Simple and efficient method for the synthesis of highly substituted imidazoles using zeolite-supported reagents

Article abstract of DOI:10.1016/j.tetlet.2010.04.013

Cu(II) nitrate impregnated zeolite has been used as an efficient supported reagent for an improved and rapid one-pot synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles in excellent yields. Condensation in the presence of supported reagents with operational simplicity, inexpensive reagents, high yield of products, and the use of non-toxic reagents makes this synthetic protocol, an attractive one.

Full text of DOI:10.1016/j.tetlet.2010.04.013

Tetrahedron Letters 51 (2010) 3018–3021
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Simple and efficient method for the synthesis of highly substituted
imidazoles using zeolite-supported reagents
*
K. Sivakumar, A. Kathirvel, A. Lalitha
Department of Chemistry, Periyar University, Salem 636 011, Tamil Nadu, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 12 December 2009
Revised 2 April 2010
Accepted 6 April 2010
Available online 10 April 2010
Cu(II) nitrate impregnated zeolite has been used as an efficient supported reagent for an improved and
rapid one-pot synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles in excellent yields.
Condensation in the presence of supported reagents with operational simplicity, inexpensive reagents,
high yield of products, and the use of non-toxic reagents makes this synthetic protocol, an attractive one.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Imidazoles
Cu(II) nitrate
Zeolite
Cyclo-condensation
Supported reagent
The imidazole ring system is one of the most important substruc-
ture found in a large number of natural products and pharmacolog-
ically active compounds1–5 and the members of this class of
compounds are known to possess NO synthase inhibition and
antifungal, antimycotic, antibiotic, antiulcerative, antibacterial,
antitumor, and CB1 receptor antagonistic activities.6,7 Various
substituted imidazoles act as inhibitors of p38 MAP kinase8a and
B-Raf kinase,8b glucagon receptors,9 plant growth regulators,10
therapeutic agents,11 and pesticides.12 Accordingly, a number of
synthetic methods have been reported for the construction of this
important structure.
Recently, multi-component reactions (MCRs) have attracted
considerable attention since they are performed without the need
to isolate any intermediate and save both energy and raw materials
and also reduce time.13 In 1882, Radziszewski and Japp reported
the first synthesis of the highly substituted imidazole from a
1,2-dicarbonyl compound, different aldehydes, and ammonia.14,15
Also a number of methods have been developed for the synthesis
of 1,2,4,5-tetrasubstituted imidazoles and 2,4,5-trisubstituted
imidazoles. The syntheses of 1,2,4,5-tetrasubstituted imidazoles
are carried out by four-component condensation of a 1,2-dike-
of a 1,2-diketone with an aryl nitrile and primary amine under
microwave irradiation,21a by hetero-Cope rearrangement,21b and
by N-alkylation of trisubstituted imidazoles.21c On the other hand,
2,4,5-trisubstituted imidazoles are generally synthesized by
three-component cyclo-condensation of a 1,2-diketone/a-hydrox-
yketone with an aldehyde and ammonium acetate, which comprise
the use of microwaves,22a–d refluxing in acetic acid,22e–g silica sulfu-
ric acid,22h NiCl2Á6H2O/Al2O3,22i ZrCl4,22j ionic liquids,22k and
CAN.22l
These methods are suitable for certain synthetic conditions,
however, many of these procedures are associated with one or
more disadvantages such as expensive reagents, longer reaction
times, tedious work-up procedure, low selectivity, and large
amounts of catalysts which would eventually result in the genera-
tion of large amounts of toxic waste.
Many organic reactions have been devised in which reagents are
supported on various inorganic solid supports. These solid-sup-
ported reagents have several advantages over various conventional
reagents. Laszlo and co-workers have successfully investigated
reagents like iron(III) nitrate supported on K-10 montmorillonite
and copper(II) nitrate supported on K-10. The variety and versatility
of these supported reagent-based organic synthesis reported in
recentyears are the formation of new carbon–carbon bonds in cyclo-
addition reaction,23 porphyrin synthesis by condensation of pyrrole
with aldehydes,24 oxidation of alcohols to aldehydes or ketones,25
benzoins to benzils,26 hydrolytic cleavage of thioacetals,27 prepara-
tion of azides from hydrazines,28 and nitration of phenols.29
In this Letter, we have presented a novel, mild, and efficient
method for the synthesis of tri and tetrasubstituted imidazoles
tone/
a-hydroxyketone with an aldehyde, primary amine, and
ammonium acetate using microwaves,16a molecular iodine,16b
HClO4–SiO2,16c heteropolyacid,16d,e silica gel/NaHSO4,16f -proline,17
L
FeCl3Á6H2O,18 BF3ÁSiO2,19 and silica-supported Wells-Dawson
acid.20 In addition, they can also be accessed by the condensation
* Corresponding author. Tel.: +91 427 2345271; fax: +91 427 2345124.
