Cu nanoparticles immobilized on modified magnetic zeolite for the synthesis of 1,2,3-triazoles under ultrasonic conditions

Article abstract of DOI:10.1002/aoc.4774

Magnetically recoverable copper nanoparticle-loaded natural zeolite (CuNPs/MZN) as an efficient catalyst was synthesized. The Fe₃O₄ magnetic nanoparticles were immobilized into the pores of natural clinoptilolite zeolite, which were

Full text of DOI:10.1002/aoc.4774

Received: 4 May 2018
DOI: 10.1002/aoc.4774
Revised: 13 November 2018
Accepted: 25 November 2018
F U L L P A P E R
Cu nanoparticles immobilized on modified magnetic zeolite
for the synthesis of 1,2,3‐triazoles under ultrasonic
conditions
Mohammad Mehdi Khakzad Siuki | Mehdi Bakavoli
| Hossein Eshghi
Department of Chemistry, Faculty of
Magnetically recoverable copper nanoparticle‐loaded natural zeolite (CuNPs/
MZN) as an efficient catalyst was synthesized. The Fe3O4 magnetic nanoparti-
cles were immobilized into the pores of natural clinoptilolite zeolite, which
were modified with epichlorohydrine and ethylenediamine species and then
CuNPs were decorated on the surface of functionalized zeolite (CuNPs/
MZN). The catalysts were successfully characterized by Fourier
transform‐infrared, CHN, thermogravimetric analysis, inductively coupled
plasma, X‐ray diffraction, scanning electron microscopy and transmission elec-
tron microscopy techniques. The 1,2,3‐triazoles were readily synthesized
through using the catalyst in high yields and short reaction times under ultra-
sonic conditions via CuAAC reactions of aryl azides and terminal alkynes. The
CuNPs/MZN was easily separated from the reaction mixture by an external
magnet and reused several times successfully. The catalyst could be used for
the synthesis of various organic compounds.
Science, Ferdowsi University of Mashhad,
Mashhad 91775‐1436, Iran
Correspondence
Mehdi Bakavoli, Department of
Chemistry, Faculty of Science, Ferdowsi
University of Mashhad, Mashhad, 91775
‐1436, Iran.
Email: mbakavoli@um.ac.ir
KEYWORDS
1,2,3‐triazoles, clinoptilolite, Cu nanoparticles, magnetic zeolite, nanocomposite
1 | INTRODUCTION
thermal 1,3‐dipolar Huisgen cycloaddition[6] and CuAAC
reaction.[7]
1,2,3‐Triazoles have been widely used in many aspects
of human activities, such as industry, pharmacy, medi-
cal, biology, agriculture, etc. Their applications in
industry are in the synthesis of dyes, photographic
materials and corrosion inhibition. These compounds
are present in some agrochemicals, and also have
many applications in the synthesis of pharmaceutical
compounds such as anti‐cancer, anti‐bacterial and
anti‐HIV drugs.[1–4]
One of the most efficient and widely used methodolo-
gies for selective C–N bond‐forming reactions is click
chemistry, coined by Sharpless and Fokin, ‘click chemis-
try’ offers extremely regioselective synthesis of
1,4‐disubstituted‐1,2,3‐triazoles with high yields.[5] These
useful materials have been prepared using two methods,
There are many disadvantages in thermal 1,3‐dipolar
Huisgen cycloaddition, one of them is making two iso-
mers.[8] That is why this reaction is not common in chem-
ical synthesis. It might be desirable to develop a new
regioselective synthesis, using Cu (0) catalyst. The
CuAAC reaction was developed as a modification for
Huisgen reaction defects.[9] As was observed by Meldal
and co‐workers, this chemical ligation of azides and ter-
minal alkynes delivered exclusively the 1,4‐disubstituted
1,2,3‐triazoles.[10]
The required copper (0,I) catalysts are usually pre-
pared by in situ reduction of copper (II) salts with
sodium ascorbate[11] or NaBH4.[12] In recent studies, the
CuAAC has been proven to be accelerated by
immobilizing copper species on a large variety of solid
Appl Organometal Chem. 2019;e4774.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4774

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KHAKZAD SIUKI ET AL.
supports,[13] such as charcoal,[14] silica,[15] zeolite[16] and
polymers.[17,18] However, the immobilized catalysts are
difficult to separate from the solution, only through the
use of filter, high‐speed centrifugation or precipitation.
