Sucrose chelated auto combustion synthesis of BiFeO3 nanoparticles: Magnetically recoverable catalyst for the one-pot synthesis of polyhydroquinoline

Article abstract of DOI:10.1002/aoc.4357

Sucrose chelated Bismuth ferrite (BiFeO₃) nanoparticles as a novel heterogeneous catalyst was synthesized by an auto combustion route. Different calcination temperatures (150?°C, 450?°C, 550?°C, 650?°C, 750?°C and 850?°C) have been employed to obtain single phased BiFeO₃ nanoparticles. The perovskite structure formation and disappearance of organic phase (sucrose) was obtained by Fourier transform infrared spectroscopy (FT-IR). Phase determination and structural characterization was carried out by powder X-ray diffraction (XRD). The magnetic properties were analyzed by vibrating sample magnetometer (VSM) whereas surface area/pore volume was obtained by Brunauer–Emmett–Teller (BET). Transmission electron microscope (TEM) analyzed the particles size and morphology. Thermal stability was investigated by thermogravimetric analysis (TGA) and determination of constituent elements was carried out by X-ray Photo-Electron Spectroscopy (XPS). Raman spectroscopy confirmed the perovskite structure of the synthesized materials. The BiFeO₃ nanoparticles so obtained were employed as heterogeneous catalyst for the synthesis of polyhydroquinoline derivatives. All the polyhydroquinoline derivatives were characterized by Fourier transform infrared spectroscopy (FT-IR) and Nuclear magnetic resonance spectroscopy (¹H NMR). For the very first time ever we have used BiFeO₃ as a recyclable magnetic nanocatalyst in the one-pot four component cyclization reaction of benzaldehyde, ethylacetoacetate/methylacetoacetate, dimedone/cyclohexane-1,3-dione, and ammonium acetate for the synthesis of polyhydroquinoline derivatives without solvent under refluxing conditions to provide excellent yields of products. BiFeO₃ nanocatalyst (without any functionalization/surface coatings) shows easy magnetic separation, recyclability, reusability along with excellent yield of polyhydroquinoline derivatives in an economic and benign way.

Full text of DOI:10.1002/aoc.4357

Received: 28 November 2017
DOI: 10.1002/aoc.4357
Revised: 15 February 2018
Accepted: 22 February 2018
F U L L P A P E R
Sucrose chelated auto combustion synthesis of BiFeO3
nanoparticles: Magnetically recoverable catalyst for the one‐
pot synthesis of polyhydroquinoline
Harminder Singh
| Nidhi Garg | Priya Arora
| Jaspreet Kaur Rajput | Jigyasa
Department of Chemistry, Dr. B R
Ambedkar National Institute of
Technology, Jalandhar ‐144011, Punjab,
India
Sucrose chelated Bismuth ferrite (BiFeO3) nanoparticles as a novel heteroge-
neous catalyst was synthesized by an auto combustion route. Different calcina-
tion temperatures (150 °C, 450 °C, 550 °C, 650 °C, 750 °C and 850 °C) have
been employed to obtain single phased BiFeO3 nanoparticles. The perovskite
structure formation and disappearance of organic phase (sucrose) was obtained
by Fourier transform infrared spectroscopy (FT‐IR). Phase determination and
structural characterization was carried out by powder X‐ray diffraction
(XRD). The magnetic properties were analyzed by vibrating sample magnetom-
eter (VSM) whereas surface area/pore volume was obtained by Brunauer–
Emmett–Teller (BET). Transmission electron microscope (TEM) analyzed the
particles size and morphology. Thermal stability was investigated by thermo-
gravimetric analysis (TGA) and determination of constituent elements was car-
ried out by X‐ray Photo‐Electron Spectroscopy (XPS). Raman spectroscopy
confirmed the perovskite structure of the synthesized materials. The BiFeO3
nanoparticles so obtained were employed as heterogeneous catalyst for the syn-
thesis of polyhydroquinoline derivatives. All the polyhydroquinoline deriva-
tives were characterized by Fourier transform infrared spectroscopy (FT‐IR)
and Nuclear magnetic resonance spectroscopy (1H NMR). For the very first
time ever we have used BiFeO3 as a recyclable magnetic nanocatalyst in the
one‐pot four component cyclization reaction of benzaldehyde,
ethylacetoacetate/methylacetoacetate, dimedone/cyclohexane‐1,3‐dione, and
ammonium acetate for the synthesis of polyhydroquinoline derivatives without
solvent under refluxing conditions to provide excellent yields of products.
BiFeO3 nanocatalyst (without any functionalization/surface coatings) shows
easy magnetic separation, recyclability, reusability along with excellent yield
of polyhydroquinoline derivatives in an economic and benign way.
Correspondence
Harminder Singh, Department of
Chemistry, Dr. B R Ambedkar National
Institute of Technology, Jalandhar ‐
144011, Punjab, India.
Email: harmindersingh87@gmail.com
KEYWORDS
BiFeO3, calcination, chelation, heterogeneous catalyst, magnetic recoverable catalyst and
multicomponent reaction
Appl Organometal Chem. 2018;32:e4357.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4357

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SINGH ET AL.
reaction occurring at higher temperature. They do not
undergo oxidation, leaching in any solvent due to their
high chemical stability.
Quinolines having 1, 4‐dihydropyridine nucleus repre-
sent an important class of drugs because of their pharma-
1 | INTRODUCTION
For the past decade, magnetic nanoparticles got much
attention, due to their wide variety of application such
as drug delivery,[1] bio‐separation, magneto‐thermal ther-
apy, biomolecular sensing,[2] information storage, elec-
tronic devices,[3] magnetic resonance imaging (MRI),[4]
localizers in therapeutic hyperthermia,[5] sealing, gas sen-
sors, lithium ion batteries, pigments, magnetic mate-
rials,[6] magnetic recording media,[7] contrast agents,[8]
clinical use[9] and catalysis. Some of the magnetic mate-
rials have tremendous properties which makes them
superior over the other nanoparticles such as high surface
area, high chemical stability, high catalytic activity, recy-
clability, reusability, low cost of production, biocompati-
bility, non‐toxicity, and facile recovery from the reaction
mixture by using an external magnet.[3]
cological
properties
and
significant
biological
activity.[21,22] They have well known calcium channel ago-
nist–antagonist modulation activities[23] and thus used in
the therapeutic treatment of cardiovascular diseases[24]
such as hypertension, angina pectoris, supraventricular
tachycardia.[25] In particular, drugs such as nifedipine,
felodipine are dihydropyridiyl compounds. 1, 4‐
hydroquinoline derivatives show cerebral antischemic
activity and thus, are curative for Alzheimer's disease. So
far, literature have disclosed that these compounds possess
various biological activities such as Sedative, cognition,
antianxiety, antimutagenic, antioxidant, anticonvulsant,
Due to magnetic, photocatalytic and multiferroic prop-
erties, perovskite and its related compounds are in much
demand. BiFeO3 is one of the most promising perovskite
structured material, widely used due to its unique mag-
netic, optical and electrical properties.[10,11] Due to the
simultaneous existence of ferroelectric and antiferromag-
netic properties, BiFeO3 are potential candidates in practi-
cal point of view. The reason behind ferroelectricity is
stereo chemically active 6s2electrons in Bi3+ ion and
behind magnetism the partially filled 3d orbital of the
Fe3+ ion. The synergistic effect of both individual ions is
that the resultant BiFeO3 nanoparticles show both
ferroelectric and antiferromagnetic properties at the same
time at room temperature, demonstrating it as a one
bronchodilator,
antidiabetic,[26]
antitubercular,[27]
geroprotective, neuromodulatory, neuroprotectant, anal-
gesic,[28] hepatoprotective, vasodilator, antiatherosclerotic
activity. These compounds also exhibits certain medicinal
applications such as chemo sensitizer in tumor therapy,
memory enhancing power, platelet anti‐aggregatory activ-
ity, anti‐inflammatory activity, antithrombotic activity.[29]
In this communication, we first time ever reported
BiFeO3 nanoparticles as heterogeneous catalyst in one‐
pot four component cyclization reaction of benzaldehyde,
diketone, ethyl/methyl acetoacetate and ammonium ace-
tate under refluxing and solvent less conditions. BiFeO3
nanoparticles are not coated with any protecting agent
like silica, polymer, etc. to prevent further agglomeration
or oxidation or functionalization with any groups as com-
pared to other magnetic nanoparticles used in multicom-
ponent routes. No need of doping was done to enhance its
catalytic activity Furthermore, our catalyst is single lay-
ered, i.e. BiFeO3 nanoparticles, itself act as a catalyst.
The catalyst was employed for the synthesis of
polyhydroquinoline derivatives which are obtained with
high purity. The organic product obtained is of high
purity. The most important feature of the present protocol
is that, pure form the product obtained simply by recrys-
tallization from ethanol without using column chroma-
tography. Further, it enables high yields, mild
conditions, uncomplicated work up, low catalyst loading,
reusable and inexpensive catalyst, waste reduction, less
time consuming, reducing energy and money require-
ments. Moreover, heterogeneous catalyst with magnetic
property can be easily separated from reaction mixture
by using an external magnet and reused up to many times
without showing any considerable loss in activity. The
findings suggested that BiFeO3 nanoparticles as a new
insight in the heterogeneous catalysis with high catalytic
activity.
of the promising multiferroic material.[12,13]
A
number of methods have been reported so far, for its
synthesis.[14–20] All the existing methods lack the
nonstoichiometric formation of by‐ products BixFeyOz
during their synthesis routes along with harsh reaction
conditions, complicated work up procedure, time
consuming synthesis route, wide particle size distribution,
consumption of external energy, inhomogeneity, use of
expensive reagents and low catalytic activity. Eco‐friendly,
cost effective and effectual method therefore needs to be
developed without such kind of disadvantages.
To overcome such kind of problems, we developed a
promising technique of synthesis of BiFeO3 nanoparticles
by auto combustion, using sucrose as a chelating agent.
Our method has advantages like no requirement of any
type of washing with strong or weak acid, water or other
solvent, no need to set pH, no use of expensive equip-
ment, no use of polymerization agent, no need to build
inert atmosphere, less time consuming, impurities exists
in the form of CO2, N2 and H2O. The resultant nanoparti-
cles obtained are of high purity or single phased struc-
tured. Due to high thermal stability, they can be used in

