Application of structurally enhanced magnetite cored polyamidoamine dendrimer for knoevenagel condensation

Article abstract of DOI:10.1007/s13738-020-02071-1

In this paper, the synthesis of magnetic cored amino group terminated dendrimer (Fe₃O₄@SiO₂@PAMAM-G₂) through covalent bonding was described. This catalyst was characterized by FT-IR, XRD, FE-SEM, TEM, and TGA d

Full text of DOI:10.1007/s13738-020-02071-1

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-020-02071-1
ORIGINAL PAPER
Application of structurally enhanced magnetite cored
polyamidoamine dendrimer for knoevenagel condensation
Fatemeh Hajizadeh1 · Behrooz Maleki1 · Farrokhzad Mohammadi Zonoz1 · Amirhassan Amiri1
Received: 5 May 2020 / Accepted: 18 September 2020
© Iranian Chemical Society 2020
Abstract
In this paper, the synthesis of magnetic cored amino group terminated dendrimer (Fe3O4@SiO2@PAMAM-G2) through
covalent bonding was described. This catalyst was characterized by FT-IR, XRD, FE-SEM, TEM, and TGA detection meth-
ods. Next, the catalytic activity of this catalyst was investigated for the Knoevenagel condensation reaction of aldehydes with
malononitrile under mild and solvent-free conditions. The Fe3O4@SiO2@PAMAM-G2 could be separated from the reaction
mixture by an external magnet and reused fve times.
Keywords Modifed polyamidoamine dendrimer · Silica-coated magnetic nanoparticles · Knoevenagel condensation ·
Green chemistry
Introduction
Dendrimers are monodispersed macromolecules includ-
ing an initial core, radial branches with end-group and inte-
rior spaces in branches [10, 11]. The core, type, the number
of branches, and end-groups can be changed, so their chemi-
cal properties and structure can be controlled. The stepwise
growth of the dendrimer, will provide more active sites for
conjugation of many biological molecules such as enzymes,
proteins, genes, and drugs because the number of surface
amino groups will be doubled. In this regards, the polyami-
doamine (PAMAM) dendrimer, a highly branched dendritic
macromolecule, possesses a unique surface with amine chain
ends, and the number of surface groups can be precisely
controlled by choosing the appropriate synthetic generation.
These excellent properties of the dendrimer have led to the
use of that in the synthesis of polyamidoamine (PAMAM)
dendrimer functionalized magnetic nanoparticles. Hence,
magnetic nanoparticles coated with the PAMAM dendrimer
have attracted a lot of attention due to their many functional
groups and applications [12–21].
Much attention has already been paid to the development
of heterogenizing homogeneous catalysts to merging the
benefts of homogeneous and heterogeneous catalysts [1].
Heterogenized catalysts can be readily dissociated from the
solution reaction, but they have a difculty of low reactivity
and selectivity toward their homogeneous counterparts. For
solving this problem, nanoparticles have been used because
they possess a high specifc surface area and can be easily
controlled in the reaction mixture [2–4]. Recently, magnetic
Fe3O4 nanoparticles have been used to make core–shell par-
ticles, and the surface of magnetic nanoparticles were pro-
tected by various organic and inorganic materials such as
silica, polymers, biomolecules, and metals [5–7]. Among
them, silica was considered as one of the best materials for
coating Fe3O4 magnetic nanoparticles, due to its unique
properties such as chemical diversity in surface modifca-
tion, stability, and biocompatibility [8, 9]. The main advan-
tages of using silica are; (i) to prevent the oxidation of Fe3O4
magnetic nanoparticles, and (ii) for linking to diferent func-
tional groups and surface modifcation.
