Copper iodide nanoparticles on poly(4-vinyl pyridine) as new and green catalyst for multicomponent click synthesis of 1,4-disubstituted-1,2,3-triazoles in water

Article abstract of DOI:10.1016/j.cclet.2012.05.009

Poly(4-vinyl pyridine) supported nanoparticle of copper(I) iodide is reported as a green and recyclable catalyst for the regioselective synthesis of 1,4-disubstituted-1H-1,2,3-triazoles from benzyl halides, sodium azide and terminal alkynes in water. This

Full text of DOI:10.1016/j.cclet.2012.05.009

Available online at www.sciencedirect.com
Chinese Chemical Letters 23 (2012) 797–800
www.elsevier.com/locate/cclet
Copper iodide nanoparticles on poly(4-vinyl pyridine) as
new and green catalyst for multicomponent click synthesis
of 1,4-disubstituted-1,2,3-triazoles in water
a
b
c
Jalal Albadi a, , Mosadegh Keshavarz , Masoumeh Abedini , Masoumeh Vafaie-nezhad
*
a Khatam Al-Anbia, University of Technology, Behbahan, Iran
b Department of Chemistry, College of Science, University of Guilan, Rasht, Iran
c Department of Chemistry, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran
Received 13 March 2012
Available online 13 June 2012
Abstract
Poly(4-vinyl pyridine) supported nanoparticle of copper(I) iodide is reported as a green and recyclable catalyst for the
regioselective synthesis of 1,4-disubstituted-1H-1,2,3-triazoles from benzyl halides, sodium azide and terminal alkynes in water.
This catalyst can be recovered by simple filtration and recycled up to 8 consecutive runs without any loss of its efficiency.
# 2012 Jalal Albadi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Click chemistry; Poly(4-vinyl pyridine) supported; Nanoparticles; Copper(I) iodide; Triazoles
1,2,3-Triazoles are an important class of heterocyclic compounds that received significant attention from many
pharmaceutical and organic chemists essentially because of the broad spectrum of their biological and pharmaceutical
properties such as antibacterial, antiallergic, and anti-HIV activities. Furthermore, these compounds are used as dyes,
corrosion inhibitors, photostabilizers, and photographic materials [1–4]. The main method for the synthesis of 1,2,3-
triazoles is the Huisgen 1,3-dipolar cycloaddition reaction of azides with alkynes [5]. This cycloaddition reaction has
become the model for click reactions. Polymer-supported reagents have more and more attracted attention as insoluble
material in organic synthesis [6]. They recommend rewards such as reaction monitoring as well as improved safety, more
than ever when the non-supported reagents are toxic or unsafe as they can be easily removed from reaction medium and
recycled [7]. Additionally, employing an excess amount of reagent is permitted without the need for further purification.
There are some reports on using polymer supported CuI as recoverable catalyst for synthesis of 1,2,3-triazoles between
azides and alkynes via click reaction [8–13]. In recent years, nano-catalysis has emerged as a sustainable and competitive
alternative to conventional catalysis since the nanoparticles possess a high surface-to-volume ratio, which enhances their
activity and selectivity, while at the same time maintaining the intrinsic features of a heterogeneous catalyst [14]. In
particular, the immobilization of copper(I) salt nanoparticles (CuNPs) on high-surface-area supports allows a higher
stability and dispersity of the particles as well as a further exploitation of the special activity and recycling properties of
the catalyst. For instance, CuNPs immobilized on aluminum oxyhydroxide nanofiber, copper nitride nanoparticles
supported on a superparamagnetic mesoporous microsphere, Cu3N/Fe3N/SiO2 and copper nanoparticles on activated
* Corresponding author.
E-mail address: Jalal.albadi@gmail.com (J. Albadi).
1001-8417/$ – see front matter # 2012 Jalal Albadi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
http://dx.doi.org/10.1016/j.cclet.2012.05.009

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J. Albadi et al. / Chinese Chemical Letters 23 (2012) 797–800
N
N
N
Br
NaN3 ,
P4VPy-CuI
R
+
Water, reflux
R
Scheme 1.
carbon were found to catalyze the click cycloaddition [15–18]. These catalysts possess increased advantages over their
homogeneous counterparts. On the other hand, water has found widespread application in synthetic organic reactions as
solvent because it is not only nontoxic and readily available at low cost, but also nonflammable and environmentally
benign, providing opportunities for clean processing and pollution prevention [19]. Consequently, introduction of new
catalysts which could be used under aqueous conditions that can promote the yields and reaction times is still in demand.
Herein we wish to report the applicability of a new, green and reusable catalytic system based on Cu(I) nanoparticles
supported by poly(4-vinyl pyridine) (P4VPy-CuI) for one-pot multicomponent click synthesis of 1,4-disubstituted-1H-
1,2,3-triazoles from benzyl halides, sodium azide and terminal alkynes in water (Scheme 1).
1. Results and discussion
The copper(I) iodide catalyst immobilized on poly(4-vinyl pyridine) was readily prepared in a one-step procedure.
Poly(4-vinyl pyridine) was refluxed with a solution of CuI under N2 atmosphere in EtOH for the synthesis of polymer-
supported CuI nanoparticles. This method was developed for the effective synthesis of copper nanoparticles
incorporated heterogeneously as catalyst in some organic reactions [18].
At first, for the optimization of the reaction conditions, the reaction between benzyl bromide, phenyl acetylene and
sodium azide was chosen as a model and its behavior was studied under a variety of conditions. The best result was
achieved by carrying out the reaction of benzyl bromide, phenyl acetylene, sodium azide (with 1:1:1.1 mol ratio) in
the presence of 0.1 g of P4VPy-CuI under reflux condition in water (Table 1, entry 1). Using these optimized
conditions, the reaction of various terminal alkynes and benzyl halides was explored. All the products were cleanly
isolated with simple filtration and evaporation of solvent. The solid products were easily recrystallized from a
Table 1
Click synthesis of 1,4-disubstituted 1,2,3-triazoles catalyzed by P4VPy-CuI.
Entry Benzyl halide
Alkyne
Product
Time (min) Yield (%)a
1
N
N
N
15
15
25
90
89
88
N
N
N
CH2Br
N
2
3
CH2Cl
CH2Br
N
N
H3C
CH
3
4
5
20
30
88
87
N
N
N
H3C
CH2Br
H3C
N
N
N
H3CO
CH2Br
H3CO
O2N
6
35
86
N
N
N
O2N
CH2Br

