Fe3O4@SiO2@Propyl–ANDSA: as a new catalyst for one-pot synthesis of 4H-chromene

Article abstract of DOI:10.1007/s11164-018-3638-z

Abstract: This work describes a new method for a one-pot multicomponent condensation of a variety of aldehydes with dimedone and malononitrile in water, providing a simple and effectual procedure for preparing 4H-chromene under reflux conditions with magn

Full text of DOI:10.1007/s11164-018-3638-z

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-018-3638-z
Fe O @SiO @Propyl–ANDSA: as a new catalyst for one‑pot
3
4
2
synthesis of 4H‑chromene
1
1
1
Hassan Sanati · Zahra Karamshahi · Ramin Ghorbani‑Vaghei
Received: 12 August 2018 / Accepted: 8 October 2018
©
Springer Nature B.V. 2018
Abstract
This work describes a new method for a one-pot multicomponent condensation of
a variety of aldehydes with dimedone and malononitrile in water, providing a sim-
ple and eꢀectual procedure for preparing 4H-chromene under reꢁux conditions with
magnetic nanoparticles supported on functionalized 7-aminonaphthalene-1,3-disul-
fonic acid-functionalized silica as catalyst. (Fe O @SiO @Propyl–ANDSA) has
3
4
2
been investigated as a novel catalyst in this reaction. This protocol is novel in (1)
avoiding toxic solvents (2) introducing a catalyst with ideal features such as chemi-
cal stability, low toxicity, cost-eꢀectiveness and, most importantly, easy, fast and
comfortable separation using an external magnet.
Graphical Abstract
H
N
SO H
3
O
O
Si
OEt
SO H
3
O
Ar
O
CN
NC
CN
+
H O
2
NH2
ArCHO
O
O
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1116
-018-3638-z) contains supplementary material, which is available to authorized users.
4
*
Ramin Ghorbani-Vaghei
rgvaghei@yahoo.com
1
Department of Organic Chemistry, Faculty of Chemistry, Bu-Ali Sina University,
Hamadan 6517838683, Iran
Vol.:(012
1
3456789)
3

H. Sanati et al.
Keywords Dimedone · Malononitrile · Aldehyde · Water · Chromene
Introduction
Oftentimes, compounds with biological activity are derived from heterocyclic struc-
tures. One of the heterocyclic compounds is coumarin. Coumarin derivatives such
as 2-amino-4H-chromenes and dihydropyrano[c]chromenes are of great importance
in pharmaceuticals, and their syntheses have attracted considerable attention. Ben-
zopyran derivatives can interact with a variety of cellular targets that leads to their
extensive ranging biological activities such as antitumor, herbicidal, antihepatotoxic,
anti-inꢁammatory, diuretic, anticoagulant, antispasmolytic, estrogenic, antiviral,
antimicrobial, anti-helminthic, hypothermal, antifungal, vasodilatory, anti-HIV, anti-
oxidant, antitubercular, anticonvulsant and analgesic activities [1]. These synthetic
compounds possess a wide spectrum of pharmacological activities, e.g. as antidia-
betic, anticoagulant, antitumor and anticancer agents [2–6]. These compounds are
often synthesized from the combination of three components of aldehyde, active
methylene compounds, resorcinol or 4-hydroxycoumarin with acid or base stimula-
tion. The methods used to produce the materials are often toxic and expensive and,
on the other hand, the use of organic solvents has reduced the value of the work [3,
7
–9].
Scientists look for procedures and materials that are not harmful to the envi-
ronment, which is why they have been able to decrease the time, cost, energy and
amount of raw materials by using one-pot multicomponent organic reactions in
water [10, 11]. Organic solvents represent the biggest pollution problem in the syn-
thetic organic processes. Thus, replacing hazardous solvents with relatively benign
solvents has been one of the main domains of green chemistry [3, 12]. Water, which
is considered a green reaction medium, has gained considerable interest in view of
its low cost, safety, and nontoxic and nonꢁammable benign properties. Using syn-
thetic strategies available to organic chemistry, multi-component reactions (MCRs)
are mostly advantageous because they allow the creation of several bonds in a single
operation [13–16]. Also, MCRs contribute to the requirements of an environment-
friendly process by reducing the number of synthetic steps, energy consumption and
waste production [17, 18].
In recent decades, noble metal nanoparticles (NPs) have generated interest owing
to their extraordinary physical, chemical, and biological characteristics for possible
progressive applications in diverse research scopes, including optics, catalysis, bio-
medicine, electrochemistry, and sensors [19]. Creating harmony and compatibility
between nanoscience and green chemistry will lead to producing greener products,
enhancing the fruitfulness of nanotechnology and reducing energy [20, 21].
An important category of nanoparticles is magnetic nano catalysts. Magnetic NP
Fe O s are placed in the category of catalysts with high potency and activity; due to
3
4
their unique magnetic sensitivity, low cytotoxicity and wide surface to volume ratio,
they have attracted much attention [22].
Among all these magnetic nanoparticles, Fe O coated with silica (SiO @Fe O )
3
4
2
3
4
is an interesting support for the immobilization of organic functional groups [23].
1
3

