Sulfonic acid-functionalized Fe3O4-supported magnetized graphene oxide quantum dots: A novel organic-inorganic nanocomposite as an efficient and recyclable nanocatalyst for the synthesis of dihydropyrano[2,3-c]pyrazole and 4H-chromen

Article abstract of DOI:10.1002/aoc.6004

In this research, the main emphasis has been focused on the preparation of a novel Fe₃O₄-supported propane-1-sulfonic acid-grafted graphene oxide quantum dots (Fe₃O₄@GOQD-O-(propane-1-sulfonic acid)) that it was

Full text of DOI:10.1002/aoc.6004

Received: 2 June 2020
DOI: 10.1002/aoc.6004
Revised: 30 July 2020
Accepted: 5 August 2020
F U L L P A P E R
Sulfonic acid-functionalized Fe3O4-supported magnetized
graphene oxide quantum dots: A novel organic-inorganic
nanocomposite as an efficient and recyclable nanocatalyst
for the synthesis of dihydropyrano[2,3-c]pyrazole and
4H-chromene derivatives
Masoud Khaleghi Abbasabadi1
| Davood Azarifar1
| Hamid Reza Esmaili Zand2
1Department of Chemistry, Bu-Ali Sina
University, Hamedan, 65178, Iran
2Department of Chemistry, Iran
University of Science and Technology,
Tehran, Iran
In this research, the main emphasis has been focused on the preparation of a
novel Fe3O4-supported propane-1-sulfonic acid-grafted graphene oxide
quantum dots (Fe3O4@GOQD-O-(propane-1-sulfonic acid)) that it was readily
synthesized via a five-step procedure as a hitherto unreported magnetic
nanocatalyst. This newly prepared Fe3O4@GOQD-O-(propane-1-sulfonic acid)
nanocomposite was structurally well-established by different analytical tech-
niques including Fourier transform infrared (FT-IR), X-ray diffraction (XRD),
energy-dispersive X-ray (EDX), thermal gravimetric analysis (TGA), field
emission gun-scanning electron microscope (FESEM), high-resolution
transmission electron microscopy (HRTEM) and vibrating sample magnetome-
ter (VSM) analyses. The high catalytic performance of this nanocomposite was
exhibited in one-pot synthesis of dihydropyrano[2,3-c]pyrazole and 4H-
chromene derivatives under mild conditions. Low reaction times, excellent
yields of the products, benignity of the catalyst, easy reaction work-up and
magnetic recyclability of the catalyst are the main advantages of the present
protocol. Also, our research indicated that the Fe3O4@GOQD-O-(propane-
1-sulfonic acid) could be reused up to five times without considerable loss of
catalytic activity.
Correspondence
Masoud Khaleghi Abbasabadi,
Department of Chemistry, Bu-Ali Sina
University, 65178, Hamedan, Iran.
Email: m.khaleghi@alumni.basu.ac.ir
K E Y W O R D S
4H-chromene, dihydropyrano[2,3-c]pyrazoles, Fe3O4-supported propane-1-sulfonic acid-grafted
graphene oxide quantum dot, nanocomposite, one-pot three-component reaction
1 | INTRODUCTION
the biological and pharmaceutical industry, magnetic
resonance imaging, bioseparation, hyperthermia and
In recent decade, heterogeneous catalysts have found a
wide range of applications as eco-friendly and compatible
catalysts in several synthetic reactions and industrial
fields.[1–4] In the past decade, several studies have been
directed on the preparation and application of various
magnetic nanoparticles (MNPs) in different fields such as
catalytic processes. Also, MNPs have attracted much
research interests as highly active supports for
preparation of various supported nanocatalysts which
can be easily separated from the mixture reaction simply
by using an external magnetic field.[5] Among the hetero-
geneous catalysts, several nanoparticles (NPs) have
Appl Organomet Chem. 2020;e6004.
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https://doi.org/10.1002/aoc.6004

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KHALEGHI ABBASABADI ET AL.
received great interest due to their high catalytic activity
and interesting physical and chemical properties such as
nontoxicity, reusability, long-term stability and high sur-
face area.[6] Despite these advantages, such small parti-
cles suffer from tedious recycling and separation from the
reaction mixtures by filtration or expensive ultracentrifu-
gation that has limited their application.[7] This drawback
has been tackled by using MNPs as efficient supports
amenable to simple magnetic separation.[8] As a result,
MNPs have found wide applications in catalytic organic
reactions and industrial processes.[9,10] In this context,
Fe3O4 and Fe2O3 NPs are the most extensively studied
core magnetic supports, owing to their high surface area
with high catalyst loading ability, magnetic susceptibility,
conductivity, striking stability and catalytic activity.[11]
Among the NPs known in the recent years, carbon
nanostructured materials have attracted enormous inter-
est as efficient catalysts in different chemical processes
due to their interesting properties such as air stability,
low cost and high corrosion resistance.[12] Graphitic
materials have emerged as the most widely used carbon
materials in various fields owing to their appropriate
electrical conductivity, high mechanical strength, suitable
transparency, high surface area and proper biocompati-
bility.[13] Graphene oxide (GO) has been reported to pos-
sess oxidative catalytic activity and emerged as an air-
stable eco-friendly heterogeneous catalyst and easily
functionalized catalyst for applications in various chemi-
cal reactions.[14,15] GO is built of layers of six-membered
aromatic rings carrying various functional groups such as
hydroxyl, carboxyl and epoxy groups. Such functional
groups enable the carbon layers of GO to mediate ionic
and non-ionic interactions with a wide range of
molecules and also to perform oxidizing and acidic
activities in different reactions.[14] Among the carbon
nanomaterials, graphene quantum dots (GQDs) have
been known as a new class of compounds consisting a
single atomic layer of nanosized graphene unit.[14,15] In
recent years, GQDs have received enormous research
interest owing to its excellent structural features
including easy functionalization, low toxicity, excellent
solubility, high surface area, excellent thermal and
promising drugs, pharmaceutical agents and photoactive
materials.[18–21]
The general synthesis of dihydropyrano[2,3-c]
pyrazole derivatives involves three-component condensa-
tion reactions between malononitrile, 3-methyl-1-phenyl-
pyrazolin-5-one and aldehydes under the catalytic effect
of various catalytic systems such as piperidine,
hexadecyldimethylbenzyl
ammonium
bromide
(HDMBAB), MgO, γ-Fe2O3@Cu3Al-LDH, ionic liquids
and cupreine.[22]
Similarly, 4H-chromene derivatives have found to
exhibit intriguing pharmaceutical properties as hypoten-
sive, antimicrobial, antitumor, antileishmanial, antihu-
man immunodeficiency virus (HIV) and local anaesthetic
agents.[23] 4H-Chromenes bearing amino and nitrile
functionalities are also favoured medicinal compounds
performing potential anticancer activity.[24,25] Moreover,
a variety of functionalized 4H-chromene moieties appear
as the key building block of numerous oxygen-containing
natural products that exhibit diverse biological and
pharmacological activities such as antiallergenic,
antitumor, antineurodegenerative and anti-inflammatory
effects.[26–29] Also, various chromene derivatives have
found applications in different fields such as cosmetics,
pigments and potentially biodegradable agrochemi-
cals.[30] Conventional methods reported for the synthesis
of chromenes generally employ a three-component reac-
tion between malononitrile, 1,3-diketones and aldehydes.
These reactions utilize different catalytic systems includ-
ing hexadecyltrimethyl ammonium ionic liquids, Mg/La
mixed metal oxides, nanosilica, bromide and silica-
bonded propylpiperazine-N-sulfamic acid.[31]
In the present research, we describe for the first time
the synthesis and characterization of Fe3O4-supported
propane-1-sulfonic acid-grafted GO quantum dot
(Fe3O4@GOQD-O-(propane-1-sulfonic acid)) and its
application as an efficient and recyclable heterogeneous
magnetic nanocatalyst for one-pot three-component
synthesis of dihydropyrano[2,3-c]pyrazoles (4a–4h) and
4H-chromenes (6a–6h) (Scheme 1).
chemical
photoluminescence.[16]
Among the heterocyclic compounds of the biological
activities, 4H-pyrane-containing derivatives have
stability, biocompatibility
and
stable
emerged as an important class of heterocyclic compounds
with diverse biological activities. Pyrano[2,3-c]pyrazole
derivatives have received considerable interest owing to
their significant pharmacological and therapeutic values
as antibacterial, anticoagulant, anticancer, diuretic and
insecticidal agents.[17,18] Besides, these compounds
constitute the structural unit for the synthesis of some
SCHEME 1 Synthesis of pyrano[2,3-c]pyrazoles 4a–4h and
4H-chromenes 5a–5h under the catalysis of Fe3O4@GOQD-O-
(propane-1-sulfonic acid) nanocatalyst

