γ-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel superparamagnetic nanocatalyst promoted green synthesis of 5-(aryl)-5H-spiro[diindeno[1,2-b:2′,1′-e]pyridine-11,3′-indoline]-2′,10,12-trione derivatives

Article abstract of DOI:10.1007/s11164-018-3571-1

Abstract: Grafting of 4-(sulfoamino)butanoic acid on superparamagnetic γ-Fe₂O₃@SiO₂ nanoparticles afforded γ-Fe₂O₃@SiO₂@4-(sulfoamino)butanoic acid as a novel heterogeneous nanocatalyst, which was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry, field emission scanning electron microscopy, and thermal gravimetric analysis. In this research, we report a convenient and one-pot efficient direct protocol for the pseudo four-component preparation of 5-(aryl)-5H-spiro[diindeno[1,2-b:2′,1′-e]pyridine-11,3′-indoline]-2′,10,12-trione derivatives via cascade condensation reaction of 1,3-indandione and isatins with various aromatic amine in the presence of the catalytic amount of γ-Fe₂O₃@SiO₂@4-(sulfoamino)butanoic acid under green conditions in aqueous media. This procedure offers several advantages such as: very easy reaction conditions, simple work-up, or purification, excellent yields, high purity of the desired product, atom economy, and short reaction times. The superparamagnetic catalyst is magnetically separable and retained chemical stability after recycling for at least five consecutive runs without detectable activity loss. Graphical abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s11164-018-3571-1

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-018-3571-1(0123456789(). -, vo Vl
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c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel
superparamagnetic nanocatalyst promoted green synthesis
of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-
indoline]-20,10,12-trione derivatives
Hadi Mohammadi1 Hamid Reza Shaterian1
•
Received: 11 June 2018 / Accepted: 17 August 2018
Ó Springer Nature B.V. 2018
Abstract
Grafting of 4-(sulfoamino)butanoic acid on superparamagnetic c-Fe2O3@SiO2
nanoparticles afforded c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel
heterogeneous nanocatalyst, which was characterized by X-ray diffraction, Fourier
transform infrared spectroscopy, vibrating sample magnetometry, field emission
scanning electron microscopy, and thermal gravimetric analysis. In this research, we
report a convenient and one-pot efficient direct protocol for the pseudo four-com-
ponent preparation of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indo-
line]-20,10,12-trione derivatives via cascade condensation reaction of 1,3-
indandione and isatins with various aromatic amine in the presence of the catalytic
amount of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid under green conditions in
aqueous media. This procedure offers several advantages such as: very easy reaction
conditions, simple work-up, or purification, excellent yields, high purity of the
desired product, atom economy, and short reaction times. The superparamagnetic
catalyst is magnetically separable and retained chemical stability after recycling for
at least five consecutive runs without detectable activity loss.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11164-
018-3571-1) contains supplementary material, which is available to authorized users.
Extended author information available on the last page of the article
123

H. Mohammadi, H. R. Shaterian
Graphical abstract
Keywords c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid Á Superparamagnetic
nanocatalyst Á 5-(Aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-
20,10,12-trione Á Multi-component reactions
Introduction
Magnetic nanoparticles are of great importance for researchers due to their
applications for catalysis [1], biotechnology/biomedicine [2, 3], and magnetic
resonance imaging (MRI) [4]. Small naked nanomagnetic particles have a tendency
to form agglomerates to reduce the energy associated with the high surface area-to-
volume ratio of nanosized particles [5]; this is because they are chemically highly
active [6]. Researchers have tried to use protection strategies to chemically stabilize
naked magnetic nanoparticles by grafting or coating them with organic species such
as polymers [7], or coating with an inorganic layer, such as silica or carbon [8]. The
shell-encapsulated nanomagnetic materials can be stabilized and the nanoparticles
also used for further organocatalyst functionalizations depending on the desired
applications [9]. Functionalized nanomagnetic particles encapsulated by silica have
demonstrated potential application as catalysts in organic synthesis [10]. They act as
quasi-homogeneous systems for reactions which show high conversion of starting
materials to the desired product(s), especially in liquid-phase catalytic reactions
[11]. In addition, easy separation of magnetic particles by an external magnet
provides a simple reaction work-up produce the desired product(s) in highly pure
isolated yields [12]. Thus, functionalization and application of such coated magnetic
123

