Reactions between 1-ethynylazulenes and 7,7,8,8-tetracyanoquinodimethane (TCNQ): Preparation, properties, and redox behavior of novel azulene-substituted redox-active chromophores

Article abstract of DOI:10.1002/ejoc.200900539

[2+2] Cycloaddition/cycloreversion reactions between TCNQ and mono- or bis[2-(azulen-1-yl)ethynyl]benzene or -thiophene derivatives were examined: the corresponding TCNQ adducts, novel azulene-substituted redox-active chromophores, were produced in excell

Full text of DOI:10.1002/ejoc.200900539

FULL PAPER
DOI: 10.1002/ejoc.200900539
Reactions between 1-Ethynylazulenes and 7,7,8,8-Tetracyanoquinodimethane
(TCNQ): Preparation, Properties, and Redox Behavior of Novel Azulene-
Substituted Redox-Active Chromophores
Taku Shoji,*[a] Shunji Ito,*[b] Kozo Toyota,[a] Takeaki Iwamoto,[a] Masafumi Yasunami,[c]
and Noboru Morita[a]
Keywords: Azulenes / Cycloaddition / Donor–acceptor systems / Electrochromism / Redox chemistry
[2+2] Cycloaddition/cycloreversion reactions between TCNQ
and mono- or bis[2-(azulen-1-yl)ethynyl]benzene or -thio-
azulene-substituted chromophores was examined by cyclic
voltammetry (CV) and differential pulse voltammetry (DPV).
phene derivatives were examined: the corresponding TCNQ Significant color changes in these azulene-substituted chro-
adducts, novel azulene-substituted redox-active chromo-
phores, were produced in excellent yields. TCNE/TCNQ
double adducts were also prepared both by stepwise and by
one-pot cascade reactions. The redox behavior of these novel
mophores under electrochemical reduction conditions were
observed by visible spectroscopy.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
Azulene (C10H8) has attracted the interest of many re-
search groups as a result of its unusual properties, as well
as its beautiful blue color.[4] Recently we have reported reac-
tions between tetracyanoethylene (TCNE) and mono-,
bis-, and tris[2-(azulen-1-yl)ethynyl]benzene and -thiophene
derivatives, giving the corresponding [1,1,4,4-tetracyano-2-
(azulen-1-yl)-3-butadienyl] chromophores.[5] These new
chromophores exhibit multistep reduction waves upon cy-
clic voltammetry (CV) and differential pulse voltammetry
(DPV). Moreover, significant multistep color changes are
also observed on their electrochemical reduction.
Introduction
The powerful electron acceptor 7,7,8,8-tetracyanoquino-
dimethane (TCNQ) is well known to form a variety of
intermolecular charge-transfer (CT) complexes with various
electron donors.[1]
Reactions between TCNQ and 1-ethynylazulene deriva-
tives, however, have never been examined. As in their reac-
tions with TCNE, 1-ethynylazulene derivatives should react
with TCNQ to afford novel azulene-substituted redox-
active chromophores. Moreover, the new azulene-substi-
tuted TCNQ adducts should exhibit multistep redox activi-
ties, and significant color changes should be observed under
electrochemical reaction conditions, as in the case of
[1,1,4,4-tetracyano-2-(azulen-1-yl)-3-butadienyl] chromo-
phores.
Recently, Diederich et al. reported reactions between
TCNQ and a variety of N,N-dialkylaniline-substituted
(DAA-substituted) alkynes to afford [2+2] cycloaddition
products as a novel type of CT chromophores in excellent
yields.[2] They also reported that the chromophores exhibit
optoelectronic and redox properties. These CT chromo-
phores would be expected to show optical nonlinearities
and could be utilizable as organic-based magnets and con-
ductive materials.[3]
Here we describe [2+2] cycloaddition/cycloreversion re-
actions between TCNQ and mono- and bis[2-(azulen-1-yl)-
ethynyl]benzene and -thiophene derivatives. The electronic
properties of these novel redox-active chromophores are
[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
[b] Graduate School of Science and Technology, Hirosaki Univer- characterized by electrochemical analysis and absorption
sity,
spectroscopy.
Hirosaki 036-8561, Japan
Fax: +81-172-39-3541
E-mail: itsnj@cc.hirosaki-u.ac.jp
Results and Discussion
[c] Department of Materials Chemistry and Engineering, College
Synthesis
The mono- and bis[2-(azulen-1-yl)ethynyl]benzene and
-thiophene derivatives 1–4 were prepared by Sonogashira–
of Engineering, Nihon University,
Koriyama 963-8642, Japan
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200900539.
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Novel Redox-Active Azulene Chromophores
Hagihara reactions according to the procedure reported by
Treatment of 3 with TCNE gave the mono adduct 9 in
us recently.[5] The novel redox-active chromophores 5–8 88% yield, along with 13[5] in 4% yield (Scheme 3).[7] The
were then obtained through [2+2] cycloaddition/cyclorever- synthesis of the TCNE/TCNQ double adduct 11 was
sion reactions between 1–4 and TCNQ, as in the procedure achieved in 84% yield by treatment of 9 with TCNQ
reported by Diederich et al.[2] Treatment of 1 with TCNQ (Scheme 3). The one-pot cascade reaction of 3 with TCNE
in ethyl acetate at reflux yielded the presumed 5 in 96% and TCNQ gave 11 in 30% yield, which corresponds to a
yield. Likewise, treatment of 2 with TCNQ afforded 6 in yield of 55% per step, along with 7 (29%) and 13 (32%).
93% yield (Scheme 1). Like the reaction with TCNE, this However, the cascade reaction required a tedious separation
readily proceeded under relatively mild conditions, despite process.
the electron-withdrawing group (methoxycarbonyl) substi-
tuted on the azulene ring. The high reactivity should be
attributed to the highly electron-donating properties of the
azulene ring at the 1-position.
Scheme 1.
Similarly to the results with the monosubstituted ben-
zene and thiophene derivatives, treatment of the bis[2-
(azulen-1-yl)ethynyl] derivatives 3 and 4 with TCNQ af-
forded the novel double-substituted chromophores 7 and 8
in 94% and 92% yields, respectively (Scheme 2).
Scheme 3.
Likewise, treatment of 4 with TCNE afforded 10 in 88%
yield, along with 14[5] in 5% yield (Scheme 3). The resulting
mono adduct 10 was treated with TCNQ to give the TCNE/
TCNQ double adduct 12, with a thiophene core, in 85%
yield. The one-pot cascade reaction of 4 with TCNE and
TCNQ also afforded 12 in 30% yield, corresponding to a
yield of 55% per step, along with 8 (27%) and 14 (34%).
Scheme 2.
