Synthesis and photochromic properties of new nonsymmetric dihetarylethenes - Indole and thiophene derivatives

Article abstract of DOI:10.1007/s11172-011-0286-5

New nonsymmetric dihetarylethenes were synthesized: 3-(5-methoxy-1,2- dimethyl-1 H-indol-3-yl)-4-(3-thienyl)furan-2,5-dione and photochromic 1-alkyl-(1-aryl)-3-(5-methoxy-1,2-dimethyl-1 H-indol-3-yl)-4-(3-thienyl)-1(H)- pyrrole-2,5-diones. The absence of

Full text of DOI:10.1007/s11172-011-0286-5

Russian Chemical Bulletin, International Edition, Vol. 60, No. 9, pp. 1899—1905, September, 2011
1899
Synthesis and photochromic properties of new nonsymmetric
dihetarylethenes — indole and thiophene derivatives
N. I. Makarova,a P. V. Levchenko,a E. N. Shepelenko,b A. V. Metelitsa,a
V. S. Kozyrev,a V. P. Rybalkin,b V. A. Bren´,a and V. I. Minkina,b
aInstitute of Physical and Organic Chemistry, Southern Federal University,
194/2 prosp. Stachki, 344090 RostovꢀonꢀDon, Russian Federation.
Fax: +7 (863) 243 4667. Eꢀmail: photo@ipoc.rsu.ru
bSouthern Scientific Center, Russian Academy of Sciences,
41 prosp. Chekhova, 344006 RostovꢀonꢀDon, Russian Federation
New nonsymmetric dihetarylethenes were synthesized: 3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀ
indolꢀ3ꢀyl)ꢀ4ꢀ(3ꢀthienyl)furanꢀ2,5ꢀdione and photochromic 1ꢀalkylꢀ(1ꢀaryl)ꢀ3ꢀ(5ꢀmethoxyꢀ
1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ4ꢀ(3ꢀthienyl)ꢀ1(H)ꢀpyrroleꢀ2,5ꢀdiones. The absence of benzoꢀ
annulation in the indole moiety results in the enhancement of the efficiencies of fluorescence
and photocyclization of noncyclic isomers compared to the benzoindole derivatives.
Key words: indole, thiophene, furanꢀ2,5ꢀdione, pyrroleꢀ2,5ꢀdione dihetarylethene, synthesis,
photochromism, fluorescence, photocolorability, molecular switches.
Interest in preparing new photochromic dihetarylꢀ
ethenes is due to their ability to exist as two thermally
stable forms, which determines diverse possibilities of their
use, including that for manufacture of materials of optical
information recording and molecular switches.1—3 A speꢀ
cial role among dihetarylethenes belongs to the compounds
based on derivatives of maleic anhydride, viz., maleinimꢀ
ides, which, unlike perfluorocyclopentene derivatives of
diarylethenes, assume various structure functionalization
without a substantial change in the spectral and kinetic
characteristics predominantly determined by heterocyclic
moieties. The possibility of substitution in the bridging
moiety considerably extends areas of practical use of diꢀ
hetarylethenes with retention of the best photochromic
characteristics attained by the modification of heterocyclic
moieties. In particular, introduction of cationic moieties
is interesting for the development of hybrid supramolecuꢀ
lar structures including paramagnetic anions of heteropolyꢀ
acids and polyfunctional materials with photomodulated
magnetic characteristics. The inclusion of longꢀchain alkyl
substituents is necessary for the formation of the Langꢀ
muir—Blodgett films, and the production of photochroꢀ
mic polymers is possible using substitution by groups that
make it possible to carry out dihetarylethene copolymerꢀ
ization.
obtained 3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Нꢀbenzo[g]indolꢀ
3ꢀyl)ꢀ4ꢀ(3ꢀthienyl)ꢀ1(Н)ꢀpyrroleꢀ2,5ꢀdiones substituted
by position 1 manifest fluorescence of noncyclic isomers
along with photochromism. However, both the fluoresꢀ
cence and photocyclization of these compounds are lowly
efficient. The purpose of the present work was to enhance
the efficiency of photoinitiated processes in molecules of
nonsymmetric dihetarylethenes due to the structural modꢀ
ification of the compounds aimed at replacing the benꢀ
zoindole moiety by indole.
Results and Discussion
The starting 5ꢀmethoxyꢀ1,2ꢀdimethylindole (1) was
synthesized using a known procedure.13 3ꢀ(5ꢀDimethoxyꢀ
1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ4ꢀ(3ꢀthienyl)furanꢀ2,5ꢀdiꢀ
one (2) was obtained by the acylation of indole 1 with
oxalyl chloride followed by the treatment with a solution
of 3ꢀthienylacetic acid in the presence of triethylamine
(similarly to the method described previously9). Pyrroleꢀ
2,5ꢀdiones 3a—i were synthesized by the action of alkylꢀ
and arylamines on furanꢀ2,5ꢀdione 2 (Scheme 1).
