Palladium(II) Immobilized Onto the Glucose Functionalized Magnetic Nanoparticle as a New and Efficient Catalyst for the One-pot Synthesis of Benzoxazoles

Article abstract of DOI:10.1002/aoc.4240

Palladium(II) have been immobilized into the nano magnetic Fe₃O₄ which was functionalized with glucose in order to achieve a one-pot synthesis of 2-substituted benzoxazole derivatives with high yields in the diverse range of organic solvents. The nano catalyst is highly dispersive in polar solvents and can be easily recovered and reused for 6 runs without significant loss of its activity. Finally, the catalyst was fully characterized by FT-IR, TGA, CHN, SEM, EDX and atomic absorption spectroscopy.

Full text of DOI:10.1002/aoc.4240

Received: 16 October 2017
DOI: 10.1002/aoc.4240
Revised: 28 November 2017
Accepted: 28 November 2017
F U L L P A P E R
Palladium(II) Immobilized Onto the Glucose Functionalized
Magnetic Nanoparticle as a New and Efficient Catalyst for
the One‐pot Synthesis of Benzoxazoles
Firouz Matloubi Moghaddam
| Vahid Saberi | Sepideh Kalhor | Nazila Veisi
Laboratory of Organic Synthesis and
Natural Products, Department of
Chemistry, Sharif University of
Technology, Tehran, Iran
Palladium(II) have been immobilized into the nano magnetic Fe3O4 which was
functionalized with glucose in order to achieve a one‐pot synthesis of 2‐
substituted benzoxazole derivatives with high yields in the diverse range of
organic solvents. The nano catalyst is highly dispersive in polar solvents and
can be easily recovered and reused for 6 runs without significant loss of its
activity. Finally, the catalyst was fully characterized by FT‐IR, TGA, CHN,
SEM, EDX and atomic absorption spectroscopy.
Correspondence
Firouz Matloubi Moghaddam, Laboratory
of Organic Synthesis and Natural
Products, Department of Chemistry, Sharif
University of Technology, Azadi Street, PO
Box 111559516, Tehran, Iran
Email: matloubi@sharif.edu
KEYWORDS
Funding information
Sharif University of Technology (SUT)
benzoxazole, dispersive magnetic nanoparticle, glucose, palladium
1 | INTRODUCTION
According to the points discussed above, many
researches focusing on the biological activity of
2‐Arylbenzoxazoles are important class of heterocyclic
compounds which have been widely used in pharmaceuti-
cal industry and medicinal chemistry.[1] so far, broad range
of application of these structures such as HIV‐reverse tran-
scriptase inhibitors[2], anticancer drugs[3], cathepsin S
inhibitors,[4] 5‐HT3 receptor partial agonists,[5] DNA topo-
isomerase inhibitors,[6] peroxisomes proliferator‐activated
receptor γ (PPAR‐γ) antagonists,[7] and estrogen receptor‐β
agonists have been studied.[8] In addition, they have also
application in the treatment of stroke, depression, immune
diseases, and cerebral ischemia.[9]
benzoxazole derivatives against cancer cell lines such as
MCF‐7 and HepG2 essentially.[13] Benzoxazoles motifs
have potential use in the synthesis of dyes because of
their fluorescent nature[14] and also it is indicated that
the benzoxazole based compounds have effective use
in the synthesis of various photochromic materials[15]
mesogenic polymers[16] and liquid crystals[17,18]
,
Due to the importance of 2‐substituted benzoxazole
derivatives, many studies have been focused on the syn-
thesis and transformations of trans‐2‐[β‐(2‐Furyl)vinyl]
benzoxazole.[19]
Moreover, most of the benzoxazole containing com-
pounds exhibit biological profile. These compounds can
interact with target protein because of their structural
properties. It is demonstrated that O and N atoms of
benzoxazole which are able to form hydrogen‐bond can
affect the acceptors and the aromatic ring of benzoxazole
derivatives which have this potential to generate both π‐π
stacking and π‐cation interactions with the host molecule
might be essential for bioactivity of these structures.[10]
The benzoxazole scaffold are also present in a
number of natural products such as salvianen and
pseudosalvianen.[11,12]
In order to synthesize benzoxazole derivatives in the
past years, different methods have been developed, such
as cyclization of 2‐aminophenols with aldehydes and
carboxylic acids.[20]
Noticeably, the catalytic construction of this frame-
work has become an ideal platform to develop and
testify new catalysts including homogeneous catalysts such
as ruthenium/iridium complexes, Pd(OAc)2, RuCl3, Ortho‐
iodoxybenzoicacid (IBX), 4‐methoxy‐TEMPO (2,2,6,6‐
tetramethyl‐piperidyl‐1‐oxy), FeCl3, CuCl2, and NaCN.[21]
On the other hand, most of the reactions catalyzed by
homogeneous catalysts suffer from contamination of
Appl Organometal Chem. 2018;e4240.
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https://doi.org/10.1002/aoc.4240

