Green protocol for synthesis of MgFe2O4 nanoparticles and study of their activity as an efficient catalyst for the synthesis of chromene and pyran derivatives under ultrasound irradiation

Article abstract of DOI:10.1007/s13738-019-01783-3

In this study, the MgFe₂O₄ nanoparticles were synthesized via a green and simple approach. Then an effective procedure to synthesize 2-amino-7-hydroxy-4H-chromene and tetrahydrobenzo[b]pyran derivatives was established through the ch

Full text of DOI:10.1007/s13738-019-01783-3

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-019-01783-3
ORIGINAL PAPER
Green protocol for synthesis of MgFe2O4 nanoparticles and study
of their activity as an efcient catalyst for the synthesis of chromene
and pyran derivatives under ultrasound irradiation
Bahar Eshtehardian1 · Morteza Rouhani1 · Zohreh Mirjafary1
Received: 10 February 2019 / Accepted: 24 September 2019
© Iranian Chemical Society 2019
Abstract
In this study, the MgFe2O4 nanoparticles were synthesized via a green and simple approach. Then an efective procedure to
synthesize 2-amino-7-hydroxy-4H-chromene and tetrahydrobenzo[b]pyran derivatives was established through the chemical
reaction between diferent aldehydes, malononitrile and resorcinol (or dimedone) in the presence of MgFe2O4 nanoparticles
as a benefcial catalyst in ethanol as solvent under ultrasound irradiation. Moreover, the synthesized MgFe2O4 nanoparticles
were easily recovered by an external magnet and reused for four times without signifcant loss of their catalytic activity.
Simple, fast, efective and eco-friendly as well as quick purifcation method along with high product yields are some of the
advantages of the present chemical reaction.
Keywords MgFe2O4 · Chromene · Pyran · Ultrasound · Green · Nanoparticles
Introduction
in medicinal scafolds, particularly high spasmolytic, anti-
coagulant, diuretic and anti-anaphylactic properties [16–18].
Many of the current protocols for the synthesis of 2-amino-
4H-chromenes [19, 20] sufer from factors such as long
duration, lack of generality, use of perilous solvents and
use of hazardous amine-based catalysts. Also, this prob-
lem still exists for synthesis of tetrahydrobenzo[b]pyran
derivatives. The most popular approach for the synthesis
of tetrahydrobenzo[b]pyrans derivatives includes the one-
pot reaction of aldehydes, dimedone and malononitrile
under acidic or basic conditions [21]. However, most of the
reported approaches have disadvantages such as harmful
organic solvents, hazardous acidic condition, long reaction
times, etc. [21]. On the other hand, the catalyst character is
one of the most important factors which participate in the
various features of a chemical reaction such as general appli-
cability, yield, selectivity and duration. Therefore, explor-
ing an efcient, inexpensive, reusable and easy accessible
catalyst for synthesis of 2-amino-4H-chromenes is still an
issue of interest.
Recently, spinel ferrites structures have attained great con-
sideration due to their benefcial magnetic and electrical
characteristics [1–3]. Their molecular formula is MFe2O4
in which M is a divalent metal cation such as Mg2+, Cu2+,
Zn2+, etc. In these inorganic compounds, M2+ and Fe3+ have
been located in the tetrahedral and octahedral interstitial
positions of the fcc lattice established by O2− ions, respec-
tively [4–7]. In recent years, MgFe2O4 nanoparticles have
attracted huge attention due to their vast benefts in industry
such as being low magnetic materials [8, 9], gas sensors
[10] semiconductors [11, 12], hyperthermia [13], lithium
ion batteries [14, 15].
2-Amino-4H-chromenes are one of the most important
family members of chromenes because of their usefulness
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s13738-019-01783-3) contains
supplementary material, which is available to authorized users.
Ultrasonic irradiation has found great applications in
organic synthesis. Using ultrasound irradiation in various
organic reactions has resulted in shorter reaction durations,
higher yields and very milder reaction conditions [22, 23].
