Synthesis of redox-active, intramolecular charge-transfer chromophores by the [2+2] cycloaddition of ethynylated 2H-Cyclohepta[b]furan-2-ones with tetracyanoethylene

Article abstract of DOI:10.1002/chem.201003628

Ethynylated 2H-cyclohepta[b]furan-2-ones 5-15 have been prepared by Pd-catalyzed alkynylation of 3-iodo-5-isopropyl-2H-cyclohepta[b]furan-2-one (2) with the corresponding ethynylarenes or the reaction of 2-iodothiophene with 3-ethynyl-5-isopropyl-2H-cyclohepta[b]furan-2-one (4) under Sonogashira-Hagihara conditions. Compounds 5-15 reacted with tetracyanoethylene in a formal [2+2] cycloaddition reaction, followed by ring opening of the initially formed [2+2] cycloadducts, cyclobutenes, to afford the corresponding 1,1,4,4- tetracyanobutadienyl (TCBD) chromophores 16-26 in excellent yields. The intramolecular charge-transfer interactions between the 2H-cyclohepta[b]furan-2- one ring and TCBD acceptor moiety were investigated by UV/Vis spectroscopy and theoretical calculations. The redox behavior of the novel TCBD derivatives 16-26 was examined by cyclic voltammetry and differential pulse voltammetry, which revealed multistep electrochemical reduction properties, depending on the number of TCBD units in the molecule. Moreover, a significant color change was observed by UV/Vis spectroscopy under electrochemical reduction conditions.

Full text of DOI:10.1002/chem.201003628

DOI: 10.1002/chem.201003628
Synthesis of Redox-Active, Intramolecular Charge-Transfer Chromophores
by the [2+2] Cycloaddition of Ethynylated 2H-Cyclohepta[b]furan-2-ones
with Tetracyanoethylene
Taku Shoji,*[a] Junya Higashi,[b] Shunji Ito,[c] Tetsuo Okujima,[d]
Masafumi Yasunami,[e] and Noboru Morita[b]
Abstract: Ethynylated 2H-cyclohep-
ta[b]furan-2-ones 5–15 have been pre-
pared by Pd-catalyzed alkynylation of
3-iodo-5-isopropyl-2H-cyclohepta[b]-
furan-2-one (2) with the corresponding
ethynylarenes or the reaction of 2-io-
dothiophene with 3-ethynyl-5-isopro-
[2+2] cycloadducts, cyclobutenes, to
afford the corresponding 1,1,4,4-tetra-
cyanobutadienyl (TCBD) chromo-
phores 16–26 in excellent yields. The
intramolecular charge-transfer interac-
tions between the 2H-cyclohepta[b]fur-
an-2-one ring and TCBD acceptor
moiety were investigated by UV/Vis
spectroscopy and theoretical calcula-
tions. The redox behavior of the novel
TCBD derivatives 16–26 was examined
by cyclic voltammetry and differential
pulse voltammetry, which revealed
multistep electrochemical reduction
properties, depending on the number
of TCBD units in the molecule. More-
over, a significant color change was ob-
served by UV/Vis spectroscopy under
electrochemical reduction conditions.
pyl-2H-cyclohepta[b]furan-2-one
(4)
under Sonogashira–Hagihara condi-
tions. Compounds 5–15 reacted with
tetracyanoethylene in a formal [2+2]
cycloaddition reaction, followed by
ring opening of the initially formed
Keywords: charge transfer · cyclo-
addition · donor–acceptor systems ·
electrochemistry · heteroazulenes
Introduction
Tetracyanoethylene (TCNE) is known to be a strong or-
ganic electron acceptor. The high reactivity of TCNE
toward nucleophiles or electron-rich reagents enables us to
introduce strong acceptor moi-
Organic electron donor–acceptor systems, which feature in-
tramolecular charge-transfer (ICT) interactions, have at-
tracted considerable interest as promising candidates for the
next generation of organic electronic and optoelectronic de-
vices.[1] Therefore, the construction of molecules possessing
a donor–acceptor system is one of the most attractive sub-
jects in current organic chemistry.
eties into organic molecules.[2]
In 1981, for the first time,
Bruce et al. reported that the
reaction of electron-rich ruthe-
nium acetylides with TCNE af-
forded formal [2+2] cycloaddition products, namely, cyclo-
butene derivatives, which exhibited a ring-opening reaction
to give the corresponding 1,1,4,4-tetracyano-1,3-butadienes
(TCBDs).[3] Yamashita and co-workers have reported that
1,3-dithiol-2-ylidene derivatives also reacted with TCNE to
afford the corresponding TCBD derivatives, which showed
amphoteric redox behavior when monitored by cyclic vol-
tammetry (CV).[4] Diederich et al. also recently reported
that a variety of electron-rich alkynes reacted with TCNE to
give donor-substituted TCBDs in excellent yields.[5] Further-
more, they extensively expanded the chemistry by applying
it to other acceptor molecules, such as 7,7,8,8-tetracyanoqui-
nodimethane (TCNQ) and dicyanovinyl and tricyanovinyl
derivatives.[6] They have also reported that the new class of
chromophores obtained by the reaction was characterized
by an intense ICT interaction with a strong absorption in
the visible region and were promising third-order nonlinear
optics.[7]
[a] Dr. T. Shoji
Department of Chemistry, Faculty of Science
Shinshu University, Matsumoto 390-8621 (Japan)
Fax : (+81)263-37-2476
E-mail: tshoji@shinshu-u.ac.jp
[b] J. Higashi, Prof. Dr. N. Morita
Department of Chemistry, Graduate School of Science
Tohoku University, Sendai 980-8578 (Japan)
[c] Prof. Dr. S. Ito
Graduate School of Science and Technology
Hirosaki University, Hirosaki 036-8561 (Japan)
[d] Dr. T. Okujima
Department of Chemistry and Biology
Graduate School of Science and Engineering
Ehime University, Matsuyama 790-8577 (Japan)
[e] Prof. Dr. M. Yasunami
Department of Materials Chemistry and Engineering
College of Engineering, Nihon University
Koriyama 963-8642 (Japan)
2H-Cyclohepta[b]furan-2-one is known as a heteroazu-
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201003628.
lene; a versatile precursor for azulene derivatives.[8] Al-
5116
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 5116 – 5129

FULL PAPER
though unusual reactivity of the compound, including its de-
rivatives, has already been revealed by many research
groups,[9] there are few derivatives for applications in ad-
vanced materials with potentially useful electronic proper-
ties. Furthermore, the most common functionalization
method of 2H-cyclohepta[b]furan-2-one utilizes the electro-
philic substitution reaction. For this reason, the transition-
metal-catalyzed cross-coupling reaction of 2H-cyclohepta[b]-
furan-2-one derivatives has never been reported so far, al-
though carbon–carbon bond formation by the cross-coupling
reaction is a powerful strategy in modern organic synthesis.
Therefore, the application of a new synthetic methodology
to 2H-cyclohepta[b]furan-2-one derivatives still remains a
problem in this class of chemistry.
tion of the tosylate of 4-isopropyltropolone with dimethyl-
malonate in the presence of sodium methoxide,[8c] with N-io-
dosuccinimide (NIS) in dichloromethane at room tempera-
ture afforded 3-iodo-5-isopropyl-2H-cyclohepta[b]furan-2-
one (2) in 91% yield, which was similar to that of the iodi-
nation of azulene derivatives (Scheme 1).[10,11] The synthesis
of 2 was also established in 97% yield by using N-chlorosuc-
cinimide (NCS) with NaI in acetic acid; this iodination
method has been reported by us recently.[12]
Recently, we have also reported the reaction of mono-,
bis-, and tris(1-azulenylethynyl)benzene and the thiophene
derivatives with TCNE and TCNQ to give the correspond-
ing ICT chromophores in excellent yield.[10] We have also re-
vealed that these new chromophores exhibit multistep re-
duction waves in CV and differential pulse voltammetry
(DPV). Moreover, significant color changes were also ob-
served by the electrochemical reduction of these new deriv-
atives. Similar to the high reactivity of azulene derivatives at
the 1,3-positions, 2H-cyclohepta[b]furan-2-ones also possess
high reactivity toward electrophilic substitution reactions at
the 3-position on the five-membered ring. Thus, 3-ethynyl-
2H-cyclohepta[b]furan-2-one derivatives are expected to
show high reactivity toward the formal [2+2] cycloaddition
reaction with TCNE to afford novel TCBD derivatives with
heteroazulene moieties. Furthermore, 2H-cyclohepta[b]fur-
an-2-one-substituted TCBDs should also exhibit multistage
redox behavior, similar to the TCBD derivatives reported
previously, as well as poly-electrochromic properties.
Scheme 1. Synthesis of 3-iodo-5-isopropyl-2H-cyclohepta[b]furan-2-one
(2).
The first Pd-catalyzed cross-coupling reaction of 2 was es-
tablished under Sonogashira–Hagihara conditions.[13] The
cross-coupling reaction of 2 with trimethylsilylacetylene and
[PdACTHUNTGRNENUG(PPh3)4] as a catalyst in THF/Et3N at 508C gave 3-(tri-
methylsilylethynyl)-5-isopropyl-2H-cyclohepta[b]furan-2-one
(3) in 97% yield. Desilylation of 3 with K2CO3 in a mixed
solvent of MeOH/THF/water afforded 3-ethynyl-5-isopro-
pyl-2H-cyclohepta[b]furan-2-one (4) in 95% yield
(Scheme 2). Compounds 2, 3, and 4 are stable and showed
no decomposition even after several weeks at room temper-
ature.
Herein, we describe the first Pd-catalyzed synthesis of 3-
ethynyl-2H-cyclohepta[b]furan-2-ones, as well as transfor-
mation to the TCBD derivatives by reaction with TCNE.
The electronic properties of the new donor–acceptor sys-
tems obtained by this reaction were characterized by CV,
DPV, absorption spectroscopy, and theoretical calculations.
The data confirm the powerful ICT character of the novel
Scheme 2. TMS=trimethylsilyl.
In an effort to explore the scope of the cross-coupling re-
action, we have conducted the cross-coupling reaction of 2
with a variety of ethynylarenes. Thus, the preparation of the
corresponding 3-(arylethynyl)-2H-cyclohepta[b]furan-2-ones
was accomplished by the Pd-catalyzed alkynylation of 2 with
the corresponding ethynylarenes or the 2-iodothiophenes
with 4 under Sonogashira–Hagihara conditions. The reaction
of alkynes with electron-rich arenes gave the corresponding
products in excellent yields, whereas the reaction of an
alkyne with an electron-deficient aromatic ring, that is, 1-
ethynyl-4-nitrobenzene, produced the cross-coupling product
in a relatively low yield. The cross-coupling reaction of 2
2H-cyclohepta[b]furan-2-one-substituted
donor–acceptor
systems with respect to their electrochromic properties.
Results and Discussion
Synthesis of 3-ethynyl-2H-cyclohepta[b]furan-2-ones: Al-
though the iodine substituent on an aromatic compound is
very important in the transition-metal-catalyzed cross-cou-
pling reaction, the synthesis of 3-iodo derivatives of 2H-cy-
clohepta[b]furan-2-ones by this reaction has never been re-
ported in the literature. Thus, we first examined, the iodina-
tion of 5-isopropyl-2H-cyclohepta[b]furan-2-one (1) to pre-
pare the substrate for the Pd-catalyzed cross-coupling reac-
tion under two reaction conditions.
with ethynylbenzene, using [PdACHTUNTRGNEUNG(PPh3)4] as the catalyst, and
subsequent chromatographic purification on silica gel af-
forded the desired 5-isopropyl-3-(phenylethynyl)-2H-cyclo-
hepta[b]furan-2-one (5) in 99% yield (Scheme 3).
The reaction of 1, which could readily be prepared by the
method established by Yasunami and Takase using the reac-
Reaction of 2 with 4-ethynylaniline afforded 6 in 98%
yield. The cross-coupling reaction of 2 with N,N-dimethyl-4-
Chem. Eur. J. 2011, 17, 5116 – 5129
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5117

T. Shoji et al.
[PdACHTUNGRTNEUNG(PPh3)4] as the catalyst in 87 and 91% yield, respectively.
Tris-adduct 15 was also prepared by a simple one-pot reac-
tion involving the repeated Pd-catalyzed alkynylation of 2
with 1,3,5-triethynylbenzene[16] in 90% yield under similar
reaction conditions (Scheme 4).
Scheme 3.
ethynylaniline in the presence of the Pd-catalyst afforded 7
in 97% yield. Compound 8 was also obtained by a similar
Pd-catalyzed reaction of 2 with 1-ethynyl-4-nitrobenzene,
but in a relatively low yield (60%). The low yield of the
product should be attributable to the electron-withdrawing
nature of the p-nitro substituent, which should decrease the
reactivity of alkyne toward the transmetalation process in
the Pd-catalyzed reaction. The reaction of ethynylferrocene,
which has an electron-donating ferrocenyl group, with 2 pro-
ceeded smoothly to afford 9 in 90% yield. Similar to the re-
actions described above, the Sonogashira–Hagihara reaction
of 2 with 4 and methyl 3-ethynyl-7-isopropylazulene-1-car-
boxylate[10] gave the presumed products 10 and 11 in 91 and
95% yield, respectively.
Scheme 4.
These acetylene derivatives 5–15 possess fair solubility in
chloroform, dichloromethane, and so on. Moreover, they are
stable and showing no decomposition, even after several
weeks at room temperature. These acetylene derivatives are
utilized in further transformations for the synthesis of the
novel TCBD derivatives owing to their considerable stability
and solubility.
Reaction of 3-ethynyl-2H-cyclohepta[b]furan-2-ones with
TCNE: For the synthesis of novel TCBD derivatives, the
[2+2] cycloaddition–cycloreversion sequence of 5–15 with
TCNE was examined according to the procedure described
in the literature.[5,10] Thus, the reaction of 5 with TCNE in
ethyl acetate at reflux yielded 16 in 96% yield (Scheme 5).
The proposed reaction sequence is also shown in
Scheme 5.[17] Initially, TCNE undergoes [2+2] cycloaddition
with an acetylene moiety of 5 to afford the cyclobutene in-
termediate, as drawn in the parentheses (Scheme 5). A sub-
sequent ring-opening reaction of the cyclobutene derivative
gives the thermodynamically stable TCBD product 16. Die-
derich et al. reported that the reaction of TCNE with acety-
lene derivatives substituted by weak electron-donating
arenes, such as anisole and thiophene, required long reac-
tion periods and high reaction temperatures, for example,
110–1708C, in contrast to the high reactivity of the aniline
derivatives.[5b] The reaction of 5 proceeded at a relatively
low reaction temperature (at the refluxing temperature of
ethyl acetate) for a short reaction period. The high reactivity
of the 3-ethynyl-2H-cyclohepta[b]furan-2-one derivative
toward TCNE can be ascribed to the higher electron-donat-
ing properties of 2H-cyclohepta[b]furan-2-one at the 3-posi-
tion relative to that of anisole and thiophene derivatives.
Acetylene derivatives 6–15 were also readily reacted with
TCNE, similar to the reaction of 5, to afford the corre-
sponding TCBD derivatives 17–26. The reaction of 6, 7, and
8 with TCNE afforded the corresponding products 17, 18,
and 19 in 96, 93, and 90% yield, respectively. In contrast to
the Pd-catalyzed reaction of the acetylene derivatives, the
yield of the reaction with TCNE did not depend on the p-
Subsequently, the synthesis of 2H-cyclohepta[b]furan-2-
one-substituted ethynylthiophene derivatives 12, 13, and 14
was accomplished under similar reaction conditions. Deriva-
tive 12 was obtained by the Pd-catalyzed alkynylation of 4
with 2-iodothiophene, whereas 13 and 14 were prepared by
the reaction of 2 with the corresponding ethynylthiophene
derivatives. The reaction of 4 with 2-iodothiophene in the
presence of [PdACHTUNGTRENNUNG(PPh3)4] gave monoadduct 12 in 89% yield.
Bis-adduct 13 and bithiophene derivative 14 were obtained
by the reaction of 2 with 2,5-diethynylthiophene[14] and 5,5’-
diethynyl-2,2’-bithiophene,[15] respectively, in the presence of
5118
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 5116 – 5129

