Boehmite silylpropyl amine sulfamic acid as an efficient and recyclable catalyst for the synthesis of some pyrazole derivatives

Article abstract of DOI:10.2174/1570178614666170505113009

The design of biologically-active compounds is a challenging viewpoint in medicinal chemistry, and pyrazoles play a crucial role as biologically-active molecules. Methods: Up to now, a few examples have been reported for the synthesis of pyrazoles catalyz

Full text of DOI:10.2174/1570178614666170505113009

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RESEARCH ARTICLE
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Boehmite Silylpropyl Amine Sulfamic Acid as an Efficient and Recyclable
Catalyst for the Synthesis of some Pyrazole Derivatives
BENTHAM
S
CIENCE
Rahele Doosti1, Mohammad Bakherad1,*, Mahdi Mirzaee1,* and Khosrow Jadidi2
2
1School of Chemistry, Shahrood University of Technology, Shahrood 3619995161, Iran; Department of Chemistry,
Shahid Beheshti University, Tehran 1983963113, Iran
Abstract: Background: The design of biologically-active compounds is a challenging viewpoint in
medicinal chemistry, and pyrazoles play a crucial role as biologically-active molecules.
Methods: Up to now, a few examples have been reported for the synthesis of pyrazoles catalyzed by
heterogeneous catalysts. In this work, a new boehmite silylpropyl amine sulfamic (m-SABNPs) was
applied as a catalyst for one-pot synthesis of pyrazole derivatives.
A R T I C L E H I S T O R Y
Results: It was found that this heterogeneous sulfamic acid is a highly efficient catalyst for the synthe-
Received: November 23, 2016
ses of 5-amino-1,3-aryl-1H-pyrazole-4-carbonitriles and pyrazolopyranopyrimidines in good to excel-
Revised: February 25, 2017
lent yields and can be recovered by a simple filtration of the reaction solution and reused for five con-
Accepted: April 06, 2017
secutive runs without significant loss of catalytic activity. Moreover, its structure was characterized by
DOI:
10.2174/1570178614666170505113009
FT-IR spectroscopy, TGA, XRD, TEM and SEM techniques.
Conclusion: An efficient, and convenient method was proposed for the synthesis of pyrazole deriva-
tives catalyzed by heterogeneous sulfamic acid in high-to-excellent yields. This method offers several
advantages like milder reaction condition, shorter reaction time, cleaner reaction, and reusability of the
catalyst.
Keywords: Boehmite nanoparticle, reusable catalyst, sulfamic acid, pyrazoles.
1. INTRODUCTION
oxosulfate vanadium(IV) and hexacarbonyl molybdenum
complexes anchored onto the amine and/or Schiff base func-
tionalized BNPs [4-6].
Sulfamic acid (NH2SO3H, SA) is an odorless, non-volatile,
non-hygroscopic, incorrodible, crystalline solid acid with
outstanding catalytic properties in the heterocyclic synthesis.
Moreover, the catalytic activity of solid acids could be effi-
ciently increased by their immobilization onto a nanomate-
rial solid support with a high surface area. When the size of
such a support decreases to a nanometer scale, surface area
considerably increases, and the support can be evenly dis-
persed in solution to form a homogenous emulsion [1].
Pyrazoles and their derivatives are extensively used as
pharmaceuticals and agrochemicals, the earliest example,
antipyrine, dating from 1884 [7, 8]. Literature survey has
revealed that a number of methods have been reported for
the synthesis of pyrazole nucleus [9-11]. On the other hand,
only a few examples of the synthesis of pyrazoles in the
presence of heterogeneous catalysts such as CsF-Al2O3 [12],
silica chloride [13], and CuO/ZrO2 [14] have been mentioned
in the literature. In continuation of our studies on the applica-
tion of BNPs in organic synthesis [15, 16], herein we wish to
report a simple, rapid, and green synthetic method for the
syntheses of 5-amino-1,3-aryl-1H-pyrazole-4-carbonitriles, di-
hydropyrano[2,3-c]pyrazoles, and pyrazolopyranopyrimidines,
catalyzed by BNPs -sulfamic acid (m-SABNPs) (Scheme 1).
Boehmite is aluminum oxide hydroxide (γ-AlOOH), com-
prising additional hydroxyl groups on its surface. Among the
various techniques utilized for the production of BNPs, the
hydrothermal-assisted sol-gel hydrolysis of aluminum alkox-
ides, which is a one-pot procedure at low temperature, was
used in this work. The most encouraging property of this
method is the development of a crystalline single-phase
product with no organic residues [2, 3]. Mirzaee et al. have
recently reported the epoxidation of different olefins using
2. RESULTS AND DISCUSSION
2.1. Catalyst Preparation
*Address correspondence to these author at the School of Chemistry, Shah-
rood University of Technology, Shahrood 3619995161, Iran;
Tel: +982332395441; E-mails: m.bakherad@yahoo.com;
mmirzaee@shahroodut.ac.ir
m-SABNPs was prepared as shown in Scheme 2. Ini-
tially, BNPs were prepared according to a reported procedure
[2]. Then it was refluxed with trimethoxysilylpropyl amine
1875-6255/17 $58.00+.00
© 2017 Bentham Science Publishers

Boehmite Silylpropyl Amine Sulfamic Acid as an Efficient
Letters in Organic Chemistry, 2017, Vol. 14, No. 6 451
H2N
solvent-free / 80 ˚C
CN
(a)
ArCHO
PhNHNH2
+
+
NC
CN
N
Ph
m-SABNPs (0.02 mmol)
2
N
3
1
Ar
Ar
6
O
O
O
O
H2O / 50 ˚C
NH
ArCHO
NH2NH2
+
+
(b)
NH
+
N
m-SABNPs (0.02mmol)
2
N
O
N
H
S
1
O
O
N
S
4
H
5
H
7
Scheme (1). Synthesis of 5-amino-pyrazole-4-carbonitrile derivatives (a), pyrazolopyranopyrimidine derivatives (b) in the presence of BNPs
-sulfamic acid catalyst.
