Preparation of a novel, efficient, and recyclable magnetic catalyst, Cu(II)-OHPC-Fe3O4 nanoparticles, and a solvent-free protocol for the synthesis of coumarin derivatives

Article abstract of DOI:10.1080/00958972.2021.1954172

Cu(II) supported on 5-oxo-4,5-dihydro-pyrrole-3-carboxylic acid functionalized Fe₃O₄ nanoparticles (Cu(II)-OHPC-Fe₃O₄) as a new magnetic nanocatalyst was prepared and characterized by ICP-AES, FT-IR, XRD, SEM, TEM, TGA, XRD, VSM and EDX techniques. Prepared nanocatalyst (Cu(II)-OHPC-Fe₃O₄) is employed for Pechmann reactions between different substituted phenols and ethyl acetoacetate to obtain new products of coumarin derivatives in good to excellent yields. This green catalyst was easily removed, reused several times with no significant loss of its activity and provided clean synthesis with excellent yield and reduced time.

Full text of DOI:10.1080/00958972.2021.1954172

Journal of Coordination Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gcoo20
Preparation of a novel, efficient, and recyclable
magnetic catalyst, Cu(II)-OHPC-Fe3O4
nanoparticles, and a solvent-free protocol for the
synthesis of coumarin derivatives
Jingjing Yuan & Majid Mohammadnia
To cite this article: Jingjing Yuan & Majid Mohammadnia (2021): Preparation of a novel,
efficient, and recyclable magnetic catalyst, Cu(II)-OHPC-Fe3O4 nanoparticles, and a solvent-
free protocol for the synthesis of coumarin derivatives, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2021.1954172
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JOURNAL OF COORDINATION CHEMISTRY
https://doi.org/10.1080/00958972.2021.1954172
Preparation of a novel, efficient, and recyclable magnetic
catalyst, Cu(II)-OHPC-Fe3O4 nanoparticles, and a solvent-
free protocol for the synthesis of coumarin derivatives
Jingjing Yuana and Majid Mohammadniab
b
aHubei College of Chinese Medicine, Jingzhou, Hubei, China; Department of Chemistry, Islamic Azad
University, Tehran, Iran
ABSTRACT
ARTICLE HISTORY
Received 4 December 2020
Accepted 8 June 2021
Cu(II) supported on 5-oxo-4,5-dihydro-pyrrole-3-carboxylic acid
functionalized Fe3O4 nanoparticles (Cu(II)-OHPC-Fe3O4) as a new
magnetic nanocatalyst was prepared and characterized by ICP-AES,
FT-IR, XRD, SEM, TEM, TGA, XRD, VSM and EDX techniques.
Prepared nanocatalyst (Cu(II)-OHPC-Fe3O4) is employed for
Pechmann reactions between different substituted phenols and
ethyl acetoacetate to obtain new products of coumarin derivatives
in good to excellent yields. This green catalyst was easily removed,
reused several times with no significant loss of its activity and pro-
vided clean synthesis with excellent yield and reduced time.
KEYWORDS
Pechmann reactions;
nanocatalyst; coumarin;
nanomagnetic; Cu; 5-Oxo-
4,5-dihydro-pyrrole-3-car-
boxylic acid
1. Introduction
Design of efficient, economical, useful, separable and biocompatible catalysts have attracted
attention [1]. In fact, with expanding environmental and biological concerns, the develop-
ment of reusable and recoverable heterogeneous catalysts developed a considerable
research field. Nanomaterials specialty nanoparticles as heterogeneous catalysts with attract-
ive structures and unique catalytic activities have been employed [2]. Also, nanoparticles
could have higher catalyst loading capacity and higher dispersion than many common sup-
port matrices, resulting in enhanced catalytic activity of the supported catalysts [3].
Magnetic nanoparticles (MNPs) are potent, valuable and highly-efficient heteroge-
neous catalyst supports because of their response to a magnetic field, giving good
CONTACT Jingjing Yuan
JingjingYuan10263@Gmail.com
Hubei College of Chinese Medicine, Jingzhou, Hubei,
434020, China
ß 2021 Informa UK Limited, trading as Taylor & Francis Group

