Investigation the catalytic activity of nanofibrillated and nanobacterial cellulose sulfuric acid in synthesis of dihydropyrimidoquinolinetriones

Article abstract of DOI:10.1007/s11164-018-3402-4

Two novel types of nanocellulose-based catalyst, viz. nanofibrillated cellulose sulfuric acid (s-NFC) and nanobacterial cellulose sulfuric acid (s-BC), were prepared by a simple method and characterized by Fourier-transform infrared spectroscopy, transmis

Full text of DOI:10.1007/s11164-018-3402-4

Res Chem Intermed
https://doi.org/10.1007/s11164-018-3402-4
Investigation the catalytic activity of nanofibrillated
and nanobacterial cellulose sulfuric acid in synthesis
of dihydropyrimidoquinolinetriones
Kobra Nikoofar1 Hannaneh Heidari1 Yeganeh Shahedi1
•
•
Received: 5 September 2017 / Accepted: 19 March 2018
Ó Springer Science+Business Media B.V., part of Springer Nature 2018
Abstract Two novel types of nanocellulose-based catalyst, viz. nanofibrillated
cellulose sulfuric acid (s-NFC) and nanobacterial cellulose sulfuric acid (s-BC),
were prepared by a simple method and characterized by Fourier-transform infrared
spectroscopy, transmission electron microscopy, field-emission scanning electron
microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction anlaysis, and
nitrogen adsorption measurements. The catalytic activity of these two bio-based
solid acid catalysts was examined in a one-pot, four-component coupling reaction of
barbituric acid, dimedone, aryl aldehydes, and (hetero)aromatic amines in refluxing
ethanol. The results confirmed that s-BC promoted the speed of the mentioned
reaction more than s-NFC. The recovery and reusability of the degradable nanos-
tructures showed that they could be used in at least three runs without loss of
activity.
Keywords Nanofibrillated cellulose Á Bacterial cellulose Á
Dihydropyrimidoquinolinetriones Á Four-component reaction Á Dimedone Á
Barbituric acid
&
&
1
Kobra Nikoofar
kobranikoofar@yahoo.com; k.nikoofar@alzahra.ac.ir
Hannaneh Heidari
h.heidari@alzahra.ac.ir; hheidari12@gmail.com
Department of Chemistry, Faculty of Physics and Chemistry, Alzahra University,
Vanak, Tehran 1993893973, Iran
123

