Synthesis of Core-Shell Magnetic Supramolecular Nanocatalysts based on Amino-Functionalized Calix[4]arenes for the Synthesis of 4H-Chromenes by Ultrasonic Waves

Article abstract of DOI:10.1002/open.202000005

One of the most common phenol-formaldehyde cyclic oligomers from hydroxyalkylation reactions that exhibit supramolecular chemistry are calixarenes. These macrocyclic compounds are qualified to act as synthetic catalysts due to their specific features incl

Full text of DOI:10.1002/open.202000005

DOI: 10.1002/open.202000005
Full Papers
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Synthesis of Core-Shell Magnetic Supramolecular
Nanocatalysts based on Amino-Functionalized Calix[4]
arenes for the Synthesis of 4H-Chromenes by Ultrasonic
Waves
[
a]
[b]
[a]
[c]
Reza Eivazzadeh-Keihan, Ehsan Bahojb Noruzi, Fateme Radinekiyan, Milad Salimi Bani,
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[a]
[b]
[c]
Ali Maleki,* Behrouz Shaabani,* and Mohammad Haghpanahi*
One of the most common phenol-formaldehyde cyclic oligom-
ers from hydroxyalkylation reactions that exhibit
their upper rim and lower rim. Here, a functional magnetic
nanocatalyst was designed and synthesized by using a synthetic
amino-functionalized calix[4]arene. Its catalytic activity was
evaluated in a one-pot synthesis of 2-amino-4H-chromene
derivatives. Besides, this novel magnetic nanocatalyst was
characterized by spectroscopic and analytical techniques such
as FT-IR, EDX, FE-SEM, TEM VSM, XRD analysis.
supramolecular chemistry are calixarenes. These macrocyclic
compounds are qualified to act as synthetic catalysts due to
their specific features including being able to form host-guest
complexes, having unique structural scaffolds and their relative
ease of chemical modifications with a variety of functions on
1
. Introduction
(CAs) which are derived from the condensation reaction of
[4]
phenols with formaldehyde.
CAs have several special
[5]
A supramolecule is a complex of several molecules that
aggregate by noncovalent binding interactions such as hydro-
features: notably, they are able to form host-guest complexes
and they can host a large variety of functions on the upper rim
and lower rim. These features have qualified them to be good
[1]
gen bonding, cation-pi, anion-pi and, pi-pi interactions. Supra-
molecules are often held together and are highly dynamic
compounds. As noncovalent interactions are important in
catalysis chemistry, one important aspects of supramolecular
chemistry is designing new catalysts with unique properties.
Supramolecular catalysts accelerate reactions by (i) increasing
the effective local concentration of the reactants via
encapsulation, (ii) utilizing intermolecular forces to guide
substrates towards the transition state, (iii) stabilizing the
transition state of the reaction and reducing activation energy
[6]
[7]
candidates to act as organic chelating ligand, drug carrier
and synthetic catalysts. There are lots of example for calixarene
catalytic activities. Magnetically functionalized CAs efficiently
catalyze the coupling of electron-rich arenes with some alcohols
[8]
in water. Immobilization of lipase enzyme on N-meth-
ylglucamine based calix[4]arene magnetic nanoparticles leads
to high enantioselectivity, high conversion and fast recovery of
product in the hydrolysis reaction of Naproxen methyl ester as
[2]
[9]
compared to encapsulated free enzyme. Functionalized CAs
are capable to extract metal ions from aqueous and non-
aqueous medias due to their cavity size and their substituents
affinities to the different types of metal. Acid-amide functional-
ized CAs were used as ligand to separate uranyl and lanthanides
[3]
and (iv) approaching host and guest molecules together. One
of the prominent classes of supramolecules are calixarenes
[
a] R. Eivazzadeh-Keihan, F. Radinekiyan, Prof. A. Maleki
Catalysts and Organic Synthesis Research Laboratory, Department of
Chemistry
[10]
ions from aqueous wastes. Metal recognition properties of
CAs were studied and revealed that a novel calix[4]arene and
bile acid based macrocycle receptor exhibited high binding
affinity toward mercury, cadmium, lead, zinc, lithium, manga-
Iran University of Science and Technology
Tehran 16846-13114 (Iran)
E-mail: maleki@iust.ac.ir
[
b] E. B. Noruzi, Dr. B. Shaabani
Faculty of Chemistry, Department of Inorganic Chemistry
University of Tabriz
[11]
nese and copper metal ions. Some functionalized CAs can
play an important role as a sensor and exhibit sensing behavior
against cations and anions. A novel azocalix[4]arene based
sensor has been synthesized and characterized. Experimental
studies disclosed that this supramolecular sensor exhibits
Tabriz (Iran)
E-mail: shaabani.b@gmail.com
[c] M. Salimi Bani, Prof. M. Haghpanahi
School of Mechanical Engineering
Iran University of Science and Technology
Tehran, Iran
+
2
+2
significant sensing behavior toward Cd and Cu among a
[12]
series of selected transition metals.