KHALEGHI ABBASABADI ET AL.
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2 | EXPERIMENTAL
2.1 | General
were prepared from the above-synthesized GO
nanosheets. First, 0.6 g of GO was added to 120 ml of
N,N-dimethylformamide (DMF) as a reducing agent
and solvent, and the resulting mixture was heated at
250ꢀC for 6 h. Afterwards, the precipitated reaction
product was vacuum filtered using a 0.2-μm nylon
membrane. Finally, the GOQDs as a black solid
was obtained by evaporating the solvent under
reduced pressure using a rotary evaporator and dried
at 65ꢀC.
Chemicals including natural flake graphite (−325 mesh,
99.95%) were purchased from Merck chemical company
and used as received. Melting points of organic com-
pounds were measured in open capillary tubes with a
Buchi 510 apparatus. Fourier transform infrared (FT-IR)
spectra were recorded from KBr pellets using a Perkin
Elmer Spectrum 65 FT-IR spectrophotometer. The pro-
gress of the reactions was monitored by TLC on Silica
Gel PolyGram SIL G/UV 254 plates. NMR spectra were
recorded for samples in CDCl3 or DSMO-d6 on 90 and
400 MHz BRUKER spectrometers using Me4Si as internal
standard. Energy-dispersive X-ray (EDX) analysis of the
prepared catalyst was performed on a VG ESCALAB-
200R spectrometer equipped with a hemispherical elec-
tron analyser. Magnetic property of the catalyst sample
was measured with a vibrating sample magnetometer
(VSM) model LBKFB, Meghnatis Daghigh Kavir Co,
Iran, at room temperature. Qualitative analysis of
Fe3O4@GOQD-O-(propane-1-sulfonic acid) magnetic
nanosheets was performed on a scanning electron
microscopy (SEM) and high-resolution transmission elec-
tron microscopy (HRTEM) images were obtained using a
Zeiss model Zeiss-EM10C-100 KV field emission gun-
scanning electron microscope (FESEM). Powder X-ray
diffraction (XRD) was conducted on a PANalytical X'Pert
PRO X-Ray Diffractometer.
2.4 | Preparation of Fe3O4-supported GO
grafted with propane-1-sulfonic acid
2.4.1 | Acyl-chlorination of GOQDs
Initially, in a flask containing 60 ml of thionyl
chloride was added GO (0.3 g) with stirring at 70ꢀC
under argon for 24 h. After completion of the reaction
as monitored by TLC, the resulted acyl-chlorinated
GOQDs product was centrifuged, washed with tetrahy-
drofuran (THF) four times and finally dried under
vacuum.[12]
2.4.2 | Functionalization of GOQDs with
3-hydroxypropane-1-sulfonic acid
A total of 1 g of 3-hydroxypropane-1-sulfonic acid was
added to the acyl-chlorinated GOQDs (0.3 g). Then, the
mixture was refluxed for 72 h at 120ꢀC under argon con-
dition. The resulting solid material was washed with DI
water to obtain the dark powder GOQD-O-(propane-
1-sulfonic acid) product.[14]
2.2 | Preparation of GO
GO was synthesized following the modified Hummers'
method as previously reported.[32] In the first step, 125 ml
of H2SO4 was added to 2.5 g of graphite powder, and the
mixture was stirred for 24 h. Next, to the resulting reac-
tion mixture was slowly added 15 g of KMnO4, and the
reaction mixture was continuously stirred at 50ꢀC for
72 h. Afterwards, the resulted mixture was poured into a
beaker containing 250 ml of ice followed by addition of
25 ml of H2O2 (30%) in 250 ml of deionized (DI) water.
As a result, the mixture was turned from brown colour
into bright yellow. The resulted product was separated by
centrifugation, washed with DI water and 10% HCl solu-
tion for three times and dried at 70ꢀC.
2.4.3 | Nanomagnetization of GOQD-O-
(propane-1-sulfonic acid)
Fe3O4@GOQD-O-(propane-1-sulfonic acid) was synthe-
sized following a modified procedure reported by
Kassaee et al.[34] The feeding weight ratio of m(FeCl3):
m(GO) used in the prepared mixture was 20:1. Initially,
40 mg of previously prepared GOQD-O-(propane-
1-sulfonic acid) in 40 ml of DI water was ultrasonicated
for 30 min. Then, to the resulting mixture was added
50-ml solution of FeCl2 (300 mg) and FeCl3 (800 mg)
in DI water (40 ml) at room temperature. Afterwards,
the pH value of the mixture was increased to 11 by
adding 30% aqueous solution of ammonia (30 ml), and
the mixture was stirred at 75ꢀC for 30 min. The final
product was separated by using an external magnet,
2.3 | Synthesis of GOQDs
GO quantum dots (GOQDs) were synthesized using
a simple process as previously reported.[33] GOQDs

