Synthesis of new polyaryl-substituted imidazoles bridged on enamine or urea moieties and evaluation of their optical and electrochemical properties

Article abstract of DOI:10.1007/s11164-020-04078-y

Abstract: The reaction of the free amine group in polyaryl-substituted imidazole structures with phenyl isocyanate or dimethyl acetylenedicarboxylate gave two new series of polyaryl-substituted imidazoles: biaryl ureas or vinyl esters, respectively. Besid

Full text of DOI:10.1007/s11164-020-04078-y

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-020-04078-y
Synthesis of new polyaryl‑substituted imidazoles bridged
on enamine or urea moieties and evaluation of their optical
and electrochemical properties
Ameneh Abolghassemi Fakhree1 · Roghayeh Mohammadzadeh1 ·
Esmaeel Alipour2 · Zarrin Ghasemi1
Received: 10 October 2019 / Accepted: 2 January 2020
© Springer Nature B.V. 2020
Abstract
The reaction of the free amine group in polyaryl-substituted imidazole structures
with phenyl isocyanate or dimethyl acetylenedicarboxylate gave two new series of
polyaryl-substituted imidazoles: biaryl ureas or vinyl esters, respectively. Besides
their spectroscopic analysis, we explored the optical and electrochemical properties
of these highly conjugated scafolds. Comparing these properties in two categories
of products yielded interesting results.
Graphic abstract
Keywords Biarylureas · Cyclic voltammetry · Fluorescence emission · Polyaryl-
substituted imidazoles · Vinyl esters
*
Zarrin Ghasemi
z.ghasemi@tabrizu.ac.ir
1
2
Department of Organic and Biochemistry, Faculty of Chemistry, University of Tabriz,
Tabriz 5166614766, Iran
Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz,
Tabriz 5166614766, Iran
Vol.:(0123456789)
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A. A. Fakhree et al.
Introduction
Emitting organic compounds possessing extended π-conjugated systems have
been of great interest in recent years owing to their variety of applications in
OLEDs [1–3], solid-state lasers [4], sensors [5–7], fuorescence imaging [8–10],
nonlinear optical materials [11–13] and photophysical devices [14]. Many eforts
have been devoted to establishing structure–property relationships in order to
develop new materials with desired properties in a smart way and provide valu-
able insights into conforming fundamental properties of these systems [15, 16].
Depending on the π-electron distribution, the π-conjugated systems may adopt a
diferent impact on their π–π electronic couplings and thus charge transport rate.
An extended conjugation system is generally favored for a greater chance of π–π
stacking and narrower bandgap. Through structure optimization of the substruc-
tures within the expansion of π-conjugation, the optical absorptions, intramo-
lecular charge transfer (ICT) behaviors, and charge carrier property of photosen-
sitizers could be modifed and adjusted which would provide an alternative to
promote the overall device performance [17]. In this regard, we made a choice of
two well-known groups of intermediates for the design of such π-electron systems
including enaminoesters and aryl ureas [18–33]. The mentioned simply accessi-
ble functionalities have been achieved by various methodologies as mentioned
in the literature [34–45]. Following our recent eforts in the synthesis of various
polyaryl imidazole derivatives and evaluation of their optical properties [46–49],
herein we report the synthesis of novel diversities of this category. With this
goal, we attached the enaminoester and also biaryl urea moieties to our systems,
by reactions of free amine possessing 1,2,4,5-tetraarylimidazoles with dimethyl
acetylenedicarboxylate and phenylisocyanate, respectively. We then represent the
emission and electrochemical properties of the obtained products.
Results and discussion
We frst prepared 4-(2-aryl-4,5-diphenylimidazol-1-yl)aniline derivatives 1a–j by
acid catalyzed four-component reactions of 1,4-phenylenediamine, benzil, ammo-
nium acetate and aryl aldehyde [46–49]. The reaction of the mentioned amines
with phenyl isocyanate in dry dichloromethan gave N,N′-biarylurea products 2a–j
(Scheme 1, Table 1).