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MOGHADDAM ET AL.
systems and also the homogeneous catalysts cannot be
reused. So there is a preference for preparation of these
structures by use of heterogeneous catalysts including
activated carbon, copper nanoparticles, platinum
nanoclusters, ZnO nanoparticles, cobalt‐based nanocom-
posite catalyst.[22]
In most cases the procedure of preparation of hetero-
geneous catalysts are harsh and the solubility of catalysts
are not good in diverse solvents.
So, to cope with the problems connected to the usage
of the heterogeneous catalyst, designing new nano cata-
lysts appear to allow the medicinal chemist to assemble
a large number of potentially active compounds in a very
short period of time. Also, the simplicity of preparation
procedure of catalyst is important.
Another remarkable aspect in the synthesis of the new
heterogeneous catalyst is that this type of catalyst is reus-
able and recyclable without loss of any significant activity
after usage in several runs.
To the best of our knowledge, we were successful to
design new catalyst which is recoverable and reusable.
In addition to the properties which were mentioned above
this new catalyst is categorized as nanomagnetic ones
which can form the effective and reactive surfaces, and
also developed potential for selectivity. So, these features
cause the reaction progresses under milder conditions
and the isolation of products would be easier.
silica‐coated magnetic nanoparticles (SMNP) were syn-
thesized with hydrolysis of tetraethyl orthosilicate in
basic condition. The silica‐coated magnetic Fe3O4 nano-
particles were used to synthesize [SMNP@GLP][Cl]
nanoparticles (Scheme 1) according to the procedure
explained in the experimental section. Finally, the
[SMNP@GLP][Cl] catalyst was characterized using vari-
ous techniques.
The FT‐IR spectra of Fe3O4, SMNP, SMNP@APTES,
and [SMNP@GLP][Cl] are shown in Figure 1. The peaks
which were observed at 2857 and 2930 cm‐1 were assigned
to the stretching vibrations of the propyl chains of the
integrated SMNP@APTES moieties. The frequencies of
complex mixed vibrations of numerous groups of atoms
such as hydrogen atom, i.e., HCH, OCH, COH, and
CCH manifest themselves in this spectral range. The
broad signal at 3400 cm‐1 was obviously attributed to the
glucose's OH (hydroxyl bonds).
The particle size and morphological character of
[SMNP@GLP][Cl] were studied by scanning electron
microscopy (SEM), and the proof of identity of
[SMNP@GLP][Cl] nanoparticles was based on the analy-
sis of SEM images. The obtained SEM images of nanopar-
ticles showed apparently a spherical shape particles with
slight aggregation synthesized catalyst and a mean parti-
cle size of 28–35 nm (Figure 2).
Energy‐dispersive X‐ray spectroscopy (EDS) analysis
of the [SMNP@GLP][Cl] catalyst confirms the presence
of Si, Fe, O, and Pd atoms in the catalyst structure
(Figure 3).
The crystalline nature and surface state of
[SMNP@GLP][Cl] catalyst were analyzed by usage of
powder X‐ray diffraction (Figure 4). The peaks at 2θ
values 30.2o, 35.6o, 43.2o, 53.6o, 57.2o and 62.8o in XRD
patterns of [SMNP@GLP][Cl] catalyst correspond to
(77), (249), (40), (29), (66) and (100) diffraction planes of
Fe3O4 nanoparticles, respectively. The position and
relative intensities of all peaks were confirmed with the
standard XRD data of the Joint Committee on Powder
Diffraction Standards (JCPDS). The results of this analysis
indicating a particle size of 35 nm, calculated from the
broadening of the peak at 2θ= 35.6 using the Scherrer
equation.
The CHN analysis of SMNP@AP demonstrated
that carbon, hydrogen and nitrogen contents of the cata-
lyst were 7.82, 1.26 and 1.61 wt%, correspondingly.
According to the preceding CHN analysis loading calcu-
lation of carbon content showed that a high level of
organosilane (1.3 mmol/g) has been coated onto the
magnetic nanoparticles. Also, The CHN analysis of
SMNP@AP@GLU showed that carbon, hydrogen and
nitrogen contents of the catalyst were 12.3, 1.75 and
1.19 wt%, respectively, indicating the glucose was
In previous study[23], we tried to stabilize Cu2+ onto
the Fe3O4 which was functionalized with glucose, in order
to synthesize different derivatives of 1,2,3‐triazole via one‐
pot three‐component reaction of alkynes, alkyl halides,
and sodium azide. In this study, we made an effort to
immobilize Pd2+onto the magnetic nanoparticles of
Fe3O4–silica coated and usage of this nanocatalyst in the
synthesis of benzoxazole derivatives with 2‐aminophenol
and an aromatic aldehyde. The other important property
of this new catalyst is the usage of glucose in its structure
which causes high dispersive of catalyst in water
and other polar organic solvents because of the presence
of –OH functional groups of glucose which help to the for-
mation of hydrogen bonds between solvent and catalyst.
Another feature of our catalyst is the resistance to high
temperature and the simplicity of separation from the
reaction medium by applying an external magnetic field.
2 | RESULTS AND DISCUSSION
2.1 | Catalyst synthesis
The overall strategy for the synthesis of the catalyst is
screened in Scheme 1. In the first step, Fe3O4 nanopar-
ticles were synthesized via a conventional co‐precipita-
tion method using a solution of iron salts.[24] The

