Nano-magnetic-iron Oxides@choline Acetate as a Heterogeneous Catalyst for the Synthesis of 1,2,3-Triazoles

Article abstract of DOI:10.1007/s10562-021-03739-w

In this research, four cholines supported on core–shell iron oxides, Fe₂O₃@MgO@Ch.OAc (choline acetate), Fe₂O₃@MgO@Ch.OH (choline hydroxide), Fe₃O₄@Ch.OAc, Fe₃O₄@Ch.OH, were synthesized. The synthesized catalysts were tested in 1,2,3-triazoles synthesis by the reaction of nitromethane, aldehyde, and benzyl azide in EtOH as a green solvent. Among four synthesized heterogeneous catalysts, the Fe₂O₃@MgO@ch.OAc showed superior catalytic activity for the reaction and afforded the desired triazoles in good isolated yields under mild reaction conditions. Graphic Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s10562-021-03739-w

Catalysis Letters
https://doi.org/10.1007/s10562-021-03739-w
Nano‑magnetic‑iron Oxides@choline Acetate as a Heterogeneous
Catalyst for the Synthesis of 1,2,3‑Triazoles
Abolfazl Mohammadkhani1 · Akbar Heydari1
Received: 29 March 2021 / Accepted: 8 July 2021
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2021
Abstract
In this research, four cholines supported on core–shell iron oxides, Fe2O3@MgO@Ch.OAc (choline acetate), Fe2O3@MgO@
Ch.OH (choline hydroxide), Fe3O4@Ch.OAc, Fe3O4@Ch.OH, were synthesized. The synthesized catalysts were tested in
1,2,3-triazoles synthesis by the reaction of nitromethane, aldehyde, and benzyl azide in EtOH as a green solvent. Among
four synthesized heterogeneous catalysts, the Fe2O3@MgO@ch.OAc showed superior catalytic activity for the reaction and
aforded the desired triazoles in good isolated yields under mild reaction conditions.
Graphic Abstract
Keywords 1,2,3triazoles · Heterogeneous catalyst · Choline hydroxide · Choline acetate · Fe2O3/MgO@Ch.OAc
* Akbar Heydari
1 Introduction
heydar_a@modares.ac.ir
Abolfazl Mohammadkhani
m_abolfazl@modares.ac.ir
The triazole derivatives attracted the attention of scientists in
the early 1980s [1]. Their derivatives have exhibited impor-
tant biological activities such as anti-cancer [1], anti-HIV
1
Chemistry Department, Tarbiat Modares University,
PO Box:14155-4838 Tehran, Iran
Vol.:(0123456789)
1 3

A. Mohammadkhani, A. Heydari
[2], Src-kinase inhibitors [3], anti-microbial [4], anti-allergic
[5], and antifungal [6]. They have numerous applications in
the industry as fuorescent whiteners, dyestufs, photo stabi-
lizers of polymers, corrosion inhibitors, photographic pho-
toreceptors, and optical brightening agents [7, 8]. Therefore,
some strategies have been introduced for their synthesis such
as the azide-alkyne huisgen-cycloaddition reaction [9–15],
and the reaction of enamines and azideregents[16]. One
of the attractive synthetic methods is the three-component
reaction of aldehydes, nitromethane, and azide derivatives.
With the development of ‘cascade reactions’ as a wonderful
tool to operates plenty of organic syntheses, some scientifc
teams have been focus to improve cascade methodologies for
instance three-component reaction of aldehydes, nitrometh-
ane, and azide derivatives which interact initially to generate
an intermediate that reacts further to furnish the fnal prod-
uct, onepot,without eliminating intermediate and separation
[17].
spread DESs are produced by blending a hydrogen bond
acceptor (HBA), exemplifed by an inexpensive quaternary
ammonium salts such as choline chloride (ChCl, included
in the so-called vitamin B4) or other cholines, with a hydro-
gen bond donor (HBD) such as sugars, eggs, organic and
amino acids, urea or glycerol [30]. These days plenty of
publications have been reported for the organic synthesis
regarding the progressive organo-catalysts coordinated to
inorganic solids, due to the economical aspect, and environ-
mental dimension [31, 32]. It sounds important to examine
the activity of coordinated cholines to Lewis acid magnetic
surface, as a heterogeneous multi-functional catalyst for the
modifcation purposes [33].
Herein, Fe2O3/MgO@Ch.OAc (choline acetate), Fe2O3/
MgO@Ch.OH (choline hydroxide), Fe3O4@Ch.OAc, and
Fe3O4@Ch.OH have been evaluated as heterogeneous sys-
tems for the synthesis of 1,2,3-triazoles by the three-compo-
nent reaction of aldehydes, benzyl azide, and nitromethane
in EtOH as a green solvent with a low health and environ-
mental hazard[34]. Lewis acidity capability, low toxicity,
high surface area, simple preparation, capacity for surface
functionalization, and high recovery with an external mag-
netic feld are the advantages of magnetic nanoparticle sup-
ports [35–37].
Since the interesting work by Abbott and coworkers on
using deep eutectic solvent (DES) as a green ion liquid in
the 2003 year, sscientists have used diferent deep eutectic
solvents to synthesize new drug candidates and heterocyclic
compounds such as coumarins [18], indoles [19], and 2-ami-
nothiazoles [20]. The use of DES as a green, inexpensive,
biodegradable, non-fammable, and non-volatile compound
has reported in various felds such as organic reaction as cat-
alyst or solvent, renewable energy storage, bioengineering,
biotechnology, medicinal chemistry, biomass valorization,
extraction, and gas separation [21–29]. The most widely
Scheme 1 Schematic diagram of catalysts preparation
1 3

