Synthesis, characterization, and application of CoFe2O4@amino-2-naphthol-4-sulfonic acid as a novel and reusable catalyst for the synthesis of spirochromene derivatives

Article abstract of DOI:10.1002/aoc.6119

In the present work, 1-amino-2-naphthol-4-sulfonic acid immobilized on functionalized CoFe₂O₄ nanoparticles was successfully synthesized as a new, efficient, and recoverable catalyst and tested for the synthesis of spirochromene derivatives by a simple, green, and inexpensive procedure. This magnetically heterogeneous nanocatalyst was characterized by various techniques such as Fourier transform infrared (FT-IR), thermal gravimetric analysis (TGA)/derivative thermogravimetric (DTG), X-ray diffraction (XRD), MAP, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), vibrating sample magnetometer (VSM), Brunauer–Emmett–Teller (BET), and scanning electron microscopy (SEM) analyses. The novel synthesized nanocatalyst can be easily separated and can also be reused several times without appreciable loss in its catalytic activity. Furthermore, in comparison with previous reports, this nanocatalyst showed high thermal stability and acidic properties.

Full text of DOI:10.1002/aoc.6119

Received: 20 April 2020
DOI: 10.1002/aoc.6119
Revised: 26 July 2020
Accepted: 10 September 2020
F U L L P A P E R
Synthesis, characterization, and application of
CoFe2O4@amino-2-naphthol-4-sulfonic acid as a novel and
reusable catalyst for the synthesis of spirochromene
derivatives
Homayoun Faroughi Niya
| Nourallah Hazeri
| Maryam Fatahpour
Department of Chemistry, Faculty of
Science, University of Sistan and
Baluchestan, Zahedan, Iran
In the present work, 1-amino-2-naphthol-4-sulfonic acid immobilized on
functionalized CoFe2O4 nanoparticles was successfully synthesized as a new,
efficient, and recoverable catalyst and tested for the synthesis of spi-
rochromene derivatives by a simple, green, and inexpensive procedure. This
magnetically heterogeneous nanocatalyst was characterized by various tech-
niques such as Fourier transform infrared (FT-IR), thermal gravimetric
analysis (TGA)/derivative thermogravimetric (DTG), X-ray diffraction (XRD),
MAP, transmission electron microscopy (TEM), energy-dispersive X-ray
spectroscopy (EDS), vibrating sample magnetometer (VSM), Brunauer–
Emmett–Teller (BET), and scanning electron microscopy (SEM) analyses. The
novel synthesized nanocatalyst can be easily separated and can also be reused
several times without appreciable loss in its catalytic activity. Furthermore, in
comparison with previous reports, this nanocatalyst showed high thermal
stability and acidic properties.
Correspondence
Nourallah Hazeri, Department of
Chemistry, Faculty of Science, University
of Sistan and Baluchestan, P.O. Box
98135-674, Zahedan, Iran.
Email: nhazeri@chem.usb.ac.ir;
n_hazeri@yahoo.com
Funding information
Research Council of University of Sistan
and Baluchestan
K E Y W O R D S
1-Amino-2-naphthol-4-sulfonic acid, ANSA-CoFe2O4, magnetic nanocatalyst, recoverable
nanocatalyst, spirochromene derivatives
1 | INTRODUCTION
These materials have been extensively studied as inor-
ganic supports in the synthesis of semi heterogeneous
In recent years, nanomaterials have drawn considerable
interest due to their diverse applications in material sci-
ence, medical, biology, and chemistry.[1,2] These mate-
rials, also, have been applied broadly in the fields of
environmental remediation as nanoadsorbents for their
high reactivity, negligible internal diffusion resistance,
and high surface to volume ratio properties.[3,4] Magnetic
nanoparticles (MNPs) are one of the important groups of
nanomaterials that demonstrated individual properties
such as inhibition of centrifugation procedures and the
inevitable loss of solid catalysts in the separation process.
catalysts.[5–7] Also, MNPs are a bridge between homoge-
neous and heterogeneous catalysis for their
surface functionalization.[8–10] Furthermore, the utiliza-
tion of MNPs in catalysis systems was increased. Superior
characteristics of MNPs such as high magnetic properties
lead to its easy collection from the reaction mixture, high
surface area to volume ratio, and most importantly, eco-
friendly and nontoxic procedure.[11] Some MNPs that
used in catalytic applications include iron oxide (Fe3O4),
cobalt ferrite (Fe2CoO4), maghemite (γ-Fe2O3), and zinc
ferrite (ZnFe2O4).[12–15] Today, great attention has been
Appl Organomet Chem. 2020;e6119.
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© 2020 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.6119