MOGHADDAM ET AL.
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SCHEME 1 Immobilization of Pd on
SMNP@APTES@GLU
FIGURE
1
FT‐IR spectra of Fe3O4 (a), SMNP (b),
SMNP@APTES, (c) [SMNP@GLP][Cl], (d)
FIGURE 2 SEM image of [SMNP@GLP][Cl]
successfully immobilized onto the magnetic nanoparti-
cles. Due to calculations of carbon content in this stage,
the loading amount of glucose on functionalized MNPs
was 0.85 mmol/g.
TGA analysis was performed (Figure 5), and displays
that the decomposition of organic groups starts at 100 °C
and complete degradation continues until 550 °C. Because
the carbohydrates are unstable up 100 °C, the data from
TGA suggests that the content of the organic part is 13 %
as a consequence the high value of glucose (0.6 mmol/g)
have immobilized onto the magnetic nanoparticles.
The last method to analyze the structure of
[SMNP@GLP][Cl] was Atomic Absorption Spectroscopy
(AAS). This analysis was accomplished in order to evalu-
ate the amount of palladium loaded on magnetic nano-
particles and the consequences showed the loading is
about 0.18 mmol g‐1.

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MOGHADDAM ET AL.
FIGURE 3 EDS analysis of
[SMNP@GLP][Cl]
The reaction of 2‐aminophenol and benzaldehyde as
classical reactants was conducted using various types of
solvents at different temperatures and in the presence of
different concentrations of the catalyst. The results are
summarized in Table 1.
To demonstrate the important role of the catalyst, at
the first step two controlling reactions were performed
in the absence of catalyst at 80 °C and room temperature
and in this stage, DMF was used as solvent and K2CO3 as
a base, the results in both reactions showed the crucial
role of the catalyst (Entries 1,2). In the absence of the cat-
alyst, the reaction proceeds with very low yield. (Entry 3)
Another catalyst such as palladium is also used at
room temperature and 80 °C (Entries 4,5). The reaction
afforded the product with very high yield at 80 °C.
In order to validate the function and activity of
[SMNP@GLP][Cl] as a new heterogeneous catalyst in
the synthesis of benzoxazoles in comparison with the
classic homogeneous catalyst, we repeated the reaction
in the presence of 0.5 mol% of [SMNP@GLP][Cl] at
80 °C and room temperature. In both cases, the results
were satisfactory (Entries 6,7).
FIGURE 4 XRD patterns of [SMNP@GLP][Cl]
To optimize the amount of the catalyst, the model
experiment was repeated in the presence of 0.1 and
0.5 mol% of the catalyst and subsequently, it was found
that the reaction is completed in the presence of
0.1 mol% of the catalyst (Entries 7, 8).
To explore the principles of green chemistry the reac-
tion was also tested in water as green solvent (entry 9).
Other solvent such toluene, DMSO and DMF were used,
as the entries 9, 10, 11, 12 showed the high yield was
obtained using DMF as reaction medium.
In the next step, we explored the role of the oxidant, as
