Synthesis and characterization of active cuprous oxide particles and their catalytic application in 1,2,3-triazole synthesis via alkyne-azide cycloaddition reaction in water

Article abstract of DOI:10.1002/jhet.3723

Active cuprous oxide materials are synthesized from CuSO₄.5H₂O using sodium stannite as reducing agent in the presence of various stabilizers, viz., cetyl trimethyl ammonium bromide, sodium dodecyl sulphate, and polyvinyl pyrrolidone

Full text of DOI:10.1002/jhet.3723

Received: 29 June 2019
DOI: 10.1002/jhet.3723
Revised: 22 August 2019
Accepted: 25 August 2019
A R T I C L E
Synthesis and characterization of active cuprous oxide
particles and their catalytic application in 1,2,3‐triazole
synthesis via alkyne‐azide cycloaddition reaction in water
1
1
1
1
Micky Lanster Sawkmie | Dipankar Paul | Gitumoni Kalita | Khushboo Agarwala |
2
1
Pradip K. Maji
| Paresh Nath Chatterjee
1
Department of Chemistry, National
Institute of Technology Meghalaya,
Shillong, India
Abstract
Active cuprous oxide materials are synthesized from CuSO
.5H O using
2
4
2
Department of Polymer and Process
sodium stannite as reducing agent in the presence of various stabilizers, viz.,
cetyl trimethyl ammonium bromide, sodium dodecyl sulphate, and polyvinyl
pyrrolidone. The synthesized cuprous oxide materials are well characterized
by powder X‐ray diffraction and Fourier transform infrared spectroscopy to
ascertain their identity, while field emission scanning electron microscopy
and energy‐dispersive spectroscopy analysis were used to study their morphol-
ogy and composition, respectively. We have compared the catalytic prowess of
the various cuprous oxide materials in the cycloaddition reaction of alkynes
and azides to synthesize 1,4‐disubstituted‐1,2,3‐triazoles. A wide variety of sub-
stitutions can nicely be tolerated in our optimized reaction conditions to pro-
duce very good to excellent yields of the corresponding triazoles in water at
55 °C. The reactions are carried out in water without any assistance of organic
cosolvent or other additives, which renders the catalytic method as economical
and environment friendly.
Engineering, Indian Institute of
Technology Roorkee, Saharanpur, India
Correspondence
Paresh Nath Chatterjee, Department of
Chemistry, National Institute of
Technology Meghalaya, Bijni Complex,
Laitumkhrah, Shillong 793003,
Meghalaya, India.
Email: paresh.chatterjee@nitm.ac.in
Funding information
Scientific and Engineering Research Board
(SERB), Grant/Award Number: SB/FT/
CS‐115/2014
1
| INTRODUCTION
synthetic chemists. Inspired by the above mentioned
pioneering works on CuAAC reaction, many research
The 1,2,3‐triazole derivatives are found in several pharma-
groups have conferred their interests in developing new
methodologies for the construction of 1,2,3‐triazole moie-
[1]
ceutical compounds,
which show various biological
[2]
[3]
[4]
properties such as antiallergic, antiviral, anticancer,
ties in both the homogeneous and heterogeneous reaction
[
5]
[6]
[10]
anti‐HIV, and antimicrobial activities. Furthermore,
the 1,2,3‐triazole based compounds are also used as agro-
chemicals, corrosion inhibition (of copper and copper
alloys), dyes, photographic materials, and photo‐
medium.
In this context, the application of copper‐
based nanocatalysts in heterogeneous CuAAC reaction
has gone through paramount expansion in recent
[
11]
times.
It is now well understood that the nanocatalysts
[
7]
stabilizers, etc. Commonly, these compounds are syn-
thesized via the 1,3‐dipolar cycloaddition reaction of
organic azides with terminal alkynes. With the pioneering
show superior catalytic efficiency compared with bulk cat-
alytic materials because of the high surface‐to‐volume
[
12]
ratio of the nanoparticles.
Our continuing efforts in
[8]
[9]
contributions by Sharpless et al and Meldal et al inde-
developing new methods of synthesizing active metal(0)
species from their respective metals salts for their applica-
pendently, on Cu(I) catalyzed alkyne‐azide cycloaddition
[
13]
(
CuAAC) reaction, the regiospecific synthesis of 1,4‐disub-
tions in C─C bond forming reactions
led us to develop
stituted‐1,2,3‐triazoles became a very powerful tool to the
an alternate route to synthesize active Cu O particles from
2
J Heterocyclic Chem. 2019;1–12.
wileyonlinelibrary.com/journal/jhet
© 2019 Wiley Periodicals, Inc.
1

2
SAWKMIE ET AL.
respectively. The synthesis of cuprous oxide particles
proceeded by
Cu SO .5H O solution and freshly prepared Na SnO
2
a
wet chemical reaction between
2
4
2
2
solution as the reducing agent (standard reduction poten-
2
+
+
tial of Cu /Cu = +0.153 V and standard reduction
−3
−2
potential of SnO2 /SnO2 = −0.93 V). The reduction
completes in 2 hour resulting a brick‐red precipitate of
Cu O materials (Figure 1), which is confirmed by several
2
characterization technique such as powder XRD, FTIR,
FESEM, and EDS.
