Synthesis of N-2-aryl-substituted 1,2,3-triazoles mediated by magnetic and recoverable CuFe2O4 nanoparticles

Article abstract of DOI:10.1007/s11164-016-2457-3

An efficient and economic system for the synthesis of N-2-aryl-substituted 1,2,3-triazoles in the presence of CuFe₂O₄ was developed. The corresponding products can be obtained in good to excellent yields. It is interesting to note that the catalyst could be reused for five consecutive trials without significant decreases in its activity.

Full text of DOI:10.1007/s11164-016-2457-3

Res Chem Intermed
DOI 10.1007/s11164-016-2457-3
Synthesis of N-2-aryl-substituted 1,2,3-triazoles
mediated by magnetic and recoverable CuFe2O4
nanoparticles
Dao-Qing Dong1 Hui Zhang1 Zu-Li Wang1
•
•
Received: 23 November 2015 / Accepted: 19 January 2016
Ó Springer Science+Business Media Dordrecht 2016
Abstract An efficient and economic system for the synthesis of N-2-aryl-substi-
tuted 1,2,3-triazoles in the presence of CuFe2O4 was developed. The corresponding
products can be obtained in good to excellent yields. It is interesting to note that the
catalyst could be reused for five consecutive trials without significant decreases in
its activity.
Keywords Triazoles Á Chalcone Á CuFe2O4 nanoparticles
Introduction
1,2,3-triazoles are the core structure in a large number of natural products and
biologically and pharmaceutically active molecules [1–9], thus developing an
efficient method for the synthesis of 1,2,3-triazoles have aroused great attention in
organic synthesis. At present, most of the methods for their synthesis are mainly
limited to the N-1 position [10–20]. However, there are only a few methods
(Scheme 1) for the functionalization of triazoles at the N-2 position [21–28]. The
general procedure for the synthesis of N-2-substituted 1,2,3-triazoles is from the
reaction of a-hydroxyketones with hydrazine [29], but the starting materials are
complex. Therefore, versatile and practical methods for the synthesis of N-2-
substituted 1,2,3-triazoles are still desirable.
In recent years, magnetic nanoparticles have been widely used in organic
transformations because of their environmentally benign, cost-effective, ease of
separation with an external magnet, and reusability properties [30–34]. Processes
&
Zu-Li Wang
wangzulichem@163.com
1
College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University,
Qingdao 266109, People’s Republic of China
123

D. Dong et al.
Scheme 1 Background of synthesis of N-2-substituted 1,2,3-triazoles
such as C–S [35, 36] and C–O [37, 38] bond formation and click reaction [39, 40],
as well as others [41–48], catalyzed by magnetic CuFe2O4 nanoparticles have been
well described. In continuation of our studies on green chemistry [41, 49–51], herein
we present an efficient and practical method for the synthesis of N-2-substituted
1,2,3-triazoles mediated by CuFe2O4 nanoparticles.
Experimental section
NMR spectra were recorded at 500 MHz for protons on Bruker Advance III HD
1
500 MHz spectrometers. H NMR chemical shifts (d) are given in ppm relative to
TMS (d = 0.0). Chemical shifts for 13C NMR spectra are reported in parts per
million (ppm) from tetramethylsilane with the solvent as the internal standard. Data
Reported as follows: chemical shift, multiplicity (s = singlet, d = doublet,
t = triplet, m = multiplet), integration, coupling constant, and identification. All
major chemicals and solvents were obtained from commercial sources and used
without further purification. CuFe2O4 were purchased directly from Sigma-Aldrich.
General procedure
A 25-mL Schlenk tube equipped with a magnetic stirring bar was charged with 3-(4-
chlorophenyl)-1-phenylprop-2-en-1-one (0.20 mmol), sodium azide (0.20 mmol),
DMSO (1 mL), and catalyst CuFe2O4 (1 equiv.). The tube was sealed and heated at
123

