Methylene dipyridine nanoparticles stabilized on Fe3O 4 as catalysts for efficient, green, and one-pot synthesis of pyrazolophthalazinyl spirooxindoles

Article abstract of DOI:10.1016/j.cattod.2013.07.018

Surface functionalization of magnetic particles is an elegant way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic particles (MPs) in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation. We have conveniently loaded base groups on magnetic particles supports in which dipyridin-2-ylmethanol is used as aminating agent. The main targets are room temperature, solvent-free conditions, rapid (immediately) and easy immobilization technique, and low cost precursors for the preparation of highly active and stable MPs with high densities of functional groups. The inorganic, magnetic, solid base catalyst was characterized via Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The catalyst is active for the synthesis of pyrazolophthalazinyl spirooxindoles and the products are isolated in high to excellent yields (90-93%). Supporting this base catalyst on magnetic particles offers a simple and non-energy-intensive method for recovery and reuse of the catalyst by applying an external magnet. Isolated catalysts were reused for new rounds of reactions without significant loss of their catalytic activity.

Full text of DOI:10.1016/j.cattod.2013.07.018

Catalysis Today 217 (2013) 80–85
Contents lists available at ScienceDirect
Catalysis Today
journal homepage: www.elsevier.com/locate/cattod
Review
Methylene dipyridine nanoparticles stabilized on Fe3O4 as catalysts
for efficient, green, and one-pot synthesis of pyrazolophthalazinyl
spirooxindoles
Seyed Mohsen Sadeghzadeh∗, Mohammad Ali Nasseri
Department of Chemistry, College of Sciences, Birjand University, P.O. Box 97175-615, Birjand, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 April 2013
Received in revised form 20 July 2013
Accepted 29 July 2013
Available online 12 September 2013
Surface functionalization of magnetic particles is an elegant way to bridge the gap between heterogeneous
and homogeneous catalysis. The introduction of magnetic particles (MPs) in a variety of solid matrices
allows the combination of well-known procedures for catalyst heterogenization with techniques for
magnetic separation. We have conveniently loaded base groups on magnetic particles supports in which
dipyridin-2-ylmethanol is used as aminating agent. The main targets are room temperature, solvent-
free conditions, rapid (immediately) and easy immobilization technique, and low cost precursors for
the preparation of highly active and stable MPs with high densities of functional groups. The inorganic,
magnetic, solid base catalyst was characterized via Fourier transform infrared spectroscopy (FT-IR), X-
ray diffraction (XRD), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM) and
vibrating sample magnetometer (VSM). The catalyst is active for the synthesis of pyrazolophthalazinyl
spirooxindoles and the products are isolated in high to excellent yields (90–93%). Supporting this base
catalyst on magnetic particles offers a simple and non-energy-intensive method for recovery and reuse
of the catalyst by applying an external magnet. Isolated catalysts were reused for new rounds of reactions
without significant loss of their catalytic activity.
Keywords:
Fe3O4\methylene dipyridine
Magnetic nanoparticles
Pyrazolophthalazinyl spirooxindoles
One-pot synthesis
Green chemistry
© 2013 Elsevier B.V. All rights reserved.
Contents
1.
2.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Experimental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
2.1.
2.2.
2.3.
2.4.
2.5.
2.6.
General procedure for the preparation of Fe3O4 nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
81
General procedure for the preparation of Fe3O4\SiO2 nanoparticles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
General procedure for the preparation of Fe3O4\SiO2\3-chloropropyltriethoxysilane nanoparticles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
General procedure for the preparation of Fe3O4\SiO2\propyltriethoxysilane\methylene dipyridine nanoparticles . . . . . . . . . . . . . . . . . . . . . .
81
General procedure for the synthesis of pyrazolophthalazinyl spirooxindoles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Data for compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
2.6.1.
2.6.2.
2.6.3.
2.6.4.
2.6.5.
Compound (5a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Compound (5b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Compound (5c) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
82
Compound (5d) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Compound (5e) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
3.
Results and dscussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
3.1.
3.2.
3.3.
3.4.
3.5.
3.6.