On the other hand, we decided to use aromatic amines in the reaction with
dimethyl acetylenedicarboxylate to obtain enaminoesters [34–38]. Initially,
we examined this reaction with commercial aniline derivatives at ambient tem-
perature in the presence of MgSO4 incorporated nanosilica (Mg2+/NS) catalyst
[46] and earned products 4a–e in good yields (Table 2). This catalyst which
had shown good activity in the multi-component synthesis of substituted pyr-
roles [46] decreased the reaction time of acetylenediester with anilines rela-
tive to catalyst-free conditions (Table 2). We then treated the amines 1a–e with
1 3

Synthesis of new polyaryl-substituted imidazoles bridged…
Scheme 1 Synthesis of biaryl ureas (2a–j) and enaminoesters (3a–e)
Table 1 The synthesized
Entry Ar
Amine Product Time (h) Yield (%)
biarylureas 2a–j and vinyl esters
3a–e
1
C6H5
1a
1b
1c
2a
2b
2c
2d
2e
2f
16
12
2
65
80
92
89
65
77
82
90
60
70
77
82
69
88
53
2
3
4-MeC6H4
4-ClC6H4
4
5
3,4-(MeO)2C6H3 1d
2-thienyl
5
1e
1f
14
10
7
6
4-FC6H4
7
4-MeOC6H3
1 g
2 g
2 h
2i
8
9
4-isopropylC6H4 1 h
3
2-NO2C6H4
3-thienyl
C6H5
4-MeC6H4
4-ClC6H4
1i
1j
1a
1b
1c
28
12
2
10
11
12
13
14
15
2j
3a
3b
3c
3d
3e
2
2.1
1.5
2
3,4-(MeO)2C6H3 1d
2-thienyl 1e
Table 2 Nano-catalyst capability for synthesis of enaminoesters (4a–e)
Entry
R
Product
Time (h)
Yield (%)
1
2
3
4
5
2-Br
4a
4b
4c
4d
4e
1.5
1.5
0.5
1
85
73
87
82
84
2,6-dichloro
2,6-dimethyl
4-Cl
H
1
1 3

A. A. Fakhree et al.
acetylenedicarboxylate under the same conditions and gained no product at room
temperature. However, heating of the reaction mixture at 80 °C resulted in the
desired vinyl esters 3a–e (Scheme 1 and Table 1). It is worth noting that the ste-
reochemistry of the products 3a–e and also 4a–e was estimated as E as described
in the literature [50–52].
In order to investigate the optical properties, UV–Vis and fuorescence spectra of
the obtained compounds (2a–j, 3a–e and 4a–c) were recorded in ethanol at a con-
centration of 10−6 M. The absorption and emission spectra and their optical param-
eters are presented in Fig. 1 and Table 3, respectively. We also studied the corre-
sponding spectra for amine precursors (1a–e) in order to the comparison of their
optical properties with the obtained products (Fig. 2, Table 3).
All compounds display an intense absorption band with a maximum at wave-
length (λmax) between 260 and 306 nm, which their molar extinction coefcient con-
frms the strong π–π* transitions. The increase in conjugation of π-system of aryl
ureas (2a–e) and enamines (3a–e) compared to amine precursors (1a–e) resulted
in the bathochromic shift of the absorption bands and also an increase in molar
Fig. 1 The absorption and emission spectra of compounds (2a–j, 3a–e and 4a–c) in ethanol (10−6 M)
1 3

Synthesis of new polyaryl-substituted imidazoles bridged…
Table 3 Absorption and emission spectral data of the π-extended pyrrole derivatives in ethanol
Compound
λamax,abs (nm)
λbmax,em (nm)
ɛ×104
Stokes shiftc
Фd
(L mol−1 cm−1
)
(nm)
1a
1b
1c
1d
1e
2a
2b
2c
2d
2e
2f
258
260
264
254
252
272
268
274
270
270
272
270
272
274
274
294
286
288
306
282
320
312
280
406
404
418
410
428
410
396
408
404
416
410
398
402
400
394
418
422
420
438
428
454
488
478
1.29
1.30
1.32
1.27
1.26
1.36
1.34
1.37
1.35
1.35
1.36
1.35
1.36
1.37
1.37
1.47
1.42
1.44
1.53
1.42
1.60
1.56
1.40
148
144
154
156
176
138
128
134
134
146
138
128
130
126
120
124
164
132
132
146
134
176
198
0.10
0.14
0.13
0.15
0.12
0.29
0.30
0.35
0.58
0.27
0.30
0.32
0.35
0.01
0.25
0.05
0.05
0.05
0.12
0.06
0.00
0.01
0.00
2 g
2 h
2i
2j
3a
3b
3c
3d
3e
4a
4b
4c
aAbsorption, bemission, cstokes shift=λem −λabs, dquantum yield
Fig. 2 The absorption and emission spectra of compounds (1a–e) in ethanol (10−6 M)
1 3

A. A. Fakhree et al.
Fig. 3 Cyclic voltammograms of 1a–e, 2a–e and 3a–e in CH2Cl2 containing 0.1 M TBAP Experimental
conditions: analyte concentration 1 mM, scan rate: 50 mV/S
Table 4 The oxidation
Amine
Eox (v)
Urea
Eox (v)
Enamine
Eox (v)
potentials of 1a–e, 2a–e and
3a–e
1a
1b
1c
1d
1e
1.17, 1.42
1.22, 1.47
1.12, 1.56
1.19, 1.48
1.18, 1.43
2a
2b
2c
2d
2e
0.88, 1.41
0.94, 1.32
1.24, 1.49
0.90, 1.38
0.89, 1.35
3a
3b
3c
3d
3e
1.33
1.25
1.31
1.25
1.21
extinction coefcient, as expected (Table 3). These shifts were more noticeable in
vinyl esters than aryl urea derivatives which could be attributed to higher planariza-
tion of the molecules with vinyl ester moieties.
