One-pot synthesis of 4,4-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols) catalyzed by Br?nsted acidic ionic liquid supported on nanoporous Na+-montmorillonite

Article abstract of DOI:10.1016/j.molliq.2015.04.027

Na⁺-MMT-[pmim]HSO₄, obtained from the immobilization of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium hydrogen sulfate ionic liquid on nanoporous Na⁺-montmorillonite, was used as catalyst for the simple and efficient synt

Full text of DOI:10.1016/j.molliq.2015.04.027

Journal of Molecular Liquids 208 (2015) 291–297
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
One-pot synthesis of
4,4 -(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols)
catalyzed by Brönsted acidic ionic liquid supported on
nanoporous Na+-montmorillonite
⁎
Farhad Shirini , Mohadeseh Seddighi, Masoumeh Mazloumi, Masoumeh Makhsous, Masoumeh Abedini
Department of Chemistry, College of Science, University of Guilan, Rasht 41335, Post Box: 1914, Islamic Republic of Iran
a r t i c l e i n f o
a b s t r a c t
Available online xxxx
Na+-MMT-[pmim]HSO4, obtained from the immobilization of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium
hydrogen sulfate ionic liquid on nanoporous Na+-montmorillonite, was used as catalyst for the simple and
efficient synthesis of 4,4 -(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ol) derivatives via the one-
pot condensation of phenyl hydrazine, ethyl acetoacetate and aldehydes. These reactions were performed at
80 °C under solvent free conditions with high yields in short reaction times. Low loading of the catalyst, simple
experimental procedure and use of an inexpensive catalyst are some of advantages of the procedure. Also this
catalyst can be reused several times without loss of its catalytic activity.
Keywords:
Montmorillonite
Immobilization of ionic liquid
3-Methyl-1-phenyl-5-pyrazolone
4,4 -(Arylmethylene)-bis-(1H-pyrazol-5-ols)
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
Over the last years, ionic liquids (ILs) have been extensively used in
almost all application fields of chemistry such as organic and inorganic
Heterocyclic compounds are widely distributed in nature and are
essential to life. Pyrazoles are important classes of heterocyclic com-
pounds that occur widely in the pharmaceutical industry. For example,
compounds containing 2,4-dihydro-3H-pyrazol-3-one structural motif,
including 4,4 -(arylmethylene)-bis-(1H-pyrazol-5-ols), have attracted
an interest because they exhibit a wide range of biological activities
such as antimalarial [1], antifungal [2], anti-inflammatory [3], antimi-
crobial [4], antinociceptive [5], analgesic [6], fungicide [7] and antitumor
[8] activities. Additionally, they are applied as important intermediates in
organic synthesis [9] and as bis-Schiff bases [10]. 4,4 -(Arylmethylene)-
bis-(1H-pyrazol-5-ols) were also used as pesticides [11], antiviral [12]
and ligand [13]. The main synthetic method for the preparation of
this type of compounds is based on the condensation of aldehydes with
3-methyl-1-phenyl-5-pyrazolone. Therefore, a variety of catalysts and
reagents have been used to facilitate this reaction [13–22]. Although
these procedures provide an improvement in the synthesis of these
heterocyclic compounds, many of them suffer from disadvantages such
as long reaction times, harsh reaction conditions, the need of excess
amounts of the reagent, the use of organic solvents, the use of toxic
reagents and non-recoverability of the catalyst. Therefore, introducing
of simple, efficient and mild procedures with easily separable and
reusable solid catalysts to overcome these problems is still in demand.
syntheses, catalysis, electrochemistry and chromatography. It is due to
their remarkable properties such as non-flammability, negligible
vapor pressure, wide liquid range and high thermal, chemical and
electrochemical stability. However, their high cost, large consumption
and difficult recovery and the separation of products cause limitations
in the large-scale application of them. Furthermore, the ionic liquids
(especially Brönsted acidic ionic liquids) have some degree of instability
in the presence of air and moisture. Immobilization of the ionic liquids
on the surface of a solid support is a useful way to combine the advan-
tageous characteristics of ionic liquids and solid properties. In other
words, the immobilized ionic liquids offer the additional features com-
pared to the pure ionic liquids that facilitate the handling, separation
and reuse procedures, and minimizing the amount of IL utilized in
reactions [23].
