4,5-Imidazoledicarboxylic acid immobilized on Fe3O4 magnetic nanoparticles: Preparation, characterization, and application as a recyclable and efficient nanocatalyst in the sonochemical condensation reaction

Article abstract of DOI:10.1002/jccs.201700455

A green synthesis of benzimidazole derivatives using recyclable magnetic 4,5-imidazoledicarboxylic is described. The magnetic 4,5-imidazoledicarboxylic (Fe₃O₄@ImDCA) nanocatalyst was characterized completely by infrared spectroscopy

Full text of DOI:10.1002/jccs.201700455

Received: 12 December 2017
DOI: 10.1002/jccs.201700455
Revised: 11 January 2018
Accepted: 12 January 2018
A R T I C L E
4,5-Imidazoledicarboxylic acid immobilized on Fe3O4 magnetic
nanoparticles: Preparation, characterization, and application as
a recyclable and efficient nanocatalyst in the sonochemical
condensation reaction
Mohadesseh Shah Hosseini | Hossein Ghafuri | Hamid Reza Esmaili Zand
Catalysts and Organic Synthesis Research
A green synthesis of benzimidazole derivatives using recyclable magnetic 4,5-
Laboratory, Department of Chemistry, Iran
University of Science and Technology,
imidazoledicarboxylic is described. The magnetic 4,5-imidazoledicarboxylic
(Fe3O4@ImDCA) nanocatalyst was characterized completely by infrared spectros-
copy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), scanning electron
Tehran, Iran
Correspondence
Hossein Ghafuri, Catalysts and Organic Synthesis
microscopy (SEM), and powder X-ray diffraction (XRD), and benzimidazoles
Research Laboratory, Department of Chemistry,
1
Iran University of Science and Technology,
P.O. Box 16846-13114, Tehran, Iran.
Email: ghafuri@iust.ac.ir
were characterized by their melting points, FT-IR, and H NMR. The current
approach provides a number of advantages in terms of high yields, low reaction
times, the use of green media, and easy work-up.
KEYWORDS
benzimidazoles, Fe3O4@ImDCA, recoverable nanocatalyst, sonochemical
synthesis
more efficient ones.[4–12] Only a few types of solid carbox-
ylic acid nanocatalysts have been reported because of their
1
| INTRODUCTION
1H-Imidazole is a highly polar compound and plays a sig-
nificant role in organic synthesis. It can be converted to a
highly acidic compound by changing to imidazolecarboxylic
acid.[1] This kind of imidazole has more catalytic activity
than 1H-imidazole as an acidic catalyst because of its
carboxylic acid groups. In addition of this, owing to the
existence of the carboxylic acid group in its structure, the
H-bond in the C2 position of this compound has more
acidic properties.
In recent years, many kinds of inorganic nanomaterials
and solid catalysts have been widely reported.[2] Of the two
different approaches for the synthesis of solid catalysts, one
focuses on the possibility of modification under operating
low stability. Strong interaction is essential to improve the
stability of these kinds of solid nanocatalysts, which limits
the accessible solid supports. In 4,5-imidazoledicarboxylic
acid (ImDCA),[13,14] the carboxylic groups are placed at the
4,5-positions of imidazole, which makes it possible to attach
the imidazole to a solid surface because of the closeness of
its carboxylic groups to each other.
Magnetic nanocatalysts are known to be efficient solid
catalyst supports because of their facile recyclability by an
external magnetic field. Among the various techniques, the
sonochemical approach is an effective method to enhance
the catalytic ability of magnetic nanoparticles. Ultrasound
leads to the acceleration of reactions in both homogeneous
and heterogeneous catalytic systems and promotes the reac-
tion with milder reaction conditions.[15–17] Two important
factors should be considered for ultrasound-induced reac-
tion: the acoustic field and the bubble field. The existence
conditions, and the other focuses on
a reductionist
approach.[3] In the latter approach, which is mostly used in
surface rearrangement, the information gained is used to
explain the behavior of the premodified catalysts to produce
© 2018 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J. Chin. Chem. Soc. 2018;1–6.