Fluorescence properties of the synthesized molecules were studied, which
showed the intense emission of blue light in visible area at about 400 nm. The quan-
tum yields were calculated using anthracene as standard (Φ=0.27) and are repre-
sented in Table 3. The aryl urea derivatives (2a–e) had the highest quantum yields
compared with both amines 1a–e and also vinyl esters 3a–e. Furthermore, the prod-
ucts bearing dimethoxyphenyl group (1d, 2d and 3d) showed the higher quantum
yields. Moderate values of Stokes shifts (120–176 nm) were observed, indicating
low overlap between their absorption and emission spectra.
The electrochemical properties of compounds 1a–e, 2a–e and 3a–e were ana-
lyzed by cyclic voltammetry (CV) in the presence of tetrabutyl ammonium perchlo-
rate (TBAP) as supporting electrolyte, and the results are listed in Table 3. Repre-
sentative CVs of the chosen compounds are presented in Fig. 3.
Electrochemical data show that all three classes of compounds including 1a–e,
2a–e and 3a–e have an oxidation peak around 0.88–1.25 v. This peak can be attrib-
uted to the oxidation of nitrogen in the imidazole ring whose electron pair does not
participate in the aromatic system [53, 54]. The positive charge resulting from this
oxidation can be sustained by electron resonance of the high conjugated aromatic
system.
As can be seen in Table 4, there is also another oxidation peak in voltammograms
of amines 1a–e and urea derivatives 2a–e. By considering the lack of a similar peak
1 3

Synthesis of new polyaryl-substituted imidazoles bridged…
in the derivatives 3a–e (possessing electron defcient vinyldiester group), it can be
probably related to the oxidation of free amine (in 1a–e) or attached urea group (in
2a–e). Furthermore, the cyclic voltammograms of compounds 4a–e did not exhib-
ited anodic or cathodic peaks, indicating that these compounds are electro-inactive.
Conclusion
In summary, new polyaryl-substituted imidazole compounds with attached vinyl
ester and aryl urea groups were synthesized and their optical and electrochemical
properties were investigated. Optical studies of the products implied noticeable
increased quantum yields in the urea derivatives. Electrochemical experiments dem-
onstrated an oxidation peak around 0.88–1.25 v for all three classes of compounds,
1a–e, 2a–e and 3a–e, and the other oxidation peak for 1a–e and 2a–e. It should be
noted that except for compounds 4a, 4d and 4e [55–57], all of other products are
novel.
Experimental section
Materials and analytical methods
Melting points were measured on an Electrothermal MEL-TEMP apparatus (model
1202D) and are uncorrected. FT-IR spectra were recorded (in KBr) with a Tensor
27-Bruker spectrometer and Shimadzu FT-IR 8101 M and were reported in cm−1.
1H NMR and 13C NMR spectra were recorded on a Bruker Spectrospin Avance 400
spectrometer operating at 400 MHz and 100 MHz, respectively. Chemical shifts
are reported in parts per million (ppm) relative to tetramethylsilane as internal
standard. Elemental analyses were measured by Vario EL III apparatus (Elemen-
tar Co.). UV–Vis absorption and Fluorescence emission spectra were recorded
on CYTATION 5 Imaging Reader System (BIOTEK). The fuorescence quantum
yields (Ф) were determined in ethanol (10−6 M) via the comparative method using
anthracene as standard (Φ=0.27). The value of Ф was calculated using the equa-
tion: Φx =(As ×Fx ×n2x ×Фs)/(Ax ×Fs ×ns2), where F is the integrated area under the
emission spectrum, A is the absorbance at the excitation wavelength (300 nm), and
n is the refractive index of solvent (which is ethanol for both standard and samples,
nx =ns =1.36). The subscripts S and X correspond to the reference and the sample,
respectively. Electrochemical experiments were accomplished using an AUTOLAB
PGSTAT 30 electrochemical analysis system and GPES 4.9 software packet (Eco
Chemie., The Netherlands). CV measurements were recorded at room tempera-
ture with a conventional three electrode confguration consisting of a glassy carbon
working electrode, a platinum counter electrode, and a saturated calomel electrode
(SCE) as reference electrode. Preparative thin-layer chromatography (PLC) was
performed on prepared glass-backed plates using silica gel (Merck Kieselgel 60
PF254+366). All starting materials were purchased from commercial sources and used
without further purifcation.
