Magnetic nanoparticle supported ionic liquid as novel and effective heterogeneous catalyst for synthesis of substituted imidazoles under ultrasonic irradiation

Article abstract of DOI:10.1007/s00706-013-1015-6

The ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl)imidazolium chloride was immobilized on Fe₃O₄ nanoparticles and used as an efficient and reusable catalyst for the one-pot synthesis of 1,2,4,5-tetrasubstituted imidazoles at room

Full text of DOI:10.1007/s00706-013-1015-6

Monatsh Chem (2013) 144:1389–1396
DOI 10.1007/s00706-013-1015-6
ORIGINAL PAPER
Magnetic nanoparticle supported ionic liquid as novel
and effective heterogeneous catalyst for synthesis of substituted
imidazoles under ultrasonic irradiation
Javad Safari Zohre Zarnegar
•
Received: 18 August 2012 / Accepted: 10 May 2013 / Published online: 12 July 2013
Ó Springer-Verlag Wien 2013
Abstract The ionic liquid 1-methyl-3-(3-trimethoxysi-
lylpropyl)imidazolium chloride was immobilized on Fe O4
and environmentally friendly synthetic processes is now
possible by using ionic liquids [1, 2].
3
nanoparticles and used as an efficient and reusable catalyst
for the one-pot synthesis of 1,2,4,5-tetrasubstituted imida-
zoles at room temperature under ultrasonic irradiation. The
immobilized ionic liquid catalysts proved to be effective
and easily separated from the reaction media by applying
an external magnetic field. This procedure has many
obvious advantages compared to those reported in the
previous literatures, including avoiding the use of harmful
catalysts, reacting at room temperature, high yields, and
simplicity of the methodology.
In recent years, ionic liquids have attracted increasing
interest in the context of green synthesis [3–6]. Although
ionic liquids were initially introduced as alternative green
reaction media because of their unique chemical and
physical properties of nonvolatility, nonflammability,
thermal stability, and controlled miscibility [4–6], nowa-
days they have evolved beyond this, showing their
significant role in controlling reactions as catalysts [7, 8].
Though ionic liquids possessed such promising advan-
tages, their widespread practical application was still
hampered by several drawbacks: (1) high viscosity, which
resulted in only a minor part of ionic liquids taking part in
the catalyzed reaction, (2) homogeneous reaction, which
was difficult for product separation and catalyst recovery,
and (3) consequently high costs for the use of relatively
large amounts of ionic liquids [9, 10]. Therefore, in order
to solve these problems mentioned earlier, immobilized
ionic liquid catalyst combining the advantageous charac-
teristics of ionic liquids, inorganic acids, and solid acids
were proposed [11, 12].
Keywords Ionic liquid ꢀ Imidazole ꢀ 1-Methyl-3-
(
3-trimethoxysilylpropyl)imidazolium chloride ꢀ
Magnetic nanoparticles ꢀ Ultrasonic irradiation
Introduction
In the past decade, many investigations have been con-
ducted to try to develop greener chemical processes and
synthetic methods because of environmental consider-
ations. Several new methods and novel-designed materials
have been developed to make the chemical reactions
cleaner and more benign. For example, performing safer
On the other hand, magnetic nanoparticles (MNPs) have
received a great deal of attention because of their potential
biomedical applications in fields such as drug delivery
[13, 14], magnetic resonance imaging [15], biomolecular
sensors [16], bioseparation [17], and magneto-thermal
therapy [18]. Additionally, recent studies show that mag-
netic nanoparticles are excellent supports for catalysts [19].
The supported catalysts proved to be effective and easily
separated from the reaction media by applying an external
magnetic field.
J. Safari (&) ꢀ Z. Zarnegar
Laboratory of Organic Chemistry Research,
Department of Organic Chemistry, College of Chemistry,
University of Kashan, 87317-51167 Kashan, Iran
e-mail: Safari@kashanu.ac.ir
Imidazole derivatives are a very interesting class of
heterocyclic compounds because they have many phar-
macological properties and play important roles in
Z. Zarnegar
e-mail: zohrehzarnegar@yahoo.com
123

1
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J. Safari, Z. Zarnegar
biochemical processes [20, 21]. In recent years, the
synthesis of 2,4,5-trisubstituted imidazoles has been
performed by catalysts such as Yb(OPf)3 [22], ZrCl4
Results and discussion
Characterization of the prepared IL-MNPs
[
[
23], NiCl ꢀ6H O/Al O [24], silica sulfuric acid (SSA)
2
2
2 3
25], polymer-supported ZnCl [26], and phosphomo-
2
Scheme 2 shows the sequence of events in the functionali-
zation of MNPs with 1-methyl -3-(3-trimethoxysilylpropyl)-
1H-imidazol-3-ium chloride. In the first step, the magnetite
nanoparticles of 18–20 nm were prepared by coprecipita-
tion of iron(II) and iron(III) ions in basic solution at
85 °C using the method described by Massart [43]. Then,
1-methyl-3-(3-trimethoxysilylpropyl)imidazolium chloride
(IL) was prepared from the reaction of N-methylimidazole
with (3-chloropropyl)trimethoxysilane at 80 °C. In the
second step, the external surface of MNPs was coated with
IL to obtain IL-MNPs (Scheme 2).
