Novel design of recyclable copper(II) complex supported on magnetic nanoparticles as active catalyst for Beckmann rearrangement in poly(ethylene glycol)

Article abstract of DOI:10.1002/aoc.4344

Copper complex-functionalized magnetic core–shell nanoparticles (Fe₃O₄@SiO₂-Lig-Cu) were prepared and characterized using various techniques. The activity of the new catalyst was tested for the Beckmann rearrangement. The reaction conditions allow for the conversion of a wide variety of aldoximes, including aromatic and heterocyclic ones, to amides in good to excellent yields. High efficiency, mild reaction conditions, easy work-up, use of poly(ethylene glycol) as a green medium and simple purification of products are important advantages of this system. Moreover, the eco-friendly heterogeneous nanocatalyst could be easily recovered from the reaction mixture using an external magnet and reused several times.

Full text of DOI:10.1002/aoc.4344

Received: 4 December 2017
DOI: 10.1002/aoc.4344
Revised: 4 February 2018
Accepted: 11 February 2018
F U L L P A P E R
Novel design of recyclable copper(II) complex supported on
magnetic nanoparticles as active catalyst for Beckmann
rearrangement in poly(ethylene glycol)
Mahdi Keyhaniyan | Ali Shiri
| Hossein Eshghi
| Amir Khojastehnezhad
Department of Chemistry, Faculty of
Science, Ferdowsi University of Mashhad,
Mashhad, Iran
Copper
complex‐functionalized
magnetic
core–shell
nanoparticles
(Fe3O4@SiO2‐Lig‐Cu) were prepared and characterized using various tech-
niques. The activity of the new catalyst was tested for the Beckmann rearrange-
ment. The reaction conditions allow for the conversion of a wide variety of
aldoximes, including aromatic and heterocyclic ones, to amides in good to
excellent yields. High efficiency, mild reaction conditions, easy work‐up, use
of poly(ethylene glycol) as a green medium and simple purification of products
are important advantages of this system. Moreover, the eco‐friendly heteroge-
neous nanocatalyst could be easily recovered from the reaction mixture using
an external magnet and reused several times.
Correspondence
Ali Shiri, Department of Chemistry,
Faculty of Science, Ferdowsi University of
Mashhad, Mashhad, Iran.
Email: alishiri@um.ac.ir
Funding information
Ferdowsi University of Mashhad Research
Council, Grant/Award Number: 3/41331
KEYWORDS
aldoximes, amides, Beckmann rearrangement, Fe3O4@SiO2‐Lig‐Cu, magnetic core–shell
nanoparticles
1 | INTRODUCTION
catalytic activity in various types of organic reactions, there
are two major drawbacks. First, easy aggregation of these
Today, in the chemical industry, there is a growing need
for green and more sustainable processes. As is well
documented, use of catalytic reactants is a better choice
than strategies in which stoichiometric reagents are used.
Homogeneous catalysis approaches, due to uniform and
well‐defined reactive centres of the catalysts, facilitate
mixing of the catalyst with the reaction mixture and
attracted as much attention as heterogeneous ones.
However, there are some problems like the cost and toxicity
associated with metals used as catalysts in homogeneous
methods, together with the loss of catalyst after one run.[1]
To compensate for the deficiencies related to homogeneous
catalysts, much efforts have been applied to combine the
advantages of homogeneous and heterogeneous catalysis.[2,3]
In this respect, metal nanoparticles have appeared and have
been widely used in biomedicine, electronic devices,
spectroscopy and especially in catalytic systems.[4] Although
these nanoparticles with their large surface area show high
nanoparticles with high surface energy deactivates the
catalyst. Second, the small size of metal nanoparticles
results in difficulty in separation and recovery from a
reaction mixture.[5] In order to solve these issues, utilization
of a catalyst support on which to load the metal nanoparticles
has emerged. Recently, magnetic supports have been
considered as the best choice duo to their eliminating the
requirement of catalyst filtration and centrifugation.
