 16b into the 3,3Ј-un-
substituted 1,1Ј-biazulenes 18a and 18b. In 1962, Hafner
and Moritz reported that 1,3-dialkylazulenes undergo elec-
trophilic ipso-substitution (such as Friedel–Crafts acylation
and Vilsmeier formylation) at the 1- and/or 1,3-positons.[18]
We found that in an analogous manner to the reaction of
1,3-dialkylazulenes, 3,3Ј-formyl-1,1Ј-biazulene (17a)[11]
could be obtained in 90% yield by the Vilsmeier for-
mylation of 15a. The reaction also proceeded with 15b, 16a,
and 16b, affording the corresponding 3,3Ј-formyl-1,1Ј-bi-
azulenes 17a and 17b in 92, 65, and 72% yields (Table 4).
This represents the first example in the field of azulene
chemistry of methylthio and phenylthio substituents acting
as leaving groups during electrophilic ipso-substitution.
Thus, the methyl- and phenylthio groups can be regarded
as a synthon of the formyl group which acts as a highly
versatile functional group in organic synthesis. It should be
noted, however, that Friedel–Crafts acylation of 15a,b and
16a,b with acetyl chloride in the presence of AlCl3 led to
the decomposition of these compounds. Conversion into
the 3,3Ј-unsubstituted 1,1Ј-biazulenes 18a and 18b from the
formyl compounds 17a and 17b was established by reaction
with pyrrole in acetic acid;[19] 1,1Ј-biazulene (18a) and 6,6Ј-
tert-butyl-1,1Ј-biazulene (18b) were obtained in 71 and 80%
yields, respectively (Scheme 6).[20]
Scheme 6.
–1.97 V owing to the formation of a radical anion. In con-
trast, the electrochemical reduction of 8a, 9a, 10a, and 11a
exhibits irreversible reduction waves between –1.60 and
–1.83 V. The electrochemical oxidation of 1,3-bis(methyl-
and phenylthio)azulenes 11a, 11b, 13a, and 13b results in
reversible waves between +0.20 and +0.48 V arising from
the oxidation of an azulene ring to give a radical cation
species, while electrochemical oxidation of 8a, 8b, 10a, and
10b results in irreversible waves between +0.28 and +0.46 V.
These results indicate that the tert-butyl group at the 6-posi-
tion increases the persistence of the azulene radical anion,
while 1,3-bis(methyl- and phenylthio) substituents stabilize
the radical cation. Previously, Kurihara et al. reported oxi-
dation potentials for 3-methylthio- and 3-butylthioguaiazul-
enes, with two-stage oxidation waves at +0.44 V and +1.01
to +1.06 V (vs. SCE).[21] Compounds 9a,b and 11a,b exhibit
similar two-step oxidation behavior, but our results reveal
the electrochemical reduction of these compounds for the
first time. Since the reduction potential becomes less nega-
Table 4. Synthesis of 3,3Ј-formyl-1,1Ј-biazulene derivatives.
Entry
Substrate
Product, % yield
1
2
3
4
15a
15b
16a
16b
17a, 90
17b, 92
17a, 65
17b, 72
Cyclic and differential pulse voltammetry (CV, DPV) tive as the number of sulfur substituents on the five-
were used to examine the redox behavior of 8a,b–11a,b and membered ring increases, for example, 8a (–1.83 V) and 9a
to clarify the electrochemical properties of 1-azulenyl (–1.73 V), it is safe to assume that the addition of sulfur
methyl and phenyl sulfides and 1,3-bis(methyl- and phen- substituents increases the electron affinity of the azulene
ylthio)azulenes. The redox potentials (vs. Ag/AgNO3) are ring.
summarized in Table 5 and the reduction and oxidation
The redox potentials of 1,1Ј-biazulene derivatives 15a,
waves of 9b are shown in Figure 1. The electrochemical re- 15b, 16a, and 16b obtained from CV and DPV experiments
duction of 6-tert-butylazulene derivatives 8b, 9b, 10b, and are summarized in Table 6 and the reduction and oxidation
11b exhibits reversible reduction waves between –1.75 and waves of 16b are shown in Figure 2. The electrochemical
Eur. J. Org. Chem. 2008, 1242–1252
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1245

T. Shoji, N. Morita et al.
FULL PAPER
Table 5. Redox potentials[a] of compounds 8a,b–11a,b.
cyclic voltammograms of 15a, 15b, and 16a contain a re-
versible oxidation wave, but an irreversible reduction wave
is observed in the case of 15b and 15a. We recently reported
that the cyclic voltammogram for the parent 1,1Ј-biazulene
(18a) contains two-stage oxidation waves at +0.30 and
+0.62 V with poor reversibility under similar conditions.[22]
Compounds 15a and 16a exhibit first oxidation potentials
red
red
ox
ox
ox
Sample E1 [V] E2 [V] E1 [V]
E2 [V]
E3 [V]
8a
8b
(–1.83)
–1.97
(–1.93)
(–2.15)
(–2.16)
(–2.15)
(+0.34)
–
–
(+0.28)
+0.26
(+0.24)
+0.20
(+0.19)
(+0.50)
–
–
9a
9b
(–1.73)
–1.86
(–1.84)
(–1.75)
–1.91
(+0.70)
(+0.91)[b]
(–2.18)
(–2.16)
(+0.76)
–
–
Table 6. Redox potentials[a] of 1,1Ј-biazulene derivatives 15a,b and
16a,b.
10a
10b
–
(–1.88)
(–2.19)
(–2.18)
(–2.20)
(+0.42)
+0.48
(+0.46)
+0.44
–
–
(+0.95)
–
red
red
red
ox
ox
Sample E1 [V] E2 [V] E3 [V]
E1 [V]
E2 [V]
11a
11b
(–1.60)
–1.75
(–1.72)
(+0.70)
15a
+0.17
(+0.15)
+0.09
(–1.87)
(–1.76)
(–2.06)
(–2.04)
(–1.96)
(–2.14)
(–2.16)
(–2.18)
(–2.16)
–
(+0.38)
(+0.30)
(+0.48)
(+0.74)
(+0.42)
(+0.80)
15b
16a
16b
(+0.06)
[a] Redox potentials were measured by CV and DPV [V vs. Ag/
AgNO3, 1 m in benzonitrile containing 0.1  Et4NClO4, Pt elec-
trode (i.d.: 1.6 mm), scan rate: 100 mVs–1, and Fc/Fc+ = +0.15 V].
In the case of reversible waves, redox potentials measured by CV
are presented. Peak potentials measured by DPV are shown in pa-
(–1.69)
–1.88
(–1.86)
(+0.33)
+0.19
(+0.18)
ox
rentheses. [b] The E4 value was observed at +1.18 V by DPV.
[a] Redox potentials were measured by CV and DPV [V vs. Ag/
AgNO3, 1 m in benzonitrile containing 0.1  Et4NClO4, Pt elec-
trode (i.d.: 1.6 mm), scan rate: 100 mVs–1, and Fc/Fc+ = +0.15 V].
In the case of reversible waves, redox potentials measured by CV
are presented. Peak potentials measured by DPV are shown in pa-
rentheses.
Figure 1. Cyclic voltammograms of (a) the reduction and (b) the
oxidation of 9b in benzonitrile containing 0.1  Et4NClO4 as a sup-
porting electrolyte.
reduction and oxidation of 16b result in reversible redox
waves arising from single-electron transfer to generate a
radical anion and a radical cation species, respectively. The supporting electrolyte.
