Synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazole derivatives using silica-bonded propyl-S-sulfonic acid as recyclable solid acid catalyst

Article abstract of DOI:10.1002/cjoc.201280016

A highly selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles from the reaction of o-phenylenediamine and aromatic aldehydes in the presence of silica-bonded propyl-S-sulfonic acid (SBSSA) at 80°C in water in good to excellent yields was devel

Full text of DOI:10.1002/cjoc.201280016

FULL PAPER
DOI: 10.1002/cjoc.201280016
Synthesis of 2-Aryl-1-arylmethyl-1H-1,3-benzimidazole
Derivatives Using Silica-bonded Propyl-S-sulfonic
Acid as Recyclable Solid Acid Catalyst
Ghaem Ahmadi-Ana, Sayed Mohammada
Baghernejad, Mojtabaa
Niknam, Khodabakhsh*,a,b
a Chemistry Department, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran
b Chemistry Department, Faculty of Sciences, Persian Gulf University, Bushehr, 75169, Iran
A highly selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles from the reaction of o-phenylene-
diamine and aromatic aldehydes in the presence of silica-bonded propyl-S-sulfonic acid (SBSSA) at 80 ℃ in water
in good to excellent yields was developed.
Keywords
silica-bonded propyl-S-sulfonic acid, aldehydes, 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles,
o-phenylenediamine, water
propyl)sulfanyl]propyl)ester[21] under various reaction
conditions.
Introduction
The benzimidazole nucleus is of significant impor-
tance to medicinal chemistry. Benzimidazoles are
components of vitamin B12 and are related to the DNA
base purine and the stimulant caffeine.[1] Interest in
benzimidazole-containing structures stems from their
widespread occurrence in molecules that exhibit sig-
nificant activity.[2,3] In light of the affinity they display
towards a variety of enzymes and protein receptors, me-
dicinal chemists would certainly classify them as ‘privi-
leged sub-structures’ for drug design.[4,5]
Recently, silica-bonded propyl-S-sulfonic acid
(SBSSA) was prepared by reaction of 3-mercaptopro-
pylsilica (MPS) and chlorosulfonic acid (Scheme 1).
This solid acid was used as a catalyst in the synthesis of
acylals,[22] silyl ethers,[23] quinoxalines,[24] coumarins,[25]
bis-pyrazol-5-ols,[26] acridines,[27] trisubstituited imida-
zoles,[28] α-amino nitriles,[29] bis-indolylmethanes,[30]
and 2,3-dihydroquinazolin-4(1H)-ones.[31]
Scheme 1 Preparation of silica-bonded propyl-S-sulfonic acid
The traditional synthesis of benzimidazoles involves
the reaction between o-phenylenediamines and carbox-
ylic acid or its derivatives (nitriles, amidates and or-
thoesters) under harsh dehydrating conditions.[6,7] Ben-
zimidazoles have also been prepared on solid-phase to
provide a combinatorial approach.[8] The most popular
strategies for their synthesis utilize o-nitroanilines as
intermediates or resort to direct N-alkylation of an un-
substituted benzimidazole.[9] A number of synthetic pro-
tocols that involve intermediate o-nitroanilines have
evolved to include the synthesis of benzimidazoles on
solid support.[10] Another method for the synthesis of
these compounds is the reaction of o-phenylenediamines
with aldehydes in the presence of acidic catalysts such
as sulfamic acid,[11] silica sulfuric acis,[12] Zn-proline,[13]
[Hbim]BF4,[14] Fe(ClO4)3,[15] M(HSO4)n,[16] 1-heptane-
sulfonic acid sodium salt,[17] poly(N,N-dibromo-N-ethyl-
(SBSSA)
O
OH
SH
toluene, reflux, 18 h
(MeO)3Si
SH
O
O
Si
SiO2
OH
OH
SiO2
O
O
(1) ClSO3H/t-Bu-OMe/4 h
Si
S SO3H
SiO2
(2) wash with MeOH
O
SBSSA
Water emerged as a useful alternative solvent for
several organic reactions owing to many of its potential
advantages such as safety, economy, easy availability,
nontoxicity and environmental concern.[32-34] Reactions
in water have been very useful to the synthetic chemist
for many years, and their utility is reflected by the many
studies to discover new processes with which they can
be performed catalytically and chemoselectively.
benzene-1,3-disulfonamide),[18]
[HSO4],[19] acetic acid[20] and sulfuric acid ([3-(3-silica-
[(CH2)4SO3HMIM]-
*
E-mail: khniknam@gmail.com, niknam@pgu.ac.ir; Fax: 0098-771-4545188
Received May 23, 2011; accepted October 18, 2011.
