Core-shell structured magnetic silica supported propylamine/molybdate complexes: An efficient and magnetically recoverable nanocatalyst

Article abstract of DOI:10.1039/c9nj01160a

In the present study, a novel core-shell structured magnetic silica supported propylamine/molybdate complex (Fe₃O₄@SiO₂/Pr-NMo[Mo₅O₁₈]) is prepared, characterized and applied as an effective and easil

Full text of DOI:10.1039/c9nj01160a

View Article Online
View Journal
NJC
New Journal of Chemistry
Accepted Manuscript
A journal for new directions in chemistry
This article can be cited before page numbers have been issued, to do this please use: A. Zarnegaryan, D.
Elhamifar and M. Neysi, New J. Chem., 2019, DOI: 10.1039/C9NJ01160A.
Volume 42
This is an Accepted Manuscript, which has been through the
Number
6
21 March 2018
Pages 3963-4776
Royal Society of Chemistry peer review process and has been
accepted for publication.
NJC
New Journal of Chemistry
rsc.li/njc
A journal for new directions in chemistry
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 1144-2546
PAPER
Chechia Hu, Tzu-Jen Lin et al.
Yellowish and blue luminescent graphene oxide quantum dots
prepared via a microwave-assisted hydrothermal route using
H2O2 and KMnO4 as oxidizing agents
rsc.li/njc

Page 1 of 25
New Journal of Chemistry
1
2
3
4
5
View Article Online
DOI: 10.1039/C9NJ01160A
supported
Core-shell
structured
magnetic
silica
6
7
8
9
propylamine/molybdate complex: An efficient and magnetically
recoverable nanocatalyst
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Maryam Neysi, Ali Zarnegarian and Dawood Elhamifar*
Department of Chemistry, Yasouj University, Yasouj, 75918-74831, Iran
Email: d.elhamifar@yu.ac.ir
Abstract: In the present study, a novel core-shell structured magnetic silica supported
propylamine/molybdate
complex
(Fe3O4@SiO2/Pr-N=Mo[Mo5O18])
is
prepared,
characterized and applied as effective and easily recoverable nanocatalyst. The chemical
composition, crystalline structure, thermal stability, morphology and particle size of this
nanomaterial were studied using Fourier transform infrared (FT-IR) spectroscopy, energy
dispersive X-ray (EDX), transmission electron microscopy (TEM), powder X-ray diffraction
(PXRD), scanning electron microscopy (SEM), thermal gravimetric (TG) and vibration
sample magnetometer (VSM) analyses. This nanomaterial was used as efficient and
magnetically reusable catalyst for the synthesis of pyrano-pyrazole derivatives under
moderate conditions and gave corresponding products in high yield and selectivity.
Keywords: Core-shell nanostructure, Polyoxometalate, Pyrano-pyrazoles, Recoverable
nanocatalyst, Green synthesis.
1

New Journal of Chemistry
Page 2 of 25
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
1. Introduction
5
6
7
8
9
Because of coating with a shell layer, the properties of magnetic nanoparticles such as
thermal, chemical and mechanical stability and also chemical reactivity are increased.1-3 The
core-shell structured materials have diverse applications in fields of electronics, biomedicine,
optic, catalysis, chemical analysis, etc. In recent years, core-shell nanomaterials containing
magnetic iron oxide cores and silica shells have received many attention4-10 due to their
advantages such as easy preparation, magnetically recoverability, reducing the collective
conductivity and high stability.1, 11 In these materials, silica protects the magnetic core against
agglomeration and oxidation.1 Moreover, the silica shell can easily be modified with several
organic and inorganic species to deliver effective and reusable catalysts. Some of recently
reported magnetic catalytic systems involving silica shell are Fe3O4@SiO2-APTMS-Cu,12
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Fe3O4@SiO2@Cu,13
Fe3O4@SiO2@mSiO2@TiO2,14
Fe3O4@SiO2-sulfuric
acid,
15Fe3O4@SiO2-PhSO3H,16 Fe3O4@SiO2@mSiO2-Pd(0)17 and Fe3O4@SiO2/IL.18
On the other hand, polyoxometalates (POMs) are very interested in the fields of catalysis,
oxidation, reduction and medicine, because their nanometer size and also their excellent
redox potential.19-21 The catalytic and photochemical properties, acidity and basicity of POM
clusters can be tuned by changing their composition. Hexamolybdates are a group of POMs
that have been widely used in several important inorganic and organic reactions due to their
thermal stability and radiation resistant.22-27 However, the solubility and non-recoverability of
POMs in various media, limit their widespread applications in several processes. Therefore,
the immobilization of these clusters on solid supports is an important subject especially in
catalytic processes. To date, several materials such as silica, polymer and magnetic particles
have been used as support to immobilize POMs. Some of recently developed systems are
Fe3O4@SiO2@NH-NH-PW,28
Fe3O4@SiO2@KCC-1/IL/H3PW12O40,29
Fe3O4@TC-
2