The Knoevenagel condensation is a powerful method
for the synthesis of α, β-unsaturated compounds. This con-
densation has attracted much attention due to its economi-
cal, cleanliness, and efciency in the synthesis of diferent
organic material. There are diverse synthetic strategies
for the Knoevenagel reaction like utilization of various
catalysts such as Rare-earth (RE) exchanged NaY zeolite
[RE(72%)NaY] [22], cetyltrimethyl ammonium bromide
(CTMAB) [23], MgO/ZrO2 [24], Zn2+ exchanged Hß (Znß)
* Behrooz Maleki
b.maleki@hsu.ac.ir
1
Department of Chemistry, Hakim Sabzevari University,
Sabzevar 96179-76487, Iran
Vol.:(0123456789)
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Journal of the Iranian Chemical Society
[25], poly(vinyl chloride) supported tetraethylenepentamine
(PVC-TEPA) [26], Na2S/Al2O3 [27], magnesium fuoride
(MgF2) [28], Ni–SiO2 [29], Ceria-zirconia (C/Z-30/70) [30],
La2O3–MgO/KOH [31], guanidine supported on magnetic
nanoparticles Fe3O4 (Fe3O4@guanidine) [32], BEA or TS-1
or CuBTC or FeBTC [33], gallium chloride (GaCl3) [34],
polyvinyl amine coated Fe3O4@SiO2 (Fe3O4@SiO2-PVAm)
[35], Fe3O4@UiO-66-NH2 [36], N-(3-trimethoxysilylpropyl)
diethylenetriamine) coated (Fe3O4@SiO2-3N) [37], Fe3O4@
P4VP@ZIF-8 [38], magnetic Fe3O4@SiO2@Ni-Zn-Fe lay-
ered double hydroxide (LDH) (Fe3O4@SiO2@Ni-Zn-Fe
LDH) [39], and fber (PANPF-3) [40]. Although most of
the reported methods have practical synthetic procedures,
they endure some disadvantages such as using expensive
organic solvents, harsh and hazardous reaction conditions,
long reaction times, unacceptable yields, and tedious work-
up procedure. Therefore, a simple method which utilizes
mild and efective catalysts under green conditions is still
a favorite topic.
of particles, the synthesized catalyst was used from a feld
emission scanning electron microscopy (FE-SEM) Hitachi
model S-4160.
Preparation of the magnetic cored amino group
terminated dendrimer (Fe3O4@SiO2@PAMAM‑G2)
The synthesis of the Fe3O4@SiO2@PAMAM-G2 was
accomplished according to the procedure described in detail
in the literature [14]. However, a retread on the main aspects
of the synthesis route would be benefcial to clearly illustrate
the underneath.
Preparation of nanomagnetic Fe3O4
The precursors of FeCl2·4H2O and FeCl3·6H2O with a molar
ratio of 1: 2 were dissolved in 20 ml of deionized water. The
pH of the solution was increased to 10 by adding a dropwise
5 ml of NH3. The resulting solution is stirred vigorously
at room temperature for 1 h. The fnal nanoparticles were
extracted by an external magnetic feld. Separated nanopar-
ticles were washed several times with ethanol, deionized
water, and then were dried in a vacuum oven at 60° C for 8 h.
Based on our research interests [41, 42], herein, we
report an efcient synthesis of 2-benzylidenemalononitriles
in the presence of Fe3O4@SiO2@PAMAM-G2 at 50 °C
(Scheme 1).
Preparation of silica‑coated nanomagnetic (Fe3O4@SiO2)
Experimental
After ultra-sonication of iron nanoparticles for 30 min, a
5 ml of tetraethyoxysilane (TEOS) added to the Fe3O4 solu-
tion. The solution is stirred vigorously at room temperature
for 5 h. After completing the reaction, the nanoparticles
were collected by an external magnet feld. The product was
washed three times with deionized water, ethanol, and then
dried in a vacuum oven at 60 °C for 12 h.
