H3PMo12O40-immobilized chitosan/Co3O4: A novel and recyclable nanocomposite for the synthesis of pyrimidinedione derivatives

Article abstract of DOI:10.1002/aoc.4748

An efficient three-component reaction of aromatic aldehydes, 6-aminouracil/6-amino-1,3-dimethyluracil and 4-hydroxycoumarin in the presence of a novel heterogeneous catalyst H₃PMo₁₂O₄₀-immobilized Co₃O₄

Full text of DOI:10.1002/aoc.4748

Received: 9 August 2018
DOI: 10.1002/aoc.4748
Revised: 25 October 2018
Accepted: 8 November 2018
F U L L P A P E R
H3PMo12O40‐immobilized chitosan/Co3O4: A novel and
recyclable nanocomposite for the synthesis of
pyrimidinedione derivatives
Javad Safari1 | Mona Tavakoli1
| Mohammad Ali Ghasemzadeh2
1 Department of Organic Chemistry,
Faculty of Chemistry, University of
Kashan, Kashan 87317, Iran
2 Department of Chemistry, Qom Branch,
Islamic Azad University, Qom, Iran
An efficient three‐component reaction of aromatic aldehydes, 6‐aminouracil/
6‐amino‐1,3‐dimethyluracil and 4‐hydroxycoumarin in the presence of a novel
heterogeneous catalyst H3PMo12O40‐immobilized Co3O4/chitosan led to a
synthesis of a new class of pyrimidinedione derivatives under reflux conditions.
The magnetically recoverable nanocomposite of Co3O4/chitosan/H3PMo12O40
was fully characterized by Fourier transform‐infrared spectrophotometry,
scanning electron microscopy, X‐ray powder diffraction, energy‐dispersive
X‐ray spectroscopy, vibrating‐sample magnetometry and N2 adsorption–
desorption by Brunauer–Emmett–Teller analysis. Results show that Keggin‐
type 12‐molybdophosphoric acid immobilized into the network of the
cross‐linked chitosan with super‐paramagnetic Co3O4 nanoparticles. The pres-
ent method offers several advantages, such as simple procedure, short reaction
times and excellent yields of products. The novelty of the catalyst, high cata-
lytic activity, easy separation from the reaction with an external magnetic
field and reusability of the catalyst in six consecutive runs are additional eco‐
friendly attributes of this catalytic system.
Correspondence
Javad Safari, Department of Organic
Chemistry, Faculty of Chemistry,
University of Kashan, Kashan 87317, Iran.
Email: safari_jav@yahoo.com;
safari@kashanu.ac.ir
Funding information
Research Council of the University of
Kashan
KEYWORDS
Co3O4/chitosan/H3PMo12O40, heterogeneous catalyst, multi‐component reaction, nanocomposite,
pyrimidinedione
1 | INTRODUCTION
physiological and biological activities.[5,6] Coumarin
derivatives have been used for their anti‐HIV,[7] antibacte-
Multi‐component reactions (MCRs) are effective tools in
organic reactions to form several carbon–carbon and
carbon–heteroatom bonds and produce a great level of
diversity.[1] MCRs are an important area of research in
organic chemistry because of their advantages, such as
ease of execution, high degree of atom, combinatorial
and medicinal economy compared with multi‐step
reactions.[2–4]
rial,[8] anti‐inflammatory,[9] anti‐edema,[10] anticoagu-
lant[11] and antioxidant activities.[12] Also, they have
been applied in diverse ailments, such as cancer, burns,
cardiovascular and rheumatic diseases.[13] On the other
hand, heterocyclic compounds containing nitrogen atoms
such as pyrimidine and its derivatives have found applica-
tions in biologically active and medicinal compounds.[14]
Owing to the wide range of pharmacological and
biological activities of coumarin and pyrimidine, there is
always high interest for organic chemists to develop a new
route for the synthesis of this class of heterocycles.
Over the last 20 years, heterocycles containing couma-
rin molecules in their structures have attracted a
great deal of attention in various pharmacological,
Appl Organometal Chem. 2019;e4748.
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© 2019 John Wiley & Sons, Ltd.
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SAFARI ET AL.
Additionally, the design of efficient, recyclable and valuable
catalysts is important from a green chemistry point of view.
Magnetic nanoparticles (MNPs) as a solid support
material have been widely utilized for the design of het-
erogeneous catalysts in many MCRs.[15–18] Other impor-
tant features of these magnetic catalysts are high
stability, low toxicity, easy synthesis and high catalytic
activities. In addition, the magnetic properties of the
catalyst allow facile separation from the reaction mixture
through means of an external magnetic field.[19–23]
Among metal oxides, spinel‐type cobalt oxide
NPs (Co3O4 NPs) are an important class of magnetic mate-
rial that have been extensively investigated for their great
effects on proton relaxation, and formation of organic–
metal compounds and metal–biopolymer systems.[24,25]
Chitosan is a naturally derived cationic polysaccha-
ride that is readily subjected to chemical modification
due to the presence of three reactive sites, including a pri-
mary amine and two primary or secondary hydroxyl
groups per N‐acetyl glucosamine unit.[26]
In the past decade, the use of heteropolyacids (HPAs)
and related polyoxometalate compounds in the structure
of catalysts has been employed in many selective transfor-
mations of organic substances.[27] The supported HPA
catalysts have several advantages, such as strong Brønsted
acidity, higher stability, low toxicity and high catalytic
activity, which make them economically and environ-
mentally attractive in studying the catalytic process.[28–32]
In this work, we report a novel magnetic Co3O4/chito-
san/H3PMo12O40 nanocomposite (Figure 1), in which 12‐
molybdophosphoric acid (PMo) molecules immobilized
chitosan/Co3O4 NPs as an efficient and recoverable cata-
lyst for the synthesis of a new class of pyrimidinediones
derivatives via a three‐component reaction of aromatic
aldehyde, 6‐aminouracil/6‐amino‐1,3‐dimethyluracil and
4‐hydroxycoumarin.
