Click approach to the three-component synthesis of novel β-hydroxy-1,2,3-triazoles catalysed by new (Cu/Cu2O) nanostructure as a ligand-free, green and regioselective nanocatalyst in water

Article abstract of DOI:10.1002/aoc.3947

Copper nanostructures were produced as an effective and regioselective catalyst for the synthesis of 1,2,3-triazoles from a wide range of raw materials, such as sodium azide, epoxides and terminal alkynes, in water via a one-pot three-component click reac

Full text of DOI:10.1002/aoc.3947

Received: 16 April 2017
DOI: 10.1002/aoc.3947
Revised: 25 May 2017
Accepted: 29 May 2017
F U L L PA P E R
Click approach to the three‐component synthesis of novel β‐
hydroxy‐1,2,3‐triazoles catalysed by new (Cu/Cu2O) nanostructure
as a ligand‐free, green and regioselective nanocatalyst in water
Hadi Esmaeili‐Shahri1 | Hossein Eshghi2
| Jalil Lari1 | Seyyed Amin Rounaghi3
1 Department of Chemistry, Faculty of
Science, Payame Noor University, PO Box
19395‐3697, Tehran, Iran
2 Department of Chemistry, Faculty of
Sciences, Ferdowsi University of Mashhad,
Mashhad, Iran
3 Department of Materials Engineering,
Birjand University of Technology, Birjand
9719866981‐236, Iran
Copper nanostructures were produced as an effective and regioselective catalyst for
the synthesis of 1,2,3‐triazoles from a wide range of raw materials, such as sodium
azide, epoxides and terminal alkynes, in water via a one‐pot three‐component click
reaction. The new heterogeneous catalyst was prepared by a simple ball mill reduc-
tion of CuO with NaBH4 using a ball‐to‐powder weight ratio of 50:1 under air atmo-
sphere at room temperature. The catalyst was fully characterized using scanning
electron microscopy, energy‐dispersive X‐ray analysis, Fourier transform infrared
spectroscopy and X‐ray diffraction. The copper nanostructures catalysed both ring
opening and triazole cyclization steps. Products were obtained in high yields and
short reaction times. The reactions were performed at ambient temperature in water
as a green solvent. The Cu/Cu2O nanostructures revealed high reusability and high
stability via a simple recycling process.
Correspondence
Hossein Eshghi, Department of Chemistry,
Faculty of Sciences, Ferdowsi University of
Mashhad, Mashhad, Iran.
Email: heshghi@um.ac.ir
KEYWORDS
click chemistry, copper nanostructures, epoxides, green chemistry, triazoles
1 | INTRODUCTION
chemistry offers extremely regioselective synthesis of 1,4‐
disubstituted 1,2,3‐triazoles with high yields.[12,13] 1,4‐
The preparation of nanoparticles and their use in chemistry
have led to big developments in the science of chemistry.
This is a potent and growing research field in modern chem-
istry.[1] One of the features of nanostructures is their catalytic
properties in organic synthesis.[2] Metallic nanocatalysts
afford very high surface areas which are effective in catalytic
performances.[3] Recyclable copper nanocatalysts also have
been shown to be effective in organic chemistry reactions.[4]
1,2,3‐Triazoles are an important and useful class of com-
pounds in pharmaceuticals and agrochemicals.[5–7] Various
substituents at 1‐ and 4‐positions of triazoles provide biolog-
ical activities such as anti‐cancer, anti‐bacterial and anti‐HIV
activities.[8,9] Triazoles have widespread use in synthesis.[10]
In addition, triazoles are used in various industries to prevent
corrosion.[11] One of the most efficient and widely used
methodologies for selective C–N bond forming reactions is
‘click’ chemistry. Coined by Sharpless and Fokin, click
Disubstituted 1,2,3‐triazoles were achieved via one‐pot
ring‐opening and cycloaddition steps simultaneously, and
finally purified. β‐Hydroxy‐1,4‐disubstituted 1,2,3‐triazoles
were synthesized in the presence of Cu(I) catalyst from a
wide range of terminal alkynes, epoxides and sodium azide
through a three‐component click reaction.[14,15]
Recently, β‐hydroxy‐1,2,3‐triazoles have been synthe-
sized via magnetic nano‐iron oxide‐catalysed reaction. This
catalytic system needs harsh reaction conditions in compar-
ison with those required for nanocopper catalysts.[16] The
use of special catalysts such as the Cu(II)–azide complex
[Cu(H2L)(N3)]⋅CH3OH yielded two compounds through
ring opening of an asymmetric epoxide in different posi-
tions. These compounds are formed by ring opening of
asymmetric epoxide from two different positions.[17] Also,
coupling alkynes, organic halides and NaN3 in the pres-
ence of Cu2O nanocrystals has been used to produce
Appl Organometal Chem. 2017;e3947.