An ideal solution to this problem is using the magnetic
property.[19]
SCHEME 1 Synthesis of 1,2,3‐triazoles in the presence of
nanomagnetic catalyst (CuNPs/MZN)
Metal nanoparticles are very attractive catalysts com-
pared with bulk catalysts as they have a high surface to
volume ratio and their surface atoms are very active.[20]
Numerous review articles highlight the use of many dif-
ferent types of organic and inorganic reactions of noble
metal nanoparticles suspended in colloidal solutions as
well as those adsorbed onto different supports as cata-
lysts.[21] Copper and copper oxide nanoparticles are of
significant technological interest.[22] Copper, in the
nanoform, has been known for the past decade to show
fascinating catalytic activity for the various organic reac-
tions.[23] Cu nanoparticles are of great interest in a broad
technological arena including catalysis and energy
conversion.[24]
Ultrasound‐assisted organic synthesis, as a synthetic
approach, is a powerful technique that is used to acceler-
ate organic reactions. The notable features of the ultra-
sound approach are enhanced reaction rates, formation
of pure products in high yields, and easier manipula-
tion.[25,26] Ultrasound has been recognized as an impor-
tant technique for green and sustainable synthetic
processes.[27]
zeolite as a catalyst for the synthesis of 1,2,3‐triazoles
derivatives (Scheme 1).
2 | EXPERIMENTAL
2.1 | Chemicals
All solvents were purchased from Merck. Natural
clinoptilolite zeolite was purchased from Afrazand,
Semnan, Iran. Iron (III) chloride hexahydrate, iron (II)
chloride tetrahydrate, sodium hydroxide, copper (II) ace-
tate, sodium borohydride, ethylene glycol, ethanol,
hydrochloric acid and other compounds were obtained
from Sigma‐Aldrich in analytical grade and used without
further purification.
2.2 | Apparatus
The melting point of the products was determined with
an Electrothermal Type 9100 melting point apparatus.
The Fourier transform‐infrared (FT‐IR) spectra were
recorded on an Avatar 370 FT‐IR Thermal Nicolet spec-
trometer. Mass spectra were recorded on a 5973 Network
Natural or synthetic zeolites[28] are microporous alu-
minosilicate mineral compounds that are widely used as
waste water and gas treatment, catalysts, molecular sieve,
and also in nuclear processing, agriculture, advanced
materials, and recently as nanocomposites in organic syn-
thesis.[29,30] Magnetic zeolites have been produced by
modifying their surface and inner pores with a magnetic
component.[31] Use of magnetic adsorbents provides eas-
ier separation and avoids tedious and time consuming
work‐ups.[32] Recently, green zeolite/Fe3O4 nanocompos-
ites have been synthesized, characterized[33] and used in
organic transformations.
In continuation of our success in the synthesis of
organic compounds via multi‐component reactions,[34–36]
in this report we present the results of an extended inves-
tigation on the activity of the clinoptilolite/Fe3O4 nano-
composite containing immobilized Cu (0) nanoparticles
(CuNPs/MZN) in the synthesis of propargylamines,[36] as
an efficient and powerful catalyst for the synthesis of
1,2,3‐triazoles derivatives that facile separation of the cat-
alyst using an external magnet, and the recyclability of
the catalyst (up to five times) is one of the other important
benefits of this system. To the best of our knowledge, there
are no examples of the use of zeolite nanomagnetic cata-
lysts, especially Cu decorated on functionalized magnetic
1
Mass Selective Detector. H‐NMR and 13C‐NMR spectra
were measured (CDCl3) with
a Bruker DRX‐300
AVANCE spectrometer at 300 and 75 MHz, respectively.