Chin. J. Chem. 2012, 30, 517—521
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
517

Ghaem Ahmadi-Ana, Baghernejad & Niknam
FULL PAPER
Results and Discussion
donating substituents gave the desired benzimidazoles
3b—3e in a short reaction times (10 to 30 min) and very
good to excellent yields (Table 2). Arylaldehydes with
electron-withdrawing substituents such as 4-fluoro- and
4-cyano-benzaldehyde gave the corresponding ben-
zimidazoles 3h, and 3j in very good yields.
During the course of our studies towards the devel-
opment of new routes to the synthesis of highly substi-
tuted heterocycles using solid acid catalysts,[21-31] we
found a valid and an efficient procedure for the synthe-
sis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles via
one-pot condensation reaction between o-phenylenedi-
amine and aldehydes in the presence of SBSSA as an
inexpensive solid acid catalyst (Eq. 1).
Table 2 Synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimida-
zoles catalyzed by SBSSA at 80 ℃ in watera
Entry
Ar (3)
C6H5-
Product Time/min Yieldb/% m.p./℃ Ref.
O
1
2
3
4
5
6
7
8
9
3a
3b
3c
3d
3e
3f
20
10
20
20
30
25
35
30
30
35
25
87
93
92
88
90
92
90
84
91
92
75
130—132 [11]
129—131 [19]
150—151 [19]
128—130 [19]
139—140 [13]
135—137 [19]
161—163 [11]
82—84 [13]
154—156 [13]
190—192 [20]
92—94 [19]
O
Si
S SO3H
SiO2
4-MeO-C6H4-
2-MeO-C6H4-
4-Me-C6H4-
2-Me-C6H4-
4-Cl-C6H4-
2-Cl-C6H4-
4-F-C6H4-
NH2
NH2
O
ArCHO
+
water/80 oC
2
1
N
(1)
3g
3h
3i
Ar
N
Ar
3
4-Br-C6H4-
10 4-NC-C6H4-
11 2-Furyl
3j
3k
To study the effect of catalyst loading on the synthe-
sis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles, the
a Reaction conditions: 1,2-phenylenediamine (1 mmol), aldehyde
(2 mmol), and SBSSA (0.05 g) at 80 ℃ in water (5 mL). b Iso-
lated yield.
reaction
between
o-phenylenediamine
and
4-methylbenzaldehyde was chosen as the model reac-
tion in water under reflux conditions (Table 1).
Some possible mechanisms of this condensation re-
action had been reported before by Ravi et al.[13] and
Jadhav and co-workers.[17] In the proposed mechanism
(Scheme 2), aromatic aldehyde was activated by SBSSA
during the reaction. Initially Schiff’s base formation was
formed between arylenediamine and substituted aro-
matic aldehydes followed by cyclization, and
1,3-hydride transfer.
Table 1 The reaction of o-phenylenediamine with 4-methoxy-
benzaldehyde in the presence of different amounts of SBSSA at
80 ℃ in watera
Entry
Amount of catalyst/g
Product Time/min Yieldb/%
1
2
3
3
4
—
—
3
180
35
20
10
15
—
87
90
93
92
0.01
0.03
0.05
0.1
3
Scheme
2
Plausible mechanism for the synthesis of
3
2-aryl-1-arylmethyl-1-benzo[d]imidazoles
3
a
Reaction conditions: 1,2-phenylenediamine (1 mmol), aldehyde
Ar
H
OH
O
O Si
(2 mmol) at 80 ℃ in water (5 mL). b Isolated yield.
S-SO3-H
SiO2
H2N
H2N
N
O
O
The results show clearly that SBSSA is an effective
catalyst for this transformation and in the absence of
SBSSA the reaction did not take place even after 3 h
(Table 1, Entriy 1). As indicated in Table 1, the best
result has been obtained with amount of 0.05 g (0.16
mol%) SBSSA in terms of reaction time and isolated
yield. The higher the catalyst loading (0.1 g), the longer
time the condensation to accomplish (Table 1, Entry 4).