In recent years, clays as nanostructured materials have been widely
used in organic transformations as solid acid catalysts [24–27]. The main
reasons for use of clays are the large specific surface area, chemical and
mechanical stability, layered structure and high cation exchange capac-
ity as well as accessibility, easy modification, cheapness and non-
corrosiveness. One such clay is montmorillonite (MMT), which consists
of two tetrahedral silicate sheets with a central aluminum octahedral
sheet, exhibits a net negative charge on the lamellar surface and causes
them to adsorb cations, such as Na+ or Ca+ for compensation. Layers of
MMT have a thickness of about 1 nm and a length of 100 nm or a little
more, so MMT is a structurally well-ordered nanoporous material.
⁎
Corresponding author.
E-mail address: shirini@guilan.ac.ir (F. Shirini).
http://dx.doi.org/10.1016/j.molliq.2015.04.027
0167-7322/© 2015 Elsevier B.V. All rights reserved.

292
F. Shirini et al. / Journal of Molecular Liquids 208 (2015) 291–297
2.3. Preparation of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium
chloride supported on sodium montmorillonite (Na+-MMT-[pmim]Cl)
1.2 g (4 mmol) of [pmim]Cl was dissolved in 25 mL of CH2Cl2 and
treated with 2 g of sodium montmorillonite. The reaction mixture was
refluxed with stirring for 3 days. Then, the reaction mixture was cooled
to room temperature, the solid was isolated by filtration and washed
with 20 mL of boiling dichloromethane to remove the unreacted ionic
liquid. In the next step, the material was dried to obtain MMT-[pmim]Cl.
The amount of chloride in MMT-[pmim]Cl was determined by potenti-
ometric titration methods [28]. For this purpose, 0.5 g of MMT-[pmim]Cl
in 50 mL water was titrated with 0.l M AgNO3. As shown in Fig. 1, the
change happened at 5.1 mL of consumed AgNO3. On the basis of these
studies it can be concluded that Na+-MMT-[pmim]Cl has 1.02 mmol
of Clˉ per gram of this reagent.
Fig. 1. Potentiometric titration and its first derivative curves of Na+-MMT-[pmim]Cl
with AgNO3.
2.4. Preparation of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium
hydrogen sulfate supported on sodium montmorillonite (Na+-MMT-
[pmim]HSO4)
However, they require the cation exchange or surface modification to
increase their active sites for better interaction with reactants.
3 g of Na+-MMT-[pmim]Cl was suspended in 20 mL of dry CH2Cl2.
Under vigorous stirring and in an ice bath (0 °C) 3 mmol of concentrated
H2SO4 (97%) was added dropwise to this mixture. The mixture was then
warmed to room temperature and heated under reflux for 30 h. When
the formed HCl was completely distilled off the solution was cooled
and CH2Cl2 was removed under vacuum to afford Na+-MMT-
[pmim]HSO4 as the product (Scheme 1).
2. Experimental
2.1. General
Chemicals were purchased from Fluka, Merck, and Aldrich chemical
companies. All yields refer to the isolated products. Products were
characterized by comparison of, their physical constants, IR and NMR
spectroscopy with authentic samples and those reported in the litera-
ture. The purity determination of the substrate and reaction monitoring
were accompanied by TLC on silica gel polygram SILG/UV 254 plates.
2.5. Catalyst characterization
2.5.1. Instrumentation
The FT-IR spectra were run on a VERTEX 70 Brucker company
(Germany). Thermogravimetric analyses (TGA) were performed on
Polymer Laboratories PL-TGA thermal analysis instrument (England).
Samples were heated from 25 to 600 °C at ramp 10 °C/min under N2 at-
mosphere. Scanning electron microphotographs (SEM) were obtained
on a SEM-Philips XL30. X-ray diffraction (XRD) measurements were
performed at room temperature on diffractometer Model XRD 6000,
PHILIPS Xpert pro using Co-Kα radiation (K = 1.7890 A°) with the
beam voltage and a beam current of 40 kV and 30 mA, respectively.
