Three-component synthesis of alkylammonium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,5-dihydropyrrol-1-ides

Article abstract of DOI:10.1007/s11164-018-3325-0

This study presents a three-component reaction between malononitrile dimer, α-diketone and aliphatic amine that leads to the formation of previously undescribed alkylammonium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-dimethyl-2,5-dihydropyrrol-1-ides. This reaction is a novel approach for modification of donor–acceptor chromophores containing the buta-1,3-diene-1,1,3-tricarbonitrile moiety.

Full text of DOI:10.1007/s11164-018-3325-0

Res Chem Intermed
https://doi.org/10.1007/s11164-018-3325-0
Three-component synthesis of alkylammonium
4-cyano-5-(dicyanomethylene)-2-hydroxy-2,5-
dihydropyrrol-1-ides
Sergey V. Fedoseev1 Mikhail Yu. Belikov1 Mikhail Yu. Ievlev1
•
•
•
Oleg V. Ershov1 Viktor A. Tafeenko2
•
Received: 3 December 2017 / Accepted: 6 February 2018
Ó Springer Science+Business Media B.V., part of Springer Nature 2018
Abstract This study presents a three-component reaction between malononitrile
dimer, a-diketone and aliphatic amine that leads to the formation of previously
undescribed alkylammonium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-dime-
thyl-2,5-dihydropyrrol-1-ides. This reaction is a novel approach for modification of
donor–acceptor chromophores containing the buta-1,3-diene-1,1,3-tricarbonitrile
moiety.
Keywords Buta-1,3-diene-1,1,3-tricarbonitrile fragment Á Pyrroles Á Cyano
groups Á Donor–acceptor chromophores
Introduction
Donor–acceptor chromophores are an important group of the practically useful
organic compounds because of their various application areas. [1–4] A polycyano
substituted moiety is often used as a strong acceptor in these molecules. For the last
10–15 years, tricyanofuran (TCF) derivatives have been one of the most intensively
studied groups of the cyano-substituted chromophores containing the buta-1,3-
diene-1,1,3-tricarbonitrile (BDTC) acceptor (Scheme 1). These derivatives have
been used as essential components of luminescent probes and labels [5–7], non-
linear materials [3, 8–11], solar cells [12–14], and solid-state fluorescent dyes [15].
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11164-
018-3325-0) contains supplementary material, which is available to authorized users.
&
Oleg V. Ershov
oleg.ershov@mail.ru
1
2
Ulyanov Chuvash State University, Moskovsky pr., 15, Cheboksary, Russia 428015
Lomonosov Moscow State University, Leninskie gori, 1, Moscow, Russia 119991
123

S. V. Fedoseev et al.
Scheme 1 Chromophores with the BDTC acceptor
Structural analogues of the TCF derivatives, such as tricyanopyrroles TCP and
ylidene malononitrile dimer derivatives YMND, containing the similar BDTC
moiety, also have been investigated in recent years (Scheme 1). An analysis of the
literature shows that the most-studied area is the creation of a highly conjugated p-
bonding system via introduction of a substituent in the fourth position of the BDTC
fragment. [3, 5–17] In contrast, the possibilities of modification of other reaction
centers, such as the fifth position in TCF, the first position in TCP, and the amino
group in YMND, have been given much less attention. There are sparse examples in
the literature that acceptor properties of TCF could be increased by varying the
substituent in the fifth position of the furan ring, [18] and that non-linear
characteristics of TCP derivatives could be improved by N-alkylation. [19, 20]
Expanding the group of known structures containing the BDTC fragment, as well as
increasing the number of approaches to their modification, is now of increasing
interest to researchers.
Hydroxytricyanopyrroles (HTCP) are the closest structural analogues of TCF,
TCP and YMND (Scheme 1). [21–24] In contrast to well-known analogues, the
chemical properties of HTCP derivatives are almost unstudied. Only the conversion
of the hydroxyl to an alkoxy group is described in the literature. [23] The purpose of
this work is to show the possibility of a targeted modification of HTCP derivatives
which is not described or impossible for the known analogues.
Experimental
Materials and methods
The progress of reactions and the purity of the products were monitored by TLC on
Sorbfil plates (spots were visualized under UV light, by treatment with iodine vapor,
or by heating). The IR spectra were recorded on an FSM-1202 spectrometer with
Fourier transform from samples dispersed in mineral oil. The NMR spectra were
measured in DMSO-d6 on a Bruker DRX-500 spectrometer using tetramethylsilane
as an internal reference. Elemental analyses were performed using a Perkin–Elmer
2400 CHN elemental analyzer. The mass spectra (electron impact, 70 eV) were
obtained on a Finnigan MAT INCOS-50 spectrometer. Melting points were
determined on an OptiMelt MPA100 device.
Crystals of compounds 3f suitable for X-ray analysis were grown at room
temperature from a mixture of ethyl acetate. The data of 3f were collected by using
123