The carbonyl groups of the furanꢀ2,5ꢀdione moiety of
dihetarylethene 2 appear in the IR spectra as stretching
vibration bands at 1750 and 1820 cm–1. The IR spectra of
3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ4ꢀ(3ꢀthiꢀ
enyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdiones 3 substituted in position 1
exhibit the characteristic stretching vibration bands of
the carbonyl groups of the imide moiety in the region
Various derivatives of maleic anhydride and maleinꢀ
imides containing thiophene,4—6 selenophene, indole,7
benzothiophene,8,9 thienopyrrole,10 and coumarin11 fragꢀ
ments were synthesized, and nonsymmetric dihetarylꢀ
ethenes exhibit the most interesting properties. Earlier12
1689—1704 cm–1
.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1866—1872, September, 2011.
1066ꢀ5285/11/6009ꢀ1899 © 2011 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 9, September, 2011
Makarova et al.
Scheme 1
3: R = Ph (a), 4ꢀMeC6H4 (b), 4ꢀMeOC6H4 (c), 4ꢀClC6H4 (d), Bn (e), Bui (f), cycloꢀС5H9 (g), cycloꢀC7H13 (h), cycloꢀC12H23 (i)
The 1Н NMR spectra of solutions of compounds 2 and
3 in the strong field contain three threeꢀproton singlet
signals of the indole moiety: of the 2ꢀmethyl (δ ~2.40,
Nꢀmethyl (δ ~3.50), and 5ꢀmethoxy groups (δ ~3.72).
The downfield regions of these spectra exhibit signals
of three aromatic protons of the indole cycle in positions
4, 6, and 7 at δ ~6.35, ~6.80, and 7.20, respectively, with
the chemical shifts and spinꢀspin coupling constants (J)
characteristic of the 5ꢀmethoxyindole substituent; the sigꢀ
nals of protons of the thiophene ring in positions 4 and 5
are observed in the region δ 7.10—7.30, and the signals of
those in position 2 are observed in the region of 8.00 ppm.
Their chemical shifts and J constants are also characterisꢀ
tic of thiophene substituted in position 3, which allows
one to ascribe the structure of open form А to these diꢀ
hetarylethenes (Scheme 2). In addition, the signals of
protons of the substituents at the pyrrolic nitrogen atom
are detected in the 1Н NMR spectra of solutions of
compounds 3a—i. Thus, compound 2 has the strucꢀ
ture of 3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ4ꢀ(3ꢀ
thienyl)furanꢀ2,5ꢀdione, and compounds 3a—i are
3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ4ꢀ(3ꢀthiꢀ
enyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdiones substituted at the pyrrolic
nitrogen atom (see Scheme 2).
cients at the absorption band maxima take values of
(6.08—9.59)•103 L mol–1 cm–1. The hypsochromic shift
of the longꢀwavelength absorption band maxima, whose
value is 7—8 nm, is observed in the series of pyrroledione
derivatives 3a—i on going from compounds 3a—d with
Nꢀaryl substituents to dihetarylethenes 3f—i with Nꢀalkyl
substituents (Table 1). The characteristics of the EAS of
furandione 2 are similar to the corresponding parameters
of Nꢀalkylꢀsubstituted pyrrolediones (see Table 1).
The mentioned correlations between the structure and
absorption properties of dihetarylethenes based on 5ꢀmethꢀ
oxyindole coincide with those determined earlier12 for
analogous dihetarylethenes based on 5ꢀmethoxyꢀ1Нꢀ
benzo[g]indole. It should be mentioned that benzoannulaꢀ
tion in the indole moiety results in the hypsochromic
shift of the longꢀwavelength absorption band maxima by
~10 nm in nonsymmetric dihetarylethenes based on both
furandione and pyrroledione.
Dihetarylethenes 2 and 3a—i possess fluorescence with
band maxima at 533—555 nm. The fluorescence excitaꢀ
tion spectra are well consistent with the absorption specꢀ
tra, evidencing unambiguously that the observed fluoresꢀ
cence belongs to noncyclic isomers А of dihetarylethenes
2 and 3a—i (Fig. 1, see Table 1).
The electronic absorption spectra (EAS) of the synꢀ
thesized nonsymmetric dihetarylethenes are characterꢀ
ized by longꢀwavelength absorption bands with maxiꢀ
ma at 453—461 nm. The molar absorption coeffiꢀ
The fluorescence efficiency of compounds 2 and 3a—i
vary in wide ranges depending on the structure (see Table 1).