Synthesis of N-2-aryl-substituted 1,2,3-triazoles mediated…
80 °C for 24 h. Then 2-F-C6H4NO2 (0.20 mmol) was added to the mixture, and the
reaction continued at 80 °C for 5 h. After completion of the reaction, the catalyst
was separated from the reaction mixture with an external magnet, and the reaction
mixture was extracted with ethyl acetate, dried with anhydrous Na2SO4, and
concentrated under vacuum. The residue was chromatographed on a silica gel
column eluted with a mixture of petroleum ether and ethyl acetate to give pure
products.
After catalyst was washed successively with diethyl ether and dried in an oven at
60 °C for 4 h, it was reused directly for the next time without further purification.
The recovered catalyst was recovered and reused for five consecutive trials without
loss of its activity.
(2-(2-nitrophenyl)-5-phenyl-2H-1,2,3-triazol-4-yl)(phenyl)methanone(2a) yellow
solid, 1H NMR (500 MHz, CDCl3) d 8.12 (d, J = 7.5 Hz, 2H), 8.07 (d, J = 8.0 Hz,
1H), 8.01–7.88 (m, 3H), 7.80 (t, J = 7.7 Hz, 1H), 7.66 (t, J = 7.5 Hz, 2H), 7.55 (t,
J = 7.7 Hz, 2H), 7.51–7.43 (m, 3H). 13C NMR (126 MHz, CDCl3) d 187.52,
151.37, 144.12, 143.84, 136.76, 133.85, 133.06, 132.00, 130.56, 129.75, 129.74,
128.90, 128.73, 128.54, 128.53, 126.23, 125.80, 125.10.
(5-(4-chlorophenyl)-2-(2-nitrophenyl)-2H-1,2,3-triazol-4-yl)(phenyl)methanone(2b)
1
white solid, H NMR (500 MHz, CDCl3) d 8.02 (d, J = 7.0 Hz, 2H), 7.94 (d,
J = 8.5 Hz, 1H), 7.86 (d, J = 8.0 Hz, 1H), 7.80 (d, J = 8.5 Hz, 2H), 7.69 (t,
J = 7.8 Hz, 1H), 7.56 (dd, J = 8.0 Hz, 7.5 Hz, 2H), 7.45 (t, J = 7.5 Hz, 2H), 7.35
(d, J = 8.5 Hz, 2H). 13C NMR (126 MHz, CDCl3) d 187.35, 150.42, 144.01,
143.85, 136.67, 135.88, 133.94, 133.11, 131.91, 130.57, 130.31, 129.92, 128.79,
128.56, 127.26, 125.80, 125.14.
(2-(2-nitrophenyl)-5-(4-nitrophenyl)-2H-1,2,3-triazol-4-yl)(phenyl)methanone(2c)
white solid, 1H NMR (500 MHz, CDCl3) d 8.24 (d, J = 9.0 Hz, 2H), 8.13–8.01 (m,
4H), 7.96 (dd, J = 8.0 Hz, 1.0 Hz, 1H), 7.91 (dd, J = 8.1 Hz, 1.1 Hz, 1H), 7.74 (td,
J = 7.5 Hz, 1.0 Hz, 1H), 7.65–7.56 (m, 2H), 7.47 (t, J = 7.5 Hz, 2H). 13C NMR
(126 MHz, CDCl3) d 187.03, 149.31, 148.43, 144.47, 143.94, 136.41, 135.09,
134.17, 133.25, 131.81, 130.60, 130.32, 129.95, 128.65, 125.94, 125.27, 123.70.
(5-(4-fluorophenyl)-2-(2-nitrophenyl)-2H-1,2,3-triazol-4-yl)(phenyl)methanone(2d)
yellow solid, 1H NMR (500 MHz, CDCl3) d 8.13–8.06 (m, 2H), 8.01 (dd,
J = 8.0 Hz, 1.0 Hz, 1H), 7.96–7.86 (m, 3H), 7.76 (td, J = 8.0 Hz, 1.0 Hz, 1H),
7.62 (td, J = 7.5, 3.4 Hz, 2H), 7.52 (t, J = 8.0 Hz, 2H), 7.18–7.10 (m, 2H). 13C
NMR (126 MHz, CDCl3) d 187.39, 164.68, 162.69, 150.57, 143.90, 143.86, 136.75,
133.85, 133.05, 131.07, 131.01, 130.54, 129.83, 128.53, 125.75, 125.10, 124.94,
124.91, 115.68, 115.51.
(2-(2-nitrophenyl)-5-(p-tolyl)-2H-1,2,3-triazol-4-yl)(phenyl)methanone(2e) yellow
solid,1H NMR (500 MHz, CDCl3) d 8.12–8.05 (m, 2H), 8.03 (dd, J = 8.0 Hz,
1.0 Hz, 1H), 7.92 (dd, J = 8.0 Hz, 1.0 Hz, 1H), 7.83–7.73 (m, 3H), 7.65–7.58 (m,
2H), 7.55–7.47 (m, 2H), 7.24 (s, 2H), 2.40 (s, 3H). 13C NMR (126 MHz, CDCl3) d
187.55, 151.44, 144.02, 143.83, 139.84, 136.86, 133.75, 132.99, 132.02, 130.54,
129.63, 129.25, 128.79, 128.50, 125.85, 125.73, 125.05, 21.43.
123