Materials and instruments
The chemical materials and solvents were purchased from
Merck and Aldrich Chemical Companies and were employed
without further purifcation. The IR spectra were recorded
on a Bruker IFS-88 instrument using KBr disks in the region
1
of 400–4000 cm−1. The H-NMR and 13C-NMR spectra
were recorded on a Bruker AC-300 spectrometer using
tetramethylsilan as an internal standard. X-ray powder dif-
fraction (XRD) data were collected on an XD-3A difrac-
tometer using Cu Kα radiation, and with the scanning rate
set to 3° min−1. Thermogravimetric analyses were performed
on the TGA-50 Shimadzu thermal analyzer in the fowing
air atmosphere with the heating rate of 10 °C min−1 in the
temperature region of 50–650 °C. The transmission electron
microscopy (TEM) analysis was performed with a nitrogen
fow using a Zeiss EM-900 instrument at an acceleration
voltage of 80 kV. To study the morphology and distribution
Preparation of the amino functionalized silica‑coated
magnetic nanoparticles (Fe3O4@SiO2@Pr‑NH2)
1 g of silica-coated nanoparticles was dispersed in 20 ml
of dry toluene. After the ultra-sonication of the solution,
0.25 ml (3-aminopropyl) tri-methoxysilane (APTES) and
5 drops of glacial acetic acid were added gradually under
mechanical stirring. The solution was refuxed at 60 °C for
three days. After cooling to room temperature, the magnetic
nanoparticles were separated by an external magnetic feld.
Scheme 1 Synthesis of 2-ben-
zylidene malononitriles
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Finally, the nanoparticles were washed three times with the
dry methanol and dried in the oven for 24 h.
by fltration and recrystallized from the ethanol (3 ml) to get
2-benzylidene malononitrile derivatives (3a-k).
Preparation of magnetic cored esteric group terminated
dendrimer
2‑Benzylidene malononitrile (3a) 1H NMR (400 MHz,
DMSO-d6): δ 7.90 (d, 2H, J=7.0 Hz), δ 7.80 (s, 1H), δ 7.55
(m, 3H); 13C NMR (100 MHz, DMSO-d6) δ (ppm): 82.54,
112.45, 113.64, 116.44, 124.33, 130.64, 130.74, 134.50,
159.98; IR (KBr, cm−1): 2219, 1614, 1434, 750, 673.
1 g of amino-functionalized magnetic nanoparticle (Fe3O4@
SiO2@Pr-NH2) was dispersed in a 15 ml of anhydrous meth-
anol and was sonicated for 30 min. Then, a 1.5 ml of methyl
acrylate was added and the mixture was heated at 60 °C for
3 days. Afterward, the mixture was cooled down to room
temperature. The particles were separated by applying an
external magnetic feld and washed several times with the
dry methanol and dried under a vacuum for 24 h. The pre-
pared product was denoted as (Fe3O4@SiO2@PAMAM-
G0.5). Similarly, the Fe3O4@SiO2@PAMAM-G1.5 was
prepared from the Fe3O4@SiO2@PAMAM-G1 using the
same procedure.
2‑(3‑Nitrobenzylidene) malononitrile (3b) 1H NMR
(400 MHz, DMSO-d6): δ 8.66 (s, 1H), δ 8.49 (d, 1H,
J = 8.0 Hz), δ 8.35 (d, 1H, J = 8.0 Hz), δ 7.90 (s, 1H), δ
7.84 (d, 1H, J=8.0 Hz); 13C NMR (100 MHz, DMSO-d6)
δ (ppm): 81.55, 113.61, 114.78, 116.53, 122.26, 122.53,
131.08, 132.86, 158.30, 162.10; IR (KBr, cm−1): 2225,
1593, 1525, 1350, 815, 669.
2‑(4‑Nitrobenzylidene) malononitrile (3c) 1H NMR
(400 MHz, DMSO-d6): δ 8.40 (d, 2H, J = 8.8 Hz), δ 8.09
(d, 2H, J = 8.8 Hz), δ 7.90 (s, 1H); 13C NMR (100 MHz,
DMSO-d6) δ (ppm): 87.45, 111.58, 112.60, 116.38, 131.35,
135.78, 150.35, 156.95;; IR (KBr, cm−1): 2225, 1577, 1514,
1344, 840, 678.
Fe3O4@SiO2@PAMAM-G1.5: 1 g of Fe3O4@SiO2@
PAMAM-G1 was dispersed in a 30 ml of the anhydrous
methanol and a 5 ml of the methyl acrylate.
Preparation of magnetic cored amino group terminated
dendrimer
1 g of the magnetic cored esteric group terminated den-
drimer (Fe3O4@SiO2@PAMAM-G0.5) was dispersed in
20 ml of anhydrous methanol and was sonicated for 30 min.
