Poly N,N-dimethylaniline-formaldehyde supported on silica-coated magnetic nanoparticles: a novel and retrievable catalyst for green synthesis of 2-amino-3-cyanopyridines

Article abstract of DOI:10.1007/s11164-017-3200-4

Preparation and application of novel and reusable magnetic nanoparticles with poly N,N-dimethylaniline-formaldehyde support as a heterogeneous basic catalyst have been described. The reported catalyst was characterized by Fourier transform infrared spectr

Full text of DOI:10.1007/s11164-017-3200-4

Res Chem Intermed
https://doi.org/10.1007/s11164-017-3200-4
Poly N,N-dimethylaniline-formaldehyde supported
on silica-coated magnetic nanoparticles: a novel
and retrievable catalyst for green synthesis of 2-amino-
3-cyanopyridines
Sajad Asadbegi1 Mohammad Ali Bodaghifard1,2
•
•
Akbar Mobinikhaledi1
Received: 14 July 2017 / Accepted: 11 November 2017
Ó Springer Science+Business Media B.V., part of Springer Nature 2017
Abstract Preparation and application of novel and reusable magnetic nanoparticles
with poly N,N-dimethylaniline-formaldehyde support as a heterogeneous basic
catalyst have been described. The reported catalyst was characterized by Fourier
transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction
patterns, transmission electron microscopy, energy dispersive X-ray spectroscopy,
thermogravimetric analysis and vibrating sample magnetometry. The catalytic
performance of this organic-inorganic hybrid nanomaterial has been studied for the
green synthesis of 2-amino-3-cyanopyridine derivatives through one-pot four-
component reactions. An eco-friendly method, short reaction time, high yield and
easy work-up procedure are the advantages of this new methodology over earlier
ones.
Keywords 2-Amino-3-cyanopyridines Á Magnetic nanoparticles Á Multi-component
reactions Á Green synthesis
Introduction
Nitrogen-containing heterocycles play important roles in biology. They have an
important place among natural and synthetic products because of their special
properties as key elements of various drugs [1]. The pyridine nucleus has appeared
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11164-
017-3200-4) contains supplementary material, which is available to authorized users.
&
Mohammad Ali Bodaghifard
mbodaghi2007@yahoo.com; m-bodaghifard@araku.ac.ir
1
2
Department of Chemistry, Faculty of Science, Arak University, Arak 38156-88349, Iran
Institute of Nanosciences and Nanotechnology, Arak University, Arak 38156-88349, Iran
123

S. Asadbegi et al.
as a privileged scaffold in view of its spread in numerous pharmaceuticals, natural
products and functional materials [2, 3]. Pyridines are also involved in supramolec-
ular structures [4], materials and surfaces [5], coordination chemistry [6] and
organocatalysis [7]. Polysubstituted pyridines are significant because such scaffolds
constitute structures of many organic functional materials and natural products
[8, 9].
Among them, 2-amino-3-cyanopyridine derivatives have attracted important
attention due to their biological activities such as antibacterial [10], antiviral [11],
antimicrobial [12], antifungal [13], anti-inflammatory [14] and antitumor [15]
properties. They are known as adenosine receptor antagonists, potent inhibitors of
HIV-1 integrase [16], IKK-b inhibitors [17] and antiexcitotoxic agents [18].
Therefore, development of synthetic methodologies for the preparation of 2-amino-
3-cyanopyridine derivatives from readily available substrates under mild reaction
conditions continues to attract much interest in organic chemistry [19].
The synthetic methods for preparation of numerous types of 2-amino-3-
cyanopyridine derivatives include utilization of corresponding 2-chloro derivatives
as substrates [20], reaction of chalcones with ammonium acetate [21], condensation
of arylidene malononitrile, ketones and ammonium acetate [22] and one-pot four-
component reactions [23–28]. However, some of these reported procedures have
limitations such as the use of toxic solvents [18], expensive metal catalysts [2],
harsh reaction conditions [29] and complicated reaction and work-up procedures
[30].
Heterogeneous catalysis is of superb importance in several areas of the energy-
consuming and chemical industries [31–33]. Nanocatalysts are more efficient than
normal heterogeneous catalysts due to their extremely small size and great surface
area-to-volume ratio [34]. In the past decade, considerable attention has been paid to
the Fe3O4 magnetic nanoparticles (MNPs) in several different fields due to their
unrivaled properties such as biocompatibility, low toxicity, high surface area,
superparamagnetic behavior and adaptability for large-scale production [35, 36].
Above all, the Fe3O4 MNPs are simply produced and can be easily separated by an
external magnet from the reaction mixture and reused [37]. Due to the strong
dipole–dipole attraction, pure Fe3O4 MNPs tend to form large aggregates. Large
cluster formations have limited functional groups and lose their special properties
[38]. Coating a silica layer on MNPs improves the performance and stability of
these nanomaterials [39, 40]. Furthermore, functionalization of silica-coated
nanoparticles can be conjugated with a range of various chemical entities and
promote their use in numerous chemical processes [41–45]. In our continued interest
on preparation and application of functionalized MNPs [46–48], we wish to report a
highly efficient process for the synthesis of 2-amino-3-cyanopyridine derivatives via
one-pot multi-component reactions using novel and designed poly N,N-dimethy-
laniline-formaldehyde supported on silica-coated Fe3O4 MNPs (PDMAF-MNPs) as
a catalyst under green conditions (Scheme 1).
123