Thermogravimetric analysis (TGA) was performed on a
Shimadzu Thermogravimetric Analyzer (TG‐50). Trans-
mission electron microscope (TEM) images were acquired
on a TEM microscope Leo 912 AB120 KV Zeiss, Ger-
many. Inductively coupled plasma was obtained using a
Varian, VISTA‐PRO, CCD, Australia. X‐ray diffraction
(XRD) patterns were collected using a Braker D4 X‐ray
diffractometer with Ni‐filtered Cu KR radiation (40 kV,
30 MA). Elemental analysis was carried out using CHNS
(O) Analyzer Model FLASH EA 1112 series made by
Thermo Finnigan.
2.3 | Catalyst preparation
Based on our previous report,[36] the magnetic zeolite
nanocomposite (Zeolite/Fe3O4) was synthesized by a
chemical co‐precipitation technique using ferric and

KHAKZAD SIUKI ET AL.
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ferrous ions, and followed by preparation of functional-
ized magnetic nanocomposite of clinoptilolite zeolite with
epichlorohydrine and ethylenediamine linker, and then
in situ generation of CuNPs on the surface of composite
(Scheme 2).
129.0, 129.5, 130.2, 141.3, 147.1, 148.3. MS: m/z
(%) = 266 (M+).
2.4.3 |
1‐(4‐bromophenyl)‐4‐Phenyl‐1H‐1,2,3‐triaz-
ole (Table 2, entry 3)
2.4 | Synthesis of 1,2,3‐triazoles via the
White solid, m.p.: 232–234°C. 1H‐NMR (CDCl3, 300
MHz), δ = 7.35–7.91 (m, 9H), 8.17 (s, 1H); 13C‐NMR (75
MHz, CDCl3), δ = 117.2, 121.7, 122.3, 125.7, 128.5,
128.7, 128.8, 129.8, 130.8, 132.8, 135.9.
reaction of aryl azide and terminal alkyne
To a solution of aryl azide (1.1 mmole), terminal alkyne
(1.0 mmole) in a mixture of H2O/EtOH (1:1; 2 mL),
CuNPs/MZN catalyst (10.0 mg) was added and the mix-
ture was stirred at 50°C for 0.5–3 hr. The progress of the
reaction was monitored by thin‐layer chromatography
and, upon completion of the reaction, the reaction mix-
ture was diluted with EtOAc and the catalyst was
removed by an external magnet, washed with acetone
and dried overnight to be ready for the next run. The
organic layer was dried over anhydrous Na2SO4, followed
by evaporation under reduced pressure to remove the sol-
vent. The residue was purified by recrystallization from
ethanol to afford corresponding 1,2,3‐triazole. The prod-
uct was identified by melting point, CHN, mass spectrom-
etry, 1H‐NMR and 13C‐NMR spectroscopy (See
Supporting Information).
2.4.4 | 4‐Phenyl‐1‐p‐tolyl‐1,2,3‐triazole
(Table 2, entry 4)
White solid, m.p.: 174–175°C. 1H‐NMR (CDCl3, 300
MHz), δ = 2.42 (s, 3H), 7.32 (m, 3H), 7.44 (t, 2H), 7.65
(d, 2H), 7.90 (m, 2H), 8.14 (s, 1H). 13C‐NMR (75 MHz,
CDCl3), δ = 21.0, 117.6, 120.4, 125.8, 128.3, 128.8, 130.2,
130.3, 134.7, 138.8, 148.2. MS: m/z (%) = 235 (M+).
2.4.5 |
1‐(4‐chlorophenyl)‐4‐Phenyl‐1H‐1,2,3‐triazo-
le (Table 2, entry 5)
2.4.1 | 1‐(4‐diphenyl)‐1H‐1,2,3‐Triazole
Yellow solid, m.p.: 227–229°C. 1H‐NMR (300 MHz,
CDCl3), δ = 7.40–7.74 (m, 5H), 7.95–8.03 (M, 4H), 9.34
(s, 1H). 13C‐NMR (75 MHz, CDCl3), δ = 120.17, 122.14,
125.84, 128.83, 129.51, 130.40, 130.54, 133.46, 135.89,
147.95.
(Table 2, entry 1)
1
Pale yellow solid, m.p.: 183–184°C. H‐NMR (300 MHz,
CDCl3): δ = 7.28–7.81 (m, 6H), 7.93 (d, 2H), 8.22 (d,
2H), 8.52 (s, 1H); 13C‐NMR (75 MHz, CDCl3): δ = 148.3,
136.9, 130.1,129.6, 128.8, 128.6, 128.3, 125.7, 120.4, 117.5.