SINGH ET AL.
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NMR was MNOVA and for drawing chemical structures
was ChemDraw ultra 8.0.
2 | EXPERIMENTAL SECTION
2.1 | Materials
Bismuth nitrate (pentahydrate), Sucrose (extra pure) and
Ferric nitrate (extra pure, nonahydrate) were purchased
from Loba Chemie. Nitric acid (70%) were supplied by
Merck. All these were used as such without any further
purification.
2.3 | Synthesis of BiFeO3 nanoparticles
In a typical method, Bi(NO3)3.5H2O (2.5 mmol) was dis-
solved in 5 ml of distilled water and Fe(NO3)3.9H2O
(2.5 mmol) in 10 ml of 3 M HNO3. Both the solutions
were sonicated for 10 minutes separately. Then both
the solutions were mixed together and again sonicated
for 15 minutes. After this Sucrose (5 mmol) was added
to it. Then the mixture was stirred for 30 minutes for
complete dissolution. Then the whole mixture was col-
lected in a beaker and heated on the hot plate and tem-
perature was maintained at ≈100 °C. A continues
heating for 30 minutes, results into evaporation, auto
ignition followed by evolution of large quantities of
gases. The black powder obtained was then calcinated
at different temperatures i.e. 150 °C, 450 °C, 550 °C,
650 °C, 750 °C and 850 °C.
2.2 | Methods
The crystal structure of prepared magnetic nanoparticles
catalyst was investigated by X‐ray diffraction (XRD) using
a Panlytical XPERTPRO (NPD) X‐ray diffractometer with
Cu Kα radiation (λ = 0.154 nm), in the 2θ range 10°–80°.
Fourier transform IR (FT‐IR) spectroscopy was carried
out by using Agilent Cary 600 in the range 400–
4000 cm‐1. The morphology was studied using transmis-
sion electron microscopy (TEM). The sample was pre-
pared by dispersion of nanoparticles in ethanol, which
were deposited on a carbon‐coated Cu grid, and after dry-
ing, analysis was performed using a Hitachi S7500 instru-
ment. The magnetic properties were measured using a
vibrating sample magnetometer (VSM, Princeton Applied
Research model155) at room temperature with a maxi-
mum magnetic field range of +1 T to −1 T. Thermogravi-
metric analysis (TGA) was performed on the catalyst
using an EXSTAR6000TG/DTA 6300 instrument in the
temperature range 50−700 °C at a heating rate of 10 °C/
min under nitrogen atmosphere. Surface area and pore
characteristics were characterized using Quanta Chrome
Nova‐1000 surface analyzer instrument under liquid
nitrogen temperature with vacuum degassing at 110 °C
for 3 hrs. The specific surface area was calculated using
the BET equation. Surface properties were studied by
using X‐ray photoelectron spectroscopy (XPS, PHI 5000
Versa Prob II, FEI Inc.). Raman spectra were recorded
on Renishaw Invia Raman Microscope equipped with
argon laser (514 nm) as source of excitation. The organic
products were characterized by 1H nuclear magnetic reso-
nance spectroscopy at 400 MHz with the aid of Advance
400 spectrophotometer using tetramethylsilane as the
internal standard and CDCl3 solvent. Softwere used for
2.4 | Synthesis of Polyhydroquinoline
derivatives (Scheme 1)
A mixture of benzaldehyde (1 mmol), ethyl acetoacetate
(1 mmol) or methyl acetoacetate (1 mmol),
dimedone(1 mmol) or cyclohexane‐1,3‐dione (1 mmol)
and ammonium acetate (1.5 mmol) in the presence of cat-
alytic amount of BiFeO3 nanoparticles(5 mg) was refluxed
on water bath for the appropriate time. The completion of
the reaction was indicated by TLC. The reaction mixture
was cooled to room temperature and then dissolved in
ethanol. The catalyst was separated magnetically and
the solid product was filtered, followed by recrystalliza-
tion from ethanol to get the desired product in pure form.
3 | RESULTS AND DISCUSSION
For the preparation of single phase perovskite BiFeO3
nanoparticles, auto combustion method was used by
using sucrose as a complexing agent/fuel. The sucrose
undergoes hydrolysis in the presence of nitric acid and
converted into glucose and fructose. As there was large
number of COOH and OH groups in the complexing
SCHEME 1 Method of synthesis of
polyhydroquinoline derivatives by BiFeO3
nanoparticles

4 of 23
SINGH ET AL.
agent, further converted into saccharic acid, glyocolic acid
and trihydroxy‐butyric acid. These groups form complex
with the metal ions[30]. During the calcination process
the complexing agent decomposes, mass of the gases gen-
erated which leads to the formation of highly crystalline
and single phased perovskite BiFeO3 nanoparticles as
shown below.
3.1 | Characterization of the as prepared
catalyst
The FT‐IR spectroscopy was carried out to study the dis-
appearance of organic phase and appearance of perov-
skite structure with the increase in calcination
temperature. FT‐IR analysis of different samples prepared
at different calcination temperature (150 °C, 450 °C,
550 °C and 650 °C) has been done as shown in Figure 1.
A broad peak from 3000‐3400 cm‐1 of OH stretching mode
of H2O has been observed in case of BiFeO3 nanoparticles
prepared at 150 °C. As we increased the calcination tem-
perature to 450 °C, 550 °C and 650 °C, we observed the
complete removal of moisture from the surface of sam-
ples. Further, in case of calcination temperature of
150 °C, several peaks of C‐OH and C‐O‐C stretching
bonds around 1060 cm‐1, 1139 cm‐1, 1165 cm‐1 were
observed. This might be the presence of unreacted sucrose
molecule in the sample. The elimination of these peaks
goes on increasing with increase in calcination tempera-
ture i.e. 450 °C, 550 °C and 650 °C. In case of 650 °C,
the sharp peaks around 819 cm‐1, 522 cm‐1 and 437 cm‐1
were corresponding to the Bi‐O, Fe‐O stretching vibration
and O‐Fe‐O bending vibrations of FeO6 groups.[30,31] This
confirmation revealed the perovskite structure of BiFeO3
nanoparticles synthesized at 650 °C. The sharpness of
these peaks goes on increasing as we increased the calci-
nation temperature i.e. from 150 °C to 650 °C, demon-
strated the completion of bond formation (Bi‐O and Fe‐
O)[32] and high degree of crystallization.
BiðNO3Þ3 þ FeðNO3Þ3 þ C12H22O11 þ 9=2O2 → BiFeO3
þ12CO2 þ 3N2 þ 11H2O
FIGURE 1 Comparison study of Fourier transforms infrared (FT‐
IR) spectra of BiFeO3 calcinated at 150 °C, 450 °C, 550 °C and 650 °C
FIGURE 2 XRD analysis of BiFeO3 nanoparticles calcinated at (a) 150 °C, (b) 450 °C, (c) 550 °C, (d) 650 °C, (e)750 °C, (f) 850 °C