Page 3 of 25
New Journal of Chemistry
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
PANI@TPA,30
Fe3O4@SiO2@ADMPT/H6P2W18,31
Fe3O4@D-NH2-HPA32
and
5
6
Fe3O4@SiO2/Salen/Mn/IL/HPW.33
7
8
9
Pyrano-pyrazole derivatives are very important organic compounds in the pharmaceutical
industry that are considered as the main structure of many biological drugs.34-37 Some
pharmacological activities of these compounds are anti-cancer, anti-inflammatory, anti-
fungal, anti-virus and anti-bacterial.38-39 The preparation of pyrano-pyrazoles has been
reported in the presence of homogeneous unrecoverable catalysts such as L-prolin,40
isonicotinic acid,36 [(Dsim) AlCl4]41 and ionic liquid.42 Due to problems of the homogeneous
systems such as catalyst and product separation, recently several recyclable heterogeneous
catalysts such as Fe3O4,43 RHA@Melamine,44 γ-alumina,45 SiO2-TMG46 and
Fe3O4@mesoporous SBA-1547 have been reported in this matter. However, the latter systems
also suffer from some problems such as the use of toxic organic solvents, harsh conditions
and high catalyst loading. Therefore, the preparation of new recoverable catalysts to
overcome the aforementioned restrictions is an important challenge in the synthesis of
pyrano-pyrazole derivatives. According to the above mentioned subjects, in the present study,
a simple, inexpensive and environmentally friendly method has been developed for the
preparation of a novel magnetic silica supported propylamine/molybdate catalyst that is very
effective and easily recoverable catalyst for synthesis of pyrano-pyrazoles under moderate
conditions (Scheme 1).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2. Experimental section
2.1. General
All chemicals including iron (II) chloride tetrahydrate (99%), iron (III) chloride hexahydrate
(98%), ammonia (28%), concentrated HCl, tetraethoxysilane (TEOS), (3-
3

New Journal of Chemistry
Page 4 of 25
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
aminopropyl)trimethoxysilane (APTMS), dimethyl sulfoxide, toluene and benzaldehyde
5
6
derivatives were purchased from Fluka and Merck companies.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2.2. Preparation of Fe3O4@SiO2 nanoparticles
For this, firstly the Fe3O4 nanoparticles (NPs) were prepared according to our previous
procedure.48 These NPs (0.5 g) were then completely dispersed in a solution containing water
(10 mL) and ethanol (40 mL) at room temperature for 30 min. After that, ammonia (4 mL,
28%) was added in the reaction vessel. To the resulting mixture, TEOS (0.5 mL) was
dropwise added and stirred at room temperature for 16 h. After completion of the reaction,
the product was separated using an external magnetic field and dried at 60 °C for 6 h. The
final material was denoted as Fe3O4@SiO2.
2.3. Preparation of the Fe3O4@SiO2/Pr-NH2
For this purpose, Fe3O4@SiO2 (0.5 g) was completely dispersed in toluene (25 mL) at room
temperature. Then, (3-aminopropyl)-trimethoxysilane (0.26 g) was added to the reaction
vessel and the resulting mixture was stirred at 100 °C for 24 h. The obtained precipitate was
removed using a magnetic field, washed completely with EtOH, dried at 70 °C for 6 h and
denoted as Fe3O4@SiO2/Pr-NH2.
2.4. Preparation of the Fe3O4@SiO2/Pr-N=Mo[Mo5O18]
To do this, the Fe3O4@SiO2/Pr-NH2 nanomaterial (0.25 g) was completely dispersed in
dimethyl sulfoxide (40 mL) at 25 °C. After that, the [Mo6O182-] (0.2 g) was added to reaction
vessel and it was stirred at 25 °C for 24 h. Then, the final material was washed with ethanol
and water several times, collected using a magnetic field and dried at 70 °C for 6 h.49 The
obtained product was denoted as Fe3O4@SiO2/Pr-N=Mo[Mo5O18].
4