c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel…
nanoparticles in catalysis and easy separation are important to develop these
strategies for organic processes and synthesis [13]. Functionalized organocatalysts
on nano-superparamagnetic compounds coated by silica are considered a very
important class of materials with broad application in many biological aspects
[14, 15]. Nano-superparamagnetic transition metal oxides such as iron are one of the
most adjustable systems which also have applications in medical, industrial, and
biological systems, in addition to their important roles in catalysis and organic
synthesis [16–18]. Studies of this new kind of organometallic compound grafting of
organocatalysts on superparamagnetic c-Fe2O3@SiO2 nanoparticles has attracted
the consideration of researchers in organic chemistry. In the present research, we
report preparation of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid for the first
time. This superparamagnetic compound as catalyst was applied for synthesizing a
series of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-
trione derivatives via pseudo cascade four-component condensation reaction of 1,3-
indandione and isatins with various aromatic amines in the presence of a catalytic
amount of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid under green conditions in
aqueous media (Scheme 1).
Experimental
All materials were purchased from Merck and Aldrich Companies. Nuclear
magnetic resonance (NMR) spectra were determined using a Brucker Avance
300 MHz instruments in DMSO-d6 as a deuterated solvent. Melting points were
determined in open capillaries using a BUCHI510 melting point apparatus. Thin-
layer chromatography (TLC) was performed on silica-gel Poly Gram SIL G/UV 254
plates and progress of reactions was monitored by TLC. Fourier transform infrared
(FT-IR) spectra were recorded using KBr disks on a JASCO FT-IR 460 Plus
spectrophotometer. Elemental compositions were determined with a Leo 1450 VP
scanning electron microscope equipped with an SC7620 energy-dispersive
spectrometer (SEM–EDS) presenting a 133-eV resolution at 20 kV. Power X-ray
diffraction (XRD) was performed on a Bruker D8-Advance X-ray diffractometer
X
O
NH
O
NH2
O
O
O
O
NHSO3H (Catalyst)
X
N
2
O
H2O
N
N
M
N
H
1
2
3
Y
4a-p
Y
M
= γ-Fe2O3@SiO2@4-(sulfoamino)butanoic acid
Catalyst:
NHSO3H
Scheme 1 Synthesis of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-trione
derivatives in the presence of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as nanocatalyst
123