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KHALEGHI ABBASABADI ET AL.
washed with DI water for several times and dried
at 65ꢀC.
3 | SELECTED DATA
3.1 | 6-Amino-3-methyl-1,4-diphenyl-
1,4-dihydropyrano[2,3-c]pyrazole-
5-carbonitrile (4a)
2.5 | General procedure for the synthesis
of 1,4-dihydropyrano[2,3-c]pyrazole
derivatives
White solid; m.p. 170ꢀC to 173ꢀC; IR (KBr) (νmax/cm−1):
3471, 3324, 3194, 3063, 2917, 2198, 1659, 1593, 1516, 1385,
1
To a mixture of aldehyde 1 (1 mmol), malononitrile
(66 mg, 1 mmol) and 3-methyl-1-phenyl-1H-pyrazol-
5(4H)-one (174 mg, 1 mmol) in DI water (5 ml) was
added the catalyst Fe3O4@GOQD-O-(propane-1-sulfonic
acid) (20 mg), and the mixture was stirred under room
temperature for an appropriate time (Table 4). After com-
pletion of the reaction as monitored by TLC, the reaction
mixture was diluted with hot ethanol (15 ml) and stirred
for 5 min. Then, the catalyst was isolated by using an
external magnet. The remaining supernatant liquid was
evaporated under reduced pressure to leave the crude
product which was purified by recrystallization from
absolute EtOH. All the synthesized products 4a–4h were
known compounds and were characterized by their phys-
ical properties and spectral (FT-IR, 1H NMR and 13C
NMR) analysis and compared with the reported
corresponding data (Table 3). The characterization data
for the selected products are available online in the
supporting information section provided at the end of the
article.
1265, 1066, 827, 753, 686, 651. H NMR (90 MHz, CDCl3)
δ: 1.89 (s, 3H, CH3), 4.66–4.69 (d, 3H, CH, NH2), 7.28–7.61
(m, 10H, H Ar) ppm. 13C NMR (100 MHz, DMSO-d6)
δ: 13.0, 37.2, 58.7, 99.1, 116.5, 120.4, 126.6, 127.5, 128.2,
129.0, 129.8, 138.0, 144.0, 144.3, 145.7, 159.8 ppm.
3.2 | 6-Amino-4-(p-chlorophenyl)-
3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]
pyrazole-5-carbonitrile (4c)
White solid; m.p. 183ꢀC to 186ꢀC; IR (KBr) (νmax/cm−1):
3393, 3280, 3170, 2924, 2224, 2192, 1660, 1605, 1513,
1456, 1370, 1278, 1128, 1073, 936, 834, 759, 692, 669, 572.
1H NMR (400 MHz, DMSO-d6) δ: 1.80 (s, 3H, CH3), 4.74
(s, 1H, CH), 7.28–7.81 (m, 11H, H Ar and NH2) ppm.
13C NMR (100 MHz, DMSO-d6) δ: 13.0, 36.5, 58.2, 98.7,
120.3, 120.4, 120.5, 126.7, 129.0, 129.6, 130.2, 132.1, 138.0,
143.1, 144.4, 145.7, 159.9 ppm.
3.3 | 6-Amino-4-(p-methoxyphenyl)-
3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]
pyrazole-5-carbonitrile (4e)
2.6 | General procedure for the synthesis
of 4H-chromene derivatives
To a mixture of aromatic aldehyde 1 (1 mmol),
malononitrile (66 mg, 1 mmol) and dimedone (14 mg,
1 mmol) in DI water (5 ml) was added Fe3O4@GOQD-O-
(propane-1-sulfonic acid) (20 mg), and the resulting mix-
ture was stirred at room temperature for an appropriate
time (Table 5). After completion of the reaction as moni-
tored by TLC, 15 ml of hot EtOH was added to the
resulting reaction mixture and the catalyst was magneti-
cally separated by using an external magnet. The solvent
was removed under reduced pressure to leave the crude
residue which was recrystallized from absolute EtOH to
afford the pure product. The synthesized products 6a–6h
were all known compounds and were characterized
White solid; m.p. 170ꢀC to 173ꢀC; IR (KBr) (νmax/cm−1):
3390, 3321, 3204, 3022, 2191, 1660, 1583, 1513, 1391,
1
1259, 11,249, 1128, 1109, 1026, 839, 759, 692, 573. H
NMR (90 MHz, DMSO-d6) δ: 1.78 (s, 3H, CH3), 3.74 (s,
3H, CH3), 4.62 (s, 1H, CH), 6.84–7.82 (m, 11H, H Ar,
NH2) ppm. 13C NMR (100 MHz, DMSO-d6) δ: 12.4, 36.1,
54.6, 59.1, 98.3, 113.4, 119.8, 125.5, 128.4, 128.7, 135.0,
137.4, 143.6, 145.2, 158.0, 158.9 ppm.
3.4 | 6-Amino-4-(3-bromophenyl)-
3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]
pyrazole-5-carbonitrile (4h)
1
based on their melting points and spectral (FT-IR, H
NMR and 13C NMR) analysis and compared with the
reported corresponding data (Table 4). The characteriza-
tion data for the selected products are available online in
the supporting information section provided at the end of
the article.
White solid; m.p. 161ꢀC to 164ꢀC; IR (KBr) (νmax/cm−1):
3450, 3324, 3195, 2199, 1660, 1593, 1518, 1487, 1456, 1391,
1
1126, 1065, 859, 751, 686. H NMR (400 MHz, DMSO-d6)
δ: 1.81 (s, 3H, CH3), 4.75 (s, 1H, CH), 7.29–7.35 (m, 5H,
H Ar), 7.47–7.52 (m, 4H, H Ar), 7.79–7.81 (m, 2H, NH2)

