Synthesis and photochromic properties of dithienylmaleimides with sulfur-containing fragments

Article abstract of DOI:10.1007/s11172-012-0295-z

A number of sulfur-containing dithienylmaleimide derivatives were synthesized. Spectral and kinetic characteristics of the compounds obtained were studied, which showed that all the dithienylethenes synthesized possessed photochromic properties.

Full text of DOI:10.1007/s11172-012-0295-z

Russian Chemical Bulletin, International Edition, Vol. 61, No. 11, pp. 2109—2113, November, 2012
2109
Synthesis and photochromic properties of dithienylmaleimides
with sulfurꢀcontaining fragments
O. Yu. Kuznetsova,a I. V. Platonova,a B. V. Lichitskii,a M. M. Krayushkin,a and V. A. Barachevskiib
aN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328. Eꢀmail: mkray@ioc.ac.ru
bCenter of Photochemistry, Russian Academy of Sciences,
7a ul. Novatorov, 119421 Moscow, Russian Federation.
Fax: +7 (495) 936 1255. Eꢀmail: barva@photonics.ru
A number of sulfurꢀcontaining dithienylmaleimide derivatives were synthesized. Spectral
and kinetic characteristics of the compounds obtained were studied, which showed that all the
dithienylethenes synthesized possessed photochromic properties.
Key words: synthesis, dithienylmaleic anhydrides, sulfurꢀcontaining dithienylmaleimides,
photochromism, photocoloration, photodecoloration.
Diarylethenes are subject to the valence isomerization
between two thermally stable forms: open and cyclic.1
These compound are the most promising candidates for
the development on their basis of molecular photoswitchꢀ
es1,2 and carriers of information of large capacity used for
recording, processing, and storage of data.2—4 Photoꢀ
chromic compounds, which can be used for such a purꢀ
pose, should possess a certain set of operating characterisꢀ
tics: the thermal stability of both isomeric forms, the high
quantum yield, as well as the high fatigue resistance of
phototransformations.
1,2ꢀDithienylethenes, in particular, the products conꢀ
taining maleic anhydride or maleimide fragments as the
ethene bridge,2 are one class of photochromic compounds
meeting these conditions. Photocontrolled systems develꢀ
oped based on photochromic dithienylmaleimides and
nanoparticles of noble metals are of special interest.5 To
bring into being efficient molecular interactions of photoꢀ
chromic compounds with nanoparticles of noble metals,
the presence of a fragment providing binding of the photoꢀ
chromic molecule with the metal nanoparticle is necesꢀ
sary in the structure of photochrom. Thiol groups can
serve as such fragments,6,7 however, the synthesis of the
corresponding derivatives meets certain difficulties caused
by their low stability.
Results and Discussion
Synthesis of dithienylmaleimides with sulfide substituꢀ
ents in the bridging fragment. In the present work, we synꢀ
thesized a number of sulfurꢀcontaining dithienylmaleimꢀ
ides in order to subsequently compare complexation propꢀ
erties of these products.
In the literature, we found descriptions of several
approaches to the preparation of photochromic dithienylꢀ
substituted maleimide derivatives based on the correspondꢀ
ing maleic anhydrides and primary aliphatic and aromatic
amines.8,9 The starting dithienylmaleic anhydride (1a) was
obtained by the oxidation of furanone 2 with atmospheric
oxygen in the presence of anhydrous potassium carbonate
(Scheme 1).
Scheme 1
The purpose of the present work was to develop an
approach to the synthesis of photochromic dithienylꢀ
maleic anhydrides with thiazole substituents, to functionꢀ
alize the bridging fragment of the products obtained
with sulfurꢀcontaining nitrogen nucleophiles, and to study
spectral and kinetic characteristics of the compounds synꢀ
thesized.