Intramolecular Charge-Transfer Chromophores
FULL PAPER
similar reaction conditions. The reaction of 12 with TCNE
afforded 23 in 99% yield. Although a relatively long reac-
tion period was required, the synthesis of 24 and 25 was es-
tablished in 92 and 90% yields, respectively, under similar
reaction conditions. The tris-adduct 15 was also reacted with
TCNE in 1,2-dichloroethane at reflux instead of ethyl ace-
tate as the solvent, because of low solubility of 15 in ethyl
acetate, to afford 26 in 88% yield. These novel TCBDs 16–
26 were obtained as stable reddish crystals and could be
stored in the crystalline state under ordinary conditions.
Scheme 5.
Spectroscopic properties: The new compounds 2–26 were
fully characterized by the spectral data, as shown in the Ex-
perimental Section. Mass spectra of 2–26 ionized by ESI,
FAB, or EI showed the correct molecular ion signals. The
characteristic stretching vibration band of the ethynyl
moiety of 3–15 was observed at n=2097–2208 cmꢀ1 in the
IR spectra, except for the symmetrically substituted acety-
substituent of the benzene ring. These results indicate the
strong electron-donating property of the 2H-cyclohepta[b]-
furan-2-one moiety. Ferrocene-substituted TCBD 20 was
also obtained in 89% yield by the reaction of 9 with TCNE
in ethyl acetate at refluxing. The reaction of symmetrically
substituted alkyne 10 and azulene-substituted alkyne 11 with
TCNE yielded the corresponding adducts 21 and 22 in 98%
yield.
lene derivative 10. The TCBDs 16–26 exhibited a character-
ꢀ1
ꢁ
istic C N stretching band at n=2191–2225 cm in their IR
spectra. These results are consistent with the structures of
these products.
The [2+2] cycloaddition–cycloreversion sequence of thio-
phene derivatives 12, 13, and 14 with TCNE also afforded
the corresponding TCBDs 23, 24, and 25, respectively, under
The UV/Vis spectra of 2–26 in CH2Cl2 are shown in the
Supporting Information. The UV/Vis spectra of 3–15
showed characteristic absorption bands arising from the 2H-
cyclohepta[b]furan-2-one moiety in the visible region. In the
thiophene derivatives 12–14, bathochromic shifts were ob-
served owing to the extension of the p-electron system
along with increasing of their extinction coefficients. The ab-
sorption maxima (lmax) and the coefficients (loge) of the
TCNE-adducts 16–26 are summarized in Table 1.
Table 1. Absorption maxima [nm] and their coefficients (loge) of 2H-cy-
clohepta[b]furan-2-one-substituted TCBDs 16–26 in dichloromethane.
Sample
lmax [nm] (loge)
Sample
lmax [nm] (loge)
16
17
18
19
20
21
498 (4.27)
495 (4.48)
491 (4.54)
499 (4.21)
484 (4.27), 645 (3.31)
498 (4.54)
22
23
24
25
26
504 (4.46)
494 (4.42)
491 (4.67)
504 (4.82)
499 (4.73)
Most of the new TCBD derivatives showed intense CT
absorption bands in CH2Cl2 in the visible region. Solvato-
chromism was observed as a characteristic feature of dipolar
molecules.[18] A noticeable spectral feature of 16 was the
presence of a distinct absorption band at 498 nm in CH2Cl2,
which blueshifted to 492 nm in less-polar hexane, suggesting
the ICT nature of this band (Figure 1). It is assumed that
the first excited-state has a larger dipole moment that that
of the ground state due to the ICT character from the 2H-
cyclohepta[b]furan-2-one to the TCBD unit.
As similar with 15, compounds 16, 17, and 18 showed a
broad CT absorption band at 498, 495, and 491 nm, respec-
tively (Table 1). Although the longest wavelength absorption
Chem. Eur. J. 2011, 17, 5116 – 5129
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5119

T. Shoji et al.
spectrum of azulene-substituted chromophore 22 featured a
strong absorption band at 504 nm. The CT absorption bands
of bis-substituted thiophene and bithiophene derivatives 24
and 25 displayed larger absorption coefficients than that of
mono-substituted derivative 23. The spectrum of 24 dis-
played a CT absorption band at 491 nm (loge =4.67). The
coefficient of 24 was almost twice as large as that of 23
(lmax =494 nm, loge=4.42), although the absorption maxima
were observed at almost the same wavelengths. Bis-substi-
tuted 25 exhibited a more intense CT absorption band (loge
=4.82) than those of 23 and 24. The absorption maximum
of 25 (lmax =504 nm) exhibited a bathochromic shift relative
to those of 23 and 24, resulting from the extension of the p-
electron system by bithiophene unit. In compound 26, a
strong CT absorption was observed at lmax =499 nm. The in-
tensity of the absorption band was three times larger than
that of 16. The similarity of the absorption maxima of 16
and 26 suggests less effective conjugation of the three
TCBD units of 26 by the 1,3,5-arrangement in the benzene
ring.
Figure 1. UV/Vis spectra of 16 in dichloromethane (black line) and in
hexane (gray line).
maxima of 16–19 resembled each other, the absorption coef-
ficients of 17 and 18 were about twice as large as those of 16
and 19. These differences might be ascribed to the effective
conjugation of 17 and 18 with the phenyl substituent, as il-
lustrated in Scheme 6.
To elucidate the nature of the absorption bands of 16 and
21, time-dependent density functional theory (TD-DFT) cal-
culations at the B3LYP/6-31G** level[20] were carried out on
model compounds 16’ and 21’, in which the isopropyl groups
in 16 and 21 were replaced with H groups (Table 2). The
Table 2. Electronic transitions for 16’ and 21’ derived from the computed
values based on B3LYP/6-31G** method and experimental values from
16 and 21.
Sample Experimental
Computed values
Composition of band[a]
/
lmax [nm] (loge) lmax [nm] Strength CI coefficients
16’
21’
16: 498 (4.27)
21: 495 (4.48)
470
489
0.1374
0.0664
H-1!L/ꢀ0.24
H!L/0.88
H!L+2/ꢀ0.36
H-1!L+1/0.45
H!L/0.88
Scheme 6.
[a] H=HOMO; L=LUMO; CI=configuration interaction.
The UV/Vis spectrum of the TCBD derivative with the
ferrocene substituent, 20, exhibited two broad absorption
bands at 484 and 645 nm, which reflect the existence of two
different CT absorption bands. Previously, Mochida and Ya-
mazaki reported that 2,5-dicyano-3-ferrocenyl-hexa-2,4-di-
frontier Kohn–Sham orbitals of these compounds are shown
in the Supporting Information. Judging from a comparison
between the experimental and the theoretical UV/Vis spec-
tra, the absorption maxima of 16’ and 21’ could be assigned
due to overlap for some transitions. The ICT of 16’ originat-
ed from the HOMO located on 2H-cyclohepta[b]furan-2-
one and the HOMO-1 located at benzene ring to the
LUMO that was mainly located on the TCBD moiety, al-
though the contribution of HOMO-1!LUMO transition
was relatively low. As shown in the Supporting Information,
the HOMO and LUMO of 21’ showed a symmetrical orbital
with respect to the symmetrical structure. The ICT of 21’
confirmed that the longest absorption band arose from the
HOMO located at the two 2H-cyclohepta[b]furan-2-ones to
the LUMO located mainly on the TCBD moiety. The strong
absorption of 21 was attributed to the overlapping of the
dual CT absorption from the two 2H-cyclohepta[b]furan-2-
one moieties to the TCBD unit.
ACHTUNGTRENNUNGenedinitrile (27) exhibited a broad absorption at 632 nm in
dichloromethane.[19] They also concluded that the absorption
band could be assigned to ICT arising from the p–p* transi-
tion between ferrocene and the TCBD moiety. Therefore,
the longest wavelength absorption of compound 20 at
645 nm should be ascribed to the ICT absorption from ferro-
cene to the TCBD unit.
Although symmetrically sub-
stituted compound 21 showed
an absorption at 498 nm, which
was same wavelength as that of
16 (498 nm), the absorption co-
efficient of 21 was about two-
fold larger than that of 16. The
5120
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 5116 – 5129

Intramolecular Charge-Transfer Chromophores
FULL PAPER
Electrochemistry: To clarify the electrochemical properties,
the redox behavior of 16–26 was examined by CV and DPV.
Measurements were carried out with a standard three-elec-
trode configuration. Tetraethylammonium perchlorate
(0.1m) in benzonitrile was used as the supporting electrolyte
with a platinum wire and disk as the auxiliary and working
electrodes, respectively. All measurements were carried out
under an argon atmosphere, and potentials were related to
an Ag/Ag+ reference electrode and Fc/Fc+ as an internal
reference, which discharged at +0.15 V. The redox poten-
tials (in V vs. Ag/AgNO3) of TCNE adducts 16–26 are sum-
marized in Table 3.
Table 3. Redox potentials of 2H-cyclohepta[b]furan-2-one-substituted
TCBDs 16–26.
Figure 2. Cyclic voltammogram of the reduction of 19 (1 mm) in benzoni-
trile containing Et4NClO4 (0.1m) as the supporting electrolyte; scan
Sample Method
Ex1ꢂ [V]
(+1.48)
(+1.02)
(+0.94)
(+1.49)
Er1ed [V]
Er2ed [V]
rate=100 mVsꢀ1
.
16
CV (DPV)
G
ꢀ0.51 (ꢀ0.49) ꢀ0.96 (ꢀ0.94)
ꢀ0.65 (ꢀ0.63) ꢀ1.02 (ꢀ1.00)
ꢀ0.67 (ꢀ0.65) ꢀ1.03 (ꢀ1.01)
ꢀ0.05 (ꢀ0.03) ꢀ0.40 (ꢀ0.38)
+0.47 (+0.49) ꢀ0.70 (ꢀ0.68) ꢀ1.03 (ꢀ1.01)
ꢀ0.47 (ꢀ0.45) ꢀ0.84 (ꢀ0.82)
ꢀ0.56 (ꢀ0.54) ꢀ0.95 (ꢀ0.93)
ꢀ0.55 (ꢀ0.53) ꢀ0.91 (ꢀ0.89)
ꢀ0.29 (ꢀ0.27) ꢀ0.48 (ꢀ0.46)
ꢀ0.46 (ꢀ0.44) ꢀ0.57 (ꢀ0.55)
ꢀ0.37 (ꢀ0.35) ꢀ0.55 (ꢀ0.53)
ꢀ0.61 (ꢀ0.59) ꢀ1.03 (ꢀ1.01)
ꢀ0.64 (ꢀ0.63) ꢀ1.03 (ꢀ1.02)
ꢀ0.31 (ꢀ0.29) ꢀ0.54 (ꢀ0.52)
ꢀ0.40 (ꢀ0.39) ꢀ0.57 (ꢀ0.56)
17
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
CV (DPV)
ACHTUNGTRENNUNG
18
ACHTUNGTRENNUNG
19[b]
20
ACHTUNGTRENNUNG
21
ACHTUNGTRENNUNG
22[c]
23
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
24[d]
25[e]
26[f]
28[10a]
29[10a]
30[10a]
31[10a]
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
[a] Redox potentials were measured by CV and DPV [V vs. Ag/AgNO3,
1 mm in benzonitrile containing Et4NClO4 (0.1m), Pt electrode (internal
diameter: 1.6 mm), scan rate=100 mVsꢀ1, 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] E3red
and Er4ed were observed at ꢀ0.81 (ꢀ0.79) and ꢀ1.08 V (ꢀ1.06 V) by CV
(DPV), respectively. [c] Er3ed was observed at ꢀ1.94 and ꢀ1.92 V by CV
and DPV, respectively. [d] E3red was observed at ꢀ1.00 and ꢀ0.98 V by
CV and DPV, respectively. [e] The Er3ed was observed at ꢀ0.87 and
ꢀ0.85 V by CV and DPV, respectively. [f] Er3ed, E4red and E5red were ob-
served at ꢀ0.72 (ꢀ0.70), ꢀ1.00 (ꢀ0.98) and ꢀ1.11 V (ꢀ1.09 V) on CV
(DPV), respectively.
Scheme 7. Presumed redox behavior of 18. SEM=single-electron moiety.
Electrochemical reduction of 20, 21, and 22 also showed
reversible multistage reduction waves by CV, which could
be attributed to the formation of a radical anionic, dianion-
ic, and so on, species. Ferrocene-substituted 20 exhibited a
reversible two-step reduction wave, the potentials of which
were identified at ꢀ0.70 and ꢀ1.03 V by CV, due to the for-
mation up to a dianionic species. A reversible oxidation
wave was also observed at +0.47 V for 20 by CV, which
could be ascribed to the electrochemical oxidation of the
ferrocene moiety. The oxidation potential of 20 was much
more positive than that of the parent ferrocene (+0.15 V).
This was attributed to the electron-withdrawing nature of
the substituted TCBD moiety. The electrochemical reduc-
tion of 21 showed a reversible two-stage wave by CV (ꢀ0.47
and ꢀ0.84 V) by the formation of up to a dianionic species.
The electrochemical reduction of 22 also displayed a reversi-
ble three-stage reduction wave by CV (ꢀ0.56, ꢀ0.95, and
ꢀ1.94 V). The three-stage reduction may have included the
reduction of the azulene ring in addition to that of the
TCBD moiety. The first reduction potential of 21 (ꢀ0.47 V)
All TCBD chromophores 16–26 showed reversible reduc-
tion waves by CV. As shown in Table 3, TCBD chromo-
phores with benzene substituents (16–19) displayed reversi-
ble two- or four-stage reduction waves, depending on the p-
substituent on the benzene ring. In particular, the TCBD de-
rivative with a p-nitrobenzene substituent (19) exhibited a
reversible four-stage reduction wave, as shown in Figure 2.
These results should be attributable to the generation of tet-
raanionic species owing to further electron acceptance by
the p-nitrobenzene moiety, as illustrated in Scheme 7. The
first reduction potential of 19 (ꢀ0.05 V) was less negative
than those of 16 (ꢀ0.51 V), 17 (ꢀ0.65 V), and 18 (ꢀ0.67 V).
These results reflect that the NO2 substituent on the ben-
zene ring directly results in a decrease of the LUMO level
of the molecule.
Chem. Eur. J. 2011, 17, 5116 – 5129
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5121

