Praseodymium(iii) anchored on CoFe2O4 MNPs: An efficient heterogeneous magnetic nanocatalyst for one-pot, multi-component domino synthesis of polyhydroquinoline and 2,3-dihydroquinazolin-4(1: H)-one derivatives

Article abstract of DOI:10.1039/c9nj05468e

In the present study, a facile technique to immobilize praseodymium(iii) complex on the surface of magnetic nanoparticles by using available materials is reported. The prepared samples were characterized by chemical and physical methods such as FTIR, SEM, XRD and EDX and were tested in the synthesis of polyhydroquinoline and 2,3-dihydroquinazolin-4(1H)-one derivatives. It was observed that the yields of the reactions in the presence of the prepared nanocatalyst were good to excellent. More importantly, the use of a recoverable and novel magnetic nanocatalyst in these reactions is the outstanding feature of this protocol.

Full text of DOI:10.1039/c9nj05468e

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Praseodymium (III) anchored on the CoFe2O4 MNPs: An efficient
heterogeneous magnetic nanocatalyst for one-pot, multi-component domino
synthesis of polyhydroquinoline and 2,3-Dihydroquinazolin-4(1H)-one
derivatives
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Taiebeh Tamoradi, a, Seyedeh Masoumeh Mousavi,b Masoud Mohammadic
a Department of Chemistry, Islamic Azad University, Izeh, Iran.
e-mail: t.tabss@yahoo.com
b Department of Environmental Planning, Tehran University, Tehran, Iran.
Department of Chemistry, Faculty of Science, Ilam University, Ilam, Iran
c
Abstract
In the present study, a facile technique to immobilize praseodymium (III) complex on the surface
of magnetic nanoparticles was reported by available materials. The prepared samples were
characterized by chemical and physical methods such as FT-IR, TGA, SEM, XRD and EDX
techniques and were tested in the synthesis of polyhydroquinoline and 2,3-Dihydroquinazolin-
4(1H)-one derivatives. It was observed that the yields of the reactions in the presence of the
prepared nanocatalyst were good to excellent. More importantly, the use of a recoverable and
novel magnetic nanocatalyst in these reactions is the outstanding feature of this protocol.
Keywords:
Magnetic.
Praseodymium,
nanocatalyst,
polyhydroquinoline,
2,3-
Dihydroquinazolin-4(1H)-one
1. Introduction
 Address correspondence to Department of Chemistry, Islamic Azad University, Izeh, Iran; e-mail:
t.tabss@yahoo.com (T. Tamoradi).

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Green Chemistry has exclusively attracted much attention due to its application to control
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chemical innovation and to improve environmental and economic fields. 1–5 The design of ideal
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5–8
catalysts can affect green chemical processes.
In comparison to the homogeneous catalysts,
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heterogeneous ones have been exclusively studied because of their easy recovery.
During
the previous decade, carbon nanotubes,11–13 molecular sieves, magnetic nanoparticles
,
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metal oxides (metal ferrites), 6,15 silica nanoparticles,16 SBA-15, 7,17 SBA-16, 18 MCM-41, 19
MCM-48, 20 FSM-16, 21–23 alumina, 24 heteropoly acids,25 graphene oxide, 26 Boehmite, 27
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polymers and ionic liquids have been developed as ideal catalytic supports. In this sense,
CoFe2O4 which can be regarded as one of the most prominent supports showed the ability for the
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heterogenization of homogeneous catalysts.
Besides, some of the previously-mentioned
supported metals and ligands such as heteropolyacids,31 ionic liquids or some polymers
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are more expensive. Heretofore, these nanoparticles have attracted a considerable interest
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because of their prominent applications such as high surface area, excellent activity,
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environment-friendly,
facile synthesis,
non-toxic properties,
mechanical and chemical
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stability and high concentration of surface OH groups. Crystallographic results of magnetic
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ferrites can be considered as inverse spinel structures which generally have the formula of
AB2O4, where A is M2+ such as Fe2+, Mg2+, Mn2+, Cu2+, Zn2+, Ni2+ and Co2+, B is M3+ such as
Fe3+ and Al3+ .6, 15
On other hand, polyhydroquinoline and 2,3-Dihydroquinazolin-4(1H)-one , as N-containing
heterocyclic compounds, have unique applications in material science, in organometallic
chemistry as effective stabilizers of metallopeptide structures and in the production of
industrially important chemicals and biological products i.e. drugs for the treatment of
cardiovascular diseases and diuretic and vasodilating behavior, and also antipyretic, antitumor,