The synthesis of the thiazoleꢀcontaining maleic anꢀ
hydride 1b is given in Scheme 2. The condensation of
thienylchloroketone 3 with thioacetamide resulted in thiꢀ
enylthiazole 4, whose chloroacetylation furnished haloꢀ
ketone 5. The reaction of compound 5 with (2,5ꢀdimethylꢀ
thiophenꢀ3ꢀyl)acetic acid resulted in the formation of the
target maleic anhydride 1b.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2092—2097, November, 2012.
1066ꢀ5285/12/6111ꢀ2109 © 2012 Springer Science+Business Media, Inc.

2110
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 11, November, 2012
Kuznetsova et al.
Scheme 2
Scheme 3
We studied the reaction of dithienylmaleic anhydride
1b with 2ꢀ(methylthio)aniline (6) and 2ꢀ(benzylthio)ꢀ
ethylamine (7) (Scheme 3). The reaction was carried out
by reflux in ethanol in the presence of catalytic amounts of
pꢀtoluenesulfonic acid. In the case of aliphatic amine 7,
the reaction proceeded faster than with aromatic amine 6,
that was attributable to the different nucleophilicity of
these amines. This resulted in the synthesis of sulfurꢀconꢀ
taining maleimides 8 and 9 (see Scheme 3).
Synthesis of Nꢀthiocarbamideꢀsubstituted dithienylꢀ
maleimide. Earlier, we have shown10 that photochromic
dithienylperfluorocyclopentenes, in which the thiosemiꢀ
carbazide fragment was bonded to the thiophene rings,
formed stable complexes with silver nanoparticles. In the
present work, we suggest an approach enabling one to
incorporate a thiosemicarbazide fragment into the bridgꢀ
ing maleimide ring. It should be noted that there are no
literature data describing reactions of disubstituted maleic
anhydrides with thiosemicarbazides.
The reaction of dithienylmaleic anhydrides 1a,b with
unsubstituted thiosemicarbazide was carried out by proꢀ
longed reflux in acetic acid (Scheme 4). As a result, maleꢀ
imides 10a,b containing a thiocarbamide fragment at the
ring nitrogen atom were obtained in moderate yields
(35—40%).
When the reaction was carried out with phenylthioꢀ
semicarbazide under similar conditions, the target prodꢀ
uct 11 was not isolated. The desired condensation was
successfully carried out by reflux in PriOH in the presence
of catalytic amount of pꢀtoluenesulfonic acid (Scheme 5).
To sum up, we suggested a general approach enabling
one to synthesize dithienylꢀsubstituted maleimides conꢀ
taining sulfide and thiocarbamide fragments at the nitroꢀ
gen atom of the bridging ring.
Spectral and kinetic studies of photochromic properties
of dithienylmaleimides with sulfurꢀcontaining fragments. The
results of the studies are given in Table 1 and in Fig. 1.
Figure 1 demonstrates typical absorption spectra of the
initial open and the photoinduced cyclic form of the syntheꢀ
sized dithienylmaleimides with sulfurꢀcontaining fragments.

Synthesis and photochromic properties
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 11, November, 2012 2111
Scheme 4
D
1.0
380
2
0.8
0.6
0.4
0.2
3
1
500
400
600
/nm
Fig. 1. Absorption spectra of compound 10b in acetonitrile
(C = 4•10–5 mol L–1) before irradiation (1), after UV irradiation
through the UFSꢀ1 light filter (2) and subsequent irradiation
with visible light through the ZhSꢀ16 light filter (3).
1, 10: R = Me (a),
(b)
the thiazole substituent in the thiophene fragment (comꢀ
pounds 8, 9, 10b, and 11), the position of the absorption
bands of the cyclic form slightly depends on the nature of
substituents in the structure of the bridge. In this case,
only the introduction of the benzylthioethyl group (comꢀ
pound 9) led to a hypsochromic shift of the absorption
band of the cyclic form.