OH
OH
OH
OH
OH
NH2
Hydrothermal
hydrolysis
5h / 100 ˚C
(MeO)3Si
(MSPA)
NH2
Al(OSBu)3
O
O
Si
OH
reflux,24h, dry toluene
OH
OH
OH
(AFBNPs)
(BNPs)
Me3SiCl
r.t.,24,dry CH2Cl2
OH
Si(CH3)3
O
OH
Si(CH3)3
O
O
OH
S
O
N
NH2
ClSO3H
r.t., 6h, dry CH2Cl2
O
O
H
O
Si
OH
Si
OH
O
O
O
Si(CH3)3
Si(CH3)3
(m-AFBNPs)
(m-SABNPs)
Scheme (2). Synthesis of m-SABNPs catalyst.
(MSPA) in dry toluene for 24 h in order to graft the –O3Si
(CH2)3NH2 group on the hydroxyl-covered surface of BNPs,
affording amino functional boehmit nanoparticles (AFBNPs).
Then some of the unreacted surface hydroxyl groups in
AFBNPs were blocked using trimethylsilyl chloride in order
to stabilize the catalyst in acidic media. The amine groups in
the methylated product (m-AFBNPs) were then changed to
sulfamic acid by reaction with chlorosulfunic acid, which led
to the formation of m-SABNPs. The catalyst produced was
characterized by FT-IR spectroscopy, and the TGA, DTA,
XRD, BET, TEM, SEM, and EDX techniques.
BNPs characteristic bands, showed new bands at 2939 and
1566 cm-1, which were assigned to the ν(C-H) and ν(N-H)
stretching of the grafted n-propyl amine groups, respectively.
Partial blocking the surface hydroxyl groups in AFBNPs was
confirmed by significant reductions in the ν(O-H) stretching
of both the m-AFBNPs and m-SABNPs samples in the range
of 3300-3400 cm-1 (Figs. 1c and d). Elimination of some sur-
face hydroxyl groups also clearly reduced the Al-OH-related
vibrations in the FT-IR spectrum of m-AFBNPs (Fig. 1c).
Anew growth of the eliminated band in the range of 940-
1080 cm-1 in the FT-IR spectrum of m-SABNPs, which was
assigned to the SO3-H moiety, confirmed the support of sul-
famid acid onto the surface of BNPs.
2.2. Catalyst Characterization
Fig. (2) shows the XRD patterns for the BNPs, AFBNPs,
m-AFBPNs, and m-SABNPs samples. The PXRD pattern for
BNPs (Fig. 2a) confirmed crystallization of the single-phased
boehmite [2]. The PXRD patterns for AFBNPs, m-AFBNPs
and m-SABNPs (Figs. 2b, 2c and 2d) clearly showed the
retention of the boehmite structure during functionalization,
partial hydroxyl group blocking and preparation of the
The FT-IR spectra for BNPs (a), AFBNPs (b), m-AFBNPs
(c), and m-SABNPs (d) are showed in Fig. (1). A broad band
was observed in the range of 3400-3300 cm-1 in the BNPs and
AFBNPs samples, which was assigned to the ν(O-H) stretch-
ing of their surface hydroxyl groups. BNPs also showed its
characteristic bands in 1076, 756, and 493 cm−1, which were
assigned to the ν (O-H) stretching and δ (Al-OH) groups.
The IR spectrum for AFBNPs (Fig. 1b), in addition to the

452 Letters in Organic Chemistry, 2017, Vol. 14, No. 6
Doosti et al.
Fig. (1). FT-IR spectra for BNPs (a), AFBNPs (b), m-AFBNPs (c), and m-SABNPs (d).
700
600
500
400
300
200
100
0
d
c
b
a
10
20
30
40
50
60
70
80
2ꢀ
Fig. (2). XRD patterns for BNPs (a), AFBNPs (b), m-AFBPNs (c), and m-SABPNs (d).
a
b
Fig. (3). Transmission electron microscopy images for BNPs (a) and m-SABNPs (b).

Boehmite Silylpropyl Amine Sulfamic Acid as an Efficient
Letters in Organic Chemistry, 2017, Vol. 14, No. 6 453
a
b
Fig. (4). Scanning electron micrographs for BNPs (a) and m-SABPNs (b).
m-SABNPs catalyst. Calculation of the average particle size
using the PXRD pattern according to the Scherer equation
showed 10-nm particles for BNPs. This was confirmed by
the transmission electron microscopy (TEM) images for
BNPs and m-SABNPs (Figs. 3a and 3b). In these images,
needle-shaped BNPs can be seen over 50-nm long and up to
10-nm wide.
of covalently grafted sulfamid acid onto the surface of 1.00 g
of m-SABNPs.
Fig. (6) shows the TG/DTG thermogram of the m-
SABPNs catalyst. There are two important weight loss re-
gions in the TG curve. The first one is in the temperature
range of 110-360ºC, accompanied by an endothermic peak in
DTG curve, which could be related to the decomposition of
the organic residue onto the surface of BNPs. The other
weight loss was observed in the temperature range of 470-
560ºC, accompanied by other endothermic peaks in the DTG
curve, which could be related to the dehydroxylation of
boehmite and the crystallization of γ-alumina.