http://www.jccs.wiley-vch.de
1

2
SHAH HOSSEINI ET AL.
of a strong acoustic field results in microbubbles due to cav-
itation. The collapse of microbubbles transfers energy from
the acoustic wave to the inner space of the bubbles. This
energy substantially increases chemical processing. The
interaction between the acoustic waves and the chemical
system is the key principle in sonochemical reactions.[18–20]
There are some restrictions in the synthesis of solid cata-
lysts, so emerging new strategies for synthesizing solid cata-
lysts and using a wider category of such catalysts pose
significant challenges. The present study uses the reduction-
ist approach for the synthesis a heterogeneous acidic nano-
catalyst, and examines the use of the imidazole structure by
adopting the characteristics of nanomaterials. A wide range
of high-performance catalysts can be formed by imidazoles
with enantioselectivity, regioselectivity, and shape selectiv-
ity, and having the dual advantages of large surface areas
and recoverability.
Benzimidazoles, a large chemical family of imidazoles,
have many applications in medicinal and pharmaceutical
chemistry. Owing to their special structures, benzimidazole-
containing drugs display a wide range of biological activi-
ties (Figure 1). Several benzimidazole-based drugs with
great therapeutic potential have been used to treat numerous
types of diseases. Owing to their pharmaceutical value, the
search for and development of synthesis of benizmidazoles
is an attractive subject in pharmaceutical and medicinal
chemistry.[21]
Here, in order to use the mild acidic H in the C2 posi-
tion, the two hydroxyl groups of COOH, and also NH in
imidazole’s skeleton, ImDCA was synthesized. This catalyst
has four key active sites, which leads to high catalytic activ-
ity in organic synthesis. By various linkers like (3-chloro-
propyl)trimethoxysilane and dibromopropane, the NH group
of imidazole involves covalent bonding and cannot play a
catalytic role, but in ImDCA , by electrostatic bonding from
carboxylic acids, both N atoms of imidazole are free, which
can therefore participate in the reaction as an active part of
the catalyst. Because of the huge catalytic ability of mag-
netic nanoparticles,[22–25] we designed a nanomagnetic
imidazole with much larger surface area than normal homo-
geneous imidazole to take advantage of the properties of
Fe3O4 and ImDCA. As far as we know, no magnetic
ImDCA nanocatalysts have been reported so far. The cata-
lytic activity of the Fe3O4@ImDCA, because of the acidic
character of Fe3O4 and the carboxylic acids of imidazole, is
higher than that of normal imidazoles. To improve our pre-
vious report on benzimidazole synthesis,[26] taking advan-
tage of the remarkable imidazolium-based catalyst,
magnetic catalyst, and sonication condition in organic syn-
thesis, we describe for the first time the successful synthesis
of Fe3O4@ImDCA and their application to the sonochem-
ical synthesis of benzimidazoles (Scheme 1).
2
| RESULTS AND DISCUSSION
Because of noteworthy advantages of imidazolium-based
catalysts, Fe3O4@ImDCA as a magnetic nanocatalyst was
synthesized successfully for the first time. To synthesize
ImDCA, selective dichromate oxidation of imidazole was
repeated to realize the optimum conditions and, after defi-
nite modifications of the oxidation reactions, ImDCA was
isolated. Because of the solubilization of the imidazole dur-
ing the oxidation of imidazole and also of the exothermic
reaction, the required concentration of H2SO4 and tempera-
ture control were critical.