This is may be due to the decrease of the nucleophilicity
of o-phenylenediamine when the acidic catalyst loading
was increased.
Several aromatic aldehydes with different substitu-
ents on the aromatic ring were subjected to the conden-
sation reaction. As shown in Table 2, arylaldehydes
without substituents gave the desired benzimidazoles in
good yields (3a, 3k). Aldehydes bearing electron-
Ar
2
H
H2N
1
Ar
Ar
N
N
N
- H2O
- H2O
ArCHO
H
H2N
Ar
OH
H+
Ar
Ar
Ar
Ar
+
N
N
N
N
H
Ar
Ar
N
N
3
H
The possibility of recycling of the catalyst was ex-
amined. For this reason, the reaction of o-phenylene-
518
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© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2012, 30, 517—521

Synthesis of 2-Aryl-1-arylmethyl-1H-1,3-benzimidazole Derivatives
diamine with 4-methylbenzaldehyde in the presence of
SBSSA was studied at 80 ℃ in water. Upon comple-
tion, the reaction mixture was filtered and washed with
warm ethanol. The product was recrystallized from hot
water-ethanol (V∶V＝1∶1). The recycled catalyst was
reused four times without any treatment. No observation
of appreciable loss in its catalytic activities was shown
(Figure 1).
group, the FT-IR absorption range of the O＝S＝O
asymmetric and symmetric stretching modes lie in
1176.5 and 1072.3 cm－1 respectively, the S—O stretch-
ing mode lies in 550—700 cm－ and that of S—S
1
－
1
stretching mode lies from 400 to 500 cm . FT-IR spec-
trum shows the overlap asymmetric and symmetric
stretching bands of SO2 with Si—O—Si stretching
bands in the silica functionalized S-sulfonic acid. The
spectrum also shows a broad OH stretching absorption
from 3600 to 2491.9 cm－1 (Figure 2).
Figure 1 Recyclability of silica bonded propyl-S-sulfonic acid
(0.05 g) as catalyst in the condensation reaction of o-phenylene-
diamine (1 mmol) and 4-methoxybenzaldehyde (2 mmol) in wa-
ter (5 mL) at 80 ℃. Reaction time＝10 min.
Figure 2 FT-IR spectra of silica-bonded propyl-S-sulfonic acid.
pH analysis of the SBSSA
In conclusion, heterogeneous conditions, green sol-
vent, easy and clean work-up, high yields and recovery
of the catalyst makes this method practical for the syn-
thesis of benzimidazole derivatives.
To an aqueous suspension of 0.1 g SBSSA, NaOH
－
1
(1.8 mL, 0.1 mol•L ) was added. This is equal to a
loading of 1.8 mmol SO3H/g. So, all of the SH func-
tional groups in 3-mercaptopropylsilica were sulfonated.
According to previous reports,[35] the loading of
3-mercaptopropylsilica is 0.33 mmol/g.
Experimental
General
General procedure for the synthesis of 2-aryl-1-
arylmethyl-1H-1,3-benzimidazoles derivatives
Chemicals were purchased from Fluka, Merck and
Aldrich Chemical Companies. All the products were
To a mixture of o-phenylenediamine (1 mmol), aro-
matic aldehyde (2 mmol) in water (5 mL), SBSSA (0.05
g) were added and the reaction mixture was stirred in an
oil bath at 80 ℃ for the appropriate time (see Table 2).
The progress of the reaction was monitored by TLC.
After completion of the reaction, the mixture was fil-
tered and the precipitates were solved in hot ethanol (10
mL×3) and filtered to afford the desired product. Fi-
nally the crude product was recrystallized from wa-
ter-ethanol (V∶V＝1∶1). The recovered catalyst was
dried and reused for subsequent runs.
1
characterized by comparison of their IR, H NMR and
13C NMR spectroscopic data and their melting points
with the reported values.[11-20] Silica-bonded propyl-
S-sulfonic acid (SBSSA) was prepared according to
previously reported procedure.[22,23]
Catalyst perparation
To a magnetically stirred mixture of 3-mercapto-
propylsilica (5 g) in tert-buylmethyl ether (20 mL),
chlorosulfonic acid (1.0 g, 9 mmol) was added dropwise
at 0 ℃ during 2 h. After addition was complete, the
mixture was stirred for 2 h until HCl gas evolution was
stopped. Then, the mixture was filtered and washed with
methanol (30 mL) and dried at room temperature to ob-
tain silica-bonded propyl-S-sulfonic acid (SBSSA) as
cream powder (5.22 g). Sulfur content of the samples by
conventional elemental analysis was 16.12%. The
FT-IR spectrum of the catalyst is shown in Figure 2.