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antidefibrillatory, antihistamine, antibiotic, analgesic, antihypertonic, antidepressant,
geroprotective and bronchodilator drugs and the ability to modulate calcium channels. 38
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In this regard, a number of transition metal (Pd, Cu, La, etc) complexes which is employed for
catalytic applications can be grafted on the surface of magnetic nanoparticles. 8, 14, 15 But, up to
date, there are few reports from grafted praseodymium complexes onto the surface of
functionalized CoFe2O4 in the synthesis of 2,3-Dihydroquinazolin-4(1H)-one and
polyhydroquinoline derivatives.
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Thus far, 2,3-Dihydroquinazolin-4(1H)-one and polyhydroquinoline derivatives were obtained in
the presence of various catalysts despite the fact that the reported methods have some significant
problems such as tedious workups, use of expensive catalysts, being time-consuming, or having
expensive reactor and solvent. In this work, a facile, inexpensively green protocol was reported
for the synthesis of N-containing heterocyclic compounds using the functionalized CoFe2O4
MNPs with Pr complex as a heterogeneous recyclable catalyst (Scheme 1).

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O
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O
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NOAc
+
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Scheme 1 synthesis of polyhydroquinoline and 2,3-Dihydroquinazolin-4(1H)-one derivatives
in the presence of a CoFe2O4@Pr catalyst.
2. Experimental
2.1. Materials
Metal ions, 3,5-Pyrazoledicarboxylic acid monohydrate, all solvents and reagents have been
purchased from Merck, Flucka or Aldrich and used without further purification.
2.2. Measurement

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Powder X-ray diffraction (XRD) measurements of the samples and Fourier transform
infrared (FTIR) spectra were recorded using Co radiation source with a wave length=
1.78897 Å, 40 kV and Bruker VERTEX 80 v model using the KBr pellets, respectively.
Moreover, elemental analysis of all samples and TGA measurement were performed by
energy-dispersive X-ray spectroscopy (EDAX, TSCAN) and Shimadzu DTG-60 instrument,
respectively. The external morphology of the catalyst was investigated by FESEM-TESCAN
MIRA3.
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2.3. Preparation of CoFe2O4@Pr nanocatalyst
In this procedure, 1.5 mL of 3-chloropropyltrimethoxysilane (CPTMS) and 1 g of the
synthesized CoFe2O4 nanoparticles, in accordance to the reported methods in the literature, 39
were taken in dry toluene (20 mL) under reflux conditions for 24 h. The black powder (the
functionalized CoFe2O4 with CPTMS) was separated using a magnetic field and washed with
hexane. Afterwards, 1.5 mL of triethylamine was added to a mixture, containing 0.38 g of
3,5-pyrazoledicarboxylic acid monohydrate (3,5-PCA) in 20 mL dry toluene, and, then, was
refluxed for 48 h. The solution turned dark brown indicating the formation of the product
which was isolated by magnetic decantation. Subsequently, the final product was washed
several times with deionized water and ethanol (functionalized CoFe2O4 with 3,5-PCA).
Finally, 1 g of Pr (NO3)3.5H2O was dissolved in a suspension containing 1 g of the
functionalized CoFe2O4 with 3,5-PCA in 20 mL ethanol in order to give the nanocatalyst.
After the reaction ended, the nanocatalyst was separated using magnetic field and, then,
washed with ethanol.
2.4. General Procedure for the Synthesis of 2,3-dihydroquinazolin-4(1H)-ones