Then, a 2.5 ml of the ethylene diamine was added and the
mixture was heated at 60 °C for 3 days. Afterward, the mix-
ture was cooled down to room temperature. The particles
were separated by applying an external magnetic feld and
washed several times with the anhydrous methanol and dried
under a vacuum for 24 h. The prepared product was denoted
as (Fe3O4@SiO2@PAMAM-G1). Similarly, the Fe3O4@
SiO2@PAMAM-G2 was prepared from the Fe3O4@SiO2@
PAMAM-G1.5 using the same procedure.
Results and discussion
Synthesis of catalyst
The synthesis of the Fe3O4@SiO2@PAMAM-G2 used in
the present study is reported in the previous work [14]. In
this research, for the frst time, the catalytic efciency of
the Fe3O4@SiO2@PAMAM-G2 in the organic transforma-
tion is investigated. To the best of our knowledge, there are
not reports on Fe3O4@SiO2@PAMAM-G2 in organic reac-
tion. This is the frst report of the catalytic application of the
Fe3O4@SiO2@PAMAM-G2 in an organic transformation.
Therefore, the frst catalytic application of Fe3O4@SiO2@
PAMAM-G2 in knoevenagel condensation is the novelty of
the present work.
Fe3O4@SiO2@PAMAM-G2: 1 g of the Fe3O4@SiO2@
PAMAM-G1.5 was dispersed in a 40 ml of the anhydrous
methanol and a 5 ml of the ethylene diamine.
The divergent synthesis of the PAMAM-G2 dendrimer
on the silica coated amagnetic iron oxide nanoparticle is
discussed. Initially, the Fe3O4 was prepared by the conven-
tional coprecipitation method, subsequently the controlled
silica coating was carried out on the Fe3O4 nanoparticle
for a better protection and achieving the spherical morphol-
ogy with the sustainable magnetic retentivity. It was fur-
ther functionalized with the APTES to develop. The amino
silanated material was labeled as the Fe3O4@SiO2@Pr-NH2
nanohybrid material with propylamine surface groups. Sub-
sequently, the magnetic cored amino group terminated den-
drimer (Fe3O4@SiO2@PAMAM-G2) was prepared by the
General procedure for Knoevenagel condensation
A mixture of the aldehyde (1 mmol), malononitrile
(1.2 mmol), and Fe3O4@SiO2@PAMAM-G2 (6 mg), was
added to a bottom fask ftted with a refux condenser (5
drops of ethanol was used as solvent for solid aldehydes).
Then, the mixture was mechanically stirred at 50 °C in an oil
bath under solvent-free condition. The reaction progress was
monitored by the TLC and after the completion of this reac-
tion, the catalyst was separated by an external magnet. The
resulting solid product was poured onto ice and was isolated
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Journal of the Iranian Chemical Society
consecutive repeating the Michael addition and amidation
reactions (Scheme 2).
bond. In Fig. 1C, the peaks 1558 and 2932 cm−1 corre-
spond to the methylene -CH2 group, and the C-H chain and
the peak at about 1104 cm−1 belong to the Si–O-Si bond.
Also, in the IR spectrum of the Fe3O4@SiO2@PAMAM-
G0.5 (G0.5) and Fe3O4@SiO2@PAMAM-G1.5 (G1.5),
bands at 1737 and 1732 cm−1, are related to the carbonyl
group of esters. In generations Fe3O4@SiO2@PAMAM-
G1 (G1) and Fe3O4@SiO2@PAMAM-G2 (G2), this peak
(C=O) is removed. The characteristic band 1625 cm−1 is
Catalyst characterizations
In the IR spectrum of Fe3O4 magnetic nanoparticles, peaks
at 561, 1622, and 3418 cm−1 corresponding to Fe–O and
hydroxyl groups on the surface of Fe3O4 (Fig. 1A). The
peak around 1094 cm−1 in Fig. 1B is assigned to the Si–O
Scheme 2 Synthesis of
magnetic cored amino group
terminated dendrimer
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Journal of the Iranian Chemical Society
Fig. 1 FT-IR spectra of (A)
Fe3O4, (B) Fe3O4@SiO2, and
(C) Fe3O4@SiO2@Pr-NH2
in the left; Fe3O4@SiO2@
PAMAM-G2 in diferent
generations from G0.5-G2 in the
right
for the group –CO–NH. These results indicated that the
Michael addition and amidation reactions were success-
fully performed, and the PAMAM dendrimer through the
covalent bonding was successfully grafted onto magnetic
nanoparticles.