Nano-magnetic-iron Oxides@choline Acetate as a Heterogeneous Catalyst for the Synthesis…
Fig. 1 FT-IR spectrum of preparation of Fe2O3@MgO (A), Fe2O3/MgO@Ch.OAc (B), and Fe2O3/MgO@Ch.OH (C) Fe3O4@Ch.OH, and
Fe3O4@Ch.OAc (D)
points of products were measured with an Electrothermal
9100 apparatus and were uncorrected. IR spectra (with
spectroscopic grade KBr) were recorded by Nicolet IR100
instrument and the spectra were obtained over the region
400–4000 cm−1 The magnetic measurement experiments
were obtained by using a vibrating magnetometer/alter-
nating gradient force magnetometer (MD Co., Iran, www.
mdk-magnetic.com). X-ray difraction pattern (XRD) was
determined by a Philips X‐Pert 1710 diffraction meter.
Energy-Dispersive X-ray spectroscopy (EDX) spectra and
2 Materials and Methods
2.1 Chemicals and Materials
All chemicals were purchased from Merck, Aldrich, or Fluka
were used without further purifcation. The NMR spectra
were recorded on a BRUKERDRX-300AVANCE Advance
spectrometer. Gas chromatography was performed on a
Trace GC ultra from the Thermo Company equipped with
an FID detector and Rtx®-1 capillary column. Melting
1 3

A. Mohammadkhani, A. Heydari
Fig. 1 (continued)
Field Emission Scanning Electron Microscopy (FE-SEM)
images were recorded on Tescan MIRA3 FE-SEM (http://
www.tescan.co.kr/product/em/em02). Thermal Gravimetry-
Analysis (TGA): Netzsch:- TGA 209 F1.
2.2.2 Preparation of Choline Hydroxide
A mixture of choline chloride (1 mol) and sodium hydroxide
(1 mol) was refuxed in methanol (500 mL) for 12 h. As a
result of inion exchange, the sodium chloride settled as sedi-
ment. The cooled bulk was fltered and methanol solution
was evaporated under reduced pressure to aford the choline
hydroxide.
2.2 General Produce
2.2.1 Preparation of Choline Acetate
A mixture of choline chloride (1 mol) and sodium acetate
(1 mol) was refuxed in methanol (500 mL) for 12 h. As a
result of inion exchange, the sodium chloride settled as sedi-
ment. The cooled bulk was fltered and methanol solution
was evaporated under reduced pressure to aford the choline
acetate.
2.2.3 Preparation of Fe2O3@MgO
Fe3O4 nanoparticles were prepared by heating a mixture
of 100 mL aqueous solution of FeCl2·4H2O (5 mmol),and
FeCl3·6H2O (10 mmol) to 85 °C. Then, ammonia (20 mL
27 wt %) was added dropwise into the above solution under
1 3