Transmission electron microscopy (TEM) analysis was performed on a
Philips model CM 30 instrument.
2.2. Preparation of 1-methyl-3-(trimethoxysilylpropyl)-imidazolium
chloride ([pmim]Cl)
A mixture of 10 mmol of 1-methylimidazole and 10 mmol of (3-
chloropropyl)trimethoxysilane was refluxed at 90 °C for 30 h. Then,
the reaction mixture was cooled down. The crude product was washed
with Et2O (2 × 5 mL) and dried under vacuum. The product as a slightly
yellow viscous oil was obtained.
Scheme 1. Preparation of the acidic ionic liquid immobilized on Na+-MMT (Na+-MMT-[pmim]HSO4).

F. Shirini et al. / Journal of Molecular Liquids 208 (2015) 291–297
293
Fig. 2. FT-IR spectra of Na+-MMT and Na+-MMT-[pmim]HSO4.
2.5.2. IR analysis
with the ionic liquid [30]. The absorption of the S_O asymmetric
stretching mode appeared at 1170 cm−1 and its symmetric stretching
mode lie in 1060 cm−1, so the broad band around 1046 cm−1 can
be assigned to the stretching modes of Si–O and S_O bands which
are overlapped together. The S–O stretching modes of sulfuric acid
functional group lie around 620 and 890 cm−1 proving the successful
preparation of the catalyst [31].
The infrared spectra of Na+-MMT and Na+-MMT-[pmim]HSO4 are
presented in Fig. 2. The FT-IR spectrum of pristine clay displays
the peak at 3632 cm−1 that can be attributed to the OH units in Na+-
MMT. The peaks at 3423 and 1641 cm−1 correspond to the –OH
stretching vibration of free H2O onto the Na+-MMT structure and the
bands at 1043 and 919 cm−1 can be collectively attributed to Si–O
stretching vibrations [27,29].
The Na+-MMT-[pmim]HSO4 is also characterized on the basis of its
FT-IR (Fig. 2). The peaks at 1576 and 1635 cm−1 can be assigned to
C_N and C_C bands of the attached imidazolium ring. Additional
bands at 3159, 2948 and 1461 cm−1 were due to C–H stretching and
deformation vibrations, confirming the functionalization of the material
2.5.3. SEM analysis
The samples of Na+-MMT and Na+-MMT-[pmim]HSO4 were also
analyzed by scanning electron microscopy (SEM) for determining the
size distribution, particle shape and surface morphology, as represented
in Fig. 3. The pictures show that the original structure of Na+-MMT is
Fig. 3. SEM images of Na+-MMT (a) and Na+-MMT-[pmim]HSO4 (b,c).

294
F. Shirini et al. / Journal of Molecular Liquids 208 (2015) 291–297
sodium montmorillonite is obviously bigger than that of Na+-MMT, in-
dicating that the ionic liquid has been intercalated into montmorillonite
interlayer spaces [32]. This increase in the basal spacing can lead to the
better interaction between the reactants in the acid catalysis reactions,
in comparison with the montmorillonite. From the d-spacing of Na+
-
MMT-[pmim]HSO4 the existence of one molecule of ionic liquid
between the clay layers could be estimated [33].
2.5.5. Transmission electron microscopy (TEM)
In addition to XRD, the TEM was also applied to visualize the spatial
morphology of Na+-MMT-[pmim]HSO4, as shown in Fig. 5. The dark
line represents the intersection silicate layers of MMT while the gray
background represents the interlayer organic compounds. The results
indicated that after incorporation of ionic liquid with MMT the interca-
lated nanostructure was obtained. Furthermore, clusters or agglomerat-
ed clay platelets could be seen in these images.
Fig. 4. XRD patterns of Na+-MMT in comparison with Na+-MMT-[pmim]HSO4.