lybdic acid [27]. Also some catalysts used for 1,2,4,5-
tetrasubstituted imidazoles including silica gel or zeolite
InCl ꢀ3H O [28], silica gel/NaHSO [29], HClO –SiO
3
2
4
4
2
[
[
30], heteropolyacids [31], BF ꢀSiO [32], FeCl ꢀ6H O
3
2
3
2
33], and alumina [34] are applied as common cata-
lysts for 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted
imidazoles.
Despite their potential utility, some of these methods are
not environmentally friendly and suffer from one or more
disadvantages, for example, hazardous reaction conditions,
complex workup and purification, strongly acidic condi-
tions, high temperature, use of toxic metal catalysts, poor
yields, occurrence of side reactions, and long reaction time.
Therefore, the development of clean, high-yielding, and
environmentally friendly approaches is still a challenge for
organic chemists in the synthesis of highly substituted
imidazoles [21].
Figure 1 shows the Fourier transform infrared (FTIR)
spectra of both the unfunctionalized and functionalized
magnetic nanoparticles. The Fe–O stretching vibration near
-
1
-1
580 cm , O–H stretching vibration near 3,432 cm , and
-
1
O–H deformed vibration near 1,625 cm were observed
for both as shown in Fig. 1a, b. The significant features
observed in Fig. 1b are the appearance of the peaks at
-
1
-1
Ionic liquids (ILs) have been used as efficient catalysts
for an improved and rapid synthesis of imidazoles [35–37].
Zang et al. [38] synthesized 2-aryl-4,5-diphenyl imidazoles
using ionic liquid 1-ethyl-3-methylimidazole acetate as
catalyst at room temperature under ultrasonic irradiation.
The ionic liquid N-methyl-2-pyrrolidonium hydrogen sul-
fate has been used as an efficient and reusable catalyst for
the one-pot synthesis of 2,4,5-trisubstituted and 1,2,4,5-
tetrasubstituted imidazoles under thermal solvent-free
conditions in excellent yields [39].
1,007 cm (Si–O stretching) and at 2,800 cm (–CH2
stretching). These results provided the evidence that IL-
methyl was successfully attached to the surface of Fe O
3
4
nanoparticles.
Figure 2 presents the XRD diffraction patterns of the
prepared MNPs and IL-MNPs. The position and relative
intensities of all peaks conform well with the standard
XRD pattern of Fe O (JCPDS card no. 79-0417), indi-
3
4
cating retention of the crystalline cubic spinel structure
during functionalization of MNPs. The XRD patterns of the
particles show eight characteristic peaks and reveal a cubic
iron oxide phrase (2h = 30.35, 35.95, 43.45, 53.70, 57.25,
62.88, 71.37, 74.46°). These are related to their corre-
sponding indices (2 2 0), (3 1 1), (4 0 0), (3 3 1), (4 2 2),
(3 3 3), (4 4 0), and (5 3 1), respectively [35]. It is implied
that the resultant nanoparticles are pure Fe O with a spinel
During the last 3 decades, ultrasound-accelerated organic
chemical reactions have been increasingly developed by
researchers across the globe for the synthesis of organic
molecules. Ultrasoundirradiationoffersanalternativeenergy
source for organic reactions that are ordinarily accomplished
by heating. Ultrasound-assisted reactions proceed by the
formation, growth, and collapse of acoustic bubbles in the
reaction medium. These directly help in shortening the time
span of reactions and increasing the yield of products [40].
