New push–pull chromophores. Synthesis of 2-[4-Aryl-3-cyano-5-hydroxy-5-methyl-1H-pyrrol-2(5H)-ylidene]malononitriles

Article abstract of DOI:10.1134/S1070428016100122

2-Aminoprop-1-ene-1,1,3-tricarbonitrile (malononitrile dimer) reacted with 1-arylpropane-1,2-diones in ethanol in the presence of piperidine to give new donor–acceptor chromophores, 2-[4-aryl-3-cyano-5-hydroxy-5-methyl-1H-pyrrole-2(5H)-ylidene]malononitriles.

Full text of DOI:10.1134/S1070428016100122

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2016, Vol. 52, No. 10, pp. 1440–1443. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © S.V. Fedoseev, M.Yu. Belikov, O.V. Ershov, I.N. Bardasov, V.A. Tafeenko, 2016, published in Zhurnal Organicheskoi Khimii, 2016,
Vol. 52, No. 10, pp. 1450–1453.
New Push–Pull Chromophores. Synthesis of 2-[4-Aryl-3-cyano-
5-hydroxy-5-methyl-1H-pyrrol-2(5H)-ylidene]malononitriles
S. V. Fedoseeva,* M. Yu. Belikova, O. V. Ershova, I. N. Bardasova, and V. A. Tafeenkob
a I.N. Ul’yanov Chuvash State University, Moskovskii pr. 15, Cheboksary, 428015 Russia
*e-mail: sergey.fedoseev88@gmail.com
b Faculty of Chemistry, Moscow State University, Leninskie gory 1, Moscow, 119991 Russia
Received May 5, 2016
Abstract—2-Aminoprop-1-ene-1,1,3-tricarbonitrile (malononitrile dimer) reacted with 1-arylpropane-1,2-
diones in ethanol in the presence of piperidine to give new donor–acceptor chromophores, 2-[4-aryl-3-cyano-5-
hydroxy-5-methyl-1H-pyrrole-2(5H)-ylidene]malononitriles.
DOI: 10.1134/S1070428016100122
Donor–acceptor (push–pull) chromophores have
attracted much attention over the past decades due to
their potential applications in photovoltaics [1, 2] and
optoelectronics [3–5], as well as in the design of non-
linear optical materials [6] and in other fields [7, 8].
Nowadays, the most promising push–pull chromo-
phores are those based on tricyanofuran (TCF) and
tricyanopyrrole (TCP) [9–13]. The main structural unit
of their molecules is a conjugated system connecting
the acceptor buta-1,3-diene-1,1,3-tricarbonitrile
(BDTC) fragment and various electron-donating
groups (Scheme 1).
presence of a hydroxy group in their molecules is
expected to extend the ways of their further directed
modifications with the goal of endowing them with
desired properties. A synthetic approach to hydroxytri-
cyanopyrroles is based on the reaction of malononitrile
dimer (MND, 2-aminoprop-1-ene-1,1,3-tricarbonitrile)
with 1,2-dicarbonyl compounds [14–16] (Scheme 2).
Scheme 2.
R
CN
CN
CN
R
R
O
O
CN
CN
R
+
CN
N
HO
NH2
MND
H
Scheme 1.
HTCP-1
Acceptor
The reactions described in [14–16] were carried out
Donor
CN
Donor
O
CN
mainly with 1,2-dicarbonyl compounds having similar
substituents at the carbonyl groups. Therefore, the
potential of this approach was not completely realized
since it remained unclear how the nature of the R sub-
stituent affects the regioselectivity of the formation of
hydroxytricyanopyrroles (HTCP-1). According to [17],
R1
R2
CN
CN
CN
CN
O
N
H
TCF
TCP
Taking into account practical importance of buta-
1,3-diene-1,1,3-tricarbonitrile-based push–pull chromo-
phores, in the present work we made an attempt to
synthesize tricyanofuran and tricyanopyrrole analogs
containing the above acceptor fragment and additional
reaction centers. There are a few published data on
hydroxytricyanopyrroles (HTCP) that are close
analogs of TCF and TCP [14–17] (Schemes 2, 3). The
Scheme 3.
O
O
R1
CN
CN
R1
NC
R2
CN
+
CN
N
H
R2
O
HO
CN
CN
TCNE
HTCP-2
1440