The surface morphology of the BNPs and m-SABNPs
samples were also investigated by scanning electron micros-
copy (Fig. 4). These micrographs showed that the surface
morphology of BNPs changed completely during the prepa-
ration of the m-SABNPs catalyst, and that its surface poros-
ity was wiped out. This was also confirmed by comparison
of the BET surface areas of the samples at different stages
during the catalyst preparation. The BET results showed that
the surface area of this sample decreased dramatically by
amine functionalization of BNPs from 326 to 27 m2/g. The
BET decrease was continued by changing the amine group to
sulfamic acid with a slower rate, and the BET surface area of
the m-SABNPs catalyst reached only 6 m2/g.
EDX analysis (Fig. 5) also confirmed the presence of
sulfur atoms on the surface of m-SABNPs in addition to the
carbon, oxygen, nitrogen, aluminum, and silicon atoms.
Furthermore, elemental analysis showed that the nitrogen
content of AFBNPs was 0.93%, which meant that 0.66 mmol
of the pendant amine groups were covalently bounded to the
surface of 1.00 g of AFBNPs. According to this analysis, the
carbon content of m-AFBNPs was 18.8 mmol that by con-
sidering of those related to amine groups, it showed that 5.6
mmol trimethylsilane were covalently bounded to the surface
of 1.00 g of m-AFBNPs for partial blocking of surface hy-
droxyl groups. This is the minimum amount of this blocking
agent which could protect the catalyst from dissolving in
acidic medium of the next step of catalyst preparation. Also,
this analysis showed that the sulfur content of m-SABNPs
was 1.95%, which confirmed that 92.4% of the amine groups
were changed to sulfamid acid, and it contained 0.61 mmol
Fig. (5). EDX analysis of m-SABPNs.

454 Letters in Organic Chemistry, 2017, Vol. 14, No. 6
Doosti et al.
20
0
0
-10
-20
-30
-40
-50
-60
-70
-80
a
-20
b
-40
-60
-80
-100
-120
-140
0.00
100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00
Temperature [ºC]
Fig. (6). TGA diagram of m-SABPNs catalyst (a) and DTA diagram of m-SABPNs catalyst (b).
Table 1. Optimization of reaction conditions for synthesis of 6aa.
H2N
CN
Ph
Catalyst
N
Ph
PhCHO
PhNHNH2
+
+
NC
CN
N
6a
Entry
Solvent
Catalyst (mg)
Temp. (ºC )
Time (min)
Yield (%)b
1
2
H2O
30
30
30
30
30
30
30
30
30
50
10
----
30
Reflux
Reflux
80
120
150
120
120
120
120
120
45
60
45
75
35
30
10
40
95
94
92
87
20
49
EtOH
3
DMF
4
CH3CN
Reflux
Reflux
Reflux
Reflux
80
5
THF
6
1,4-dioxane
CHCl3
7
8
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
9
100
45
10
11
12
13c
80
45
80
60
80
180
45
80
aReaction conditions: benzaldehyde (1.0 mmol), phenyl hydrazine (1.0 mmol), malononitrile (1.0 mmol), catalyst, solvent (3 mL).
bIsolated yield.
cIn the presence of BNPs.
2.3. Catalytic Activity
tions at 80ºC were higher than those obtained in solvents like
H2O, EtOH, DMF, CH3CN, THF, 1,4-dioxane, and CHCl3
(Table 1, entries 1-7). Increasing the temperature did not
improve the reaction yield (Table 1, entry 9). Also the yield
was reduced by increasing the amount of m-SABNPs (Table
1, entry 10). When the reaction was carried out in the ab-
sence of a catalyst, only a low product yield was obtained,
even after the reaction time was prolonged to 3 h (Table 1,
In our initial screening experiments, benzaldehyde, phen-
ylhydrazine, and malononitrile were selected as the model
substrates to optimize the reaction conditions, and the results
obtained were tabulated in Table 1. Firstly, several solvents
were screened for the reaction in the presence of a catalytic
amount of m-SABNPs. The results obtained showed that the
efficiency and yield of the reaction under solvent-free condi-

Boehmite Silylpropyl Amine Sulfamic Acid as an Efficient
Letters in Organic Chemistry, 2017, Vol. 14, No. 6 455
Table 2. Synthesis of 5-amino-pyrazole-4-carbonitrile derivatives 6a.
H2N
CN
solvent-free / 80 ˚C
ArCHO
PhNHNH2
+
+
NC
CN
N
Ph
m-SABNPs (0.02 mmol)
N
Ar
6
Entry
Ar
Product
Reaction Time (min)
Yield (%)b
M.p. (ºC) (Lit.) [Ref.]
1
2
C6H5
6a
6b
6c
6d
6e
6f
45
50
45
50
40
35
40
45
50
30
25
35
25
25
20
35
35
25
35
30
95
87
90
86
91
91
88
94
93
90
92
90
93
86
94
93
95
85
89
95
160-162(159-160) [17]
115-117(118-120) [18]
101-103(106-108) [18]
126-128(130-132) [17]
100-102(105-107) [17]
160-161(160-161) [19]
Oil
4-Me-C6H4
4-MeO-C6H4
2-MeO-C6H4
4-Me2N-C6H4
2-OH- C6H3
3
4
5
6
7
2-OH-4-OMe- C6H3
3,5-(OMe)2-4-OH-C6H2
2,3,4-(OMe)3-C6H2
4-Cl-C6H4
6g
6h
6i
8
175-177
9
146-148
10
11
12
13
14
15
16
17
18
19
20
6j
128-130(128-130) [17]
134-136(245-247) [20]
150-152
2,4-Cl2C6H3
6k
6l
2,6-Cl2C6H3
2-F- C6H4
6m
6n
6o
6p
6q
6r
6s
93-95
3-F- C6H4
110-112
4-F- C6H4
Oil(oil) [21]
3-Br- C6H4
80-82
4-Br- C6H4
157-160(163-165) [21]
160-162(160-161) [19]
121-123(129-130) [19]
163-165(164-166) [18]
2-NO2-C6H4
3-NO2-C6H4
4-NO2-C6H4
6t
aReaction conditions: aldehyde (1.0 mmol), phenyl hydrazine (1.0 mmol), malononitrile (1.0 mmol), catalyst (0.02 mmol m-SABNPs), solvent free, 80ºC.