Four states with four different amounts of ImDCA were
examined to synthesize Fe3O4@ImDCA: Condition 1 (2.3 g
FeCl3.6H2O, 1.1 g FeCl2.4H2O, and 1 mmol IMDCA);
Condition 2 (2.3 g FeCl3.6H2O, 1.1 g FeCl2.4H2O, and
3 mmol IMDCA); Condition 3 (2.3 g FeCl3.6H2O, 1.1 g
FeCl2.4H2O, and 7 mmol IMDCA); and condition 4 (2.3 g
FeCl3.6H2O, 1.1 g FeCl2.4H2O, and 10 mmol IMDCA). It
was found that best mixture of Fe3O4 and ImDCA for syn-
thesizing magnetic ImDCA was condition 2 using 2.3 g
FeCl3.6H2O, 1.1 g FeCl2.4H2O, and 0.45 g ImDCA
To obtain a heterogeneous magnetic nanocatalyst, both
Fe3O4@ImDCA and Fe3O4@SiO2@ImDCA were synthe-
sized and compared. Fe3O4@SiO2@ImDCA was found to
be unsuitable for our purpose. Contrary to the general
belief, it had very low thermal resistance and was destroyed
after a slight temperature increase. On the other hand,
Fe3O4@ImDCA gave very good results.
2.1 | Characterization of the catalyst
After the modification and synthesis of Fe3O4@ImDCA,
the synthesized nanocatalyst was thoroughly characterized
by Fourier transform infrared spectroscopy (FT-IR), scan-
ning electron microscopy (SEM), energy dispersive X-ray
spectroscopy (EDX), and X-ray diffraction (XRD).
Functionalization of the nanoparticles can be proved by
FT-IR. The FT-IR spectra under three different conditions
of synthesis of magnetic 1-H-imidazole-4,5-dicarboxylic
acid are shown in Figure 1. As can be seen from this figure,
there are no peaks suggesting the attachment of imidazole
FIGURE 1 Some bioactive benzimidazoles

SHAH HOSSEINI ET AL.
3
H
HN
O
N
HO
OH
O
OH
OH
HO
HO
OH
OH
H
N
H
N
N
O
O
O
O
O
O
FeCl2. 4H2O + FeCl 3. 6H2O+ NH3
H
H
Fe3O4
H
N
N
H
N
O
N
O
HO
OH
NH
H
SCHEME 1 Synthesis of Fe3O4@ImDCA
to Fe3O4 under Conditions 1 and 4; only Condition 2 shows
the correct peaks. Under Condition 2, the FT-IR spectra
show peaks in the range 3600–2500 cm−1 attributed to the
acidic and alcoholic groups. The stretching peaks of C–H
appear at 3091, 2916, and 2850 cm−1, and the stretching
peaks of C–N appear at 1527 cm−1 and the stretching peaks
of C–C at 1350 cm −1. The peaks at 1097 and 1049 cm−1
are related to the C−O bond of carboxylic acid and Fe3O4
(Figure 2)
FIGURE 3 XRD pattern of Fe3O4@ImDCA
FIGURE 4 EDS results for Fe3O4@ImDCA
The XRD pattern of Fe3O4@ImDCA is shown in
Figure 3. The positions and intensities of the peaks are in
agreement with the standard XRD pattern of Fe3O4 (JCPDS
Card No. 19-0629). The XRD patterns of the particles show
six characteristic peaks including those at 2θ = 22.98ꢀ,
30.25ꢀ, 32.67ꢀ, 35.76ꢀ, 57.27ꢀ, and 62.91ꢀ, which shows
that the functionalization process did not change the phase
of the resulting nanoparticles.
The EDS results for Fe3O4@ImDCA (Figure 4) show
the existence of oxygen and Fe in FE3O4 as well as nitrogen
and carbon due to the presence of imidazole that was
attached to Fe3O4. As can be seen, atomic composition of
the elements is 6.45% C, 2.83% N, 63.20% O, and
27.51% Fe.
The SEM image confirmed that Fe3O4@ImDCA was
made up of identical nanometer-sized particles. The imidaz-
ole particles are uniformly distributed on the surface of
Fe3O4. As illustrated in Figure 5, the particle size was stud-
ied by SEM and the identification of Fe3O4@ImDCA was
based on the analysis of the SEM images. It was confirmed
that the catalyst was made up of nanometer-sized particles
of less than 40 nm. Figure 5 shows that the Fe3O4@ImDCA
nanoparticles have a core–shell structure and spherical
morphology.