The highest fluorescence quantum yields attaining values
of 0.20—0.22 are observed for Nꢀalkyl pyrrolediones 3e—i.
Scheme 2

Dihetarylethenes: structures and photochromism
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 9, September, 2011
1901
Table 1. Spectral absorption and spectral fluorescence characteristics of isomeric forms of dihetarylethenes 2
and 3a—i in heptane at 293 K
Comꢀ
pound
Initial form, А
Fluorescence
Emission,
Photoinduced form, В,
absorbance,
Absorbance,
max/nm
(ε•10–3
λ
max/nm
λ
Excitation,
Quantum
yield, φ
)
λ
max/nm
λ
max/nm
2
453 (7.40)
461 (6.08)
461 (6.67)
461 (7.22)
467 (8.29)
458 (7.33)
453 (9.59)
454 (7.40)
453 (9.00)
453 (7.70)
462
463
462
458
468
459
455
455
454
455
540
551
552
550
555
534
533
534
533
534
0.02
0.12
0.04
0.001
0.13
0.20
0.20
0.20
0.22
0.21
—
563
563
563 sh
572
553
552
551
551
552
3a
3b
3c
3d
3e
3f
3g
3h
3i
Among the Nꢀaryl derivatives, the fluorescence quantum
yields vary from 0.001—0.04 for compounds 3b,c with elecꢀ
tronꢀreleasing substituents in the phenyl ring to 0.12 and
0.13 for unsubstituted dihetarylethene 3a and 4ꢀchloroꢀ
substituted compound 3d, respectively. A comparison of
the fluorescence efficiency of the indole derivatives conꢀ
sidered in the present work and the corresponding benzoꢀ
indole derivatives of nonsymmetric dihetarylethenes studꢀ
ied earlier12 makes it possible to draw an important conꢀ
clusion: benzoannulation to the indole moiety of nonsymꢀ
metric dihetarylethenes based on furandione and pyrroleꢀ
dione decreases the fluorescence quantum yields of the
open isomers by a factor of 10—30.
duces their coloration accompanied by the appearance
and growth of absorption bands in the longꢀwavelength
region of the EAS and also by a decrease in the characterꢀ
istic bands of transitions S0 → S1 of dihetarylethenes (Fig. 2).
The longꢀwavelength absorption band maxima lie in the
region 551—572 nm (see Table 1). This behavior is charꢀ
acteristic of the photocyclization of dihetarylethenes
А → В.1
The influence of structural peculiarities of dihetarylꢀ
ethenes on the positions of the longꢀwavelength absorpꢀ
tion band maxima of closed isomers В is manifested to the
same extent as for open forms А (see Table 1).
Unlike the starting forms А, closed isomers В have no
fluorescence.
For the quantitative characterization of the phototransꢀ
formations, we determined the values of "colorability" reꢀ
presenting the product of the quantum yield of the photoꢀ
The differences caused by the ethene ring structure are
observed upon irradiation of solutions of dihetarylethenes
2 and 3a—i in hexane. The irradiation of furandione derivꢀ
ative 2 does result in any visible changes in the EAS. On
the contrary, photolysis of solutions of pyrrolediones inꢀ
A
Ifl (arb. units)
ε/L mol–1 cm–1
10
0.5
15000
4
0.4
8
12000
0.3
6
1
9000
3
0.2
0.1
0
1
4
6000
3000
0
2
2
300
400
500
600
700 λ/nm
300
400
500
600
700
λ/nm
Fig. 2. Electronic absorption spectra of a solution of dihetꢀ
arylethene 3a in heptane before (1) and after consecutive irradiꢀ
ation with λ = 436 nm (2—4) recorded at an interval of 2 min
(С = 4•10–5 mol L–1, l = 1 cm, T = 293 K).
Fig. 1. Fluorescence (1) (λ = 460 nm), fluorescence excitaꢀ
tion (2) (λapp = 560 nm), and absorption (3) spectra of a solution
of compound 3b in heptane (T = 293 K).
exc

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 9, September, 2011
Makarova et al.