Fe O @SiO @Propyl–ANDSA: as a new catalyst for one-pot…
3
4
2
In fact, Fe O coated with silica shells prevents the accumulation of magnetic nano-
3
4
particles and improves the chemical stability of these nanoparticles [24]. Therefore,
various studies have focused on the activation of a wide range of diverse groups,
such as organic compounds, metals and polymers, on the surface of the magnetic
supports for catalytic activities [9, 20, 25, 26].
Experimental
Materials and instrumentation
Chemicals were purchased from Fluka, Merck and Aldrich chemical companies. The
1
chromene products were characterized by comparison of their spectral ( H NMR,
1
3
and C NMR) and physical data with authentic samples. Fourier transform infra-
red (FT-IR) spectra were recorded with a Shimadzu 435-U-04 FT spectrophotometer
from KBr pellets. Melting points were measured with a BUCHI 510 apparatus in
open capillary tubes.
Preparation of Fe O @SiO @Propyl–ANDSA
3
4
2
We prepared 7-aminonaphthalene-1,3-disulfonic acid-functionalized Fe O /SiO
2
3
4
3
+
2+
nanoparticles through a co-precipitation method of Fe and Fe ions as recounted
in the literature [27]. Typically, ferric chloride (FeCl 6H O: 11.3 g, 0.0418 mol)
3
2
and ferrous chloride (FeCl 4H O: 5.648 g, 0.0209 mol) were dissolved in 100 mL
2
2
of deionized water. The mixed solution of ferrous and ferric salts was stirred vigor-
ously at 85 °C for 30 min, then 25 mL of ammonia (28% aqueous solution) was
quickly injected into the reaction mixture under severe stirring. After lapse of
another 30 min at 85 °C, the formed black Fe O colloidal particles were extracted
3
4
by a magnet and further rinsed with distilled water followed by EtOH. Finally, the
attained Fe O NPs were dried at 80 °C in an oven [28].
3
4
The Fe O coated with SiO was obtained through an adjusted Stöber method
3
4
2
[
21]. The Stöber process is an example of a sol–gel process for covering the surface
of iron oxide nanoparticles with a layer of silica. An amount of 1.0 g of the MNPs
was homogeneously dispersed in a mixture of 80 mL of deionized water, 20 mL of
EtOH and 2.0 ml of 28 wt% concentrated ammonia aqueous solution (NH ·3H O)
3
2
and 3 mL tetraethylorthosilicate (TEOS) and stirred vigorously at room temperature
for 2 h to achieve core–shell MNPs (Fe O @SiO MNPs) [29, 30].
3
4
2
The chloropropyl-modiꢂed silica-coated MNPs were prepared based on the fol-
lowing procedure [27]. 3 g of Fe O -silica coated (Fe O @SiO ), 50.0 mL of
3
4
3
4
2
toluene and (3-chloropropyl) triethoxysilane (2.0 mL) were mixed into a 250 mL
round ꢁask under reꢁux conditions at 110 °C for 12 h. The resulting functionalized
Fe O @SiO @Cl MNPs were collected, washed twice with toluene and ethanol and
3
4
2
dried at 50 °C until completely dry [31].
Thereafter, the Fe O @SiO @Cl MNPs (20 mg) were dispersed in 50 mL dry
3
4
2
toluene for 15 min, after which 60 mg of 7-aminonaphthalene-1,3-disulfonic acid
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H. Sanati et al.
(
ANDSA) was added. This mixture was stirred for 24 h under reꢁux conditions.
After performing the steps of separating with a magnet, and washing with toluene
and ethanol, the MNPs were dried at 80 °C for 12 h. The precipitate nano particles
Fe O @SiO @Propyl-7-aminonaphthalene-1,3-disulfonic acid as a MNPs-ANDSA
3
4
2
catalyst was accomplished (Scheme 1) [4].
General procedure for the synthesis of 2‑amino‑7,7‑dimethyl‑4‑(4‑methylphenyl)
‑5‑oxo‑5,6,7,8‑tetrahydro‑4H‑chromene‑3‑carbonitrile
To a mixture of 4-methylbenzaldehyde (0.120 g, 1 mmol) and malononitrile
(
0.066 g, 1 mmol) in water (5 mL), dimedone (0.14 g, 1 mmol) and Fe O @SiO @
3 4 2
Scheme 1 Preparation of Fe O @SiO @Propyl–ANDSA
3
4
2
1
3