2.5.6. Surface area and pore distribution measurements
N2 adsorption–desorption measurements based on BET and BJH
methods were performed to obtain more information about the cata-
changed and the particles are clearly less stacked in the intercalated
clays. This opening of the layers suggests that the interlayer space may
be occupied by the organic molecules. These images also show that
Na+-MMT-[pmim]HSO4 appears as particles with irregular plate-like
shapes.
lyst. The adsorption–desorption isotherm of Na+-MMT and Na+
-
MMT-[pmim]HSO4 is shown in Fig. 6a. Both samples exhibited type V
isotherm with H3 hysteresis loop categories according to the literature
[34], which indicates the micro and mesopore structures of samples
with slit-like pores [35]. These results also prove that the textural prop-
erties of Na+-MMT were substantially maintained over immobilization
of ionic liquid. BET surface areas, the total pore volumes (Vt),Vmicrop
(estimated by t-plot method) and pore diameters for Na+-MMT and
Na+-MMT-[pmim]HSO4 were presented in Table 1. A decrease in BET
surface area from Na+-MMT (156.0 m2/g) to Na+-MMT-[pmim]HSO4
(133.4 m2/g) was indicated that the ionic liquid may be successfully
2.5.4. Powder X-ray diffraction
Fig. 4 represents the X-ray diffractograms of samples, containing so-
dium montmorillonite and Na+-MMT-[pmim]HSO4 to demonstrate the
expansion of the montmorillonite layers. The calculated basal spacing
for the Na+-MMT is 10.3 Ǻ with 2θ = 8.6° and for Na+-MMT-
[pmim]HSO4 is 16.4 Ǻ. The basal spacing of the ionic liquid anchored
Fig. 5. TEM images of Na+-MMT-[pmim]HSO4.

F. Shirini et al. / Journal of Molecular Liquids 208 (2015) 291–297
295
Fig. 6. The N2 adsorption–desorption isotherm (a), and pore size distribution (b) of Na+-MMT and Na+-MMT-[pmim]HSO4.
Table 1
indicate that the immobilized acid catalyst has great thermal stability
and is apparently stable up to about 270 °C.
Pore structure parameters of Na+-MMT-[pmim]HSO4 derived from the N2 adsorption–
desorption isotherms.
Sample
SBET (m2/g) Vt (cm3/g) Vmicrop (cm3/g) DBJH (nm)
2.6. General procedure for the synthesis of 4,4 -(arylmethylene)-bis-
(3-methyl-1-phenyl-1H-pyrazol-5-ols) derivatives (2)
Na+-MMT
156.0
56.44
48.97
0.0344
0.0275
2.51
2.50
Na+-MMT-[pmim]HSO4 133.4
Phenyl hydrazine (2 mmol) was added to a mixture of Na+-MMT-
[pmim]HSO4(50 mg) and ethyl acetoacetate (2 mmol) at 100 °C and
was stirred for 1 min. Then the aldehyde (1 mmol) was added and the
resulting mixture was stirred for the appropriate time (Table 1). After
completion of the reaction (monitored by TLC), EtOH (10 mL) was
added and the catalyst was separated by filtration. Then water was
added and the precipitated product was separated by filtration in high
purity.
intercalated to Na+-MMT layers. The curves of pore size distribution
evaluated from desorption data by utilizing the BJH model are also
shown in Fig. 6b.
2.5.7. Thermal analysis
Thermogravimetric analysis (TGA) was performed for characteriza-
tion of Na+-MMT-[pmim]HSO4 in comparison with sodium montmoril-
lonite. Fig. 7 provides the TGA curve of pristine clay (Na+-MMT) and
catalyst. The TGA curve of Na+-MMT displays a weight loss below
100 °C which is corresponding to the loss of the physically adsorbed
water and interlayer H2O, also there is a slight weight loss in the range
of 100–600 °C, possibly corresponding to dehydroxylation of sodium
montmorillonite [27].
3-Methyl-1-phenyl-5-pyrazolone (1): 1H NMR (DMSO-d6, 400 MHz):
δ = 2.38 (3H, s, CH3), 3.36 (2H, s,CH3), 7.35 (1H, t, J = 7.6 Hz), 7.52 (2H,
t, J = 8 Hz), 7.85 (2H, d, J = 8.0 Hz)ppm; 13C NMR (DMSO-d6, 100 Mz):
δ = 13.14, 109.37, 121.29, 127.12, 129.55, 137.68, 140.97, 154.00,
161.15.
