Surface modified SPIONs-Cr(VI) ions-immobilized organic-inorganic hybrid as a magnetically recyclable nanocatalyst for rapid synthesis of polyhydroquinolines under solvent-free conditions at room temperature

Article abstract of DOI:10.1002/aoc.4245

In this work, a magnetic hybrid dichromate nanocomposite with triphenylphosphine surface modified superparamagnetic iron oxide nanoparticles (SPIONs) as a recyclable nanocatalyst was designed, prepared and characterized by Fourier transform infrared spect

Full text of DOI:10.1002/aoc.4245

Received: 4 October 2017
DOI: 10.1002/aoc.4245
Revised: 30 November 2017
Accepted: 3 December 2017
F U L L P A P E R
Surface modified SPIONs‐Cr(VI) ions‐immobilized organic‐
inorganic hybrid as a magnetically recyclable nanocatalyst
for rapid synthesis of polyhydroquinolines under solvent‐
free conditions at room temperature
Ali Maleki
| Negar Hamidi | Saied Maleki | Jamal Rahimi
Catalysts and Organic Synthesis Research
Laboratory, Department of Chemistry,
Iran University of Science and
In this work,
a
magnetic hybrid dichromate nanocomposite with
triphenylphosphine surface modified superparamagnetic iron oxide nanoparti-
cles (SPIONs) as a recyclable nanocatalyst was designed, prepared and charac-
terized by Fourier transform infrared spectroscopy (FT‐IR) spectra, X‐ray
diffraction (XRD) pattern analysis, vibrating sample magnetometer (VSM)
curves, X‐ray fluorescence (XRF) analysis, thermogravimetric analysis (TGA),
scanning electron microscopy (SEM) and transmission electron microscopy
(TEM) images and dynamic light scattering (DLS) analysis. Then, it was used
in a green and efficient procedure for one‐pot multicomponent synthesis of
polyhydroquinoline derivatives by the condensation of aldehydes, dimedone
or 1,3‐cyclohexadione, ethyl acetoacetate and ammonium acetate. This protocol
includes some new and exceptional advantages such as short reaction times,
low catalyst loading, high yields, solvent‐free and room temperature conditions,
easy separation and reusability of the catalyst.
Technology, Tehran 16846‐13114, Iran
Correspondence
Ali Maleki, Catalysts and Organic
Synthesis Research Laboratory,
Department of Chemistry, Iran University
of Science and Technology, Tehran 16846‐
13114, Iran.
Email: maleki@iust.ac.ir
KEYWORDS
Fe3O4 nanocomposite, green conditions, heterogeneous nanocatalyst, multicomponent reaction,
polyhydroquinoline
1 | INTRODUCTION
Polyhydroquinoline and 1,4‐dihydropyridine deriva-
tives include a broad spectrum of pharmacologically
Nowadays, multicomponent reaction is not an unfamiliar
topic to the chemists and pharmacists. From the begin-
ning of its introduction to the scientific world, it has
drawn enormous attention to itself due to its exceptional
advantages in comparison to conventional procedures,
the advantages that tempts every scientist in chemistry
and pharmacy to use it in the various compounds synthe-
sis. Chemists and pharmacists implement multicompo-
nent reactions method significantly because in this way
they are able to achieve their targets in brief time and also
they could save material, energy and money.[1]
active compounds that, in recent years, have drawn much
attention to themselves because of their diverse pharma-
cological and therapeutic properties such as vasodilator,
hepatoprotective, antiatherosclerotic, bronchodilator,
antitumor, geroprotective and antidiabetic activities.[2–8]
Therefore, various methods have been reported for their
synthesis because of their biological, industrial and syn-
thetic importance. However, most of these methods have
significant disadvantages, the use of high temperatures,
expensive metal precursors, environmentally harmful
catalysts, harsh reaction conditions, long reaction times
Appl Organometal Chem. 2018;e4245.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4245

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MALEKI ET AL.