Calix[n]arene capped
E-mail: panahi4m@gmail.com
silver nanoparticles have ability to act as antibacterial agents
Supporting information for this article is available on the WWW under
https://doi.org/10.1002/open.202000005
[13]
against Gram positive and Gram negative bacteria, endonu-
[14]
[15]
©
2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This
clease enzyme inhibitors
and anti-oxidants.
The recent
is an open access article under the terms of the Creative Commons Attri-
bution Non-Commercial NoDerivs License, which permits use and distribu-
tion in any medium, provided the original work is properly cited, the use is
non-commercial and no modifications or adaptations are made.
straightforward andimpressive method for synthesizing organic
and inorganic compounds is called Sonochemistry. Sonochem-
istry is an area of chemistry which is connected with the
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application of high ultrasound energy to the reaction mixture.
Ultrasounds are sound waves with high frequencies (greater
than 16 KHz). The most important and efficient factor in
Sonochemistry is cavitation. The cavitation that is caused by
ultrasonic waves, travels through the liquid and accelerates the
chemical reactions. Cavitation refers to the formation, growth,
and implosion of micro-bubbles for short span of time in a
liquid. This factor makes extreme high pressures (up to
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[16]
5
00 atm), temperatures (up to 5000°C) and cooling rate (109°C/
s) at the center of the collapsed bubbles which is called hot
spots. They activate reactions by supplying the activation
energy in the micro environment and enhance the formation of
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[17]
nano-sized structures. Energy efficiency, feasible at ambient
temperature, enhanced product selectivity, high yield, shorter
reaction time, enhanced reaction rates, moderate reaction
condition, the formation of non-aggregated products and waste
minimization are considerable advantages of ultrasonic-assisted
[
18]
methods compared to other conventional techniques. In the
last decade, conforming to the multiple capabilities and
imperative role of Fe O magnetic nanoparticles (MNPs) in the
3
4
synthesis of a wide range of Fe O -based nano structural
3
4
composites, the application of these magnetic nanoparticles
have been extended in different scientific fields. On the other
hand, the surface of these magnetic nanoparticles is capable of
being easily functionalized by applying proper modification
[19]
methods. For instance, a diversity of Fe O -based optical and
3
4
electrochemical biosensors have been emerged in order to
Scheme 1. Schematic preparation of core-shell MNCACAs and its catalytic
activity in one-pot three-components synthesis of 2-amino-4H-chromene
derivatives.
[
20]
[21]
identify cancer toxic proteins, cancer biomarkers, different
mycotoxins
[22]
[23]
and pathogenic viruses.