SINGH ET AL.
5 of 23
XRD is an analytical technique, used for phase deter-
temperature, all the secondary phases were removed
completely and pure form of single phase BiFeO3 nano-
particles was generated. The average particle size was cal-
culated by using Scherrer's formula D= kλ/β cos ϴ, where
λ is the wavelength, β is the corrected diffraction line full‐
width at half maximum, k is a constant (having a value of
0.94) and ϴ is Bragg's angle, by using different planes like
(012), (104) and (110). The average size obtained for sam-
ples calcinated at different temperatures 150 °C, 450 °C,
550 °C and 650 °C was 5.74, 11.79, 69.3 and 70.01 nm
respectively as shown in Figure 3. The increase in average
particles size with increasing calcination temperature was
attributed to the formation of cluster and the particle
collision.[36] Further it was due to the improvement in dif-
fraction peaks intensity and increment in diffraction peak
sharpness with increase in temperature which results into
enlarged particle size.[37]
mination of crystalline materials. For this purpose, XRD
analysis of BiFeO3 nanoparticles calcinated at a different
range of temperatures like 150 °C, 450 °C, 550 °C,
650 °C, 750 °C and 850 °C was carried out as shown in
Figure 2. At low temperature i.e. 150 °C, there was no
any characteristic peak observed or we can say that its
pattern looks like a pattern of amorphous materials. Fur-
ther, to obtain the pure form of BiFeO3 nanoparticles, it
undergoes calcination at different range of temperatures
like 450 °C, 550 °C, 650 °C, 750 °C and 850 °C. The main
diffraction peaks of BiFeO3 nanoparticles started
appearing at 450 °C along with secondary minor impurity
phases like Bi2Fe4O9 and Bi36Fe24O57 corresponding to
2ϴ = 25.75o, 30.33o, 48.41o, 49.30o and 24.64o, 30.31o,
33.28o, 42.07o, 43.43o, 54.29o and 55.55o respectively. The
reason for the formation of secondary phases was attrib-
uted to the comparable oxygen affinity of both Fe and
Bi ion. On further increasing temperature around
550 °C, the intensity of secondary phases decreases along
with sharpening of main diffraction peaks. When the
sample was further calcinated at 650 °C, the main diffrac-
tion peaks of BiFeO3 nanoparticles were observed at
22.5o, 31.78o, 32.0o, 38.96o, 39.09o, 46.05o, 51.47o, 51.73o,
55.54o, 55.59o and 55.87o corresponding to (012), (104),
(110), (006), (202), (024), (116), (122), (214), (018) and
(300) miller indices respectively. All the major peaks
exactly matched with the JCPDS Card no. 86‐1518.[12]
The above results concluded that sample prepared at
650 °C, having main diffraction more sharpened along
with almost elimination of secondary phases. So more
will be the calcination temperature more will be the
sharpening and purity of the sample,[14,33] i.e. pure perov-
skite form of BiFeO3 nanoparticles was obtained,[34] this
result was also in agreement as discussed earlier in FT‐
IR analysis. Further to check whether 650 °C was the
optimum calcination temperature for the synthesis of
BiFeO3 nanoparticles, further the sample was also calci-
nated at 750 °C and 850 °C. When the comparison of dif-
fraction peaks of sample calcinated at 750 °C has been
carried out with the sample calcinated at 650 °C, it has
been observed that two new impurity peaks i.e. at 14.79o
and 32.99o started appearing of Bi2O3, Bi3Fe4O9,
VSM technique was used for the detection of magnetic
behavior exhibited by the nanoparticles. For this purpose
the study of magnetic hysteresis M (H) of samples calci-
nated at different range of temperatures was carried out
at room temperature over a magnetic field of
1 T as
shown in Figure 4. Magnetic character of all prepared
samples at different range of calcination temperatures
was carried out. All the samples show narrow hysteresis
cycle which indicates their soft magnetic character. Basi-
cally the magnetic character possessed by the BiFeO3
nanoparticles was due to the existence of Fe3+ and excess
of O vacancies.[34] The values of saturation magnetization
(Ms) for BiFeO3 nanoparticles synthesized at different cal-
cination temperature are 0.60 emu/g, 5.68 emu/g,
2.54 emu/g and 0.43 emu/g for 150 °C, 450 °C, 550 °C
and 650 °C, respectively. The reason for low Ms value of
the sample calcinated at 150 °C might be the little bit
[34]
[35]
Bi2Fe4O4
and Bi36Fe24O57,
respectively. On further
increasing temperature at 850 °C, the sample almost
completely lost its main diffraction peaks of pure form.
The diffraction pattern mainly consists of impurities of
secondary phase at 2ϴ = 14.79o, 28.99o, 29.81o, 33.80o,
47.27o and 49.49o, these phases may be attributed to the
[34]
[35]
formation of Bi2O3, Bi3Fe4O9
and Bi2Fe4O4.
So,
from the above discussion it was clear that 650 °C was
the optimum calcination temperature for the formation
of single phase perovskite BiFeO3 nanoparticles. At this
FIGURE 3 Average size of BiFeO3 nanoparticles calcinated at
150 °C, 450 °C, 550 °C and 650 °C

6 of 23
SINGH ET AL.
FIGURE 4 VSM of BiFeO3 nanoparticles calcinated at 150 °C, 450 °C, 550 °C and 650 °C
formation of Fe‐O, O‐Fe‐O bonds as also revealed by FT‐
IR in Figure 1. Further increase in Ms value was due to
appearance or forming of Fe‐O and O‐Fe‐O bonds in the
samples i.e. at 450 °C. Beyond 450 °C, the reason for the
decrease in the magnetization with increasing calcination
temperature for synthesis is due to the increase in the
bond length of Bi‐Fe bond and bond angle of Fe‐O‐Fe,
O‐Fe‐O bonds.[38] Another reason for a decrease in the
value of magnetic saturation with increasing calcination
temperature was due to the fact that some grains at
higher temperature do not possess a spontaneous mag-
netic moment and therefore they were unable to contrib-
ute in the magnetization.[39] The value of Ms 0.43 emu/g
clearly demonstrated that pure form of BiFeO3 nanoparti-
cles obtained at 650 °C, shows ferromagnetic character.
This value of magnetization saturation was sufficient to
separate it from the reaction mixture by applying strong
magnet, which further enhanced its use as magnetically
separable catalyst in the organic reactions.[40]
calculated by XRD i.e. in our case at 650 °C, the grain size
shown by TEM analysis was around 123 nm. This may be
due to the fact that grain contains sub grains which were
separated by low‐angle grain boundaries.[41] Further-
more, no agglomeration of particles observed because of
the reason that the particles were well dispersed before
TEM analysis.[37] The particles obtained were spherical
in nature.
For the determination of different constituent ele-
ments present in the resultant perovskite single phase
BiFeO3 nanoparticles, XPS analysis has been carried out
as shown in Figure 6. Binding energies of the different
constituent like Bi, Fe and O elements have been calcu-
lated. For bismuth ions, the values of binding energies
for spin component 3/2 and 5/2 were 157.0 eV and
162.3 eV respectively with value of spin orbit splitting of
5.3 eV from Bi‐O bond.[42] This observation demonstrated
that the bismuth ion was present as Bi3+. Further for Fe
2p, the values of two wide doublet peaks of binding ener-
gies were found at 708.4 eV and 722.0 eV having spin
orbit splitting energy of 13.6 for Fe 2p3/2 and Fe 2p1/2
respectively.[43] This shows that Fe ion was present as[44]
Fe3+. No extra peak for other oxidation state of Fe was
observed. This investigation was in good agreement with
the previous existing literature.[45–47] The value of binding
For the determination of the particle size and mor-
phology, TEM analysis has been carried out by using cop-
per grid. Figure 5 shows the TEM analysis of samples
prepared at lower and higher range of calcination temper-
atures 150 °C and 650o. In this analysis the grain size has
been found to be large as compared to the average size

SINGH ET AL.
7 of 23
FIGURE 5 TEM image of BiFeO3 nanoparticles calcinated at (a)
150 °C and (b) 650 °C
energy near at 527.7 eV was due to the O 1 s, which fur-
ther confirmed the existence of oxygen in the O2‐ binding
energy state.[43] All these results were in good agreement
with the XPS data of other reported BiFeO3 nanoparti-
cles.[48] In XPS, when a photon of light is absorbed by
an atom of molecules, ionization and emission of inner
electron occurs. In case of Bi, inner electrons were present
in 4f orbital whereas in case of Fe they were present in 2p
orbital. The low value of binding energy of Bi as com-
pared to Fe, confirmed that 4f inner electrons require
low energy (experience less nuclear charge) for ionization
as compared to 2p orbital (experience more nuclear
charge). Therefore Bi ion shows the high oxidative prop-
erty as compared to Fe in BiFeO3. Moreover, the reason
FIGURE 6 XPS of BiFeO3 nanoparticles of elements (a) Bi, (b)
Fe, (c) O
for the low value of spin‐orbit splitting i.e. 5.3 eV for Bi
as compared to 13.6 eV for Fe was dependent upon the
1/r3 value, where r is the radius of orbit.[49,50]

8 of 23
SINGH ET AL.
TABLE 1 Surface area and pore volume analysis of samples pre-
pared at different temperature
Sample
(BiFeO3)
Surface
Area(m2/g)
Pore
Volume(cc/g)
Sr.No
1.
2.
3.
4.
150 °C
450 °C
550 °C
650 °C
6.412
2.183
1.888
1.604
0.005
0.003
0.005
0.002
BET technique was used for the determination of sur-
face area and pore volume. The BET analysis of BiFeO3
nanoparticles, prepared by using sucrose as chelating
agent and further calcinated at different range of temper-
ature has been carried out as shown in Table 1. As
expected surface area and porosity was reduced with
increasing calcination temperature, because there was
increase in particle size with increasing temperature as
also calculated by XRD earlier. Surface area calculated
by BET was directly related to the average diameter of
the material. There was decrease in the amount of
nitrates with increasing calcination temperature, results
into increment in size as in our case at 650 °C; size was
70 nm (by XRD) and decrease into lattice strain. More-
over at highest temperature nanoparticles are in most
crystalline form as already cleared in XRD analysis and
have smallest surface area.[51]
FIGURE 8 TGA analysis of BiFeO3 nanoparticles calcinated at
calcinated at 150 °C, 450 °C, 550 °C and 650 °C
273, 352, 370, 450, 465, 524 cm‐1 as shown in Figure 7.
The internal vibrations of FeO6 octahedra was responsible
for the appearance of modes above 200 cm‐1 and modes
below 200 cm‐1 were caused by the Bi atoms of the perov-
skite layer which corresponds to a rigid layer.[53] The
above observed results were in good agreement with the
XRD analysis confirming the perovskite structure of
BiFeO3 nanoparticles.
Raman spectroscopy is regarded as a very sensitive
technique for the determination of crystalline and local
structure within the material. The Raman spectra of pur-
est form of BiFeO3 nanoparticles obtained at 650 °C has
been carried out. According to symmetry consideration
the Raman spectrum must consists of 13(4A1+9E) active
modes.[52] In our case 4A1 modes were observed at 135,
169, 214, 469 cm‐1 and 9E modes were at 104, 122, 263,
The thermal stability of as‐prepared nanoparticles has
been shown in Figure 8. In a case of calcination at 650 °C,
the initial weight loss of 0.10% occurred from 0‐251 °C,
this can be attributed to the loss of moisture, H2O etc.
from the surface of nanoparticles. On further increasing
the temperature from 251‐403 °C, weight loss observed
was 0.30%, which proved that reaction start occurring that
leads to the formation of BiFeO3 nanoparticles. A small
weight loss(0.20%) was also observed in the range of
403‐595 °C, this may be attributed to the decomposition
of organic impurities before 595 °C.[37] The weight loss
above 595 °C was attributed to the decomposition of
nitrate species. With increasing the calcination tempera-
ture the stability increases as weight percentage left for
the samples calcinated at 150 °C, 450 °C, 550 °C and
650 °C was 44.2, 96.8, 98.7 and 99.4 respectively. The rea-
son for higher weight percentage left with increasing tem-
perature from 150 °C to 650 °C could be ascribed to the
formation of stable single phase of BiFeO3 nanoparticles
as proved earlier by XRD results.
After full structural confirmation of the as synthesized
catalyst, the catalytic performance was surveyed on the
model reaction. For optimization of model reaction for
the synthesis of polyhydroquinoline derivatives by using
benzaldehyde (1 mmol), dimedone (1 mmol), ethyl
FIGURE 7 Raman Spectra of BiFeO3 nanoparticles