and large quantity of volatile organic solvents limit the
implementation of these techniques. In addition, in
most of the reported methods, catalysts are damaged
in the work‐up process and cannot be recovered and
reused. Consequently, the design of efficient and
recoverable catalysts for the synthesis of and
polyhydroquinolines seems to be essential. One method
that is considered an environmentally benign process
is the designing of the heterogeneous catalysts because
these systems are easy to handle, recover and are green
processes.[9]
Nanoparticles are much more reactive than the
particulate metal counterpart because catalysis happens
on metal surface. Therefore, due to small sizes and large
surface areas of nanoparticles, heterogeneous catalysts
are often used in the form of nanoparticles. In recent
decade, SPIONs, as a main group of separation materials,
has drawn significant attention to itself in chemistry and
material science, due to its crucial applications in
manufacturing catalysts for the synthesis of various
biological active compounds. In addition, SPIONs has
excellent properties such as magnetism and insolubility
that enable the catalyst to be easily separated with an
external magnetic field and reused frequently without
considerable loss of catalytic activity.[10–19]
2 | RESULTS AND DISCUSSION
2.1 | Characterization of the magnetite
nanocatalyst
2.1.1 | FT‐IR spectrum of the prepared
nanocatalyst
To confirm the preparation of magnetite‐dichromate
nanomaterials, the FT‐IR spectrum of the prepared
nanocatalyst was obtained. As shown in Figure 1, bands
centered at 584, 635, 797, 1097, 810, 2930, 2984, 770, 805,
895, 915 (νasymmetric Cr=O (A1)), 954 cm‐1 (νsymmetric
Cr=O (E)) approved the preparation of the magnetite
nanocatalyst.
2.1.2 | XRD pattern analysis of the mag-
netite nanocatalyst
To study the structure and phase purity of the magnetite
nanocatalyst X‐ray diffraction patterns (XRD) were used.
The sharp peaks in the XRD patterns verified good crys-
tallinity of the prepared samples (Figure 2). The results
are in agreement with standard patterns of inverse cubic
spinel magnetite (Fe3O4) crystal structure (JCPDS No.
19‐0629) showing eight diffraction peaks at 2θ about
18.17°, 30.24°, 35.64°, 43.39°, 53.69°, 57.20°, 62.95° and
74.25° corresponding to (1 1 1), (2 2 0), (3 1 1), (4 0 0), (4
2 2), (5 1 1), (4 4 0) and (5 3 3). The crystallite sizes were
calculated using Scherrer's formula. The crystallite size
of the magnetite nanocatalyst was about 19.3 nm accord-
ing to the XRD peak at 35.64°.
In continuation of our recent works in order to
applying heterogeneous nanocatalysts in organic
synthesis,[20,21] herein, a magnetic dichromate hybrid
with triphenylphosphine surface modified SPIONs,
2‐
Fe3O4@SiO2@PPh3@Cr2O7
as
a
recoverable and
efficient composite nanocatalyst is prepared and used
for the synthesis of polyhydroquinolines 5a‐t via a
multicomponent reaction of various aldehydes 1,
dimedone or 1,3‐cyclohexadione 2, ethyl acetoacetate 3
and ammonium acetate 4 under solvent‐free conditions
at room temperature (Scheme 1). Although some recent
works dealing with the catalytic synthesis of
polyhydroquinoline and dihydropyridine derivatives
using magnetic nanoparticles,[22–26] but, this method
can be considered as a greener approach for the efficient
and rapid synthesis of biologically active substituted
polyhydroquinolines by using a recyclable nanocatalyst
under mild reaction conditions. To the best of our
knowledge, the present report can be regarded as a new
and first solvent‐free and room temperature protocol for
the synthesis of polyhydroquinolines catalyzed by a
hybrid nanocomposite.
2.1.3 | SEM image of the magnetite
nanocatalyst
Scanning electron microscopy (SEM) image was used to
study the morphology and particle size distribution in
the surface of the nanostructured nanocatalyst
(Figure 3). The SEM image illustrated that the magnetite
nanocatalyst particles are spherical with a mean diameter
of 25 nm with uniform size and good dispersity.