K. Nikoofar et al.
Introduction
Cellulose is one of the most abundant natural biopolymers available on Earth. This
biopolymer shows special properties including abundance, nontoxicity, biodegrad-
ability, biocompatibility, controlled morphology, and high surface reactivity due to
hydroxyl (–OH) groups on the surface [1, 2]. These unique properties make it an
attractive material for wide applications. Cellulose and its derivatives are considered
to be good organic or inorganic supports for catalytic applications [3, 4]. Various
studies have reported cellulose sulfuric acid as a recyclable catalyst for various acid-
catalyzed reactions [5–8].
On the other hand, within the family of cellulose derivatives, nanocellulose
generally covers cellulosic materials in which at least one dimension of the fiber is
in the nanoscale range. Nanocellulose offers enhanced properties such as
hydrophilicity, high specific surface area, and chemical modifiability using a wide
range of reactions [9]. Cellulose nanocrystals and porous cellulose hydrogels can be
used as both stabilizers and reducing agents for synthesis of metal catalysts [10–12].
Nanocellulose can be classified into three types of material, viz. nanocrystalline
cellulose (NCC), nanofibrillated cellulose (NFC), and bacterial cellulose (BC),
produced by acid hydrolysis, mechanical treatment, and bacterial species, respec-
tively [13, 14]. Both NCC and NFC can be isolated from plant-based cellulosic
fibers. Compared with NCC, use of NFC is more economical and cost-effective due
to its production using mechanical methods. BC is a pure form of cellulose that can
be obtained from fermentation of low-molecular-weight sugars, while NC is a
composite derived from cellulose and hemicellulose. The high purity and crystalline
structure of BC are particularly helpful for improving its properties [9, 15].
Multicomponent reactions (MCRs) are significant tools for versatile preparation
of a wide variety of organic and potent medicinal molecules efficiently [16],
offering advantages such as environmentally friendliness, atom economy, and
avoidance of time-wasting protection–deprotection steps, making them better than
multistep organic syntheses. Multifunctionalized heterocycles have attracted special
attention due to their multiple and diverse properties. Among this class of
compounds, pyrimidine derivatives show biological and medicinal activities such as
cancer chemotherapic and anti-human immunodeficiency virus (HIV) effects
[17, 18]. Pyrimidine fused heterocycles (PFHs) can be found in alkaloids, drugs,
antibiotics, agrochemicals, and natural products. Some PFH derivatives are used as
antileukemic drugs, potassium-conserving diuretics, and antiallergy drugs. They
also possess inflammatory, antioxidant, anticancer, antimicrobial, and antiviral
actions [19–21].
A variety of barbituric acid derivatives, a motif of the mentioned dihydropy-
rimidoquinolinetriones, have been broadly applied as drugs for treatment of cancer
and osteoporosis [22]. Dihydroprimido[4,5-b]quinolinetriones demonstrate a wide
range of activities, including antioxidant [23], antitumor [24], and antiviral effects
[25]. In 2011, Khalafi-Nezhad and Panahi prepared this class of compounds via one-
pot, four-component reaction of aldehydes, amines, dimedone, and barbituric acid in
presence of tungstophosphoric acid (H3PW12O40) in refluxing ethanol [26]. In 2015,
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Investigation the catalytic activity of nanofibrillated and nanobacterial…
Bhusare et al. used [Msim]Cl ionic liquid to catalyze this four-component
condensation to afford the desired products [27]. Their initial assays indicated
good inhibition activity of some derivatives against the human breast cancer cell
line MCF7. Based on our search results, no other papers describing preparation of
this class of compounds have been published. According to the unique properties of
nanocellulose and the worthwhile properties and applications of dihydropyrimido-
quinolinetriones, we prepared two novel kinds of sulfuric acid-embedded nanocel-
lulose, viz. nanofibrillated cellulose sulfuric acid (s-NFC) and bacterial
nanocellulose sulfuric acid (s-BC), for the first time. These two nanostructures
were characterized by Fourier-transform infrared (FTIR) spectroscopy, transmission
electron microscopy (TEM), field-emission scanning electron microscopy (FE-
SEM), and energy-dispersive X-ray spectroscopy (EDS) analysis. Their catalytic
activity was examined in preparation of dihydropyrimidoquinolinetriones through
one-pot, four-component reactions of substituted benzaldehydes, aniline derivatives,
dimedone, and barbituric acid in refluxing ethanol. It must be mentioned that, in
2016, Sadeghi and Sowlat Tafti reported nanocrystalline cellulose (NCC) sulfuric
acid as catalyst for synthesis of pyrano[4,3-b]pyrans [28]. Presence of sulfuric acid
as a functional group on the surface of nanocellulose increases the surface polarity
and acidity and thereby the catalytic efficiency of nanocellulose-OSO3H [29].
Experimental
Materials and instrumentation
All chemicals were purchased from Merck, Aldrich, and Alfa Aesar chemical
companies and were used without further purification. Commercial-grade cellulose
nanofibers (NFC and BC) were supplied from Nano Novin Polymer Co., Iran. NFC
is produced from lignocellulosic sources such as wood and agricultural residues by
mechanical force (grinding), i.e., a top-down mechanism. BC hydrogel is produced
via a bottom-up approach by some bacteria species, especially Acetobacter xylinum
in aqueous culture [29, 30].
The morphology of the samples was analyzed using a Tescan Mira2 field-
emission scanning electron microscope. The samples were coated with gold using a
vacuum sputter-coater. EDS analysis was carried out using a SAMx-analyzer. TEM
images were taken with Philips model MC30 and Zeiss model EM10C instruments.
IR spectra were recorded from KBr disk using an FT-IR Bruker Tensor 27
instrument. Melting points were determined on an Electrothermal 9200 analyzer and
are uncorrected. X-ray diffraction patterns were obtained using a Philips PW1730
X-ray diffractometer with Cu Ka radiation at 40 kV and 30 mA. Samples were
scanned in the 2h range between 10° and 80°. 1H and 13C nuclear magnetic
resonance (NMR) spectra were recorded using a Bruker DRX (400 MHz) device.
Reaction progress was monitored by thin-layer chromatography (TLC) using
commercially available silica gel sheets. Preparative layer chromatography (PLC)
was carried out on 20 9 20 cm2 plates, coated with a 1-mm-thick layer of Merck
silica gel PF254, prepared by applying the silica as slurry and drying in air. The
123