The collapse of cavities in the irradiated medium causes
the formation of the hot spots with local temperatures and
* Morteza Rouhani
rouhani.morteza@gmail.com;
morteza.rouhani@alumni.znu.ac.ir
1
Department of Chemistry, Science and Research Branch,
Islamic Azad University, Tehran, Iran
Vol.:(0123456789)
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Journal of the Iranian Chemical Society
spectrometer at 500 and 125 MHz, respectively. Sonica-
tion was performed in a Heisler ultrasonic bath (made in
Germany) with a nominal power of 200 W. The catalyst
sample was characterized using a scanning electron micro-
scope (SEM) equipped with EDX detector (TESCAN Vega
Model), at 30 kV with a gold coating. X-ray difraction
(XRD) analysis of the catalyst sample was performed with
scanning range from 4° to 70° (Bruker D8 Advance, with
Cu Kα radiation, λ = 0.154060 nm). Moreover, the ICP-
AES (PerkinElmer, Optima 7300 DV), TGA (PerkinElmer,
4000), BET (Micromeritics Gemini 2375), VSM (Meghnatis
Daghigh Kavir, LBKFB) and TEM (Zeiss-EM10C-100 kV)
analyses were carried out for characterization of the synthe-
sized MgFe2O4 nanoparticles.
R
OH
OH
CN
3
HO
O
NH2
))), EtOH, 65 oC
MgFe2O4 NPs
5
R
O
R
1
CHO
+
O
CN
NC
2
CN
4
O
))), EtOH, 65 o
C
O
NH2
MgFe2O4 NPs
6
Green procedure for the synthesis of MgFe2O4 nano‑
particles
Scheme 1 Synthesis of 2-amino-7-hydroxy-4H-chromene (5) and
tetrahydrobenzo[b]pyran (6) derivatives with MgFe2O4 nanoparticles
as a catalyst in ethanol under ultrasonic irradiation
For the synthesis of MgFe2O4 nanoparticles, 0.2 g traga-
canth gum was dissolved in 40 mL of double distilled water
and stirred at 70 °C for 80 min. Then, 1 mmol of MgSO4
and 2 mmol Fe(NO3)3.9H2O were added to the above-men-
tioned tragacanth clear solution and the resulting mixture
was heated in 75 °C for 12 h to obtain a brown resin. Finally,
the mixture was calcined at 600 °C in air to obtain MgFe2O4
nanoparticles.
pressures to the extent of several hundred Celsius degrees
and bars, respectively. This huge energy transfers to the
present molecules in the reaction medium and consider-
ably increases their inherent energy. Therefore, much more
amounts of molecules can reach the minimum activation
energy of the reaction. This phenomenon causes the consid-
erable increase in the reaction rate and decreases the reaction
time. Thus, using ultrasound irradiations, various organic
reactions can be performed in shorter reaction time, with
higher yield and under very calm conditions [24–26].
Herein, as a part of our continued interest in investiga-
tion about the efects of ultrasound irradiation on the mul-
ticomponent reactions [27–35], we wish to report an efec-
tive, simple and eco-friendly procedure for the synthesis of
2-amino-7-hydroxy-4H-chromenes and tetrahydrobenzo[b]
pyrans with MgFe2O4 nanoparticles as an efcient catalyst
in ethanol under ultrasonic waves (Scheme 1).
General procedure for the synthe‑
sis of 2‑amino‑7‑hydroxy‑4H‑chromene
and tetrahydrobenzo[b]pyran derivatives
under ultrasound irradiation
A mixture of aromatic aldehyde 1 (1 mmol), malononitrile
2 (1 mmol), resorcinol 3 or dimedone 4 (1 mmol) EtOH
(5 ml) and MgFe2O4 (0.003 g) was sonicated in a bath soni-
cator for the appropriate time. After the completion of the
reaction (controlled by TLC), the MgFe2O4 nanoparticles
were separated by the external magnet and the solvent was
evaporated. Finally, the remained solid product was purifed
with n–hexane/ethyl acetate in a PLC tank.