Scheme 5
Table 1. Spectral and kinetic characteristics of dithienylmaleꢀ
imides with sulfurꢀcontaining fragments
A
B
Comꢀ



DB DB/DA kAB kBA
pound /nm /M–1 cm–1 /nm
s–1
8
382
405
380
403
367
400
382
407
384
6750
6000
6000
5500
5750
6250
7750
7000
4250
552 0.24
0.89 0.32 0.01
1.38 0.39 0.01
0.32 0.53 0.02
0.65 0.31 0.01
0.41 0.25 0.01
9
544 0.33
515 0.08
556 0.20
552 0.07
10a
10b
11
The reverse photoinduced transformations of the absorpꢀ
tion spectra under the influence of UV (see Fig. 1, curve 2)
and visible (see Fig. 1, curve 3) irradiation indicate that
the compounds 8—11 possess photochromic properties.
Analysis of the results of spectral and kinetic studies of
photochromism given in Table 1 show that all the syntheꢀ
sized compounds exhibit photochromic properties charꢀ
acteristic of diarylethenes.
From Table 1, it is seen that the introduction of the
thiazole group into the thiophene ring (cf. the data for
compounds 10a and 10b) leads to a bathochromic shift of
the absorption maxima of both the open and the cyclic
form. For the latter, it reached 41 nm. As it follows from
the comparison of spectroscopic data for compounds with
Note: A and B are the wavelengths in the absorption maxima of
the open and the cyclic forms, respectively;  is the coefficient of
molar extinction in the absorption maxima of the open form A;
B
D is the maximum photoinduced change in the optical density
of solution in the absorption maximum of cyclic form in the
photostationary state; DB/DA is the maximum photoinduced
change in the optical density of solution in the absorption maxiꢀ
mum of cyclic form in the photostationary state normalized on
the value of optical density in the absorption maximum of open
form; kAB, kBA are the rate constants of the process of photoꢀ
coloration of solution upon irradiation through the UFSꢀ1 light
filter and photodecoloration through the ZhSꢀ11 light filter, reꢀ
spectively.

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Kuznetsova et al.
= [DB0]exp(–kt)) of solutions of diarylethenes are monoexpoꢀ
nential. In this case, the molar extinction coefficients of the
colored forms in the maxima of their bands of the longwave
absorption were assumed to be approximately equal, which can
be justified for a number of the structurally similar compounds.
The concentration of irradiated solutions was selected in such
a way as to provide the similar amount of the absorbed light.
1H and 13C NMR spectra were recorded on a Bruker AMꢀ300
(300 MHz) spectrometer. Melting points were measured a Boetꢀ
ius heating stage and were not corrected. Reaction progress and
purity of compounds obtained were monitored by TLC (Merck
Silica gel 60 F254 plates, eluent ethyl acetate—hexane).
For all the diarylethenes under study, considerable
photoinduced changes in optical density in the absorption
maximum of the cyclic form were found. In this case, the
introduction of the thiazole substituent into the thiophene
fragment (cf. data for compounds 10a and 10b) increases
susceptibility to UV irradiation evaluated by the value of
the normalized photoinduced optical density, whereas the
phenyl substituent in the bridging fragment (compound 11)
decreases it. Diarylethene with the benzylthioethyl subꢀ
stituent (compound 9) is characterized by the highest susꢀ
ceptibility to UV irradiation (see Table 1). Compound 8 is
also highly light susceptible.
From Table 1, it follows that the rate constant of photoꢀ
coloration decreases upon the introduction of additional
substituents in both the thiophene and the bridging fragꢀ
ment (cf. data for compounds 10a, 10b, and 11). Among
compounds with the thiazole fragment, the nature of subꢀ
stituents in the maleimide bridge (compounds 8, 9, and
10b) virtually does not affect the rate of photocoloration.
The process of photodecoloration under the influence
of visible irradiation is characterized by virtually identiꢀ
cal rate constants for all the compounds under study
(see Table 1).