2 | EXPERIMENTAL
2.1 | General information
Chemical reagents of high purity were purchased from
the Merck Chemical Company. Melting points were
determined in open capillaries using an Electrothermal
Mk3 apparatus and are uncorrected. 1H‐NMR spectra
were recorded with a Bruker DRX‐400 spectrometer at
400 MHz. Fourier transform‐infrared spectroscopy (FT‐
IR) spectra were obtained with potassium bromide pellets
in the range 400–4000 cm−1with a Perkin‐Elmer 550
spectrometer. UV–Vis measurements were obtained with
a GBC cintra6 UV–Vis spectrophotometer. Nanostruc-
tures were characterized using a Holland Philips Xpert
X‐ray powder diffraction (XRD) diffractometer (CuK,
radiation, = 0.154056 nm), at a scanning speed of 2
min−1 from 10º to 100º (2). Scanning electron micro-
scope (SEM) characterization was performed on a FEI
Quanta 200 SEM operated at a 20 kV accelerating voltage.
Magnetic properties were characterized by a vibrating‐
sample magnetometer (VSM, MDKFD, University of
Kashan, Kashan, Iran) at room temperature. The composi-
tional analysis was performed by energy‐dispersive X‐ray
spectroscopy (EDX; Kevex, Delta Class I). The specific
surface area was measured via Brunauer–Emmett–Teller
(BET) N2 adsorption–desorption method by using a
BELSORP‐mini IIinstrument.
2.2 | Preparation of Co3O4 NPs
Co3O4 MNPs were prepared according to a previously
reported procedure by Linetal.[33] First, cobalt nitrate
hexahydrate (8.60 g) was dissolved in 100 mL of ethanol
and the mixture was vigorously stirred. Then, the mixture
FIGURE 1 Preparation process of Co3O4/chitosan/PMo

SAFARI ET AL.
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was heated to 50°C and kept for 30 min; finally, oxalic acid
(2.14 g) was added quickly to the solution and the reaction
mixture was stirred for 2 h at 50°C. The formed precipitate
including cobalt (II) oxalate was collected by centrifuges
and, then, the prepared cobalt (II) oxalate powder was
calcined at 400°C for 2 h to produce Co3O4 NPs.
until completion of the reaction. After completion of the
reaction as indicated by thin‐layer chromatography, the
catalyst was separated by an external magnet. Then the
reaction mixture was allowed to cool at room tempera-
ture, and the resulting precipitate was filtered, washed
and recrystallized with ethanol and water.
2.3 | Preparation of H3PMo12O40
2.6 | Analytical data of selected products
The heteropolyoxometalate H3PMo12O40 was prepared
using chemical coprecipitation described in the litera-
ture.[34] In short, 200 mL of a solution of Na2MoO4
(3 M) was added successively to 3.5 mL of 85% H3PO4
and 150 mL of 70% HClO4. The disodium salt
Na2HPMo12O40 precipitated from the yellow solution.
After filtering the mixture, the obtained powder was air‐
dried. H3PMo12O40 was obtained from a solution of 50 g
Na2HPMo12O40 in 50 mL of H2O, acidified by 10 mL of
37% HC1, and extracted by 80 mL Et2O. Water was added
to the heavy layer and yellow crystals of H3PMo12O40
were precipitated.
2.6.1 | 6‐Amino‐5‐((4‐hydroxy‐2‐oxo‐2H‐
chromen‐3‐yl)(phenyl)methyl)‐1,3
dimethylpyrimidine‐2,4(1H,3H)‐dione (4a)
White solid; yield: 83%; IR (KBr): 3433, 3233, 1695, 1667,
1
1616, 1568, 1510 cm−1; H‐NMR (400 MHz, DMSO‐d6):
14.00 (s, 1H, OH), 7.84 (d, J = 7.6 Hz, 1H, Ar‐H), 7.65
(t, J = 7.2 Hz, 1H, Ar‐H), 7.44 (d, J = 8.0 Hz, 1H, Ar‐H),
7.35 (d, J = 7.6 Hz, 2H, Ar‐H), 7.34 (s, 2H, NH2), 7.23
(t, J = 7.6 Hz, 2H, Ar‐H), 7.15 (d, J = 5.6 Hz, 2H, Ar‐H),
5.63 (s, 1H, CH), 3.38 (s, 3H, CH3), 3.14 (s, 3H, CH3)
ppm; anal. calcd for C22H19N3O5: C, 65.18; H, 4.72; N,
10.37%; found: C, 65.08; H, 4.78; N, 10.31%.
2.4 | Procedure for the preparation of
Co3O4/CS/PMo
2.6.2 | 6‐Amino‐5‐((4‐chlorophenyl)(4‐
hydroxy‐2‐oxo‐2H‐chromen‐3‐yl)methyl)‐1,3‐
dimethylpyrimidine‐2,4(1H,3H)‐dione (4b)
For the synthesis of chitosan/Co3O4 core‐shell (CS‐
Co3O4), 0.5 g of Co3O4 NPs was added to a solution con-
taining 0.5 g of chitosan in 50 mL of 0.05 M acetic acid
solution. The resulting mixtures were heated to 40°C,
and 12 mL of 4 wt% glutaraldehyde aqueous solution
was added drop by drop under mechanical agitation.