Facile isolation of catalyst from reaction mixture through
a simple magnetic decantation is the main advantage of
magnetic nanoparticle (MNP)‐supported catalysts.[6]
The amide bond is considered as one of the most
important linkages in organic chemistry. Moreover, in bio-
logical chemistry, the formation of amide bonds is argued
as the most important chemical transformation owing to
the widespread appearance of amides in pharmaceuticals,
natural products and peptides.[7] Amides in conjugation
with other aliphatic, aromatic and heterocyclic rings
Appl Organometal Chem. 2018;e4344.
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Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4344

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KEYHANIYAN ET AL.
produce various types of biological activity. They possess a
wide spectrum of biological activities like antituberculosis,
anticonvulsant, analgesic, anti‐inflammatory, insecticidal,
antifungal and antitumour properties.[8–12]
low catalyst loading and involving relatively cheap metals.
Therefore, in the work reported here, we designed and pre-
pared a novel magnetic nanocatalyst (Fe3O4@SiO2‐Lig‐Cu)
as illustrated in Scheme 1. The catalytic activity of the pre-
pared nanocatalyst was investigated in the transformation
of aldoximes to amides in poly(ethylene glycol) (PEG) as
a green medium at 80 °C (Scheme 2).
In the conventional approach, amides are synthesized
by coupling of carboxylic acids and amines in the pres-
ence of a stoichiometric coupling agent or application of
activated carboxylic acid derivatives which is not desir-
able due to low atom economy.[13,14] The metal‐catalysed
rearrangement of aldoximes has emerged in recent years
as a promising strategy to achieve amide transforma-
tions.[15] In recent decades several catalysts such as
CuO–ZnO/C,[16] Au/TiO2,[17] [Pd(cinnamyl)Cl]2,[18]
2 | RESULTS AND DISCUSSION
2.1 | Preparation and Characterization of
Catalyst
bis(allyl)–ruthenium(IV),[19]
[RuCl2(η6‐p‐cymene)],[20]
CuSO4⋅5H2O,[22]
At first, Fe3O4 MNPs were prepared by a chemical co‐pre-
cipitation method using FeCl2⋅4H2O and FeCl3⋅6H2O as
precursors.[34] In the next step, the prepared nanoparticles
were easily coated with a layer of SiO2 in a mixture of
aqueous ammonia, tetraethylorthosilicate (TEOS) and
ethanol via a sol–gel method to afford Fe3O4@SiO2 MNPs.
These MNPs were allowed to react with (3‐aminopropyl)
triethoxysilane and then with 3‐chloropropane‐1,2‐diol
to give Fe3O4@SiO2‐Lig MNPs. Finally, copper(II) acetate
was grafted on the modified Fe3O4@SiO2 MNPs leading to
Fe3O4@SiO2‐Lig‐Cu (Scheme 1). The prepared catalyst
was characterized using various techniques including
Fourier transform infrared (FT‐IR) spectroscopy, X‐ray
diffraction (XRD), scanning electron microscopy (SEM),
transmission electron microscopy (TEM), energy‐disper-
sive X‐ray (EDX) analysis, thermogravimetric analysis
(TGA), vibrating sample magnetometry (VSM) and induc-
tively coupled plasma (ICP) anlysis.
[RuCl2(η6‐C6Me6){P(NMe2)3}],[21]
{CoIII–ZnII} heterometallic complexes,[23] KMnO4/
[24]
NH3(l)
,
Al2O3/MeSO2Cl,[25]
ZnCl2/K2CO3,[26]
RuCl(PPh3)3,[27] Cu2O,[28] CuCl2,[29] Cs2CO3,[30] ZnO,[31]
SBA‐15/En–Cu[32] and Rhodococcus rhodochrous cells[33]
have been used for primary amide preparation from
aldoximes. Despite the development of these reported pro-
cedures for conversion of aldoximes to amides, there are
still limitations in some respects, including harsh reaction
conditions, specially prolonged reaction times, use of
microwave power and high temperature, lack of general-
ity and use of high‐cost or less readily available reagents.