Three-component synthesis of alkylammonium…
an STOE diffractometer Pilatus100 K detector, focusing mirror collimation Cu Ka
˚
(1.54086 A) radiation, rotation method mode. STOE X-AREA software was used
for cell refinement and data reduction. Data collection and image processing were
performed with X-Area 1.67. Intensity data were scaled with LANA (part of
X-Area) in order to minimize differences of intensities of symmetry-equivalent
reflections (multi-scan method). The structures were solved and refined with the
SHELX
program,
cell
parameters:
a = 11.5827(7),
b = 10.5732(5),
3
˚
˚
c = 17.3732(10) A, V = 2085.16 A , a = 90, b = 101.467(5), c = 90,
V = 586.0(3), space group P 21/n, Z = 4. Absorption correction was not applied.
The non-hydrogen atoms were refined by using the anisotropic full matrix least-
square procedure. The final R-factor was 5.71%. Molecular geometry calculations
were performed with the SHELX program, and the molecular graphics were
prepared by using DIAMOND software.
Synthesis and spectral data
Typical procedure for the preparation of alkylammonium 4-cyano-5-(di-
cyanomethylene)-2-hydroxy-2,3-dimethyl-2,5-dihydropyrrol-1-ides 3a–m To
a
solution of 1 mmol of the appropriate 1,2-diketone 1 in 1.5 ml ethanol, 1 mmol
of the malononitrile dimer and 3 mmol of the corresponding amine were added. The
reaction mixture was stirred for 2–3 h at room temperature until the reaction was
complete (TLC). The precipitated product was filtered, washed with cold i-PrOH
then dried in a vacuum desiccator over CaCl2.
Piperidin-1-ium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-diphenyl-2,5-dihy-
1
dropyrrol-1-ide 3a Mp 125–126 °C (dec.). H NMR (500.13 MHz, DMSO-d6):
d 1.51–1.56 (2H, m, CH2(CH2)2), 1.58–1.63 (4H, m, CH2(CH2)2), 2.94–2.97 (4H,
m, N(CH2)2), 7.14–7.18 (1H, m, C6H5), 7.21–7.28 (5H, m, C6H5), 7.37–7.39 (2H,
m, C6H5), 7.78–7.81 (2H, m, C6H5). 13C NMR (125.67 MHz, DMSO-d6): d 21.72,
22.37, 43.86, 102.16, 104.66, 114.79, 121.31, 125.01, 127.97, 128.19, 128.30,
128.40, 129.10, 131.47, 140.86, 161.05, 175.85. MS, (EI, 70 eV): m/z (%) 324 [M-
BH]? (11). IR (mineral oil, cm-1): 3342 (OH); 2197, 2153 (C:N); 1600 (C=C).
Anal. Calcd for C25H23N5O: C, 73.33; H, 5.66; N, 17.10. Found: C, 73.12; H, 5.74;
N, 16.96.
Morpholin-4-ium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-diphenyl-2,5-dihy-
1
dropyrrol-1-ide 3b Mp 162–163 °C (dec.). H NMR (500.13 MHz, DMSO-d6):
d 2.86–2.89 (4H, m, N(CH2)2), 3.60–3.63 (4H, m, O(CH2)2), 7.21–7.30 (3H, m,
C6H5), 7.36–7.47 (5H, m, C6H5), 7.81–7.83 (2H, m, C6H5). 13C NMR (125.67 MHz,
DMSO-d6): d 44.04, 64.82, 99.55, 103.71, 113.79, 117.53, 125.27, 127.98, 128.20,
128.43, 128.61, 129.30, 131.67, 139.07, 160.95, 173.55. MS, (EI, 70 eV): m/z (%)
324 [M-BH]? (38). IR (mineral oil, cm-1): 3381 (OH); 2195, 2155 (C:N); 1603
(C=C). Anal. Calcd for C24H21N5O2: C, 70.06; H, 5.14; N, 17.02. Found: C, 69.93;
H, 5.21; N, 16.90.
Propan-1-aminium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-diphenyl-2,5-di-
hydropyrrol-1-ide 3c Mp 145–146 °C (dec.). 1H NMR (500.13 MHz, DMSO-
123

