Synthesis and redox behavior of 1,3-bis(methylthio-) and 1,3-bis(phenylthio)azulenes bearing 2- and 3-thienyl substituents by palladium-catalyzed cross-coupling reaction of 2- and 6-haloazulenes with thienylmagnesium ate complexes

Article abstract of DOI:10.1002/ejoc.200900508

Preparation of thienylazulenes3-6 was established by the palladium-catalyzed cross-coupling reaction of the corresponding haloazulenes with thienylmagnesium ate complexes, which were readily prepared from the corresponding bromothiophenes. The reaction of 3-6 with several sulfoxides in the presence of Tf₂O, followed by treatment with triethylamine afforded the corresponding 1,3-bis(methylthio)- and 1,3-bis(phenylthio)-2- and 6-thienylazulenes 7-12 in good yields. Redox behavior of the novel azulene derivatives with 2- and 3-thienyl-substituted 3-12 was examined by cyclic voltammetry and differential pulse voltammetry, which revealed amphoteric redox behavior.

Full text of DOI:10.1002/ejoc.200900508

FULL PAPER
DOI: 10.1002/ejoc.200900508
Synthesis and Redox Behavior of 1,3-Bis(methylthio-) and
1,3-Bis(phenylthio)azulenes Bearing 2- and 3-Thienyl Substituents by
Palladium-Catalyzed Cross-Coupling Reaction of 2- and 6-Haloazulenes with
Thienylmagnesium Ate Complexes
Taku Shoji,*[a] Shunji Ito,*[b] Kozo Toyota,[a] Takeaki Iwamoto,[a] Masafumi Yasunami,[c]
and Noboru Morita*[a]
Keywords: Arenes / Cross-coupling / Electrophilic substitution / Cyclic voltammetry
Preparation of thienylazulenes 3–6 was established by the
palladium-catalyzed cross-coupling reaction of the corre-
sponding haloazulenes with thienylmagnesium ate com-
plexes, which were readily prepared from the corresponding
bromothiophenes. The reaction of 3–6 with several sulfoxides
in the presence of Tf2O, followed by treatment with triethyl-
amine afforded the corresponding 1,3-bis(methylthio)- and
1,3-bis(phenylthio)-2- and 6-thienylazulenes 7–12 in good
yields. Redox behavior of the novel azulene derivatives with
2- and 3-thienyl-substituted 3–12 was examined by cyclic
voltammetry and differential pulse voltammetry, which re-
vealed amphoteric redox behavior.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
stitution reaction might be difficult owing to the low reac-
tivity of azulene towards electrophilic reagents at the 2- and
6-positions. We also reported the synthesis of several aryl-
azulene derivatives by utilizing transition-metal-catalyzed
cross-coupling reactions, for example, Suzuki–Miyaura and
Stille coupling reactions, of azulenyl metal reagents.[8] Such
azulenyl metal reagents might be useful for the multiple
substitution by azulenyl groups. However, preparation of
the metal reagents for transition-metal-catalyzed reactions
are sometimes difficult for azulene derivatives and the most
promising azulenylborane reagents are relatively unstable
and undergo easy hydrolysis to afford hydrocarbon deriva-
tives.[9] Therefore, development of a general and efficient
method for the preparation of arylazulene derivatives from
readily available reagents would be important if azulene de-
rivatives were considered in the production of advanced
materials. In 2003, Mongin et al. reported a one-pot pro-
cedure for the preparation of tri(quinolinyl)magnesium lith-
ium ate complexes by a bromine–metal exchange reaction
of bromoquinolines followed by subsequent palladium-cat-
alyzed cross-coupling of the ate complexes with heteroaryl
halides to give 2-, 3-, and 4-heteroarylquinolines.[10] Similar
palladium-catalyzed cross-coupling reactions of 2- and 6-
haloazulenes with tris(heteroaryl)magnesium lithium ate
complexes will establish the new and efficient synthetic
Introduction
The transition-metal-catalyzed cross-coupling reaction is
one of the most important tools for the preparation of bi-
aryl and/or polyaryl compounds in modern organic synthe-
sis, because the structure is often found in a variety of com-
pounds such as organic conductors, liquid crystals, and
pharmaceutical and agrochemical compounds.[1] Therefore,
many transition-metal-catalyzed aryl–aryl cross-coupling
reactions, for example, Stille,[2] Suzuki–Miyaura,[3] Negi-
shi,[4] and Ullmann-type reactions,[5] have been developed
to construct or modify such compounds.
Azulene (C10H8) has attracted the interest of many re-
search groups owing to its unusual properties as well as its
beautiful blue color.[6] Recently, we reported the synthesis
of N-containing 1-heteroaryl-, 1,3-bis(heteroaryl)-, and 5-
heteroarylazulenes utilizing a two-step sequence involving
an electrophilic substitution reaction, followed by a base-
induced aromatization reaction.[7] However, preparation of
2- and 6-heteroarylazulenes utilizing the electrophilic sub-
[a] Department of Chemistry, Graduate School of Science, Tohoku
University,
Sendai 980-8578, Japan
Fax: +81-22-795-7714
E-mail: shoji-azulene@m.tains.tohoku.ac.jp
nmorita@m.tains.tohoku.ac.jp
[b] Graduate School of Science and Technology, Hirosaki Univer- route to 2- and 6-heteroarylazulenes.[11]
sity,
Herein, we report the details of the palladium-catalyzed
Hirosaki 036-8561, Japan
Fax: +81-172-39-3541
E-mail: itsnj@cc.hirosaki-u.ac.jp
[c] Department of Materials Chemistry and Engineering, College
of Engineering, Nihon University,
Koriyama 963-8642, Japan
cross-coupling reaction of 2- and 6-haloazulenes with thien-
ylmagnesium lithium ate complexes, which were prepared
from commercially available 2- and 3-bromothiophenes, to
afford 2- and 6-(2- and 3-thienyl)azulenes.[12]
Eur. J. Org. Chem. 2009, 4307–4315
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FULL PAPER
There has been considerable interest in sulfur-substituted optimize the amount of the palladium catalyst, the reaction
aromatic compounds. There is a wide range of applications was examined by utilizing several catalytic amounts. Thus,
for these compounds, such as electroluminescent devices, to obtain the highest yield, at least 5 mol-% of palladium
organic conductors, liquid crystals, and polymer stabiliz- catalyst was required as shown in Table 1.