2.2 | Catalytic applications of Fe3O4@ImDCA in a
condensation reaction
To study the various conditions for the synthesis of benz-
imidazoles, in the no-catalyst condition, the product was
formed in 18 h with 10% yield. But without ultrasonication
and in the presence of Fe3O4@ImDCA, the reaction was
completed in 1 h with 68% yield. To study the various con-
ditions for the synthesis of benzimidazoles by sonication, in
no-catalyst condition reaction was completed in 210 min
with 23% yield. The reaction in the presence of
FIGURE 2 FT-IR spectra of Fe3O4@ImDCA under Conditions
FIGURE 5 FE-SEM image of Fe3O4@ImDCA
1, 2, and 4

4
SHAH HOSSEINI ET AL.
TABLE 1 Optimization of benzimidazole synthesis
TABLE 3 Variation of o-phenylenediamines and aldehydes in
benzimidazole synthesisa
Catalyst
(wt %)
Yield (%)b
90
Entry
Catalyst
—
Time (h)
Yield (%)a
Entry
1
R1
H
R2
Ph[3a]
Time (min)
1
2
3
4
—
18
6
10
26
50
68
5
[3b]
[3c]
Fe3O4
10
2
H
4-NO2C6H4
5
86
Imidazole
10
4
3
H
3-NO2C6H4
5
97
[3d]
Fe3O4@dicarboxylic
acid imidazole
10
1
4
H
4-ClC6H4
8
89
[3e]
5
H
4-OHC6H4
7
95
Entry
Solvent
—
Temp. (ꢀC)
Time (min)
Yield (%)b
[3f]
6
H
4-OCH3C6H4
10
5
70
5
6
7
8
—
10
10
10
210
240
70
23
37
85
95
[3g]
7
H
4-BrC6H4
76
Fe3O4
Imidazole
[3h]
8
H
2,4-Cl-C6H3
6
90
[3i]
9
H
2,6-Cl-C6H3
10
8
87
Fe3O4@dicarboxylic
acid imidazole
5
[3j]
10
11
12
13
14
15
16
17
18
19
20
H
4-CNC6H4
68
[3k]
H
4-N(CH3)2C6H4
10
8
55
Entry
9
Solvent
EtOH
Temp. (ꢀC)
Time (min)
Yield (%)
[3l]
CH3
H
2,6-Cl-C6H3
93
25
5
95
[3m]
2-Cl-C6H4
8
73
10
EtOH
40
5
85
[3n]
H
2,4-OH-C6H3
8
68
11
EtOH
60
5
85
[3o]
CH3
CH3
CH3
CH3
NO2
NO2
2-Cl-C6H4
6
56
Entry
12
Solvent
EtOH
Temp.(ꢀC)
Time (min)
Yield (%)
[3p]
2,4-Cl-C6H3
6
60
25
25
25
25
25
25
5
5
5
5
5
5
95
—
78
40
—
—
[3q]
4-Cl-C6H4
5
86
13
H2O
Thiophene[3r]
10
12
10
50
14
CH2Cl2
CHCl3
CH3CN
Solvent free
[3s]
3-NO2C6H4
53
15
[3t]
4-NO2C6H4
58
16
a
17
Room temperature, by ultrasonic sonication, EtOH.
a
All reactions by stirring at room temperature; yield of isolated product after
purification.
b
character of NO2. In addition, the 4-N(CH3)2C6H4 substituent,
due to its electron-donating character, took a longer reaction
time. As shown in Table 3, 16 kinds of benzimidazoles were
obtained and their syntheses were confirmed by their precise
melting points. All of them had reasonable reaction times and
good to high yields.
The recyclability of this catalyst was also examined in
this reaction. It was found that in five reaction runs, the
recovery of the catalyst could be achieved successfully
(Table 4).
All reactions by sonication at room temperature; yield of isolated product after
purification.