Page 5 of 25
New Journal of Chemistry
1
2
3
4
2.5. Procedure for the synthesis of 6-amino-2H, 4H-pyrano[2,3-c]pyrazoVlieew-5Ar-ticle Online
DOI: 10.1039/C9NJ01160A
5
6
carbonitriles using Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For this, Fe3O4@SiO2/Pr-N=Mo[Mo5O18] (0.01 g) was added to reaction vessel containing
benzaldehyde (1 mmol), malononitrile (1 mmol), ethylacetoacetate (1 mmol), and hydrazine
hydrate (1 mmol). This mixture was placed in an ultrasonic bath and the reaction progress
was monitored using TLC at room temperature. After completion of the reaction, hot ethanol
(10 mL) was added and the catalyst was removed using an external magnet. The resulted
mixture was hotly placed in an ice bath to precipitate desired pyrano-pyrazol products. The
pure products were obtained after recrystallization in EtOH.
2.6. Procedure for the recovery of Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst
For this purpose, the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] catalyst (0.01 g) was added to a
mixture of benzaldehyde, malononitrile, ethylacetoacetate and hydrazine hydrate at room
temperature. After completion of the reaction under ultrasonic irradiations, the catalyst was
removed using an external magnet. The recovered catalyst was added in the next run under
the same conditions as the first run. These steps were repeated for at least nine times and the
corresponding yield was calculated.
2.7. Procedure for study of catalyst-leaching during the synthesis of 6-amino-2H, 4H-
pyrano[2,3-c]pyrazole-5- carbonitriles
For this purpose, the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] catalyst (0.01 g) was added to a
reaction mixture of benzaldehyde, malononitrile, ethylacetoacetate and hydrazine hydrate at
room temperature. After about 40% of the reaction was progressed under ultrasonic
irradiations, the catalyst was separated using an external magnet and the catalyst-free mixture
5

New Journal of Chemistry
Page 6 of 25
1
2
3
4
was placed in an ultrasonic bath for another 1 h. Interestingly, no significant progressViwewaAsrticle Online
DOI: 10.1039/C9NJ01160A
5
6
7
8
observed in this case indicating no leaching of active catalytic species during applied
conditions.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3. Results and discussion
In order to prepare the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] catalyst, firstly, magnetic silica
nanoparticles were synthesized and modified with propylamine species to deliver
Fe3O4@SiO2/Pr-NH2 nanomaterial. The Fe3O4@SiO2/Pr-NH2 was then reacted with
hexamolybdate ions to give desired Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst (Scheme
1). The chemical and structural properties of the Fe3O4@SiO2/Pr-N=Mo[Mo5O18]
nanomaterial were investigated using FT-IR, VSM, SEM, TEM, EDX and PXRD analyses.
6

Page 7 of 25
New Journal of Chemistry
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1) Toluene, 20 min, r. t.
1) H2O, EtOH, 30 min, r. t.
Fe3O4
Fe3O4
2) NH3
APTMS,24 h, reflux
2)
3) TEOS, 16 h, r. t.
Fe3O4
Fe3O4@SiO2
N
1) DMSO, r. t.
Fe3O4
Fe3O4
2) [Mo6O19]2-, 24 h, r. t.
100 C, 2 h
N
N
N
Fe3O4@SiO2/ Pr-NH2
Fe3O4@SiO2/ Pr-N=Mo[Mo5O18
]
APTMS:
(3-Aminopropyl)trimethoxysilane
O
O Si
O
:
NH2
: Mo6O18
Scheme 1. Preparation of the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst
The identification and determination of organic functional groups were carried out using FT-
IR spectroscopy (Figure 1). For samples Fe3O4@SiO2, Fe3O4@SiO2/Pr-NH2 and
Fe3O4@SiO2/Pr-N=Mo[Mo5O18], the peaks cleared at 586 and 3350-3500 cm-1, are,
7

New Journal of Chemistry
Page 8 of 25
1
2
3
4
5
6
7
8
9
View Article Online
respectively assigned to Fe-O and O-H bonds. Moreover, the peaks at 878 and 10D9O9I: 1c0m.10-319/aCr9eNJ01160A
related to the symmetric and asymmetric vibrations of the Si-O-Si bonds. For
Fe3O4@SiO2/Pr-NH2 and Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanomaterials, the bands appeared
at 2923 cm-1 are corresponded to C-H bonds of propyl groups. Interestingly, for the
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] catalyst, the peaks cleared at 1515 and 1662 cm-1 are due to
Mo-O and Mo=N bonds, respectively. These data confirm high stability and well
immobilization of propylamine and molybdate species onto Fe3O4@SiO2 surface.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. FT-IR spectra of a) Fe3O4@SiO2, b) Fe3O4@SiO2@Pr-NH2 and c) Fe3O4@SiO2/Pr-
N=Mo[Mo5O18]
8

