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

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 BiFeO₃nanoparticles. 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 BiFeO₃as 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.

BiFeO₃nanocatalyst (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

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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. BiFeO₃is 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, BiFeO₃are 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 BiFeO₃nanoparticles 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

BiFeO₃nanoparticles 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. BiFeO₃nanoparticles, 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 BiFeO₃nanoparticles 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 Bi_xFe_yO_z

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 BiFeO₃nanoparticles

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, N₂and 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.

3 of 23

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 BiFeO₃nanoparticles

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 CDCl₃solvent. 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 BiFeO₃nanoparticles(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 BiFeO₃nanoparticles 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^‐1of OH stretching mode

of H₂O has been observed in case of BiFeO₃nanoparticles

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^‐1were

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^‐1and 437 cm^‐1

were corresponding to the Bi‐O, Fe‐O stretching vibration

and O‐Fe‐O bending vibrations of FeO₆groups.^[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.

BiðNO₃Þ₃þ FeðNO₃Þ₃þ C₁₂H₂₂O₁₁þ 9=2O₂→ BiFeO₃

þ12CO₂þ 3N₂þ 11H₂O

FIGURE 1 Comparison study of Fourier transforms infrared (FT‐

IR) spectra of BiFeO₃calcinated at 150 °C, 450 °C, 550 °C and 650 °C

FIGURE 2 XRD analysis of BiFeO₃nanoparticles 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 BiFeO₃nano-

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 BiFeO₃nanoparticles 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 BiFeO₃nanoparticles, 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 BiFeO₃nanoparticles started

appearing at 450 °C along with secondary minor impurity

phases like Bi₂Fe₄O₉and Bi₃₆Fe₂₄O₅₇corresponding to

2ϴ = 25.75^o, 30.33^o, 48.41^o, 49.30^oand 24.64^o, 30.31^o,

33.28^o,42.07^o, 43.43^o, 54.29^oand 55.55^orespectively. 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 BiFeO₃nanoparticles were observed at

22.5^o, 31.78^o, 32.0^o, 38.96^o, 39.09^o, 46.05^o, 51.47^o, 51.73^o,

55.54^o, 55.59^oand 55.87^ocorresponding 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 BiFeO₃nanoparticles 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

BiFeO₃nanoparticles, 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 14.79^o

and 32.99^ostarted 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 BiFeO₃nanoparticles 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 Bi₃₆Fe₂₄O_57,

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 = 14.79^o, 28.99^o, 29.81^o, 33.80^o,

47.27^oand 49.49^o, these phases may be attributed to the

[34]

[35]

formation of Bi₂O₃, Bi₃Fe₄O₉

and Bi₂Fe₄O_4.

So,

from the above discussion it was clear that 650 °C was

the optimum calcination temperature for the formation

of single phase perovskite BiFeO₃nanoparticles. At this

FIGURE 3 Average size of BiFeO₃nanoparticles calcinated at

150 °C, 450 °C, 550 °C and 650 °C

6 of 23

SINGH ET AL.

FIGURE 4 VSM of BiFeO₃nanoparticles 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 BiFeO₃nanoparti-

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

BiFeO₃nanoparticles, 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 2p_3/2and Fe 2p_1/2

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 650^o. 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 BiFeO₃nanoparticles 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 O^2‐binding

energy state.^[43]All these results were in good agreement

with the XPS data of other reported BiFeO₃nanoparti-

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 BiFeO₃nanoparticles 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/r³value, 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 BiFeO₃nanoparticles calcinated at

calcinated at 150 °C, 450 °C, 550 °C and 650 °C

273, 352, 370, 450, 465, 524 cm^‐1as shown in Figure 7.

The internal vibrations of FeO₆octahedra was responsible

for the appearance of modes above 200 cm^‐1and modes

below 200 cm^‐1were 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

BiFeO₃nanoparticles.