So, in order to overcome these drawbacks, we wanted to
identify a heterogeneous catalyst for use under green con-
ditions, which was cheap, effective at lower catalyst load-
ing in short reaction time and could be used under milder
conditions than those previously reported.
Inspired by the above discussion and considering green
and sustainable chemistry, it is highly desirable to develop
a new catalytic system for use under mild conditions, with
The FT‐IR spectra of Fe3O4, Fe3O4@SiO2,
Fe3O4@SiO2‐NH2, Fe3O4@SiO2‐Lig, fresh Fe3O4@SiO2‐
Lig‐Cu and reused Fe3O4@SiO2‐Lig‐Cu are compared in
SCHEME 1 Preparation of magnetic nanocatalyst (Fe3O4@SiO2‐Lig‐Cu)

KEYHANIYAN ET AL.
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at 943 cm−1 appeared attributed to asymmetric vibration
of the Si―O―Si bond and the symmetric stretching of
the Si―OH bond, respectively. For Fe3O4@SiO2‐NH2
(Figure 1c), 3‐aminopropyltriethoxysilane was grafted to
the Fe3O4@SiO2 framework, which was recognized by
the methylene C―H stretching and ―NH bending vibra-
SCHEME 2 Synthesis of amide derivatives via Beckmann
rearrangement in presence of Fe3O4@SiO2‐Lig‐Cu
tion bands at 2925 and 1646 cm−1 [36]
Appearance of a
.
broad absorption band at around 3000–3600 cm−1
attributed to ―OH and ―NH stretching frequencies
and, furthermore, an increase of the intensity of C―H
stretching vibration confirm the successful reaction
between 3‐chloro‐1,2‐propanediol and Fe3O4@SiO2‐NH2
(Figure 1d). The FT‐IR spectrum of fresh Fe3O4@SiO2‐
Lig‐Cu is the same as previous spectra (Figure 1e). Unfor-
tunately, the absorption bands related to coordination of
Cu(II) with nitrogen and oxygen were covered by
stretching vibration frequencies of Fe―O and Si―O
bonds.[37] For solving this issue, a new expanded FT‐IR
spectrum of Figure 1(e) was studied (Figure 2). The
absorption bands at 428 and 450 cm−1 confirm the suc-
cessful immobilization of Cu with nitrogen (Cu―N) and
oxygen (Cu―O) groups. Finally, The FT‐IR spectrum of
reused catalyst (Figure 1f) shows that the structure of
the catalyst remains almost the same after five recycles.
The morphological features were studied using the
SEM technique. The SEM image of Fe3O4@SiO2‐Lig‐Cu
(Figure 3) demonstrates that the MNPs are almost spher-
ical, narrowly distributed and well dispersed. Also, the
particle size of the nanocatalyst was investigated using
the TEM technique (Figure 4). The TEM image of the
sample shows the average size of Fe3O4@SiO2‐Lig‐Cu
magnetic nanocatalyst particles is between approximately
20 and 25 nm in diameter.
Figure 1. A strong band at around 465–563 cm−1 appeared
in the spectra of all the MNPs which can be assigned to
the stretching vibration of Fe―O bond. The broad charac-
teristic band at 3420 cm−1 is related to O―H stretching
vibration, demonstrating the presence of hydroxyl groups
on the surface of Fe3O4 MNPs.[35] In comparison with
Figure 1(a), in Figure 1(b), the intensity of the band of
the Fe―O bond significantly weakens and a strong
absorption peak at 1096 cm−1 and weak absorption peak
FIGURE 1 FT‐IR spectra of (a) Fe3O4 MNPs, (b) Fe3O4@SiO2
MNPs, (c) Fe3O4@SiO2‐NH2 MNPs, (d) Fe3O4@SiO2‐Lig, (e) fresh
Fe3O4@SiO2‐Lig‐Cu MNPs and (f) Fe3O4@SiO2‐Lig‐Cu MNPs after
five cycles
The signal of Cu element along with other elements
including Fe, Si, O and C in the EDX spectrum of the
FIGURE 2 Expanded FT‐IR spectrum of Fe3O4@SiO2‐Lig‐Cu MNPs between 400 and 1000 cm−1

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KEYHANIYAN ET AL.