Page 9 of 25
New Journal of Chemistry
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
The powder X-ray diffraction analysis of the Fe3O4@SiO2, Fe3O4@SiO2/Pr-NH2 and
5
6
7
8
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] is shown in Figure 2. Interestingly, for all samples this
analysis illustrated the same pattern with seven signals at 2Ө = 30.30, 36, 43, 54, 57.5 and 63
degrees corresponding to the Miller indices of 220, 311, 400, 422, 511 and 440, respectively.
This confirms the high stability of spinel structure of magnetic iron oxide nanoparticles
during catalyst preparation. Also, the decrease in intensity of PXRD peaks for
Fe3O4@SiO2/Pr-NH2 and Fe3O4@SiO2/Pr-N=Mo[Mo5O18] indicates the successful
immobilization of organic groups and polyoxometalate ions onto Fe3O4@SiO2 nanoparticles.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 2. The powder X-ray diffraction pattern of a) Fe3O4@SiO2, b) Fe3O4@SiO2/Pr-NH2
and c) Fe3O4@SiO2/Pr-N=Mo[Mo5O18] materials.
9

New Journal of Chemistry
Page 10 of 25
1
2
3
4
5
6
7
8
9
View Article Online
The scanning electron microscopy (SEM) was carried out to show the particle DdOiIs: t1r0i.1b0u39t/iCo9nNJ01160A
and morphology of the synthesized catalyst. This image showed the presence of well
distributed spherical particles with mean size of 80 nm for the material (Figure 3).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 3. The SEM analysis of the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst
The TEM image also showed spherical particles with a core-shell structure for designed
catalyst (Figure 4).
10

Page 11 of 25
New Journal of Chemistry
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 4. The TEM image of the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst
The vibrating sample magnetometer (VSM) analysis was used to determine the magnetic
properties of the catalyst. The result showed that the magnetic saturation of the catalyst is 38
emu/g confirming the high magnetic properties of designed material (Figure 5). This is very
important characteristic, especially in the field of catalysis.
11

New Journal of Chemistry
Page 12 of 25
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 5. The VSM analysis of the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst
The EDX analysis confirmed the presence of desired elements in the Fe3O4@SiO2/Pr-
N=Mo[Mo5O18] catalyst. This showed the signals of Si, C, N, Mo, O and Fe elements
proving well immobilization and high stability of silica, propylamine and molybdate moieties
onto magnetic iron oxide cores (Figure 6a). Element mapping analysis was also performed to
show the amount and distribution of elements in the catalyst network. According to this
analysis, it is clear that all elements are successfully and uniformly distributed in network of
material (Figure 6b).
12

Page 13 of 25
New Journal of Chemistry
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
b
Figure 6. a) EDX spectrum and b) EDX mapping of the Fe3O4@SiO2/Pr-N=Mo[Mo5O18]
nanocatalyst
13

New Journal of Chemistry
Page 14 of 25
1
2
3
4
Thermal stability of the catalyst was studied at 0 to 800 ⁰C using thermal gravimetric anaVliyewsAisrticle Online
DOI: 10.1039/C9NJ01160A
5
6
7
8
(TGA). The weight loss of the catalyst during the temperature rise is shown in two steps
(Figure 7). The first weight loss at temperature range of 25-200 ⁰C (about 4%) is related to
the removal of water and organic solvents remained during the catalyst preparation steps. The
main weight loss at temperature range of 201-500 °C (about 9%) is due to removal of
supported propylamine groups.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 7. TG analysis of the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst
After characterization, the catalytic efficiency of designed Fe3O4@SiO2/Pr-N=Mo[Mo5O18]
material was investigated in the synthesis of 6-amino-2H, 4H-pyrano[2,3-c]pyrazole-5-
carbonitriles (Table 1). In order to optimize the reaction conditions, the effect of several
parameters such as catalyst loading and solvent on the condensation of benzaldehyde,
malononitrile, ethylacetoacetate and hydrazine hydrate was investigated under ultrasonic
irradiations (Table 1). Under solvent-free media only a low yield of desired product was
14

