Functionalized Silver Nanoparticle Catalyzed [3+2] Cycloaddition Reaction: Greener Route to Substituted-1,2,3-triazolines

Article abstract of DOI:10.1007/s10562-015-1653-x

The [3+2] cycloaddition reaction between nitroolefins and alkyl/aryl azides was studied using functionalized silver nanoparticles (FnAgNPs) of average diameter 23 ± 1 nm as catalyst produced by the plant extract Protorhus longifolia. We found FnAgNPs to c

Full text of DOI:10.1007/s10562-015-1653-x

Catal Lett
DOI 10.1007/s10562-015-1653-x
Functionalized Silver Nanoparticle Catalyzed [3+2] Cycloaddition
Reaction: Greener Route to Substituted-1,2,3-triazolines
Nanjundaswamy Marishetty Hemmaragala1 Heidi Abrahamse
•
1
Blassan Plackal Adimuriyil George1 Ramesh Gannimani2 Patrick Govender2
•
•
•
Received: 23 September 2015 / Accepted: 1 November 2015
Ó Springer Science+Business Media New York 2015
Abstract The [3?2] cycloaddition reaction between
nitroolefins and alkyl/aryl azides was studied using func-
tionalized silver nanoparticles (FnAgNPs) of average
diameter 23 1 nm as catalyst produced by the plant
extract Protorhus longifolia. We found FnAgNPs to cat-
alyze the reactions efficiently yielding a series of 1,5-dis-
ubstituted-1,2,3-triazolines under mild reaction conditions
with no side products. The catalytic activity of FnAgNPs
was compared with naked AgNPs and FnAgNPs found to
be very effective. Except solvents, the whole experiments
do not require any chemical/reagent which makes the
process green.
Graphical Abstract
Na+ N-
N
N
N
N+
NO2
Functionalized AgNPs
R2
+
N
R1
Toluene, 80°C
R2
R1
R1 = H, CH3, OCH3, OH, NO2 and Br
R2 = Phenyl and Benzyl groups
61-88%
Keywords Functionalized silver nanoparticles Á
Protorhuslongifolia Á Catalysis Á [3?2]cycloaddition Á 1,
5-Disubstituted-1, 2, 3-triazolines
1 Introduction
Electronic supplementary material The online version of this
article (doi:10.1007/s10562-015-1653-x) contains supplementary
material, which is available to authorized users.
The use of soluble form of gold started in 290 AD for
artwork purposes [1]. However, researchers are attracted to
explore the synthesis and use of gold nanoparticles after
Michael Faraday’s experiment on the reduction of
chloroaurate salts by phosphorous in CS2 to obtain deep red
colloidal solutions of gold [2]. Since then, thousands of
research articles reported the synthesis, properties and
assembly of nanoparticles employing numerous method-
ologies and materials [1]. More recently, nanomaterials
& Nanjundaswamy Marishetty Hemmaragala
nswamyorg@gmail.com
1
Laser Research Centre, Faculty of Health Sciences,
University of Johannesburg,
P. O. Box 17011, Doornfontein 2028, South Africa
2
School of Life Sciences, Westville Campus, University of
KwaZulu-Natal, Durban 4000, South Africa
123

N. M. Hemmaragala et al.
technologies found new applications in all possible areas of
human needs and the use of nanomaterials to catalyze
organic reactions is one of the most important claims [3].
Consequently the synthesis of a plethora of organic mole-
cules by homogeneous and heterogeneous catalysis under
mild reaction conditions, easy work-up procedures and
with less polluting processes has been realized [4]. In
particular, silver and gold nanoparticles become an
important tool for chemists and biologists owing to their
wide spectra of applications in constructing bio-molecules
and even as prime agents for drug delivery [5, 6]. The size
and the shape of silver and gold nanoparticles can be varied
to express various colors by surface plasmon absorption
leading to a plethora of diverse biological and chemical
applications [7]. Therefore, the synthesis of Ag and Au
nanoparticles and the discovery of their applications is
critical and current interest.
heterocyclic compounds are efficient drug candidates.