K. Nikoofar et al.
products were characterized by comparison of their melting point as well as
1
spectroscopic data (FT-IR, H and 13C NMR).
Preparation of nanofibrillated cellulose sulfuric acid (s-NFC)
and nanobacterial cellulose sulfuric acid (s-BC)
Both nanocellulose sulfuric acids (s-NFC and s-BC) were prepared according to
previous studies with slight modification [28]. A volume of 0.4 mL chlorosulfonic
acid was added dropwise to well-stirred slurry containing 1.00 g of each
nanocellulose source (NFC or BC) in n-hexane at 0 °C during 20 min. After
completion of the addition, the mixture was stirred for 2 h at room temperature to
remove HCl from the reaction vessel. Then the mixture was filtered, and the
collected solid washed with methanol (30 mL) and air-dried at room temperature to
obtain s-NFC and s-BC nanostructures as tough black solids.
General procedure for synthesis of dihydropyrimidoquinolinetriones
catalyzed by s-NFC and s-BC
A mixture of aldehydes (1a–h, 1 mmol), amines (2a–g, 1 mmol), dimedone (3,
1 mmol), barbituric acid (4, 1 mmol), and s-NFC or s-BC (0.024 g) in refluxing
ethanol (5 mL) was stirred for appropriate reaction time monitored by TLC (n-
hexane/EtOAc eluent, 3:2). After reaction completion, methanol (5 mL) was added,
followed by filtering. The solid residue was washed with further methanol
(2 9 5 mL). Product purification was achieved by plate chromatography to give
corresponding solid products 5a–j in high yield.
5,10-Bis(4-hydroxyphenyl)-8,8-dimethyl-8,9-dihydropyrimido[4,5-b]quinoline-
2,4,6(1H,3H,5H,7H,10H)-tri-one (5d)
Black solid. M.p. 166–169 °C; IR (KBr, cm-1) t: 3419, 1739, 1650, 1485, 1239; 1H
NMR (DMSO-d6, 400 MHz) (d, ppm): 3.72 (s, 3H, –OCH3), 6.99–8.4 (m, –ArH),
10.92 (s, 1H, NH), 11.69 (s, 1H, NH); 13C NMR (d): 27.4, 33.3, 52.5, 84.5, 112.4,
118.4, 120.1, 125.3, 125.5, 126.2, 127.6, 127.7, 128.6, 129.4, 130.5, 150.5, 151.2,
160.5, 162.3. GC-mass: m/z 378 ([M?-2]Me), 314 (M?–CH2CHCO2Me), 302
([M?]-aniline), 284 ([M?]–CO2, –NHCOEt), 270 ([M?]–C6H5NO2).
5-(4-Hydroxy-3-methoxyphenyl)-10-(2-nitrophenyl)-8,8-dimethyl-8,9-dihydropy-
rimido[4,5-b]quinoline-2,4,6(1H,3H,5H,7H,10H)-trione (5e)
Orange solid. M.p. 180–182 °C; IR (KBr, cm-1) t: 3400, 1710, 1671, 1595, 1464,
1362, 1271; 1H NMR (DMSO-d6, 400 MHz) (d, ppm): 2.23 (s, 3H, –CH3), 3.56 (s,
3H, –OCH3), 6.61–7.96 (m, –ArH), 9.99 (s, 1H, NH), 10.33 (s, 1H, NH); 13C NMR
(d): 27.4, 33.3, 52.5, 84.5, 112.4, 118.4, 120.1, 125.3, 125.5, 126.2, 127.6, 127.7,
128.6, 129.4, 130.5, 150.5, 151.2, 160.5, 162.3. GC-mass: m/z 378 ([M?-2]-Me),
314 (M?–CH2CHCO2Me), 302 ([M?]-aniline), 284 ([M?]–CO2, –NHCOEt), 270
([M?]–C6H5NO2).
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Investigation the catalytic activity of nanofibrillated and nanobacterial…
5-(1H-Pyrrol-2-yl)-10-(1H-5-methylpyrazol-3-yl)-8,8-dimethyl-8,9-dihydropy-
rimido[4,5-b]quinoline-2,4,6(1H,3H,5H,7H,10H)-trione (5i)
Black solid. M.p. 243–246 °C; IR (KBr, cm-1) t: 3419, 1730, 1610, 1576, 1408,
1
1268; H NMR (DMSO-d6, 400 MHz) (d, ppm): 3.15 (s, 3H, –OCH3), 6.93–8.57
(m, –ArH), 9.16 (s, 1H, NH), 10.47 (s, 1H, NH), 10.94 (s, 1H, NH); 13C NMR (d):
27.4, 33.3, 52.5, 84.5, 112.4, 118.4, 120.1, 125.3, 125.5, 126.2, 127.6, 127.7, 128.6,
129.4, 130.5, 150.5, 151.2, 160.5, 162.3. GC-mass: m/z 378 ([M?-2]–Me), 314
(M?–CH2CHCO2Me), 302 ([M?]-aniline), 284 ([M?]–CO2, –NHCOEt), 270
([M?]–C6H5NO2).
Fig. 1 FT-IR spectrum of (a) NFC, (b) s-NFC, (c) BC, and (d) s-BC
123