Table 2. Characteristics of photochromic transformations of dihetarylethenes 3a—i in heptane at 293 K
Comꢀ
pound
Photochemical processes
Thermoꢀ
bleaching,
kBA•10–5/s–1
Coloration,
Bleaching,
Φ
AB/Φ
BA
B
B
•103
Φ
•ε
•103
Φ
•ε
AB max
BA max
L mol–1 cm–1
3a
3b
3c
3d
3e
3f
3g
3h
3i
1.7
2.2
—
1.9
1.6
2.3
2.1
1.9
2.6
2.2
2.3
—
2.0
2.8
2.4
2.6
2.8
2.8
0.77
0.96
—
0.95
0.57
0.96
0.81
0.68
0.93
14.0
17.3
12.8
9.8
2.6
6.6
1.4
1.7
1.9
reaction (Φ) on the value of molar absorption coefficient
at the longꢀwavelength absorption band maximum of the
photoinduced form (εmaxВ). The efficiencies of cyclizaꢀ
tion photoreactions expressed in terms of "colorability"
(ΦАВ•εmaxВ) are listed in Table 2. The values obtained for
colorabilities of dihetarylethenes 3a—i based on 5ꢀmethꢀ
oxyindole exceed the colorability of dihetarylethenes
based on 5ꢀmethoxyꢀ1Нꢀbenzoindole by a factor of
3—4.12 The estimation of the quantum yields of photoꢀ
Closed isomers B of dihetarylethenes 3a—i exhibit phoꢀ
tochemical activity related to photoinduced ring opening
resulting in the formation of the starting forms А of diꢀ
hetarylethenes. The values obtained for efficiencies of phoꢀ
tocyclization reactions В → А, estimated using parameter
ΦВА•εmax, depend on the substituent at the nitrogen atom
of the pyrroledione moiety: they are higher in the case of
alkyl substituents of compounds 3e—i (see Table 2). The
ratio of quantum yields of the forward and backward phoꢀ
toreactions (ΦАВ/ΦВА) for compounds 3a—i is 0.57—0.96
and indicates that the efficiencies of the cyclization and
ring opening photoreactions are approximately equal in
the most part of cases, unlike the benzoindole derivatives
for which the ratio is 0.19—0.28 (see Table 2).12 The estiꢀ
mated values of quantum yields for photoreactions В → А
of dihetarylethenes 3a—i are 0.20—0.28 as in the case of
the benzoindole analogs.
cyclization ΦАВ of pyrrolediones of the indole series at
В
the averaged value of molar extinction coefficient εmax
=
= 10 000 L mol–1 cm–1 taken from the literature data14—19
gives the values 0.16—0.26. It is noteworthy that in the
case of methoxyꢀsubstituted dihetarylethene 3c the level
of photocoloration is ultimately low, which does not allow
one to estimate quantitatively the efficiency of photoꢀ
cyclization.
The established dependence of the efficiencies of
photoinitiated processes, viz., fluorescence and photoꢀ
cyclization, in molecules of nonsymmetric dihetarylꢀ
ethenes on the benzoannulation of the indole moiety can
be related to the influence of these structural modificaꢀ
tions on the position of conformational equilibrium of the
noncyclic isomers. It is most likely that the benzoannulaꢀ
tion of the indole fragment increases the content of isoꢀ
mers existing in the "inactive" parallel conformation
(Аꢀsyn) and thus decreases the fluorescence and photoꢀ
cyclization efficiencies.
After irradiation was stopped, the very low (at 293 K)
backward thermal recyclization В → А is observed, whose
kinetics obeys the multiexponential law. The rate conꢀ
stants of dark reactions В → А in heptane (see Table 2) are
(1.4—17.3)•10–5•s–1. Thermal recyclization of Nꢀaryl deꢀ
rivatives of dihetarylethenes 3a—d is faster than that for
Nꢀalkyl compounds 3e—i. This is probably caused by the
additional stabilization of the closed form in the latter due
to more pronounced electronꢀdonor properties of the alkyl
substituents.
No complete photoconversion of the initial form A to
cyclic form B is observed for compounds 3a—i. Prolonged
irradiation results in the establishment of the photostaꢀ
tionary state, which is indicated by a rather high level of
the relative fluorescence intensity of cyclic forms А under
the conditions where UV irradiation does not already inꢀ
duce changes in the EAS (Fig. 3). The photostationary
state exists due to the very low rate constants of backward
thermal processes, which is evidently caused by the strong
overlapping of the absorption bands attributed to transiꢀ
tion S0 → S1 of the initial form А and transition S0 → S2 of
photoinduced isomer В, which inevitably leads to the exꢀ
citation of form B upon the excitation of form А. The low
yield of photocoloration of 4ꢀmethoxyphenylꢀsubstituted
dihetarylethene 3c can be a consequence of the appearꢀ
ance of the photostationary state with an insignificant conꢀ
tent of cyclic isomers В.
Dihetarylethenes 3a—i are resistant to photodegradaꢀ
tion. For instance, no decrease in the absorbance of the
photostationary state was observed within 10 cycles phoꢀ
tocoloration—photobleaching (Fig. 4).