ers.[13] Therefore, development of general synthetic pro-
cedures and modification methods for sulfur-substituted
aromatic compounds would have vital importance. Nucleo-
philic substitution reactions or metal-catalyzed coupling re-
actions of aromatic compounds bearing halogen substitu-
ents with thiols are frequently utilized to prepare sulfur-
substituted aromatic compounds. A major drawback of this
sort of approach is that the reaction often required harsh
conditions, such as strong basic conditions, high reaction
temperatures, and longer reaction periods.[13,14] Although a
variety of sulfur-substituted compounds has been synthe-
sized previously in the context of azulene chemistry,[15] little
attention has been paid to the development of a facile and
selective synthetic method for the preparation of sulfur-sub-
stituted azulene derivatives. Recently, we also reported the
synthesis of several azulenyl methyl sulfides via azulenethi-
ols, but the procedure requires multiple reaction sequences
and tedious separation processes.[16] More recently, we re-
ported the novel synthesis of 1,3-bis(methylthio)- and 1,3-
bis(phenylthio)azulenes, which exhibited reversible ampho-
teric redox properties upon cyclic voltammetry (CV).[17]
Therefore, incorporation of 1,3-bis(methylthio) and 1,3-bi-
s(phenylthio) substituents into (2- and 3-thienyl)azulenes is
expected to induce novel multiple-redox properties in the 2-
and 6-(2- and 3-thienyl)azulene derivatives.
Scheme 1.
Table 1. Comparison of the amount of Pd catalyst with the yields
of 3.
Entry
Catalyst
% Yield of 3
% Recovery of 1
1
2
3
4
none
0
99
79
33
0
1 mol-% PdCl2(PPh3)2
3 mol-% PdCl2(PPh3)2
5 mol-% PdCl2(PPh3)2
16
64
94
The magnesium ate complex prepared from 3-bromo-
thiophene was also treated with 1 efficiently to afford cross-
coupling product 4 in 96% yield (Scheme 2).
Herein, we also report the reaction of 2- and 6-(2- and
3-thienyl)azulenes with several sulfoxides in the presence of
trifluoromethanesulfonic anhydride (Tf2O), followed by
treatment with triethylamine to afford the corresponding
1,3-bis(methylthio)- and 1,3-bis(phenylthio)-2- and 6-thien-
ylazulenes, and their redox properties were examined by CV
and differential pulse voltammetry (DPV).
Scheme 2.
The cross-coupling reaction of 6-bromoazulene (2) with
the thienylmagnesium ate complexes was also conducted
under similar reaction conditions employed for the cross-
coupling reaction of 1. The magnesium ate complexes pre-
pared from 2- and 3-bromothiophenes were efficiently
treated with 2 to afford the corresponding coupling prod-
ucts 5 and 6 in 94 and 98% yield, respectively (Schemes 3
and 4). Thienylazulenes 3–6 possess fair solubility in com-
mon organic solvents, such as hexane, ethyl acetate, and
Results and Discussion
Synthesis of Thienylazulenes
Previously, we reported the preparation of azulenyl-
lithium and magnesium reagents utilizing halogen–metal
exchange reaction and their reactivities toward several elec-
trophiles.[9] Lithium (2-thienyl)magnesate reagent was pre-
pared in situ under similar reaction conditions utilizing the
reaction of haloazulenes reported by us. To a solution of n-
butylmagnesium chloride (nBuMgCl) in diethyl ether was
added n-butyllithium (nBuLi) in hexane at 0 °C to give a
lithium tri(n-butyl)magnesate reagent.[18] After the mixture
was stirred at the same temperature for 30 min, 2-bromo-
thiophene was added dropwise to the mixture at 0 °C. Then,
a solution of 2-iodoazulene (1) and PdCl2(PPh3)2 in diethyl
ether was added dropwise to the mixture at 0 °C. The mix-
ture was warmed to room temperature and stirred for 24 h
to complete the cross-coupling reaction. The crude product
was isolated and purified by the usual workup procedure to
Scheme 3.
afford 2-(2-thienyl)azulene (3) in 94% yield (Scheme 1). To Scheme 4.
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Synthesis and Redox Behavior of 1,3-Bis(methylthio- and phenylthio)azulenes
so on. Moreover, these compounds are stable and show no
decomposition even after several weeks at room tempera-
ture.
Scheme 6.
Preparation of 1,3-Bis(methylthio)- and 1,3-Bis(phenylthio)-
thienylazulenes
We applied our synthetic procedure of 1-azulenyl methyl
and phenyl sulfides and 1,3-bis(methylthio)- and 1,3-bis-
The similar reaction of thienylazulenes 5 and 6 with
(phenylthio)azulenes via 1-azulenylsulfonium and 1,3-
azulenediylsulfonium ions[17] to the synthesis 1,3-bis(meth-
ylthio)- and 1,3-bis(phenylthio)thienylazulenes. The results
for the preparation of thienylazulenes from 3–6 with triflate
and sulfoxide are summarized in Table 2.
DMSO and methyl phenyl sulfoxide was also investigated
to introduce the 1,3-bis(methylthio) and 1,3-bis(phenylthio)
moieties into the azulene ring. The reaction of 5 and 6 with
DMSO in the presence of Tf2O, followed by treatment with
triethylamine afforded 10 and 11 in 84 and 86% yield,
respectively (Schemes 7 and 8). Compound 6 was also
treated with methyl phenyl sulfoxide in the presence of Tf2O
to afford desired product 12 in 73% yield (Scheme 8), but
the reaction of 5 with methyl phenyl sulfoxide in the pres-
ence of Tf2O did not afford the presumed 1,3-bis(phenyl-
thio)-6-(2-thienyl)azulene as similar with the reaction of 4
with methyl phenyl sulfoxide. New products 7–12 are stable
and can be stored at room temperature.
Table 2. Synthesis of 1,3-bis(methylthio)- and 1,3-bis(phenylthio)-
thienylazulenes 7–12.
Entry
Substrate
Sulfoxide
Product, % Yield
1
2
3
4
5
6
7
8
3
3
4
4
5
5
6
6
DMSO
MeS(O)Ph
DMSO
MeS(O)Ph
DMSO
MeS(O)Ph
DMSO
MeS(O)Ph
7, 87
8, 72
9, 89
decomp.