Interestingly, more than 90 percent of new drug molecules,
drug intermediates and other bio-molecules are heterocy-
cles [24]. 1,2,3-Triazoles are an important class of hete-
rocycles and are widely used in the construction of
promising novel bio-molecules [25]. Indeed, the deriva-
tives of 1,2,3-triazoles are known to possess antifungal
[26], antiviral [27] antibacterial [28] and antitumor activi-
ties [29]. For example, analogues of zanamivir embedding
the 1,2,3-triazole nucleus has been successfully screened as
anti-HIV [30]. Additionally, cyclopentenyl carbocyclic
nucleosides, conjugated with 1,2,3-triazoles has been
reported as potent antiviral agent against orthopoxviruses
and severe acute respiratory syndrome [31]. 3-Arylethyl-
nyltriazolyl ribonucleosides are shown to possess potent
anticancer activity on the drug-resistant pancreatic cancer
cell line MiaPaca-2 [32]. Phokodylo et al. recently reported
the conjugation of 1,2,3-triazole with oxadiazoles and thi-
azoles to afford compounds that are active against mela-
noma, colon and breast cancer [33]. For these reasons, the
scientific community showed an increasing interest in
search of easy routes for the synthesis of 1,2,3-triazoles
[34]. There are three major methods for the synthesis of
1,2,3-triazole moiety, all involving a [3?2] cycloaddition
reaction of azides with alkynes, nitriles and nitro olefins,
respectively. These reactions have been carried out
employing a number of metal catalysts and toxic reagents
under various reaction conditions and still there is a scope
in developing easy and environmentally friendly process to
obtain 1,2,3-triazoles [35].
In this context, numerous methods have been established
for the production of Ag and Au nanoparticles. However,
chemical methods suffer for the use of toxic reagents that
can be also adsorbed onto the surface of nanoparticles [8].
Use of plant extracts for the extracellular synthesis of silver
nanoparticles in a top-down reduction fashion is very
interesting and has been extensively studied [9]. These
methods comprise less cumbersome procedures and are
considered to be highly convenient due to milder reaction
conditions, reproducibility and easy availability of plant
materials. Plant extract mediated silver nanoparticles very
often have unique chemical and biological properties and
are interesting as catalysis to construct bioactive com-
pounds [10]. The phytochemicals present in the plant
extracts reduces the metal ions to produce nanoparticles
and often at the same time the functionalization of the
surface of nanoparticles can occur [11]. This functional-
ization is responsible for the increase of the biocompati-
bility of nanoparticles and the functionalized nanoparticles
are also attributed to be stable colloidal form due to steric
repulsion between the organic moieties. The influence of
chemical composition of plant extract significantly affects
the size and shape of the nanoparticles and the catalytic
properties as well [12]. Therefore there is an increasing
interest in exploring plant extracts for the production of
silver nanoparticles and to study their shape, size and the
catalytic activities. Current reports on the synthesis of sil-
ver and gold nanoparticles using plant extracts include peel
of mango [13], lemon [14], Satsuma mandarin [15], root
extract of Zingiber officinale [16], sea weed Chaetomorpha
linum [17], flower extracts of Gnidia glauca [18], Nyc-
tanthes arbortristis [19], Carthamus tinctorius L [20], leaf
extracts of Gliricidia sepium [21], seed extracts of Abel-
moschus esculentus [22], and Acacia farnesiana [23].
On the other hand, heterocyclic chemistry is playing
major role in synthetic organic chemistry especially as
2 Results and Discussion
In continuation of our research on the synthesis, function-
alization, and use of nanoparticles, [36, 37], herein we
report the synthesis of 1,5-disubstituted-1,2,3-triazoles via
[3?2] cycloaddition reaction of nitroolefins and azides.