Dihetarylethenes: structures and photochromism
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 9, September, 2011
1903
Ifl (arb. units)
a Cary Eclipse fluorimeter (Varian). The fluorescence quantum
yields were determined by the Parker—Rice method20 using
3ꢀmethoxybenzanthrone in toluene (ϕ = 0.1, λ = 365 nm) as
a standard luminophore.21 The solutions were irradiated with
a DRShꢀ250 mercury lamp using a set of interferential light
filters to pick out mercury spectral lines in a quartz cell (l = 1 cm).
The kinetic photocoloration curves of dihetarylethene solutions
were recorded directly during irradiation on a Cary 50 spectroꢀ
photometer with an attachment for thermostatic control of the
samples. A xenon lamp with a monochromator for picking out
narrow spectral lines (Newport) was used as a radiation source.
The absorbance intensity was determined using a Newport 2935
power meter for optical radiation. The optical radiation intensiꢀ
ty at the wavelengths used (460 and 580 nm) was 4.17•1015 and
1.33•1015 photon s–1, respectively. The slope ratio of the tanꢀ
gent at the initial time moment was calculated from the kinetic
500
400
300
200
100
1
4
500
600
700
800 λ/nm
Fig. 3. Fluorescence spectra of a solution of dihetarylethene 3a
in heptane (С = 4•10–5 mol L–1) before (1) and after consecuꢀ
tive irradiation with λ = 436 nm (2—4) recorded at an interval of
2 min at the excitation wavelength 420 nm, 293 K, and a layer
thickness of 1 cm.
photocoloration and photobleaching curves to determine paꢀ
В
rameters Φ •ε
and Φ •ε В. In experiments on the deꢀ
АВ max
ВА max
termination of Φ •ε В and Φ •ε В, the absorbance of soluꢀ
АВ max
ВА max
tions of the dihetarylethenes studied at the irradiation waveꢀ
lengths was selected to be equal. The 1Н NMR spectra were
obtained on a Varian Unityꢀ300 spectrometer (300 MHz) in
CDCl3 and DMSOꢀd6 using HMDS as an external standard.
Vibrational spectra were detected on a Varian Excalibur 3100
FTꢀIR by the frustrated total internal reflection (FTIR) method.
5ꢀMethoxyꢀ1,2ꢀdimethylindole (1) was synthesized accordꢀ
ing to a procedure described earlier,13 m.p. 67—68 °C.
A
0.12
3ꢀ(5ꢀMethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ4ꢀ(3ꢀthienyl)fuꢀ
ranꢀ2,5ꢀdione (2). Oxalyl chloride (0.26 mL, 3 mmol) was added
dropwise to a solution of compound 1 (0.5 g, 3 mmol) in 1,2ꢀdiꢀ
chloroethane (5 mL) at 0 °C. The reaction mixture was stored
for 30 min, then the solvent was distilled off, and a solution of
3ꢀthiopheneacetic acid (0.43 g, 3 mmol) and triethylamine
(2.1 mL, 15 mmol) in 1,2ꢀdichloroethane (7 mL) was added to
the dry residue. The mixture was stored for 15 min at 0 °C and
then refluxed for 1 h and cooled. The precipitate that formed
was filtered off, the solvent was distilled off, the product was
purified by column chromatography (silica gel—chloroform),
and chloroform was distilled off. The product was recrystallized
from MeOH. The yield was 0.2 g (18.9%), red crystals, m.p.
203—204 °C. IR, ν/cm–1: 1750, 1820 (C=O). 1Н NMR (CDCl3),
δ: 2.42, 3.53, 3.75 (all s, 3 H each, Me, NMe, OMe); 6.32 (d, 1 H,
Н(4) of indole, J = 2.3 Hz); 6.84 (dd, 1 H, Н(6) of indole,
J1 = 2.3 Hz, J2 = 8.8 Hz); 7.20—7.26 (m, 3 H, Н(4) of thiophene,
Н(7) of indole, Н(5) of thiophene); 8.11 (dd, 1 H, Н(2) of
thiophene, J1 = 2.9 Hz, J2 = 1.3 Hz). Found (%): C, 64.01;
H, 4.05; N, 3.83. C19H15NO4S. Calculated (%): C, 64.58;
H, 4.28; N, 3.96.
0.08
0.04
0
0
2
4
6
8
10
n
Fig. 4. Change in the absorbance of a solution of dihetarylethene
3a in heptane at the absorption band maximum of form B
(564 nm) upon the repetition of photocoloration cycles (irradiaꢀ
tion with λ = 436 nm for 6 min)—photobleaching (irradiation
with λ = 546 nm for 6 min); n is the number of cycles.