bIsolated yield.
entry 12). To find out the roles of BNPs and m-SABNPs
during the reactions, synthesis of pyrazole 6a was examined
in the presence of BNPs. As shown in Table 1, the products
were obtained in 49% yield in the presence of BNPs. The
generality of this three-component reaction was studied un-
der the optimal reaction conditions by varying the structures
of the aldehydes involved. The results obtained are summa-
rized in Table 2.
were condensed into the corresponding 5-amino-1,3-aryl-
1H-pyrazole-4-carbonitriles in high yields.
The excellent efficiency of m-SABNPs, as a catalyst, in
the synthesis of pyrazoles motivated us to explore its effi-
cacy for the synthesis of the pyranopyrazolopyrimidine de-
rivatives. For this purpose, the condensation reaction of ben-
zaldehyde, hydrazine hydrate, malononitrile, and thiobarbi-
turic acid were taken into consideration using the catalyst
0.02 mmol (30 mg) in water (Table 3). As shown in Table 3,
in the absence of the catalyst, low product yields were ob-
tained after 1 h (Table 3, entries1-2). Also the impact of the
temperature on the conversion was studied, and the results
obtained were tabulated in Table 3. It is obvious that at room
temperature, low yield of 7a was formed (Table 3, entry 2).
With increase in the temperature from room temperature to
80ºC, the yield of 7a was found to increase. We obtained the
As shown in this table, the variation in the electronic
properties and the position of the functional groups on the
aromatic ring of the aldehyde did not show a clear effect on
the reaction yields. Furthermore, the steric effects of the sub-
stituents at the ortho-position of the aromatic aldehyde did
not have a clear effect on the reaction yields. On the other
hand, benzaldehydes with electron-donating groups (Table 2,
entries 2-9) or electron-withdrawing groups (entries 10-20)

456 Letters in Organic Chemistry, 2017, Vol. 14, No. 6
Doosti et al.
Table 3. Effects of various solvents and temperature on synthesis of pyranopyrazolopyrimidine 7aa.
O
O
Ph
O
Catalyst
NH
PhCHO
NH2NH2
+
+
NH
+
N
N
O
N
H
S
O
O
O
N
S
H
H
7a
Entry
Solvent
Reaction Temp. (ºC)
Time (min)
Yield (%)c
1b
2
H2O
H2O
r.t
r.t
60
60
15
15
60
15
15
15
15
15
15
5
35
3
H2O
50
80
50
50
50
50
50
50
50
95
4
H2O
95
5
Neat
48
6
EtOH
CHCl3
DMF
72
7
43
8
83
9
THF
Trace
28
10
11
CH3CN
1,4-dioxane
15
aReaction conditions: Ethyl acetoacetate (1.0 mmol), hydrazine hydrate (1.0 mmol), benzaldehyde (1.0 mmol), thiobarbituric acid (1.0 mmol), catalyst.
bCatalyst-free.
cIsolated yield.
benzaldehyde, phenylhydrazine, and malononitrile at 80ºC
under solvent-free conditions. As shown in Fig. (7), the cata-
lyst was recovered by a simple filtration, and reused over 5
runs without a substantial decrease in its activity even after 5
runs. The average yield for five successive runs was 93%,
which obviously shows the practical recyclability of this
catalyst.
best results at 50ºC (Table 3, entry 3). When the reaction was
carried out under solvent-free conditions, the target product
was obtained in low yield (Table 3, entry 5). Moreover, the
model reaction was examined in the presence of m-SABNPs
at 50ºC in several solvents including EtOH, CHCl3, DMF,
THF, CH3CN, and 1,4-dioxane (Table 3, entries 6-11).
Among all these solvents, H2O was found to be the best one,
affording the highest product yield (Table 3, entry 3).
Also various pyranopyrazolopyrimidine derivatives were
synthesized via four-component condensation reactions of
several aromatic aldehydes, hydrazine hydrate, malononi-
trile, and thiobarbituric acid under the same reaction condi-
tions (Table 4). As it is evident in this table, all reactions
proceeded efficiently, and the desired products were pro-
duced in good-to-high yields in relatively short reaction
times without the formation of any by-product. The reactions
proceeded rapidly for the aromatic aldehydes with electron-
withdrawing or electron-donating groups at different posi-
tions of the ring (Table 4, entries 1-10) and heteroaryl alde-
hydes (Table 4, entries 11-13), and the desired products were
isolated in high yields without any side-product formation in
short reaction times.
95
95
93
91
89
100
80
60
40
1
2
3
4
5
Fig. (7). Synthesis of product 6a catalyzed by recycled catalyst.