XRD measurements of the synthesized Cu O materials
2
were performed to know the crystalline nature of the dif-
ferent Cu O samples. Figure 2 shows the XRD pattern of
2
Cu O‐CTAB, Cu O‐SDS, Cu O‐PVP, and Cu O materials.
2
2
2
2
The observed diffraction peaks at 2θ = 30.33, 36.47,
2.41, 52.29, 61.47, 73.80, and 77.46° correspond to (110),
4
SCHEME 1 Synthesis of active Cu
2
O
particles and their
(111), (200), (211), (220), (311), and (222) planes, respec-
applications in CuAAC reaction [Color figure can be viewed at
wileyonlinelibrary.com]
tively, of the cuprous oxide present in the Cu O‐CTAB
sample (Figure 2A). The diffraction peaks at 2θ = 29.70,
2
36.54, 42.54, 52.64, 61.67, 73.88, and 77.76° corresponds
copper (II) salt using sodium stannite as the reducing
agent for catalyzing the CuAAC reaction (Scheme 1). Four
to (110), (111), (200), (211), (220), (311), and (222) planes,
respectively, of the cuprous oxide present in the Cu O‐
2
different Cu O materials have been synthesized via the
SDS sample (Figure 2B). The diffraction peaks at 2θ =
29.62, 36.52, 42.54, 52.64, 61.67, 73.73, and 77.69° corre-
sponds to (110), (111), (200), (211), (220), (311), and (222)
planes, respectively, of the cuprous oxide present in the
2
reduction of CuSO solution by freshly prepared sodium
4
stannite (Na SnO ) solution in the presence of stabilizers
2
2
such as cetyl trimethyl ammonium bromide (CTAB),
sodium dodecyl sulphate (SDS), and polyvinyl pyrrolidone
Cu O‐PVP sample (Figure 2C). The diffraction peaks at
2
(
PVP) and in absence of any stabilizer. After characterizing
2θ = 29.62, 36.49, 42.29, 52.72, 61.57, 73.73, and 77.59° cor-
the four cuprous oxide materials using powder X‐ray dif-
fraction (XRD), Fourier transform infrared (FTIR), field
emission scanning electron microscopy (FESEM), and
energy‐dispersive spectroscopy (EDS), we have compared
their potential as a catalyst in the alkyne‐azide cycloaddi-
tion reaction. In this regard, excellent yields of 1,4‐disub-
stituted‐1,2,3‐triazoles were obtained in water under an
air atmosphere in a few hours. In addition to developing
an alternative approach to synthesize cuprous oxide mate-
rials, the present work also demonstrates their excellent
catalytic efficiency in alkyne‐azide cycloaddition reaction.
The use of water as a solvent without the assistance of
organic co‐solvent, additives, or inert atmosphere in the
responds to (110), (111), (200), (211), (220), (311), and (222)
planes, respectively, of the Cu O sample (Figure 2D). The
2
above mentioned XRD patterns of the four samples are in
good agreement with the crystalline Cu O with JCPDS
2
[
14]
Card No. 05‐0667 and are phase pure.
We have recorded the FTIR spectra (Figure 3) of all the
four varieties of Cu O samples to ascertain the formation of
2
Cu(I)─O bond. As per the literature, the stretching mode of
−
1
the Cu(I)─O bond of cuprous oxide absorbs at 630.3 cm
[
15]
in the infrared region. With minor differences, we have
noticed a strong absorption peak corresponding to the
stretching vibration of the Cu(I)─O bond in all the four
varieties of Cu O samples, as shown in Figure 3.
2
Cu O‐catalyzed protocol reported here makes it an attrac-
After confirming the identity of Cu O, we have
2
2
tive alternative for laboratory synthesis of triazoles.
analyzed the morphology of the synthesized samples
using FESEM technique (Figure 4). We have observed that
the Cu O‐CTAB sample predominantly exhibits flake
2
2
| RESULTS AND DISCUSSION
morphology with the thickness of the flakes being around
20 to 30 nm and the lateral size of around 200 to 300 nm
(Figures 4A and 4B). All the other three samples namely
Our investigation started with the synthesis of active
Cu O materials in both the absence and presence of stabi-
2
lizers (such as CTAB, SDS, and PVP) via a redox‐driven
Cu
2
O‐SDS, Cu
2
O‐PVP, and Cu O predominantly exhibit
2
path (Scheme 1). Cu O materials synthesized in presence
spherical morphology (with the spheres having a diameter
of 1‐2 μm), while a minor fraction of the material also
shows flake structure (Figures 4C‐4E). This may be due
to the reason that the reduction of Cu (II) salt is kinetically
2
of CTAB is hereafter referred to as Cu O‐CTAB, and like-
2
wise, Cu O materials synthesized in presence of SDS or
2
PVP will be referred to as Cu O‐SDS and Cu O‐PVP,
2
2

SAWKMIE ET AL.