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FAROUGHI NIYA ET AL.
paid to cobalt ferrite (CoFe2O4) nanocrystals with spinel
structure due to their superior characteristics, such as
high saturation magnetization, large surface area-to-
2 | EXPERIMENTAL
2.1 | General
volume
ratio,
and
shape-dependent
magnetic
behavior.[16–22] As a review of previous studies, many
functionalized CoFe2O4 MNPs have been reported as a
heterogeneous catalyst in multicomponent reactions
Melting points and infrared (IR) spectra of all compounds
were determined using an Electro thermal 9100 apparatus
and a Fourier transform infrared (FT-IR)-JASCO-460 plus
1
(MCRs)
such
as
CoFe2O4@SiO2@CPTMS,[13]
CoFe2O4@SiO2-PTA,[24]
spectrometer. The H and 13C nuclear magnetic resonance
CoFe2O4@SiO2-SO3H,[23]
(NMR) spectra of known compounds were recorded on a
Bruker DRX-300 Avance instrument in 300 MHz for H
CoFe2O4/TMU-17-NH2,[25] CoFe2O4@l-asparagine-Cu/
Ni,[26] CoFe2O4@glycine-M,[27] CoFe2O4@Pr.[28]
1
NMR using dimethyl sulfoxide (DMSO) as a solvent. All
reagents and solvents were obtained from Aldrich and
Merck and were used without further purification. Field
emission scanning electron microscope (FESEM) and
transmission electron microscopy (TEM) images of the syn-
Spiro heterocycles play a superior role in modern
organic chemistry. Synthesis of new spiro heterocycles
has been widely reported such as spiro[chromene-4,30-
indoles],
spiro[indole-3,40-quinolines],
and
spiropyranopyrazoles.[29–31] Among various spiro hetero-
cycles, chromene-containing spirooxindoles have
attracted significant attention because of their remark-
able biological properties including antianaphylactic,
anticancer, anticoagulant, diuretic, and spasmolitic activ-
ities. These compounds usually were synthesized through
a three-component reaction of acenaphthoquinone or
isatin with cyanoacetic ester or malononitrile and
1,3-dicarbonyl compounds.[32–35]
thesized nanoparticles were obtained by a MIRA3
TESCAN-XMU scanning electron microscope and a Leo
912 AB transmission electron microscope, respectively. The
magnetic properties of the synthesis nanoparticles were
studied by vibrating sample magnetometer (VSM) of Lake
Shore Cryotronics Company. The thermal behavior of the
synthesis nanoparticles was studied by a TG 209F3
NETZSCH thermo-gravimetric analysis.
In continuation of the development of the synthesis
of CoFe2O4 MNPs as a green catalyst in MCRs, herein,
1-amino-2-naphthol-4-sulfonic acid (ANSA) has been
successfully immobilized onto CoFe2O4 nanostructured
and further used as a novel efficient and reusable
nanocatalyst with excellent catalytic activity for the syn-
thesis of spirochromene derivatives via the reaction of
one equivalent of 1,2-diketones and malononitrile with
one equivalent of different CH-activated compounds
(Scheme 1).
2.2 | Synthesis of the magnetic CoFe2O4
nanoparticles
A total of 2.0 mmol of FeCl3.6H2O and 1.0 mmol of
CoCl2.6H2O were dissolved in 100 ml of distilled water under
nitrogen flow. Then, a KOH solution (1 M) was slowly added
to the salt solution dropwise under vigorous stirring at
1000 rpm. After reaching the pH to 11–12, the mixture was
refluxed for 3 h at 140ꢀC. Finally, the synthesized CoFe2O4
SCHEME 1 Synthesis of spirochromene in the presence of ANSA-CoFe2O4 as a magnetic nanocatalyst