SINGH ET AL.
9 of 23
SCHEME 2 Optimization of various
reaction conditions on model reaction
acetoacetate (1 mmol) and ammonium acetate (1.5 mmol)
various types of reaction conditions like effect of catalyst's
calcination temperature, screening of the amount of cata-
lyst, effect of temperature, screening of the solvent, etc.
were studied as in Scheme 2.
and 650 °C (Entry 1 & 6, Table 2), poor yield of desired
product was obtained.
In the second stage, we checked the synthesis in the
presence of different catalytic amounts of BiFeO3 nano-
particles prepared at calcination temperature 650 °C.
Without using any catalyst, reaction took 60 minutes for
its completion, producing a yield of 49% (Entry 1,
Table 3). Variable amount of BiFeO3 (2.5, 5, 10, 15 mg)
was taken and reactions proceed to completion in 5, 3,
5, 12 minutes providing a yield of 89, 97, 90, and 79 %
respectively (Entry 2‐5, Table 3). Thus, 5 mg of catalyst
is enough to catalyze the reaction. Notably, increasing
or decreasing the amount of the catalyst did not decrease
the reaction time and increase the product's yield. Thus,
5 mg of catalyst was considered to be the optimized
amount for the reaction.
After deciding the optimum calcination temperature
and appropriate amount of BiFeO3 nanoparticles for cata-
lytic activity in synthesis of polyhydroquinoline deriva-
tives, next we examined the effect of temperature on the
reaction time and yield. The reaction was carried out at
room temperature, 40 °C, 60 °C, 80 °C and under
Condensation reaction was carried out for one‐pot
synthesis of polyhydroquinoline derivative using 5 mg
amount of catalyst prepared at different calcination tem-
peratures; different yields of product were obtained.
When catalyst prepared by calcination at a temperature
of 150 °C, 450 °C, 550 °C was used, low yields were
obtained and better results were obtained with the cata-
lyst prepared at a calcination temperature of 650 °C, pro-
viding an excellent yield of 97% within 3 minutes (as
shown in Table 2). This might be due to formation of pure
single phase of BiFeO3 nanoparticles as discussed earlier
in result and discussion section. The reaction with cata-
lyst prepared at higher calcination temperature 750 °C
and 850 °C was also considered (Entry 7 & 8, Table 2),
with 15% and 41% of yields observed respectively. Fur-
ther, reaction was also tried with BiFeO3 prepared by
using without chelating agent and calcinated at 150 °C
TABLE 2 Effect of calcination temperature on catalyst performancea
Entry
Catalyst
Calcination temperature(°C)
Chelating agent
Time(min)
Yield(%)b
1
2
3
4
5
6
7
8
BiFeO3
BiFeO3
BiFeO3
BiFeO3
BiFeO3
BiFeO3
BiFeO3
BiFeO3
150
150
450
550
650
650
750
850
‐
Sucrose
Sucrose
Sucrose
Sucrose
‐
5
6
3
4
3
3
4
4
10
81
79
83
97
14.5
15
41
Sucrose
Sucrose
aReaction conditions: Benzaldehyde (1 mmol), Dimedone (1 mmol), Ethyl acetoacetate (1 mmol), Ammonium acetate (1.5 mmol) catalyst (5 mg),), solvent free,
refluxing on water bath.
bIsolated Yield.

10 of 23
SINGH ET AL.
TABLE 3 Effect of catalytic amounta
Entry
BiFeO3(mg)
Time(min)
Yield(%)b
1
2
3
4
5
0
60
5
49
89
97
90
79
2.5
5
3
10
15
5
12
aReaction conditions: Benzaldehyde (1 mmol), Dimedone (1 mmol), Ethyl acetoacetate (1 mmol), Ammonium acetate (1.5 mmol), solvent free, refluxing on
water bath.
bIsolated Yield.
TABLE 4 Effect of temperaturea
Entry
BiFeO3 (mg)
Condition
Time(min)
Yield (%)b
1
2
3
4
5
6
5
5
5
5
5
5
R.T
‐
Trace
28
40 °C
60 °C
80 °C
Refluxing
U.S
15
6
13
9
24
3
97
‐
‐
aReaction conditions: Benzaldehyde (1 mmol), Dimedone (1 mmol), Ethyl acetoacetate (1 mmol), Ammonium acetate (1.5 mmol), R.T = room temperature, U.S.
= Ultra Sonication.
bIsolated Yield.
refluxing, the yield came out be the trace, 28, 13, 24 and
97% respectively (Entry 1‐5, Table 4). The observation
demonstrated that under refluxing was the ideal tempera-
ture condition to carry the reaction with excellent yield.
Further, we also investigated the reaction under ultra
sonication at room temperature for 30 minutes, but no
reaction occurred (Entry 6, Table 4).
After, establishing the optimum catalytic amount of
the catalyst for the reaction, next we focused on the sol-
vents with varying polarities. When attempts were made
to try the reaction in the presence of different solvents
with 5 mg amount of BiFeO3 nanoparticles, remarkable
changes in yield and reaction time were observed. This
clearly indicated that the solvent have an important effect
on reaction. When CH3OH:H2O(1:1) mixture was used as
a solvent, it took 2 minutes to complete the reaction and
afford a yield of 87% while when C2H5OH:H2O (1:1) mix-
ture was used, a yield of 73% was obtained in 3 min
(Entry 5‐6, Table 5). In the presence of water, methanol
and DCM, reaction proceeded gradually and took a time
period of 120, 122, 152 minutes for its completion, fur-
nishing a yield of 66, 74, and 77% respectively (Entry 2‐3
& 8, Table 5). Reaction took 12 hours with ethanol con-
tributing a yield of 86 % (Entry 4, Table 5). While with sol-
vents like acetonitrile, THF and toluene, a prolonged
reaction time of nearly 24 hrs was observed with a yield

SINGH ET AL.
11 of 23
TABLE 5 Screening of the solventa
Entry
Solvent(2 ml)
Time(min)
Yield (%)b
1
‐
3
120
122
12 hrs
2
97
66
74
86
87
73
‐
2
H2O
3
CH3OH
C2H5OH
CH3OH: H2O
C2H5OH: H2O
DMF
4
5
6
3
7
‐
8
DCM
152
24 hrs
24 hrs
24 hrs
77
75
79
70
9
CH3CN
THF
10
11
Toluene
aReaction conditions: Benzaldehyde (1 mmol), Dimedone (1 mmol), Ethyl acetoacetate (1 mmol), Ammonium acetate (1.5 mmol), refluxing on water bath.
bIsolated Yield.
of 75, 79, and 70% respectively (Entry 9‐11, Table 5). No
reaction took place when DMF was used as a solvent
(Entry 7, Table 5). However, under solvent free condi-
tions, yield of the product improved significantly in short
reaction time in comparison with other protic, aprotic,
polar and non‐polar solvents (Entry 1, Table 5). Thus
the reaction precedes smoothly using 5 mg of BiFeO3
nanoparticles calcinated at a temperature of 650 °C as cat-
alyst under solvent free conditions providing excellent
yields of product.
After optimizing various reaction conditions on the
model reaction, next step was to find out the applicability
of this protocol for synthesizing various derivatives under
identical conditions. For this purpose, different
substituted aldehyde, dimedone/cyclohexane‐1,3‐dione
and alkyl acetoacetate were employed for the synthesis
of polyhydroquinoline derivatives. After completion of
the reaction, the reaction product was dissolved in EtOH
and catalyst was separated from by using an external
magnet followed by recrystallization to give pure prod-
ucts. The products were obtained in excellent yields. The
products obtained as in Table 6, were characterized by
1H NMR and FT‐IR.
as shown in Scheme 3. The proposed mechanism could
be of two forms. Coupling of aldehyde with active methy-
lene compound forms the Knoevenagel product as shown
in step 2 and step 2’, followed by Michael addition to form
the final product as shown in step 3 and step 3’.
The recyclability of the catalysts is one the most
important advantage, which makes them useful in com-
mercial application. In order to investigate this issue,
the recyclability of the catalyst was checked on the model
reaction under identical conditions as given Table 7.
Heterogeneous catalyst has advantages like easy
recovery, recyclability and reusability. Isolation of desired
product and catalyst recovery by the traditional filtration
method is difficult due to the chance of moving of catalyst
into the product side, due to its nano size. Further tech-
niques including extraction of product requires lots of sol-
vents. To overcome these problems, magnetic nano
catalyst is the alternative.[54–57] Due to the ferromagnetic
character, the catalyst was recovered from the reaction
mixture after the completion of the reaction by using an
external magnet. The obtained catalyst was washed with
EtOH and dried in an oven at 50 °C. After this, it was
recycled up to five cycles with very little loss in activity
and percentage yield. The reason for little loss in activity
was due to adsorption of organic molecules on the surface
of catalyst which might be not removed during washing,
results into the blockage of catalytic active site of the cat-
alyst. The average isolated yield up to five successive runs
The reasonable mechanism for the formation of
desired product is represented as in Scheme 3. Basically,
BiFeO3 nanoparticles show Lewis acid properties due to
the presence of metal‐free orbital on the metal centers
which further enhanced the activation of carbonyl group