10, 84
decomp.
11, 86
12, 73
The reaction of 3 with DMSO in the presence of Tf2O
(3 equiv.), followed by treatment with Et3N afforded 1,3-
bis(methylthio)-2-(2-thienyl)azulene (7) in 87% yield. 1,3-
Bis(phenylthio)-2-(2-thienyl)azulene (8) was also prepared
in 72% yield, when methyl phenyl sulfoxide was used as a
reagent under similar reaction conditions (Scheme 5).
Scheme 7.
Scheme 8.
Spectroscopic Properties
Compounds 3–12 were fully characterized by various
spectroscopic techniques (see the Experimental Section).
Mass spectra (EI or ESI) of 3–12 showed the correct molec-
ular ion peaks. The UV/Vis spectra of 3, 7, 8 and 6, 11, 12
Scheme 5.
Compound 9 was obtained in 89% yield as a sole prod- in dichloromethane are shown in Figures 1 and 2, respec-
uct, when the reaction of 4 was carried out with Tf2O tively. Thienylazulene derivatives 3–12 in dichloromethane
(3 equiv.) and an excess amount of DMSO (Scheme 6). showed characteristic absorptions arising from the azulene
However, the reaction of 4 with methyl phenyl sulfoxide as skeleton in the visible region. The longest wavelength ab-
a reagent did not afford the presumed 1,3-bis(phenylthio)- sorption maxima of 7–12 showed a bathochromic shift
2-(3-thienyl)azulene, but the reaction suffered from decom- compared with those of thioazulenes 13–16 (Figure 3) [13;
position of the starting materials instead. These results λmax = 628 nm (logε = 2.47), 14; λmax = 600 nm (logε =
would be attributable to the instability of the intermediate 2.53), 15; λmax = 604 nm (logε = 2.56), and 16; λmax
=
bis(sulfonium) ion, that is, the 2-(3-thienyl)azulene-1,3-diyl- 560 nm (logε = 2.63)],[17] probably due to expansion of π
bis(methylphenylsulfonium) ion.
conjugation by the thienyl substituents.
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T. Shoji, S. Ito, K. Toyota, T. Iwamoto, M. Yasunami, N. Morita
FULL PAPER
ents at the 1,3-positions and the 4,8-H protons of the azul-
ene ring, in a manner similar to that of the N-containing
heterocycles.
Redox Behavior of Thienylazulene Derivatives
To clarify the electrochemical properties, the redox be-
havior of thienylazulene derivatives 3–12 was examined by
CV and DPV. Measurements were carried out with a stan-
dard three-electrode configuration. Tetraethylammonium
perchlorate (0.1 ) in benzonitrile was used as a supporting
electrolyte with platinum wire auxiliary and working elec-
trodes. All measurements were carried out under an argon
atmosphere and potentials were related to an Ag/AgNO3
reference electrode and Fc/Fc+ as an internal reference,
which discharges at +0.15 V under these conditions. The
redox potentials (in volts vs. Ag/AgNO3) of thienylazulenes
3–6, 1,3-bis(methylthio)- and 1,3-bis(phenylthio)thienyla-
zulenes 7–12, and 1,3-bis(methylthio)- and 1,3-bis(phenyl-
thio)azulenes 13–16 are summarized in Table 3. The cyclic
voltammograms for 6 and 11 are shown in Figures 4 and 5,
respectively.
Figure 1. UV/Vis spectra of 3 (black line), 7 (gray line), and 8
(broken line) in dichloromethane.
Table 3. Redox potentials [V][a] of 3–12, 1,3-bis(methylthio)- and
1,3-bis(phenylthio)azulenes 13–16, and guaiazulene derivatives 17–
19.[b]
Sample
E1red
E2red
E1ox
E2ox
E3ox
E4ox
3
–1.80
(–1.78) (–2.13) (+0.59)
4
5
6
–1.87
(–1.85) (–2.15) (+0.56)
–1.72
(–1.70) (–2.15) (+0.65) (+0.99)
–1.82
(–1.80) (–2.15) (+0.62) (+0.97)
(–1.62) (–2.13) (+0.56) (+0.82) (+1.00)
(–1.53) (–2.19) (+0.76) (+0.97) (+1.30) (+1.50)
(–1.68) (–2.16) (+0.51) (+0.74) (+0.97)
–1.66
(–1.64) (–2.16) (+0.21) (+0.71) (+1.35) (+1.55)
–1.57 +0.23 +0.72
(–1.55) (–2.12) (+0.22) (+0.72) (+1.32) (+1.50)
–1.54 +0.47
Figure 2. UV/Vis spectra of 6 (black line), 11 (gray line), and 12
(broken line) in dichloromethane.
7
8
9
10
+0.23
11
12
(–1.52) (–2.19) (+0.45) (+0.77) (+0.92) (+1.53)
Figure 3. 1,3-bis(methylthio)- and 1,3-bis(phenylthio)azulenes 13–
16.
13[17]
14[17]
15[17]
16[17]
+0.26
(–1.73) (–2.15) (+0.24) (+0.70) (+0.91) (+1.18)
+0.48
(–1.60) (–2.18) (+0.46) (+0.70) (+0.95)
–1.86
(–1.84) (–2.18) (+0.19) (+0.76)
–1.75 +0.44
1H NMR spectroscopic analysis of thienylazulene deriva-
tives 3–12 in CDCl3 revealed characteristic chemical shifts
attributable to the azulene and thiophene system in the aro-
matic region. Recently, we reported the low-field shift of
the 4-H proton of the azulene ring upon binding of N-con-
taining heterocycles with the azulene ring at the 1-position;
this shift probably results from intramolecular interaction
between the nitrogen atom of the heterocycles and the 4-H
proton of the azulene ring.[17] In compounds 7–12, chemical
shifts of the 4,8-H protons were also observed at lower field
compared with those of 3–6. This may be attributable to
+0.20
(–1.72) (–2.20) (+0.42) (+0.80)
17[c][19]
18[c][19]
19[c][19]
+0.44 +1.01[d]
+0.44 +1.06[d]
+0.40 +0.71
[a] Redox potentials were measured by CV and DPV [V vs. Ag/
AgNO3, 1 m in benzonitrile containing Et4NClO4 (0.1 ), 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. The peak potentials measured by DPV are shown in
parentheses. [b] Redox potentials were measured in acetonitrile.
the intramolecular interaction between the sulfur substitu- [c] V vs. SCE. [d] Irreversible waves.