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In order to investigate the catalytic activity of CoFe2O4@Pr, 2-aminobenzamide (1 mmol),
aldehyde (1 mmol) and catalyst (0.05 g) in ethanol (2 mL) were mixed in the reflux
conditions 40. After the synthesis of 2,3-dihydroquinazolin-4(1H)-ones was indicated by
TLC, the catalyst was separated by an external magnet, washed with ethanol and, then, the
crude solid was obtained by crystallization from the hot ethanol with excellent yield.
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2.5. General Procedure for the Synthesis of Polyhydroquinolines
In other investigation, dimedone (1 mmol), ethyl acetoacetate (1 mmol), aldehyde (1 mmol),
ammonium acetate (1.2 mmol) and CoFe2O4@Pr catalyst (0.04 g) were stirred in ethanol (2
mL) in the reflux conditions 5,15. After the synthesis of polyhydroquinolines was indicated by
TLC, the catalyst was separated by an external magnet, washed with ethanol and, then, the
crude solid was obtained by crystallization from hot ethanol. Finally, a pure product was
obtained with excellent yield.
2.6. Selected Spectral Data
2.6.1. 2-(4-Chlorophenyl)-2,3-dihydroquinazolin-4(1H)-one
1H NMR (400 MHz, DMSO): δH: 8.31 (s, 1H), 7.62–7.39 (m, 5H), 7.27–7.2 (t, 1H), 6.74–6.63
(m, 2H), 7.14 (s, 1H), 6.75–6.65 (m, 2H), 5.77 (s, 1H) ppm.
2.6.2
Ethyl-4-(3,4-dimethoxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-
carboxylate
1H NMR (400 MHz, DMSO): δH=9.07 (s, 1H), 6.81–6.75 (m, 2H), 6.66–6.63 (d, J = 8, 1H),
4.82 (s, 1H), 4.04–3.98 (q, J = 7.1, 2H), 3.71–3.68 (d, J = 4.4, 5H), 2.43–2.41 (d, J = 17.2, 2H),

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2.36–2.27 (m, 4H), 2.24–2.18 (d, J = 16, 1H), 2.03–1.98 (d, J = 16, 1H), 1.20–1.14 (t, J = 6.8,
3H), 1.02 (s, 3H), 0.91 (s, 3H) ppm.
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2.6.3.
Ethyl-4-(4-methoxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-
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carboxylate
1H NMR (400 MHz, DMSO): δH= 9.06 (s, 1H), 7.09–7.05 (d, J = 8.4, 2H), 6.78–6.75 (d, J =
8.4, 2H), 4.82 (s, 1H), 4.04–3.97 (q, J = 7.3, 2H), 3.7 (s, 3H), 2.51–2.45 (d, J = 29.2, 1H), 2.33–
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1.03 (s, 3H), 0.89 (s, 3H)
2. Results and discussion
2.1. Catalyst preparation
After the synthesis of CoFe2O4 nanoparticles, the surface of nanoparticles was modified with
CPTMS.39 Then, the modified nanoparticle reacted with 3,5-pyrazoledicarboxylic acid
monohydrate ( 3,5-PCA) as a ligand. Finally, the magnetic praseodymium nanocatalyst was
synthesized by reacting the functionalized CoFe2O4 with 3,5-PCA and Pr(NO3)3.5H2O (Scheme
2). It should be mentioned that 3,5-PCA is a green and available ligand. Also, 3,5-PCA has
suitable groups for immobilization on CoFe2O4 surface and interaction with Pr.