2.4.6 |
2.4.2 |
1‐(phenyl)‐1H‐1,2,3‐Triazole‐4‐yl‐methanol
(Table 2, entry 6)
1‐(4‐nitrophenyl)‐4‐Phenyl‐1,2,3‐triazole
(Table 2, entry 2)
1
White solid, m.p.: 115–118°C. H‐NMR (DMSO‐d6, 300
Orange solid, m.p.: 254–255°C. 1H‐NMR (300 MHz,
DMSO‐d6), δ = 7.34 (t, 1H), 7.51 (t, 2H), 7.99 (m, 2H),
8.30 (m, 2H), 8.53 (m, 2H), 9.57 (s, 1H). 13C‐NMR (75
MHz, DMSO‐d6), δ = 120.4, 120.9, 125.9, 126.1, 128.4,
MHz), δ = 4.73 (1H, d), 5.46 (td, 2H), 7.56–7.62 (m, 1H),
7.68–7.73 (m, 2H), 8.00–8.03 (m, 2H), 8.77 (s, 1H).
13C‐NMR (DMSO‐d6, 75 MHz), δ = 55.7, 120.6, 121.6,
129.1, 130.5, 137.4, 149.8.
SCHEME 2 Preparation of
nanomagnetic catalyst (CuNPs/MZN)

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KHAKZAD SIUKI ET AL.
2.4.7 |
2.4.12 |
1‐(4‐nitrophenyl)‐1H‐1,2,3‐Triazole‐4‐yl‐me-
thanol (Table 2, entry 7)
1‐Benzyl‐1H‐1,2,3‐triazol‐4‐yl‐methanol
(Table 2, entry 13)
1
White solid, m.p.: 201–202°C. H‐NMR (DMSO‐d6, 300
White solid, m.p. 75–78°C. 1H‐NMR (300 MHz,
DMSO‐d6), δ = 4.58 (s, 2H), 5.56 (s, 2H), 7.20–7.30 (m,
5H), 8.15 (s, 1H). 13C‐NMR (75 MHz, DMSO‐d6), δ =
53.40, 55.22, 123.66, 128.46, 128.66, 129.18, 136.14, 148.26.
MHz), δ = 4.63 (s, 2H), 5.52 (s, 1H), 8.05–8.08 (d, 2H),
8.24–8.27 (d, 2H), 8.72 (s, 1H). 13C‐NMR (DMSO‐d6, 75
MHz), δ = 55.31, 120.42, 121.49, 125.67, 141.17, 146.65,
150.13.
3 | RESULTS AND DISCUSSION
2.4.8 | [1‐(4‐bromo‐phenyl)‐1H‐[1,2,3]
triazol‐4‐yl]‐Methanol (Table 2, entry 8)
As shown in Scheme 2, CuNPs/MZN catalyst was pre-
pared in three steps. First, the MZN was synthesized by
green quick precipitation method and epichlorohydrine–
ethylenediamine covalently bonded to negative oxygen
related to aluminosilicate groups on the surface of zeolite
or hydroxyl groups of Fe3O4 NPs.[36] Later, the ligands
were activated with NaOH solution in EtOH and treated
with copper (II) acetate, which was complexed to N, N
and O available on linker and zeolite. Finally, Cu (II)
nanoparticles were reduced to Cu (0) with NaBH4 as
reductant.[43]
Yellowish solid, m.p.: 134–135°C. 1H‐NMR (300 MHz,
CDCl3), δ = 4.67 (s, 2H), 5.56 (s, 2H), 7.63–7.81 (m, 4H),
8.61 (s, 1H). 13C‐NMR (75 MHz, CDCl3), δ = 55.42,
121.30, 121.56, 122.08, 133.09, 136.21, 149.65.