The X-ray powder difraction analyses of nanoparticles
were performed to identify the crystal structure. All refec-
tion peaks in the Fe3O4@SiO2@PAMAM-G2 within the 2θ
range 25–65° were recorded (Fig. 2b). The characteristic
peaks at 2θ = 30.1°, 35.4°, 43.1°, 53.4°, 57.0°, and 62.6°
were observed, which are in agreement with the XRD peaks
of Fe3O4 nanoparticles. Also, the X-ray difraction (XRD)
pattern of recycled Fe3O4@SiO2@PAMAM-G2 is shown in
Fig. 2c. To confrm that the Fe3O4 is stable, after fve runs
of recyclability, we compared the XRD of fresh and reused
Fe3O4@SiO2@PAMAM-G2 after fve runs with the XRD of
standard Fe3O4 (Fig. 2a). The results shows XRD of fresh
Fe3O4@SiO2@PAMAM-G2 is similar to XRD of standard
Fe3O4, and also there is almost no change after fve perfor-
mance run compared to peaks of standard Fe3O4, in terms
of position and intensity of peaks.
The TEM analysis was used to investigate the morphol-
ogy, size and distribution of the Fe3O4@SiO2@PAMAM-
G2. The TEM image of the catalyst in Fig. 3 clearly shows
core–shell structure, with Fe3O4@SiO2 as the core and
Fig. 2 XRD spectrum of a Fe3O4, b fresh Fe3O4@SiO2@PAMAM-
G2 and c Fe3O4@SiO2@PAMAM-G2 after fve cycles
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Journal of the Iranian Chemical Society
Fig. 3 a TEM image of Fe3O4@SiO2@PAMAM-G2. b TEM image of Fe3O4@SiO2@PAMAM-G2 after fve cycles
Fig. 4 EDX pattern of Fe3O4@
SiO2@PAMAM-G2
polyamidoamine (PAMAM) dendrimer as the shell. The
efect of recycling process on nanoparticle distribution was
also investigated via TEM analysis (Fig. 3b). The results
revealed that recycling process has not changed the morphol-
ogy and size of the nanoparticles.
The chemical identity of Fe3O4@SiO2@PAMAM-G2
was confrmed by EDX analysis (Fig. 4). The EDX spec-
trum shows peaks of elements Fe (24.27%), Si (9.46%),
O (41.89%), N (4.09%), and C (20.3%) which is given in
Fig. 4 as components of the synthesized Fe3O4@SiO2@
PAMAM-G2.