1 3

A. A. Fakhree et al.
General procedure for the synthesis of urea derivatives 2a–j
A mixture of substituted amine 1 (1 mmol) and phenyl isocyanate (1.5 mmol) in dichlo-
romethane (5 mL) was stirred under argon at ambient temperature. After completion of
the reaction which was monitored by TLC (Table 1), the obtained solid was fltered and
washed with ethyl acetate.
1‑phenyl‑3‑[4‑(2,4,5‑triphenyl‑1H‑imidazol‑1‑yl)phenyl]urea (2a)
White solid; yield 65% (0.33 g); mp>300 °C; FTIR (KBr): 3358, 3059, 1655, 1602,
1
1442, 1554, 844, 694 cm−1; H NMR (400 MHz, DMSO-d6) δ: 6.9 (m, 1H, Ar–H),
7.15 (d, J=8.6 Hz, 2H, Ar–H), 7.18–7.43 (m, 17H, Ar–H), 7.48 (d, J=7.2 Hz, 2H,
Ar–H), 8.72 (s, 1H, NH), 8.85 (s, 1H, NH); 13C NMR (100 MHz, DMSO-d6) δ: 118.1,
118.4, 118.5, 122.2, 126.5, 126.6, 128.3, 128.4, 128.5, 128.6, 128.9, 129.3, 130.2,
130.5, 130.6, 131.2, 131.6, 134.5, 136.8, 139.5, 139.7, 140.0, 146.3, 152.5; Anal. calcd.
for C34H26N4O: C 80.61, H 5.17, N 11.06; found: C 80.45, H 5.09, N 10.09.
1‑{4‑[4,5‑diphenyl‑2‑(p‑tolyl)‑1H‑imidazol‑1‑yl]phenyl}‑3‑phenylurea (2b)
White solid; yield 80% (0.41 g); mp>300 °C; FTIR (KBr): 3313, 3055, 2922, 2861,
1649, 1602, 1444, 1556, 696 cm−1; 1H NMR (400 MHz, DMSO-d6) δ: 3.34 (s, 3H,
CH3), 6.97 (t, J=7.3 Hz, 1H, Ar–H), 7.10–7.42 (m, 21H, Ar–H), 7.47 (d, J=7.3 Hz,
2H, Ar–H), 8.69 (s, 1H, NH), 8.81 (s, 1H, NH); 13C NMR (100 MHz, DMSO-d6)
δ: 20.7, 117.91, 118.00, 118.23, 118.33, 122.06, 126.36, 128.16, 128.19, 128.37,
128.48, 128.79, 128.83, 129.21, 130.15, 131.16, 131.30, 137.81, 139.84, 146.24,
152.28; Anal. calcd. for C35H28N4O: C 80.74, H 5.42, N 10.76; found: C 80.65, H
5.34, N 10.52.
1‑{4‑[2‑(4‑chlorophenyl)‑4,5‑diphenyl‑1H‑imidazol‑1‑yl]phenyl}‑3‑phenylurea
(2c)
White solid; yield 92% (0.49 g); mp>300 °C; FTIR (KBr): 3314, 3057, 1649,
1603,1445, 1555, 1098, 837, 696 cm−1; 1H NMR (400 MHz, DMSO-d6) δ:
6.95–6.99 (m, 1H, Ar–H), 7.18 (d, J=8.3 Hz, 2H, Ar–H), 7.22–7.42 (m, 15H,
Ar–H), 7.48 (d, J=7.5 Hz, 2H, Ar–H), 8.70 (s, 1H, NH), 8.83 (s, 1H, NH); 13C
NMR (100 MHz, DMSO-d6) δ: 117.9, 118.0, 118.2, 118.3, 122.0, 126.3, 126.5,
128.1, 128.3, 128.5, 128.8, 129.1, 129.3, 129.8, 130.3, 131.1, 131.8, 133.0, 134.3,
136.8, 139.2, 139.9, 145.0, 152.2; Anal. calcd. for C34H25ClN4O: C 75.48, H 4.66, N
10.36; found: C 75.36, H 4.54, N 10.24.
1‑{4‑[2‑(3,4‑dimethoxyphenyl)‑4,5‑diphenyl‑1H‑imidazol‑1‑yl]
phenyl}‑3‑phenylurea (2d)
White solid; yield 89% (0.50 g); mp>300 °C; FTIR (KBr): 3291, 3053, 2934,2839,
1
1715, 1259, 1073, 696 cm−1; H NMR (400 MHz, DMSO-d6) δ: 3.56 (s, 3H,
1 3

Synthesis of new polyaryl-substituted imidazoles bridged…
–OCH3), 3.72 (s, 3H, –OCH3), 5.76 (s, 1H, Ar–H), 6.88 (d, J=8.3 Hz, 1H, Ar–H),
6.95–7.43 (m, 19H, Ar–H), 7.48 (d, J=7.3 Hz, Ar–H), 8.70 (s, 1H, NH), 8.82 (s,
1H, NH); 13C NMR (100 MHz, DMSO-d6) δ: 55.1, 111.2, 111.8, 118.1, 118.3,
120.9, 122.0, 122.9, 126.4, 128.1, 128.3, 128.4, 128.8, 129.3, 130.4, 130.6, 131.1,
134.5, 136.4, 139.4, 139.8, 146.1, 147.9, 148.8, 152.3; Anal. calcd. for C36H30N4O3:
C 76.31, H 5.34, N 9.89; found: C 76.25, H 5.22, N 9.70.