H. Mohammadi, H. R. Shaterian
with Cu Ka (k = 0.154 nm) radiation. The magnetic property of c-Fe2O3@SiO2
was measured with vibrating sample magnetometry/alternating gradient force
magnetometry (VSM/AGFM). Thermal gravimetric analysis (TGA) was done on a
thermal analyzer with a heating rate of 10 °C min-1 over a temperature range of
25–800 °C under flowing compressed N2.
Preparation of c-aminobutyric acid supported on c-Fe2O3@SiO2 magnetic
nanoparticles
Preparation of c-Fe2O3
The Fe3O4 nanoparticles were prepared according to a previously reported
procedure [19, 20]. FeCl2Á4H2O (1.25 g) and FeCl3Á6H2O (3.33 g) were dissolved
in water (80 mL) separately, followed by the two iron salt solutions being mixed
under continuous stirring (800 rpm). Then, a NH4OH solution (%25, 70 mL) was
drop added to the stirring mixture at room temperature at 3 h and stirred
continuously for 1 h; the black products were collected by an external magnet.
Then, Fe3O4 magnetic nanoparticles (MNPs) were washed three times with water
and ethanol and dried at 60 °C for 12 h. Fe3O4 nanoparticles at this stage were
heated at 300 °C in a furnace for 3 h to convert Fe3O4 to sustainable c-Fe2O3
nanoparticles.
Preparation of c-Fe2O3@SiO2
c-Fe2O3 nanoparticles (1 g) were dispersed in ethanol (40 mL) and the resulting
mixture was stirred for 1 h at 40 °C. Subsequently, tetraethyl orthosilicate (TEOS,
2 mL) was charged to the reaction vessel, and the mixture was continuously stirred
for 24 h [20]. The silica-coated nanoparticles were collected by an external magnet,
followed by washing three times with ethanol and drying at 70 °C in a vacuum for
12 h; c-Fe2O3@SiO2 was obtained.
Preparation of c-aminobutyric acid supported on c-Fe2O3@SiO2 nanoparticles
c-Fe2O3@SiO2 (800 mg) was dispersed in water (80 mL) under ultrasonic
irradiation for 30 min. Subsequently, c-aminobutyric acid (1 g) was charged to
the reaction vessel and the mixture was continuously stirred for 16 h at 90 °C. c-
Fe2O3@SiO2-c-aminobutyric acid nanoparticles were removed from the reaction
solution using an external magnet and washed several times with water and ethanol
and dried at 60 °C.
Conversion of the c-Fe2O3@SiO2-c-aminobutyric acid MNPs to c-Fe2O3@SiO2@4-
(sulfoamino)butanoic acid MNPs
A dispersion of 800 mg of the prepared magnetic c-Fe2O3@SiO2-c-aminobutyric
acid nanoparticles in 40 mL chloroform was ultra-sonicated for 30 min. Then,
chlorosulfonic acid (0.5 mL, 7.5 mmol) was added drop-wise and the resulting
123

c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel…
reaction mixture was stirred for 4 h. The resulted brown powder was separated
using an external magnet, washed with ethanol several times, and dried 12 h at
60 °C (Scheme 2). The structure of successful synthesis of c-Fe2O3@SiO2-c-
aminobutyric acid MNPs was confirmed by FT-IR, EDX, SEM, VSM, XRD, and
TGA analysis.
General procedure for the direct synthesis of 5-(aryl)-5H-spiro[diindeno[1,2-
b:20,10-e]pyridine-11,30-indoline]-20,10,12-trione derivatives using c-
Fe2O3@SiO2@4-(sulfoamino)butanoic acid nanoparticles
c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid MNPs (5 mg) were added to a
mixture 1,3-indandione (1.0 mmol), isatin (0.5 mmol), and aniline (0.5 mmol in
water (3 mL). The reaction mixture was stirred at 60 °C in an oil bath. After
completion of the reaction, the reaction mixture was cooled to room temperature.
The solid crude product was separated by filtration, and ethanol was added to the
Calcination
300 oC, 3h
NH3
H2O
Fe3O4
-Fe O
γ
2
3
2 FeCl3.6H2O + FeCl2.4H2O
TEOS
SiO2
O
-aminobutyric acid
γ
γ
-Fe2O3
SiO2
-Fe O
γ
.
NH2
2
3
O
O
.
NH2
O
SiO2
-Fe O
SiO2
O
O
ClSO3H
CH2Cl2
O
γ
.
NH2
2
3
-Fe O
γ
.
NHSO3H
2
3
O
O
=
.
NHSO3H
O
Scheme 2 Synthesis of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as nanocatalyst
123