Experimental
Some spectroscopic data of the synthesized com‑
pounds
Chemical and apparatus
All chemical reagents were purchased from commercial
sources and utilized without further purifcation. All reac-
tions were controlled by thin layer chromatography (TLC)
established on pre-coated glass-backed plates Merck 60
HF254 (0.25 mm) with UV light. Melting points were deter-
mined by Electrothermal 9100 apparatus and are uncor-
rected. FT-IR spectra were recorded using a Shimadzu
8400 s FT-IR spectrometer. 1H and 13C NMR spectra were
measured (CDCl3 solution) with a Bruker DRX-500 Avance
2‑Amino‑3‑cyano‑7‑hydroxy‑4‑(2‑fuorophenyl)‑
4H‑chromene (5d)
M.p.: 216–218 °C; yield (85%); IR (KBr, υmax cm−1): 3431
(OH), 3225 (NH2), 2174 (CN), 1641 (C‚C vinyl nitrile),
1
1556 (C‚C aromatic); H NMR (500 MHz, DMSO-d6):
4.79 (s, 1H), 6.21 (d, 1H, Ar), 6.41 (dd, H), 6.62 (d, 1H,
H-Ar), 6.88 (s, 2H, NH2), 7.11–7.24 (m, 4H, Ar) ppm; 13
C
NMR (125 MHz, DMSO-d6): 55.15, 101.62, 111.14, 113.41,
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Journal of the Iranian Chemical Society
114.02, 114.85, 120.10, 125.21, 128.14, 131.01, 131.54,
138.21, 149.11, 157.01, 158.85, 160.14 ppm.
of the Scherrer equation) [35]. Furthermore, the crystallinity
of the MgFe2O4 nanoparticles has been preserved well after
4th cycle of usage (Fig. 1b).
2‑Amino‑3‑cyano‑7‑hydroxy‑4‑(3‑chlorophenyl)‑4H‑chrom
ene (5f)
The scanning electron microscopy (SEM) image afrmed
the morphology and particle size of MgFe2O4 nanoparticles
(Fig. 2). As displayed in Fig. 2, the size of particles diam-
eters is in the range of nanometers both in the fresh (a) and
spent after 4th cycle of usage (b).
M.p.: 107–111 °C; yield (89%); IR (υmax, cm−1): 3423 (OH),
3342 (NH2), 2189 (CN), 1652 (C‚C vinyl nitrile), 1579 (C‚C
1
aromatic); H NMR (500 MHz, DMSO-d6): 4.70 (s, 1H),
The energy-dispersive spectroscopy (EDX) revealed
the elemental compositions of the MgFe2O4 nanoparticles
(Fig. 3). The EDX analysis afrmed the presence of O, Fe
and Mg in the synthesized nanocatalyst. The quantifcation
EDX analysis results demonstrate that the above-mentioned
elements exist in expectable proportions in the synthesized
MgFe2O4 nanoparticles (Table 1).
6.28 (d, 1H, Ar), 6.41 (dd, 1H, Ar), 6.59 (d, 1H, Ar), 6.89
(s, 2H, NH2), 7.01–7.32 (m, 4H, Ar), 9.71 (s, 1H, OH) ppm;
13C NMR (125 MHz, DMSO-d6): 55.43, 101.56, 110.21,
114.47, 112.89, 120.85, 127.59, 130.12, 130.47, 132.16,
131.31, 132.02, 149.15, 149.22, 158.96, 160.14 ppm.
2‑Amino‑7,7‑dimethyl‑5‑oxo‑4‑phenyl‑5,6,7,8‑tetrahy‑
dro‑4H‑chromene‑3‑carbonitrile (6a)
The FT-IR spectrum of synthesized MgFe2O4 nano-
particles demonstrates areas of the absorption between
4000–1000 and 1000–400 cm−1. The strong band of OH
(3415 cm−1) shows that a vast number of OH groups are
located on the surface of the MgFe2O4 nanoparticles. At
the range of 1000–400 cm−1, there are a high-frequency
band in the ~ 613 cm−1 and the low-frequency band in
the~434 cm−1. The high-frequency band is attributed to the
stretching intrinsic vibration of unit cell of the spinel in the
tetrahedral site, and the lower one is ascribed to the stretch-
ing vibration of Fe–O in octahedral site. Both of these peaks
are the typical bands for spinel structure (Fig. 4).