NEW PUSH–PULL CHROMOPHORES.
1441
Scheme 4.
Donor
R
Acceptor
CN
R
CN
CN
CN
O
O
Piperidine, EtOH
Me
HO
+
CN
N
H
Me
NH2
MND
CN
1a–1c
2a–2c
R = H (a), Me (b), MeO (c).
structures like hydroxytricyanopyrroles HTCP-2 can
also be prepared from tetracyanoethylene and 1,3-di-
carbonyl compounds (Scheme 3).
ring, so that donor–acceptor chromophore system can
be obtained without further modification of the
hydroxytricyanopyrrole structure. Analogous approach
was applied to the synthesis of tricyanofuran deriva-
tives as fluorescent probes for visualization of biologi-
cal processes [18, 19].
Compounds obtained by the above method possess
an electron-withdrawing group (R1CO) conjugated
with the acceptor buta-1,3-diene-1,1,3-tricarbonitrile
fragment, whereas donor–acceptor chromophores like
TCF and TCP contain an electron-withdrawing substit-
uent in that position (Scheme 1). Therefore, reactions
of 1,3-dicarbonyl compounds with tetracyanoethylene
seem hardly suitable for the synthesis of donor–
acceptor hydroxytricyanopyrrole chromophores.
The above listed limitations intrinsic to known
methods of synthesis of hydroxytricyanopyrroles, as
well as increased interest in buta-1,3-diene-1,1,3-
tricarbonitrile chromophores, prompted us to study the
reaction of malononitrile dimer with unsymmetrical
1,2-diketones with substituents of different natures at
the carbonyl groups. Our study was aimed at synthe-
sizing new hydroxytricyanopyrroles in which the
polyene chain is extended due to conjugation of the
acceptor hydroxytricyanopyrrole fragment with an aro-
matic substituent on the pyrrole ring. The reaction of
malononitrile dimer with 1-arylpropane-1,2-diones 1a–
1c in ethanol in the presence of piperidine afforded
2-[4-aryl-3-cyano-5-hydroxy-5-methyl-1H-pyrrole-
2(5H)-ylidene]malononitriles 2a–2c in 53–61% yield
(Scheme 4).
The structure of 2a–2c was confirmed by IR,
1H NMR, and mass spectra. The IR spectra of 2a–2c
contained absorption bands due to stretching vibrations
of the conjugated cyano groups (2225–2228 cm–1) and
primary amino group (3413–3375 cm–1). In the
1H NMR spectra of 2a–2c, the NH proton signal was
located at δ 10.64‒10.77 ppm, the OH proton gave
a broadened signal at δ 7.32‒7.33 ppm, aromatic
proton signals were observed in the region δ 7.19‒
8.16 ppm (ortho-protons resonated in a weaker field),
and the 5-CH3 protons resonated at δ 1.50‒1.53 ppm.
In addition, a signal from the substituent in the
benzene ring was present (δ 2.41 and 3.84 ppm for Me
and MeO group in 2b and 2c, respectively). Com-
pounds 2a–2c showed in the mass spectra the molec-
ular ion peak [M]+ with a relative intensity of 22–29%
and [M – CH3]+ ion peak with an intensity of 45–77%.
The structure of 2b was unambiguously determined by
X-ray analysis (see figure, CCDC entry no. 1476503).
Scheme 5 shows a probable mechanism of the
formation of compounds 2. Basic conditions, on the
one hand, force the keto–enol equilibrium of 1,2-di-
ketone to shift toward intermediate A and, on the other
hand, favor formation of carbanion B from malono-
nitrile dimer. Presumably, the acetyl carbonyl group in
Variation of the aromatic substituent in initial
diketone 1a–1c ensures introduction of an electron-
donating fragment into the 4-position of the pyrrole
Scheme 5.
CN
CN
CN
CN
Ar
O
BH
Ar
1a–1c
+
MND
+
2a–2c
CN
CN
–BH2
HO
CH2
NH2
NH2
Me
O
A
B
C
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 10 2016