S. V. Fedoseev et al.
d6): d 0.89 (3H, t, J = 7.5 Hz, CH2CH3), 1.47–1.55 (2H, m, CH2CH3), 2.69–2.72
(2H, m, CH2CH2), 7.14–7.18 (1H, m, C6H5), 7.20–7.27 (5H, m, C6H5), 7.36–7.39
(2H, m, C6H5), 7.78–7.81 (2H, m, C6H5). 13C NMR (125.67 MHz, DMSO-d6): d
10.76, 20.64, 40.55, 102.90, 104.82, 114.97, 121.27, 124.95, 127.93, 128.17,
128.36, 129.10, 130.71, 131.46, 141.11, 161.04, 176.16. MS, (EI, 70 eV): m/z (%)
324 [M-BH]? (54). IR (mineral oil, cm-1): 3401 (OH); 2196, 2162 (C:N); 1595
(C=C). Anal. Calcd for C23H21N5O: C, 72.04; H, 5.52; N, 18.26. Found: C, 71.90;
H, 5.59; N, 18.14.
Piperidin-1-ium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2-methyl-3-phenyl-2,5-
1
dihydropyrrol-1-ide 3d Mp 126–127 °C (dec.). H NMR (500.13 MHz, DMSO-
d6): d 1.30 (3H, s, CH3), 1.52–1.56 (2H, m, CH2(CH2)2), 1.57–1.62 (4H, m,
CH2(CH2)2), 2.93–2.96 (4H, m, N(CH2)2), 7.53–7.55 (3H, m, C6H5), 7.98–8.01 (2H,
m, C6H5). 13C NMR (125.67 MHz, DMSO-d6): d 21.87, 22.58, 25.40, 43.99, 99.34,
103.21, 114.30, 119.62, 128.09, 128.70, 130.06, 131.26, 159.79, 175.01. MS, (EI,
70 eV): m/z (%) 262 [M-BH]? (14). IR (mineral oil, cm-1): 3359 (OH); 2198, 2154
(C:N); 1607 (C=C). Anal. Calcd for C20H21N5O: C, 69.14; H, 6.09; N, 20.16.
Found: C, 68.91; H, 6.14; N, 20.01.
Morpholin-4-ium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2-methyl-3-phenyl-2,5-
1
dihydropyrrol-1-ide 3e Mp 120–121 °C (dec.). H NMR (500.13 MHz, DMSO-
d6): d 1.44 (3H, s, CH3), 2.78–2.81 (4H, m, N(CH2)2), 3.56–3.59 (4H, m, O(CH2)2),
7.58–7.63 (3H, m, C6H5), 8.01–8.04 (2H, m, C6H5). 13C NMR (125.67 MHz,
DMSO-d6): d 24.55, 44.66, 65.60, 96.18, 102.15, 113.04, 116.26, 128.37, 128.96,
132.26, 160.05, 172.70. MS, (EI, 70 eV): m/z (%) 262 [M-BH]? (38). IR (mineral
oil, cm-1): 3372 (OH); 2195, 2152 (C:N); 1603 (C=C). Anal. Calcd for
C19H19N5O2: C, 65.32; H, 5.48; N, 20.04. Found: C, 65.20; H, 5.55; N, 19.91.
Piperidin-1-ium
4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-di(thiophen-2-yl)-
2,5-dihydropyrrol-1-ide 3f Mp 138–139 °C (dec.). 1H NMR (500.13 MHz,
DMSO-d6): d 1.53–3.57 (2H, m, CH2), 1.61–1.65 (4H, m, 2CH2), 2.98–3.01 (4H,
m, N(CH2)2), 6.77–6.80 (1H, m, CHTh), 6.84–6.87 (1H, m, CHTh), 7.20–7.23 (1H,
m, CHTh), 7.35–7.37 (1H, m, CHTh), 7.83–7.85 (1H, m, CHTh), 7.94–7.97 (1H, m,
CHTh). NMR (125.67 MHz, DMSO-d6): d 21.56, 22.14, 43.69, 99.15, 100.21,
114.71, 119.75, 123.89, 125.19, 126.57, 128.02, 131.69, 132.89, 133.75, 146.23,
160.61, 167.66. MS, (EI, 70 eV): m/z (%) 336 [M-BH]? (8). IR (mineral oil, cm-1):
3395 (OH); 2199, 2165 (C:N); 1584 (C=C). Anal. Calcd for C21H19N5OS2: C,
59.83; H, 4.54; N, 16.61. Found: C, 59.75; H, 4.62; N, 16.45.
Crystallographic data (excluding structure factors) for the structure in this paper
(3f) have been deposited with the Cambridge Crystallographic Data Centre as
supplementary publication number CCDC 1574658. Copies of the data can be
obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK [fax: ? 44 (0) 1223 336033 or e-mail: http://deposit@ccdc.cam.ac.uk].
Morpholin-4-ium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-di(thiophen-2-yl)-
2,5-dihydropyrrol-1-ide 3g Mp 147–148 °C (dec.). 1H NMR (500.13 MHz,
DMSO-d6): d 2.91–2.94 (4H, m, N(CH2)2), 3.64–3.67 (4H, m, O(CH2)2),
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Three-component synthesis of alkylammonium…
6.87–6.90 (2H, m, 2CHTh), 7.23–7.26 (1H, m, 1CHTh), 7.41 (1H, dd, J = 1.4,
J = 4.9 Hz, 1CHTh), 7.89 (1H, dd, J = 1.0, J = 3.9 Hz, 1CHTh), 8.02 (1H, dd,
J = 1.0, J = 5.0 Hz, 1CHTh). 13C NMR (125.67 MHz, DMSO-d6): d 42.64, 63.33,
97.36, 97.81, 113.26, 117.93, 123.32, 124.56, 125.70, 127.17, 130.28, 132.41,
133.52, 144.17, 159.48, 165.68. MS, (EI, 70 eV): m/z (%) 336 [M-BH]? (82), 111
(100). IR (mineral oil, cm-1): 3391 (OH); 2193, 2168 (C:N); 1590 (C=C). Anal.
Calcd for C20H17N5O2S2: C, 56.72; H, 4.05; N, 16.54. Found C, 56.68; H, 4.11; N,
16.44.
Propan-1-aminium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-di(thiophen-2-yl)-
2,5-dihydropyrrol-1-ide 3h Mp 136–137 °C (dec.). 1H NMR (500.13 MHz,
DMSO-d6): d 0.89 (3H, t, J = 7.5 Hz, CH2CH3), 1.49–1.57 (2H, m, CH2CH3),
2.71–2.74 (2H, m, CH2N), 6.73 (1H, dd, J = 1.1, J = 3.6 Hz, 1CHTh), 6.83–6.85
(1H, m, 1CHTh), 7.19–7.21 (1H, m, 1CHTh), 7.32 (1H, dd, J = 1.2, J = 5.0 Hz,
1CHTh), 7.82 (1H, dd, J = 1.0, J = 3.9 Hz, 1CHTh), 7.92 (1H, dd, J = 1.0,
J = 5.0 Hz, 1CHTh). 13C NMR (125.67 MHz, DMSO-d6): d 9.68, 19.42, 39.39,
98.76, 100.31, 114.02, 119.92, 122.39, 123.76, 125.37, 126.79, 130.94, 131.35,
131.99, 145.96, 159.65, 167.49. MS, (EI, 70 eV): m/z (%) 336 [M-BH]? (24). IR
(mineral oil, cm-1): 3378 (OH); 2191, 2160 (C:N); 1586 (C=C). Anal. Calcd for
C19H17N5OS2: C, 57.70; H, 4.33; N, 17.71. Found: C, 57.63; H, 4.40; N, 17.59.
Butan-1-aminium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-di(thiophen-2-yl)-
2,5-dihydropyrrol-1-ide 3i Mp 133–134 °C (dec.). 1H NMR (500.13 MHz,
DMSO-d6): d 0.88 (3H, t, J = 7.4 Hz, CH2CH3), 1.28–1.35 (2H, m, CH2CH2-
CH3), 1.45–1.52 (2H, m, CH2CH2CH3), 2.74–2.78 (2H, m, CH2N), 6.72–6.74 (1H,
m 1CHTh), 6.83–6.85 (1H, m, 1CHTh), 7.18–7.21 (1H, m, 1CHTh), 7.31–7.33 (1H,
m, 1CHTh), 7.81–7.83 (1H, m, 1CHTh), 7.91–7.93 (1H, m, 1CHTh). 13C NMR
(125.67 MHz, DMSO-d6): d 12.32, 17.92, 27.98, 37.47, 98.69, 100.17, 113.97,
119.91, 122.44, 123.80, 125.38, 126.80, 130.91, 131.41, 132.06, 145.87, 159.65,
167.39. MS, (EI, 70 eV): m/z (%) 336 [M-BH]? (40). IR (mineral oil, cm-1): 3392
(OH); 2199, 2161 (C:N); 1593 (C=C). Anal. Calcd for C20H19N5OS2: C, 58.66; H,
4.68; N, 17.10. Found C, 58.59; H, 4.73; N, 16.99.
Piperidin-1-ium
4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-bis(5-methylthio-
phen-2-yl)-2,5-dihydropyrrol-1-ide 3j Mp 109–110 °C (dec.). 1H NMR
(500.13 MHz, DMSO-d6): d 1.52–3.57 (2H, m, CH2), 1.59–1.64 (4H, m, 2CH2),
2.34 (3H, s, CH3), 2.50 (3H, s, CH3), 2.96–2.99 (4H, m, N(CH2)2), 6.51–6.53 (1H,
m, CHTh), 6.55–6.56 (1H, m, CHTh), 6.92 (1H, dd, J = 1.0, J = 3.9 Hz, 1CHTh),
7.67 (1H, d, J = 3.9 Hz, 1CHTh). 13C NMR (125.67 MHz, DMSO-d6): d 15.30,
15.64, 22.18, 22.80, 44.29, 98.45, 101.17, 115.57, 121.19, 123.90, 125.02, 127.34,
130.40, 134.07, 138.68, 144.66, 148.49, 161.07, 168.58. MS, (EI, 70 eV): m/z (%)
364 [M-BH]? (4). IR (mineral oil, cm-1): 3390 (OH); 2191, 2153 (C:N); 1577
(C=C). Anal. Calcd for C23H23N5OS2: C, 61.44; H, 5.16; N, 15.58. Found: C, 61.27;
H, 5.21; N, 15.47.
Morpholin-4-ium dicyano(4-cyano-2-hydroxy-2,3-bis(5-methylthiophen-2-yl)-2H-
pyrrol-5-yl)methanide 3k Mp 155–156 °C (dec.). 1H NMR (500.13 MHz,
123