2.4.9 |
1‐(4‐methylphenyl)‐1H‐1,2,3‐triazole‐4‐yl‐M-
ethanol (Table 2, entry 9)
1
White solid, m.p.: 125–127°C. H‐NMR (DMSO‐d6, 300
MHz), δ = 2.28 (s, 3H), 4.66 (d, 2H), 5.48 (s, 1H), 7.65
(d, 2H), 7.99 (d, 2H), 8.89 (s, 1H). 13C‐NMR (DMSO‐d6,
75 MHz), δ = 21.1, 59.0, 120.0, 121.6, 130.9, 132.7, 135.3,
150.4.
2.4.10 |
1‐(4‐chlorophenyl)‐1H‐1,2,3‐triazole‐4‐yl‐M-
ethanol (Table 2, entry 10)
White solid, m.p.:144–146°C. 1H‐NMR (DMSO‐d6, 300
MHz), δ = 4.67 (d, 2H), 5.54 (t, 1H), 7.53–7.56 (d, 2H),
7.86–7.89 (d, 2H), 8.62 (s, 1H). 13C‐NMR (DMSO‐d6, 75
MHz), δ = 54.38, 121.38, 121.87, 130.12, 133.24, 135.84,
149.67.
FIGURE 1 Fourier transform‐infrared (FT‐IR) (down to up) (a)
zeolite, (b) magnetic zeolite (MZ), (c) MZE, (d) MZN, (e) CuNPs/
MZN
2.4.11 | 1‐Benzyl‐4‐phenyl‐1H‐1,2,3‐triazole
(Table 2, entry 12)
1H‐NMR (CDCl3, 300 MHz), δ = 5.63 (s, 2H), 7.30–7.37
(m, 3H), 7.42–7.45 (m, 5H), 7.70 (s, 1H), 7.83–7.85 (m,
2H). 13C‐NMR (CDCl3, 75 MHz), δ = 54.27, 119.47,
125.72, 128.09, 128.19, 128.7, 128.82, 129.19, 130.56,
134.71, 148.28. MS: m/z (%) = 235 (M+). Anal. calcd for
C15H13N3 (235.284): C, 76.57; H, 5.57; found: C, 76.40;
H, 5.69.
FIGURE 2 Energy‐dispersive X‐ray (EDS) analysis of final
catalyst (CuNPs/MZN)

KHAKZAD SIUKI ET AL.
5 of 9
The prepared catalyst, CuNPs/MZN, was character-
ized by FT‐IR, TGA, scanning electron microscopy
(SEM), TEM, energy‐dispersive X‐ray (EDX), XRD, and
vibrating‐sample magnetometer (VSM).
FT‐IR spectroscopy was used for characterization of
the catalyst structure (Figure 1). The FT‐IR spectrum of
clinoptilolite is dominated by some of the major zeolite
framework bands in the range of 720–790 cm−1 υs (Si‐O),
1020 cm−1 (Si‐OH), 1130 cm−1 υas (Si‐O and Al‐O) and
3550 cm−1 for isolated silanol (Si‐OH) (Figure 1a).[44]
The strong adsorption bands at 573 cm−1 can be
attributed to the stretching vibration of the Fe‐O band,
which confirms the presence of Fe3O4 nanoparticles
(Figure 1b–d).[45] The broad absorption band at 3444 cm
−1
is related to the stretching vibration of OH, demon-
strating the presence of hydroxyl groups on the surface
FIGURE 5 Magnetization curve of CuNPs/MZN
TABLE 1 Optimization of solvent, temperature and amount of
catalyst
Catalyst Temp. Time Yield
Entry Solvent
(mg)
(°C)
(hr) (%)a
1
2
H2O
–
–
–
–
–
5
5
5
5
5
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
24
24
24
24
24
10
10
10
10
10
Trace
Trace
Trace
Trace
Trace
12
MeOH
3
EtOH
4
n‐hexane
H2O/EtOH (1:1, 2 mL)
H2O
5
FIGURE 3 (a) The scanning electron microscopy (SEM) image of
CuNPs/MZN. (b) The transmission electron microscopy (TEM)
image of CuNPs/MZN
6
7
MeOH
15
8
EtOH
18
9
n‐hexane
Trace
30
10
H2O/MeOH (1:1, 2
mL)
11
12
13
14
15
16
H2O/EtOH (1:1, 2 mL) 10
H2O/EtOH (1:1, 2 mL) 10
H2O/EtOH (1:1, 2 mL) 10
H2O/EtOH (1:1, 2 mL) 10
H2O/EtOH (1:1, 2 mL) 10
H2O/EtOH (1:1, 2 mL) 10
30
40
50
50
80
50
10
10
5
45
60
85
2.5 93
2.5 93
98b
2
aBased on isolated yield.