In conclusion, the results of spectral and kinetic studꢀ
ies indicate that the introduction of the thiazole fragment
into the thiophene ring of diarylethene leads to a bathoꢀ
chromic shift of the absorption bands of both forms, to the
increase in light susceptibility to UV irradiation, to the
formation of cyclic form with higher value of optical denꢀ
sity. The change in the nature of substituents in the maleꢀ
imide bridge has considerably smaller influence on the
spectroscopic characteristics of both forms, except of the
sulfide substituents, whose introduction causes a considꢀ
erable increase in the susceptibility to UV irradiation.
Furanone 2,11 2ꢀ(methylthio)aniline (6),12 2ꢀ(benzylthio)ꢀ
ethylamine (7),13 2ꢀchloroacetylꢀ5ꢀmethylthiophene (3),14 and
2,5ꢀdimethylꢀ3ꢀthienylacetic acid15 were obtained according to
the procedures described in the literature.
3,4ꢀBis(2,5ꢀdimethylꢀ3ꢀthienyl)furanꢀ2,5ꢀdione (1a). A mixꢀ
ture of furanone 2 (0.1 g, 0.33 mmol) and (0.1 g, 0.66 mmol)
potassium carbonate in DMF (5 mL) was stirred for 16 h at 80 C.
Then, the reaction mixture was poured into water (20 mL) and
extracted with ethyl acetate (3×20 mL). The organic layer was
discarded, the aqueous layer was diluted with concentrated
hydrochloric acid (2 mL), a precipitate formed was filtered off,
washed with water and diethyl ether on the filter. The yield was
0.065 g (65%), m.p. 202—204 C (see Ref. 16: m.p. 203—204 C).
1H NMR (CDCl3), : 1.92 (s, 6 H, 2 CH3); 2.42 (s, 6 H, 2 CH3);
6.78 (s, 2 H, 2 HHet).
2ꢀMethylꢀ4ꢀ(5ꢀmethylꢀ2ꢀthienyl)ꢀ1,3ꢀthiazole (4). A mixture
of chloroketone 3 (1 g, 5.73 mmol) and thioacetamide (0.51 g,
6.87 mmol) in ethanol (20 mL) was refluxed for 2 h. Then, the
mixture was poured into water (50 mL), followed by the addition
of potassium hydroxide (0.77 g, 0.013 mol). A precipitate formed
was filtered off and washed with water. The yield was 78%,
1
m.p. 66—68 C. H NMR (CDCl3), : 2.48 (s, 3 H, CH3); 2.72
(s, 3 H, CH3); 6.69 (s, 1 H, CHHеt); 7.09 (s, 1 H, CHHеt); 7.21
(s, 1 H, CHHеt). Found (%): C, 55.43; H, 4.69; N, 7.25. C9H9NS2.
Calculated (%): C, 55.35; H, 4.64; N, 7.17.
2ꢀChloroꢀ1ꢀ[2ꢀmethylꢀ5ꢀ(2ꢀmethylꢀ1,3ꢀthiazolꢀ4ꢀyl)ꢀ3ꢀthiꢀ
enyl]ethanone (5). Chloroacetyl chloride (0.35 g, 3.07 mmol)
was added dropwise to a mixture of thienylthiazole 4 (0.5 g,
2.56 mmol) and aluminum chloride (1.2 g, 8.97 mmol) in
dichloromethane (25 mL). The reaction mixture was stirred for
2 h at room temperature. Then, the mixture was poured into
water (100 mL) and extracted with chloroform (3×50 mL). The
organic layer was washed with saturated aqueous sodium hydroꢀ
gen carbonate (3×100 mL) and water (3×100 mL), dried with
Na2SO4, the solvent was evaporated. The residue was recrystalꢀ
lized from hexane. The yield was 86%. m.p. 97—99 C. 1H NMR
(CDCl3), : 2.72 (s, 3 H, CH3); 2.80 (s, 3 H, CH3); 4.60 (s, 2 H,
CH2); 7.19 (s, 1 H, CHHеt); 7.52 (s, 1 H, CHHеt). Found (%):
C, 48.82; H, 3.86; N, 5.27. C11H10ClNOS2. Calculated (%):
C, 48.61; H, 3.71; N, 5.15.