In this work, our objective is to functionalize magnetite
nanoparticles with 1-methyl-3-(3-trimethoxysilylpropyl)-
imidazolium chloride to obtain a heterogeneous catalyst for
the synthesis of 1,2,4,5-tetrasubstituted imidazoles. To the
best of our knowledge, there are no reports on the synthesis
of highly substituted imidazoles catalyzed by magnetic
nanoparticle-supported ionic liquid under ultrasonic irra-
diation. The heterogeneous catalyst could be recovered
easily and reused many times without significant loss of its
catalytic activity (Scheme 1).
3
4
structure and that the grafting process did not induce any
phase change of Fe O .
3
4
The crystal size of MNP and IL-MNP nanoparticles can
be determined from the XRD pattern using Debye-Scher-
rer’s equation.
0
:94k
Dðh k lÞ ¼
b cos h
where D(h k l) is the average crystalline diameter, 0.94 is
the Scherrer’s constant, k is the X-ray wavelength, b is the
half width of XRD diffraction lens, and h is the Bragg’s
angle in degrees. Here, the (3 1 1) peak of the highest
intensity was picked out to evaluate the particle diameter of
1
23

Synthesis of substituted imidazoles under ultrasonic irradiation
1391
Scheme 1
CHO
O
R
N
MNPs-IL
+
+
R
NH2 + 4 NH OAc
4
1
O
N
R
EtOH/u.s/r.t.
1
R
1
2
3
4
5a-5n
6 5
R=C H , n-Pr
Fig. 2 XRD patterns of a MNPs, b IL-MNPs
the nanoparticles. MNPs and IL-MNPs were calculated to
be 12 nm and 30 nm, respectively.
The IL-functionalized magnetic Fe O nanoparticles
3
4
could be separated to the sidewall of the container after
0 s using a magnet of 2,000 G, suggesting the obtained
3
magnetic nanoparticles had an excellent magnetic respon-
sivity, which prevents composite nanoparticles from
aggregation and enables them to redisperse rapidly when
the magnetic field is removed.
The SEM image in Fig. 3a shows that magnetite Fe O
3
4
nanoparticles have a mean diameter of about 18 nm and a
nearly spherical shape. Figure 3b shows that IL-MNP
particles still keep the morphological properties of Fe O
3
4
except for a slightly larger particle size and smoother
surface (more than 20 nm in size), where silica is uni-
formly coated on the Fe O particles to form a silica shell.
3
4
The magnetization curve for Fe O nanoparticles and
3
4
IL-MNPs is shown in Fig. 4. Room temperature-specific
magnetization (M) versus applied magnetic field (H) curve
measurements of the sample indicates a saturation mag-
-
1
netization value (M ) of 40.5 emu g , lower than that of
s
Fig. 1 The comparative FT-IR spectra for a MNPs and b IL-MNPs
123

1
392
J. Safari, Z. Zarnegar
Fig. 3 The SEM images of
a MNPs and b IL-MNPs
product. Optimization of the reaction conditions was
undertaken to increase the yield employing catalyst load-
ings in a wide variety of solvents. The results were
summarized in Table 1. The yield increased to 94 % using
0
.1 g of IL-MNPs (Table 1, entry 2). However, a reduction
in yield was observed by decreasing the catalyst loading to
.05 g (Table 1, entry 3). In the absence of the catalyst, the
0
reaction proceeded sluggishly (Table 1, entry 4). Obvi-
ously, the catalyst is an essential component of the
reaction.
The investigation of reaction medium for the process
revealed that reaction solvents played a significant role in
the model reaction. We examined different solvents such as
water, EtOH, THF, CH CN, and CH Cl on a model
Fig. 4 Magnetization curves for the prepared MNPs and IL-MNPs at
room temperature
3
2
2
reaction under ultrasound irradiation at room temperature
Table 1, entries 5–8). Furthermore, the effect of ultra-
(
-
1
bare magnetic nanoparticles (60.1 emu g ) because of the
coated shell. In Fig. 4 we can also see that the two mag-
netization curves both follow a Langevin behavior over the
sound irradiation on the reaction was also studied. The
model reaction was carried out with stirring at room tem-
perature. The reaction failed to give low yield under high-
speed stirring conditions (Table 1, entry 9). It was apparent
that the ultrasound irradiation accelerates this transforma-
tion under ambient conditions. The reason may be the
phenomenon of cavitation produced by ultrasound [45].
Hence, the conditions of Table 1, entry 2 were the opti-
mized reaction conditions.
applied magnetic field and the coercivity (H ) could be
C
ignored, which can be considered as superparamagnetism
[
44].