E-mail address: lalitha2531@yahoo.co.in (A. Lalitha).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.04.013

K. Sivakumar et al. / Tetrahedron Letters 51 (2010) 3018–3021
3019
Table 2
O
Synthesis of 1,2,4,5-tetraphenylimidazole (1a) using different supported reagents
Ph
Ph
Ph
under classical heating conditiona
CHO
NH2
Ph
NH4OAC
O
Yieldb (%)
N
N
Entry
Catalyst
Temp (°C)/time (min)
R2
or
+
+
Cu(NO3)2-Zeolite
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Cu(NO3)2/zeolite-HY
Fe(NO3)3/zeolite-HY
Bi(NO3)3/zeolite-HY
Co(NO3)2/zeolite-HY
Mn(NO3)2/zeolite-HY
Ni(NO3)2/zeolite-HY
Cu(NO3)2/MCM-41
Fe(NO3)3/MCM-41
Bi(NO3)3/MCM-41
Co(NO3)2/MCM-41
Mn(NO3)2/MCM-41
Ni(NO3)2/MCM-41
ZnCl2/MCM-41
80/30
60/30
96
91
88
45
19
18
89
77
56
11
—
—
56
31
Charred
9216f
9016c
9219
R2
O
R1
R1
Ph
120/30
120/60
120/60
120/60
80/30
Ph
OH
1a-v
Scheme 1.
60/30
120/60
120/90
120/90
120/90
80/90
120/90
80/60
140/120
140/6
O
Ph
N
Ph
NH
Ph
CHO
Ph
Cu(NO3)2-Zeolite
Zeolite-HY
Cu(NO3)2
SiO2/NaHSO4 (400 mg)
SiO2/HClO4 (1 mol %)
BF3/SiO2 (21 mol %)
O
NH4OAC
or
+
+
R3
O
R3
Ph
140/120
Ph
a
The reaction condition: benzaldehyde (1 mmol), benzil (1 mmol), 4-chloro
OH
2a-j
aniline (1 mmol), ammonium acetate (1 mmol), and catalyst (0.03 g) (metal salt
loading = 1 mmol gÀ1 of solid support).
b
Scheme 2.
Yields refer to isolated products.
Table 3
Table 1
Cu(NO3)2–zeolite catalyzed synthesis of 1,2,4,5-tetrasubstituted imidazoles
Synthesis of 1-(4-chlorophenyl)-2,4,5-triphenylimidazole 1a using Cu(NO3)2–zeolite
in different solvents
Entry Product –R1
–R2
Reaction time
Benzil Benzoin Benzil Benzoin
0.5
Yielda
Entry
Solvent
Temperature °C
Time (h)
Yielda (%)
1
2
3
4
5
6
Methanol
Ethanol
Acetonitrile
Chloroform
Dichloromethane
Solvent-free
65
70
70
50
45
80
3
3
3
6
6
0.5
56
53
41
22
12
96
1
2
3
4
5
1a
1b
1c
1d
1e
1f
–H
2-Cl
2-OH
2-NO2
4-NO2
–H
4-Cl
4-OCH3 0.5
4-Cl
2-Cl
2-NO2
–H
–H
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
96
92
76
86
93
96
95
86
94
86
97
93
86
86
95
86
84
79
86
63
67
77
92
80
72
73
82
94
92
79
90
75
82
87
72
82
79
80
77
80
82
52
62
72
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
6
7
8
9
1g
1h
1i
4-OCH3
4-Cl
2-Cl
a
Yields refer to isolated products.