FEDOSEEV et al.
at 500.13 MHz using tetramethylsilane as internal
1442
C13
standard. The mass spectra (electron impact, 70 eV)
were obtained on a Shimadzu GCMS-QP 2010 SE
instrument. The elemental compositions were deter-
mined using a Vario Micro cube CHN analyzer. The
X-ray diffraction data for a single crystal of 2b were
acquired on a STOE StadiVari Pilatus 100K diffrac-
tometer (MoKα radiation) using STOE X-Area soft-
ware for data collection and processing. The structure
was solved by the direct method (SHELXS-97) [20],
and the molecular structure was plotted using
DIAMOND [21]. The X-ray diffraction study was
carried out at the General Chemistry Department,
Faculty of Chemistry, Moscow State University.
C11
C12
C10
C9
O1
C7
C8
C6
C3
C2
C4
N1
C14
N2
C5
C17
Initial 1-arylpropane-1,2-diones 1a–1c were syn-
thesized by oxidation of the corresponding propio-
phenones with selenium dioxide in dioxane [22].
C16
N4
2-[3-Cyano-5-hydroxy-5-methyl-4-phenyl-1H-
pyrrol-2(5H)-ylidene]malononitrile (2a). Malono-
nitrile dimer, 0.396 g (3 mmol), was dissolved in 5 mL
of ethanol, and 0.592 g (4 mmol) of 1-phenylpropane-
1,2-dione (1a) and three drops of piperidine were
added. When the reaction was complete (TLC), the
mixture was diluted with water and extracted with
ethyl acetate (5×2 mL), the extract was dried over
anhydrous sodium sulfate and evaporated to a volume
of 3 mL, and the residue was purified by column
chromatography using ethyl acetate as eluent; a yellow
fraction was collected. The eluate was evaporated to
dryness, the residue was treated with carbon tetra-
chloride, and the precipitate was filtered off. If neces-
sary, the product was additionally recrystallized from
propan-2-ol–water (3:1 by volume). The product was
dried in a vacuum desiccator over CaCl2. Yield 0.480 g
(61%), mp 167–168°C. IR spectrum, ν, cm–1: 3402
C15
N3
ORTEP representation of the molecule of 2-[3-cyano-5-hy-
droxy-5-methyl-4-(4-methylphenyl)-1H-pyrrol-2(5H)-
ylidene]malononitrile (2b).
diketone 1 is deactivated due to enolization, and nu-
cleophilic attack by carbanion B is directed at the aroyl
carbonyl group with formation of amino ketone C. The
subsequent intramolecular heterocyclization involving
the amino group and acetyl fragment yields final
product 2.
Thus, the reaction of unsymmetrical 1-arylpropane-
1,2-diones 1a–1c with malononitrile dimer gives new
donor–acceptor chromophores, 2-[4-aryl-3-cyano-5-
hydroxy-5-methyl-1H-pyrrol-2(5H)-ylidene]malono-
nitriles 2a–2c in which the conjugation system com-
prises the aryl and buta-1,3-diene-1,1,3-tricarbonitrile
fragments.
1
(NH), 2225 (C≡N). H NMR spectrum (DMSO-d6), δ,
ppm: 1.50 s (3H, CH3), 7.33 br.s (1H, OH), 7.60–
7.69 m (3H, m-H, p-H), 8.02–8.05 m (2H, o-H),
10.77 s (1H, NH). Mass spectrum, m/z (Irel, %): 262
(29) [M]+, 247 (77) [M – 15]+. Found, %: C 68.43;
H 3.95; N 21.22. C15H10N4O. Calculated, %: C 68.69;
H 3.84; N 21.36. M 262.27.
EXPERIMENTAL
The purity of the isolated compounds was checked
by TLC on Sorbfil PTSKh-AF-A-UF plates; spots
were visualized by UV irradiation, treatment with
iodine vapor, or thermal decomposition. The melting
points were measured on an OptiMelt MPA100
melting point apparatus. The IR spectra were recorded
from samples dispersed in mineral oil on an FSM-1202
Compounds 2b and 2c were synthesized in
a similar way.
2-[3-Cyano-5-hydroxy-5-methyl-4-(4-methyl-
phenyl)-1H-pyrrol-2(5H)-ylidene]malononitrile
(2b). Yield 0.480 g (58%), mp 144–145°C. IR spec-
trum, ν, cm–1: 3413 (NH), 2228 (C≡N). 1H NMR spec-
trum (DMSO-d6), δ, ppm: 1.50 s (3H, CH3), 2.41 s
(3H, C6H4CH3), 7.32 br.s (1H, OH), 7.43–7.46 m (2H,
1
spectrometer with Fourier transform. The H NMR
spectra were taken on a Bruker DRX-500 spectrometer
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 10 2016