These new azulene-substituted chromophores 5 and 6 and
the multivalent charge-transfer chromophores 7, 8, 11, and
12 are stable, deep-colored crystals and, like the [1,1,4,4-
tetracyano-2-(azulen-1-yl)-3-butadienyl] chromophores, are
storable in the crystalline state at room temperature.
Recently, Diederich and co-workers have reported one-
pot cascade reactions with TCNE, TTF, and diacetylenes
for the construction of novel multivalent charge-transfer
chromophores.[6] However, cascade reactions with TCNE,
TCNQ, and bisalkynes had never been reported. We thus
investigated the preparation of the TCNE/TCNQ double
adducts 11 and 12 as novel multivalent charge-transfer
Spectroscopic Properties
chromophores both by stepwise and also by one-pot cas-
cade reactions of 3 and 4 with TCNE and TCNQ in order troscopic data, as shown in the Supporting Information.
to explore their physical and electrochemical properties. The reported NMR assignments were confirmed by experi-
Compounds 5–12 were fully characterized by their spec-
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FULL PAPER
ments such as the HMQC, HMBC, and NOE techniques.
The mass spectra of 5–12 ionized by ESI showed the correct
molecular ion peaks. The characteristic stretching-vibration
band of the CϵN group was observed at 2220 to 2208 cm–1
in the IR spectra of 5–12. These results are consistent with
the structures of these products.
UV/Vis spectra of 5–12 in CH2Cl2 and in hexane are
shown in the Supporting Information. Their absorption
maxima and coefficients (logε) are summarized in Table 1.
As would be expected from their structures, the TCNQ ad-
ducts 5–8, 11, and 12 showed characteristic CT absorptions
in the visible region and solvatochromism was also ob-
served. Compound 5 exhibited weak and strong absorp-
tions at λmax = 393 and 641 nm in CH2Cl2, and the largest
solvent effect was observed when the solvent was changed
from CH2Cl2 to hexane (λmax = 598 nm). Compound 6 ex-
hibited a strong CT absorption at λmax = 626 nm in
CH2Cl2, and a hypsochromic shift of 31 nm was observed
upon the measurement in hexane (Figure 1).
Figure 2. UV/Vis spectra of 7 (black line) and 8 (gray line) in
dichloromethane.
Compound 11 in CH2Cl2 exhibited two strong absorp-
tions at λmax = 432 and λmax = 586 nm corresponding to
the dual chromophores. The solvent effect was also ob-
served, with the two CT absorptions showing hypsochromic
shifts of 21 nm and 20 nm, respectively, with a change in
the solvent to hexane. Two CT absorptions were also ob-
Table 1. Absorption maxima [nm] and coefficients (logε) of 5–8,
11, and 12 in dichloromethane and in hexane.
Sample
λmax (logε)
CH2Cl2
hexane
served for 12 in CH2Cl2, at λmax = 432 nm and λmax
=
5
393 (4.26), 641 (4.43)
362 (4.40), 626 (4.47)
358 sh (4.75), 627 (4.70)
391 (4.67), 590 (4.69)
432 (4.90), 586 (4.64)
432 (4.73), 586 (4.46)
391 (4.28), 598 (4.42)
362 sh (4.39), 595 (4.48)
380 sh (4.48), 636 (4.46)
388 (4.39), 574 (4.39)
411 (4.89), 566 (4.62)
418 (4.69), 562 (4.43)
586 nm (Figure 3). The largest solvent effect was observed
(see Supporting Information) when the solvent was changed
from CHCl3 (λmax = 588 nm) to hexane (λmax = 562 nm).
6
7
8
11
12
Figure 3. UV/Vis spectra of 11 (black line) and 12 (gray line) in
dichloromethane.
Figure 1. UV/Vis spectra of 5 (black line) and 6 (gray line) in
dichloromethane.
Redox Potentials
Compound 7 exhibited a strong CT absorption at λmax
= 627 nm in CH2Cl2. Inconsistently with the expansion of
To clarify their electrochemical properties, the redox be-
the π-conjugation, the CT absorption of 7 showed a hyp- havior of 5–12 was examined by cyclic voltammetry (CV)
sochromic shift of 14 nm relative to 5. When the solvent and differential pulse voltammetry (DPV). Measurements
of 7 was changed to hexane, the CT absorption maximum were made with use of a standard three-electrode configura-
exhibited a bathochromic shift of 9 nm, but the broad ab- tion. Tetraethylammonium perchlorate (0.1 ) in benzoni-
sorption band now reached into the near-infrared region. trile was used as a supporting electrolyte with platinum wire
Two absorption bands were observed for 8 in all solvents, auxiliary and working electrodes. All measurements were
and a hypsochromic shift was again observed on changing carried out under argon, and potentials were related to the
the solvent to hexane (Figure 2).
reference electrode formed by Ag/Ag+ with use of Fc/Fc+,
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Novel Redox-Active Azulene Chromophores
which discharges at +0.15 V, as internal reference. The re-
The bis adduct 7 exhibited a reversible two-step re-
dox potentials of 5–12 (in volts vs. Ag/AgNO3) are summa- duction wave attributable to two-electron transfer in each
rized in Table 2.
step, the potentials of which were identified by DPV as
–0.38 V and –0.55 V, to form dianionic and tetraanionic
species, respectively. A reversible four-step wave was ob-
served in 8 upon CV at –0.31 V, –0.43 V, –0.61 V, and
–1.94 V, in which the third reduction wave should be re-
garded as two-electron transfer in one step to form up to
pentaanionic species (Figure 5).
Table 2. Redox potentials[a] of 5–14.
Sample Er1ed [V]
Er2ed [V]
Er3ed [V]
Er4ed [V]
Er5ed [V]
5
–0.43
(–0.41)
–0.44
–0.59
(–0.58)
–0.58
(–0.90)
(–1.91)
(–1.93)
(–1.93)
(–2.03)
(–2.16)
6
(–0.46)
(–0.57)
7
–0.38 (2e) –0.55 (2e)
(–0.38)
–0.31
(–0.55)
–0.43
8
–0.61 (2e) –1.90
(–0.31)
–0.57
(–0.56)
–0.61
(–0.59)
–0.32
(–0.30)
–0.32
(–0.30)
–0.46
(–0.45)
–0.31
(–0.41)
–0.98
(–0.96)
–0.92
(–0.89)
–0.41
(–0.39)
–0.40
(–0.38)
–0.64
(–0.63)
–0.54
(–0.59)
–1.62
(–1.61)
–1.62
(–1.60)
–0.77
(–0.75)
–0.77
(–0.75)
–1.01
(–1.00)
–1.10 (2e)
(–1.09)
(–1.88)
–1.94
(–1.92)
–1.88
(–1.86)
–1.00
(–0.98)
–0.99
(–2.15)
(–2.16)
9
10
11
12
13[5]
14[5]
(–2.16)
–1.96
(–1.94)
–1.95
(–0.97)
–1.11
(–1.09)
(–1.93)
(–1.90)
(–2.15)
(–0.29)
(–0.52)
(–1.89)
[a] Redox potentials were measured by CV and DPV [V vs.