XRD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FT-IR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermo-gravimetric analysis (TGA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Magnetic properties of the Fe3O4\SiO2\dipyridine MNP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
TEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Catalytic activity of Fe3O4\SiO2\dipyridine MNPs for the one-pot synthesis of pyrazolophthalazinyl spirooxindoles . . . . . . . . . . . . . . . . . . . . 84
82
82
∗
Corresponding author. Tel.: +98 561 2502065; fax: +98 561 2502065.
E-mail addresses: SM Sadeghzadeh@yahoo.com, sadeghzadeh sm@yahoo.com
(S.M. Sadeghzadeh).
0920-5861/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.cattod.2013.07.018

S.M. Sadeghzadeh, M.A. Nasseri / Catalysis Today 217 (2013) 80–85
81
4.
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
85
85
1. Introduction
distilled water, followed by the addition of PEG (1.0 g, MW 6000).
(2) Sodium hydroxide (NaOH) was added to the solution and the
pH value was controlled in the range 12 ≤ pH ≤ 13. (3) Different
amount of hydrazine hydrate (N2H4·H2O, 80% concentration) was
added to the above suspension. The reaction was continued for
about 24 h at room temperature. During this period, the pH value
was adjusted by NaOH and kept in the range 12 ≤ pH ≤ 13. The black
Fe3O4 NPs were then rinsed several times with ionized water.
In recent years, core–shell multi-components have attracted
intense attention because of their potential applications in catalysis
[1]. Different from single-component that can only supply people
with one function, the core–shell multi-components can inte-
grate multiple functions into one system for specific applications
[2–6]. Moreover, the interactions between different components
can greatly improve the performance of the multi-components
system and even generate new synergetic properties. Among
the core–shell structured composites, the composites with mag-
netic core and functional shell structures have received especial
attention because of their potential applications in catalysis, drug
storage/release, selective separation, chromatography, and chem-
ical or biologic sensors [7–12]. The magnetic core has good
magnetic responsibility, and can be easily magnetized. Therefore,
the composites with magnetic core can be conveniently collected,
separated or fixed by external magnet [13]. Spiro compounds
represent an important class of naturally occurring substances
characterized by highly pronounced biological properties. The
spirooxindole system is the core structure of many pharmacological
agents and natural alkaloids [14–18].
2.2. General procedure for the preparation of Fe3O4\SiO2
nanoparticles
0.02 mol of Fe3O4 MNPs were dispersed in a mixture of 80 mL of
ethanol, 20 mL of deioned water and 2.0 mL of 28 wt% concentrated
ammonia aqueous solution (NH3·H2O), followed by the addition
of 0.20 g of tetraethyl orthosilicate (TEOS). After vigorous stirring
for 24 h, the final suspension was repeatedly washed, filtered for
several times and dried at 60 ◦C in the air.
2.3. General procedure for the preparation of
Fe3O4\SiO2\3-chloropropyltriethoxysilane nanoparticles
Herein we report the fabrication of base group incorporated into
a mesoporous hyperbranched propyltriethoxysilane shell that are
coated on magnetic nanoparticles which catalyzed the synthesis
Pyrazolophthalazinyl Spirooxindoles under solvent-free conditions
at room temperature (Scheme 1).
2 mmol of Fe3O4\SiO2 MNPs and 20 mL THF were mixed
together in
a beaker, and then 20 mmol of NaH was dis-
persed in to the mixture by ultrasonication. 22 mmol 3-
chloropropyltriethoxysilane was added drop-wise at room temper-
ature and stirred for another 16 h at 60 ◦C. The resultant products
were collected and washed with ethanol and deionized water in
sequence, and then dried under vacuum at 60 ◦C for 2 h for further
use.
2. Experimental
Chemical materials were purchased from Fluka and Merck in
high purity. Melting points were determined in open capillaries
using an Electrothermal 9100 apparatus and were uncorrected.
Morphology was analyzed using transmission electron microscopy
(TEM) on a JEOL-2010. Powder X-ray diffraction data were obtained
using Bruker D8 Advance model with Cu K␣ radition. Mass spec-
tra were recorded on Shimadzu GCMS-QP5050 Mass Spectrometer.