Evaluation of the catalytic activity of IL/MNPs through
the synthesis of 1,2,4,5-tetrasubstituted imidazoles
To show the merit of the present work in comparison
with reported results in the literature, we compared results
of IL-MNPs with reported catalysts in the synthesis of
1,2,4,5-tetrasubstituted imidazoles. As shown in Tables 1
and 2, the immobilized ionic liquid can act as a suitable
catalyst with respect to reaction times and yields of the
products.
Initially, we sought a green, facile, and efficient method for
the synthesis of 1,2,4,5-tetrasubstituted imidazoles cata-
lyzed by IL-MNPs under ultrasonic irradiation at room
temperature (Scheme 1). Our investigation began with the
evaluation of IL-MNPs as a catalyst in the reaction of
benzil (1 mmol), benzaldehyde (1 mmol), aniline
(
1 mmol), and ammonium acetate (5 mmol) at 40 kHz
The substrate scope of the reaction was then evaluated
using a variety of structurally diverse aldehydes and
amines. The presence of electron withdrawing groups on
under sonication. The use of 0.15 g of IL-MNPs in ethanol
afforded an 87 % yield (Table 1, entry 1) of the desired
1
23

Synthesis of substituted imidazoles under ultrasonic irradiation
1393
Table 1 Optimization of the
a
Entry
Catalyst
Amount of catalyst/g
Solvent
Condition
Time/min
Yield/%
reaction conditions for synthesis
of 1,2,4,5-tetrasubstituted
imidazoles
1
2
3
4
5
6
7
8
9
IL/MNPs
IL/MNPs
IL/MNPs
No catalyst
IL/MNPs
IL/MNPs
IL/MNPs
IL/MNPs
IL/MNPs
0.15
0.1
0.05
0
EtOH
EtOH
EtOH
EtOH
Water
THF
Ultrasound
Ultrasound
Ultrasound
Ultrasound
Ultrasound
Ultrasound
Ultrasound
Ultrasound
High speed stirring
Ultrasound
Ultrasound
Ultrasound
Ultrasound
30
30
30
30
30
30
30
30
120
30
30
30
30
87
94
67
10
15
40
45
20
70
40
48
45
48
0.1
0.1
0.1
0.1
0.1
0.1
01
CH
CH
3
CN
Cl
2
2
EtOH
EtOH
EtOH
EtOH
EtOH
1
0
AlCl
3
Benzil (1 mmol), benzaldehyde
(1 mmol), aniline (1 mmol),
and ammonium acetate
11
MgCl
2
1
1
2
3
WCl
ZrCl
6
4
0.1
0.1
(
5 mmol)
a
Isolated yield based on
aldehyde
Table 2 Synthesis of 1,2,4,5-
tetrasubstituted imidazoles
catalyzed by IL-MNPs under
ultrasonication at room
1
a
Entry
R
R
Product
Time/min
Yield/%
M.p./°C
1
2
3
4
5
6
7
8
9
H
C
C
C
C
C
C
C
C
C
C
6
6
6
6
6
6
6
6
6
6
H
H
H
H
H
H
H
H
H
H
5
5
5
5
5
5
5
5
5
5
5a
5b
5c
5d
5e
5f
30
25
28
15
30
30
30
33
20
28
20
13
25
25
94
92
90
95
80
75
58
80
84
87
94
95
91
89
216–218 [46]
184–186 [47]
186–188 [46]
160–163 [48]
243–246 [49]
252–254 [48]
282–285 [47]
177–180 [46]
207–211 [48]
178–180
3-Me
4-Me
4-Cl
temperature (Scheme 1)
3-NO
2-OH
4-OH
2
5g
5h
5i
4-OMe
2-OMe
3,4-(OMe)
H
10
11
12
13
14
2
5j
n-Pr
n-Pr
n-Pr
n-Pr
5k
5l
87–89
4-Cl
85–87
4- Me
4-OMe
5m
5n
78–83
76–80
a
Isolated yield
the aromatic aldehydes and primary amines produced high
yields of 1,2,4,5-tetrasubstituted imidazoles.
observed in Fig. 6, the XRD of the recovered magnetite
nanocatalyst was indexed according to the magnetite phase
(JCPDS card no. 79-0417), and so there is no considerable
change in its magnetic phase. Therefore, the heterogeneous
nanocatalyst is stable during synthesis of tetrasubstituted
imidazoles.
Most of the products are known and were identified by
comparison of their physical and spectral data with those of
authentic samples. All melting points compared satisfac-
torily with those reported in the literature.