Ag/AgNO3, 1 m in benzonitrile containing Et4NClO4 (0.1 ), Pt
electrode (internal diameter: 1.6 mm), scan rate: 100 mVs–1, and
Fc/Fc+ = +0.15 V]. In cases of reversible waves, redox potentials
measured by CV are presented. The peak potentials measured by
DPV are shown in parentheses.
Figure 5. Cyclic voltammograms for the reduction of 8 (1 m) in
benzonitrile containing Et4NClO4 (0.1 ) as a supporting electro-
lyte; scan rate: 100 mV s–1.
Electrochemical reduction of 5 showed a reversible two-
step wave at the half-wave potentials of –0.44 V and –0.59 V
upon CV, probably due to the formation of a radical an-
ionic and a dianionic species, respectively (Figure 4). The
electrochemical reduction of 5 also exhibited irreversible
waves at –0.90 V, –1.93 V, and –2.14 V upon DPV, probably
due to the reduction of the substituted azulene moiety.
The first reduction potentials of 7 and 8 were less nega-
tive than those of 5 and 6. This indicates that increasing the
number of the azulene-substituted chromophores reduces
the LUMO levels and enhances their π-accepting properties.
Recently, we have reported the redox behavior of com-
pounds 13 and 14 (Scheme 3), which exhibit reversible
multistep reduction waves.[3] The first reduction potentials
of compounds 7 and 8 are very similar to those of 13 and
14 (13: E1red = –0.46 V; 14: E1red = –0.31 V). These results
indicated that these novel azulene-substituted chromo-
phores have π-accepting abilities comparable to those of the
[1,1,4,4-tetracyano-2-(azulen-1-yl)-3-butadienyl] chromo-
phores 13 and 14.
The redox behavior of the TCNE/TCNQ double adducts
11 and 12 was also examined. Electrochemical reduction of
11 showed a reversible five-step reduction wave at the half-
wave potentials of –0.32 V, –0.41 V, –0.77 V, –1.00 V, and
–1.96 V upon CV, probably due to the formation of up to a
pentaanionic species including reduction of the substituted
azulene moieties (Figure 6). The TCNE/TCNQ double ad-
duct 12 with a thiophene core also exhibited a reversible
five-step reduction wave, the potentials of which were iden-
tified at –0.32 V, –0.40 V, –0.77 V, –0.99 V, and –1.96 V
upon CV, owing to the formation of up to a pentaanionic
species. The first reduction potentials of 11 and 12 were
Figure 4. Cyclic voltammograms for the reduction of 5 (1 m) in
benzonitrile containing Et4NClO4 (0.1 ) as a supporting electro-
lyte; scan rate: 100 mV s–1.
The electrochemical reduction of 6 also showed a revers- comparable with those of 7 and 8, so the first reduction
ible two-step reduction wave upon CV at –0.44 V and wave might be attributable to the reduction of the dicya-
–0.58 V, due to the formation of up to dianionic species.
noquinodimethane moieties in 11 and 12.
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T. Shoji, S. Ito, K. Toyota, T. Iwamoto, M. Yasunami, N. Morita
FULL PAPER
presumed closed-shell dianionic and tetraanionic species
produced by electrochemical reduction under the condi-
tions of the spectral measurements.
Figure 6. Cyclic voltammograms for the reduction of 11 (1 m) in
benzonitrile containing Et4NClO4 (0.1 ) as a supporting electro-
lyte; scan rate: 100 mV s–1.
The oxidation of these compounds produced voltammo-
grams that were characterized by irreversible waves, proba-
bly due to the oxidation of the substituted azulene rings to
form unstable radical cationic species.
Electrochromic Analysis
To examine the color changes during the electrochemical
reactions, the spectral changes of compounds 5–8, 11, and
12 were monitored by visible spectroscopy. Constant-cur-
rent reduction was applied to solutions of 5–8, 11, and 12,
with a platinum mesh as the working electrode and a wire
counter electrode, and visible spectra were measured in ben-
zonitrile containing Et4NClO4 (0.1 ) as a supporting elec-
trolyte at room temperature under electrochemical re-
duction conditions (see the Supporting Information).
Figure 7. Continuous change in visible spectra of 7 in benzonitrile
containing Et4NClO4 (0.1 ): constant-current electrochemical re-
duction (50 uA) at 30 sec intervals (top) and reverse oxidation (bot-
tom) of the reduced species (50 uA) at 30 sec intervals.
We have recently reported the redox behavior of 14,
which exhibited a two-step reversible color change under
electrochemical reduction, with rather high reversibility. It
therefore appears that the dicyanoquinodimethane struc-
tures in 7 and 8 stabilize the reduced species less than is the
case in 14. The UV/Vis spectra of the TCNE/TCNQ double
adducts 11 and 12 also showed color changes from green
to yellow, and the reverse oxidation of the yellow-colored
solutions also regenerated the visible spectra of the green-
colored 11 and 12, but incompletely.
The longest-wavelength absorption of 5, at λmax
=
650 nm, gradually decreased and the color of the solution
changed from green to orange during the electrochemical
reduction. The green color of the solution of 6 also changed
to orange during the electrochemical reduction. These
changes were accompanied by increases in the broad ab-
sorption bands up to the near-infrared region. Reverse oxi-
dation of these orange-colored solutions regenerated the
visible spectra of the green-colored 5 and 6, but incom-
pletely, although good reversibility had been observed upon
CV.
When the UV/Vis spectra of 7 were measured under elec-
trochemical reduction conditions, the absorption of 7 at
λmax = 648 nm in the visible region also gradually de-
Conclusions
In summary, novel azulene-substituted redox-active chro-
creased, with increment of a new absorption in the near- mophores 5–8 were prepared in excellent yields through the
infrared region (Figure 7). The absorption bands of 8 in the reactions between TCNQ and the 1-ethynylazulene deriva-
visible region also gradually disappeared during the electro- tives 3 and 4 . The TCNE/TCNQ double adducts 11 and
chemical reduction. The color of the solution gradually 12 were also prepared both by stepwise and also by one-
changed from deep green to yellow during the electrochemi- pot cascade reactions with TCNE and TCNQ. Analysis by
cal reduction. Reverse oxidation regenerated the absorp- CV and DPV showed that these compounds 5–8, 11, and
tions of 7 and 8, but again incompletely. The low reversibil- 12 exhibit multistep reduction properties. Moreover, signifi-
ity for the reduction of 7 and 8 indicates instability of the cant color changes were observed during the electrochemi-
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Novel Redox-Active Azulene Chromophores
cal reduction. In attempts to improve the electrochromic
properties, preparation of novel azulene-substituted multi-
valent charge-transfer chromophores with different π-elec-
tron cores is now in progress in our laboratory.