Poly N,N-dimethylaniline-formaldehyde supported on silica…
PDMAF-MNPs
Scheme 1 The synthesis of 2-amino-3-cyanopyridine derivatives using novel poly N,N-dimethylaniline-
formaldehyde supported on silica-coated Fe3O4 magnetic nanoparticles (PDMAF-MNPs) as an efficient
catalyst
Results and discussion
Characterization of novel PDMAF-MNPs catalyst
PDMAF supported on silica-coated MNPs was prepared via the procedure
demonstrated in Scheme 2. Fourier transform infrared (FT-IR) spectroscopy, field
emission scanning electron microscopy (FE-SEM), energy dispersive X-ray
spectroscopy (EDS), transmission electron microscopy (TEM), vibrating sample
magnetometry (VSM), X-ray diffraction (XRD) and thermogravimetric analysis
(TGA) were used to identify and characterize the green, mild, safe and novel
magnetic catalyst.
The FT-IR of bare Fe3O4 MNPs, Fe3O4@SiO2 core–shell MNPs (silica-coated
MNPs), Fe3O4@SiO2-pr-NH2 (3-aminopropyl-functionalized silica-coated MNPs)
and PDMAF-MNPs are shown in Fig. 1. In curve 1a, the spectrum of Fe3O4
nanoparticles relevant to the bending vibration of Fe–O shows an absorption around
578 cm-1. Absorption bond appearance at 1096 cm-1 (asymmetric stretching),
955 cm-1 (symmetric stretching), 815 cm-1 (in-plane bending) and 457 cm-1
(rocking mode) for the Si–O–Si group confirms the formation of an SiO2 shell
(Fig. 1b). The twisting vibration mode of H–O–H adsorbed in the silica shell
displays a weak band at 1615 cm-1, and the stretching vibration mode of Si–OH
appeared as a broad band in the range 3200–3500 cm-1. Alkyl group moieties are
confirmed by the weak bands at 2935 and 2960 cm-1 related to C–H symmetric and
asymmetric stretching modes (Fig. 1c, d). Furthermore, bands appearing at
1450–1650 cm-1 (C=C in aromatic rings) indicate formation of PDMAF (Fig. 1d).
123

S. Asadbegi et al.
PDMAF-MNPs
Scheme 2 Preparation of novel poly N,N-dimethylaniline-formaldehyde supported on silica-coated
Fe3O4 magnetic nanoparticles (PDMAF-MNPs)
Fig. 1 The FT-IR spectrum of a Fe3O4, b Fe3O4@SiO2, c Fe3O4@SiO2-pr-NH2 and d PDMAF-MNPs
Therefore, the achieved results show that the materials are added in each section and
the MNP catalyst is formed successfully.
FE-SEM was used to determine the size and morphology of the prepared
PDMAF-MNPs catalyst (Fig. 2a). PDMAF-MNPs, as can be seen in Fig. 2a, have a
mean diameter of about 20–30 nm and have a nearly spherical shape, indicating the
nanocatalyst has a large surface area. TEM analysis shows a grey silica shell about
5–10 nm thick on a dark Fe3O4 core which indicates silica is successfully anchored
to the MNPs, and the average size of the synthesized nanoparticles is 15–30 nm
(Fig. 2b).
123