The possibility of recycling the catalyst was examined
using the reaction of benzil, benzaldehyde, aniline, and
ammonium acetate under optimized conditions. Upon
completion, the catalyst was separated by an external
magnet and was washed with acetone, and the recycled
catalyst was saved for the next reaction. The recycled
catalyst could be reused six times without any further
treatment. No observation of any appreciable loss in the
catalytic activity of nanocatalyst was observed (Fig. 5). As
In summary, we have been able to introduce an efficient
and environmentally friendly approach for the synthesis of
biologically active tetrasubstituted imidazoles by one-pot
four-component condensation of benzil, aldehydes, amines,
and ammonium acetate using IL-MNPs as a recyclable
catalyst under ultrasonication at room temperature. Cor-
rosiveness, safety, less waste, ease of separation, and
recovery are all among desirable factors for the chemical
industry, which we have considered in our green chemistry
123

1
394
J. Safari, Z. Zarnegar
approach. The approach has several benefits, for example,
low waste, easy workup, short reaction time, and high
yields.
and multiplet (m). FT-IR spectra were obtained with
-
potassium bromide pellets in the range 400–4,000 cm
1
with a Perkin-Elmer 550 spectrometer. Mass spectrum was
recorded by a QP-1100EX Shimadzu spectrometer. The
element analyses (C, H, N) were obtained from a Carlo
ERBA Model EA 1108 analyzer carried out on a Perkin-
Elmer 240c analyzer. The UV–vis measurements were
obtained with a GBC cintra 6 UV–vis spectrophotometer.
Nanostructures were characterized using a Holland Philips
Xpert X-ray powder diffraction (XRD) diffractometer
(CuK, radiation, k = 0.154056 nm) at a scanning speed of
2°/min from 2h = 10° to 100°. Scanning electron micros-
copy (SEM) was performed on a FEI Quanta 200 SEM
operated at a 20-kV accelerating voltage. The samples for
SEM were prepared by spreading a small drop containing
nanoparticles onto a silicon wafer and being dried almost
completely in air at room temperature for 2 h; they then
were transferred onto SEM conductive tapes. The trans-
ferred sample was coated with a thin layer of gold before
measurement. Sonication was performed in a UP 400S
ultrasonic processor equipped with a 3-mm-wide and
Experimental
Chemical reagents in high purity were purchased from
Merck Chemical Co. All materials were of commercial
reagent grade. Melting points were determined in open
1
capillaries using an Electrothermal Mk3 apparatus.
H
1
3
NMR and C NMR spectra were recorded with a Bruker
DRX-400 spectrometer at 400 and 100 MHz, respectively.
NMR spectra were obtained in DMSO-d6 and CDCl3
solutions and are reported as parts per million (ppm)
downfield from tetramethylsilane as internal standard. The
abbreviations used are: singlet (s), doublet (d), triplet (t),
140-mm-long probe, which was immersed directly into the
reaction mixture. The operating frequency was 40 kHz,
and the output power was 0–400 W using manual
adjustment.
Preparation of the magnetic Fe O nanoparticles
4
3
(MNPs)
Fe O –MNPs were prepared using chemical coprecipita-
3
4
tion as described in the literature [41] with little
Fig. 5 Recyclability of IL-MNPs in the reaction of benzil (1 mmol),
benzaldehyde (1 mmol), aniline (1 mmol), and ammonium acetate
modification. Typically, 20 mmol of FeCl ꢀ6H O and
3
2
3
1
0 mmol of FeCl ꢀ4H O were dissolved in 75 cm of
(
5 mmol) under ultrasonic waves (40 kHz) at room temperature
2
2
Fig. 6 XRD patterns of
recovered IL-MNPs after four
recoveries
1
23

Synthesis of substituted imidazoles under ultrasonic irradiation
1395
distilled water in a three-necked round-bottom flask
3
250 cm ) under Ar atmosphere for 1 h. Thereafter, under
separated by an external magnet, and the reaction mix-
ture was dissolved in acetone and filtered. The filtrate
was concentrated on a rotary evaporator under reduced
pressure and the solid product obtained was washed with
water and recrystallized from acetone–water (9:1, v/v).
Pure products were obtained in excellent yields, as
summarized in Table 2.
(
3
rapid mechanical stirring, 10 cm of NaOH (10 M) was
added to the solution within 30 min with vigorous
mechanical stirring and ultrasound treatment. After being
rapidly stirred for 1 h, the resultant black dispersion was
heated to 85 °C for 1 h. The black precipitate formed was
isolated by magnetic decantation, exhaustively washed
with double-distilled water, then ethanol, and dried at
2-(3,4-Dimethoxyphenyl)-1,4,5-triphenyl-1H-imidazole
(
5j, C H N O )
2
9 24 2 2
6
0 °C in vacuum.