XRD analysis was applied to identify the crystalline
structure of Fe3O4@SiO2‐Lig‐Cu. As indicated in
Figure 6, six diffraction peaks at 2θ = 30.31°, 35.64°,
43.31°, 53.86°, 57.24° and 62.83° are attributed to the
(220), (311), (400), (422), (511) and (440) crystal planes
of magnetite (Fe3O4)[39] with cubic phase according to
JCPDS card no. 19–0629 (Figure 6a) which indicates the
pure crystalline structure of magnetite. As shown in
Figure 6(b), the XRD pattern of Fe3O4@SiO2‐Lig‐Cu
shows a broad peak at 2θ = 23° which is attributed to
the amorphous silica shell,[40] in addition to the six dif-
fraction peaks of Fe3O4 MNPs. No marked changes occur
in the number of peaks, but due to the silica coating, the
characteristic peaks of Fe3O4 become weak in Figure 6
(b). The average crystallite size of Fe3O4 MNPs calculated
using the Debye–Scherrer equation (d = Kλ/βcos θ) is
about 23 nm on (311) crystal plan. These results indicate
that the crystal structure of Fe3O4 core remains
unchanged after coating with silica shell. The peaks
related to Cu(II) acetate appeared between 2θ = 10° and
25°, but because of the overlap with broad silica peak in
these regions, the characterization of mentioned peaks is
impossible.[41,42] Moreover, the XRD pattern of reused
catalyst after five runs is shown in Figure 6(c) that con-
firms the structure of the catalyst remains almost the
same after five runs.
FIGURE 3 SEM image of Fe3O4@SiO2‐Lig‐Cu
TGA was used to confirm the high thermal stability of
the Fe3O4@SiO2‐lig‐Cu catalyst. As we can see in Figure 7,
there are two main weight losses. Firstly, the weight loss
(4%) at around 100–380 °C is allocated to physically and
hydrogen bonded water on the support. The second weight
loss (6%) in the range 400–550 °C is related to the organic
parts which are anchored to the Fe3O4@SiO2 surface. Based
on the TGA analysis results, ligand grafting had been
successfully accomplished.
FIGURE 4 TEM images of Fe3O4@SiO2‐Lig‐Cu
Fe3O4@SiO2‐Lig‐Cu catalyst shows the successful immo-
bilization of Cu(II) acetate and organic compounds on
Fe3O4@SiO2 MNPs. As can be seen in Figure 5, no addi-
tional peak related to other impurities appeared in the
spectrum, except for Al that corresponds to aluminium
stubs and Au related to the gold sputtering technique for
EDX. Samples were processed for SEM–EDX analysis by
mounting the drop‐exposed, fixed specimens on alumin-
ium stubs. The specimens then were overcoated with
sputtered gold.[38]
It is of great importance that the core–shell material
should
possess
sufficient
magnetic
and
superparamagnetic properties for its practical application.
FIGURE 6 XRD patterns of (a) standard Fe3O4, (b) fresh
Fe3O4@SiO2‐Lig‐Cu MNPs and (c) reused Fe3O4@SiO2‐Lig‐Cu
FIGURE 5 EDX pattern of Fe3O4@SiO2‐Lig‐Cu

KEYHANIYAN ET AL.
