Fe3O4@silica sulfuric acid nanoparticles: An efficient reusable nanomagnetic catalyst as potent solid acid for one-pot solvent-free synthesis of indazolo[2,1-b]phthalazine-triones and pyrazolo[1,2-b]phthalazine-diones

Article abstract of DOI:10.1016/j.molcata.2013.03.003

Regarding the green chemistry's goals, silica-coated magnetite nanoparticles (MNPs) open up new avenue to introduce an amazing and efficient system for facilitating catalyst recovery in different organic reactions. Therefore, in this paper the preparation

Full text of DOI:10.1016/j.molcata.2013.03.003

Journal of Molecular Catalysis A: Chemical 373 (2013) 46–54
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Fe3O4@silica sulfuric acid nanoparticles: An efficient reusable nanomagnetic
catalyst as potent solid acid for one-pot solvent-free synthesis of
indazolo[2,1-b]phthalazine-triones and pyrazolo[1,2-b]phthalazine-diones
Ali Reza Kiasat∗, Jamal Davarpanah
Chemistry Department, College of Science, Shahid Chamran University, Ahvaz 61357-4-3169, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Regarding the green chemistry’s goals, silica-coated magnetite nanoparticles (MNPs) open up new avenue
to introduce an amazing and efficient system for facilitating catalyst recovery in different organic reac-
tions. Therefore, in this paper the preparation of sulfuric acid functionalized silica-coated magnetite
nanoparticles with core–shell structure (Fe3O4@silica sulfuric acid) are presented by using Fe3O4 spheres
as the core and silica sulfuric acid nanoparticles as the shell. The catalyst was characterized by infrared
spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM),
X-ray diffraction (XRD) spectroscopy, and vibrating sample magnetometer (VSM). Ability of this nano-
magnetic solid acid catalyst in the one-pot three-components condensation reaction of phthalhydrazide,
aromatic aldehydes and cyclic or acyclic 1,3-diketones are also described. Utilization of easy reaction con-
ditions, catalyst with high catalytic activity and good reusability, and simple magnetically work-up, makes
this methodology as an interesting option for the economic synthesis of indazolo[2,1-b]phthalazine-
triones and pyrazolo[1,2-b]phthalazine-diones.
Received 12 December 2012
Received in revised form 5 March 2013
Accepted 6 March 2013
Available online xxx
Keywords:
Silica-coated magnetite nanoparticles
Fe3O4@silica sulfuric acid
Indazolo[2,1-b]phthalazine-trione
Pyrazolo[1,2-b]phthalazine-diones
Multi-component reaction
© 2013 Elsevier B.V. All rights reserved.
1. Introduction
Moreover, these compounds also could be promising materi-
als for new luminescence or fluorescence probes. Generally, the
In recent years, to minimize waste and atom economy in the
use of raw materials, the target of science and technology has been
shifting toward more environment friendly, sustainable resources
and reusable catalysts [1]. Thus, the development of silica-coated
magnetite nanoparticles as attractive candidates in the search for
supporting of catalysts is currently a subject of increasing interest
[2–4]. Functionalized magnetic nanoparticles can be easily sepa-
rated and recycled from the products by an external magnet. This
kind of separation prevents the loss of solid catalyst in the process
and is not time-consuming. It also enhances products purity and
optimizes operational costs [5–8].
In the past few decades, heterocyclic chemistry has been one
of the most important disciplines in organic synthesis and phar-
maceutical chemistry [9]. Heterocycles containing the phthalazine
moiety are a class of compounds, which are highly recognized in the
field of medicine and organic chemistry [10] due to their antimicro-
bial [11], anticonvulsant [12], antifungal [13], anticancer [14] and
anti-inflammatory activities [15].
formation of phthalazine derivatives was carried out by the treat-
ment of phthalhydrazide with aromatic aldehydes and cyclic or
acyclic 1,3-diketones under acidic conditions [16]. Many of the
reported methods are efficient, however, in some methods the cata-
lyst recovery/reuse is not possible [17–22]. Therefore, the discovery
of new and inexpensive catalysts for the preparation of phthalazine
derivatives under mild conditions is of prime importance.