In other examples,
distinctive Fe O -based scaffolds have been applied in tissue
3
4
engineering with high potent efficiency in attachment, differ-
[24]
entiation and cellular proliferation. Also, the bio performance
of these magnetic nanoparticles with distinctive structures have
sized. In the next step, Fe O NPs were synthesized by applying
3
4
coprecipitation method. Afterwards, the other three synthetic
[25]
been approved in in-vitro therapeutic hyperthermia therapy.
steps which include functionalization processes of synthetic Fe O4
3
In addition, these forefront nanoparticles can be employed as
alternative catalytic supports due to their high surface area,
outstanding stability, high dispersion and superb catalytic
NPs were carried out by using TEOS and CPTMS inorganic shells
and as well synthetic amino-functionalized calix[4]arene as an
organic shell. In the following, to determine the characteristics of
this novel magnetic nanocomposite, the required spectral and
analytical techniques were applied. The generation of new func-
tional groups and also the other main functional groups were
conceded with qualitative FT-IR spectra. EDX analysis was used for
elemental detection. The size and morphology of designed
magnetic nanocomposite were characterized by FE-SEM and TEM
images. Eventually, its crystalline phase and magnetic properties
were evaluated by XRD pattern and VSM analysis respectively. The
characterization of this novel magnetic nanocomposite is dis-
cussed in the following.
[26]
recyclability. Conforming to the catalytic activity of Fe O -
3
4
[27]
based nanocomposites in multicomponent reactions, in this
research, an efficient and functional magnetic nanocomposite
based on amino-functionalized calix[4]arenes (MNCACAs) was
designed, synthesized and characterized with different spectral
and analytical FT-IR, EDX, FE-SEM, TEM, XRD and VSM
techniques. Besides, the catalytic efficiency and performance of
MNCACAs as a new nano scale catalyst was evaluated in the
one-pot three condensation reaction of 2-amino-4H-chromene
derivatives (Scheme 1).
2. Results and Discussion
2.1. Evaluation of MNCACAs Characterization
A new magnetic nanocomposite based on Fe O NPs and their
2.1.1. FT-IR analysis
3
4
functionalization processes with organic and inorganic molecules
was designed and synthesized. The synthetic process of MNCACAs
was achieved in five synthetic main steps (Scheme 1). In the first
step, 5,11,17,23-Tetra-4-tert-butyl-25,27-di(aminoetboxy)-26,28-di-
hydroxycalix[4]arene as a last synthetic organic shell was synthe-
According to qualitative importance of FT-IR analysis in
characterization of functional groups, the synthetic process of
designed MNCACAs was monitored by this spectroscopic
technique (Figure 1a–d). In this respect, Figure 1a shows the FT-
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secondary amine were characterized by observing two absorb-
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À 1
À 1
ance band around 1639 cm and 1500 cm . The NÀ H out of
plane bending vibration mode was determined due to the
À 1
presence of an absorbance band at 802 cm . A sharp and
À 1
almost broad absorbance band around 1100 cm was ascribed
to CÀ N stretching vibration mode of amine which has been
overlapped with asymmetric vibration mode of SiÀ OÀ Si. As well
as, well as, it can be deduced that the absorbance of C=C
stretching vibration mode has been covered by NÀ H bending
vibration mode of primary amine.
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2.1.2. EDX Analysis
As could be seen, the EDX spectrum of designed MNCACAs is
indicated in Figure 2. Based on obtained results from EDX
analysis, the observed iron peak was related to the synthetic
MNPs. The presence of Silicon peak was implied to the
functionalization processes of synthetic MNPs and coating SiO2
and CPTMS layers on their surface. Two carbon and oxygen
peaks can be attributed to the presence of three different TEOS,
CPTMS and amino-functionalized calix[4]arenes shells. As well
as, the presence of nitrogen peak can be ascribed to the amino
groups of synthetic amino-functionalized calix[4]arenes layer.
Alongside of mentioned elements, the presence of gold peaks
was attributed to the gold sputtering technique of EDX analysis.
Figure 1. FT-IR spectra of (a) unfunctionalized Fe
Fe /SiO /CPTMS, (d) MNCACAs.