Fe O @SiO @Propyl–ANDSA: as a new catalyst for one-pot…
3
4
2
Propyl–ANDSA (0.05 g) were added; then, the reaction mixture was stirred under
reꢁux conditions for 30 min (the progress of the reaction was monitored by TLC
n-hexan/aceton 7:3). After the completion of the reaction, using an external magnet,
the catalyst was separated, and then water was removed and crude product dissolved
in hot ethanol (5 mL). Finally, recrystallization of product from EtOH/H O aꢀord to
2
2
3
-amino-7,7-dimethyl-4-(4-methylphenyl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-
-carbonitrile in 86% yield as a white solid. M.p.: 212–213 °C (lit. 211–212 °C)
1
[
22]. H NMR (400 MHz, CDCl ) δ (ppm): 7.10–7.15 (m, 4H), 4.52 (s, 2H), 4.40 (s,
3
1
3
1
H), 2.47 (s, 2H), 2.32 (s, 3H), 2.25 (m, 2H), 1.14 (s, 3H), 1.07 (s, 3H); C NMR
(
100 MHz, CDCl ) δ (ppm): 196.0, 161.4, 157.4, 140.3, 136.7, 129.3, 127.4, 118.7,
3
1
14.1, 63.8, 50.7, 40.7, 35.1, 32.2, 28.9, 27.7, 21.1.
2
‑Amino‑7,7‑dimethyl‑4‑(4‑methylphenyl)‑5‑oxo‑5,6,7,8‑tetrahydro‑4H‑
chromene‑3‑carbonitrile White solid. M.p.: 210–212 °C (lit. 214–216 °C) [32].
1
H NMR (400 MHz, CDCl ) δ (ppm): 7.10–7.15 (m, 4H), 4.52 (s, 2H), 4.40 (s,
3
1
3
1
H), 2.47 (s, 2H), 2.32 (s, 3H), 2.25 (m, 2H), 1.14 (s, 3H), 1.07 (s, 3H); C NMR
(
100 MHz, CDCl ) δ (ppm): 196.0, 161.4, 157.4, 140.3, 136.7, 129.3, 127.4, 118.7,
3
1
14.1, 63.8, 50.7, 40.7, 35.1, 32.2, 28.9, 27.7, 21.1.
2
‑Amino‑7,7‑dimethyl‑4‑(4‑flourophenyl)‑5‑oxo‑5,6,7,8‑tetrahydro‑4H‑
1
chromene‑3‑carbonitrile: White solid. M.p.: 201–202 °C (lit. 200 °C) [33]. H
NMR (400 MHz, DMSO-d ) δ (ppm): 7.10–7.21 (m, 4H), 7.06 (s, 2H), 4.22 (s,
6
1
H), 2.51 (s, 2H), 2.26 (d, J=16 Hz, 1H), 2.12 (d, J=16 Hz, 1H), 1.07 (s, 3H),
1
3
1
.05 (s, 3H); C NMR (100 MHz, DMSO-d ) δ (ppm): 196.2, 163.0, 161.4 (d,
6
1
4
3
J
=241 Hz), 159.0, 141.4 (d, J =2 Hz), 129.5 (d, J =8 Hz), 120.1, 115.5
C-F
C-F
C-F
2
(
d, J =21 Hz), 113.1, 58.6, 50.4, 35.4, 32.3, 28.8, 27.3.
C-F
2
‑Amino‑7,7‑dimethyl‑4‑(3,4‑dimethoxyphenyl)‑5‑oxo‑5,6,7,8‑tetrahy‑
1
dro‑4H‑chromene‑3‑carbonitrile White solid. M.p.: 189–190 °C. H NMR
(
400 MHz, CDCl ) δ (ppm): 6.76–6.83 (m, 4H), 4.63 (br, 2H), 4.38 (s, 1H), 3.89
3
(
s, 3H), 3.86 (s, 3H), 2.47 (s, 2H), 2.28 (d, J=16.4 Hz, 1H), 2.23 (d, J=16.4 Hz,
1
3
1
1
4
H), 1.14 (s, 3H), 1.07 (s, 3H); C NMR (100 MHz, CDCl ) δ (ppm): 196.1, 161.5,
3
57.6, 148.9, 148.0, 136.1, 119.5, 118.9, 114.1, 11.3, 111.1, 63.2, 55.9, 55.8, 50.7,
0.7, 35.1, 32.2, 29.0, 27.5.
2
‑Amino‑7,7‑dimethyl‑4‑(4‑(trifluoromethyl)phenyl)‑5‑oxo‑5,6,7,8‑tetrahy‑
dro‑4H‑chromene‑3‑carbonitrile White solid. M.p.: 216–217 °C (lit. 217–218 °C)
1
[
34]. H NMR (400 MHz, DMSO-d ) δ (ppm): 7.68 (d, J=7.6 Hz, 2H), 7.39 (d,
6
J=7.6 Hz, 2H), 7.15 (s, 2H), 4.31 (s, 1H), 2.55 (s, 2H), 2.28 (d, J=16 Hz, 1H), 2.13
d, J=16 Hz, 1H), 1.06 (s, 3H), 0.97 (s, 3H).
(
2
‑Amino‑7,7‑dimethyl‑4‑(2‑naphthyl)‑5‑oxo‑5,6,7,8‑tetrahydro‑4H‑chromene‑3‑car‑
1
bonitrile White solid. M.p.: 257–258 °C (lit. 258–260 °C) [35]. H NMR
(
400 MHz, DMSO-d ) δ (ppm):7.86–792 (m, 3H), 7.70 (s, 1H), 7.46–7.53 (m, 2H),
6
7
.29–7.32 (m, 1H),7.10 (s, 2H), 4.38 (s, 1H), 2.57 (s, 2H), 2.28 (d, J=16 Hz, 1H),
1
3