FIGURE 4 Thermogravimetric analysis (TGA) analysis of MZN
bUnder ultrasonic conditions.

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KHAKZAD SIUKI ET AL.
TABLE 2 Synthesis of 1,2,3‐triazoles 3a–n using CuNPs/MZN as catalysta
Melting point (°C)
Time
(hr)
Yield
(%)c
Entry
R
R1
Productb
Found
Reported
1
1a
Ph
2
91
183–184
181–183[37]
2
3
4
1b
1c
1d
Ph
Ph
Ph
2
98
254–255
232–234
174–175
254[37]
232[37]
174[37]
2
95
90
2.5
5
6
7
8
1e
1a
1b
1c
Ph
3
96
95
90
90
227–229
115–118
201–202
134–135
228[37]
CH2OH
CH2OH
CH2OH
2
116–118[38]
201–202[38]
135–137[39]
3
2.5
9
1d
CH2OH
3
91
125–127
124–125[40]
10
11
1e
1b
CH2OH
CH2Br
2.5
3
90
91
144–146
151–153
144–145[41]
152–154[42]
12
13
1f
1f
Ph
0.5
96
95
128–130
75–78
129–131[40]
75–77[41]
CH2OH
0.75
14
1f
CH2Br
1
95
123–125
124–126[42]
aReaction conditions: azides (2a–f; 1.1 mmol), terminal alkynes (2a–c; 1 mmol), CuNPs/MZN MNPs (3 mol %), 50°C in EtOH:H2O (1:1).
bThe known products were identified by comparing their melting points and 1H‐NMR and 13C‐NMR.
cIsolated yields.
of materials (Figure 1a–e). The epoxy rings that are
anchored on the surface of zeolite and Fe3O4 composite,
(MZE), are characterized by the methylene C‐H
stretching at 2950 cm−1 and C‐O‐C vibration stretching
at 1240–1260 cm−1. The bonds at 3436 and 3700 cm−1
are due to stretching of the NH2, and N‐H bonds or

KHAKZAD SIUKI ET AL.
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overtone peaks of C‐O stretching bonds at 1233 cm−1 at
MZN (Figure 1d). In all cases, vibration frequency was
covered by the broad band of stretching vibration O‐H
and asymmetric vibration of the Si–O–Si and Al‐O‐Al
bonds, respectively. The decreased intensity of the vibra-
tion band at 3400–3700 cm−1 of CuNPs/ MZN can be
attributed to the coordination of Cu nanoparticles to N,
N and O species, which are available on the surface of
the composite.[45] The elemental analysis obtained from
the EDS analysis confirms the existence of all elements
(Fe, Si, Al, O, Na, K, Cu, Ca) in structures of catalyst
(Figure 2).
The morphological features were studied using the
SEM technique. The SEM image of CuNPs/MZN
(Figure 3a) demonstrates that these modified
copper‐loaded MZ NPs are almost spherical, in aggre-
gated form due to the magnetic nature of catalyst. Also,
the particle size of CuNPs/MZN was studied using the
TEM technique. The TEM image of the sample
(Figure 3b) shows that the average sizes of Fe3O4 and
CuNPs are approximately between 10 and 15 nm in
diameter.
better than aprotic and non‐polar solvents. Finally, the
highest yield was obtained when the reaction was per-
formed in a mixture of EtOH and H2O with the ratio
1:1 in the presence of 10 mg of catalyst at 50°C (entry
14). Moreover, ultrasonic conditions have been selected
for the model reaction, and the yield of the reaction
was greater than under non‐ultrasound conditions
(entry 16).