KHALEGHI ABBASABADI ET AL.
5 of 18
ppm. 13C NMR (100 MHz, DMSO-d6) δ: 13.1, 36.8, 58.0,
98.5, 120.4, 120.6, 122.3, 126.7, 127.5, 129.8, 130.5, 130.9,
131.3, 138.0, 144.4, 145.6, 146.9, 160.0 ppm.
1410, 1366, 1261, 1215, 1160, 1139, 1033, 1015, 859, 561,
530, 487. H NMR (300 MHz, DMSO-d6) δ: 0.93 (s, 3H,
CH3), 1.02 (s, 3H, CH3), 2.05–2.27 (m, 2H, CH2), 2.50
(s, 2H, CH2), 4.15 (s, 1H, CH), 6.98–7.27 (m, 6H, H Ar
and NH2) ppm; 13C NMR (100 MHz, DMSO-d6) δ: 27.2,
28.8, 32.2, 35.9, 38.9, 50.4, 58.8, 113.1, 120.2, 127.1, 127.6,
128.8, 145.1, 158.9, 163.1, 196.4 ppm.
1
3.5 | 6-Amino-3-methyl-4-(naphthalen-
2-yl)-1-phenyl-1,4-dihydropyrano[2,3-c]
pyrazole-5-carbonitrile (4i)
White solid; m.p. 192ꢀC to 195ꢀC; IR (KBr) (νmax/cm−1):
3.9 | 2-Amino-4-(p-cholorphenyl)-
7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carbonitrile (6d)
3471, 3327, 2195, 1662, 1595, 1519, 1366, 1126, 1069,
1
814, 749. H NMR (400 MHz, DMSO-d6) δ: 1.77 (s, 3H,
CH3), 4.88 (s, 1H, CH), 7.35–7.91 (m, 14H, H Ar and
NH2) ppm. 13C NMR (100 MHz, DMSO-d6) δ: 13.5, 37.4,
58.5, 98.8, 120.4, 120.5, 126.3, 126.4, 126.6, 126.6, 126.7,
128.0, 128.2, 128.9, 129.8, 132.7, 133.3, 138.0, 141.3, 144.4,
145.8, 159.9, 159.9 ppm.
White solid; m.p. 211ꢀC to 214ꢀC; IR (KBr) (νmax/cm−1):
3379, 3323, 3180, 2958, 2942, 2887, 2188, 1675, 1634,
1390, 1286, 1215, 1093, 1014, 884, 854, 769, 639, 620, 576.
1H NMR (90 MHz, DMSO-d6) δ: 0.94 (s, 3H, CH3), 1.03
(s, 3H, CH3), 2.15 (s, 2H, CH2), 2.50 (s, 2H, CH2), 4.195
(s, 1H, CH), 7.05–7.30 (s, 6H, H Ar and NH2) ppm; 13C
NMR (100 MHz, DMSO-d6) δ:14.0, 20.7, 26.8, 28.3, 31.8,
35.1, 49.9, 57.7, 59.7, 112.3, 119.5, 128.2, 129.1, 131.1,
143.7, 158.5, 162.6, 170.3 ppm.
3.6 | 6-Amino-3-methyl-1-phenyl-
4-(pyridin-3-yl)-1,4-dihydropyrano[2,3-c]
pyrazole-5-carbonitrile (4j)
White solid; m.p. 227ꢀC to 229ꢀC; IR (KBr) (νmax/cm−1):
3365, 3299, 2191, 1659, 1588, 1519 cm−1
;
1H NMR
3.10 | 2-Amino-7,7-dimethyl-4-(p-
nitrophenyl)-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carbonitrile (6g)
(400 MHz, DMSO-d6) δ:1.86 (s, 3H, CH3), 4.87 (s, 1H,
C H), 7.41–8.63 (m, 11H, H Ar and NH2) ppm; 13C
NMR (400 MHz, DMSO-d6) δ: 12.5, 34.1, 57.1, 97.6, 119.8,
120.0, 123.8, 126.2, 129.0, 129.3, 135.5, 137.4, 138.9, 143.9,
145.0, 149.0, 149.1, 159.5, 159.6 ppm.
Cream solid; m.p. 178ꢀC to 181ꢀC; IR (KBr) (νmax/cm−1):
3406, 3316, 3176, 2977, 2942, 2183, 1672, 1631, 1521,
1493, 1390, 1296, 1159, 1031, 855, 729, 629, 617, 574, 561.
1H NMR (90 MHz, DMSO-d6) δ: 0.96 (s, 3H, CH3), 1.04
(s, 3H, CH3), 2.17 (s, 2H, CH2), 2.53 (s, 2H, CH2), 4.37
(s, 1H, CH), 7.18–7.18 (m, 4H, H Ar), 8.12 (s, 2H, NH2)
ppm. 13C NMR (100 MHz, DMSO-d6) δ: 26.9, 28.2, 31.8,
35.6, 39.6, 49.8, 56.9, 111.7, 119.3, 123.7, 128.6, 146.2,
152.3, 158.5, 163.1, 195.7 ppm.
3.7 | 2-Amino-7,7-dimethyl-5-oxo-
4-phenyl-5,6,7,8-tetrahydro-4H-chromene-
3-carbonitrile (6a)
White solid; m.p. 235ꢀC to 237ꢀC; IR (KBr) (νmax/cm−1):
3394, 3324, 3251, 3212, 2960, 2889, 1680, 1604, 1413, 1371,
1249, 1214, 1159, 1138, 1071, 1036, 838, 695, 578. 1H NMR
(90 MHz, CDCl3) δ: 1.04 (s, 3H, CH3), 1.11 (s, 3H, CH3),
2.23 (s, 2H, CH2), 2.45 (s, 2H, CH2), 4.41 (s, 1H, CH), 4.45
(s, 2H, NH2), 7.24 (s, 5H, H Ar) ppm; 13C NMR
(75.5 MHz, DMSO-d6) δ: 26.8, 28.4, 31.8, 35.5, 49.9, 58.3,
112.7, 119.7, 127.1, 128.3, 144.7, 158.4, 162.5, 195.6 ppm.
3.11 | 2-Amino-4-(m-chlorophenyl)-
7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carbonitrile (6i)
White solid, m.p. 222ꢀC to 225ꢀC, IR (KBr) (νmax/cm−1):
3394, 3329, 3198, 2960, 2199, 1682, 1654, 1604, 1370,
1214. 1H NMR (90 MHz, DMSO-d6) δ: 0.94 (s, 3H,
CH3), 1.01 (s, 3H, CH3), 2.07–2.27 (m, 2H, CH2), 2.51
(s, 2H, CH2), 4.198 (s, 1H, CH), 7.091–7.34 (m, 6H,
H Ar, NH2) ppm. 13C NMR (100 MHz DMSO-d6)
δ: 27.2, 28.7, 32.2, 35.7, 50.3, 58.0, 112.4, 120.0, 126.3,
127.1, 127.4, 130.7, 133.3, 147.6, 158.9, 113.4,
196.3 ppm.
3.8 | 2-Amino-7,7-dimethyl-4-(p-
fluorphenyl)-5-oxo-5,6,7,8-tetrahydro-4H-
chromene-3-carbonitrile (6b)
White solid; m.p. 188ꢀC to 190ꢀC; IR (KBr) (νmax/cm−1):
3354, 3178, 3100, 2960, 2190, 1674, 1636, 1603, 1504,