The magnetic measurement was carried out in a vibrating sam-
ple magnetometer (VSM – 4 inch, Daghigh Meghnatis Kashan Co.,
Kashan, Iran) at room temperature. NMR spectra were recorded in
DMSO on a Bruker Advance DRX-400 MHz instrument spectrom-
eter using TMS as internal standard. IR spectra were recorded on
a Perkin Elmer 781. The purity determination of the products and
reaction monitoring were accomplished by TLC on silica gel poly-
gram SILG/UV 254 plates.
2.4. General procedure for the preparation of
Fe3O4\SiO2\propyltriethoxysilane\methylene dipyridine
nanoparticles
2 mmol of Fe3O4\SiO2\3-chloropropyltriethoxysilane were dis-
persed in a mixture of 80 mL of ethanol, 20 mL of deioned water
and 2.0 mL of 28 wt% concentrated ammonia aqueous solution
(NH3·H2O), followed by the addition of 20 mmol of compound
dipyridin-2-ylmethanol. After vigorous stirring for 24 h, the final
suspension was repeatedly washed, filtered for several times and
dried at 60 ◦C in the air.
2.5. General procedure for the synthesis of pyrazolophthalazinyl
spirooxindoles
2.1. General procedure for the preparation of Fe3O4 nanoparticles
A mixture of phthalic anhydride (1 mmol), isatin (1 mmol), mal-
ononitrile (1 mmol), hydrazine (1 mmol), and Fe3O4\dipyridine
MNPs (0.0008 g) was stirred at room temperature under solvent-
free conditions for 50 min. Upon completion, the progress of the
The synthesis procedure is illustrated as follows: (1) 0.01 mol
FeCl2·4H2O and 0.03 mol FeCl3·6H2O were dissolved in to 200 mL
Scheme 1. Synthesis of pyrazolophthalazinyl spirooxindoles catalyzed by Fe3O4\methylene dipyridine at room-temperature under solvent-free.

82
S.M. Sadeghzadeh, M.A. Nasseri / Catalysis Today 217 (2013) 80–85
reaction was monitored by TLC when the reaction was completed,
EtOH was added to the reaction mixture and the Fe3O4\methylene
MNPs was separated by external magnet. Then the solvent was
removed from solution under reduced pressure and the resulting
product purified by recrystallization using ethanol.
2.6.5. Compound (5e)
IR (KBr) ꢀ cm−1: 3423, 3315, 1750, 1702, 1660, 1610, 1557, 1472,
1455, 1383, 1337, 1310, 1263, 1212, 1142, 1085, 1032, 840, 775,
701; 1H NMR; ı, ppm: 11.50 (s, 1H, NH), 8.45 (s, 1H, ArH), 8.34 (d,
J = 7.5 Hz, 1H, ArH), 8.19 (d, J = 8.0 Hz, 1H, ArH), 7.99–8.03 (m, 3H,
ArH), 7.75 (br s, 2H, NH2), 7.07 (d, J = 7.5 Hz, 1H, ArH).
2.6. Data for compounds
3. Results and dscussion
2.6.1. Compound (5a)
We report the synthesis of a magnetic particle-based solid base
with a high density of methylene dipyridine base groups and dis-
cuss its performance as a novel strong and stable solid base. W were
intrigued by the possibility of applying dipyridin-2-ylmethanol and
nanotechnology for the design of a novel, active, recyclable, and
magnetically recoverable quinuclidin base derivative for the first
time (Fig. 1).
IR (KBr) ꢀ cm−1: 3439, 3350, 2209, 1756, 1678, 1653, 1465, 1364,
1257, 1163; 1H NMR; ı, ppm: 10.92 (s, 1H, NH), 8.32 (s, 2H, NH2),
8.30–8.32 (m, 1H, ArH), 7.98–8.06 (m, 3H, ArH), 7.30 (d, J = 7.0 Hz,
1H, ArH), 7.21 (t, J = 7.5 Hz, 1H, ArH), 6.88 (t, J = 7.5 Hz, 1H, ArH), 6.83
(d, J = 7.5 Hz, 1H, ArH); 13C NMR; ı, ppm: 173.0, 156.8, 153.3, 152.5,
142.5, 135.8, 134.5, 131.3, 129.5, 128.6, 128.4, 127.3, 125.7, 125.5,
123.4, 114.7, 110.8, 70.5, 60.8.