3
FIGURE 1 Digital images showing the formation of brick‐red colored Cu
2
O materials from CuSO4.5H
2
O [Color figure can be viewed at
wileyonlinelibrary.com]
2 2 2 2
FIGURE 2 X‐ray diffraction pattern of the synthesized A, Cu O‐CTAB, B, Cu O‐SDS, C, Cu O‐PVP, and D, Cu O particles
controlled by the strong reductant Na SnO , and hence,
PVP are also confirmed by EDS analysis of Cu O‐SDS
2
2
2
the particles turn to preferably have a spherical shape
and the stabilizers though controlled the growth to nm
range but could not have specific control over their shapes.
and Cu O‐PVP samples, respectively (Figure 4F). The
EDS spectra of all the four synthesized cuprous oxides
samples are shown in Figure 5.
2
The elemental compositions of all the synthesized Cu O
After characterizing of the synthesized Cu O materials,
2
2
materials were obtained by EDS analysis (Figure 4F).
The presence of carbon, nitrogen, and bromine apart from
we have tested their catalytic prowess in the alkyne‐azide
cycloaddition reaction. Initially, we took benzyl
bromide 1a, phenylacetylene 2a, and sodium azide 3
as representative substrates and tested different reaction
conditions. At the outset, we have evaluated the potential
copper and oxygen in the Cu O‐CTAB sample establishes
2
the presence of the stabilizer (CTAB) on the metal oxide.
Similarly, the incorporation of the stabilizers SDS and

4
SAWKMIE ET AL.
4a (Table 1, entry 5). When we used aqueous EtOH
(1:1), the yield of 4a improved to 70% (Table 1, entry 6).
Encouraged by the results, we have tested water as the
only solvent for the CuAAC reaction and obtained 78%
yield of the desired product (Table 1, entry 7) at 25 °C.
We also studied the effect of temperature and noticed that
the reaction proceeds better when the temperature is
raised to 55 °C generating a significant 91% yield of 4a
(Table 1, entry 8). Similarly, we checked the effect of tem-
perature on the catalytic efficiency of the other cuprous
oxide materials and noted an increase in the yield of the
desired product in comparison to the corresponding reac-
tion at room temperature (Table 1, entries 9‐11). How-
ever, Cu O‐CTAB remained the catalyst of choice as the
2
yield of the desired product is significantly higher than
other cuprous oxide materials. Further increase in the
temperature to 80 °C does not improve the yield of the
addition product appreciably (Table 1, entry 12). On vary-
ing the amount of the catalyst employed in the reaction,
we noted that the use of 4 mg catalyst produces optimum
results (Table 1, entries 8 and 13‐14).
2
FIGURE 3 Fourier transform infrared spectra of A, Cu O‐SDS, B,
Cu O‐PVP, C, Cu O‐CTAB, and D, Cu O materials
2 2 2
of all four synthesized Cu O materials as catalysts in
2
CuAAC reaction (Table 1, entries 1‐4) in EtOH solvent
at 25 °C. Out of the four Cu O materials, we have noted
2
that the Cu O‐CTAB shows better catalytic efficiency in
2
alkyne‐azide cycloaddition reaction than the other Cu O
materials. This observation can be explained on the basis
After optimization of the reactions conditions, we have
tested the substrate scope of the method using various
alkyl halides 1 and alkynes 2. Initially, we reacted several
structurally and functionally diverse alkyl halides (1a‐i)
with sodium azide 3 and phenylacetylene 2a under the
optimized reaction conditions to produce triazoles 4a‐h
(Table 2, entries 1‐9). We have noticed that the presence
of electron‐donating or electron‐withdrawing group on
the aromatic ring of the benzyl halide does not signifi-
cantly affect the yield of the corresponding product. We
were pleased to find that the reaction proceeds well when
2
of available surface area on the Cu O catalysts. Cu O‐
2
2
CTAB, predominantly exhibiting flake morphology, offers
significantly higher surface area available for catalysis
compared with the other varieties showing spherical mor-
phology. Although Cu O‐CTAB ascended as the catalyst
2
of choice, the underwhelming yield of 64% of the product
4
a obtained at 25 °C in EtOH needs to be addressed.
Accordingly, we have changed the solvent to i‐PrOH
and obtained an even lower yield of the desired product
FIGURE 4 A, Field emission scanning electron microscopy (FESEM) image of Cu
2
O‐CTAB sample. B, FESEM image of Cu
O‐PVP sample. E, FESEM image of Cu
O samples obtained from energy‐
2
O‐CTAB
sample at higher magnification. C, FESEM image of Cu O‐SDS sample. D, FESEM image of Cu
2
2
2
O
sample and F, table showing the atomic percentages of various elements present in the corresponding Cu
dispersive spectroscopy analysis [Color figure can be viewed at wileyonlinelibrary.com]
2

SAWKMIE ET AL.
