HClO4-sio2 nanoparticles: An efficient and versatile catalyst for synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles

Article abstract of DOI:10.3184/174751915X14229010768505

The reaction between aromatic aldehydes, malononitrile and 3-methyl-1-phenyl-2-pyrazoline-5-one catalysed by silica supported perchloric acid nanoparticles (HClO₄-sio₂ nanoparticles) in solvent H₂O under reflux provided a

Full text of DOI:10.3184/174751915X14229010768505

112 RESEARCH PAPER
VOL. 39 FEBRUARY, 112–114
JOURNAL OF CHEMICAL RESEARCH 2015
HClO4–SiO2 nanoparticles: an efficient and versatile catalyst for synthesis
of 1,4-dihydropyrano[2,3-c]pyrazoles
Bahareh Sadeghia*, Mona Shirkhania and Alireza Hassanabadib
aDepartment of Chemistry, Yazd Branch, Islamic Azad University, PO Box 89195-155, Yazd, Iran
bDepartment of Chemistry, Zahedan Branch, Islamic Azad University, PO Box 98135-978, Zahedan, Iran
The reaction between aromatic aldehydes, malononitrile and 3‑methyl‑1‑phenyl‑2‑pyrazoline‑5‑one catalysed by silica
supported perchloric acid nanoparticles (HClO4–SiO2 nanoparticles) in solvent H2O under reflux provided a simple and efficient
one‑pot route for the synthesis of 1,4‑dihydropyrano[2,3‑c]pyrazoles in excellent yields.
Keywords: HClO4–SiO2 nanoparticles, 1,4-dihydropyrano[2,3-c]pyrazoles, 3-methyl-1-phenyl-2-pyrazoline-5-one, aromatic
aldehydes, malononitrile
Green chemistry is the design of chemical products and
processes that reduce or eliminate the use or generation of
hazardous substances. Organic reactions in water without
using hazardous organic solvents have attracted a great deal of
interest in both academic and industrial research because, in
addition to environmental concerns, there are beneficial effects
of aqueous solvents on the rate and selectivity of important
organic transformations.1
of 3-methyl-1-phenyl-2-pyrazoline-5-one 1, an aromatic
aldehyde 2 and malononitrile 3 in the presence of 0.006 g
HClO4–SiO2 NPs catalyst in water (Scheme 1).
Thestablecatalystiseasilyprepared11 andusedforpreparation
of 1,4-dihydropyrano[2,3-c]pyrazole derivatives. To optimise
the reaction conditions, the reaction of benzaldehyde,
malononitrile and 3-methyl-1-phenyl-2-pyrazoline-5-one
was used as a model reaction. In order to establish the better
catalytic activity of HClO4–SiO2 NPs, we have compared the
reaction using other catalysts at room temperature and for
20 min. The results are listed in Table 1. The results show that
HClO4–SiO2 NPs is a more efficient catalyst with respect to the
reaction time and exhibits broad applicability giving products
in similar or better yield (Table 1, entry 5).
There are
a many procedures described to prepare
1,4-dihydropyrano[2,3-c]pyrazoles such as one-pot three-
component condensations of malononitrile, aldehyde and
3-methyl-1-phenyl-2-pyrazolin-5-one using KF/Al2O3 in DMF at
room temperature,2 sulfamic acid in ethanol,3 CsF,4 solvent-free
reaction conditions along with microwave irradiation technique
using piperidine as the base have also been introduced for the
synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles.5 but most of
them are toxic. The need to reduce the amount of toxic waste
and by-products arising from chemical processes requires
increasing emphasis on the use of less toxic and environmentally
compatible materials in the design of new synthetic methods.
One of the most promising approaches is using water as reaction
media. Recently, much attention has focused on the use of water
as green solvent in various organic transformations. Water is a
desirable solvent for chemical reactions because it is safe, non-
toxic, environmentally friendly, readily available, and cheap
compared to organic solvents.5–8 Hence, we have developed an
efficient procedure for the one-pot three-component synthesis
of biologically active 1,4-dihydropyrano[2,3-c]pyrazoles in the
presence of HClO4–SiO2 nanoparticles (HClO4–SiO2 NPs) as a
solid phase acidic catalyst, and application of environmentally
benign water and solid acid catalyst represents powerful green
procedure.
In order to determine the optimum quantity of HClO4–SiO2
NPs, model reaction was carried out at reflux in water condition.
HClO4–SiO2 NPs (0.006 g) gave an excellent yield in 20 min
(Table 2, entry 2). We performed the effect of various solvents
on the synthesis of 4a. This reaction was carried out in various
solvents such as water, ethanol, and CH2Cl2. The best results
in terms of yield and time obtained in water and the results are
listed in Table 2 (Table 2).
It is also found that HClO4–SiO2 NPs can be effectively
recovered from the reaction mixture during the work-up
procedure. After completion of the reaction the mixture was
filtered off to separate the catalyst and then dry the solid
Table 1 Evaluation of the activity of different catalysts and HClO4–SiO2
NPs for the synthesis of 4a
Entry
Catalyst
Time/min
Yield/%a
1
2
3
4
5
–
20
20
20
20
20
10
40
65
75
94
KF/Al2O3
Sulfamic acid
CsF
Results and discussion
In continuation of our investigations of the application of solid
acids in organic synthesis9–11 we investigated the synthesis of
1,4-dihydropyrano[2,3-c]pyrazole derivatives by condensation
HClO4–SiO2 NPs
aIsolated yield.
Ar
H3C
H3C
CN
CN
O
O
HClO4-SiO2 Nanoparticles
Reflux,
+
+
N
N
N
H O ,
20 min
Ar
H
2
CN
N
O
NH2
Ph
3
2
Ph
1
4
Scheme 1 The condensation of aromatic aldehydes, malononitrile and 3–methyl‑1‑phenyl‑2‑pyrazoline‑5‑one using HClO4–SiO2 NPs as a catalyst.
* Correspondent. E-mail: sadeghi@iauyazd.ac.ir