H. Sanati et al.
2
.10 (d, J=16 Hz, 1H), 1.06 (s, 3H), 0.97 (s, 3H); 13C NMR (100 MHz, DMSO-d )
6
δ (ppm):196.2, 163.1, 159.0, 142.5, 133.3, 132.5, 128.6, 128.1, 127.9, 126.7, 126.1,
1
26.0, 120.3, 113.0, 58.6, 50.5, 36.4, 32.3, 28.9, 27.2.
4
,4′‑(1,4‑Phenylene)bis(2‑amino‑7,7‑dimethyl‑5‑oxo‑5,6,7,8‑tetrahydro‑4H‑
1
chromene‑3‑carbonitrile) White solid. M.p.: 262–264 °C. H NMR (400 MHz,
DMSO-d ) δ (ppm): 7.06 (s, 4H), 6.98 (s, 4H), 4.15 (s, 2H), 2.55 (s, 4H), 2.10–
6
1
3
2
.28 (m, 4H), 0.93–1.07 (s, 12H); C NMR (100 MHz, DMSO-d ) δ (ppm): 196.2,
6
1
63.2, 159.1, 143.4, 127.5, 120.3, 113.2, 58.9, 50.4, 40.9, 35.5, 32.4, 28.7, 27.7.
Results and discussion
To date, for producing magnetic core–shell nanoparticles, various methods includ-
ing co-precipitation, hydrothermal method, the reverse micelle method, laser pyroly-
sis techniques, thermal decomposition of iron oleate, etc. have been used [20]. The
generally employed technique for synthesizing magnetite nanoparticles is the tem-
plating master plan, which consists of two steps. First, magnetic particles are cre-
ated through various processes, and as-prepared particles usually have rather hard
surfaces, which make surface modiꢂcation almost unavoidable before being used as
supports or templates. Second, modiꢂed magnetic particles are used as templates
and they are coated with various materials [9, 20].
Encouraged by the interesting biological activities associated with chromene
derivatives, and as part of our ongoing program towards the synthesis of heterocyclic
compounds, we decided to apply a green medium for the preparation of 2-amino-
7
,7-dimethyl-4-(arylsubstituted)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carboni-
trile. The reaction conditions were optimized by the reactions of 3-nitrobenzalde-
hyde (1.0 mmol), dimedone (1.0 mmol), and malononitrile (1.0 mmol) in diꢀerent
solvents in the presence of Fe O @SiO @Propyl–ANDSA under reꢁux conditions
3
4
2
(
Scheme 2, Fig. 1 and Table 1).
As can be seen from Table 1, water was identiꢂed as the best solvent for this
reaction. The reaction completed in 15 min yielding 88% of 2-amino-7,7-dime-
thyl-4-(3-nitrophenyl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile after
a simple workup. Therefore, water has been applied for the synthesis of all of
Scheme 2 Optimization of reaction conditions
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3