Nano-magnetic-iron Oxides@choline Acetate as a Heterogeneous Catalyst for the Synthesis…
Fig. 2 TGA of Fe2O3/MgO@Ch.OAc (blue line), Fe2O3/MgO@Ch. OH (gray line), Fe3O4@Ch.OAc (orange line), and Fe3O4@Ch.OH (yellow
line),
stirring to reach pH=10–11. After stirring for 1 h at room
temperature and the resulting black dispersion was heated to
refux for 1 h. brown precipitate was separated by an external
magnet,and then washed several times with deionized water
until the efuent solution pH was neutral.The particles were
also washed with ethanol and suspended in ethanol. MgNO3
or MgCl2 (5 mmol) with an excess of water (1:20) was added
to the ethanol suspension of magnetite nanoparticles under
sonication. The reaction mixture was kept under sonication
for 1 h and heated, subsequently stirred for 12 h, at 70 °C
under stirring.particles separated by an external magnet
washed once with ethanol, and recovered by an external
magnet. The obtained powder (magnetite nanoparticles
coated with magnesium hydroxide) was calcined in air at
400 °C for 4 h.
The catalyst was washed with EtOH and acetone dried at
50 °C for 12 h.
2.2.6 Preparation of Fe3O4@Ch.OH
A mixture of Fe3O4 (0.5 g), EtOH (3 mL), and choline
hydroxide (4 mmol) were stirred for 15 min at 25 °C. Then,
the mixture was stirred at 90 °C for 12 h. The Burnt brown-
orang catalyst was separated by potent magnet decantation.
The catalyst was washed with EtOH and acetone dried at
50 °C for 12 h.
2.2.7 Preparation of Fe3O4@ Ch.OAc
A mixture of Fe3O4 (0.5 g), EtOH (3 mL), and choline ace-
tate (4 mmol) were stirred for 15 min at 25 °C. Then, the
mixture was stirred at 90 °C for 12 h. The Burnt brown-
orang catalyst was separated by potent magnet decantation.
The catalyst was washed with EtOH and acetone dried at
50 °C for 12 h.
2.2.4 Preparation of Fe2O3/MgO@Ch.OH
A mixture of Fe2O3/MgO (0.5 g), EtOH (3 mL), and choline
hydroxide (4 mmol) were stirred for 15 min at 25 °C. Then,
the mixture was stirred at 90 °C for 12 h. The Burnt brown-
orang catalyst was separated by potent magnet decantation.
The catalyst was washed with EtOH, and acetone dried at
50 °C for 12 h.
2.2.8 General Procedure for the Synthesis of 1,2,3 triazoles
A mixture of catalyst (100 mg), aldehyde (2.5 mmol),
nitromethane (2.5 mmol), benzyl azides (2.5 mol) in EtOH
(2 mL) were stirred at 85 °C. After completion of the reac-
tion (TLC), the magnetic catalyst was separated by an exter-
nal magnet. The reaction solution was diluted with water
(2 mL) and chloroform (2 ×2 mL) and water. The organic
layer was separated and then concentrated under reduced
2.2.5 Preparation of Fe2O3/MgO@ Ch.OAc
A mixture of Fe2O3/MgO (0.5 g), EtOH (3 mL), and choline
acetate (4 mmol) were stirred for 15 min at 25 °C. Then,
the mixture was stirred at 90 °C for 12 h. The Burnt brown-
orang catalyst was separated by potent magnet decantation.
1 3

A. Mohammadkhani, A. Heydari
Fig. 3 SEM images of Fe2O3/MgO@Ch.OAc (A), Fe2O3/MgO@Ch.OH (B) Fe3O4@Ch.OAc (A), and Fe3O4@Ch.OH (B’)
pressure. The pure product was obtained by recrystallization
with CHCl3: n-Hexane (1:3).
water. The organic layer was separated and then concen-
trated under reduced pressure.
2.2.9 General Procedure for Synthesis of Benzyl Azide
3 Results and Discussion
A mixture of Benzyl halide(1 mmol), DMF (2 ml), and
sodium azide(1.5 mmol), were stirred at 85 °C for 5 h. After
completion of the reaction (TLC), the magnetic catalyst was
separated by an external magnet. The reaction solution was
diluted with water (2 mL) and chloroform (2 × 2 mL) and
3.1 Characterization of Catalyst
The process for the synthesis of Fe2O3/MgO@Ch.OAc,
Fe2O3/MgO@Ch.OH, Fe3O4@Ch.OAc, and Fe3O4@Ch.OH
1 3