2.4. Catalyst Recyclability
3. EXPERIMENTAL
The reusability of a catalyst is one of its most significant
advantages, and makes it useful for industrial and commer-
cial applications. Therefore, the reusability of the m-
SABNPs catalyst was investigated for the reaction between
All the chemicals used were purchased from Merck or
Fluka Chemical Companies. All the known compounds were
identified by comparison of their melting points and 1H

Boehmite Silylpropyl Amine Sulfamic Acid as an Efficient
Letters in Organic Chemistry, 2017, Vol. 14, No. 6 457
Table 4. Synthesis of pyranopyrazolopyrimidine derivativesa.
O
O
O
Ar
O
H2O/50˚C
NH
ArCHO
NH2NH2
+
+
NH
+
N
m-SABNPs
N
O
N
H
S
O
O
N
S
H
H
7
Entry
Ar
Product
Reaction Time (min)
Yield (%)b
Mp (ºC) (Lit.) [Ref.]
1
2
Ph
7a
7b
7c
7d
7e
7f
15
20
20
25
15
20
20
10
10
15
20
15
20
95
91
87
90
83
94
87
90
94
90
92
93
86
222-221 (220-221) [22]
204-205
2-OH-C6H4
4-MeO-C6H4
2-MeO-C6H4
2-Cl-C6H4
3
224-225
4
219-220
5
286-287
6
2,6-Cl2-C6H3
4-Br-C6H4
226-227
7
7g
7h
7i
216-217
8
3-NO2-C6H4
4-NO2-C6H4
211-212 (212-213) [22]
234-235
9
10
11
12
13
2, 3, 4 (OMe)3-C6H2
2'-Furanyl
7j
235-236
7k
7l
205-206
2'-Thiophenyl
189-190
2'-Pyridinyl
7m
239-240
aReaction conditions: Hydrazine hydrate (1.0 mmol), ethyl acetoacetate (1.0 mmol), thiobarbituric acid (1.0 mmol), aldehyde (1.0 mmol) in 4 mL water, catalyst (0.02mmol m-
SABNPs), 50ºC.
bIsolated yield.
NMR data with the corresponding data reported in the litera-
ture. NMR spectra were recorded on a Bruker Avance 300
MHz instrument. FT-IR spectra were obtained as potassium
bromide pellets in the range of 400-4000 cm−1 on a Bomem
MB series spectrometer. Powder X-ray diffraction (XRD)
patterns were collected using a Philips PW-1800 or STOE
diffractometer with Cu Kα radiation. Elemental analyses
were performed using a Thermo Finnigan Flash EA micro-
analyzer. Electron microscopy was performed with a JEOL
JSM-6360LV transmission electron microscope (TEM).
Scanning electron microscopy (SEM) studies were con-
ducted on a MIRA3TESCAN-XMU instrument. Thermogra-
vimetric (TG) analyses were carried out with a Rheometric
trimethoxysilane. The solution was refluxed for 24 h, and the
amine-functionalized BPNs powder (AFBNPs) obtained was
filtered-off, washed with toluene (2 × 20 mL) and methanol
(2 × 20 mL), and dried in vacuum at 100 ºC for 10 h. Then
1.0 g of AFBNPs was dispersed in 30 mL of dichloro-
methane, and 10 mmol (1.08 g) of trimethylsillyl chloride
was added to this suspension. After stirring the mixture for
24 h at room temperature, the methylated AFBNPs powder
(m-AFBNPs) obtained was filtered-off and washed for 3
times with dichloromethane, toluene, and acetone, and dried
at 70ºC for 3 h. Then 1.0 g of m-AFBNPs was dispersed in
dry dichloromethane in ultrasonic bath for 10 min. Subse-
quently, 5 mmol (0.58 g) chlorosulfonic acid was added
dropwise over a period of 10 min, and the mixture was
stirred for another 6 h at room temperature. Then, the final
sulfamid-supported product (m-SABNPs) was filtered-off
and washed with dichloromethane, ethanol, and acetone,
respectively, to remove the unreacted compounds, and then
dried at 50ºC overnight.
Scientific STA-1500 or BAHR Thermo analyse GmbH with
-1
a heating rate of 10°C min
Emmett-Teller (BET).
in air and used Brunauer-
3.1. Preparation of Boehmite Nanoparticles-supported
Sulfamic Acid (m-SABNPs)
Aluminium 2-butoxide was prepared according to the
general method reported for the synthesis of aluminium
alkoxides. Then, it was used for the preparation of BNPs, as
reported earlier [8]. Then, 1.0 g powder prepared was added
to a 100-mL round-bottom flask, which contained 50 mL
anhydrous toluene and 5 mmol (0.89 g) of (3-aminopropyl)
3.2. General Procedure for Preparation of 5-Amino-
Pyrazole-4-carbonitrile Derivatives (6)
To a mixture of aromatic aldehyde (1.0 mmol), malononi-
trile 1.0 mmol (0.066 g), and phenyl hydrazine1.0 mmol (0.1g)
in a test tube was added 0.02mmol (30 mg) of m-SABPNs.

458 Letters in Organic Chemistry, 2017, Vol. 14, No. 6
Doosti et al.
The resulting mixture was heated with stirring at 80ºC for an
appropriate time, and the reaction progress was monitored by
TLC. At the end of the reaction, the mixture was cooled
down, and then an excess amount of hot ethanol was added
to it. Subsequently, it was filtered to remove the catalyst, and
after evaporation of the solvent, the residue was crystalized
from ethyl acetate to afford the pure product. The structures
of the compounds were characterized by the spectroscopic
data and elemental analysis, comparing them with their spec-
troscopic data and physical properties reported in the litera-
ture. In order to recover the catalyst, the separated catalyst
was washed twice with ethanol (5 mL) and reused after dry-
ing.