Fe O @SiO @Propyl–ANDSA: as a new catalyst for one-pot…
3
4
2
Fig. 1 The structure of Fe O @
3
4
SiO @Propyl–ANDSA
2
Table 1 Optimization of various
Yield (%)a
Entry
Solvent
Time (h)
solvents on the synthesis of
2
-amino-7,7-dimethyl-4-(3-
1
2
3
4
5
6
Ethanol
Acetonitrile
n-hexane
Dichloromethane
Ethyl acetate
Water
5
24
24
24
24
15 min
96
nitrophenyl)-5-oxo-5,6,7,8-
tetrahydro-4H-chromene-3-
carbonitrile
b
15
b
76
52
b
b
34
88
3
-Nitrobenzaldehyde/Dimedone/Malononitrile: 1/1/1 (mmol)
a
Isolated yield
b
Product puriꢂed by preparative TLC
the chromene derivative compounds.Because water is non-toxic, inexpensive
and environmentally friendly,it is an excellent alternative to hazardous organic
solvents and is widely used as a green solvent for organic reactions. With the
optimal reaction conditions [aldehyde (1 mmol), dimedone (1 mmol) and malo-
nonitrile (1 mmol), water as solvent, and reꢁux conditions] in hand, the scope of
the domino reaction of aromatic aldehydes with dimedone and malononitrile was
explored. The results are summed up in Table 2.
From a mechanistic point of view, for this multicomponent reaction we pro-
pose a plausible reaction pathway which is outlined in Scheme 3.
In the ꢂrst step, the carbonyl group of aldehyde is activated in the presence
of Fe O @SiO @Propyl–ANDSA catalyst and forms the active intermediate I.
3
4
2
Then malonitrile is reacted via Knoevenagel transformation with intermediate I
and forms α-cyanocinnamonitrile. In the next step one molecule of dimedone
condenses with the product of the previous step to produce intermediate II.
Then cyclization occurs by nucleophilic attack of the OH group to the cyanide
group, creating intermediate III. Eventually, the 4H-chromene derivatives are
obtained.
Characterization of prepared Fe O @SiO @Propyl–ANDSA
3
4
2
Fe O @SiO @ Propyl–ANDSA nanoparticles were characterized using FT‐IR
3
4
2
spectroscopy, SEM, TEM, TGA, X-ray diꢀraction (XRD), X-ray photoelectron
spectroscopy (XPS), VSM, EDX.
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H. Sanati et al.
Table 2 Preparation of 2-amino-7,7-dimethyl-4-(arylsubstituted)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-
3
-carbonitrile (4) via combination of dimedone (3), malonoitrile (2) and aromatic aldehydes (1) in the
presence of Fe O @SiO @Propyl–ANDSA in water under reꢁux conditions
3
4
2
Time
Yield
Entry
1
Aldehyde
Product
a
(
min)
(%)
30
86
96
98
2
3
4
5
25
70
110
35
99
99
6
7
100
10
99
96
1
3