Thus, we synthesized the new representatives of the
class of nonsymmetric dihetarylethenes: photochemically
inactive 3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ4ꢀ
(3ꢀthienyl)furanꢀ2,5ꢀdione and photochromic 1ꢀalkylꢀ(1ꢀ
aryl)ꢀ3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Нꢀindolꢀ3ꢀyl)ꢀ4ꢀ(3ꢀ
thienyl)ꢀ1(Н)ꢀpyrroleꢀ2,5ꢀdiones. The absence of benꢀ
zoannulation in the indole moiety results in the enhanceꢀ
ment of the fluorescence and photocyclization efficiencies
of the noncyclic isomers. Recyclization processes of the
products of photolysis of pyrrolediones occur in both the
ground and excited states.
Synthesis of 1ꢀarylꢀ3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀ
yl)ꢀ4ꢀ(3ꢀthienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdiones 3a—d (general proceꢀ
dure). The corresponding arylamine (0.42 mmol) was added to
a solution of compound 2 (0.28 mmol) in AcOH (4 mL). The
reaction mixture was refluxed for 2 h and then cooled, the solꢀ
vent was evaporated to 2 mL, the precipitate that formed
was filtered off, and the obtained product was recrystallized
from BuOH.
3ꢀ(5ꢀMethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ1ꢀphenylꢀ4ꢀ(3ꢀ
thienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdione (3a). The yield was 0.1 g (83%),
orange crystals, m.p. 200—201 °C. IR, ν/cm–1: 1706 (C=O).
1Н NMR (CDCl3), δ: 2.39, 3.52, 3.72 (all s, 3 H each, Me,
NMe, OMe); 6.40 (d, 1 H, Н(4) of indole, J = 2.3 Hz); 6.79 (dd,
Experimental
Electronic absorption spectra were obtained on a Cary 100
spectrophotometer (Varian). Fluorescence was measured on

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Russ.Chem.Bull., Int.Ed., Vol. 60, No. 9, September, 2011
Makarova et al.
1 H, Н(6) of indole, J1 = 2.3 Hz, J2 = 8.8 Hz); 7.15 (dd, 1 H,
Н(4) of thiophene, J1 = 2.9 Hz, J2 = 5.1 Hz); 7.18 (d, 1 H, Н(7)
of indole, J = 8.8 Hz); 7.22 (dd, 1 H, Н(5) of thiophene, J1 = 1.3 Hz,
J2 = 5.1 Hz); 7.28—7.58 (m, 5 H, Ar); 8.08 (dd, 1 H, Н(2) of
thiophene, J1 = 2.9 Hz, J2 = 1.3 Hz). Found (%): C, 70.07; H,
4.61; N, 6.50. C25H20N2O3S. Calculated (%): C, 70.07; H, 4.70;
N, 6.54.
C, 70.57; H, 4.95; N, 6.29. C26H22N2O3S. Calculated (%):
C, 70.57; H, 5.01; N, 6.33.
1ꢀ(isoꢀButyl)ꢀ3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ4ꢀ
(3ꢀthienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdione (3f). The yield was 0.09 g
(64%), orange crystals, m.p. 138—139 °C. IR, ν/cm–1: 1702
1
(C=O). Н NMR (CDCl3), δ: 0.95 (d, 6 H, Me, J = 6.8 Hz);
2.10 (m, 1 H, CH); 2.34 (s, 3 H, Me); 3.40—3.48 (m, 2 H,
NСН2); 3.51 (s, 3 Н, NМе); 3.70 (s, 3 H, OMe); 6.35 (d, 1 H,
Н(4) of indole, J = 2.3 Hz); 6.78 (dd, 1 H, Н(6) of indole,
J1 = 2.3 Hz, J2 = 8.8 Hz); 7.12 (dd, 1 H, Н(4) of thiophene,
J1 = 2.9 Hz, J2 = 5.1 Hz); 7.15 (d, 1 H, Н(7) of indole, J = 8.8 Hz);
7.17 (dd, 1 H, Н(5) of thiophene, J1 = 1.3 Hz, J2 = 5.1 Hz); 8.02
(dd, 1 H, Н(2) of thiophene, J1 = 2.9 Hz, J2 = 1.3 Hz). Found (%):
C, 67.57; H, 5.88; N, 6.79. C23H24N2O3S. Calculated (%):
C, 67.62; H, 5.92; N, 6.86.