2
J. YUAN AND M. MOHAMMADNIA
Scheme 1. Pechmann reactions to prepare coumarin derivatives with Cu(II)-OHPC-Fe3O4 as nano
magnetic catalyst.
recyclability, reusability, easy separation and great specific surface area [4–8]. Also,
MNPs have other unique characteristics such as good biocompatibility and biodegrad-
ability, efficiency, easy accessibility and low toxicity [9, 10].
The construction of novel magnetically separable catalytic systems has developed
as an alternative for improving the effective separation of heterogeneous catalysts
[11]. Surface-functionalization of MNPs can occur via immobilization of various organic
or inorganic non-magnetic active new materials in biotechnology and catalysis
[12, 13]. Some of these different chemical materials include types of metal complexes,
functional groups and metal nanoparticles (e.g. Pd, Si or Cu) [14].
Particular additives, which can be copper ligands, make better reaction rates and
lead to couplings carried out at milder temperatures in the presence of decreased
amounts of copper or with a higher support area. At the present, many ligands have
been employed such as 1,10-phenanthroline and its derivatives [15], ethylene glycol
[16], N,N-dimethylglycine [17], diethylsalicylamide, oxime-type and Schiff-base ligands
[18], amino acids [19], aminoarenethiolate [20], phosphine ligands [21], etc.
Coumarin and its derivatives are a valuable class of benzopyrones bound in struc-
tural units of several natural products and exhibit applications in pharmacologic,
pharmaceutics, agricultural and perfume industry [22]. They have displayed consider-
able biological activities, such as antitumor [23], anti-HIV [24] and antioxidative [25]
activities. Hence, to broaden biological activities of coumarin derivatives, researchers
have interest in the development of new methods for their preparation. In general,
coumarins have been synthesized by Pechmann [26], Perkin [27], Knoevenagel [28],
Reformatsky [29], Wittig reactions [30] and Flash Vacuum Pyrolysiso methods [31].
The Pechmann reaction is a significant method for synthesizing coumarins that pro-
ceeds from very simple starting materials, phenols and keto esters or unsaturated car-
boxylic acids using different catalysts such as nanocrystalline sulfated-zirconia [32], Zr-
TMS-TFA-25 [33], furic acid [26], Fe3O4@SiO2@Et-PhSO3H [34], trifluoroacetic acid [35],
Bi(NO3)3-5H2O [36], TiCl4 [37], ZrOCl2ꢀ8H2O/SiO2 [38], ionic liquids [39] and sulfonic
acid nanoreactor [40].
However, each of these has its own advantages but also suffers from one or more
disadvantages, such as long reaction times, low yields, use of harmful organic solvents,
requirement of excess of catalyst and reagents, and harsh reaction conditions.
Researchers are endeavoring to develop effective alternative catalysts to synthesize
coumarin derivatives via the Pechmann method.

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3
Figure 1. FT-IR spectra of Fe3O4, OHPC, OHPC-Fe3O4 and Cu(II)-OHPC-Fe3O4.
In this study, we synthesize Cu(II) supported on 5-oxo-4,5-dihydro-pyrrole-3-carbox-
ylic acid functionalized Fe3O4 nanoparticles (Cu(II)-OHPC-Fe3O4) as a new magnetic
nanocatalyst and tested its catalytic application for synthesis of coumarin derivatives
from two component reactions of various substituted phenols and ethyl acetoacetate
in solvent-free conditions (Scheme 1). The prepared nanocatalyst is characterized by
XRD, ICP-AES, SEM, TEM, FT-IR, TGA, VSM and EDX techniques.
2. Results and discussion
2.1. Characterization of the prepared Cu(II)-OHPC-Fe3O4 magnetic nanoparticles
2.1.1. Fourier transforms infrared (FT-IR) analysis
FT-IR spectra of the nanoparticles of Fe3O4, OHPC, OHPC-Fe3O4 and Cu(II)-OHPC-Fe3O4
are displayed in Figure 1. In FT-IR spectrum OHPC-Fe3O4 NPs show two absorption
peaks at 2924 and 2853 cmꢁ1 which can be assigned to the symmetric stretching of
C–H group. The adsorption peaks at 1633 and 1441 cmꢁ1 correspond to the asymmet-
ric and symmetric stretching vibration of COO (carboxylate group) and C ¼ N of 5-oxo-