S. V. Fedoseev et al.
DMSO-d6): d 2.38 (3H, s, CH3), 2.54 (3H, s, CH3), 2.95–2.98 (4H, m, N(CH2)2),
3.66–3.69 (4H, m, O(CH2)2), 6.61 (1H, d, J = 3.4 Hz, 1CHTh), 6.77 (1H, d,
J = 3.5 Hz, 1CHTh), 7.02 (1H, d, J = 3.9 Hz, 1CHTh), 7.81 (1H, d, J = 3.9 Hz,
1CHTh). 13C NMR (125.67 MHz, DMSO-d6): 14.84, 15.40, 43.43, 64.02, 95.07,
96.07, 113.71, 116.33, 125.12, 125.22, 127.83, 128.74, 135.72, 139.72, 140.77,
151.59, 160.22, 164.81. MS, (EI, 70 eV): m/z (%) 364 [M-BH]? (12). IR (mineral
oil, cm-1): 3369 (OH), 2192, 2150 (C:N), 1584 (C=C). Anal. Calcd for
C22H21N5O2S2: C, 58.52; H, 4.69; N, 15.51. Found: C, 58.46; H, 4.75; N, 15.39.
Propan-1-aminium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-bis(5-methylthio-
phen-2-yl)-2,5-dihydropyrrol-1-ide 3l Mp 143–144 °C (dec.). 1H NMR
(500.13 MHz, DMSO-d6): d 0.89 (3H, t, J = 7.5 Hz, CH2CH3), 1.49–1.56 (2H,
m, CH2CH3), 2.34 (3H, s, CH3), 2.49 (3H, s, CH3), 2.70–2.74 (2H, m, CH2N),
6.50–6.52 (1H, m, 1CHTh), 6.54–6.55 (1H, m, 1CHTh), 6.92 (1H, dd, J = 1.0,
J = 3.9 Hz, 1CHTh), 7.66 (1H, d, J = 3.8 Hz, 1CHTh). 13C NMR (125.67 MHz,
DMSO-d6): 11.23, 15.30, 15.63, 21.01, 40.97, 98.64, 101.48, 115.66, 121.55,
123.78, 124.98, 127.28, 130.48, 133.95, 138.58, 144.86, 148.27, 161.17, 168.80.
MS, (EI, 70 eV): m/z (%) 364 [M-BH]? (14). IR (mineral oil, cm-1): 3439 (OH);
2192, 2164 (C:N); 1585 (C=C). Anal. Calcd for C21H21N5OS2: C, 59.55; H, 5.00;
N, 16.53. Found: C, 59.48; H, 5.07; N, 16.39.
Butan-1-aminium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-bis(5-methylthio-
phen-2-yl)-2,5-dihydropyrrol-1-ide 3m Mp 142–143 °C (dec.). 1H NMR
(500.13 MHz, DMSO-d6): d 0.88 (3H, t, J = 7.4 Hz, CH2CH3), 1.27–1.35 (2H,
m, CH2CH2CH3), 1.45–1.51 (2H, m, CH2CH2CH3), 2.33 (3H, s, CH3), 2.49 (3H, s,
CH3), 2.73–2.77 (2H, m, CH2N), 6.50–6.52 (1H, m, 1CHTh), 6.53–6.55 (1H, m,
1CHTh), 6.91–6.93 (1H, m, 1CHTh), 7.66 (1H, d, J = 3.8 Hz, 1CHTh). 13C NMR
(125.67 MHz, DMSO-d6): 13.38, 14.82, 15.14, 19.01, 29.18, 38.60, 98.26, 101.15,
115.23, 121.24, 123.22, 124.47, 126.76, 130.03, 133.39, 138.03, 144.50, 147.66,
160.65, 168.43. MS, (EI, 70 eV): m/z (%) 364 [M-BH]? (24). IR (mineral oil,
cm-1): 3434 (OH); 2187, 2160 (C:N); 1584 (C=C). Anal. Calcd for C22H23N5OS2:
C, 60.39; H, 5.30; N, 16.00. Found: C, 60.31; H, 5.36; N, 15.86.
Typical procedure for the preparation of 2-(3-cyano-5-hydroxy-1H-pyrrol-2(5H)-
ylidene)malononitriles 4a–d To a suspension of 1 mmol of the corresponding salt
3 in 5 ml of the mixture water/ethanol (9/1), 1 ml of 10% hydrochloric acid was
added. The reaction mixture was stirred for 1.5–2 h at room temperature until the
reaction was complete (TLC). The precipitated product was filtered, washed with
water until a neutral reaction, then dried in a vacuum desiccator over CaCl2.
2-(3-Cyano-5-hydroxy-4,5-di(thiophen-2-yl)-1H-pyrrol-2(5H)-ylidene)malononi-
1
trile 4a Mp 230–231 °C (dec.). H NMR (500.13 MHz, DMSO-d6): d 7.29–7.36
(3H, m, C6H5), 7.44–7.54 (5H, m, C6H5), 7.84–7.87 (2H, m, C6H5). 8.07 (1H, s,
OH), 11.22 (1H, s, NH). 13C NMR (125.67 MHz, DMSO-d6): d 46.52, 96.08,
102.68, 112.68, 113.73, 114.83, 125.71, 128.34, 128.57, 128.84, 129.00, 132.81,
137.06, 160.80, 170.76. MS, (EI, 70 eV): m/z (%) 324 [M]? (52). IR (mineral oil,
123