K. Nikoofar et al.
Results and discussion
Characterization of s-NFC and s-BC
Consistent structure of the catalysts was found by FTIR, TEM, FE-SEM, and EDS.
The FTIR spectra of nanocellulose and nanocellulose sulfuric acid are shown in
Fig. 1, revealing dominant peaks at approximately 3300–3400 and 2900 cm-1
,
corresponding to stretching vibrations of OH and CH groups, respectively. Other
peaks such as those at 1635 cm-1 (H–O–H bending vibration) were also observed in
the spectra. For s-NFC and s-BC, three peaks at 1010–1100, 1200–1250, and
650 cm-1 were related to symmetric, and asymmetric O=S=O and S–O stretching
vibration peaks, respectively [31]. The OH vibration in nanocellulose sulfuric acid
was broader due to overlap between OH vibrations of sulfonic group with the OH
vibration of cellulose.
The morphology and size of the two different forms of nanocellulose (NFC and
BC) and sulfonated nanocelluloses were studied using FE-SEM. For NFC, fibrous
Fig. 2 FE-SEM of a nanofibrillated cellulose (NFC), b nanocellulose sulfuric acid (s-NFC), c bacterial
cellulose (BC), and d bacterial cellulose sulfuric acid (s-BC)
123

Investigation the catalytic activity of nanofibrillated and nanobacterial…
network structure and fibril aggregates were observed (Fig. 2a). In contrast to NFC,
BC possessed individualized, more uniform and slender nanofibers (Fig. 2c). In
s-NFC, brighter aggregates appearing on the darker surface are bumps produced by
sulfonic acid modification (Fig. 2b), however EDS spot analysis showed higher
amount of sulfur in these spots. s-BC showed a more disperse structure on the
surface with higher content of sulfur (Fig. 2d).
Figure 2d also shows that the porosity of bacterial cellulose was reduced after
sulfonic acid modification. Nitrogen adsorption measurements also indicated that
incorporation of sulfonic acid groups in the nanocellulose structure decreased the
pore diameter, Brunauer–Emmett–Teller (BET) surface area, and pore volume
compared with native nanocellulose. The structural parameters for neat BC and
s-BC are presented in Table 1. The decrease in the surface area of s-BC could be
due to reaction of the surface sites with chlorosulfonic acid, causing the surface to
become crowded with OSO3H and thus blocking pores, as reported by Hello et al.
[32].
As seen in Fig. 3, EDS analysis revealed C and O as the main elements present in
the nanocellulose. The spectrum obtained for sulfonated nanocellulose indicated
presence of sulfur on the surface. The sulfur loading on NFC and BC measured by
EDS analysis was 7.97 and 11.06 wt%, respectively.
TEM images of the nanostructures were taken to examine the structural shape
and size of the nanofibers. The NFC scaffold appeared as twisted and entangled
nanofibers on TEM (Fig. 4a). The dimension of a single nanocellulose fiber could
be measured as *100 nm (Fig. 4b). TEM of BC showed individual fibrils with
width of approximately 10 nm and length of several micrometers (Fig. 4c, d).
The crystalline structure of NFC and BC was determined by X-ray diffraction
(XRD) analysis (Fig. 5). In this study, NFC exhibited characteristic peaks related to
cellulose lattice planes located at 2h = 15.76° (101), 22.65° (002), and 34.4° (040)