The thermal stability of magnetic cored amino group
terminated dendrimer was evaluated by TGA (Fig. 5). As
it is seen in this curve, at the range of 50–700 °C, there are
Fig. 5 TGA analysis of Fe3O4@SiO2@PAMAM-G2
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Journal of the Iranian Chemical Society
Table 1 Optimization of
Entry
Catalyst (g)
Conditions
Time (min)
Yielda (%)
Reaction Conditions for 3a
1
2
3
4
5
6
7
8
Fe3O4@SiO2@PAMAM-G2 (0.006 g)
Fe3O4@SiO2@PAMAM-G2 (0.006 g)
Fe3O4@SiO2@PAMAM-G2 (0.006 g)
Fe3O4@SiO2@PAMAM-G2 (0.006 g)
Fe3O4@SiO2@PAMAM-G2 (0.006 g)
Fe3O4@SiO2@PAMAM-G2 (0.006 g)
Fe3O4@SiO2@PAMAM-G2 (0.006 g)
Fe3O4@SiO2@PAMAM-G2 (0.005 g)
Fe3O4@SiO2@PAMAM-G2 (0.004 g)
Fe3O4@SiO2@PAMAM-G2 (0.007 g)
Fe3O4@SiO2 (0.006 g)
Solvent-free/50 °C
Water/50 °C
Toluene/50 °C
Ethanol/50 °C
Solvent-free/rt
Solvent-free/40 °C
Solvent-free/60 °C
Solvent-free/50 °C
Solvent-free/50 °C
Solvent-free/50 °C
Solvent-free/50 °C
Solvent-free/50 °C
30
30
30
30
30
30
30
30
30
30
30
30
95
40
10
64
40
79
95
86
75
93
9
10
11
12
b
–
c
b
–
–
b
c
aIsolated yield; No product 3a observed; This reaction was carried out in the absence of Fe3O4@SiO2@
PAMAM-G2
several decomposition steps for the composition of Fe3O4@
SiO2@PAMAM-G2. The loss of weight at the temperature
of 150 to 570 °C, is related to the decomposition of the
PAMAM dendrimer from the Fe3O4@SiO2 surface. At the
frst decomposition step (at the temperatures under 150 °C),
a weight loss of 3.5% can be assigned to the removal of
physically adsorbed water and surface hydroxyl groups. A
second steady mass loss (about 13 wt%) occurred between
150 and 570 °C possibly attributed to the organic group’s
decomposition.
the catalyst (Table 1, entry 11) which confrms catalyst plays
an important role in the reaction progress.
A probable mechanism for the reaction is indicated in
Scheme 3. The Knoevenagel condensation is occurred by
nucleophilic attack of activated malononitrile to iminium ion
to produce the 2-benzylidenemalononitrile [37].
To illustrate the applicability of this reaction, the direct
reaction worked well with a variety of aryl aldehydes
including those bearing electron-donating and electron-
withdrawing groups such as OH, Me, OMe, Cl, (Me)2N,
and NO2, and the desired compounds were obtained in
high-to-excellent yields (Table 2). Furthermore, the het-
eroaromatic and aliphatic aldehyde reacted smoothly with
malononitrile in the presence of Fe3O4@SiO2@PAMAM-
G2 (Table 2, entries 12–14). Encouraged by the observa-
tions, the condensation was studied using terephthalalde-
hyde. The bis-substituted derivative was produced in 90%
yield, when 2.5 mmol of malononitrile was used (Table 2,
entry 15).
Catalytic study
After synthesis and characterization of the magnetic
cored amino group terminated dendrimer (Fe3O4@SiO2@
PAMAM-G2), its catalytic performance was investigated in
reaction condensation between aldehydes with malononi-
trile. For this purpose, 0.006 g of magnetic nanocatalyst was
added to a mixture of benzaldehyde (1 mmol) and malon-
onitrile (1.2 mmol) at 50 °C under solvent-free conditions.
Then, the mixture was stirred for an appropriate time in an
oil bath, and the reaction was monitored by TLC. After the
completion of the reaction, the product was purifed (experi-
mental section). In order to obtain the best conditions for our
reaction, we optimized the parameters as listed in Table 1.
The excellent route was in the presence of 0.006 g of mag-
netic nanocatalyst under the solvent-free condition at 50 °C
(Table 1, entry 1). No product was found in the absence of
Reusability study
The reusability of the Fe3O4@SiO2@PAMAM-G2 was
studied in the model reaction under optimized conditions.
At the end of the reaction, the catalyst was separated by an
external magnetic feld and then was washed with ethanol
and dried. Results indicated that the recycled nanocata-
lyst was reused in at least fve condensation reaction runs
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Journal of the Iranian Chemical Society
Scheme 3 Possible mechanism
for the synthesis of benzylidene
malononitrile derivatives in
the presence of Fe3O4@SiO2@
PAMAM-G2
without signifcant loss of its catalytic activity as shown
in Fig. 6.
for similar condensation (Table 3). As it can be seen, this
catalyst has equal or slightly higher efciency than other
catalysts.