3.3.4. 5-Amino-3-(2-fluorophenyl)-1-phenyl-1H-
pyrazole-4-carbonitrile (6m)
1
258 mg (93% yield); H NMR (CDCl3, 300 MHz) δ:
6.79-6.84 (m, 1H, ArH), 6.94-7.10 (m, 4H, ArH), 7.15-7.24
(m, 3H, ArH), 7.69 (s, 1H, ArH), 7.91 (s, 2H, NH); 13C
NMR (CDCl3, 75 MHz) δ:67.2, 112.6, 116.8, 119.8, 123.3,
124.1, 126.6, 129.1, 130.1, 131.4, 141.2, 149.3, 156.2, 165.2;
Anal. calcd for C16H11FN4: C: 69.06; H: 3.98; N: 20.13;
found: C: 69.63; H: 3.86; N: 20.24.
3.3.5. 5-Amino-3-(3-bromophenyl)-1-phenyl-1H-
pyrazole-4-carbonitrile (6p)
308 mg (93% yield); 1H NMR (CDCl3, 300 MHz) δ: 6.94
(m, 1H, ArH), 7.15-7.86 (m, 7H, ArH), 7.86 (s, 1H, ArH),
8.10 (S, 2H, NH); 13C NMR (CDCl3, 75 MHz) δ: 57.2,
114.1, 119.3, 124.4, 128.2, 129.0, 130.6, 131.1, 132.9, 149.1,
153.7, 162.1; Anal. calcd for C16H11BrN4: C: 56.66; H: 3.27;
N: 16.52; found: C: 56.21; H: 3.24; N: 16.24.
3.3. General Procedure for Synthesis of Pyrazolopyra-
nopyrimidine Derivatives (7)
Ethyl acetoacetate 1mmol (0.13g) and m-SABPNs
0.02mmol (30 mg) were added to a solution of hydrazine
hydrate 1mmol (0.06g) in H2O. Then, an aromatic aldehyde
(1mmol) and thiobarbituric acid 1mmol (0.14g) were added
to the mixture, and the mixture was refluxed for an appropri-
ate time. The reaction progress was monitored by TLC. After
completion of the reaction, the mixture was cooled, and the
precipitate formed was filtered-off, dried, and dissolved in
hot ethyl acetate to separate the catalyst. The pure product
3.3.6. 5-Amino-3-(4-bromophenyl)-1-phenyl-1H-
pyrazole-4-carbonitrile (6q)
322 mg (95% yield); 1H NMR (CDCl3, 300 MHz) δ: 6.77
(t, 1H, j 7.2Hz, ArH), 7.10 (d, 2H, j 7.5, ArH), 7.21-7.26 (m,
2H, ArH), 7.55-7.63 (m, 4H, ArH), 7.84 (s, 2H, NH); 13C
NMR(CDCl3, 75 MHz) δ:58.1, 115.2, 119.1, 124.4, 128.2,
130.1, 131.6, 131.7, 132.4, 148.3, 153.4, 161.3; anal. calcd
for C16H11BrN4: C: 56.66; H: 3.27; N: 16.52; found: C:
56.06; H: 3.39; N: 16.35.
was obtained after recrystallization from ethyl acetate
.
3.3.1. 5-Amino-3-(2-hydroxyphenyl)-1-phenyl-1H-
pyrazole-4 carbonitrile (6f)
1
3.4. Spectral Data for Some Representative Pyra-
zolopyrano- Pyrimidine Derivatives
256 mg (91% yield); HNMR (CDCl3, 300 MHz) δ:6.79
(t,1H, j7.2 Hz, ArH), 6.86-7.00 (m,4H), 7.15-7.28 (m, 3H,
ArH), 7.56 (dd, 1H, J 1.6Hz and 7.6Hz, ArH), 8.17(S, 2H,
NH), 10.43(S, 1H, OH); 13CNMR(CDCl3, 75 MHz) δ:111.83,
115.91, 119.81, 120.21, 121.65, 125.45, 129.20, 130.05,
130.25, 138.14, 145.73, 151.02, 152.30, 156.52. Anal. calcd
for C16H12N4O: C, 69.55; H, 4.38; N, 20.28; found: C: 69.36;
3.4.1. 3-Methyl-4-(2-hydroxyphenyl)-7-thioxo-4,6,7,8-
tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-
5(1H)-one (7b)
1
298 mg (91% yield); H NMR (DMSO-d6, 300 MHz) δ:
2.29 (s, 3H), 5.65 (s, 1H), 6.97 (t, J = 7.2 Hz), 7.41 (t, J = 7.5
Hz), 7.70 (d, J = 7.2 Hz), 11.65 (s, 2H) ppm; 13C NMR
(DMSO-d6, 75 MHz) δ = 10.4, 89.1, 113.1, 114.0, 118.1,
121.1, 126.6, 128.6, 134.9, 143.5, 144.59, 152.1, 161.6,
171.9 ppm; Anal. Calcd. for C15H12N4O3S: C, 54.87; H, 3.68;
H: 4.17; N: 20.37
.
3.3.2. 5-Amino-3-(2, 3, 4-trimethoxyphenyl)-1-phenyl-
1H-pyrazole-4-carbonitrile (6i)
325 mg (93% yield); 1H NMR (CDCl3, 300 MHz) δ: 3.92
(s, 3H, OCH3), 3.94 (s, 3H, OCH3), 3.95 (s, 3H, OCH3),
6.77 (d, 1H, j 8.7, ArH), 6.89 (t, 1H, j 7.2, ArH) 7.15(d, 2H, j
7.8, ArH), 7.28-7.34(m, 1H, ArH), 7.73-7.76(m, 2H, ArH),
7.98 (S, 2H, NH); 13C NMR (CDCl3, 75 MHz) δ:56.21, 58.26,
60.21, 110.10, 115.17, 121.44, 124.43, 130.16, 131.15,
131.75, 139.18,141.39, 151.62, 152.57, 159.10; Anal. calcd
for C19H18N4O3: C: 65.13; H: 5.18; N: 15.99; found: C:
N, 17.06. Found: C, 54.66; H, 3.59; N, 17.25
.