4-Cl
4-CH3
4-CH3
–H
4-CH3
–H
10
11
12
13
14
15
16
17
18
19
20
21
22
1j
1k
1l
2-OH
4-NO2
4-NO2
4-Cl
4-OCH3
4-Cl
using supported reagents (Schemes 1 and 2). Out of range of zeolite
supported metal nitrates, Cu(NO3)2 has attracted much attention
because of its suitable acidity, eco-friendliness, easy availability,
and low cost thereby acting as a promising table top reagent.
The typical procedure for 1,2,4,5-tetrasubstituted imidazoles
involves impregnating the mixture of zeolite-supported metal
nitrate (supported reagent) and ammonium acetate (ammonia
source) with a dichloromethane solution of benzil, benzaldehyde,
and 4-chloroaniline and was used as a model reaction to optimize
the reaction conditions.30,31 Among the tested solvents such as
methanol, ethanol, acetonitrile, chloroform, dichloromethane, and
solvent-free system, the formation of product 1a was more facile
and proceeded to give highest yield, only under solvent-free reac-
tion conditions (Table 1).
1m
1n
1o
1p
1q
1r
1s
1t
2-Cl
2-NO2
4-NO2
–H
4-CH3
4-CH3
2-Cl
2-OH
3-NO2
4-Cl
Furfural 2-NO2
Furfural 4-NO2
Furfural –H
1u
1v
a
Yields refer to pure isolated solid products, characterized by mp, spectral (IR,
1H, 13C NMR, and mass) data.
To evaluate and optimize the catalytic system, four-component
condensation to give 1a was examined with different solid acids
and supported Lewis acid catalysts (Table 2). Interestingly, it was
found that Cu(NO3)2 supported on zeolite-HY with low loading
[one gram of zeolite-HY-supported copper(II) nitrate reagent
contains about 0.241 g of Cu(NO3)2 (1 mmol)] was proved to be
an efficient catalyst and gave exclusively 1-(4-chlorophenyl)-
2,4,5-triphenylimidazole 1a in 96% yield in 30 min under sol-
vent-free conditions (Table 2).
From these experiments it was clearly demonstrated that
the zeolite-supported cupric nitrate was indeed an effective
catalyst and was convincingly superior to the reported procedures
(Table 2, entries 16–18) with respect to reaction time, amount of
catalyst and yields; and under solvent-free conditions. In order to
evaluate the generality of the process, several diversified examples
illustrating the present method for the synthesis of 1,2,4,5-tetra-
substituted imidazoles 1a–v were studied (Table 3).
The cyclo-condensation of benzil/benzoin with various
aromatic aldehydes bearing electron-withdrawing groups (such
as nitro and halide) or electron-releasing groups (such as methyl,
hydroxyl, mono, di, or tri methoxy groups), substituted anilines,
and ammonium acetate was carried out in the presence of
Cu(NO3)2–zeolite as a catalyst. The yields obtained were good to
excellent without the formation of any side products such as the
formation of 2,4,5-trisubstituted imidazoles, oxidized products of
anilines, and aldehydes , which are normally observed under the
influence of strong acids. The results obtained in the current meth-
od are illustrated in Table 3. All the products obtained were fully

3020
K. Sivakumar et al. / Tetrahedron Letters 51 (2010) 3018–3021
Table 4
led to the conclusion that the catalyst is reusable without consider-
able loss in activity.
Cu(NO3)2–zeolite catalyzed synthesis of 2,4,5-trisubstituted imidazoles
Entry
Product
-R3
Reaction time
Benzil Benzoin
Yielda
Benzoin
In summary, this Letter describes a convenient and efficient
procedure for the synthesis of tetra and trisubstituted imidazoles
through the one-pot cyclo-condensation reaction using zeolite-
HY-Cu(NO3)2 as a solid supported reagent. Present methodology
offers very attractive features such as reduced reaction times, high-
er yields, and economic viability of the catalyst, when compared
with conventional methods as well as with other catalysts, which
will have wide scope in organic synthesis. The simple procedures
combined with easy recovery and reuse of this catalyst make this
method economic, environmentally benign synthesis of tetra and
trisubstituted imidazoles of biological and medicinal importance.
The catalyst can be prepared easily with readily available inexpen-
sive reagents, which is heterogeneous and non-hazardous.