M.p.: 229–231 °C; yield (86%); IR (KBr, νmax): 1674 (C=O),
1
2185 (CN), 2952 (H-Csp3), 3254 (N–H), 3341 (N–H); H
NMR (500 MHz, DMSO-d6) 0.95 (s, 3H, CH3), 1.03 (s, 3H,
CH3), 2.00 and 2.25 (2d, J=16.0 Hz, 2H, CH2), 2.47–2.52
(m, 2H, CH2), 4.17 (s, 1H, CH), 7.03 (s, 2H, NH2),
7.00–7.13 (m, 3H, 3CHAr), 7.28 (t, J=7.2 Hz, 2H, 2CHAr);
13C NMR (100 MHz, DMSO-d6) 26.54, 27.45, 31.88, 38.87,
39.29, 50.02, 58.36, 112.78, 119.83, 126.66, 144.81, 155.55,
162.61, 195.81 ppm.
Thermogravimetric analysis (TGA) is the evaluation of
the mass change of a sample during temperature increase.
This method is benefcial for studying of a decomposition
reaction, specifying purity and organic content in a sample,
etc. Figure 5 shows a TGA curve for dry sample of synthe-
sized MgFe2O4 nanoparticles. It can be seen that the TGA
curve shows continues decline due to the weight loss by
heating and decomposition of organic impurities. The net
weight loss is found to be 96.90% in the temperature range
studied.
2‑Amino‑4‑(3‑methoxyphenyl)‑7,7‑dime‑
thyl‑5‑oxo‑5,6,7,8‑tetrahydro‑4H‑chromene‑3‑carbonitrile
(6e)
°
M.p.: 208–211 C; yield (90%); IR (KBr, νmax) 1665
(C=O), 2174 (CN), 3247 (N–H), 3365 (N–H) cm−1; H
1
NMR (500 MHz, DMSO-d6) 0.95 (s, 3H, CH3), 1.02 (s, 3H,
CH3), 2.07 and 2.23 (2d, J=16.0 Hz, 2H, CH2), 2.43 and
2.50 (s, 2H, CH2), 3.70 (s, 3H, OCH3), 4.06 (s, 1H, CH),
6.90 (s, 2H, NH2), 6.49–6.94 (m, H, 4CHAr); 13C NMR
(125 MHz, DMSO-d6) δ: 26.64, 28.56, 31.79, 38.80, 39.29,
50.06, 55.58, 58.73, 113.03, 119.39, 119.93, 145.25, 158.34,
162.61, 197.21 ppm.
The magnetic characteristics of the synthesized MgFe2O4
were determined by a vibrating sample magnetometer
(VSM). The magnetic hysteresis curve is demonstrated in
Fig. 6. The recorded M–H loop shows that the synthesized
sample was ferromagnetic. The saturation magnetization
value was 8.56 emu/g. Also, the magnetic properties do not
show considerable decline after 4th cycle of usage (Fig. 6).
Moreover, transmission electron microscopy (TEM)
images show that MgFe2O4 nanoparticles have spherical
morphology and the average particles size is 36 nm (Fig. 7).
Table 2 shows the ICP-AES data both for the fresh and
the used catalyst. The results show that there is no leaching
of the metals happen during the reaction in the synthesized
MgFe2O4 catalyst. Also, the hot infltration method was used
and the presence of metals analyzed in the fltrate by ICP-
AES analysis. The results in Table 2 show the absence of Mg
Results and discussion
Structural analysis of MgFe2O4 nanocatalyst
Figure 1a shows the XRD pattern of the synthesized
MgFe2O4 nanoparticles. It can be seen that there is a high
phase purity and good agreement with the existed XRD
pattern for MgFe2O4 nanoparticles (JCPDS No. 71-1232).
Average crystalline size of the synthesized MgFe2O4 nano-
particles was obtained to be 30–35 nm (determined by use
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Journal of the Iranian Chemical Society
Fig. 1 The XRD pattern of the a
fresh and b spent after 4th cycle
of usage MgFe2O4 nanoparticles
and Fe in the fltrate obtained and approves the entire metal
active sites during the reaction.
to the capillary type condensation of the nitrogen gas in
the thin holes of the catalyst. The BET surface area and
total pore volume for pores with diameter less than 145 nm
at P/Po = 0.98 of the synthesized MgFe2O4 catalyst are
10.5 m2 g−1 and 0.18 cm3 g−1, respectively, which demon-
strate that synthesized catalyst has porous structure.