The catalyst is a solid, and the solid state IR spectrum
was recorded using the KBr disk technique. For silica
(SiO2), the major peaks are broad anti symmetric Si—
1-Benzyl-2-phenylbenzimidazole (3a): m.p. 130—
1
132 ℃ (Lit.[11] 129—130 ℃); H NMR (CDCl3, 400
MHz) δ: 5.37 (s, 2H), 7.02 (dd, J1＝8.1 Hz, J2＝1.5 Hz,
2H), 7.11—7.17 (m, 2H), 7.21—7.27 (m, 4H), 7.33—
7.39 (m, 3H), 7.59—7.62 (m, 2H), 7.79 (dd, J1＝8.7 Hz,
J2＝1.0 Hz, 1H); 13C NMR (CDCl3, 100 MHz) δ: 48.42,
110.59, 120.02, 122.73, 123.09, 126.01, 127.82, 128.80,
129.11, 129.30, 129.97, 130.09, 136.09, 136.42, 143.20,
154.22.
1-(4-Methoxybenzyl)-2-(4-methoxyphenyl)-1H-ben-
zimidazole (3b): m.p. 129—131 ℃ (Lit.[19] 129—130
℃); 1H NMR (CDCl3, 500 MHz) δ: 3.81 (s, 3H), 3.88 (s,
3H), 5.41 (s, 2H), 6.89 (dt, J1＝6.9 Hz, J2＝2.4 Hz, 2H),
7.01 (dt, J1＝8.8 Hz, J2＝2.4 Hz, 2H), 7.06 (d, J＝8.7
O—Si stretching from 1200 to 1000 cm－ and symmet-
ric Si—O—Si stretching near 802 cm , and bending
1
－
1
－
1
modes lie near 470 cm . For sulfonic acid functional
Chin. J. Chem. 2012, 30, 517—521
© 2012 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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519

Ghaem Ahmadi-Ana, Baghernejad & Niknam
FULL PAPER
Hz, 2H), 7.24—7.26 (m, 2H), 7.31—7.34 (m, 1H), 7.68
(dt, J1＝8.8 Hz, J2＝2.4 Hz, 2H), 7.88 (d, J＝8.0 Hz,
1H); 13C NMR (CDCl3, 125 MHz) δ: 48.33, 55.71,
55.80, 110.85, 114.63, 114.86, 120.09, 122.75, 123.00,
123.20, 127.64, 128.86, 131.15, 136.46, 154.47, 159.56,
161.37.
1-(2-Methoxybenzyl)-2-(2-methoxyphenyl)-1H-ben-
zimidazole (3c): m.p. 150—151 ℃ (Lit.[19] 149—152
℃); 1H NMR (CDCl3, 500 MHz) δ: 3.59 (s, 3H), 3.77 (s,
3H), 5.24 (s, 2H), 6.70 (d, J＝6.8 Hz, 1H), 6.76 (t, J＝
7.4 Hz, 1H), 6.83 (d, J＝8.2 Hz, 1H), 6.96 (d, J＝8.3 Hz,
1H), 7.05 (t, J＝7.5 Hz, 1H), 7.17—7.28 (m, 4H), 7.45
(dt, J1＝7.9 Hz, J2＝1.6 Hz, 1H), 7.54 (dd, J1＝7.5 Hz,
J2＝1.6 Hz, 1H), 7.86 (d, J＝8.0 Hz, 1H); 13C NMR
(CDCl3, 125 MHz) δ: 44.07, 55.59, 55.63, 110.40,
111.25, 111.31, 120.07, 120.83, 121.25, 122.56, 123.03,
124.83, 127.26, 128.23, 128.89, 131.98, 132.82, 156.96,
158.04.