4,4 -(2-Methylphenylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-
5-ol): 1H NMR (DMSO-d6, 400 MHz): δ = 2.29 (9H, s, CH3), 4.94 (1H,
s,CH3), 7.10-7.15 (3H, m,), 7.24 (2H, t, J = 7.0 Hz), 7.44 (4H, t, J =
8.0 Hz), 7.51 (1H, d, J = 7.0 Hz), 7.72 (4H, d, J = 8.0 Hz), 12.36 (1H,
s), 13.43(1H, s)ppm; 13C NMR (DMSO-d6, 100 Mz): δ = 12.35, 20.20,
31.85, 120.77, 125.93, 126.60, 128.50, 129.40, 130.93, 135.72, 140.34.
The TGA analysis of Na+-MMT-[pmim]HSO4 shows a completely dif-
ferent decomposition from Na+-MMT. A small mass loss appeared at
b100 °C because of the loss of water and a greater mass loss started
from 270 °C can be attributed to the decomposition of the immobilized
ionic liquid moieties anchored on the clay surface [36]. These results
3. Results and discussion
On the basis of the information obtained from the studies on Na+-
MMT-[pmim]HSO4, we anticipated that this reagent can be used as an
Table 2
Optimization of the reaction conditions for the reaction of phenyl hydrazine, ethyl
acetoacetate and 4-chlorobenzaldehyde catalyzed by Na+-MMT-[pmim]HSO4.
Entry
Catalyst (mg)
Solvent
Temperature (°C)
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
9
50
50
50
50
50
50
50
40
60
EtOH
H2O
CH3CN
–
–
–
–
–
–
Reflux
Reflux
Reflux
80
60
100
110
100
100
4 h
4 h
5 h
15
80
10
10
25
12
60
90
50
91
90
92
92
90
92
Fig. 7. TGA curves of Na+-MMT and Na+-MMT-[pmim]HSO4.

296
F. Shirini et al. / Journal of Molecular Liquids 208 (2015) 291–297
Ar
O
O
Me
N
Me
N
Na+-MMT-[pmim]HSO4
100 o 1 min
ArCHO
OEt
Ph-NH-NH2
N
O
+
N
C,
N
N
Ph
OH
HO
Ph
Ph
1
2
(a-r)
Scheme 2. One-pot synthesis of 4,4 -(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols).
efficient solid acid catalyst for the promotion of the reactions which
need the use of an acidic catalyst to speed-up. So we were interested
to investigate the applicability of this reagent in the promotion of the
corresponding
4,4 -(arylmethylene)-bis-(3-methyl-1-phenyl-1H-
pyrazol-5-ols) in short reaction times with good to excellent isolated
yields (Table 3, entries 1–14). Furthermore, 2-naphthaldehyde as a
polycyclic aromatic aldehyde also provided the desired product in
very good yield (Table 3, entry 15). This method was also found to be
useful for the usage of dialdehydes. In this reaction, 4 equivalents of 3-
methyl-1-phenyl-5-pyrazolone successfully condensed with 1 equiva-
lent of terephthaldialdehyde and di-4,4 -(phenylmethylene)-bis-(3-
methyl-1-phenyl-1H-pyrazol-5-ol) was obtained in high yield at short
time that shows the practical synthetic efficiency of this
reaction(Table 3, entry 16).
In order to show the efficiency of the presented method, we
have compared our result obtained for the synthesis of 4,4 -(4-
chlorophenylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ol)
catalyzed by Na+-MMT-[pmim]HSO4 with some of the other results re-
ported in the literature (Table 4). This method avoids disadvantages of
the other procedures such as long reaction times, toxic reagents, high
temperature, organic solvents, excess reagents and low yield. It is also
important to note that the reported procedures for the synthesis of
4,4 -(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols) are
based on the condensation of aldehydes with 3-methyl-1-phenyl-5-
pyrazolone, while our method is based on the one-pot condensation
of phenyl hydrazine, ethyl acetoacetate and aldehydes. On the basis of
the obtained results we believe that the reaction proceed via the in-
situ generation of 3-methyl-1-phenyl-5-pyrazolone (1) which in reac-
tion with aldehydes produces the requested products. This comparison
also clarifies an important point about the catalyst. As it can be seen,
Na+-MMT and Na+-MMT-[pmim]Cl are also able to catalyze this type
of reactions but in longer reaction times rather than Na+-MMT-
synthesis
of
4,4 -(arylmethylene)-bis-(3-methyl-1-phenyl-1H-
pyrazol-5-ols).