To confrm the catalyst efciency of MgFe2O4 nanopar-
ticles, a reaction was also carried out in the absence of the
catalyst and very low conversion was obtained. Furthermore,
to see the efect of heterogeneous catalyst on the reaction, an
experiment was done homogeneously as a reference using
Mg2+ and Fe3+ ions under the same ratio where very low and
negligible reaction proceeded. All these observations con-
frm the catalytic role of MgFe2O4 active sites in the catalyst.
We also studied the porous character of the MgFe2O4
catalyst by evaluation of the nitrogen adsorption–desorp-
tion isotherm in Fig. 8. It shows the isotherm with a hyster-
esis loop between 0.8 and 1.0 P/P0 which can be attributed
In order to achieve the optimum reaction conditions, the
reaction of benzaldehyde, malononitrile and resorcinol under
ultrasonic waves has been remarked as a model reaction.
Study on the efects of the various solvents
In order to study the solvent efect on the reaction progress
and also achieve the optimum solvent conditions for the
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Journal of the Iranian Chemical Society
Fig. 2 SEM images of the fresh
a and spent after 4th cycle of
usage b MgFe2O4 nanoparticles
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Journal of the Iranian Chemical Society
THF and DMF aforded low yields of products (21%, 15%
and 18%, respectively). Also, the results showed that the
reaction under classical stirring conditions needs much more
time for completion compared with sonic conditions (49%
after 120 min). Based on the obtained results of this study,
it is obvious that EtOH was the best solvent for this reaction.
Comparison of ultrasonic irradiation frequency
and reaction medium temperature
In order to investigate the efect of ultrasound irradiation
frequency and reaction temperature, the standard model
reaction was also carried out in 60, 70, 80, 90 and 100 kHz
frequencies and at 45, 55, 65, 75 and 85 °C temperatures
(Table 4). When the ultrasound frequency was 60 kHz, the
yield of the product was 64% after 21 min (Table 4, entry 1).
With the increase in irradiation frequency and temperature
of the reaction medium from 60 to 80 kHz and from 45 to
65 °C, respectively, the reaction yields were improved from
64 to 74%. (Table 4, entries 1–3). Further increasing the
ultrasound frequency and temperature caused the undesir-
able decrease in the product yield 68% and 52% (Table 4,
entries 4 and 5). The precise assessment of the reasons of
this phenomenon is to know the amounts of the activation
energies. However, Safari et al. [24] have suggested that the
rate of the reaction is very low at a temperature below 60 °C
and at higher temperatures some sort of undesirable polym-
erization of the Knoevenagel condensation product might
decrease the yield of the product. Therefore, the results
demonstrated that the ultrasound irradiation frequency of
80 kHz, EtOH as a solvent and reaction temperature of 65 °C
were the optimum conditions of the standard model reaction.
The efects of the ultrasound irradiation are due to cavi-
tation phenomenon, the formation, growth and collapse of
bubbles in an irradiated liquid [36]. Collapsing bubbles are
produced, centralized “hot spots” with a temporary local
high pressures and temperature are created, fastening the
condensation reaction (such as Knoevenagel reaction in
here). Also, sonication causes very efcient and vigorous
stirring in reaction medium via improving the mass transfer
and sever reaction mixture turbulence [37, 38]. All of these
cases can cause the reaction to occur quickly. Now, we focus
on the role of ultrasound waves in our study reaction. The
proposed mechanism for the formation of products is pre-
sented in Scheme 2. On the basis of the chemistry of Kno-
evenagel under ultrasonic irradiation condition, it is sensible
to presume that the frst step may include condensation of
aldehyde 1 and malononitrile 2 to produce the condensed
product 3 (Knoevenagel condensation). This intermediate
may be attacked by the resorcinol 4 (or dimedone 5) via a
Michael addition to form 1:1:1 adduct (6 and 8). This adduct
may undergo intramolecular cyclization to aford the isolated
fnal product after a [1, 3] H-shift (7 and 9). These steps are
Fig. 3 EDX graph of the a fresh and spent after 4th cycle of usage, b
MgFe2O4 nanoparticles
Table 1 The EDX analysis data for the synthesized MgFe2O4 nano-
particles
Element
Weight percent
Atomic percent
Mg
Fe
O
12.14
52.36
35.49
12.85
26.48
66.67
reaction, the standard model reaction was carried out in
the neat conditions (Table 3, entry 1) and also using vari-
ous solvents, i.e., n-hexane, CH3CN, THF, DMF and EtOH
(Table 3, entry 2–6). Also, in order to reveal the ultrasound
irradiation efects on the reaction conditions, the model reac-
tion was performed in the classical stirring at room tempera-
ture. The best result was achieved by the reaction of benza-
ldehyde (1 mmol), malononitrile (1 mmol) and resorcinol
(1 mmol) in EtOH by ultrasound irradiation (200 W, 10 kHz)
in 30 min with 54% yield (Table 3, entry 6). The reaction did
not proceed in neat conditions and in n-hexane as a solvent.