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3.12 | 2-Amino-7,7-dimethyl-5-oxo-
4-(thiophen-2-yl)-5,6,7,8-tetrahydro-4H-
chromene-3-carbonitrile (6j)
illustrates that the structure of GO has remained intact in
the presence of DMF during the synthesis of GOQD. This
result combined with the TEM analysis clearly confirmed
the successful synthesis of GOQD in the presence of
DMF.[33]
White solid, m.p. 200ꢀC to 202ꢀC, IR (KBr) (νmax/cm−1):
3382, 3321, 3208, 2963, 2878, 2198, 1678, 1660, 1602,
1466, 1374, 1214. H NMR (400 MHz, DMSO-d6) δ: 0.98
The absorption band at 1022 cm−1 in the spectrum of
the magnetized 1-propane sulfonic acid-grafted GOQDs
Fe3O4@GOQD-O-(propane-1-sulfonic acid) (Figure 1c)
corresponds to the vibrational frequency of ν(S O)
related to the SO3H group. Also, the presence of SO3
1
(s, 3H, CH3), 1.05 (s, 3H, CH3), 2.1–2.2 (s, 2H, CH2),
2.4–2.5 (s, 2H, CH2), 4.5 (s, 1H, CH), 6.6–6.9 (m, 2H,
H Ar), 7.1–7.3 (s, H, H CS, s, 2H, NH2) ppm. 13C NMR
(400 MHz DMSO-d6) δ: 26.4, 28.6, 30.3, 31.7, 49.8, 57.9,
112.8, 119.5, 123.9, 124.3, 126.7, 149.2, 158.8, 162.4,
195.5 ppm.
group was confirmed by the peak at 1221 cm−1 [10,45]
In
.
addition, the peaks at 2920 and 2850 cm−1 in Figure 1c
are assigned to C H stretching vibrations of the propyl
group attached to the sulfonic acid group. In the spec-
trum of Fe3O4@GOQD-O-(propane-1-sulfonic acid), the
absorption bands observed at around 620 and 485 cm−1
are related to the Fe O stretching vibrations.[46,47] As
seen in the spectrum of the magnetized sulfonated
GOQDs, the stretching frequency of the carboxyl and
ester groups has been shifted from 1730 cm−1 to a lower
frequency at 1618 cm−1 that could be explained by the
change of COOH groups to carboxylate (COO−) groups
upon magnetization with Fe3O4.[48] These results indi-
cated that the GOQD was successfully modified with
propane-1-sulfonic acid group as supported by the spec-
trum of the magnetic Fe3O4 NPs.
4 | RESULTS AND DISCUSSION
4.1 | Characterization of the catalyst
Fe3O4@GOQD-O-(propane-1-sulfonic acid)
The Fe3O4@GOQD-O-(propane-1-sulfonic acid) mag-
netic nanosheets were prepared by a simple five-step
procedure presented in Scheme 2. As shown in this
scheme, GO was initially prepared according to the
Hummers' method.[32] Then, GOQDs was synthesized
by a simple process from freshly prepared GO via
treatment with N,N-DMF at 250ꢀC for 6 h.[33] In the
next step, the GOQD-O-(propane-1-sulfonic acid)
nanosheets were obtained by acyl-chlorination
The XRD patterns obtained from the GO and the pre-
pared Fe3O4@GOQD-O-(propane-1-sulfonic acid) are
illustrated in Figure 2a,b. According to Figure 2a, GO
exhibits main diffraction peaks at 2θ = 11.95ꢀ and 42.45ꢀ
corresponding to the indices (002) and (100), respec-
tively.[49] The peak at 2θ = 11.8ꢀ exhibited by GO has
been significantly shifted at about 2θ = 24ꢀ as a result of
magnetization with Fe3O4. The relative intensities and
positions of all the peaks shown at 2θ = 30.39ꢀ, 35.74ꢀ,
43.36ꢀ, 57.31ꢀ and 62.93ꢀ in the XRD pattern of
Fe3O4@GOQD-O-(propane-1-sulfonic acid) are in com-
pliance with standard XRD pattern of magnetite Fe3O4
(JCPDS Card No. 79-0417).[50] These results indicated
that the GOQDs films were successfully magnetized
with Fe3O4 and grafted with propane-1-sulfonic acid
group.[48–51]
The elemental composition of the Fe3O4@GOQD-O-
(propane-1-sulfonic acid) was established by EDX
analysis. The EDX images obtained from the samples
(Figure 3) clearly indicated the expected components
(C, O, S and Fe) of the Fe3O4@GOQD-O-(propane-
1-sulfonic acid). The atomic weight ratios of the
corresponding elements calculated from the EDX analy-
sis are listed in Table 1. These results provided further
evidence for successful grafting of GOQDs films with
propane-1-sulfonic acid group and magnetization with
Fe3O4 MNPs.
of
GOQDs
followed
by
modification
acid. Finally,
with
the
3-hydroxypropane-1-sulfonic
Fe3O4@GOQD-O-(propane-1-sulfonic acid) magnetic
nanosheets were obtained by coprecipitation of ferrous
(Fe2+) and ferric (Fe3+) ions in the presence of the
prepared GOQD-O-(propane-1-sulfonic acid) according
to the method reported by Kassaee et al.[34]
The structure of the synthesized magnetic nanosheets
was fully characterized by different analytical techniques
as described below.
Figure 1 illustrates the FT-IR spectra of the GO,
GOQDs, and Fe3O4@GOQD-O-(propane-1-sulfonic acid)
magnetic nanosheets. The peaks at 1717, 1627 and
1107 cm−1 shown in the spectra of GO and GOQDs are
assigned to the stretching vibrations of C O, C C and
C O groups, respectively.[44] The O H stretching vibra-
tion due to the hydroxy, carboxylic and enolic groups of
the GO is observed in the range 2760–3440 cm−1 for all
three compounds. Also, the peak shown at 1388 cm−1 in
the spectra of the GO and GOQDs can be attributed to
the asymmetric stretching vibration of the C O C
moiety in the epoxide groups which has appeared in
Figures 1a and 2b. Similarity shown between the infrared
spectra of GO (Figure 1a) and GOQDs (Figure 1b)

KHALEGHI ABBASABADI ET AL.
7 of 18
SCHEME 2 Synthetic route to nanomagnetic Fe3O4-supported 1-propane sulfonic acid-grafted graphene oxide quantum dots
Fe3O4@GOQDs-O-(propane-1-sulfonic acid)
FIGURE 1 Comparative Fourier transform infrared (FT-IR)
spectra for (a) graphene oxide (GO), (b) graphene oxide quantum
FIGURE 2 X-ray diffraction (XRD) patterns of (a) graphene
oxide (GO) and (b) Fe3O4@GOQD-O-(propane-1-sulfonic acid)
dots (GOQDs) and (c) Fe3O4@GOQD-O-(propane-1-sulfonic acid)

8 of 18
KHALEGHI ABBASABADI ET AL.
at around 212ꢀC is attributed to the decomposition of
the oxygen-containing groups on the surface of GOQDs.
The third and fourth total weight loss happening in the
range 240ꢀC to 600ꢀC is due to the complete removal of
the organic and inorganic segments from the surface of
GOQD.[34,52,53] These results clearly provide further
evidence for successful functionalization of GOQDs by
1-propane sulfonic acid group and its magnetization
with Fe3O4 NP as well.
The scanning electron microscope (FESEM) analysis
was performed on the prepared nanosheets of GO,
GOQDs and Fe3O4@GOQD-O-(propane-1-sulfonic acid)
in order to find their morphology and size distribution.
As revealed from the comparison between the FESEM
patterns of the naked GO and GOQD, no prominent
change on the morphology of GO films has occurred as a
result of cutting by DMF. Transition electron microscopic
(TEM) analysis was conducted on the GOQDs nanosheets
in order to study the structure of the GOQDs clusters.
The TEM images obtained from GOQDs (Figure 5c) indi-
cates the number of GOQDs clusters as well as its size
distribution. The SEM images displayed in Figure 5 indi-
cated that the Fe3O4@GOQD-O-(propane-1-sulfonic acid)
nanocomposite is composed of wrinkled thin films
closely associated with each other to form disordered
solids and randomly accumulated. Moreover, the FESEM
image of the Fe3O4@GOQD-SO Fe3O4@GOQD-O-(pro-
pane-1-sulfonic acid) catalyst (Figure 5c) indicated that
the Fe3O4 NPs exhibited a regularly spherical morphol-
ogy on Fe3O4@GOQD-O-(propane-1-sulfonic acid) which
are made up of nanosized films.[45]
FIGURE 3 The energy-dispersive X-ray (EDX) images of
Fe3O4@GOQD-O-(propane-1-sulfonic acid)
TABLE 1 Elemental quantitative analysis of
Fe3O4@GOQD-O-(propane-1-sulfonic acid) derived from
energy-dispersive X-ray (EDX)
Fe3O4@GOQD-O-(propane-1-sulfonic acid)
Element
Weight%
6.86
Atomic%
14.41
C
O
33.39
52.79
S
17.21
13.59
Fe
Total
42.54
19.21
100.00
100.00
Thermal stability of the Fe3O4@GOQD-O-(propane-
1-sulfonic acid) nanosheets was studied by thermal
gravimetric analysis (TGA). According to the TGA ther-
mogram shown in Figure 4, the first weight loss
(ꢁ4.34) of the Fe3O4@GOQD-O-(propane-1-sulfonic
acid) takes place below 120ꢀC due to the thermal
desorption of the adsorbed water and remaining organic
solvent. The second weight loss of about 8% occurring
The morphology and size distribution of the prepared
GOQDs was investigated using TEM images. As shown
in Figure 6, the numbers of quantum dots, size distribu-
tion and clusters of the GOQDs were clearly shown, and
the average diameter was estimated to be in the range
5–11 nm. The results obtained from TEM image of the
GOQDs nanosheets indicated that the GO has been
successfully converted to the GOQDs.[54]
In addition to the above-mentioned FT-IR, TGA,
XRD, EDX, SEM and TEM analyses, the magnetization
behaviour of the prepared Fe3O4@GOQD-O-(propane-
1-sulfonic acid) was examined by VSM analysis at 300 K.
According to the typical curves of magnetization versus
the applied magnetic field of Fe3O4@GOQD-O-(propane-
1-sulfonic acid) shown in Figure 7, the saturation magne-
tization (Ms) value of Fe3O4@GOQD-O-(propane-
1-sulfonic acid) was found to be 49 emu g−1. This
saturation magnetization value approved the super-
paramagnetic property of the Fe3O4@GOQD-O-(propane-
1-sulfonic acid) nanocatalyst which enables it to be
efficiently separated from the reaction mixture simply by
using an external magnet.
FIGURE 4 Thermal gravimetric analysis (TGA) curves of
Fe3O4@GOQD-O-(propane-1-sulfonic acid)