T. Shoji et al.
was rather less negative than those of 20 (ꢀ0.70 V) and 22
(ꢀ0.56 V), which indicated that the 2H-cyclohepta[b]furan-
2-one substituent on TCBD decreased the LUMO level
compared with the ferrocene and azulene rings.
Similar to compounds 16–22, electrochemical reduction of
the TCBD derivative with a thiophene substituent (23)
showed a reversible two-stage reduction wave by CV (ꢀ0.55
and ꢀ0.91 V) attributed to the formation of dianionic spe-
cies. A reversible three-stage wave was observed in bis-
adduct 24 by CV (ꢀ0.29, ꢀ0.48, and ꢀ1.00 V), in which the
third reduction wave was a two-electron transfer in one step
to form a tetraanionic species (Figure 3). The electrochemi-
thiophene core resulted in large shifts of the first reduction
potentials (e.g., 23: ꢀ0.55, 24: ꢀ0.29, and 25: ꢀ0.46 V). The
first reduction potential of 24 and 25 reflects the difference
in the spacer between the two TCBD moieties. The reduc-
tion wave of 25 is indicative of two overlapping one-electron
transfers, which means that the two TCBD moieties in the
molecule are reduced independently. The two TCBD units
in 24 might be closer than those in 25; therefore, intramolec-
ular electrostatic interactions between the two TCBD units
decreases the reduction potential that results from the de-
crease in the LUMO level in 24. The electrochemical reduc-
tion of 26 exhibited a reversible five-step reduction wave,
the potentials of which were identified at ꢀ0.35, ꢀ0.53,
ꢀ0.70, ꢀ0.98, and ꢀ1.09 V by DPV, which were attributed
to the formation up to a pentaanionic species.
With respect to the TCBD derivatives, we have already
reported the redox properties of TCBD derivatives with 1-
azulenyl substituents 28, 29, 30, and 31.[10] These compounds
exhibited first oxidation and reduction potentials at +1.27
to +1.32 V, and at ꢀ0.31 to ꢀ0.64 V, respectively. In particu-
lar, compound 31 exhibited a reversible five-stage reduction
wave within a narrow potential range of 0.71 V (from ꢀ0.39
to ꢀ1.10 V). Diederich et al. also reported that the com-
pound with three N,N-dialkylaniline (DAA)-substituted
TCBD units connected through a 1,3,5-benzentriyl spacer
had a six-stage reversible one-electron reduction wave
within a narrow potential range of 1.00 V (from ꢀ0.69 to
ꢀ1.69 V vs. Fc/Fc+).[5b] Similar to azulene derivative 31, the
reduction of 26 also exhibited a reversible five-stage reduc-
tion within a narrow potential range of 0.76 V (from ꢀ0.37
to ꢀ1.11 V), and the less negative first reduction potential
was comparable with those reported in the literatures.[10]
2H-Cyclohepta[b]furan-2-one-substituted TCBDs 16, 23, 24,
and 26 showed less positive oxidation potentials than those
of the corresponding azulene-substituted TCBDs 28, 29, 30,
and 31, although the reduction potentials were higher than
those of the azulene derivatives. It followed from these re-
sults that the 2H-cyclohepta[b]furan-2-one moiety possessed
a lower electron-donating property than the 1-azulenyl-sub-
stituent.
Figure 3. Cyclic voltammogram of the reduction of 24 (1 mm) in benzoni-
trile containing Et4NClO4 (0.1m) as the supporting electrolyte; scan
rate=100 mVsꢀ1
.
cal reduction of bithiophene derivative 25 also showed a re-
versible three-step reduction wave by CV (ꢀ0.46, ꢀ0.57,
and ꢀ0.87 V) due to the formation of up to a tetraanionic
species (Figure 4). In the reduction of thiophene derivatives
23, 24, and 25, the introduction of TCBD substituents to the
Electrochromic analysis: Electrochromism is observed in re-
versible redox systems that exhibit significant color changes
in different oxidation states. Stabilization of the redox cycle
is very important in the construction of electrochromic ma-
terials because the molecules that are utilized for this appli-
cation require high redox stabilities.[21] Hꢁnig et al. proposed
the concept of a violene–cyanine (V–C) hybrid for the pro-
duction of stabilized organic electrochromic materials.[22]
The hybrid was made up of a violene-type redox system
containing delocalized closed-shell polymethine (e.g., cya-
nine) dyes as end groups. Therefore, the redox system with
the hybrid structure should provide the color of cyanine dye
by an overall two-electron transfer, as illustrated in
Scheme 8. The cyanine-type substructure that is generated
by the two electron-transfer is represented by the bold line
in the general structure.
Figure 4. Cyclic voltammogram of the reduction of 25 (1 mm) in benzoni-
trile containing Et4NClO4 (0.1m) as the supporting electrolyte; scan
rate=100 mVsꢀ1
.
5122
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 5116 – 5129

Intramolecular Charge-Transfer Chromophores
FULL PAPER
reduction, with the development of new absorptions in the
visible region at 665 nm. However, reverse oxidation of the
brown-colored solution did not regenerate the spectrum of
16, although good reversibility was observed in the two-step
reduction on CV. The poor reversibility of the color changes
might be attributable to the instability of the presumed dia-
nionic species under the conditions for spectral measure-
ments.
The longest absorptions of 17 and 18 gradually decreased
and the color of the solution changed from red to yellow
during the electrochemical reduction. However, reversible
oxidation of the yellow-colored solution did not regenerate
the spectrum of the corresponding starting compounds com-
pletely. The UV/Vis spectrum of 19 was measured under
electrochemical reduction conditions; the absorption of 19
in the visible region gradually decreased with the appear-
ance of a new absorption band in the near-infrared region.
In contrast to the results on the electrochemical reduction
of 17 and 18, reverse oxidation regenerated the original ab-
sorptions of 19. The good reversibility for the redox process
of 19 indicates the generation of stabilized anionic species
because of substitution by an electron-withdrawing group at
the p-position of the benzene ring.
The orange color of the solution of 20 changed to yellow
during electrochemical reduction, but reverse oxidation of
the orange-colored solution regenerated the UV/Vis spec-
trum of 20. When the UV/Vis spectrum of 21 was measured
under electrochemical reduction conditions, the absorption
in the visible region gradually decreased and a new absorp-
tion in the visible region at 670 nm, which was beyond to
near-infrared region, gradually developed. The reverse oxi-
dation decreased the new absorption band, but did not re-
generate the absorption band of 21 completely. The color of
the solution of 22 gradually changed from red to colorless
and electrochemical reduction led to the disappearance of
the new absorption band. However, reverse oxidation of the
generated colorless solution did not regenerate the spectrum
of 22. The absorption bands of 23 in the visible region also
gradually disappeared during electrochemical reduction, but
reverse oxidation regenerated the absorption of 23 incom-
pletely. Significant reversible color changes were also ob-
served in thiophene derivatives 24 and 25. When the spec-
tral changes of 24 were measured during the electrochemical
reduction, the absorption in the visible region gradually de-
creased with the development of new absorptions at 635 nm,
which were in the near-infrared region. Reverse oxidation
decreased the new absorptions and the original color of 24
was regenerated (Figure 5). A reversible color change was
observed in the visible spectra of 25 under electrochemical
reduction conditions. At the beginning, new absorptions in
the visible region at 700 nm, which reached to the near-in-
frared region, gradually developed and the orange color of
the solution changed to yellow during the electrochemical
reduction. On reverse oxidation, the new absorption in the
near-infrared region decreased and the original absorption
of 25 in the visible region was regenerated. The reversible
color change and development of the absorption up to the
Scheme 8. General structure of Hꢁnigꢂs violene–cyanine hybrids.
Contrary to the violene-type redox system, both colored
and discolored species consist of closed-shell structures.
Therefore, persistency of the electrochromic system would
be improved by adopting the hybrid structure.
We have reported the synthesis of various azulene-substi-
tuted, redox-active chromophores with the aim of creating
stabilized electrochromic materials.[23] As a part of this
study, we have also reported several 1-azulene-substituted
novel TCBDs, as described herein, in which we identified
some novel hybrid structures of V and C with the redox ac-
tivities.[10,24] The bis(1-azulene)-substituted TCBD (30),
which exhibits multiple color changes during the electro-
chemical reduction, is a successful example of an extension
of the V–C hybrid structure. Similar to 1-azulene-substituted
TCBDs, 2H-cyclohepta[b]furan-2-one TCBDs 16–26 might
be used as examples of redox systems for the extensions of
the V–C hybrid system with multielectron transfer. Thus,
the UV/Vis spectra of TCBDs 16–26 were monitored to clar-
ify the color changes observed during the electrochemical
reactions.
A constant-current reduction was applied to solutions of
16–26 with a platinum mesh as the working electrode and a
wire counter electrode. UV/Vis spectra were measured in
degassed benzonitrile containing Et4NClO4 (0.1m) as the
supporting electrolyte at room temperature under electro-
chemical reduction conditions (see the Supporting Informa-
tion). The longest absorption of 16 at 498 nm gradually de-
creased, and thus, the color of the solution gradually
changed from orange to pale green during electrochemical
Chem. Eur. J. 2011, 17, 5116 – 5129
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5123

T. Shoji et al.
or 1,3,5-benzenetriyl spacers. Strong intramolecular CT ab-
sorption bands were found in the UV/Vis spectra of these
2H-cyclohepta[b]furan-2-one-substituted TCBDs, the transi-
tion states of which were characterized by TD-DFT calcula-
tions. An analysis by CV and DPV showed that compounds
16–26 exhibited a multistep reduction wave, depending on
the number of TCBD units in the molecule. Moreover, a sig-
nificant color change was observed during electrochemical
reduction. In particular, thiophene derivatives 24 and 25 ex-
hibited a significant color change, arising from the genera-
tion of thienoquinoid structures during electrochemical re-
duction. These results showed that 24 and 25 behaved like a
V–C hybrid, a concept proposed by Hꢁnig and co-work-
ers,[22] in view of the formation of the stabilized thienoqui-
noid formed by the two-electron reduction.
These results would warrant the use of these donor–ac-
ceptor systems as organic electronic and optoelectronic ma-
terials. To evaluate the scope of this class of molecules in-
vestigated by this research, the preparation of novel 2H-cy-
clohepta[b]furan-2-one chromophores connected with vari-
ous p-electron cores is now in progress in our laboratory.
Experimental Section
General: Melting points were determined with a Yanagimoto MPS3
micro melting apparatus and are uncorrected. Mass spectra were ob-
tained with JEOL HX-110, Hitachi M-2500, or Bruker APEX II instru-
ments, usually at 70 eV. IR and UV/Vis spectra were measured with Shi-
madzu FTIR-8100M and Hitachi U-3410 spectrophotometers, respective-
ly. 1H and 13C NMR spectra were recorded with a JEOL GSX 400 spec-
trometer (at 400 and 100 MHz, respectively), or a JEOL JNM A500 spec-
trometer (at 500 and 125 MHz, respectively). Gel permeation
Figure 5. Continuous change in the UV/Vis spectrum of 24: constant-cur-
rent electrochemical reduction (100 mA, top) and reverse oxidation of the
reduced species (50 mA, bottom) in benzonitrile containing Et4NClO4
(0.1m) at 30 s intervals.
chromatography (GPC) purification was performed with
a TSKgel
G2000H6 instrument with CHCl3 as an eluent. Voltammetry measure-
ments were carried out with a BAS 100B/W electrochemical workstation
equipped with Pt working and auxiliary electrodes and a reference elec-
trode formed from Ag/AgNO3 (0.01m) in acetonitrile containing tetrabu-
tylammonium perchlorate (0.1m). Elemental analyses were performed at
the Research and Analytical Center for Giant Molecules, Graduate
School of Science, Tohoku University.
near-infrared region of 24 and 25 suggested the formation of
a stabilized closed-shell dianionic species with a thienoqui-
noid structure in the two-electron reduction, as well as the
phenomenon observed in azulene derivatives.[10a,24] Although
the color of the solution of 26 gradually changed from red
to yellow under electrochemical reduction, reverse oxidation
of the yellow-colored solution did not regenerate the origi-
nal color of 26.
Compound 2: N-Iodosuccinimide (1.69 g, 7.51 mmol) was added to a so-
lution of 1 (1.18 g, 6.27 mmol) in CH2Cl2 (20 mL) at room temperature.
The resulting mixture was stirred at the same temperature for 40 min
under an Ar atmosphere. After the solvent was removed under reduced
pressure, the crude product was purified by column chromatography on
silica gel with CH2Cl2/AcOEt as the eluent to give 2 as orange crystals
(1.79 g, 91%). M.p. 111.5–113.08C (MeOH); 1H NMR (500 MHz,
CDCl3): d=7.20 (d, J=1.5 Hz, 1H; H4), 7.05 (dd, J=11.5, 9.0 Hz, 1H;
H7), 6.89 (dd, J=11.5, 1.5 Hz, 1H; H6), 6.87 (d, J=9.0 Hz, 1H; H8), 2.92
(sept, J=7.0 Hz, 1H; iPr), 1.30 ppm (d, J=7.0 Hz, 6H; iPr); 13C NMR
(100 MHz, CDCl3): d=167.0, 158.8, 158.6, 153.2, 133.2, 132.7, 126.9,
113.1, 62.1, 39.6, 23.6 ppm; IR (KBr disk): nmax =3296 (m), 2926 (w), 2863
(w), 1771 (w), 1725 (s, C=O), 1634 (m), 1595 (s), 1510 (s), 1495 (s), 1462
(m), 1416 (m), 1387 (m), 1366 (w), 1314 (w), 1294 (m), 1269 (s), 1229 (s),
1130 (w), 1071 (w), 1053 (m), 1040 (w), 1015 (w), 938 (w), 912 (w), 897
(m), 891 (m), 855 (w), 795 (m), 752 (w), 741 (m), 712 (w), 650 (m), 613
(w), 592 (w), 426 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=270 (4.30),
391 (4.25), 405 nm (4.25); HRMS (ESI): m/z calcd for [C12H11IO2+Na]+:
336.9696; found: 336.9695; elemental analysis calcd (%) for C12H11IO2: C
45.88, H 3.53; found: C 45.79, H 3.64.
Conclusion
Several 3-ethynyl-2H-cyclohepta[b]furan-2-one derivatives
(5–15) were prepared by the Sonogashira–Hagihara reac-
tion. A series of 2H-cyclohepta[b]furan-2-one-substituted
TCBD chromophores (16–26) were synthesized in a one-
step procedure consisting of the formal [2+2] cycloaddition
reaction of 5–15 with TCNE, followed by the ring-opening
reaction of the initially formed cyclobutene derivatives. Sim-
ilar to the synthesis of monomeric TCBDs 16–23, dimeric
and trimeric TCBDs 24–26 were also prepared in excellent
yields from 2H-cyclohepta[b]furan-2-one-substituted alkynes
connected with 2,5-thiophenediyl and 5,5’-bithiophenediyl
Compound 3: [Pd
ACHTUNGTREN(UNNG PPh3)4] (107 mg, 0.093 mmol) was added to a degassed
solution of (608 mg, 1.94 mmol), trimethylsilylacetylene (261 mg,
2
5124
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 5116 – 5129