H. Mohammadi, H. R. Shaterian
reaction mixture and heated to separate c-Fe2O3@SiO2@4-(sulfoamino)butanoic
acid by an external magnet. The nanocatalyst was washed with ethanol three times
and dried. The warm ethanolic solution containing crude product was cooled until
precipitated pure product was formed. The known pure products were characterized
and their physical data were compared with those of known compounds.
Experimental characterization data and spectra of the new
compounds
5-(3,4-dichlorophenyl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-
trione (4k) Red powder; mp [ 300 °C. IR (KBr; mmax/cm-1): 3398, 1710, 1623. 1H
NMR (300 MHz, DMSO-d6): dH (ppm) 5.66 (2H, d, J = 6.9 Hz, H–Ar), 6.87–8.74
(13H, m, H–Ar), 10.67 (1H, s, NH). 13C NMR (75 MHz, DMSO-d6): dC (ppm)
46.07, 97.80, 109.54, 112.26, 121.80, 121.98, 122.13, 125.14, 127.42, 129.12,
130.83, 132.67, 133.31, 134.76, 135.23, 135.35, 136.48, 138.03, 142.58, 156.94,
177.83, 190.06.
5-(3,5-dichloroophenyl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-
trione (4l) Red powder; mp [ 300 °C. IR (KBr; mmax/cm-1): 3394, 1702, 1690. 1H
NMR (300 MHz, DMSO-d6): dH (ppm) 5.75 (2H, d, J = 6.9 Hz, H–Ar), 6.87–8.56
(13H, m, H–Ar), 10.67 (1H, s, NH). 13C NMR (75 MHz, DMSO-d6): dC(ppm)
46.01, 109.54, 112.26, 121.62, 121.99, 122.21, 125.17, 129.14, 130.06, 130.89,
132.41, 132.64, 133.31, 134.75, 135.88, 136.43, 140.29,142.53, 155.76, 177.84,
190.04.
50-chloro-5-(3,5-dichlorophenyl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indo-
line]-20,10,12-trione (4m) Red powder; mp [ 300 °C. IR (KBr; mmax/cm-1): 3377,
1725, 1698. 1H NMR (300 MHz, DMSO-d6): dH (ppm) 5.66 (2H, d, J = 6.9 Hz, H–
Ar), 6.89–8.57 (12H, m, H–Ar), 10.82 (1H, s, NH). 13C NMR (75 MHz, DMSO-
d ): dC (ppm) 46.25, 110.97, 111.57, 121.76, 122.33, 125.26, 126.25, 129.02,
6
129.85, 130.06, 131.04, 132.43, 132.58, 133.37, 135.84, 136.36, 140.23, 141.26,
156.12, 177.68, 190.04.
50-chloro-5-(3-chlorophenyl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-
20,10,12-trione (4n) Red powder; mp [ 300 °C. IR (KBr; mmax/cm-1): 3360, 1702,
1
1687. H NMR (300 MHz, DMSO-d ): dH (ppm) 5.55 (2H, d, J = 7.5 Hz, H–Ar),
6
6.89–8.97 (12H, m, H–Ar), 10.82 (1H, s, NH). 13C NMR (75 MHz, DMSO-d6): dC
(ppm) 46.32, 110.93, 111.42, 121.81, 122.24, 124.91, 125.30, 126.57,127.17,
128.98, 129.38, 131.48, 133.17, 134.14, 136.43, 136.48, 139.49, 141.59, 142.72,
143.47, 156.41, 177.80, 190.06.
Results and discussion
New c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a catalyst was synthesized
based on the following procedure (Scheme 2). The magnetic nanocatalyst was
characterized using different techniques such as XRD, SEM, EDS, VSM, TGA, and
123