Benzil
1
2
3
4
5
6
7
8
9
2a
2b
2c
2d
2e
2f
2g
2h
2i
4-Cl
2-Cl
2-OH
2-NO2
4-NO2
–H
4-OCH3
Furfural
2-Br 6-OH
2-OH 4-OMe
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
98
92
86
87
93
96
85
77
71
81
91
80
72
75
82
94
81
72
62
72
10
2j
A
Yields refer to pure isolated solid products, characterized by mp, spectral (IR,
1H, 13C NMR, and mass) data.
Acknowledgment
characterized by spectroscopic methods such as IR, 1H NMR, 13C
NMR, and mass spectroscopy and also by making a comparison
with the reported spectral data. The simplicity, together with the
use of inexpensive, non-toxic, and environmentally benign nature
of Cu(NO3)2–zeolite catalyst under solid state reaction condition
is another remarkable feature of the procedure. From these results,
it is clear that ring substituent like methoxy was not affected and
the carbonyl derivative was not oxidized further.
In order to explore the applicability of this method, the same
reaction conditions were applied for the synthesis of 2,4,5-trisub-
stituted imidazoles 2a–j via a similar one-pot, three-component
condensation of 1,2-diketone (1 mmol), aldehyde (1 mmol), and
ammonium acetate (2 mmol) as depicted in Scheme 2.30,31
We studied the synthesis of 2-(4-chlorophenyl)-4,5-diphenyl-
1H-imidazole (2a) using benzil, ammonium acetate, and 4-chloro
benzaldehyde under different temperatures and with various
mol % of Cu(NO3)2 in zeolite (Scheme 2). The compound 2a was iso-
lated with 98% yield using optimized reaction conditions (maxi-
mum % conversion at 80 °C and 1 mmol Cu(NO3)2 in zeolite-HY).
Fascinated by the higher yields under mild reaction conditions,
the same procedure has been extended for the synthesis of a range
of 2-aryl-4,5-diphenyl-1H-imidazoles and the results are summa-
rized in Table 4.
We gratefully acknowledge financial support from the Jaw-
aharlal Nehru memorial fund, New Delhi 11, India.
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The structures of compounds 2a–j were deduced from their 1H
and 13C NMR, and IR spectral data and also confirmed from their
melting points. The three-component condensation was also per-
formed in the absence of Cu(NO3)2 on silica gel under classical
heating; however, the yield of 2a was low (ꢀ50%) illustrating the
superiority of the supported reagent.
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aldehyde, benzil, and NH4OAc to provide the trisubstituted imida-
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a catalyst was run for five consecutive cycles, furnishing the
corresponding imidazole, with 96%, 94%, 93%, 92%, and 92% isolated
yields which proved the efficiency of the catalyst for multiple usage.
Similar studies in the synthesis of tetrasubstituted imidazoles also

K. Sivakumar et al. / Tetrahedron Letters 51 (2010) 3018–3021
3021
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(Cq), 134.06 (Cq), 134.17 (Cq), 144.45 (C@N), 156.39 (Cq).
2-(4-Nitrophenyl)-1,4,5-triphenyl-1H-imidazole (1k):17 mp, 190–192 °C; IR (KBr,
cmÀ1): max 3057, 1590, 1513, 1342; 1H NMR (DMSO-d6) d: 8.12 (d, 2H), 7.63–
m
7.08 (m, 17H, Ar-H); 13C NMR (DMSO-d6) d: 123.4 (2C, CHarom), 124.0 (2C,
CHarom), 124.2 (2C, CHarom), 127.4 (2C, CHarom), 127.8 (CHarom), 128.2 (CHarom),
128.4 (2C, CHarom), 128.6 (2C, CHarom), 129.4 (Cq), 131.6 (Cq), 132.4 (Cq), 136.5
(Cq), 137.2 (Cq), 137.9 (Cq), 144.3 (C@N), 147.4 (Cq).