Poly N,N-dimethylaniline-formaldehyde supported on silica…
Fig. 2 a FE-SEM image and b TEM image of PDMAF-MNPs
EDS analysis indicates the presence of N and C in the PDMAF-MNPs (Fig. 3).
Additionally, the presence of Si, O and Fe signals confirms that the iron oxide
particles are loaded into the silica. The higher intensity of the Si and O peaks
compared with the Fe peaks indicates that the Fe3O4 nanoparticles were trapped by
SiO2.
The crystalline structures of Fe3O4 and PDMAF-MNPs were studied by XRD
(Fig. 4). The relative intensities and position of all peaks agree well with the
standard XRD pattern of Fe3O4 (JCPDS card no. 85-1436), indicating retention of
the crystalline cubic spinel structure during the silica coating procedure and
123

S. Asadbegi et al.
Fig. 3 EDS spectrum of PDMAF-MNPs nanocatalyst
Fig. 4 XRD patterns of a Fe3O4 MNPs and b PDMAF-MNPs
functionalization of MNPs. The characteristic peaks at 2h = 30.2°, 35.7°, 43.2°,
53.6°, 57.1°, 62.8° and 74.4° for pure Fe3O4 nanoparticles, which were marked
respectively by their indices (220), (311), (400), (422), (511), (440) and (533) were
also observed for Fe3O4 and PDMAF-MNPs [49]. This shown that modification on
the surface of Fe3O4 nanoparticles did not lead to their phase change. The mean size
of the crystallites was calculated by applying Scherrer’s equation: D = 0.9k/b cosh,
where k is the wavelength of the X-rays, b is the broadening of the diffraction line
measured at half of its maximum intensity in radians, h is the Bragg diffraction
˚
angle and D is the average diameter in A. The peak at 2h = 35.7° is selected to
calculate the crystallite size, according to the result calculated by Scherrer’s
equation, it is found that the diameter of PDMAF-MNPs obtained is about 21 nm
which is in the range determined using FE-SEM and TEM analysis (Fig. 2).
The TGA curve of PDMAF-MNPs showed an initial weight loss up to 235 °C,
which was attributed to the removal of physically adsorbed solvent and surface
hydroxyl groups (Fig. 5). The major weight loss beyond about 235 °C to nearly
575 °C is attributed to the decomposition of the organic moiety in the
123

Poly N,N-dimethylaniline-formaldehyde supported on silica…
Fig. 5 TGA curves of PDMAF-MNPs
nanocomposite. Therefore, the catalyst is reasonably stable up to 235 °C and it is
safe to carry out the reaction under heterogeneous conditions. And so, this weight
loss step gives the organic supported ratios of the magnetic catalyst and the PDMAF
supported on the Fe3O4@SiO2 MNPs was approximately 21 wt%.
The magnetic properties of Fe3O4 MNPs and PDMAF-MNPs were characterized
by VSM. Figure 6 shows the typical room temperature magnetization curves of bare
Fe3O4 MNPs (Fig. 6a), and PDMAF-MNPs (Fig. 6b). The hysteresis curve allows
determination of the coercivity (Hc), remanent magnetization (Mr) and saturation
magnetization (Ms). The magnetization of samples could be completely saturated at
high fields of up to
8000.0 Oe and the Ms of samples changes from 53.5 to
31.1 emu g-1 due to the formation of a silica shell and organic layer around the
Fe3O4 core. The hysteresis loops show the superparamagnetic behaviour of the
Fe3O4 and PDMAF-MNPs in which Mr and Hc are close to zero (Mr = 0.85 and
1.15 emu g-1 and Hc = 6.50 and 11.85 Oe, respectively) [50].
Fig. 6 Magnetic hysteresis loops of a Fe3O4 MNPs and b PDMAF-MNPs
123