2.1.4 | Thermal stability properties of the
nanocatalyst
The thermal stability and composition ratio in the obtained
nanocomposite was measured through the TGA under air
SCHEME 1 Synthesis of
polyhydroquinolines 5a‐t

MALEKI ET AL.
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FIGURE 1 FT‐IR spectrum of the magnetite nanocatalyst
FIGURE 2 XRD pattern of the magnetite nanocatalyst
into iron oxides at the elevated temperature, respectively.
The composition ratio of the nanocomposite can be
estimated from the residual mass percentage. The
magnetic content was about 20%. The first weight loss
stage (below 100°C) can be ascribed to the evaporation of
water molecules in the composition. The next weight loss
stage was started from about 400 to complete at 700°C that
was because of the decomposition of the core/shell. No
further obvious decomposition exhibits a high thermal
stability in comparison with similar structures.
2.1.5 | Magnetic properties of the magne-
tite nanocatalyst
The magnetic property of the nanocomposite was
characterized using a vibrating sample magnetometer
(VSM) at room temperature. The magnetization curves
for SPIONs, Fe3O4@SiO2 and Fe3O4@SiO2@PPh3@Cr2O7
nanoparticles did not show hysteresis in the magnetiza-
tion for the three types of nanoparticles. In addition,
neither coercivity nor remanence was observed which
suggested that the three nanoparticles were
FIGURE 3 SEM image of the magnetite nanocatalyst
atmosphere with heating rate of 10°C min‐1 within temper-
ature range of 0–800°C. As illustrated in Figure 4, the TGA‐
DTA and mass loss curves depicting the variations of the
residual masses of the samples with temperature. The
organic material and magnetite of the sample were
completely burned to generate gas products and converted

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MALEKI ET AL.
FIGURE 4 TGA‐DTA of the nanocomposite
superparamagnetic. The measured saturation magnetiza-
tions were about 54 emu g‐1 for SPIONs, about 40 emu
g‐1 for Fe3O4@SiO2 and about 29 emu g‐1 for the magne-
tite nanocatalyst. The saturation magnetization signifi-
cantly decreased after preparation of core‐shell
Fe3O4@SiO2 and nanocatalyst. However, the prepared
the magnetite nanocatalyst still maintained good mag-
netic properties and could be completely and quickly sep-
arated from the reaction medium easily by a magnet.
Furthermore, for the measurement of the quantity of
chromium XRF analysis was used. According to the
results, the quantity of chromium was approximately
2‐
2.5%. Therefore, the immobilization of Cr2O7 was equal
with 0.03 mol/100 g.
FIGURE 5 TEM image of the Fe3O4@SiO2 core/shell
FIGURE 6 DLS analysis of the nanocomposite

MALEKI ET AL.
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Transmission electron microscopy (TEM) image was
Therefore, this DLS can be another evidence for the claim
of multilayer nanostructure formation.
used to confirm the core/shell morphology in the nano-
structure including Fe3O4 as dark core and SiO2 light shell
(Figure 5).
To study the particle size distribution vs intensity,
dynamic light scattering (DLS) analysis was provided. As
can be seen in Figure 6, after immobilization of the next
two shells on the Fe3O4@SiO2 core/shell, the particles’
diameter has been increased to higher than 100 nm.
2.2 | Catalytic performance of the
magnetite nanocatalyst
To investigate the effect of solvent, the condensation reac-
tion of an equimolar amount of 4‐cholorobenzaldehyde,
dimedone, ethyl acetoacetate, and ammonium acetate in
H2O, CH3CN, CH2Cl2, C2H5OH and under solvent‐free
conditions at room temperature using 0.003 g of the
magnetite nanocatalyst was carried out to produce the
specified product 5d (Table 1). The optimized condition
was the solvent‐free condition; because, it was performed
in short reaction time and in excellent yield. To the best of
our knowledge, the resulted yield and time for this
reaction could not be obtained under similar reaction
conditions, neither in the absence of any catalyst nor
other catalysts which have been used yet. Therefore, it
can be said that the prepared catalyst plays an important
role in the reaction which lead to the synthesis of
polyhydroquinoline derivatives.