2-(4-Nitrophenyl)-4,5-diphenyl-1-p-tolyl-1H-imidazole (1l):16c mp, 217–219 °C;
IR (KBr): m ;
max 1591, 1507, 1337 cmÀ1 1H NMR (DMSO-d6) d: 2.14 (s, 3H, CH3),
7.17–7.49 (m, 18H, Ar–H). 13C NMR (DMSO-d6) d: 21.31 (CH3), 122.9 (2C,
CHarom), 124.8 (2C, CHarom), 127.2 (2C, CHarom), 128.7 (2C, CHarom), 128.9
(CHarom), 129.24 (2C, CHarom), 129.39 (2C, CHarom), 131.53 (Cq), 133.29 (Cq),
134.05 (Cq), 134.39 (Cq), 136.83 (Cq), 137.22 (Cq), 144.26 (C@N), 147.43 (Cq),
148.03 (Cq).
23. (a) Laszlo, P.; Lucchetti, J. Tetrahedron Lett. 1982, 25, 1567; (b) Laszlo, P.;
Lucchetti, J. Tetrahedron Lett. 1984, 25, 2147; (c) Laszlo, P.; Lucchetti, J.
Tetrahedron Lett. 1984, 25, 4387.
24. Cornalis, A.; Laszlo, P.; Pennetreau, P. Clays Clay Miner. 1983, 18, 437.
25. (a) Cornalis, A.; Laszlo, P. Synthesis 1980, 849; (b) Cornalis, A.; Herve, P. Y.;
Laszlo, P. Tetrahedron Lett. 1982, 23, 5035.
26. Bessemann, M.; Cornalis, A.; Laszlo, P.; Acad, C. R. Sci. Ser. C 1984, 299, 427.
27. Balogh, M.; Cornalis, A.; Laszlo, P. Tetrahedron Lett. 1984, 25, 3313.
28. Laszlo, P.; Polla, E. Tetrahedron Lett. 1984, 25, 3701.
29. Lalitha, A.; Sivakumar, K. Synth. Commun. 2008, 38, 1745–1752.
30. To 0.241 g of Cu(NO3)2Á3H2O (1 mmol) dissolved in 15 ml of acetone, 1 g of
activated zeolite-HY (obtained by activating the NH4-Y form of zeolite in a
muffle furnace at about 500 °C for 12 h) was added at once with stirring over a
magnetic stirrer for 2 h. Then the solvent was removed in a rotary evaporator.
The blue powder formed was dried further at 130 °C under reduced pressure.
The reagent was stored in a vessel sealed with para film.
2-(4-Chlorophenyl)-1,4,5-triphenyl-1H-imidazole (1m):19 mp, 152–154 °C; IR
(KBr): mmax 1600, 1580; 1H NMR (DMSO-d6) d: 7.31–7.65 (m, 15H), 7.69–7.70
(d, 2H), 7.94–7.97 (d, 2H); 13C NMR (DMSO-d6) d: 124.2 (2C, CHarom), 124.7 (2C,
CHarom), 125.2 (2C, CHarom), 126.8 (CHarom), 128.3 (CHarom), 130.3 (CHarom),
130.6 (2C, CHarom), 132.9 (2C, CHarom), 134.3 (2C, CHarom), 136.8 (Cq), 138.1 (Cq),
139.0 (Cq), 139.2 (Cq), 139.5 (Cq), 139.8 (Cq), 140.1 (Cq), 144.4 (C@N).
2-(1,4,5-Triphenyl-1H-imidazol-2-yl)phenol (1q):16b mp, 254–256 °C; IR (KBr):
mmax 1605, 1579 cmÀ1 1H NMR (DMSO-d6) d: 6.60–6.67 (d, 2H), 6.94–6.96 (d,
;
2H), 7.19–7.43 (m, 15H); 13C NMR (DMSO-d6) d: 115.8 (CHarom), 122.1 (Cq),
122.7 (CHarom), 125.2 (2C, CHarom), 126.5 (2C, CHarom), 127.9 (CHarom), 128.3
(CHarom), 129.2 (2C, CHarom), 130.8 (2C, CHarom), 131.9 (CHarom), 135.1 (CHarom),
136.5 (Cq), 137.6 (Cq), 139.7 (Cq), 140.1 (Cq), 140.4 (Cq), 144.3 (C@N), 156.7 (Cq).