Page 15 of 25
New Journal of Chemistry
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
obtained (Table 1, entry 1). In EtOH and acetonitrile, respectively, 75% and 55% yield were
5
6
7
8
resulted (Table 1, entries 2, 3). While, in nonpolar solvents such as n-hexane only a trace
conversion was seen (Table 1, entry 4). Interestingly, the highest conversion and yield were
obtained in water (Table 1, entry 5). In the next, the effect of catalyst loading was studied. It
was found that with increasing the catalyst amount from 0.004 to 0.01 g, the yield is
increased and the higher amount of catalyst has not significant effect on the reaction progress
(Table 1, entry 5-8). According to these results, the use of 0.01 g of catalyst and water as
environmentally-friendly solvent at room temperature under ultrasonic irradiations were
selected as optimum conditions. In order to prove that actually molybdate centers act as
catalytic sites or not, in next study the reaction was performed using Mo-free Fe3O4@SiO2
and Fe3O4@SiO2/Pr-NH2 materials under conditions the same as Fe3O4@SiO2/Pr-
N=Mo[Mo5O18] (Table 1, entries 9, 10). The results showed that for both of Mo-free samples,
only a low yield of desired product is delivered indicating that the reaction is mainly
catalyzed by immobilized molybdate sites.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
15

New Journal of Chemistry
Page 16 of 25
1
2
3
4
View Article Online
Table 1. The effect of solvent, temperature and catalyst loading in the synDthOeI:s10is.10o39f/C69-NJ01160A
5
6
7
amino-2H,4H-pyrano[2,3-c]pyrazole-5-carbonitriles
using
Fe3O4@SiO2/Pr-
N=Mo[Mo5O18] catalysta
8
9
O
O
O
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
H
H3C
OEt
H3C
CN
Catalyst
+
N
N
H
O
NH2
.H2O
H2N NH2
NC
CN
Entry
Solvent
Catalyst (g)
Yield (%)
1
2
-
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] (0.01)
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] (0.01)
30
75
EtOH
3
4
CH3CN
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] (0.01)
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] (0.01)
55
n-Hexane
Trace
5
H2O
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] (0.01)
95
6
H2O
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] (0.012)
95
7
8
H2O
H2O
H2O
H2O
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] (0.008)
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] (0.004)
Fe3O4@SiO2/Pr-NH2 (0.01)
85
48
14
6
9
10
Fe3O4@SiO2 (0.01)
a All reactions were performed at room temperature for 8 min.
After optimization of the reaction conditions, the efficiency of designed catalyst in the
synthesis of different derivatives of dihydropyrano[2, 3-c]pyrazoles was investigated (Table
2). It was found that all aromatic aldehydes involving both electron-donating and electron-
withdrawing substituents give corresponding coupling products in high yields (Table 2). In
addition, the heterocyclic aromatic aldehydes such as furan-2-carbaldehyde and thiophene-2-
16

Page 17 of 25
New Journal of Chemistry
1
2
3
4
5
6
7
8
9
View Article Online
carbaldehyde also gave corresponding dihydropyrano[2, 3-c]pyrazoles in high yielDdOsI:(1T0.a10b3l9e/C29N, J01160A
entries 6, 7). These results confirm high performance of the designed catalyst for the
preparation of a wide range of 6-amino-2H,4H-pyrano[2,3-c]pyrazole-5-carbonitrile
derivatives applicable in drug synthesis.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 2. Preparation of 6-amino-2H, 4H-pyrano[2,3-c]pyrazole-5-carbonitrile derivatives
in the presence of Fe3O4@SiO2/Pr-N=Mo[Mo5O18] catalyst
R
O
O
O
H
H3C
OEt
H3C
CN
Catalyst (0.01 g)
+
R
H2O, r. t.
N
N
H
O
NH2
.H2O
H2N NH2
NC
CN
Entry
Aldehyde
C6H5CHO
Time
(min)
Yield
(%)
M. P.
Found
M. P.
Reported
1
2
3
4
5
8
95
240-243
206-209
260-262
180-182
231-233
243-24534
p-MeO
C6H4CHO
15
20
10
12
89
91
90
92
208-21034
262-26436
179-18044
233-23534
m-
OHC6H4CHO
p-Br C6H4CHO
p-Cl C6H4CHO
Furan-2-
carbaldehyde
6
7
20
20
88
86
230-232
222-224
230-23150
224-226 50
Thiophene-2-
carbaldehyde
17

New Journal of Chemistry
Page 18 of 25
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
To study the recoverability and reusability of the designed catalytic system, the condensation
5
6
7
8
between benzaldehyde, malonitrile, ethylacetoacetate and hydrazine hydrate in the presence
of Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst was selected as a test model. After
completion of the reaction, the catalyst was removed through an external magnetic field and
reused in the next run charged with starting materials and the reaction progress was
monitored. These steps were repeated several times and the yield of each run was calculated.
The results showed that the designed nanocatalyst can be recovered and reused at least nine
times without significant decrease in its performance (Figure 8). This confirms high stability
and durability of this catalyst under applied conditions.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 8. The recoverability of the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] nanocatalyst
In the next, the PXRD analysis of the recovered catalyst was performed to study its chemical
stability under applied media (Figure 9). As shown, the pattern of this analysis is the same as
PXRD of fresh catalyst confirming high stability of crystalline structure of iron oxide NPs
during reaction conditions.
18