On the other hand, multicomponent coupling reactions (MCRs)
have become powerful tools in organic, combinatorial and medic-
inal chemistry [23] with the rapid generation of molecular
complexity and diversity with predefined functionality [24].
Solvent-free multicomponent is an eco-friendly approach, which
opens up numerous possibilities for conducting rapid organic syn-
thesis and functional group transformations [25–28].
The aim of this protocol is to highlight the synergistic
effects of the combined use of multicomponent coupling reac-
tions under solvent-free conditions and application of solid
Brönsted acid catalyst supported on nanostructure materi-
als with inherent magnetic property for the development
of new eco-compatible strategy for heterocyclic synthesis.
Therefore, we now wish to explore a straightforward conver-
gent one-pot synthesis of indazolo[2,1-b]phthalazine-triones and
pyrazolo[1,2-b]phthalazine-diones derivatives using Fe3O4@silica
∗
Corresponding author. Tel.: +98 611 3331746; fax: +98 611 3331746.
E-mail addresses: akiasat@scu.ac.ir, akiasat@yahoo.com (A.R. Kiasat).
1381-1169/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2013.03.003

A.R. Kiasat, J. Davarpanah / Journal of Molecular Catalysis A: Chemical 373 (2013) 46–54
47
Scheme 1. Preparation of indazolo [2,1-b] phthalazine-triones and pyrazolo[1,2-b]phthalazine-diones catalyzed by Fe3O4@silica sulfuric acid.
sulfuric acid as an proficient, mild, harmless to the envi-
ronment, recyclable, non-toxic and magnetic powerful solid
acid catalyst with good stability toward humidity, under
solvent-free conditions through domino Knoevenagel condensa-
tion/Michael addition/intramolecular cyclodehydration sequence
(Scheme 1).
ion-exchange pH-analysis demonstrated a loading of 1.89 mmol
SO3 H g−1
.
The FT-IR spectra of Fe3O4@silica sulfuric acid is shown in
Fig. 1. The FT-IR analysis of the Fe3O4@silica sulfuric acid exhibits
basic characteristic peak at approximately 580 cm−1, which was
attributed to the presence of Fe O vibration and the bands at
1092 cm−1, 800 cm−1 and 447 cm−1 come from Si
O Si asym-
metric stretching vibration, symmetric stretching vibration and
bending vibration, respectively. The presence of sulfonyl group is
confirmed by 1217 and 1124 cm−1 bands that were covered by a
stronger absorption of Si O bond at 1092 cm−1. In addition, the
Si OH group peak at 900 cm−1 was disappeared for Fe3O4@silica
sulfuric acid [29]. The spectrum also shows a broad OH stretching
2. Results and discussions
Fe3O4@silica sulfuric acid core–shell composite, that Fe3O4
spheres as the core and silica sulfuric acid nanoparticles as the
shell, was prepared by a simple, low cost and convenient method.
Magnetite nanoparticles were synthesized by the co-precipitation
of FeCl2 and FeCl3 in ammonia solution. To improve the chemi-
cal stability of magnetite nanoparticles, their surface engineering
was successfully performed by the suitable deposition of silica
onto nanoparticles surface by the ammonia-catalyzed hydrolysis
of tetraethylorthosilicate (TEOS). Next, The SiO2 spheres served as
support for the immobilization of SO3H groups by simple mixing of
core–shell composite and chlorosulfonic acid in CH2Cl2 (Scheme 2).
Fe3O4@silica sulfuric acid nanocomposite was characterized by
FT-IR, SEM, HRTEM, XRD, VSM and ion exchange pH-analysis. The
absorption around 2800–3700 cm−1
.
The morphology and particle size distribution of Fe3O4,
Fe3O4@SiO2 and Fe3O4@silica sulfuric acid nanostructures were
performed by measuring SEM using a Philips XL30 scanning elec-
tron microscope. According to Fig. 2, Fe3O4@silica sulfuric acid has
spherical shape with nano dimension ranging from 90 to 170 nm.