2-(3-Nitrophenyl)-4,5-diphenyl-1-p-tolyl-1H-imidazole (1r):16c mp, 150–151 °C;
31. A solution of benzil or benzoin (1 mmol), aldehyde (1 mmol), amine (1 mmol),
and ammonium acetate (1 mmol) in dichloromethane (10 mL) was added to
supported reagent (300 mg) [one gram of zeolite-HY-supported copper(II)
nitrate reagent contains about 0.241 g of Cu(NO3)2 (1 mmol)] in a reaction
tube. The solvent was allowed to evaporate and the dry residue was heated at
80 °C for specified time in an oil bath. The progress of reaction was monitored
by TLC. After completion of the reaction, the crude product from the reaction
mixture was dissolved in ethanol and the catalyst was separated by filtration.
The filtrate was evaporated under reduced pressure to remove ethanol and the
resulting product was washed with water. The solid product was then
crystallized from hot ethanol. After extraction of the product, the supported
reagent was washed thrice with ethanol and dried under vacuum before reuse.
1,2,4,5-Tetraphenyl-1H-imidazole (1f):19 mp, 220 °C; IR (KBr): mmax 1595,
IR (KBr): m ;
max 1598, 1498, 1413 cmÀ1 1H NMR (DMSO-d6) d: 2.27 (s, 3H, CH3),
7.17–8.85 (m, 18H, Ar–H). 13C NMR (DMSO-d6) d: 21.31 (CH3), 122.87 (CHarom),
123.28 (2C, CHarom), 126.80 (CHarom), 127.25 (2C, CHarom), 128.71 (CHarom),
128.82 (2C, CHarom), 129.32 (2C, CHarom), 129.01 (CHarom), 129.12 (CHarom),
130.39 (Cq), 130.47 (Cq), 131.55 (Cq), 132.23 (Cq), 132.70 (Cq), 134.01 (Cq),
134.30 (Cq), 144.15 (C@N), 149.02 (Cq).
A solution of benzil or benzoin (1 mmol), aldehyde (1 mmol), ammonium
acetate (2 mmol), and 10 mL of dichloromethane was added to 300 mg of the
zeolite-HY-Cu(NO3)2 mixture in a reaction tube. The solvent was allowed to
evaporate and the dry residue was heated at 80 °C for specified time. The
progress of reaction was monitored by TLC. After completion of the reaction,
the crude product from the reaction mixture was dissolved in ethanol and the
catalyst was separated by filtration. The filtrate was evaporated under reduced
pressure to remove ethanol and the resulting product was washed with water.
The solid product was then crystallized from hot ethanol.
1572 cmÀ1 1H NMR (DMSO-d6) d: 7.24–7.47 (m, 20H); 13C NMR (DMSO-d6)
;
d: 124.1 (2C, CHarom), 124.5 (2C, CHarom), 125.1 (2C, CHarom), 126.9 (CHarom),
128.3 (CHarom), 129.1 (CHarom), 130.3 (CHarom), 130.6 (2C, CHarom), 132.9 (2C,
CHarom), 134.3 (2C, CHarom), 136.8 (Cq), 139.0 (Cq), 139.2 (Cq), 139.5 (Cq), 139.8
(Cq), 140.1 (Cq), 144.6 (C@N).
2-(4,5-Diphenyl-1H-imidazol-2-yl)-phenol (2c):17 mp, 205 °C; IR (KBr): mmax
1214, 1638, 2466, 2988, 3430, 3594; 1H NMR (DMSO-d6) d: 6.87–6.95 (d, 2H),
6.97–7.01 (d, 2H), 7.17–7.23 (m, 10H), 12.74 (br s, 1H); 13C NMR (DMSO-d6) d:
114.8 (CHarom), 116.4 (Cq), 118.1 (CHarom), 126.8 (2C, CHarom), 127.2 (CHarom),
127.8 (2C, CHarom), 129.1 (CHarom), 130.3 (CHarom), 135.2 (Cq), 136.1 (Cq), 136.4
(Cq), 138.1 (Cq), 147.7 (C@N), 156.6 (Cq).
2-(4-Methoxyphenyl)-1,4,5-triphenyl-1H-imidazole (1g):16b mp, 183–184 °C; IR
(KBr): m ;
max 1617, 1576 cmÀ1 1H NMR (DMSO-d6) d: 3.74 (s, 3H), 6.80–6.84 (d,
2H), 7.20–7.38 (m, 15H), 7.49–7.51 (d, 2H); 13C NMR (DMSO-d6) d: 54.7 (OCH3),
115.2 (2C, CHarom), 124.2 (2C, CHarom), 126.1 (CHarom), 127.7 (CHarom), 128.1
(2C, CHarom), 128.2 (2C, CHarom), 128.4 (2C, CHarom), 128.7 (2C, CHarom), 130.1
(Cq), 132.3 (Cq), 132.7 (Cq), 134.9 (Cq), 136.7 (Cq), 137.1 (Cq), 146.5 (C@N),159.4
(Cq).