Experimental Section
TCNQ (153 mg, 0.75 mmol) was added to a solution of 2 (167 mg,
0.50 mmol) in ethyl acetate (10 mL). The resulting mixture was
heated at reflux for 3 h under Ar. The solvent was removed under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with CH2Cl2/ethyl acetate (1:1) and preparative
GPC with CHCl3 to give 6 (250 mg, 93%); m.p. 160.0–166.0 °C
(AcOEt). 1H NMR (600 MHz, CDCl3): δ = 9.92 (s, 1 H, 8-H), 8.36
(d, J = 10.0 Hz, 1 H, 4-H), 8.18 (s, 1 H, 2-H), 7.71 (dd, J = 4.1,
1.1 Hz, 1 H, 3Ј-H), 8.02 (d, J = 10.0 Hz, 1 H, 6-H), 7.87 (dd, J =
5.2, 1.1 Hz, 1 H, 5Ј-H), 7.70 (dd, J = 10.0, 10.0 Hz, 1 H, 5-H), 7.81
(dd, J = 5.2, 4.1 Hz, 1 H, 4Ј-H), 7.23–7.19 (m, 2 H, 3ЈЈ-, 5ЈЈ-H),
7.14–7.09 (m, 2 H, 2ЈЈ-, 6ЈЈ-H), 3.96 (s, 3 H, CO2Me), 3.32 (sept, J
= 6.8 Hz, 1 H, iPr), 1.47 (d, J = 6.8 Hz, 6 H, iPr) ppm. 13C NMR
(150 MHz, CDCl3): δ = 164.70 (CO2Me), 162.66 (b-C), 154.95 (7-
C), 154.01 (4ЈЈ-C), 145.00 (a-C), 144.89 (3-C), 143.71 (3a-C), 142.83
(2-C), 141.71 (6-C), 140.29 (8-C), 138.16 (2Ј-C), 137.78 (5Ј-C),
136.64 (3Ј-C), 136.13 (4-C), 135.97 (3ЈЈ- or 5ЈЈ-C), 133.81 (3ЈЈ- or
5ЈЈ-C), 132.08 (1ЈЈ-C), 131.10 (5-C), 130.07 (4Ј-C), 125.72 (2ЈЈ- or
6ЈЈ-C), 125.29 (2ЈЈ- or 6ЈЈ-C), 123.37 (8a-C), 119.06 (1-C), 114.13
[C(CN)2], 144.03 [C(CN)2], 113.51 [C(CN)2], 112.61 [C(CN)2],
80.79 [C(CN)2], 74.78 [C(CN)2], 51.60 (CO2Me), 39.39 (iPr), 24.50
General: For general and electrochemical measurement details see
the Supporting Information. Assignment of peaks in the H NMR
spectra was accomplished by decoupling, NOE, and/or COSY ex-
periments.
1
{4-[3,3-Dicyano-1-[5-isopropyl-3-(methoxycarbonyl)azulen-1-yl]-2-
phenylprop-2-en-1-ylidene]cyclohexa-2,5-dien-1-ylidene}malononi-
trile (5)
(iPr) ppm. IR (KBr disk): νmax = 2960 (w), 2208 (s), 1699 (s), 1602
˜
TCNQ (153 mg, 0.75 mmol) was added to a solution of 1 (164 mg,
0.50 mmol) in ethyl acetate (10 mL). The resulting mixture was
heated at reflux for 2 h under Ar. The solvent was removed under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with CH2Cl2/ethyl acetate (1:1) and Bio-Beads
with CH2Cl2 to give 5 (256 mg, 96%); m.p. 127.0–132.0 °C (Ac-
OEt). 1H NMR (600 MHz, CDCl3): δ = 9.90 (s, 1 H, 8-H), 8.29
(d, J = 10.0 Hz, 1 H, 4-H), 8.19 (s, 1 H, H2), 8.00 (d, J = 10.0 Hz,
1 H, 6-H), 7.71 (d, J = 5.6 Hz, 2 H, 2Ј-, 6Ј-H), 7.67 (dd, J = 10.0,
10.0 Hz, 1 H, 5-H), 7.56 (t, J = 5.6 Hz, 1 H, 4Ј-H), 7.49 (t, J =
5.6 Hz, 2 H, 3Ј-, 5Ј-H), 7.20–7.18 (m, 2 H, 2ЈЈ-, 6ЈЈ-H), 7.12–7.09
(m, 2 H, 3ЈЈ-, 5ЈЈ-H), 3.96 (s, 3 H, CO2Me), 3.30 (sept, J = 6.8 Hz,
1 H, iPr), 1.46 (d, J = 6.8 Hz, 6 H, iPr) ppm. 13C NMR (150 MHz,
CDCl3): δ = 172.55 (Cb), 164.65 (CO2Me), 154.80 (7-C), 153.71
(4ЈЈ-C), 145.49 (a-C), 144.73 (3-C), 143.75 (3a-C), 143.32 (2-C),
141.58 (6-C), 140.20 (8-C), 136.24 (2ЈЈ- or 6ЈЈ-C), 136.19 (4-C),
134.74 (1Ј-C), 133.79 (2ЈЈ- or 6ЈЈ-C), 133.69 (1ЈЈ-C), 133.66 (4Ј-C),
130.89 (5-C), 129.73 (3Ј,5Ј-C), 129.50 (2Ј,6Ј-C), 125.79 (3ЈЈ- or 5ЈЈ-
C), 125.42 (3ЈЈ- or 5ЈЈ-C), 124.08 (8a-C), 118.82 (1-C), 114.05
[C(CN)2], 113.98 [C(CN)2], 112.93 [C(CN)2], 112.19 [C(CN)2],
87.41 [C(CN)2], 74.93 [C(CN)2], 51.54 (CO2Me), 39.31 (iPr), 24.43
(m), 1521 (m), 1506 (s), 1444 (s), 1421 (s), 1407 (m), 1384 (s), 1361
(s), 1305 (w), 1276 (w), 1217 (s), 1193 (s), 1139 (w), 1128 (w), 1085
(w), 1062 (w), 1047 (w), 1020 (w), 999 (w), 972 (w), 929 (w), 877
(w), 840 (m), 812 (w), 779 (w), 729 (w), 669 (w), 657 (w), 565 (w),
466 (w), 416 (w) cm–1. UV/Vis (CH2Cl2): λ (ε, Lmol–1 cm–1) = 304
(4.58), 314 sh (4.56), 364 (4.40), 626 (4.47) nm. HRMS (ESI) calcd.
for C33H22N4O2S + Na+ [M + Na]+ 561.1361; found 561.1356.