12 of 23
SINGH ET AL.
TABLE 6 Synthesis of various polyhydroquinoline derivatives with various aromatic aldehydesa
Aromatic
aldehyde
Alkyl
acetoacetate
Time
(min)
S.No.
Diketone
Product
Yield(%)b
m.p./[lit.](°C)
1
2a
3a
3
97
225‐226/228‐229[23]
1a
2
3
2a
3a
3a
2
90
96
256‐257/258‐260[54]
1b
1c
2a
6
181‐183/182‐184[55]
4
5
6
2a
2a
2a
3a
3a
3a
2
3
94
97
91
255‐257/257‐258[54]
242‐243/242‐244[54]
162‐165/175‐177[55]
1d
1e
1f
16
(Continues)

SINGH ET AL.
13 of 23
TABLE 6 (Continued)
Aromatic
aldehyde
Alkyl
acetoacetate
Time
(min)
S.No.
Diketone
Product
Yield(%)b
m.p./[lit.](°C)
7
2a
3a
13
94
200‐201/196‐198[55]
1g
8
9
2a
2a
3a
3a
9
76
72
243‐245/242‐244[55]
203‐204/207‐209[54]
1 h
15
1i
1j
10
2a
3a
16
79
233‐235/235‐236[56]
11
12
2a
2a
3a
3a
11
92
94
198‐200/201‐203[57]
236‐238/235‐237[58]
1k
1l
1
13
2b
3a
2
90
260‐262/not reported
1a
(Continues)

14 of 23
SINGH ET AL.
TABLE 6 (Continued)
Aromatic
aldehyde
Alkyl
acetoacetate
Time
(min)
S.No.
Diketone
Product
Yield(%)b
m.p./[lit.](°C)
257‐258/258‐259[59]
14
2b
3a
6
86
1k
1l
15
16
2b
3a
3a
2
96
97
230‐232/(new)
2b
8
218‐220/220‐221[26]
1m
17
18
2b
2b
3a
3a
3
2
89
98
210‐212/(new)
1j
1i
233‐235/ (not reported)
19
20
2b
2b
3a
3a
21
92
96
190‐192/(not reported)
197‐198/(not reported)
(Continues)
1f
3
1g

SINGH ET AL.
15 of 23
TABLE 6 (Continued)
Aromatic
aldehyde
Alkyl
acetoacetate
Time
(min)
S.No.
Diketone
Product
Yield(%)b
m.p./[lit.](°C)
264‐266/263‐265[54]
21
2b
3a
1
95
1d
22
2b
3a
3
93
254‐256/256‐258[54]
1b
1c
23
24
2b
2b
3a
3a
3
3
94
99
234‐236/(new)
259‐261/(new)
1e
1a
25
26
27
2b
2b
2b
3b
3b
3b
10
88
80
72
262‐264/(not reported)
264‐266/(new)
4
1j
1i
9
>280(new)
(Continues)

16 of 23
SINGH ET AL.
TABLE 6 (Continued)
Aromatic
aldehyde
Alkyl
acetoacetate
Time
(min)
S.No.
Diketone
Product
Yield(%)b
m.p./[lit.](°C)
254‐256/254‐255[60]
28
2b
2b
2b
3b
4
4
5
89
1d
29
30
3b
3b
96
89
>280/(new)
1c
1e
198‐200/216[58]
31
32
2b
2b
3b
3b
25
95
87
>280/(new)
1n
1g
2
242‐245/(new)
was 92.8% (Figure 9, Table 7). In Figure 10, FT‐IR image,
the position of peaks in BiFeO3 nanoparticles after
reusing up to five cycles have almost the same position
as in fresh BiFeO3 nanoparticles. So observation demon-
strated that no significant change has been occurring in
BiFeO3 nanoparticles. Furthermore, precipitation tests
were performed to check whether Bi3+ ions leached from
the surface of the catalyst or not. Firstly, solid product
was washed with distilled water. Then the filtrate was
divided into three parts. In the first part, dilute NaOH
was added, no white ppt of Bi(OH)3 was found, In the
second part dilute HCl was added, no white ppt of BiOCl
was observed. In the third part, potassium iodide solution
was added, no white ppt of BiI3 formed. These three pre-
cipitation tests demonstrated that no Bi3+ ions were
leached from the surface of the catalyst, show the stability
of the catalyst during the course of the reaction.
Further our catalyst was not light sensitive; this was
investigated by keeping the recovered catalyst at room
temperature for 48 hrs. It has been found that there was
no change in color observed in the recovered catalyst.
This study demonstrated the light insensitivity of as‐

SINGH ET AL.
17 of 23
FIGURE 9 Recyclability of BiFeO3 nanoparticles up to fifth cycle
SCHEME 3 Proposed mechanism of the reaction
which minimizes the catalyst loss during separation.
Moreover, our catalyst was prepared by simple, cheap
and commercial available materials and recycled up to five
times without considerable loss in activity. This catalyst is
better in terms of stability, reusability, non‐toxicity, cost
and ease of separation from the reaction mixture.
synthesized catalyst after recyclability. In addition, no
special care has to be taken to handle or store the as‐ pre-
pared catalyst for further use during the recycling process,
because it does not have any air or moisture sensitive
nature.[58,59] This was also confirmed by FT‐IR of the
recovered catalyst after fifth cycle, in which a broad peak
in the range of 3200‐3400 cm‐1 of OH was absent in
Figure 10, showing moisture insensitive nature of as‐syn-
thesized catalyst.
In order to describe the catalytic activity of our catalyst,
we compared the results with the different reported cata-
lyst in the literature on the model reaction as in Table 8.
This magnetically separable catalyst leads higher yield of
product in least reaction time than other catalyst. The
attractive feature of our catalyst is that it was separated
from the reaction mixture by using an external magnet,
3.2 | Spectral data of compounds
3.2.1 | Table 6, entry 1 (5a): ethyl 1,4,5,6,7,8‐
hexahydro‐2,7,7‐trimethyl‐5‐oxo‐4‐
phenylquinoline‐3‐carboxylate
Melting point: 225‐226 °C. White crystalline. FT‐IR (KBr,
ⱱ, cm‐1): 3291, 3221, 3085, 1699, 1611, 1070, 694 cm‐1, 1H
NMR (CDCl3, 400 MHz, δ, ppm): 0.93 (s, 3H), 1.17 (s, 3H),
1.20 (t, 3H), 2.16‐2.30 (m, 4H), 2.36 (s, 3H), 4.04 (q, 2H),
5.04 (s, 1H), 5.98 (s, 1H, N‐H), 7.16‐7.30 (m, 5H).
TABLE 7 Effect of recyclability of the catalyst on the reaction time and yielda
Entry
Cycle
Time (min)
Yield (%)b
1.
2.
3.
4.
5.
1
2
3
4
5
3
4
6
4
4
97
94
92
91
90