FAROUGHI NIYA ET AL.
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nanoparticles (black precipitate) were separated by an exter-
nal magnet and washed several times with water and ethanol
and dried for 3 h at 60ꢀC in an oven.
2.5.2 | 20-amino-2,50-dioxo-50H-spiro
[indoline-3,40-pyrano[3,2-c]chromene]-30-
carbonitrile (4b)
mp: 288–290ꢀC [36]. IR (KBr): νmax 3295, 3196, 2205, 1711,
1
2.3 | Synthesis of magnetite
nanoparticles coated by 1-amino-
2-naphthol-4-sulfonic acid
1673 cm−1; H NMR (DMSO-d6, 300 MHz) δ = 7.49–8.35
(m, 10H, Ar-H, and NH2), 8.37 (s, 1H, NH) ppm.
An appropriate amount of synthesized CoFe2O4
nanoparticles (0.2 g) was ultrasonically dispersed in
20 ml of ethanol (96%) for 20 min. Then, to this suspen-
sion, 0.4 g of 1-amino-2-naphthol-4-sulfonic acid was
added. The reaction mixture was refluxed for 24 h at
100ꢀC under N2 atmosphere. Finally, the achieved
ANSA-CoFe2O4 nanoparticles were separated by an
external magnet and washed several times with water,
ethanol, and acetonitrile to remove unreacted material
and dried at 60ꢀC.
2.5.3 | 70-amino-2,20,40-trioxo-10,20,30,40-
tetrahydrospiro[indoline-3,50-pyrano[2,3-d]
pyrimidine]-60-carbonitrile (4c)
mp: 270–273ꢀC [36]. IR (KBr): νmax 3354, 3305, 3142,
1
2955, 2203, 1721, 1673, 1617, 1112; H NMR (DMSO-d6,
300 MHz): δ = 6.82 (d, 1H, J = 7.5 Hz, ArH), 6.94 (t, 1H,
J = 7.5 Hz, ArH), 7.15–7.21 (m, 2H, ArH), 7.39 (s, 2H,
NH2), 10.51 (s, 1H, NH), 11.16 (s, 1H, NH), 12.33 (s, 1H,
NH) ppm.
2.4 | General procedure for three-
component synthesis of spirochromene
derivatives
2.5.4 | 70-amino-10,30-dimethyl-2,20,40-
trioxo-10,20,30,40-tetrahydrospiro[indoline-
3,50-pyrano[2,3-d]pyrimidine]-60-
carbonitrile (4d)
A mixture of CH-acid (1.0 mmol), ethyl cyanoacetate or
malononitrile (1.0 mmol), acenaphthoquinone or isatin
derivatives (1.0 mmol), and ANSA-CoFe2O4 (10 mg) in
H2O:EtOH (2:1) (6 ml) was magnetically stirred at 40ꢀC
in an oil bath, and the reaction was monitored by thin-
layer chromatography (TLC). After completion of the
reaction, the product was dissolved in hot ethanol and
DMSO, and the ANSA-CoFe2O4 nanocatalyst was conve-
niently removed from the solution by an external magnet.
Finally, the resulting solution was cooled to room tem-
perature and the crude product was crystallized to afford
the pure products. The pure products were identified by
IR, MP, and 1H-NMR. The spectra of selected compounds
have been reported in the Supporting Information.
mp: 215–218ꢀC [36]. 1H NMR (DMSO-d6, 300 MHz):
δ = 3.04 (s, 3H, CH3), 3.41 (s, 3H, CH3), 6.84 (d, 1H,
J = 7.8 Hz, ArH), 6.93 (td, 1H, J = 7.2 Hz, J = 0.6 Hz,
ArH), 7.13–7.22 (m, 2H, ArH), 7.59 (s, 2H, NH2),10.53 (s,
1H, NH) ppm.
2.5.5 | Ethyl70-amino-5-bromo-10,30-
dimethyl-2,20,40-trioxo-10,20,30,40-
tetrahydrospiro[indoline-3,50-pyrano[2,3-d]
pyrimidine]-60-carboxylate (4e)
mp: 227–228ꢀC [36]. 1H NMR (DMSO-d6, 300 MHz):
δ = 0.87 (t, 3H, J = 7.2 Hz, CH3), 3.04 (s, 3H, CH3), 3.42
(s, 3H, CH3), 3.46 (q, 2H, J = 7.2 Hz, OCH2), 6.68 (d, 1H,
J = 8.1 Hz, ArH), 7.20 (1H, d, J = 1.8 Hz, ArH), 7.26 (dd,
J = 8.1 Hz, J = 2.1 Hz, 1H, ArH), 8.13 (s, 2H, NH2),10.42
(s, 1H, NH) ppm.
2.5 | Selected spectra for seven known
products are given below
2.5.1 | 2-amino-7,7-dimethyl-20,5-dioxo-
5,6,7,8-tetrahydrospiro[chromene-4,30-
indoline]-3-carbonitrile (4a)
2.5.6 | 20-amino-70,70-dimethyl-2,50-dioxo-
50,60,70,80-tetrahydro-2H-spiro
[acenaphthylene-1,40-chromene]-30-
carbonitrile (4g)
mp: 289–292ꢀC [36]. IR (KBr): νmax 3377, 3314, 3141,
1
2959, 2190, 1723, 1682, 1293 cm−1; H NMR (DMSO-d6,
300 MHz) δ = 1.03 (s, 6H, 2CH3), 2.15 (s, 2H, CH2), 2.57
(s, 2H, CH2), 6.81–7.24 (m, 6H, Ar-H, and NH2), 10.42 (s,
1H, NH) ppm.
mp: 269–270ꢀC [36]. 1H NMR (DMSO-d6, 300 MHz): 1.03
(s, 6H, 2CH3), 2.09 (dd, 2H, J = 16.02 Hz, J = 12.03 Hz,