M.p.: 178–180 °C; UV–vis (EtOH): k
= 311 nm; IR
max
-
1 1
1
-Methyl-3-(3-trimethoxysilylpropyl)-1H-imidazol-3-ium
(KBr): ꢀm = 3,045, 1,617, 1,578 cm ; H NMR (400 MHz,
chloride (IL)
-Methylimidazole (13.6 cm , 0.17 mol) and 31 cm (3-
chloropropyl)trimethoxysilane (0.17 mol) were refluxed at
DMSO-d ): d = 3.61 (s, J = 8.4 Hz, 6H), 6.85 (d,
6
3
3
13
J = 8.8 Hz, 2H), 7.15–7.33 (m, 16H) ppm; C NMR
1
(100 MHz, DMSO-d ): d = 55.9, 112.7, 115.6, 121.2,
6
8
0 °C for 3 days in the absence of any catalyst and solvent
under Ar atmosphere. The unreacted materials were
122.0, 122.3, 123.8, 126.9, 128.7, 130.1, 130.5, 132.5,
132.8, 150.4, 152.8, 153.3 ppm; MS (70 eV): m/z
?
(%) = 432 (M , 55), 417 (50), 402 (44), 77 (32).
3
washed by diethyl ether (3 9 8 cm ). The diethyl ether
was removed under reduced pressure at room temperature,
followed by heating under high vacuum, to yield a
yellowish viscous liquid. Isolated yield was 98 %. The
product was identified through the spectroscopic data,
which were confirmed by comparison with those reported
in the literature [42].
2
,4,5-Triphenyl-1-propyl-1H-imidazole (5k, C H N )
24 22 2
M.p.: 87–89 °C; UV–vis (EtOH): kmax = 284 nm; IR
-
1
1
(
KBr): ꢀm = 3,025, 1,597, 1,479 cm
;
H
NMR
(400 MHz, DMSO-d ): d = 0.51 (t, J = 6.8 Hz, 3H),
6
1.32 (m, J = 6.8 Hz, 2H), 3.81 (t, J = 7.2 Hz, 2H),
1
7.10–7.55 (m, 13H), 7.7 (d, J = 6.8 Hz, 2H) ppm;
3
C
NMR (100 MHz, DMSO-d ): d = 11.5, 24.0, 53.6, 121.5,
6
Modification of magnetic nanoparticles with IL
to obtain IL-MNPs
1
1
3
22.8, 124.0, 125.2, 126.2, 126.9, 128.4, 128.8, 130.1,
?
32.8, 156.7 ppm; MS (70 eV): m/z (%) = 338 (M , 68),
23 (65), 309 (57), 295 (43), 15 (40).
Freshly prepared magnetite nanoparticles (2 g) were sus-
3
pended in 250 cm ethanol (95 %) and sonicated for
2-(4-Chlorophenyl)-4,5-diphenyl-1-propyl-1H-imidazole
6
0 min. The resulting suspension was mechanically stirred,
(5l, C H N Cl)
2
4 21 2
3
followed by addition of a solution of 100 cm ethanol
M.p.: 85–87 °C; UV–vis (EtOH): kmax = 294 nm; IR
(KBr): ꢀm = 3,025, 1,645, 1,489 cm
3
95 %) containing 6 g IL (18.5 mmol) and 1 cm concen-
-1 1
;
(
H
NMR
trated ammonia (28 %). Stirring under Ar was continued
for 36 h. The modified magnetite nanoparticles were
magnetically separated and washed three times with
(400 MHz, DMSO-d ): d = 0.51 (t, J = 6.8 Hz, 3H),
6
1.34 (m, J = 6.8 Hz, 2H), 3.81 (t, J = 7.2 Hz, 2H), 7.15-
1
3
7.30 (m, 12H), 7.34 (d, J = 7.2 Hz, 2H) ppm; C NMR
3
3
5
0 cm ethanol (95 %) and then dissolved in 200 cm
methanol and stirred mechanically for 30 min. Ether
(100 MHz, DMSO-d ): d = 11.5, 24.2, 53.5, 121.5, 122.7,
6
124.3, 125.8, 126.2, 127.0, 128.4, 129.1, 130.4, 132.8,
?