Intramolecular Charge-Transfer Chromophores
FULL PAPER
2.66 mmol), CuI (36 mg, 0.19 mmol), and triethylamine (20 mL) in THF
(20 mL). The resulting mixture was stirred at 508C for 2 h under an Ar
atmosphere. The reaction mixture was poured into a 10% aqueous solu-
tion of NH4Cl and was extracted with chloroform. The organic layer was
washed with brine, dried over MgSO4, and concentrated under reduced
pressure. The residue was purified by column chromatography on silica
gel with chloroform as the eluent to give 3 as orange needles (570 mg,
97%). M.p. 111.5–113.08C (MeOH); 1H NMR (500 MHz, CDCl3): d=
7.40 (d, J=1.5 Hz, 1H; H4), 7.07 (dd, J=11.5, 9.0 Hz, 1H; H7), 6.93 (dd,
J=9.0, 0.5 Hz, 1H; H8), 6.87 (ddd, J=11.5, 1.5, 0.5 Hz, 1H; H6), 2.90
(sept, J=7.0 Hz, 1H; iPr), 1.30 (d, J=7.0 Hz, 6H; iPr), 0.29 ppm (s, 9H;
TMS); 13C NMR (100 MHz, CDCl3): d=167.9, 158.3, 157.7, 152.7, 133.57,
133.55, 125.8, 114.6, 106.0, 95.0, 94.2, 39.4, 23.6, 0.5 ppm; IR (KBr disk):
Compound 6: [PdACTHNGUTERN(NUG PPh3)4] (58 mg, 0.050 mmol) was added to a degassed
solution of 2 (314 mg, 1.00 mmol), 4-ethynylaniline (176 mg, 1.50 mmol),
CuI (19 mg, 0.10 mmol), and triethylamine (5 mL) in THF (5 mL). The
resulting mixture was stirred at 508C for 2 h under an Ar atmosphere.
The reaction mixture was poured into a 10% aqueous solution of NH4Cl
and was extracted with dichloromethane. The organic layer was washed
with brine, dried over MgSO4, and concentrated under reduced pressure.
The residue was purified by column chromatography on silica gel with di-
chloromethane as the eluent to give 6 as brown crystals (297 mg, 98%).
M.p. 173.0–174.08C (MeOH); 1H NMR (400 MHz, CDCl3): d=7.42 (d,
J=1.6 Hz, 1H; H4), 7.38 (dd, J=8.4, 2.4 Hz, 2H; H2’,6’), 7.00 (dd, J=11.6,
8.8 Hz, 1H; H7), 6.87 (dd, J=8.8, 0.8 Hz, 1H; H8), 6.80 (ddd, J=11.6,
1.6, 0.8 Hz, 1H; H6), 6.64 (dd, J=8.4, 2.4 Hz, 2H; H3’,5’), 3.88 (s, 2H;
NH2), 2.88 (sept, J=6.8 Hz, 1H; iPr), 1.29 ppm (d, J=6.8 Hz, 6H; iPr);
13C NMR (100 MHz, CDCl3): d=167.7, 157.3, 156.9, 150.2, 147.0, 133.0,
132.7, 132.5, 125.3, 114.6, 113.4, 112.1, 100.4, 94.7, 38.9, 23.0 ppm; IR
(KBr disk): nmax =3464 (m), 3369 (m), 3213 (w), 2959 (m), 2926 (w), 2870
ꢁ
nmax =2963 (w), 2932 (w), 2905 (w), 2139 (m, C C), 1763 (s, C=O), 1593
(m), 1523 (s), 1503 (m), 1485 (w), 1462 (w), 1431 (w), 1399 (w), 1333 (w),
1298 (m), 1277 (s), 1246 (s), 1202 (w), 1134 (w), 1082 (w), 1032 (w), 928
(w), 907 (w), 855 (s), 841 (s), 789 (m), 756 (m), 708 (w), 646 (w),
419 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=273 (4.30), 282 (4.30), 410
(4.30), 426 nm (4.33); HRMS (ESI): m/z calcd for [C17H20O2Si+Na]+:
307.1125; found: 307.1123; elemental analysis calcd (%) for C17H20O2Si:
C 71.79, H 7.09; found: C 71.64, H 6.98.
ꢁ
(w), 2199 (m, C C), 1734 (s, C=O), 1620 (m), 1603 (s), 1541 (m), 1508
(s), 1461 (w), 1429 (m), 1400 (w), 1383 (w), 1364 (w), 1344 (w), 1296 (m),
1281 (m), 1261 (w), 1223 (m), 1178 (w), 1157 (w), 1059 (w), 1036 (w), 903
(w), 833 (m), 779 (m), 756 (m), 642 (w), 527 cmꢀ1 (m); UV/Vis (CH2Cl2):
lmax (loge)=232 (4.43), 270 (4.42), 283 (4.38), 303 (4.30), 435 nm (4.39);
HRMS (ESI): m/z calcd for [C20H17NO2+Na]+: 326.1151; found:
326.1150; elemental analysis calcd (%) for C20H17NO2·1/5H2O: C 78.26,
H 5.71, N 4.56; found: C 78.11, H 5.89, N 4.67.
Compound 4: K2CO3 (1.38 g, 10.0 mmol) was added to a solution of 3
(540 mg, 1.90 mmol) in MeOH (10 mL), THF (3 mL), and water (3 mL).
The resulting mixture was stirred at room temperature for 3 h. The reac-
tion mixture was poured into water and extracted with chloroform. The
organic layer was washed with brine, dried over MgSO4, and concentrat-
ed under reduced pressure. The residue was purified by column chroma-
tography on silica gel with chloroform as the eluent to give 4 as orange
needles (381 mg, 95%). M.p. 77.0–78.08C (MeOH); 1H NMR (400 MHz,
CDCl3): d=7.45 (dd, J=1.6, 0.8 Hz, 1H; H4), 7.11 (dd, J=11.6, 8.8 Hz,
1H; H7), 7.00 (dd, J=8.8, 1.2 Hz, 1H; H8), 6.92 (ddd, J=11.6, 1.2,
Compound 7: [Pd
solution of
ACHTUNGTRENNUNG
2
(218 mg, 1.50 mmol), CuI (19 mg, 0.10 mmol), and triethylamine (5 mL)
in THF (5 mL). The resulting mixture was stirred at 508C for 2 h under
an Ar atmosphere. The reaction mixture was poured into a 10% aqueous
solution of NH4Cl and was extracted with dichloromethane. The organic
layer was washed with brine, dried over MgSO4, and concentrated under
reduced pressure. The residue was purified by column chromatography
on silica gel with dichloromethane as the eluent to give 7 as brown crys-
tals (322 mg, 97%). M.p. 138.0–142.08C (MeOH); 1H NMR (400 MHz,
CDCl3): d=7.45 (dd, J=8.4, 2.4 Hz, 2H; H2’,6’), 7.42 (d, J=1.2 Hz, 1H;
H4), 6.98 (dd, J=11.6, 8.8 Hz, 1H; H7), 6.84 (dd, J=8.8, 0.8 Hz, 1H; H8),
6.78 (ddd, J=11.6, 1.2, 0.8 Hz, 1H; H6), 6.66 (ddd, J=8.4, 2.4, 1.6 Hz,
2H; H3’,5’), 3.01 (s, 6H; NMe2), 2.88 (sept, J=6.8 Hz, 1H; iPr), 1.29 ppm
(d, J=6.8 Hz, 6H; iPr); 13C NMR (100 MHz, CDCl3): d=167.7, 157.4,
156.6, 150.2, 149.9, 132.8, 132.6, 132.4, 125.3, 113.1, 111.7, 109.6, 101.0,
95.1, 77.5, 40.1, 38.8, 23.0 ppm; IR (KBr disk): nmax =2966 (w), 2834 (w),
ꢁ
0.8 Hz, 1H; H6), 3.60 (s, 1H; C CH), 2.92 (sept, J=6.8 Hz, 1H; iPr),
1.30 ppm (d, J=6.8 Hz, 6H; iPr); 13C NMR (100 MHz, CDCl3): d=168.2,
158.8, 157.6, 153.1, 133.7, 133.5, 125.7, 115.0, 92.8, 87.5, 74.4, 39.5,
ꢁ
23.6 ppm; IR (KBr disk): nmax =2969 (w), 2928 (w), 2874 (w), 2097 (w, C
C), 1802 (w), 1761 (s, C=O), 1593 (m), 1522 (s), 1499 (m), 1485 (m), 1331
(w), 1314 (w), 1300 (w), 1275 (m), 1246 (m), 1080 (w), 1059 (w), 1040
(w), 1026 (w), 920 (w), 891 (w), 878 (w), 797 (m), 756 (w), 708 (w), 693
(w), 660 (w), 648 (w), 608 cmꢀ1 (m); UV/Vis (CH2Cl2): lmax (loge)=271
(4.33), 276 sh (4.31), 402 (4.26), 418 nm (4.28); HRMS (ESI): m/z calcd
for [C14H12O2+Na]+: 235.0730; found: 235.0728; elemental analysis calcd
(%) for C14H12O2·1/10H2O: C 78.56, H 5.74; found: C 78.44, H 5.73.
ꢁ
2808 (w), 2191 (w, C C), 1751 (s, C=O), 1611 (s), 1595 (m), 1543 (w),
1514 (s), 1497 (m), 1462 (w), 1445 (w), 1425 (w), 1398 (w), 1364 (m),
1339 (w), 1302 (w), 1279 (m), 1225 (m), 1188 (w), 1157 (w), 1123 (w),
1070 (w), 1059 (w), 1040 (w), 1026 (w), 943 (w), 930 (w), 903 (w), 812
(m), 785 (w), 758 (w), 644 (w), 530 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax
(loge)=234 (4.46), 263 sh (4.30), 278 (4.40), 298 (4.43), 311 sh (4.38), 364
sh (3.83), 449 nm (4.39); found: 354.1454; HRMS (ESI): m/z calcd for
[C22H21NO2+Na]+: 354.1465; elemental analysis calcd (%) for
C22H21NO2·1/2H2O: C 77.62, H 6.51, N 4.11; found: C 77.79, H 6.43, N
4.08.
Compound 5: [PdACHTUNGTRENNUNG(PPh3)4] (58 mg, 0.050 mmol) was added to a degassed
solution of 2 (314 mg, 1.00 mmol), phenylacetylene (154 mg, 1.51 mmol),
CuI (19 mg, 0.10 mmol), and triethylamine (5 mL) in THF (5 mL). The
resulting mixture was stirred at 508C for 15 h under an Ar atmosphere.
The reaction mixture was poured into a 10% aqueous solution of NH4Cl
and was extracted with dichloromethane. The organic layer was washed
with brine, dried over MgSO4, and concentrated under reduced pressure.
The residue was purified by column chromatography on silica gel with di-
chloromethane as the eluent to give 5 as orange needles (285 mg, 99%).
M.p. 114.0–115.08C (MeOH); 1H NMR (500 MHz, CDCl3): d=7.58–7.56
(m, 2H; m-Ph), 7.48 (d, J=1.5 Hz, 1H; H4), 7.37–7.34 (m, 3H; o-, p-Ph),
7.06 (dd, J=11.5, 9.0 Hz, 1H; H7), 6.94 (dd, J=9.0, 1.0 Hz, 1H; H8), 6.87
(ddd, J=11.5, 1.5, 0.5 Hz, 1H; H6), 2.92 (sept, J=7.0 Hz, 1H; iPr),
1.31 ppm (d, J=7.0 Hz, 6H; iPr); 13C NMR (100 MHz, CDCl3): d=167.9,
158.1, 157.9, 151.6, 133.6, 133.3, 132.1, 129.0, 128.8, 125.9, 123.5, 114.4,
99.8, 94.4, 80.1, 39.5, 23.6 ppm; IR (KBr disk): nmax =3050 (w), 2965 (w),
Compound 8: [PdACTHNUTRGNE(UNG PPh3)4] (58 mg, 0.050 mmol) was added to a degassed
solution of 2 (314 mg, 1.00 mmol), 1-ethynyl-4-nitrobenzene (220 mg,
1.50 mmol), CuI (19 mg, 0.10 mmol), and triethylamine (5 mL) in THF
(5 mL). The resulting mixture was stirred at 508C for 24 h under an Ar
atmosphere. The reaction mixture was poured into a 10% aqueous solu-
tion of NH4Cl and was extracted with dichloromethane. The organic
layer was washed with brine, dried over MgSO4, and concentrated under
reduced pressure. The residue was purified by column chromatography
on silica gel with dichloromethane as the eluent to give 8 as reddish
brown crystals (200 mg, 60%). M.p. 187.5–190.58C (MeOH); 1H NMR
(400 MHz, CDCl3): d=8.23 (dd, J=8.8, 2.0 Hz, 2H; H3’,5’), 7.70 (dd, J=
8.8, 2.0 Hz, 2H; H2’,6’), 7.52 (d, J=1.2 Hz, 1H; H4), 7.18 (dd, J=11.2,
9.2 Hz, 1H; H7), 7.06 (dd, J=9.2, 0.8 Hz, 1H; H8), 6.98 (ddd, J=11.2,
1.2, 0.8 Hz, 1H; H6), 2.98 (sept, J=6.8 Hz, 1H; iPr), 1.34 ppm (d, J=
6.8 Hz, 6H; iPr); 13C NMR (100 MHz, CDCl3): d=167.1, 158.9, 157.6,
151.9, 146.9, 133.9, 133.3, 132.0, 130.0, 125.61, 123.7, 115.1, 97.4, 92.3,
85.4, 39.2, 23.2 ppm; IR (KBr disk): nmax =2963 (w), 2928 (w), 2866 (w),
ꢁ
2926 (w), 2870 (w), 2193 (w, C C), 1750 (s, C=O), 1601 (m), 1592 (m),
1524 (s), 1497 (s), 1480 (m), 1447 (w), 1431 (w), 1397 (w), 1385 (w), 1366
(w), 1339 (m), 1312 (w), 1285 (w), 1219 (m), 1061 (w), 1038 (w), 924 (w),
911 (w), 878 (w), 789 (w), 766 (m), 756 (w), 706 (w), 693 (w), 652 (w),
640 (w), 594 (w), 571 (w), 532 (w), 419 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax
(loge)=237 (4.42), 281 (4.33), 296 (4.30), 319 (3.34), 426 nm (4.40);
HRMS (ESI): m/z calcd for [C20H16O2+Na]+: 311.1043; found: 311.1041;
elemental analysis calcd (%) for C20H16O2: C 83.31, H 5.59; found: C
83.08, H 5.71.
Chem. Eur. J. 2011, 17, 5116 – 5129
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5125