The reactions have been catalyzed by functionalized silver
nanoparticles obtained by the plant source Protorhus
longifolia. Protorhus longifolia belongs to the Anacar-
diaceae family which is widely distributed throughout
South Africa [38]. The bark and leaves of Protorhus
longifolia are used in traditional medicine to treat hemi-
plegic paralysis, heart burn and stomach bleed [39]. We
were interested in using the aqueous seed extract of these
species as a reducing agent for the production of silver
nanoparticles and to study their catalytic activity in [3?2]
cycloaddtion reaction between nitroolefins and azides for
the syntheses of substituted 1,2,3-triazoles. In a typical
experiment, 2 ml of plant extract was added to 25 ml of
sterile 1 mM silver nitrate solution and incubated with
continuous stirring on the rotary shaker at 120 rpm for 24 h
123

Functionalized Silver Nanoparticle Catalyzed [3?2] Cycloaddition Reaction: Greener Route…
at 30 °C. After the addition of the seed extract, the silver
nitrate solution changed from colorless to brown color
indicating the reduction of Ag?. Both the intensity in color
of the reaction mixture and absorbance increased with the
time as the reaction proceeded. The progress of the reaction
for the formation of AgNPs was monitored by the peri-
odical measurement of UV absorbance at 400–500 nm,
Fig. 1. Upon the completion of reaction, the colloidal
solution was centrifuged at 4000 rpm for 20 min and the
residue washed with distilled water to remove unreacted
material. The infra-red spectrum of the obtained silver
nanoparticles revealed the presence of organic functional
groups on the surface of silver nanoparticles to form a
capping agent. Figure 2 shows the main absorptions at
3258, 1629, 1514, 1055 cm-1 in IR spectroscopy. The
broad peak at 3258 cm-1 indicates strong stretching
Fig. 2 FTIR spectra of functionalized AgNPs
vibrations of -OH functional groups and at 1055 cm-1 for
ether linkages or –C–O– groups. The absorbance at
1629 cm-1 might be the stretching vibrations of alkene
groups–C=C–. Additionally, the observed peaks can also
be attributed to polyols such as flavones, terpenoids and
polysaccharides present in the seed extract. The function-
alized silver nanoparticles have been thoroughly charac-
terized by scanning electron microscopy and transmission
electron microscopy (TEM) as depicted in Fig. 3. The
AgNPs arising from the reaction mixture were repeatedly
centrifuged and re-dispersed in sterile distilled water prior
to SEM and TEM analysis to remove any unreacted plant
material and metal ions. SEM analysis confirmed that
particles are of a nano-size. The spherical shape of the
nanoparticles is shown in the SEM images. The EDX
analysis confirmed that the particles were composed of
element silver. TEM analysis showed that silver nanopar-
ticles were poly-dispersed and predominantly spherical or
polyhedral in shape. The majority of the silver nanoparti-
cles were 23 1 nm in size and the embedded fig-
ure clearly shows the morphology of silver nanoparticles.
The selected area diffraction pattern clearly indicated that
the AgNPs formed by the reduction of metal ions by the
seed extract are polycrystalline in nature with clear lattice
fringes, characteristic of crystalline nature of the obtained
nanoparticle.
After characterization of the AgNps, we were excited to
know their efficiency as catalyst for the [3?2] cycloaddtion
reactions between nitroolefins and azides for the synthesis
of 1,5-disubstituted-1,2,3-triazolines. Thus, a solution of
(2-nitroethenyl)benzene (1a) (150 mg, 1.0 mmol) in
toluene (5 mL) was prepared in a 10 mL round bottomed
flask fitted with a magnetic stirrer. Then, phenyl azide (2a)
(155 mg, 1.3 equiv.) and AgNPs (100 mg) were added and
the reaction mixture heated at 80 °C. The reaction was
monitored via TLC by the disappearance of starting
material (2-nitroethenyl) benzene. Upon completion of the
reaction, the reaction flask was cooled, and the mixture was
centrifuged. The residue (AgNPs) was separated by simple
filtration. The filtrate was evaporated off under reduced
pressure to afford the crude product which was purified by
column chromatography over silica gel, using ethyl acet-
ate/hexane (1.5: 8.5) as eluent, to afford 118 mg of solid
1,5-diphenyl-1H-1,2,3-triazole (3a) in 61 % yield. Further,
the effect of catalyst loading, reaction times and the effi-
cacy of functionalized AgNps over naked AgNP were
studied and the results are shown in Table 1. 80 mg of
functionalized AgNps are necessary and sufficient to cat-
alyze the reaction and to afford the maximum reaction
yield. Moreover, functionalized AgNPs are more efficient
catalysts than naked AgNPs. Triggered by these results, we
wanted to extend the suitability of the method to the
reactions of different substituted nitroolefins bearing
Fig. 1 Monitoring the synthesis of AgNPS: UV–Vis spectra
123