Nano-magnetic-iron Oxides@choline Acetate as a Heterogeneous Catalyst for the Synthesis…
Fig. 4 EDS images of Fe2O3/MgO@Choline acetate (A), Fe2O3/MgO@Ch. OH (B), Fe3O4@Ch.OAc (A’) and Fe3O4@Ch.OH (B’)
Fig. 5 VSM curve of Fe3O4,
Fe2O3@MgO, Fe2O3/MgO@
VSM
80
Ch.OAc Fe2O3/MgO@Ch.OH,
Fe3O4,@Ch.OAc, and Fe3O4,@
60
Ch.OH
40
Fe3O4
20
Fe2O3@MgO
Fe2O3-MgO@Ch.OH
Fe2O3-MgO@Ch.OAc
Fe3O4@Ch.OAc
0
-20
-40
-60
-80
-10000 -8000 -6000 -4000 -2000
0
2000 4000 6000 8000 10000
Fe3O4@Ch.OH
are illustrated in Scheme 1. The Fe3O4 was synthesized
according to the previous report [38]. The Fe3O4@Ch.OAc
or Ch. OH-composite was synthesized by the reaction of
Fe3O4 magnetic powder and choline acetate or hydroxide
in ethanol at 85 °C for 8 h. The catalyst was separated and
washed with ethanol and acetone and dried in the oven at
60 °C. The Fe2O3@MgO was obtained by the reaction of
Fe3O4 with magnesium nitrate and ammonium hydroxide
(27%Wt) at 70 °C for 12 h. The magnetic powder was sepa-
rated and heated in a furnace until 400 °C for 4 h to aford
the fne orange-brown powder. In the next step, choline ace-
tate or choline hydroxide and Fe2O3@MgO were refuxed in
ethanol at 85 °C for 12 h to aford the Fe2O3@MgO@Ch.X
(X=OH or OAc).
The synthesized catalysts were characterized by FT-IR,
thermos-gravimetric analysis (TGA), field emission
1 3

A. Mohammadkhani, A. Heydari
Fig. 6 XRD pattern of Fe2O3/MgO( A-blue line) Fe2O3/MgO@Cholines (A red line)
Fig. 7 XRD pattern Fe3O4(A-red line) Fe3O4@Cholines (B black line)
scanning electron microscopy (FESEM), energy-dispersive
x-ray spectroscopy (EDS), vibrating sample magnetometer
(VSM), and x-ray difraction (XRD) measurements.
respectively (Fig. 1B-red line) [39]. The spectra of choline
hydroxide show characteristics bonds at 3421, 1959, and
1357 and 1054 cm−1 assigned to the –OH, C-H sp3, C–N,
and C–O groups, respectively [40, 41] (Fig. 1C-green
line). The FT-IR spectra of all catalysts show broadband
at 540–580 cm−1 for the stretching vibration of the Fe–O
bonds assigned to the spinel form of iron oxide (Fig. 1D)
[42]. The peak at 1621 cm−1 for the O–H bond of Fe3O4
The FT-IR spectra of the choline acetate, choline
hydroxide, Fe3O4@cholines, and Fe2O3@MgO@cholines
are shown in Fig. 1 [33]. The FT-IR spectrum of choline
acetate shows characteristic bands at 1738 and 1411 cm−1
for the C=O group of acetate and the C–N bond,
1 3