D. Dong et al.
(5-(3,4-dimethylphenyl)-2-(2-nitrophenyl)-2H-1,2,3-triazol-4-yl)(phenyl)methanone
(2f) yellow solid,1H NMR (500 MHz, CDCl3) d 8.17–8.05 (m, 2H), 8.02 (dt,
J = 23.2, 11.6 Hz, 1H), 7.92 (dd, J = 8.0 Hz, 1.0 Hz, 1H), 7.75 (tt, J = 12.1,
6.1 Hz, 1H), 7.62 (ddd, J = 13.0, 9.4, 6.7 Hz, 4H), 7.50 (dd, J = 19.2, 11.6 Hz,
2H), 7.18 (t, J = 12.6 Hz, 1H), 2.31 (d, J = 2.0 Hz, 6H). 13C NMR (125 MHz,
CDCl3) d 187.56, 151.56, 144.08, 138.52, 136.91, 136.79, 133.69, 132.97, 132.10,
130.51, 129.85, 129.79, 129.59, 128.47, 126.39, 126.18, 125.82, 125.05, 77.27,
77.02, 76.76, 19.78, 19.71.
(4-bromophenyl)(5-(4-fluorophenyl)-2-(2-nitrophenyl)-2H-1,2,3-triazol-4-yl)
methanone(2g) yellow solid, 1H NMR (500 MHz, CDCl3) d 7.97 (ddd, J = 17.1,
12.7, 5.9 Hz, 6H), 7.78 (t, J = 7.5 Hz, 1H), 7.65 (dd, J = 14.8, 8.3 Hz, 3H), 7.15 (t,
J = 8.0 Hz, 2H). 13C NMR (126 MHz, CDCl3) d 186.11, 164.76, 162.77, 150.82,
143.83, 143.50, 135.52, 133.09, 131.98, 131.89, 131.80, 131.16, 131.10, 129.94,
129.27, 125.68, 125.13, 124.78, 115.71, 115.53. HRMS (ESI) calculated for
C21H12BrFN4O3: 488.99661(M ? Na)?, Found: 488.99690.
(4-methoxyphenyl)(2-(2-nitrophenyl)-5-(p-tolyl)-2H-1,2,3-triazol-4-yl)methanone
(2h) yellow solid,1H NMR (500 MHz, CDCl3) d 8.06 (dd, J = 9.0 Hz, 28.5 Hz,
3H), 7.92 (d, J = 8.0 Hz, 1H), 7.76 (d, J = 8.0 Hz, 3H), 7.61 (t, J = 8.0 Hz, 1H),
7.29–7.19 (m, 2H), 6.99 (d, J = 9.0 Hz, 2H), 3.90 (s, 3H), 2.39 (s, 3H). 13C NMR
(126 MHz, CDCl3) d 186.06, 164.30, 151.03, 144.37, 143.80, 139.68, 133.01,
132.95, 132.09, 129.74, 129.45, 129.25, 128.65, 125.96, 125.70, 125.01, 113.85,
55.57, 21.41.
(4-methoxyphenyl)(2-(2-nitrophenyl)-5-(4-nitrophenyl)-2H-1,2,3-triazol-4-yl)
1
methanone(2i) white solid, H NMR (500 MHz, CDCl3) d 8.30 (d, J = 9.0 Hz,
2H), 8.16–8.07 (m, 4H), 8.04 (dd, J = 8.0 Hz, 1.0 Hz, 1H), 7.98 (dd, J = 8.0 Hz,
1.5 Hz, 1H), 7.81 (td, J = 7.5 Hz, 1.0 Hz, 1H), 7.74–7.64 (m, 1H), 7.02 (d,
J = 8.5 Hz, 2H), 3.92 (s, 3H). 13C NMR (126 MHz, CDCl3) d 185.40, 164.65,
148.93, 148.35, 144.86, 135.22, 133.21, 133.18, 131.86, 130.17, 129.80, 129.26,
125.90, 125.22, 123.71, 114.03, 55.64.
(5-(4-chlorophenyl)-2-(2-nitrophenyl)-2H-1,2,3-triazol-4-yl)(4-methoxyphenyl)
1
methanone(2j) yellow solid, H NMR (500 MHz, CDCl3) d 8.10 (d, J = 8.0 Hz,
2H), 8.02 (d, J = 8.0 Hz, 1H), 7.93 (d, J = 7.5 Hz, 1H), 7.85 (d, J = 8.5 Hz, 2H),
7.77 (t, J = 7.5 Hz, 1H), 7.63 (t, J = 7.5 Hz, 1H), 7.41 (d, J = 8.0 Hz, 2H), 7.00
(d, J = 8.5 Hz, 2H), 3.90 (s, 3H). 13C NMR (126 MHz, CDCl3) d 185.77, 164.44,
150.01, 144.38, 143.82, 135.74, 133.07, 131.95, 130.17, 129.74, 129.54, 128.78,
127.39, 125.75, 125.09, 113.92, 55.60.
(4-chlorophenyl)(5-(4-chlorophenyl)-2-(2-nitrophenyl)-2H-1,2,3-triazol-4-yl)
1
methanone(2k) white solid, H NMR (500 MHz, CDCl3) d 8.11–7.99 (m, 3H),
7.95 (dd, J = 8.0 Hz, 1.0 Hz, 1H), 7.91–7.84 (m, 2H), 7.78 (td, J = 8.0 Hz, 1.5 Hz,
1H), 7.69–7.61 (m, 1H), 7.50 (d, J = 8.5 Hz, 2H), 7.47–7.40 (m, 2H). 13C NMR
(126 MHz, CDCl3) d 185.87, 150.64, 143.67, 140.51, 136.04, 135.03, 133.11,
123