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2.2 | Catalytic Application of Fe3O4@SiO2‐
Lig‐Cu
Catalytic activity of the synthesized magnetic
nanocatalyst was investigated in order to prepare aro-
matic and heteroaromatic amides through Beckmann
rearrangement. To achieve the maximum yield and effi-
ciency for preparation of amides, experimental conditions
must be carefully optimized. For this purpose, conversion
of 4‐methylbenzaldoxime to 4‐methylbenzamide was
selected as a model reaction. Initially, the influences of
solvent and catalyst were investigated, and the results
are summarized in Table 1. As can be seen, no progress
in the reaction was observed in the absence of catalyst
even after 24 h (entry 1). Employing toluene, ethanol
and water as solvents led to moderate yields in the pres-
ence of the nanocatalyst (entries 5, 6 and 8). Compared
with those solvents, higher yields of 70 and 65% were
observed when dimethylformamide (DMF) and CH3CN
were adopted (entries 9 and 10). Surprisingly, the progress
of reaction was observed in a satisfactory time with PEG
as a green solvent (entry 11).
After that the effects of catalyst loading and tempera-
ture were examined. Increasing the catalyst loading from
3 to 5 mol% led to enhanced efficiency (entries 13 and
14). On the other hand, a yield of only 30% was achieved
by reducing the catalyst loading to 2 mol% (entry 12).
Conducting the reaction at 60 °C reduced the reaction
yield and elevated temperature of 100 °C also led to
decreased yield (entries 16 and 17). So, the best result in
terms of yield as well as reaction time was observed in
PEG at 80 °C with 4 mol% of catalyst (entry 14). This reac-
tion was also carried out in presence of copper acetate
(Cu(OAc)2). In comparison to the prepared catalyst, the
homogeneous copper acetate was not efficient for this
reaction and the yield of the reaction was only 80% after
180 min (entry 18).
FIGURE 7 TGA curve of Fe3O4@SiO2‐Lig‐Cu MNPs
Magnetic hysteresis measurements for the catalyst were
done in an applied magnetic field at room temperature,
with the field sweeping from −15 000 to +15 000 Oe. As
shown in Figure 8, the M(H) hysteresis loop for the sam-
ples was completely reversible, showing that the MNPs
exhibit superparamagnetic characteristics. The hysteresis
loops reached saturation up to the maximum applied
magnetic field. The magnetic saturation value of the sam-
ple is 12 emu g−1 at room temperature. These MNPs
showed high permeability in magnetization and their
magnetization was sufficient for magnetic separation with
a conventional magnet.
Finally, the copper content of the prepared
Fe3O4@SiO2‐Lig‐Cu was determined using ICP analysis.
According to this, the amount of copper in the catalyst
is 2.05 mmol g−1. This result shows the good immobiliza-
tion of Cu(II) on Fe3O4@SiO2‐Lig MNPs.
Encouraged by the optimization results, a broad range
of differently substituted aromatic aldoximes were
investigated for amide bond formation (Table 2). Various
aromatic aldoximes bearing electron‐donating substitu-
ents such as a methoxy group (entry 12) as well as
electron‐withdrawing nitro group (entry 6) were applied
in this transformation to afford the corresponding
products 1–20 in good to excellent yields. Moreover, α,β‐
unsaturated cinnamaldoxime as a suitable substrate was
applied successfully to obtain the desired product in 87%
yield (entry 16). To our disappointment, ortho‐methoxy‐
substituted aldoxime only provided low yield of product;
however, a high yield of 89% was achieved for ortho‐
chloro‐substituted aldoxime into primary amide 8.
Meanwhile, moderate transformation was observed for
2‐hydroxy‐substituted aldoxime, which generated
FIGURE 8 Magnetization curve of Fe3O4@SiO2‐Lig‐Cu

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KEYHANIYAN ET AL.