3 4 3 4 2
O NPs, (b) Fe O /SiO , (c)
3
O
4
2
IR spectrum of synthetic unfunctionalized Fe O4 NPs. As
3
illustrated, the existence of hydroxyl groups on the surface of
Fe O NPs was approved by observing a broad band at a region
3
4
À 1
of 3400 cm which was related to their stretching vibration
[
28]
À 1
mode.
attributed to FeÀ O stretching vibration mode of magnetic
phase. The first functionalization process of Fe O NPs by
A sharp absorption peak around 570 cm
was
[
29]
3
4
alkoxysilane molecules of TEOS was confirmed by appearance
of new absorption bands (Figure 1b). As indicated, the OÀ H
stretching vibration mode was confirmed by observing a broad
2.1.3. FE-SEM and TEM Imaging Studies
According to the surface imaging results, the FE-SEM images of
MNCACAs is indicated in Figure 3a. As could be observed, the
unique structure with sphere morphology and almost uniform
distribution was characterized for synthetic MNCACAs. Follow-
ing the sphere morphology, the formation of core-shell
structures was determined due to TEM imaging result (Fig-
ure 3b). As well as, the resulted TEM image confirmed that
MNPs were well functionalized. Alongside these observations,
comforting to the resulted histogram distribution, the average
diameter of sphere nanostructures was estimated between 40
to 50 nm (Figure 3c).
À 1 [30]
band in the range of 3200–3600 cm . A small absorption
À 1
band around 1637 cm were attributed to the OÀ H stretching
vibration mode of Si-OH and twisting vibration mode of
adsorbed HÀ OÀ H in silica shell. As well as, three absorption
À 1
peaks near 475 and also around 800 and 1100 cm were
determined the existence of bending, symmetric and asymmet-
[
29À 31]
ric vibration modes of SiÀ OÀ Si.
Alongside of mentioned
absorption peaks, coating CPTMS molecules on the functional-
ized surface of Fe O NPs was characterized due to observing
3
4
À 1
two weak absorption bands around 1409 and 2855 cm which
they ascribed to stretching vibration modes of Si-CH and CH .
2
2
These new absorption bands can concede the interaction
accomplishment between CPTMS molecules and coated silica
[32]
layer. Apart from the mentioned absorbance bands, coating
the synthetic amino-functionalized calix[4]arene as a third shell
on functionalized Fe O NPs was confirmed by generation of
3
4
new absorbance bands. As could be seen in Figure 1d, a broad
À 1
band at the region of 3200–3600 cm was attributed to the
OÀ H stretching vibration modes which have been covered the
NÀ H stretching modes of primary amine and secondary amine.
In comparison of Figure 1c, the intensity of hydroxyl broad
absorption band has been increased. According to this
observation, it can be concluded that this increment is due to
the presence of hydroxyl groups of synthetic amino-functional-
ized calix[4]arene shell on the functionalized surface of MNPs.
The NÀ H bending vibration modes of primary amine and
Figure 2. EDX spectrum of MNCACAs.
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crystalline peaks of MNPs were characterized with their related
indices (2 2 0), (3 1 1), (4 0 0), (5 1 1) and (4 4 0).
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2.1.5. VSM Analysis
In general, saturation magnetization value (M ) of modified and
s
unmodified magnetic nanoparticles are determined by vibrat-
ing-sample magnetometer. The hysteresis loop curves of
unmodified MNPs and core-shell MNCACAs are indicated in
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Figure 5a–b. As illustrated, in comparison of unmodified Fe O4
3
MNPs which shows a considerable saturation magnetization
À 1
value (76.20 emu.g ), the saturation magnetization value of
À 1
MNCACAs has been reduced (56.47 emu.g ). According to this
reduction, it can be concluded that this reduction is due to
functionalization processes and existence of three different
coated layers on the surface of Fe O MNPs.
3
4
Figure 3. (a) FE-SEM image, (b) TEM image of MNCACAs, (c) Histogram of
particle size distribution of MNCACAs.