Synthesis of N-2-aryl-substituted 1,2,3-triazoles mediated…
131.87, 130.37, 130.00, 128.85, 127.14, 125.72, 125.15. HRMS (ESI) calculated for
C21H12Cl2N4O3: 461.01810 (M ? Na)?, Found: 461.01787.
(5-(4-methoxyphenyl)-2-(2-nitrophenyl)-2H-1,2,3-triazol-4-yl)(4-nitrophenyl)
methanone(2l) yellow solid,1H NMR (500 MHz, CDCl3) d 8.36 (d, J = 9.0 Hz,
2H), 8.23 (d, J = 8.5 Hz, 2H), 8.04 (d, J = 8.0 Hz, 1H), 7.98–7.88 (m, 3H), 7.78 (t,
J = 9.0, Hz, 1H), 7.65 (t, J = 7.5 Hz, 1H), 7.01 (d, J = 9.0 Hz, 2H), 3.88 (s, 3H).
13C NMR (126 MHz, CDCl3) d 185.54, 161.15, 152.04, 150.43, 143.78, 142.89,
141.91, 133.06, 131.69, 131.39, 130.69, 129.97, 125.56, 125.09, 123.50, 120.72,
114.00, 77.28, 77.02, 76.77, 55.39. HRMS (ESI) calculated for C22H15N5O6:
468.09125 (M ? Na)?, Found: 468.09145.
(4-methoxyphenyl)(2-(2-nitrophenyl)-5-phenyl-2H-1,2,3-triazol-4-yl)methanone
(2m) yellow solid,1H NMR (500 MHz, CDCl3) d 8.16–8.09 (m, 2H), 8.06 (dd,
J = 8.0 Hz, 1.5 Hz, 1H), 7.94 (dd, J = 8.5 Hz, 1.5 Hz, 1H), 7.83–7.75 (m, 3H),
7.64 (td, J = 7.5 Hz, 1.5 Hz, 1H), 7.26 (d, J = 8.0 Hz, 2H), 7.04–6.98 (m, 2H),
3.93 (s, 3H). 13C NMR (126 MHz, CDCl3) d 186.00, 164.34, 150.93, 144.45,
143.79, 133.04, 132.04, 129.59, 128.82, 128.75, 128.54, 125.75, 125.05, 113.87,
55.60.
(4-chlorophenyl)(2-(2-nitrophenyl)-5-phenyl-2H-1,2,3-triazol-4-yl)methanone
(2n) yellow solid,1H NMR (500 MHz, CDCl3) d 8.15–8.03 (m, 3H), 8.02–7.87
(m, 3H), 7.80 (td, J = 8.0 Hz, 1.5 Hz, 1H), 7.72–7.63 (m, 1H), 7.59–7.41 (m, 5H).
13C NMR (126 MHz, CDCl3) d 186.01, 151.58, 143.72, 140.39, 135.09, 133.08,
131.91, 131.86, 129.85, 128.96, 128.86, 128.58, 128.54, 125.71, 125.10.
(4-bromophenyl)(2-(2-nitrophenyl)-5-phenyl-2H-1,2,3-triazol-4-yl)methanone
1
(2o) yellow solid, H NMR (500 MHz, CDCl3) d 7.98–7.93 (m, 1H), 7.92–7.87
(m, 2H), 7.87–7.76 (m, 3H), 7.69 (td, J = 7.5 Hz, 1.0 Hz, 1H), 7.62–7.51 (m, 3H),
7.43–7.33 (m, 3H). 13C NMR (126 MHz, CDCl3) d 186.20, 151.61, 143.80, 143.69,
135.53, 133.09, 131.99, 131.86, 129.87, 129.24, 128.98, 128.59, 128.55, 125.72,
125.11.
(4-nitrophenyl)(2-(2-nitrophenyl)-5-phenyl-2H-1,2,3-triazol-4-yl)methanone(2p) yellow
solid, 1H NMR (500 MHz, CDCl3) d 8.29 (d, J = 4.0 Hz, 2H), 8.18 (d,
J = 14.0 Hz, 2H), 7.98 (d, J = 8.0 Hz, 1H), 7.92–7.80 (m, 3H), 7.72 (t,
J = 8.0 Hz, 1H), 7.56 (dt, J = 15.2, 7.9 Hz, 1H), 7.47–7.34 (m, 3H). 13C NMR
(126 MHz, CDCl3) d 185.39, 152.18, 150.48, 143.82, 143.18, 141.67, 133.16,
131.69, 131.43, 130.15, 129.16, 128.58, 128.34, 125.67, 125.16, 123.56.
(2-benzyl-5-phenyl-2H-1,2,3-triazol-4-yl)(phenyl)methanone(2q) yellow solid, 1
H
NMR (500 MHz, CDCl3) d 7.96 (d, J = 7.6 Hz, 2H), 7.72 (d, J = 6.9 Hz, 2H),
7.48 (t, J = 7.3 Hz, 1H), 7.45–7.17 (m, 10H), 5.58 (s, 2H). 13C NMR (126 MHz,
CDCl3) d 187.90, 150.07, 142.33, 137.35, 134.56, 133.36, 130.51, 129.70, 129.14,
128.93, 128.79, 128.66, 128.39, 128.33, 128.23, 59.30.
123