TABLE 1 Optimization of amount of Fe3O4@SiO2‐Lig‐Cu nanocatalyst and effect of solvent and temperature for preparation of 4‐
methylbenzamide (3)a
Entry
Catalyst (mol%)
Solvent (1 ml)
Temp. (°C)
Time (h)
Yield (%)
1
—
4
4
4
4
4
4
4
4
4
4
2
3
4
5
4
4
4
Solvent‐free
Solvent‐free
CH2Cl2
CH2Cl2
Toluene
EtOH
r.t.
24
24
24
24
24
24
24
24
24
24
5
0
0
2
80
3
r.t.
0
4
Reflux
Reflux
Reflux
80
0
5
50
45
20
50
70
65
72
30
65
85
85
45
62
80
6
7
Glycerol
H2O
8
Reflux
80
9
DMF
10
11
12
13
14
15
16
17
18c
CH3CN
PEG
Reflux
80
PEG
80
5
PEG
80
5
PEGb
PEGb
80
1
80
1
PEGb
60
5
PEGb
100
80
5
PEG
3
aReaction conditions: 4‐methylbenzaldoxime (1 mmol), Cu(OAC)2 (4 mol%) and PEG.
bPEG (0.5 ml) was used.
cCu(OAC)2 was applied as a catalyst.
corresponding amide 18 in 60% yield. It is noteworthy that
this catalytic system was also applied for heteroaromatic
substrates such as those with pyridyl, thienyl and furanyl
moieties. Surprisingly, for all heteroaromatic aldoximes,
excellent yield of desired amides was achieved (entries
14, 19 and 20).
reaction mixture using an external magnet, washed with
water and ethanol, dried at 80 °C overnight and then used
in the next run. The catalyst could be used at least five
times with only a slight reduction in activity, which
clearly demonstrates the practical reusability of this
catalyst.
The reactivity of some selected aldoximes in
Beckmann rearrangement in the same reaction time
(60 min) was investigated (Table 3). We selected
aldoximes bearing both electron‐donating and electron‐
withdrawing substituents in ortho, meta and para posi-
tions (entries 1–8) as well as some aromatic and
heteroaromatic systems (entries 9 and 10). Similar to
results in Table 1, aldoximes with electron‐withdrawing
substituents (entries 2, 5 and 6) give higher yields com-
pared to those with electron‐donating groups (entries 3
and 4). Also, the heteroaromatic furyl system (entry 10)
afforded better yield, while a bulky system like naphthyl
gave a low yield (entry 9).
A plausible mechanism for the conversion of aldoxime
to amide in the presence of Cu‐immobilized modified
Fe3O4 MNPs has been studied (Scheme 3). This involves
activation of aldoxime with Cu(II) Lewis acid followed
by dehydration and then formation of five‐membered
cyclic intermediate, which leads to the final amide
product.
3 | EXPERIMENTAL
3.1 | Chemicals and Apparatus
Melting points of products were recorded with an Electro-
thermal type 9200 melting point apparatus. FT‐IR spectra
were recorded with a Nicolet Avatar 370 FT‐IR spectrom-
eter. NMR spectra were obtained with a Bruker AC
instrument at 300 MHz in DMSO‐d6. Mass spectra were
obtained with a Varian Mat CH‐7 at 70 eV. The crystal
The possibility of recycling and reusing the
Fe3O4@SiO2‐Lig‐Cu MNPs was examined using the same
model reaction under the aforementioned optimized reac-
tion conditions (Figure 9). Upon completion of the first
run, the magnetic nanocatalyst was separated from the

KEYHANIYAN ET AL.