4
J. YUAN AND M. MOHAMMADNIA
Figure 2. XRD patterns of Fe3O4 (a), OHPC-Fe3O4 (b) and Cu(II)-OHPC-Fe3O4 (c) nanoparticles.
4,5-dihydro-pyrrole-3-carboxylate moiety. Also, adsorption bands at 590 and 620 cmꢁ1
attributed to Fe-O groups confirm the presence of Fe3O4 nanoparticles in the prepared
catalyst. Hence, the obtained data from FT-IR spectroscopy prove the existence of the
nonmagnetic particle and heterocyclic moiety in the structure of OHPC-Fe3O4 nanopar-
ticle (Figure 1). In the FT-IR spectra of Cu(II)-OHPC-Fe3O4 (Figure 1), the C ¼ N and
COO (1639 and 1445 cmꢁ1) stretching bands were shifted to the higher wavenumbers,
which exhibited coordination of nitrogen and oxygen to the metal center (Figure 1).
2.1.2. X-ray diffraction (XRD) analysis
Powder X-ray diffraction patterns of Fe3O4 nanoparticle, OHPC-Fe3O4 and Cu(II)-OHPC-
Fe3O4 nanoparticle are shown in Figure 2. As can be seen in Figure 2(c), the peaks at
2h ¼ 42.87ꢂ, 50.26ꢂ and 74.56ꢂ assigned with the (111), (200) and (220) were assigned
to Cu(II) [41]. Also 2h ¼ 30.2ꢂ, 35.30ꢂ, 43. 3ꢂ, 53.65ꢂ, 57.3ꢂ and 62.8ꢂ peaks correspond-
ing to the (220), (311), (400), (422), (511) and (440) were obtained due to the cubic spi-
nel structure of Fe3O4 NPs. Therefore, the results obtained from XRD spectra
confirmed the presence of the Cu on organic group moiety in the nanoparticles con-
taining Cu(II)-OHPC-Fe3O4.
2.1.3. EDX analysis of the catalyst
EDX analysis of Cu(II)-OHPC-Fe3O4 is displayed in Figure 3. As it can be seen, Cu(II)-
OHPC-Fe3O4 is composed of the expected elements in the structure of the catalyst
including Carbon (C), Oxygen (O), Nitrogen (N), Iron (Fe), Copper (Cu) and Chlorine
(Cl), indicating that Cu has been grafted to OHPC-Fe3O4.

JOURNAL OF COORDINATION CHEMISTRY
5
Figure 3. EDX spectrum of Cu(II)-OHPC-Fe3O4.
2.1.4. ICP-AES analysis
The inductively coupled plasma–atomic emission spectroscopy (ICP-AES) analysis
shows the weight percentage of the Cu to be 9% in Cu(II)-OHPC-Fe3O4.
2.1.5. Thermogravimetric analysis (TGA)
The thermal behavior of Cu(II)-OHPC-Fe3O4 was investigated by thermogravimetric
analysis (TGA) under an air atmosphere with a heating rate of 10 ꢂC minꢁ1 from 0 to
800 ꢂC (Figure 4). The composition ratio of the catalyst can be appraised from the
residual mass percentage. As displayed in Figure 4, the small weight loss of about
0.51% at temperatures lower than 120 ꢂC is likely due to the removal of the adsorbed
water and remaining organic solvents. Other weight loss steps with a total loss of
about 8.14% from 120 to 760 ꢂC can be related to the decomposition of the organic
group and Cu(II) the Cu(II)-OHPC-Fe3O4. Based on these results, grafting of Cu(II)-
OHPC-Fe3O4 on the Fe3O4 nanoparticles is asserted. The amount of adsorbed Cu(II)-
OHPC calculated by Equation (1) is 0.5 mmol gꢁ1
.
À
Á
ð Þ
ð Þ
mmolCu II ꢁOHPC ¼ weightloss=100 ꢃ MwCu II ꢁ OHPC ꢃ 1000 ¼ 0:4mmol (1)
2.1.6. Transmission electron microscopy (TEM)
The morphology of the OHPC-Fe3O4 nanoparticles and Cu(II)-OHPC-Fe3O4 nanopar-
ticles were investigated by TEM (Figure 5). The average particle size distribution
increases from 14 nm in OHPC-Fe3O4 nanoparticles to 17 nm in Cu(II)-OHPC-Fe3O4
nanoparticles, which is in good agreement with the crystallite size estimated from
XRD. Comparison of experimental results showed grafting of OHPC and Cu(II)-OHPC

6
J. YUAN AND M. MOHAMMADNIA
Figure 4. TGA diagram of Cu(II)-OHPC-Fe3O4 nanoparticles.
Figure 5. TEM micrographs of (a) OHPC-Fe3O4 and (b) Cu(II)-OHPC-Fe3O4 nanoparticles.
groups on the Fe3O4 nanoparticles. The TEM images of OHPC-Fe3O4 and Cu(II)-OHPC-
Fe3O4 displayed a sphere-like structure.
2.1.7. Scanning electron microscopy (SEM)
The morphological features and size details of synthesized OHPC-Fe3O4 nanoparticles
and Cu(II)-OHPC-Fe3O4 nanoparticles were studied by scanning electron microscopy
(SEM) (Figure 6). The SEM image shows that OHPC-Fe3O4 nanoparticles have a mean
diameter of about 16 nm and Cu(II)-OHPC-Fe3O4 nanoparticles with more than 20 nm
in size. Comparison of experimental results showed grafting of OHPC and Cu(II)-OHPC

