KSF supported 10-molybdo-2-vanadophosphoric acid as an efficient and reusable catalyst for one-pot synthesis of 2,4,5-trisubstituted imidazole derivatives under solvent-free condition

Article abstract of DOI:10.1016/S1872-2067(15)60830-0

The one-pot three-component cyclocondensation has been developed involving the reaction of benzil with an aromatic aldehydes and ammonium acetate under thermal solvent-free conditions in the presence of a KSF supported 10-molybdo-2-vanadophosphoric acid catalyst. 10-Molybdo-2-vanadophosphoric acid was immobilized on KSF with a 20% loading, which showed the highest catalytic activity. The catalyst was fully characterized using FT-IR spectroscopy, thermal analysis, XRD and SEM analysis techniques. There are several distinct advantages to this protocol, including high yields, short reaction time, operational simplicity and a recyclable catalyst with a facile work-up procedure.

Full text of DOI:10.1016/S1872-2067(15)60830-0

Chinese Journal of Catalysis 36 (2015) 1054–1059
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
Article
KSF supported 10-molybdo-2-vanadophosphoric acid as an efficient
and reusable catalyst for one-pot synthesis of 2,4,5-trisubstituted
imidazole derivatives under solvent-free condition
Laxmikant D. Chavan, Sunil G. Shankarwar *
Department of Chemistry, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431 004, M.S., India
A R T I C L E I N F O
A B S T R A C T
Article history:
The one-pot three-component cyclocondensation has been developed involving the reaction of
benzil with an aromatic aldehydes and ammonium acetate under thermal solvent-free conditions in
the presence of a KSF supported 10-molybdo-2-vanadophosphoric acid catalyst. 10-Molybdo-2-
vanadophosphoric acid was immobilized on KSF with a 20% loading, which showed the highest
catalytic activity. The catalyst was fully characterized using FT-IR spectroscopy, thermal analysis,
XRD and SEM analysis techniques. There are several distinct advantages to this protocol, including
high yields, short reaction time, operational simplicity and a recyclable catalyst with a facile
work-up procedure.
Received 2 February 2015
Accepted 4 March 2015
Published 20 July 2015
Keywords:
2
,4,5-Trisubstituted imidazole
Heteropoly acid
0-Molybdo-2-vanadophosphoric acid
©
2015, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Published by Elsevier B.V. All rights reserved.
1
KSF clay
Heterogeneous catalyst
1
.
Introduction
properties. To date, more than 100 HPAs of a variety of differ-
ent compositions and structure have been reported in the liter-
ature [3]. Among them, only the Keggin-structure HPAs have
been reported to play a significant role in catalysis because
they are readily available and possess relatively high thermal
stability [4]. Keggin type HPAs can be represented by the for-
The development of eco-friendly, efficient and economical
methods for the synthesis of biologically interesting com-
pounds remains one of the principle aims of synthetic chemis-
try [1]. The field of green chemistry has rapidly developed
during the last 10 years following the recognition that envi-
ronmentally friendly products and processes represent eco-
nomically attractive long term synthetic strategies. The im-
portant areas of green chemistry include the development of
novel chemical processes that show intrinsically high atom
economies, pronounced energy savings, low levels of waste
production and facile work-up procedures, as well as avoiding
the use of hazardous chemicals [2].
mula H8-x[XM12
O
40], where X is a hetero atom (usually P5+ or
4+
Si ), x is the oxidation state of the catalyst and M is its addenda
atom (most frequently W6+ or Mo ). The M ions can be sub-
6+
6+
stituted by many other metal ions, including V , Co and Zn2+
[5]. HPAs can be used either directly as a bulk material or in
their supported form in both homogeneous and heterogeneous
systems. HPAs are highly soluble in polar solvents, but insolu-
ble in non-polar solvents. There are several advantages to
HPAs, including their multifunctionality, structural mobility,
non-corrosive nature, strong Brӧnsted acidity, reusability,
non-toxicity and experimental simplicity [6]. However, there
5+
2+
Heteropoly acids (HPAs) have been widely used as homo-
geneous and heterogeneous acid catalysts for the oxidation of
numerous substrates because of their unique physicochemical
*
Corresponding author. Tel: +91-240-2403311; Fax: +91-240-2403311; E-mail: shankarwar_chem@yahoo.com
DOI: 10.1016/S1872-2067(15)60830-0 | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 36, No. 7, July 2015

Laxmikant D. Chavan et al. / Chinese Journal of Catalysis 36 (2015) 1054–1059
1055
are also several disadvantages associated with the use of HPAs
as catalysts, including their low surface areas and problems
associated with their separation from the reaction mixture. It is
envisaged that supported HPAs could be used to overcome
some of the problems described above, and a number of porous
supports with high surface areas such as silica, zirconia, clay,
active carbon and zeolite have been reported as supports for
HPAs [7].