Furthermore, applying polar aprotic solvents, i.e., CH3CN,
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Journal of the Iranian Chemical Society
Fig. 4 FT-IR spectrum of the synthesized MgFe2O4 nanoparticles
Fig. 5 TGA curve of the synthesized MgFe2O4 nanoparticles
continuously done on the extent surface of catalyst and also
in the presence of ultrasound irradiation. We believed that
the passage of the ultrasonic waves through the reaction mix-
ture plays a signifcant role in the Knoevenagel condensation
and Michael addition steps due to the high local pressures,
while one of these steps may be the rate-determining step in
the reaction. Moreover, MgFe2O4 nanoparticles as a Lewis
acid probably interact with the oxygen atom in the carbonyl
group of the aldehyde, and therefore, activates it for con-
densation with malononitrile in the Knoevenagel reaction.
Furthermore, MgFe2O4 activates cyanide group of the prod-
uct (3) for attacking by resorcinol 4 (or dimedone 5) via a
Michael addition and permits the reaction to be carried out
efectively on its vast surface area. [27–29, 35].
Generality of the synthesis under ultrasound irra‑
diation
After fnding more efective solvent (EtOH), temperature
(65 °C) and frequency (80 kHz) for the standard model
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Journal of the Iranian Chemical Society
Table 2 ICP-AES data for fresh and spent MgFe2O4 catalysts after
4th cycle
Element
Weight percenta
Weight percentb
Weight
percentc
Mg
Fe
13.24
53.15
11.47
50.82
–
–
aFresh catalyst
bSpent catalyst after 4th cycle
cAfter hot fltration
7) was accelerated signifcantly along with higher yield
(Table 5, entry 1). The corresponding 2-amino-7-hydroxy-
4H-chromene (5a–h) and tetrahydrobenzo[b] pyran (6a–h)
derivatives were formed in good-to-excellent yields. The
results are summarized in Table 5.
Fig. 6 Magnetic hysteresis curve of the fresh (blue) and spent after
4th cycle of usage (red) MgFe2O4 nanoparticles
reaction, the generality of the reaction was investigated by
applying several substituted aldehydes with malononitrile
and resorcinol (or dimedone) under ultrasonic irradiation
(Table 5). As is mentioned earlier, the efect of ultrasound
on the reaction is that it can signifcantly shorten the reac-
tion time compared with classical conditions. It can be seen
that the similar efects were also seen in our experiments.
The obtained results in Table 5 demonstrate that ultrasound
has more benefcial efects than classical stirring. Obviously,
the lazy chemical reaction which was carried out under clas-
sical stirring in more longer duration (see Table 5, entry
Comparison of the catalytic efciency of MgFe2O4
nanoparticles
Also, the efciency of diferent catalysts in synthesis of
2-amino-7-hydroxy-4H-chromene and tetrahydrobenzo[b]
pyran derivatives has been compared and summarized in
Table 6. Entries 1–4 belong to 2-amino-7-hydroxy-4H-
chromene derivatives and entries 5–8 belong to tetrahy-
drobenzo [b] pyran derivatives. The role of the MgFe2O4
Fig. 7 TEM images of the syn-
thesized MgFe2O4 nanoparticles
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Journal of the Iranian Chemical Society
Fig. 8 N2 adsorption–desorption isotherm of MgFe2O4 nanoparticles
nanoparticles as catalyst was carried out by performing
the model reaction (5a product) in the absence of it. It was
observed that the 5a product was produced in low 34% yield.
It can be seen that the best yields in short reaction times can
be attributed to the efcient synthetic MgFe2O4 nanoparti-
cles as catalyst.