(Fig. 5a). The diffraction pattern of BC showed the typical diffraction peaks of
native cellulose at 14.3°, 16.8°, 22.5°, and 34.4°, corresponding to diffraction from
101, 101, 002, and 040 planes, respectively (Fig. 5b). In NFC, as compared with
BC, the presence of a single peak at 15.76° instead of two distinct peaks at
2h = 14.3° and 16.8° can be related to presence of noncellulosic compounds such
as hemicellulose and the difference in the cellulose crystal structure of NFC [33].
These XRD results indicate presence of hemicellulose in NFC and high purity and
crystalline structure for BC.
Table 1 BET surface area, pore volume, and pore diameter of BC and s-BC
Entry
Sample
SBET (m2 g-1
)
Total pore volume (cm3 g-1
)
Mean pore diameter (nm)
1
2
BC
4.332
0.011613
10.723
9.482
s-BC
0.71526
0.0016955
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K. Nikoofar et al.
(a)
(b)
Fig. 3 EDS of a s-NFC and b s-BC
Catalytic activity of s-NFC and s-BC in synthesis
of dihydropyrimidoquinolinetriones
The catalytic activity of the prepared cellulosic-based nanostructures was investi-
gated in preparation of dihydropyrimido[4,5-b]quinolinetriones. To optimize the
reaction conditions, the one-pot, one-step reaction of N,N-dimethylbenzaldehyde
(1b, 1 mmol), 4-methoxyaniline (2d, 1 mmol), dimedone (3, 1 mmol), and
barbituric acid (4, 1 mmol) was first considered as model reaction to determine
the effect of various parameters (Table 2). The results showed that, in absence of
solvent, the reaction proceeded smoothly (Table 2, entries 1, 2). The model reaction
progressed in presence of H2O or ethanol solvent at room temperature and also
under reflux condition. The best results were obtained in refluxing ethanol
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Investigation the catalytic activity of nanofibrillated and nanobacterial…
Fig. 4 TEM images of a NFC and b zoomed view on a single NFC fiber, c BC, and d zoomed view on a
single BC fiber
(entries 3–6). It seems that elevating the temperature affected the reaction progress.
Investigation of the amount of s-NFC catalyst revealed 0.024 g as the best amount
(Table 2, entries 6–8). The condensation was also carried out in catalyst-free
conditions, but the desired product was not successfully achieved (entry 9). These
results confirm the promoting effect of s-NFC in preparation of 8,9-dihydro-8,8-
dimethyl-5-(4-N,N-dimethyldiphenyl)-10-(4-methoxydiphenyl)pyrimido[4,5-b]qui-
nolone-2,4,6(1H,3H,5H,7H,10H)-trione (5b). All experiments occurred in one-pot,
one-step mode.
Based on the optimized condition, the reaction of aldehydes (1a–h), amines (2a–
g), dimedone (3), and barbituric acid (4) proceeded in presence of s-NFC (0.024 g)
in refluxing ethanol (Scheme 1). The results are summarized in column A of
Table 3, showing that benzaldehyde (1a) and its electron-donating as well as
electron-withdrawing derivatives underwent the four-component condensation with
aniline (2a) well (entries 1–5, column A). Indole-3-carbaldehyde (1f), as a hindered
heteroaromatic aldehyde, was also examined for this condensation, with good
results (entries 6, 7). To show the wide range of efficacy of the procedure,
123