KHALEGHI ABBASABADI ET AL.
9 of 18
FIGURE 5 Field emission gun-
scanning electron microscope (FESEM)
images of (a) graphene oxide (GO),
(b) graphene oxide quantum dots
(GOQDs) and (c) Fe3O4@GOQD-O-
(propane-1-sulfonic acid)
FIGURE 6 Transition
electron microscopic (TEM)
images of graphene oxide
quantum dots (GOQDs)
4.2 | Catalytic activity
yield of the product dihydropyrano[2,3-c]pyrazole was
obtained when the reaction was carried out in H2O as the
solvent at room temperature using 10-mg catalyst loading
(Entry 2).
Similarly, in order to find the optimal conditions
for the possible formation of 4H-chromene derivatives,
we chose to study one-pot three-component reaction
The
catalytic
capability
of
the
synthesized
Fe3O4@GOQD-O-(propane-1-sulfonic acid) magnetic
nanosheets was examined in one-pot synthesis of
dihydropyrano[2,3-c]pyrazole and 4H-chromene deriva-
tives. The procedure involves three-component reactions
between aromatic aldehyde, malononitrile and 3-methyl-
1-phenyl-1H-pyrazol-5(4H)-one or dimedone as shown in
Scheme 3. p-Nitrobenzaldehyde was chosen as the test
aromatic compound in this reaction to optimize different
reaction parameters such as solvent, temperature and cat-
alyst loading. According to the results summarized in
Table 2, the best result in terms of the reaction rate and
between
4-nitrobenzaldehyde,
malononitrile
and
5,5-dimethyl-1,3-cyclohexanedione (dimedone) as model
reaction (Scheme 4). The effects of different reaction
parameters including the solvent, temperature and cata-
lyst loading on this reaction were studied. According to
the experimental results summarized in Table 3, the best
result in terms of the reaction rate and yield of the

10 of 18
KHALEGHI ABBASABADI ET AL.
SCHEME 4 Screening the reaction parameters for model
synthesis of 2-amino-4-(p-nitrophenyl)-7,7-dimethyl-5-oxo-
5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile
product was obtained when the reaction was carried out
in H2O at room temperature in the presence of 10 mg of
the catalyst (Entry 2). Indispensable use of the catalyst
Fe3O4@GOQD-O-(propane-1-sulfonic acid) in the
reaction was verified by carrying out the reaction under
the optimal conditions without using the catalyst and
noticed that no detectable amount of the respected prod-
uct was formed (Entry 14).
FIGURE 7 Vibrating sample magnetometer (VSM) image of
Fe3O4@GOQD-O-(propane-1-sulfonic acid)
Following the remarkable effect of Fe3O4@GOQD-O-
(propane-1-sulfonic acid) as an efficient nanocatalyst in
the model reaction, the generality and scope of the reac-
tion was established by using a diverse series of aromatic
aldehydes 1a–1h in the reaction under optimal condi-
tions (Schemes 5 and 6). The experimental results sum-
marized in Tables 4 and 5 demonstrated that all the
reactions proceeded smoothly to afford the products in
excellent yields (90–98%) irrespective of the nature of the
SCHEME 3 Screening the reaction parameters for the model
synthesis of 6-amino-3-methyl-4-(p-nitrophenyl)-1-phenyl-
1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile
TABLE 2 Screening the reaction parameters for the model synthesis of
6-amino-3-methyl-4-(p-nitrophenyl)-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (Scheme 3)
Entry
Catalyst loading (mg)
Solvent
No solvent
H2O
Temperature (ꢀC)
Time (min)
Yield[a] (%)
1
10
25
25
25
25
25
50
80
100
rt
280
45
trace
98
2
10
3
10
EtOH
THF
120
180
220
40
50
4
10
30
5
10
DMF
H2O
42
6
10
75
7
10
H2O
35
85
8
10
H2O
30
85
9
10
H2O
10
98
10
11
12
13
14
5
H2O
rt
55
80
20
H2O
rt
60
70
30
H2O
rt
80
78
40
H2O
rt
80
82
No catalyst
H2O
rt
240
trace
Note: Conditions: 4-nitrobenzaldehyde (1.1 mmol), 4-hydroxyquinolin-2(1H)-one (1 mmol), malononitrile (1.1 mmol), solvent (5 ml).
aIsolated yields.