the results show, the yield of the product decrease in the
absence of oxygen atmosphere. (Entries 12, 13)
FIGURE 5 TGA analysis of SMNP@AP@GLU
2.2 | Catalytic activity
Our investigation centered on the activity of the synthe-
sized catalyst for the reaction of 2‐aminophenol (1) and
benzaldehyde (2) which was selected as a model for the
synthesis of benzoxazoles (Scheme 2).

MOGHADDAM ET AL.
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SCHEME 2 Synthesis of benzoxazoles
catalyzed with [SMNP@GLP][Cl]
TABLE 1 Control experiment for synthesis of bezoxazoles catalyzed by palladium supported [SMNP@GLP][Cl]a
Entry
Catalyst
Cat. Loading (mol %)
Oxidant
Base
Solvent
T (°C)
Time (h)
Yield (%)b
1
‐
‐
‐
K2CO3
DMF
rt
24
0
2
‐
‐
‐
O2
O2
O2
O2
O2
O2
O2
O2
O2
‐
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
‐
DMF
DMF
DMF
DMF
DMF
DMF
DMF
H2O
80
80
rt
24
24
24
24
24
24
24
24
24
24
24
24
18
18
18
18
18
0
10c
14
97
10
93
93
64
43
85
21
42
93
55
37
14
10
3
‐
‐
4
PdCl2
1
5
PdCl2
1
80
rt
6
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
[SMNP@GLP][Cl]
SMNP
0.5
0.5
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
1
7
80
80
80
80
80
80
80
80
80
80
80
80
8
9
10
11
12
13
14
15
16
17
18
Toluene
DMSO
DMF
DMF
DMF
DMF
DMF
DMF
DMF
O2
O2
O2
O2
O2
O2
K2CO3
NaOAc
NaHCO3
K2CO3
K2CO3
SMNP@AP@GLU
1
aReaction conditions: 2‐aminophenol (0.75 mmol), benzaldehyde (0.5 mmol), base (1 mmol),vsolvent (2 ml).
bIsolated yield.
cMainly recovery of the starting materials.
Finally, to optimize the base, different bases have also
been used examined and the results showed that K2CO3 is
an effective base for this reaction (Entries 14, 15, 16), as a
result entry 14 was selected as the optimized reaction
conditions.
For the evaluated effect of SMNP and SMNP@-
AP@GLU on reaction yield, the reaction was conduct in
optimized reaction condition and summary in Table 1
(Entries 16 and 17).
After achieving the optimized reaction conditions, a
wide range of benzoxazoles was synthesized from various
aldehydes and aminophenols (Table 2). Aldehydes
containing electron withdrawing group gave the product
in high yields (Entries 4, 12). Furthermore, our
experiments showed that increasing the number of
withdrawing groups on the structure of benzaldehyde
have a progressive influence on the yields of the products
(Entry 11). Using 2‐Chlorobenzaldehyde and in compari-
son with 4‐Chlorobenzaldehyde causes the decrease in
the yield of the product and this could be caused by the
steric effect (Entry 10). The electron donating groups on
the aldehyde moiety causes the decrease in the yield of
the products in comparison to the benzaldehyde moieties
with withdrawing groups (Entries 3,5,6). Aromatic
aldehydes have better function in compare to aliphatic
ones (Entry 7). Finally, in our approach to the
benzoxazole derivatives, we used various derivatives of
the 2‐aminophenol. The experiments displayed that the