c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel…
FT-IR. The XRD patterns of c-Fe2O3, c-Fe2O3@SiO2, c-Fe2O3 @SiO2-c-
aminobutyric acid, and c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid had six
characteristic peaks which have good accordance with the cubic structure of
maghemite (c-Fe2O3; JCPDS file No 04-0755; Fig. 1). The positions of all the peaks
indicated retention of the crystalline structure during functionalization of the MNPs
and the grafting process did not change the phase of the c-Fe2O3 nanoparticles. The
XRD patterns of c-Fe2O3 @SiO2 and c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid
confirmed that SiO2 and 4-(sulfoamino)butanoic acid formed an amorphous phase;
their patterns showed only a crystalline pattern for the c-Fe2O3 nanoparticles (Fig. 1).
Figure 2 presents the field-emission SEM (FE-SEM) image of c-Fe2O3@-
SiO2@4-(sulfoamino)butanoic acid showing a spherical morphology (Fig. 2a) and
an average nanoparticles size of 14 nm using a histogram curve (Fig. 2b).
The components of the c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid were
analyzed using EDS. EDS basically gives quality elemental information [21]. The
EDS spectrum in Fig. 3 shows the presence of Fe, O, Si, C, S, and N atoms in the
catalyst.
The VSM diagram shows the magnetic properties of the synthesis catalyst
(Fig. 4). The hysteresis loops of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid were
measured. Magnetization (emu g-1) as a function of applied field (Oe) is depicted in
Fig. 4 with the confined field from -10,000 to 10,000Oe. The superparamagnetic
behavior of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid nanocrystals illustrates a
small particle size. As can be observed, the saturation magnetization value of c-
Fe2O3@SiO2@4-(sulfoamino)butanoic acid is 13 amu g-1.
Fig. 1 XRD pattern of a c-Fe2O3, b c-Fe2O3 @SiO2, c c-Fe2O3 @SiO2-c-aminobutyric acid, and d c-
Fe2O3@SiO2@4-(sulfoamino)butanoic acid
123

H. Mohammadi, H. R. Shaterian
Fig. 2 a FE-SEM image of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid; b Particle size distribution
histogram of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid
The thermal stability of the c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid was
investigated by TGA (Fig. 5). Small weight loss occurs below 180 °C and is due to
physically adsorbed water. There are two exothermic peaks accompanied with a
mass loss of 42% in the temperature range of 180–620 °C in the differential thermal
analysis (DTA) curve of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid. These peaks
were mainly attributed to the decomposition of organic groups grafted to the c-
Fe2O3@SiO2 surface and –SO3H loaded on aminopropyl groups. The peak higher
than 620 °C most probably corresponds to a phase transition in which the
amorphous phase is converted to a crystalline phase.
The characterization of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid was con-
firmed by FT-IR spectroscopy (Fig. 6) which showed spectra of: (a) c-Fe2O3@SiO2,
(b) c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid, and (c) c-aminobutyric acid. The
C–H stretching vibration peak appears at 2930 cm-1. The Fe–O stretching vibration
was observed 550–650 cm-1 and the stretching mode of Si–O–Si showed a strong
broad peak at about 1099–1220 cm-1. The functionalization of SO3H groups on the
MNPs-c-aminobutyric acid surface was confirmed by the absorption of S–O and
S=O stretching bands of the –SO3H moiety at 998–1220 cm-1 in the FT-IR
123

c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel…
Fig. 3 EDS spectrum of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid
Fig. 4 VSM diagram of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid
spectrum. In addition, in the spectrum of c-Fe2O3@SiO2@4-(sulfoamino)butanoic
acid, the peak at 3405 cm-1 was probably attributed to the –SO2–OH groups, which
is overlapped by the C–H stretching vibration.
123

H. Mohammadi, H. R. Shaterian
Fig. 5 Thermogravimetric of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid
Fig. 6 FT-IR spectra: a c-Fe2O3@SiO2, b c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid, and c c-
aminobutyric acid
123