Then, the reactant mixtures were heated and stirred for
1 h at 40°C and 1 h at 60°C. The cross‐linking chitosan‐
coated Co3O4 (CS‐Co3O4) was formed in the process.
For the preparation of Co3O4/CS/PMo materials, 20
mL of aqueous solution containing H3PMo12O4 (0.045 g
mL−1) was added to the mixture and stirred for 0.5 h at
60°C. Finally, the black gel products were separated by
centrifugation, washed several times with deionized
water and ethanol, and dried in vacuum at 60°C for 8 h.
White solid; yield: 95%; IR (KBr): 3408, 3243, 1697, 1663,
1
1617, 1570, 1508 cm−1; H‐NMR (400 MHz, DMSO‐d6):
13.98 (s, 1H, OH), 7.84 (d, J = 7.8 Hz, 1H, Ar‐H), 7.65
(t, J = 6.1 Hz, 1H, Ar‐H), 7.44 (d, J = 6.6 Hz, 1H, Ar‐H),
7.36 (t, J = 6.2 Hz, 1H, Ar‐H), 7.36 (s, 2H, NH2), 7.28 (d,
J = 6.1 Hz, 2H, Ar‐H), 7.18 (d, J = 6.8 Hz, 2 H, Ar‐H),
5.62 (s, 1H, CH), 3.38 (s, 3H, CH3), 3.15 (s, 3H, CH3)
ppm; anal. calcd for C22H18ClN3O5: C, 60.08; H, 4.13;
N, 9.55%; found: C, 60.10; H, 4.18; N, 9.50%.
2.6.3 | 6‐Amino‐5‐((4‐hydroxy‐2‐oxo‐2H‐
chromen‐3‐yl)(4‐isopropylphenyl)methyl)‐
1,3‐dimethylpyrimidine‐2,4(1H,3H)‐dione
(4c)
2.5 | General procedure for the synthesis
of pyrimidinedione catalyzed by Co3O4/CS/
PMo nanocomposite
White solid; yield: 80%; IR (KBr): 3399, 3229, 1696, 1613,
1
1570, 1508 cm−1; H‐NMR (400 MHz, DMSO‐d6): 13.98
A mixture of 4‐hydroxycoumarin (1 mmol, 0.162 g), aro-
matic aldehydes (1 mmol) and Co3O4/CS/PMo (0.005 g)
was dissolved in EtOH (5 mL) and stirred under reflux
condition for 15 min. Afterwards, 6‐aminouracil (1 mmol,
0.127 g) or 6‐amino‐1,3‐dimethyluracil (1 mmol, 0.155 g)
was added to the solution and stirring was continued
(s, 1H, OH), 7.84 (d, J = 7.2 Hz, 1H, Ar‐H), 7.65 (t, J =
7.2 Hz, 1H, Ar‐H), 7.44 (d, J = 8.4 Hz, 1H, Ar‐H), 7.37
(t, J = 7.6 Hz, 1H, Ar‐H), 7.32 (s, 2H, NH2), 7.10 (d, J =
7.6 Hz, 2H, Ar‐H), 7.04 (d, J = 7.2 Hz, 2H, Ar‐H), 5.57
(s, 1H, CH), 3.37 (s, 3H, CH3), 3.14 (s, 3H, CH3), 2.84–
2.80 (m, 1H, CH), 1.17 (d, 6H, 2CH3) ppm; anal. calcd

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SAFARI ET AL.
for C25H25N3O5: C, 67.10; H, 5.63; N, 9.39%; found: C,
67.05; H, 5.78; N, 9.31%.
Ar‐H), 7.93 (s, 1H, Ar‐H), 7.85 (d, J = 7.6 Hz, 1H, Ar‐H),
7.68 (d, J = 7.6 Hz, 2H, Ar‐H), 7.54 (t, J = 8.0 Hz, 1H,
Ar‐H), 7.45 (d, J = 8.8 Hz, 1H, Ar‐H), 7.42 (s, 2H, NH2),
7.37 (t, J = 7.6 Hz, 1H, Ar‐H), 5.76 (s, 1H, CH), 3.38
(s, 3H, CH3), 3.14 (s, 3H, CH3) ppm; anal. calcd for
C22H18N4O7: C, 58.67; H, 4.03; N, 12.44%; found: C,
58.70; H, 4.10; N, 12.28%.
2.6.4 | 6‐Amino‐5‐((4‐bromophenyl)(4‐
hydroxy‐2‐oxo‐2H‐chromen‐3‐yl)methyl)‐1,3‐
dimethylpyrimidine‐2,4(1H,3H)‐dione (4d)
White solid; yield: 91%; IR (KBr): 3410, 3223, 1698, 1663,
1615, 1596, 1507 cm−1; H‐NMR (400 MHz, DMSO‐d6):
1
2.6.8 | 6‐Amino‐5‐((4‐hydroxy‐2‐oxo‐2H‐
chromen‐3‐yl)(4‐nitrophenyl)methyl)‐1,3‐
dimethylpyrimidine‐2,4(1H,3H)‐dione (4h)
13.98 (s, 1H, OH), 7.83 (d, J = 7.2 Hz, 1H, Ar‐H), 7.66
(t, J = 7.6 Hz,1H, Ar‐H), 7.43–7.39 (m, 4H, Ar‐H), 7.36
(s, 2H, NH2), 7.12 (d, J = 8.0 Hz, 2H, Ar‐H), 5.58 (s, 1H,
CH), 3.37 (s, 3H, CH3), 3.14 (s, 3H, CH3) ppm; anal. calcd
for C22H18BrN3O5: C, 54.56; H, 3.75; N, 8.68%; found: C,
54.61; H, 3.78; N, 8.75%.