1-(4-Fluorobenzyl)-2-(4-fluorophenyl)-1H-ben-
1
zimidazole (3h):[13] m.p. 82—84 ℃; H NMR (CDCl3,
500 MHz) δ: 5.41 (s, 2H), 7.00—7.06 (m, 4H), 7.16 (dt,
J1＝7.6 Hz, J2＝2.0 Hz, 2H), 7.22 (d, J＝8.0 Hz, 1H),
7.28 (dt, J1＝7.6 Hz, J2＝0.9 Hz, 1H), 7.34 (dt, J1＝7.6
Hz, J2＝0.9 Hz, 1H), 7.63—7.67 (m, 2H), 7.88 (d, J＝
8.0 Hz, 1H); 13C NMR (CDCl3, 125 MHz) δ: 48.21,
110.83, 116.45, 116.52, 116.69, 120.31, 123.61, 123.95,
128.02, 128.08, 131.69, 131.75, 132.15, 136.10, 154.00.
1-(4-Bromobenzyl)-2-(4-bromophenyl)-1H-ben-
zimidazole (3i):[13] m.p. 154—156 ℃; 1H NMR (CDCl3,
500 MHz) δ: 5.38 (s, 2H), 6.95 (d, J＝8.36 Hz, 2H),
7.20 (d, J＝8.0 Hz, 1H), 7.28 (t, J＝7.8 Hz, 1H), 7.34 (t,
J＝7.6 Hz, 1H), 7.47 (d, J＝8.4 Hz, 2H), 7.52 (d, J＝
8.1 Hz, 2H), 7.60 (d, J＝8.4 Hz, 2H), 7.87 (d, J＝8.0 Hz,
1H); 13C NMR (CDCl3, 125 MHz) δ: 48.31, 110.77,
120.55, 123.61, 124.03, 127.99, 131.08, 132.58, 132.79,
135.50, 152.50.
1-(4-Methylbenzyl)-2-(4-methylphenyl)-1H-ben-
zimidazole (3d): m.p. 128—130 ℃ (Lit.[19] 128—130
℃); 1H NMR (CDCl3, 500 MHz) δ: 2.33 (s, 3H), 2.40 (s,
3H), 5.41 (s, 2H), 6.99 (d, J＝7.8 Hz, 2H), 7.13 (d, J＝
7.8 Hz, 2H), 7.19—7.26 (m, 4H), 7.30 (t, J＝7.3 Hz,
1H), 7.59 (d, J＝7.8 Hz, 2H), 7.86 (d, J＝8.0 Hz, 1H);
13C NMR (CDCl3, 125 MHz) δ: 21.50, 21.85, 48.65,
110.96, 120.18, 123.06, 123.33, 126.32, 127.44, 129.61,
129.88, 130.13, 133.81, 136.45, 137.90, 140.55, 154.68.
1-(2-Methylbenzyl)-2-(2-methylphenyl)-1H-ben-
4-{[2-(4-Cyanophenyl)-1H-benzimidazol-1-yl]meth-
yl}benzonitrile (3j): m.p. 190—192 ℃ (Lit.[20] 190—
1
191 ℃); H NMR (CDCl3, 400 MHz) δ: 5.44 (s, 2H),
7.12 (t, J＝7.5 Hz, 3H), 7.25 (dt, J1＝7.5 Hz, J2＝1.0
Hz, 1H), 7.32 (dt, J1＝7.5 Hz, J2＝1.3 Hz, 1H), 7.59 (d,
J＝8.3 Hz, 2H), 7.67—7.69 (m, 4H), 7.83 (d, J＝8.1 Hz,
1H); 13C NMR (CDCl3, 100 MHz) δ: 48.16, 110.24,
112.42, 113.89, 118.07, 120.76, 123.71, 124.37, 126.59,
129.28, 129.69, 132.71, 133.19, 134.09, 135.93, 141.07,
143.17, 151.72.