Figure 2. Cyclic voltammograms of (a) the reduction and (b) the
oxidation of 16b in benzonitrile containing 0.1  Et4NClO4 as a
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Synthesis of 1-Azulenyl Sulfides and 1,1Ј-Biazulenes
2901 (m), 1682 (s), 1585 (m), 1560 (w), 1537 (w), 1508 (w), 1485
(w), 1429 (m), 1325 (m), 1271 (w), 1209 (s), 1180 (s), 1128 (s), 1051
(m), 1041 (m), 1005 (m), 983 (w), 962 (w), 873 (w), 837 (m), 802
(m), 790 (s), 750 (s), 723 (m), 675 (w), 598 (w), 571 (w), 545 (w),
518 (w), 463 (w), 447 (s), 436 (w), 409 (w) cm–1. UV/Vis (CH2Cl2):
λmax (logε) = 283 (4.39), 291 (4.40), 335 (3.59), 350 (3.53), 512
(3.05) nm. 1H NMR (400 MHz, [D6]acetone): δ = 8.82 (d, J =
10.0 Hz, 1 H, 8-H), 8.70 (d, J = 4.4 Hz, 1 H, 2-H), 8.62 (d, J =
10.0 Hz, 1 H, 4-H), 8.02 (t, J = 10.0 Hz, 1 H, 6-H), 7.73 (t, J =
10.0 Hz, 1 H, 7-H), 7.67 (t, J = 10.0 Hz, 1 H, 5-H), 7.62 (d, J =
4.4 Hz, 1 H, 4-H), 3.54 (s, 6 H, 1-S+Me2) ppm. 13C NMR
(100 MHz, CDCl3): δ = 207.41 (C=O), 144.43, 141.68, 141.64,
140.94, 136.95, 135.92, 129.00, 128.73, 120.98, 118.50 (q, J =
298.2 Hz, TfO–), 104.92, 31.04 (1-S+Me2) ppm. C14H13F3O2S·H2O:
C 53.39, H 4.61; found C 53.22, H 4.28.
at +0.15 and +0.33 V, respectively, with second potentials
at +0.38 and +0.48 V. These results indicate that the
π-donating properties are increased markedly by the pres-
ence of the methylthio groups, while the effect appears to
be smaller in the case of the phenylthio groups. The two
sulfur substituents increase the reversibility of the electro-
chemical oxidation reaction.
Conclusions
We have described a novel and efficient synthesis for 1-
azulenyl methyl and phenyl sulfides, 1,3-bis(methyl- and
phenylthio)azulenes, and 1,1Ј-biazulenes that offers a
number of significant advantages over the methods re-
ported previously. Azulenes react with sulfoxides in the
presence of acid anhydrides to afford the corresponding 1-
azulenylsulfonium ions. The reaction of 1-azulenylsulfon-
ium ions with Et2NH affords 1-azulenyl methyl and phenyl
sulfides which then react with MCPBA to form 1-azulenyl
methyl and phenyl sulfoxides. In a metal-free synthesis, the
1-azulenyl methyl and phenyl sulfoxides react with an acid
to afford 1,1Ј-biazulene derivatives. The methyl- and phen-
ylthio groups of the 1,1Ј-biazulene derivatives are readily
converted into formyl groups by the Vilsmeier reaction.
3,3Ј-Formyl-1,1Ј-biazulenes react with pyrrole in acetic acid
to afford 1,1Ј-biazulenes, including the unsubstituted 1,1Ј-
biazulene. Further expansion of the π-electron systems
using the 1,1Ј-biazulene core is now being investigated in
our laboratory along with the physical properties of the new
compounds formed.
1,3-Azulenediylbis(dimethylsulfonium) Bis(trifluoromethanesulfon-
ate) (3a2+·2TfO–): Trifluoromethanesulfonic anhydride (677 mg,
2.4 mmol) in CH2Cl2 (10 mL) was added dropwise to a solution of
1a (128 mg, 1.00 mmol) and DMSO (1 mL) in CH2Cl2 (10 mL).
The resulting solution was stirred at room temperature for 2 h. The
solvent was removed under reduced pressure. The residue was dis-
solved in a small amount of CH2Cl2 and then precipitated by the
addition of excess Et2O. The precipitate was collected by filtration
and recrystallized from EtOH to give 3a2+·2TfO– (521 mg, 95%) as
prism-shaped orange crystals; m.p. 178.0–178.5 °C (dec.). HRMS
2+
(ESI): calcd. for C14H18S2
[M – 2TfO–]2+ 250.0850; found
250.0840. IR (KBr): νmax = 3076 (m), 3030 (s), 2941 (m), 1585 (m),
˜
1454 (m), 1437 (m), 1419 (s), 1334 (m), 1271 (m), 1257 (m), 1282
(s), 1224 (s), 1178 (s), 1209 (s), 1157 (s), 1143 (s), 1062 (m), 1030
(s), 1001 (m), 978 (w), 877 (w), 758 (m), 638 (s), 603 (w), 572 (m),
518 (m), 463 (w), 434 (w), 418 (w) cm–1. UV/Vis (CH2Cl2): λmax
(logε) = 261 sh (4.28), 289 (4.72), 327 (3.94), 342 sh (3.76), 481
1
(3.00) nm. H NMR (600 MHz, [D6]acetone): δ = 9.76 (s, 1 H, 2-
H), 9.29 (d, J = 10.0 Hz, 2 H, 4,8-H), 8.58 (t, J = 10.0 Hz, 1 H, 6-
H), 8.28 (t, J = 10.0 Hz, 2 H, 5,7-H), 3.63 (s, 12 H, 1,3-
S+Me2) ppm. C16H18F6O6S4: C 35.03, H 3.31; found C 35.16, H
3.29.
Experimental Section
General: Melting points were determined with a Yanagimoto MP-
S3 micro melting apparatus and are uncorrected. Mass spectra were
obtained with a JEOL HX-110, a Hitachi M-2500, or a Bruker
APEX II instrument, usually at 70 eV. IR and UV spectra were
measured with a Shimadzu FTIR-8100M and a Hitachi U-3410
spectrophotometer, respectively. 1H and 13C NMR spectra were re-
corded with a JEOL GSX 400 (400 and 100 MHz), a JEOL JNM
A500 (500 and 125 MHz), or a Bruker AM 600 spectrometer (600
and 150 MHz). Gel permeation chromatography (GPC) purifica-
tion was performed with a TSKgel G2000H6 instrument. Voltam-
metry measurements were carried out with a BAS 100B/W electro-
chemical workstation equipped with Pt working and auxiliary elec-
trodes and a reference electrode formed from Ag/AgNO3 (0.1 )
in a tetrabutylammonium perchlorate (0.1 )/acetonitrile solution.
Elemental analyses were performed at the Research and Analytical
Center for Giant Molecules, Graduate School of Science, Tohoku
University.
–
(1-Azulenyl)diphenylsulfonium Trifluoroacetate (4a+·CF3CO2 ): Tri-
fluoroacetic anhydride (252 mg, 1.20 mmol) in CH2Cl2 (10 mL)
was added dropwise to a solution of 1a (128 mg, 1.00 mmol) and
diphenyl sulfoxide (1.01 g, 5.00 mmol) in CH2Cl2 (10 mL). The re-
sulting solution was stirred at room temperature for 1 h. The sol-
vent was removed under reduced pressure. The residue was washed
–
several times with Et2O to give 4a+·CF3CO2 (422 mg, 99%) as a
purple oil. HRMS (ESI): calcd. for C22H17S+ [M – TfO–]+
313.1051; found 313.1045. IR (KBr): ν
= 3092 (w), 3065 (w),
˜
max
1778 (s), 1738 (s), 1687 (s), 1538 (m), 1541 (w), 1477 (m), 1446 (m),
1402 (s), 1379 (m), 1313 (w), 1269 (m), 1194 (s), 1142 (s), 1070 (w),
1048 (w), 1022 (w), 999 (w), 873 (w), 792 (m), 746 (m), 708 (m),
684 (m), 613 (w), 592 (w), 561 (w), 505 (w), 486 (w), 466 (w), 443
(w), 426 (w) cm–1. UV/Vis (CH2Cl2): λmax (logε) = 300 (4.43), 335
sh (3.68), 358 (3.80), 405 (2.93), 512 (2.94) nm. 1H NMR
(400 MHz, [D6]acetone): δ = 9.04 (d, J = 10.0 Hz, 1 H, 8-H), 8.74
(d, J = 10.0 Hz, 1 H, 4-H), 8.10 (d, J = 10.0 Hz, 1 H, 2-H), 7.99
(d, J = 4.4 Hz, 1 H, 2-H), 7.81 (t, J = 10.0 Hz, 1 H, 7-H), 7.75 (t,
J = 10.0 Hz, 1 H, 5-H), 7.67–7.60 (m, 10 H, 1-S+Ph2) ppm. 13C
NMR (100 MHz, CDCl3): δ = 145.69, 143.24, 143.02, 142.10,
138.26, 134.26, 131.71, 130.73, 130.64, 130.41, 128.91, 122.16,
99.65 ppm. C24H17F3O2S·1.15CH2Cl2: C 57.63, H 3.71; found C
57.87, H 3.47.