Pale yellow solid; yield: 92%; IR (KBr): 3382, 3211, 1667,
1
1619, 1571, 1514 cm−1; H‐NMR (400 MHz, DMSO‐d6):
13.96 (s, 1H, OH), 8.10 (d, J = 7.1 Hz, 2H, Ar‐H), 7.85
(d, J = 6.3 Hz, 1H, Ar‐H), 7.67 (t, J = 6.3 Hz, 1H, Ar‐H),
7.48–7.44 (m, 1H, Ar‐H), 7.43 (s, 2H, NH2), 7.19 (t, J =
6.0 Hz, 1H, Ar‐H), 5.75 (s, 1H, CH), 3.39 (s, 3H, CH3),
3.15 (s, 3H, CH3) ppm; anal. calcd for C22H18N4O7: C,
58.67; H, 4.03; N, 12.44%; found: C, 58.55; H, 4.10; N,
12.38%.
2.6.5 | 6‐Amino‐5‐((4‐fluorophenyl)(4‐
hydroxy‐2‐oxo‐2H‐chromen‐3‐yl)methyl)‐1,3‐
dimethylpyrimidine‐2,4(1H,3H)‐dione (4e)
White solid; yield: 93%; IR (KBr): 3430, 3235, 1693, 1651,
1
1617, 1570, 1505 cm−1; H‐NMR (400 MHz, DMSO‐d6):
14.00 (s, 1H, OH), 7.83 (d, J = 8.0 Hz,1H,Ar‐H), 7.65
(t, J = 7.6 Hz, 1H, Ar‐H), 7.43 (d, J = 8.4 Hz, 1H, Ar‐H),
7.37 (d, J = 7.6 Hz, 1H, Ar‐H), 7.34 (s, 2H, NH2), 7.17
(t, J = 8.0 Hz, 2H, Ar‐H), 7.04 (t, J = 8.8 Hz, 2H, Ar‐H),
5.60 (s, 1H, CH), 3.37 (s, 3H, CH3), 3.14 (s, 3H, CH3)
ppm; anal. calcd for C22H18FN3O5: C, 62.41; H, 4.29; N,
9.92%; found: C, 62.45; H, 4.38; N, 8.85%.
2.6.9 | 6‐Amino‐5‐(1‐(4‐hydroxy‐2‐oxo‐2H‐
chromen‐3‐yl)‐2‐methylpropyl)‐1,3‐
dimethylpyrimidine‐2,4(1H,3H)‐dione (4i)
White solid; yield: 81%; IR (KBr): 3403, 3209, 1702, 1615,
1
1570, 1500 cm−1; H‐NMR (400 MHz, DMSO‐d6): 13.00
(s, 1 H, OH), 8.00–7.95 (m, 1H, Ar‐H), 7.58–7.50 (m, 1H,
Ar‐H), 7.35–7.20 (m, 2H, Ar‐H), 6.43 (s, 2H, NH2), 3.68
(d, J = 11 Hz, 1H, CH), 3.51 (s, 3H, CH3), 3.40 (s, 3H,
CH3), 3.20–3.31 (m, 1H, CH), 1.10 (d, 6H, 2CH3) ppm;
anal. calcd for C19H21N3O5: C, 61.45; H, 5.70; N, 11.31%;
found: C, 61.40; H, 5.72; N, 11.29%.
2.6.6 | 6‐Amino‐5‐((4‐hydroxy‐2‐oxo‐2H‐
chromen‐3‐yl)(p‐tolyl)methyl)‐1,3‐
dimethylpyrimidine‐2,4(1H,3H)‐dione (4f)
White solid; yield: 87%; IR (KBr): 3401, 3224, 1697, 1616,
1
1569, 1508 cm−1; H‐NMR (400 MHz, DMSO‐d6): 13.97
(s, 1H, OH), 7.83 (d, J = 8.0 Hz, 1H, Ar‐H), 7.65 (t, J =
8.0 Hz, 1H, Ar‐H), 7.43 (d, J = 8.0 Hz, 1H, Ar‐H), 7.36
(t, J = 7.6 Hz, 1H, Ar‐H), 7.31 (s, 2H, NH2), 7.04 (d, J =
8.4 Hz, 2H, Ar‐H), 7.78 (d, J = 8.8 Hz, 2H, Ar‐H), 5.56
(s, 1H, CH), 3.37 (s, 3H, CH3), 3.14 (s, 3H, CH3) ppm;
anal. calcd for C23H21N3O5: C, 65.86; H, 5.05; N, 10.02%;
found: C, 65.90; H, 5.10; N, 10.08%.
2.6.10 | 6‐Amino‐5‐((4‐hydroxy‐2‐oxo‐2H‐
chromen‐3‐yl)(phenyl)methyl)pyrimidine‐
2,4(1H,3H)‐dione (4j)
White solid; yield: 82%; IR (KBr): 3413, 3192, 1714, 1703,
1
1622, 1580, 1504 cm−1; H‐NMR (400 MHz, DMSO‐d6):
14.05 (s, 1H, OH), 11.08 (s, 1H, NH), 10.78 (s, 1H, NH),
7.81 (d, J = 7.6 Hz, 1H, Ar‐H), 7.64 (t, J = 7.2 Hz, 1H,
Ar‐H), 7.41 (d, J = 8.4 Hz, 1H, Ar‐H), 7.35 (t, J = 7.2 Hz,
1H, Ar‐H), 7.24 (t, J = 7.2 Hz, 2H, Ar‐H), 7.14 (t, J = 7.6
Hz, 2H, Ar‐H), 7.06 (t, J = 7.2 Hz, 1H, Ar‐H), 6.62
(s, 2H, NH2), 5.50 (s, 1H, CH) ppm; anal. calcd for
C20H15N3O5: C, 63.66; H, 4.01; N, 11.14%; found: C,
63.60; H, 4.15; N, 11.08%.