resulting hot solution was then allowed to cool to room tem-
perature. The 10-molybdo-2-vanadophosphoric acid was then
extracted with diethyl ether (500 mL), and air was passed
through the heteropoly etherate to remove the diethyl ether.
The resulting solid was dissolved in water, and the aqueous
solution was concentrated under vacuum in a desiccator over
concentrated sulfuric acid until the first crystals appeared, and
then allowed to crystallize further. The resulting large red
crystals were collected by filtration, washed with water and air
dried (yield, 30% based on molybdate) [21].
2,4,5-Trisubstituted imidazoles has attracted considerable
attention from synthetic chemists working in a variety of dif-
ferent field because of their wide range of biological properties,
including their anti-allergic [8], antitumor [9], an-
ti-inflammatory [10], antibacterial [11] and analgesic [12].
Compounds belonging to this structural class are also known as
inhibitors of p38 MAP kinase [13], fungicides, herbicides, glu-
cagon receptors [14], growth regulators and therapeutic
agents. A variety of different procedures have been developed
for the synthesis of 2,4,5-trisubstituted imidazoles, with the
majority of these process involving nitriles and esters [15,16]
as starting materials. The first synthesis of the 2,4,5-triphenyl
imidazoles was reported by Japp and Radziszewski via the
condensation of 1,2-dicarbonyl compounds with a variety of
different aldehydes and ammonia [17,18]. Following on from
this, numerous classical methods have been reported in the
literature for the synthesis of 2,4,5-trisubstituted imidazoles
2.1.2. Preparation of KSF-supported
10-molybdo-2-vanadophosphoric acid H
5
[PMo10
V
2
O
40] 30H O
2
For preparation of the KSF-supported 10-molybdo-2-van-
dophosphoric acid catalysts, KSF montmorillonite was dried in
an oven at 120 °C for 2 h prior to being used as a support. To
prepare the catalyst loaded with 10, 20, 30 and 40 wt% of
10-molybdo-2-vandophosphoric acid on to the KSF supports,
the appropriate amounts of 10-molybdo-2-vandophosphoric
acid were dissolved in 6 mL of dry methanol. The resulting
solutions were added to pre-dried KSF in a dropwise manner
under constant stirring with a glass rod. For the initial addition
of the 10-molybdo-2-vandophosphoric acid solutions, the clay
was in its powdered form, but quickly turned into a paste fol-
lowing the addition of the 10-molybdo-2-vandophosphoric acid
solution. However, after being stirred for 10 min, the paste
turned into a free flowing powder. Following the impregnation
process, all of the catalysts were dried at room temperature for
24 h. The catalysts were ground and sieved before being cal-
cined at 200 °C for 3 h to give some uniformity to their particle
size.
[19,20]. However, there are limitations associated with some of
these methods, including the requirement for expensive and
toxic catalysts, long reaction time, harsh reaction conditions,
low product yields and difficulties associated with the recovery
and reusability of the catalysts. With this in mind, there is an
urgent need for the development of clean processes utilizing
eco-friendly and green catalysts, which can be readily recycled
at the end of reactions.
2.2. Characterization techniques
Herein, we describe the preparation of a series of
KSF-supported 10-molybdo-2-vanadophosphoric acid catalysts
and their characterization by FT-IR spectroscopy, thermal
analysis, XRD and SEM analysis techniques. These catalysts
were subsequently used for one-pot synthesis of
FT-IR spectra were obtained on a Bruker Model 3000 hype-
rion microscope equipped with a vertex 80 FT-IR system
(Bruker, Germany). FEG-SEM images were recorded on a
JSM-7600F microscope (Jeol, USA), which was operated at 30
kV. XRD patterns were obtained on a Philips X’pert MPD Sys-
2,4,5-trisubstituted imidazoles by the reaction of benzyl with a
series of aromatic aldehydes and ammonium acetate under
thermal, solvent-free conditions.
tem (Philips, Netherlands) using Cu K
α
radiation. The TG-DTA
measurements for the samples were recorded on a Diamond
TG-DTA Thermal Analyzer (PerkinElmer) with about 10 mg of
sample in a platinum crucible at a heating rate of 10 °C/min in
2
.