Fe O @SiO @Propyl–ANDSA: as a new catalyst for one-pot…
3
4
2
Table 2 (continued)
Time
Yield
Entry
Aldehyde
Product
a
(
min)
(%)
b
8
180
60
9
235
20
79
89
1
1
0
1
30
30
83
86
12
1
1
1
3
4
5
5
75
88
98
15
10
1
3

H. Sanati et al.
Table 2 (continued)
Time
Yield
Entry
Aldehyde
Product
a
(
min)
(%)
1
6
15
98
95
98
1
1
7
8
20
15
19
15
97
10
99
20
Aldehyde/dimedone/malononitrile: 1/1/1 (mmol)
a
Isolated yield
Product puriꢂed by preparative TLC
b
FT‑IR spectra
FT-IR analysis was used to conꢂrm the functional groups in the synthesized cata-
lysts. The FT-IR spectrum of magnetic Fe O MNPs shows a characteristic Fe–O
3
4
1
3

Fe O @SiO @Propyl–ANDSA: as a new catalyst for one-pot…
3
4
2
Scheme 3 Mechanistic pathway for the synthesis of the chromenes
Fig. 2 FT-IR spectra: a Fe O ; b Fe O @SiO ; c Fe O @SiO @Cl MNPs; d Fe O @SiO @Propyl–
3
4
3
4
2
3
4
2
3
4
2
ANDSA
1
3

H. Sanati et al.
−
1
−1
−
absorption around 579 cm , O–H stretching vibration near 3432 cm (Fig. 2a,
1
b). Fe O /SiO displays characteristic FT-IR peaks at around 1097 cm (asym-
3
4
2
−
1
−1
metric stretching), 802 cm (in plane bending) and 470 cm (rocking mode)
for the Si–O–Si group and conꢂrms the formation of the SiO shell (Fig. 2b).
2
−
1
The peak at 2887 cm corresponds to the C–H stretching vibrations of the alkyl
group of propyl–Cl (apparent in the spectrum. in Fig. 2d). All peaks assigned to
−
1
SiO are shifted, the asymmetric stretching vibration shifts to 476 cm , symmet-
2
−
1
−1
ric stretching vibration to 807 cm and bending vibration to 1105 cm .
−
1
The presence of sulfonyl moiety is evidenced with 1215 and 1152 cm bands
−
1
that are covered with a stronger absorption of Si–O bond at 1105 cm . A
decline in the intensities of Si–O–Si peaks showed that ANDSA groups with two
groups of SO H were successfully attached to the surface of Fe O @SiO @Cl
3
3
4
2
nanoparticles.
−
1
The increase in the intensity and width of the band at 3062 cm shows that there
are more OH groups under the MNP surface after the sulfonation. According to the
results, the functional groups on the surface of the MNPs are grafted properly [29].
EDX spectrum
Fe O @SiO @Propyl–ANDSA was analysed using EDX as shown in Fig. 3. The
3
4
2
presence of Si, O, N and Fe signals in Fig. 3 indicates that the iron oxide particles
are loaded into silica, with the higher intensity of the Si peak compared with Fe
peaks showing Fe O nanoparticles coated with SiO . The characteristic peaks
3
4
2
of S and N in Fig. 3 reveal that the iron oxide nanoparticles have been coated
with ANDSA. This analysis makes it clear that Fe O @SiO @Propyl–ANDSA
3
4
2
has been successfully synthesized.
Fig. 3 EDX spectrum of Fe O @SiO @Propyl–ANDSA
3
4
2
1
3