JOURNAL OF COORDINATION CHEMISTRY
7
Figure 6. The SEM images of OHPC-Fe3O4 and Cu(II)-OHPC-Fe3O4 nanoparticles.
Figure 7. Room temperature magnetization curves of Fe3O4, OHPC-Fe3O4 and Cu(II)-OHPC-Fe3O4
nanoparticle.
groups on the Fe3O4 nanoparticles. The SEM images of OHPC-Fe3O4 and Cu(II)-OHPC-
Fe3O4 displayed a sphere-like structure.
2.1.8. Magnetic properties of the catalyst
A vibrating sample magnetometer (VSM) was employed for characterizing the mag-
netic properties of Fe3O4, OHPC-Fe3O4 and Cu(II)-OHPC-Fe3O4 at 300 K (Figure 7). The
magnetization curves for these nanoparticles display no hysteresis in their magnetiza-
tions. As shown in Figure 7, the saturation magnetization values for Fe3O4, OHPC-

8
J. YUAN AND M. MOHAMMADNIA
Table 1. Optimization conditions for reactions of ethyl acetoacetate (1 mmol) and catechol
(1 mmol) in the presence of different amounts of the Cu(II)-OHPC-Fe3O4 as nanocatalyst at various
temperatures under solvent-free conditions.
Amount of catalyst
Entry
(mol %)
Temperature (ꢂC)
Time (h)
Yield (%)a
1
2
3
4
0.5
1
2
0.5
1
25
25
25
70
70
10
10
10
5
–
Trace
26
50
5
4
60
6
2
70
4
76
7
8
9
10
11
12
0.2
0.5
1
100
100
100
100
100
100
2
88
95
96
Trace
Trace
–
1.5
1.5
10
10
10
OHPC-Fe3O4 (3 mol%)
Fe3O4 (3 mol%)
Without catalyst
aYields refer to isolated pure product.
Fe3O4 and Cu(II)-OHPC-Fe3O4 were 72.1, 56.02 and 52.1 emu gꢁ1, respectively. A
decrease of the saturation magnetization of Cu(II)-OHPC-Fe3O4 is observed due to the
grafting of Cu on the surface of OHPC-Fe3O4 nanoparticles. These differences are
because of the various coating layers and their thicknesses on the surface of MNPs.
The prepared catalyst has excellent magnetic characteristics and can be quickly sepa-
rated from the reaction media by an external magnet.
2.2. Catalytic application of Cu(II)-OHPC-Fe3O4 as nanocatalyst for Pechmann
reactions to prepare coumarin derivatives
To find optimum conditions, the reaction of ethyl acetoacetate (1 mmol) and catechol
(1 mmol) in the presence of the Cu(II)-OHPC-Fe3O4 as nanocatalyst was selected as a
model reaction. The reaction was carried out with various amounts of Cu(II)-OHPC-
Fe3O4 as catalyst (0.2, 0.5, 1 and 2 mol %) at several temperatures (25, 70, 100 ꢂC) in
the absence of solvent. According to the obtained results (Table 1), optimum condi-
tions were 0.5 mol % of Cu(II)-OHPC-Fe3O4 as catalyst at 100 ꢂC in the absence of solv-
ent (Table 1, entry 8).
Then, different phenols were used in the reactions to prepare the corresponding
products in high to excellent yields (Table 2). As can be seen in Table 2, the reactions
with the electron-donating or electron-withdrawing substituents on phenols give the
products in high to excellent yields (Table 2). According to a literature survey [22], the
suggested mechanism for the formation of the products is shown in Scheme 2.
In order to compare the present work with reported results for the preparation of
coumarin derivatives, the data are provided in Table 3. The obtained results exhibited
that Cu(II)-OHPC-Fe3O4 is the better catalyst because of the short time reaction, good
yields and low temperature of the product.
We also investigated recycling of the Cu(II)-OHPC-Fe3O4 as catalyst under solvent-
free conditions using the model reaction of ethyl acetoacetate (1 mmol) and catechol
(1 mmol) (Table 2, entry 1). After completion of the reaction, the reaction mixture was
dissolved in dichloromethane. Then, Cu(II)-OHPC-Fe3O4 as catalyst were separated by
an external magnet for subsequent experiments to check reusability under similar

JOURNAL OF COORDINATION CHEMISTRY
9
Table 2. Three-component reactions of ethyl acetoacetate (1 mmol) and various phenols in the
presence of Cu(II)-OHPC-Fe3O4 (0.5 mol %) as nanocatalyst under solvent-free conditions at 100 ꢂC.
Melting point (ꢂC)
Entry
1
Phenols
Time (h)
1.5
Yield (%)
94
TON
188
TOF (1/h)
125
Found
Reported [Ref.
182–184
183–185 [42]
2
3
3
90
95
180
190
60
89–90
87–89 [43]
1.5
127
166
163–165 [43]
4
5
1.5
2
93
94
186
188
124
94
280
279–281 [42]
139–142 [35]
140–141
6
7
8
2
2
2
90
92
91
180
184
182
90
92
91
261–263
240–241
170–171
260–262 [44]
239–240 [44]
171–173 [45]
9
2.5
91
182
73
152–154
153–155 [45]
10
11
2.5
2
89
93
178
186
71
93
180–181
130–131
178–180 [45]
129–132 [46]
12
3
89
178
59
137–138
135–139 [47]
aYields refer to the isolated pure products.