C33H22N4O2S (538.62): calcd. C 73.59, H 4.12, N 10.40; found C
77.41, H 4.41, N 10.35.
2,2Ј-(1,4-Phenylenebis{[1,1-dicyano-3-[5-isopropyl-3-(methoxycarb-
onyl)azulen-1-yl]prop-1-en-2-yl-3-ylidene]cyclohexa-2,5-diene-4,1-
diylidene})dimalononitrile (7)
(iPr) ppm. IR (KBr disk): νmax = 2962 (w), 2208 (s), 1699 (s), 1600
˜
(m), 1521 (m), 1504 (s), 1442 (s), 1421 (s), 1400 (m), 1382 (s), 1303
(w), 1272 (w), 1128 (w), 1109 (w), 1085 (w), 1047 (w), 1026 (w),
1001 (w), 974 (w), 902 (w), 840 (w), 808 (w), 779 (w), 767 (w), 729
(w), 692 (w), 663 (w), 648 (w), 466 (w) cm–1. UV/Vis (CH2Cl2): λ
(ε, Lmol–1 cm–1) = 292 (4.34), 393 (4.26), 641 (4.43) nm. HRMS
(ESI) calcd. for C35H24N4O2 + Na+ [M + Na]+ 555.1797; found
555.1791. C35H24N4O2·1/10CHCl3 (532.19): calcd. C 77.42, H 4.46,
N 10.29; found C 77.41, H 4.54, N 10.22.
TCNQ (306 mg, 1.50 mmol) was added to a solution of 3 (289 mg,
0.50 mmol) in ethyl acetate (10 mL). The resulting mixture was
heated at reflux for 6 h under Ar. The solvent was removed under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with CH2Cl2/ethyl acetate (1:1) and Bio-Beads
with CH2Cl2 to give 7 (464 mg, 94%); m.p. 225.0–229.0 °C (Ac-
OEt). 1H NMR (600 MHz, CDCl3): δ = 9.90 (s, 2 H, 8-H), 8.20
(d, J = 10.0 Hz, 2 H, 4-H), 8.10 (s, 2 H, 2-H), 8.03 (d, J = 10.0 Hz,
2 H, 6-H), 7.74 (s, 4 H, Ph), 7.68 (dd, J = 10.0, 10.0 Hz, 2 H, 5-
{4-[3,3-Dicyano-1-[5-isopropyl-3-(methoxycarbonyl)azulen-1-yl]-2-
thienylprop-2-en-1-ylidene]cyclohexa-2,5-dien-1-ylidene}malononi-
trile (6)
Eur. J. Org. Chem. 2009, 4316–4324
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4321

T. Shoji, S. Ito, K. Toyota, T. Iwamoto, M. Yasunami, N. Morita
FULL PAPER
H), 7.23–7.18 (m, 4 H, 3ЈЈЈ-, 5ЈЈЈ-, 3ЈЈЈЈ-, 5ЈЈЈЈ-H), 7.04–7.02 (m, 4 UV/Vis (CH2Cl2): λ (ε, Lmol–1 cm–1) = 240 (4.76), 294 (4.82), 314
H, 2ЈЈЈ-, 6ЈЈЈ-, 2ЈЈЈЈ-, 6ЈЈЈЈ-H), 3.96 (s, 6 H, CO2Me), 3.32 (sept, J sh (4.71), 391 (4.67), 590 (4.69) nm. HRMS (ESI) calcd. for
= 6.5 Hz, 2 H, iPr), 1.46 (d, J = 6.5 Hz, 12 H, iPr) ppm. 13C NMR
(150 MHz, CDCl3): δ = 169.82, 164.55 (CO2Me), 155.26 (7-, 7Ј-C),
C62H40N8O4S + Na+ [M + Na]+ 1015.2791; found 1015.2785.
C62H40N8O4S·1/2CHCl3 (993.10): calcd. C 71.39, H 4.09, N 10.64;
153.40 (4ЈЈЈ-, 4ЈЈЈЈ-C), 144.74 (1-, 1Ј-C), 143.76 (3a-, 3aЈ-C), 143.42, found C 71.30, H 3.88, N 10.64.
142.69 (2-, 2Ј-C), 141.96 (6-, 6Ј-C), 140.55 (8-, 8Ј-C), 138.45 (Ph-
1-[2-[5-Isopropyl-3-(methoxycarbonyl)azulen-1-yl]-1,1,4,4-tetracy-
anobutadien-3-yl]-4-[[5-isopropyl-3-(methoxycarbonyl)azulen-1-yl]-
ethynyl]benzene (9)
C), 136.14, (4-, 4Ј-C) 135.93 (3ЈЈЈ-, 3ЈЈЈЈ- or 5ЈЈЈ-, 5ЈЈЈЈ-C), 133.75
(3ЈЈЈ-, 3ЈЈЈЈ- or 5ЈЈЈ-, 5ЈЈЈЈ-C), 133.12 (1ЈЈЈ-, 1ЈЈЈЈ-C), 131.10 (5-, 5Ј-
C), 130.29 (Ph-C), 126.28 (2ЈЈЈ-, 2ЈЈЈЈ- or 6ЈЈЈ-, 6ЈЈЈЈ-C), 126.06
(2ЈЈЈ-, 2ЈЈЈЈ- or 6ЈЈЈ-, 6ЈЈЈЈ-C), 123.07 (8a-, 8aЈ-C), 119.14 (1-, 1Ј-C),
113.81 [C(CN)2], 113.76 [C(CN)2], 112.20 [C(CN)2], 111.61
[C(CN)2], 89.66 [C(CN)2], 76.29 [C(CN)2], 51.73 (CO2Me), 39.41
(iPr), 24.50 (iPr) ppm. IR (KBr disk): ν
= 2962 (w), 2210 (s),
˜
max
1699 (s), 1600 (m), 1521 (m), 1506 (s), 1442 (s), 1421 (s), 1400 (m),
1380 (s), 1355 (m), 1303 (w), 1278 (w), 1218 (s), 1193 (s), 1128 (w),
1107 (w), 1085 (w), 1047 (w), 1033 (w), 904 (w), 840 (w), 777 (w),
729 (w), 663 (w), 648 (w), 468 (w) cm–1. UV/Vis (CH2Cl2): λ (ε,
Lmol–1 cm–1) = 238 (4.87), 292 (4.94), 362 (4.74), 627 (4.70) nm.