KHALEGHI ABBASABADI ET AL.
11 of 18
TABLE 3 Screening the reaction parameters for model synthesis of
2-amino-4-(p-nitrophenyl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (Scheme 4)
Entry
Catalyst loading (mg)
Solvent
No solvent
H2O
Temperature (ꢀC)
Time (min)
Yield[a] (%)
1
10
25
25
240
15
10
97
2
10
3
10
EtOH
THF
25
100
280
120
55
45
4
10
25
25
5
10
DMF
H2O
25
35
6
10
50
72
7
10
H2O
80
50
85
8
10
H2O
100
rt
40
87
9
10
H2O
15
97
10
11
12
13
14
5
H2O
rt
50
79
20
30
H2O
rt
40
81
H2O
rt
40
82
40
H2O
Reflux
Reflux
30
87
No catalyst
H2O
320
Trace
Note: Conditions: 4-nitrobenzaldehyde (1.1 mmol), 4-hydroxyquinolin-2(1H)-one (1 mmol), malononitrile (1.1 mmol), solvent (5 ml).
aIsolated yields.
SCHEME 5 Synthesis of 1,4-dihydropyrano[2,3-c]
pyrazole derivatives catalysed by Fe3O4@GOQD-O-
(propane-1-sulfonic acid)
SCHEME 6 Synthesis of 2-amino-4-aryl-
7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-
3-carbonitrile derivatives catalysed by Fe3O4@GOQD-O-
(propane-1-sulfonic acid)
substituting groups attached to the aldehydes. However,
the aromatic aldehydes carrying electron-withdrawing
groups appear to act more readily in this reaction.
on the reaction. However, when these parts are jointly
present in the Fe3O4@GOQD-O-(propane-1-sulfonic acid)
nanocomposite film can display high promotional
effect in the synthesis of the titled reaction products
(Schemes 7 and 8).
According to the experimental results summarized
in Tables 6 and 7, the magnetic nanocomposite film
(Fe3O4@GOQD-O-(propane-1-sulfonic acid)) exhibited
high catalytic activity in comparison with the catalytic
activities of the bare Fe3O4, GO and GOQDs under the
same optimal conditions. The high EcoScale score of the
present protocol compared with different other catalysts
calculated from the reported method demonstrated that
the present catalyst is greener in comparison with
other catalysts examined in Tables 6 and 7.[55] All the
fragments present in the catalyst perform a synergistic
effect on the synthesis of dihydropyrano[2,3-c]pyrazole
and 4H-chromene derivatives. According to the Tables 6
and 7, every part of the catalyst including GO, GOQD
and Fe3O4 NP has individually low improvement effect
As summarized in Table 8, the experimental data
resulted from the present protocol are compared with
those reported by other research groups for the synthesis
of 1,4-dihydropyrano[2,3-c]pyrazoles and 4H-chromenes
employing different catalytic systems. From this
comparison, it became evident that the present protocol
is more eco-friendly and straightforward and the newly
presented Fe3O4@GOQD-O-(propane-1-sulfonic acid)
nanocomposite film performs high catalytic activity in
the titled reactions. Therefore, the present method
could be considered as a suitable alternative method
for the synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles
and 4H-chromene derivatives.

12 of 18
KHALEGHI ABBASABADI ET AL.
TABLE 4 Synthesis of 1,4-dihydropyrano[2,3-c]pyrazole derivatives catalysed by Fe3O4@GOQD-O-(propane-1-sulfonic acid) (Scheme 5)
m.p. (ꢀC)
Entry
Ar
Product
4a
Time (min)
Yield[a] (%)
Found
163–166
145–148
183–186
173–176
170–173
190–193
186–189
161–164
192–195
226–229
-
Reported
1
C6H5
25
93
161–163 (Guo et al.[35]
145–146 (Guo et al.[35]
184–187 (Sharanina et al.[36]
174–177 (Sharanina et al.[36]
171–172 (Sharanina et al.[36]
190–191 (Sharanina et al.[36]
)
)
2
2-ClC6H4
4-ClC6H4
4-FC6H4
4b
30
95
3
4c
30
96
)
)
)
)
4
4d
20
97
5
4-MeOC6H4
3-NO2C6H4
4-NO2C6H4
3-BrC6H4
Naphthalen-2-yl
Pyridin-3-yl
Thiopen-2-yl
Furan-2-yl
n-C3H7
4e
45
95
6
4f
30
90
7
4g
10
98
186–188 (Saha et al.[37]
)
160–163 (Farahi et al.[38]
)
8
4h
4i
45
96
9
30
95
-
10
11
12
13
4j
40
94
227–229 (Vasuki et al.[22]
)
4k
4l
180
180
180
Trace
Trace
Trace
-
-
-
-
4m
-
Note: Conditions: aldehyde (1.1 mmol), 3-methyl-1-phenyl-2-pyrazolin-5-one (1 mmol), malononitrile (1.1 mmol), H2O (5 ml), catalyst
(10 mg), room temperature.
aIsolated yields.
TABLE 5 Synthesis of 2-amino-4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile derivatives catalysed by
Fe3O4@GOQD-O-(propane-1-sulfonic acid) (Scheme 6)
m.p. (ꢀC)
Entry
Ar
Product
6a
Time (min)
Yield[a] (%)
Found
232–235
188–190
207–210
211–214
211–214
209–212
178–181
203–206
222–225
201–204
-
Reported
1
C6H5
35
30
40
20
40
45
15
45
15
25
180
180
93
231–233 (Azarifar et al.[39]
189–191 (Fang et al.[40]
211–213 (Azarifar et al.[39]
212–214 (Khaksar et al.[41]
212–214 (Khaksar et al.[41]
210–211 (Balalaie et al.[42]
178–180 (Balalaie et al.[42]
)
204–205 (Sarrafi et al.[43]
222–224 (Azarifar and Abbasi[21]
)
200–202 (Vasuki et al.[22]
)
)
)
2
4-FC6H4
4-MeC6H4
4-ClC6H4
2-ClC6H4
3-NO2C6H4
4-NO2C6H4
4-HOC6H4
3-ClC6H4
Thiopen-2-yl
Furan-2-yl
n-C3H7
6b
95
)
3
6c
93
4
6d
6e
94
)
)
5
96
6
6f
92
)
7
6g
97
8
6h
6i
91
)
9
95
10
11
12
6j
93
6k
6l
Trace
Trace
-
-
-
Note: Conditions: aldehyde (1.1 mmol), dimedone (1 mmol), malononitrile (1.1 mmol), H2O (5 ml), catalyst (10 mg), room temperature.
aIsolated yields.
TABLE 6 Comparative catalytic activity of Fe3O4@GOQD-O-(propane-1-sulfonic acid) nanoparticles under optimal conditions for
synthesis of 6-amino-3-methyl-4-(4-nitrophenyl)-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile based on EcoScale percentages
and other reaction parameters
Entry
Catalyst
Time (min)
Yield (%)
Catalyst loading (g)
EcoScale (%)
1
2
3
4
GO
120
80
61
65
68
98
0.1
0.1
0.1
0.1
80
82
70
90
GOQDs
Fe3O4
60
Fe3O4@GOQD-O-(propane-1-sulfonic acid)
10