N. M. Hemmaragala et al.
Fig. 3 Clockwise from top left a HRTEM micrograph; b Histogram, SAED pattern; Lattice fringes; c SAED pattern; d EDX pattern; e SEM
morphology and f Lattice fringes
123

Functionalized Silver Nanoparticle Catalyzed [3?2] Cycloaddition Reaction: Greener Route…
Table 1 Catalytic loading of
Entry
Catalyst (mg)
Time
Yields (%)
functionalized AgNPs and
comparison of the results with
naked AgNPs for the reaction
between (2-
Naked AgNP
Fn-AgNP (h)
Naked AgNP
Fn-AgNP
1
2
3
4
5
6
7
8
9
10
20
30
40
50
80
100
80
80
10
20
30
40
50
80
100
80
80
18
18
18
18
18
18
18
12
10
Trace
Trace
32
nitroethenyl)benzene and
phenyl azide
Trace
\5 % on TLC
41
\5 % on TLC
57
12
18
25
15
12
59
63
65
61
55
respectively methoxy, nitro, bromo, chloro, tolyl, hydroxyl
and cyano groups with phenyl and benzyl azides to get the
corresponding 1,5-disubstituted-1,2,3-triazoles, Scheme 1
and Table 2. Table 2, entry 1 reports the best comprise
between catalyst loading, reaction time and yield achieved
during the screening reported in Table 1 (entry 8). The
reaction works well with phenyl azide (2a) and arylni-
troolefins 1b-d bearing both ED or EW groups on the aryl
moiety yielding the corresponding triazoles 3b–d in
64–75 % yield (entries 2–4). A similar result (3e, 62 %
yield) was obtained working with (E)-2-(2-nitro-
vinyl)thiophene (1e), entry 5. Moreover, Fn-AgNP effi-
ciently catalyzed the reaction of nitroolefins 1 with benzyl
azide (2b) entries 6–14. Thus, model nitroolefin 1a as well
as substituted nitroolefins 1b, c, f, g, nitrovinylthiophene 1e
afforded the corresponding triazoles 3f–j, n in 65–88 %
yield, entries 6–10, 14. Good results were obtained also
with ortho-substituted nitroolefins 1h, j (entries 11, 13; 3k,
3m; 86 %) whereas worst yield (3l, 24 %) were observed
with (E)-4-(2-nitrovinyl)benzonitrile 1i. In this latter case,
a mixture of products namely the 4-(1-benzyl-1H-1,2,3-
triazol-5-yl) benzonitrile and 4-(1-benzyl-1H-1,2,3-triazol-
5-yl)[5-phenyl-1H-1,2,3,4-tetrazole], were expected, but
only 4-(1-benzyl-1H-1,2,3-triazol-5-yl) benzonitrile in
24 % yield was isolated after 18 h.
3 Experimental Section
3.1 Materials and Methods
Silver nitrate, (AgNO3) was of analytical grade reagents
purchased from Merck Germany. 1 % JIK bleach was
purchased from Reckitt Benckiser, South Africa. Seeds of
Protorhus longifolia were collected from Westville cam-
pus, University of KwaZulu-Natal (GPS co-ordinates
-29.817897, 30.942771). UV–Vis measurements have
been studied at room temperature as function of time using
Specord 210, Analytikjena spectrometer. 1 mM AgNO3
solution was used as the blank. FTIR-ATR Spectroscopy
measurements have been recorded by making pellets of
functionalized nanoparticles. Scanning Electron Micro-
scopy for morphological studies of the synthesized AgNPs
was carried out using scanning electron microscopy
(FEGSEM ZEISS ULTRAPLUS). Samples prepared by
adding a drop of sonicated nanoparticle solution over the
carbon tape glued over metal stub. The samples thus
obtained were coated with carbon and observed at 10000 X
magnification. The energy dispersive X-ray analysis (EDX)
was done at 20 kV using AZTEC software for the analysis.