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N2
Reflux, 1 h
CPTMS
Co Fe2O4
NP
FeCl3.6H2O
CoCl2.6H2O
Toluene, Reflux
24 h
Toluene, Reflux
3,5-PCA
48 h
Pr (NO3)3.5H2O
Ethanol, 16 h
Scheme 2 General route for the fabrication of CoFe2O4@Pr.
2.2. Catalyst characterization
The modification of CoFe2O4 with praseodymium complex was confirmed using Fourier
transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy,
scanning electron microscopies and mapping analysis.
The SEM analysis was performed to assay the surface morphology of the obtained nanocatalysts
(Fig. 1). The SEM images depict particles’ homogeneous size and shape 30.

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Fig.1 SEM images of CoFe2O4@Pr in at 500 nm (a) and 200 nm (b).
Besides, confirming praseodymium complex immobilization onto the CoFe2O4 was studied using
EDX analysis. The element composition of CoFe2O4@Pr was taken by energy-dispersive X-ray
spectroscopy (EDX) analysis which illustrated N, O, Fe, C, Si, Co, Fe and Pr species in the
prepared nanocatalyst (Fig. 2). Moreover, the amount of Pr loaded on the modified magnetic
nanoparticles was found to be 0.7 mmol g−1.

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Fig.2 EDX spectrum of CoFe2O4@Pr.
FT-IR spectra of CoFe2O4, the coated CoFe2O4 with CPTMS, the coated CoFe2O4 with 3,5-PCA
and CoFe2O4@Pr were taken to confirm the synthesis of the samples (Fig. 3). In the mentioned
samples, absorption bands around 589 and 3460 cm-1 indicated the presence of metal-oxygen
(Fe-O or Co-O) bond and hydroxyl functional group (O-H), respectively. 6,15,41 FT.IR spectrum
of the coated CoFe2O4 with CPTMS, the coated CoFe2O4 with 3,5-PCA and CoFe2O4@Pr clearly
shows peaks at approximately 2850-2950 cm−1 due to the presence of C–H stretching vibrations
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of the immobilized CPTMS on CoFe2O4 nanoparticles. Also, FT.IR spectrum of the coated
CoFe2O4 with 3,5-PCA and CoFe2O4@Pr shows peaks at approximately 1600 cm−1 and 1700
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nanoparticles’ coating and successful synthesis of the nanocatalyst were approved using FT-IR
spectrum.
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Fig. 3 FT-IR spectra of CoFe2O4 (black curve), coated CoFe2O4 with CPTMS (red curve), coated
CoFe2O4 with 3,5-PCA (blue curve) and CoFe2O4@Pr (green curve).
The phase and the crystal features of CoFe2O4@Pr nanocatalyst were unraveled by powder X-ray
diffraction (Fig. 4). The obtained XRD patterns approved the polycrystalline spinel structures of
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cobalt ferrite (CoFe2O4) with standard pattern for JCPDS Card No. 22-1086. In the Fig. 4, 2θ
values at 21, 36, 42, 51, 64, 68 and 75 attributed to (1 1 1), (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1
1), and (4 4 0) planes in which the successful synthesis of the nanocatalyst was confirmed. 43

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Fig. 4 The XRD patterns of CoFe2O4@Pr nanocatalyst.
In order to evaluate the dispersion of Pr active site in the catalyst, EDX atomic mapping analysis
of the nanocatalyst was investigated. It was found that N, O, Fe, C, Co, Fe and Pr species were
dispersed in the composite .44 Thus, the successful linkage of Pr complex on the surface of
CoFe2O4 was also confirmed by the X-ray map analysis.