HRMS (ESI) calcd. for C64H42N8O4 + Na+ [M + Na]+ 1009.3227;
found 1009.3221. C64H42N8O4·1/2H2O (987.07): calcd. C 77.17, H
4.35, N 11.25; found C 77.19, H 4.47, N 11.19.
TCNE (320 mg, 2.50 mmol) was added to a solution of 3 (1.15 g,
2.00 mmol) in ethyl acetate (20 mL). The resulting mixture was
heated at reflux for 2 h under Ar. The solvent was removed under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with CH2Cl2/ethyl acetate (1:1) and Bio-Beads
with CH2Cl2 to give 9 (1.25 g, 88%) as purple crystals, and 13
(67 mg, 4%) as reddish purple crystals; m.p. 165.0–168.0 °C (de-
2,2Ј-(2,5-Thiophenediylbis{[1,1-dicyano-3-(5-isopropyl-3-(methoxy-
carbonyl)azulen-1-yl)prop-1-en-2-yl-3-ylidene]cyclohexa-2,5-diene-
4,1-diylidene})dimalononitrile (8)
1
comp.). H NMR (400 MHz, CDCl3): δ = 10.04 (dd, J = 2.0 Hz,
1 H, 4-H), 9.78 (dd, J = 2.0 Hz, 1 H, 4Ј-H), 8.66 (d, J = 10.0 Hz,
1 H, 8-H), 8.51 (s, 1 H, 2-H), 8.50 (d, J = 10.0 Hz, 1 H, 8Ј-H), 8.35
(s, 1 H, 2Ј-H), 8.17 (d, J = 10.0 Hz, 1 H, 6-H), 8.00 (dd, J = 10.0,
10.0 Hz, 1 H, 7-H), 7.90–7.88 (m, 3 H, 6Ј-H, 2ЈЈ-, 6ЈЈ-H), 7.77 (d,
J = 8.8 Hz, 2 H, 3ЈЈ-, 5ЈЈ-H), 7.60 (dd, J = 10.0, 10.0 Hz, 1 H, 7Ј-
H), 3.97 (s, 3 H, CO2Me), 3.96 (s, 3 H, CO2Me), 3.37 (sept, J =
6.8 Hz, 1 H, iPr), 3.27 (sept, J = 6.8 Hz, 1 H, iPr), 1.48 (d, J =
6.8 Hz, 6 H, iPr), 1.44 (d, J = 6.8 Hz, 6 H, iPr) ppm. 13C NMR
(100 MHz, CDCl3): δ = 167.90, 165.22, 164.3824, 160.69, 157.08,
151.68, 146.20, 145.38, 143.32, 142.56, 142.49, 141.99, 141.82,
140.80, 139.83, 138.77, 137.60, 136.21, 132.30, 132.27, 131.17,
130.46, 129.94, 128.25, 119.48, 115.74, 113.69, 112.48, 112.32,
111.51, 107.65, 93.43, 92.45, 86.19, 80.67, 51.70, 51.25, 39.48,
TCNQ (306 mg, 1.50 mmol) was added to a solution of 4 (292 mg,
0.50 mmol) in ethyl acetate (10 mL). The resulting mixture was
heated at reflux for 12 h under Ar. The solvent was removed under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with CH2Cl2/ethyl acetate (1:1) and preparative
GPC with CHCl3 to give 8 (457 mg, 92%) as purple crystals; m.p.
230.0–234.0 °C (CHCl3). 1H NMR (600 MHz, CDCl3): δ = 9.91 (s,
2 H, 8-, 8Ј-H), 8.24 (d, J = 10.0 Hz, 2 H, 4-, 4Ј-H), 8.10 (s, 2 H,
2-, 2Ј-H), 8.05 (d, J = 10.0 Hz, 2 H, 6-, 6Ј-H), 7.93 (s, 2 H, 3ЈЈ-,
4ЈЈ-H), 7.69 (dd, J = 10.0, 10.0 Hz, 2 H, 5-, 5Ј-H), 7.21 (dd, J =
9.6, 1.6 Hz, 2 H, 3ЈЈЈ-, 3ЈЈЈЈ-H), 7.17 (dd, J = 9.6, 1.6 Hz, 2 H,
5ЈЈЈ-, 5ЈЈЈЈ-H), 7.01 (dd, J = 9.6, 1.6 Hz, 2 H, 2ЈЈЈ-, 2ЈЈЈЈ-H), 6.98
(dd, J = 9.6, 1.6 Hz, 2 H, 6ЈЈЈ-, 6ЈЈЈЈ-H), 3.98 (s, 6 H, CO2Me), 3.33
(sept, J = 6.8 Hz, 2 H, iPr), 1.47 (d, J = 6.8 Hz, 12 H, iPr) ppm.
13C NMR (150 MHz, CDCl3): δ = 164.54 (CO2Me), 160.28 (b-,
bЈЈ-C), 155.48 (7-, 7Ј-C), 153.55 (4ЈЈЈ-, 4ЈЈЈЈ-C), 145.18 (2ЈЈ-, 5ЈЈ-C),
145.02 (3-, 3Ј-C), 143.68 (3a-, 3aЈ-C), 142.30 (a-, aЈ-C), 142.19 (2-,
2Ј-C), 142.10 (6-, 6Ј-C), 140.54 (8-, 8Ј-C), 136.49, (4-, 4Ј-C) 135.68
(3ЈЈ-, 4ЈЈ-C), 135.58 (2ЈЈЈ-, 2ЈЈЈЈ-C), 132.97 (6ЈЈЈ-, 6ЈЈЈЈ-C), 132.58
(1ЈЈЈ-, 1ЈЈЈЈ-C), 131.60 (5-, 5Ј-C), 126.20 (5ЈЈЈ-, 5ЈЈЈЈ-C), 125.93
(3ЈЈЈ-, 3ЈЈЈЈ-C), 122.25 (8a-, 8aЈ-C), 119.26 (1-, 1Ј-C), 113.81
[C(CN)2], 113.77 [C(CN)2], 112.58 [C(CN)2], 111.71 [C(CN)2],
85.37 [C(CN)2], 76.11 [C(CN)2], 51.78 (CO2Me), 39.42 (iPr), 24.50
39.29, 24.57, 24.46 ppm. IR (KBr disk): νmax = 2961 (m), 2220 (m),
˜
2185 (s), 1697 (s), 1597 (m), 1552 (w), 1525 (m), 1494 (s), 1444 (s),
1418 (s), 1365 (m), 1319 (w), 1296 (w), 1272 (w), 1236 (m), 1213
(s), 1178 (m), 1134 (w), 1076 (w), 1033 (w), 1001 (w), 962 (w), 898
(w), 875 (w), 844 (w), 808 (w), 777 (w), 746 (w), 729 (w), 663 (w),
648 (w), 590 (w) cm–1. UV/Vis (CH2Cl2): λ (ε, Lmol–1 cm–1) = 242
(4.75), 300 (4.80), 348 sh (4.51), 400 (4.47), 508 (4.45) nm. HRMS
(ESI) calcd. for C46H34N4O4 + Na+ [M + Na]+ 729.2478; found
729.2472. C46H34N4O4·H2O (706.79): calcd. C 76.23, H 5.01, N
7.73; found C 75.98, H 5.05, N 7.81.