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Synthesis and Redox Behavior of 1,3-Bis(methylthio- and phenylthio)azulenes
moiety. Further electrochemical reduction produced an
irreversible wave at –2.15 V upon DPV. Compound 4 exhib-
ited reversible and irreversible reduction waves, whose po-
tentials were identified at –1.85 and –2.15 V, respectively,
upon DPV attributable to the formation of a radical an-
ionic and a dianionic species. The electrochemical reduction
of 5 also exhibited reversible and irreversible reduction
waves, whose potentials were identified at –1.70 and
–2.15 V, respectively, upon DPV. Electrochemical reduction
of 6 showed a reversible reduction wave at half-wave poten-
tial of –1.82 V upon CV, which can be ascribed to the for-
mation of a radical anionic species (Figure 4). Further elec-
trochemical reduction also produced an irreversible wave at
–2.15 V upon DPV.
The redox behaviors of 1,3-bis(methylthio)- and (phen-
ylthio)thienylazulenes 7–12 were also examined by CV and
DPV. Electrochemical reduction and oxidation of 7 exhib-
ited irreversible waves upon CV. Their potentials were de-
termined by DPV as shown in Table 3. As similar with 7,
electrochemical reduction and oxidation of 2-thienylazulene
derivatives 8 and 9 also showed irreversible waves, although
2-thienylazulenes 3 and 4 showed reversible reduction waves
upon CV. These results were attributable to the instability
of radical cationic and anionic species of 1,3-bis(methyl-
thio)- and 1,3-bis(phenylthio)-2-thienylazulene derivatives
7–9. 6-Thienylazulene derivatives 10–12 exhibited reversible
reduction and oxidation waves upon CV. Electrochemical
reduction of 10 showed a reversible wave at half-wave po-
tential of –1.66 V upon CV and an irreversible reduction
wave, whose potential was identified at –2.16 V upon DPV.
A reversible oxidation wave of 10 was observed at +0.23 V
upon CV due to the generation of a radical cationic species.
Electrochemical reduction and oxidation of 11 and 12 also
showed reversible redox waves owing to the generation of a
stable radical anionic and cationic species (Figure 5, top
and bottom). These results indicate that the thienyl substit-
uent at the 6-position of azulene ring stabilizes the radical
anionic and cationic states compared with those at the 2-
position.
Figure 4. Cyclic voltammogram of the reduction of 6 (1 m) in
benzonitrile containing Et4NClO4 (0.1 ) as a supporting electro-
lyte; scan rate = 100 mVs–1.
Previously, Kurihara et al. reported the oxidation poten-
tials for sulfur-substituted guaiazulene derivatives 17, 18,
and 19 (Figure 6), which exhibit two-step oxidation waves
at +0.40 to +0.44 V and +0.71 to +1.06 V (V vs. SCE).[19]
Recently, we also reported that 1,3-bis(methylthio)- and 1,3-
bis(phenylthio)azulenes 13–16 exhibit multistep oxidation
waves at relatively lower first oxidation potentials upon CV
within these compounds as similar with those of guaia-
zulene derivatives 17–19. Although 2-thienylazulene deriva-
tives 7 and 8 did not show a decrease in the oxidation po-
tentials with sulfur substituents at the 1- and 3-positions, 6-
thienylazulene derivatives 10–12 showed reversible oxi-
dation waves at the similar lower potential region with
those of 13–16. The more positive first oxidation potentials
Figure 5. Cyclic voltammograms of (top) reduction and (bottom)
oxidation of 11 (1 m) in benzonitrile containing Et4NClO4 (0.1 )
as a supporting electrolyte; scan rate = 100 mVs–1.
Thienylazulenes 3–6 exhibit a reversible reduction wave of 7–9 should be ascribed to the less effective conjugation
upon CV. Electrochemical reduction of 3 showed a revers- of the 1- and 3-sulfur substituents owing to steric interac-
ible reduction wave at a half-wave potential of –1.80 V upon tion of the 2-thienyl group with the azulene ring. Moreover,
CV, which can be ascribed to the formation of a radical the first reduction waves of 10–12 exhibited slightly less
anionic species produced by the reduction of the azulene negative potentials compared with those of 13–16. These
Eur. J. Org. Chem. 2009, 4307–4315
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2-(2-Thienyl)azulene (3): To a solution of nBuMgCl (0.9  in THF,
1.4 mL) in diethyl ether (10 mL) was added nBuLi (1.6  in hexane,
1.5 mL) at 0 °C. After the mixture was stirred at the same tempera-
ture for 30 min, 2-bromothiophene (179 mg, 1.10 mmol) was added
dropwise. The resulting mixture was stirred at 0 °C for 1 h. To the
mixture was dropwise added a solution of 1 (254 mg, 1.00 mmol)
and PdCl2(PPh3)2 (35 mg, 0.05 mmol) in diethyl ether (20 mL) at
0 °C, and the mixture was stirred at room temperature for 24 h.
The reaction mixture was poured into water and extracted with
hexane. The organic layer was washed with brine, dried with
results indicate that the thienyl substituents on the azulene
ring at the 6-position decrease the LUMO level and the 1,3-
bis(methylthio)- and 1,3-bis(phenylthio) substituents in-
crease the HOMO level. Consequently, compounds 10–12
show high amphoteric redox properties within these com-
pounds. Comparison of the first oxidation potentials of
compounds 11 (+0.23 V) and 12 (+0.47 V) shows the meth-
ylthio moiety has greater electron-donating properties than
the phenylthio group on azulene ring at the 1- and 3-posi-
tions. Therefore, compounds 10 and 11 exhibit the highest MgSO4, and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene to
amphoteric redox properties within these compounds.