1ꢀCyclopentylꢀ3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ
4ꢀ(3ꢀthienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdione (3g). The yield was 0.11 g
(94%), orange crystals, m.p. 199—200 °C. IR, ν/cm–1: 1702
(C=O). 1Н NMR (CDCl3), δ: 1.48—1.72 (m, 2 H, CH2); 1.82—2.20
(m, 6 H, CH2); 2.34, 3.51, 3.69 (all s, 3 H each, Me, NMe,
OMe); 4.56 (m, 1 H, NCH); 6.36 (d, 1 H, Н(4) of indole,
J = 2.3 Hz); 6.77 (dd, 1 H, Н(6) of indole, J1 = 2.3 Hz,
J2 = 8.8 Hz); 7.07—7.18 (m, 3 H, Н(4) of thiophene, Н(7) of
indole, Н(5) of thiophene); 8.01 (m, 1 H, Н(2) of thiophene).
Found (%): C, 68.51; H, 5.71; N, 6.59. C24H24N2O3S. Calculatꢀ
ed (%): C, 68.55; H, 5.75; N, 6.66.
1ꢀCycloheptylꢀ3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ
4ꢀ(3ꢀthienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdione (3h). The yield was 0.12 g
(96%), orange crystals, m.p. 158—159 °C. IR, ν/cm–1: 1702
(C=O). 1Н NMR (CDCl3), δ: 1.40—1.75 (m, 6 H, CH2);
1.75—1.90 (m, 4 H, CH2); 2.14—2.32 (m, 2 H, CH2); 2.34, 3.51,
3.69 (all s, 3 H each, Me, NМе, OMe); 4.12—4.26 (m, 1 H,
CH); 6.34 (d, 1 H, Н(4) of indole, J = 2.5 Hz); 6.77 (dd, 1 H,
Н(6) of indole, J1 = 2.5 Hz, J2 = 8.8 Hz); 7.07—7.18 (m, 3 H,
Н(4) of thiophene, Н(7) of indole, Н(5) of thiophene);
8.00 (m, 1 H, Н(2) of thiophene). Found (%): C, 69.58; H, 6.24;
N, 6.19. C26H28N2O3S. Calculated (%): C, 69.62; H, 6.29;
N, 6.24.
1ꢀCyclododecylꢀ3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ
4ꢀ(3ꢀthienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdione (3i). The yield was 0.13 g
(90%), orange crystals, m.p. 139—140 °C. IR, ν/cm–1: 1702
(C=O). 1Н NMR (CDCl3), δ: 1.15—2.20 (m, 22 H, CH2); 2.34,
3.51, 3.69 (all s, 3 H each, Me, NMe, OMe); 4.39 (m, 1 H,
NCH); 6.35 (d, 1 H, Н(4) of indole, J = 2.4 Hz); 6.77 (dd, 1 H,
Н(6) of indole, J1 = 2.4 Hz, J2 = 8.9 Hz); 7.11 (dd, 1 H, Н(4) of
thiophene, J1 = 2.9 Hz, J2 = 5.1 Hz); 7.15 (d, 1 H, Н(7) of
indole, J = 8.9 Hz); 7.16 (dd, 1 H, Н(5) of thiophene, J1 = 1.3 Hz,
J2 = 5.1 Hz); 8.02 (dd, 1 H, Н(2) of thiophene, J1 = 2.9 Hz,
J2 = 1.3 Hz) Found (%): C, 71.72; H, 7.35; N, 5.38. C31H38N2O3S.
Calculated (%): C, 71.78; H, 7.38; N, 5.40.
3ꢀ(5ꢀMethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ1ꢀ(4ꢀmethylꢀ
phenyl)ꢀ4ꢀ(3ꢀthienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdione (3b). The yield was
0.1 g (81%), orange crystals, m.p. 202—203 °C. IR, ν/cm–1
:
1700 (C=O). 1Н NMR (CDCl3), δ: 2.38, 2.39 (both s, 3 H, Me);
3.51, 3.71 (both s, 3 H each, NMe, OMe); 6.39 (d, 1 H, Н(4) of
indole, J = 2.3 Hz); 6.79 (dd, 1 H, Н(6) of indole, J1 = 2.3 Hz,
J2 = 8.8 Hz); 7.14 (dd, 1 H, Н(4) of thiophene, J1 = 2.9 Hz,
J2 = 5.1 Hz); 7.17 (d, 1 H, Н(7) of indole, J = 8.8 Hz); 7.22 (dd,
1 H, Н(5) of thiophene, J1 = 1.2 Hz, J2 = 5.1 Hz); 7.24—7.39
(m, 4 H, Ar); 8.08 (dd, 1 H, Н(2) of thiophene, J1 = 2.9 Hz,
J2 = 1.2 Hz). Found (%): C, 70.49; H, 4.98; N, 6.29. C26H22N2O3S.
Calculated (%): C, 70.57; H, 5.01; N, 6.33.