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Copyright © 2017 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.3947

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ESMAEILI‐SHAHRI ET AL.
various types of 1,4‐disubstituted 1,2,3‐triazoles with high
regioselectivity under green conditions with high effi-
ciency.[18,19] Also, CuO has rarely been used as a catalyst
to provide 1,2,3‐triazoles but Cu2O is selective and its use
is much more general.[20–22]
of the catalyst and elemental compositions were investi-
gated with scanning electron microscopy (SEM) and
energy‐dispersive X‐ray (EDX) analysis using a TESCAN
Mira 3 scanning electron microscope, operated at 20 kV.
Ball milling is a simple method to prepare a wide
range of nanocatalysts through the solid state with the
possibility of use on a large scale.[23] Other methods that
provide copper nanoparticles from reduced Cu(II) (chemi-
cal and electrochemical methods) cannot be used on a
large scale. Conventional chemical methods generate
impurity products and isolation of products is difficult
and time‐consuming.[24–27]
In the work reported here, Cu/Cu2O nanostructures
(NSs) were synthesized via a ball mill reduction method
for first time and investigated in the one‐pot three‐compo-
nent regioselective synthesis of novel 1,4‐disubstituted
1,2,3‐triazoles (Scheme 1). This catalytic system revealed
an excellent performance. 1,4‐Disubstituted 1,2,3‐triazoles
were synthesized in water as a green solvent at room tem-
perature and in high yield. The Cu/Cu2O NSs as a hetero-
geneous catalyst can be separated from a reaction mixture
via simple filtration and reused three times without loss of
catalytic activity.
2.2 | Synthesis of Cu/Cu2O NSs
In a typical experiment, 2.69 g (33.8 mmol) of CuO was
mixed with 0.32 g (8.46 mmol) of NaBH4 to give a CuO‐
to‐NaBH4 molar ratio of 4. The mixture was loaded into a
hardened steel vial along with hardened steel balls
(10 mm in diameter) to give a ball‐to‐powder weight ratio
of 50:1. The milling method was conducted with a high‐
energy planetary ball mill in ambient atmosphere with a
rotating speed of 250 rpm for 1 h. In the purification step,
before using the catalyst in the click reaction for 1,2,3‐tri-
azole synthesis, the product was washed with distilled
water (2 × 10 ml) and methanol (2 × 10 ml) to eliminate
boron oxides and unused NaBH4.