3.1. XRD
2.6.2. Compound (5b)
IR (KBr) ꢀ cm−1: 3356, 3317, 2210, 1741, 1721, 1695, 1658, 1626,
1603, 1556, 1543, 1535, 1495, 1434, 1373, 1264, 1202, 1165, 1149,
820, 702; 1H NMR; ı, ppm: 10.82 (s, 1H, NH), 8.33 (s, 2H, NH2), 8.31
(d, J = 8.0 Hz, 1H, ArH), 8.06 (d, J = 7.5 Hz, 1H, ArH), 7.98–8.03 (m, 2H,
ArH), 7.32 (s, 1H, ArH), 7.13 (d, J = 8.0 Hz, ArH), 6.82 (d, J = 8.0 Hz, 1H,
ArH), 2.24 (s, 3H, CH3); 13C NMR; ı, ppm: 172.5, 156.5, 152.5, 151.3,
139.7, 135.2, 134.5, 131.6, 130.5, 128.6, 127.8, 127.5, 127.3, 125.4,
125.4, 114.1, 110.2, 69.7, 60.6, 20.8.
The structural properties of synthesized Fe3O4\SiO2\Methylene
dipyridine MNP was analyzed by X-ray power diffraction
(XRD). As shown in Fig. 2, XRD patterns of the synthesized
Fe3O4\SiO2\methylene dipyridine nanoparticle display several rel-
atively strong reflection peaks in the 2ꢁ region of 20◦–70◦, which
is quite similar to those of Fe3O4 nanoparticles reported by other
group. The discernible six diffraction peaks in Fig. 2a can be indexed
to (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1), and (4 4 0) which match
well with the database of magnetite in JCPDS (JCPDS card No.
19-0629) file. Besides the peak of iron oxide, the XRD pattern
of Fe3O4\SiO2\methylene dipyridine core–shell nanoparticles pre-
sented a broad featureless XRD peak at low diffraction angle, which
corresponded to the amorphous state SiO2 shells (Fig. 2b) (JCPDS
card No. 29-0085).
2.6.3. Compound (5c)
IR (KBr) ꢀ cm−1: 3361, 3250, 2210, 1768, 1708, 1665, 1646, 1620,
1553, 1475, 1411, 1363, 1257, 1167, 1134, 1115, 1029, 827, 698; 1
H
NMR; ı, ppm: 11.09 (s, 1H, NH), 8.40 (s, 2H, NH2), 8.31 (d, J = 8.0 Hz,
1H, ArH), 8.01–8.09 (m, 3H, ArH), 7.73 (d, J = 2.0 Hz, 1H, ArH), 7.40
(dd, J = 8.5, 2.0 Hz, 1H, ArH), 7.00 (d, J = 8.0 Hz, 1H, ArH); 13C NMR;
ı, ppm: 172.3, 156.3, 152.7, 151.8, 141.1, 135.2, 134.6, 130.3, 128.6,
127.5, 127.4, 127.3, 127.2, 126.4, 124.8, 114.5, 111.5, 69.7, 59.1.
3.2. FT-IR
The successful synthesis of the Fe3O4\dipyridine nanoparticles
were confirmed by the FTIR spectra. Peak appeared at 3100 cm−1
,
2930 cm−1, 1090 cm−1, and 590 cm−1 are due to the stretching of
the C H aromatic group, the C H aliphatic group, O Si group, and
Fe O group in the Fe3O4\dipyridine MNP (Fig. 2c).
2.6.4. Compound (5d)
IR (KBr) ꢀ cm−1: 3392, 3358, 2218, 1757, 1699, 1661, 1622, 1611,
1571, 1552, 1481, 1443, 1375, 1275, 1260, 1162, 1145, 1124, 812,
806, 700; 1H NMR; ı, ppm: 11.09 (s, 1H, NH), 8.40 (s, 2H, NH2), 8.32
(dd, J = 8.5, 2.0 Hz, ArH), 8.00–8.09 (m, 3H, ArH), 7.80 (d, J = 2.0 Hz,
1H, ArH), 7.48 (dd, J = 8.5, 2.0 Hz, 1H, ArH), 6.90 (d, J = 8.5 Hz, 1H,
ArH); 13C NMR; ı, ppm: 172.1, 156.4, 152.7, 152.0, 141.3, 135.1,
134.3, 133.2, 128.6, 127.5, 127.6, 127.5, 127.4, 127.1, 114.5, 114.4,
112.4, 69.6, 59.7.