1
zimidazole (3e): m.p. 139—140 ℃; H NMR (CDCl3,
2-(2-Furyl)-1-(2-furylmethyl)-1H-benzimidazole
1
500 MHz) δ: 2.15 (s, 3H), 2.24 (s, 3H), 5.18 (s, 2H),
6.64 (d, J＝7.6 Hz, 1H), 7.01—7.03 (m, 1H), 7.13—
7.35 (m, 10H), 7.88 (d, J＝8.0 Hz, 1H); 13C NMR
(CDCl3, 125 MHz) δ: 19.48, 20.24, 46.21, 110.98,
120.41, 122.86, 123.32, 126.07, 126.46, 126.80, 127.98,
130.09, 130.30, 130.81, 131.02, 134.41, 135.26, 135.42,
138.80, 154.27; IR (KBr) ν: 3050, 2950, 1600, 1475,
(3k): m.p. 92—94 ℃ (Lit.[19] 92—95 ℃); H NMR
(CDCl3, 500 MHz) δ: 5.66 (s, 2H), 6.26 (dd, J1＝16.7
Hz, J2＝1.7 Hz, 2H), 6.62—6.63 (m, 1H), 7.30—7.33
(m, 4H), 7.50—7.52 (m, 1H), 7.65—7.67 (m, 1H),
7.79—7.81 (m, 1H); 13C NMR (CDCl3, 125 MHz) δ:
42.19, 108.92, 110.51, 110.98, 112.62, 114.03, 120.00,
123.62, 123.88, 143.16, 144.63, 149.82.
1,4-Diphenylene-4,4'-(methylene)bis(3-methyl-1-
phenyl-1H-pyrazol-5-ol) (4): m.p. 213—216 ˚C; 1H
NMR (500 MHz, DMSO-d6) δ: 2.29 (s, 12H), 5.05 (s,
2H), 7.17 (s, 4H), 7.22 (t, J＝7.1 Hz, 4H), 7.41 (t, J＝
7.8 Hz, 8H), 7.69 (d, J＝7.9 Hz, 8H), 12.41 (brs, 2H)
14.11 (s, 2H); 13C NMR (125 MHz, DMSO-d6) δ: 12.51,
33.69, 121.50, 127.84, 129.72, 140.93, 147.07, 155.01;
IR (KBr) ν: 3410, 3020, 1590, 1490, 1410, 1350, 1290,
1120, 1020, 850, 745, 690 cm－ 1. Anal. calcd for
C48H42N8O4: C 72.52, H 5.32, N 14.09; found C 72.35,
H 5.29, N 13.85.
－
1
1450, 1390, 1350, 1280, 1160, 840, 685 cm . Anal.
calcd for C22H20N2: C 84.58, H 6.45, N 8.97; found C
84.41, H 6.42, N 8.82.
1-(4-Chlorobenzyl)-2-(4-chlorophenyl)-1H-ben-
zimidazole (3f): m.p. 135—137 ℃ (Lit.[19] 136—138
1
℃); H NMR (CDCl3, 500 MHz) δ: 5.39 (s, 2H), 7.01
(d, J＝8.5 Hz, 2H), 7.19 (d, J＝8.0 Hz, 1H), 7.25—7.35
(m, 4H), 7.43 (dd, J1＝6.8 Hz, J2＝1.7 Hz, 2H), 7.59
(dd, J1＝6.8 Hz, J2＝1.7 Hz, 2H), 7.86 (d, J＝8.0 Hz,
1H); 13C NMR (CDCl3, 125 MHz) δ: 48.23, 110.74,
120.58, 123.52, 123.94, 127.69, 128.73, 129.59, 129.82,
130.87, 134.32, 135.04, 136.33, 136.83, 143.42, 153.27.
1-(2-Chlorobenzyl)-2-(2-chlorophenyl)-1H-ben-
zimidazole (3g): m.p. 161—163 ℃ (Lit.[11] 160—162
Acknowledgment
1
This work was financially supported by the Research
Council of Persian Gulf University, Bushehr, Iran. And
Manchester University is gratefully acknowledged for
running FT-IR, and NMR.
℃); H NMR (CDCl3, 500 MHz) δ: 5.36 (s, 2H), 6.64
(d, J＝6.9 Hz, 1H), 7.07 (dt, J1＝7.1 Hz, J2＝0.5 Hz,
1H), 7.14—7.22 (m, 2H), 7.25—7.34 (m, 4H), 7.42—
7.45 (m, 2H), 7.51 (d, J＝8.0 Hz, 1H), 7.89 (d, J＝8.0
Hz, 1H); 13C NMR (CDCl3, 125 MHz) δ: 46.16, 110.98,
120.76, 123.19, 123.85, 127.40, 127.55, 128.20, 129.43,
130.03, 130.35, 131.88, 132.56, 132.82, 133.68, 134.79,
135.21, 143.37, 151.90.
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Synthesis of 2-Aryl-1-arylmethyl-1H-1,3-benzimidazole Derivatives
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