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MOGHADDAM ET AL.
TABLE 2 Synthesis of benzoxazole derivatives catalyzed with [SMNP@GLP][Cl]a
Entry
1
2
3
Time (h)
Yieldb (%)
m.p. (°C) found (lit)
1
18
93
101 (100)26a
2
3
15
21
90
83
148 (149)26a
55 (53)26b
4
15
95
208 (206)26c
5
6
22
20
86
94
107
112 (111)26a
7
9
48
20
trace
90
‐
79 (81)26d
10
11
16
15
85
91
63 (61)26c
123 (123)26e
12
14
95
200 (203)26f
13
14
15
19
17
21
90
93
83
100 (101)26c
150 (151)26b
89 (88)26g
(Continues)

MOGHADDAM ET AL.
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TABLE 2 (Continued)
Entry
1
2
3
Time (h)
Yieldb (%)
m.p. (°C) found (lit)
16
20
95
170 (172)26g
17
18
21
18
91
87
81 (83)26h
137 (139)26i
SCHEME 3 Scale‐up experiment
TABLE 3 Comparison of the catalytic efficiency of [SMNP@GLP][Cl] with other catalysts for the synthesis of 2‐Phenyl‐1,3‐benzoxazole
(3a)
o
Entry
1
Catalyst
Yield %
Temp. C
Solvent
Ref.
Cu‐Nanoparticles
93
100
MeOH
[27a]
2
3
4
5
CuFe2O4
94
95
96
93
110
100
120
80
Toluene
H2O
[27b]
TSAMNP
[27c]
vanadium(IV)–salen‐SiO2
[SMNP@GLP][Cl]
Xylene
DMF
[27d]
This Work
applying of 2‐aminophenols with the electron‐donating
group had noticeable impact in the promotion of the
yields of the products (Entries 13‐16).
In the next step, in order to investigate the scalability
of our optimized reaction conditions, the reaction was
conducted in gram scale under optimized conditions
(Scheme 3). Results clearly showed that the procedure is
effectively scalable and neither loss of yield was observed
nor extended reaction times were required.
To show the efficiency and capability of the present
protocol in the synthesis of different benzoxazole deriva-
tives, Table 3 compares some of the obtained result in this
strategies in comparison to other reports. It is obvious that
an efficient methodology in terms of the use of a reusable
magnetic catalyst, catalyst loading, and good to excellent
yields has been developed.
The plausible mechanism which proves the expe-
rimental results that are described above and the
precedent literature,[25] is proposed in Scheme 4, in fact
[SMNP@GLP][Cl] as nano catalyst initialize the reaction
by activation of the carbonyl group of benzaldehyde to
facilitate the formation of imine structure A, in the next
step, the interaction of [SMNP@GLP][Cl] and imine A
causes the formation of π‐complexes which is the prelim-
inary point of intramolecular nucleophilic reaction and
formation of five‐membered ring intermediate B, also it
should be mentioned that β‐elimination is the key step
to generate benzoxazole ring 3a and also this mechanism