give 3 (198 mg, 94%) as blue crystals. M.p. 143.0–144.0 °C (de-
comp.). MS (70 eV): m/z (%) = 210 (100) [M+]. IR (KBr): ν = 3053
˜
(w), 2924 (w), 1576 (m), 1537 (m), 1471 (m), 1410 (m), 1400 (w),
1223 (w), 1205 (m), 1034 (w), 947 (m), 898 (m), 835 (m), 808 (s),
725 (m), 690 (m) cm–1. UV/Vis (CH2Cl2): λ (logε) = 309 (4.69), 318
(4.72), 371 (sh., 3.92), 392 (4.21), 412 (4.27), 571 (2.60), 609 (2.58),
1
666 (sh., 2.23) nm. H NMR (400 MHz, CDCl3): δ = 8.22 (d, J =
10.0 Hz, 2 H, 4,8-H), 7.58 (dd, J = 4.0, 1.2 Hz, 1 H, 5Ј-H), 7.53 (s,
2 H, 1,3-H), 7.47 (t, J = 10.0 Hz, 1 H, 6-H), 7.36 (dd, J = 4.0,
1.2 Hz, 1 H, 3Ј-H), 7.14 (t, J = 10.0 Hz, 2 H, 5,7-H), 7.13 (dd, J =
4.0, 1.2 Hz, 1 H, 4Ј-H) ppm. 13C NMR (100 MHz, CDCl3): δ =
143.70, 141.75, 141.39, 136.48, 135.87, 128.80, 126.92, 126.08,
124.55, 114.43 ppm. C14H10S (210.30): calcd. C 79.96, H 4.79;
found C 79.73, H 4.87.
Figure 6. Sulfur-substituted guaiazulene derivatives 17, 18, and 19.
Conclusions
2-(3-Thienyl)azulene (4): To a solution of nBuMgCl (0.9  in THF,
1.4 mL) in diethyl ether (10 mL) was added nBuLi (1.6  in hexane,
1.5 mL) at 0 °C. After the mixture was stirred at the same tempera-
ture for 30 min, 3-bromothiophene (179 mg, 1.10 mmol) was added
dropwise. The resulting mixture was stirred at 0 °C for 1 h. To the
mixture was dropwise added a solution of 1 (254 mg, 1.00 mmol)
and PdCl2(PPh3)2 (35 mg, 0.05 mmol) in diethyl ether (20 mL) at
0 °C, and the mixture was stirred at room temperature for 24 h.
The reaction mixture was poured into water and extracted with
hexane. The organic layer was washed with brine, dried with
MgSO4, and concentrated under reduced pressure. The residue was
We have described a novel and efficient synthetic method
for thienylazulenes 3–6 that offers a number of advantages
over the methods reported previously. Haloazulenes reacted
with thienylmagnesium ate complexes in the presence of a
palladium catalyst to afford the corresponding thienylazul-
enes 3–6 under mild reaction conditions. The reaction of
thienylazulenes with sulfoxides in the presence of Tf2O fol-
lowed by treatment with triethylamine afforded 1,3-bis(me-
thylthio)- and 1,3-bis(phenylthio)azulenes 7–12. Thienyl-
azulenes 3–6 showed a reversible one-stage reduction wave purified by column chromatography on silica gel with toluene to
give 4 (202 mg, 96%) as blue crystals. M.p. 132.0–133.0 °C (de-
due to the formation of a stable radical anionic species. Al-
though, 1,3-bis(methylthio)- and 1,3-bis(phenylthio)-2-thi-
enylazulenes 7–9 did not display reversible redox waves, 1,3-
bis(methylthio)- and 1,3-bis(phenylthio)-6-thienylazulenes
10–12 exhibited oxidation and reduction waves with high
reversibility upon CV probably due to the formation of sta-
bilized radical cationic and anionic species.
comp.). MS (70 eV): m/z (%) = 210 (100) [M+]. IR (KBr): ν
=
˜
max
3096 (m), 1578 (m), 1543 (m), 1466 (m), 1412 (m), 1388 (m), 1350
(w), 1296 (w), 1267 (w), 1211 (m), 1174 (w), 1086 (w), 1014 (w),
949 (m), 897 (w), 870 (m), 816 (m), 783 (s), 725 (m), 688 (w), 667
(w), 617 (w), 580 (m) cm–1. UV/Vis (CH2Cl2): λ (logε) = 299 (4.80),
309 (4.78), 359 (sh., 3.86), 376 (4.10), 393 (4.19), 570 (2.90), 600
1
(2.90), 665 (sh., 2.50) nm. H NMR (400 MHz, CDCl3): δ = 8.25
(d, J = 10.0 Hz, 2 H, 4,8-H), 7.77 (dd, J = 4.8, 0.8 Hz, 1 H, 2Ј-H),
7.62 (dd, J = 4.8, 0.8 Hz, 1 H, 4Ј-H), 7.55 (s, 2 H, 1,3-H), 7.48 (t,
J = 10.0 Hz, 1 H, 6-H), 7.41 (dd, J = 4.8, 0.8 Hz, 1 H, 5Ј-H), 7.14
(t, J = 10.0 Hz, 2 H, 5,7-H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 144.52, 141.28, 138.82, 136.00, 135.51, 135.50 127.04, 126.18,
123.81, 122.73 ppm. C14H10S·1/10H2O (210.30): calcd. C 79.28, H
4.85; found C 79.31, H 4.99.
Experimental Section
General Remarks: Melting points were determined with a Yanagim-
oto MPS3 micromelting apparatus and are uncorrected. Mass spec-
tra 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 recorded with a JEOL GSX 400 a Bruker Avance 400 instru-
ment. Voltammetry measurements were carried out with a BAS
100B/W electrochemical workstation equipped with Pt working
and auxiliary electrodes and a reference electrode formed from Ag/
AgNO3 (0.01 ) in acetonitrile containing tetrabutylammonium
perchlorate (0.1 ). Elemental analyses were performed at the Re-
search and Analytical Center for Giant Molecules, Graduate
School of Science, Tohoku University.
6-(2-Thienyl)azulene (5): To a solution of nBuMgCl (0.9  in THF,
1.4 mL) in diethyl ether (10 mL) was added nBuLi (1.6  in hexane,
1.5 mL) at 0 °C. After the mixture was stirred at the same tempera-
ture for 30 min, 2-bromothiophene (179 mg, 1.10 mmol) was added
dropwise. The mixture was stirred at 0 °C for 1 h. To the mixture
was dropwise added a solution of 2 (207 mg, 1.00 mmol) and
PdCl2(PPh3)2 (35 mg, 0.05 mmol) in diethyl ether (20 mL) at 0 °C
and stirred at room temperature for 24 h. The reaction mixture was
poured into water and extracted with hexane. The organic layer
was washed with brine, dried with MgSO4, and concentrated under
4312
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 4307–4315

Synthesis and Redox Behavior of 1,3-Bis(methylthio- and phenylthio)azulenes
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with toluene to give 5 (198 mg, 94%) as blue
crystals. M.p. 160.0–161.0 °C. MS (70 eV): m/z (%) = 210 (100)
126.98, 125.91, 118.49, 20.51 ppm. C16H14S3 (302.48): calcd. C
63.53, H 4.67; found C 63.32, H 4.78.