2.3 | Synthesis of β‐Hydroxy‐1,2,3‐triazoles
(3a–3 l)
Terminal alkyne (1.0 mmol), epoxide (1.0 mmol) and
sodium azide (0.078 g,1.2 mmol) were stirred in
water(5 ml) in the presence of the Cu/Cu2O NSs
(0.01 g).The reaction mixture was monitored by TLC
using n‐hexane–ethyl acetate (4:1). After completion of
the reaction, the mixture was diluted with ethyl acetate
(3 ml). In the following the whole reaction mixture was
centrifuged for separation of the catalyst. The heteroge-
neous catalyst was washed three times with methanol
and dried at room temperature. The reaction mixture was
added to water (5 ml) and extracted with ethyl acetate
(3 × 10 ml). Organic phases were washed with saturated
brine and dried with anhydrous Na2SO4. The solvent
was removed under vacuum and the required triazole
was obtained. To increase the purity of products we used
column chromatography with a silica gel column and
ethyl acetate–hexane as eluent. Products 3b, 3e, 3 g,
3 h, 3 k and 3 l are reported for the first time, but prod-
ucts 3a, 3c, 3d and 3f have been reported in the literature,
2 | EXPERIMENTAL
2.1 | Instrumentation and reagents
All reagents were obtained from Merck and used without
further purification. The melting points of products were
obtained with an Electrothermal Type 9100 melting point
apparatus. The 1H NMR and 13C NMR spectra were
recorded with a Bruker DRX 300 Avance spectrometer
at 300 and 75 MHz, applying DMSO‐d6 or CDCl3 as
deuterated solvents. Chemical shifts were measured in
ppm downfield from tetramethylsilane as internal standard.
Phase characterization and microstructure of the catalyst
were investigated using X‐ray diffraction (XRD) with a
Philips X'Pert X‐ray diffractometer using Cu Kα radiation
(λ = 0.154056 nm). The diffraction data were obtained
over a 2θ range of 5–95° with a step width of 0.02°. Fou-
rier transform infrared (FT‐IR) spectra were collected with
a Thermo Nicolet (USA) Avatar 370 infrared spectrometer,
using KBr pellets at room temperature. The morphology
1
previously. All products (3a–3 l) were confirmed using H
NMR, 13C NMR and FT‐IR spectra.
2.3.1 | 1‐phenyl‐2‐(4‐phenyl‐1H‐1,2,3‐triazol‐
1‐yl)ethanol (3a)[14,16,20,28]
White solid; yield 75%; m.p. 121.5–124.5 °C. IR (KBr, ν,
cm−1): 764, 1043, 1078, 1226, 1429, 1460, 1489, 1610,
1
2928, 3091, 3124, 3385. H NMR (CDCl3, 300 MHz, δ,
SCHEME 1 Multicomponent synthesis of β‐hydroxy‐1,2,3‐triazoles
from epoxides
ppm): 7.76 (s, 1H), 7.73 (dd, 2H, J1
=
7.0,

ESMAEILI‐SHAHRI ET AL.
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2.3.2 | 2‐(4‐phenyl‐1H‐1,2,3‐triazol‐1‐yl)
butane (3b)
Colourless solid; yield 72%; m.p. 71.5–72.8 °C. IR (KBr, ν,
cm−1): 698, 721, 860, 957, 1076, 1165, 1358, 1458, 2970,
1
3128, 3356. H NMR (CDCl3, 300 MHz, δ, ppm): 7.75 (s,
1H), 7.61–7.64 (dd, 2H, J1 = 9, J2 = 6.9 Hz), 7.19–7.32
(m, 3H), 4.39–4.45 (dd, 2H, J1 = 22.8, J2 = 11 Hz), 4.12–
4.20 (dd, 1H, J1 = 13.8, J2 = 5.7 Hz), 3.99 (b, OH), 1.48–
1.54 (m, 2H), 0.98 (t, 3H).
FIGURE 1 XRD pattern of Cu/Cu2O nanostructures
2.3.3 | 2‐(4‐phenyl‐1H‐1,2,3‐triazol‐1‐yl)
cyclohexanol (3c)[14,28]
Bright solid; yield 68%; m.p. 177–179 °C. IR (KBr, ν, cm−1):
J2 = 1.5 Hz), 7.29–7.41 (m, 8H), 5.71 (dd, 1H, J1 = 8.2,
J2 = 3.8 Hz), 4.61–4.68 (m, 1H), 4.35 (b, OH), 4.23–4.27
(m, 1H), 3.85 (t, 1H).
873, 960, 1001, 1029, 1070, 1146, 1230, 1295, 1363, 1450,
FIGURE 2 (a) SEM image of Cu/Cu2O
nanostructures. (b) EDX spectrum of cu/
Cu2O nanostructures

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ESMAEILI‐SHAHRI ET AL.