FE3O4@ImDCA in EtOH and at room temperature was
completed in 5 min with 95% yield. In another study, we
found that by changing the amount of catalyst from 10 to
50 wt%, there was no change in the product yield (Table 1).
Also, this magnetic nanocatalyst compared to other cata-
lytic systems showed greater catalytic activity (Table 2).
Benzimidazole synthesis was studied by varying
o-phenylenediamines and aldehydes. The reactions were car-
ried out under sonication at room temperature and the product
yields were between 56 and 95%. As can be seen, 2,4-Cl-
C6H3 and 2,4-OH-C6H3 substituents, because of their hinder-
ing character, gave lower yields and took longer reaction
times. Also, the NO2 substituent of aniline gave lower yield
and took a longer time due to the electron-withdrawing
2.3 | Mechanism of benzimidazole synthesis
According to the obtained results, we propose a mechanism
for this reaction. First, the oxygen group in the aldehyde is
activated by free NH, CH, and OH groups of COOH, and
one NH2 of o-phenylenediamine was added to it. After acti-
vation of imine with the catalyst and condensation of the
second NH2 group, an intermediate was formed. Oxidation
of the intermediate took place in air, and the final benzimid-
azole was formed. Both the H atom in C-2, OH groups in
COOH, and also NH play a key role as active catalytic parts
in the Fe3O4@4,5- ImDCA nanocatalyst (Scheme 2)
TABLE 2 Optimization of the benzimidazole synthesis with different
catalytic systems
Entry
Catalyst
Time (min)
Temp.
Reflux
100
Solvent
EtOH
Yield
68[27]
69[28]
91[29]
74[27]
78[30]
95
1
2
3
4
5
6
Nano-ZnO
95
300
45
90
12
5
Zeolite
Dioxane
EtOH
Scolecite
70
Nano-alumina
Fe3O4/Collagene
Fe3o4/imidazolea
Reflux
r.t.
EtOH
TABLE 4 Reusability of the Fe3O4@ImDCA nanocatalyst
EtOH
Reaction cycle
Yield
First
Second
Third
Fourth
Fifth
r.t.
EtOH
96
95
95
93
92
a
This reaction was carried out under sonication.

SHAH HOSSEINI ET AL.
5
3
|
EXPERIMENTAL
compound was dissolved in 45 mL 0.1 M NaOH, and
45 mL 0.1 M HCl was added to it dropwise. The synthe-
sized ImDCA was filtrated and isolated. The obtained bright
white powder was dried for 24 h at 60 ꢀC in a vacuum oven
(m.p. 283–285 ꢀC).
3.1 | Materials and methods
All solvents and chemicals were of reagent grade and pur-
chased from Merck and Aldrich (Darmstadt, Germany). The
ultrasonic reactions were carried out at room temperature in
an Elmasonic (Singen, Germany) S 60 H (220–240 V) soni-
cator with a frequency of 37 kHz and an effective ultrasonic
power of 150 W and total power of 550 W. FT-IR spectra
were recorded using a Shimadzu IR-470 spectrometer
(Shimadzu Corp., Kyoto, Japan) in the 400–4000 cm–1
region. NMR spectra were recorded using a Bruker DRX-
500 Avance spectrometer (Bruker, Billerica, Massachusetts,
USA). Field-emission scanning electron microscopy (FE-
SEM) images were recorded using a Sigma Zeiss micro-
scope (Zeiss, München, Germany). Energy dispersive X-ray
(EDX Korea) spectra were recorded on a Numerix DXP-
X10P instrument. X-ray diffraction (XRD) measurements
were carried out on a JEOL JDX-8030 diffractometer
(Tokyo, Japan), and melting points were checked by an
Electrothermal 9100 apparatus (Staffordshire, ST15
OSA, UK).