NEW PUSH–PULL CHROMOPHORES.
1443
7. Bureš, F., RSC Adv., 2014, vol. 4, p. 58826.
8. Michinobu, T., Chem. Soc. Rev., 2011, vol. 40, p. 2306.
9. Yang, Y., Xiao, H., Wang, H., Liu, F., Bo, S., Liu, J.,
Qiu, L., Zhen, Z., and Liu, X., J. Mater. Chem. C., 2015,
vol. 3, p. 11423.
m-H), 7.97–8.00 m (2H, o-H), 10.71 s (1H, NH). Mass
spectrum, m/z (Irel, %): 276 (22) [M]+, 277 (62) [M –
15]+. Found, %: C 69.68; H 4.46; N 20.14. C16H12N4O.
Calculated, %: C 69.55; H 4.38; N 20.28. M 276.29.
2-[3-Cyano-5-hydroxy-4-(4-methoxyphenyl)-5-
methyl-1H-pyrrol-2(5H)-ylidene]malononitrile (2c).
Yield 0.464 g (53%), mp 156–157°C. IR spectrum, ν,
10. Elder, D.L., Benight, S.J., Song, J., Robinson, B.H., and
Dalton, L.R., Chem. Mater., 2014, vol. 26, p. 872.
1
11. Cho, M.J., Seo, J., Oh, H.S., Jee, H., Kim, W.J.,
Kim, K.H., Hoang, M.H., Choi, D.H., and Prasad, P.N.,
Sol. Energy Mater. Sol. Cells, 2012, vol. 98, p. 71.
12. Wu, J., Xiao, H., Qiu, L., Zhen, Z., Liu, X., and Bo, S.,
RSC Adv., 2014, vol. 4, p. 49737.
13. Johns, V.K., Peng, P., DeJesus, J., Wang, Z., and
Liao, Y., Chem. Eur. J., 2014, vol. 20, p. 689.
14. Howard, G.E.J., US Patent no. 3178448, 1965; Chem.
Abstr., 1965, vol. 63, p. 3741.
cm–1: 3375 (NH), 2217 (C≡N). H NMR spectrum
(DMSO-d6), δ, ppm: 1.53 s (3H, CH3), 3.84 s (3H,
OCH3), 7.19–7.22 m (2H, m-H), 7.33 br.s (1H, OH),
8.13–8.16 m (2H, o-H), 10.64 s (1H, NH). Mass spec-
trum, m/z (Irel, %): 292 (29) [M]+, 276 (45) [M – 15]+.
Found, %: C 65.62; H 4.19; N 19.09. C16H12N4O2. Cal-
culated, %: C 65.75; H 4.14; N 19.17. M 292.30.
This study was performed under financial support
by the Russian Foundation for Basic Research (project
no. 16-33-60156 mol_a_dk).
15. Ducker, J.W. and Gunter, M.J., Aust. J. Chem., 1974,
vol. 27, p. 2229.
16. Thierrichter, V. and Junek, N., Monatsh. Chem., 1979,
vol. 110, p. 729.
REFERENCES
17. Ducker, J.W. and Gunter, M.J., Aust. J. Chem., 1973,
vol. 26, p. 1551.
18. Lu, Z., Liu, N., Lord, S.J., Bunge, S.D., Moerner, W.E.,
and Twieg, R.J., Chem. Mater., 2009, vol. 21, p. 797.
19. Lord, S.J., Lu, Z., Wang, H., Willets, K.A., Schuck, P.J.,
Lee, H.D., Nishimura, S.Y., and Twieg, R.J., J. Phys.
Chem. A, 2007, vol. 111, p. 8934.
1. Malytskyi, V., Simon, J.-J., Patrone, L., and Rai-
mundo, J.-M., RSC Adv., 2015, vol. 5, p. 354.
2. Duan, C., Hu, X., Chen, K.-S., Yip, H.-L., Li, W.,
Huang, F., Jen, A.K.-Y., and Cao, Y., Sol. Energy Mater.
Sol. Cells., 2012, vol. 97, p. 50.
3. Michinobu, T., Chem. Soc. Rev., 2011, vol. 40, p. 2306.
4. Chiu, M., Jaun, B., Beels, M.T.R., Biaggio, I., Gissel-
brecht, J.-P., Boudon, C., Schweizer, W.B., Kivala, M.,
and Diederich, F., Org. Lett., 2012, vol. 14, p. 54.
20. Sheldrick, G.M., Acta Crystallogr., Sect. A, 2008,
vol. 64, p. 112.
21. Brandenburg, K., DIAMOND, Release 2.1d, Bonn,
Germany: Crystal Impact, 2000.
22. Becker, H.G.O., et al., Organikum. Organisch-
chemisches Grundpraktikum, Weinheim: Wiley, 2004,
22nd ed. Translated under the title Organikum,
Moscow: Mir, 2008, vol. 2, p. 16.
5. Jeux, V., Segut, O., Demeter, D., Alévêque, O.,
Leriche, P., and Roncali, J., ChemPlusChem, 2015,
vol. 80, p. 697.
6. Liu, J., Gao, W., Kityk, I.V., Liu, X., and Zhen, Z., Dyes
Pigm., 2015, vol. 122, p. 74.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 10 2016