T. Shoji et al.
ꢁ
2191 (w, C C), 1765 (m, C=O), 1740 (m, C=O), 1589 (m), 1516 (s, NO2),
to give 11 as brown needles (417 mg, 95%). M.p. 190.0–193.08C
(MeOH); 1H NMR (400 MHz, CDCl3): d=9.74 (s, 1H; H4’), 8.74 (d, J=
10.0 Hz, 1H; H8’), 8.50 (s, 1H; H2’), 7.84 (d, J=10.0 Hz, 1H; H6’), 7.55
(dd, J=10.0, 10.0 Hz, 1H; H7’), 7.53 (s, 1H; H4), 7.03 (dd, J=11.6,
9.2 Hz, 1H; H7), 6.91 (d, J=9.2 Hz, 1H; H8), 6.83 (d, J=11.6 Hz, 1H;
H6), 3.97 (s, 3H; CO2Me), 3.43 (sept, J=6.8 Hz, 1H; iPr), 2.93 (sept, J=
6.8 Hz, 1H; iPr), 1.43 (d, J=6.8 Hz, 6H; iPr), 1.33 ppm (d, J=6.8 Hz,
6H; iPr); 13C NMR (100 MHz, CDCl3): d=167.6, 165.4, 157.4, 157.1,
150.8, 149.8, 144.7, 142.4, 141.3, 139.5, 138.3, 136.5, 132.8, 132.7, 127.8,
125.3, 115.1, 113.5, 108.8, 95.0, 94.8, 83.9, 51.2, 39.2, 38.9, 24.6, 23.1 ppm;
1493 (s), 1475 (m), 1464 (m), 1435 (w), 1400 (w), 1373 (w), 1339 (s, NO2),
1312 (m), 1277 (m), 1261 (w), 1229 (w), 1175 (w), 1105 (w), 1061 (w),
1038 (w), 930 (w), 853 (m), 804 (w), 758 (w), 746 (w), 710 (w), 685 (w),
665 (w), 650 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=237 (4.39), 271
(4.23), 310 sh (3.83), 353 sh (3.82), 380 sh (3.94), 446 nm (4.43); HRMS
(ESI): m/z calcd for [C20H15NO4+Na]+: 356.0893; found: 356.0892; ele-
mental analysis calcd (%) for C20H15NO4·1/2H2O: C 70.17, H 4.71, N
4.09; found: C 70.35, H 4.78, N 4.05.
Compound 9: [PdACHTUNGTRENNUNG(PPh3)4] (58 mg, 0.050 mmol) was added to a degassed
ꢁ
IR (KBr disk): nmax =2964 (m), 2933 (w), 2871 (w), 2185 (m, C C), 1747
solution of 2 (314 mg, 1.00 mmol), ethynylferrocene (211 mg, 1.00 mmol),
CuI (19 mg, 0.10 mmol), and triethylamine (5 mL) in THF (5 mL). The
resulting mixture was stirred at 508C for 2 h under an Ar atmosphere.
The reaction mixture was poured into a 10% aqueous solution of NH4Cl
and was extracted with dichloromethane. The organic layer was washed
with brine, dried over MgSO4, and concentrated under reduced pressure.
The residue was purified by column chromatography on silica gel with di-
chloromethane as the eluent to give 9 as brown crystals (384 mg, 90%).
(s, C=O), 1687 (s, C=O), 1591 (s), 1542 (s), 1508 (s), 1496 (s), 1481 (m),
1446 (s), 1419 (s), 1379 (m), 1328 (w), 1309 (m), 1269 (m), 1211 (s), 1193
(s), 1166 (s), 1122 (m), 1068 (m), 1049 (m), 1035 (m), 1010 (w), 916 (m),
879 (w), 866 (w), 800 (w), 785 (m), 771 (m), 756 (m), 740 (w), 705 (w),
644 (m), 599 (w), 588 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=242
(4.63), 282 (4.66), 316 sh (4.45), 461 nm (4.43); HRMS (ESI): m/z calcd
for [C29H26O4+Na]+: 461.1729; found: 461.1723; elemental analysis calcd
(%) for C29H26O4: C 79.43, H 5.98; found: C 79.33, H 6.00.
1
M.p. 99.0–102.08C (MeOH); H NMR (400 MHz, CDCl3): d=7.39 (d, J=
0.8 Hz, 1H; H4), 7.01 (dd, J=10.8, 9.6 Hz, 1H; H7), 6.88 (dd, J=9.6,
0.8 Hz, 1H; H8), 6.81 (dd, J=10.8, 0.8 Hz, 1H; H6), 4.55 (dd, J=2.0,
2.0 Hz, 2H; H2’,5ꢂ of Fc), 4.28 (dd, J=2.0, 2.0 Hz, 2H; H3’,4ꢂ of Fc), 4.26 (s,
5H; Cp of Fc), 2.89 (sept, J=6.8 Hz, 1H; iPr), 1.31 ppm (d, J=6.8 Hz,
6H; iPr); 13C NMR (100 MHz, CDCl3): d=167.5, 157.4, 157.0, 150.6,
132.8, 132.6, 125.2, 113.3, 98.8, 94.9, 75.5, 71.7, 70.2, 69.1, 64.8, 38.9,
23.1 ppm; IR (KBr disk): nmax =3108 (w), 3100 (w), 3058 (w), 2980 (w),
Compound 12: [PdACTHNUTRGNEUNG(PPh3)4] (15 mg, 0.013 mmol) was added to a degassed
solution of 4 (53 mg, 0.25 mmol), 2-iodothiophene (88 mg, 0.42 mmol),
CuI (5 mg, 0.02 mmol), and triethylamine (5 mL) in THF (5 mL). The re-
sulting mixture was stirred at 508C for 3 h under an Ar atmosphere. The
reaction mixture was poured into a 10% aqueous solution of NH4Cl and
was extracted with dichloromethane. The organic layer was washed with
brine, dried over MgSO4, and concentrated under reduced pressure. The
residue was purified by column chromatography on silica gel with di-
chloromethane as the eluent to give 12 as reddish orange needles (66 mg,
89%). M.p. 101.0–103.08C (MeOH); 1H NMR (400 MHz, CDCl3): d=
7.45 (d, J=1.2 Hz, 1H; H4), 7.34 (dd, J=3.6, 1.2 Hz, 1H; H3ꢂ of Th), 7.33
(dd, J=5.2, 1.2 Hz, 1H; H5ꢂ of Th), 7.09 (dd, J=11.2, 8.8 Hz, 1H; H7),
7.03 (dd, J=5.2, 3.6 Hz, 1H; H4ꢂ of Th), 6.96 (dd, J=8.8, 0.8 Hz, 1H;
H8), 6.89 (ddd, J=11.2, 1.2, 0.8 Hz, 1H; H6), 2.92 (sept, J=6.8 Hz, 1H;
iPr), 1.30 ppm (d, J=6.8 Hz, 6H; iPr); 13C NMR (100 MHz, CDCl3): d=
167.2, 157.9, 157.4, 151.0, 133.2, 132.8, 132.3, 127.7, 127.2, 125.5, 123.0,
114.2, 93.5, 92.2, 83.2, 39.0, 23.1 ppm; IR (KBr disk): nmax =3100 (w),
ꢁ
2961 (w), 2928 (w), 2874 (w), 2207 (w, C C), 1786 (w), 1750 (s, C=O),
1595 (m), 1539 (m), 1501 (s), 1451 (m), 1424 (w), 1412 (w), 1385 (w),
1327 (w), 1308 (m), 1287 (m), 1223 (m), 1105 (w), 1067 (w), 1034 (w), 999
(w), 936 (w), 903 (w), 880 (w), 862 (w), 843 (w), 820 (m), 806 (w), 789
(m), 754 (w), 743 (w), 706 (w), 681 (w), 640 (w), 594 (w), 532 (w), 513
(w), 504 (m), 448 (m), 461 (w), 444 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax
(loge)=274 (4.35), 422 (4.29), 516 nm sh (3.67); HRMS (ESI): m/z calcd
for [C24H20FeO2+Na]+: 419.0705; found: 419.0705; elemental analysis
calcd (%) for C24H20FeO2·1/3H2O: C 71.66, H 5.18; found: C 71.63, H
5.20.
ꢁ
3075 (w), 2982 (w), 2965 (w), 2951 (w), 2928 (w), 2193 (w, C C), 1740 (s,
Compound 10: [PdACHTUNGTRENNUNG(PPh3)4] (14 mg, 0.012 mmol) was added to a degassed
C=O), 1636 (w), 1592 (s), 1541 (m), 1509 (s), 1501 (s), 1464 (w), 1435
(m), 1420 (w), 1395 (w), 1364 (w), 1352 (w), 1329 (w), 1310 (w), 1271 (s),
1225 (m), 1202 (w), 1186 (w), 1057 (w), 893 (w), 880 (w), 851 (w), 822
(w), 797 (w), 756 (w), 749 (w), 708 (w), 696 (m), 652 (w), 644 (w), 596
(w), 585 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=260 (4.33), 271 sh
(4.29), 296 sh (4.09), 310 (4.31), 431 nm (4.38); HRMS (ESI): m/z calcd
for [C18H14O2S+Na]+: 317.0607; found: 317.0605; elemental analysis
calcd (%) for C18H14O2S·1/6H2O: C 72.70, H 4.86; found: C 72.76, H
4.84.
solution of 2 (75 mg, 0.24 mmol), 4 (50 mg, 0.24 mmol), CuI (6 mg,
0.03 mmol), and triethylamine (5 mL) in THF (5 mL). The resulting mix-
ture was stirred at 508C for 2 h under an Ar atmosphere. The reaction
mixture was poured into a 10% aqueous solution of NH4Cl and was ex-
tracted with dichloromethane. The organic layer was washed with brine,
dried over MgSO4, and concentrated under reduced pressure. The residue
was purified by column chromatography on silica gel with dichlorome-
thane as the eluent to give 10 as brown needles (85 mg, 91%). M.p.
268.5–270.08C (MeOH); 1H NMR (400 MHz, CDCl3): d=7.58 (dd, J=
1.6, 0.8 Hz, 1H; H4), 7.08 (dd, J=11.6, 9.2 Hz, 1H; H7), 6.96 (dd, J=9.2,
0.8 Hz, 1H; H8), 6.89 (ddd, J=11.6, 1.6, 0.8 Hz, 1H; H6), 2.95 (sept, J=
6.8 Hz, 1H; iPr), 1.31 ppm (d, J=6.8 Hz, 6H; iPr); 13C NMR (100 MHz,
CDCl3): d=167.3, 158.1, 157.5, 150.5, 133.2, 133.0, 126.1, 114.2, 93.7, 89.8,
39.1, 23.1 ppm; IR (KBr disk): nmax =3056 (w), 2979 (w), 2955 (w), 2924
(w), 2867 (w), 1790 (w), 1759 (s, C=O), 1630 (w), 1588 (m), 1547 (m),
1518 (m), 1489 (s), 1466 (m), 1433 (m), 1391 (w), 1341 (w), 1300 (w),
1283 (m), 1273 (m), 1237 (m), 1076 (w), 1005 (w), 903 (w), 876 (w), 795
(m), 754 (w), 741 (w), 706 (w), 677 (w), 646 (w), 608 cmꢀ1 (w); UV/Vis
(CH2Cl2): lmax (loge)=235 (4.57), 263 (4.59), 304 sh (3.78), 367 sh (3.92),
394 sh (4.09), 421 sh (4.26), 485 nm (4.51); HRMS (ESI): m/z calcd for
[C26H22O4+Na]+: 421.1410; found: 421.1411; elemental analysis calcd
(%) for C26H22O4·1/4H2O: C 77.50, H 5.63; found: C 77.21, H 5.62.
Compound 13: [Pd
ACHTUNGTRNEN(UNG PPh3)4] (58 mg, 0.050 mmol) was added to a degassed
solution of (628 mg, 2.00 mmol), 2,5-diethynylthiophene (132 mg,
2
1.00 mmol), CuI (19 mg, 0.10 mmol), and triethylamine (10 mL) in THF
(10 mL). The resulting mixture was stirred at 508C for 12 h under an Ar
atmosphere. The reaction mixture was poured into a 10% aqueous solu-
tion of NH4Cl and was extracted with dichloromethane. The organic
layer was washed with brine, dried over MgSO4, and concentrated under
reduced pressure. The residue was purified by column chromatography
on silica gel with dichloromethane as the eluent to give 13 as red crystals
(439 mg, 87%). M.p. 221.0–222.08C (MeOH); 1H NMR (400 MHz,
CDCl3): d=7.46 (s, 2H; H4), 7.21 (s, 2H; Th), 7.12 (dd, J=11.6, 9.2 Hz,
2H; H7), 6.99 (d, J=9.2 Hz, 2H; H8), 6.93 (d, J=11.6 Hz, 2H; H6), 2.95
(sept, J=6.8 Hz, 2H; iPr), 1.32 ppm (d, J=6.8 Hz, 12H; iPr); 13C NMR
(100 MHz, CDCl3): d=167.1, 158.3, 157.5, 151.2, 133.5, 133.1, 132.2,
Compound 11: [PdACHTUNGTRENNUNG(PPh3)4] (58 mg, 0.050 mmol) was added to a degassed
125.6, 124.7, 114.5, 93.0, 91.8, 84.9, 39.1, 23.1 ppm; IR (KBr disk): nmax
=
solution of 2 (314 mg, 1.00 mmol), methyl 3-ethynyl-7-isopropylazulene-
1-carboxylate (252 mg, 1.00 mmol), CuI (19 mg, 0.10 mmol), and triethyl-
amine (5 mL) in THF (5 mL). The resulting mixture was stirred at 508C
for 3 h under an Ar atmosphere. The reaction mixture was poured into a
10% aqueous solution of NH4Cl and was extracted with dichlorome-
thane. The organic layer was washed with brine, dried over MgSO4, and
concentrated under reduced pressure. The residue was purified by
column chromatography on silica gel with dichloromethane as the eluent
ꢁ
2980 (w), 2201 (w, C C), 1741 (s, C=O), 1635 (w), 1592 (m), 1532 (w),
1504 (m), 1433 (w), 1342 (w), 1312 (w), 1272 (w), 1260 (w), 1250 (w),
1064 (w), 1036 (w), 928 (w), 895 (w), 881 (w), 792 (m), 755 (m), 750 (m),
707 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=233 (4.65), 266 (4.55), 331
(4.14), 349 (4.16), 465 nm (4.65); HRMS (FAB): m/z calcd for
[C32H24O4S+H]+: 505.1474; found: 505.1499; elemental analysis calcd
(%) for C32H24O4S: C 76.17, H 4.79; found: C 76.36, H 4.84.
5126
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 5116 – 5129