–
(1-Azulenyl)dimethylsulfonium Trifluoroacetate (2a+·CF3CO2 ): Tri-
fluoroacetic anhydride (252 mg, 1.20 mmol) in CH2Cl2 (10 mL)
was added dropwise to a solution of 1a (128 mg, 1.00 mmol) and
DMSO (1 mL) in CH2Cl2 (10 mL). The resulting solution was
stirred at room temperature for 1 h. The solvent was removed under
reduced pressure. The residue was washed several times with Et2O
–
to give 2a+·CF3CO2 (300 mg, 99%) as a purple oil. HRMS (ESI):
calcd. for C12H13S+ [M – CF3CO2–]+ 189.0738; found 189.0732. IR
1,3-Azulenediylbis(diphenylsulfonium) Bis(trifluoromethanesulfon-
(KBr): ν
= 3453 (s), 3400 (s), 3088 (m), 3044 (m), 3028 (m),
ate) (5a2+·2TfO–): Trifluoromethanesulfonic anhydride (677 mg,
˜
max
Eur. J. Org. Chem. 2008, 1242–1252
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1247

T. Shoji, N. Morita et al.
FULL PAPER
2.40 mmol) in CH2Cl2 (10 mL) was added dropwise to a solution H), 8.35 (t, J = 9.6 Hz, 2 H, 5,7-H), 8.26 (dd, J = 6.8, 1.2 Hz, 4 H,
of 1a (128 mg, 1.00 mmol) and diphenyl sulfoxide (1.01 g,
5.00 mmol) in CH2Cl2 (10 mL). The resulting solution was stirred
at room temperature for 2 h. The solvent was removed under re-
duced pressure. The residue was dissolved in a small amount of
CH2Cl2 and then precipitated by the addition of a large amount of
Et2O. The precipitate was collected by filtration and recrystallized
from EtOH to give 5a2+·2TfO– (733 mg, 92%) as prism-shaped
orange crystals; m.p. 208.0–210.0 °C (EtOH). HRMS (ESI): calcd.
o-Ph), 7.71 (m, 6 H, m- and p-Ph), 4.18 (s, 6 H, 1,3-S+Me) ppm.
C26H22F6O6S4: C 46.42, H 3.30; found C 46.51, H 3.42.
1-Azulenyl Methyl Sulfide (8a):[3] Et2NH (10 mL) was added to a
solution of 2a+·CF3CO2 (302 mg, 1.00 mmol) in EtOH (10 mL).
–
The solution was refluxed for 30 min. The reaction mixture was
cooled to room temperature and the solvent was removed under
reduced pressure. The resulting crude product was purified by col-
umn chromatography on silica gel with hexane/AcOEt (4:1) as elu-
ent to give 8a (173 mg, 99%) as a dark-blue oil. 1H NMR
(400 MHz, CDCl3): δ = 8.59 (d, J = 9.6 Hz, 1 H, 8-H), 8.22 (d, J
= 9.6 Hz, 1 H, 4-H), 7.94 (d, J = 4.0 Hz, 1 H, 2-H), 7.55 (t, J =
9.6 Hz, 1 H, 6-H), 7.34 (d, J = 4.0 Hz, 1 H, 3-H), 7.18 (t, J =
9.6 Hz, 1 H, 7-H), 7.11 (t, J = 9.6 Hz, 1 H, 5-H), 2.45 (s, 3 H, -
SCH3) ppm. 13C NMR (100MHz, CDCl3): δ = 142.01, 140.28,
139.24, 138.76, 137.40, 135.75, 124.04, 123.53, 122.20, 117.77,
20.96 ppm.
for C34H26S22 [M – 2TfO–]+ 498.1476; found 498.1464. IR (KBr):
+
ν
= 3084 (w), 3061 (w), 3046 (w), 3034 (w), 1581 (w), 1537 (w),
˜
max
1477 (w), 1446 (m), 1425 (m), 1379 (m), 1313 (w), 1273 (s), 1250
(s), 1236 (s), 1224 (s), 1178 (m), 1167 (m), 1149 (m), 1130 (m), 1101
(w), 1066 (w), 1030 (s), 1026 (s), 997 (w), 803 (w), 763 (m), 742
(m), 686 (m), 682 (m), 638 (s), 603 (w), 572 (w), 517 (m), 507 (m),
484 (w), 457 (w) cm–1. UV/Vis (CH2Cl2): λmax (logε) = 300 (4.65),
329 (4.03), 351 (3.98), 480 (3.05) nm. 1H NMR (600 MHz, [D6]-
acetone): δ = 9.63 (d, J = 10.0 Hz, 2 H, 4,8-H), 8.75 (t, J = 10.0 Hz,
1 H, 6-H), 8.61 (s, 1 H, 2-H), 8.44 (t, J = 10.0 Hz, 2 H, 5,7-H),
7.99 (d, J = 7.3 Hz, 8 H, o-Ph), 7.83 (t, J = 7.3 Hz, 4 H, p-Ph),
7.75 (t, J = 7.3 Hz, 8 H, m-Ph) ppm. C36H26F6O6S4: C 54.26, H
3.29; found C 54.27, H 3.51.
6-tert-Butyl-1-azulenyl Methyl Sulfide (8b): Trifluoroacetic anhy-
dride (504 mg, 2.40 mmol) in CH2Cl2 (10 mL) was added to a solu-
tion of 1b (184 mg, 1.00 mmol) and DMSO (390 mg, 5.00 mmol)
in CH2Cl2 (10 mL). The resulting solution was stirred at room tem-
perature for 30 min. The solvent was removed under reduced pres-
sure. EtOH (10 mL) and Et2NH were added to the residue and the
mixture was refluxed for 30 min. The solvent was removed under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with hexane/AcOEt (4:1) as eluent to give 8b
(225 mg, 96% from 1b) as a dark-blue oil. MS (EI): m/z (%) = 230
–
(1-Azulenyl)methylphenylsulfonium Trifluoroacetate (6a+·CF3CO2 ):
Trifluoroacetic anhydride (252 mg, 1.20 mmol) was added to a
solution of 1a (128 mg, 1.00 mmol) and methyl phenyl sulfoxide
(420 mg, 3.00 mmol) in CH2Cl2 (10 mL). The resulting solution
was stirred at room temperature for 10 min. The solvent was re-
moved under reduced pressure. The residue was washed several
(100) [M]+, 215 (77), 200 (10), 185 (10), 167 (9). IR (KBr): ν
=
˜
max
times with Et2O to give 6a+·CF3CO2 (362 mg, 99%) as a purple
–
2964 (m), 1581 (s), 1549 (w), 1477 (m), 1400 (s), 1368 (w), 1304
(w), 1253 (w), 1236 (w), 1057 (w), 997 (w), 966 (w), 929 (w), 841
(m), 821 (w), 765 (w), 711 (w), 675 (w), 453 (w) cm–1. UV/Vis
(CH2Cl2): λmax (logε) = 253 (4.05), 290 sh (4.48), 296 (4.51), 335
– +
oil. HRMS (ESI): calcd. for C17H15S+ [M – CF3CO2 ] 251.0894;
found 251.0889. IR (KBr): ν
= 3096 (w), 3032 (w), 2937 (w),
˜
max
1778 (s), 1740 (s), 1686 (m), 1583 (m), 1541 (w), 1487 (w), 1477
(w), 1456 (w), 1448 (m), 1402 (m), 1381 (m), 1317 (w), 1304 (w),
1271 (w), 1186 (s), 1147 (s), 1074 (w), 1043 (w), 983 (w), 873 (w),
810 (m), 794 (m), 746 (m), 706 (m), 684 (m), 638 (w), 609 (w), 594
(w), 569 (w), 551 (w), 518 (w), 486 (w), 449 (w), 428 (w) cm–1. UV/
Vis (CH2Cl2): λmax (logε) = 286 sh (4.62), 294 (4.67), 334 (3.90),
354 (3.95), 514 (2.87), 538 sh (2.83) nm. 1H NMR (400 MHz, [D6]-
acetone): δ = 9.17 (d, J = 10.0 Hz, 2 H, 8-H), 8.94 (d, J = 10.0 Hz,
1 H, 4-H), 8.72 (d, J = 4.8 Hz, 1 H, 2-H), 8.27 (t, J = 10.0 Hz, 1
H, 6-H), 8.09 (dd, J = 6.8, 1.2 Hz, 2 H, o-Ph), 4.08 (s, 3 H, 1-
S+Me) ppm. 13C NMR (100 MHz, [D6]acetone): δ = 207.41 (C=O),
145.87, 143.25, 143.08, 142.46, 137.48, 136.75, 134.68, 132.23,
131.43, 130.80, 130.48, 130.10, 122.43, 117.66 (q, J = 284.2 Hz,
TfO–), 103.19, 31.28 (1-S+Me) ppm. C19H15F3O2S·1.10CH2Cl2: C
52.73, H 3.79; found C 53.03, H 3.49.