1568, 1743, 2857, 2933, 3133, 3304, 3382. 1H NMR
(CDCl3, 300 MHz, δ, ppm): 7.67 (s, 1H), 7.57–7.64 (dd,
2H, J1 = 13.8, J2 = 6.3 Hz), 7.19–7.44 (m, 3H), 3.96–4.16
(m, 1H), 1.08–2.13 (m, 8 H).
2868, 2930, 2956, 3060, 3260. 1H NMR (CDCl3, 300 MHz,
δ, ppm): 7.90 (s, 1H), 7.77–7.79 (m, 2H), 7.29–7.44 (m,
3H), 4.60 (dd, 2H, J1 = 13.8, J2 = 10.2 Hz), 4.44 (dd, 2H,
J1 = 14, J2 = 7 Hz), 4.28 (b, OH), 3.40–3.55 (m, 3H), 1.54–
1.63 (m, 2H), 1.33–1.45 (m, 2H), 0.94 (t, 3H). 13C NMR
(CDCl3, 75.6 MHz, δ, ppm): 13.9, 19.2, 31.6, 53.2, 69.2,
71.4, 71.5, 121.2, 125.6, 128.1, 128.8, 130.4, 147.5.
2.3.4 | 3‐Phenoxy‐2‐(4‐phenyl‐1H‐1,2,3‐
triazol‐1‐yl)propane (3d)[14,16,28]
Brown oily compound; yield 78%. IR (KBr, ν, cm−1): 691,
2.3.6 | 2‐(4‐(Hydroxymethyl)‐1H‐1,2,3‐triazol‐
1‐yl)‐2‐phenylethanol (3f)[14]
754, 1044, 1115, 1175, 1245, 1495, 1599, 1733, 2947,
1
2929, 3062, 3351. H NMR (CDCl3, 300 MHz, δ, ppm):
Colourless solid; yield 84%; m.p. 110–111.8 °C. IR (KBr, ν,
cm−1): 657, 735, 845, 1012, 1061, 1115, 1229, 1461, 1638,
1742, 2868, 2932, 2962, 3154, 3355. 1H NMR (CDCl3,
300 MHz, δ, ppm): 7.99 (s, 1H), 7.10–7.17 (m, 5 H), 5.61
(dd, 1H, J1 = 9, J2 = 5.1 Hz), 5.15 (b, 2H, OH) 4.36 (s,
2H), 4.08–4.12 (dd, 1H, J1 = 11.4, J2 = 9 Hz), 3.85 (dd,
1H, J1 = 11.4, J2 = 5.1 Hz). 13C NMR (CDCl3, 75.6 MHz,
δ, ppm): 55.6, 63.5, 66.5, 122.8, 127.6, 128.6, 129.0,
138.0, 148.2.
7.87 (s, 1H), 7.70–7.73 (d, 2H), 7.29–7.42 (m, 4H), 6.94–
7.04 (m, 4H), 4.71–4.77 (m, 1H), 4.25 (dd, 1H, J1 = 14,
J2 = 7.8 Hz), 3.97 (dd, 1H, J1 = 11, J2 = 5.4 Hz), 3.37–
3.39 (m, 1H), 2.93 (m, 1H), 2.78 (dd, 1H, J1 = 4.8,
J2 = 2.1 Hz). 13C NMR (CDCl3, 75.6 MHz, δ, ppm): 53.2,
68.8, 68.8, 114.5, 121.4, 121.5, 125.5, 128.2, 128.8, 129.5,
130.1, 147.3, 158.
2.3.5 | 3‐Butoxy‐2‐(4‐phenyl‐1H‐1,2,3‐triazol‐
1‐yl)propanol (3e)
Light brown oily compound; yield 80%. IR (KBr, ν, cm−1):
2.3.7 | 3‐Phenoxy‐2‐(4‐(hydroxymethyl)‐1H‐
1,2,3‐triazol‐1‐yl)propanol (3 g)
696, 766, 829, 988, 1089, 1116, 1229, 1437, 1466, 1744,
Brown oily compound; yield 80%. IR (KBr, ν, cm−1): 698,
721, 860, 957, 1076, 1165, 1358, 1458, 2970, 3128, 3356.