Three-component synthesis of alkylammonium…
cm-1): 3466, 3338 (OH, NH); 2216 (C:N); 1647, 1586 (C=C). Anal. Calcd for
C20H12N4O: C, 74.06; H, 3.73; N, 17.27. Found: C, 74.01; H, 3.80; N, 17.09.
2-(3-Cyano-5-hydroxy-4,5-di(thiophen-2-yl)-1H-pyrrol-2(5H)-ylidene)malononi-
1
trile 4c Mp 192–193 °C (dec.). H NMR (500.13 MHz, DMSO-d6): d 6.97–7.00
(1H, m, 1CHTh), 7.11 (1H, dd, J = 1.1, J = 3.7 Hz, 1CHTh), 7.31–7.34 (1H, m,
1CHTh), 7.57 (1H, dd, J = 1.1, J = 5.1 Hz, 1CHTh), 8.02 (1H, dd, J = 0.8,
J = 4.0 Hz, 1CHTh), 8.20 (1H, dd, J = 0.8, J = 5.0 Hz, 1CHTh), 8.33 (1H, s,
OH), 11.29 (1H, s, NH). 13C NMR (125.67 MHz, DMSO-d6): d 46.35, 94.15, 95.91,
113.02, 113.78, 114.79, 126.24, 127.24, 127.50, 129.11, 130.26, 135.68, 137.67,
141.95, 160.15, 163.30. MS, (EI, 70 eV): m/z (%) 336 [M]? (41). IR (mineral oil,
cm-1): 3477, 3386 (OH, NH); 2221 (C:N); 1656, 1582 (C=C). Anal. Calcd for
C16H8N4OS2: C, 57.13; H, 2.40; N, 16.66. Found: C, 56.92; H, 2.44; N, 16.57.
2-(3-Cyano-5-hydroxy-4,5-bis(5-methylthiophen-2-yl)-1H-pyrrol-2(5H)-ylidene)-
1
malononitrile 4d Mp 207–208 °C (dec.). H NMR (500.13 MHz, DMSO-d6): d
2.40 (3H, s, CH3), 2.56 (3H, s, CH3), 6.66–6.68 (1H, m, 1CHTh), 6.88 (1H, d,
J = 3.6 Hz, 1CHTh), 7.07–7.08 (1H, m, 1CHTh), 7.89 (1H, d, J = 4.0 Hz,
1CHTh), 8.22 (1H, s, OH), 11.17 (1H, s, NH). 13C NMR (125.67 MHz, DMSO-d6):
d 14.86, 15.51, 45.58, 93.73, 94.90, 113.05, 113.76, 114.76, 125.54, 125.92, 128.19,
128.28, 136.71, 139.18, 140.42, 153.25, 160.04, 163.23. MS, (EI, 70 eV): m/z (%)
364 [M]? (22). IR (mineral oil, cm-1): 3546, 3372 (OH, NH); 2212 (C:N); 1648,
1585 (C=C). Anal. Calcd for C18H12N4OS2: C, 59.32; H, 3.32; N, 15.37. Found: C,
59.23; H, 3.42; N, 15.20.
An alternative way to synthesize salts 3d, e To a suspension of 1 mmol of HTCP
4b in 1.5 ml of ethanol, 1.1 mmol of the corresponding amine was added. The
reaction mixture was stirred for 2–3 h at room temperature until the reaction was
complete (TLC). The precipitated product was filtered, washed with cold i-PrOH,
then dried in a vacuum desiccator over CaCl2.
Results and discussion
We chose the formation of ionic fragment A (Scheme 2) as a novel approach for
modification of HTCP chromophores by the action of the various bases on the NH-
group.
It should be noted that there are few examples in the literature of salts with the
fragment A, and they do not include a BDTC acceptor. Among these salts, several
compounds are known as ionic liquids [25], photoelectrochemical photocurrent
Scheme 2 The fragment of the
compounds studied in this work
123