D. Dong et al.
Results and discussion
In order to optimize the reaction conditions, we chose chalcone as a model
substrate. In our initial experiment, the effect of various solvents and temperatures
were examined. When reactions were conducted in dimethyl sulfoxide (Table 1,
entry 2), a high yield was obtained. The use of N, N-dimethylformamide (Table 1,
entry 1) as the solvent led to slower reaction. Poor yields of the desired products
were obtained when reactions were conducted in dioxane (Table 1, entry 3) and
THF (Table 1, entry 4). When toluene (Table 1, entry 5), CH3CN (Table 1, entry 6),
and PhCl (Table 1, entry 7) were used, only trace amounts of the desired products
were isolated. To our disappointment, when reaction temperature was elevated from
80 to 100 °C, there was no great improvement on the yield (Table 1, entry 8). But
the yield was slightly decreased when the reaction was conducted at 60 °C (Table 1,
entry 9). Furthermore, neither increased nor decreased loading of catalyst CuFe2O4
gave any obvious improvement in the yields. (Table 1, entry 10–11).
After completion of the search for the optimized reaction conditions, we chose a
variety of structurally diverse chalcones with wide range of functional groups to
understand the scope and generality of this reaction (Table 2). It was found that the
nature of the substituent and its position in the aromatic ring (R1 or R2) showed
some impact on the yields of the desired products. It is interesting to note that
chalcones with electron-withdrawing groups showed slightly higher yield than those
with electron-donating groups. But most reactions proceeded smoothly to afford the
corresponding N-2-aryl-substituted 1,2,3-triazoles in good to excellent yields. In
addition to 1-fluoro-2-nitrobenzene, we also tried alkyl halide such as benzyl
chloride, and to our delight, a high yield of the corresponding product was obtained
in 87 % yield (Scheme 2). All products were fully characterized based on the
Table 1 Optimization of the
reaction conditions
Entry
CuFe2O4 (equiv)
T (°C)
Solvent
Yield (%)
1
1
80
80
80
80
80
80
80
100
60
80
80
DMF
79
90
2
1
DMSO
Dioxane
THF
3
1
23
4
1
16
5
1
Toluene
CH3CN
PhCl
Trace
Trace
Trace
89
6
1
Reaction conditions: 1a
(0.2 mmol), NaN3 (0.2 mmol),
in designated solvent (1 mL) for
24 h under air, then 2-NO2-
C6H4F (0.2 mmol) was added to
the mixture and the reaction
continued for 5 h. Isolated
yields
7
1
8
1
DMSO
DMSO
DMSO
DMSO
9
1
82
10
11
0.5
1.5
76
88
123