1‑{4‑[4,5‑diphenyl‑2‑(thiophen‑2‑yl)‑1H‑imidazol‑1‑yl]phenyl}‑3‑phenylurea (2e)
White solid; yield 65% (0.33 g); mp>300 °C; FTIR (KBr): 3373, 3065, 1656,
1
1608,1443, 1555, 845, 693 cm−1; H NMR (400 MHz, DMSO-d6) δ: 6.58 (d,
J=3.1 Hz, 1H, Ar–H), 6.93–6.99 (m, 2H, Ar–H), 7.17 (t, J=7.1 Hz, 1H, Ar–H),
7.23–7.50 (m, 18H, Ar–H), 8.73 (s, 1H, NH), 8.90 (s, 1H, NH); 13C NMR (100 MHz,
DMSO-d6) δ: 118.1, 118.2, 118.3, 122.1, 125.3, 126.3, 126.5, 127.0, 127.5, 128.19,
128.5, 128.8, 129.3, 129.6, 130.1, 131.0, 134.1, 136.6, 139.3, 140.5, 141.6, 152.3;
Anal. calcd. for C32H24N4OS: C 74.98, H 4.72, N 10.93, S, 6.25; found: C 74.73, H
4.58, N 10.81, S, 6.13.
1‑{4‑[2‑(4‑fuorophenyl)‑4,5‑diphenyl‑1H‑imidazol‑1‑yl]phenyl}‑3‑phenylurea (2f)
White solid; yield 77% (0.40 g); mp>300 °C; FTIR (KBr): 3315, 3057, 1648,
1
1601,1444, 1559, 1096, 696 cm−1; H NMR (400 MHz, DMSO-d6) δ: 6.97 (t,
J=7.3 Hz, 1H, Ar–H), 7.15–7.49 (m, 24H, Ar–H), 8.70 (s, 1H, NH), 8.83 (s, 1H,
NH); 13C NMR (100 MHz, DMSO-d6) δ: 115.1, 115.3, 118.0, 118.3, 122.0, 126.3,
126.4, 127.0, 128.1, 128.4, 128.5, 128.8, 129.1, 129.9, 130.4, 131.1, 131.5, 134.4,
136.6, 139.4, 139.9, 145.2, 152.3, 160.7, 163.1; Anal. calcd. for C34H25FN4O: C
77.84, H 4.80, F 3.62, N 10.68; found: C 77.74, H 4.69, F 3.57, N 10.45.
1‑{4‑[2‑(4‑methoxyphenyl)‑4,5‑diphenyl‑1H‑imidazol‑1‑yl]phenyl}‑3‑phenylurea
(2g)
White solid; yield 82% (0.44 g); mp>300 °C; FTIR (KBr): 3313, 3054, 2931,2832,
1644, 1603, 1443, 1555, 1250, 1060, 696 cm−1; 1H NMR (400 MHz, DMSO-d6) δ:
3.73 (s, 3H, –OCH3), 6.87 (d, J=7.0 Hz, 2H, Ar–H), 6.97 (t, J=7.3 Hz, 1H, Ar–H),
7.14–7.43 (m, 18H, Ar–H), 7.48 (d, J=7.4 Hz, 2H, Ar–H), 8.69 (s, 1H, NH), 8.81
(s, 1H, NH); 13C NMR (100 MHz, DMSO-d6) δ: 55.1, 113.6, 117.9, 118.2, 118.3,
122.0, 122.9, 126.3, 128.1, 128.2, 128.4, 128.8, 129.2, 129.5, 130.2, 130.6, 131.1,
134.5, 136.4, 139.3, 139.7, 139.8, 146.1, 152.2, 159.1; Anal. calcd. for C35H28N4O2:
C 78.34, H 5.26, N 10.44; found: C 78.19, H 5.16, N 10.37.