2.6.7 | 6‐Amino‐5‐((4‐hydroxy‐2‐oxo‐2H‐
chromen‐3‐yl)(3‐nitrophenyl)methyl)‐1,3‐
dimethylpyrimidine‐2,4(1H,3H)‐dione (4g)
Pale yellow solid; yield: 85%; IR (KBr): 3459, 3208, 1703,
1672, 1612, 1570, 1520 cm−1
;
1H‐NMR (400 MHz,
DMSO‐d6): 13.96 (s, 1H, OH), 8.05 (d, J = 8.0 Hz, 1H,

SAFARI ET AL.
5 of 12
(622) planes of cubic normal spinel Co3O4 (JCPDS No.
74–1656).[24,25,35] So, these characteristic diffraction peaks
indicate the presence of magnetite NPs in the catalyst. As
shown in Figure 2b, the weak, broad diffraction hump in
the 2θ‐range ∼20º to 30º typically originates from an
amorphous material, which in this case corresponds to
the amorphous chitosan/PMo phase. The average particle
size of these Co3O4 is estimated to be about 22 nm
according to the Debye–Scherrer equation.
The SEM image and size distribution of Co3O4/CS/
PMo nanocomposite are shown in Figure 3. The analysis
of SEM images shows an almost monodispersed spherical
shape of Co3O4/CS/PMo nanocomposite. Figure 3b shows
the particle size distribution of the nanocomposite. It is
clear that the diameter sizes of the Co3O4/CS/PMo are
approximately in the range of 15–40 nm with an average
particle size of about 25–30 nm.
2.6.11 | 6‐Amino‐5‐((4‐chlorophenyl)(4‐
hydroxy‐2‐oxo‐2H‐chromen‐3‐yl)methyl)
pyrimidine‐2,4(1H,3H)‐dione (4k)
White solid; yield: 93%; IR (KBr): 3398, 3163, 1720, 1690,
1
1620, 1571, 1507 cm−1; H‐NMR (400 MHz, DMSO‐d6):
14.06 (s, 1H, OH), 11.12 (s, 1H, NH), 10.81 (s, 1H, NH),
7.80 (d, J = 8.0 Hz, 1H, Ar‐H), 7.64 (t, J = 7.6 Hz, 1H,
Ar‐H), 7.42 (d, J = 8.0 Hz, 1H, Ar‐H), 7.35 (t, J = 7.6 Hz,
1H, Ar‐H), 7.28 (d, J = 8.0 Hz, 2H, Ar‐H), 7.16 (d, J =
8.0 Hz, 2H, Ar‐H), 6.66 (s, 2H, NH2), 5.48 (s, 1H, CH)
ppm; anal. calcd for C20H14ClN3O5: C, 58.33; H, 3.43; N,
10.20%; found: C, 58.38; H, 3.48; N, 10.33%.
2.6.12 | 6‐Amino‐5‐((4‐fluorophenyl)(4‐
hydroxy‐2‐oxo‐2H‐chromen‐3‐yl)methyl)
pyrimidine‐2,4(1H,3H)‐dione (4l)
The FT‐IR spectra of (a) Co3O4 NPs, (b) chitosan, (c)
H3PMo12O4 and (d) Co3O4/CS/PMo are shown in
Figure 4. The FT‐IR spectra of the cobalt oxide NPs were
confirmed by two strong stretching vibrations at 567 and
664 cm−1, which are related to Co–O bond (Figure 4a).
Also, the presence of peaks at 567 and 662 cm−1 of
Co3O4 indicates the successful cross‐linking of chitosan
on the Co3O4 particle surface by glutaraldehyde as
cross‐linker (Figure 4d). The main bonds appearing in
the chitosan spectrum are due to the O‐H streching vibra-
tion near 3408 cm−1 superimposed on the N─H
stretching bond and intermolecular hydrogen bonds of
the polysaccharide. The characteristic absorption peaks
of –CH2 stretching vibration and –CH3 stretching vibra-
White solid; yield: 90%; IR (KBr): 3396, 3175, 1714, 1700,
1
1622, 1587, 1505 cm−1; H‐NMR (400 MHz, DMSO‐d6):
14.05 (s, 1H, OH), 11.10 (s, 1H, NH), 10.79 (s, 1H, NH),
7.81 (d, J = 7.6 Hz, 1H, Ar‐H), 7.64 (t, J = 7.6 Hz, 1H,
Ar‐H), 7.42 (d, J = 8.4 Hz, 1H, Ar‐H), 7.35 (d, J = 7.6
Hz, 1H, Ar‐H), 7.15 (t, J = 7.6 Hz, 2H, Ar‐H), 7.05 (d, J
= 8.4 Hz, 2H, Ar‐H), 6.64 (s, 2H, NH2), 5.48 (s, 1H, CH)
ppm; anal. calcd for C20H14FN3O5: C, 60.76; H, 3.57; N,
10.63%; found: C, 60.68; H, 3.50; N, 10.55%.