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J. YUAN AND M. MOHAMMADNIA
Scheme 2. The suggested mechanism for formation of coumarin derivatives in the presence of
Cu(II)-OHPC-Fe3O4 as nanocatalyst.
Table 3. Comparison the results of Cu(II)-OHPC-Fe3O4 as nanocatalyst for pechmann reactions to
prepare coumarin derivatives with other catalysts.
Entry
Catalyst
Conditions
Time
Yield (%)a [Ref]
1
2
3
4
5
Fe3O4@SiO2@Et-PhSO3H (0.3 mol%)
Cu-BTC@SiO2@Fe3O4 (5 mol%)
ZrO2–Al2O3–Fe3O4 (1.00 g)
PANF-PAMSA (5 mol%)
Solvent free, 120 ꢂC
Solvent free, 130 ꢂC
Toluene, reflux
2 h
5 h
4 h
4h
93 [34]
95 [48]
65 [49]
95 [50]
95
Toluene, reflux
Cu(II)-OHPC-Fe3O4 (0.5 mol%)
Solvent free, 100 ꢂC
1.5
[Present work]
aYields refer to isolated pure products.
reaction conditions. The results showed that Cu(II)-OHPC-Fe3O4 are a stable catalyst in
reaction media and can be reused four times without significant loss of catalytic activ-
ity. The yield of the product obtained in the final cycle was almost 88%, indicating
that Cu leaching of the recovered catalyst was negligible. This high recyclability of
Cu(II)-OHPC-Fe3O4 demonstrated the significance of this catalyst for practical applica-
tions (Figure 8).
However, the ICP-AES, FT-IR, SEM, EDX, XRD and TEM analysis of recycled Cu(II)-
OHPC-Fe3O4 (after four times recycling) are provided and shown in Figures 9–13.
The FT-IR spectra of recovered Cu(II)-OHPC-Fe3O4 are illustrated in Figure 9. The
peaks around 2930 and 2852 cmꢁ1, for asymmetric and symmetric vibrations of C–H
stretching can be obviously found. The adsorption peaks at 1630 and 1450 cmꢁ1 cor-
responds to the asymmetric and symmetric stretching vibration of the C ¼ N and C-H
(aromatic) of organic moiety. The adsorption bands at 586 and 447 cmꢁ1 were

JOURNAL OF COORDINATION CHEMISTRY
11
Figure 8. The recycling of the Cu(II)-OHPC-Fe3O4 as nanocatalyst.
Figure 9. FT-IR spectrum of Cu(II)-OHPC-Fe3O4 nanoparticles after four times recycling.
attributed to Fe-O stretching band and 3443 cmꢁ1 corresponded to broad OH groups
on magnetic surface of Fe3O4. Therefore, the obtained data from FT-IR spectroscopy
can be proved the existence of the nonomagnetic particle, heterocyclic moiety and Cu
in the structure of Cu(II)-OHPC-Fe3O4 magnetic nanoparticle. (Figure 9).
Morphology of synthesized of Cu(II)-OHPC-Fe3O4 nanoparticles were investigated by
TEM that shown in Figure 10. Particles are observed to have spherical morphology
from Figure 10. Average particle size is estimated about 17 nm from the TEM micro-
graphs. Also, the SEM image of the Cu (II)-OHPC-Fe3O4 nanoparticle is shown (Figure
11). The SEM image of Cu (II)-OHPC-Fe3O4 showed a spherelike structure. The EDX ana-
lysis and XRD spectrum of recycled Cu (II)-OHPC-Fe3O4 (after four times recycling) was
provided and compared with fresh catalyst (Figures 12 and 13). Therefore, based on

12
J. YUAN AND M. MOHAMMADNIA
Figure 10. TEM analysis of Cu(II)-OHPC-Fe3O4 nanoparticles after four times recycling.
Figure 11. SEM analysis of Cu (II)-OHPC-Fe3O4 nanoparticles after four times recycling.
Figure 12. EDX analysis of Cu (II)-OHPC-Fe3O4 nanoparticles after four times recycling.