2-(4-Nitro-phenyl)-4,5-diphenyl-1H-imidazole (2e):17 mp 196 °C; IR (KBr): mmax
845, 1448, 1528, 1542, 1604, 3058; 1H NMR (DMSO-d6) d: 7.25–7.57 (m, 10H),
7.68 (d, 2H), 8.52 (d, 2H), 12.52 (br s, 1H); 13C NMR (DMSO-d6) d: 124.2 (2C,
CHarom), 125.2 (2C, CHarom), 126.3 (2C, CHarom), 127.6 (CHarom), 132.8 (2C,
CHarom), 133.1 (Cq), 135.2 (Cq), 138.3 (Cq), 144.7 (Cq), 164.8 (C@N).
2,4,5-Triphenyl-1H-imidazole (2f):17 mp, 272 °C; IR (KBr): mmax 1216, 1640,
2474, 2993, 3438; 1H NMR (DMSO-d6) d: 7.40–8.14 (m, 15H), 12.60 (br s, 1H);
13C NMR (DMSO-d6) d: 127.1 (2C, CHarom), 127.2 (CHarom), 128.5 (2C, CHarom),
129.1 (Cq), 131.5 (CHarom), 137.2 (Cq), 138.2 (Cq), 168.7 (C@N).
1,2-Bis(4-chlorophenyl)-4,5-diphenyl-1H-imidazole (1h):16e mp, 189–190 °C; IR
(KBr): mmax 1599, 1497, 1412 cmÀ1 1H NMR (DMSO-d6) d: 6.92–7.63 (m, 18H,
;
Ar-H). 13C NMR (DMSO-d6) d: 122.84 (2C, CHarom), 126.98 (2C, CHarom), 127.90
(CHarom), 128.15 (2C, CHarom), 129.21 (2C, CHarom), 129.82 (2C, CHarom), 129.82
(2C, CHarom), 130.01 (Cq), 130.12 (Cq), 130.39 (Cq), 130.47 (Cq), 131.55 (Cq),
132.23 (Cq), 132.70 (Cq), 138.01 (Cq), 144.08 (C@N).
2-(4-Methoxy-phenyl)-4,5-diphenyl-1H-imidazole (2g):17 mp, 224 °C; IR (KBr):
mmax 1226, 1640, 2462, 2892, 3424; 1H NMR (DMSO-d6) d: 3.86 (s, 3H), 6.92–
6.98 (d, 2H), 7.24–7.60 (m, 10H), 8.02–8.05 (d, 2H), 12.52 (br s, 1H); 13C NMR
(DMSO-d6) d: 54.6 (CH3), 113.2 (CHarom), 114.9 (2C, CHarom), 126.7 (2C, CHarom),
126.9 (CHarom), 127.5 (2C, CHarom), 127.9 (Cq), 129.6 (2C, CHarom), 132.8 (Cq),
133.2 (Cq), 154.7 (Cq), 158.1 (C@N).
2-(2-Hydroxyphenyl)-4,5-diphenyl-1-p-tolyl-1H-imidazole (1j):16e mp, 227–
229 °C; IR (KBr): mmax 1600, 1539, 1482, 1411 cmÀ1 1H NMR (DMSO-d6) d:
;
2.38 (s, 3H, CH3), 6.41–7.42 (m, 18H, Ar–H), 13.21 (s, 1H, OH). 13C NMR (DMSO-
d6) d: 20.45 (CH3), 113.72 (CHarom), 116.81 (Cq), 121.97 (CHarom), 125.85 (2C,
CHarom), 126.46 (CHarom), 126.75 (2C, CHarom), 128.24 (2C, CHarom), 128.36 (2C,
CHarom), 128.57 (Cq), 129.45 (Cq), 129.73 (Cq), 129.97 (Cq), 130.71 (Cq), 131.14