Nano-magnetic-iron Oxides@choline Acetate as a Heterogeneous Catalyst for the Synthesis…
Table 1 Optimization of 1,2,3-triazoles
Entry
Cat
solvent
Base
Temperature (°C)
Yield (%)*
1
2
3
4
5
6
7
8
Fe3O4
Fe2O3@MgO
Fe2O3/MgO@Ch.OAc
Fe2O3/MgO@Ch.OH
Fe3O4@Ch.OAc
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
MeCN
Toluene
H2O
MeOH
EtOH/H2O (1/5)
EtOH
EtOH
EtOH
EtOH
EtOH
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
85
85
85
85
85
85
25
60
85
85
85
85
85
85
85
85
85
85
85
Trace
Trace
72%
67%
42%
47%
Trace
%35
%34
Trace
Trace
%56
%25
59%
75%
39%
78%
89%
86%
Fe3O4@Ch.OH
Fe2O3/MgO@Ch.OAc
Fe2O3/MgO@Ch.OAc
Fe2O3/MgO@Ch.OAc
Fe2O3/MgO@Ch.OAc
Fe2O3/MgO@Ch.OAc
Fe2O3/MgO@Ch.OAc
Fe2O3/MgO@Ch.OAc
Fe2O3/MgO@Ch.OA
Fe2O3/MgO@Ch.OAC
Fe2O3/MgO@Ch.OAC
Fe2O3/MgO@Ch.OAC
Fe2O3/MgO@Ch.OAC
Fe2O3/MgO@Ch.OAC
9
10
11
12
13
14a
15b
15
16c
17d
18d
KOH
NaOAC
K2CO3
Na2CO3
EtOH
Benzaldehyde (2.5 mmol), nitromethane (2.5 mmol), benzylazide (2.5 mmol), Cat: 100 mg, for 5 h
*Isolated yield
aCat=70 mg
bCat=140 mg, the reaction conversion is 100%
cReaction time=4.5 h
dReaction time=3.5 h
[43] (Fig. 1A), shifted to 1609 cm−1 [44] (Fig. 1D) which
confrms the coordination of choline acetate and hydrox-
ide (Fig. 1D-green and red). The FT-IR peak of choline
acetate in Fe2O3/Mg@Ch.OAc (1642 cm−1) and choline
hydroxide in Fe2O3/Mg@Ch.OH (1664 cm−1) shift to 1607
and 1632 cm−1, respectively (Fig. 1 blue-B and red-C). It
is due to the surface chelation of Fe2O3/MgO to organic
groups [44] (Fig. 1B, C).
Ch.OAc. Thermal analysis shows that the catalysts have
thermal stability until 200 °C (Fig. 2). Also, 17% weight loss
of Fe2O3/MgO@ Ch. OH initiated from 170 °C and contin-
ued to 620 °C which showed that the catalysts have thermal
stability until 170 °C (Fig. 2). As can be seen from Fig. 2,
the TGA cures of the Fe3O4@Ch.OA and Fe3O4@Ch.OH
showed weight losses about 13% and 15%, respectively.
The surface morphology of fresh Fe2O3/MgO@Ch.OAc,
Fe2O3/MgO@Ch.OH, Fe3O4@Ch.OAc, and Fe3O4@Ch.OH
nanocomposites were detected by FE-SEM separately
(Fig. 3). They show the formation of spherical particles
with an average size of 23, 38, 26, 28 nm, respectively. The
EDS analysis of Fe2O3/Mg@cholines and Fe3O4@cholines
The TGA was further used to investigate the composition
and thermal resistance of the catalysts (Fig. 2). The TGA
curve of the Fe2O3/MgO@ Ch.OAc shows a weight loss
at~100 °C which is associated with the physically adsorbed
H2O. The 10% weight loss at 220–620 °C is related to the
decomposition of organic groups from the Fe2O3/Mgo@
1 3