1H NMR (CDCl3, 300 MHz, δ, ppm): 7.79 (s, 0.4H), 7.75
(s, 0.6H), 7.26 (m, 2H), 6.99 (m, 1H), 6.86 (m, 2H), 3.60–
4.69 (m, complex, 9H). 13C NMR (CDCl3, 75.6 MHz, δ,
ppm): 53.5, 68.9, 71.3, 72.3, 121.0, 125.4, 128.7, 129.7,
134.2, 147.0.
2.3.8 | 3‐Phenoxy‐2‐(4‐(phenoxymethyl)‐1H‐
1,2,3‐triazol‐1‐yl)propanol (3 h)
Light brown oily compound; yield 73%. IR (KBr, ν, cm−1):
884, 994, 1039, 1079, 1122, 1173, 1243, 1292, 1457, 1495,
1
1598, 1731, 2847, 2928, 3040, 3063, 3290, 3370. H NMR
FIGURE 3 FT‐IR spectrum of Cu/Cu2O nanostructures
TABLE 1 Optimization of reaction conditions
Entry
Solvent
Toluene
DMF
Temperature (°C)
Catalyst loading (mg)
Yield (%)
1
2
3
4
5
6
25
25
25
25
25
25
0
10
10
0.5
1
0
40
55
47
75
78
Ethanol
Water
Water
Water
1.5

ESMAEILI‐SHAHRI ET AL.
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TABLE 2 Synthesis of 1,4‐disubstituted β‐hydroxy‐1,2,3‐triazoles (3a–3 l)
Alkyne
Epoxide
Product
Yield (%)
1
2
75
72
3
4
68
78
5
80
6
7
8
84
80
73
(Continues)

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ESMAEILI‐SHAHRI ET AL.
TABLE 2 (Continued)
Alkyne
Epoxide
Product
Yield (%)
9
70
10
65
(CDCl3, 300 MHz, δ, ppm): 7.81 (s, 1H), 7.28–7.41 (m, 4H),
6.92–7.03 (m, 6H), 4.72 (AB, q, 2H), 4.25 (dd, 1H, J1 = 12,
J2 = 3 Hz) 3.97 (dd, 1H, J1 = 12, J2 = 6 Hz), 3.36–3.41 (m,
1H), 2.93 (dd, 1H, J1 = 9, J2 = 6 Hz), 2.78 (dd, 1H, J1 = 6,
J2 = 3 Hz) 2.85 (b, OH). 13C NMR (CDCl3, 75.6 MHz, δ,
ppm): 45.1, 51.4, 56.6, 68.5, 114.5, 115.5, 122.1, 122.5,
124.5, 129.6, 130.0, 143.5, 158.3, 158.9.
NMR (CDCl3, 75.6 MHz, δ, ppm): 13.8, 19.2, 31.6, 53.5,
64.3, 69.1, 69.6, 116.1, 124.4, 126.1, 129.3, 143.5, 156.7.
3 | RESULTS AND DISCUSSION
Ball‐milled reduction of CuO with NaBH4 gave Cu/Cu2O
NSs which were characterized using XRD, SEM, EDX and
FT‐IR. The XRD pattern of the catalyst, presented in
Figure 1, reveals crystalline copper. It is obvious that CuO
is reduced to Cu2O and Cu NSs. The Cu2O characteristic dif-
fraction peaks are at 2θ = 36.5°, 42.2°, 61.24° and 74.1° in
the XRD pattern, indexed to (111), (200), (220) and
(311),[29] and characteristic diffraction peaks of Cu nanopar-
ticles are observed at 2θ = 43°, 50.32°, 74° and 90° in the
XRD pattern. XRD peaks indexed to (111), (200) and (220)
represent face‐centred cubic structure and agree well with
Miller index.[29,30] Peaks at 2θ = 23.5° and 34° in the XRD
pattern are related to B‐containing compounds such as B6O.