S. V. Fedoseev et al.
switches [26] or catalysts of thermal decomposition of energetic compounds [27].
The importance of structures A containing pyrrole rings is also supported by the
practical significance of the cyano-substituted pyrrolides. They have been proven to
be ionic liquids for SO2 capture [28], ionic micropropellants [29] and luminophores.
[30–32].
An essential structural feature of the HTCP derivatives, in contrast to TCF, TCP
and YMND, is a cyclic a-aminoalcohol moiety. According to the literature it is
quite unstable in the presence of bases, and undergoes ring-opening to form
molecules containing amino and carbonyl groups (structure B on Scheme 3)
[33, 34]. Therefore, we have another urgent theoretical problem: are the ionic
structures A stable enough to be isolated as solids, or will the pyrrole cycle undergo
ring-opening in the presence of bases (Scheme 3)?
An approach we have used in this work is the reaction of malononitrile dimer
(MND) with 1,2-diketones. This process was previously described for symmetrical
[24] as well as for unsymmetrical a-diketones [22] to form HTCP derivatives.
Synthesis of HTCP was carried out in ethanol in the presence of a catalytic amount
of piperidine. For the synthesis of ionic structures A, we modified this approach. It
was found that previously undescribed alkylammonium 4-cyano-5-(di-
cyanomethylene)-2-hydroxy-2,3-dimethyl-2,5-dihydropyrrol-1-ides 3a–m could be
isolated in 15–89% yields using a three-component interaction between MND,
corresponding 1,2-diketone and excess of aliphatic amine (Scheme 4; Table 1).
Synthesis of compounds 3 is characterized by using a threefold excess of amine
and a minimal amount of ethanol as a solvent. The structures of compounds 3 were
confirmed by IR, 1H and 13C NMR spectroscopy, mass spectrometry (see ESI). The
1H NMR spectra exhibited signals of alkyl, aryl substituents and amine fragments
1
with typical values of chemical shifts. The characteristic of H NMR spectra is an
?
absence of clear signals of OH and NH2 protons. These signals are broadened or
missing, probably due to an exchange process with protons of water which is present
in DMSO-d6 as an impurity.
The 13C NMR spectra of salts 3 exhibited signals of downfielded signals of
C-atoms of fifth and third positions of the pyrrole cycle at 167.5–170.8 and
Scheme 3 The plausible transformations of HTCP derivatives under the action of bases
123