3.3. Thermo-gravimetric analysis (TGA)
The thermal behavior of Fe3O4\SiO2\methylene dipyridine
MNPs is shown in Fig. 2d. This was evaluated to be 1.5% according
to the TG analysis. The analysis showed two decreasing peaks. First
Fig. 1. Schematic illustration of the synthesis for Fe3O4\dipyridine.

S.M. Sadeghzadeh, M.A. Nasseri / Catalysis Today 217 (2013) 80–85
83
Fig. 2. XRD analysis of (a) Fe3O4, (b) Fe3O4\SiO2\methylene dipyridine, (c) FTIR spectra of Fe3O4\dipyridine, (d) TGA diagram of Fe3O4\SiO2\methylene dipyridine MNPs, (e)
room-temperature magnetization curves of the Fe3O4, Fe3O4\SiO2, and Fe3O4\SiO2\dipyridine MNP.
peak appears at temperature around 130–150 ◦C due to desorption
of water molecules from the catalyst surface. This is followed by a
second peak at 425–450 ◦C, corresponding to the loss of the organic
spacer group.
contribution of the thick SiO2 resulted in a low mass fraction of the
Fe3O4 magnetic substance. Nevertheless, there was only smaller
difference of saturation magnetization between Fe3O4\SiO2 and
Fe3O4\SiO2\dipyridine. This is because thin outermost layer dipyri-
dine shell cannot cause a larger mass fraction change of the Fe3O4
magnetic substance from Fe3O4\SiO2 to Fe3O4\SiO2\dipyridine.
Though the saturation magnetization of Fe3O4\SiO2\dipyridine
particles is less than the magnetite nanoparticles as magnetic core,
it may be believed to possess enough strong magnetic attraction
for effectively magnetic separation.
3.4. Magnetic properties of the Fe3O4\SiO2\dipyridine MNP
Fig. 2e presented the magnetic hysteresis loops of the
uncoated Fe3O4 powder (a), Fe3O4\SiO2 powder (b) and
Fe3O4\SiO2\Dipyridine powder (c) in an applied field of 10 kOe at
300 K. It is clearly seen from these magnetic hysteresis loops that
all the samples have stronger magnetism with negligible coercivity
and remanence at room temperature. Their saturation magneti-
zation was 68.86, 33.40 and 25.84 emu/g, respectively. Compared
with the uncoated Fe3O4 particles, the saturation magnetization of
the Fe3O4\SiO2 MNP obviously decreased because the diamagnetic
3.5. TEM
The size and structure of the Fe3O4\SiO2\Methylene dipyridine
MNPs were also evaluated using transmission electron microscopy
(TEM) (Fig. 3). The average size of Fe3O4 MNP is about 10–15 nm
Fig. 3. (a) TEM image of Fe3O4 MNPs, (b) TEM image of Fe3O4\SiO2 MNPs, (c) TEM image of Fe3O4\SiO2\methylene dipyridine MNPs, (d) Fe3O4\dipyridine MNPs after reuse
ten times. Agglomeration of Fe3O4\dipyridine MNPs can be seen.

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S.M. Sadeghzadeh, M.A. Nasseri / Catalysis Today 217 (2013) 80–85
Table 1
Solvent screening for the reaction between phthalic anhydride, isatin, malononitrile,
and hydrazine.a
Yield (%)b
Solvent
Entry
80
73
H2O
EtOH
1
2
51
32
CH3CN
THF
3
4
39
21
73
trace
trace
trace
77
65
56
CH2Cl2
Toluene
EtOAC
n-Hexane
CHCl3
Dioxane
MeOH
DMSO
DMF
5
6
7
8
9
10
11
12
13
14
92
Solvent free
a
Reaction conditions: phthalic anhydride (1 mmol), isatin (1 mmol), malonon-
itrile (1 mmol), Hydrazine (1 mmol), and magnetic nanocatalyst (0.001 g) at
room-temperature for 60 min.
b
Isolated yields.