Page 19 of 25
New Journal of Chemistry
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 9. The PXRD analysis of the recovered nanocatalyst
Finally, the catalytic performance of our designed material was compared with some of
recently catalysts used in the synthesize of 6-amino-2H,4H-pyrano[2,3-c]pyrazole-5-
carbonitriles. This study showed that in terms of reaction time, catalyst loading and recycling
times, the Fe3O4@SiO2/Pr-N=Mo[Mo5O18] is better than the most of previous catalysts
confirming the sustainability and higher efficiency of the present catalyst (Table 3).
19

New Journal of Chemistry
Page 20 of 25
1
2
3
4
5
6
7
View Article Online
Table 3. A comparison study between our designed catalyst and recentDlyOI: 1r0e.1p0o39r/tCe9dNJ01160A
heterogeneous catalysts in the synthesis of 6-amino-2H,4H-pyrano[2,3-c]pyrazole-5-
carbonitriles
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Entry
Catalyst
Conditions Recovery
times
Yield
(%)
Ref.
34
1
2
MgO
CH3CN, Cat. (0.05
-
95
90
g), r.t., 12 min
36
40
Isonicotinic acid
[(Dsim) AlCl4]
Solvent free, Cat.
(10 mol%), 85 °C,
10 min
4
3
4
Solvent free, Cat. (7
mol%), 80 °C, 1
min
4
5
90
91
37
41
THAM
Fe3O4
EtOH/H2O, Cat.
(0.03 g), r.t, 120
min
5
6
H2O, Cat. (0.015 g),
r.t, 60 min
8
9
73
95
Fe3O4@SiO2/ Pr-
N=Mo[Mo5O18]
H2O, Cat. (0.01 g),
r.t, 8 min
This
work
Abbreviations: (Dsim) AlCl4: Disulfonic acid imidazolium chloroaluminate; THAM: Tris-
hydroxylmethylaminomethane.
The mechanism of this reaction is proposed in Scheme 2. In general, in this catalytic system,
the Fe3O4@SiO2 acts as a magnetically recoverably support, propylamine acts as a linker
and/or spacer to treatment with Mo-sites for immobilization, the Mo species act as acidic
20

Page 21 of 25
New Journal of Chemistry
1
2
3
4
View Article Online
sites to active electrophiles and oxygens act as basic sites to active nucleohphilDeOsI:(1S0.1c0h3e9/mC9eNJ01160A
5
6
2).51
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Fe3O4@SiO2
H
H
N C
C N
NC
CN
OEt
Ph
O
O
-H2O ,
-EtOH
-H2O
Ph
CN
CN
NH2 .H2O
NH2
O
N
H
O
N
H
H
(1)
(2)
Fe3O4@SiO2
Fe3O4@SiO2
N
C
Ph
CN
Ph
Ph
O
Me
H
H
CN
CN
NH
N
N
N
N
O
N
H
O H
N
N
N
O
H
N
H
(3)
Fe3O4@SiO2
Fe3O4@SiO2
Fe3O4@SiO2
Ph
Me
N
CN
O
=
=
Mo
N
O
NH2
H
(4)
Scheme 2. Proposed mechanism for the synthesis of pyrano-pyrazoles in the presence of
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] catalyst
21

New Journal of Chemistry
Page 22 of 25
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
4. Conclusion
5
6
7
8
9
In summary, in the present study a novel magnetic nanocatalyst called Fe3O4@SiO2/Pr-
N=Mo[Mo5O18] was prepared and characterized. The FT-IR, TG and EDX analyses
confirmed well immobilization and high stability of silica, propylamine and molybdate
species on magnetic iron oxide nanoparticles. The VSM analysis confirmed good magnetic
properties of the catalyst. The PXRD analysis of the catalyst showed high stability of
magnetic iron oxide NPs during material preparation. The SEM and TEM analyses
demonstrated spherical particles with core-shell structure for the designed catalyst. The
Fe3O4@SiO2/Pr-N=Mo[Mo5O18] catalyst was effectively applied in the synthesis of 6-amino-
2H,4H-pyrano[2,3-c]pyrazole-5-carbonitriles under green conditions at room temperature.
The recovery and leaching tests showed high stability and durability of the present catalyst
under applied conditions.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Acknowledgements
The authors acknowledge the Yasouj University and Iran National Science Foundation
(INSF) for supporting this work.
.
22