Experimental
1
air. H NMR spectra were recorded on a Bruker Avance 400
2
.1. Catalyst preparation
spectrometer (Bruker), and 13C NMR spectra were recorded on
a Bruker DRX-300 instrument (Bruker) using TMS as an inter-
nal reference standard. Mass spectra were recorded on a Wa-
ters UPLC-TQD mass spectrometer using electrospray ioniza-
tion. The uncorrected melting points of the compounds were
recorded in an open capillary tube in a paraffin bath.
2
.1.1. Preparation of 10-molybdo-2-vanadophosphoric acid
40]·30H
Sodium metavanadate (24.4 g, 0.20 mol) was dissolved in
boiling water (100 mL), and the resulting solution was mixed
with a solution of Na HPO (7.1 g, 0.050 mol) in water (100
H
5 2
[PMo10V O
2
O
2
4
mL). The mixture was then cooled to room temperature and
treated with concentrated sulfuric acid (5 mL), which caused
the solution to become red in color. The mixture was then
2.3. General procedure for synthesis of 2,4,5-trisubstituted
imidazoles using KSF supported H
5
[PMo10
V
2
O
40]·30H O as a
2
catalyst
treated with a solution of Na
2
MoO
4
·2H O (121 g, 0.50 mol) in
2
water (200 mL), followed by concentrated sulfuric acid (85
mL), which was added slowly with vigorous stirring, and the
A mixture of benzil (1 mmol), an aromatic aldehyde (1
mmol), ammonium acetate (2 mmol) and 20% H
5
PMo10
V O /
2 40

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Laxmikant D. Chavan et al. / Chinese Journal of Catalysis 36 (2015) 1054–1059
KSF (0.1 g) was heated in the oil bath at 110 °C for the appro-
priate time. The progress of reaction was monitored by thin
layer chromatography (TLC). Upon completion of the reaction,
the mixture was cooled to room temperature and then treated
with hot ethanol to separate the catalyst, which was collected
from residue. The filtrate was then poured into 50 mL of
ice-water to give a precipitate, which was collected by filtration,
washed with ice-water and recrystallized from ethanol to give
compounds 4a–4n in high yields. The recovered catalyst was
washed with ethanol (10 mL) and calcined at 140 °C for 1 h
before reusing.
(
a)
(b)
Fig. 2. FEG-SEM images of the KSF clay (a) and 20% H
b).
5
PMo10V O40/KSF
2
(
four characteristic IR bands in its FT-IR spectra in the range of
–
1
2
.3.1. Spectral data for selected 2,4,5-trisubstituted imidazoles
700–1200 cm . The four characteristic IR bands of unsup-
ported H 40 appeared at 1063 (P–O stretching), 962
2
-(3,4,5-Trimethoxyphenyl)-4,5-diphenyl-1H-imidazole
5
PMo10
2
V O
1
(4i): Off-white solid; H NMR (CDCl
3
, 400 MHz): δ = 3.96 (s,
(M=O stretching), 865 (inter-octahedral M–O–M stretching)
and 780 cm–1 (intra-octahedral M–O–M stretching). After being
supported on KSF clay, some of the characteristic bands of the
6
(
3
H), 3.91 (s, 3H), 7.32 (d, J = 6 Hz, 2H), 7.35–7.37 (m, 8H), 7.58
d, 2H); 13C NMR: δ = 128.6, 127.8, 102.8, 56.3; IR (KBr, cm–1):
448, 1649, 1588, 1243, 731; EI-MS: m/z = 387 [M+H]+.