JOURNAL OF CHEMICAL RESEARCH 2015 113
Table 2 Optimisation amount of HClO4–SiO2 NPs for the synthesis of 4aa
Entry
Catalyst (amount)
Cond./Sol.
Time/min
Yield/%b
1
2
3
4
5
6
7
HClO4–SiO2 NPs (0.004 g)
HClO4–SiO2 NPs (0.006 g)
HClO4–SiO2 NPs (0.008 g)
HClO4–SiO2 NPs (0.006 g)
HClO4–SiO2 NPs (0.006 g)
HClO4–SiO2 NPs (0.006 g), 2nd run
HClO4–SiO2 NPs (0.006 g), 3rd run
100 °C/H2O
100 °C/H2O
100 °C/H2O
80 °C/EtOH
40 °C/CH2Cl2
100 °C/H2O
100 °C/H2O
20
20
20
20
20
20
20
85
94
95
87
83
88
85
aReaction condition: 5 mL of solvent under reflux, 1 mmol of benzaldehyde, 1 mmol of 3‑methyl‑1‑phenyl‑2‑pyrazoline‑
5‑one, and 1 mmol of malononitrile.
bIsolated yields.
Preparation of compounds 4a–g; general procedure
mixture of 3-methyl-1-phenyl-2-pyrazoline-5-one (1 mmol),
residue. When the model reaction was carried out by the
recovered HClO4–SiO2 NPs for two cycles, the corresponding
1,4-dihydropyrano[2,3-c]pyrazole was obtained in good yield.
To study the scope of the reaction, a series of aromatic
aldehydes, malononitrile and 3-methyl-1-phenyl-2-pyrazoline-
5-one catalysed by HClO4–SiO2 NPs were examined. The
results are shown in Table 3. In all cases, aromatic aldehyde
substituted with either electron-donating or electron-
withdrawing groups underwent the reaction smoothly and gave
products in excellent yields.
A
aromatic aldehyde (1 mmol), malononitrile (1 mmol), HClO4–SiO2
NPs (0.006 g) and H2O (5 mL) was placed in a round-bottom flask.
The materials were mixed and refluxed in water for the 20 min. After
completion of the reaction, the solvent was evaporated and then,
dichloromethane was added to the mixture and filtered to remove
the catalyst. By evaporation of the solvent, the crude product was
re-crystallised from hot ethanol to obtain the pure compound.
1
The compounds 4a–g were characterised by their H NMR
and IR spectroscopy and elemental analyses.5,12
In summary, HClO4–SiO2 NPs has been prepared as a
new catalyst and it has advantages in the preparation of
1,4-dihydropyrano[2,3-c]pyrazole such as shorter reaction
times, simple work-up, and affords excellent yield. The solid
phase acidic catalyst was re-usable several times without
appreciable loss of activity. The present method does not involve
any hazardous organic solvent. Therefore, this procedure could
be classified as green chemistry.
Experimental
Melting points were determined with an Electrothermal 9100
apparatus. Elemental analyses were performed using a Costech ECS
4010 CHNS–O analyser. IR spectra were recorded on a Shimadzu
IR-470 spectrometer. 1H NMR spectra were recorded on Bruker
DRX-500 Avance spectrometer for solutions in d6-DMSO using TMS
as an internal standard. The chemicals for this work were purchased
from Fluka (Buchs, Switzerland) and were used without further
purification. HClO4–SiO2 NPs was prepared as previously described
in the literature.11
The reagent was prepared by a combination of 70% aqueous HClO4
(1.8 g, 12.5 mmol) and 23.7 g of nano silicagel in 70 mL diethyl
ether were stirred for 3 h at room temperature. The mixture was
concentrated and the residue dried under vacuum at 100 °C for 72 h to
afford HClO4–SiO2 NPs (0.5 mmol g–1) as a free flowing power. The
dimensions of nanoparticles were observed with SEM (Fig. 1). The
sizes of particles are between 20 and30 nm.
Fig. 1 The SEM images of HClO4–SiO2 NPs.
Table 3 Reaction between an aromatic aldehyde, malononitrile and 3–methyl‑1‑phenyl‑2‑pyrazoline‑5‑one using
HClO4–SiO2 NPs (0.006 g) in H2O at reflux.
M.p./°C
Entry
Ar
Product
Time/min
Yield/%
Found
171–172
177–179
176–177
173–176
196–198
213–215
191–193
Reported [Ref.]
170–171 [5]
177–178 [12]
175–176 [5]
171–172 [5]
195–196 [5]
210–212 [12]
190–191 [5]
1
2
3
4
5
6
7
C6H5
4‑MeC6H4
4‑ClC6H4
4‑MeOC6H4
4‑NO2C6H4
4‑OHC6H4
3‑NO2C6H4
4a
4b
4c
4d
4e
4f
20
20
20
20
20
20
20
94
86
91
93
87
85
91
4g
aPure isolated product.