5
FIGURE 5 Energy‐dispersive spectroscopy spectra of A, Cu
2
O‐CTAB, B, Cu
2
O‐SDS, C, Cu
2
O‐PVP. and D, Cu
2
O samples [Color figure can
be viewed at wileyonlinelibrary.com]
a
TABLE 1 Optimization of reaction conditions
b
Entry
Solvent
Catalyst
Temperature, °C
Yield of 4a, %
1
2
3
4
5
6
7
8
9
EtOH
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
Cu
2
2
2
2
2
2
2
2
2
2
2
2
2
2
O‐CTAB
O‐SDS
O‐PVP
O
25
25
25
25
25
25
25
55
55
55
55
80
55
55
64
53
50
40
60
70
78
91
76
71
52
92
82
93
EtOH
EtOH
EtOH
i‐PrOH
EtOH:H
O‐CTAB
O‐CTAB
O‐CTAB
O‐CTAB
O‐SDS
O‐PVP
O
2
O (1:1)
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
O
O
O
O
O
O
O
O
10
11
12
13
14
O‐CTAB
O‐CTAB
O‐CTAB
c
d
a
2
Reaction conditions: 1a (1.2 mmol), 2a (1 mmol), 3 (1.2 mmol), Cu O catalysts (4 mg), solvent (3 mL), temperature, time 2 h.
b
Isolated yields.
c
Catalyst 2 mg.
d
Catalyst 6 mg.
allyl bromide 1i is used instead of 1a generating 82% yield
of the desired product 4h (Table 2, entry 9). We have also
tested several terminal acetylenes 2b‐f to react with ben-
zyl bromide 1a and sodium azide 3 in our reaction
conditions to generate the corresponding triazoles 4 in
good to excellent yields (Table 2, entries 10‐14). It is to
be noted that the hydroxyl group in the propargyl alcohol
2f was unaffected in our reaction medium (Table 2, entry

6
SAWKMIE ET AL.
a
2
TABLE 2 Cu O‐CTAB catalyzed synthesis of substituted 1,2,3‐triazoles in water
b
Entry
Alkyl halide 1
Alkyne 2
Product 4
Yield, %
1
91
2
3
4
93
90
91
5
6
7
86
88
90
8
9
89
82
89
1
0
(Continues)

SAWKMIE ET AL.
7
TABLE 2 (Continued)
b
Entry
Alkyl halide 1
Alkyne 2
Product 4
Yield, %
11
91
1
1
1
1
1
1
2
3
4
5
6
7
87
83
80
90
78
61
c
d
e
a
Reaction conditions: 1 (1.2 mmol), 2 (1 mmol), 3 (1.2 mmol), Cu
2
O‐CTAB (4 mg), H
2
O (3 mL), 55 °C, time 2 h.
b
c
Isolated yields.
Reaction conditions: 1 (6 mmol), 2 (5 mmol), 3 (6 mmol), Cu
2 2
O‐CTAB (20 mg), H O (15 mL), 55 °C, Time 2 h.
d
Cu
2
O‐CTAB reused after entry 1.
e
Cu
2
O‐CTAB reused after entry 16.
1
4). We also tested the scalability of the developed
to the slow surface oxidation of the catalyst to CuO as
understood by its indicative greenish‐brown color after
the third cycle.
method by carrying out the reaction in 5 mmol scale
where we have obtained 90% (1.06 g) of the desired prod-
uct 4a. Furthermore, the catalyst Cu O‐CTAB can be
With the knowledge of relevant literature, we propose
the probable reaction mechanism outlined in Scheme 2.
The reaction may be initiated with the interaction of
2
reused for subsequent alkyne‐azide cycloaddition reaction
as shown in Table 2 (entry 1, 16‐17) although the catalytic
efficiency decreases gradually. The decrease in the cata-
active Cu O particles and the alkyne 2 to eventually form
2
1
0d
lytic activity of the Cu O catalyst may be attributed
the copper acetylide intermediate A.
Alkyl azide is
2

8
SAWKMIE ET AL.
optimized reaction conditions revealed that water serves
as the best solvent to generate excellent yields of
1,4‐disubstituted‐1,2,3‐triazoles thereby making the devel-
oped method environmental friendly. We have demon-
strated that the method tolerates wide varieties of
alkynes and benzyl halides. Further potential for applica-
tion of the synthesized Cu O materials in the domain of
2
catalysis is currently being explored in our laboratory.
4
| EXPERIMENTAL
.1 | General remarks
4
All reagents and solvents are of AR grade and were pur-
chased from Alfa Aesar, Spectrochem, Merck Pvt. Ltd.,
or Sisco Research Laboratories Pvt. Ltd. and used without
further purification unless otherwise stated. All the reac-
tions were done in oven‐dried glass apparatus in an air
atmosphere. Reactions were monitored by thin‐layer
chromatography on silica gel 60 F254 using UV light as a
visualizing agent. Melting points reported are uncor-
rected. Powder XRD analysis was done in a PW1710 dif-
fractometer (Philips) and processed by JCPDS software.