-(2-Furyl)-4,5-diphenyl-1H-imidazole (4l): Black solid;
CDCl , 400 MHz): δ = 3.75 (m, 1H), 6.55 (m,2H), 7.03 (d, J = 10
Hz, 1H), 7.41–7.54 (m, 4H), 7.84–8.19 (m, 6H); 13C NMR: δ =
45.48, 142.2, 138.8, 128.6, 127.8, 127.1, 112.0, 107.5; IR (KBr,
H
5
PMo10V O40/KSF were observed at 1060 (P–O stretching),
2
872 (inter-octahedral M–O–M stretching) and 782 cm–1 (in-
tra-octahedral M–O–M stretching), whereas its remaining
bands merged with those of the KSF clay. This result indicated
2
(
3
1
5
that H PMo10
V O40 had been successfully immobilized on the
2
–1
cm ): 3366, 3057, 1641, 1618, 1126, 731; EI-MS: m/z = 287
M+H]+.
-(3-Pyridyl)-4,5-diphenyl-1H-imidazole (4m): Off-white
KSF support via the formation of strong chemical interaction
between the two components.
[
2
1
solid; H NMR (CDCl
m, 4H), 7.38–7.43 (m, 4H), 7.48–7.51 (m, 2H), 7.55 (d, J = 6.8
Hz, 1H), 8.36 (d, J = 8 Hz, 1H), 8.4 (d, 1H), 9.1 (s, 1H); 13C NMR: δ
3
, 400 MHz): δ = 3.71 (m, 1H), 7.29–7.36
3.1.2. SEM Analysis
(
Figure 2 shows the surface morphologies of the synthesized
catalysts. Figure 2(a) shows the surface morphology of the KSF
clay, and Figure 2(b) shows the surface morphology of the 20%
=
1
=
148.8, 145.7, 143.0, 133.5, 128.5, 128.2, 127.9, 127.6, 126.6,
–1
23.9; IR (KBr, cm ): 3367, 3053, 1623, 1246, 765; EI-MS: m/z
H
5
PMo10V O40/KSF catalyst. These images clearly show that the
2
298 [M+H]+.
surface morphology of the KSF clay was altered as a conse-
quence of the deposition and insertion of the catalyst onto its
surface.
3
.
Results and discussion
3
3
.1. Characterization of the catalysts
3.1.3. Thermal analysis
Figure 3 shows the results for the thermal analysis of un-
.1.1. FT-IR Analysis
5 2
supported H PMo10V O40, KSF clay and 20% H
5
PMo10
V O /
2 40
Figure 1 shows the FT-IR spectra of the unsupported
KSF. The TGA results for H
5
PMo10 40 revealed a mass loss of
V O
2
H
5
PMo10
V
2
O
40, KSF clay and 20% H
5
PMo10
V
2
O
40/KSF. The pri-
about 7% up to a temperature of 130 °C, which was attributed
to the loss of free and adsorbed water. The gradual mass loss of
mary structure of H PMo10 40 was identified based on the
5
V O
2
1
00
(
3)
2)
8
72
(3)
9
0
0
(1)
(
7
82
(2)
8
1060
70
60
(1)
780
865
1063
962
50
2
000 1800 1600 1400 1200 1000 800 600
50 100 150 200 250 300 350 400 450 500
1
o
Wavenember (cm )
Temperature ( C)
Fig. 1. FT-IR spectra of the unsupported H
5 2
PMo10V O40 (1), KSF clay (2)
Fig. 3. Thermal analyses of unsupported H
and 20% H 40/KSF (3).
5
PMo10V O40 (1), KSF clay (2)
2
and 20% H 40/KSF (3).
5 2
PMo10V O
5
PMo10V O
2

Laxmikant D. Chavan et al. / Chinese Journal of Catalysis 36 (2015) 1054–1059
1057
d-spacing (d001) values of about 0.991 and 0.318 nm. Several
other peaks were also observed in the diffractogram of
100
(
3)
H
5
PMo10
V
2
O
40, which indicated that H
5
PMo10
V O40 was crystal-
2
9
8
7
6
5
0
0
0
0
0
line in nature. The XRD pattern of the KSF clay contained two
intense peaks with 2θ values of 19.97° and 26.76°, which cor-
responded to basal d-spacing (d001) values of about 0.444 and
(
1)
(
2)
0
.333 nm. These data confirmed that the KSF clay was crystal-
line in nature. The peaks in the XRD pattern of 20%
40/KSF were less intense than those observed in
the individual diffractograms, which indicated that the im-
pregnation of the H 40 on KSF was resulting in a de-
H
5
PMo10V O
2
5
PMo10
V O
2
crease in its crystallinity.