Fe O @SiO @Propyl–ANDSA: as a new catalyst for one-pot…
3
4
2
XRD patterns
The XRD patterns of MNPs, Fe O @SiO @Cl MNPs, Fe O @SiO @Pro-
3
4
2
3
4
2
pyl–ANDSA and ANDSA are depicted in Fig. 4. The positions and relative intensi-
ties of all peaks conform well to the standard XRD pattern of Fe O (JCPDS card
3
4
no. 85–1436), showing retention of the crystalline cubic spinel structure during
functionalization of MNPs. The XRD pattern of Fe O @SiO @Propyl–ANDSA
3
4
2
clearly reaꢃrms the coating of ANDSA on Fe O @SiO @Cl MNPs as indicated by
3
4
2
the diꢀraction peaks (2θ) at 18.5°, 20°, 25.5°, 27.5°, 29°, 30.5° and 32°.
Through the Scherrer formula, the average particle size is found to be 59 nm,
matching the one measured from SEM images.
Morphology and particle size of Fe O @SiO @Propyl–ANDSA
3
4
2
The surface morphology of Fe O @SiO @Propyl–ANDSA was characterized
3
4
2
using SEM and TEM, as shown in Fig. 5. Figure 5a shows that these nanopar-
ticles are nearly spherical with nanometric dimensions ranging from 41.5 to
9
4.1 nm in size and with smooth surfaces. From Fig. 5b, it is revealed that iron
oxide nanoparticles are entrapped successfully in the silica shell, for which the
average particle size is about 50–80 nm, conforming to the average particle sizes
obtained from SEM and XRD. Surrounded by an amorphous silica shell, a dark
MNP core is displayed with the images of the silica‐coated MNPs.
Fig. 4 XRD patterns: a Fe O ; b Fe O @SiO @Cl MNPs; c Fe O @SiO @Propyl–ANDSA; d ANDSA
3
4
3
4
2
3
4
2
1
3

H. Sanati et al.
Fig. 5 Morphology and particle size of Fe O @SiO @Propyl–ANDSA: a SEM image; b TEM images
3
4
2
Thermogravimetric analysis
The TGA curve of Fe O @SiO @Propyl–ANDSA shows the mass loss of the
3
4
2
organic materials while being decomposed upon heating (Fig. 6). The TGA curve
of Fe O @SiO @Propyl–ANDSA can be divided into several regions corre-
3
4
2
sponding to diꢀerent mass loss ranges. Situated below 200 °C, the ꢂrst region
displays a mass loss attributed to loss of trapped water or adsorbed solvent from
the catalyst. The weight loss at higher temperature (346–385 °C) can be mainly
ascribed to the evaporation and subsequent decomposition of SO H groups.
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3