TEM obtained after sonication for 15 min to disrupt any
possible aggregate. A small amount of this sonicated
Scheme 1 Synthesis of
substituted-1,2,3-triazolines
from nitroolefins and azides
catalyzed by functionalized
AgNP
N
N
NO
2
+
N
Fn-AgNP
N
N
-
N
R
+
R
2
2
Toluene, 80 °C
10-18h
R1
R1
2a-b
1a-j
3a-n
R1= H, Br, CH3, CN, OH, OCH3
R2 = phenyl and benzyl groups
61-88%
123

N. M. Hemmaragala et al.
Table 2 Synthesis of 1,5-disubstituted-1,2,3-triazolines by the reaction of nitroolefins and azides catalyzed by Functionalized AgNPs
Entry
Nitroolefin
(1a-j)
Azide
2a, 2b
Reaction
time (h)
Product
(3a-n)
Yield(%)
N
N
N3
NO2
N
1
12
13
61
1a
1b
2a
3a
N
N
NO2
N3
N
2
64
72
75
H3CO
OCH3
3b
N
N
NO2
N3
N
3
4
10
18
O2
N
1c
1d
NO2
3c
N
N
N
NO2
N3
Br
Br
3d
N
N
N
N3
S
NO2
S
5
6
13
18
62
80
1e
1a
3e
N
N
N
NO2
N3
2b
3f
N
N
N
NO2
7
N3
18
18
18
76
H3C
CH3
1f
3g
N
N
N
NO2
N3
8
74
H3CO
OCH3
1b
1g
3h
N
N
N
NO2
N3
9
65
HO
3i
OH
123

Functionalized Silver Nanoparticle Catalyzed [3?2] Cycloaddition Reaction: Greener Route…
Table 2 continued
Entry
Nitroolefin
(1a-j)
Azide
2a, 2b
Reaction
time (h)
Product
(3a-n)
Yield(%)
N
N
N
NO2
N3
10
18
18
18
12
12
88
86
24
86
68
O2
N
NO2
NO2
1c
3j
N
N
N
NO2
N3
11
12
13
14
NO2
1h
3k
N
N
NO2
N
N3
NC
1i
3l
CN
Cl
N
N
N
NO2
N3
Cl
1j
3m
3n
N
N
S
N3
NO2
N
S
1e
suspension was placed on carbon coated copper grid and
dried under infrared light for solvent evaporation. High-
resolution TEM images were obtained on JEOL TEM
model no 2100 operating at accelerating voltage of 200 kV
and 0.23 nm resolution. Nitroolefins were synthesized
according to a previous procedure. All solvents were of
analytical grade and purified wherever necessary according
to standard procedures prior to use. TLCs were run on pre-
coated silica gel on aluminium plates obtained from
Whatmann Inc. All reactions were performed at 80 °C.
Bu¨chi B-540 apparatus was used to obtain the melting
points of all solid compounds. Bruker- TENSOR-FTIR
with a magnetic stirrer. Then, azides (2a,b) (1.3 equiv.) and
AgNPs (80 mg) were added and the reaction mixture
heated at 80 °C. The reaction was monitored via TLC by
the disappearance of starting nitroolefins. Upon completion
of the reaction, the reaction flask was cooled, and the
mixture was centrifuged. The residue (AgNPs) was sepa-
rated by simple filtration. The filtrate was evaporated off
under reduced pressure to afford the crude products which
were purified by column chromatography over silica gel,
using ethyl acetate/hexane (1.5: 8.5)] as eluent. The cor-
responding triazoles 3a–n were isolated, see Table 2 for
details.
1
instrument was used to record IR spectroscopy. H NMR
and 13C NMR spectra were recorded on Bruker Avance
400 and 100 MHz spectrometer respectively, chemical
shifts were reported in (ppm) with TMS as internal stan-
dard. Yields of pure isolated compounds after column
chromatography (70–230) mesh silica gel) are reported.
4 Conclusion
In summary, a benign procedure for the syntheses of 1,5-
diphenyl-1H-1,2,3-triazolines employing functionalized
silver nanoparticles produced in green way has been pro-
posed. Except the use of solvents, the entire process does
not involve any chemical reagents neither to produce the
nanoparticles nor to catalyze the reactions. Therefore we
believe the procedure would be of general use for synthetic
chemists.