S. Asadbegi et al.
Synthesis of 2-amino-3-cyanopyridine derivatives catalysed by PDMAF-
MNPs
After characterization of the prepared PDMAF-MNPs, the catalytic activity of this
nanomaterial was examined in the synthesis of 2-amino-3-cyanopyridine deriva-
tives. To find the suitable reaction conditions, a one-pot four-component reaction of
benzaldehyde 1a (1 mmol), cyclohexanone 2a (1 mmol), malononitrile 3 (1 mmol)
and ammonium acetate 4 (1.5 mmol) was selected and examined as a model under a
variety of conditions.
We used different solvents like acetonitrile, EtOH, THF and H2O under reflux
conditions. Results showed that ethanol serves as the best solvent with respect to
having a green nature, polarity and clean workup procedure for this synthesis
(Table 1, entry 2). For the synthesis completion, various amounts of PDMAF-MNPs
displayed that 40 mg of the nanocatalyst is sufficient (Table 1, entry 5). By
lowering the reaction temperature, the yield of the product was decreased to 68%
(Table 1, entry 8). To define the role of PDMAF-MNPs as a catalyst for the
preparation of 2-amino-3-cyanopyridine derivatives, the model reaction was carried
out with Fe3O4, Fe3O4@SiO2, N,N-dimethylaniline and without the catalyst
(Table 1, entries 9–12). With respect to yield of product and reaction time, the
best results are attained using PDMAF-MNPs as the catalyst.
Table 1 Optimization of reaction conditions for synthesis of 2-amino-3-cyanopyridine derivatives
Entry
Catalyst (mg)
Solvent
Temp. (°C)
Time (h)
Yield (%)a
1
PDMAF-MNPs (20)
PDMAF-MNPs (20)
PDMAF-MNPs (20)
PDMAF-MNPs (20)
PDMAF-MNPs (40)
PDMAF-MNPs (60)
PDMAF-MNPs (40)
PDMAF-MNPs (40)
–
CH3CN
EtOH
THF
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
50
3
75
86
78
71
92
88
87
68
51
82
81
75
2
3
3
3
4
H2O
3
5
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
2.5
2.5
4
6
7
8
r.t.
7
9
Reflux
Reflux
Reflux
Reflux
6
10
11
12
N,N-dimethylaniline
Fe3O4
2
2.5
2.5
Fe3O4@SiO2
Reaction conditions: benzaldehyde (1 mmol), malononitrile (1 mmol), cyclohexanone (1 mmol),
ammonium acetate (1.5 mmol)
aIsolated yield; r.t. room temperature
123

Poly N,N-dimethylaniline-formaldehyde supported on silica…
Table 2 The synthesis of 2-amino-3-cyanopyridines using PDMAF-MNPs as a catalyst
Entry Aldehyde
Ketone
Product Time Yield M.p. (°C) [Lit.
(h)
(%)a Refs.]
1
2
3
4
5
6
Benzaldehyde
Cyclohexanone 5a
Cyclohexanone 5b
Cyclohexanone 5c
Cyclohexanone 5d
Cyclohexanone 5e
Cyclopentanone 5f
2.5
92
86
93
92
89
91
237–239
[234–235] [22]
4-
Dimethylaminobenzaldehyde
3
245–247
3-Nitrobenzaldehyde
4-Chlorobenzaldehyde
4-Methoxybenzaldehyde
Benzaldehyde
2
231–233
[230–232] [51]
2
254–256
[258–259] [52]
3
238–240
[232–234] [25]
2.5
225–227
[220–221] [24]
7
8
9
4-Chlorobenzaldehyde
Cyclopentanone 5g
Cyclopentanone 5h
Cyclopentanone 5i
2
3
3
88
85
87
244–246
230–232
234–236
2,4-Dichlorobenzaldehyde
4-
Dimethylaminobenzaldehyde
10
11
4-Methoxybenzaldehyde
Cyclopentanone 5j
Cycloheptanone 5k
3
90
88
220–222
[217–218] [22]
Benzaldehyde
2.5
221–223
[227–228] [53]
12
13
14
15
3-Nitrobenzaldehyde
Cycloheptanone 5l
Cycloheptanone 5m
Cycloheptanone 5n
Cycloheptanone 5o
2
3
2
3
90
78
85
83
213–215
228–230
234–236
2,4-Dichlorobenzaldehyde
4-Chlorobenzaldehyde
4-Methoxybenzaldehyde
223–225
[225–227] [25]
16
17
18
19
20
21
22
23
24
Benzaldehyde
Acetophenone
Acetophenone
Acetophenone
Acetophenone
Acetophenone
2-Butanone
5p
5q
5r
5s
1.5
2
89
85
82
86
87
85
87
77
79
181–183
[176–177] [54]
4-Chlorobenzaldehyde
4-Methoxybenzaldehyde
4-Nitrobenzaldehyde
4-Methylbenzaldehyde
Benzaldehyde
234–236
[233–235] [55]
2
179–181
[177–180] [56]
1
222–224
[223–225] [57]
5t
2
164–166
[160–161] [54]
5u
5v
5w
5x
3
240–241
[240–241] [24]
2-Chlorobenzaldehyde
4-Methoxybenzaldehyde
4-Bromobenzaldehyde
2-Butanone
2.5
3.5
2.5
252–254
[251–252] [53]
2-Butanone
276–277
[275–277] [2]
2-Butanone
265–266
[265–266] [24]
123