2-[2-[5-Isopropyl-3-(methoxycarbonyl)azulen-1-yl]-1,1,4,4-tetracy-
anobutadien-3-yl]-5-[[5-isopropyl-3-(methoxycarbonyl)azulen-1-yl]-
ethynyl]thiophene (10)
(iPr) ppm. IR (KBr disk): νmax = 2960 (w), 2208 (s), 1699 (s), 1600
˜
(m), 1521 (m), 1506 (s), 1442 (s), 1419 (s), 1400 (s), 1382 (s), 1363
TCNE (320 mg, 2.50 mmol) was added to a solution of 4 (1.17 g,
(s), 1303 (w), 1284 (m), 1217 (s), 1193 (s), 1128 (w), 1085 (w), 1045 2.00 mmol) in ethyl acetate (20 mL). The resulting mixture was
(w), 1029 (w), 999 (w), 972 (w), 929 (w), 898 (m), 877 (w), 840 (m), heated at reflux for 2 h under Ar. The solvent was removed under
810 (w), 777 (w), 729 (w), 669 (w), 655 (w), 468 (w), 416 (w) cm–1. reduced pressure. The residue was purified by column chromatog-
4322
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 4316–4324

Novel Redox-Active Azulene Chromophores
raphy on silica gel with CH2Cl2/ethyl acetate (1:1) and Bio-Beads
with CH2Cl2 to give 10 (1.25 g, 88%) as purple crystals, and 14
(84 mg, 5%) as reddish purple crystals; m.p. 226.0–228.0 °C (de-
1 H, iPr), 1.48 (d, J = 6.8 Hz, 6 H, iPr), 1.46 (d, J = 6.8 Hz, 6 H,
iPr) ppm. 13C NMR (100 MHz, CDCl3): δ = 169.70, 166.92,
164.48, 164.14, 158.96, 157.59, 155.14, 153.41, 146.29, 144.77,
comp.). 1H NMR (400 MHz, CDCl3): δ = 10.01 (dd, J = 2.0 Hz, 1 143.74, 143.57, 142.95, 142.90, 142.08, 142.00, 141.95, 141.87,
H, 4-H), 9.79 (s, 1 H, 4Ј-H), 8.62 (d, J = 10.0 Hz, 1 H, 8-H), 8.53
(d, J = 10.0 Hz, 1 H, 8Ј-H), 8.49 (s, 1 H, 2-H), 8.28 (s, 1 H, 2Ј-H),
8.18 (d, J = 10.0 Hz, 1 H, 6-H), 8.02 (dd, J = 10.0, 10.0 Hz, 1 H,
140.98, 140.42, 139.17, 137.68, 136.11, 136.02, 135.73, 133.99,
133.31, 132.59, 131.12, 130.57, 130.48, 126.19, 125.95, 123.21,
119.84, 119.06, 118.77, 113.87, 113.81, 113.36, 112.35, 112.26,
7-H), 7.96 (d, J = 4.0 Hz, 1 H, 3ЈЈ-H), 7.92 (d, J = 10.0 Hz, 1 H, 111.62, 111.25, 110.50, 90.53, 89.92, 80.29, 75.73, 51.74, 51.56,
6Ј-H), 7.65 (dd, J = 10.0, 10.0 Hz, 1 H, 7Ј-H), 7.42 (d, J = 4.0 Hz, 39.44, 39.27, 24.36 ppm. IR (KBr disk): ν = 2962 (m), 2210 (s),
˜
max
1 H, 3ЈЈ-H), 3.97 (s, 3 H, CO2Me), 3.96 (s, 3 H, CO2Me), 3.36 1701 (s), 1602 (w), 1504 (s), 1442 (s), 1419 (s), 1400 (m), 1382 (m),
(sept, J = 6.8 Hz, 1 H, iPr), 3.27 (sept, J = 6.8 Hz, 1 H, iPr), 1.48
1365 (m), 1290 (w), 1217 (s), 1193 (s), 1136 (w), 1087 (w), 1047 (w),
1031 (w), 999 (w), 931 (w), 879 (w), 842 (w), 812 (w), 779 (w), 729
(d, J = 6.8 Hz, 6 H, iPr), 1.44 (d, J = 6.8 Hz, 6 H, iPr) ppm. 13C
NMR (100 MHz, CDCl3): δ = 165.07, 164.41, 159.92, 157.73, (w), 671 (w), 594 (w), 561 (w), 518 (w), 470 (w), 441 (w), 408
157.07, 152.44, 146.34, 145.51, 143.41, 142.51, 142.43, 142.24,
142.00, 140.70, 140.25, 139.11, 138.23, 137.94, 137.89, 137.85,
136.44, 134.47, 132.75, 132.38, 128.87, 119.39, 118.76, 116.33,
113.59, 113.31, 112.48, 112.24, 106.66, 101.60, 101.59, 100.46,
87.039, 80.55, 78.16, 51.68, 51.34, 39.49, 39.35, 24.55, 24.47 ppm.
(w) cm–1. UV/Vis (CH2Cl2): λ (ε, Lmol–1 cm–1) = 240 (4.96), 262
(4.91), 296 (4.96), 432 (4.90), 586 (4.64) nm. HRMS (ESI) calcd.
for C58H38N8O4 + Na+ [M + Na]+ 933.2914; found 933.2909.
C58H38N8O4 (910.97): calcd. C 76.23, H 5.01, N 7.73; found C
75.98, H 5.05, N 7.81.
IR (KBr disk): ν
= 2960 (m), 2218 (m), 2171 (s), 1701 (s), 1488
˜
max
Compound 12
(s), 1448 (s), 1415 (s), 1402 (s), 1365 (s), 1348 (s), 1274 (w), 1238
(m), 1213 (s), 1180 (m), 1134 (m), 1112 (m), 1064 (m), 1049 (m),
1031 (w), 964 (w), 918 (w), 898 (w), 873 (w), 840 (w), 806 (m), 775
(m), 732 (w), 686 (w), 659 (w), 648 (w), 590 (w), 559 (w), 540 (w),
505 (w), 461 (w), 441 (w) cm–1. UV/Vis (CH2Cl2):
λ (ε,
Lmol–1 cm–1) = 240 (4.73), 298 (4.73), 382 sh (4.39), 410 (4.44), 550
(4.61) nm. HRMS (ESI) calcd. for C44H32N4O4S + Na+ [M +
Na]+ 735.2042; found 735.2036. C44H32N4O4S (712.82): calcd. C
74.14, H 4.52, N 7.86; found C 73.77, H 4.76, N 7.97.