At first, we focused our attention to study the synthesis of 4,4 -(aryl
methylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols). For optimiza-
tion of the reaction conditions, the reaction between phenyl hydrazine,
ethyl acetoacetate and 4-chlorobenzaldehyde to the corresponding
product was selected as a model reaction and the various conditions in-
cluding amount of the catalyst, solvent and temperature were examined
(Table 2). For choosing the reaction media, different solvents such as
EtOH, H2O, CH3CN and solvent-free conditions were used and the best
results were obtained in the absence of solvent, probably due to the in-
crease in the concentration and also increase in the effective contacts of
the reactants. Then more experiments were performed and observed
that 50 mg of Na+-MMT-[pmim]HSO4 was the optimal catalyst loading
for this reaction, and higher catalyst loading did not improve the yield of
the product to a greater extent. Finally the optimal reaction condition
for this reaction was obtained using 50 mg of Na+-MMT-[pmim]HSO4
at 100 °C under solvent free conditions (Scheme 2).
After optimization of the reaction conditions and in order to estab-
lish the effectiveness and the acceptability of the method, we explored
the protocol with a variety of simple readily available substrates under
the optimal conditions. The results were presented in Table 3. It was ob-
served that under similar conditions, a wide range of aromatic alde-
hydes containing electron-withdrawing as well as electron-donating
groups such as Cl, Br, F, CH3, OCH3, NO2, SCH3 and CNin the ortho,
meta, and para positions of the benzene ring easily converted to the
Table 3
Preparation of pyrano[2,3-d]pyrimidinone derivatives catalyzed by Na+-MMT-[pmim]HSO4.
Entry
Ar
Product
Time (min)
Yield (%)
Melting point (°C)
Found
Reported
1
2
3
4
5
6
7
8
C6H5–
2-ClC6H4–
4-ClC6H4–
4-BrC6H4–
2a
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
2o
2q
14
14
10
10
10
20
30
30
20
45
10
15
25
25
25
70
91
89
92
91
91
90
87
89
90
89
90
91
90
93
91
84
167–169
240–242
207–209
210–212
188–190
230–232
213–215
192–194
173–175
228–230
164–166
226–228
204–206
208–210
202–204
216–218
169–171 [20]
236–237 [14]
207–209 [14]
215 [37]
180–182 [20]
–
4-FC6H4–
2-CH3C6H5–
2-CH3OC6H5–
3-CH3OC6H5–
4-CH3OC6H5–
2-NO2C6H4–
3-NO2C6H4–
4-NO2C6H4–
4-CH3SC6H5–
4-CNC6H5–
2-Naphthyl–
210–213 [16]
193–194 [37]
172–174 [16]
221–222 [16]
152–154 [20]
225–227 [15]
201–203 [15]
206–208 [20]
206–208 [18]
209–212 [38]
9
10
11
12
13
14
15
16

F. Shirini et al. / Journal of Molecular Liquids 208 (2015) 291–297
297
Table 4
Comparison of the result obtained from the synthesis 4,4 -(4-chlorophenylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) in the presence of Na+-MMT-[pmim]HSO4 with those ob-
tained using some of the other catalysts.
Entry
Catalyst (loading)
Reaction conditions
Time (min)
Yield (%)
Ref.
1
2
3
4
SDS (5 mol%)
Reflux/H2O
Reflux/EtOH
EtOH, US, r.t.