Fe O @SiO @Propyl–ANDSA: as a new catalyst for one-pot…
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Fig. 6 TGA curve of Fe O @SiO @Propyl–ANDSA
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Thus, the catalyst is stable up to 300 °C, establishing that it can be safely used in
organic reactions at temperatures in the region of 200 °C.
Magnetic properties
In Fig. 7, the magnetic properties of the catalyst are shown as determined using
VSM. The magnetization curves of Fe O nanoparticles and Fe O @SiO @Pro-
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pyl–ANDSA are shown.
The saturation magnetization of Fe O @SiO @Propyl– ANDSA is found to be
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2
−1
−1
1
0 emu g , seen to be much lower than that of bare Fe O MNPs (58 emu g ).
3 4
X‑ray photoelectron spectroscopy
Collected XPS spectra were analyzed using Casa XPS software. All spectra were
calibrated using the adventitious C 1 s peak with a ꢂxed value of 284.8 eV. Fig-
ure 8a displays the surface chemical changes using precise XPS analysis. The cor-
responding carbon, oxygen, sulfur, nitrogen, iron and silicon content percentages,
conꢂrmed reasonably by EDX results, are shown in Fig. 3. Strong observed C and O
signals suggest successful formation of Fe O @SiO @Propyl–ANDSA. In Fig. 8b
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observed at 284.8 eV (C–C/is a large peak C–H) followed by ꢂve smaller shoul-
ders at 285.8 eV (C–O bonding) and 283.2 eV (C–Si bonding) indicating that a
propyl group is coordinated with Fe O @SiO . Peaks at 285.9 eV (C–N bonding),
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2
86.8 eV (C–S bonding) and 284.0 eV (C=C bonding) reveal that ANDSA is also
successfully coordinated with Fe O @SiO @Propyl. The various carbon bonds and
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their percentages are listed in Table 3.
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H. Sanati et al.
Fig. 7 Magnetization curves: a Fe O ; b Fe O @SiO @Propyl–ANDSA
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A new 7-aminonaphthalene-1,3-disulfonic acid-functionalized Fe O /SiO mag-
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netite mnanoparticle was synthesized through the surface modiꢂcation of magnetic
iron oxide nanoparticles by 7-aminonaphthalene-1,3-disulfonic acid.
Iron oxide nanoparticles were synthesized via a coprecipitation method and
the surface modiꢂcation process was achieved through treating the nanoparticles
with tetraethyl orthosilicate (TEOS), chloropropyl trimethoxy silane (CPTS) and
piperazine.
Conclusion
Desirable properties of catalysts include ease of separation and reusability. The use
of nano catalysts in this context requires that they be supported on a solid surface.
The use of Fe O @SiO @Propyl–ANDSA nanoparticles meets criteria for reactions
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that require catalysts that are chemically stable, uniform in size, and well-dispersed
in liquid media, preferably in water. Therefore, they can be substituted in other het-
erogeneous catalytic systems.
This protocol has various beneꢂts such as avoiding toxic solvents, high yield and
procedural simplicity. Recyclability of the magnetic catalyst and ease of separation,
add to the desirability of Fe O @SiO @Propyl–ANDSA as a non-hazardous and
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reasonable solid acid catalyst.
Using a catalytic eꢃciency of FT-IR, XRD, TGA, SEM, TEM, XPS, EDX and
VSM spectroscopy in a one-pot multicomponent condensation of a variety of alde-
hydes with dimedone and malononitrile in water, a simple and eꢀective method for
preparing 2-amino-7,7-dimethyl-4-(arylsubstituted)-5-oxo-5,6,7,8-tetrahydro-4H-
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Fe O @SiO @Propyl–ANDSA: as a new catalyst for one-pot…
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Fig. 8 XPS analysis of Fe O @SiO @Propyl–ANDSA: a element content; b various carbon bonds
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H. Sanati et al.
Table 3 Carbon bonds and their
C=C (%) C–C (%) C–O (%) C–S (%) C–N (%) C–Si (%)
percentages
1
2.57
34.04
28.43
12.61
9.71
2.78
chromene-3-carbonitrile with Fe O @SiO @propyl–ANDSA activity was con-
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ꢂrmed as a catalyst condition.
Acknowledgements The authors wish to thank Bu-Ali Sina University, Center of Excellence Develop-
mental of Environmentally Friendly Methods for Chemical Synthesis (CEDEFMCS) for ꢂnancial support
to carry out this research.
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