TABLE 1 Optimization of the reaction conditions in the synthesis
of 5d at room temperature
Entry Solvent
Catalyst (g) Time (min) Yielda (%)
1
2
3
4
5
6
7
8
9
‐
‐
240
20
20
20
20
45
70
90
80
<40
80
95
95
91
89
55
60
65
‐
0.02
‐
0.003
0.004
0.008
0.003
0.003
0.003
0.003
‐
‐
C2H5OH
H2O
CH3CN
CH2Cl2
To investigate the catalytic performance of the
magnetite nanocatalyst, a pilot experiment was imple-
mented. This experiment was done by the reaction of an
aIsolated yields.
TABLE 2 Synthesis of polyhydroquinolines 5a‐t in the presence of the nanocatalyst under solvent‐free conditions at room temperature
Entry
Ar
R1
R2
Product
5a
Time (min)
Yielda (%)
1
C6H5
CH3
CH3
25
90
2
4‐MeOC6H4
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
5b
5c
5d
5e
5f
10
11
20
20
15
15
25
20
25
20
21
25
15
15
8
90
91
95
87
82
90
80
92
95
95
95
92
93
91
95
95
98
90
95
3
4‐MeC6H4
4
4‐ClC6H4
5
2‐ClC6H4
6
4‐OHC6H4
7
3‐OHC6H4
5g
5h
5i
8
4‐NO2C6H4
9
2,4‐Cl2‐C6H3
4‐OH‐3‐MeOC6H4
2‐OH‐4,6‐MeOC6H2
4‐BrC6H4
10
11
12
13
14
15
16
17
18
19
20
5j
5k
5l
4‐CNC6H4
5m
5n
5o
5p
5q
5r
5s
5t
Thiophen‐2‐carbaldehyde
Furan‐2‐carbaldehyde
4‐MeOC6H4
4‐MeC6H4
H
H
9
4‐ClC6H4
H
H
15
15
10
4‐OHC6H4
H
H
Thiophen‐2‐carbaldehyde
H
H
aIsolated yields.

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MALEKI ET AL.
aldehyde, dimedone or 1,3‐cyclohexadione, ethyl
acetoacetate, and ammonium acetate in the presence of
a catalytic amount of the magnetite nanocatalyst under
solvent‐free conditions at room temperature to afford
polyhydroquinolines 5a‐t (yield = 80‐95%). As indicated
in Table 2, the reaction was carried out successfully with
a wide range of aromatic and heteroaromatic aldehydes
carrying either electron‐donating or electron‐withdrawing
substituent in the ortho, meta, and para positions.
The main advantage of heterogeneous solid catalysts
in organic transformations is their reusability. The pres-
ent nanocatalyst was readily recovered from the reaction
mixture as outlined in the experimental section. The sep-
arated catalyst was washed with ethanol, dried and reused
in the subsequent reactions at least five times without sig-
nificant reduction in its activity. For example, the reaction
of 4‐cholorobenzaldehyde with dimedone, 3 and 4 in the
presence of the magnetite nanocatalyst (0.003 g) gave
the product ethyl 2,7,7‐trimethyl‐4‐(4‐cholorophenyl)‐5‐
oxo‐1,4,5,6,7,8‐hexahydroquinoline‐3‐carboxylate 5d
in 95% yield at room temperature. The results are sum-
marized in Figure 7.