Synthesis of N-2-aryl-substituted 1,2,3-triazoles mediated…
Table 2 Substrate scope of N-2-aryl-substituted 1,2,3-triazoles
R2
O2N
O
O
N
.
u
e
a
N
,
1
C
F
2O4
N3
N
.
2
-
-
2 NO2 C6H4F
N
R1
R2
1
2
R1
Entry
1
1
2
Yield (%)a
90
O
O
N
N
1a
N
NO2
2a
O
Cl
O
2
94
Cl
1b
N
N
N
NO2
2b
2c
O
O2
N
O
3
4
92
85
O2N
N
1c
N
N
NO2
O
F
O
F
1d
N
N
N
NO2
2d
O
5
6
78
80
O
1e
N
N
N
NO2
2e
O
O
N
N
1f
N
NO2
2f
O
r
B
7
82
F
O
r
B
F
1g
N
N
N
NO2
2g
123

D. Dong et al.
Table 2 continued
Entry
8
1
2
Yield (%)a
70
O
O
O
N
OCH
3 1h
N
N
NO2
2h
O
9
O
81
O2N
O
N
O2N
OCH
3 1i
N
N
NO2
2i
O
10
86
O
Cl
O
Cl
OCH
3 1j
N
N
N
NO2
2j
Cl
O
11
84
Cl
O
N
Cl
Cl
1k
N
N
NO2
2k
O
NO2
12
93
O
O
N
H3CO
NO
2 1l
N
N
NO2
2l
O
13
75
O
O
N
OCH
3 1m
N
N
NO2
2m
123