Transmission electron microscopy (TEM) revealed that iron
oxide nanoparticles had entrapped in the silica shell successfully,
in which an average particle size is about 40–60 and the diameter of
FeCl3.6H2O
+
NH4OH, N2
80 oC, 30 min
Fe3O4
MNP
FeCl2.4H2O
TEOS, H2O\ EtOH, N2
NH4OH, rt, 12h
SiO2
SiO2
OSO3H
OSO3H
OSO3H
OH
ClSO3H, CH2Cl2
rt, 30 min
MNP
MNP
OH
OH
2
2
O i S
O i S
Fe3O4 @ Silica sulfuric acid
Fe3O4 @ Silica
Scheme 2. Schematic diagram for the synthesis of Fe3O4@silica sulfuric acid.

48
A.R. Kiasat, J. Davarpanah / Journal of Molecular Catalysis A: Chemical 373 (2013) 46–54
Fig. 3. TEM image of Fe3O4@silica sulfuric acid.
Fig. 1. FT-IR spectra of Fe3O4@silica sulfuric acid. (For interpretation of the refer-
ences to color in figure legend, the reader is referred to the web version of the
article.)
the magnetic core is about 20–40 nm, much smaller than the sizes
obtained from the SEM measurements (Fig. 3). Images of the silica-
coated magnetic nanoparticles display dark MNP cores surrounded
by an amorphous silica shell.
The magnetic property of the catalyst was studied by vibrating-
sample magnetometer (VSM). The diagram of magnetization for
Fe3O4@SiO2 and Fe3O4@silica sulfuric acid MNPs are depicted
in Fig. 4. The saturation magnetization of Fe3O4@SiO2 and
Fe3O4@silica sulfuric acid MNPs were found to be 17 and 38 emu/g,
Fig. 4. VSM magnetization curves of the (a) Fe3O4@SiO2 and (b) Fe3O4@silica sul-
furic acid nanoparticles.
Fig. 2. SEM images of (a) Fe3O4, (b) Fe3O4@SiO2 and (c) Fe3O4@silica sulfuric acid.

A.R. Kiasat, J. Davarpanah / Journal of Molecular Catalysis A: Chemical 373 (2013) 46–54
49
Fig. 5. X-ray diffraction for Fe3O4@SiO2 and Fe3O4@silica sulfuric acid.
respectively, which are much lower than bare Fe3O4 MNPs
(63.2 emu/g) [30].
Subsequently, with optimal conditions in hand, to study the
scope and limitations of the protocol, a wide range of substituted
aldehydes, phthalhydrazide and cyclic or acyclic diketones such
as dimedone and acetylacetone were allowed to undergo three-
component condensation in the presence of Fe3O4@silica sulfuric
acid under solvent free conditions (Table 2).
As shown in Table 2, the aldehydes with both electron donat-
ing and withdrawing groups were participated in the condensation
reaction with equal efficiency. Thus, the nature and position of sub-
stitution in the aromatic ring did not affect the reactions much.
The meta-substituted aromatic aldehydes (Table 2, entries 6–8) as
well as sterically hindered ortho-substituted aromatic aldehydes
(Table 2, entry 11), both undergo condensation reaction without
any difficulty.
The possibility of the magnetic recycling of catalyst was also
examined. For this reason, the reaction of benzaldehyde, dime-
done, and phthalhydrazide in the presence of Fe3O4@silica sulfuric
acid was studied. In this procedure, after completion of the reac-
tion, hot ethanol was added and the catalyst was easily separated
from the product by attaching an external magnet onto the reaction
vessel, followed decantation of the reaction solution. The remain-
ing catalyst was washed with ethanol to remove residual product
and dried under vacuum and reused in a subsequent reaction. For
example, the reaction of benzaldehyde, dimedone, and phthalhy-
drazide afforded to the corresponding product at 100% conversion
and isolated yield of 88 to 83% in six consecutive runs. The aver-
age chemical yield for six consecutive runs was 85%, which clearly
demonstrates the practical recyclability of this catalyst (Fig. 6).
It should be point out that no special handling precaution
regarding exposure to air/moisture need to be taken in the use of
Fe3O4@silica sulfuric acid as catalyst.