Reflux/H2O
1 h
50
45
91.5
90
90
[14]
[15]
[16]
[17]
Silica-bonded S-sulfonic acid (100 mg)
[HMIM]HSO4 (10 mol%)
PEG-SO3H (1.5 mol%)
30
94
5
6
7
8
9
10
11
Silica Sulfuric Acid (80 mg)
SASPSPE (100 mg)
70 °C/EtOH:H2O
Reflux/EtOH
Reflux/EtOH
100 °C/solvent free
100 °C/solvent free
100 °C/solvent free
100 °C/solvent free
70
2.2 h
50
45
18
90
85
95
90
92
Mixture
92
[18]
[19]
[21]
This work
This work
This work
This work
[P4VPy-BuSO3H]HSO4 (10 mol%)
Na+-MMT (50 mg)
Na+-MMT-[pmim]Cl(50 mg)
[pmim]HSO4 (5 mol%)
30
10
Na+-MMT-[pmim]HSO4 (50 mg, 5 mol%)
[pmim]HSO4, and the mixture of products were obtained in the pres-
ence of [pmim]HSO4 as catalyst. These results give clear evidence to
confirm the important role of the covalently bounded ionic liquid and
also HSO−4 group in the catalyst to obtain the best performance.
To check the reusability of the catalyst, the reaction of phenyl hydra-
zine, ethyl acetoacetate and 4-chlorobenzaldehyde under the optimized
reaction conditions was studied again. When the reaction was complet-
ed, ethanol was added and the catalyst was separated by filtration. The
recovered catalyst was washed with ethanol, dried and reused for the
same reaction. This process was carried out over eight runs and all reac-
tions led to the desired products without significant changes in terms of
the reaction time and yield which clearly demonstrates practical
recyclability of this catalyst (Fig. 8).
Acknowledgments
We are thankful to the University of Guilan Research Council for the
partial support of this work.
References
[1] B.N. Acharya, D. Saraswat, M. Tiwari, A.K. Shrivastava, R. Ghorpade, S. Bapna, M.P.
Kaushik, Eur. J. Med. Chem. 45 (2010) 430.
[2] M. Kidwai, R.J. Mohan, Korean Chem. Soc. 48 (2004) 177.
[3] Sugiura, S. Ohno, O. Ohtani, K. Izumi, T. Kitamikado, H. Asai, K. Kato, M. Hori, H.
Fujimura, J. Med. Chem. 20 (1997) 80.
[4] H. Bayrak, A. Demirbas, N. Demirbas, S.A. Karaoglu, Eur. J. Med. Chem. 45 (2010)
4726.
[5] K.H. Carlsson, I. Jurna, Naunyn Schmiedeberg's Arch. Pharmacol. 335 (1987) 154.
[6] G. Mariappan, P.B. Saha, L. Sutharson, A. Haldar, Indian J. Chem. B 49 (2010) 1671.
[7] R.K. Tewari, R.K. Mishra, S.K. Srivastava, S.C. Bahel, Pestic. Res. J. 2 (1990) 24.
[8] R.V. Antre, A. Cendilkumar, R. Nagarajan, D. Goli, R.J. Oswal, J. Sci. Res. 4 (2012) 183.
[9] W.S. Hamama, Synth. Commun. 31 (2001) 1335.
4. Conclusion
[10] T. Ren, S. Liu, G. Li, J. Zhang, J. Guo, W. Li, L. Yang, Spectrochim. Acta A 97 (2012) 167.
[11] M. Londershausen, Pestic. Sci. 48 (1996) 269.
In conclusion, in this study we have introduced Na+-MMT-
[pmim]HSO4 as a highly powerful supported acidic ionic liquid for
the simple and efficient synthesis of 4,4 -(arylmethylene)-bis-(3-
methyl-1-phenyl-1H-pyrazol-5-ols). The obtained results show that
the catalytic activity of Na+-MMT-[pmim]HSO4 is convincingly superior
to other reported procedures in the terms of reaction times and yields.
Lower loading of the catalyst, simple experimental procedure, and use
of inexpensive and reusable catalyst are other advantages of the proce-
dure. Furthermore, this process avoids problems associated with organ-
ic solvent and liquid acid use, which makes it a useful and attractive
strategy in view of economic and environmental advantages. Further
work to explore this catalyst in other organic transformations is in
progress.