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Fig. 5 The X‐ray map analysis of CoFe2O4@Pr nanocatalyst
2.3. Catalytic studies
The catalytic activity of CoFe2O4@Pr was tested for the synthesis of 2,3-dihydroquinazolin-
4(1H)-ones with a selected condensation of 4-chlorobenzaldehyde and 2-aminobenzamide as the

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model reaction (Scheme 3) 45. Then, the effects of the solvent, temperature and catalyst
concentration were evaluated for the model reaction, in which the best results were observed in
the presence of 0.05 g of the catalyst in EtOH under reflux condition. We try to summarize the
results in Table 1. It was found that no product was observed in the absence of the catalyst. In
order to confirm the generality of this method, a wide variety of aromatic aldehydes bearing
electron-donating and electron-withdrawing substituents reacted with 2-aminobenzamide. The
results (Table 2) indicated that the products were obtained in short time and excellent yields.
O
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CONH2
C
O
CoFe2O4@Pr
EtOH, Reflux
NH
+
R
H
NH2
N
H
R
Scheme 3 CoFe2O4@Pr catalyzed the synthesis of 2,3-dihydroquinazolin-4(1H)-ones.
Table 1. Optimization of the reaction conditions for the synthesis of 2,3-dihydroquinazolin-
4(1H)-ones
Entry
1
Solvent Catalyst (mg) Time (min) Temperature (ºC)
Yield (%)a
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
H2O
-
1 day
60
60
60
60
60
60
60
60
60
60
60
60
60
60
reflux
reflux
reflux
reflux
reflux
reflux
reflux
80
NRb
46
63
79
88
97
97
20
43
45
51
72
35
43
64
2
10
20
30
40
50
55
50
50
50
50
50
50
50
50
3
4
5
6
7
8
9
H2O
reflux
80
10
11
12
13
14
15
PEG
DMSO
DMF
80
80
Acetone
n-hexane
EtOAc
reflux
reflux
reflux

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2
3
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5
6
7
8
9
16
17
18
19
20
21
22
Solvent-free
Solvent-free
EtOH
50
50
50
50
50
50
50
60
60
60
60
60
60
60
80
100
25
46
53
NRb
37
EtOH
40
EtOH
50
64
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
EtOH
60
82
EtOH
70
91
a Isolated yield.
bNo reaction.
tTable 2. Synthesis of 2,3-dihydroquinazolin-4(1H)-ones in the presence of CoFe2O4@Pr
Time
(min)
Melting point
(ºC)
Entry
Aldehyde
Product
Yield (%)a
97
O
NH
1
60
193-194
206-208
OHC
Cl
N
H
Cl
O
Cl
NH Cl
2
90
96
OHC
N
H
O
NH
3
4
OHC
OH
120
120
94
87
278-280
182-183
N
H
OH
O
NH
OHC
OMe
N
H
OMe
O
NH
OHC
5
180
88
193-195
N
H
NO2
NO2
O
OMe
NH
6
7
90
88
89
210-212
220-222
OMe
OMe
N
H
OHC
OMe
O
NH
OHC
Me
120
N
H
Me

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2
3
4
5
6
7
8
9
O
O2N
OHC
NH NO2
8
9
120
91
93
188-190
N
H
O
MeO
OHC
NH OMe
80
163-165
N
H
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
O
NH
10
11
12
13
OHC
120
90
92
94
89
92
165-167
201-203
195-197
167-169
N
H
O
NH
OHC
Br
N
H
Br
O
NH
OHC
NO2
300
220
N
H
NO2
O
Cl
NH Cl
OHC
Cl
N
H
Cl
O
NH
OHC
14
400
400
94
93
174-176
175-177
N
H
Br
Br
O
Br
NH Br
15
OHC
N
H
a Isolated yield.
Based on our experimental results, we propose the following mechanism for the CoFe2O4@Pr
catalyzed for the synthesis of 2,3-Dihydroquinazolin-4(1H)-ones via the cyclocondensation of
46
anthranilamide with aldehydes (Scheme 4). The first step involves the nucleophilic attack of
the nitrogen of the anthranilamide’s amino group on the carbonyl carbon of the aldehyde,
promoted by the Pr as a Lewis acid catalyst, in order to form the hydroxyl intermediate (I). Next,
the catalyst promotes the formation of the Schiff base (II) from intermediate (I) through the