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FAROUGHI NIYA ET AL.
CH2), 2.64 (dd, 2H, J = 19.35 Hz, J = 13.5 Hz, CH2),
7.32–8.28 (m, 8H, ArH, and NH2) ppm.
CoFe2O4 MNPs was described (Scheme 2). Then, the syn-
thesized CoFe2O4@ANSA nanocatalyst was characterized
by scanning electron microscopy (SEM), X-ray mapping,
energy-dispersive X-ray spectroscopy (EDS), FT-IR, dif-
ferential thermal analysis (DTA), thermal gravimetric
analysis (TGA), X-ray diffraction (XRD), Brunauer–
Emmett–Teller (BET), and VSM techniques.
2.5.7 | 20-amino-2,50-dioxo-2H,50H-spiro
[acenaphthylene-1,40-pyrano[3,2-c]
chromene]-30-carbonitrile (4h)
To confirm the immobilization of 1-amino-
2-naphthol-4-sulfonic acid on the surface of CoFe2O4
MNPs, FT-IR spectroscopy was initially applied.
1
mp: 288–291ꢀC [36]. H NMR (DMSO-d6, 300 MHz): 7.50
(d, 1H, J = 8.1 Hz, ArH), 7.57 (t, 1H, J = 7.5 Hz, ArH),
7.64–7.81 (m, 5H, ArH, NH2), 7.89 (t, 1H, J = 7.8 Hz, ArH),
7.99–8.07 (m, 3H, ArH), 8.36 (d, 1H, J = 7.8 Hz, ArH) ppm.
Figure
1
shows the FT-IR spectra of CoFe2O4
(a), ANSA-CoFe2O4 (b) nanoparticles. As can be seen,
the band at 618 cm−1 is assigned to Fe O and Co O
bonds in CoFe2O4 (Figure 1a) which shifts to 595 cm−1
after coating with ANSA (Figure 1b). The broad band at
3373 cm−1 is attributed to adsorbed water molecules
and the Co OH stretching vibration. The bands at
1046–1200 cm−1 are assigned to the stretching mode of
the S O and S O bands of SO3H groups on the
ANSA-CoFe2O4 surface.
3 | RESULTS AND DISCUSSION
3.1 | Catalyst characterizations
In this study, an applied strategy for the synthesis of the
1-amino-2-naphthol-4-sulfonic acid supported on
SCHEME 2 Preparation of ANSA-CoFe2O4
FIGURE 1 Fourier transform infrared (FT-IR) spectra of CoFe2O4 (a) and CoFe2O4@ANSA (b) magnetic nanoparticles (MNPs)