3.4.2. 3-Methyl-4-(4-methoxyphenyl)-7-thioxo-4,6,7,8-
tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-
5(1H)-one (7c)
297 mg (87% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.21 (s, 3H), 3.68 (s, 3H), 5.36 (s, 1H), 6.76 (d, J = 8.4 Hz,
2H), 6.94 (d, J = 8.4 Hz), 10.16 (s, 2H) ppm; 13C NMR
(DMSO-d6, 75 MHz) δ = 10.0, 30.3, 55.9, 91.4, 104.9, 125.1,
132.6, 132.7, 138.8, 143.3, 148.0, 150.5, 160.6, 171.3 ppm;
Anal. Calcd. for C16H14N4O3S: C, 56.13; H, 4.12; N, 16.36.
Found: C, 56.30; H, 4.20; N, 16.55.
65.24; H: 5.17; N: 15.80
.
3.3.3. 5-Amino-3-(2, 6-dichlorophenyl)-1-phenyl-1H-
pyrazole-4-carbonitrile (6l)
296 mg (90% yield); 1H NMR (CDCl3, 300 MHz) δ: 6.95
(t, 1H, j 7.2, ArH), 7.13-7.19 (m, 3H, ArH), 7.29-7.40 (m, 4H,
ArH), 7.91 (s, 2H, NH); 13C NMR (CDCl3, 75 MHz) δ: 57.1,
119.20, 123.6, 125.7, 126.3, 127.8, 128.9, 129.3, 130.7, 134.7,
136.4, 139.1, 149.1, 157.3; Anal. calcd for C16H10Cl2N4: C:
3.4.3. 3-Methyl-4-(2-methoxyphenyl)-7-thioxo-4,6,7,8-
tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-
5(1H)-one (7d)
307 mg (90% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.26 (s, 3H), 3.63 (s, 3H), 5.58 (s, 1H) 6.80 (d, J = 6.9 Hz,
58.38; H: 3.06; N: 21.54; found: C: 58.26; H: 3.13; N: 21.69
.

Boehmite Silylpropyl Amine Sulfamic Acid as an Efficient
Letters in Organic Chemistry, 2017, Vol. 14, No. 6 459
1H), 7.07 (t, J = 6.9 Hz), 7.34 (d, J = 6.9 Hz), 11.14 (s, 2H)
ppm; 13C NMR (DMSO-d6, 75 MHz) δ = 9.9, 29.9, 56.1,
96.1, 105.3, 111.4, 111.7, 120.3, 127.6, 127.8, 130.1, 139.7,
143.5, 160.4, 172.8 ppm; Anal. Calcd. for C16H14N4O3S:
C, 56.13; H, 4.12; N, 16.36. Found: C, 56.34; H, 4.22; N,
16.17.
59.7, 60.1, 91.6, 104.3, 106.6, 123.3, 129.2, 131.1, 139.7,
141.6, 143.5, 151.7, 161.5, 161.7, 172.1ppm; Anal. Calcd.
for C18H18N4O5S: C, 53.72; H, 4.51; N, 13.92. Found: C,
53.91; H, 4.60; N, 14.10.
3.4.9. 3-Methyl-4-(2'-furanyl)-7-thioxo-4,6,7,8-
tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-
5(1H)-one (7k)
3.4.4. 3-Methyl-4-(2-chlorophenyl)-7-thioxo-4,6,7,8-
tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-
5(1H)-one (7e)
287 mg (83% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.27 (s, 3H), 5.39 (s, 1H), 6.99 (d, J = 8.4 Hz), 7.03 (d, J =
8.4 Hz), 7.19-7.33 (m, 1H), 11.52 (s, 2H) ppm; 13C NMR
(DMSO-d6, 75 MHz) δ = 11.1, 30.3, 88.2, 127.8, 128.9,
129.2, 130.9, 131.2, 134.2, 151.8, 152.6, 156.6, 161.0 (C13),
172.2 ppm; Anal. Calcd. for C15H11ClN4O2S: C, 51.95; H,
3.20; N, 16.16. Found: C, 51.76; H, 3.29; N, 16.34.
278 mg (92% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.08 (s, 3H), 5.41 (s, 1H), 6.46 (s, 1H), 6.85 (t, J = 4.2 Hz,
1H), 7.33 (d, J = 5.1 Hz, 1H), 10.01 (s, 2H) ppm; 13C NMR
(DMSO-d6, 75 MHz) δ = 10.0, 27.7, 80.1, 102.2, 105.9,
110.2, 138.8, 141.1, 155.5, 163.6, 174.1 ppm; Anal. Calcd.
for C13H10N4O3S: C, 51.65; H, 3.33; N, 18.53. Found: C,
51.84; H, 3.42; N, 18.34
.
3.4.10. 3-Methyl-4-(2'-thiophenyl)-7-thioxo-4,6,7,8-
tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-
5(1H)-one (7l)
296 mg (93% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.21 (s, 3H), 5.51 (s, 1H), 6.59 (d, J = 3.0 Hz, 1H), 6.80-6.88
(m, 1H), 7.25 (d, J = 5.1 Hz, 1H), 11.34 (s, 2H) ppm; 13C
NMR (DMSO-d6, 75 MHz) δ = 10.3, 30.9, 79.6, 95.4, 104.1,
112.6, 112.9, 127.5, 128.2, 136.2, 163.4, 173.0 ppm; Anal.