Intramolecular Charge-Transfer Chromophores
FULL PAPER
Compound 14: [Pd
G
Compound 17: The procedure used for the preparation of 16 was adopted
here. The reaction of
6 (303 mg, 1.00 mmol) with TCNE (154 mg,
solution of (628 mg, 2.00 mmol), 5,5’-diethynyl-2,2’-bithiophene
2
1.20 mmol) in ethyl acetate (10 mL) at reflux for 1 h afforded 17 as red-
dish brown crystals (414 mg, 96%). M.p. 149.0–152.08C (CH2Cl2/hexane);
1H NMR (400 MHz, CDCl3): d=7.72–7.67 (m, 3H; H7, H2’,6’), 7.60–7.49
(m, 3H; H4,6,8), 6.66 (d, J=8.8 Hz, 2H; H3’,5’), 4.70 (s, 2H; NH2), 3.17
(sept, J=6.8 Hz, 1H; iPr), 1.41 ppm (d, J=6.8 Hz, 6H; iPr); 13C NMR
(100 MHz, CDCl3): d=166.0, 165.1, 163.9, 161.5, 159.6, 153.1, 149.0,
138.0, 137.4, 133.5, 129.6, 121.7, 120.6, 114.6, 113.9, 113.4, 112.4, 111.7,
(214 mg, 1.00 mmol), CuI (19 mg, 0.10 mmol), and triethylamine (5 mL)
in THF (5 mL). The resulting mixture was stirred at 508C for 12 h under
an Ar atmosphere. The reaction mixture was poured into a 10% aqueous
solution of NH4Cl and was extracted with dichloromethane. The organic
layer was washed with brine, dried over MgSO4, and concentrated under
reduced pressure. The residue was purified by column chromatography
on silica gel with dichloromethane as the eluent to give 14 as red crystals
(534 mg, 91%). M.p. 255.0–257.08C (MeOH); 1H NMR (400 MHz,
CDCl3): d=7.45 (s, 2H; H4), 7.24 (d, J=4.0 Hz, 2H; H3,3ꢂ of Th), 7.13–
7.08 (m, 4H; H7, H4,4ꢂ of Th), 6.98 (d, J=9.2 Hz, 2H; H8), 6.91 (d, J=
11.6 Hz, 2H; H6), 2.94 (sept, J=6.8 Hz, 2H; iPr), 1.32 ppm (d, J=6.8 Hz,
12H; iPr); 13C NMR (100 MHz, CDCl3): d=167.2, 158.1, 157.5, 151.0,
138.4, 133.4, 133.3, 133.0, 125.7, 124.2, 122.4, 114.4, 93.3, 92.2, 85.1, 39.1,
ꢁ
101.0, 84.0, 40.2, 23.8 ppm; IR (KBr disk): nmax =2972 (w), 2220 (w, C
N), 1754 (m, C=O), 1631 (m), 1604 (m), 1585 (m), 1471 (s), 1453 (s),
1408 (w), 1344 (m), 1332 (m), 1320 (m), 1276 (m), 1255 (w), 1232 (w),
1182 (m), 1068 (w), 1045 (w), 950 (w), 908 (w), 844 (w), 834 (w), 807 (w),
770 (w), 719 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=256 (4.44), 307 sh
(4.10), 387 (4.30), 495 nm (4.48); HRMS (EI): m/z calcd for
[C26H17N5O2]+: 431.1382; found: 431.1377; elemental analysis calcd (%)
for C26H17N5O2: C 72.38, H 3.97, N 16.23; found: C 72.22, H 4.11, N
16.30.
ꢁ
23.1 ppm; IR (KBr disk): nmax =2965 (w), 2190 (w, C C), 1740 (s, C=O),
1594 (m), 1533 (m), 1492 (s), 1438 (w), 1401 (w), 1334 (w), 1303 (w),
1270 (m), 1247 (m), 1211 (w), 1079 (w), 1017 (w), 934 (w), 903 (w), 879
(m), 805 (m), 792 (m), 769 (w), 741 (w), 730 (w), 710 cmꢀ1 (w); UV/Vis
(CH2Cl2): lmax (loge)=235 (4.68), 268 (4.59), 374 (4.38), 472 nm (4.74);
HRMS (FAB): m/z calcd for [C36H26O4S2+H]+: 587.1351; found:
587.1356; elemental analysis calcd (%) for C36H26O4S2: C 73.70, H 4.47;
found: C 73.76, H 4.44.
Compound 18: The procedure used for the preparation of 16 was adopt-
ed here. The reaction of 7 (331 mg, 1.00 mmol) with TCNE (154 mg,
1.20 mmol) in ethyl acetate (10 mL) at reflux for 1 h afforded 18 as red-
dish brown crystals (427 mg, 93%). M.p. 239.0–240.58C (CH2Cl2/hexane);
1H NMR (400 MHz, CDCl3): d=7.80 (d, J=9.2 Hz, 2H; H2’,6’), 7.61 (dd,
J=9.6, 9.6 Hz, 1H; H7), 7.56 (d, J=9.6 Hz, 1H; H8), 7.51 (d, J=9.6 Hz,
1H; H6), 7.50 (s, 1H; H4), 6.74 (d, J=9.2 Hz, 2H; H3’,5’), 3.16 (s, 6H;
NMe2), 3.16 (sept, J=6.8 Hz, 1H; iPr), 1.40 ppm (d, J=6.8 Hz, 6H; iPr);
13C NMR (100 MHz, CDCl3): d=164.8, 164.7, 163.7, 162.0, 159.6, 154.3,
149.1, 137.7, 137.1, 133.2, 129.4, 120.3, 119.8, 114.6, 114.1, 112.4, 111.9,
111.7, 101.3, 84.2, 74.0, 40.1, 23.7 ppm; IR (KBr disk): nmax =2984 (w),
Compound 15: [Pd
ACHTUNGTRENNUNG(PPh3)4] (58 mg, 0.050 mmol) was added to a degassed
solution of (628 mg, 2.00 mmol), 1,3,5-triethynylbenzene (75 mg,
2
0.50 mmol), CuI (19 mg, 0.10 mmol), and triethylamine (5 mL) in THF
(5 mL). The resulting mixture was stirred at 508C for 12 h under an Ar
atmosphere. The reaction mixture was poured into a 10% aqueous solu-
tion of NH4Cl and was extracted with dichloromethane. The organic
layer was washed with brine, dried over MgSO4, and concentrated under
reduced pressure. The residue was purified by column chromatography
on silica gel with dichloromethane as the eluent to give 15 as orange crys-
tals (319 mg, 90%). M.p. >300.08C (AcOEt); 1H NMR (400 MHz,
CDCl3): d=7.73 (s, 3H; phenyl (Ph)), 7.52 (s, 3H; H4), 7.12 (dd, J=9.2,
9.2 Hz, 3H; H7), 6.99 (d, J=9.2 Hz, 3H; H8), 6.94 (d, J=9.2 Hz, 3H; H6),
3.02 (sept, J=6.8 Hz, 3H; iPr), 1.34 ppm (d, J=6.8 Hz, 18H; iPr);
13C NMR (100 MHz, CDCl3): d=167.5, 158.4, 157.5, 151.5, 133.8, 133.4,
132.8, 125.9, 123.9, 114.5, 97.6, 93.1, 81.1, 39.2, 23.2 ppm; IR (KBr disk):
ꢁ
ꢁ
2967 (w), 2221 (m, C N), 2212 (m, C N), 1756 (m, C=O), 1603 (s), 1579
(m), 1517 (w), 1474 (s), 1437 (m), 1408 (w), 1384 (s), 1348 (m), 1334 (w),
1319 (w), 1298 (w), 1276 (m), 1254 (w), 1212 (m), 1192 (m), 1175 (m),
1116 (w), 1067 (w), 941 (w), 843 (w), 827 (m), 807 (w), 766 (w), 747 (w),
718 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=255 (4.49), 309 sh (4.08),
390 sh (4.13), 448 (4.47), 491 nm (4.54); HRMS (EI): m/z calcd for
[C28H21N5O2]+: 459.1695; found: 459.1689; elemental analysis calcd (%)
for C28H21N5O2: C 73.19, H 4.61, N 15.24; found: C 73.33, H 4.52, N
15.30.
Compound 19: The procedure used for the preparation of 16 was adopt-
ed here. The reaction of 8 (333 mg, 1.00 mmol) with TCNE (154 mg,
1.20 mmol) in ethyl acetate (10 mL) at reflux for 2 h afforded 19 as red-
dish brown crystals (415 mg, 90%). M.p. 195.0–198.08C (CH2Cl2/hexane);
1H NMR (400 MHz, CDCl3): d=8.40 (d, J=9.2 Hz, 2H; H3’,5’), 7.99 (d,
J=9.2 Hz, 2H; H2’,6’), 7.84 (dd, J=11.2, 9.6 Hz, 1H; H7), 7.72 (d, J=
9.6 Hz, 1H; H8), 7.68 (d, J=11.2 Hz, 1H; H6), 7.49 (s, 1H; H4), 3.25
(sept, J=6.8 Hz, 1H; iPr), 1.45 ppm (d, J=6.8 Hz, 6H; iPr); 13C NMR
(100 MHz, CDCl3): d=166.5, 166.4, 164.4, 160.1, 158.4, 150.1, 148.9,
139.0, 137.9, 137.7, 131.7, 130.5, 124.4, 121.7, 112.0, 111.5, 111.1, 110.8,
100.0, 91.1, 82.8, 77.6, 40.5, 23.9 ppm; IR (KBr disk): nmax =2978 (w),
ꢁ
nmax =2962 (w), 2208 (w, C C), 1748 (s, C=O), 1593 (m), 1519 (s), 1497
(s), 1467 (w), 1432 (m), 1412 (m), 1335 (w), 1300 (w), 1274 (m), 1236 (w),
1208 (w), 1069 (w), 934 (w), 910 (w), 867 (m), 793 (m), 756 (m), 708 (w),
675 (m), 656 cmꢀ1 (m); UV/Vis (CH2Cl2): lmax (loge)=234 (4.89), 277
(4.71), 298 (4.70), 439 nm (4.90); HRMS (FAB): m/z calcd for
[C48H36O6+H]+: 709.2590; found: 709.2581; elemental analysis calcd (%)
for C48H36O6: C 81.34, H 5.12; found: C 81.20, H 5.35.
Compound 16: TCNE (48 mg, 0.38 mmol) was added to a solution of 5
(72 mg, 0.25 mmol) in ethyl acetate (5 mL). The resulting mixture was
heated at reflux for 30 min under an Ar atmosphere. The solvent was re-
moved under reduced pressure. The residue was purified by column chro-
matography on silica gel with ethyl acetate as the eluent and on Bio-
Beads with CH2Cl2 as the eluent to give 16 as reddish brown crystals
(100 mg, 96%). M.p. 110.0–114.08C (CH2Cl2/hexane); 1H NMR
(500 MHz, CDCl3): d=7.79 (dd, J=7.5, 1.0 Hz, 2H; o-Ph), 7.74 (dd, J=
ꢁ
2221 (m, C N), 1749 (m, C=O), 1577 (m), 1527 (w), 1454 (s), 1405 (w),
1351 (m), 1316 (m), 1276 (m), 1252 (w), 950 (w), 862 (w), 852 (w), 835
(w), 809 (w), 773 (w), 761 (w), 752 (w), 714 cmꢀ1 (w); UV/Vis (CH2Cl2):
lmax (loge)=254 sh (4.51), 270 (4.55), 276 (4.55), 327 sh (4.14), 410 (3.95),
499 nm (4.21); HRMS (EI): m/z calcd for [C26H15N5O4]+: 461.1124;
found: 461.1132; elemental analysis calcd (%) for C26H15N5O4: C 67.68,
H 3.28, N 15.18; found: C 67.45, H 3.50, N 15.26.
11.0, 9.5 Hz, 1H; H7), 7.67–7.62 (m, 2H; m-Ph), 7.59–7.55 (m, 3H; H6,8
,
p-Ph), 7.45 (d, J=1.5 Hz, 1H; H4), 3.21 (sept, J=7.0 Hz, 1H; iPr),
1.44 ppm (d, J=7.0 Hz, 6H; iPr); 13C NMR (100 MHz, CDCl3): d=168.9,
166.0, 164.5, 160.3, 160.2, 149.5, 138.8, 137.9, 134.5, 132.9, 130.9, 130.3,
130.0, 121.4, 112.7, 112.4, 112.2, 112.0, 100.9, 88.0, 84.1, 40.8, 24.3 ppm;
Compound 20: The procedure used for the preparation of 16 was adopt-
ed here. The reaction of 9 (110 mg, 0.278 mmol) with TCNE (54 mg,
0.42 mmol) in ethyl acetate (5 mL) at reflux for 2 h afforded 20 as red-
dish brown crystals (129 mg, 89%). M.p. 92.0–94.58C (CH2Cl2/hexane);
1H NMR (400 MHz, CDCl3): d=7.63 (dd, J=10.8, 9.2 Hz, 1H; H7), 7.52
(dd, J=9.2, 0.8 Hz, 1H; H8), 7.46 (ddd, J=10.8, 1.2, 0.8 Hz, 1H; H6),
7.37 (d, J=1.2 Hz, 1H; H4), 5.22 (ddd, J=2.8, 1.2, 1.2 Hz, 1H; H2 or H5
of Fc), 4.97 (ddd, J=2.8, 2.8, 1.2 Hz, 1H; H3 or H4 of Fc), 4.84 (ddd, J=
2.8, 2.8, 1.2 Hz, 1H; H3 or H4 of Fc), 4.76 (ddd, J=2.8, 1.2, 1.2 Hz, 1H;
H2 or H5 of Fc), 4.49 (s, 5H; Cp of Fc), 3.13 (sept, J=6.8 Hz, 1H; iPr),
1.42 (d, J=6.8 Hz, 3H; iPr), 1.40 ppm (d, J=6.8 Hz, 3H; iPr); 13C NMR
(100 MHz, CDCl3): d=173.0, 164.6, 163.2, 159.3, 157.9, 149.0, 137.7,
ꢁ
IR (KBr disk): nmax =2967 (w), 2224 (w, C N), 1757 (s, C=O), 1684 (w),
1653 (w), 1647 (w), 1636 (w), 1582 (m), 1559 (w), 1541 (w), 1474 (s), 1458
(s), 1406 (w), 1341 (w), 1316 (m), 1275 (m), 1250 (w), 1229 (w), 947 (w),
806 (w), 766 (w), 718 (w), 693 (w), 664 (w), 419 cmꢀ1 (w); UV/Vis
(CH2Cl2): lmax (loge)=253 (4.44), 270 sh (4.40), 298 sh (4.21), 372 sh
(3.96), 392 (3.99), 498 nm (4.27); HRMS (ESI): m/z calcd for
[C26H16N4O2+Na]+: 439.1165; found: 439.1164; elemental analysis calcd
(%) for C26H16N4O2·1/2H2O: C 66.98, H 3.85, N 11.57; found: C 67.12, H
3.66, N 11.91.
Chem. Eur. J. 2011, 17, 5116 – 5129
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5127