JOURNAL OF COORDINATION CHEMISTRY
13
Figure 13. XRD patterns of Cu (II)-OHPC-Fe3O4 nanoparticles after four times recycling.
the obtained results, the Cu (II)-OHPC-Fe3O4 catalyst has not changed after four recy-
cling and its activity is similar to the new prepared catalyst.
The results demonstrated that Cu(II)-OHPC-Fe3O4 catalyst could be reused without los-
ing its efficiency after four times. It should be said that there was low Cu leaching (about
9%) during the reaction and the catalyst showed high stability even after four cycles.
3. Experimental
3.1. Chemicals and apparatus
The X-ray powder diffraction (XRD) of the prepared catalyst was carried out on a
Philips PW 1830 X-ray diffractometer with CuKa source (k ¼ 1.5418 Å) in a range of
Bragg’s angle (10–80ꢂ) at temperature 25 ꢂC. Fourier transform infrared (FT-IR) spec-
trum was performed using
a
FT-IR spectrometer (Vector 22-Bruker) from
400–4000 cmꢁ1 at room temperature. Scanning electron microscopy (SEM) analysis
was recorded using a VEGA//TESCAN KYKY-EM 3200 microscope (acceleration voltage
26 kV). Transmission electron microscopy (TEM) experiments were done on a Philips
EM 208 electron microscope (EHT ¼ 15.00 Kv). The elemental analysis of catalyst was
appraised by energy dispersive X-ray (EDX), VEGA3 XUM/TESCAN. Thermogravimetric
analysis (TGA) was performed on a Stanton Red craft STA-780 (London, UK). NMR spec-
tra were performed with a Bruker DRX-400 AVANCE instrument (300.1 MHz for 1H,
75.4 MHz for 13C). The spectra were evaluated in DMSO-d6 as a solvent. Magnetic
measurements were carried out using a vibrating sample magnetometer (VSM, MDK,
and Model 7400). The metal loading was determined by inductively coupled plasma-
atomic emission spectrometry (ICP-AES). Melting points were evaluated on an
Electrothermal 9100 apparatus.
3.2. General procedure
3.2.1. Preparation of 5-oxo-4,5-dihydro-pyrrole-3-carboxylic acid functionalized
Fe3O4 nanoparticles (OHPC-Fe3O4)
First, FeCl3ꢀ6H2O (4.865 g, 0.018 mol) and FeCl2ꢀ4H2O (1.789 g, 0.0089 mol) were added
to 100 ml deionized water and sonicated until the salts dissolved completely. After
that, a specific amount of 5-oxo-4,5-dihydro-pyrrole-3-carboxylic acid (OHPC) (6.35 g,

14
J. YUAN AND M. MOHAMMADNIA
Scheme 3. Preparation of OHPC-Fe3O4 nanoparticles.
0.05 mol) and NH4OH (10 ml) solution were added until the pH was increased at which
a black suspension formed. The prepared suspension was then refluxed at 100 ꢂC for
6 h, with strong stirring. OHPC-Fe3O4 nanoparticles separated from the aqueous solu-
tion by magnetic decantation, washed with deionized water several times and then
dried in an oven overnight (Scheme 3). All synthesis steps were done under
N2 atmosphere.
3.2.2. Preparation of Cu(II)-OHPC-Fe3O4 nanoparticles
To prepare Cu(II)-OHPC-Fe3O4 nanoparticles the obtained OHPC-Fe3O4 (0.5 g) was dis-
persed in 50 ml of ethanol by sonication for 30 min, and then 0.045 g of CuCl2 was
added to the above mixture, forming a brown suspension which was refluxed with
strong stirring for 8 h. The catalyst (Cu(II)-OHPC-Fe3O4) was separated from the solu-
tion by an external magnetic field, washed with deionized water several times, and
dried in an oven overnight (Scheme 4). All steps were carried out under N2 flow.
3.2.3. General procedure for Pechmann reactions to prepare coumarin derivatives
by Cu(II)-OHPC-Fe3O4 as nanoctalyst
To a mixture of ethyl acetoacetate (1 mmol) and phenol derivatives was added 0.5 mol
% Cu(II)-OHPC-Fe3O4 as nanocatalyst at 100 ꢂC under solvent-free conditions. When
the reaction was completed (as monitored by TLC (n-hexane/EtOAc, 9:1, Rf valence:
0.52)), the reaction mixture was cooled to room temperature. After that, the reaction
mixture was dissolved in dichloromethane (10 ml) and Cu(II)-OHPC-Fe3O4 nanoparticle
catalyst was separated by an external magnet for 5 min. The solution containing the
product was removed by vacuum and the residual solid was recrystallized using etha-
nol. The product was obtained as a powder. Eventually, the isolated catalyst was
washed several times with dried CH2Cl2, dried under vacuum at 60 ꢂC to give the pure
Cu(II)-OHPC-Fe3O4 nanoparticle catalyst.
Selected spectra for two known products are given below:

JOURNAL OF COORDINATION CHEMISTRY
15
Scheme 4. Preparation of Cu(II)-OHPC-Fe3O4 nanoparticles.
1
7-Hydroxy-4-methylcoumarin (Table 2, entry 1): H NMR (400 MHz; DMSO-d6):dH
¼
2.32 (brs, 3H), 6.11 (s, 1H), 6.70 (d, J ¼ 2.4 Hz, 1H), 6.78–6.82 (dd, J ¼ 8.8 Hz, J ¼ 2.4 Hz,
1H), 7.56 (d, J ¼ 8.8 Hz, 1H), 10.51 (brs, 1H) ppm.; 13C-NMR (100 MHz, DMSO-d6): dC ¼
18.1, 102.2, 110.1, 112.1, 113.2, 127.0, 154.1, 155.7, 160.0, 161.2 ppm.
1
5,7-dihydroxy-4-methylcoumarin (Table 2, entry 4): H NMR (400 MHz; DMSO-d6): dH
¼ 10.34 (s, 1H), 7.39–7.36 (d, J ¼ 8.75 Hz, 1H), 6.83–6.79 (d, J ¼ 8.5 Hz, 1H), 6.06 (s, 1H),
2.31 (s, 3H), 2.11 (s, 3H) ppm.; 13C NMR (100 MHz, DMSO-d6): dC ¼ 11.2, 18.6, 110.3,
111.1, 112.1, 112.4, 123.5, 153.2, 154.1, 159.3, 160.8 ppm.
4. Conclusion
The preparation of 5-oxo-4,5-dihydro-pyrrole-3-carboxylic acid functionalized Fe3O4
nanoparticles (Cu(II)-OHPC-Fe3O4) as efficient, novel and reusable heterogeneous nano-
catalysts are reported. The nano magnetic catalyst was characterized by XRD, ICP-AES,
SEM, TEM, FT-IR, TGA, VSM and EDX techniques and employed for Pechmann reactions
between different substituted phenols and ethyl acetoacetate to synthesize various
coumarin derivatives. Cu(II)-OHPC-Fe3O4 nano magnetic catalyst has an average par-
ticle size of 26 nm. The nanocatalyst was recovered by filtration and reused for several
cycles. Advantages for the prepared nanocatalyst include high specific surface area,
good accessibility, high chemical and thermal stability, reducing the leaching of theses
nanocatalyst into the bio environment, having organic groups for easier modification
and less accumulation of them than other nanocatalysts.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Funding
This research was supported by the Hubei College of Chinese Medicine, Jingzhou, Hubei,
in China.