(Fig. 3a). After being coated with a SiO2 layer, the typical core–shell
structure of the Fe3O4\SiO2 MNPs can be observed. The dis-
persity of Fe3O4\SiO2 MNPs is also improved, and the average
size increases to about 20–30 nm (Fig. 3b). The average size of
Fe3O4\SiO2\methylene dipyridine MNPs is about 35–50 nm, but
the aggregation of the Fe3O4\SiO2\methylene dipyridine is more
evident than that of Fe3O4\SiO2 MNPs (Fig. 3c).
3.6. Catalytic activity of Fe3O4\SiO2\dipyridine MNPs for the
one-pot synthesis of pyrazolophthalazinyl spirooxindoles
We thought to optimize the reaction conditions, the same reac-
tion was carried out in various solvents under similar conditions.
In this study, it was found that solvent-free is a more efficient and
superior solvent (Table 1, Entries 14) over other solvents (Table 1,
Entries 1–13) with respect to reaction time and yield of the desired
pyrazolophthalazinyl spirooxindoles.
At this stage, the amount of catalyst necessary to promote the
reaction efficiently was examined. It was observed that the varia-
tion for Fe3O4\dipyridine MNP had an effective influence. The best
amount of Fe3O4\dipyridine MNP is 0.0008 g which afforded the
desired product in 92% yields (Fig. 4a).
Under the optimal conditions, the reaction progress in the pres-
ence of 0.0008 g of Fe3O4\dipyridine MNPs was monitored by GC
(Fig. 4b). Using this catalyst system, excellent yields of pyrazoloph-
thalazinyl spirooxindoles can be achieved in 50 min. No apparent
by-products were observed by GC in all the experiments and the
cyclic carbonate was obtained cleanly in 92% yield.
Fig. 4. (a) Effect of increasing amount of Fe3O4\dipyridine MNPs on the preparation
of pyrazolophthalazinyl spirooxindoles, (b) reaction progress monitored by GC, and
(c) reuses performance of the catalysts.
It is important to note that the magnetic property of
Fe3O4\dipyridine MNPs facilitates its efficient recovery from the
reaction mixture during work-up procedure. The activity of the
recycled catalyst was also examined under the optimized condi-
tions. After the completion of reaction, the catalyst was separated
by an external magnet, washed with methanol and dried at the
pump. The recovered catalyst was reused for ten consecutive cycles
without any significant loss in catalytic activity (Fig. 4c).
Amount of leached catalysts after each catalytic cycle is shown
in Fig. 5, which clearly demonstrates the practical recyclability and
stability of this catalyst. The Fe3O4\dipyridine MNP before use can
be seen result in the change of the morphology and size of the
obtained Fe3O4\dipyridine MNP after reuse ten times (Fig. 3d).
In order to show the unique catalytic behavior of
Fe3O4\dipyridine MNPs in these reactions, we have performed
one-pot reaction of phthalic anhydride, isatin, malononitrile, and
Fig. 5. Amount of leached catalysts after each catalytic cycle.
hydrazine in the presence of a catalytic amount of H3PW12O40
,

S.M. Sadeghzadeh, M.A. Nasseri / Catalysis Today 217 (2013) 80–85
85
Table 2
4. Conclusions
Comparison of the catalytic efficiency of Fe3O4\dipyridine MNPs with some
catalysts.
In conclusion, we have developed the current important areas of
heterogenization of methylene dipyridine, which is a rapidly devel-
oping research area. The main objectives are room temperature,
solvent-free conditions, a rapid (immediately) and easy immobi-
lization technique, and low cost precursors for the preparation
of highly active and stable MPs with high densities of functional
groups. Furthermore, applying the young area of magnetic particles
which are intrinsically not magnetic, but can readily be magne-
tized by an external magnet, can have a positive effect on high
activity on one hand and separation and recycling on the other
hand.
Entry
1
Catalyst
Time (h)
1
Yield (%)a
92
Fe3O4\dipyridine
MNPs
H3PW12O40
NbCl5
PEG-SO3H
InCl3
Pd(PPh3)4
Cerium (IV)
ammonium
nitrate
2
3
4
5
6
7
1
1
1
1
1
1
12
trace
28
trace
13
trace
a
Isolated yield, conditions: catalyst (0.0008 mmol), phthalic anhydride (1 mmol),
isatin (1 mmol), malononitrile (1 mmol), hydrazine (1 mmol), room temperature,
solvent-free.
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