Three-component synthesis of alkylammonium…
Scheme 4 Synthesis of alkylammonium 4-cyano-5-(dicyanomethylene)-2-hydroxy-2,3-dimethyl-2,5-
dihydropyrrol-1-ides 3a–m
Table 1 Synthesis of compounds 3a–m
Entry
Ar
R1
R2
R3
Product
Yield (%)a
1
C6H5
C6H5
(CH2)5
3a
3b
3c
3d
3e
3f
78
85
83
15
18
82
89
80
81
67
63
64
73
2
C6H5
C6H5
(CH2)2O(CH2)2
n-C3H7
3
C6H5
C6H5
H
4
C6H5
CH3
(CH2)5
5
C6H5
CH3
(CH2)2O(CH2)2
(CH2)5
6
2-Th
2-Th
7
2-Th
2-Th
(CH2)2O(CH2)2
n-C3H7
3g
3h
3i
8
2-Th
2-Th
H
H
9
2-Th
2-Th
n-C4H9
10
11
12
13
5-Me-2-Th
5-Me-2-Th
5-Me-2-Th
5-Me-2-Th
5-Me-2-Th
5-Me-2-Th
5-Me-2-Th
5-Me-2-Th
(CH2)5
3j
(CH2)2O(CH2)2
n-C3H7
3k
3l
H
H
n-C4H9
3m
Reagents and conditions: compound 1 (1 mmol), MND (1 mmol), amine 2 (3 mmol), EtOH (1.5 mL),
r.t., 2–3 h
aIsolated yields
160.1–161.1 ppm, respectively, and signals of C-atoms of the second and the fourth
position of pyrrole ring at 95.5–100.82 and 101.35–104.10 ppm. The characteristic
of 13C NMR spectra is an appearance of signals of three cyano groups as two peaks:
one of them at 112.23–115.56 ppm is fairly clear, while the second at
117.32–121.85 ppm, probably corresponding to anionic cyano groups, is broadened.
Also 13C NMR spectra are missing signals of C(CN)2 atom of BDTC-moiety,
probably due to its anionic character. The mass spectra are characterized by the
presence of peaks of [M–NHR2R3]? fragments with 4–82% intensity.
To unambiguously prove the structure of salts 3, a single crystal X-ray diffraction
analysis was carried out for compound 3f (Fig. 1).
The result of the implemented reaction (Scheme 4) is the developed novel
approach to the modification of chromophores with BDTC-moiety. The formation
of salts 3 is probably facilitated by the delocalization of the negative charge between
the nitrogen atom of the pyrrole ring and ylidene malononitrile moiety. As a result,
an alternative process of the pyrrole ring-opening was not realized (Scheme 3).
123

S. V. Fedoseev et al.
Fig. 1 Molecular structure of 3f
with the atom-numbering
scheme. Displacement ellipsoids
are drawn at the 50% probability
level and H atoms are drawn as
small spheres of arbitrary radii
Further, we were able to successfully neutralize the series of morpholinium salts
3b, e, g, k to isolate corresponding HTCP 4a–d (Scheme 5; Table 2). The reaction
was carried out using diluted hydrochloric acid and led to the isolation of 2-(3-
cyano-5-hydroxy-1H-pyrrol-2(5H)-ylidene)malononitriles 4a–d in excellent
89–95% yields.
Thienyl substituted pyrroles 4c, d which were prepared according to this
procedure are previously undescribed. Moreover, we have found that the known
synthetic procedures [21–24] are not so efficient in this case, as they allowed us to
isolate compounds 4c, d in lower yields. This fact increases the value of the
developed approach to the synthesis of salts 3 and the subsequent synthesis of
pyrroles 4 on their basis.
The structures of compounds 4 were confirmed by IR, 1H and 13C NMR
spectroscopy, mass spectrometry (see ESI). Mass spectra showed molecular ion
peaks with 22–52% intensity. 1H NMR spectra are characterized with the
downfielded NH-singlets at 11.17–11.29 ppm and the signals of hydroxyl protons
at 8.06–8.33 ppm. The 13C NMR spectra of heterocycles 4 exhibited the
downfielded signals of C3- and C5-atoms of the pyrrole cycle at 163.24–170.67
Scheme 5 Synthesis of 2-(3-cyano-5-hydroxy-1H-pyrrol-2(5H)-ylidene)malononitriles 4a–d
123