Weak peaks at 2θ = 36.5°, 39° and 49° are related to
CuO.[30,31]
2.3.9 | 3‐Butoxy‐2‐(4‐(phenoxymethyl)‐1H‐
1,2,3‐triazol‐1‐yl)propanol (3 k)
Dark brown oily compound; yield 70%. IR (KBr, ν, cm−1):
883, 992, 1011, 1034, 1119, 1173, 1241, 1299, 1377, 1456,
1459, 1599, 2870, 2932, 2957, 3149, 3327. 1H NMR
(CDCl3, 300 MHz, δ, ppm): 7.79 (s, 1H), 7.15–7.36 (m,
2H), 6.69–7.07 (m, 3H), 5.17 (b, 1H), 4.71 (AB, q, 2H),
4.56 (dd, 1H, J1 = 12, J2 = 3 Hz),4.40 (dd, 1H, J1 = 20.0,
J2 = 9.0 Hz), 4.21 (m, 1 H), 4.05 (m, 1H), 3.36–3.63 (m,
3H), 1.51–1.65 (m, 2H), 1.27–1.42 (m, 2H), 0.92 (t, 3H,
J = 7.5 Hz). 13C NMR (CDCl3, 75.6 MHz, δ, ppm): 13.9,
19.2, 31.6, 53.1, 55.7, 61.7, 69.1, 71.4, 114.8, 114.9, 121.3,
124.4, 129.5, 143.9, 158.1.
Figure 2(a) shows a SEM image of the catalyst particles.
The SEM image of the synthesized catalyst confirms that Cu
nanoparticles are spherical but not very well defined, and the
particle size is in the nanometre size range. The EDX spec-
trum shows Cu and O elements (Figure 2b).
2.3.10 | 3‐Butoxy‐2‐[4‐((4‐chlorophenoxy)
methyl)‐1H‐1,2,3‐triazol‐1‐yl]propanol (3 l)
The FT‐IR spectrum of the catalyst (Figure 3).shows the
Light brown oily compound; yield 65%. IR (KBr, ν, cm−1):
508, 666, 822, 915, 1006, 1037, 1093, 1244, 1491, 1595,
2867, 2928, 3063, 3097, 3424. 1H NMR (CDCl3,
300 MHz, δ, ppm): 7.77 (s, 1H), 7.21–7.29 (m, 2H), 6.89–
6.92 (m, 2H), 5.17 (b, 1H), 4.67 (AB, q, 2H), 4.56 (dd, 1H,
J1 = 12, J2 = 3 Hz), 4.41 (dd, 1H, J1 = 20.0, J2 = 9.0 Hz),
4.19 (m, 1 H), 3.89–3.96 (m, 1H), 3.34–3.48 (m, 3H),
1.51–1.60 (m, 2H), 1.25–1.41 (m, 2H), 0.91 (t, 3H). 13C
presence of bands at 457 and 530 cm−1 corresponding to
SCHEME 2 Regioselectivity in azide attack to epoxides

ESMAEILI‐SHAHRI ET AL.
7 of 8
TABLE 3 Comparison of efficiency of various catalysts in synthesis of 3a
Entry
Catalyst
Yield (%)
Time (h)
Temperature (°C)
Ref.
1
2
3
4
5
6
Fe2O3
ZnO
81
Trace
95
5
24
0.8
2
100
100
r.t.
16
16
14
Meso‐tetra(2‐chlorophenyl)porphyrin cu@MWCNTa
Meso‐tetra(2‐chlorophenyl)porphyrin‐cu
Cu(II)–azide complex [cu(H2L)(N3)]⋅CH3OH
(Cu/Cu2O) nanostructure
82
r.t.
14
91
8
r.t.
17
75
2
r.t.