1,3-Bis(phenylthio)-2-(2-thienyl)azulene (8): Trifluoromethanesul-
fonic anhydride (423 mg, 1.50 mmol) in CH2Cl2 (10 mL) was added
to a solution of 3 (105 mg, 0.50 mmol) and methyl phenyl sulfoxide
(350 mg, 2.50 mmol) in CH2Cl2 (10 mL). The resulting mixture was
stirred at room temperature for 30 min. The solvent was removed
under reduced pressure. To the residue was added EtOH (10 mL)
and Et3N (10 mL), and the mixture was heated at reflux for 30 min.
The solvent was removed under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene as
an eluent to give 8 (154 mg, 72%) as green crystals. M.p. 182.0–
186.0 °C. HRMS (ESI): calcd. for C26H18NaS3 [M + Na]+
[M+]. IR (KBr): ν = 3053 (w), 2924 (w), 1576 (m), 1537 (m), 1471
˜
(m), 1410 (m), 1400 (w), 1223 (w), 1205 (m), 1034 (w), 947 (m),
898 (m), 835 (m), 808 (s), 725 (m), 690 (m), 653 (w), 586 (w), 493
(w) cm–1. UV/Vis (CH2Cl2): λ (logε) = 296 (sh., 4.37), 326 (4.51),
390 (4.14), 598 (2.49), 647 (sh., 2.40), 728 (sh., 1.83) nm. 1H NMR
(400 MHz, CDCl3): δ = 8.29 (d, J = 10.0 Hz, 2 H, 4,8-H), 7.82 (t,
J = 4.0 Hz, 1 H, 2-H), 7.53 (d, J = 10.0 Hz, 2 H, 5,7-H), 7.47 (dd,
J = 4.4, 1.2 Hz, 1 H, 5Ј-H), 7.38 (dd, J = 4.4, 1.2 Hz, 1 H, 3Ј-H),
7.34 (d, J = 4.0 Hz, 2 H, 1,3-H), 7.11 (t, J = 4.4 Hz, 1 H, 4Ј-H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 148.01, 142.82, 138.82,
136.81, 135.66, 128.47, 127.32, 125.92, 121.33, 118.81 ppm.
C14H10S (210.30): calcd. C 79.96, H 4.79; found C 79.67, H 4.87.
449.0468; found 449.0463. IR (KBr): ν = 3068 (w), 3030 (w), 3001
˜
(w), 1577 (s), 1510 (m), 1477 (s), 1433 (s), 1407 (s), 1340 (w), 1326
(w), 1217 (w), 1157 (w), 1126 (w), 1078 (m), 1056 (w), 1024 (m),
997 (w), 896 (w), 883 (w), 848 (m), 827 (w), 732 (s), 707 (s), 686
(s), 617 (w), 570 (w), 511 (w), 464 (w), 435 (w) cm–1. UV/Vis
(CH2Cl2): λ (logε) = 250 (4.54), 280 (4.46), 337 (4.61), 403 (3.98),
424 (3.99), 550 (sh., 2.61), 582 (2.65) nm. 1H NMR (400 MHz,
CDCl3): δ = 8.83 (d, J = 9.6 Hz, 2 H, 4,8-H), 7.92 (dd, J = 4.0,
0.8 Hz, 1 H, 5Ј-H), 7.69 (t, J = 9.6 Hz, 1 H, 6-H), 7.45 (t, J =
9.6 Hz, 2 H, 5,7-H), 7.42 (dd, J = 4.8, 0.8 Hz, 1 H, 3Ј-H), 7.14 (t,
J = 8.0 Hz, 4 H, m-Ph), 7.05–7.01 (m, 3 H, p-Ph and 4Ј-H), 6.93
(dd, J = 8.0, 1.2 Hz, 4 H, o-Ph) ppm. 13C NMR (100 MHz,
CDCl3): δ = 149.66, 145.28, 139.63, 138.46, 136.28, 135.77, 131.05,
129.64, 128.91, 127.81, 127.04, 125.42, 124.77, 112.43 ppm.
C26H18S3 (426.62): calcd. C 73.20, H 4.25; found C 73.11, H 4.29.
6-(3-Thienyl)azulene (6): To a solution of nBuMgCl (0.9  in THF,
1.4 mL) in diethyl ether (10 mL) was added nBuLi (1.6  in hexane,
1.5 mL) at 0 °C. After the mixture was stirred at the same tempera-
ture for 30 min, 3-bromothiophene (179 mg, 1.10 mmol) was added
dropwise. The resulting mixture was stirred at 0 °C for 1 h. To the
mixture was dropwise added a solution of 2 (207 mg, 1.00 mmol)
and PdCl2(PPh3)2 (35 mg, 0.05 mmol) in diethyl ether (20 mL) at
0 °C, and the mixture was stirred at room temperature for 24 h.
The reaction mixture was poured into water and extracted with
hexane. The organic layer was washed with brine, dried with
MgSO4, and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene to
give 6 (206 mg, 98%) as blue crystals. M.p. 180.0–181.0 °C. MS
(70 eV): m/z (%) = 210 (100) [M+]. IR (KBr): ν = 3100 (m), 1572
˜
1,3-Bis(methylthio)-2-(3-thienyl)azulene (9): Trifluoromethanesul-
fonic anhydride (423 mg, 1.50 mmol) in CH2Cl2 (10 mL) was added
to a solution of 4 (105 mg, 0.50 mmol) and DMSO (195 mg,
2.50 mmol) in CH2Cl2 (10 mL). The resulting mixture was stirred
at room temperature for 30 min. The solvent was removed under
reduced pressure. To the residue was added EtOH (10 mL) and
Et3N (10 mL), and the mixture was heated at reflux for 30 min.