Three-component synthesis of alkylammonium…
Table 2 Synthesis of compounds 4a–da
Entry
Ar
R1
Product
Yielda (%)b
1
2
3
4
C6H5
C6H5
4a
4b
4c
4d
93
92
95
89
C6H5
CH3
2-Th
2-Th
5-Me-2-Th
5-Me-2-Th
aReagents and conditions: compound 3 (1 mmol), H2O/EtOH (9/1, 5 mL), 10% HCl (1 mL), r.t., 1.5-2 h
bIsolated yields
and 160.05–160.70 ppm, respectively, three signals of cyanogroups at
112.56–114.80 ppm and the upfielded signals of C-atoms of C(CN)2 moiety at
45.58–46.43 ppm.
Further, we found that salts 3 could be easily prepared from the corresponding
pyrroles 4 in moderate yields (Scheme 6).
However, for the salts 3a–c, f–m this approach is not efficient. These compounds
could be synthesized in better yields using the three-component system (Scheme 3;
Table 1). For the compounds 3d, e a stepwise manner makes sense because of the
poor yields of the three-component approach (Scheme 3; Table 1). Corresponding
pyrrole 4b could be obtained by the described method [22] in 61% yield for the
subsequent synthesis of salts 3d, e in 52–60% yields. Therefore, a total yield for two
stages is 32-37%.
Solid-state fluorescence properties are one of the most important directions in
studying compounds with the BDTC fragment, as it is related to the possibility of
practical use of chromophores with this property, for example, TCF derivatives
[5–7, 15]. It should be noted that information about the fluorescent properties of
HTCP derivatives, in contrast to TCF, TCP and YMND, is completely absent. Our
investigations showed that HTCP 4 in powder form possesses fluorescence at room
temperature. Emission maxima are in the range of 480–553 nm (Fig. 2) and depend
on the R1 and Ar substituents. For the salts 3 the emission intensity decreases
dramatically. For instance, the fluorescence intensity of pyrrole 4d is about for 5–6
times higher than for corresponding salts 3j–m (Fig. 3). Emission maxima of the
salts 3 are bathochromically shifted in comparison to the appropriate pyrrole 4. This
is clearly shown for the diphenyl derivative 4a—its emission maximum is 513 nm,
while the salts 3a–c have emission maxima in the range 542–554 nm. (Table 3).
Scheme 6 An alternative synthesis of salts 3d, e
123

S. V. Fedoseev et al.
Fig. 2 Normalized emission spectra of compounds 4a–c in the solid state
Fig. 3 Comparison of emission spectra of compound 4d and the corresponding salts 3j–k
Fluorescence quenching of the of salts 3 in comparison with pyrroles 4 is
apparently caused by crystal packing. The analysis of the XRD data of compound 3f
showed that the molecules form dimeric pairs by the hydrogen bonding between
˚
2-hydroxypyrrole moieties (N1A… O1B = N1B… O1A = 2.648 A, Fig. 4). This
apparently leads to an aggregation-caused quenching (ACQ) of the solid-state
fluorescence.
123

Three-component synthesis of alkylammonium…
Table 3 Fluorescence
Compound
kex max, nm
kem max, nm
aRel. Em. Int. I3/I4
properties of compounds 3 and 4
in solid state (powder)
4a
432
450
459
453
429
438
435
447
450
489
489
488
486
489
490
480
486
513
542
550
554
480
523
487
504, 549
550
546
546
549
551
549
543
558
555
1.0
3a
3b
3c
4b
3d
3e
4c
3f
0.10
0.10
0.18
1.0
0.23
1.36
1.0
0.13
0.06
0.07
0.06
1.0
3g
3h
3i
aRelative emission intensity is
given as the ratio between the
4d
3j
0.16
0.15
0.18
0.19
intensity of emission of salts 3
(I3, a.u.) and the appropriate
3k
pyrrole 4 (I4, a.u.). Emission
intensity of pyrroles 4 was
normalized and taken as 1.0)
3l
3m
Fig. 4 Dimeric associations in crystal of compound 3f
123

S. V. Fedoseev et al.
Conclusion
A new direction of the interaction of malononitrile dimer with 1,2-diketones was
investigated, and was realized in the presence of amines to form ionic derivatives of
pyrrole 3 as a result of the three-component reaction. This interaction is a
completely new approach for modification of chromophores containing buta-1,3-
diene-1,1,3-tricarbonitrile moiety. Also, for the first time, the solid-state fluores-
cence of HTCP derivatives was shown and characterized, while it was also found
that for HTCP salts 3 this property is less pronounced because of the features of
crystal packing.
Acknowledgements This work was supported by Russian Foundation for Basic Research, Grant No.
16-33-60156 mol_a_dc. The XRD study was carried out using the equipment purchased from the funds of
the Program of development of Moscow University and within the framework of the Agreement on
collaboration between the Chemical Department of the Lomonsov Moscow State University and the
Chemical-Pharmaceutical Department of the I.N. Ulyanov Chuvash State University.
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