2.6.13 | 6‐Amino‐5‐((4‐bromophenyl)(4‐
hydroxy‐2‐oxo‐2H‐chromen‐3 yl)methyl)
pyrimidine‐2,4(1H,3H)‐dione(4m)
tion appear at 2922 and 2880 cm−1
, respectively
(Figure 4b and d). In addition, the stretching vibration
characteristic peak of C=N at 1622 cm−1 in the FT‐IR
spectrum of Co3O4/CS/PMo is due to the cross‐linking
reaction by glutaraldehyde (Figure 4d). As indicated in
Figure 4c, the FT‐IR spectra of H3PMo12O4 were charac-
terized by the following absorption bonds: P–O stretching
at 1064 cm−1; terminal Mo=Oa at 962 cm−1; and two
bonds attributed to Mo–Ob–Mo and Mo–Oc–Mo bridge
appearing at 868 and 781 cm−1, respectively. These
absorption bonds shifted to 1056, 948, 871 and 799 cm−1
by mixing of the chitosan. These shifts confirmed the
interaction through hydrogen bonding between the –
White solid; yield: 88%; IR (KBr): 3396, 3183, 3056, 1720,
1690, 1620, 1571, 1509 cm−1; 1H‐NMR (400 MHz, DMSO‐
d6): 14.05 (s, 1H, OH), 11.21 (s, 1H, NH), 10.80 (s, 1H,
NH), 7.80 (d, J = 8.0 Hz, 1H, Ar‐H), 7.64 (t, J = 7.2 Hz,
1H, Ar‐H), 7.42–7.40 (m, 3H, Ar‐H), 7.35 (t, J = 7.2 Hz,
1H,Ar‐H), 7.10 (d, J = 8.4 Hz, 2H, Ar‐H), 6.65 (s, 2H,
NH2), 5.46 (s, 1H, CH) ppm; anal. calcd for
C20H14BrN3O5: C, 52.65; H, 3.09; N, 9.21%; found: C,
52.61; H, 3.18; N, 9.33%.
+
NH3 in the chitosan and Mo=Oa or Mo–O–Mo groups
3 | RESULTS AND DISCUSSION
in the PMo molecules. These facts are consistent with
the synthesis design, and confirm that 12‐
molybdophosphoric acid immobilized into the network
of the cross‐linked chitosan with super‐paramagnetic
Co3O4 NPs.
Elemental composition is calculated from the EDX
(Figure 5). The elemental compositions of magnetic
Co3O4/CS/PMo nanocomposite are 8.13%, 4.60%,
The magnetically heterogeneous catalyst Co3O4/CS/PMo
is characterized by XRD, SEM, FT‐IR, EDX,VSM and
BET analysis.
The XRD patterns of Co3O4 and Co3O4/CS/PMo are
shown in Figure 2.
There are eight diffraction peaks that related to the
(111), (220), (311), (222), (400), (511), (440), (620) and

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SAFARI ET AL.
FIGURE 2 X‐ray powder diffraction (XRD) of (a) Co3O4 magnetic nanoparticles (MNPs) and (b) Co3O4/CS/PMo nanocomposite
FIGURE 3 (a) Scanning electron microscopy (SEM) images of Co3O4/CS/PMo nanocomposite. (b) Particle size distribution of Co3O4/CS/
PMo nanocomposite
36.59%, 0.94%, 9.47% and 32.71% for C, N, O, P, Co and
Mo, respectively. These data demonstrate the formation
of Co3O4/CS/PMo nanocomposite.
attributed to the existence of non‐magnetic materials on
the surface of Co3O4 MNPs. Thus, such a magnetic prop-
erty for Co3O4/CS/PMo nanocomposite is strong enough
to be quickly and easily separated from the reaction mix-
ture by a magnetic field.
The surface area properties were determined by the
BET method. The BET surface area and total pore vol-
ume of Co3O4/CS/PMo nanocomposite were 6.61 m2 g−1
and 3.18 cm3 g−1, respectively (Figure 7). It can be
observed that the surface area of Co3O4/CS/PMo
decreases gradually due to the chitosan polymer and
heavy atoms (i.e. Mo) of PMo clusters that constitute
the frameworks.
The magnetic properties of Co3O4 and Co3O4/CS/PMo
nanocomposite were investigated with VSM at room tem-
perature, as shown in Figure 6. The absence of a hystere-
sis loop in the curve indicates that there are no remanent
magnetization and coercivity in bare Co3O4 NPs and
Co3O4/CS/PMo nanocomposite at room temperature,
which testifies to their super‐paramagnetic behaviors.
The results of VSM show that the saturation magnetiza-
tion value of Co3O4/CS/PMo (35.23 emu g−1) was lower
than pure Co3O4 NPs (52.37 emu g−1). The decrease is

SAFARI ET AL.
7 of 12
FIGURE 4 Fourier transform‐infrared
(FT‐IR) spectra of (a) pure Co3O4
nanoparticles (NPs), (b) chitosan, (c)
H3PMo12O4 and (d) Co3O4/CS/PMo
nanocomposite
FIGURE 5 Energy‐dispersive X‐ray spectroscopy (EDX) analysis of Co3O4/CS/PMo nanocomposite
FIGURE 6 Vibrating‐sample
magnetometry (VSM) magnetization
curves of (a) Co3O4 magnetic
nanoparticles (MNPs) and (b) Co3O4/CS/
PMo nanocomposite

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SAFARI ET AL.