FESEM and EDS analyses were carried out in supra, Carl
Zeiss Pvt. Ltd. Instrument and Oxford link (ISIS 300) con-
nected to the FESEM machine, respectively. FTIR studies
were done in a PerkinElmer SpectrumTwo instrument
2
SCHEME 2 Probable reaction mechanism of the active Cu O
catalyzed formation of 1,4‐disubstituted‐1,2,3‐triazole from benzyl
halide 1 and terminal alkyne 2 [Color figure can be viewed at
wileyonlinelibrary.com]
generated in situ in the reaction medium from the reac-
tion of sodium azide 3 and alkyl halide 1, which coordi-
nates with the intermediate A to form an unusual
copper metallocycle B. The intermediate B immediately
undergoes reductive elimination to produce copper
+
triazolide complex C, which in the presence of H yields
1
13
the desired 1,4‐disubstituted‐1,2,3‐triazole releasing the
using KBr pellets. H and C NMR spectra were mea-
1
0d
1
active Cu(I) catalyst in the reaction medium. However,
alternative pathways involving structurally different
intermediates cannot be ruled out.
sured on a Bruker Avance II ( H NMR: 400 MHz and
1
3
C NMR: 100 MHz) spectrometer. Chemical shifts are
reported in ppm from tetramethylsilane (TMS), with the
solvent resonance as the internal standard (unless other-
wise mentioned, chloroform: δ 7.26 ppm). Data are
reported as follows: chemical shifts, multiplicity (s=sin-
glet, d=doublet, t=triplet, q=quartet, br=broad,
dd=double doublet, m=multiplet), coupling constant (in
3
| CONCLUSION
In summary, we have synthesized four different types of
1
3
Cu O materials by reduction of copper sulphate with
Hz), integration. C NMR spectra were recorded at 100
MHz with proton decoupling. Chemical shifts are
reported in ppm from tetramethylsilane (TMS) with the
solvent resonance as the internal standard (unless other-
wise mentioned, chloroform: δ 77.0 ppm).
2
freshly prepared sodium stannite solution in the presence
and absence of stabilizers. The as‐synthetized Cu O mate-
2
rials have been characterized by various analytical tech-
niques, such as powder XRD, FTIR, FESEM and EDS.
We have observed that Cu O materials when synthesized
2
in presence of CTAB had predominantly flake morphol-
ogy with the thickness of the flakes being around 20 to
4.2 | Preparation of sodium stannite
3
0 nm. In contrast, the absence of stabilizer or the use
(Na SnO ) solution
2
2
of PVP and SDS as stabilizers during the synthesis of
Cu O materials yielded majorly spherical micro‐particles
In a 100 mL beaker, 1.5 mmol (338.4 mg) of SnCl .2H O
2 2
2
of diameters around 1 to 2 μm. We have also studied
was dissolved in 15 mL of distilled water to which 3 mL
of 5 M NaOH was added and stirred. The milky white
suspension turned into a colorless Na SnO solution,
the catalytic prowess of the four different types of Cu O
2
materials in the CuAAC reaction and found that the
2
2
Cu O‐CTAB sample shows better catalytic property by
which was further diluted by adding water to make up
2
virtue of its high surface area. The Cu O‐CTAB catalyzed
the volume up to 50 mL. The as‐synthesized Na SnO2
2
2

SAWKMIE ET AL.
9
solution is ready to be used for the preparation of cuprous
oxide materials.
mL of the freshly prepared Na SnO
solution
2
2
[
13]
(as synthesized above) was added to it. The light blue
solution of Cu SO immediately turned to green color
2
4
upon addition of the alkaline Na SnO solution, and the
2
2
4
.3 | Preparation of different Cu O
2
stirring was further continued for 2 hour till the entire
solution turned to brick‐red. Then the solution was cen-
trifuged at 7000 rpm for 10 min, and the brick‐red solid
material was washed several times with distilled water till
the washings were neutral to pH. Finally, the solid mate-
rial was washed with ethanol and dried under vacuum.
materials
4
.3.1 | Preparation of Cu O material in the
2
presence of CTAB stabilizer
In a 250 mL beaker, 10 mL of 10 mM aqueous solution of
CTAB was added to a solution of 1 mmol (249.7 mg) of
CuSO .5H O in 100 mL of distilled water. The resulting
The sample is represented as Cu O‐PVP.