Finally, the catalytic performance of Fe3O4@SiO2@
PAMAM-G2 was compared to catalysts previously reported
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Journal of the Iranian Chemical Society
Table 2 Catalytic efciency of
the magnetic cored amino group
terminated dendrimer (Fe3O4@
SiO2@PAMAM-G2) for the
synthesis of 2-benzylidene
malononitrile derivatives under
solvent-free condition
Entry
1
Products
Yielda (%)
95
Time (min)
30
mp (°C)
Found
Lit.
81–8223
80–81
(3a)
2b
92
89
30
30
102–104
159–161
101–10327
161–16227
(3b)
3b
(3c)
4
93
30
114–115
113–11427
(3d)
5
6
88
83
20
25
101–103
79–80
102–10440
80–8127
(3e)
(3f)
7b
84
90
25
20
85–87
84–8632
(3g)
8b
164–166
162–16323
(3h)
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Journal of the Iranian Chemical Society
Table 2 (continued)
Entry
9b
Products
Yielda (%)
80
Time (min)
mp (°C)
Found
Lit.
40
147–149
134–136
148–15040
(3i)
10
83
85
50
137–13827
179–18023
(3j)
11b
50
180–182
(3k)
12
13
89
87
20
25
96–97
83–85
95–9637
84–8640
(3l)
(3m)
14
82
90
50
25
124–125
266–268
122–12327
260–26239
(3n)
15b,c
(3o)
aIsolated yields; b5 drops of ethanol was used; cterephthalaldehyde (1 mmol), and malononitrile (2.5 mmol)
were used
is confirmed with FT-IR, XRD, FE-SEM, EDS, TGA,
Conclusions
and TEM. The benefts of this reaction including; good to
excellent yields, decrease reaction times, simple work-up,
and reusable for fve times without any signifcant loss of
activity.
In conclusion, we have developed a novel, efcient, and
green method for synthesis of benzylidene malononitrile
derivatives by magnetic Fe3O4@SiO2@PAMAM-G2 which
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Journal of the Iranian Chemical Society
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1
2
3
4
5
9. B. Maleki, N. Nasiri, R. Tayebee, A. Khojastehnezhad, H.A.
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Runs
10. K. Esumi, Dendrimers for nanoparticle synthesis and dispersion
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Fig. 6 Reusability of Fe3O4@SiO2@PAMAM-G2
Table 3 Comparison of
Entry
Conditions
Time (min)
Yield (%)
Methods for the Synthesis of
benzylidene malononitrile
derivatives
3a
Fe3O4@SiO2@PAMAM-G2/Solvent-free/50 °C (Present work)
RE(72%)NaY/CH3CN/rt22
30
720
90
20
360
60
95
78
91
93
16
75
90
93
100
82
73
93
99
92
93
88
68
91
94
94
75
90
95
88
87
97
CTMAB/H2O/rt23
MgO/ZrO2/Solvent-free/60°C24
Znß/Solvent-free/140°C25
PVC-TEPA/EtOH/refux26
Na2S/Al2O3/CH2Cl2/refux27
20
MgF2/EtOH/rt28
150
900
50
60
12
120
90
30
90
20
60
10
90
900
60
300
30
120
90
Ni–SiO2/Toluene/refux29
C/Z-30/70/EtOH/refux30
Fe3O4@UiO-66-NH2-3/DMF/80°C36
Fe3O4@SiO2-3N/Water/75°C37
Fe3O4@P4VP@ZIF-8/Toluene/23°C38
Fe3O4@SiO2@Ni-Zn-Fe/EtOH/refux40
Fe3O4@SiO2@PAMAM-G2/Solvent-free/50 °C (Present work)
CTMAB/H2O/rt23
3d
MgO/ZrO2/Solvent-free/60°C24
PVC-TEPA/EtOH/refux26
Na2S/Al2O3/CH2Cl2/refux27
MgF2/EtOH/rt28
Ni–SiO2/Toluene/refux29
La2O3–MgO/KOH/Solvent-free/rt31
Fe3O4@guanidine/PEG:H2O/rt32
Fe3O4@SiO2-3N/Toluene/75°C37
Fe3O4@P4VP@ZIF-8/Toluene/23°C38
Fe3O4@SiO2@Ni-Zn-Fe/EtOH/refux40
1 3

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