A
proposed mechanism for the synthesis of
polyhydroquinolines in the presence of the magnetite
nanocatalyst is shown in Scheme 2. First, the magnetite
nanocatalyst catalyzes the reaction of aldehydes 1 or
NH4OAc 4 with active methylene compounds 2 or 3 to
give intermediates 6 and 7 or 8 and 9 via Knoevenagel
condensations and imine formations. Then, a Michael‐
type addition between them and then following by an
intramolecular nucleophilic attack of NH2 groups of
enamine forms to one of the carbonyl sites give the
100
95
94
93
90
89
90
80
70
60
50
40
30
20
10
0
86
Fresh
1
2
3
4
5
Run
FIGURE 7 Reusability study of the magnetite nanocatalyst in the synthesis of 5d
SCHEME 2 The proposed mechanism
for the synthesis of polyhydroquinolines in
the presence of the magnetite nanocatalyst

MALEKI ET AL.
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2‐
products 5a‐t. It was suggested that the role of Cr2O7
images of the samples were taken with Zeiss‐DSM 960A
microscope with an attached camera. Magnetic susceptibil-
ity measurements were carried out using a vibrating sample
magnetometer (VSM) by Megnetic Daghigh Daneshpajouh
Co., Kashan, Iran, in the magnetic field range of −10000 Oe
to +10000 Oe at room temperature. Transmission electron
microscopy (TEM) images were provided by Transmission
electron microscopy (TEM) analysis was performed using
a Zeiss EM 900 electron microscope (Germany) operating
at 80 kV. Dynamic light scattering (DLS) analysis was
carried out on a Malvern Instruments Ltd. Zetasizer Ver.
6.01 (England). All products were known compounds
that identified by comparison of their spectroscopic and
analytical data with those authentic samples.
ions of the nanocatalyst can be regarded as an acid‐base
reaction between CH‐acid of the methylene compounds
2 or 3 and Cr2O7 ions of the nanocatalyst. As can be
seen, it was carried out via proton transfer mechanism
not an electron transferring path. Because, oxidized
aromatic pyridine cores did not form on the obtained
products.
2‐
3 | CONCLUSIONS
In summary, we have introduced an efficient preparation,
identification and catalytic performance of magnetic
dichromate hybrid nanoparticles with triphenylphosphine
surface modified iron oxide in a four‐component conden-
sation reaction for the synthesis of polyhydroquinoline
derivatives starting from simple and readily available pre-
cursors by using under solvent‐free conditions at room
temperature. A large number of unique properties of this
catalyst were also observed including short reaction times,
easy workup procedure, significant reusability of the
catalyst, high atom economy, excellent yields and environ-
mentally benign reaction conditions.
4.2 | Preparation of
Fe3O4@SiO2@PPh3@Cr2O72‐ nanocatalyst
First, SPIONs were synthesized via co‐precipitation
method. Then, Fe3O4@SiO2 was prepared through a mod-
ified Stober method.[27] After that, silica coated SPIONs
were functionalized with triphenylphosphine. Finally,
dichroamate anion was immobilized on the surface of
phosphonium groups to give the functionalized magnetite
composite nanoparticles.
4 | EXPERIMENTAL
4.1 | General
4.3 | General procedure for synthesis of
polyhydroquinolines
All chemicals were purchased from Merck, Fluka and
Sigma‐Aldrich, and used without further purification.
All reactions and the purity of polyhydroquinolines were
monitored by thin‐layer chromatography (TLC) using alu-
minum plates coated with silica gel F254 plates (Merck)
using ethyl acetate and n‐hexane as eluents. The spots
were detected either under UV light or by placing in an
iodine chamber. Melting points were determined in open
capillaries using an Electrothermal 9100 instrument.
Chemical analyzes of the samples were carried out with
Philips‐PW1480 X‐ray fluorescence (XRF). The crystalline
phase of the nanoparticles was identified by means of X‐
ray diffraction (XRD) measurements using Cu Kα radia-
tion (λ = 1.54A°) on a Philips‐PW1800 diffractometer in
the 2θ range of 4–90°. A Netzsch Thermoanalyzer STA
504 was used for the thermogravimetric analysis (TGA)
with a heating rate of 10 °C/min under air atmosphere.