18 of 23
SINGH ET AL.
ppm): 0.90 (s, 3H), 1.05 (s, 3H), 1.18 (t, 3H), 2.15‐2.32
(m, 4H), 2.35 (s, 3H), 4.02 (q, 2H), 5.01 (s, 1H), 6.01 (s,
1H, N‐H), 6.85 (t, 2H), 7.23 (m, 2H).
3.2.4 | Table 6, entry 4 (5d): ethyl 4‐(4‐
bromophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 255‐257 °C. White crystalline. FT‐IR (KBr,
ⱱ, cm‐1): 3278, 3196, 3079, 2967, 1703, 1604, 1485, 1380,
1
1277, 1213, 1071, 843, 738, 532 cm‐1, H NMR (CDCl3,
400 MHz, δ, ppm): 0.92 (s, 3H), 1.07 (s, 3H), 1.18 (t, 3H),
2.16‐2.31 (m, 4H), 2.37 (s, 3H), 4.03 (q, 2H), 5.00 (s, 1H),
5.81 (s, 1H, N‐H), 7.16‐7.26 (m, 2H), 7.29‐7.31 (m, 2H).
FIGURE 10 Comparison study of Fourier transform infrared
(FT‐IR) spectra of BiFeO3 (Fresh) and reused BiFeO3 after fifth cycle
3.2.5 | Table 6, entry 5 (5e): ethyl 4‐(4‐
chlorophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
3.2.2 | Table 6, entry 2 (5b): ethyl 1,4,5,6,7,8‐
hexahydro‐4‐(4‐methoxyphenyl)‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 242‐243 °C. Pale yellow crytalline. FT‐IR
(KBr, ⱱ, cm‐1): 3276, 3193, 3078, 2965, 1705, 1601, 1485,
1
1380, 1278, 1068, 844 cm‐1, H NMR (CDCl3, 400 MHz,
Melting point: 256‐257 °C. Pale yellow solid. FT‐IR (KBr, ⱱ,
δ, ppm): 0.91 (s, 3H), 1.07 (s, 3H), 1.18 (t, 3H), 2.16‐2.35
(m, 4H), 2.37 (s, 3H), 4.03 (q, 2H), 5.01 (s, 1H), 5.93 (s,
1H, N‐H), 7.14‐7.16 (m, 2H), 7.22‐7.26 (m, 2H).
cm‐1): 3278, 3196, 2961, 1701, 1604, 1488, 1378, 1278, 1213,
1
1166, 1031, 849, 763 cm‐1, H NMR (CDCl3, 400 MHz, δ,
ppm): 0.93 (s, 3H), 1.07 (s, 3H), 1.20 (t, 3H), 2.17‐2.30
(m, 4H), 2.36 (s, 3H), 3.72 (s, 3H), 4.04 (q, 2H), 4.99
(s, 1H), 5.71 (s, 1H, N‐H), 6.73 (d, 2H), 7.22 (d, 2H).
3.2.6 | Table 6, entry 6 (5f): ethyl 1,4,5,6,7,8‐
hexahydro‐4‐(4‐isopropylphenyl)‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
3.2.3 | Table 6, entry 3 (5c): ethyl 4‐(4‐
fluorophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 160‐165 °C. White solid. FT‐IR (KBr, ⱱ,
cm‐1): 3285, 3207, 3084, 2964, 1704, 1602, 1478, 1367,
1280, 1214, 857 cm‐1, 1H NMR (CDCl3, 400 MHz, δ,
ppm): 0.96 (s, 3H), 1.07 (s, 3H), 1.16‐1.22 (m, 9H), 2.18‐
2.30 (m, 2H), 2.34 (s, 4H), 2.80 (m, 1H), 4.05 (q, 2H),
5.01 (s, 1H), 5.87 (s, 1H), 7.03 (d, 2H), 7.20 (d, 2H).
Melting point: 181‐183 °C. Brownish yellow. FT‐IR (KBr,
ⱱ, cm‐1): 3278, 3197, 3078, 2966, 1709, 1603, 1488, 1380,
1214, 1068, 853 cm‐1, 1H NMR (CDCl3, 400 MHz, δ,
TABLE 8 Comparison with other reported catalysts
S.
Time Yield
No. Catalyst
Amount
Solvent
Conditions (min) (%)
Ref.
[23]
1
‐
‐
H2O
Refluxing
80 °C
RT
480
10
96
94
84
95
92
94
92
94
85
97
[60]
[61]
[26]
[62]
[63]
[64]
[65]
[66]
2
‐
‐‐‐
Basic ionic liq [Bmim]OH
3
Fe3O4@ chitosan
HClO4‐SiO2
Cs2.5H0.5PW12O40
ZrCl4
0.03 g
50 mg
0.01 mmol
5 mole%
10 mol%
EtOH
140
8
4
‐
90 °C
5
Tetrabutylammonium bromide (2 mmol) 110 °C
6
6
EtOH(5 ml)
RT
120
360
120
10
7.
8.
L‐proline
EtOH
EtOH
‐
Refluxing
RT
Cerium(IV) ammonium nitrate 10 mol%
10. SBA‐Pr‐SO3H
0.05 g
5 mg/0.15 mol% ‐
80 °C
11. BiFeO3
Refluxing
3
This work

SINGH ET AL.
19 of 23
2.18‐2.30 (m, 3H), 2.35 (s, 4H), 3.74 (s, 3H), 4.05 (q, 2H),
5.03 (s, 1H), 5.93 (s, 1H), 6.65‐6.70 (m, 1H), 6.85‐6.91
(m, 2H), 7.10 (t, 1H).
3.2.7 | Table 6, entry 7 (5 g): ethyl 1,4,5,6,7,8‐
hexahydro‐4‐(3,4‐dimethoxyphenyl)‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 200‐201 °C. White powder. FT‐IR (KBr, ⱱ,
1
cm‐1): 3280, 3213, 3083, 1696, 1603, 1031, 731 cm‐1, H
3.2.12 | Table 6, entry 12 (5 l): ethyl 1,4,5,6,
7,8‐hexahydro‐4‐(2,4‐dimethoxyphenyl)‐
2,7,7‐trimethyl‐5‐oxoquinoline‐3‐carboxylate
NMR (CDCl3, 400 MHz, δ, ppm): 0.95 (s, 3H), 1.19 (s,
3H), 1.20 (s, 3H), 2.18‐2.32 (m, 4H), 2.38 (s, 3H), 3.80 (s,
3H), 3.83 (s, 3H), 4.07 (q, 2H), 5.00 (s, 1H), 5.75 (s, 1H,
N‐H), 6.69 (d, 1H),6.80 (d, 1H), 6.92 (s, 1H).
Melting point: 236‐238 °C. Pale yellow crystalline. FT‐IR
(KBr, ⱱ, cm‐1): 3292, 3213, 3085, 1695, 1603, 1035,
1
708 cm‐1, H NMR (CDCl3, 400 MHz, δ, ppm): 0.92 (s,
3.2.8 | Table 6, entry 8 (5 h): ethyl 4‐(furan‐
2‐yl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐trimethyl‐5‐
oxoquinoline‐3‐carboxylate
3H), 1.05 (s, 3H), 1.20 (t, 3H), 2.11‐2.18 (m, 4H), 2.28 (s,
3H), 3.73 (s, 6H), 4.02 (q, 2H), 5.15 (s, 1H), 5.81 (s, 1H),
6.34‐6.36 (m, 2H), 7.20 (t, 1H).
Melting point: 243‐245 °C. Black powder. FT‐IR (KBr, ⱱ,
cm‐1): 3236, 3146, 3059, 1713, 1640, 1466, 1364, 1242,
1
1210, 1121, 1049, 744 cm‐1, H NMR (CDCl3, 400 MHz,
3.2.13 | Table 6, entry 13 (5 m): methyl
1,4,5,6,7,8‐hexahydro‐2,7,7‐trimethyl‐5‐oxo‐4‐
phenylquinoline‐3‐carboxylate
δ, ppm): 1.02 (s, 3H), 1.09 (s, 3H), 1.26 (t, 3H), 2.22‐2.35
(m, 5H), 2.36‐2.41 (m, 2H), 3.73 (q, 2H), 5.29 (s, 1H),
5.83 (s, 1H), 6.15 (d, 1H), 6.19‐6.20 (m, 2H).
Melting point: 260‐262 °C. White crystalline. FT‐IR (KBr,
ⱱ, cm‐1): 3291, 3085, 2966, 1699, 1611, 1484, 1380, 1280,
1210, 1149, 1070, 837, 760 cm‐1, 1H NMR (CDCl3,
400 MHz, δ, ppm): 0.91 (s, 3H), 1.06 (s, 3H), 2.16‐2.35
(m, 4H), 2.37 (s, 3H), 3.61 (s, 3H), 5.05 (s, 1H), 5.79
(s, 1H), 7.10‐7.12 (m, 1H), 7.18‐7.22 (m, 2H), 7.24‐7.28
(m, 1H).
3.2.9 | Table 6, entry 9 (5i): ethyl 4‐(2‐
chlorophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 203‐204 °C. Pale yellow solid. FT‐IR (KBr, ⱱ,
cm‐1): 3291, 3205, 3076, 2962, 1696, 1480, 1378, 1280, 1070,
1
836, 749, 506 cm‐1, H NMR (CDCl3, 400 MHz, δ, ppm):
0.93 (s, 3H), 1.05 (s, 3H), 1.17 (s, 3H), 2.11‐2.20 (m, 4H),
2.30 (s, 3H), 4.03 (q, 2H), 5.36 (s, 1H), 5.90 (s, 1H),
7.00‐7.15 (m, 2H), 7.20‐7.24 (m, 1H), 7.35‐7.36 (m, 1H).
3.2.14 | Table 6, entry 14 (5n): methyl 1,4,5,
6,7,8‐hexahydro‐4‐(3‐methoxyphenyl)‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
3.2.10 | Table 6, entry 10 (5j): ethyl 4‐(3‐
bromophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 257‐258 °C. Pale yellow crytalline. FT‐IR
(KBr, ⱱ, cm‐1): 3296, 2903, 1705, 1604, 1483, 1379, 1269,
1215, 1167, 1048, 882, 770 cm‐1, 1H NMR (CDCl3,
400 MHz, δ, ppm): 0.93 (s, 3H), 1.09 (s, 3H), 2.12‐2.25
(m, 4H), 2.36 (s, 3H), 3.61 (s, 3H), 3.75 (s, 3H), 5.05 (s,
1H), 6.00 (s, 1H), 6.60‐6.70 (m, 1H), 6.80‐6.90 (m, 2H),
7.09‐7.18 (m, 1H).
Melting point: 233‐235 °C. Pale yellow crystalline. FT‐IR
(KBr, ⱱ, cm‐1): 3274, 3200, 3076, 2964, 1703, 1603, 1485,
1380, 1281, 1211, 1072, 877, 769, 511 cm‐1, 1H NMR
(CDCl3, 400 MHz, δ, ppm): 0.95 (s, 3H), 1.07 (s, 3H),
1.20 (t, 3H), 2.18‐2.30 (m, 3H), 2.37 (s, 4H), 4.05 (q, 2H),
5.01 (s, 1H), 5.90 (s, 1H), 7.06‐7.08 (t, 1H), 7.20‐7.26 (m,
2H), 7.38‐7.39 (m, 1H).
3.2.15 | Table 6, entry 15 (5o): methyl 1,4,5,
6,7,8‐hexahydro‐4‐(2,4‐dimethoxyphenyl)‐
2,7,7‐trimethyl‐5‐oxoquinoline‐3‐carboxylate
3.2.11 | Table 6, entry 11 (5 k): ethyl 1,4,5,
6,7,8‐hexahydro‐4‐(3‐methoxyphenyl)‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 230‐232 °C. Yellow crystalline. FT‐IR (KBr,
ⱱ, cm‐1): 3290, 3217, 3091, 1701, 1602, 1036, 708 cm‐1, 1H
NMR (CDCl3, 400 MHz, δ, ppm): 0.93 (s, 3H), 1.05 (s, 3H),
2.12‐2.29 (m, 4H), 2.33 (s, 3H), 3.57 (s, 3H), 3.73 (s, 3H),
3.76 (s, 3H), 5.15 (s, 1H), 5.81 (s, 1H), 6.35‐6.36 (m, 2H),
7.16‐7.18 (m, 1H).
Melting point: 198‐200 °C. Pale yellow. FT‐IR (KBr, ⱱ,
cm‐1): 3303, 3220, 2961, 1696, 1599, 1483, 1376, 1262,
1209, 1152, 1035, 860, 767 cm‐1, 1H NMR (CDCl3,
400 MHz, δ, ppm): 0.94 (s, 3H), 1.06 (s, 3H), 1.20 (t, 3H),