The structure of Fe3O4@SiO2 and Fe3O4@silica sulfuric acid
were analyzed by X-ray diffraction (XRD) spectroscopy. XRD dia-
gram of the bare MNPs displayed patterns consistent with the
patterns of spinel ferrites described in the literature (Fig. 5) [29].
The same peaks were observed in the both of the Fe3O4@SiO2 and
Fe3O4@silica sulfuric acid XRD patterns, indicating retention of the
crystalline spinel ferrite core structure during the silica-coating
process.
The average MNPs core diameter of Fe3O4@SiO2 and
Fe3O4@silica sulfuric acid were calculated to be 7.4 and 8.9 nm,
respectively from the XRD results by Scherrer’s equation [31,32].
After characterization of the Fe3O4@silica sulfuric acid catalyst,
we have tested its catalytic activity in the preparation of phtha-
lazine derivatives. In the preliminary stage of investigation, we
focused on a three-component process for the model reaction of
phthalhydrazide (1 mmol), dimedone (1 mmol) and bezaldehyde
(1.1 mmol) under solvent-free conditions at 100 ◦C in the absence
and presence of Fe3O4@silica sulfuric acid. It was found that in
the absence of nanomagnetic solid acid catalyst, only trace of the
desired product was observed on TLC plate even after 2 h of heat-
ing (Table 1). When the reaction was performed in the presence of
Fe3O4@silica sulfuric acid, it proceeded rapidly to give the desired
product.
It should be pointed out that in the presence of Fe3O4 nano parti-
cle or Fe3O4@SiO2, this three-component process was sluggish and
even after 2 h of heating a considerable amount of starting material
recovered unchanged (Table 1).
As shown in Table 1, 0.075 g of the magnetic nano Fe3O4@silica
sulfuric acid and solvent-free conditions are the best operative
experimental conditions (Table 1). Increasing the amount of cata-
lyst does not improve the yield of the product any further, whereas
decreasing the amount of catalyst leads to decrease in the product
yield (Scheme 3).
A comparison of the efficacy of Fe3O4@silica sulfuric acid cat-
alyst with some of those reported in the literature is presented
in Table 3. The model reaction of, dimedone, phthalhydrazide
and benzaldehyde was considered as a representative example

50
A.R. Kiasat, J. Davarpanah / Journal of Molecular Catalysis A: Chemical 373 (2013) 46–54
Table 1
The one-pot three component reaction of phthalhydrazide (1 mmol), dimedone (1 mmol) and bezaldehyde (1.1 mmol) under different conditions.
Entry
Solvent
Catalyst (g)
T (◦C)
Time (min)
Yielda (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
CH3CN
EtOH
EtOH-H2O
H2O
0.075
0.075
0.075
0.075
–
Reflux
Reflux
Reflux
Reflux
100
100
100
100
110
120
80
50
100
100
100
100
120
120
120
120
120
60
60
35
35
35
40
60
40
40
120
120
30
35
40
35
Trace
60
73
88
75
71
55
45
80
81
11
13
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
0.025
0.05
0.075
0.075
0.075
0.075
0.075
0.1
0.15
0.1 (Fe3O4)
0.1 (Fe3O4@SiO2)
a
Isolated yield.
CHO
O
O
O
0.075 g cat, 100 o
C
O
O
O
N
N
NH
NH
+
+
Solvent - Free
35 min
O
Scheme 3. Solvent-free three component reaction of phthalhydrazide (1 mmol), dimedone (1 mmol) and bezaldehyde (1.1 mmol).
(Table 3). As it is seen in addition to having the general advan-
tages attributed to the inherent magnetic property of nanocatalysts,
Fe3O4@silica sulfuric acid is an equally or more efficient catalyst for
this three-component reaction.
The purity determination of the products and reaction monitor-
ing were accomplished by TLC on silica gel PolyGram SILG/UV 254
plates. X-ray diffraction (XRD) patterns of samples were taken on
a Philips X-ray diffractometer Model PW 1840. The particle mor-
phology was examined by SEM (Philips XL30 scanning electron
microscope) and TEM (Zeiss – EM10C – 80 kV).