c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel…
O
NH
O
NH2
O
O
NHSO3H
O
2
O
N
N
H
O
1
2
3
4a
NHSO3H
-Fe O @SiO @4-(Sulfoamino)butanoic acid
γ
2
3
2
Scheme 3 Synthesis of 5-phenyl-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-
trione
Optimization of the reaction conditions
To evaluate the activity of the c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as
nanocatalyst, firstly, the one-pot and pseudo four-component reaction of 1,3-
indandione (1 mmol), isatin (0.5 mmol), and aniline (0.5 mmol; Scheme 3) was
chosen as a model reaction to optimize the reaction conditions such as molar ratio of
the catalyst, temperature, and solvents (Tables 1, 2, and 3).
In order to show the unique catalytic behavior of c-Fe2O3@SiO2@4-(sul-
foamino)butanoic acid as nanocatalyst and to compare its activity with other
catalysts, the model reaction was carried out in the presence of catalytic amounts of
Fe3O4 NMPs, p-TSA, AcOH, citric acid, sulfamic acid, PEG-OSO3H, c-aminobu-
tyric acid, oxalic acid dihydrate:proline, and FeCl3Á6H2O in different solvents and
also solvent-free conditions. The results are summarized in Table 1. With regard to
Table 1, the c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid showed better activity
and excellent yield of the product (95%) in a minimum time period (20 min) was
obtained at 60 °C in aqueous media in the presence of 5 mg of c-Fe2O3@SiO2@4-
(sulfoamino)butanoic acid (Table 1, entry 6). The reaction in the presence of c-
aminobutyric acid as a non-supported catalyst on MNPs gave the desired product in
moderate yield (50y %) at 80 °C. Thus, immobilization of c-aminobutyric acid on
c-Fe2O3@SiO2 increased the activity of the organocatalyst and enabled recycla-
bility of the catalyst (Table 1, entry 11). We also examined the model reaction in the
absence of any catalyst (Table 1, entry 12), the experimental result of which showed
that the catalyst is necessary for preparation of the desired product.
In terms of choosing the best solvent for the reaction of 1,3-indandione (1 mmol),
isatin (0.5 mmol), and aniline (0.5 mmol; Scheme 3), different solvents were
studied in the presence of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid (Table 2).
The best result was obtained after 20 min in aqueous media at 60 °C with excellent
yield of the product (95%) in water (Table 2, entry 5). Water is a more appropriate
green solvent for synthesis of the desired product because of cost, safety, and
environmental concerns.
Varying the amount of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as nano-
magnetic catalyst was investigated for the synthesis of 5-(aryl)-5H-
123

H. Mohammadi, H. R. Shaterian
Table 1 Preparation of 5-phenyl-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-trione
in the presence of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid, Fe3O4 NMPs, p-TSA, AcOH, citric
acid, sulfamic acid, PEG-OSO3H, c-aminobutyric acid, oxalic acid dehydrate:proline, and FeCl3Á6H2O in
different solvents and solvent-free conditions
Entry Catalyst
Conditions
Time
Yield
(%)a,b
Citation
1
2
3
4
5
6
FeCl3Á6H2O (7 mol%)
Fe3O4 MNPs (5 mol%)
CH3CN (reflux) 2 h
Water (80 °C) 2 h
CH3CN (reflux) 1 h
60
75
81
60
–
[24]
–
p-TSA (30 mol%)
AcOH (30 mol%)
Water (reflux)
Water (80 °C)
Water (60 °C)
1 h
[23]
[23]
–
PEG-OSO3H (20 mol%)
10 min 90
20 min 95
c-Fe2O3@SiO2@4-(sulfoamino)butanoic
acid (5 mg)
7
8
Oxalic acid dihydrate: proline(5 mL)
Water (80 °C)
Solvent-free
20 min 94
30 min 85
[22]
–
c-Fe2O3@SiO2@4-(sulfoamino)butanoic
acid(5 mg)
(90 °C)
9
Sulfamic acid (25 mol%)
Citric acid (20 mol%)
c-Aminobutyric acid (25 mol%)
No catalyst
Water (80 °C)
Water (80 °C)
Water (80 °C)
Water (100 °C)
1 h
1 h
1 h
24 h
65
–
–
–
–
10
11
12
50
50
Trace
aReaction conditions: 1,3-indandione (1 mmol), isatin (0.5 mmol), and aniline (0.5 mmol) in different
conditions
bYield refers to isolated pure products
Table 2 Preparation of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-trione
in the presence of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid (5 mg) in different solvents and also
solvent-free conditions
Entry
Solvent
Time (min)
Temperature (°C)
Yield (%)a,b
1
2
3
4
5
6
EtOH (3 mL)
60
60
70
75
80
25
85
95
80
CH3CN (3 mL)
CH2Cl2 (3 mL)
Solvent-free
70
120
30
Reflux
90
H2O (3 mL)
20
60
H2O:EtOH (1:1; 3 mL)
45
70
aReaction conditions: 1,3-indandione (1 mmol), isatin (0.5 mmol), and aniline (0.5 mmol)
bYield refers to isolated pure products
spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-trione in water media
(Table 3). The optimum amount of the catalyst for maximum conversion was found
to be 5 mg at 60 °C (Table 3, entry 4). Increasing the amount of c-Fe2O3@SiO2@4-
(sulfoamino)butanoic acid had no effect in the product yield (Table 3, entry 5). For
optimization of the temperature, the reaction was performed at different
123