2
4
2
solution was stirred gently at room temperature and 50
mL of the freshly prepared Na SnO solution (as synthe-
2
2
4
.3.4 | Preparation of Cu O material in the
2
sized above) was added to it. The light blue solution of
Cu SO immediately turned to green color upon addition
absence of a stabilizer
2
4
of the alkaline Na SnO solution and the stirring was fur-
2
2
A solution of 1 mmol (249.7 mg) of CuSO .5H O in
4
2
ther continued for 2 hour till the entire solution turned to
brick‐red. Then the solution was centrifuged at 7000 rpm
for 10 min, and the brick‐red solid material was washed
several times with distilled water till the washings were
neutral to pH. Finally, the solid material was washed
with ethanol and dried under vacuum. The sample is rep-
1
00 mL of distilled water was stirred gently at room
temperature, and 50 mL of the freshly prepared Na SnO2
solution (as synthesized above) was added to it. The light
blue solution of Cu SO immediately turned to green
2
2
4
color upon addition of the alkaline Na SnO solution,
2
2
and the stirring was further continued for 2 hour till the
entire solution turned to brick‐red. Then the solution
was centrifuged at 7000 rpm for 10 min, and the
brick‐red solid material was washed several times with
distilled water till the washings were neutral to pH.
Finally, the solid material was washed with ethanol and
dried under vacuum.
resented as Cu O‐CTAB.
2
4
.3.2 | Preparation of Cu O material in the
2
presence of SDS stabilizer
In a 250 mL beaker, 10 mL of 10 mM aqueous solution of
SDS was added to a solution of 1 mmol (249.7 mg) of
CuSO .5H O in 100 mL of distilled water. The resulting
4
2
solution was stirred gently at room temperature and 50
mL of the freshly prepared Na SnO solution (as synthe-
4
.4 | Typical procedure for Cu O‐CTAB
2
2
2
catalyzed synthesis of triazole 4a.
sized above) was added to it. The light blue solution of
Cu SO immediately turned to green color upon addition
2
4
A 25 mL round‐bottomed flask equipped with a magnetic
bar and water condenser was charged with benzyl bro-
mide 2a (142 μL, 1.2 mmol), sodium azide 3 (78 mg, 1.2
mmol), and 3 mL of distilled water and allowed to stir
for 15 min at room temperature. After 15 min,
of the alkaline Na SnO solution, and the stirring was
2
2
further continued for 2 hour till the entire solution turned
to brick‐red. Then the solution was centrifuged at 7000
rpm for 10 min, and the brick‐red solid material was
washed several times with distilled water till the washings
were neutral to pH. Finally, the solid material was
washed with ethanol and dried under vacuum. The sam-
phenylacetylene 1a (110 μL, 1.0 mmol) and Cu O‐CTAB
2
materials (4 mg) were added and the reaction mixture
was placed in a pre‐heated oil bath at 55 °C. The progress
of the reaction was monitored by thin‐layer chromatogra-
phy. After completion of the reaction, the reaction mix-
ture was extracted with EtOAc (3 × 10 mL), washed
with water (2 × 10 mL) and brine water (2 × 10 mL),
and dried over anhydrous Na SO . The combined organic
ple is represented as Cu O‐SDS.
2
4
.3.3 | Preparation of Cu O material in
2
presence of PVP stabilizer
2
4
In a 250 mL beaker, 10 mL of PVP solution in water (0.4%
m/v) was added to a solution of 1 mmol (249.7 mg) of
CuSO .5H O in 100 mL of distilled water. The resulting
solvent was evaporated under reduced pressure, and the
crude product was purified by crystallization to obtain
91% isolated yield of the corresponding 1,2,3‐triazole
derivative 4a.
4
2
solution was stirred gently at room temperature and 50

10
SAWKMIE ET AL.
4
1
.5 | Analytical data of
,4‐disubstituted‐1,2,3‐triazoles 4
4.5.6 | 1‐(4‐Methylbenzyl)‐4‐phenyl‐1H‐
[
11h]
1,2,3‐triazole (4f)
1
4
.5.1 | 1‐Benzyl‐4‐phenyl‐1H‐1,2,3‐triazole
White solid. M. P. = 113°C. H NMR (400 MHz, CDCl
): δ
3
[
11h]
(4a)
(ppm) 2.35 (s, 3H), 5.52 (s, 3H), 7.20‐7.41 (m, 7H), 7.64 (s,
H), 7.79 (d, J = 7.7 Hz, 2H). C NMR (100 MHz, CDCl3):
δ (ppm) 21.2, 54.01, 119.6, 125.7, 128.2, 128.8, 129.8, 130.5,
1
3
1
1
White solid. M. P. = 120°C. H NMR (400 MHz, CDCl ): δ
3
(
ppm) 5.56 (s, 2H), 7.29‐7.44 (m, 8H), 7.67 (s, 1H),
131.6, 138.8, 148.1.
13
7
5
1
.78‐7.80 (m, 2H). C NMR (100 MHz, CDCl ): δ (ppm)
3
4.2, 119.6, 125.7, 128.1, 128.2, 128.8, 128.8, 129.2, 130.5,
34.7, 148.2.