T. Shoji et al.
136.9, 128.1, 120.2, 114.0, 113.5, 112.1, 112.0, 99.8, 84.2, 79.4, 75.9, 75.4,
74.6, 72.6, 72.4, 72.3, 40.1, 23.9, 23.6 ppm; IR (KBr disk): nmax =3119 (w),
[C24H14N4O2S+Na]+: 445.0730; found: 445.0729; elemental analysis calcd
(%) for C24H14N4O2S·3/4H2O: C 66.12, H 3.58, N 12.85; found: C 66.12,
H 3.77, N 12.77.
ꢁ
3110 (w), 3102 (w), 2966 (w), 2872 (w), 2220 (w, C N), 1752 (m, C=O),
1583 (w), 1522 (m), 1472 (s), 1403 (w), 1380 (w), 1340 (w), 1316 (w), 1275
(m), 1251 (w), 1321 (w), 1108 (w), 1044 (w), 1003 (w), 803 (w), 762 (w),
751 (w), 717 (w), 668 (w), 650 (w), 500 (w), 483 (w), 443 (w), 420 (w),
403 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=271 sh (4.33), 316 (4.06),
374 sh (4.07), 386 (4.08), 484 (4.27), 645 nm (3.31); HRMS (ESI): m/z
calcd for [C30H20FeN4O2+Na]+: 547.0828; found: 547.0828; elemental
analysis calcd (%) for C30H20FeN4O2·1/4H2O: C 68.13, H 3.91, N 10.56;
found: C 68.15, H 4.01, N 10.44.
Compound 24: The procedure used for the preparation of 16 was adopt-
ed here. The reaction of 13 (253 mg, 0.501 mmol) with TCNE (154 mg,
1.20 mmol) in ethyl acetate (10 mL) at reflux for 12 h afforded 24 as red
crystals (380 mg, 92%). M.p. 136.0–140.08C (CH2Cl2/hexane); 1H NMR
(400 MHz, CDCl3): d=7.98 (s, 2H; H3,4 of Th), 7.84 (dd, J=10.4,
10.0 Hz, 2H; H7), 7.65 (d, J=10.0 Hz, 2H; H8), 7.61 (d, J=10.4 Hz, 2H;
H6), 7.54 (s, 2H; H4), 3.25 (sept, J=6.8 Hz, 2H; iPr), 1.45 ppm (d, J=
6.8 Hz, 12H; iPr); 13C NMR (100 MHz, CDCl3): d=166.6, 163.6, 160.1,
156.5, 156.5, 148.6, 141.9, 139.1, 137.9, 136.1, 130.7, 121.7, 111.8, 111.8,
111.5, 111.2, 98.7, 86.0, 82.6, 40.5, 23.8 ppm; IR (KBr disk): nmax =2981
Compound 21: The procedure used for the preparation of 16 was adopted
here. The reaction of 10 (18 mg, 0.05 mmol) with TCNE (8 mg,
0.06 mmol) in ethyl acetate (5 mL) at reflux for 2 h afforded 21 as red-
dish crystals (23 mg, 98%). M.p. 279.0–281.58C (CH2Cl2/hexane);
1H NMR (400 MHz, CDCl3): d=7.64 (d, J=1.2 Hz, 2H; H4), 7.61 (dd,
J=11.2, 9.2 Hz, 2H; H7), 7.49 (ddd, J=11.2, 1.2, 0.8 Hz, 2H; H6), 7.47
(dd, J=9.2, 0.8 Hz, 2H; H8), 3.20 (sept, J=6.8 Hz, 2H; iPr), 1.44 ppm (d,
J=6.8 Hz, 12H; iPr); 13C NMR (100 MHz, CDCl3): d=164.7, 159.3,
158.6, 149.1, 137.3, 137.1, 130.4, 120.1, 112.6, 112.4, 100.3, 84.4, 80.2, 40.1,
23.8 ppm; IR (KBr disk): nmax =3067 (w), 3021 (w), 2967 (w), 2930 (w),
ꢁ
(w), 2965 (w), 2930 (w), 2225 (m, C N), 1765 (m, C=O), 1582 (m), 1521
(m), 1459 (s), 1406 (w), 1316 (m), 1275 (m), 1251 (m), 1179 (w), 1068
(w), 1045 (w), 1026 (w), 950 (w), 807 (m), 768 (w), 717 cmꢀ1 (w); UV/Vis
(CH2Cl2): lmax (loge)=255 (4.79), 278 sh (4.58), 344 (4.30), 423 (4.65),
491 nm (4.67); HRMS (FAB): m/z calcd for [C44H24N8O4S+H]+:
761.1719; found: 761.1727; elemental analysis calcd (%) for
C44H24N8O4S: C 69.46, H 3.18, N 14.73; found: C 69.33, H 3.43, N 14.77.
Compound 25: The procedure used for the preparation of 16 was adopt-
ed here. The reaction of 14 (294 mg, 0.501 mmol) with TCNE (154 mg,
1.20 mmol) in ethyl acetate (10 mL) at reflux for 12 h afforded 25 as red
crystals (379 mg, 90%). M.p. 165.0–169.08C (CH2Cl2/hexane); 1H NMR
(400 MHz, CDCl3): d=7.96 (d, J=4.0 Hz, 2H; H3,3ꢂ of Th), 7.80 (dd, J=
10.8, 9.6 Hz, 2H; H7), 7.67 (d, J=9.6 Hz, 2H; H8), 7.64 (d, J=10.8 Hz,
2H; H6), 7.56 (d, J=4.0 Hz, 2H; H4,4ꢂ of Th), 7.55 (s, 2H; H4), 3.25 (sept,
J=6.8 Hz, 2H; iPr), 1.46 ppm (d, J=6.8 Hz, 12H; iPr); low solubility
hampered the measurement of the 13C NMR spectrum; IR (KBr disk):
ꢁ
2872 (w), 2217 (m, C N), 1744 (s, C=O), 1619 (w), 1580 (m), 1518 (m),
1464 (s), 1451 (s), 1397 (m), 1366 (w), 1335 (w), 1308 (m), 1275 (s), 1250
(m), 1200 (w), 1090 (w), 1046 (w), 951 (w), 909 (w), 835 (w), 814 (w), 768
(w), 718 (w), 700 (w), 654 (w), 610 (w), 498 (w), 446 cmꢀ1 (w); UV/Vis
(CH2Cl2): lmax (loge)=253 (4.64), 244 sh (4.58), 268 (4.62), 337 sh (3.89),
420 (4.35), 498 nm (4.54); HRMS (ESI): m/z calcd for [C32H22N4O4+Na]+:
549.1533; found: 549.1534; elemental analysis calcd (%) for
C32H22N4O4·1/4H2O: C 72.37, H 4.27, N 10.55; found: C 72.34, H 4.36, N
10.54.
ꢁ
nmax =2966 (w), 2928 (w), 2857 (w), 2223 (w, C N), 1759 (m, C=O), 1584
(w), 1522 (m), 1469 (s), 1459 (s), 1423 (m), 1342 (w), 1318 (m), 1275 (m),
1252 (w), 1064 (w), 1046 (w), 1027 (w), 947 (w), 805 (m), 768 (w),
718 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=254 (4.70), 278 sh (4.53),
342 (4.10), 504 nm (4.82); HRMS (FAB): m/z calcd for
[C48H26N8O4S2+H]+: 843.1597; found: 843.1591; elemental analysis calcd
(%) for C48H26N8O4S2: C 68.40, H 3.11, N 13.29; found: C 68.11, H 3.23,
N 13.50.
Compound 22: The procedure used for the preparation of 16 was adopt-
ed here. The reaction of 11 (439 mg, 1.00 mmol) with TCNE (154 mg,
1.20 mmol) in ethyl acetate (10 mL) at reflux for 1 h afforded 22 as red-
dish brown crystals (556 mg, 98%). M.p. 168.0–170.08C (CH2Cl2/hexane);
1H NMR (400 MHz, CDCl3): d=10.01 (d, J=1.6 Hz, 1H; H4’), 8.66 (s,
1H; H2), 8.46 (d, J=10.0 Hz, 1H; H8’), 8.09 (d, J=10.0 Hz, 1H; H6’), 7.88
(t, J=10.0 Hz, 1H; H7’), 7.73 (dd, J=10.8, 9.6 Hz, 1H, H7), 7.63 (d, J=
9.6 Hz, 1H; H6), 7.56 (d, J=10.8 Hz, 1H; H8), 7.52 (s, 1H; H4’), 3.56 (s,
3H; CO2Me), 3.34 (sept, J=6.8 Hz, 1H; iPr), 3.20 (sept, J=6.8 Hz, 1H;
iPr), 1.47 (d, J=6.8 Hz, 6H; iPr), 1.42 ppm (d, J=6.8 Hz, 6H; iPr);
13C NMR (100 MHz, CDCl3): d=165.2, 164.7, 164.3, 161.8, 160.8, 159.8,
156.5, 149.2, 146.1, 143.9, 142.7, 141.9, 140.4, 138.0, 137.4, 137.3, 132.0,
129.5, 120.7, 120.7, 119.0, 114.1, 113.3, 112.5, 111.5, 101.6, 84.6, 80.0, 51.6,
Compound 26: The procedure used for the preparation of 16 was adopt-
ed here. The reaction of 15 (141 mg, 0.199 mmol) with TCNE (128 mg,
1.00 mmol) in 1,2-dichloroethane (10 mL) for 12 h afforded 26 as red
crystals (192 mg, 88%). M.p. 185.0–189.08C (CH2Cl2/hexane); 1H NMR
(400 MHz, CDCl3): d=8.18 (s, 3H; Bz), 7.81 (dd, J=11.2, 11.2 Hz, 3H;
H7), 7.67 (d, J=11.2 Hz, 3H; H8), 7.65 (d, J=11.2 Hz, 3H; H6), 7.58 (s,
3H; H4), 3.26 (sept, J=6.8 Hz, 3H; iPr), 1.45 ppm (d, J=6.8 Hz, 18H;
iPr); 13C NMR (100 MHz, CDCl3): d=166.4, 165.0, 164.3, 160.4, 156.3,
148.8, 139.0, 137.9, 134.5, 134.0, 132.3, 121.8, 112.2, 112.0, 111.0, 110.5,
98.3, 92.6, 82.1, 40.6, 23.8 ppm; IR (KBr disk): nmax =2965 (w), 2931 (w),
ꢁ
40.2, 39.4, 24.5, 23.8 ppm; IR (KBr disk): nmax =2966 (w), 2220 (m, C N),
1759 (m, C=O), 1705 (m, C=O), 1583 (m), 1471 (s), 1419 (m), 1367 (w),
1315 (w), 1277 (w), 1244 (w), 1213 (w), 1178 (w), 810 (w), 777 cmꢀ1 (w);
UV/Vis (CH2Cl2): lmax (loge)=254 (4.60), 279 sh (4.52), 301 sh (4.47),
399 (4.28), 504 nm (4.46); HRMS (ESI): m/z calcd for [C35H26N4O4+Na]+:
589.1852; found: 589.1846; elemental analysis calcd (%) for C35H26N4O4:
C 74.19, H 4.63, N 9.89; found: C 74.11, H 4.69, N 9.85.
ꢁ
2220 (w, C N), 1753 (m, C=O), 1580 (w), 1518 (w), 1455 (s), 1404 (w),
1315 (m), 1274 (s), 1247 (w), 1177 (w), 1089 (w), 947 (w), 804 (w), 764
(w), 717 (w), 698 (w), 668 cmꢀ1 (w); UV/Vis (CH2Cl2): lmax (loge)=257
(4.95), 266 (4.95), 414 (4.49), 499 nm (4.73); HRMS (FAB): m/z calcd for
[C66H36N12O6+H]+: 1093.2959; found: 1093.2959; elemental analysis calcd
(%) for C66H36N12O6: C 72.52, H 3.32, N 15.38; found: C 72.44, H 3.50, N
15.43.
Compound 23: The procedure used for the preparation of 16 was adopt-
ed here. The reaction of 12 (70 mg, 0.24 mmol) with TCNE (45 mg,
0.35 mmol) in ethyl acetate (5 mL) in reflux for 6 h afforded 24 as red-
dish brown crystals (45 mg, 99%). M.p. 96.0–98.58C (CH2Cl2/hexane);
1H NMR (400 MHz, CDCl3): d=8.03 (dd, J=4.0, 1.2 Hz, 1H; H3 of Th),
7.98 (dd, J=5.2, 1.2 Hz, 1H; H5 of Th), 7.77 (dd, J=10.8, 9.6 Hz, 1H;
H7), 7.65 (dd, J=9.6, 0.8 Hz, 1H; H8), 7.61 (ddd, J=10.8, 1.2, 0.8 Hz,
1H; H6), 7.51 (d, J=1.2 Hz, 1H; H4), 7.34 (dd, J=5.2, 4.0 Hz, 1H; H4 of
Th), 3.22 (sept, J=6.8 Hz, 1H; iPr), 1.44 ppm (d, J=6.8 Hz, 6H; iPr);
13C NMR (100 MHz, CDCl3): d=165.7, 163.4, 159.9, 158.7, 148.9, 138.4,
137.8, 137.6, 136.9, 136.9, 135.5, 130.0, 129.9, 121.0, 112.6, 112.2, 112.0,
111.5, 99.8, 83.1, 79.8, 40.3, 23.8 ppm; IR (KBr disk): nmax =3102 (w),
Acknowledgements
This work was partially supported by a Grant-in-Aid for Research Activi-
ty Start-up (Grant 22850007 to T.S.) from the Ministry of Education, Cul-
ture, Sports, Science, and Technology, Japan.
ꢁ
2967 (w), 2930 (w), 2872 (w), 2222 (m, C N), 1755 (s, C=O), 1619 (w),
1582 (w), 1530 (w), 1472 (s), 1459 (s), 1406 (s), 1366 (m), 1348 (m), 1316
(m), 1275 (s), 1250 (m), 1233 (m), 1204 (w), 1063 (w), 1044 (w), 945 (w),
806 (w), 766 (w), 733 (w), 718 (w), 660 (w), 650 (w), 492 cmꢀ1 (w); UV/
Vis (CH2Cl2): lmax (loge)=254 (4.43), 271 sh (4.33), 324 sh (4.11), 340
(4.14), 354 (4.14), 385 (4.17), 494 nm (4.42); HRMS (ESI): m/z calcd for
[1] a) J. L. Brꢃdas, C. Adant, P. Tackx, A. Persoons, B. M. Pierce, Chem.
Rev. 1994, 94, 243–278; b) M. Bendikov, F. Wudl, D. F. Perepichka,
Chem. Rev. 2004, 104, 4891–4945; c) S. Hꢁnig, E. Herberth, Chem.
Rev. 2004, 104, 5535–5563; d) T. Baumgartner, R. Rꢃau, Chem. Rev.
5128
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 5116 – 5129