1
(3.62), 351 (3.65), 588 (2.53) nm. H NMR (400 MHz, CDCl3): δ
= 8.55 (d, J = 10.0 Hz, 1 H, 8-H), 8.22 (d, J = 10.0 Hz, 1 H, 4-H),
7.86 (d, J = 3.6 Hz, 1 H, 2-H), 7.43 (dd, J = 10.0, 1.2 Hz, 1 H, 7-
H), 7.35 (dd, J = 10.0, 1.2 Hz, 1 H, 5-H), 7.28 (d, J = 3.6 Hz, 1 H,
3-H), 2.46 (s, 3 H, 1-SMe), 1.46 (s, 9 H, 6-tBu) ppm. 13C NMR
(100 MHz, CDCl3): δ = 161.7, 140.0, 138.9, 137.4, 135.7, 134.0,
121.2, 120.9, 120.8, 116.6, 38.2 (s, 6-tBu), 31.5 (q, 6-tBu), 20.4 (1-
SMe) ppm. C15H18S: C 78.21, H 7.88; found C 78.21, H 7.99.
1,3-Bis(methylthio)azulene (9a):[3] Et2NH (10 mL) was added to a
solution of 3a2+·2TfO– (548 mg, 1.00 mmol) in EtOH (10 mL). The
solution was refluxed for 30 min. The reaction mixture was cooled
to room temperature and the solvent was removed under reduced
pressure. The resulting crude product was purified by column
chromatography on silica gel with hexane/AcOEt (4:1) as eluent to
give 9a (219 mg, 99%) as a dark-blue oil. 1H NMR (400 MHz,
CDCl3): δ = 8.52 (d, J = 9.6 Hz, 2 H, 4,8-H), 7.98 (s, 1 H, 2-H),
7.62 (t, J = 9.6 Hz, 1 H, 6-H), 7.21 (t, J = 9.6 Hz, 2 H, 5,7-H), 2.48
(s, 6 H, 1-SMe) ppm. 13C NMR (100 MHz, CDCl3): δ = 141.41,
139.75, 139.00, 135.29, 123.48, 121.29, 20.07 ppm.
1,3-Azulenediylbis(methylphenylsulfonium) Bis(trifluoromethanesul-
fonate) (7a2+·2TfO–): Trifluoromethanesulfonic anhydride (667 mg,
2.40 mmol) was added to a solution of 1a (128 mg, 1.00 mmol) and
methyl phenyl sulfoxide (841 mg, 6.00 mmol) in CH2Cl2 (10 mL).
The resulting solution was stirred at room temperature for 1 h. The
solvent was removed under reduced pressure. The residue was
washed several times with Et2O to give 7a2+·2TfO– (600 mg, 89%)
as prism-shaped orange crystals; m.p. 150.0–152.0 °C (MeOH).
HRMS (ESI): calcd. for C24H22S22+ [M – 2TfO–]+ 374.1163; found
6-tert-Butyl-1,3-bis(methylthio)azulene (9b): Trifluoromethanesulfo-
nic anhydride (677 mg, 2.40 mmol) in CH2Cl2 (10 mL) was added
to a solution of 1b (184 mg, 1.00 mmol) and DMSO (390 mg,
5.00 mmol) in CH2Cl2 (10 mL). The resulting solution was stirred
at room temperature for 30 min. The solvent was removed under
374.1152. IR (KBr): ν
= 3076 (m), 3032 (m), 2932 (m), 1583
˜
max
(m), 1537 (w), 1479 (m), 1448 (s), 1419 (s), 1383 (s), 1224 (s), 1155
(s), 1072 (w), 1030 (s), 997 (m), 985 (m), 877 (w), 835 (w), 758 (s), reduced pressure. EtOH (10 mL) and Et2NH (10 mL) were added
748 (s), 684 (m), 638 (s), 601 (w), 572 (m), 518 (w), 499 (w), 480 to the residue and the mixture was refluxed for 30 min. The solvent
(w), 468 (m), 455 (w), 439 (w), 414 (w) cm–1. UV/Vis (CH2Cl2):
was removed under reduced pressure. The residue was purified by
λmax (logε) = 226 (4.61), 290 (4.69), 324 (3.97), 342 (3.89), 476 column chromatography on silica gel with hexane/AcOEt (4:1) as
1
(3.03) nm. H NMR (400 MHz, [D6]acetone): δ = 9.85 (s, 1 H, 2-
eluent to give 9b (265 mg, 95% from 1b) as dark-blue crystals; m.p.
H), 9.53 (d, J = 9.6 Hz, 2 H, 4,8-H), 8.66 (t, J = 9.6 Hz, 1 H, 6- 49.0–51.0 °C. HRMS (ESI): calcd. for C16H20S2 [M]+ 276.1006;
+
1248
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1242–1252

Synthesis of 1-Azulenyl Sulfides and 1,1Ј-Biazulenes
found 276.1001. IR (KBr): νmax = 2964 (s), 2914 (s), 2866 (m), 2824 = 9.6 Hz, 2 H, 4,8-H), 8.17 (s, 1 H, 2-H), 7.74 (t, J = 9.6 Hz, 1 H,
˜
(w), 1581 (s), 1547 (w), 1475 (s), 1435 (m), 1404 (s), 1383 (m), 1361
(s), 1292 (m), 1253 (m), 1232 (w), 1196 (w), 1180 (w), 1107 (w),
1062 (m), 1018 (w), 968 (m), 922 (w), 875 (m), 846 (m), 819 (m),
6-H), 7.38 (t, J = 9.6 Hz, 2 H, 5,7-H), 7.15 (t, J = 7.6 Hz, 4 H, m-
Ph), 7.05 (t, J = 7.6 Hz, 2 H, p-Ph), 7.01 (d, J = 7.6 Hz, 4 H, o-
Ph) ppm. 13C NMR (100 MHz, CDCl3): δ = 149.97, 143.80, 140.35,
702 (w), 677 (m), 615 (m), 482 (w), 468 (w), 451 (w) cm–1. UV/Vis 140.06, 136.93, 129.30, 126.70, 126.69, 125.56, 115.88 ppm.
(CH2Cl2): λmax (logε) = 240 (4.28), 304 (4.48), 322 sh (4.28), 346
6-tert-Butyl-1,3-bis(phenylthio)azulene (11b): Trifluoromethanesul-
fonic anhydride (667 mg, 2.40 mmol) in CH2Cl2 (20 mL) was added
sh (3.91), 376 sh (3.72), 406 (3.51), 604 (2.56) nm. 1H NMR
(400 MHz, CDCl3): δ = 8.47 (d, J = 10.0 Hz, 2 H, 4,8-H), 7.84 (s,
to a solution of 1b (184 mg, 1.00 mmol) and methyl phenyl sulfox-
1 H, 2-H), 7.41 (d, J = 10.0 Hz, 2 H, 5,7-H), 2.46 (s, 6 H, 1-SMe),
ide (841 mg, 6.00 mmol) in CH2Cl2 (20 mL). The resulting solution
was stirred at room temperature for 10 min. The solvent was re-
moved under reduced pressure. EtOH (20 mL) and Et2NH (20 mL)
1.45 (s, 9 H, 6-tBu) ppm. 13C NMR (100 MHz, CDCl3): δ = 163.75,
141.80, 139.38, 135.02, 122.45, 121.13, 39.16 (s, 6-tBu), 32.36 (q, 6-
tBu), 20.97 (1-SMe) ppm. C16H20S2: calcd. C 69.51, H 7.29; found
were added to the residue and the mixture was refluxed for 10 min.
C 69.61, H 7.11.