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MOGHADDAM ET AL.
SCHEME 4 The plausible mechanism of the formation of benzoxazole structure catalyzed by [SMNP@GLP][Cl]
FIGURE 6 Reuse of [SMNP@GLP][Cl]
in synthesis of benzoxazoles
demonstrates that the presence of O2 is necessary for the
progress of the reaction because it has an effect on the oxi-
dizing of Pd(0) in the structure of [SMNP@GLP][Cl] and
the regeneration of Pd(II).
analysis of the catalyst after 6 runs were performed and
showed no significant metal leaching of the catalyst.
3 | CONCLUSION
In conclusion [SMNP@GLP][Cl] nanoparticles were
employed in the synthesis of benzoxazoles using various
types of aldehydes and aminophenols in DMF. This
catalyst is readily prepared from available starting mate-
rials and also is a reusable catalyst having the very good
stability to air, moisture and elevated temperatures. The
proposed procedure applied here for the synthesis of
benzoxazoles can conduct the reactions under milder
conditions compared to previous reports using other
catalytic systems and also leads to better yields in approx-
imately shorter times. Finally, because of total removal of
the metal‐based catalyst from the reaction media, the
procedure can be applied in pharmaceutical processes
2.3 | Reusability
To check the reusability of the catalyst, the reaction was
performed under the optimized reaction conditions. After
measuring its yield, the nanoparticles of the catalyst were
separated using a magnet. These nanoparticles after
washing with water and drying on air were employed in
the same reaction for the second run. This process was
repeated 6 times and each time, measuring the isolated
yields exactly confirmed that the catalytic efficiency of
the catalyst was not changed and nanoparticles were not
deactivated during catalysis the reactions (Figure 6).
To explore leaching of the catalyst, atomic absorption