S. Asadbegi et al.
Table 2 continued
Entry Aldehyde
Ketone
Product Time Yield M.p. (°C) [Lit.
(h)
(%)a Refs.]
25
4-Methylbenzaldehyde
2-Butanone
5y
3.5
74
256–258
[259–260] [22]
The bracketed values are reported melting points in literature
Reaction conditions: aldehyde (1 mmol), malononitrile (1 mmol), ketone (1 mmol), ammonium acetate
(1.5 mmol)
aIsolated yield; M.p. melting point
With the optimized reaction conditions in hand, we then assessed the substrate
scope of this reaction. As shown in Table 2, various aldehydes reacted with
malononitrile, ammonium acetate and ketone derivatives to give the corresponding
2-amino-3-cyanopyridines with good to excellent yields under optimized condi-
tions. Arylaldehydes with electron-donating or electron-withdrawing groups could
lead to the favored products 5a–y. Aliphatic aldehydes were also used, but did not
afford the desired products. As detailed in Table 2, electron-donating groups
decrease the rate and hence increase the time of reaction, and electron-withdrawing
groups increase the rate and decrease the reaction’s time.
A possible mechanism for the synthesis of 2-amino-3-cyanopyridines catalysed
with PDMAF-MNPs is shown in Scheme 3. The formation of 2-amino-4-phenyl-
5,6,7,8-tetrahydroquinoline-3-carbonitrile (5a) can be rationalized by the initial
formation of benzylidenemalononitrile (I) as an intermediate via the standard
Knoevenagel condensation of benzaldehyde and malononitrile in the presence of
PDMAF-MNPs as a catalyst. Michael addition of cyclohexanone (2a) to the
activated double bond of the (I) provides adduct (II). Next, a nucleophilic attack of
ammonium acetate (4) on the carbonyl group of (III) affords the intermediate (IV).
Intramolecular cyclization of these intermediates following oxidation produced the
target product (5a).
Scheme 3 Possible mechanism for the synthesis of compound 5a using PDMAF-MNPs
123

Poly N,N-dimethylaniline-formaldehyde supported on silica…
Table 3 Comparison of PDMAF-MNPs with other catalysts described in the literature for the synthesis
of 2-amino-4-phenyl-5,6,7,8-tetrahydroquinoline-3-carbonitrile
Entry Catalyst
Condition
Time Yielda
(%)
Refs.
1
2
3
4
5
6
7
8
Fe3O4/cellulose nanoparticles
EtOH (r.t.)
3
90
90
66
92
[25]
[58]
[22]
[2]
Au/MgO
EtOH (70)
2.5
4
–
Benzene (reflux)
EtOH (reflux)
Neat (80)
[Yb(PFO)3]
Fe3O4 nanoparticles
Graphene oxide
Cu/C nanocatalyst
4
2.15 86
[26]
[27]
[54]
[51]
Water (80)
5
8
4
86
84
82
Acetonitrile (80)
Ionic liquid (r.t.)
1-Butyl-3-methylimidazolium
hydroxide
9
–
Trifluoroethanol
(reflux)
6
80
92
[55]
10
PDMAF-MNPs
EtOH (reflux)
2.5
Present
work
Reaction conditions: benzaldehyde (1 mmol), malononitrile (1 mmol), cyclohexanone (1 mmol),
ammonium acetate (1.5 mmol)
aIsolated yields; r.t. room temperature
To compare the applicability of our catalyst with other catalysts used for the
synthesis of 2-amino-3-cyanopyridine derivatives, the results of these catalysts in
the condensation reaction of benzaldehyde, malononitrile, cyclohexanone and
ammonium acetate under optimized conditions have been tabulated in Table 3. As
can be seen, the catalytic system reported in this paper has benefits in terms of
simple conditions, short reaction times and excellent yields.
Catalyst recovery and reusability
Recyclability of this magnetic nanocatalyst was studied in the relation between
benzaldehyde (1 mmol), malononitrile (1 mmol), cyclohexanone (1 mmol) and
ammonium acetate (1.5 mmol). After accomplishment of the reaction, the
nanocatalyst was recovered easily using an external magnet, washed successively
with EtOH, double-distilled water and then dried. The catalyst could be used at least
six times without significant loss of activity (Fig. 7). The XRD and FT-IR studies of
the catalyst after six runs confirmed its stability. The recovered catalyst had no
distinct change in structure, as apparent from a comparison of its XRD and FT-IR
spectra with that of fresh catalyst (Fig. 8).
123