K. Nikoofar et al.
Fig. 5 XRD patterns of (a) NFC and (b) BC
ammonium acetate (2f) was also utilized as amine source to obtain the
corresponding product 5h successfully (entry 8). Use of pyrrole-2-carbaldehyde
(1g) and 3-amino-1,2,4-triazole (2g), as a potent pharmaceutically heteroaromatic
amine, resulted in the interesting molecule 5i in good yield (entry 9). The selectivity
of the protocol was also examined using terephthaldehyde (1h) with 4-methoxyani-
line (2c). The corresponding product of condensation was observed at both
aldehydic functional groups (entry 10). We also changed the amount of catalyst
from 0.048 to 0.024 g, but no byproduct, related to condensation of one aldehyde
position of terephthaldehyde, was observed.
In the next step, the catalytic activity of the other prepared nanocatalyst s-BC was
examined to obtain the desired dihydropyrimido[4,5-b]quinolinetrione derivatives.
The results are presented in column B of Table 3. As seen, use of s-BC shortened
the reaction times. According to these results and the BET and SEM results for
sulfonated nanocellulose (Table 1, Fig. 2c, d), increasing the catalytic activity of the
s-BC sample, despite the porosity reduction, represents the dominant effect of the
sulfonic acid substitution.
All products were isolated and characterized by their melting point and
1
spectroscopic data (FT-IR, H NMR, 13C NMR, and mass) in comparison with
authentic samples.
Finally, the reusability and recovery of the synthesized biobased nanocatalyst
investigated
was
in
preparation
of
8,8-dimethyl-5,10-diphenyl-8,9-
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Investigation the catalytic activity of nanofibrillated and nanobacterial…
Table 2 Investigation of reaction conditions for synthesis of 5b
Entry
s-NFC amount (g)/solvent (5 mL)/temp. (°C)
Time (min)
Yield (%)a
1
2
3
4
5
6
7
8
9
a
0.024/-/rt
300
240
210
120
130
90
18
5
0.024/-/70
0.024/H2O/rt
35
55
60
90
75
85
8
0.024/H2O/reflux
0.024/EtOH/rt
0.024/EtOH/reflux
0.016/EtOH/reflux
0.04/EtOH/reflux
-/EtOH/reflux
170
150
400
Isolated yield
Scheme 1 Synthesis of dihydropyrimido[4,5-b]quinolinetriones using s-NFC or s-BC
123

K. Nikoofar et al.
Table 3 Synthesis of dihydropyrimido[4,5-b]quinolinetriones in the presence of s-NFC (column A) and
s-BC (column B) in refluxing ethanola
A
B
Entry
Product
Mp (°C)b
Time
(min)
Yield
(%)
Time
(min)
Yield
(%)
92, 90,
90c
1
5a
5b
45
40
94
231–233 [26]
2
3
90
90
85
70
91
263–264 [26]
256–257 [26]
5c
60
50
83
166–169
new
4
5d
105
95
90
94
180–182
new
5
6
5e
5f
90
93
93
80
90
91
165
150
252–254 [26]
275–277 [26]
7
5g
105
95
95
90
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Investigation the catalytic activity of nanofibrillated and nanobacterial…
Table 3 continued
A
B
Entry
Product
Mp (°C)b
Time
(min)
Yield
(%)
Time
(min)
Yield
(%)
8
5h
5i
75
90
60
88
208–210 [26]
243–246
New
9
75
90
65
88
10d
5j
90
55
80
54
301–303 [26]
aAmine (1 mmol), aldehyde (1 mmol), dimedone (1 mmol), and barbituric acid (1 mmol) in presence of
0.024 g of s-NFC (column A) or s-BC (column B)
bReference of known compounds
cResults for recovery and reusability of catalyst
d1h:2b:3:4 at molar ratio of 1:2:2:2 in presence of 0.048 g of each catalyst
dihydropyrimido[4,5-b]quinoline-2,4,6(1H,3H,5H,7H,10H)-trione (5a). After reac-
tion completion, ethanol (10 mL) was added to the reaction mixture, and the
catalyst was filtered and washed with further ethanol (2 9 5 mL). After evaporation
of the solvent followed by air drying, the solid residue was utilized in another run.
The results in Table 3 (column A, entry 1) show that the catalyst could be recovered
and reused simply in at least three runs without loss of activity, in agreement with
green catalytic reaction principles.
Conclusions
We developed a convenient, efficient, and ecofriendly protocol for synthesis of
dihydroprimido[4,5-b]quinolinetriones through one-pot one-step four-component
reaction of dimedone, barbituric acid, benzaldehydes, and amines in refluxing
ethanol in presence of two newly synthesized kinds of nanocellulose sulfuric acid,
123

K. Nikoofar et al.
viz. s-NFC and s-BC. We found that sulfonation played a more important role in
their catalytic activity in comparison with porosity. The procedure offers several
advantages, including mild and neutral condition, good product yield, short reaction
time, operational simplicity, minimum environmental impact, and easy workup. The
catalysts are also biodegradable and reusable, in agreement with green chemistry
principles.
Acknowledgements The researchers greatly appreciate the Research of Alzahra University for their
financial support of this study.
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