1‑{4‑[2‑(4‑isopropylphenyl)‑4,5‑diphenyl‑1H‑imidazol‑1‑yl]phenyl}‑3‑phenylurea
(2h)
White solid; yield 90% (0.49 g); mp>300 °C; FTIR (KBr): 3317, 3054, 2959,2869,
1
1647, 1604, 1446, 1557, 696 cm−1; H NMR (400 MHz, DMSO-d6) δ: 1.16 (d,
1 3

A. A. Fakhree et al.
J=6.8 Hz, 6H, CH3), 2.79–2.89 (m, 1H, CH3), 6.96 (t, J=7.3 Hz, 1H, Ar–H),
7.14–7.44 (m, 21H, Ar–H), 7.47 (d, J=7.2 Hz, 2H, Ar–H), 8.75 (s, 1H, NH), 8.90
(s, 1H, NH); 13C NMR (100 MHz, DMSO-d6) δ: 23.7, 33.1, 117.9, 118.0, 118.27,
118.3, 122.1, 126.2, 126.4, 128.0, 128.1, 128.3, 128.5, 128.8, 129.3, 130.2, 130.5,
131.1, 131.4, 134.5, 136.6, 139.4, 139.9, 146.2, 148.5, 152.3; Anal. calcd. for
C37H32N4O: C 80.99, H 5.88, N 10.21; found: C 80.76, H 5.71, N 10.17.
1‑{4‑[2‑(3‑nitrophenyl)‑4,5‑diphenyl‑1H‑imidazol‑1‑yl]phenyl}‑3‑phenylurea (2i)
White solid; Yield 60% (0.33 g); mp>300 °C; FTIR (KBr): 3305, 3079, 1663, 1608,
1
1443, 1350, 696 cm−1; H NMR (400 MHz, DMSO-d6) δ: 6.97 (t, J=7.3 Hz, 1H,
Ar–H), 7.19 (m, 16H, Ar–H), 7.50 (d, J=7.8 Hz, 2H, Ar–H), 7.60 (t, J=8.0 Hz, 1H,
Ar–H), 7.80 (d, J=7.9 Hz, 1H, Ar–H), 8.15 (td, J=8.2 Hz, J=1.3 Hz, 1H, Ar–H),
8.25 (s, 1H, Ar–H), 8.71 (s, 1H, NH), 8.87 (s, 1H, NH); 13C NMR (100 MHz,
DMSO-d6) δ: 118.2, 118.3, 118.4, 122.1, 122.4, 122.8, 126.4, 126.7, 128.3, 128.6,
128.8, 129.1, 129.5, 130.1, 131.1, 131.8, 132.5, 134.1, 137.3, 139.4, 140.4, 143.8,
147.6, 152.3; Anal. calcd. for C34H25N5O3: C 74.03, H 4.57, N 12.70; found: C
73.88, H 4.28, N 12.54.
1‑{4‑[4,5‑diphenyl‑2‑(thiophen‑3‑yl)‑1H‑imidazol‑1‑yl]phenyl}‑3‑phenylurea (2j)
White solid; yield 70% (0.35 g); mp>300 °C; FTIR (KBr): 3366, 3059, 1656,
1
1603,1443, 1556, 844, 695 cm−1; H NMR (400 MHz, DMSO-d6) δ: 6.97 (t,
J=7.2 Hz, 1H, Ar–H), 7.07 (s, 1H, Ar–H), 7.14–7.52 (m, 16H, Ar–H), 8.72 (s, 1H,
NH), 8.87 (s, 1H, NH); 13C NMR (100 MHz, DMSO-d6) δ: 118.2, 118.3, 122.0,
123.5, 126.1, 126.3, 127.3, 128.1, 128.3, 128.4, 128.8, 129.3, 129.8, 130.4, 131.0,
131.5, 134.4, 136.3, 139.4, 140.3, 142.8, 152.37; Anal. calcd. for C32H24N4OS: C
74.98, H 4.72; N 10.93, S 6.25; found: C 74.81, H 4.55; N 10.82, S 6.18.
General procedure for the synthesis of vinyl esters 3a–e and 4a–e
A mixture of substituted amine 1 (0.5 mmol) and dimethylacetylene dicarboxy-
late (0.5 mmol) and the catalyst (Mg2+/N.S, 0.01 g) was stirred at 80 °C in toluene
(3 mL). After completion of the reaction which was monitored by TLC (Table 1),
the mixture was cooled down to room temperature. The catalyst was removed with
centrifuging and the solution was concentrated under vacuum. The obtained crude
solid was then purifed: products 3a-e were purifed by preparative TLC (n hexane/
ethyl acetate 15:3) and Products 4a-e were simply recrystallized in ethyl acetate.