Synthesis of N-2-aryl-substituted 1,2,3-triazoles mediated…
Table 2 continued
Entry
14
1
2
Yield (%)a
85
O
Cl
O
N
Cl
1n
N
N
NO2
2n
r
B
O
15
81
O
N
r
B
1o
N
N
NO2
2o
NO2
O
16
82
O
N
NO
2 1p
N
N
NO2
2p
Reaction conditions: 1 (0.2 mmol), NaN3 (0.2 mmol), CuFe2O4 (1 equiv) in the DMSO (1 mL), at 80 °C
for 24 h, under air, then 2-NO2-C6H4F (0.2 mmol) was added to the mixture, and the reaction continued
for 5 h
Scheme 2 Synthesis of 2q
spectroscopic data. To put the structure beyond any ambiguity, a single crystal of
2m was cultivated by slow evaporation of solvent from its solution in a mixture of
ethyl acetate and n-hexane, and its X-ray molecular structure (CCDC 1407347) was
determined (Fig. 1).
To screen the recyclability of the CuFe2O4, a more practical method was applied
to the reaction using chalcone as substrate under present reaction conditions
(Table 3). After separation of the product from the reaction mixture and the
recovery of CuFe2O4 catalyst with an external magnet, fresh starting materials were
charged into the reaction system after the catalyst was washed successively with
diethyl ether and dried in an oven at 60 °C for 4 h. The reactions still proceeded
well, and high yields were obtained at the end of the reaction. The catalyst CuFe2O4
123

D. Dong et al.
Fig. 1 X-ray crystal structures of 2 m
Table 3 Recovery and reuse of CuFe2O4
Entry
Yielda (%)
1
2
3
4
5
90
91
89
89
87
Reaction conditions: 1a (0.2 mmol), NaN3 (0.2 mmol), CuFe2O4 (1equiv) in DMSO (1 mL), at 80 °C for
24 h, under air, then 2-NO2-C6H4F(0.2 mmol) was added to the mixture, and the reaction continued for
5 h
can be recycled five times without significant losses of its catalytic activity. The
CuFe2O4 nanoparticles were also characterized by SEM spectrum (Fig. 2). The
SEM images analysis of the recovered CuFe2O4 particles revealed that the
morphology of the catalyst remains unchanged, even after five cycles.
Next, the reaction of chalcone with sodium azide was tested in the presence of
one equivalent of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) as a radical
scavenger. No significant difference was observed in the yield (Scheme 3), ruling
out the presence of radicals during the reaction.
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Synthesis of N-2-aryl-substituted 1,2,3-triazoles mediated…
before
after
Fig. 2 SEM images of CuFe2O4 nanoparticles before and after
Scheme 3 Reaction in the presence of TEMPO under the optimized reaction conditions
Scheme 4 Proposed mechanism for this reaction
Although the mechanism for this reaction was not clear, according to the
literature3f and our experiment, a plausible mechanism was proposed (Scheme 4).
Firstly, intermediate B was produced from the reaction of chalcones A with sodium
azide in the presence of CuFe2O4, then nucleophilic reaction of intermediate B with
aryl halide occurred to provide the final product C.
Conclusions
In conclusion, we have developed an efficient and economic system for the
synthesis of N-2-aryl-substituted 1,2,3-triazoles in the presence of CuFe2O4. The
reaction could generate the corresponding products in good to excellent yields under
the present reaction conditions. Furthermore, the catalyst could be recovered and
123

D. Dong et al.
recycled with an external magnet and reused for five consecutive trials without
significant decreases in its activity. To explore more effective and economic system
for organic synthesis is being done in our laboratory.
Acknowledgments Financial support from the National Natural Science Foundation of China
(21402103), the China Postdoctoral Science Foundation (150030), the research fund of Qingdao
Agricultural University’s High-level Person (631303), and the Scientific Research Foundation of
Shandong Province Outstanding Young Scientist Award (BS2013YY024) were gratefully acknowledged.
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