2
.2. Evaluation of Catalytic Activity of Core-Shell MNCACAs in
Synthesis of 2-Amino-4H-Chromene Derivatives
2
.1.4. XRD Pattern
2
.2.1. Optimization of Different Parameters in Synthesis of
As could be seen, the XRD pattern of MNCACAs is determined
in Figure 4a–b. Based on obtained results from the observed
diffraction angles (2θ=30.25, 35.67, 43.43, 53.65, 57.44, 62.88),
the status and intensity of all of the crystalline peaks were
complied with the standard XRD pattern of MNPs (JCPDS card
2-Amino-4H-Chromene Derivatives
In this part, the catalytic performance of MNCACAs was
evaluated in synthesis of 2-amino-4H-chromene derivatives. In
this regard, in order to optimize the reaction condition, the
one-pot three component condensation reaction including
[33]
No. 01-079-0417). Alongside of this compliance, the observed
Figure 4. (a) XRD pattern of MNCACAs, (b) reference of synthetic MNPs in
the structure of MNCACAs
3 4
Figure 5. Hysteresis loop curves of (a) unmodified Fe O NPs and (b)
MNCACAs.
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benzaldehyde (1 mmol), dimedone (1 mmol) and manolononi-
trile (1.5 mmol) was applied as a model reaction. Different
parameters including the reaction time, catalyst amount and
solvent were investigated to find the optimum reaction
condition (Table 1, entries 1–17). Primarily, in the absence of
synthetic MNCACAs, the process of model reaction was
monitored by using TLC and no specific progression was
observed under the room temperature and ultrasonic bath
of equal amount of bare MNPs and synthetic amino-functional-
ized calix[4]arene (Table 1, entries 4–5), the catalytic activity of
MNCACAs disclosed the higher yield percentage of product
(84%) in a same reaction time (Table 1, entry 6). Apparently, the
functionalization process of modified MNPs by synthetic amino-
functionalized calix[4]arene was accompanied with excellent
catalytic activity. Apart from catalytic evaluation of designed
magnetic nanocomposite, the highest yield percentage of
isolated product (93%) was obtained in the presence of
20.00 mg of nanocatalyst (Table 1, entries 6–9) and using
ethanol (Table 1, entries 7, 13–17). Alongside of catalyst amount
and examining different solvents, it was determined that time
increment has not any specific effect in reaction progression
and 15 min was considered as optimum reaction time (Table 1,
entries 7,10–12).
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(60 Hz) condition (Table 1, entries 1–2). In the next step, in the
presence of 10.00 mg of synthetic magnetic nanocatalyst, the
model reaction was examined in two different room temper-
ature and ultrasonic bath (60 Hz) (Table 1, entries 3,6).
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As could be observed, due to presence of magnetic nano-
catalyst, it can mention that ultrasonic irradiations as a leading
factor can move forward the reaction to higher yield percent-
age of product and shorter reaction time (Table 1, entry 6).
Therefore, the ultrasonic bath condition (60 Hz) was determined
as an optimized reaction condition. Apart from determining
reaction condition, the catalytic impact of each part of designed
magnetic nanocatalyst was evaluated. Owing to obtained
results from ultrasonic bath reaction condition, in comparison
In order to evaluate the catalytic efficiency of designed
MNCACAs, wide range of aromatic aldehydes including elec-
tron-withdrawing and electron-releasing substituents (1), dime-
done (2), malononitrile (3) were applied to synthesize various 2-
amino-4H-chromene derivatives (4a–l) under the optimized
reaction condition. As summarized in Table 2, the isolated 2-
[a]
Table 1. Optimization of different parameters due to considering the model reaction.
[b]
Entry
Catalyst/[mg]
Solvent
Time/[min]
Condition/Temperature/[°C]
Yield /[%]
1
2
3
4
5
6
7
8
9
–
–
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
Dichloromethane
acetone
DMF
methanol
Water
90
90
60
15
15
15
15
15
15
10
20
30
15
15
15
15
15
r.t./25
N.R
N.R
Ultrasonic bath/25
r.t./25
MNCACAs 10.00 mg
Fe
66%
20%
40%
84%
93%
86%
86%
80%
93%
93%
68%
66%
56%
60%
85%
3
O
4
NPs 10.00 mg
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasonic bath/25
Ultrasound/25
Amino-functionalized calix[4]arene 10.00 mg
MNCACAs 10.00 mg
MNCACAs 20.00 mg
MNCACAs 30.00 mg
MNCACAs 40.00 mg
MNCACAs 20.00 mg
MNCACAs 20.00 mg
MNCACAs 20.00 mg
MNCACAs 20.00 mg
MNCACAs 20.00 mg
MNCACAs 20.00 mg
MNCACAs 20.00 mg
MNCACAs 20.00 mg
1
1
0
1
12
1
1
1
3
4
5
16
1
7
[a] The model reaction condition: benzaldehyde (1 mmol), dimedone (1 mmol), malononitrile (1.5 mmol), ethanol (7 mL), ultrasonic bath condition at room
temperature (25°C). [b] Isolated yield.