3ꢀ(2,5ꢀDimethylthiophenꢀ3ꢀyl)ꢀ4ꢀ[2ꢀmethylꢀ5ꢀ(2ꢀmethylꢀ
thiazolꢀ4ꢀyl)thiophenꢀ3ꢀyl]furanꢀ2,5ꢀdione (1b). A mixture of
(0.11 g, 0.622 mmol) (2,5ꢀdimethylthiophenꢀ3ꢀyl)acetic acid,
2ꢀchloroꢀ1ꢀ[2ꢀmethylꢀ5ꢀ(2ꢀmethylthiazolꢀ4ꢀyl)ꢀthiophenꢀ3ꢀ
yl]ethanone 5 (0.17 g, 0.622 mmol), and anhydrous potassium
carbonate (0.28 g, 2 mmol) in DMF (4 mL) was stirred for 16 h
at 80 C. Then, the reaction mixture was poured into water and
extracted with ethyl acetate (3×30 mL), the organic layer was
discarded, the aqueous solution was acidified with 10% aq. hydroꢀ
Experimental
Spectrophotometric measurements (photostationary specꢀ
tra), as well as kinetics studies of the photocoloration and photoꢀ
decoloration processes in the photoinduced cyclic form of comꢀ
pound under study in solution were performed on a Varian Cary
50 Bio spectrophotometer (Australia). Acetonitrile from Aldrich
was used as the solvent, with the concentration of the solution
being 4•10–5 mol L–1. The measurements were made in 2ꢀmm
thick (kinetic measurements) and 10ꢀmm thick quartz cuvettes
(spectrophotometric measurements).
Hamamatsu lightning cureTM LC lamps (50—60 Hz, Japan)
and UFSꢀ1, ZhSꢀ11, and ZhSꢀ16 colored optical glasses were
used for the irradiation. The irradiance through the UFSꢀ1 and
ZhSꢀ16 light filters was 140 and 30 W m–2, respectively.
The rate constants of photocoloration and photodecoloraꢀ
tion of solutions of diarylethenes were determined from the moꢀ
noexponential kinetic curves using the Origin program.
The efficiency of photocoloration and photodecoloration was
evaluated based on the rate constant k, which was determined
on the suggestion that the kinetic curves of photocoloration
([DB] = [DB](1 – exp(–kt))) and photodecoloration ([DB] =

Synthesis and photochromic properties
Russ.Chem.Bull., Int.Ed., Vol. 61, No. 11, November, 2012 2113
1
chloric acid to pH = 2, followed by the addition of ethyl acetate
(30 mL) and stirring for 3 h at room temperature. Then, the
organic layer was separated, the aqueous layer was extracted
with ethyl acetate (2×30 mL), the extracts were dried with
Na2SO4. The solvent was evaporated, the residue was subjected
to chromatography on silica gel (eluent hexane—ethyl acetate
(3 : 1)) and recrystallized from diethyl ether. The yield was 56%,
m.p. 273—274 C. H NMR (DMSOꢀd6), : 1.89 (s, 3 H, CH3);
1.98 (s, 3 H, CH3); 2.40 (s, 3 H, CH3); 2.68 (s, 3 H, CH3); 6.70
(s, 1 H, CHHеt); 7.39 (s, 1 H, CHHеt), 7.78 (s, 1 H, CHHеt); 8.17
(s, 1 H, NH); 8.39 (s, 1 H, NH). Found (%): C, 50.83; H, 3.98;
N, 12.02. C20H18N4O2S4. Calculated (%): C, 50.61; H, 3.82;
N, 11.80.