The solvent was removed under reduced pressure. The residue was
purified by column chromatography on silica gel with hexane as
1-Azulenyl Phenyl Sulfide (10a):[3] Et2NH (10 mL) was added to a
solution of 6a+·CF3CO2 (364 mg, 1.00 mmol) in EtOH (10 mL). eluent to give 11b (369 mg, 92%) as purple crystals; m.p. 125.0–
–
The solution was refluxed for 30 min. The reaction mixture was
cooled to room temperature and the solvent was removed under
reduced pressure. The resulting crude product was purified by col-
umn chromatography on silica gel with hexane/AcOEt (4:1) as elu-
130.0 °C. HRMS (ESI): calcd. for C26H24S2+ [M]+ 400.1319; found
400.1314. IR (KBr): νmax = 3071 (w), 3053 (w), 2951 (w), 2864 (w),
˜
1579 (s), 1475 (s), 1437 (m), 1410 (s), 1394 (w), 1360 (m), 1327 (w),
1296 (w), 1250 (w), 1234 (w), 1178 (w), 1101 (w), 1080 (w), 1022
(m), 997 (w), 922 (w), 898 (w), 844 (m), 819 (w), 736 (m), 688 (m),
ent to give 10a (231 mg, 98%) as dark-blue crystals; m.p. 80.0–
1
81.5 °C (ref.[3] 84–84.5 °C). H NMR (400 MHz, CDCl3): δ = 8.68 675 (w), 613 (w), 595 (w), 490 (w), 464 (w), 447 (w) cm–1. UV/Vis
(d, J = 9.6 Hz, 1 H, 8-H), 8.38 (d, J = 9.6 Hz, 1 H, 4-H), 8.03 (d,
J = 3.6 Hz, 1 H, 2-H), 7.69 (t, J = 9.6 Hz, 1 H, 6-H), 7.46 (d, J =
(CH2Cl2): λmax (logε) = 238 (4.45), 254 sh (4.39), 290 (4.49), 302
(4.49), 370 sh (3.75), 560 (2.63) nm. H NMR (400 MHz, CDCl3):
1
3.6 Hz, 1 H, 3-H), 7.33–7.24 (m, 2 H, 5,7-H), 7.13 (t, J = 7.6 Hz, δ = 8.65 (d, J = 10.8 Hz, 2 H, 4,8-H), 8.09 (s, 1 H, 2-H), 7.59 (d,
2 H, m-Ph), 7.03 (t, J = 7.6 Hz, 1 H, p-Ph), 6.95 (d, J = 7.6 Hz, 2 J = 10.8 Hz, 2 H, 5,7-H), 7.15 (t, J = 8.0 Hz, 4 H, m-Ph), 7.04 (t,
H, o-Ph) ppm. 13C NMR (100 MHz, CDCl3): δ = 143.49, 142.30, J = 8.0 Hz, 2 H, p-Ph), 7.01 (d, J = 8.0 Hz, 4 H, o-Ph), 1.44 (s, 9
141.49, 138.60, 137.26, 135.77, 131.00, 129.16, 128.69, 125.88,
124.72, 124.52, 117.78, 114.88 ppm.
H, 6-tBu) ppm. 13C NMR (100 MHz, CDCl3): δ = 164.82, 149.30,
142.64, 140.46, 135.88, 129.23, 126.51, 125.35, 124.99, 114.79,
39.43 (s, 6-tBu), 32.27 (q, 6-tBu) ppm. C20H20S: C 77.95, H 6.04;
found C 77.65, H 5.85.
6-tert-Butyl-1-azulenyl Phenyl Sulfide (10b): Trifluoroacetic anhy-
dride (756 mg, 3.60 mmol) in CH2Cl2 (20 mL) was added to a solu-
tion of 1b (184 mg, 1.00 mmol) and methyl phenyl sulfoxide (1.26 g,
9.00 mmol) in CH2Cl2 (30 mL). The resulting solution was stirred
at room temperature for 30 min. The solvent was removed under
reduced pressure. EtOH (20 mL) and Et2NH (20 mL) were added
to the residue and the mixture was refluxed for 10 min. The solvent
was removed under reduced pressure. The residue was purified by
column chromatography on silica gel with hexane/CH2Cl2 (4:1) as
eluent to give 10b (274 mg, 94%) as a purple oil. HRMS (ESI):
1-Azulenyl Methyl Sulfoxide (12a):[3] 70% MCPBA (260 mg) in
CH2Cl2 (20 mL) was added to a solution of 8a (174 mg, 1.00 mmol)
in CH2Cl2 (20 mL). The mixture was stirred at 0 °C for 5 min. The
reaction mixture was poured into 10% NaHCO3, extracted with
CH2Cl2, dried with MgSO4, and concentrated under reduced pres-
sure. The residue was purified by reversed-phase column
chromatography (ODS with 70% MeOH) to give 12a (183 mg,
1
96%) as a purple oil. H NMR (500 MHz, CDCl3): δ = 8.83 (d, J
calcd. for C20H20S+ [M]+ 292.1286; found 292.1280. IR (KBr): ν
= 9.5 Hz, 1 H, 8-H), 8.43 (d, J = 9.5 Hz, 1 H, 4-H), 8.31 (d, J =
4.5 Hz, 1 H, 2-H), 7.76 (t, J = 9.5 Hz, 1 H, 6-H), 7.44 (d, J =
4.5 Hz, 1 H, 3-H), 7.40 (t, J = 9.5 Hz, 1 H, 7-H), 7.37 (t, J =
9.5 Hz, 1 H, 5-H), 2.97 [s, 3 H, 1-S(O)Me] ppm. 13C NMR
˜
max
= 3071 (w), 2964 (m), 2905 (w), 2868 (w), 1583 (s), 1551 (w), 1477
(s), 1439 (w), 1402 (s), 1363 (w), 1304 (w), 1250 (w), 1236 (w), 1180
(w), 1157 (w), 1080 (w), 1024 (w), 1005 (w), 931 (w), 895 (w), 843
(m), 821 (w), 769 (w), 736 (m), 713 (w), 690 (m), 675 (w), 617 (w), (100 MHz, CDCl3): δ = 142.91, 139.20, 138.76, 137.38, 134.16,
605 (w), 484 (w), 449 (w) cm–1. UV/Vis (CH2Cl2): λmax (logε) = 236 133.33, 127.69, 125.93, 125.65, 118.30, 42.02 [1-S(O)Me] ppm.
(4.40), 286 (4.68), 296 (4.68), 350 sh (3.82), 368 sh (3.57), 556 (2.62),
6-tert-Butyl-1-azulenyl Methyl Sulfoxide (12b): 70% MCPBA
1
590 sh (2.58), 656 sh (2.14) nm. H NMR (400 MHz, CDCl3): δ =
(260 mg) in CH2Cl2 (20 mL) was added to a solution of 8b (230 mg,
8.60 (d, J = 10.0 Hz, 1 H, 8-H), 8.33 (d, J = 10.0 Hz, 1 H, 4-H),
1.00 mmol) in CH2Cl2 (20 mL). The mixture was stirred at 0 °C
7.94 (d, J = 4.0 Hz, 1 H, 2-H), 7.49 (dd, J = 10.0, 1.2 Hz, 2 H, 5,7-
H), 7.37 (d, J = 4.0 Hz, 1 H, 3-H), 7.13 (t, J = 8.0 Hz, 2 H, m-Ph),
for 5 min. The reaction mixture was poured into 10% NaHCO3,
extracted with CH2Cl2, dried with MgSO4, and concentrated under
reduced pressure. The residue was purified by reversed-phase col-
7.13 (d, J = 8.0 Hz, 1 H, p-Ph), 6.96 (d, J = 8.0 Hz, 2 H, o-Ph),
1.46 (s, 9 H, 6-tBu) ppm. 13C NMR (100 MHz, CDCl3): δ = 163.21,
umn chromatography (ODS with 70% MeOH) to give 12b (241 mg,
143.14, 141.49, 141.26, 140.82, 136.81, 135.19, 129.117, 129.115,
126.24, 125.03, 123.29, 117.60, 114.36, 39.22 (s, 6-tBu), 32.35 (q, 6-
tBu) ppm. C20H20S: C 82.14, H 6.89; found C 82.00, H 6.85.
98%) as a purple oil. HRMS (ESI): calcd. for C15H18OS + Na+
[M + Na]+ 269.0976; found 269.0971. IR (KBr): ν
= 2966 (m),
˜
max
2870 (w), 1585 (s), 1552 (w), 1402 (s), 1294 (s), 1240 (w), 1190 (w),
1172 (m), 1126 (s), 1024 (m), 964 (m), 848 (m), 760 (m), 758 (m),
713 (w), 711 (w), 677 (w), 584 (w), 534 (m), 501 (w) cm–1. UV/Vis
(CH2Cl2): λmax (logε) = 256 (3.66), 289 sh (4.60), 298 (4.66), 321
1,3-Bis(phenylthio)azulene (11a):[3] Et2NH (10 mL) was added to a
solution of 7a2+·2TfO– (548 mg, 1.00 mmol) in EtOH (10 mL). The
solution was refluxed for 30 min. The reaction mixture was cooled
to room temperature and the solvent was removed under reduced
pressure. The resulting crude product was purified by column
chromatography on silica gel with hexane/AcOEt (4:1) as eluent to
give 11a (210 mg, 95%) as dark-blue crystals; m.p. 121.0–123.0 °C
1
(3.66), 345 (3.77), 357 (3.49), 520 (2.86) nm. H NMR (400 MHz,
CDCl3): δ = 8.83 (d, J = 10.0 Hz, 1 H, 8-H), 8.42 (d, J = 10.0 Hz,
1 H, 4-H), 8.22 (d, J = 4.4 Hz, 1 H, 2-H), 7.64 (dd, J = 10.0, 1.2 Hz,
1 H, 7-H), 7.60 (dd, J = 10.0, 1.2 Hz, 1 H, 5-H), 7.37 (d, J = 4.4 Hz,
1 H, 3-H), 2.46 [s, 3 H, 1-S(O)Me], 1.48 (s, 9 H, 6-tBu) ppm. 13C
(ref.[3] 127–128.5 °C). H NMR (400 MHz, CDCl3): δ = 8.72 (d, J
1
Eur. J. Org. Chem. 2008, 1242–1252
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1249