Table 2. Synthesis of 2-amino-4H-chromene derivatives by using catalytic performance of MNCACAs.
[
a]
Entry
Aldehyde
Product
Time/[min]
Yield /[%]
Melting point/[°C]
Melting point [°C]
Observed
Reported
[
34]
1
2
3
4
5
6
7
8
9
benzaldehyde
4a
4b
4c
4d
4e
4f
4g
4h
4i
20
25
25
25
30
15
10
15
18
20
10
15
93
88
87
85
85
94
95
92
90
90
92
95
228–230
218–220
198–200
206–207
250–252
209–2011
211–213
249–251
207–209
205–207
158–160
227–229
229–231[
35]
4-methylbenzaldehyde
2-methoxybenzaldehyde
4-hydoxybenzaldehyde
2,4-dihydroxybenzaldehyde
2,4-dichlorobenzaldehyde
3-nitrobenzaldehyde
2,6-dichlorobenzaldehyde
4-chlorobenzaldehyde
4-bromobenzaldehyde
4-nitrobenzaldehyde
4-cyanobenzaldehyde
217–219
[36]
198–199[
37]
38]
39]
207–208[
249–251
[
208–210
[40]
211–213[
41]
42]
43]
250–252[
207–209
[
1
1
0
1
4j
4k
4l
204–206
[38]
157–159[
44]
12
226–228
[a] Isolated yield.
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amino-4H-chromene derivatives are prepared in high-to-excel-
lent yield percentage (Table 2, entries 1–12).
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
2
.2.2. Catalytic Evaluation of Designed Magnetic Nanocatalyst
Compared to Other Reported Studies
In this part, the catalytic efficiency and performance of
designed magnetic nanocatalyst was compared with other
homogenous and heterogeneous catalysts which were pro-
posed for the synthesis of 2-amino-4H-chromene derivatives. In
this regard, the comparison was done based on main parame-
ters such as catalyst amount, time and temperature condition
and yield percentage of isolated product.
As illustrated, the comparative results are summarized in
Table 3. Due to considering the model reaction which includes
benzaldehyde (1 mmol), dimedone (1 mmol) and malononitrile
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
(1.5 mmol), all of the mentioned studies were accompanied
with some main problematic factors like using high temper-
ature, reaction accomplishment in a long term interval, low
yield percentage of isolated product, catalytic inefficiency of
presented catalyst in reaction progression (Table 3, entries 1–6).
On the other side, the designed MNCACAs as a new nano-
catalyst is accompanied with unique features and specific
advantages. Being as a heterogeneous nanocatalyst and own-
ing potential magnetic property prepare a simple separation
condition from reaction media. In addition, its considerable
catalytic performance in the synthesis of 2-amino-4H-chromene
derivative (4a) was confirmed via higher yield of the isolated
product and shorter reaction time (Table 3, entry 6).
Scheme 2. Plausible mechanism for synthesis of 2-amino-4H-chromene
derivatives by using MNCACAs.
In the next step, a Michael addition reaction between
intermediate I and activated dimedone (2) leads to generation
of intermediate II. In the final step which is followed by
cyclization and tautomerizaton reactions, the 2-amino-4H-
chromene derivatives are formed.