This work
aMWCNT, multi‐walled carbon nanotubes.
stretching of Cu─O, whereas that at 629 cm−1 is attributed to
Cu2O.[29,30] Also, the characteristic peaks at 1045 and weak
peaks at 1397–1605 cm−1 in the spectrum correspond to
B─O vibrations.[32]
The reaction of sodium azide, phenylacetylene and sty-
rene oxide was chosen as a model reaction. In the absence
of catalyst, no cyclic product was obtained in toluene as a sol-
vent after 48 h stirring at room temperature (Table 1). Then,
we focused on the use of the nanocopper catalyst in various
solvents. The results showed that the reaction was effective
in polar solvents and water was selected as the main solvent
for the synthesis of triazoles.
Then, the model reaction was carried out in the presence
of 5, 10 and 15 mg of catalyst. Also, 10 mg of catalyst was
used at 25, 50 and 75 °C. Although 50 and 75 °C led to good
yields, preferably the reaction was performed at room temper-
ature (Table 1, entries 1–4 and 6). Thus, the optimized reac-
tion conditions were 10 mg of nanocatalysts in water at room
temperature for 2 h.
Under these conditions, the click reaction was extended
to a variety of epoxides. The results are presented in
Table 2. We examined the reactions with several epoxides
to produce regioselective products with good yields.
Then, the performances of various catalysts in the model
reaction (styrene oxide, sodium azide and phenylacetylene in
a 1:1:1 molar ratio) were compared (Table 3). Cu/Cu2O NSs
as a catalyst was used in water without using any toxic co‐cat-
alyst at room temperature, in contrast to some nanoparticles
or nanohybrids which catalyse the same reaction at high tem-
perature or in the presence of a co‐catalyst.
4 | CONCLUSIONS
We have developed a simple and useful method for the syn-
thesis of β‐hydroxy‐1,4‐disubstituted 1,2,3‐triazoles via a
three‐component reaction of epoxide, sodium azide and
alkyne with Cu/Cu2O NSs as a catalyst in water, without
using any toxic co‐catalyst or solvent at ambient temperature.
This protocol can be used to produce a diverse range of single
regioisomer products. Some of these β‐hydroxy‐1,4‐disubsti-
tuted 1,2,3‐triazoles have been synthesized for the first time.
The Cu/Cu2O NSs can be easily recycled and reused without
significant loss of catalytic activity. Also the ball milling
approach that was used in the preparation of the Cu/Cu2O
NSs is a simple method and provides the nanocatalyst
through a solid‐state reaction.
The use of aliphatic epoxides yields
a
single
regioisomer through preferential attack at more hindered
terminal carbon atom. Regioselectivity is decreased in
the case of aromatic epoxides but also gives more
substituted regioisomers 3a–3 l in good yields. Epoxide
activated by the nanocopper catalyst is effective in azide
attack to more hindered terminal carbon atom of epoxide.
This eventually leads to the production of more substituted
regioisomers 3a–3 l (Scheme 2).
To investigate catalyst recyclability, the reaction of
phenylacetylene, styrene oxide and sodium azide as model
reaction was examined. For this purpose, after completion
of the reaction, the mixture was centrifuged in a test tube
and was then decanted to separate the heterogeneous catalyst.
The heterogeneous catalyst was washed several times with
methanol and dried at room temperature for 20 min. The
nanocatalyst was reused three times without much change
in yields with the three runs giving yields of 75, 73 and
70%, respectively.
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How to cite this article: Esmaeili‐Shahri H, Eshghi
H, Lari J, Rounaghi SA. Click approach to the three‐
component synthesis of novel β‐hydroxy‐1,2,3‐
triazoles catalysed by new (cu/Cu2O) nanostructure as
a ligand‐free, green and regioselective nanocatalyst in
water. Appl Organometal Chem. 2017;e3947. https://
doi.org/10.1002/aoc.3947
[16] M. Murty, M. R. Katiki, D. Kommula, Can. Chem. Trans. 2016, 4,
47.