20 of 23
SINGH ET AL.
3.2.16 | Table 6, entry 16 (5p): methyl 1,4,5,
6,7,8‐hexahydro‐4‐(3,4,5‐trimethoxyphenyl)‐
2,7,7‐trimethyl‐5‐oxoquinoline‐3‐carboxylate
3.2.21 | Table 6, entry 21 (5u): methyl 4‐(4‐
bromophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 218‐220 °C. White crystalline. FT‐IR (KBr,
ⱱ, cm‐1): 3285, 3221, 3082, 1699, 1597, 1013, 709 cm‐1, 1H
NMR (CDCl3, 400 MHz, δ, ppm): 0.98 (s, 3H), 1.08 (s, 3H),
2.15‐2.23 (m, 4H), 2.37 (s, 3H), 3.65 (s, 3H), 3.78 (s, 9H),
5.03 (s, 1H), 5.94 (s, 1H), 6.51 (s, 2H).
Melting point: 264‐266 °C. Pale yellow. FT‐IR (KBr, ⱱ,
cm‐1): 3292, 3199, 3080, 2958, 1681, 1605, 1487, 1382,
1
1329, 1212, 1005, 841 cm‐1, H NMR (CDCl3, 400 MHz,
δ, ppm): 0.91 (s, 3H), 1.07 (s, 3H), 2.17‐2.32 (m, 4H),
2.39 (s, 3H), 3.61 (s, 3H), 5.01 (s, 1H), 5.76 (s, 1H), 7.15‐
7.18 (m, 2H), 7.30‐7.32 (m, 2H).
3.2.17 | Table 6, entry 17 (5q): methyl 4‐(3‐
bromophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
3.2.22 | Table 6, entry 22 (5a’): methyl 1,4,5,
6,7,8‐hexahydro‐4‐(4‐methoxyphenyl)‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 210‐212 °C. Pale yellow crystalline. FT‐IR
(KBr, ⱱ, cm‐1): 3281, 3208, 3079, 2965, 1710, 1606, 1479,
Melting point: 254‐256 °C. White solid. FT‐IR (KBr, ⱱ,
cm‐1): 3280, 3186, 2961, 1705, 1605, 1495, 1381, 1251,
1213, 1171, 1069, 845, 774 cm‐1, 1H NMR (CDCl3,
400 MHz, δ, ppm): 0.93 (s, 3H), 1.07 (s, 3H), 2.17‐2.31
(m, 4H), 2.38 (s, 3H), 3.61 (s, 3H), 3.73 (s, 3H), 5.00 (s,
1H), 5.72 (s, 1H), 6.72‐6.74 (m, 2H), 7.19‐7.26 (d, 2H).
1
1380, 1213, 1076, 857 cm‐1, H NMR (CDCl3, 400 MHz,
δ, ppm): 0.94 (s, 3H), 1.07 (s, 3H), 2.18‐2.31 (m, 4H),
2.38 (s, 3H), 3.61 (s, 3H), 5.03 (s, 1H), 5.93 (s, 1H), 7.08
(t, 1H), 7.20‐7.30 (m, 2H), 7.35‐7.36 (m, 1H).
3.2.18 | Table 6, entry 18 (5r): methyl 4‐(2‐
chlorophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
3.2.23 | Table 6, entry 23 (5b’): methyl 4‐(4‐
fluorophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 233‐235 °C. Yellow crystalline. FT‐IR (KBr,
ⱱ, cm‐1): 3280, 3208, 2955, 1705, 1608, 1491, 1379, 1216,
1031, 834 cm‐1, 1H NMR (CDCl3, 400 MHz, δ, ppm):
0.93 (s, 3H), 1.06 (s, 3H), 2.12‐2.28 (m, 4H), 2.29 (s, 3H),
3.60 (s, 3H), 5.38 (s, 1H), 6.27 (s, 1H), 7.00‐7.10 (m, 1H),
7.11‐7.15 (m, 1H), 7.20‐7.30 (m, 1H), 7.32‐7.34 (m, 1H).
Melting point: 234‐236 °C. White solid. FT‐IR (KBr, ⱱ,
cm‐1): 3285, 3205, 3079, 2963, 1682, 1605, 1486, 1383,
1221, 1153, 1073, 848, 769 cm‐1, 1H NMR (CDCl3,
400 MHz, δ, ppm): 0.95 (s, 3H), 1.06 (s, 3H), 2.12‐2.31
(m, 4H), 2.38 (s, 3H), 3.59 (s, 3H), 5.02 (s, 1H), 5.67 (s,
1H), 6.84‐6.88 (m, 2H), 7.22‐7.24 (d, 2H).
3.2.19 | Table 6, entry 19 (5 s): methyl 1,4,5,
6,7,8‐hexahydro‐4‐(4‐isopropylphenyl)‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
3.2.24 | Table 6, entry 24 (5c’): methyl 4‐(4‐
chlorophenyl)‐1,4,5,6,7,8‐hexahydro‐2,7,7‐
trimethyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 190‐192 °C. White solid. FT‐IR (KBr, ⱱ,
1
cm‐1): 3277, 3203, 3082, 1701, 1607, 1018, 777 cm‐1, H
Melting point: 259‐261 °C. White solid. FT‐IR (KBr, ⱱ,
NMR (CDCl3, 400 MHz, δ, ppm): 0.95 (s, 3H), 1.07 (s,
3H), 1.18 (d, 6H), 2.15‐2.30 (m, 4H), 2.35 (s, 3H), 2.80 (q,
1H), 3.61 (s, 3H), 5.03 (s, 1H), 5.96 (s, 1H), 7.03 (d, 2H),
7.17 (d, 2H).
cm‐1): 3288, 3205, 3082, 2963, 1683, 1606, 1486, 1382,
1
1332, 1220, 1141, 1080, 843, 735 cm‐1, H NMR (CDCl3,
400 MHz, δ, ppm): 0.90 (s, 3H), 1.06 (s, 3H), 2.12‐2.31
(m, 4H), 2.37 (s, 3H), 3.61 (s, 3H), 5.01 (s, 1H), 5.72 (s,
1H), 7.13‐7.19 (m, 2H), 7.20‐7.24 (m, 2H).
3.2.20 | Table 6, entry 20 (5 t): methyl 1,4,5,
6,7,8‐hexahydro‐4‐(3,4‐dimethoxyphenyl)‐
2,7,7‐trimethyl‐5‐oxoquinoline‐3‐carboxylate
3.2.25 | Table 6, entry 25 (5d’): methyl 1,4,5,
6,7,8‐hexahydro‐2‐methyl‐5‐oxo‐4‐
phenylquinoline‐3‐carboxylate
Melting point: 197‐198 °C. White solid. FT‐IR (KBr, ⱱ,
1
cm‐1): 3280, 3198, 3072, 1699, 1598, 1030, 734 cm‐1, H
NMR (CDCl3, 400 MHz, δ, ppm): 0.94 (s, 3H), 1.07 (s,
3H), 2.19‐2.33 (m, 4H), 2.39 (s, 3H), 3.62 (s, 3H), 3.80 (s,
3H), 3.83 (s, 3H), 5.02 (s, 1H), 5.76 (s, 1H), 6.70‐6.75 (m,
2H), 6.92‐6.93 (m, 1H).
Melting point: 262‐264 °C. White solid. FT‐IR (KBr, ⱱ,
cm‐1): 3281, 3174, 3048, 2949, 1693, 1647, 1483, 1363,
1229, 834 cm‐1, 1H NMR (CDCl3, 400 MHz, δ, ppm):
1.92‐2.08 (s, 4H), 2.35‐2.47 (s, 5H), 3.59 (s, 3H), 5.10 (s,