Dimethyl 2‑{[4‑(2,4,5‑triphenyl‑1H‑imidazol‑1‑yl)phenyl]amino}maleate (3a)
Pale yellow solid; Yield 77% (0.40 g); mp 120–122 °C; FTIR (KBr): 3452, 3068,
1
2876, 1743, 1611, 1521, 1444, 1286, 1034, 777, 750 cm−1; H NMR (400 MHz,
CDCl3) δ: 3.55 (s, 3H, CH3-ester), 3.73 (s, 3H, CH3-ester), 5.45 (s, 1H, vinylic H),
6.73 (d, J=8.6 Hz, 2H, Ar–H), 6.93 (d, J=8.6 Hz, 2H, Ar–H), 7.12–7.45 (m, 14H,
1 3

Synthesis of new polyaryl-substituted imidazoles bridged…
Ar–H), 7.58 (d, J=7.5 Hz, 2H, Ar–H), 9.59 (s, 1H, N–H); 13C NMR (100 MHz,
CDCl3) δ: 168.6, 163.4, 146.1, 145.8, 139.2, 137.1, 133.2, 131.8, 130.1, 129.7,
129.5, 129.3, 128.0, 127.9, 127.3, 127.3, 127.1, 127.1, 126.9, 126.3, 125.6, 119.8,
111.0, 94.4, 51.6, 50.3; Anal. calcd. for C33H27N3O4: C 74.84, H 5.14, N 7.93;
found: C 74.62, H 5.04, N 7.76.
Dimethyl 2‑{[4‑(4,5‑diphenyl‑2‑(p‑tolyl)‑1H‑imidazol‑1‑yl)phenyl]amino}maleate
(3b)
Pale yellow solid; Yield 82% (0.44 g); mp 164–166 °C; FTIR (KBr): 3431,
1
3068, 2876, 1743, 1611, 1521, 1440, 1145, 1034, 828, 781, 704 cm−1; H NMR
(400 MHz, CDCl3) δ: 2.31 (s, 3H, CH3 Methyl), 3.56 (s, 3H, CH3-ester), 3.74 (s,
3H, CH3-ester), 5.45 (s, 1H, vinylic H), 6.73 (d, J=6.8 Hz, 2H, Ar–H), 6.93 (d,
J=6.6 Hz, 2H, Ar–H), 7.06 (d, J=8.0 Hz, 2H, Ar–H), 7.11–7.26 (m, 11H, Ar–H),
7.31 (d, J=8.1 Hz, 2H, Ar–H), 7.58 (d, J=7.78 Hz, 2H, Ar–H), 9.60 (s, 1H, N–H);
13C NMR (100 MHz, CDCl3) δ: 168.7, 163.4, 146.1, 139.2, 130.1, 129.5, 128.0,
127.9, 127.8, 127.3, 127.1, 126.9, 126.3, 125.6, 119.8, 94.4, 51.6, 50.3; Anal. calcd.
for C34H29N3O4: C 75.12, H 5.38, N 7.73; found: C 74.08, H 5.12, N 7.57.
Dimethyl 2‑{[4‑(2‑(4‑chlorophenyl)‑4,5‑diphenyl‑1H‑imidazol‑1 yl)phenyl]amino}
maleate (3c)
Pale yellow solid; Yield 69% (0.38 g); mp 188–190 °C; FTIR (KBr): 3351, 3068,
1
2871, 1747, 1611, 1521, 1444, 1286, 1145, 1034, 828,786, 704 cm−1; H NMR
(400 MHz, CDCl3) δ: 3.58 (s, 3H, CH3-ester), 3.74 (s, 3H, CH3-ester), 5.48 (s,
1H, vinylic H), 6.76 (d, J=7.7 Hz, 2H, Ar–H), 6.93 (d, J=6.7 Hz, 2H, Ar–H),
7.11–7.28 (m, 11H, Ar–H), 7.37 (d, J=8.6 Hz, 2H, Ar–H), 7.57 (d, J=8.3 Hz, 2H,
Ar–H), 9.60 (s, 1H, N–H); 13C NMR (100 MHz, CDCl3) δ: 168.5, 163.3, 145.1,
144.8, 139.2, 137.1, 133.2, 131.8, 130.1, 129.7, 129.5, 129.3, 128.0, 127.9, 127.3,
127.3, 127.1, 127.1, 126.9, 126.3, 125.6, 119.8, 111.0, 94.4, 51.6, 50.3; Anal. calcd.
for C33H26ClN3O4: C 70.27, H 4.65, N 7.45; found: C 70.15, H 4.51, N 7.33.