c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel…
Table 3 Optimization the amount of the catalyst and also selecting the best temperature for the prepa-
ration of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-trione in aqueous
media
Entry
Catalyst (mg)
Temperature (°C)
Time (min)
Yield (%)a,b
1
2
3
4
5
6
7
2
3
4
5
7
5
5
60
60
60
60
60
50
70
50
45
30
20
15
35
15
75
82
87
95
95
75
95
aReaction condition: 1,3-indandione (1 mmol), isatin (0.5 mmol), and aniline (0.5 mmol) in water (3 mL)
as solvent
bYield refers to isolated pure products
temperatures (50, 60, and 70 °C; Table 3) using c-Fe2O3@SiO2@4-(sul-
foamino)butanoic acid (5 mg) in water (3 mL); the best result was obtained at
60 °C (Table 3, entry 4).
Secondly, after optimizing the reaction conditions, the generality of this
procedure was studied on a wide range of aromatic amines and isatins for
preparation of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-
20,10,12-trione derivatives (Table 4). It was observed that the desired products
were obtained in high to excellent yields with short reaction times (Table 4, entries
1–14).
The mechanism for the formation of the desired product was suggested according
to the literature [24]. First, condensation between 1,3-indandione (1) and isatin (2)
formed intermediate (I). Second, the condensation reaction of (I) with another
molecule of 1,3-indandione produced compound (II). In the following, enamine (III)
was formed from condensation of amine with a carbonyl group (II). Then, the
intramolecular cyclization of (III) led to formation of the final desired products
(Scheme 4).
The recyclability of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as nanocata-
lyst was examined in the one-pot pseudo four-component synthesis of 5-(phenyl)-
5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-trione under opti-
mized conditions (model reaction). After completion of the reaction, the reaction
mixture was cooled to room temperature. The solid crude product was separated by
filtration, and ethanol was added to the reaction mixture and heated to separate c-
Fe2O3@SiO2@4-(sulfoamino)butanoic acid by external magnet. The nanocatalyst
was washed with ethanol for three times and dried. The recoverable nanocatalyst
was used for other reaction runs. As shown in Fig. 7, the reusable nanocatalyst was
123

H. Mohammadi, H. R. Shaterian
Table 4 Synthesis of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-indoline]-20,10,12-trione
derivatives in the presence of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid (5 mg) as nanomagnetic
catalyst at 60 °C in water (3 mL) as a green solvent
Entry
amine
isatin
product
Time(
min)
Yield
(%)a,b
Observed Lit. M.p
M.p (oC)
(oC) ,
[Ref]
O
NH2
O
N
1
NH
20
95
>300
>300
[24]
O
O
O
N
H
4a
O
N
NH2
Me
O
NH
O
O
2
20
98
>300
>300
[24]
O
N
H
Me
4b
O
N
NH2
O
NH
O
O
3
15
98
>300
>300
[24]
O
N
H
OMe
MeO
4c
O
N
NH2
Br
O
NH
O
O
4
20
94
>300
>300
[24]
O
N
H
Br
4d
O
N
O
NH
O
NH2
NO2
O
5
25
93
>300
>300
[24]
O
N
H
O2N
4e
123

c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel…
Table 4 continued
O
NH
O
O
O
NH2
N
6
20
95
>300
>300
[22]
O
N
Cl
H
4f
Cl
O
NH2
Cl
O
Cl
NH
O
7
20
94
>300
>300
[22]
O
N
O
H
N
4g
Cl
O
O
NH2
NH
Cl
O
O
O
N
N
H
8
20
94
>300
>300
[22]
Cl
Cl
4h
Cl
O
O
NH2
NO2
NH
Cl
O
O
9
25
93
>300
>300
[22]
O
N
N
H
O2N
4i
123