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9
removal of a water molecule. After amide-iminol tautomerization of the intermediate (II) was
activated by Pr, the intermediate (III) could be generated from intramolecular cyclization by
nucleophilic attack of the nitrogen of the amide group on the imine carbon, Accordingly, 1,5-
proton transfer was occurred to furnish the corresponding DHQ derivative.
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
OH+
NH
O
NH
1,5- proton transfer
O
N
R
N
R
H
(III)
R
H
Catalyst
O
Amide-Iminol
Tautomerism
N
O
R
R
H
N
O
R
NH
NH2
H2N
H2N
H
(II)
O
H
H
O
N
R
NH2
H2O
O
(I)
Scheme 4. Proposed mechanism for the synthesis of quinazolinones in the presence of CoFe2O4@Pr.
Moreover, the synthesis of polyhydroquinoline derivatives was tested in the presence of
CoFe2O4@Pr. Initially, a mixture of 4-chlorobenzaldehyde (1 mmol), dimedone (1 mmol), ethyl
acetoacetate (1 mmol) and ammonium acetate (1.2 mmol) was selected as the model reaction
5,7,15
(Scheme 5).
Then, the effect of various parameters such as solvent, catalyst concentration
and temperature was investigated on the model reaction. The results of this study (Table 3) show

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2
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4
5
6
7
8
9
that the best conditions were obtained in the presence of 0.04 g of the catalyst in EtOH under
reflux conditions. Finally, a wide variety of aromatic aldehydes bearing electron-donating and
electron-withdrawing substituents were selected for the synthesis of polyhydroquinoline.
Besides, the products were obtained in short reaction time and excellent yields (Table 4).
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
O
R
O
O
O
O
OEt
OEt
CoFe2O4@Pr
EtOH, Reflux
+
+
R
NH4OAc
+
H
N
H
O
O
Scheme 5 CoFe2O4@Pr catalyzed the one-pot synthesis of polyhydroquinoline derivatives.
Table 3. Optimization of reaction conditions for the synthesis of polyhydroquinolines
Temperature Yield
Catalyst
(mg)
Entry Solvent
Time (min)
(%)a
NRb
(ºC)
reflux
-
1
EtOH
EtOH
1 day
90
90
90
90
90
90
90
90
90
90
90
2
20
30
40
50
40
40
40
40
40
40
40
reflux
reflux
reflux
reflux
80
75
89
3
EtOH
4
EtOH
97
5
H2O
32
6
PEG
64
7
DMSO
DMF
80
83
8
80
89
9
EtOAc
Solvent-free
Solvent-free
EtOH
reflux
80
81
10
11
12
13
14
15
59
100
71
NRb
25
EtOH
EtOH
EtOH
40
40
40
90
90
90
45
60
70
37
83
89
a Isolated yield
bNo reaction.

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8
9
Table 4. Synthesis of polyhydroquinoline derivatives catalyzed by CoFe2O4@Pr.
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
Time
(min)
Melting
point (ºC)
Entry
1
aldehyde
Product
Yield (%)a
Cl
O
O
90
97
230-233
215-218
253-257
OHC
Cl
OEt
N
H
O
O
2
3
400
110
91
99
OHC
OEt
N
H
Me
O
O
OHC
OHC
Me
OEt
N
H
NO2
O
O
4
5
7
8
NO2
400
600
600
120
89
87
97
91
235-238
178-180
246-249
192-194
OEt
N
H
NO2
O
O
OHC
OEt
NO2
N
H
OMe
O
O
OHC
OMe
OEt
N
H
Br
O
Br
O
OHC
OEt
N
H