FAROUGHI NIYA ET AL.
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FESEM images of CoFe2O4 and ANSA-CoFe2O4
nanoparticles are shown in Figure 2. As can be seen, a
significant change in the surface morphology of CoFe2O4
MNPs occurs after coting 1-amino-2-naphthol-4-sulfonic
acid. Also, the size distribution and the surface morphol-
ogy of CoFe2O4 MNPs (3a) and ANSA-CoFe2O4 (3b) are
TEM images were used to investigate the nanostruc-
ture morphology of ANSA-CoFe2O4. As shown in
Figure 6, TEM images of ANSA-CoFe2O4 nanoparticles
displayed a cubic shape with an average size about
17.42 nm (Figure 7) that confirmed FESEM results. Fur-
thermore, ANSA-CoFe2O4 nanoparticles were identified
as a core-shell structure.
different.
The
CoFe2O4
and
ANSA-CoFe2O4
nanoparticles have an average size of approximately
19.46 and 27.94 nm, respectively. (Figure 3a,b). This
change in size is due to the immobilization of ANSA on
the surface of CoFe2O4 MNPs.
To study the thermal behavior of ANSA-CoFe2O4
nanoparticles, TGA analysis was applied. As shown in
Figure 8, the TGA curve of ANSA-CoFe2O4 shows three
weight-loss steps. A small weight loss (3.84%) between
0ꢀC and 280ꢀC is attributed to the desorption of adsorbed
solvents and materials. A second, larger weight loss
between 280 and 380ꢀC could be attributed to the
immobilized sulfuric acid groups (SO3H). The organic
residue on the surface of ANSA-CoFe2O4 nanoparticles
was decomposed between 380ꢀC and 500ꢀC. In accor-
dance with the TGA curve (total mass loss of 16.99%),
169.9 mg of ANSA was loaded on 1 g of CoFe2O4
nanoparticles. And the further weight loss at above
500ꢀC can be attributed to the change of catalyst
The distribution of elements in CoFe2O4 and ANSA-
CoFe2O4 nanoparticles was investigated by EDS analysis
(Figure 4a,b). As can be seen, the presence of nitrogen
(N, 3.96%), carbon (C, 28.00%), and sulfur (S, 3.68%)
elements confirm the successful synthesis of ANSA-
CoFe2O4 (Figure 4b). Also, Figure 5 illustrates the
X-ray mapping of ANSA-CoFe2O4 nanoparticles. As can
be seen, the homogenous presence of 1-amino-2-naph-
thol-4-sulfonic acid on the surface of CoFe2O4 MNPs
was confirmed.
FIGURE 2 Field emission
scanning electron microscope (FESEM)
images of CoFe2O4 (a) and
CoFe2O4@ANSA (b) magnetic
nanoparticles (MNPs)