Using these optimized reaction conditions, the scope
of the reaction was extended to various azides and differ-
ent terminal alkynes. According to the results shown in
Table 2, all aryl azides carrying either electron‐donating
or electron‐withdrawing groups reacted successfully and
gave the products in high yields within a short reaction
time. Benzyl azide compared with phenyl azides required
shorter reaction time (entries 12–14). Both the aromatic
The thermal stability of the MZN was characterized
by TGA. The TGA curve in Figure 4 demonstrates the
weight loss up to 200°C that was related to the loss of
absorbed water molecules on the support or trapped
water (nearly 10%) in the inner pores of zeolite. The sec-
ond weight loss is related to the decomposition of organic
compounds in the temperature range of 190–600°C.[45]
Therefore, the result confirms that the ligand was grafted
successfully.
FIGURE 6 Recycling experiment for catalyst
The magnetic behavior of CuNPs/MZN was proved by
VSM. As illustrated in Figure 5, the value of the satura-
tion magnetic moment of the catalyst is 22 emμ g−1
which indicates the catalyst is super‐paramagnetic.
,
The catalytic performance of the novel CuNPs/MZN
as an efficient magnetic nanocatalyst was investigated
for the synthesis of 1,2,3‐triazoles compounds via click
reactions. After determining the molar ratios of reactants
based on mechanistic investigations and previously
reported literatures, the other reaction conditions such
as solvent, amount of catalyst and temperature were
optimized.
In order to optimize the amount of catalyst, solvent
and temperature, the reaction of 4‐nitrophenyl azide
and phenyl acetylene was selected as a model reaction.
At first, this reaction was also carried out in the absence
and presence of different amounts of catalyst (Table 1).
No product was obtained in the absence of the catalyst
in some polar and non‐polar solvents after 24 hr
(Table 1, entries 1–5). Increasing the amount of catalyst
to 10 mg improved the yield of the reaction (entries 6–
14). Also, the reaction was carried out in polar solvents
FIGURE 7 Transmission electron microscopy (TEM) photograph
of CuNPs/MZN after five consecutive cycles

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KHAKZAD SIUKI ET AL.
4 | CONCLUSIONS
Eco‐friendly CuNPs/MZN proved to be an efficient cata-
lyst for the synthesis of 1,2,3‐triazoles from aryl azide
and terminal alkynes. This efficient catalyst could be eas-
ily recycled by means of an external magnet and reused
without significant loss of catalytic activity for five cycles.
The advantages of this catalyst compared with previously
synthesized catalysts are easier work‐up due to its magne-
tism and low reaction time. Based on preliminary mecha-
nistic investigations, this reaction proceeds through the
combination of aryl azide as an intermediate and the
Cu‐acetylide that is formed by zeolite assistance.
SCHEME
3
Proposed mechanism for the synthesis of
1,2,3‐triazoles in the presence of nanomagnetic catalyst
ACKNOWLEDGEMENTS
The authors gratefully acknowledge the partial support of
this study by the Ferdowsi University of Mashhad
Research Council (grant no. 3/39646).
and aliphatic terminal acetylenes gave the corresponding
triazoles in excellent yields and high purity.
3.1 | Stability and reusability of catalyst
ORCID
Although a small amount of catalyst (10.0 mg) was uti-
lized, it could easily be filtered and recovered by using a
magnet on the outer wall of the container (after addition
of acetone) and reused. Good catalyst performance in the
coupling of aryl azide and terminal alkyne was observed
over five consecutive cycles (Figure 6). The TEM images
of catalyst after five reuses (recovered) were studied. As
shown in Figure 7, the TEM photograph of the recovered
nanocatalyst shows that the structure of the catalyst
remains almost the same after five reuses. In addition,
the weight of the recovered catalyst is the same as the
amount of fresh catalyst used the first time in the reaction.
Mehdi Bakavoli https://orcid.org/0000-0003-2801-1118
Hossein Eshghi https://orcid.org/0000-0002-8417-220X
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How to cite this article: Khakzad Siuki MM,
Bakavoli M, Eshghi H. Cu nanoparticles
immobilized on modified magnetic zeolite for the
synthesis of 1,2,3‐triazoles under ultrasonic
conditions. Appl Organometal Chem. 2019;e4774.
https://doi.org/10.1002/aoc.4774
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