3ꢀ(5ꢀMethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ1ꢀ(4ꢀmethoxyꢀ
phenyl)ꢀ4ꢀ(3ꢀthienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdione (3c). The yield was
0.1 g (81%), orange crystals, m.p. 161—162 °C. IR, ν/cm–1
:
1
1704 (C=O). Н NMR (CDCl3), δ: 2.39, 3.51, 3.71, 3.82 (all s,
3 H each, C(2)Me, NMe, OMe, OMe); 6.39 (d, 1 H, Н(4) of
indole, J = 2.4 Hz); 6.79 (dd, 1 H, Н(6) of indole, J1 = 2.4 Hz,
J2 = 8.8 Hz); 6.94—7.02 (m, 2 H, Ar); 7.14 (dd, 1 H, Н(4) of
thiophene, J1 = 2.9 Hz, J2 = 5.1 Hz); 7.17 (d, 1 H, Н(7) of
indole, J = 8.8 Hz); 7.21 (dd, 1 H, Н(5) of thiophene, J1 = 1.2 Hz,
J2 = 5.1 Hz); 7.28—7.38 (m, 2 H, Ar); 8.07 (dd, 1 H, Н(2) of
thiophene, J1 = 2.9 Hz, J2 = 1.2 Hz). Found (%): C, 68.03;
H, 4.78; N, 6.09. C26H22N2O4S. Calculated (%): C, 68.11;
H, 4.84; N, 6.11.
1ꢀ(4ꢀChlorophenyl)ꢀ3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ
4ꢀ(3ꢀthienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdione (3d). The yield was 0.11 g
(87%), orange crystals, m.p. 199—200 °C. IR, ν/cm–1: 1702
(C=O). 1Н NMR (CDCl3), δ: 2.39, 3.51, 3.72, (all s, 3 H each,
Me, NMe, OMe); 6.38 (d, 1 H, Н(4) of indole, J = 2.5 Hz); 6.79
(dd, 1 H, Н(6) of indole, J1 = 2.5 Hz, J2 = 8.9 Hz); 7.15 (dd, 1 H,
Н(4) of thiophene, J1 = 2.9 Hz, J2 = 5.1 Hz); 7.18 (d, 1 H, Н(7)
of indole, J = 8.9 Hz); 7.21 (dd, 1 H, Н(5) of thiophene, J1 = 1.2 Hz,
J2 = 5.1 Hz); 7.44 (m, 4 H, Ar); 8.07 (dd, 1 H, Н(2) of thiophene,
J1 = 2.9 Hz, J2 = 1.2 Hz). Found (%): C, 64.62; H, 4.25; N, 5.89.
C25H19ClN2O3S. Calculated (%): C, 64.86; H, 4.14; N, 6.05.
Synthesis of 1ꢀalkylꢀ3ꢀ(5ꢀdimethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ
3ꢀyl)ꢀ4ꢀ(3ꢀthienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdiones 3e—i (general proceꢀ
dure). The corresponding alkylamine (0.42 mmol) and DMAP
(4 mg) were added to a solution of compound 2 (0.28 mmol) in
butanol (10 mL). The obtained reaction mixture was refluxed for
3 h and then cooled. The solvent was evaporated to 2 mL,
and the precipitate that formed was filtered off and washed
with MeOH. The product obtained was recrystallized from
butanol.
This work was financially supported by the Federal
Target Program "Scientific and Scientific—Pedagogical
Personnel of the Innovative Russia in 2009—2013" (State
Contract No. P2260).
1ꢀBenzylꢀ3ꢀ(5ꢀmethoxyꢀ1,2ꢀdimethylꢀ1Hꢀindolꢀ3ꢀyl)ꢀ4ꢀ(3ꢀ
thienyl)ꢀ1Hꢀpyrroleꢀ2,5ꢀdione (3e). The yield was 0.11 g (89%),
orange crystals, m.p. 149—150 °C. IR, ν/cm–1: 1702 (C=O).
1Н NMR (CDCl3), δ: 2.34, 3.49, 3.69 (all s, 3 H each, Me,
NMe, OMe); 4.80 (s, 2 H, CH2); 6.33 (d, 1 H, Н(4) of indole,
References
J = 2.4 Hz); 6.77 (dd, 1 H, Н(6) of indole, J1 = 2.4 Hz, J2
=
= 8.8 Hz); 7.07—7.18 (m, 3 H, Н(4) of thiophene, Н(7) of
indole, Н(5) of thiophene); 7.24—7.50 (m, 5 H, Ar); 8.01 (dd, 1 H,
Н(2) of thiophene, J1 = 2.8 Hz, J2 = 1.2 Hz). Found (%):
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Received October 14, 2010;
in revised form March 28, 2011