3. Experimental
3.1. General
3.2. Preparation of Fe3O4 superparamagnetic nanoparticles,
MNPs
Iron (II) chloride tetrahydrate (99%), iron (III) chloride hexahy-
drate (98%), aromatic aldehydes and other chemical materials were
purchased from Fluka and Merck companies and used without fur-
ther purification. Products were characterized by comparison of
their physical data, IR and 1H NMR and 13C NMR spectra with
known samples. NMR spectra were recorded on a Bruker Advance
DPX 400 MHz instrument spectrometer using TMS as internal stan-
dard. IR spectra were recorded on a BOMEM MB-Series 1998 FT-IR
spectrometer.
MNPs were synthesized by co-precipitation of FeCl3.6H2O
and FeCl2.4H2O in ammonia solution, according to the reported
procedure [34]: 15.136 g (55.987 mmol) FeCl3.6H2O and 6.346 g
(31.905 mmol) FeCl2·4H2O were dissolved in 0.64 L deionized
water under nitrogen at 90 ◦C and added to a ammonium hydrox-
ide 25% solution (0.08 L) with vigorous mechanical stirring. After
the color of bulk solution turned to black the reaction was carried
out for 60 min in N2 atmosphere. The resulting black MNPs were
isolated by applying a permanent external magnet, washed 3 times
with deionized water and then dried under vacuum at 60 ◦C for 12 h.
3.3. Preparation of silica coated magnetic nanoparticles,
Fe3O4@silica
The synthesized Fe3O4 nanoparticles (2 g) were diluted with
0.12 L water and 0.45 L ethanol. The suspension was dispersed
under ultrasonification for 25 min. In the presence of a constant
nitrogen flux and at room temperature, ammonium hydroxide 25%
solution (0.01 L) was added to the suspension. Then under contin-
uous mechanical stirring, 0.002 L TEOS was slowly added to this
dispersion and after stirring for 12 h, silica was formed on the
surface of magnetite nanoparticles through hydrolysis and conden-
sation of TEOS. The coated particles were finally separated from the
liquid by a magnetic decantation and washed several times with
deionized water. Then dried under vacuum at 60 ◦C overnight [35].
Fig. 6. Recyclability of Fe3O4@silica sulfuric acid.

A.R. Kiasat, J. Davarpanah / Journal of Molecular Catalysis A: Chemical 373 (2013) 46–54
51
Table 2
Solvent-free synthesis of indazolo[2,1-b]phthalazine-triones and pyrazolo[1,2-b]phthalazine-diones catalyzed by Fe3O4@silica sulfuric acid.
Entry
Aldehyde
Diketone
Product
Time (min)
Yielda (%)
O
O
CHO
O
O
O
N
N
1
35
88
Cl
CHO
Cl
O
O
O
O
O
O
2
3
4
35
30
40
90
O
N
N
NO2
CHO
NO2
O
O
O
94
O
N
N
OH
CHO
OH
O
O
O
85
O
N
N
CN
CHO
CN
O
O
O
5
30
92
O
N
N
O
O
F
CHO
O
O
O
N
N
6
35
90
F
O

52
A.R. Kiasat, J. Davarpanah / Journal of Molecular Catalysis A: Chemical 373 (2013) 46–54
Table 2 (Continued)
Entry
Aldehyde
Diketone
Product
Time (min)
Yielda (%)
Cl
CHO
O
O
O
O
O
N
N
7
35
90
Cl
O
O
Me
CHO
O
O
N
N
8
35
88
Me
O
Me
CHO
Me
O
O
O
O
9
40
86
O
N
N
OMe
O
CHO
OMe
O
O
O
O
10
40
85
N
N
O2N
O
CHO
CHO
O
O
NO2
O
N
N
11
35
90
O
O
O
O
O
CH3
12
N
N
45
85
H3C
CH3
CH3
O

A.R. Kiasat, J. Davarpanah / Journal of Molecular Catalysis A: Chemical 373 (2013) 46–54
53
Table 2 (Continued)
Entry
Aldehyde
Diketone
Product
Time (min)
Yielda (%)
NO2
CHO
O
O
O
O
O
O
13
14
15
35
88
87
84
O
CH3
H3C
CH3
CH3
CH3
N
N
NO2
CH3
CN
CHO
CN
O
O
O
35
O
H3C
N
N
CH3
CH3
Cl
CHO
Cl
O
O
O
40
O
H3C
N
N
CH3
CH3
a
Isolated yield.