Page 23 of 25
New Journal of Chemistry
1
2
3
4
View Article Online
DOI: 10.1039/C9NJ01160A
References
5
6
7
8
9
1
2
3
M. B. Gawande, Y. Monga, R. Zboril, R. Sharma, Coord. Chem. Rev., 2015, 288, 118-143.
F. Ahangaran, A. Hassanzadeh, S. Nouri, Int. Nano Lett., 2013, 3(23), 1-5.
B. Mirhosseini-Eshkevari, M. A. Ghasemzadeh, J. Safaei-Ghomi, Res. Chem. Intermed.,
2015, 41, 7703-7714.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
4
5
6
7
L. M. Rossi, N. J. Costa, F. P. Silva, R. Wojcieszak, Green Chem., 2014, 16, 2906-2933.
A. Maleki, Tetrahedron, 2012, 68, 7827-7833.
M. Zhang, Y.-H. Liu, Z.-R. Shang, H.-C. Hu, Z.-H. Zhang, Catal. Commun., 2017, 88, 39-44.
M.-N. Chen, L.-P. Mo, Z.-S. Cui, Z.-H. Zhang, Curr. Opin. Green Sustain. Chem., 2019. 15,
27-37.
M. Zhang, P. Liu, Y.-H. Liu, Z.-R. Shang, H.-C. Hu, Z.-H. Zhang, RSC Adv., 2016, 6,106160-
106170.
X.-N. Zhao, H.-C. Hu, F.-J. Zhang, Z.-H. Zhang, Appl. Catal., A: Gen. 2014, 482, 258-265.
H.-Y. Zhang, X.-P. Hao, L.-P. Mo, S.-S. Liu, W.-B. Zhang, Z.-H. Zhang, New J. Chem.,
2017, 41, 7108-7115.
Y. Xiong, Z. Zhang, X. Wang, B. Liu, J. Lin, Chem. Eng. J., 2014, 235, 349-355.
M. Karimi, L. Ghandi, D. Saberi, A. Heydari, New J. Chem., 2018, 42, 3900-3908.
C. Ram, S. Sivamani, T. Micha Premkumar, V. Hariram, ARPN J. Eng. Appl. Sci., 2017, 12,
6397-6406.
D. K. Yi, S. S. Lee, J. Y. Ying, Chem. Mater., 2006, 18, 2459-2461.
K. Rajkumari, J. Kalita, D. Das, L. Rokhum, RSC Adv., 2017, 7, 56559-56565.
H. Moghanian, A. Mobinikhaledi, A. Blackman, E. Sarough-Farahani, RSC Adv., 2014, 4,
28176-28185.
W. Li, B. Zhang, X. Li, H. Zhang, Q. Zhang, Appl. Catal., A: Gen. 2013, 459, 65-72.
N. Azgomi, M. Mokhtary, J. Mol. Catal. A: Chem., 2015, 398, 58-64.
A. Proust, B. Matt, R. Villanneau, G. Guillemot, P. Gouzerh, G. Izzet, Chem. Soc. Rev., 2012,
41, 7605-7622.
S.-S. Wang, G.-Y. Yang, Chem. Rev., 2015, 115, 4893-4962.
D. Ravelli, S. Protti, M. Fagnoni, Acc. Chem. Res., 2016, 49, 2232-2242.
Z.-K. Qu, K. Yu, Z.-F. Zhao, Z.-h. Su, J.-Q. Sha, C.-M. Wang, B.-B. Zhou, Dalton Trans.,
2014, 43, 6744-6751.
J. Kang, B. Xu, Z. Peng, X. Zhu, Y. Wei, D. R. Powell, Angew. Chem. Int. Ed., 2005, 44,
6902-6905.
G. R. Bertolini, C. L. Cabello, M. Munoz, M. Casella, D. Gazzoli, I. Pettiti, G. Ferraris, J.
Mol.Catal. A: Chem., 2013, 366, 109-115.
M. Lu, Y. Wei, B. Xu, C. F. C. Cheung, Z. Peng, D. R. Powell, Angew. Chem. Int. Ed., 2002,
41, 1566-1568.
L. Zhu, Y. Zhu, X. Meng, J. Hao, Q. Li, Y. Wei, Y. Lin, Chem. Eur. J., 2008, 14, 10923-
10927.
Y. Zhu, L. Wang, J. Hao, P. Yin, J. Zhang, Q. Li, L. Zhu, Y. Wei, Chem. Eur. J., 2009, 15,
3076-3080.
B. Maleki, N. Nasiri, R. Tayebee, A. Khojastehnezhad, H. A. Akhlaghi, RSC Adv., 2016, 6,
79128-79134.
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
S. M. Sadeghzadeh, RSC Adv., 2016, 6, 75973-75980.
L. Fang, G. Wang, W. Guo, Colloids Surf. A: Physicochem. Eng. Asp. 2017, 533, 204-212.
M. Ghanbari, S. Moradi, M. Setoodehkhah, Green Chem. Lett. Rev., 2018, 11, 111-124.
A. Jamshidi, B. Maleki, F. Mohammadi Zonoz, R. Tayebee, Mater. Chem. Phys. 2018, 209, 46-
59.
S. M. Sadeghzadeh, RSC Adv., 2015, 5, 17319-17324.
M. Babaie, H. Sheibani, Arabian J. Chem., 2011, 4, 159-162.
K. S. Dalal, Y. A. Tayade, Y. B. Wagh, D. R. Trivedi, D. S. Dalal, B. L. Chaudhari, RSC
Adv., 2016,6, 14868-14879.
33
34
35
23