Nꢀ{3ꢀ(2,5ꢀDimethylꢀ3ꢀthienyl)ꢀ4ꢀ[2ꢀmethylꢀ5ꢀ(2ꢀmethylꢀ
1,3ꢀthiazolꢀ4ꢀyl)ꢀ3ꢀthienyl]ꢀ2,5ꢀdioxoꢀ2,5ꢀdihydroꢀ1Hꢀpyrrolꢀ1ꢀ
yl}ꢀN´ꢀphenylthiourea (11). A mixture of dithienylmaleic anꢀ
hydride 1b (0.1 g, 3.73•10–4 mol), phenylthiosemicarbazide
(0.045 g, 3.8•10–4 mol), and pꢀtoluenesulfonic acid (5 mg,
3•10–5 mol) in propanꢀ2ꢀol (15 mL) was refluxed for 16 h. Then,
the mixture was poured into water, a precipitate formed was
filtered off and dried. The residue was subjected to chromatograꢀ
phy on silica gel (eluent hexane—ethyl acetate (3 : 1)). The yield
was 36%, m.p. 276—279 C. 1H NMR (DMSOꢀd6), : 1.89 (s, 3 H,
CH3); 1.98 (s, 3 H, CH3); 2.39 (s, 3 H, CH3); 2.60 (s, 3 H, CH3);
6.67—6.80 (m, 3 H, CHarom); 7.11—7.15 (m, 2 H, CHarom); 7.48
(s, 1 H, CHHеt); 7.70—7.80 (m, 2 H, CHarom); 9.94 (s, 1 H, NH).
Found (%): C, 56.85; H, 4.21; N, 10.32. C26H22N4O2S4. Calcuꢀ
lated (%): C, 56.70; H, 4.03; N, 10.17.
1
m.p. 181—183 C. H NMR (CDCl3), : 1.98 (s, 6 H, 2 CH3);
2.41 (s, 3 H, CH3); 2.74 (s, 3 H, CH3); 6.78 (s, 1 H, CHHеt); 7.21
(s, 1 H, CHHеt); 7.42 (s, 1 H, CHHеt). Found (%): C, 56.97;
H, 3.87; N, 3.57. C19H15NO3S3. Calculated (%): C, 56.84;
H, 3.77; N, 3.49.
3ꢀ(2,5ꢀDimethylꢀ3ꢀthienyl)ꢀ4ꢀ[2ꢀmethylꢀ5ꢀ(2ꢀmethylꢀ1,3ꢀ
thiazolꢀ4ꢀyl)ꢀ3ꢀthienyl]ꢀ1ꢀ[2ꢀ(methylthio)phenyl]ꢀ1Hꢀpyrroleꢀ
2,5ꢀdione (8). A mixture of dithienylmaleic anhydride 1b (0.4 g,
1 mmol) and 2ꢀ(methylthio)aniline 6 (0.15 g, 1.1 mmol) in acetic
acid (15 mL) was refluxed for 20 h. Then, the mixture was poured
into water, a precipitate formed was filtered off, dried, and subꢀ
jected to chromatography on silica gel (eluent hexane—ethyl
1
acetate (3 : 1)). The yield was 57%, m.p. 118—121 C. H NMR
(DMSOꢀd6), : 1.90 (s, 3 H, CH3); 1.98 (s, 3 H, CH3); 2.41
(s, 3 H, CH3); 2.48 (s, 3 H, CH3); 2.70 (s, 3 H, CH3); 6.72 (s, 1 H,
CHHеt); 7.31—7.62 (m, 5 H, CHarom); 7.79 (s, 1 H, CHHеt).
Found (%): C, 59.96; H, 4.37; N, 5.48. C26H22N2O2S4. Calcuꢀ
lated (%): C, 59.74; H, 4.24; N, 5.36.