Fourier transform infrared (FT‐IR) spectra were recorded
using Perkin‐Elmer Spectrum RXI FT‐IR spectrometer;
using pellets of the nanomaterials diluted with KBr. The
1H NMR spectra were recorded on Bruker DRX‐300
Avance spectrometer at 300.13 MHz. The elemental anal-
yses were performed with an Elementar Analysensysteme
GmbH VarioEL. Scanning electron micrograph (SEM)
To a mixture of an aldehyde (1 mmol), dimedone or 1,3‐
cyclohexadione (1 mmol), ethyl acetoacetate (1 mmol),
and ammonium acetate (1 mmol) in a 10 ml round
bottom flask, the magnetite nanocatalyst (0.003 g) was
added. The mixture was homogenized and stirred at room
temperature for the appropriate time. The progress of the
reaction was monitored by TLC. After completion of the
reaction, EtOAc (5 ml) was added, and the catalyst was
removed from the reaction mixture by an external mag-
net. The pure polyhydroquinolines were obtained by
recrystallization from EtOH. The recycled nanocatalyst
was used for subsequent runs under the same conditions
without significant loss of its catalytic activity.
4.4 | Characterization data of the selected
products
4.4.1 | Ethyl 2,7,7‐trimethyl‐5‐oxo‐4‐p‐tolyl‐
1,4,5,6,7,8‐hexahydroquinoline‐3‐carboxyl-
ate (5c)
IR (KBr) (υmax, cm‐1) = 3276, 3205, 2958, 1701, 1647, 1604,
1
1492, 1379, 1215, 1033. H NMR (300 MHz, CDCl3): δH
(ppm) = 0.96 (3H, s, CH3), 1.08 (3H, s, CH3), 1.26 (3H, t,

8 of 8
MALEKI ET AL.
[4] A. C. Gaudio, A. Korokovas, Y. Takahata, J. Pharm. Sci. 1994,
83, 1110.
J = 7.2 Hz, CH3), 2.26 (3H, s, CH3), 2.22‐2.34 (4H, m,
2CH2), 2.38 (3H, s, CH3), 4.16 (2H, q, J = 7.2 Hz,
OCH2), 5.43 (1H, s, CH), 6.19 (1H, br s, NH); 6.84 (2H,
d, J = 7.5 Hz, H‐Ar), 7.03 (2H, d, J = 7.5 Hz, H‐Ar). Anal.
Calcd for C22H27NO3: C, 74.76; H, 7.70; N, 3.96. Found: C,
74.71; H, 7.66; N, 4.03.
[5] P. P. Mager, R. A. Coburn, A. J. Solo, D. J. Triggle, H. Rothe,
QSAR, Drug Des. Disc. 1992, 8, 273.
[6] M. F. Gordeev, D. V. Patel, E. M. Gordon, J. Org. Chem. 1996,
61, 924.
[7] R. Miri, H. Niknahad, G. Vesal, A. Shafiee, IL Farmaco 2002,
57, 123.
4.4.2 | Ethyl 4‐(4‐chlorophenyl)‐2,7,7‐
trimethyl‐5‐oxo‐1,4,5,6,7,8‐hexahydroquino-
line‐3‐carboxylate (5d)
[8] A. Dondoni, A. Massi, E. Minghini, S. Sabbatini, V. Bertoasi,
J. Org. Chem. 2003, 68, 6172.
[9] M. Poliakoff, P. Licence, Nature 2007, 450, 810.
IR (KBr) (υmax, cm‐1) = 3274, 3205, 3076, 2960, 1704, 1647,
1604, 1488, 1380, 1278, 1215, 1070. H NMR (300 MHz,
[10] A. Maleki, E. Akhlaghi, R. Paydar, Appl. Organometal. Chem.
2016, 30, 382.
1
CDCl3): δH (ppm) = 0.93 (3H, s, CH3), 1.08 (3H, s, CH3),
1.20 (3H, t, J = 7.1 Hz, CH3), 2.06‐2.31 (4H, m, 2CH2),
2.38 (3H, s, CH3), 4.06 (2H, q, J = 7.1 Hz, OCH2), 5.03
(1H, s, CH), 6.23 (1H, br s, NH), 7.16 (2H, d, J = 8.1 Hz,
H‐Ar), 7.26 (2H, d, J = 8.4 Hz, H‐Ar). Anal. Calcd for
C21H24ClNO3: C, 67.46; H, 6.47; N, 3.75. Found: C,
67.32; H, 6.54; N, 3.82.