3.2. Catalytic activity
Various amounts of H
the effect of the composition of the catalyst on the conversion,
and the results are summarized in Table 1. Pure KSF clay
showed only moderate catalytic activity in terms of the reaction
time and the yield of the desired product (Table 1, entry 2).
5
0
100 150 200 250 300 350 400 450 500
o
Temperature ( C)
Fig. 3. Thermal analyses of unsupported H
and 20% H 40/KSF (3).
5
PMo10V O40 (1), KSF clay (2)
2
5
PMo10
V O40/KSF were used to study
2
5
PMo10V O
2
about 4% up to 500 °C was attributed to the release of more
hydrated or structural water. The TGA results for the KSF clay
showed a steady mass loss of about 19% up to 500 °C, which
was attributed to the loss of physisorbed and interlayer water,
as well as dehydroxylation reactions resulting from the break-
ing of the structural –OH groups on the support. The TGA re-
Bulk H
5
PMo10
2
V O40 gave a good yield of the product but only
after an extended reaction time (Table 1). In terms of optimiz-
ing the amount of catalyst immobilized on the KSF support, it
was observed that 20% H
yield of the desired product over a short reaction time (Table 1,
entry 4). However, increasing the loading of the H
catalyst on the KSF support from 10% to 20% led to a signifi-
cant increase in the yield (Table 1, entries 3 and 4). Further
increases in the loading, however, resulted in a decrease in the
yield of the reaction because of the leaching of the catalyst from
the support. The increase in activity of the catalyst following its
immobilization on the KSF support was attributed to the high
dispersion of the H
would lead to an increase in its surface area and the number of
active sites compared with the bulk H 40 catalyst.
5 2
PMo10V O40/KSF gave an excellent
sults for 20% H
% up to a temperature of 140 °C, which was attributed to the
loss of free and adsorbed water. A gradual mass loss of about
% was observed up to 500 °C, which was caused by the re-
5
PMo10
V
2
O40/KSF showed a mass loss of about
3
5 2 40
PMo10V O
7
lease of more hydrated or structural water. Taken together,
these results indicated that the thermal stability of
PMo10V O40 increased following its immobilization on the
KSF support. This increase in the thermal stability could be
attributed to the formation of intermolecular bonding interac-
H
5
2
5 2
PMo10V O40 catalyst on the support, which
tions between KSF and H
5
PMo10V O .
2 40
5
PMo10
V O
2
3
.1.4. XRD measurements
Figure shows the XRD patterns of unsupported
40, KSF clay and 20% H 40/KSF. The XRD
PMo10 40 showed two intense peaks with 2θ
values of 8.90° and 27.98°, which corresponded to basal
Considering the above observations we next carried out a
series of reactions using benzil (1 mmol), aromatic aldehydes
4
H
5
PMo10
pattern of H
V
2
O
5
PMo10
2
V O
(1 mmol) and ammonium acetate (2 mmol) in presence of 20%
5
V O
2
H
5
PMo10V O
2
40/KSF (0.1 g) at 110 °C under solvent free condi-
tions. Most importantly, aromatic aldehydes with substituent’s
bearing either electron-donating or electron-withdrawing
groups reacted successfully in the presence of 20%
H
5
PMo10V O40/KSF as a catalyst. In all cases the expected
2
Table 1
Effect of various H
(3)
5
[PMo10V O40] loadings of the efficiency of the cata-
2
lyst.
Time
Isolated
yield (%)
85
Entry
Catalyst
T/(°C)
(min)
(2)
1
2
3
4
5
6
H
5
2
[PMo10V O40] 30H
2
O
110
110
110
110
110
110
45
75
55
25
30
32
KSF
71
(1)
10% H
20% H
30% H
40% H
5
PMo10
PMo10
PMo10
PMo10
V
2
O
2
O
2
O
2
O
40 / KSF
40 / KSF
40 / KSF
40 / KSF
78
92
90
89
5
V
V
V
10
20
30
40
50
60
70
80
5
o
2/( )
5
Reaction conditions: benzil (1 mmol), benzaldehyde (1mmol), ammo-
Fig. 4. XRD patterns of unsupported H
0% H 40/KSF (3).