Calcd. for C13H10N4O2S2: C, 49.04; H, 3.17; N, 17.60.
Found: C, 49.23; H, 3.09; N, 17.79.
3.4.5. 3-Methyl-4-(2,6-dichlorophenyl)-7-thioxo-4,6,
7,8-tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]
pyrimidin-5(1H)-one (7f)
358 mg (94% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.13 (s, 3H), 5.63 (s, 1H), 7.16 (d, J = 7.8 Hz), 7.30 (d, J =
8.1 Hz), 7.39-7.45 (m, 1H), 11.38 (s, 2H) ppm; 13C NMR
(DMSO-d6, 75 MHz) δ = 11.2, 30.4, 88.8, 127.7, 128.9,
129.0, 129.6, 131.3, 132.0, 132.2, 151.4, 152.2, 167.7, 172.3
ppm; Anal. Calcd. for C15H10Cl2N4O2S: C, 47.26; H, 2.64; N,
14.70. Found: C, 47.47; H, 2.73; N, 14.90.
3.4.11. 3-Methyl-4-(2'-pyridinyl)-7-thioxo-4,6,7,8-
tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-
5(1H)-one (7m)
269 mg (86% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.01 (s, 3H), 4.99 (s, 1H), 7.21 (t, J = 7.2 Hz, 1H), 7.36 (d, J
= 8.1 Hz, 1H), 7.69-7.75 (m, 1H), 8.44 (d, J = 4.8 Hz, 1H),
11.35 (s, 2H) ppm; 13C NMR (DMSO-d6, 75 MHz) δ = 10.4,
36.4, 91.2, 103.2, 121.2, 122.4, 128.2, 137.0, 138.7, 141.8,
143.6, 162.4, 172.2 ppm; Anal. Calcd. for C14H11N5O2S: C,
53.66; H, 3.54; N, 22.35. Found: C, 53.45; H, 3.63; N, 22.52.
3.4.6. 3-Methyl-4-(4-bromophenyl)-7-thioxo-4,6,7,8-
tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-
5(1H)-one (7g)
340 mg (87% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.24 (s, 3H), 5.67 (s, 1H), 6.98 (d, J = 8.4 Hz), 7.34 (d, J =
8.4 Hz), 11.53 (s, 1H), 11.61 (s, 1H) ppm; 13C NMR
(DMSO-d6, 75 MHz) δ = 10.0, 33.1, 88.7, 125.1, 126.3,
127.2, 130.9, 131.1, 138.6, 139.3, 149.7, 155.3, 163.0, 173.1
ppm; Anal. Calcd. for C15H11BrN4O2S: C, 46.05; H, 2.83; N,
14.32. Found: C, 46.24; H, 2.91; N, 14.50.
CONCLUSION
We demonstrated an environmentally friendly method for
the syntheses of 5-amino-1, 3-aryl-1H-pyrazole-4-carbonitriles
and pyrazolopyranopyrimidines using m-SABNPs as an effi-
cient and reusable nanocatalyst. This method offers several
advantages like milder reaction condition, shorter reaction
time, cleaner reaction, green and reusability of the catalyst,
and high reaction yield. Moreover, this novel heterogeneous
catalyst could be easily separated and reused for at least 5
repeated cycles without an appreciable loss in its catalytic
activity.
3.4.7. 3-Methyl-4-(4-nitrophenyl)-7-thioxo-4,6,7,8-
tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]pyrimidin-
5(1H)-one (7i)
336 mg (94% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.24 (s, 3H), 5.48 (s, 1H), 7.30 (d, J = 8.4 Hz), 8.10 (d, J =
8.4 Hz), 11.50 (s, 2H) ppm; 13C NMR (DMSO-d6, 75 MHz)
δ = 9.9, 30.8, 96.0, 105.4, 126.1, 127.1, 128.1, 131.3, 139.0,
143.7, 154.6, 163.2, 172.9 ppm; Anal. Calcd. for
C15H11N5O4S: C, 50.42; H, 3.10; N, 19.60. Found: C, 50.60;
H, 3.01; N, 19.25
.
CONSENT FOR PUBLICATION
3.4.8. 3-Methyl-4-(2,3,4-trimethoxyphenyl)-7-thioxo-
4,6,7,8-tetrahydropyrazolo-[4',3':5,6]pyrano[2,3-d]
pyrimidin-5 (1H)-one(7j)
Not applicable.
362 mg (90% yield); 1H NMR (DMSO-d6, 300 MHz) δ =
2.03 (s, 3H), 3.88 (s, 3H), 3.94 (s, 6H), 4.94 (s, 1H), 6.66 (d,
J = 8.7 Hz, 1H), 6.96 (d, J = 8.7 Hz, 1H), 11.42 (br, 2H)
ppm; 13C NMR (DMSO-d6, 75 MHz) δ = 10.4, 27.2, 55.5,
CONFLICT OF INTEREST
The authors confirm that this article content has no con-
flict of interest.

460 Letters in Organic Chemistry, 2017, Vol. 14, No. 6
Doosti et al.
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SUPPLEMENTARY MATERIAL
Supplementary material is available on the publisher’s
web site along with the published article.
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DISCLAIMER: The above article has been published in Epub (ahead of print) on the basis of the materials provided by the author. The Edito-
rial Department reserves the right to make minor modifications for further improvement of the manuscript.