The solvent was removed under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene as
an eluent to give 9 (135 mg, 89%) as green crystals. M.p. 122.0–
124.0 °C. HRMS (ESI): calcd. for C16H14NaS3 [M + Na]+
(s), 1554 (m), 1508 (m), 1457 (s), 1444 (w), 1402 (s), 1346 (m), 1304
(w), 1255 (m), 1217 (m), 1199 (w), 1182 (m), 1093 (m), 1055 (m),
983 (w), 970 (w), 891 (m), 862 (m), 841 (s), 781 (s), 754 (s), 690
(m), 667 (m), 609 (m), 572 (w), 543 (w), 505 (m), 461 (w) cm–1.
UV/Vis (CH2Cl2): λ (logε) = 307 (4.75), 376 (4.07), 589 (2.56), 635
(sh., 2.48), 705 (sh., 1.99) nm. 1H NMR (400 MHz, CDCl3): δ =
8.35 (d, J = 10.8 Hz, 2 H, 4,8-H), 7.82 (t, J = 4.0 Hz, 1 H, 2-H),
7.58 (dd, J = 4.4, 1.6 Hz, 1 H, 2Ј-H), 7.49–7.41 (m, 4 H, 5,7,4Ј,5Ј-
H), 7.38 (d, J = 4.0 Hz, 2 H, 1,3-H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 146.65, 145.23, 139.33, 137.11, 136.33, 127.97, 126.94,
123.65, 122.72, 118.88 ppm. C14H10S·1/10H2O (210.30): calcd. C
79.28, H 4.85; found C 79.42, H 4.89.
325.0155; found 325.0150. IR (KBr): ν = 3105 (w), 3087 (w), 3053
˜
(w), 3022 (w), 2910 (m), 2844 (w), 2819 (w), 1581 (m), 1448 (m),
1438 (m), 1417 (m), 1402 (s), 1359 (m), 1305 (w), 1284 (m), 1201
(m), 1139 (w), 1076 (w), 1004 (w), 956 (m), 902 (m), 854 (s), 792
(s), 736 (s), 711 (s), 696 (m), 686 (m), 617 (w), 599 (w), 578 (w),
503 (w), 422 (w) cm–1. UV/Vis (CH2Cl2): λ (logε) = 248 (4.37), 323
(4.61), 385 (sh., 3.78), 412 (sh., 3.51), 580 (sh., 2.53), 607 (2.54) nm.
1H NMR (400 MHz, CDCl3): δ = 8.80 (d, J = 10.0 Hz, 2 H, 4,8-
H), 8.06 (dd, J = 3.2, 1.2 Hz, 1 H, 2Ј-H), 7.86 (dd, J = 4.8, 1.2 Hz,
1 H, 5Ј-H), 7.65 (t, J = 10.0 Hz, 1 H, 6-H), 7.36 (dd, J = 4.8,
3.2 Hz, 1 H, 4Ј-H), 7.37 (t, J = 10.0 Hz, 2 H, 5,7-H), 2.11 (s, 6 H,
Me) ppm. 13C NMR (100 MHz, CDCl3): δ = 149.63, 142.36,
138.03, 136.00, 135.59, 129.40, 126.30, 125.43, 124.28, 119.18,
20.31 ppm. C16H14S3 (302.48): calcd. C 63.53, H 4.67; found C
63.44, H 4.69.
1,3-Bis(methylthio)-2-(2-thienyl)azulene (7): Trifluoromethanesul-
fonic anhydride (338 mg, 1.20 mmol) in CH2Cl2 (10 mL) was added
to a solution of 3 (105 mg, 0.50 mmol) and DMSO (195 mg,
2.50 mmol) in CH2Cl2 (10 mL). The resulting mixture was stirred
at room temperature for 30 min. The solvent was removed under
reduced pressure. To the residue was added EtOH (10 mL) and
Et3N (10 mL), and the mixture was heated at reflux for 30 min.
The solvent was removed under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene as
an eluent to give 7 (132 mg, 87%) as green crystals. M.p. 91.0–
93.0 °C. HRMS (ESI): calcd. for C16H14NaS3 [M + Na]+ 325.0155;
found 325.0150. IR (KBr): ν = 3089 (w), 2979 (w), 2914 (w), 1573
˜
(m), 1508 (m), 1433 (s), 1404 (s), 1361 (w), 1342 (w), 1278 (w), 1215
(w), 1124 (w), 1055 (w), 962 (w), 935 (w), 883 (w), 848 (m), 736 (s),
707 (s), 586 (w), 574 (w), 507 (w) cm–1. UV/Vis (CH2Cl2): λ (logε) 1,3-Bis(methylthio)-6-(2-thienyl)azulene (10): Trifluoromethanesul-
= 255 (sh., 4.19), 286 (4.30), 337 (4.61), 407 (sh., 3.87), 424 (3.95),
576 (sh., 2.56), 608 (2.60) nm. 1H NMR (400 MHz, CDCl3): δ =
8.82 (d, J = 10.0 Hz, 2 H, 4,8-H), 8.30 (dd, J = 4.4, 1.2 Hz, 1 H,
fonic anhydride (423 mg, 1.50 mmol) in CH2Cl2 (10 mL) was added
to a solution of 5 (105 mg, 0.50 mmol) and DMSO (195 mg,
2.50 mmol) in CH2Cl2 (10 mL). The resulting mixture was stirred
5Ј-H), 7.64 (t, J = 10.0 Hz, 1 H, 6-H), 7.36 (dd, J = 5.2, 1.2 Hz, 1 at room temperature for 30 min. The solvent was removed under
H, 3Ј-H), 7.39 (t, J = 10.0 Hz, 2 H, 5,7-H), 7.13 (dd, J = 5.2, reduced pressure. To the residue was added EtOH (10 mL) and
4.4 Hz, 1 H, 4Ј-H), 2.11 (s, 6 H, Me) ppm. 13C NMR (100 MHz,
Et3N (10 mL), and the mixture was heated at reflux for 30 min.
CDCl3): δ = 146.80, 142.97, 137.83, 136.65, 135.66, 130.03, 128.59, The solvent was removed under reduced pressure. The residue was
Eur. J. Org. Chem. 2009, 4307–4315
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4313

T. Shoji, S. Ito, K. Toyota, T. Iwamoto, M. Yasunami, N. Morita
FULL PAPER
purified by column chromatography on silica gel with toluene as
an eluent to give 10 (127 mg, 84%) as green oil. HRMS (ESI):
calcd. for C16H14NaS3 [M + Na]+ 325.0155; found 325.0150. IR
Acknowledgments
This work was partially supported by the Global Center of Excel-
lence (GCOE) project and the International Center of Research &
Education for Molecular Complex Chemistry of the Ministry of
Education, Culture, Sports, Science, and Technology, Japan.