SINGH ET AL.
21 of 23
1H), 5.85 (s, 1H), 7.03‐7.10 (m, 1H), 7.19‐7.24 (m, 2H),
7.26‐7.29 (m, 2H)
1.98‐2.01 (m, 4H), 2.32‐2.46 (m, 5H), 3.62 (s, 3H), 5.05
(s, 1H), 5.76 (s, 1H), 7.23‐7.24 (m, 4H).
3.2.31 | Table 6, entry 31 (5j’): methyl 1,4,5,
6,7,8‐hexahydro‐4‐(2‐hydroxy‐3‐methoxyphenyl)‐
2‐methyl‐5‐oxoquinoline‐3‐carboxylate
3.2.26 | Table 6, entry 26 (5e’): methyl 4‐(3‐
bromophenyl)‐1,4,5,6,7,8‐hexahydro‐2‐
methyl‐5‐oxoquinoline‐3‐carboxylate
Melting point:: >280 °C. Yellow solid. FT‐IR (KBr,
ⱱ, cm‐1): 3287, 3199, 3070, 2954, 1706, 1637, 1469, 1367,
1240, 856 cm‐1, 1H NMR (CDCl3, 400 MHz, δ, ppm):
1.89‐2.01 (m, 4H), 2.36‐2.47 (m, 5H), 3.51 (s, 3H), 3.82
(s, 3H), 5.16 (s, 1H), 5.98 (s, 1H), 6.55‐6.57 (m, 1H),
6.69‐6.72 (m, 2H), 9.28(s, 1H).
Melting point: 264‐266 °C. White solid. FT‐IR (KBr, ⱱ,
cm‐1): 3281, 3174, 3048, 2949, 1693, 1647, 1483, 1363,
1229, 834 cm‐1, 1H NMR (CDCl3, 400 MHz, δ, ppm):
1.98‐2.01 (m, 4H), 2.36‐2.47 (m, 5H), 3.63 (s, 3H), 5.06
(s, 1H), 5.77 (s, 1H), 7.06‐7.08 (m, 2H), 7.21‐7.24 (m,
1H), 7.26‐7.33 (m, 1H).
3.2.32 | Table 6, entry 32 (5 k’): methyl 1,4,
5,6,7,8‐hexahydro‐4‐(3,4‐dimethoxyphenyl)‐
2‐methyl‐5‐oxoquinoline‐3‐carboxylate
3.2.27 | Table 6, entry 27 (5f’): methyl 4‐(2‐
chlorophenyl)‐1,4,5,6,7,8‐hexahydro‐2‐
methyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 242‐245 °C. White crystalline. FT‐IR (KBr,
ⱱ, cm‐1): 3310, 3075, 3025, 2954, 1700, 1660, 1472, 1379,
1229, 853 cm‐1, 1H NMR (CDCl3, 400 MHz, δ, ppm):
1.96‐1.99 (m, 4H), 2.32‐2.39 (m, 5H), 3.64 (s, 3H), 3.88
(s, 3H), 5.42 (s, 1H), 5.72 (s, 1H), 6.65‐6.74 (m, 2H),
6.94(m, 1H).
Melting point: >280 °C. White crystalline. FT‐IR (KBr, ⱱ,
cm‐1): 3287, 3202, 3075, 2949, 1697, 1649, 1488, 1361,
1231, 859 cm‐1, 1H NMR (CDCl3, 400 MHz, δ, ppm):
1.96‐1.97 (m, 4H), 2.38‐2.42 (m, 5H), 3.58 (s, 3H), 5.38
(s, 1H), 5.90 (s, 1H), 6.98‐7.03 (m, 1H), 7.12‐7.24 (m,
1H), 7.25‐7.26 (m, 1H), 7.50‐7.54 (m, 1H).
3.2.28 | Table 6, entry 28 (5 g’): methyl 4‐(4‐
bromophenyl)‐1,4,5,6,7,8‐hexahydro‐2‐
methyl‐5‐oxoquinoline‐3‐carboxylate
4 | CONCLUSIONS
This work provides fundamental data for the synthesis of
highly catalytic active BiFeO3 nanoparticles by auto‐com-
bustion technique. The developed method is green, fast
and convenient, cost‐effective, less time consuming,
energy saving and reducing waste generation. XRD dif-
fraction patterns confirm the optimum calcination tem-
perature and desired single phase structured material.
Magnetic measurements indicate that, the ferromagnetic
character which encouraged us to use them as heteroge-
neous catalyst in organic synthetic transformation reac-
tion. Perovskite structure is confirmed by FT‐IR, XRD
and Raman spectroscopy. TEM study revealed the spher-
ical nature of nanoparticles. XPS, study finds the constit-
uents atoms and the oxidation states of BiFeO3
nanoparticles. Further, this catalyst promotes the forma-
Melting point: 254‐256 °C. White solid. FT‐IR (KBr, ⱱ,
cm‐1): 3283, 3203, 3066, 2955, 1702, 1648, 1483, 1302,
1227, 833 cm‐1, 1H NMR (CDCl3, 400 MHz, δ, ppm):
1.96‐1.99 (m, 4H), 2.31‐2.39 (m, 5H), 3.58 (s, 3H), 5.04
(s, 1H), 5.82 (s, 1H), 7.14‐7.20 (m, 2H), 7.29‐7.31 (m, 2H).
3.2.29 | Table 6, entry 29 (5 h’): methyl 4‐(4‐
fluorophenyl)‐1,4,5,6,7,8‐hexahydro‐2‐
methyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: >280 °C. White crystalline. FT‐IR (KBr, ⱱ,
cm‐1): 3265, 3173, 3054, 2950, 1699, 1648, 1478, 1364,
1232, 845 cm‐1, 1H NMR (CDCl3, 400 MHz, δ, ppm):
1.98‐2.01 (m, 4H), 2.34‐2.46 (m, 5H), 3.59 (s, 3H), 5.11
(s, 1H), 5.73 (s, 1H), 6.85‐6.86 (m, 2H), 7.23‐7.24 (m, 2H).
tion
of
biologically
important
high
quality
polyhydroquinoline derivatives from aromatic aldehyde,
ethylacetoacetate/methylacetoacetate, dimedone/cyclo-
hexane‐1,3‐dione and ammonium acetate under refluxing
without any solvent. Catalytic study explored the effect of
catalyst's calcination temperature, screening of the
amount of catalyst, effect of temperature, screening of
the solvent and recyclability. The method offers advan-
tages such as clean reaction, low catalyst loading, recycla-
bility and reusability of catalyst, high yields of products,
3.2.30 | Table 6, entry 30 (5i’): methyl 4‐(4‐
chlorophenyl)‐1,4,5,6,7,8‐hexahydro‐2‐
methyl‐5‐oxoquinoline‐3‐carboxylate
Melting point: 198‐200 °C. White crystalline. FT‐IR (KBr,
ⱱ, cm‐1): 3279, 3211, 3084, 2959, 1703, 1649, 1473, 1363,
1228, 835 cm‐1, 1H NMR (CDCl3, 400 MHz, δ, ppm):

22 of 23
SINGH ET AL.
[14] N. Das, R. Majumdar, A. Sen, H. S. Maiti, Mater. Lett. 2007, 61,
short reaction times and use of various substrates, which
makes it a useful and attractive strategy for the synthesis
of polyhydroquinoline derivatives. We reported here low
cost bare magnetic nanoparticles which are thermally
and chemically stable apart from other magnetic catalysts
(Fe3O4, CuFe2O4, CoFe2O4 etc). Further, such single lay-
ered structured materials may bring new insight into the
designing of highly efficient heterogeneous catalyst and
potential technological applications.
2100.
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Villegas, J. Eur. Ceram. Soc. 2011, 31, 3047.
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ACKNOWLEDGMENTS
We are thankful to IIT Ropar for XRD and NMR, CIL IIT
Roorkee for VSM, BIT Bengaluru for BET, IIT Kanpur for
XPS, NIT Hamirpur for Raman spectroscopy, SAIF, Pan-
jab University Chandigarh for TEM, Department of
Chemistry NIT Jalandhar for FT‐IR, TGA. Three of the
authors (H.S., P. A, and J.) are thankful to UGC, MHRD
and NIT Jalandhar for providing the research fellowship.
[20] A. Hernández‐Ramírez, A. Martínez‐Luévanos, A. F. Fuentes,
A. G. D. Nelson, R. C. Ewing, S. M. Montemayor, J. Alloys
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Harminder Singh http://orcid.org/0000-0002-8599-0554
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How to cite this article: Singh H, Garg N,
Arora P, Rajput JK, Jigyasa. Sucrose chelated auto
combustion synthesis of BiFeO3 nanoparticles:
Magnetically recoverable catalyst for the one‐pot
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