A. Mohammadkhani, A. Heydari
Table 2 Screening of the derivatives 1,2,3triazoles synthesis
Product 4
R1
R2
Yield (%)*
Yield (%)**
M.P.(°C)
Ref
a
b
c
d
e
f
g
h
i
j
k
l
m
n
H
H
H
H
H
H
3-Me
4-OMe
4-NO2
4-Me
4-OMe
4-Me
4-Me
4-Me
H
73
70
62
74
69
68
70
74
61
70
73
74
70
74
86
85
76
88
82
84
81
87
76
84
86
88
83
85
131–133
117–119
140–141
150–152
116–117
84–85
146
141–143
168
128–129
149–151
133–134
202–203
167
[49]
[50]
[51]
[51]
[52]
[53]
[54]
[55]
[56]
[57]
[58]
[59]
[51]
[60]
4-OMe
4-NO2
4-Br
2,4 Cl
3-OMe
H
H
H
H
4-Me
4-OMe
4-Br
3-OMe
*isolated yield without base /**isolated yield in the presence of K2CO3
(Fig. 4) exhibited the presence of their main elements in the
composites.
To determine the crystalline structure of the Fe2O3/
MgO@Cholines, its XRD pattern was studied in a domain of
10°–80°. There are not many changes in the XRD pattern of
Fe2O3@MgO (red line) and Fe2O3/MgO@Cholines acetate
and hydroxide nano-magnetic (blue line) (Fig. 6). The dif-
fractions at 2Ɵ (Cu)=30, 35.6, 36.8, 42.9 53.8, 57.2,62.2
and 62.7 can be assigned to the (220), (311), (222),(400),
(442), (511), (440), and (531), crystalline planes of cubic
lattices structure of Fe2O3 (JCPDS card No. 39–1346 [46]).
Moreover, the difractions at 2Ɵ (Co)=21.08, 50.3 and 73.8
can be ascribed to MgO (JCPDS 4–829) [47, 48] (Fig. 6).
The XRD pattern of the Fe3O4 and Fe3O4@Cholines
(Fig. 7) show difraction peaks at around 2Ɵ(Cu) = 30.3°,
35.7°, 43.3°, 53.7°, 57.3°, and 62.9° which can be assigned
to the (220), (311), (400),(422), (511), and (440) crystalline
planes of cubic lattices structure of Fe3O4 (JCPDS19–62).
The magnetic hysteresis loop measurements of the Fe2O3/
MgO@Ch.OAc, Fe2O3/MgO@Ch.OH, Fe3O4@Ch.OAc,
and Fe3O4@Ch.OH are less than Fe3O4 [37] and Fe2O3@
MgO [45] (58.5 and 42.6 emus.g-1) and indicate saturation
magnetization value of 29.84, 27.7, 46.9, and 45.3, respec-
tively. This diminution of MS value can indicate the change
of Fe3O4 into γ-Fe2O3 during the heating [46] or coating
magnesium oxide on iron oxide [45]. The incorporation
of cholines on the surface of Fe3O4 and Fe2O3@MgO may
reduce saturation magnetization values (Fig. 5).
100
Monitoring Of Hot Filtration Test
Conversion of Benzaldehyde
80
60
40
20
0
3.2 The Catalytic Activity of the Catalysts
After synthesized and characterization the catalysts, their
catalytic activity was tested in 1,2,3-triazoles synthesis. The
reaction of benzaldehyde 1a, nitromethane 2, and benzyl
azide 3a was chosen as a model reaction. First, the model
reaction was carried out using Fe3O4, Fe2O3@MgO, Fe2O3/
MgO@Ch.OH, Fe2O3/MgO@Ch.OAc, Fe3O4@Ch.OAc,
0
1
2
3
4
TIME (H)
Fig. 8 Hot fltration Test
1 3

Nano-magnetic-iron Oxides@choline Acetate as a Heterogeneous Catalyst for the Synthesis…
Fig. 9 Recyclability of Fe2O3/
MgO@Ch.OAc
Recyclability of Fe2O3/MgO@Ch.OAc
89
87
84
81
78
78
100
90
80
70
60
50
40
30
20
10
0
73
72
71
69
73
69
66
63
59
K2CO3
NaOAc
Free Base
1
2
3
4
5
NUMBER OF RUN
Free Base
NaOAc
K2CO3
Fig. 10 XRD of reuse Fe2O3/
MgO@Ch. OAcA: the frst
step reuse and E: the last step
of reuse
1 3