H. Mohammadi, H. R. Shaterian
Table 4 continued
O
NH2
Cl
Cl
O
NH
O
O
N
10
18
98
>300
>300
[22]
H
O
N
OMe
MeO
4j
Cl
O
NH
O
NH2
O
O
Cl
New
11
25
94
>300
O
N
N
H
Compound
Cl
Cl
Cl
Cl
4k
O
NH2
NH
O
O
O
New
12
13
14
20
95
>300
N
O
Cl
Cl
Compound
Cl
N
H
Cl
4l
Cl
O
O
NH2
NH
O
Cl
O
New
25
93
>300
O
N
N
H
Cl
Cl
Compound
Cl
Cl
4m
Cl
O
O
NH2
NH
O
Cl
O
New
20
94
>300
O
N
N
H
Cl
Compound
Cl
4n
123

c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel…
Table 4 continued
O2N
O
O
NH2
NH
O
15
>300
[23]
O2N
O
19
93
>300
O
N
N
H
4o
Br
O
NH
O
>300
[23]
O
O
NH2
16
18
92
>300
N
Br
O
N
H
4p
aReaction conditions: 1,3-indandione (1 mmol), isatins (0.5 mmol) and aromatic amines (0.5 mmol) in
water (3 mL)
bYield refer to isolated pure products
used for at least five runs. The catalyst kept its stability without any loss of any
significant activity.
Conclusion
c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel organometallic heteroge-
neous nanomagnetic catalyst has been successfully synthesized and characterized by
several techniques such as XRD, FT-IR, VSM, FE-SEM, EDS, and TGA. This
efficient nano-organometallic catalyst was successfully used for the pseudo four-
component preparation of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-e]pyridine-11,30-
indoline]-20,10,12-trione derivatives under green conditions in aqueous media. Easy
reaction conditions, simple work-up, or purification, excellent yields, high purity of
the desired product, and short reaction times are some advantages of this protocol.
The superparamagnetic nanocatalyst is magnetically separable and stable in the
reaction media without detectable activity loss.
123

H. Mohammadi, H. R. Shaterian
H
O
N
O
X
O
N
N
4a-n
M
Y
NHSO3H
HO3SHN
H
N
O
O
O
X
O
2
1
H
N
O
O
X
O
III
NH
H
N
O
N
O
X
M
Y
OH
O
NHSO3H
NH2
O
N
M
3
I
Y
H
N
O
O
X
O
HN
X
II
O
OH2
O
O
O
O
NHSO3H
O
1
O
NHSO3H
-Fe O @SiO @4-(Sulfoamino)butanoic acid
γ
2
3
2
Scheme 4 The proposed mechanism for the synthesis of 5-(aryl)-5H-spiro[diindeno[1,2-b:20,10-
e]pyridine-11,30-indoline]-20,10,12-trione in the presence of c-Fe2O3@SiO2@4-(sulfoamino)butanoic
acid as nanocatalyst
123

c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as a novel…
Fig. 7 Reusability of c-Fe2O3@SiO2@4-(sulfoamino)butanoic acid as nanomagnetic catalyst
Acknowledgements We are grateful for the financial support from the Research Council of University of
Sistan and Baluchestan.
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123

H. Mohammadi, H. R. Shaterian
Affiliations
Hadi Mohammadi1 Hamid Reza Shaterian1
•
&
Hamid Reza Shaterian
hrshaterian@chem.usb.ac.ir
1
Department of Chemistry, Faculty of Sciences, University of Sistan and Baluchestan,
P.O. Box 98135-674, Zahedan, Iran
123