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FAROUGHI NIYA ET AL.
FIGURE 3 The size histogram of CoFe2O4 (a) and CoFe2O4@ANSA (b) magnetic nanoparticles (MNPs)
FIGURE 4 Energy-dispersive X-ray spectroscopy (EDS) spectrum of CoFe2O4 (a) and CoFe2O4@ANSA (b) magnetic
nanoparticles (MNPs)
structure. TGA analysis results confirmed the immobili-
zation of ANSA on the surface of CoFe2O4 MNPs. Also,
the DTG curve indicated that ANSA-CoFe2O4
nanoparticles are stable below 337ꢀC.
occurs after the immobilization of ANSA on the surface
of CoFe2O4 MNPs.
The factors of surface area, pore distribution, and
pore volume of ANSA-CoFe2O4 MNPs have been deter-
mined by the BET analysis. Nitrogen adsorption/desorp-
tion isotherm, BET plot, and Barrett, Joyner, and
Halenda (BJH) pore size distribution for ANSA-CoFe2O4
MNPs are shown in Figure 11a–c. According to N2
adsorption/desorption, the pore volume of ANSA-
CoFe2O4 MNPs is 0.659 cm3 g−1. The BJH and BET ana-
lyses displayed that the average pore diameter and the
available surface area for ANSA-CoFe2O4 MNPs are
1.85 nm and 2.87 m2 g−1, respectively. As regards the
average pore diameter is less than 2 nm, so the ANSA-
CoFe2O4 nanocatalyst is microporous.
The XRD patterns of CoFe2O4 (curve a) and ANSA-
CoFe2O4 nanoparticles (curve b) are illustrated in
Figure 9. According to JCPDS card no. 03–0864, The
XRD diffraction pattern of CoFe2O4 displays seven dif-
fraction peaks at 18.24ꢀ, 30.06ꢀ, 35.45ꢀ, 43.47ꢀ, 53.88ꢀ,
57.17ꢀ, and 62.73ꢀ, which are assigned to (1 1 1), (2 2 0),
(3 1 1), (4 0 0), (4 2 2), (5 1 1), (4 4 0) crystallographic
faces of magnetite. In the XRD pattern of ANSA-CoFe2O4
(Figure 9b), the reflection of the amorphous organic layer
(ANSA) could be seen at 2θ = 0ꢀ–20ꢀ as a broad band,
that confirmed the immobilization of ANSA on the sur-
face of CoFe2O4 MNPs.
The magnetic property of CoFe2O4 and ANSA-
CoFe2O4 nanoparticles was investigated using room-
temperature VSM analysis. As shown in Figure 10, the
magnetic saturation (Ms) values of CoFe2O4 and ANSA-
CoFe2O4 are about 28.41, 29.45 emu g−1, respectively. No
significant change in the Ms values of ANSA-CoFe2O4
3.2 | Catalytic study
To demonstrate the catalytic activity of ANSA-CoFe2O4
nanoparticles,
the
synthesis
of
spirochromene
derivatives was investigated in the presence of

FAROUGHI NIYA ET AL.
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FIGURE 5 The X-ray mapping of CoFe2O4@ANSA magnetic nanoparticles (MNPs)
FIGURE 6 Transmission electron
microscopy (TEM) images of
CoFe2O4@ANSA magnetic
nanoparticles (MNPs)

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FAROUGHI NIYA ET AL.
FIGURE 7 The size histogram of
CoFe2O4@ANSA magnetic
nanoparticles (MNPs)
FIGURE 8 Thermal gravimetric
analysis (TGA) and derivative
thermogravimetric (DTG) curves of
CoFe2O4@ANSA magnetic
nanoparticles (MNPs)
FIGURE 9 X-ray diffraction (XRD) pattern of CoFe2O4 (a) and CoFe2O4@ANSA (b) magnetic nanoparticles (MNPs)