A. Mohammadkhani, A. Heydari
and Fe3O4@Ch.OH as a catalyst in EtOH under refux con-
ditions for 5 h (Table 1, entries 1–6). As can be seen in
Table 1, the reaction in the presence of the Fe2O3/MgO@
Ch.OAc aforded a higher isolated yield (72%, Entry 3).
Therefore, the Fe2O3/MgO@Ch.OAc was selected as a
superior catalyst for further studies. The reaction was tested
at lower temperatures. It was found that the lower reaction
temperatures led to lower yields (entries 7 and 8). The vari-
ous solvents such as H2O, H2O/EtOH, MeOH, MeCN, and
toluene were investigated (entries 9–13). It was found that
the superior solvent was EtOH (entry 3). The amount of
catalyst was optimized in the reaction (entries 14 and 15).
As can be seen in Table 1, the 100 mg of the catalyst pro-
duced the desired product in a higher isolated yield (Entry
3). Finally, the role of bases such as KOH, NaOAc, Na2CO3,
and K2CO3 was investigated in the model reaction (entries
15–18). Notably, the reaction in the presence of K2CO3 led
to a higher isolated yield in a shorter reaction time (entry
17).
Fig. 11 SEM images of reuse Fe2O3/MgO@Ch.OAc
Having acquired the optimal conditions in hand, we next
intended to explore the scope of the reaction. Various ben-
zyl azides and aldehydes containing electrons donating and
electron-withdrawing functionalities were tested in the reac-
tion (Table 2). As can be seen in Table 2, The various substi-
tuted benzyl azides could be successfully reacted with nitro
styrenes (formed in situ by Henry’s reaction of nitromethane
and aldehydes) to generate 1,2,3-triazoles in good isolated
yields. The proposed mechanism can be found with more
details in supporting information.
3.3 Recyclability Heterogeneous Catalyst
After the study of the catalytic activity of the Fe2O3/MgO@
Ch.OAc, its heterogeneous nature was investigated. First, a
hot fltration test was done for the reaction of benzaldehyde
1a, nitromethane 2, and benzyl azide 3a under optimized
conditions to test the choline leaching from the heterogene-
ous catalyst through the reaction. After 1 h, the reaction was
Fig. 12 VSM of reuse Fe2O3/MgO@Ch.OAc
Table 3 compares the efciency of various methods for synthesis of 1,2,3,triazoles
Entry
Solvent
Time
Additives
Temperature (°C)
Maximum Yield
Reference
1
2
4
5
6
7
8
9
DMSO
DMSO
H2O
Overnight
5 min
12 h
10 min
45 min
3 h
30 min
30 min
5.5 h
AlCl3
Cu-Fe2O4
Cu-Fe2O4
Pd-MCM-41/Na2CO3
Fe3O4@SiO2@Propyl-HMTA
PEG capped ZnO
Al-MCM-41/piperidine
sulfated zirconia/ piperidine
Fe2O3/MgO@Ch.OAc
Fe2O3/MgO@Ch.OAc/k2CO3
70
95%
90%
85%
82%
95%
98%
90%
90%
70–74%
89%
[61]
[17]
[62]
[63]
[64]
[65]
[66]
[66]
120-M.W.a,700w
R.T
120
110
100
DMF
DMSO
PEG-400
DMF
DMF
EtOH
EtOH
80 -M.Wa
80 -M.Wa
85
10
11
This work
This work
3.5 h
85
aMW microwave
1 3

Nano-magnetic-iron Oxides@choline Acetate as a Heterogeneous Catalyst for the Synthesis…
stopped and the catalyst was separated by a magnet. During
further heating of the fltrates for 2.5 h, no signifcant pro-
gress was detected (Fig. 8). Then, the recyclability of the
catalyst was investigated in the model reactions. The hetero-
geneous catalyst could be recycled at least fve times without
signifcant loss of activity (Fig. 9). The structure of reused
catalyst after fve runs was investigated by FT-IR (Fig. 1),
XRD (Fig. 10), FE-SEM (Fig. 11), and VSM (Fig. 12). All
analyses showed that the structure of reused Fe2O3/MgO@
Ch.OAc was similar to the fresh catalyst. All results confrm
this reaction occurs mainly via a heterogeneous route.
Table 3 compares the efciency of Fe2O3/MgO@Ch.OAc
with some reported catalysts in the 1,2,3-triazoles synthesis.
It shows that the Fe2O3/MgO@Ch.OAc has good catalytic
efciency in mild reaction conditions for the 1,2,3-triazoles
synthesis.
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