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TABLE 2 Conversion of oximes into amides (1–20) using
Fe3O4@SiO2‐Lig‐Cu nanocatalysta
Entry Ar
Time (h) Yield (%) M.p. (°C)
1
C6H5
1
1
1
1
1
1
1
1
1
1
1
2
3
1.5
3
1
3
3
2
2
87
90
85
93
85
92
90
89
95
80
93
70
90
95
75
87
67
60
98
98
126–127[16]
189–191[17]
154–156[16]
152–154[18]
88–90[19]
2
4‐BrC6H4
3
4‐MeC6H4
4‐iso‐PrC6H4
3‐MeC6H4
4‐NO2C6H4
3‐BrC6H4
4
5
6
199–200[20]
157–159[21]
135–137[22]
170–172[23]
222–224[24]
170–171[25]
163–165[16]
138–139[26]
155–157[27]
196–198[28]
145–147[29]
236–238[30]
138–140[31]
182–184[32]
140–142[33]
7
FIGURE 9 Recyclability of catalyst for preparation of 4‐
methylbenzamide (3)
8
2‐ClC6H4
9
4‐ClC6H4
was performed with a Leo 912AB (120 kV) microscope
(Zeiss, Germany). ICP analysis was carried out with a
Varian VISTA‐PRO, CCD (Australia). Elemental compo-
sitions were determined with EDX analysis (model 7353,
Oxford Instruments, UK), with 133 eV resolution. TGA
was performed with a Shimadzu thermogravimetric
analyser (TG‐50) under air atmosphere at a heating rate
10
11
12
13
14
15
16
17
18
19
20
4‐CNC6H4
3‐OHC6H4
4‐OMeC6H4
3,4‐(Cl)2C6H3
4‐Pyridyl
2‐Naphthyl
C6H5CH═CH
2‐OH,5‐BrC6H3
2‐OH
of 10 °C min−1
.
3.2 | Preparation of Fe3O4@SiO2 Core–
Shell
2‐Thiophenyl
2‐Furyl
Hydrolysis of TEOS in basic solution via the Stober
method was applied to prepare core–shell Fe3O4@SiO2
nanospheres.[43] An amount of 0.10 g of freshly prepared
iron oxide was dispersed in 40 ml of ethanol (98%) and
10 ml of deionized water for 30 min. Then 1.5 ml of
ammonia (25 wt%) was added and the resulting mixture
was stirred at 40 °C for 30 min and TEOS (2.0 ml) was
added and stirring was continued for 24 h at 40 °C. The
aReaction conditions: aldoxime (1 mmol), catalyst (4 mol%), PEG (0.5 ml) at
80 °C.
structure of the catalyst was analysed using XRD with a
Bruker D8 ADVANCE diffractometer using a Cu target
(λ = 1.54 Å). The magnetic property of the catalyst was
measured using VSM (model 7400, Lake Shore). TEM
TABLE 3 Conversion of oximes into selected amides using Fe3O4@SiO2‐Lig‐Cu nanocatalyst in the same reaction timea
Entry
Ar
Time (h)
Yield (%)
1
2
C6H5
1
1
1
1
1
1
1
1
1
1
87
95
55
40
92
80
92
38
58
88
4‐ClC6H4
3
4‐OMeC6H4
2‐OHC6H4
4‐NO2C6H4
4‐CNC6H4
3‐OHC6H4
2‐OH,5‐BrC6H3
2‐Naphthyl
2‐Furyl
4
5
6
7
8
9
10
aReaction conditions: aldoxime (1 mmol), catalyst (4 mol%), PEG (0.5 ml) at 80 °C.

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KEYHANIYAN ET AL.
3.5 | Preparation of Cu Immobilized on
Fe3O4@SiO2‐Lig
Ligand‐functionalized MNPs (0.1 g) were sonicated in tol-
uene (20 ml) for 10 min. A solution of Cu(OAc)2 (0.2 M)
was added to the dispersed MNPs and the mixture was
sonicated for 20 min. Then, the resulting mixture was
stirred at 60 °C for 24 h. After completion, the catalyst
was washed three times with water and ethanol to remove
the unreacted salt and finally dried at 80 °C for 6 h.