2.2.4. Reusability Study of MNCACAs Catalyst
2
.2.3. Mechanistic Study of Synthetic Magnetic Nanocatalyst in
Synthesis of 2-Amino-4H-Chromene Derivatives
Based on the green chemistry perspectives and significant
importance of recovery and recyclability factors in design and
fabrication of novel nanocatalyst, the catalytic reusability of
MNCACAs was examined in synthesis of 2-amino-4H-chromene
derivatives. For this purpose, after each reaction completion,
the nanocatalyst was simply separated from reaction media due
to its considerable magnetic property. Afterwards, the sepa-
rated nanocatalyst was washed with ethanol solvent and then,
for the subsequent catalytic run, it was kept in an oven (80°C)
to dry for an overnight. In the next step, the constant amount
of dried nanocatalyst was reused for model reaction. As
indicated in Figure 6, without any distinctive reduction in
In this work, the primary amino groups of designed magnetic
nanocatalyst are acted as leading and synergic catalytic factors
in order to advance the synthesis of 2-amino-4H-chromene
derivatives. As illustrated, the outline of proposed mechanism is
determined in Scheme 2. Conforming to the reported studies in
[49]
synthesis of 2-amino-4H-chromene derivatives,
in the first
step, due to catalytic capability of designed magnetic nano-
catalyst in activation, a Knoevenagel condensation reaction
between activated malononitrile (3) and activated substituted
aldehyde (1) is carried out and the intermediate I is generated.
[
a]
Table 3. Evaluation of catalytic activity of synthetic MNCACAs with other reported studies in synthesis of 2-amino-4H-chromene derivatives.
[b]
Entry
Catalyst
Amount of catalyst/[mg]
Solvent/Temperature condition
Time/[min]
Yield /[%]
Reference
1
2
3
4
5
6
Fe @MCM-41@Zr-piperazine-MNPs
AIL@MNP
Mg(ClO4)2
3
O
4
30.00 mg
60.00 mg
25 w%
5 mol%
0.25 g
EtOH/H
2
O/75°C
40
25
180
300
30
74%
89%
90%
90%
92%
93%
[42]
[45]
[46]
[47]
[48]
Present study
Solvent-free/90°C
EtOH/Reflux
RE(POF)
MgO
3
EtOH/60°C
EtOH/H
2
O/Reflux
MNCACAs
20.00 mg
EtOH/Ultrasonic bath (25°C)
15
[
a] The model reaction conditions: benzaldehyde (l mmol), dimedone (1 mmol), malononitrile (1.5 mmol), MNCACAs catalyst (20.00 mg), ethanol (7 mL),
ultrasonic bath condition at room temperature (25°C). [b] Isolated yield.
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vibrating-sample magnetometer (VSM) analysis was accomplished
by LBKFB model-magnetic Kashan kavir (5000 Oe) to measure the
saturation magnetization value of designed magnetic nanocompo-
site. The fabrication process of synthesized magnetic nanocompo-
site was characterized by obtained results from spectral and
analytical data and as well, its catalytic activity was evaluated in
synthesis of 2-amino-4H-chromene derivatives.
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
Preparation of SiO
layered Fe O NPs coated by second CPTMS
3 4
2
layer (Fe O /SiO À Cl): The second functionalization process of
3
4
2
Fe O NPs by CPTMS molecules was accomplished by the following
3
4
[25c]
steps.
First, 0.69 g of functionalized Fe O NPs (Fe O /SiO ) was
3 4 3 4 2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
mixed with 100 mL of dried toluene at 60°C under the mechanical
stirring condition. After a while, 1 mL of CPTMS solution was added
dropwisely to the mixture solution. Then, owing to mentioned
thermal reaction condition (60
°
C), the suspension solution was
Figure 6. Catalytic reusability of synthetic MNCACAs in synthesis of 4a after
catalytic run.
kept under the mechanical stirring condition for 18 h. After the
mentioned time (18 h), the obtained magnetic product was
separated from the reaction media and it was washed with dried
toluene for several times. Afterwards, it was kept in a vacuum oven
to dry completely.
5
catalytic activity, it was found that the designed magnetic
nanocatalyst can be simply recycled at least for five runs.