[11] A. Maleki, M. Aghaei, N. Ghamari, Appl. Organometal. Chem.
2016, 30, 939.
[12] A. Maleki, M. Kamalzare, Catal. Commun. 2014, 53, 67.
[13] A. Maleki, M. Aghaei, N. Ghamari, Chem. Lett. 2015, 44, 259.
[14] M. A. Zolfigol, R. Ayazi‐Nasrabadi, S. Baghery, Appl.
Organometal. Chem. 2016, 30, 273.
[15] A. Maleki, Ultrason. Sonochem. 2018, 40, 460.
[16] A. Maleki, S. Azadegan, Inorg. Nano‐Met. Chem. 2017, 47,
917.
4.4.3 | Ethyl 2,7,7‐trimethyl‐5‐oxo‐4‐
(thiophen‐2‐yl)‐1,4,5,6,7,8‐hexahydroquino-
line‐3‐carboxylate (5n)
[17] A. Maleki, M. Aghaei, R. Paydar, J. Iran. Chem. Soc. 2017, 14,
485.
[18] A. Maleki, Tetrahedron Lett. 2013, 54, 2055.
[19] A. Maleki, RSC Adv. 2014, 4, 64169.
IR (KBr) (υmax, cm‐1) = 3274, 3207, 2960, 1701, 1647, 1604,
1
1492, 1379, 1215, 1072. H NMR (300 MHz, CDCl3): δH
[20] A. Maleki, R. Rahimi, S. Maleki, N. Hamidi, RSC Adv. 2014, 4,
(ppm) = 1.04 (3H, s, CH3), 1.10 (3H, s, CH3), 1.27 (3H, t,
J = 7.1 Hz, CH3), 2.22‐2.34 (4H, m, 2CH2), 2.38 (3H, s,
CH3), 4.16 (2H, q, J = 7.1 Hz, OCH2), 5.42 (1H, s, CH),
6.19 (1H, br s, NH), 6.84 (2H, d, J = 1.8 Hz, H‐Ar), 7.03
(1H, t, J = 2.1 Hz, H‐Ar). Anal. Calcd for C19H23NO3S:
C, 66.06; H, 6.71; N, 4.05. Found: C, 67.11; H, 6.63; N,
3.94.
29765.
[21] A. Maleki, M. Rabbani, S. Shahrokh, Appl. Organometal. Chem.
2015, 29, 809.
[22] R. Kardooni, A. R. Kiasat, H. Motamedi, J. Taiwan Inst. Chem.
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Khakyzadeh, RSC Adv. 2014, 4, 32142.
[24] D. Li, J. Wang, F. Chen, H. Jing, RSC Adv. 2017, 7, 4237.
ACKNOWLEDGEMENTS
[25] A. Maleki, M. Kamalzare, M. Aghaei, J. Nanostruct. Chem.
2015, 5, 95.
The authors gratefully acknowledge the partial support
from the Research Council of the Iran University of
Science and Technology.
[26] A. Maleki, A. R. Akbarzade, A. R. Bhat, J. Nanostruct. Chem.
2017, 7, 309.
[27] A. Maleki, Tetrahedron 2012, 68, 7827.
ORCID
How to cite this article: Maleki A, Hamidi N,
Maleki S, Rahimi J. Surface modified SPIONs‐
Cr(VI) ions‐immobilized organic‐inorganic hybrid
as a magnetically recyclable nanocatalyst for rapid
synthesis of polyhydroquinolines under solvent‐free
conditions at room temperature. Appl Organometal
Chem. 2018;e4245. https://doi.org/10.1002/aoc.4245
Ali Maleki http://orcid.org/0000-0001-5490-3350
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