MOGHADDAM ET AL.
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was admixed to the above mixture while stirring and the
resulting mixture was refluxed for 40 h. The final product
was washed with methanol (3×30 ml).
4 | EXPERIMENTAL
4.1 | Reagents and analyses
All chemicals were purchased from Merck and used with-
out any additional purification. 1H NMR and 13C NMR
spectra were recorded on a Bruker (Avance DRX‐500)
spectrometer using CDCl3 as solvent at room tempera-
ture. Chemical shifts δ were reported in ppm relative to
tetramethylsilane as an internal standard. FTIR spectra
of samples were taken using an ABB Bomem MB‐100
FTIR spectrophotometer. The structures of the prepared
materials were observed using a Philips XL30 scanning
electron microscope (SEM), thermo gravimetric analysis
(TGA) was acquired under air atmosphere with a TGA
Q 50 thermo gravimetric analyzer. CHN analysis was
done by LECO Truspec.
4.4 | Synthesis of [SMNP@GLP][Cl]
In a round bottom flask equipped with a magnetic stirring
bar, SMNP@AP (2 g), were added to 10 mL MeOH and
sonicated for 40 min. Then, 3 g (16.6 mmol) of glucose
and 1 g NaBH3CN (16.6 mmol) was added to above
mixture. The mixture was stirred and heated to 45 °C
for 12 h. The product was extracted by an external
magnet, washed with methanol/water (1:1) three times
(3×20 ml).Then 0.05 g of PdCl2 and 0.2 g of KCl were
added to round bottom flask which contained 3 ml water
and stirring for 40 min, in order to for saturated mixture
of K2PdCl4. In the next step, 0.4 g of SMNP@AP@GLU
was added to the above solution and 10 ml of methanol
was admixed to the resulting mixture and stirring con-
tinues at room temperature for 24 h. The final product
was extracted by an external magnet, washed with water
three times (3×20 ml) and dried under reduced pressure.
4.2 | Synthesis of SMNP nanoparticles
In a three‐necked flasks, a solution of FeCl3 (10.8 g) and
FeCl2 (4 g) were mixed and the dilution of the solution
was done with deionized water (50 mL). The solution
was adjusted to pH 10, using a solution of ammonium
hydroxide (28% v/v) which was added drop wise, during
the addition of ammonium hydroxide, nitrogen gas was
purged to the system to create inert atmosphere and the
resulting solution was mechanically stirred at room tem-
perature for 20 min. The magnetic nanoparticles were
separated from the mixture by applying of an external
magnetic field using a magnet and washed with deionized
water (30 ml) and ethanol (3×30 ml) (yield 95%). The
synthesized Fe3O4 nanoparticles were dispersed in
ethanol (80 ml) with the aid of ultrasonic waves for
20 min (ultrasonic power: 100 W). These magnetic nano-
particles were used to synthesize the Fe3O4 Silica‐coated
nanoparticles as follows: In a round bottom flask, 3 ml
tetraethyl orthosilicate (TEOS) was added dropwise to
the above solution. Afterward, the mixture was treated
with 3 ml ammonium hydroxide (28% v/v) during a
15 min interval while it was being stirred vigorously.
Stirring the mixture was continued for more than 12 h
at 40 °C. Finally, the product (SMNP) was collected using
an external magnet and washed three times with ethanol
(30 ml) and dried under decreased pressure using a rotary
evaporator.
4.5 | General procedure for synthesis
benzoxazoles
A round bottom flask was charged with 0.5 mmol benzal-
dehyde and 0.75 mmol 2‐aminophenol, 1 mmol K2CO3
and the catalyst (0.1 mol%) and DMF (2 ml). At the first
step, the reaction mixture was stirred for 5 minutes at
room temperature, then the temperature of the reaction
system was increased drastically up to 80 (°C) and the
oxygen gas was bubbled into the flask simultaneously.
The reaction mixture was stirred for 18 hours, the
completion of the reaction was monitored by TLC
(EtOAc/n‐hexane, 2:1). In all of the case, after completion
of the reaction, the product was worked up and purified
as stated by the following process: the mixture was diluted
with ethyl acetate and water. The organic layer was
washed with brine, dried over MgSO4, and concentrated
under reduced pressure using a rotary evaporator. Finally,
the recrystallization of the product was done with ethyl
acetate/n‐hexane.at last, in each cases, we tried to
collect [SMNP@GLP][Cl] catalyst, by applying ab exter-
nal magnetic field (all procedure in details and character-
ization data are available in supporting information).
4.3 | Immobilization of (3‐aminopropyl)
triethoxysilane on SMNP(SMNP@AP)
4.5.1 | 2‐Phenyl‐1,3‐benzoxazole(3a)
1
White solid (181.3 mg, 93%, mp: 101‐102 °C). H NMR
The synthesized magnetic nanoparticles of SMNP (2 g)
were added to 10 ml of toluene and sonicated for
40 min. Then, 3 ml of (3‐aminopropyl) triethoxysilane
(500 MHz, CDCl3, TMS) δ 8.32‐8.30 (m, 2H), 7.83−7.81
(d, J= 9 Hz, 1H), 7.64‐7.62 (d, J= 9 Hz, 1H), 7.59−7.57
(m, 3H), 7.41‐7.39 (m, 2H). 13C NMR (CDCl3, 125 MHz)

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MOGHADDAM ET AL.
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ACKNOWLEDGMENTS
We gratefully acknowledge the funding support received
for this project from the Sharif University of Technology
(SUT), Islamic Republic of Iran.
ORCID
Firouz Matloubi Moghaddam http://orcid.org/0000-0002-
8418-9888
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