S. Asadbegi et al.
Fig. 7 Recyclability of PDMAF-MNPs in the synthesis of 2-amino-3-cyanopyridines
Fig. 8 a XRD and b FT-IR spectra of fresh catalyst and that reused six times
Conclusions
In this study, a green and efficient process has been developed for synthesis of
2-amino-3-cyanopyridine derivatives using PDMAF-MNPs as a novel, efficient and
recyclable magnetic catalyst. The nanocatalyst was characterized using FT-IR
spectroscopy, FE-SEM, XRD, TEM, VSM, EDS and TGA. The noticeable features
123

Poly N,N-dimethylaniline-formaldehyde supported on silica…
of this method are simple workup procedure, short reaction time and high yield.
Various ketones and aromatic aldehydes led to the corresponding 2-amino-3-
cyanopyridines in good to excellent yields. In all reactions, the catalyst could be
easily isolated using an external magnetic field and recovered for six times without
significant loss of activity.
Experimental
General procedure for preparation of PDMAF-MNPs
In the beginning, Fe3O4 MNPs were synthesized by using the chemical co-
precipitation of Fe3? and Fe2? ions as defined in the literature [59]. Typically,
FeCl3Á6H2O (10 mmol) and FeCl2Á4H2O (5 mmol) were dissolved in 100 ml of
deionized water. The mixture was heated in an N2 atmosphere and at a temperature
of 80 °C for 1 h, and then 10 ml of concentrated ammonia (25%) was quickly
injected into the reaction mixture in one portion. The solution was stirred under N2
for another 1 h and then cooled to room temperature. The black precipitate was
collected by magnetic decantation, washed with distilled water until neutrality,
washed and dried at 60 °C under vacuum. Surfaces of the MNPs with a layer of
¨
silica were covered by using the Stober method [60]. Fe3O4 MNPs (1.0 g) were
homogeneously dispersed with 25 wt% concentrated aqueous ammonia solution
(1.5 ml) in a mixture of ethanol (40 ml) followed by the addition of 1.4 ml of
tetraethylorthosilicate (TEOS). After stirring for 12 h under an N2 atmosphere at
room temperature, the Fe3O4@SiO2 was isolated from the solution, washed and
dried at 25 °C under vacuum. In the following, aminopropyl-modified silica-coated
Fe3O4 MNPs were synthesized according to the described procedure [61]. In 50 ml
of dry toluene, 1.0 g of Fe3O4@SiO2 MNPs was dispersed using an ultrasonic bath
to yield a uniform suspension, and using a syringe, 2.0 g of 3-aminoropropyl-
trimethoxysilane (APTS) was then added. The mixture was stirred for 48 h at 60 °C
under an N2 atmosphere. The aminopropyl-functionalized solid Fe3O4@SiO2-pr-
NH2 MNPs were washed with toluene, separated and then dried under vacuum.
Finally, N,N-dimethylaniline (5 mmol) and formaldehyde (10 mmol) dissolved in
50 ml of DMF was added to 1 g of Fe3O4@SiO2-pr-NH2 and the mixture was
refluxed for 24 h. Obtained hybrid nanoparticles named as PDMAF-MNPs were
collected, washed and dried.
General procedure for the synthesis 2-amino-3-cyanopyridines catalysed
by PDMAF-MNPs
Aldehyde (1.0 mmol), malononitrile (1.0 mmol), ketone (1.0 mmol) and ammo-
nium acetate (1.5 mmol) were dissolved in EtOH (10 ml), and PDMAF-MNPs
(40 mg) were added to a round-bottomed flask equipped with a magnetic stir bar
and a condenser. The mixture was stirred and refluxed for the appropriate time
detailed in Table 2. Progress of the reaction was monitored by thin-layer
chromatography (TLC). After completion of the reaction, the catalyst was recovered
123

S. Asadbegi et al.
from the reaction mixture by using an external magnet. The corresponding solid
product 5 was obtained with the addition of water to the mixture, and recrystallized
from EtOH affording the pure 2-amino-3-cyanopyridines. The recovered PDMAF-
MNPs were washed with EtOH, distilled water, dried under reduced pressure and
reused.
Acknowledgements We gratefully acknowledge the financial support of this work by the research
council of Arak University.
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