3.4. Preparation of SO3H functionalized silica-coated magnetite
nanoparticles, Fe3O4@silica sulfuric acid
(1 M, 0.025 L) with an initial pH 5.9, the Fe3O4@silica sulfuric acid
(100 mg) was added and the resulting mixture stirred for 24 h after
which the pH of solution decreased to 2.10. This is equal to a loading
of 1.98 mmol SO3 H g−1 of acidic catalyst. Additionally, this result
confirmed by back-titration analysis of the catalyst.
A 0.5 L suction flask was equipped with a constant pressure
dropping funnel. The gas outlet was connected to a vacuum system
through an adsorbing solution of alkali trap. Fe3O4@silica (2.5 g)
was added into the flask and dispersed by ultrasonic for 10 min in
CH2Cl2 (0.075 L). chlorosulfonic acid (1.75 g, ca. 0.001 L, 15 mmol)
in CH2Cl2 (0.02 L) was added dropwise over a period of 30 min at
room temperature. After completion of the addition, the mixture
was shaken for 90 min, while the residual HCl was eliminated by
suction. Then the Fe3O4@silica sulfuric acid was separated from the
reaction mixture by a magnetic field and washed several times with
dried CH2Cl2. Finally, Fe3O4@silica sulfuric acid was dried under
vacuum at 60 ◦C.
3.6. Typical procedure for the preparation of
3,4-dihydro-3,3-dimethyl-13-phenyl-2 H-indazolo[2,1-
b]phthalazine-1,6,11-trione
A
mixture of phthalhydrazide (0.16 g, 1 mmol), dime-
done (0.14 g, 1 mmol), benzaldehyde (0.13 g, 1.2 mmol), and
Fe3O4@silica sulfuric acid (0.1 g) was heated at 100 ◦C for 35 min
(TLC). After satisfactory completion of the reaction and cooling, the
reaction mixture was washed with hot ethanol and the catalyst
was removed by a magnetic field. The solid residue was isolated
and purified by recrystallization in hot EtOH. The desired pure
product(s) was characterized by comparison of their physical data
with those of known.
3.5. Sulfonic acid loading of Fe3O4@silica sulfuric acid
Sulfonic acid loading was calculated based on titration of the
proton-exchanged brine solutions. To an aqueous solution of NaCl
Table 3
Comparison of the efficacy of Fe3O4@silica sulfuric acid catalyst with some of those reported in the literature.
Entry
Catalyst
Catalyst loading (mol %)
Time (min)
Yield (%)
Ref.
1
2
3
4
5
6
p-Toluenesulfonic acid
(S)-camphorsulfonic acid.
[bmim]BF4/H2SO4
Mg(HSO4)2
Silica supported PPA
Fe3O4@silica sulfuric acid
30
10
15
11.5
0.1 g
0.075 g
10
35
30
10
7
93
80
96
85
91
88
[9]
[16]
[20]
[21]
[33]
This work
35

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A.R. Kiasat, J. Davarpanah / Journal of Molecular Catalysis A: Chemical 373 (2013) 46–54
3.7. Selected spectral data
SEM, TEM, XRD and VSM. The catalytic activity of this
solid acid nanocomposite, was probed through the one-pot
3,4-Dihydro-3,3-dimethyl-13-(4-nitrophenyl)-2-H-
synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11-trione and 1H-
indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (Table 2, entry
3): M.P. = 225–227 ◦C. 1H NMR (DMSO-d6, 400 MHz): ı = 1.10 (s,
3H), 1.14 (s, 3H), 2.27 (s, 2H), 3.20 (AB system, dd, 1H, J = 18.8 Hz
and J = 2.0 Hz), 3.32 (AB system, d, 1H, J = 18.8 Hz), 6.44 (s, 1H),
7.79–7.82 (m, 2H), 7.96–8.01 (m, 2H), 8.09–8.12 (m, 4H). 13C NMR
(DMSO-d6, 100.6 MHz): ı = 28.3, 28.4, 34.8, 37.7, 50.6, 64.2, 116.8,
123.8, 127.2, 128.0, 128.9, 129.2, 129.7, 134.3, 135.0, 145.3, 147.6,
152.3, 154.4, 155.9,192.3. IR (KBr) (vmax, cm−1): 2973, 1697, 1617,
1660, 1525, 1368, 1148, 1102, 858, 701.