Dimethyl 2‑{[4‑(2‑(3,4‑dimethoxyphenyl)‑4,5‑diphenyl‑1H‑imidazol‑1‑yl)phenyl]
amino}maleate (3d)
White solid; Yield 88% (0.51 g); mp 172–174 °C; FTIR (KBr): 3452, 3089,
1
2961, 1735, 1679, 1611, 1521, 1440, 1281, 1226, 1145, 1034, 786, 704 cm−1; H
NMR (400 MHz, CDCl3) δ: 3.58 (s, 3H, CH3-ester), 3.75 (s, 3H, CH3-ester), 3.77
(s, 3H, CH3 Methoxy), 3.88 (s, 3H, CH3 Methoxy), 5.50 (s, 1H, vinylic H), 6.75
(dd, J=3.6 Hz, J=0.80 Hz, 1H, Ar–H), 6.84 (d, J=11.4 Hz, 2H, Ar–H), 6.88 (t,
J=4.3 Hz, 1H, Ar–H), 7.09–7.26 (m, 11H, Ar–H), 7.58 (d, J=7.8 Hz, 2H, Ar–H),
9.65 (s, 1H, N–H); 13C NMR (100 MHz, CDCl3) δ: 168.8, 163.5, 146.1, 139.2,
130.1, 129.5, 128.0, 127.9, 127.8, 127.3, 127.1, 126.9, 126.3, 125.6, 119.8, 94.4,
54.8, 54.6, 51.6, 50.3; Anal. calcd. for C35H31N3O6: C 71.29, H 5.30, N 7.13; found:
C 71.20, H 5.19, N 7.05.
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A. A. Fakhree et al.
Dimethyl 2‑{[4‑(4,5‑diphenyl‑2‑(thiophen‑2‑yl)‑1H‑imidazol‑1‑yl)phenyl]amino}
maleate (3e)
White solid; Yield 53% (0.12 g); mp 110–112 °C; FTIR (KBr): 3453, 3068, 2961,
1
1747, 1611, 1521, 1286, 1230, 1145, 1034, 781, 704 cm−1; H NMR (400 MHz,
CDCl3) δ: 3.59 (s, 3H, CH3-ester), 3.75 (s, 3H, CH3-ester), 5.50 (s, 1H, vinylic H),
6.75 (dd, J=3.7 Hz, J=0.9 Hz, 1H, Ar–H), 6.84 (d, J=8.6 Hz, 2H, Ar–H), 6.88 (d,
J=4.2 Hz, 1H, Ar–H), 7.09–7.26 (m, 12H, Ar–H), 7.58 (d, J=7.5 Hz, 2H, Ar–H),
9.65 (s, 1H, N–H); 13C NMR (100 MHz, CDCl3) δ: 168.5, 163.3, 145.1, 144.8,
139.2, 137.1, 133.2, 131.8, 130.1, 129.7, 129.5, 129.3, 128.0, 127.9, 127.3, 127.3,
127.1, 127.1, 126.9, 126.3, 125.6, 119.8, 111.5, 94.4, 51.7, 50.4; Anal. calcd. for
C31H25N3O4S: C 69.52, H 4.70, N 7.85, S 5.99; found: C 69.38, H 4.70, N 7.63, S
5.80.
Dimethyl 2‑[(2,6‑dichlorophenyl)amino]maleate (4b)
Pale yellow solid; Yield 73% (0.22 g); mp 108–110 °C; FTIR (KBr): 3450, 3068,
2961, 1743, 1670, 1623, 1286, 1140, 1034, 777 cm−1; 1H NMR (400 MHz, CDCl3)
δ: 3.70 (s, 3H, CH3-ester), 3.78 (s, 3H, CH3-ester), 5.67 (s, 1H, vinylic H), 7.05
(t, J=8.0 Hz, 1 H, Ar–H), 7.30 (d, J=8.0 Hz, 2 H, Ar–H) 9.59 (s, 1H, N–H); 13C
NMR (100 MHz, CDCl3) δ: 169.1, 162.1, 146.3, 134.6, 130.3, 127.2, 125.4, 92.0,
51.8, 50.3; Anal. calcd. for C12H11Cl2NO4: C 47.39, H 3.65, N 4.61; found: C 47.22,
H 3.49, N 4.46.
Dimethyl 2‑[(2,6‑dimethylphenyl)amino]maleate (4c)
Pale yellow solid; Yield 87% (0.23 g); mp 100–102 °C; FTIR (KBr): 3367, 3301,
1
2961, 1747, 1675, 1611, 1440, 1220, 1149, 1038, 969, 820, 786 cm−1; H NMR
(400 MHz, CDCl3) δ: 2.24 (s, 6H, CH3 Methyl), 3.56 (s, 3H, CH3-ester), 3.74 (s,
3H, CH3-ester), 5.31 (s, 1H, vinylic H), 7.01–7.05 (m, 3 H, Ar–H), 9.27 (s, 1H,
N–H); 13C NMR (100 MHz, CDCl3) δ: 169.6, 162.9, 150.4, 136.5, 134.7, 127.0,
125.8, 87.2, 51.4, 51.4, 49.9, 49.9; Anal. calcd. for C14H17NO4: C 63.87, H 6.51, N
5.32; found: C 63.75, H 6.42, N 5.18.
Acknowledgements Authors thank the research afairs of the University of Tabriz for their fnancial
support.
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