135.6, 156.6 ppm; MS (70 eV): m/z (%) = 435 (M , 55),
3
50 cm ) was added and the modified nanoparticles were
(
3
magnetically separated, washed with 50 cm ether, and
dried under vacuum for 24 h. Typically, 3–3.5 g of
brownish black powder could be obtained.
432 (53), 417 (50), 402 (44), 77 (32).
2-(4-Methylphenyl)-4,5-diphenyl-1-propyl-1H-imidazole
(
5m, C H N )
25 24 2
General procedure for the synthesis of 1,2,4,5-
tetrasubstituted imidazoles
M.p.: 78–83 °C; UV–vis (EtOH): kmax = 294 nm; IR
-1 1
;
(KBr): ꢀm = 3,028, 1,620, 1,497 cm
H
NMR
(
400 MHz, DMSO-d ): d = 0.52 (t, J = 6.8 Hz, 3H),
6
To a solution of benzil (1 mmol), aldehyde (1 mmol),
1.30 (m, J = 6.8 Hz, 2H), 2.50 (s, 3H), 3.80 (t,
0
.4 g ammonium acetate (5 mmol), and primary aliphatic
J = 7.2 Hz, 2H), 7.12-7.35 (m, 12H), 7.50 (d, J = 8 Hz,
13
3
or aromatic amine (1 mmol) in 10 cm ethanol, 0.1 g
MNPs-IL was added and the reaction mixture was
exposed to ultrasonic irradiation at room temperature.
The progress of the reaction was followed by TLC. After
the reaction had been completed, the catalyst was
2H) ppm; C NMR (100 MHz, DMSO-d ): d = 11.3,
6
22.0, 24.2, 53.4, 121.1, 122.9, 124.0, 125.3. 126.2, 127.0,
127.9, 128.8, 130.2, 130.9, 133.0, 142.4, 156.2 ppm; MS
?
(70 eV): m/z (%) = 352 (M , 70), 323 (52), 309 (59), 295
(46), 15 (37).
123

1
396
J. Safari, Z. Zarnegar
2
-(4-Methoxyphenyl)-4,5-diphenyl-1-propyl-1H-imidazole
19. Hu A, Yee GT, Lin W (2005) J Am Chem Soc 127:12486
2
2
0. Puratchikody A, Doble M (2007) Bioorg Med Chem Lett 15:1083
1. Safari J, Khalili SD, Rezaei M, Banitaba SH, Meshkani F (2010)
Monatsh Chem 141:1339
(
5n, C H N O)
2
5 24 2
M.p.: 76–80 °C; UV–vis (EtOH): kmax = 305 nm; IR
(
-
1
1
KBr): ꢀm = 3,016, 1,628, 1,510 cm
400 MHz, DMSO-d ): d = 0.50 (t, J = 6.8 Hz, 3H),
;
H
NMR
22. Shen M, Cai C, Yi W (2008) J Fluorine Chem 129:541
23. Sharma GVM, Jyothi Y, Sree Lakshmi P (2006) Synth Commun
(
6
3
6:2991
1
.33 (m, J = 6.8 Hz, 2H), 3.05 (s, 3H), 3.81 (t,
2
4. Heravi MM, Bakhtiari K, Oskooie HA, Taheri S (2007) J Mol
Catal A: Chem 263:279
J = 7.2 Hz, 2H), 7.10-7.30 (m, 12H), 7.46 (d, J = 8 Hz,
1
3
2
2
1
H) ppm; C NMR (100 MHz, DMSO-d ): d = 11,5,
25. Shaabani A, Rahmati A, Farhangi E, Badri Z (2007) Catal
Commun 8:1149
2
2
5:1461
28. Sharma SD, Hazarika P, Konwar D (2008) Tetrahedron Lett
9:2216
6
4.3, 53.4, 55.9, 117.1, 121.2, 122.8, 123.8, 125.3, 126.2,
6. Wang L, Cai C (2009) Monatsh Chem 140:541
7. Jadhave SD, Kokare ND, Jadhave SD (2009) J Heterocycl Chem
26.8, 128.7, 130.1, 132.0, 132.6, 156.7, 160.8 ppm; MS
?
70 eV): m/z (%) = 368 (M , 59), 337 (52), 323 (59), 309
(
4
(
48), 234 (46), 31 (30).
4
Acknowledgments We gratefully acknowledge the financial sup-
port from the Research Council of the University of Kashan for
supporting this work by Grant No. 256722/I.