T. Shoji, N. Morita et al.
FULL PAPER
NMR (100 MHz, CDCl3): δ = 163.88, 141.72, 137.85, 136.41, poured into 1  NaOH and extracted with toluene, dried with
133.35, 132.51, 127.03, 124.18, 124.05, 117.75, 42.04 [1-S(O)Me], MgSO4, and concentrated under reduced pressure. The residue was
38.79 (s, 6-tBu), 31.68 (q, 6-tBu) ppm. C15H18OS: C 73.13, H 7.36; purified by column chromatography on silica gel with hexane/Ac-
found C 73.17, H 7.48.
1-Azulenyl Phenyl Sulfoxide (13a):[3] 70% MCPBA (260 mg) in
CH2Cl2 (20 mL) was added to
1.00 mmol) in CH2Cl2 (20 mL). The mixture was stirred at 0 °C
for 5 min. The reaction mixture was poured into 10% NaHCO3,
extracted with CH2Cl2, dried with MgSO4, and concentrated under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with CH2Cl2/AcOEt (1:1) as eluent to give 13a
OEt (4:1) as eluent to give 15a (68 mg, 39%) as brown crystals;
m.p. 138.0–140 °C (hexane). HRMS (ESI): calcd. for C30H20N2 +
H+ [M + H]+ 409.1705; found 409.1699. MS (EI): m/z (%) = 345
(100) [M]+, 330 (45), 315 (19), 300 (12), 282 (12), 239 (10), 158 (19),
a solution of 10a (236 mg,
109 (20), 84 (10). IR (KBr): ν
= 3038 (w), 2918 (w), 1568 (s),
˜
max
1483 (m), 1444 (w), 1396 (s), 1298 (m), 1263 (w), 1211 (w), 985 (w),
960 (w), 941 (w), 927 (m), 860 (m), 735 (s), 572 (w), 557 (w) cm–1.
UV/Vis (CH2Cl2): λmax (logε) = 242 (4.43), 278 (4.56), 402 (4.07),
638 (2.81) nm. 1H NMR (400 MHz, CDCl3): δ = 8.62 (d, J =
10.4 Hz, 1 H, 8-H), 8.24 (d, J = 10.4 Hz, 1 H, 4-H), 8.11 (s, 1 H,
2-H), 7.59 (t, J = 10.4 Hz, 1 H, 6-H), 7.20 (t, J = 10.4 Hz, 1 H, 7-
H), 7.06 (t, J = 10.4 Hz, 1 H, 5-H), 2.56 (s, 3 H, 3,3Ј-SMe) ppm.
13C NMR (100 MHz, CDCl3): δ = 140.45, 139.55, 139.17, 138.23,
136.45, 135.65, 125.13, 123.68, 123.14, 121.63, 20.29 (3,3Ј-
SMe) ppm. C22H18S2: C 76.26, H 5.24; found C 75.98, H 5.46.
1
(240 mg, 95%) as a purple oil. H NMR (500 MHz, CDCl3): δ =
9.00 (d, J = 10.0 Hz, 1 H, 8-H), 8.42 (d, J = 10.0 Hz, 1 H, 4-H),
7.89 (d, J = 4.0 Hz, 1 H, 2-H), 7.79 (d, J = 10.0 Hz, 1 H, 6-H),
7.65 (dd, J = 7.0, 1.5 Hz, 2 H, o-Ph), 7.46 (t, J = 10.0 Hz, 1 H, 7-
H), 7.42–7.40 (m, 3 H, m- and p-Ph), 7.40 (t, J = 10.0 Hz, 1 H, 5-
H), 7.34 (d, J = 4.0 Hz, 1 H, 3-H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 145.48, 143.41, 139.37, 138.92, 138.88, 136.13, 134.64,
129.95, 128.81, 128.20, 126.46, 126.37, 124.50, 118.47 ppm.
6,6Ј-Di-tert-butyl-3,3Ј-bis(methylthio)-1,1Ј-biazulene (15b)
6-tert-Butyl-1-azulenyl Phenyl Sulfoxide (13b): 70% MCPBA
(260 mg) in CH2Cl2 (20 mL) was added to a solution of 10b
(230 mg, 1.00 mmol) in CH2Cl2 (20 mL). The mixture was stirred
at 0 °C for 5 min. The reaction mixture was poured into 10%
NaHCO3, extracted with CH2Cl2, dried with MgSO4, and concen-
trated under reduced pressure. The residure was purified by column
chromatography on silica gel with CH2Cl2 as eluent and reversed-
phase column chromatography (ODS with 70% MeOH) to give
13b (300 mg, 97%) as purple crystals; m.p. 99.0–102.0 °C. HRMS
(ESI): calcd. for C20H20OS + Na+ [M + Na]+ 331.1133; found
Reaction with CF3CO2H: CF3CO2H (10 mL) was added to a solu-
tion of 12b (246 mg, 1.00 mmol) in CH2Cl2 (10 mL). The reaction
mixture was poured into 1  NaOH and extracted with toluene,
dried with MgSO4, and concentrated under reduced pressure. The
residue was purified by column chromatography on silica gel with
hexane/AcOEt (4:1) as eluent to give 15b (183.5 mg, 80%) as green
crystals.
Reaction with 60% HPF6: 60% HPF6 (5 mL) was added to a solu-
tion of 12b (246 mg, 1.00 mmol) in CH2Cl2 (10 mL). The reaction
mixture was poured into 1  NaOH and extracted with toluene,
dried with MgSO4, and concentrated under reduced pressure. The
residue was purified by column chromatography on silica gel with
hexane/AcOEt (4:1) as eluent to give 15b (210 mg, 81%) as green
crystals; m.p. 93.0–95.0 °C (hexane). MS (EI): m/z (%) = 458 (17)
331.1127. IR (KBr): νmax = 3055 (w), 2964 (m), 2907 (w), 2868 (w),
˜
1583 (s), 1551 (w), 1475 (m), 1442 (m), 1400 (s), 1365 (w), 1304
(w), 1282 (w), 1257 (w), 1238 (w), 1186 (w), 1161 (m), 1147 (w),
1082 (w), 1035 (s), 1022 (s), 997 (w), 925 (w), 898 (w), 844 (m), 821
(w), 746 (m), 736 (m), 713 (w), 692 (m), 675 (w), 617 (w), 599 (w),
528 (w), 480 (m), 451 (w) cm–1. UV/Vis (CH2Cl2): λmax (logε) =
290 sh (4.63), 298 (4.74), 348 (3.89), 360 sh (3.65), 526 (2.65), 558
[M]+, 412 (29), 276 (49), 261 (35), 84 (100). IR (KBr): νmax = 2963
˜
(m), 2916 (w), 2868 (w), 1576 (s), 1477 (m), 1406 (s), 1361 (m),
1304 (w), 1252 (m), 1061 (w), 1018 (w), 964 (m), 935 (m), 870 (w),
837 (m), 821 (w), 677 (w), 619 (w), 582 (w), 451 (w) cm–1. UV/Vis
(CH2Cl2): λmax (logε) = 290 (4.66), 303 sh (4.62), 367 (3.98), 407
1
sh (2.59), 614 sh (2.12) nm. H NMR (400 MHz, CDCl3): δ = 8.93
(d, J = 10.4 Hz, 1 H, 8-H), 8.36 (d, J = 10.4 Hz, 1 H, 4-H), 7.79
(d, J = 4.0 Hz, 1 H, 2-H), 7.65 (m, 3 H, 7-H, o-Ph), 7.42 (t, J =
8.0 Hz, 1 H, m-Ph), 7.38 (t, J = 8.0 Hz, 1 H, m-Ph), 7.24 (d, J =
4.0 Hz, 1 H, 3-H), 1.45 (s, 9 H, 6-tBu) ppm. 13C NMR (100 MHz,
CDCl3): δ = 166.25, 148.00, 144.34, 140.21, 137.50, 135.95, 132.05,
131.00, 129.62, 127.03, 126.81, 126.76, 125.60, 120.12, 41.13 (s, 6-
tBu), 34.00 (q, 6-tBu) ppm. C20H20OS·H2O: C 76.98, H 6.59; found
C 76.77, H 6.33.