16
J. YUAN AND M. MOHAMMADNIA
References
[1] M.M. Heravi, B.A. Jani, F. Derikvand, F.F. Bamoharram, H.A. Oskooie. Catal. Commun., 10,
272 (2008).
[2] H.R. Shaterian, J. Farbodeh, M. Mohammadnia. Phosphorus Sulfur Relat. Elem., 188, 850
(2013).
[3] H. Veisi, A. Sedrpoushan, S. Hemmati. Appl. Organometal. Chem., 29, 825 (2015).
[4] T. Chakraborty, A. Sarkar, T. Chattopadhyay. J. Coord. Chem., 72, 3430 (2019).
[5] T. Chakraborty, R. Mondal, R. Ghanta, A. Chakraborty, T. Chattopadhyay. Appl. Organomet.
Chem., 34, e5695 (2020).
[6] M. Bagherzadeh, M.M. Haghdoost, F.M. Moghaddam, B.K. Foroushani, S. Saryazdi, E.
Payab. J. Coord. Chem., 66, 3025 (2013).
[7] A. Chakraborty, T. Chakraborty, M.I. Menendez, T. Chattopadhyay. ACS Omega., 4, 11558
(2019).
ꢀ
[8] A. Chakraborty, T. Chowdhury, M.I. Menendez, T. Chattopadhyay. ACS Appl. Mater.
Interfaces, 12, 38530 (2020).
[9] L. Danqing, J. Ming, L. Li, M. Mohammadnia. Appl. Organomet. Chem., 34, e5820 (2020).
[10] J. Chen, L. Dai, J. Li, M. Mohammadnia. Appl. Organomet. Chem., 34, e5708 (2020).
[11] E. Rafiee, S. Eavani. Green Chem., 13, 2116 (2011).
[12] H. Tang, C.H. Yu, W. Oduoro, H. He, S.C. Tsang. Langmuir, 24, 1587 (2008).
[13] R. Cano, D.J. Ramon, M. Yus. J. Org. Chem., 76, 5547 (2011).
[14] M.A. Zolfigol, V. Khakyzadeh, A.R. Moosavi-Zare, A. Rostami, A. Zare, N. Iranpoor, M.H.
Beyzavi, R. Luque. Green Chem., 15, 2132 (2013).
[15] R.K. Gujadhur, C.G. Bates, D. Venkataraman. Org. Lett., 3, 4315 (2001).
[16] F.Y. Kwong, A. Klapars, S.L. Buchwald. Org. Lett., 4, 581 (2002).
[17] D. Ma, Q. Cai. Org. Lett., 5, 3799 (2003).
[18] H.J. Cristau, P.P. Cellier, S. Hamada, J.F. Spindler, M. Taillefer. Org. Lett., 6, 913 (2004).
[19] X. Lv, Z. Wang, W. Bao. Tetrahedron, 62, 4756 (2006).
[20] H. Rao, Y. Jin, H. Fu, Y. Jiang, Y. Zhao. Chemistry, 12, 3636 (2006).
[21] Y.X. Xie, S.F. Pi, J. Wang, D.L. Yin, J.H. Li. J. Org. Chem., 71, 8324 (2006).
[22] A. Mirosanloo, D. Zareyee, M.A. Khalilzadeh. Appl. Organomet. Chem., 32, 4546 (2018).
[23] U.S. Weber, B. Steffen, C.P. Siegers. Res. Commun. Mol. Pathol. Pharmacol., 99, 193 (1998).
[24] A.D. Patil, A.J. Freyer, S.E. Drake, R.C. Haltiwanger, M.F. Bean, P.B. Taylor, M.J. Caranfa, A.L.
Breen, H.R. Bartus, R.K. Johnson, R.P. Hertzberg, J.W. Westley. J. Med. Chem., 36, 4131
(1993).
[25] B.S. Yun, I.K. Lee, I.J. Ryoo, I.D. Yoo. J. Nat. Prod., 64, 1238 (2001).
[26] H. V. Pechmann. Ber. Dtsch. Chem. Ges., 17, 929 (1884).
[27] A.C. Khandekar, B.M. Khadilkar. Synlett, 2002, 0152 (2002).
[28] G. Brufola, F. Fringuelli, O. Piermatti, F. Pizzo. Heterocycles, 43, 1257 (1996).
[29] R.L. Shriner. Org. React., 1, 1 (2004).
[30] I. Yavari, R. Hekmat-Shoar, A. Zonouzi. Tetrahedron. Lett., 39, 2391 (1998).
[31] G.A. Cartwright, H. McNab. J. Chem. Res., 8, 296 (1997).
[32] B. Tyagi, M.K. Mishra, R.V. Jasra. J. Mol. Catal. Chem., 276, 47 (2007).
[33] A. Sinhamahapatra, N. Sutradhar, S. Pahari, H.C. Bajaj, A.B. Panda. Appl. Catal. A. Gen.,
394, 93 (2011).
[34] A. Mobaraki, S. Yasham, B. Movassagh. Synlett, 26, 1263 (2015).
[35] L.L. Woods, J. Sapp. J. Org. Chem., 27, 3703 (1962).
[36] V.M. Alexander, R.P. Bhat, S.D. Samant. Tetrahedron. Lett., 46, 6957 (2005).
[37] H. Valizadeh, A. Shockravi. Tetrahedron. Lett., 46, 3501 (2005).
[38] B. Karami, M. Kiani. Catal. Commun., 14, 62 (2011).
[39] M.K. Potdar, S.S. Mohile, M.M. Salunkhe. Tetrahedron. Lett., 42, 9285 (2001).
[40] B. Karimi, D. Zareyee. Org. Lett., 10, 3989 (2008).
[41] A. Shaabani, R. Afshari, S.E. Hooshmand, A.T. Tabatabaei, F. Hajishaabanha. RSC Adv., 6,
18113 (2016).

JOURNAL OF COORDINATION CHEMISTRY
17
[42] M. Kiani, B. Karami. J. Iran. Chem. Soc., 14, 655 (2017).
[43] S. Kangari, I. Yavari, B. Maasoumi. J. Iran. Chem. Soc., 12, 1771 (2015).
[44] S. Rezayati, F. Sheikholeslami-Farahani, F. Rostami-Charati, S.A.S. Abad. Res. Chem.
Intermed., 42, 4097 (2016).
[45] F. Shirini, A. Yahyazadeh, K. Mohammadi. Res. Chem. Intermed., 41, 6207 (2015).
[46] H. Sharghi, M. Jokar. Heterocycles, 71, 2721 (2007).
[47] A.N. Brubaker, J. De Ruiter, W.L. Whitmer. J. Med. Chem., 29, 1094 (1986).
[48] Q. Li, S. Jiang, S. Ji, D. Shi, J. Yan, Y. Huo, Q. Zhang. Ind. Eng. Chem. Res., 53, 14948
(2014).
[49] A. Wang, X. Liu, Z. Su, H. Jing. Catal. Sci. Technol., 4, 71 (2014).
[50] X.L. Shi, X. Xing, H. Lin, W. Zhang. Adv. Synth. Catal., 356, 2349(2014).