5
PMo10V O40 (1), KSF clay (2) and
2
nium acetate (2 mmol) and KSF supported H
g) under solvent free conditions.
5
[PMo10
V
2
O
40]·30H O (0.1
2
2
5
PMo10V O
2

1058
Laxmikant D. Chavan et al. / Chinese Journal of Catalysis 36 (2015) 1054–1059
could then be washed several times with ethanol before being
Table 2
Synthesis of 2,4,5-trisubstituted imidazoles using 20% H
KSF as a catalyst
5
PMo10
V O
2 40
/
calcined at 140 °C and reused for a fresh reaction mixture. The
results of a recyclability study revealed that the catalyst could
be reused at least three times with only a slight reduction in its
original activity (e.g., 90% yield for the first run, 87% yield for
the second run and 83% yield for the third run). This decrease
in catalytic activity was attributed to the leaching of the catalyst
from the support.
CHO
O
N
5 2
20% H PMo10V O40/KSF
4
NH OAC
Solvent-free
110 o
R
O
N
H
R
C
Pro- Time Isolated
Melting point (°C)
duct (min) yield (%) Found Reported [Ref.]
Entry Aldehyde
CHO
1
4a
4b
25
35
92
95
273–275 274–276 [22]
241–243 240–242 [23]
4. Conclusions
CHO
A simple and convenient procedure has been developed for
the one-pot three-component cyclocondensation of benzyl with
a variety of aromatic aldehydes and ammonium acetate in the
presence of KSF-supported 10-molybdo-2-vanadophosphoric
acid catalyst under thermal, solvent-free conditions. These
reactions were carried out under solvent-free conditions over
short reaction time and gave the corresponding products in
2
OH
CHO
3
4c
30
25
78
90
283–285 285–287 [30]
250–252 252–254 [24]
Cl
CHO
4
4d
Br
CHO
good to excellent yields. The 20% H
5 2
PMo10V O40 supported on
KSF clay exhibited higher catalytic activity than the bulk
5
4e
40
94
232–234 230–232 [25]
H
5
PMo10
V
2
O
O
40 catalyst, as well as the (10% and 30%)
40 catalysts supported on KSF clay. The observed
H
5
PMo10
V
2
CH
CHO
3
increase in the catalytic activity of the KSF-supported catalysts
was attributed to the high surface area and large number of
Brӧnsted acidic sites on the catalyst. Moreover, this newly de-
veloped catalyst was thermally stable, green and inexpensive to
prepare, as well as being easy to separate from the reaction
mixture and reused several times.
6
7
8
4f
4g
4h
35
40
50
96
83
89
302–304
>300 [25]
NO
2
CHO
298–300 301–303 [26]
203–205 204–206 [28]
Br
CHO
CHO
OCH
3
Acknowledgments
The authors are thankful to the Head, Department of Chem-
istry, Dr. Babasaheb Ambedkar Marathwada University, Au-
rangabad and Principal, Jawaharlal Nehru Engineering College,
Aurangabad-431 004 (MS), India for providing the laboratory
facility.
9
4i
4j
40
45
95
219–221 220–221 [27]
OCH
3
OCH
3
CHO
1
0
1
92
84
260–262
—
H
3
CO
OCH
3
OCH
3
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CHO
OH
1
4k
4l
25
33
210–212 209–211 [28]
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2
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1
4m 35
N
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5 2
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Laxmikant D. Chavan et al. / Chinese Journal of Catalysis 36 (2015) 1054–1059
1059
Graphical Abstract
Chin. J. Catal., 2015, 36: 1054–1059 doi: 10.1016/S1872-2067(15)60830-0
KSF supported 10-molybdo-2-vanadophosphoric acid as an efficient and reusable catalyst for the one-pot synthesis of
2,4,5-trisubstituted imidazole derivatives under solvent-free condition
Laxmikant D. Chavan, Sunil G. Shankarwar *
Dr. Babasaheb Ambedkar Marathwada University, India
CHO
O
N
2
0% H PMo10V2O4 0 / KSF
5
NH OAC
4
Solvent-free
110 o
C
R
O
N
H
R
Twenty percent 10-molybdo-2-vanadophosphoric acid supported on KSF clay acts as an efficient, green and reusable solid acid catalyst
for one-pot synthesis of 2,4,5-trisubstituted imidazole derivatives.
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