Intramolecular Charge-Transfer Chromophores
FULL PAPER
2006, 106, 4681–4727; e) G. Clavier, P. Audebert, Chem. Rev. 2010,
110, 3299–3314.
[2] a) A. J. Fatiadi, Synthesis 1986, 249–284; b) A. J. Fatiadi, Synthesis
1987, 749–789; c) O. W. Webster, J. Polym. Sci. Part A 2002, 40,
210–221.
Elwahy, K. Hafner, Eur. J. Org. Chem. 2006, 791–802; e) A. H. M.
Elwahy, K. Hafner, Eur. J. Org. Chem. 2006, 3910–3916; f) A. H. M.
Elwahy, K. Hafner, Eur. J. Org. Chem. 2010, 265–274.
[12] T. Yamamoto, K. Toyota, N. Morita, Tetrahedron Lett. 2010, 51,
1364–1366.
[3] M. I. Bruce, J. R. Rodgers, M. R. Snow, A. G. Swincer, J. Chem. Soc.
Chem. Commun. 1981, 271–272.
[4] Y. Morioka, N. Yoshizawa, J. Nishida, Y. Yamashita, Chem. Lett.
2004, 33, 1190–1191.
[13] a) K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. 1975,
16, 4467–4470; b) S. Takahashi, Y. Kuroyama, K. Sonogashira, N.
Hagihara, Synthesis 1980, 627–630; c) K. Sonogashira in Compre-
hensive Organic Synthesis, Vol. 3 (Eds.: B. M. Trost, I. Fleming), Per-
gamon, Oxford, 1991, pp. 521–549; d) K. Sonogashira in Metal-Cata-
lyzed Cross-Coupling Reactions (Eds.: F. Diederich, P. J. Stang),
Wiley-VCH, Weinheim, 1998, pp. 203–229.
[14] T. X. Neenan, G. M. Whitesides, J. Org. Chem. 1988, 53, 2489–2496.
[15] T. Cardolaccia, A. M. Funston, M. E. Kose, J. M. Keller, J. R. Miller,
K. S. Schanze, J. Phys. Chem. B 2007, 111, 10871–10880.
[16] a) B. J. L. Royles, D. M. Smith, J. Chem. Soc. Perkin Trans. 1 1994,
355–358; b) H. L. Anderson, C. J. Walter, A. Vidal-Ferran, R. A.
Hay, P. A. Lowden, J. Chem. Soc. Perkin Trans. 1 1995, 2275–2279;
c) M. Osawa, H. Sonoki, M. Hoshino, Y. Wakatsuki, Chem. Lett.
1998, 1081–1082.
[17] A detailed reaction mechanism was recently reported: Y-.L. Wu,
P. D. Jarowski, W. B. Schweizer, F. Diederich, Chem. Eur. J. 2010, 16,
202–211.
[18] a) P. Suppan, N. Ghoneim, Solvatochromism, Royal Society of
Chemistry, Cambridge, 1997; b) P. Suppan, J. Photochem. Photobiol.
A 1990, 50, 293–330; c) C. Reichardt, Solvent and Solvent Effects in
Organic Chemistry, Wiley-VCH, New York, 2004.
[19] T. Mochida, S. Yamazaki, J. Chem. Soc. Dalton Trans. 2002, 3559–
3564.
[20] The B3LYP/6-31G** time-dependent density functional calculations
were performed with Spartanꢂ04, Wavefunction, Irvine, CA.
[21] a) K. Komatsu, K. Ohta, T. Fujimoto, I. Yamamoto, J. Mater. Chem.
1994, 4, 533–536; b) D. R. Rosseinsky, D. M. S. Monk, J. Appl. Elec-
trochem. 1994, 24, 1213–1221.
[22] a) S. Hꢁnig, M. Kemmer, H. Wenner, I. F. Perepichka, P. Bꢄuerle,
A. Emge, G. Gescheidt, Chem. Eur. J. 1999, 5, 1969–1973; b) S.
Hꢁnig, M. Kemmer, H. Wenner, F. Barbosa, G. Gescheidt, I. F. Per-
epichka, P. Bꢄuerle, A. Emge, K. Peters, Chem. Eur. J. 2000, 6,
2618–2632; c) S. Hꢁnig, I. F. Perepichka, M. Kemmer, H. Wenner,
P. Bꢄuerle, A. Emge, Tetrahedron 2000, 56, 4203–4211; d) S. Hꢁnig,
C. A. Briehn, P. Bꢄuerle, A. Emge, Chem. Eur. J. 2001, 7, 2745–
2757; e) S. Hꢁnig, A. Langels, M. Schmittel, H. Wenner, I. F. Pere-
pichka, K. Peters, Eur. J. Org. Chem. 2001, 1393–1399.
[5] a) T. Michinobu, J. C. May, J. H. Lim, C. Boudon, J.-P. Gisselbrecht,
P. Seiler, M. Gross, I. Biaggio, F. Diederich, Chem. Commun. 2005,
737–739; b) T. Michinobu, I. Boudon, J.-P. Gisselbrecht, P. Seiler, B.
Frank, N. N. P. Moonen, M. Gross, F. Diederich, Chem. Eur. J. 2006,
12, 1889–1905; c) M. Kivala, C. Boudon, J.-P. Gisselbrecht, P. Seiler,
M. Gross, F. Diederich, Angew. Chem. 2007, 119, 6473–6477;
Angew. Chem. Int. Ed. 2007, 46, 6357–6360; d) P. Reutenauer, M.
Kivala, P. D. Jarowski, C. Boudon, J. Gisselbrecht, M. Gross, F. Die-
derich, Chem. Commun. 2007, 4898–4900; e) M. Kivala, T. Stanoe-
va, T. Michinobu, B. Frank, G. Gescheidt, F. Diederich, Chem. Eur.
J. 2008, 14, 7638–7647; f) B. B. Frank, B. C. Blanco, S. Jakob, F. Fer-
roni, S. Pieraccini, A. Ferrarini, C. Boudon, J.-P. Gisselbrecht, P.
Seiler, G. P. Spada, F. Diederich, Chem. Eur. J. 2009, 15, 9005–9016;
g) M. Yamada, P. Rivera-Fuentes, W. B. Schweizer, F. Diederich,
Angew. Chem. 2010, 122, 3611–3615; Angew. Chem. Int. Ed. 2010,
49, 3532–3535; h) M. Yamada, W. B. Schweizer, F. Schoenebeck, F.
Diederich, Chem. Commun. 2010, 46, 5334–5336.
[6] a) M. Kivala, C. Boudon, J.-P. Gisselbrecht, P. Seiler, M. Gross, F.
Diederich, Chem. Commun. 2007, 4731–4733; b) M. Kivala, C.
Boudon, J.-P. Gisselbrecht, B. Enko, P. Seiler, I. B. Mꢁller, N.
Langer, P. D. Jarowski, G. Gescheidt, F. Diederich, Chem. Eur. J.
2009, 15, 4111–4123; c) S. Kato, M. Kivala, W. B. Schweizer, C.
Boudon, J.-P. Gisselbrecht, F. Diederich, Chem. Eur. J. 2009, 15,
8687–8691; d) B. B. Frank, M. Kivala, B. C. Blanco, B. Breiten,
W. B. Schweizer, P. R. Laporta, I. Biaggio, E. Jahnke, R. R. Tykwin-
ski, C. Boudon, J.-P. Gisselbrecht, F. Diederich, Eur. J. Org. Chem.
2010, 2487–2503.
[7] B. Esembeson, M. L. Scimeca, T. Michinobu, F. Diederich, I. Biag-
gio, Adv. Mater. 2008, 20, 4584–4587.
[8] a) P.-W. Yang, M. Yasunami, K. Takase, Tetrahedron Lett. 1971, 12,
4275–4278; b) A. Chen, M. Yasunami, K. Takase, Tetrahedron Lett.
1974, 15, 2581–2584; c) K. Takase, M. Yasunami, J. Synth. Org.
Chem. Jpn. 1981, 39, 1172–1182; d) T. Nozoe, P.-W. Yang, C.-P. Wu,
T.-S. Huang, T.-H. Lee, H. Okai, H. Wakabayashi, S. Ishikawa, Het-
erocycles 1989, 29, 1225–1232; e) S. Kuroda, S. Maeda, S. Hirooka,
M. Ogisu, K. Yamazaki, I. Shimao, M. Yasunami, Tetrahedron Lett.
1989, 30, 1557–1560; f) T. Nozoe, H. Wakabayashi, S. Ishikawa, C.-
P. Wu, P.-W. Yang, Heterocycles 1990, 31, 17–22; g) T. Nozoe, H.
Wakabayashi, K. Shindo, S. Ishikawa, C.-P. Wu, P.-W. Yang, Hetero-
cycles 1991, 32, 213–220; h) H. Wakabayashi, P.-W. Yang, C.-P. Wu,
K. Shindo, S. Ishikawa, T. Nozoe, Heterocycles 1992, 34, 429–434;
i) S. Kuroda, J. Yazaki, S. Maeda, K. Yamazaki, M. Yamada, I.
Shimao, M. Yasunami, Tetrahedron Lett. 1992, 33, 2825–2828; j) S.
Kuroda, Y. Obata, N. C. Thanh, R. Miyatake, Y. Horino, M. Oda,
Tetrahedron Lett. 2008, 49, 552–556.
[9] N. Morita, K. Toyota, S. Ito, Heterocycles 2009, 78, 1917–1954.
[10] a) T. Shoji, S. Ito, K. Toyota, M. Yasunami, N. Morita, Chem. Eur. J.
2008, 14, 8398–8408; b) T. Shoji, S. Ito, K. Toyota, T. Iwamoto, M.
Yasunami, N. Morita, Eur. J. Org. Chem. 2009, 4316–4324.
[11] a) K. H. H. Fabian, A. H. M. Elwahy, K. Hafner, Tetrahedron Lett.
2000, 41, 2855–2858; b) A. H. M. Elwahy, K. Hafner, Tetrahedron
Lett. 2000, 41, 2859–2862; c) A. H. M. Elwahy, K. Hafner, Tetrahe-
dron Lett. 2000, 41, 4079–4083; d) K. H. H. Fabian, A. H. M.
[23] a) S. Ito, A. Nomura, N. Morita, C. Kabuto, H. Kobayashi, S. Maeji-
ma, K. Fujimori, M. Yasunami, J. Org. Chem. 2002, 67, 7295–7302;
b) S. Ito, T. Okujima, N. Morita, J. Chem. Soc. Perkin Trans. 1 2002,
1896–1905; c) S. Ito, H. Inabe, N. Morita, K. Ohta, T. Kitamura, K.
Imafuku, J. Am. Chem. Soc. 2003, 125, 1669–1680; d) S. Ito, T.
Kubo, N. Morita, T. Ikoma, S. Tero-Kubota, A. Tajiri, J. Org. Chem.
2003, 68, 9753–9762; e) S. Ito, H. Inabe, N. Morita, A. Tajiri, Eur. J.
Org. Chem. 2004, 1774–1780; f) S. Ito, T. Kubo, N. Morita, T.
Ikoma, S. Tero-Kubota, J. Kawakami, A. Tajiri, J. Org. Chem. 2005,
70, 2285–2293; g) S. Ito, K. Akimoto, J. Kawakami, A. Tajiri, T.
Shoji, H. Satake, N. Morita, J. Org. Chem. 2007, 72, 162–172; h) S.
Ito, T. Iida, J. Kawakami, T. Okujima, N. Morita, Eur. J. Org. Chem.
2009, 5355–5364; i) T. Shoji, J. Higashi, S. Ito, N. Morita, Eur. J.
Inorg. Chem. 2010, 4886–4891; j) T. Shoji, J. Higashi, S. Ito, T. Oku-
jima, N. Morita, Eur. J.Org. Chem. 2010, 584–592.
[24] S. Ito, N. Morita, Eur. J. Org. Chem. 2009, 4567–4579.
Received: December 16, 2010
Published online: March 30, 2011
Chem. Eur. J. 2011, 17, 5116 – 5129
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5129