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 BiFeO₃nanoparticles 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^‐1and 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 BiFeO₃nanoparticles. 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 BiFeO₃nanoparticles

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 BiFeO₃nanoparticles

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 BiFeO₃nano-

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 BiFeO₃nanoparticles 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 BiFeO₃nanoparticles 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 BiFeO₃prepared by

using without chelating agent and calcinated at 150 °C

TABLE 2 Effect of calcination temperature on catalyst performance^a

Entry

Catalyst

Calcination temperature(°C)

Chelating agent

Time(min)

Yield(%)^b

1

2

3

4

5

6

7

8

BiFeO₃

150

450

550

650

750

850

‐

Sucrose

‐

5

6

3

4

3

4

10

81

79

83

97

14.5

15

41

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 amount^a

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 temperature^a

Entry

BiFeO₃(mg)

Condition

Time(min)

Yield (%)^b

1

2

3

4

5

6

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 BiFeO₃nanoparticles, 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 solvent^a

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

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,

BiFeO₃nanoparticles 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 aldehydes^a

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

2

90

96

256‐257/258‐260^[54]

1b

1c

2a

6

181‐183/182‐184^[55]

4

5

6

2a

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

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

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

2

96

97

230‐232/(new)

2b

8

218‐220/220‐221^[26]

1m

17

18

2b

3a

3

2

89

98

210‐212/(new)

1j

1i

233‐235/ (not reported)

19

20

2b

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

3a

3

94

99

234‐236/(new)

259‐261/(new)

1e

1a

25

26

27

2b

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

3b

4

5

89

1d

29

30

3b

96

89

>280/(new)

1c

1e

198‐200/216^[58]

31

32

2b

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 BiFeO₃nanoparticles after

reusing up to five cycles have almost the same position

as in fresh BiFeO₃nanoparticles. So observation demon-

strated that no significant change has been occurring in

BiFeO₃nanoparticles. 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)₃was 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 BiI₃formed. 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 BiFeO₃nanoparticles 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^‐1of 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 yield^a

Entry

Cycle

Time (min)

Yield (%)^b

1.

2.

3.

4.

5.

1

2

3

4

5

3

4

6

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 BiFeO₃after 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

Cs_2.5H_0.5PW₁₂O₄₀

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

EtOH(5 ml)

RT

120

360

120

10

7.

8.

L‐proline

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 BiFeO₃nanoparticles 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, CoFe₂O₄etc). Further, such single lay-

ered structured materials may bring new insight into the

designing of highly efficient heterogeneous catalyst and

potential technological applications.

2100.

[15] M. S. Bernardo, T. Jardiel, M. Peiteado, A. C. Caballero, M.

Villegas, J. Eur. Ceram. Soc. 2011, 31, 3047.

[16] R. Mazumder, D. Chakravarty, D. Bhattacharya, A. Sen, Mater.

Res. Bull. 2009, 44, 555.

[17] H. Y. Dai, Z. P. Chen, T. Li, R. Z. Xue, J. Chen, J. Supercond.

Novel Magn. 2013, 26, 3125.

[18] E. C. Aguiar, M. A. Ramirez, F. Moura, J. A. Varela, E. Longo,

A. Z. Simoes, Ceram. Int. 2013, 39, 13.

[19] D. Cai, J. Li, T. Tong, D. Jin, S. Yu, J. Cheng, Mater. Chem. Phys.

2012, 134, 139.

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

Compd. 2014, 584, 93.

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Gasco, J. Med. Chem. 1998, 41, 5393.

[22] D. Mauzerall, F. H. Westheimer, J. Am. Chem. Soc. 1955, 77,

2261.

[23] B. P. Bandgar, P. E. More, V. T. Kamble, J. V. Totre, Arkivoc

2008, xv(1).

ORCID

[24] F. Bossert, H. Meyer, E. Wehinger, Angew. Chemie Int. Ed.

English. 1981, 20, 762.

Harminder Singh http://orcid.org/0000-0002-8599-0554

Priya Arora http://orcid.org/0000-0002-6943-4072

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[26] M. Maheswara, V. Siddaiah, G. Lakishmi, V. Damu, Arkivoc

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How to cite this article: Singh H, Garg N,

Arora P, Rajput JK, Jigyasa. Sucrose chelated auto

combustion synthesis of BiFeO₃nanoparticles:

Magnetically recoverable catalyst for the one‐pot

synthesis of polyhydroquinoline. Appl Organometal

Chem. 2018;32:e4357. https://doi.org/10.1002/

aoc.4357

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Article Doi

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

DOI: 10.1002/aoc.4357

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