3.2 General Procedure for Fn-AgNP Catalyzed
Synthesis of 1,5-Disubstituted-1,2,3-triazoles 3a–n
A solution of nitroolefins 1a–j (1.0 mmol) in toluene
(5 mL) was prepared in 10 mL round bottomed flask fitted
123

N. M. Hemmaragala et al.
7.14–7.07 (m, 2H, Ar–H); 13C NMR (100 MHz, CDCl3) d:
136.4 (tiazolyl-C8), 133.3 (C1), 132.6 (triazolyl-C7), 132.3
(C30, C50), 130.2 (C10), 129.8 (C3, C5), 129.5 (C20, C60),
125.7 (C4), 125.2 (C2, C6), 123.4 (C40).
4.1 Spectroscopic Characterization Data
N
3
N
2
8
4
1
N
4.1.5 1-Phenyl-5-(2-thienyl)-1H-1,2,3-triazole (3e)
9
1'
5
2'
7
Yield 62 %; Brown oil [17]; 1H NMR (400 MHz, CDCl3):
d 7.89 (s, 1H, triazolyl-H), 7.55–7.48 (m, 3H, Ar–H),
7.49–7.40 (m, 2H, Ar–H), 7.36 (d, J = 5.1 Hz, 1H, thie-
nyl-H), 7.03–6.95 (m, 1H, thienyl-H), 6.94 (d, J = 3.7 Hz,
1H, thienyl-H); 13C NMR (100 MHz, CDCl3): d 136.5
(C1), 133.2 (triazolyl-C8), 132.4 (thienyl-C9), 130.1 (tria-
zolyl-C7), 129.5 (C3, C5), 128.2 (thienyl-C11), 127.7
(thienyl-C10), 127.7 (thienyl-C12), 127.1 (C4), 126.3 (C2,
C6).
6
3'
6'
4'
10
5'
Example for atom numbering
4.1.1 1,5-Diphenyl-1H-1,2,3-triazole (3a) Yield
61 %; white solid, mp: 113–114 °C (lit. 113–114 °C)22; 1H
NMR (400 MHz, CDCl3): d 7.87 (s, 1H, triazolyl-H),
7.47–7.41 (m, 3H, Ar–H), 7.40–7.32 (m, 5H, Ar–H),
7.24–7.21 (m, 2H, Ar–H) ppm; 13C NMR (100 MHz,
CDCl3) d 137.7 (triazolyl-C8), 136.6 (C1), 133.4 (triazolyl-
C7), 129.4 (C20,C60), 129.2 (C3,C5), 128.9 (C30,C50), 128.6
(C4,C40), 126.8 (C10), 125.2 (C2,C6) ppm.
4.1.6 1-Benzyl-5-phenyl-1H-1,2,3-triazole (3f)
Yield 80 %; White solid, mp: 72–73 °C (72–74 °C) [22];
1H NMR (400 MHz, CDCl3): d 7.77 (s, 1H, triazolyl-H),
7.46–7.33 (m, 3H, Ar–H), 7.34–7.26 (m, 5H, Ar–H),
7.12–7.01 (m, 2H, Ar–H), 5.58 (s, 2H, benzyl-CH2); 13C
NMR (100 MHz, CDCl3): d 138.1 (triazolyl-C9), 135.3
(triazolyl-C8), 133.2 (C1), 129.7 (C20, C60), 129.0 (C30,
C50), 128.8 (C3, C5), 128.3 (C4), 128.1 (C40), 127.1 (C2,
C6), 126.8 (C10), 52.1 (benzyl-C7).