114 JOURNAL OF CHEMICAL RESEARCH 2015
1
4a: H NMR (DMSO-d6, 500 MHz) δH (ppm): 1.90 (s, 3H, CH3),
Received 4 January 2015; accepted 23 January 2015
Paper 1503119 doi: 10.3184/174751915X14229010768505
Published online: 13 February 2015
4.66 (s, 1H,), 4.71 (s, 2H, NH2), 7.13–7.30 (m, 10H, Ph); IR (KBr) (νmax
cm−1): 3468, 3315, 2184, 1660.
4b: 1H NMR (DMSO-d6, 500 MHz) δH (ppm): 1.75 (s, 3H, CH3), 2.32
(s, 3H, CH3), 4.60 (s, 1H), 6.90 (s, 2H, NH2), 7.03–7.84 (m, 9 H, Ph); IR
(KBr) (νmax, cm−1): 3419, 3310, 2165, 1652.
4c: 1H NMR (DMSO-d6, 500 MHz) δH (ppm): 1.81 (s, 3H, CH3), 4.78
(s, 1H), 6.30 (s, 2H, NH2), 7.31–7.80 (m, 9 H, Ph); IR (KBr) (νmax, cm−1):
3473, 3329, 2201, 1659.
4d: 1H NMR (DMSO-d6, 500 MHz) δH (ppm): 1.71 (s, 3H, CH3), 3.76
(s, 3H, CH3), 4.83 (s, 1H), 6.94 (s, 2H, NH2), 6.87–7.59 (m, 9 H, Ph); IR
(KBr) (νmax, cm−1): 3392, 3325, 2190, 1660.
4e: 1H NMR (DMSO-d6, 500 MHz) δH (ppm): 1.81 (s, 3H, CH3), 4.92
(s, 1H), 6.95 (s, 2H, NH2), 7.30–8.26 (m, 9 H, Ph); IR (KBr) (νmax, cm−1):
3432, 3345, 2197, 1666.
4f: 1H NMR (DMSO-d6, 500 MHz) δH (ppm): 1.78 (s, 3H, CH3), 4.51
(s, 1H), 6.73–7.80 (m, 9 H, Ph), 7.14 (s, 3H, OH, NH2); IR (KBr) (νmax
cm−1): 3414, 3323, 2172, 1653.
,
References
1
2
C-J. Li, Chem. Rev., 2008, 105, 3095.
X.S. Wang, D.Q. Shi, L.C. Rong, C.S. Yao and G.Y. Dai, Jiego Huaxue,
2003, 22, 331.
3
4
S.V. Shinde, W.N. Jadhav, J.M. Kondre, S.V. Gampawar and N.N. Karade,
J. Chem. Res.,2008, 278.
B. Wang, Y.L. Gu, C. Luo, T. Yang, L.M. Yang and J.S. Suo, Tetrahedron
Lett., 2004, 45, 3369.
5
6
J.F. Zhou, S.J. Tu, Y. Gao and M. Ji, Chin. J. Org. Chem., 2001, 21, 742.
C.J. Li and T.H. Chan, Organic reactions in aqueous media, Wiley: New
York (1997).
7
P.A. Grieco, Ed. Organic synthesis in water. Thomson Science, Glasgow,
1998.
8
9
C.J. Li, Chem. Rev., 2005, 105, 3095.
B. Sadeghi, A. Hassanabadi and S. Bidaki, J. Chem. Res., 2011, 35, 666.
,
10 B. Sadeghi, A. Hassanabadi and E. Taghvatalab, J. Chem. Res., 2011, 35,
707.
11 B. Sadeghi, J. Chem. Res., 2013, 37, 171.
12 T.S. Jin, R.Q. Zhao and T.S. Li, Arkivoc, 2006, xi, 176.
4g: 1H NMR (DMSO-d6, 500 MHz) δH (ppm): 1.92 (s, 3H, CH3), 4.77
(s, 1H), 4.95 (s, 2H, NH2), 8.10–8.98 (m, 9 H, Ph); IR (KBr) (νmax, cm−1):
3456, 3324, 2196, 1660.

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