KHALEGHI ABBASABADI ET AL.
13 of 18
TABLE 7 Comparative catalytic activity of Fe3O4@GOQD-O-(propane-1-sulfonic acid) nanoparticles under optimal conditions for
synthesis of 2-amino-7,7-dimethyl-4-(4-nitrophenyl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile based on EcoScale percentages and
other reaction parameters
Entry
Catalyst
Time (min)
Yield (%)
Catalyst loading (g)
EcoScale (%)
1
2
3
5
GO
180
120
100
15
55
65
70
97
0.1
0.1
0.1
0.1
81
83
74
91
GOQDs
Fe3O4
Fe3O4@GOQD-O-(propane-1-sulfonic acid)
SCHEME 7 Comparative catalytic activity
of Fe3O4@GOQD-O-(propane-1-sulfonic acid)
nanoparticles under optimal conditions for
synthesis of 6-amino-3-methyl-4-(4-nitrophenyl)-
1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-
5-carbonitrile
SCHEME 8 Comparative catalytic activity
of Fe3O4@GOQD-O-(propane-1-sulfonic acid)
nanoparticles under optimal conditions for
synthesis of 2-amino-7,7-dimethyl-
4-(4-nitrophenyl)-5-oxo-5,6,7,8-tetrahydro-
4H-chromene-3-carbonitrile
TABLE 8 Comparison of the present method with other methods reported for the synthesis of 1,4-dihydropyrano[2,3-c]pyrazole
(product 4g) and 2-amino-4-aryl-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (product 6g) derivatives
Time
(min)
Yield
(%)
Entry Catalyst
Conditions
Product Reference
1
BF3/MNPs-450
BS-2G-Ti
EtOH; reflux
10
90
4g
Abdollahi-Alibeik et
al.[56]
2
H2O; 70ꢀC
90
96
4g
Sinija and
Sreekumar[57]
3
4
5
Silica-bonded N-propyl piperazine
EtOH; reflux
Glycerol; rt
H2O; rt
15
12
10
88
73
98
4g
4g
4g
Niknam et al.[58]
Abdel Hamid et al.[59]
Present work
NH4H2PO4/Al2O3
Fe3O4@GOQD-O-(propane-1-sulfonic
acid)
6
7
8
9
Pectin
[DABCO-PDO] [CH3COO]
NH4Al(SO4)2Á12H2O
Fructose
H2O: EtOH; rt
H2O; 60ꢀC
20
10
90
96
85
89
6g
6g
6g
6g
Kangani et al.[60]
Yang et al.[61]
Mohammadi et al.[62]
Pourpanah et al.[63]
EtOH; 80ꢀC
140
10
EtOH: H2O;
60ꢀC
10
Fe3O4@GOQD-O-(propane-1-sulfonic
H2O; rt
10
97
6g
Present work
acid)
4.3 | Catalytic reaction mechanism
the GO as basic and acidic groups, as well as the attached
β-alanine moiety containing both amino and acidic
groups, collectively make the catalyst Fe3O4@GOQD-O-
(propane-1-sulfonic acid) more efficient in the reaction.
The presence of various functionalities including
carbonyl, hydroxyl and epoxy groups on the surface of

14 of 18
KHALEGHI ABBASABADI ET AL.
Also, the magnetic property generated by the Fe3O4 unit
in the catalyst can promote the catalytic efficiency and
enables easy magnetic separation of the catalyst from the
reaction mixture.
A
plausible mechanism proposed to explain
the Fe3O4@GOQD-O-(propane-1-sulfonic acid)-catalysed
one-pot synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles is
depicted in Scheme 7. Likely, in the first step, the
SCHEME 9 Possible
mechanism for synthesis of
1,4-dihydropyrano[2,3-c]
pyrazole derivatives catalysed by
Fe3O4@GOQD-O-(propane-
1-sulfonic acid)
SCHEME 10 A possible
mechanism for the synthesis of
2-amino-4-aryl-7,7-dimethyl-
5-oxo-5,6,7,8-tetrahydro-
4H-chromene-3-carbonitrile
derivatives 4a–4h catalysed by
Fe3O4@GOQD-O-(propane-
1-sulfonic acid)

KHALEGHI ABBASABADI ET AL.
15 of 18
aromatic aldehyde undergoes the electrophilic addition
reaction with malononitrile under the catalytic effect of
the acidic catalyst Fe3O4@GOQD-O-(propane-1-sulfonic
acid) followed by dehydration to provide the
2-arylidenemalononitrile intermediate (I). In the next
step, nucleophilic addition of 3-methyl-1-phenyl-
2-pyrazolin-5-one to the intermediate (I) and
intramolecular cyclization occur successively to yield the
intermediate II which undergoes rearrangement to
furnish the 1,4-dihydropyrano[2,3-c]pyrazol-5-yl cyanide
derivatives 4a–4h.
A
similar mechanism can be postulated for
Fe3O4@GOQD-O-(propane-1-sulfonic
acid)-catalysed
three-component synthesis of 4H-chromene derivatives
as depicted in Scheme 10. Similar to the mechanism
shown in Scheme 9, in this mechanism too, condensa-
tion of the aldehyde with malononitrile takes place
under the catalytic activation of Fe3O4@GOQD-O-
(propane-1-sulfonic
acid)
to
produce
the
arylidenemalononitrile intermediate (I) after dehydra-
tion. Subsequently, the catalyst-induced nucleophilic
addition of the enolized dimedone to the intermediate
(I) followed by consecutive intramolecular cyclization
to provide the intermediate (II) which affords the
expected 4H-chromenes 6a–6h after rearrangement
(Schemes 9 and 10).
4.4 | Catalyst recyclability
To examine the recyclability and stability of the catalyst
Fe3O4@GOQD-O-(propane-1-sulfonic acid), we studied
the model reaction between 4-nitrobenzaldehyde,
dimedone and malononitrile under the optimized condi-
tions. In order to examine the catalyst reusability, a hot
filtration experiment was conducted and noticed that the
reaction was completely stopped by removal of the solid
catalyst. With regard to the hot filtration test and after
FIGURE 8 Recyclability of the catalyst Fe3O4@GOQD-O-
(propane-1-sulfonic acid) for model synthesis of 2-amino-4-(p-
nitrophenyl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-
3-carbonitrile (6g)
FIGURE 9 (a) The energy-
dispersive X-ray (EDX) images of the
catalyst after recycling, (b) vibrating
sample magnetometer (VSM) image of
the catalyst after recycling and
(c) Fourier transform infrared (FT-IR)
spectra for (Fe3O4@GOQD-O-(propane-
1-sulfonic acid))

16 of 18
KHALEGHI ABBASABADI ET AL.
completion of the reaction, the magnetically isolated
Fe3O4@GOQD-O-(propane-1-sulfonic acid) nanosheets
were washed with hot EtOH/H2O (1:1) several times,
oven-dried at 65ꢀC. As evidenced from Figure 8, the cata-
lyst can be recycled and reused for at least five fresh runs
without any significant loss of activity. The EDX, VSM,
and FT-IR patterns were examined on the recycled cata-
lyst and no significant changes were noticed on the
recycled catalyst during the reaction and recovery process
(Figure 9).
ORCID
Masoud Khaleghi Abbasabadi https://orcid.org/0000-
0002-1670-4542
Davood Azarifar https://orcid.org/0000-0002-7331-2748
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The Research Council of Bu-Ali Sina University and
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AUTHOR CONTRIBUTIONS
Masoud Khaleghi-Abbasabadi: Conceptualization;
data curation; formal analysis; funding acquisition; inves-
tigation; methodology; project administration; resources;
software; supervision; validation; visualization. Davood
Azarifar: Conceptualization; data curation; formal anal-
ysis; funding acquisition; investigation; methodology;
project administration; resources; software; supervision;
validation; visualization. Hamid Reza Esmaili Zand:
Conceptualization; data curation; formal analysis; inves-
tigation; methodology; resources; software; supervision;
validation; visualization.
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DATA AVAILABILITY STATEMENT
The data that supports the findings of this study are avail-
able in the supplementary material of this article.

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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: Khaleghi Abbasabadi M,
Azarifar D, Esmaili Zand HR. Sulfonic acid-
functionalized Fe3O4-supported magnetized
graphene oxide quantum dots: A novel organic-
inorganic nanocomposite as an efficient and
recyclable nanocatalyst for the synthesis of
dihydropyrano[2,3-c]pyrazole and 4H-chromene
derivatives. Appl Organomet Chem. 2020;e6004.
https://doi.org/10.1002/aoc.6004