(KBr): ν = 3095 (w), 2979 (w), 2914 (w), 1568 (s), 1512 (w), 1471
˜
(w), 1434 (w), 1398 (m), 1371 (w), 1352 (w), 1311 (w), 1292 (w),
1251 (w), 1232 (w), 1215 (w), 1184 (w), 1116 (w), 1014 (w), 960
(m), 881 (w), 860 (m), 839 (m), 775 (s), 707 (w), 690 (w), 673 (w),
642 (w), 626 (w), 607 (w), 511 (w) cm–1. UV/Vis (CH2Cl2): λ (logε)
= 248 (sh., 4.29), 341 (4.71), 394 (sh., 3.92), 636 (2.48) nm. 1H
NMR (400 MHz, CDCl3): δ = 8.48 (d, J = 10.8 Hz, 2 H, 4,8-H),
7.89 (s, 1 H, 2-H), 7.61 (dd, J = 4.4, 1.2 Hz, 1 H, 5Ј-H), 7.48 (d, J
= 10.8 Hz, 2 H, 5,7-H), 7.46–7.43 (m, 2 H, 3Ј,4Ј-H), 2.49 (s, 6 H,
Me) ppm. 13C NMR (100 MHz, CDCl3): δ = 146.65, 145.61,
140.98, 138.57, 134.74, 127.33, 126.75, 123.84, 123.00, 121.96,
20.24 ppm. C16H14S3·1/10H2O (302.48): calcd. C 63.16, H 4.70;
found C 63.20, H 4.88.
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1,3-Bis(methylthio)-6-(3-thienyl)azulene (11): Trifluoromethanesul-
fonic anhydride (423 mg, 1.50 mmol) in CH2Cl2 (10 mL) was added
to a solution of 6 (105 mg, 0.50 mmol) and DMSO (195 mg,
2.50 mmol) in CH2Cl2 (10 mL). The resulting mixture was stirred
at room temperature for 30 min. The solvent was removed under
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Et3N (10 mL), and the mixture was heated at reflux for 30 min.
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˜
(w), 1477 (w), 1419 (w), 1402 (s), 1371 (m), 1350 (m), 1323 (w),
1294 (w), 1249 (m), 1232 (m), 1180 (w), 1055 (w), 1014 (w), 975
(m), 958 (m), 837 (s), 815 (s), 794 (w), 748 (w), 705 (s), 657 (w),
626 (w), 511 (w) cm–1. UV/Vis (CH2Cl2): λ (logε) = 280 (sh., 4.10),
354 (4.72), 404 (sh., 4.09), 656 (2.55) nm. 1H NMR (400 MHz,
CDCl3): δ = 8.42 (d, J = 10.8 Hz, 2 H, 4,8-H), 7.85 (s, 1 H, 2-H),
7.55–7.51 (m, 3 H, 5,7,2Ј-H), 7.42 (d, J = 4.0 Hz, 1 H, 5Ј-H), 7.38
(d, J = 4.8, 4.0 Hz, 1 H, 4Ј-H), 2.48 (s, 6 H, Me) ppm. 13C NMR
(100 MHz, CDCl3): δ = 147.33, 144.69, 140.80, 138.38, 134.50,
128.63, 127.95, 126.45, 122.42, 121.91, 20.15 ppm. C16H14S3
(302.48): calcd. C 63.53, H 4.67; found C 63.50, H 4.62.
1,3-Bis(phenylthio)-6-(3-thienyl)azulene (12): Trifluoromethanesul-
fonic anhydride (423 mg, 1.50 mmol) in CH2Cl2 (10 mL) was added
to a solution of 6 (105 mg, 0.50 mmol) and methyl phenyl sulfoxide
(350 mg, 2.50 mmol) in CH2Cl2 (10 mL). The resulting mixture was
stirred at room temperature for 30 min. The solvent was removed
under reduced pressure. To the residue was added EtOH (10 mL)
and Et3N (10 mL), and the mixture was heated at reflux for 30 min.
The solvent was removed under reduced pressure. The residue was
purified by column chromatography on silica gel with toluene as
an eluent to give 12 (156 mg, 73%) as green crystals. M.p. 97.0–
99.5 °C. HRMS (ESI): calcd. for C16H14NaS3 [M + Na]+ 325.0155;
found 325.0150. IR (KBr): ν = 3101 (w), 3053 (w), 1579 (s), 1506
˜
(m), 1475 (s), 1436 (m), 1409 (s), 1359 (s), 1294 (w), 1272 (w), 1257
(w), 1238 (w), 1220 (w), 1184 (w), 1155 (w), 1091 (w), 1078 (m),
1024 (m), 970 (w), 873 (w), 860 (m), 842 (m), 779 (s), 740 (s), 690
(s), 609 (w), 516 (m), 486 (w), 462 (w) cm–1. UV/Vis (CH2Cl2): λ
(logε) = 248 (sh., 4.58), 344 (4.70), 583 (2.70) nm. 1H NMR
(400 MHz, CDCl3): δ = 8.67 (d, J = 10.4 Hz, 2 H, 4,8-H), 8.08 (s,
1 H, 2-H), 7.66 (d, J = 10.4 Hz, 2 H, 5,7-H), 7.60 (br. s, 1 H, 2Ј-
H), 7.42–7.41 (m, 2 H, 4Ј,5Ј-H), 7.16 (t, J = 8.0 Hz, 4 H, m-Ph),
7.07–7.02 (m, 6 H, o-, p-Ph) ppm. 13C NMR (100 MHz, CDCl3):
δ = 148.79, 147.41, 145.16, 141.88, 139.67, 135.66, 128.82, 127.23,
127.08, 126.22, 125.44, 125.05, 124.44, 115.75 ppm. C26H18S3
(426.62): calcd. C 73.20, H 4.25; found C 73.06, H 4.38.
4314
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 4307–4315

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Published Online: July 22, 2009
Eur. J. Org. Chem. 2009, 4307–4315
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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