1
(4.17), 499 (1.96), 625 (2.87) nm. H NMR (400 MHz, CDCl3): δ
= 8.55 (d, J = 10.4 Hz, 1 H, 8-H), 8.25 (d, J = 10.4 Hz, 1 H, 4-H),
8.02 (s, 1 H, 2-H), 7.38 (dd, J = 10.4, 1.2 Hz, 1 H, 7-H), 7.25 (dd,
J = 10.4, 1.2 Hz, 1 H, 5-H), 2.53 (s, 3 H, 3,3Ј-SMe), 1.45 (s, 9
H, 6-tBu) ppm. 13C NMR (100 MHz, CDCl3): δ = 163.04, 139.74,
138.38, 136.90, 135.51, 134.53, 124.90, 121.80, 121.24, 120.77,
38.60 (s, 6-tBu), 31.77 (q, 6-tBu), 20.47 (3,3Ј-SMe) ppm. C30H34S2:
C 78.55, H 7.47; found C 78.56, H 7.55.
3,3Ј-Bis(methylthio)-1,1Ј-biazulene (15a)
Reaction with CF3CO2H: CF3CO2H (10 mL) was added to a solu-
tion of 12a (190 mg, 1.00 mmol) in CH2Cl2 (10 mL). The solution
was stirred at 0 °C for 5 min. The reaction mixture was poured
into 1  NaOH and extracted with toluene, dried with MgSO4, and
concentrated under reduced pressure. The residue was purified by
column chromatography on silica gel with hexane/AcOEt (4:1) as
eluent to give 15a (154 mg, 89%) as brown crystals.
3,3Ј-Bis(phenylthio)-1,1Ј-biazulene (16a)
Reaction with CF3CO2H: CF3CO2H (10 mL) was added to a solu-
tion of 13a (252 mg, 1.00 mmol) in CH2Cl2 (10 mL). The solution
was stirred at 0 °C for 5 min. The reaction mixture was poured
into 1  NaOH and extracted with toluene, dried with MgSO4, and
concentrated under reduced pressure. The residue was purified by
column chromatography on silica gel with hexane/CH2Cl2 (4:1) as
eluent to give 16a (120 mg, 51%) as green crystals.
Reaction with 60% HPF6: 60% HPF6 (5 mL) was added to a solu-
tion of 12a (190 mg, 1.00 mmol) in CH2Cl2 (10 mL). The solution
was stirred at 0 °C for 5 min. The reaction mixture was poured
into 1  NaOH and extracted with toluene, dried with MgSO4, and
concentrated under reduced pressure. The residue was purified by
column chromatography on silica gel with hexane/AcOEt (4:1) as
eluent to give 15a (151 mg, 87%) as brown crystals.
Reaction with 60% HPF6: 60% HPF6 (5 mL) was added to a solu-
tion of 13a (252 mg, 1.00 mmol) in CH2Cl2 (10 mL). The solution
was stirred at 0 °C for 5 min. The reaction mixture was poured
into 1  NaOH and extracted with toluene, dried with MgSO4, and
concentrated under reduced pressure. The residue was purified by
column chromatography on silica gel with hexane/CH2Cl2 (4:1) as
eluent to give 15a (167 mg, 71%) as green crystals; m.p. 187.0–
Reaction with TfOH: TfOH (1 mL) was added to a solution of 12a
(190 mg, 1.00 mmol) in CH2Cl2 (10 mL). The reaction mixture was
1250
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 1242–1252

Synthesis of 1-Azulenyl Sulfides and 1,1Ј-Biazulenes
189.0 °C. HRMS (ESI): calcd. for C32H22S2 + Na+ [M + Na]+
493.1061; found 493.1055. MS (EI): m/z (%) = 470 (100) [M]+, 235
OEt (1:1) as eluent to give 17a (101 mg, 65%) as brown crystals;
m.p. 247.0–251.0 °C (ref.[11] 254–256 °C). 1H NMR (400 MHz,
CDCl3): δ = 10.45 (s, 2 H, 3,3Ј-CHO), 9.63 (d, J = 9.6 Hz, 2 H, 4-
(7). IR (KBr): ν
= 3059 (w), 3017 (w), 1570 (s), 1475 (m), 1406
˜
max
(w), 1394 (s), 1350 (w), 1327 (w), 1300 (w), 1290 (w), 1263 (w), H), 8.46 (d, J = 9.6 Hz, 2 H, 8-H), 8.40 (s, 2 H, 2-H), 7.89 (t, J =
1211 (w), 1178 (w), 1149 (w), 1095 (w), 1078 (w), 1022 (w), 997
(w), 949 (w), 935 (w), 900 (w), 893 (w), 873 (w), 835 (w), 731 (s),
687 (m), 578 (w), 515 (w), 499 (w), 478 (w), 453 (w) cm–1. UV/
9.6 Hz, 2 H, 6-H), 7.66 (t, J = 9.6 Hz, 2 H, 5-H), 7.47 (t, J =
9.6 Hz, 2 H, 7-H) ppm. 13C NMR (100 MHz. CDCl3): δ = 186.25
(s, 3,3Ј-CHO), 143.16, 142.48, 141.08, 140.66, 137.93, 137.74,
Vis (CH2Cl2): λmax (logε) = 242 (4.43), 278 (4.56), 402 (4.07), 638 129.72, 128.49, 125.61, 125.00 ppm.
1
(2.81) nm. H NMR (400 MHz, CDCl3): δ = 8.71 (d, J = 9.6 Hz,
6,6Ј-Di-tert-butyl-1,1Ј-biazulene-3,3Ј-dicarbaldehyde (17b)
2 H, 8,8Ј-H), 8.41 (d, J = 9.6 Hz, 2 H, 4,4Ј-H), 8.24 (s, 2 H, 2,2Ј-
H), 7.66 (t, J = 9.6 Hz, 2 H, 6,6Ј-H), 7.27 (t, J = 9.6 Hz, 2 H, 7,7Ј-
H), 7.20 (t, J = 9.6 Hz, 2 H, 5,5Ј-H), 7.16 (t, J = 7.6 Hz, 4 H, m-
Ph), 7.09–7.04 (m, 6 H, o- and p-Ph) ppm. 13C NMR (100 MHz,
CDCl3): δ = 144.25, 142.18, 140.06, 139.53, 139.12, 136.63, 136.27,
128.81, 128.80, 126.17, 125.29, 124.94, 124.94, 114.91 ppm.
C32H22S2: C 81.66, H 4.71; found C 81.61, H 4.81.
Vilsmeier Reaction of 15b: POCl3 (613 mg, 4.00 mmol) was added
to a solution of 15b (458 mg, 1.00 mmol) in DMF (20 mL). The
solution was stirred at 50 °C for 24 h. The reaction mixture was
poured into 1  NaOH and extracted with AcOEt, dried with
MgSO4, and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene/Ac-
OEt (1:1) as eluent to give 17b (388 mg, 92%) as brown needle-
shaped crystals.
6,6Ј-Di-tert-butyl-3,3Ј-bis(phenylthio)-1,1Ј-biazulene (16b)
Reaction with CF3CO2H: CF3CO2H (10 mL) was added to a solu-
tion of 13b (308 mg, 1.00 mmol) in CH2Cl2 (20 mL). The solution
was stirred at 0 °C for 5 min. The reaction mixture was poured
into 1  NaOH and extracted with toluene, dried with MgSO4, and
concentrated under reduced pressure. The residue was purified by
column chromatography on silica gel with hexane/CH2Cl2 (4:1) as
eluent to give 15b (152 mg, 56%) as green crystals.
Vilsmeier Reaction of 16b: POCl3 (613 mg, 4.00 mmol) was added
to a solution of 16b (583 mg, 1.00 mmol) in DMF (20 mL). The
solution was stirred at 50 °C for 24 h. The reaction mixture was
poured into 1  NaOH and extracted with AcOEt, dried with
MgSO4, and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene/Ac-
OEt (1:1) as eluent to give 17b (388 mg, 72%) as brown needle-
shaped crystals; m.p. 147.0–148.0 °C (acetone). HRMS (ESI):
calcd. for C30H30O2 + Na+ [M + Na]+ 445.2143; found 445.2138.