FAROUGHI NIYA ET AL.
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FIGURE 10 Vibrating sample magnetometer (VSM) spectra of CoFe2O4 (a) and CoFe2O4@ANSA (b) magnetic nanoparticles (MNPs)
FIGURE 11 Nitrogen adsorption/desorption isotherm (a), Brunauer–Emmett–Teller (BET) plot (b), and BJH pore size distribution
(c) of the ANSA-CoFe2O4 nanocatalyst
ANSA-CoFe2O4 nanoparticles. For achieving this
purpose, the reaction conditions (solvent, amount of
catalyst, and temperature) were first optimized and the
reaction between isatin, dimedone, and malononitrile
was chosen as a model reaction. Initially, the model
reaction carried out in different solvents in the
presence of 0.01 g of ANSA-CoFe2O4 nanocatalyst at
50ꢀC. In these conditions, The best result was obtained
in H2O:EtOH (2:1) solvent (6 ml) with 94% yields
(Table 1, entry 4). In the next step, in order to find a
better condition for the synthesis of spirochromene
derivatives, the model reaction was performed in the
different amounts of catalyst (Table 1). In the absence
of the catalyst, no significant improvement was
observed. In the presence of the different amounts of
catalyst, the yield and rate of reaction were increased.
As shown in Table 1, the high catalytic activity of
ANSA-CoFe2O4 nanoparticles was achieved in the
presence of 0.01 g of catalyst. The yield of reaction
with 0.02 g of catalyst was decreased, that is probably
because of the steric hindrance of the nanocatalyst in
the reaction mixture and reduces the impact of starting
materials. Finally, the temperature effect was explored,
and the best result was found in H2O:EtOH (2:1) in
the presence of 0.01 g of ANSA-CoFe2O4 nanocatalyst
at 40ꢀC. In this condition, the corresponding product
was obtained in 95% yields (Table 1, entry 9).
According to the optimal reaction conditions, the syn-
thesis of spirochromene derivatives was carried out using
a variety of diketones and CH-acid compounds, and the
results are summarized in Table 2. The results displayed
that the synthesis of spirochromene derivatives went well
with a broad range of diketones and CH-acid compounds
in good to excellent yields (64%–97%) and short reaction
times, which confirmed the high catalytic activity of
ANSA-CoFe2O4 nanoparticles.

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FAROUGHI NIYA ET AL.
TABLE 1 Optimization of reaction conditions for the synthesis of spirochromenes
Entry
Catalyst (g)
0.01
Solvent
Temperature (ꢀC)
Time (min)
Yield (%)
1
EtOH
50
50
50
50
50
50
50
40
r.t
40
40
5
5
87
89
87
94
90
85
79
95
88
68
79
2
0.01
H2O:EtOH (1:1)
H2O
3
0.01
5
4
0.01
H2O:EtOH (2:1)
H2O:EtOH (1:2)
H2O:EtOH (2:1)
H2O:EtOH (2:1)
H2O:EtOH (1:2)
H2O:EtOH (1:2)
H2O:EtOH (1:2)
H2O:EtOH (1:2)
5
5
0.01
5
7
0.005
5
8
0.02
5
9
0.01
5
10
11
12
0.01
5
No catalyst
CoFe2O4
15
10
TABLE 2 Synthesis of spirochromene derivatives in the presence of ANSA-CoFe2O4 (0.01 g) in EtOH:H2O (1:2) at 40ꢀC
According to the proposed mechanism shown in
Scheme 3, the ANSA-CoFe2O4 nanoparticles in the cata-
lytic cycle for the synthesis of spirochromene derivatives
act as a Lewis acid catalyst and increase the electrophilic-
ity of the carbonyl group of 1,2-diketones 3. So immedi-
ately, the Knoevenagel condensation of malononitrile
compounds 1 and olefin A. Finally, intramolecular cycli-
zation and tautomerization happen to give the
corresponding products (4a–h).
3.2.1 | Recyclability study
2
(deprotonation by ANSA-CoFe2O4 MNPs) and
1,2-diketones 3 generates olefin A. Then, intermediate
B was formed via Michael addition of CH-activated
In order to demonstrate that the ANSA-CoFe2O4
nanoparticles act as an eco-friendly and green catalyst,