29. Karimi AR, Alimohammadi Z, Azizian J, Mohammadi AA,
Mohammadzadehi MR (2006) Catal Commun 7:728
30. Kantevari S, Vuppalapati SVN, Biradar DO, Nagarapu L (2007) J
Mol Catal A: Chem 266:109
3
1. Heravi MM, Derikvand F, Bamoharram FF (2007) J Mol Catal A:
Chem 263:112
2. Sadeghi B, Mirjalili BBF, Hashemi MM (2008) Tetrahedron Lett
References
3
4
:2575
1
. Roger RD, Seddon KR, Volkov S (eds) (2003) Green industrial
applications of ionic liquids. Kluwer Academic Publishers,
Dordrecht
3
3
3. Heravi MM, Derikv F, Haghighi M (2008) Monatsh Chem 139:31
4. Usyatinsky AY, Khmelnitsky YL (2000) Tetrahedron Lett
4
1:5031
2
3
. Abu-Reziq R, Wang D, Post M, Alper H (2008) Chem Mater
3
3
5. Siddiqui SA, Narkhede UC, Palimkar SS, Daniel T, Lahoti RJ,
Srinivasan KV (2005) Tetrahedron 61:3539
6. Chary MV, Keerthysri NC, Vupallapati S, Lingaiah N, Kantevari
S (2008) Catal Commun 9:2013
2
0:2544
. Burrell AK, Sesto RED, Baker SN, McCleskey TM, Baker GA
2007) Green Chem 5:449
(
4
5
6
. Sheldon R (2001) Chem Commun 23:2399
. Wilkes JS (2002) Green Chem 4:73
. Jain N, Kumar A, Chauhan S, Chauhan SMS (2005) Tetrahedron
3
3
7. Xia M, Lu Y (2007) J Mol Catal A: Chem 265:205
8. Zang H, Su Q, Mo Y, Cheng BW, Jun S (2010) Ultrason Sono-
chem 17:749
6
1:1015
. Zang H, Wang M, Cheng BW, Song J (2009) Ultrason Sonochem
6:301
3
4
9. Shaterian HR, Ranjbar M (2011) J Mol Liquids 160:40
0. Nagargoje D, Mandhane P, Shingote S, Badadhe P, Gill C (2012)
Ultrason Sonochem 19:94
7
1
8
9
. Borikar SP, Daniel T (2011) Ultrason Sonochem 18:928
. Sahoo S, Kumar P, Lefebvre F, Halligudi SB (2009) Appl Catal
A 354:17
4
4
1. Yang D, Hu J, Fu S (2009) J Phys Chem C 113:7646
2. Chrobok A, Baj S, Pudło W, Jarzebski A (2009) Appl Catal A:
General 366:22
1
1
0. Zhu LL, Liu YH, Chen J (2009) Ind Eng Chem Res 48:3261
1. Chen W, Zhang YY, Zhu LB, Lan JB, Xie RG, You JS (2007) J
Am Chem Soc 129:13879
2. Miao J, Wan H, Guan G (2011) Catal Commun 12:353
3. Zhu Y, Fang Y, Kaskel S (2010) J Phys Chem C 114:16382
4. Neuberger T, Schoepf B, Hofmann H, Hofmann M, Rechenberg
B (2005) J Magn Magn Mater 293:483
5. Pankhurst QA, Connolly J, Jones SK, Dobson J (2003) J Phys D
Appl Phys 36:167
6. Graham DL, Ferreira HA, Freitas PP (2004) Trends Biotechnol
4
4
3. Massart R (1981) IEEE Trans Magn 17:1247
4. Jiang Y, Jiang J, Gao Q, Ruan M, Yu H, Qi L (2008) Nanotech
1
5. Kappe CO (2004) Angew Chem Int Ed 43:6250
9:75714
1
1
1
4
4
6. Kidwai M, Mothsra P, Bansal V, Somvanshi RK, Ethayathulla
AS, Dey S, Singh TP (2007) J Mol Catal A: Chem 265:177
7. Khosropour AR (2008) Ultrason Sonochem 15:659
4
4
1
1
1
1
8. Murthy SN, Madhav B, Nageswar YVD (2010) Tetrahedron Lett
5
1:5252
9. Shelke KF, Sapkal SB, Sonar SS, Madje BR, Shingate BB,
Shingare MS (2009) Bull Korean Chem Soc 30:1057
4
2
2:455
7. Wang D, He J, Rosenzweig N, Rosenzweig Z (2004) Nano Lett
:409
4
8. Jordan A, Scholz R, Wust P, Fahling H, Felix R (1999) J Magn
Magn Mater 201:413
1
23