TABLE 1 The effects of different solvent on the model reaction
Entry
Solvent
Time (min)
Yield (%)a
1
2
3
4
5
6
7
Solvent‐free (80°C)
CCl4
60
60
60
60
60
60
60
42
Trace
20
CH2Cl2
C4H8O2
EtOH
45
95
CH3CN
H2O
83
75
aYields of isolated products.
Our investigation began with the performances of the
solvents. To find the best solvent for this reaction, the
model reaction was carried out in several solvents, such
as CCl4, C4H8O2, CH2Cl2, EtOH, CH3CN, H2O and also
under solvent‐free conditions. As Table 1 shows, EtOH
was used as the most appropriate reaction medium in
terms of yield and reaction time. In addition to this, there
was no reaction observed in non‐polar CCl4 even after 60
min. The yield gradually decreased as we moved from
highly polar to less polar solvents. It seems that the
remarkable differences between the results presented in
Table 1 are related to the hydrogen bonding between eth-
anol and substrates that promote the nucleophilic attack
of the reactants.
FIGURE 7 Brunauer–Emmett–Teller (BET) analysis of Co3O4/
CS/PMo nanocomposite
In the fabrication of magnetically recoverable acid
nanocatalyst, chitosan was chosen as an enveloping
material for surface modification of the magnetic core of
Co3O4 NPs, HPA as an acid catalyst and glutaraldehydes
as cross‐linking agents to form the network chitosan
derivatives. Chitosan envelops Co3O4 NPs to isolate the
immobilized H3PMo12O40 from basic Co3O4, and creates
a significant barrier to prevent Co3O4 NPs from agglomer-
ation, leakage and dissolution under acidic conditions.
Free amines in chitosan act as not only the nucleophilic
functional groups attacking the carbonyl in glutaralde-
hyde to lead formation of the network polymer layer on
the surface of Co3O4 NPs, but also the basic functional
groups reacting with H3PMo12O40 molecules to anchor
them on the network polymer layer. The function of free
amines in chitosan sets the stage for the successful prep-
aration of magnetically recoverable nanocatalysts con-
taining HPAs.
Water has been identified as an ideal solvent in this
reaction because it is inexpensive, abundant and environ-
mentally benign. However, when the same reaction is
TABLE 2 The effect of various temperatures on the model
reaction
Entry
Temperature (°C)
Time (min)
Yield (%)a
1
2
3
4
5
6
25
50
60
70
80
90
60
60
60
60
60
60
20
35
60
84
95
95
After the characterization of the catalyst, in order to
optimize the reaction conditions, we used 4‐
chlorobenzaldehyde 1, 4‐hydroxycoumarin 2 and 6‐
amino‐1,3‐dimethyluracil 3 in the presence of Co3O4/
CS/PMo as a model reaction under different conditions
(Scheme 1).
aYields of isolated products.
SCHEME 1 Three‐component
synthesis of pyrimidinedione derivatives
catalyzed by Co3O4/CS/PMo
nanocomposite

SAFARI ET AL.
9 of 12
TABLE 3 The effects of various catalyst on the model reaction
being achieved after 60 min for the model reaction car-
ried out at 80°C. The yield of product 4b was fixed at tem-
peratures higher than 80ºC after 60 min.
Entry
Catalyst
Time (min)
Yield (%)a
1
2
3
4
5
6
MgO NPs
CuI NPs
60
60
60
60
60
60
48
65
77
83
81
95
To compare the efficiency of catalytic activity of the
Co3O4/CS/PMo with other catalysts, the model reaction
was performed in the presence of various catalysts, such
as MgO NPs, CuI NPs, Co3O4 NPs, PMo and CS/PMo
(Table 3). The results showed that the reaction in the
presence of Co3O4/CS/PMo afforded the product in
higher yield and with a shorter reaction time under reflux
conditions.
Co3O4 NPs
PMo
CS/PMo
Co3O4/CS/PMo
aYields of isolated products.NPs, nanoparticles.
To find the optimum amount of magnetic catalyst, the
model reaction was carried out using an amount of nano-
composite from 0 to 0.007 g. It was observed that no prod-
uct was obtained in the absence of the catalyst, and the
yield was obviously affected by the amount of Co3O4/
CS/PMo. Based on these results, the yield increased with
the addition of Co3O4/CS/PMo and the optimal amount
of catalyst was 0.005 g. In addition, a higher amount of
catalyst from the optimum point had no significant
changes on yield (Table 4).
carried out in ethanol, the yield of the reaction is higher
and the reaction time shorter than for water solvent.
As shown in Table 2, temperature plays an important
role in reaction time and product yield. As expected,
increasing the reaction temperature resulted in a signifi-
cant enhancement in the reaction rate, with 95% yield
TABLE 4 The effects of amount of catalyst on the model reaction
By considering the optimal conditions, we next
utilized a diversity of aldehydes to investigate three‐
component reactions under reflux conditions. As
expected, the aldehyde including substituted electron‐
withdrawing reacted faster than those with electron‐
donating groups, giving the corresponding products in
short reaction times and high yields. In general, the reac-
tions are clean and satisfactory results were observed, and
these are summarized in Table 5.
Entry
Catalyst (g)
Time (min)
Yield (%)a
1
2
3
4
5
None
0.001
0.003
0.005
0.007
60
60
60
60
60
Trace
37
88
95
95
aYields of isolated products.