pyrazolo[1,2-b]phthalazine-5,10-dione derivatives by a three-
component reaction of phthalhydrazide, cyclic or acyclic diketones
and aromatic aldehydes. The attractive features of this method are
simple procedure, cleaner reaction, use of reusable catalyst, easy
workup and performing multicomponent reaction under solvent-
free conditions.
Acknowledgement
3,4-Dihydro-3,3-dimethyl-13-(3-flourophenyl)-2-H-
We gratefully acknowledge the support of this work by Shahid
Chamran University Research Council.
indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (Table 2, entry
6): M.P. = 225–227 ◦C. 1H NMR (DMSO-d6, 400 MHz): ı = 1.11 (s,
3H), 1.13 (s, 3H), 2.27 (s, 2H), 3.18 (AB system, dd, 1H, J = 19.1 Hz
and J = 2.2 Hz), 3.33 (AB system, d, 1H, J = 19.2 Hz), 6.31 (s, 1H),
7.08–7.12 (pt, 1H), 7.31–7.39 (m, 3H), 7.96–7.98 (m, 2H), 8.01–8.12
(m, 1H), 8.26–8.29 (m, 1H). 13C NMR (DMSO-d6, 100.6 MHz):
ı = 28.3, 28.4, 34.7, 37.7, 50.7, 64.3, 114.7, 115.2, 117.0, 124.1,
127.5, 129.0, 129.7, 130.5, 134.2, 135.0, 140.8, 152.9, 154.3, 155.9,
161.3, 163.7, 192.3. IR (KBr) (vmax, cm−1): 2957, 2877, 1663, 1629,
1603, 1471, 1357, 1314, 1271, 1142, 778, 701, 684.
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3,4-Dihydro-3,3-dimethyl-13-(4-hydroxyphenyl)-2-H-
indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (Table 2, entry
4): M.P. = 225–227 ◦C. 1H NMR (DMSO-d6, 400 MHz): ı = 1.10 (s,
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J = 17.8 Hz and J = 2.0 Hz), 3.32 (AB system, d, 1H, J = 17.2 Hz), 6.20
(s, 1H), 6.86 (d, 2H, J = 8.8 Hz), 7.22 (d, 2H, J = 8.4 Hz), 7.94–7.99 (m,
2H), 8.10–8.12 (m, 1H), 8.25–8.27 (m, 1H), 9.47 (br, 1HOH). 13C
NMR (DMSO-d6, 100.6 MHz): ı = 28.4, 28.5, 34.7, 37.7, 50.8, 64.4,
115.2, 115.3, 118.0, 127.1, 127.9, 128.1, 129.2, 129.4, 134.1, 134.9,
151.4, 154.0, 155.8, 157.7, 192.4. IR (KBr) (vmax, cm−1): 3363(OH),
2960, 1674, 1657, 1634, 1362, 1271, 847, 704.
3,4-Dihydro-3,3-dimethyl-13-(4-methylphenyl)-2H-
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2897, 1663, 1654, 1603, 1600, 1497, 1085, 827, 790, 687, 627, 495.
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d, 1H, J = 18.8 Hz), 6.42 (s, 1H), 7.27–7.36 (m, 4H), 7.90–7.92 (m,
2H), and 8.31–8.40 (m, 2H). 13C NMR (CDCl3, 100.6 MHz): ı = 23.3,
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4. Conclusion
In this research, Fe3O4@silica sulfuric acid core–shell nanocom-
posite was successfully prepared and characterized by FT-IR,