References
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ylꢀ5ꢀ(2ꢀmethylꢀ1,3ꢀthiazolꢀ4ꢀyl)ꢀ3ꢀthienyl]ꢀ1Hꢀpyrroleꢀ2,5ꢀdiꢀ
one (9). A mixture of dithienylmaleic anhydride 1b (0.1 g,
3.7•10–4 mol), 2ꢀbenzylthioethylamine 7 (0.07 g, 4•10–4 mol),
and pꢀtoluenesulfonic acid (5 mg, 3•10–5 mol) in EtOH (10 mL)
was refluxed for 15 h. Then, the reaction mixture was poured
into water and filtered. A precipitate formed was dried and subꢀ
jected to chromatography on silica gel (eluent hexane—ethyl
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1
acetate (3 : 1)). The yield was 78%, m.p. 68—72 C. H NMR
(DMSOꢀd6), : 1.90 (s, 3 H, CH3); 1.98 (s, 3 H, CH3); 2.39 (s, 3 H,
CH3); 2.68 (s, 3 H, CH3, CH2); 3.70—3.82 (m, 4 H, 2 CH2); 6.71
(s, 1 H, CHHеt); 7.2—7.45 (m, 5 H, CHarom); 7.42 (s, 1 H, CHarom),
7.78 (s, 1 H, CHHеt). Found (%): C, 61.27; H, 4.89; N, 5.23.
C28H26N2O2S4. Calculated (%): C, 61.06; H, 4.76; N, 5.09.
Nꢀ[3,4ꢀBis(2,5ꢀdimethylꢀ3ꢀthienyl)ꢀ2,5ꢀdioxoꢀ2,5ꢀdihydroꢀ
1Hꢀpyrrolꢀ1ꢀyl]thiourea (10a). A mixture of dithienylmaleic anꢀ
hydride 1a (0.2 g, 6.27•10–4 mol) and thiosemicarbazide (0.07 g,
7.5•10–4 mol) in acetic acid (3 mL) was refluxed for 16 h. Then,
the mixture was poured into water, a precipitate formed was
filtered off, dried, and subjected to chromatography on silica gel
(eluent hexane—ethyl acetate (3 : 1)). The yield was 43%, m.p.
265—267 C. 1H NMR (DMSOꢀd6), : 1.84 (s, 6 H, 2 CH3); 2.40
(s, 6 H, 2 CH3); 6.68 (s, 2 H, CHHеt); 8.15 (s, 1 H, NH); 8.38
(s, 1 H, NH). 13C NMR (DMSOꢀd6), : 182.6 (C = S), 167.3
(C = O), 138.7 (Cthioph), 136.2 (Cthioph), 131.6 (Cthioph), 129.3
(Cthioph), 126.4 (C = C), 14.7 (CH3), 14.2 (CH3). Found (%):
C, 52.25; H, 4.46; N, 10.86. C17H17N3O2S3. Calculated (%):
C, 52.15; H, 4.38; N, 10.73.
14. S. Conde, D. I. Perez, A. Martinez, C. Perez, F. J. Moreno,
J. Med. Chem., 2003, 46, 4631.
Nꢀ{3ꢀ(2,5ꢀDimethylꢀ3ꢀthienyl)ꢀ4ꢀ[2ꢀmethylꢀ5ꢀ(2ꢀmethylꢀ
1,3ꢀthiazolꢀ4ꢀyl)ꢀ3ꢀthienyl]ꢀ2,5ꢀdioxoꢀ2,5ꢀdihydroꢀ1Hꢀpyrrolꢀ1ꢀ
yl}thiourea (10b). A mixture of dithienylmaleic anhydride 1b
(0.2 g, 4.96•10–3 mol) and thiosemicarbazide (0.04 g,
4.96•10–3 mol) in acetic acid (10 mL) was refluxed for 16 h.
Then, the mixture was poured into water, a precipitate formed
was filtered off, dried, and subjected to chromatography on silica
gel (eluent hexane—ethyl acetate (3 : 1)). The yield was 39%,
15. J. B. Press, J. J. McNally, J. Heterocycl. Chem., 1988, 25, 1571.
16. V. Z. Shirinyan, M. M. Krayushkin, L. I. Belen´kii, L. G.
Vorontsova, Z. A. Starikova, A. Yu. Martynkin, V. L. Ivanov,
B. M. Uzhinov, Khim. Geterotsikl. Soedin., 2001, 81 [Chem.
Heterocycl. Compd. (Engl. Transl.), 2001, 37, 77].
Received July 23, 2011;
in revised form October 16 2012