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2
3
Br
4
5
6
7
8
O
O
O
O
9
OHC
Br
320
210
420
91
91
93
247-248
201-202
172-174
OEt
N
H
OMe
9
OMe
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
OMe
10
11
OHC
OHC
OMe
OEt
N
H
OEt
O
OEt
OEt
N
H
Cl
Cl
Cl
Cl
O
O
12
15
360
240
88
92
229-234
202-204
OHC
OEt
N
H
Cl
O
CHO
Cl
O
OEt
N
H
a Isolated yield.
A plausible mechanism for the multicomponent synthesis of polyhydroquinolines on the basis
15
of previous reports has been depicted in Scheme 6. Based on this mechanism, the role of the
prepared heterogeneous complex as a Lewis acid catalyst comes from the Knoevenagel
condensation of aldehydes with active methylene compounds (dimedone or ethyl acetoacetate) in
order to produce an α,β-unsaturated compound. Finally, the nucleophilic attack (Michael
addition) of the active methylenes on the α,β-unsaturated carbonyl compounds which were
activated by Pr, formed the polyhydroquinoline product (Scheme 6).

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2
3
4
5
NH4OAc
6
7
8
9
O
H
+
HOAc
NH2
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
NH3
Ar
Ar
H
EtO
O
O
O
Ar
O
O
O
OEt
O
EtO
N
H
O
NH3
Ar
O
HOAc
+
H
OEt
O
O
NH2
Ar
H
NH4OAc
Scheme 6. Proposed mechanism for the synthesis of polyhydroquinolines in the presence of CoFe2O4@Pr.
3.4. Reusability of catalyst
The recovery of CoFe2O4@Pr was also tested for the preparation of 2-(4-chlorophenyl)-2,3-
dihydroquinazolin-4(1H)-one (a) and ethyl-4-(4-chlorophenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-
hexahydroquinoline-3 carboxylate (b). It is obvious that CoFe2O4@Pr showed excellent
performance in several consecutive cycles for the above reactions (Fig. 6).

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2
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4
5
6
7
8
9
10
11
12
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14
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17
18
19
20
21
22
23
24
25
26
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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
Fig. 6 Reusability of CoFe2O4@Pr in the synthesis of 2-(4-chlorophenyl)-2,3-dihydroquinazolin-4(1H)-one and
ethyl-4-(4-chlorophenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3 carboxylate (b).
4. Conclusion
In this study, Pr functionalized 3,5-pyrazoledicarboxylic acid monohydrate, grafted on magnetic
CoFe2O4 , were obtained as efficient and reusable catalysts. The structure of these catalysts was
characterized by FT-IR, EDX, XRD, TGA, and ICP-OES and, then, the catalytic activity of these
catalysts was proved through the oxidation reactions. The prepared catalysts have outstanding
features like high catalytic activity, easy preparation and easy separation of the catalyst, easy
work-ups, recycle exploitation and good to excellent isolated yields.
Acknowledgements
The authors are deeply grateful to Tehran University support of this research project.
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New Journal of Chemistry
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DOI: 10.1039/C9NJ05468E
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Graphical abstract
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Praseodymium (III) anchored on the CoFe2O4 MNPs: An efficient
heterogeneous magnetic nanocatalyst for one-pot, multi-component domino
synthesis of polyhydroquinoline and 2,3-Dihydroquinazolin-4(1H)-one
derivatives
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Taiebeh Tamoradi, a, Seyedeh Masoumeh Mousavi,b Masoud Mohammadic
a Department of Chemistry, Islamic Azad University, Izeh, Iran.
e-mail: t.tabss@yahoo.com
b Department of Environmental Planning, Tehran University, Tehran, Iran.
a Department of Chemistry, Faculty of Science, Ilam University, Ilam, Iran
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CoFe2O4@Pr as highly efficient and reusable heterogeneous catalyst prepared by a
simple procedure for the synthesis of polyhydroquinoline and 2,3-
Dihydroquinazolin-4(1H)-one derivatives
 Address correspondence to Department of Chemistry, Islamic Azad University, Izeh, Iran; e-mail:
t.tabss@yahoo.com (T. Tamoradi).