TABLE 5 Co3O4/CS/PMo catalyzed synthesis of pyrimidinediones derivativesa
Entry
R1
R2
Product
Time (min)
Yield (%)b
m.p. (ºC)
Lit. m.p. (ºC)
1
H
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
4a
50
60
60
45
45
60
45
35
60
50
45
35
45
83
95
80
91
93
87
85
92
81
82
93
90
88
191–193
210–212
255–256
235–236
250–252
219–220
255–256
244–246
221–222
224–226
237–238
235–237
238–240
188–192[36]
209–211[36]
257–259[36]
237–238[37]
248–250[37]
218–220[36]
257–259[38]
240–242[36]
222–224[39]
2
4‐Cl
4b
4c
3
4‐i‐Propyl
4
4‐Br
4d
4e
5
4‐F
6
4‐CH3
4f
7
3‐NO2
4 g
4 h
4i
8
4‐NO2
9
isobutyraldehyde
c
10
11
12
13
H
4j
–
c
4‐Cl
4‐F
4‐Br
H
4 k
4 l
4 m
–
c
H
–
c
H
–
aAll the reactions were carried out using 4‐hydroxycoumarin (1 mmol), aldehyde derivatives (1 mmol) and 6‐aminouracil/6‐amino‐1,3‐dimethyluracil (1 mmol),
Co3O4/CS/PMo catalyst (0.005 g) under reflux conditions.
bYields of isolated products.
cNew products.

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SAFARI ET AL.
TABLE 6 Comparison between the efficiency of this report and previously reported methods for the synthesis of 6‐amino‐5‐((4‐hydroxy‐2‐
oxo‐2H‐chromen‐3‐yl)(phenyl)methyl)‐1,3 dimethylpyrimidine‐2,4(1H,3H)‐dione
Entry
Catalyst
Conditions
Time
Yield (%)
Ref.
[36]
1
2
3
4
5
L‐proline
Reflux/ethanol
Reflux/water
4 (h)
78
76
96
84
83
[37]
[38]
[39]
Thiourea‐based organocatalyst I
Zr (HSO4)4
5 (h)
Solvent‐free/80°C
PEG 200/H2O
Reflux/ethanol
1 (h)
Absence of catalysts
Co3O4/chitosan/H3PMo12O40
4 (h)
50 (min)
This work
To show the merit of the present approach, we com-
pared some recently published works with this report.
As shown in Table 6, many reported procedures require
prolonged reaction times, while our method needed only
up to 60 min to produce high yields of products in
high purity.
chemical structure of recovered Co3O4/CS/PMo was veri-
fied using SEM image and XRD pattern. There are no sig-
nificant differences between the XRD and SEM of fresh
and recovered nanocomposite (Figure 9). In addition,
the acid sites (0.15 mmol g−1) of the catalysts reused six
times have no dramatic changes based on the acid–base
titration measurement, in comparison with acid sites of
fresh Co3O4/CS/PMo nanocomposite (0.16 mmol g−1).
These facts prove that the appearance and structure of
Co3O4/CS/PMo catalyst remained intact in recycles, and
there was no considerable deformation or leaching after
six runs.
A
plausible mechanism for the formation of
pyrimidinedione derivatives has been described in
Scheme 2. Co3O4/CS/PMo is an effective catalyst for acti-
vating nucleophiles and the C=O group by a double
hydrogen‐bonding interaction. Firstly, aldehyde 1 reacts
with 4‐hydroxy coumarin 2 via aldol condensation
followed by dehydration to give intermediate 4. Then, a
Michael addition reaction took place between intermedi-
ates 4 and 6‐aminouracil/6‐amino‐1,3‐dimethyluracil 3
in order to form intermediate 5, followed by the
tautomerization to provide the final product 6.
4 | RECYCLING AND REUSING OF
THE CATALYST
The recyclability of the catalyst is highly preferable for a
green process. For this reason, after completion of the
model reaction, the catalyst was separated by the aid of
a magnet from the reaction mixtures and washed with
deionized water and ethanol, and then dried at 60°C for
8 h. The separated catalyst was used for six cycles with
a slightly decreased activity as shown in Figure 8. The
FIGURE 8 Reusability of Co3O4/CS/PMo nanocomposite
SCHEME 2 Plausible mechanism of the reaction

SAFARI ET AL.
11 of 12
FIGURE 9 (a) Scanning electron microscopy (SEM) images of recovered Co3O4/CS/PMo nanocomposite. (b) X‐ray powder diffraction
(XRD) of recovered Co3O4/CS/PMo nanocomposite
(c) A. Maleki, J. Rahimi, O. M. Demchuk, A. Z. Wilczewska,
R. Jasiński, Ultrason. Sonochem. 2018, 43, 262.
5 | CONCLUSIONS
In this work, we have reported a new type of heteroge-
neous catalysis that the magnetic Co3O4 NP cores protect
by cross‐linked chitosan from an attack of HPA or acidic
media. Subsequently, synthesized Co3O4/CS/PMo nano-
composites have been successfully demonstrated for
the synthesis of a new class of pyrimidinedione deriva-
tives. Good yields, simple procedure, reusability of the
green catalyst, non‐toxic product and catalyst are the con-
siderable features of this method for preparation on a
larger scale.
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ACKNOWLEDGEMENTS
The authors gratefully acknowledge the financial support
from the Research Council of the University of Kashan
for supporting this work.
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ORCID
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51, 2121.
Mona Tavakoli https://orcid.org/0000-0001-8885-0744
Mohammad Ali Ghasemzadeh
https://orcid.org/0000-
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How to cite this article: Safari J, Tavakoli M,
Ghasemzadeh MA. H3PMo12O40‐immobilized
chitosan/Co3O4: A novel and recyclable
nanocomposite for the synthesis of
pyrimidinedione derivatives. Appl Organometal
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