[12] K. Sujatha, G. Shanthi, N.P. Selvam, S. Manoharan, P.T. Perumal, M. Rajendran,
Bioorg. Med. Chem. Lett. 19 (2009) 4501.
[13] M. Abbasi-Tarighat, E. Shahbazi, K. Niknam, Food Chem. 138 (2013) 991.
[14] W. Wang, S. Wang, X. Qin, J. Li, Synth. Commun. 35 (2005) 1263.
[15] K. Niknam, D. Saberi, M. Sadegheyan, A. Deris, Tetrahedron Lett. 51 (2010) 6928.
[16] H. Zang, Q. Su, Y. Mo, B. Cheng, Ultrason. Sonochem. 18 (2011) 68.
[17] A. Hasaninejad, M. Shekouhy, A. Zare, S.M.S.H. Ghattali, N. Golzar, J. Iran. Chem. Soc.
8 (2011) 411.
[18] K. Niknam, S. Mirzaee, Synth. Commun. 41 (2011) 2403.
[19] S. Tayabi, M. Baghernejad, D. Saberi, K. Niknam, Chin. J. Catal. 32 (2011) 1477.
[20] N. Iravani, J. Albadi, H. Momtazan, M. Baghernejad, J. Chin. Chem. Soc. 60 (2013)
418.
[21] K.P. Boroujeni, P. Shojaei, Turk. J. Chem. 37 (2013) 756.
[22] A. Khazaei, F. Abbasi, A.R. Moosavi-Zare, New J. Chem. (2014)http://dx.doi.org/10.
1039/c4nj01079e.
[23] M.H. Valkenberg, C. deCastro, W.F. Hölderich, Green Chem. 4 (2002) 88.
[24] S. Kantevari, S.V.N. Vuppalapati, L. Nagarapu, Catal. Commun. 8 (2007) 1857.
[25] J.S. Yadav, B.V.S. Reddy, B. Eeshwaraiah, M. Srinivas, Tetrahedron 60 (2004) 1767.
[26] B.S. Kumar, A. Dhakshinamoorthy, K. Pitchumani, Catal. Sci. Technol. 4 (2014) 2378.
[27] F. Shirini, M. Mamaghani, S.V. Atghia, Catal. Commun. 12 (2011) 1088.
[28] J. William, Handbook of Anion Determination, First ed. Butterworths-Heinemann
Ltd, London, 1979. 416.
[29] M.H. Baki, F. Shemirani, R. Khani, M. Bayat, Anal. Methods 6 (2014) 1875.
[30] S. Safaei, I. Mohammadpoor-Baltork, A.R. Khosropour, M. Moghadam, S.
Tangestaninejad, V. Mirkhani, Catal. Sci. Technol. 3 (2013) 2717.
[31] M.N. Sefat, D. Saberi, K. Niknam, Catal. Lett. 141 (2011) 1713.
[32] K. Nagy, G. Bíro, O. Berkesi, D. Benczédi, L. Ouali, I. Dékány, Appl. Clay Sci. 72 (2013)
155.
[33] K. Wang, L. Wang, J. Wu, L. Chen, C. He, Langmuir 21 (2005) 3613.
[34] J.B. Condon, Surface Area and Porosity Determinations by Physisorption, Elsevier,
2006. 1–27 (Chapter 1).
[35] H. Rojas, G. Borda, P. Reyes, M. Brijaldo, J. Valencia, J. Chil. Chem. Soc. 56 (2011) 793.
[36] A. Hasaninejad, M. Shekouhy, N. Golzar, A. Zare, M.M. Doroodmand, Appl. Catal. A
Gen. 402 (2011) 11.
[37] S. Sobhani, A. Hasaninejad, M.F. Maleki, Z.P. Parizi, Synth. Commun. 42 (2012) 2245.
[38] Z. Karimi-Jaberi, B. Pooladian, M. Moradi, E. Ghasemi, Chin. J. Catal. 33 (2012) 1945.
Fig. 8. Reusability of the catalyst.