3.3 | General procedure for the synthesis of magnetic
ImDCA
In situ synthesis of Fe3O4 and its combination with ImDCA
was used for the synthesis of magnetic ImDCA. Particu-
larly, iron(III) chloride hexahydrate (2.3 g), iron(II) chloride
tetrahydrate (1.1 G) and imidazole-4,5-dicarboxylic acid
(0.45 g, 3 mmol) were added to 100 mL deionized water
and stirred for 10 min ꢀat room temperature. Then this mix-
ture was heated to 90 C under N2 atmosphere and 10 mL
of 25% aqueous ammonia was added to the reaction drop-
wise and stirred for 1 h. After that, the mixture was cooled
to room temperature and the dark black precipitate was col-
lected by an external magnet and washed with EtOH and
distilled water.
We also examined other amounts of ImDCA (Condition
1: 1 mmol of IMDCA; Condition 2: 3 mmol of IMDCA;
Condition 3: 7 mmol of IMDCA; and Condition 4: 10 mmol
of IMDCA) and found that the best condition for synthesiz-
ing magnetic IMDCA was Condition 2 (i.e., 3 mmol of
IMDCA).
3.2 | General procedure for the synthesis of ImDCA
1-H-Imidazole-4,5-dicarboxylic acid was synthesized as
reported in the literature.[21] Specifically, 70 mL of H2SO4
was added dropwise to a flask containing 5.0 g of imidazole
and 60 mL of H2O. Then, 37 g of K2Cr2O7 was added
slowly to this mixture to obtain a green solution. The mix-
ture was stirred at room temperature. The precipitated
3.4 | General procedure for the synthesis of
benzimidazoles
The efficiency of magnetic ImDCA as a catalyst was exam-
ined by the synthesis of benzimidazole derivatives. For this,
1 mmol of o-phenylenediamine, 1.2 mmol of 3-nitrobenzal-
dehyde, and 0.015 g (10 wt%) of Fe3O4@ImDCA were
added to 4 mL of ethanol. The mixture was placed in a
sonicator at room temperature and sonicated until the reac-
tion was complete. Completion of the reaction was followed
by TLC, and the magnetic catalyst was separated by an
external magnet. After separation of the magnetic catalyst,
R1
Fe3O4
O
N
O
O
N
N
A
i
r
H
O
o
x
N
H
i
R2
d
a
H
t
i
o
n
H
R
O
ꢀ
the solution of the reaction was heated and cooled to 0 C
H
to precipitate. The final product was filtered and washed by
ethanol.
Fe3O4
O
O
O
H
O
Fe3O4
N
H
N
O
H
O
N
R1
3.5 | Selected spectral data
H
O
N
H
3.5.1
| Compound 3b
N
NH2
O
H
H
M.p. 302–304 ꢀC; 1H NMR (500 MHz, DMSO-d6)
d = 7.35 (2H, d), 7.79–7.60 (2H, s), 8.50 (4H, m), 13.39
(1H, broad, NH); 13C NMR (125 MHz, DMSO-d6): d
112 (C=C), 119, 122, 123, 128, 128, 129, 129, 129,
131, 135, 135, 144 (Ar, 12 carbons); IR (KBr, cm–1):
3028–2445, 1602, 1514, 1434, 1340, 1105.
H
R2
O
H
NH2
NH2
R
SCHEME 2 Proposed mechanism for benzimidazole synthesis

6
SHAH HOSSEINI ET AL.
[3] J. M. Thomas, Angew. Chem. Int. Ed. 1999, 38, 3588.
[4] G. P. Winter, A. R. Fersht, A. J. Wilkinson, M. Zöller, M. Smith, Nature
1982, 299, 756.
[5] A. R. Fersht, J. P. Shi, A. J. Wilkinson, D. M. Blow, P. Carter,
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[7] V. M. Cornish, D. Mendel, P. G. Schultz, Angew. Chem. Int. Ed. Engl.
1995, 34, 621.
3.5.2
| Compound 3f
M.p. 177–178 ꢀC; 1H NMR (500 MHz, DMSO-d6)
d = 3.44 (3H, s, OMe), 7.13–7.18 (1H, m), 7.44–8.4 (5H,
m), 8.67–8.65 (1H, m), 9.06 (1H, s), 13.21 (1H, broad,
NH); IR (KBr, cm–1): 3132–2547, 1612, 1502, 1440,
1251, 1178.