Compound 11
Reaction with 10 and TCNQ: TCNQ (153 mg, 0.75 mmol) was
added to a solution of 10 (354 mg, 0.50 mmol) in ethyl acetate
(10 mL). The resulting mixture was heated at reflux for 6 h under
Ar. The solvent was removed under reduced pressure. The residue
was purified by column chromatography on silica gel with CH2Cl2/
ethyl acetate (1:1) and by preparative GPC with CHCl3 to give 12
(390 mg, 85%) as deep-green crystals.
Reaction with 4 and TCNE/TCNQ: TCNE (96 mg, 0.75 mmol) and
TCNQ (153 mg, 0.75 mmol) were added to a solution of 4 (584 mg,
1.00 mmol) in ethyl acetate (20 mL). The resulting mixture was
heated at reflux for 6 h under Ar. The solvent was removed under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with CH2Cl2/ethyl acetate (1:1) and by prepara-
tive GPC with CHCl3 to give 12 (275 mg, 30%), 8 (268 mg, 27%),
and 14 (285 mg, 34%); m.p. 210.0–213.0 °C (AcOEt). 1H NMR
(400 MHz, CDCl3): δ = 9.99 (dd, J = 2.0 Hz, 1 H, 4-H), 9.94 (dd,
J = 2.0 Hz, 1 H, 4Ј-H), 8.40 (d, J = 10.0 Hz, 1 H, 8-H), 8.28 (d, J
= 10.0 Hz, 1 H, 8Ј-H), 8.22 (d, J = 10.0 Hz, 1 H, 6-H), 8.18 (s, 1
H, 2-H), 8.13 (d, J = 4.0 Hz, 1 H, 3ЈЈЈ-H), 8.06–8.00 (m, 3 H, 7,
2Ј-, 6Ј-H), 7.93 (d, J = 4.0 Hz, 1 H, 4ЈЈЈ-H), 7.71 (dd, J = 10.0,
10.0 Hz, 1 H, 7Ј-H), 7.28 (dd, J = 7.6, 2.0 Hz, 1 H, 3ЈЈ-H), 7.20
(dd, J = 7.6, 2.0 Hz, 1 H, 5ЈЈ-H), 7.06 (d, 2 H, 2ЈЈ-, 6ЈЈ-H), 3.98 (s,
3 H, CO2Me), 3.97 (s, 3 H, CO2Me), 3.38 (sept, J = 6.8 Hz, 1 H,
Reaction with 9 and TCNQ: TCNQ (153 mg, 0.75 mmol) was added
to a solution of 9 (353 mg, 0.50 mmol) in ethyl acetate (10 mL).
The resulting mixture was heated at reflux for 6 h under Ar. The
solvent was removed under reduced pressure. The residue was puri-
fied by column chromatography on silica gel with CH2Cl2/ethyl
acetate (1:1) and Bio-Beads with CH2Cl2 to give 11 (383 mg, 84%)
as deep-green crystals.
Reaction with 3 and TCNE/TCNQ: TCNE (96 mg, 0.75 mmol) and
TCNQ (153 mg, 0.75 mmol) were added to a solution of 3 (578 mg,
1.00 mmol) in ethyl acetate (20 mL). The resulting mixture was
heated at reflux for 6 h under Ar. The solvent was removed under
reduced pressure. The residue was purified by column chromatog-
raphy on silica gel with CH2Cl2/ethyl acetate (1:1) and preparative
GPC with CHCl3 to give 11 (273 mg, 30%), 7 (286 mg, 29%), and
13 (267 mg, 32%); m.p. 214.0–217.0 °C (decomp.). 1H NMR iPr), 3.33 (sept, J = 6.8 Hz, 1 H, iPr), 1.49 (d, J = 6.8 Hz, 6 H,
(400 MHz, CDCl3): δ = 10.04 (dd, J = 2.0 Hz, 1 H, 4-H), 9.92 (dd,
J = 2.0 Hz, 1 H, 4Ј-H), 8.42 (d, J = 10.0 Hz, 1 H, 8-H), 8.24 (d, J
iPr), 1.47 (d, J = 6.8 Hz, 6 H, iPr) ppm. Low solubility prevented
13C NMR spectroscopy. IR (KBr disk): ν
= 2962 (m), 2210 (s),
˜
max
= 10.0 Hz, 1 H, 8Ј-H), 8.22 (s, 1 H, 2-H), 8.21 (d, J = 10.0 Hz, 1 1701 (s), 1602 (w), 1523 (m), 1504 (s), 1442 (s), 1419 (s), 1400 (m),
H, 6-H), 8.22 (s, 1 H, 2Ј-H), 8.02 (d, J = 10.0 Hz, 1 H, 6Ј-H), 8.02 1382 (m), 1363 (m), 1290 (w), 1217 (s), 1193 (s), 1136 (w), 1087
(dd, J = 10.0, 10.0 Hz, 1 H, 7-H), 7.85 (m, 4 H, 2ЈЈ-, 3ЈЈ-, 5ЈЈ-, 6ЈЈ-
(w), 1047 (w), 1029 (w), 1001 (w), 900 (w), 842 (w), 810 (w), 779
H), 7.69 (dd, J = 10.0, 10.0 Hz, 1 H, 7Ј-H), 7.28–7.20 (m, 2 H, (w), 729 (w), 671 (w), 447 (w), 408 (w) cm–1. UV/Vis (CH2Cl2): λ
3ЈЈЈ-, 4ЈЈЈ-H), 7.11–7.06 (m, 2 H, 5ЈЈЈ-, 6ЈЈЈ-H), 3.97 (s, 6 H, (ε, Lmol–1 cm–1) = 240 (4.78), 262 sh (4.73), 296 (4.78), 432 (4.73),
CO2Me), 3.37 (sept, J = 6.8 Hz, 1 H, iPr), 3.32 (sept, J = 6.8 Hz, 586 (4.46) nm. HRMS (ESI) calcd. for C56H36N8O4S + Na+
Eur. J. Org. Chem. 2009, 4316–4324
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T. Shoji, S. Ito, K. Toyota, T. Iwamoto, M. Yasunami, N. Morita
FULL PAPER
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Received: May 15, 2009
Published Online: July 22, 2009
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Eur. J. Org. Chem. 2009, 4316–4324