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Journal of the Iranian Chemical Society
Table 3 Optimization of the reaction solvent condition for the model
Table 4 Optimization of the ultrasound irradiation frequency and
reaction temperature for the model reaction
reaction
Entry
Solvent
Method
Time (min)
Yield (%)a
Entry
Temperature Frequency
Time (min)
Yield (%)a
(◦C)
(kHz)
1
2
3
4
5
6
7
–
US
US
US
US
US
US
Stirring
30
30
30
30
30
30
120
–
–
21
15
18
54
49
1
2
3
4
5
45
55
65
75
85
60
70
80
90
100
21
16
12
10
8
64
69
74
68
52
n-Hexane
CH3CN
THF
DMF
EtOH
EtOH
aReaction conditions: benzaldehyde (1 mmol), malononitrile
(1 mmol) and resorcinol (1 mmol); 5 mL solvent; and the ultrasonic
power 200 W at room temperature in frequency of 10 kHz
separated with the external magnet and washed with extra
acetone to remove the residual product. The nanocatalyst was
reused for the new standard reaction of benzaldehyde, malon-
onitrile and resorcinol under similar reaction conditions. The
relation between the number of cycles of the reaction and the
catalytic activity in terms of yield of the products is presented
in Scheme 3. It was found that MgFe2O4 nanocatalyst could
be reused for 4 cycles with negligible loss of their activity.
Reusability of MgFe2O4 nanoparticles
The recyclability of MgFe2O4 nanocatalyst was studied. After
completion of the reaction, the MgFe2O4 nanoparticles were
Scheme 2 Proposed mechanism
for the synthesis of 2-amino-
MgFe2O4
MgFe2O4
NC
NC
CN
O
7-hydroxy-4H-chromene (7)
and tetrahydrobenzo[b]pyran
(8) derivatives in the presence
of MgFe2O4 as a catalyst under
ultrasound irradiation
O
CN
2
H MgFe2O4 NPs
H
H
R
R
))), EtOH
R
))), EtOH
3
1
OH
4
R
R
))), EtOH
HO
CN
O
CN
))), EtOH
))), EtOH
HO
O
NH
HO
O
NH2
5
O
7
6
R
R
O
O
CN
CN
))), EtOH
O
NH2
O
NH
9
8
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Journal of the Iranian Chemical Society
Table 5 Synthesis of 2-amino-
7-hydroxy-4H-chromene
Entry
Aldehyde
Product
Time (min)
Yield (%)
Melting point
Melting point
(°C, reported)
(◦C, observed)
(5a–h) and tetrahydrobenzo[b]
pyran (6a–h) derivatives in
the presence of MgFe2O4
nanoparticles as a catalyst under
ultrasound irradiation
1
2
3
4
5
6
7
8
C6H5
5a
5b
5c
5d
5e
5f
5g
5h
6a
6b
6c
6d
6e
6f
12
14
14
11
15
11
15
12
12
14
15
10
13
11
12
13
74
79
76
85
81
89
75
78
86
85
87
92
90
90
89
92
236–238
223–226
228–231
216–218
215–218
107–111
109–113
185–188
229–231
213–216
220–223
212–215
208–211
212–213
220–224
198–200
234–237 [24]
222–224 [24]
226–229 [24]
218–221 [24]
215–217 [24]
106–109 [24]
110–112 [24]
183–186 [24]
228–230 [39]
214–215 [39]
224–226 [39]
212–214 [39]
208–210 [39]
210–212 [39]
223–225 [39]
201–202 [39]
2-MeOC6H4
2-MeC6H4
2-F-C6H4
3-HOC6H4
3-Cl-C6H4
4-MeOC6H4
4-MeC6H4
C6H5
2-ClC6H4
2-NO2C6H4
3-ClC6H4
3-MeOC6H4
4-ClC6H4
4-MeC6H4
4-MeOC6H4
9
10
11
12
13
14
15
16
6g
6h
Table 6 The comparison of
catalytic activity of the synthetic
MgFe2O4 nanoparticles (entry
9) with some reported catalysts
for synthesis of 2-amino-7-
hydroxy-4H-chromene (entries
1–4) and tetrahydrobenzo [b]
pyran (entries 5–8) derivatives
Entry
Catalyst
Solvent
Time
Yield (%)
1
2
3
4
5
6
7
8
9
Na2SeO4
TBAF
EtOH/H2O
H2O
–
H2O
Neat, refux
EtOH
EtOH/H2O, refux
EtOH/refux
EtOH,))), 65 C
0.75–3 h
30–300 min
10–15 min
0.5–2 h
4–5 h
48 h
10–60 min
10–30 min
12
80–98 [40]
73–98 [41]
60–95 [42]
79–93 [43]
81–90 [44]
80–87 [45]
42–95 [46]
57–90 [47]
NaBr
TMAHa
2,2,2-Trifuoroethanol
[ADPPY][OH]b
PhB(OH)2
TTTAc
–
◦
34 (present work)
74–92 (present work)
10
MgFe2O4 nanoparticles
EtOH,))), 65 °C
10–15 min
aTetramethylammonium hydroxide
b4-Amino-1-(2,3-dihydroxypropyl) pyridinium hydroxide
cTriethylenetetraammonium trifuoro acetate
Scheme 3 Development of the
yield after several recycling
cycles of the catalyst
1 3

Journal of the Iranian Chemical Society
with AC magnetic feld for thermal coagulation therapy. J. Magn.