[8] P. G. Schultz, Angew. Chem. Int. Ed. 1999, 38, 37.
[9] F. H. Arnold, Acc. Chem. Res. 1998, 31, 125.
[10] M.s. A. Margulis, Ultrasonics 1992, 30, 152.
3.5.3
|
Compound 3l
1
ꢀ
M.p. 216–218 C; H NMR (500 MHz, CDCl3) d = 2.44
(s, 3H, Me), 7.46–7.07 (6H, m, Ar), 10.5–11.5 (1H, broad.
NH); 13C NMR (125 MHz, DMSO-d6): d 21, 124,
128, 130, 131, 133, 136, 146; IR (KBr, cm−1): 3049–2362,
1627, 1587, 1434, 1411, 1278, 783.
[11] R. M. Martin-Aranda, E. Ortega-Cantero, M. L. Rojas-Cervantes,
M. A. Vicente-Rodríguez, M. A. Banares-Munoz, Catal. Lett. 2002, 84, 201.
[12] V. Calvino-Casilda, A. J. Lopez-Peinado, R. M. Martın-Aranda,
S. Ferrera-Escudero, C. J. Duran-Valle, Carbon 2002, 42, 1363.
[13] Z. G. Gu, Y. T. Liu, X. J. Hong, Q. G. Zhan, Z. P. Zheng, S. R. Zheng,
W. S. Li, S. J. Hu, Y. P. Cai, Cryst. Growth Des. 2012, 12, 2178.
[14] R. T. Conley, J. J. Kane, S. Ghosh, Technical Report AFML-TR-71-219
1971.
[15] B. S. Singh, H. R. Lobo, D. V. Pinjari, K. J. Jarag, A. B. Pandit,
G. S. Shankarling, Ultrason. Sonochem. 2013, 20, 287.
[16] H. Zang, Y. Zhang, Y. Zang, B. W. Cheng, Ultrason. Sonochem. 2010,
17, 495.
[17] M. R. P. Heravi, Ultrason. Sonochem. 2009, 16, 361.
[18] V. Tiwari, A. Parvez, J. Meshram, Ultrason. Sonochem. 2011, 18, 911.
[19] T. J. Mason Ed., Chemistry with Ultrasound, Elsevier, London 1990.
[20] J. M. Lopez-Pestana, M. J. Avila-Rey, R. M. Martin-Aranda, Green Chem.
2002, 4, 682.
3.5.4
| Compound 3n
M.p. 280–282 ꢀC; 1H NMR (500 MHz, DMSO-d6)
d = 5.56 (1H, s, OH), 8.20–6.92 (8H, m, Ar), 12.9 (1H,
broad, NH); 13C NMR (125 MHz, DMSO-d6):
d
111, 114.7, 114.8, 119, 122.6, 122.9, 128, 129, 131, 135,
143, 159, 160; IR (KBr, cm-1): 3554–2318, 1623, 1546,
1494, 1425, 1330, 1263, 1157.
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16046.
4
| CONCLUSION
The synthesis of benzimidazole derivatives was performed
by using ultrasonication and Fe3O4@ ImDCA as a recover-
able and efficient nanocatalyst. Fe3O4@4,5-ImDCA as a
first magnetic 4,5-dicarboxylic acid imidazole was synthe-
sized successfully by an easy procedure and characterized
by FT-IR, EDX, FE-SEM, and XRD. The benzimidazole
synthesis was studied using various solvents, temperatures,
and catalysts. According to the results, our nanocatalyst
shows high activity, which can be studied in other reactions.
The current approach provides a number of advantages such
as high yields, low reaction times, and easy catalyst work-
up by an external magnetic field.
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SUPPORTING INFORMATION
ORCID
Additional Supporting Information may be found online in
the supporting information tab for this article.
Hossein Ghafuri
http://orcid.org/0000-0001-6778-985X
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