Reaction with 60% HPF6: 60% HPF6 (5 mL) was added to a solu-
tion of 13b (308 mg, 1.00 mmol) in CH2Cl2 (20 mL). The solution
was stirred at 0 °C for 5 min. The reaction mixture was poured
into 1  NaOH and extracted with toluene, dried with MgSO4, and
concentrated under reduced pressure. The residue was purified by
column chromatography on silica gel with hexane/CH2Cl2 (4:1) as
eluent to give 15b (223 mg, 77%) as green crystals; m.p. 112.0–
115.0 °C. HRMS (ESI): calcd. for C40H38S2+ [M]+ 582.2415; found
IR (KBr): ν
= 2964 (m), 2872 (w), 2723 (w), 1651 (s), 1579 (s),
˜
max
1294 (s), 1500 (m), 1460 (m), 1437 (m), 1419 (m), 1400 (m), 1363
(m), 1288 (m), 1244 (m), 1190 (w), 1163 (w), 1128 (w), 1074 (w),
877 (w), 846 (w), 814 (w), 792 (w), 675 (w), 659 (w), 559 (w) cm–1.
UV/Vis (CH2Cl2): λmax (logε) = 240 (4.52), 298 (4.85), 318 sh
1
(4.79), 424 sh (4.10), 546 (3.12) nm. H NMR (400 MHz, CDCl3):
δ = 10.46 (s, 2 H, 3,3Ј-CHO), 8.57 (d, J = 10.4 Hz, 2 H, 8-H), 8.49
(d, J = 10.4 Hz, 2 H, 4-H), 8.36 (s, 1 H, 2-H), 7.86 (dd, J = 10.4,
1.2 Hz, 2 H, 7-H), 7.70 (dd, J = 10.4, 1.2 Hz, 2 H, 5-H), 1.45 (s,
18 H, 6,6Ј-tBu) ppm. 13C NMR (100 MHz, CDCl3): δ = 186.20 (s,
3,3Ј-CHO), 165.58, 142.21, 141.39, 140.15, 137.02, 136.86, 127.77,
127.14, 125.53, 124.88, 39.06 (s, 6,6Ј-tBu), 31.81 (q, 6,6Ј-tBu) ppm.
C30H30O2·½H2O: C 83.49, H 7.24; found C 83.49, H 7.18.
582.2409. IR (KBr): νmax = 3071 (w), 2964 (m), 2905 (w), 2868 (w),
˜
1583 (s), 1551 (w), 1477 (s), 1439 (w), 1402 (s), 1363 (w), 1304 (w),
1250 (w), 1236 (w), 1180 (w), 1157 (w), 1080 (w), 1024 (w), 1005
(w), 931 (w), 895 (w), 843 (m), 821 (w), 769 (w), 736 (m), 713 (w),
690 (m), 675 (w), 617 (w), 605 (w), 484 (w), 449 (w) cm–1. UV/Vis
(CH2Cl2): λmax (logε) = 246 (4.70), 278 (4.78), 312 (4.70), 398
1
(4.22), 604 (2.97) nm. H NMR (400 MHz, CDCl3): δ = 8.63 (d, J
1,1Ј-Biazulene (18a):[9] Pyrrole (5 mL) was added to a solution of
17a (100 mg, 0.32 mmol) in acetic acid (5 mL). The solution was
stirred at room temperature for 24 h. The reaction mixture was
poured into water and extracted with hexane, dried with MgSO4,
and concentrated under reduced pressure. The crude product was
purified by column chromatography on silica gel with hexane/
CH2Cl2 (4:1) to afford 18a (62 mg, 71%) as green crystals; m.p.
= 10.0 Hz, 2 H, 8,8Ј-H), 8.43 (d, J = 10.0 Hz, 2 H, 4,4Ј-H), 8.16
(s, 2 H, 2,2Ј-H), 7.45 (dd, J = 10.0, 1.2 Hz, 2 H, 7,7Ј-H), 7.40 (dd,
J = 10.0, 1.2 Hz, 2 H, 5,5Ј-H), 7.17 (t, J = 8.0 Hz, 4 H, o-Ph), 7.07
(d, J = 8.0 Hz, 4 H, m-Ph), 7.05 (t, J = 8.0 Hz, 2 H, p-Ph) ppm.
13C NMR (100 MHz, CDCl3): δ = 164.06, 143.78, 141.41, 141.01,
138.23, 136.13, 135.55, 129.17, 126.39, 125.50, 125.12, 123.54,
123.20, 114.23, 39.19 (s, 6-tBu), 32.23 (q, 6-tBu) ppm. C40H38S2: C
82.43, H 6.57; found C 82.19, H 6.84.
1
102–104 °C (ref.[9] 104–105 °C). H NMR (400 MHz, CDCl3): δ =
8.27 (d, J = 10.0 Hz, 2 H, 4,8-H), 8.03 (d, J = 4.0 Hz, 1 H, 2-H),
7.46 (d, J = 10.0 Hz, 1 H, 6-H), 7.44 (d, J = 4.0 Hz, 1 H, 3-H),
7.04 (t, J = 10.0 Hz, 1 H, 5-H), 6.95 (t, J = 10.0 Hz, 1 H, 7-H) ppm.
1,1Ј-Biazulene-3,3Ј-dicarbaldehyde (17a)[11]
Vilsmeier Reaction of 15a: POCl3 (613 mg, 4.00 mmol) was added
to a solution of 15a (346 mg, 1.00 mmol) in DMF (20 mL). The
solution was stirred at 50 °C for 24 h. The reaction mixture was
poured into 1  NaOH and extracted with AcOEt, dried with
MgSO4, and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene/Ac-
OEt (1:1) as eluent to give 17a (280 mg, 90%) as brown crystals.
6,6Ј-Di-tert-butyl-1,1Ј-biazulene (18b): Pyrrole (3 mL) was added to
a solution of 17b (60 mg, 0.14 mmol) in acetic acid (3 mL). The
solution was stirred at room temperature for 24 h. The reaction
mixture was poured into water and extracted with hexane, dried
with MgSO4, and concentrated under reduced pressure. The crude
product was purified by column chromatography on silica gel with
hexane/CH2Cl2 (4:1) to afford 18b (41 mg, 80%) as green crystals;
Vilsmeier Reaction of 16a: POCl3 (767 mg, 5.00 mmol) was added
to a solution of 16a (235 mg, 0.50 mmol) in DMF (10 mL). The
solution was stirred at 50 °C for 24 h. The reaction mixture was
poured into 1  NaOH and extracted with AcOEt, dried with
MgSO4, and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene/Ac-
m.p. 75.0–77.0 °C. HRMS (EI): calcd. for C28H30 [M]+ 366.2348;
+
found 366.2344. IR (KBr): ν
= 2963 (s), 2903 (m), 2866 (m),
˜
max
1576 (s), 1549 (m), 1481 (m), 1460 (m), 1402 (s), 1361 (m), 1304
(w), 1252 (w), 1234 (w), 1196 (w), 1093 (w), 1057 (w), 1020 (w),
997 (w), 908 (w), 837 (s), 819 (m), 769 (m), 711 (w), 675 (w), 617
Eur. J. Org. Chem. 2008, 1242–1252
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1251

T. Shoji, N. Morita et al.
FULL PAPER
(w), 542 (w), 449 (w) cm–1. UV/Vis (CH2Cl2): λmax (logε) = 244
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1
(2.81) nm. H NMR (400 MHz, CDCl3): δ = 8.26 (d, J = 10.0 Hz,
1 H, 4-H), 8.20 (d, J = 10.4 Hz, 1 H, 8-H), 7.94 (d, J = 4.0 Hz, 1
H, 2-H), 7.35 (d, J = 4.0 Hz, 1 H, 3-H), 7.20 (dd, J = 10.0, 1.6 Hz,
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137.96, 136.37, 135.75, 135.68, 126.98, 121.38, 121.17, 117.44,
38.96 (s, 6-tBu), 32.33 (q, 6-tBu) ppm. C28H30: C 91.75, H 8.25;
found C 91.70, H 8.11.
Acknowledgments
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We are grateful to Professor Nagao Kobayashi and Dr. John Mac
of Tohoku University for valuable comments on this study. This
work was partially supported by the COE project, Giant Molecules
and Complex Systems, of the Ministry of Education, Culture,
Sports, Science, and Technology, Japan.
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Received: October 11, 2007
Published Online: January 7, 2008
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1252
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Eur. J. Org. Chem. 2008, 1242–1252