Magn. Mater 272–276(Part 3)), 2428–2429 (2004)
Conclusion
11. F.A. Benko, F.P. Kofyberg, The efect of defects on some photo-
electrochemical properties of semiconducting MgFe2O4. Mater.
Res. Bull. 21, 1183–1188 (1986)
In conclusion, we have introduced a novel, fast and efcient
method for synthesis of a series of 2-amino-7-hydroxy-
4H-chromene and tetrahydrobenzo[b] pyran derivatives in
the presence of MgFe2O4 nanoparticles as a catalyst under
ultrasound irradiation. Moreover, MgFe2O4 nanoparticles
were synthesized through a green and eco-friendly approach
by tragacanth gum. This sonochemical method has some
benefits involving high yields, mild reactions, conveni-
ent approach and short reaction times, which turns it to an
attractive synthetic approach for the synthesis of 2-amino-
7-hydroxy-4H-chromene and tetrahydrobenzo[b] pyran
derivatives.
12. P.V. Reddy, R. Satyanarayana, T. Seshagiri Rao, Electrical con-
duction in magnesium ferrite. J. Mater. Sci. Lett 3, 847–849
(1984)
13. M. Tsunehiro, K. Kensuke, K. Tatsuo, A. Hiromichi, N. Takashi,
K. Hiroyuki, W. Yuji, K. Kanji, Heating of ferrite powder by an
AC magnetic feld for local hyperthermia. Jpn. J. Appl. Phys. 41,
1620–1632 (2002)
14. N. Sivakumar, S.R.P. Gnanakan, K. Karthikeyan, S. Amaresh,
W.S. Yoon, G.J. Park, Y.S. Lee, Nanostructured MgFe2O4 as
anode materials for lithium-ion batteries. J. Alloy. Compd. 509,
7038–7041 (2011)
15. S. Ilhan, S.G. Izotova, A.A. Komlev, Synthesis and charac-
terization of MgFe2O4 nanoparticles prepared by hydrothermal
decomposition of co-precipitated magnesium and iron hydroxides.
Ceram. Int. 41, 577–585 (2015)
Acknowledgements The authors thank, Islamic Azad University, Sci-
ence and Research Branch for the support and guidance.
16. J. Safari, Z. Zarnegar, M. Heydarian, Magnetic Fe3O4 nanopar-
ticles as efcient and reusable catalyst for the green synthesis of
2-amino-4H-chromene in aqueous media. Bull. Chem. Soc. Jpn
85, 1332–1338 (2012)
Compliance with ethical statement
17. R.W. De Simone, K.S. Currie, S.A. Mitchell, J.W. Darrow, D.A.
Pippin, Privileged structures: applications in drug discovery.
Comb. Chem. High Throughput Screen. 7, 473–494 (2004)
18. J. Safari, Z. Zarnegar, M. Heydarian, Practical, ecofriendly,
and highly efcient synthesis of -amino-4H-chromenes using
nanocrystalline MgO as a reusable heterogeneous catalyst in aque-
ous media. J. Taibah Univ. Sci. 7, 17–25 (2013)
Conflict of interest We have no conficts of interest to declare.
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