New Journal of Chemistry
Page 24 of 25
1
2
3
4
5
6
7
8
9
36
37
38
M. A. Zolfigol, M. Tavasoli, A. R. Moosavi-Zare, P. Moosavi, H. G. Kruger, M. Shiri, VV.iew Article Online
Khakyzadeh, RSC Adv., 2013, 3, 25681-25685.
K. S. Pandit, P. V. Chavan, U. V. Desai, M. A. Kulkarni, P. P. Wadgaonkar, New J. Chem.,
2015, 39, 4452-4463.
R. V. Ragavan, K. M. Kumar, V. Vijayakumar, S. Sarveswari, S. Ramaiah, A. Anbarasu, S.
Karthikeyan, P. Giridharan, N. S. Kumari, Org. Med. Chem. Lett., 2013, 3, 6.
D. Das, R. Banerjee, A. Mitra, J. Chem. Pharm. Res., 2014, 6, 108-116.
D. Bhattacharjee, B. Kshiar, B. Myrboh, RSC Adv., 2016, 6, 95944-95950.
A. R. Moosavi-Zare, M. A. Zolfigol, E. Noroozizadeh, M. Tavasoli, V. Khakyzadeh, A. Zare,
New J. Chem., 2013, 37, 4089-4094.
C. Revanna, T. Swaroop, G. Raghavendra, D. Bhadregowda, K. Mantelingu, K. Rangappa, J.
Heterocycl. Chem., 2012, 49, 851-855.
M. A. E. A. A. A. El-Remaily, Tetrahedron, 2014, 70, 2971-2975.
DOI: 10.1039/C9NJ01160A
39
40
41
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
42
43
44
45
J. Davarpanah, R. Khoram, J. Nanoanalysis, 2017, 4, 20-30.
H. Mecadon, M. R. Rohman, M. Rajbangshi, B. Myrboh, Tetrahedron Lett. 2011, 52, 2523-
2525.
A. B. Atar, J. T. Kim, K. T. Lim, Y. T. Jeong, Synth. Commun., 2014, 44, 2679-2691.
J. Mondal, T. Sen, A. Bhaumik, Dalton Trans., 2012, 41, 6173-6181.
R. Mirbagheri, D. Elhamifar, M. Norouzi, New J. Chem., 2018, 42, 10741-10750.
R. Mirbagheri, D. Elhamifar, J. Alloys Compd. 2019, 790, 783-791.
R.-Y. Guo, Z.-M. An, L.-P. Mo, S.-T. Yang, H.-X. Liu, S.-X. Wang, Z.-H. Zhang,
Tetrahedron,2013, 69, 9931-9938.
46
47
48
49
50
51
J. B. Gujar, M. A. Chaudhari, D. S. Kawade, M. S. Shingare, Tetrahedron Lett., 2014, 55,
6030-6033.
24

Page 25 of 25
New Journal of Chemistry
View Article Online
DOI: 10.1039/C9NJ01160A
1
2
3
4
Graphical abstract
5
6
7
8
9
A novel core-shell structured magnetic silica supported propylamine/molybdate complex
(Fe3O4@SiO2/Pr-N=Mo[Mo5O18]) is prepared, characterized and applied as effective and easily
recoverable nanocatalyst in the synthesis of pyrano-pyrazole derivatives.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60