4.1.2 Methyl 4-(1-Phenyl-1H-1,2,3-triazol-5-yl)phenyl
Ether (3b)
Yield 64 %; Yellow oil [22]; 1H NMR (400 MHz, CDCl3)
d 7.79 (s, 1H, triazolyl-H), 7.45–7.35 (m, 5H, Ar–H),
7.18–7.12 (m, 2H, Ar–H), 6.87–6.84 (m, 2H, Ar–H), 3.80
(s, 3H, OCH3); 13C NMR (100 MHz, CDCl3): d 161.2
(triazolyl-C8), 137.5 (C1), 136.4 (C40), 133.1 (triazolyl-
C7), 130.0 (C30, C50), 129.4 (C3, C5), 129.2 (C20, C60),
125.1 (C2, C6), 119.0 (C10), 114.2 (C4), 55.1 (OCH3).
4.1.7 1-Benzyl-5-(4-methylphenyl)-1H-1,2,3-triazole (3g)
Yield 76 %; Colourless oil [22]; 1H NMR (400 MHz,
CDCl3): d 7.73 (s, 1H, triazolyl-H), 7.31–7.27 (m, 3H, Ar–
H), 7.22 (d, J = 8.0 Hz, 2H, Ar–H), 7.14 (d, J = 8.1 Hz,
2H, Ar–H), 7.05–7.02(m, 2H, Ar–H), 5.54 (s, 2H, benzyl-
CH2), 2.40 (s, 3H, Ar-CH3); 13C NMR (100 MHz, CDCl3):
d 139.5 (triazolyl-C9), 138.2 (C40), 135.7 (triazolyl-C8),
133.2 (C1), 129.7 (C30, C50), 128.8 (C3, C5), 128.8 (C20,
C60), 128.1 (C2, C6), 127.2 (C4), 123.9 (C10), 51.6 (benzyl-
C), 21.3 (CH3).
4.1.3 5-(4-Nitrophenyl)-1-phenyl-1H-1,2,3-triazole (3c)
Yield 72 %; Yellow solid, mp: 144–145 °C (144–145 °C)
1
[23]; H NMR (400 MHz, CDCl3): d 8.22–8.19 (m, 2H,
4.1.8 1-Benzyl-5-(4-methoxyphenyl)-1H-1,2,3-triazole
Ar–H), 7.97 (s, 1H, triazolyl-H), 7.51–7.43 (m, 3H, Ar–H),
7.45–7.40 (m, 2H, Ar–H), 7.38–7.32 (m, 2H, Ar–H); 13C
NMR (100 MHz, CDCl3): d 147.7 (C40), 135.5 (triazolyl-
C7), 134.2 (C1), 133.1 (triazolyl-C8), 129.8 (C10), 129.6
(C3, C5), 129.3 (C20, C60), 125.4 (C30, C50), 124.4 (C4),
124.1 (C2, C6).
(3h)
1
Yield 74 %; Pale yellow oil [22]; H NMR (400 MHz,
CDCl3): d 7.71 (s, 1H, triazolyl-H), 7.32–7.28 (m, 3H, Ar–
H), 7.16–7.13 (m, 2H, Ar–H), 7.08–7.05 (m, 2H, Ar–H),
6.95–6.91 (m, 2H, Ar–H), 5.54 (s, 2H, benzyl-CH2), 3.83
(s, 3H, Ar-OCH3); 13C NMR (100 MHz, CDCl3): d 160.6
(C40), 137.9 (triazolyl-C9), 135.6 (triazolyl-C8), 133.1
(C1), 130.3 (C20, C60), 128.8 (C3, C5), 128.1 (C4), 127.3
(C2, C6), 118.9 (C10), 114.4 (C30, C50), 55.8 (OCH3), 51.3
(benzyl-C).
4.1.4 5-(4-Bromophenyl)-1-phenyl-1H-1,2,3-triazole (3d)
Yield 75 %; Yellow solid, mp: 150–151 °C (149–151 °C)
[17]; 1H NMR (400 MHz, CDCl3): d 7.86 (s, 1H, triazolyl-
H), 7.51–7.43 (m, 5H, Ar–H), 7.37–7.31 (m, 2H, Ar–H),
123

Functionalized Silver Nanoparticle Catalyzed [3?2] Cycloaddition Reaction: Greener Route…
4.1.9 4-(1-Benzyl-1H-1,2,3-triazol-5-yl)phenol (3i)
Ar–H), 7.28–7.16 (m, 4H, Ar–H), 7.01 (dd, J = 7.6,
1.6 Hz, 1H, Ar–H), 6.95 (dd, J = 7.5, 1.7 Hz, 2H, Ar–H),
5.44 (s, 2H, benzyl-CH2); 13C NMR (100 MHz, CDCl3): d
134.8 (triazolyl-C9), 134.8 (triazolyl-C8), 134.4 (C1),
134.3 (C20), 132.0 (C10), 131.2 (C40), 129.9 (C4), 128.6
(C3, C5), 128.2 (C30), 127.7 (C2, C6), 126.9 (C60), 126.4
(C50), 52.5 (benzyl-C).