3.6 | General Procedure for Synthesis of
Aldoxime Derivatives
According to the literature,[31] NH2OH⋅HCl (0.3 g,
4.3 mmol) was added to a stirred mixture of ZnO
(0.16 g, 2 mmol) and aldehyde (1 mmol) at 80 °C in an
oil bath. The progress of the reaction was monitored by
TLC. After complete disappearance of the starting mate-
rial, CH2Cl2 (20 ml) was added and washed with water
(2 × 20 ml). The organic layer was dried (Na2SO4) and
evaporated to afford the aldoxime.
SCHEME
derivatives
3
Proposed mechanism for synthesis of amide
obtained silica‐coated MNPs were collected using a per-
manent magnet and washed three times with water and
ethanol, and dried at 60 °C for 6 h.
3.7 | General Procedure for Synthesis of
Amide Derivatives (1–20) Catalysed by
Fe3O4@SiO2‐Lig‐Cu MNPs
To a mixture of nanocatalyst (4 mol%) in PEG (0.50 ml),
benzaldoxime (1.00 mmol, 0.121 g) was added with stir-
ring. The reaction mixture was stirred at 80 °C for 1 h.
After completion of the reaction, as indicated by TLC,
the reaction mixture was diluted with water and the cata-
lyst separated using an external magnet. Then the reac-
tion mixture was extracted using ethyl acetate
(3 × 5 ml). The organic layer was dried over anhydrous
Na2SO4 and purified by crystallization from
ethylacetate–hexane (1:2) to afford the products (1–20).
All aromatic and heteroaromatic amides were previously
reported and characterized using FT‐IR spectroscopy
and mass spectrometry (see supporting information) as
well as comparison of their melting points with reported
ones.[17–33] The structure of selected products (14, 16, 19,
3.3 | Preparation of Amino‐
Functionalized Fe3O4@SiO2
According to the literature,[44] prepared Fe3O4@SiO2
(0.5 g) was sonicated in dry toluene (5 ml) for 30 min. 3‐
(Triethoxysilyl)propylamine (1 mmol, 0.179 g) was added
to the dispersed MNPs in toluene under nitrogen atmo-
sphere. The resultant mixture was stirred under reflux
conditions for 12 h under nitrogen atmosphere. Amino‐
functionalized core–shell structure was separated usinf
an external magnet and washed with toluene (3 × 5 ml)
in order to remove unreacted species and dried at 80 °C
for 6 h.
3.4 | Preparation of Ligand‐
Functionalized Fe3O4@SiO2
1
20) was further confirmed using H NMR and 13C NMR
spectroscopy (see supporting information).
As shown in Scheme 1, the modification of Fe3O4@SiO2‐
NH2 was carried out via reaction between the amino
group
and
3‐chloropropane‐1,2‐diol.
Thus,
3‐
4 | CONCLUSIONS
chloropropane‐1,2‐diol (1 mmol, 0.110 g) was added to a
dispersed mixture of Fe3O4@SiO2‐NH2 (0.5 g) in ethanol
(20 ml). The resulting mixture was refluxed under inert
atmosphere for 24 h. After completion, the product was
separated using an external magnet, washed with ethanol
and dried at 80 °C for 6 h.
In summary, a new heterogeneous catalyst (Fe3O4@SiO2‐
Lig‐Cu MNPs) was prepared. Various techniques such as
FT‐IR spectroscopy, XRD, SEM, EDX analysis, TEM,
TGA, ICP analysis and VSM were applied in order to
characterize the catalyst structure. According to XRD

KEYHANIYAN ET AL.
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SUPPORTING INFORMATION
Additional Supporting Information may be found online
in the supporting information tab for this article.
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How to cite this article: Keyhaniyan M, Shiri A,
Eshghi H, Khojastehnezhad A. Novel design of
recyclable copper(II) complex supported on
magnetic nanoparticles as active catalyst for
Beckmann rearrangement in poly(ethylene glycol).
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