4
1
.5.7 | 1‐(3‐Methylbenzyl)‐4‐phenyl‐1H‐
[16]
,2,3‐triazole (4g)
4
1
.5.2 | 1‐(4‐Bromobenzyl)‐4‐phenyl‐1H‐
1
[
11h]
White solid. M. P. = 102°C. H NMR (400 MHz, CDCl ): δ
3
(
,2,3‐triazole (4b)
ppm) 2.34 (s, 3H), 5.53 (s, 2H),), 7.11 (d, J = 6.4 Hz, 2H),
7
.17 (d, J = 7.6 Hz, 1H), 7.26‐7.33 (m, 2H), 7.40 (t, J = 7.6
1
White solid. M. P. = 139°C. H NMR (400 MHz, CDCl ): δ
(
3
13
Hz, 2H), 7.66 (s, 1H), 7.79‐7.81 (m, 2H). C NMR (100
MHz, CDCl ): δ (ppm) 21.4, 54.2, 119.5, 125.2, 125.7,
ppm) 5.46 (s, 2H), 7.11 (d, J = 8.2 Hz, 2H), 7.25 (t, J = 7.4
Hz, 1H), 7.33 (t, J = 7.5 Hz, 2H), 7.44 (d, J = 8.2 Hz, 2H),
.60 (s, 1H), 7.72 (d, J = 7.6 Hz, 2H). C NMR (100 MHz,
3
128.2, 128.8, 128.8, 129.0, 129.6, 130.5, 134.6, 139.1, 148.2.
1
3
7
CDCl ): δ (ppm) 53.5, 119.4, 122.9, 125.7, 128.3, 128.9,
3
1
29.7, 130.3, 132.3, 133.7, 148.4.
4
.5.8 | 1‐Allyl‐4‐phenyl‐1H‐1,2,3‐triazole
[17]
(4h)
4
1
.5.3 | 1‐(4‐Chlorobenzyl)‐4‐phenyl‐1H‐
[
11p]
1
,2,3‐triazole (4c)
White solid. M. P. = 63°C. H NMR (400 MHz, CDCl
ppm) 5.02 (d, J = 6.0 Hz, 2H), 5.36 (t, J = 14.1 Hz, 2H),
6.01‐6.12 (m, 1H), 7.33 (t, J = 7.3 Hz, 1H), 7.42 (t, J =
3
): δ
(
1
Pale yellow solid. M. P. = 98°C. H NMR (400 MHz,
CDCl ): δ (ppm) 5.64 (s, 2H), 7.34‐7.52 (m, 12H), 8.16‐
13
7.6 Hz, 2H), 7.77 (s, 1H), 7.83 (d, J = 7.7 Hz, 2H).
NMR (100 MHz, CDCl ): δ (ppm) 52.8, 119.5, 120.2,
125.7, 128.2, 128.8, 130.6, 131.3, 148.0.
C
3
13
8
5
1
.19 (m, 2H). C NMR (100 MHz, CDCl ): δ (ppm)
2.2, 102.5, 125.7, 125.8, 126.2, 128.7, 128.8, 129.1,
29.50, 129.9, 130.1, 131.6, 133.2, 134.6, 148.2.
3
3
4
1
.5.9 | 1‐Benzyl‐4‐(4‐bromophenyl)‐1H‐
4
1
.5.4 | 1‐(3‐Chlorobenzyl)‐4‐phenyl‐1H‐
[10c]
[
11q]
,2,3‐triazole (4i)
,2,3‐triazole (4d)
1
White solid. M. P. = 149°C. H NMR (400 MHz, CDCl ): δ
1
3
White solid. M. P. = 99°C. H NMR (400 MHz, CDCl ): δ
3
(ppm) 5.57 (s, 2H), 7.32 (d, J = 7.4 Hz, 2H), 7.40 (d, J = 6.3
(
(
(
ppm) 5.55 (s, 2H), 7.18 (d, J = 6.8 Hz, 1H), 7.30‐7.35
m, 4H), 7.41 (t, J = 7.5 Hz, 2H), 7.71 (s, 1H), 7.80‐7.82
m, 2H). C NMR (100 MHz, CDCl ): δ (ppm) 53.6,
Hz, 3H), 7.52 (d, J = 8.4 Hz, 2H), 7.67 (d, J = 8.8 Hz, 3H).
1
3
C NMR (100 MHz, CDCl ): δ (ppm) 54.3, 119.6, 122.1,
13
3
3
127.2, 128.1, 128.9, 129.2, 129.5, 131.9, 134.5, 147.2.
1
1
19.6, 125.7, 126.1, 128.1, 128.3, 128.9, 129.0, 130.3,
30.5, 135.0, 136.6, 148.4.