Yield 65 %; Yellow solid, mp: 179–181 °C (179–181 °C)
[17]; 1H NMR (400 MHz, CDCl3): d 7.70 (s, 1H, triazolyl-
H), 7.41–7.23 (m, 4H, Ar–H), 7.12–7.09 (m, 3H, Ar–H),
6.97–6.83 (m, 2H, Ar–H), 5.53 (s, 2H, benzyl-CH2), 5.30
(s, 1H, Ar-OH); 13C NMR (100 MHz, CDCl3): d 157.5
(C40), 138.3 (triazolyl-C9), 135.3 (triazolyl-C8), 132.8
(C1), 130.4 (C20, C60), 128.9 (C3, C5), 128.2 (C4), 127.4
(C2, C6), 118.4 (C10), 116.1 (C30, C50), 51.5 (benzyl-C).
4.1.14 1-Benzyl-5-(2-thienyl)-1H-1,2,3-triazole (3n)
Yield 68 %; Yellow solid, mp: 78–79 °C (77–79 °C) [17];
1H NMR (400 MHz, CDCl3): d 7.81 (s, 1H, triazolyl-H),
7.44 (dd, J = 5.1, 1.2 Hz, 1H, thienyl-H), 7.34–7.26 (m,
3H, Ar–H), 7.13–7.05 (m, 3H, Ar–H, 2H, thienyl-H, 1H),
7.02 (dd, J = 3.6, 1.2 Hz, 1H, thienyl-H), 5.66 (s, 2H,
benzyl-CH2); 13C NMR (100 MHz, CDCl3): d 135.2 (tri-
azolyl-C9), 133.7 (C1), 131.9 (thienyl-C10), 128.9 (C3,
C5), 128.4 (triazolyl-C8), 128.2 (C4), 128.1 (thienyl-C12),
127.9 (thienyl-C11), 126.8 (C2, C6), 126.4 (thienyl-C13),
52.3 (benzyl-C).
4.1.10 1-Benzyl-5-(4-nitrophenyl)-1H-1,2,3-triazole (3j)
Yield 88 %; Yellow solid, mp: 96–99 °C (96–99 °C) [24];
1H NMR (400 MHz, CDCl3): d 8.25 (d, J = 8.7 Hz, 2H,
Ar–H), 7.81 (s, 1H, triazolyl-H), 7.43 (d, J = 8.8 Hz, 2H,
Ar–H), 7.30–7.28 (m, 3H, Ar–H), 7.10–7.03 (m, 2H, Ar–
H), 5.61 (s, 2H, benzyl-CH2); 13C NMR (100 MHz,
CDCl3): d 148.3 (C40), 134.6 (triazolyl-C9), 134.1 (tria-
zolyl-C8), 131.2 (C1), 129.7 (C20, C60), 129.0 (C3, C5),
128.6 (C10), 127.6 (C4), 126.9 (C30, C50), 124.1 (C2, C6),
52.5 (benzyl-C).
4.1.11 1-Benzyl-5-(2-nitrophenyl)-1H-1,2,3-triazole (3k)
Yield 86 %; Yellow solid, mp: 149–151 °C (149–151 °C)
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[25]; H NMR (400 MHz, CDCl3): d 8.12 - 8.05 (m, 1H,
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7.74–7.66 (m, 2H, Ar–H), 7.39–7.33 (m, 2H, Ar–H),
7.31–7.25 (m, 3H, Ar–H), 7.06–6.95 (m, 2H, Ar–H), 5.56
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132.7 (C30, C50), 131.4 (C4), 129.5 (C3, C5), 129.2 (C2,
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