Functionalization process of modified Fe O NPs by synthetic
3 4
amino-functionalized calix[4]arene supramolecules: In this part, in
order to prepare the MNCACAs, first, 1.47 mg of synthetic
5,11,17,23-Tetra-4-tert-butyl-25,27-di(aminoethoxy)-26,28-dihydrox-
ycalix[4]arene was dissolved in a determined amount of ethanol
3. Conclusions
(
30 mL). After its complete dissolution, 1.00 g of magnetic chlor-
In summary, a wide range of heterogeneous magnetic nano-
catalysts were designed and synthesized. MNCACAs was
introduced as an efficient and functional new nanoscale catalyst
for the synthesis of 2-amino-4H-chromene derivatives. The
evaluation of the structural properties of MNCACAs was carried
out by FT-IR, EDX, FE-SEM, TEM, XRD and VSM analysis. The
introduction of new functional groups, determination of
structural elements, observation of unique morphology spheres,
opropyl-functionalized Fe O NPs was appended to the solution. In
3
4
the next step, the suspension solution was kept under the reflux
condition for 18 h. Due to the reaction completion after the
mentioned time, the resulted magnetic product was separated and
washed with ethanol for several times. After the elution process, it
was dried in the oven at 80°C for an overnight.
average diameter size (40–50 nm) and core-shell structure and Competing interest statement
as well as the saturation magnetization value (56.47 emu/g)
were carried out. Based on structural features and the
compounds characterization, it was disclosed that the notable
catalytic efficiency and performance of MNCACAs (20 mg) and
The authors listed in this article have no conflict of interests.
the constructive presence of ultrasonic wave irradiations Acknowledgements
(sonocatalysis) lead to synthesize high yield percentage of the
product in a shorter reaction time (15 min).
The authors gratefully acknowledge the partial support from the
Research Council of the Iran University of Science and Technology.
Experimental Section
Conflict of Interest
General: All the required chemical materials including solvents and
reagents were provided from the chemical international companies
such as Merck, Fluka and Sigma-Aldrich. The melting poip1nts of all
solid products were recorded by Electhrothermal 9100 apparatus.
The ultrasonic bath condition was generated by Elmasonic device
The authors declare no conflict of interest.
Keywords: 2-amino-4H-chromene · calixarenes · heterogeneous
catalysis · sonochemistry · supramolecular chemistry
(
S model, 60 Hz). In order to characterize the formation and
presence of new functional groups, the FT-IR spectra were taken by
the method of KBr pellets (Shimadzu IR-470 model). H NMR
1
spectrum of amino-functionalized calix[4]arene was characterized
by Avance spectrometer (Bruker DRX-500 model) at 400 MHz. The
size, morphology and structure of magnetic nanocomposite were
determined by field-emission scanning electron microscope (FE-
SEM) (ZEISS-sigma VP model) and transmission electron microscope
(TEM) (ZEISS-EM10 C-100KV). Energy-dispersive X-ray (EDX) analysis
was recorded by Oxford instrument and gold sputtering technique.
The XRD pattern of synthetic magnetic nanocomposite was
identified by Bruker device (D8 advance model) and also, the
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Manuscript received: January 11, 2020
Revised manuscript received: March 1, 2020
ChemistryOpen 2020, 9, 1–9
www.chemistryopen.org
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Full Papers
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FULL PAPERS
A novel core-shell magnetic nano-
composite based on an amino-func-
tionalized calix[4]arenes was
designed and synthesized. The
compound has resulted to be an
excellent magnetic nanocatalyst in
the one-pot synthesis of 2-amino-4H-
chromene derivatives.
R. Eivazzadeh-Keihan, E. B. Noruzi, F.
Radinekiyan, M. Salimi Bani, Prof. A.
Maleki*, Dr. B. Shaabani*, Prof. M.
Haghpanahi*
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Synthesis of Core-Shell Magnetic
Supramolecular Nanocatalysts
based on Amino-Functionalized
Calix[4]arenes for the Synthesis of
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H-Chromenes by Ultrasonic Waves