4
.5.10 | 1‐Benzyl‐4‐(4‐fluorophenyl)‐1H‐
[
11p, 11r]
4
.5.5 | 1‐(4‐Nitrobenzyl)‐4‐phenyl‐1H‐1,2,3‐
1,2,3‐triazole (4j)
[
11h]
triazole (4e)
1
White solid. M. P. = 97°C. H NMR (400 MHz, CDCl ): δ
(ppm) 5.57 (s, 1H), 7.06‐7.14 (m, 2H), 7.30‐7.40 (m, 5H),
7.62 (s, 1H), 7.75‐7.78 (m, 2H). C NMR (100 MHz,
CDCl ): δ (ppm) 54.3, 115.8 (d, J = 21.8 Hz), 119.2,
3
1
Pale yellow solid. M. P. = 149°C. H NMR (400 MHz,
CDCl ): δ (ppm) 5.71 (s, 2H), 7.33‐7.46 (m, 5H), 7.77‐
1
3
3
1
3
7
.83 (m, 3H), 8.24 (d, J = 8.4 Hz, 2H). C NMR (100
3
MHz, CDCl ): δ (ppm) 53.2, 119.7, 124.4, 125.7, 128.5,
127.4 (d, J = 8.1 Hz), 128.1, 128.9, 129.2, 134.6, 147.4,
162.6 (d, J = 247.2 Hz).
3
1
28.55, 128.9, 130.1, 141.8, 148.1, 148.7.

SAWKMIE ET AL.
11
[
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.5.11 | 1‐Benzyl‐4‐(p‐tolyl)‐1H‐1,2,3‐tri-
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White solid; M. P. = 151°C. H NMR (400 MHz, CDCl ): δ
3
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7
.32 (dd, J = 7.4, 1.9 Hz, 2H), 7.37‐7.43 (m, 3H), 7.63 (s,
1
3
1
H), 7.70 (d, J = 8.1 Hz, 2H). C NMR (100 MHz, CDCl3):
δ (ppm) 21.3, 54.2, 119.1, 125.6, 127.7, 128.1, 128.8, 129.2,
29.5, 134.7, 138.0.
2
54; (c) A. H. Banday, S. A. Shameem, B. D. Gupta, H. M.
1
Sampath Kumar, Steroids 2010, 75, 801.
[
[
5] R. Alvarez, S. Velazquez, F. San, S. Aquaro, C. De, C. F. Perno,
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4
.5.12 | 4‐(1‐Benzyl‐1H‐1,2,3‐triazol‐4‐yl)
[
11h]
3
7, 4185.
pyridine (4l)
6] M. J. Genin, D. A. Allwine, D. J. Anderson, M. R. Barbachyn,
D. E. Emmert, S. A. Garmon, D. R. Graber, K. C. Grega, J. B.
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G. E. Zurenko, J. C. Hamel, R. D. Schaadt, D. Stapert, B. H.
Yagi, J. Med. Chem. 2000, 43, 953.
1
Pale yellow solid. M. P. = 99°C. H NMR (400 MHz,
CDCl ): δ (ppm) 5.58 (s, 2H), 7.19‐7.38 (m, 5H), 7.75‐
3
7
.79 (m, 1H), 8.06 (s, 1H), 8.18 (d, J = 7.9 Hz, 1H) 8.53
1
3
(
d, J = 4.4 Hz, 1H). C NMR (100 MHz, CDCl ): δ
3
[
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(
ppm) 54.4, 120.2, 121.9, 122.9, 128.3, 128.9, 129.2, 134.3,
1
36.9, 148.7, 149.3, 150.2.
4
.5.13 | (1‐Benzyl‐1H‐1,2,3‐triazol‐4‐yl)
[
11p]
methanol (4m)
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Pale yellow gum. H NMR (400 MHz, CDCl ) δ = 3.65 (s,
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7
3
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6
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ACKNOWLEDGMENTS
Scientific and Engineering Research Board (SERB) is grate-
fully acknowledged for financial support to P. N. C (sanc-
tion order no. SB/FT/CS‐115/2014; dated 24/08/2015). D.
P. thanks NIT Meghalaya for fellowship, and G. K. thanks
TEQIP III, NIT Meghalaya for fellowship. P. N. C. thanks
Dr. S. Khatua, NEHU, and Dr. S. Sarkar, Ramakrishna Mis-
sion Vivekananda Centenary College, Rahara for useful
discussions and many help. SAIF, NEHU, and IIT Roorkee
are also acknowledged for analytical facilities.
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CONFLICT OF INTERESTS
The authors declare no conflict of interest.
2
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Ramesh, Y. V. Nageswar, Tetrahedron Lett. 2012, 53, 4595; (i)
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ORCID
Pradip K. Maji https://orcid.org/0000-0001-8112-554X
Paresh Nath Chatterjee
926
https://orcid.org/0000-0001-8154-
6
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SUPPORTING INFORMATION
5
(
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
[
[
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Khatua, Can. J. Chem. 2019, 97(1), 29; (b) M. L. Sawkmie, D.
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https://doi.org/10.1007/s12039‐019‐1625‐6
How to cite this article: Sawkmie ML, Paul D,
Kalita G, Agarwala K, Maji PK, Chatterjee PN.
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