FAROUGHI NIYA ET AL.
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SCHEME 3 The proposed
mechanism for the synthesis of
spirochromene in the presence of
ANSA-CoFe2O4
FIGURE 12 Reusability of
CoFe2O4@ANSA nanocatalyst in the synthesis
of 2-amino-7,7-dimethyl-20,5-dioxo-
5,6,7,8-tetrahydrospiro[chromene-4,30-indoline]-
3-carbonitrile
the nanocatalyst must be easily recycled and reused
without any significant reduction in its activities. The
reaction of isatin with dimedone and malononitrile
was chosen as a model reaction to examine the
recyclability of the new nanocatalyst. The reaction
was performed under the optimal reaction conditions.
Upon completion of the reaction, the corresponding
product was dissolved in hot ethanol and DMSO,
and hen the ANSA-CoFe2O4 nanocatalyst was
conveniently removed from the solution by an external
magnet. The ANSA-CoFe2O4 nanocatalyst was washed
by ethanol four to five times to remove any organic
residues and then dried at 80ꢀC in an oven and
reused in the next reactions. As can see in Figure 12,
the ANSA-CoFe2O4 nanocatalyst was reused for
six successive runs without any significant loss of
activity.
3.3 | Comparison
In order to compare the catalytic activity of the ANSA-
CoFe2O4 nanoparticles with other reported catalysts, the
compound 4a was selected as a model and the results
were summarized in Table 3. As can be seen, high yield
and good reaction time are some advantages of this pro-
cedure that confirm the high catalytic activity of the
ANSA-CoFe2O4 nanoparticles.

12 of 13
FAROUGHI NIYA ET AL.
TABLE 3 Comparison of the efficiency of ANSA-CoFe2O4 nanocatalyst with other reported catalysts in the studied reactions
Amount of
catalyst
Time
(min)
Yield
(%)
Product Catalyst
Condition
[Ref.]
4a
QUIN
20 mol%
EtOH:H2O (1:1),
70ꢀC
7
94
Oudi et al.[36]
NH4Cl
20 mol%
30 mg
Water, 70ꢀC
10
8
92
96
98
Dabiri et al.[37]
Moradi et al.[38]
SnO2 NPs
EtOH, r.t.
Fe3O4/COS@β-CD-
SO3H
20 mg
H2O, 50ꢀC
20
Mohammadian and
Akhlaghinia[39]
CoFe2O4@SiO2
10 mg
EtOH:H2O (1:1),
80ꢀC
5
2
5
98
98
95
Hemmat et al.[40]
CoFe2O4@SiO2@SO3H 10 mg
ANSA-CoFe2O4 10 mg
EtOH:H2O (1:1),
80ꢀC
Zamani-Ranjbar-Garmroodi
et al.[41]
H2O:EtOH (2:1),
40ꢀC
[This work]
3.4 | Conclusions
DATA AVAILABILITY STATEMENT
The data that support the findings of this study are avail-
able from the corresponding author upon reasonable
request.
In summary, a novel magnetic nanocatalyst, ANSA-
CoFe2O4, has been successfully fabricated via a green and
simple procedure. The analyses showed that the catalyst
has the nanometric size and highly thermally stable. The
spherical morphology of CoFe2O4 was changed to a cubic
shape after coating with ANSA. This change caused that
the magnetic property of CoFe2O4 was not decreased by
the nonmagnetic layer of ANSA anchored to the surface
of the CoFe2O4 MNPs. Then, the ANSA-CoFe2O4 MNPs
were used as a magnetically sustainable acid nanocatalyst
for the synthesis of spirochromene derivatives. This
nanocatalyst indicated a highly active heterogeneous cat-
alytic system that can be recovered and reused at least six
cycles of reaction without a significant loss in its selectiv-
ity and activity. Briefly, in comparison with other
nanocatalysts reported, the synthesized nanocatalyst has
important advantages such as easy synthesis, high stabil-
ity, reusability, and excellent yields of products along
with short reaction time that make this method useful
and attractive.
ORCID
Homayoun Faroughi Niya https://orcid.org/0000-0002-
2220-4288
Nourallah Hazeri https://orcid.org/0000-0002-0560-
7245
Maryam Fatahpour https://orcid.org/0000-0002-6735-
1644
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Homayoun Faroughi Niya: Conceptualization; formal
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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
How to cite this article: Faroughi Niya H,
Hazeri N, Fatahpour M. Synthesis,
characterization, and application of
CoFe2O4@amino-2-naphthol-4-sulfonic acid as a
novel and reusable catalyst for the synthesis of
spirochromene derivatives. Appl Organomet Chem.
2020;e6119. https://doi.org/10.1002/aoc.6119
[30] S. A. Pogosyan, R. V. Paronikyan, G. M. Stepanyan, A. G.
Grigoryan, Khim. Zh. Arm 2016, 69, 518.