J. Albadi et al. / Chinese Chemical Letters 23 (2012) 797–800
799
Table 1 (Continued )
Entry Benzyl halide
Alkyne
Product
Time (min) Yield (%)a
7
N
N
25
20
30
35
88
89
75
86
N
N
Cl
CH2Br
CH2Br
N
Cl
Cl
Cl
8
9
Br
N
Br
CH3
N
N
H3CO
H3CO
CH2Br
N
CH3
OH
O
H
H3CO
10
H2N
H2N
N
N
CH2Br
N
NH2
H3CO
11
12
N
25
40
88
82
N
CH2Br
CH2Br
N
NH2
N
N
N
N
N
N
N
13b
Cl
45
83
N
N
N
N
Cl
CH2Br
Cl
N
Cl
Cl
Cl
a
Isolated yield.
b
2 mmol of the benzyl halide was used.
mixture of ethanol/water (1:3, v/v) or in some cases from ethanol (Table 1, entries 12 and 13). It is very important to
note that the corresponding triazole was obtained in high yield and regioselectivity. Click cyclizations were
confirmed by the appearance of a singlet in the region of 7.8–8.5 ppm in 1H NMR spectra, which corresponds to the
hydrogen on 5-position of triazole ring and confirms the regioselective synthesis of 1,4-disubstituted triazole
regioisomers. It is also noteworthy that resin does not suffer from extensive mechanical degradation after running.
For a true heterogeneous catalyst, supported catalyst should not leach to the reaction mixture. Moreover the
recyclability of the supported catalyst is also important and should not suffer from mechanical degradation. To
investigate these properties for our introduced catalyst and reagent, the reaction of benzyl bromide with phenyl
acetylenewas selected again as model. Polymer supported CuI can be reused up to 8 runs without any significant yield
decreases. The copper content of the catalyst was measured with atomic emission spectroscopy after 8 runs. Almost
consistent activity was observed over 8 runs. Next we checked the leaching of CuI into the reaction mixture from the
poly(4-vinyl pyridine) support using ICP-AES. The difference between the copper content of the fresh and reused
catalysts (8th run) is only 3% which indicates the low leaching amount of copper iodide catalyst into the reaction
mixture. Finally, in order to evaluate the efficiency and superiority of our introduced catalyst, we began to run the
reaction between benzyl halide and phenyl acetylene in the presence of pure CuI at the same conditions. The obtained
results showed that pure CuI could not be reused, need much more reaction time and give the product in low yield.
In conclusion, we have developed a mild, simple and green procedure for the one-pot regiospecific synthesis of
biologically important 1,4-disubstituted-1H-1,2,3-triazoles via Huisgen 1,3-dipolar cycloaddition reaction between
terminal alkynes, benzyl halides and NaN3 using recyclable P4VPy-CuI in water as reaction medium at reflux conditions.
The introducedcatalyst can promote theyields and reaction times over 8 runswith very low leaching amounts ofsupported

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J. Albadi et al. / Chinese Chemical Letters 23 (2012) 797–800
catalyst into the reaction mixture. Moreover, ease of work-up and clean procedure, will make the present method an useful
and important addition to the present methodologies for the synthesis of 1,4-disubstituted-1,2,3-triazoles.
2. Experimental
2.1. General
All products were characterized by comparison of their spectroscopic data (1H NMR, IR) and physical, properties
with those reported in the literature. Poly(4-vinyl pyridine), 2% cross-linked DVB (mesh 50–60) which is a white
water insoluble polymer and of interest due to its high electrical conductivity was purchased from Aldrich company.
2.2. Preparation of the polymer supported catalyst
CuI (0.381 mg) was put in 30 mL ethanol, and magnetically stirred at reflux temperature for 4 h under nitrogen
atmosphere in the presence of dry poly(4-vinyl pyridine) (1.0 g, mesh 50–60). The solvent was filtered, the resin washed
with CH3CN (2 Â 20 mL) and dried under vacuum at 60 8C overnight. Theweight increasewas 0.31 g (1.63 mmol CuI),
which gave a polymer loading of 1.24 mmol CuI gÀ1. The exact copper content of poly(4-vinyl pyridine)-CuI was
measured using ICP-AES. The loading of supported catalyst was calculated to be 1.32 mmol CuI gÀ1 of resin. Scanning
electron microscopy (SEM), X-ray diffraction (XRD) analysis, atomic absorption and IR experimental techniques were
used to characterize the catalyst.
2.3. General procedure for synthesis of 1,4-disubstituted triazoles
Benzyl halide (1 mmol), alkyne (1 mmol) and sodium azide (1.1 mmol) were placed together in a round-bottom flask
containing 10 mLofwater. Poly(4-vinylpyridine)-CuI(0.1 g)was added to the mixture. The suspension was magnetically
stirred under reflux conditions for appropriate time according to Table 1. After completion of the reaction as followed by
TLC (n-hexane:ethyl acetate, 4:1), the resin was filtered and washed with hot ethanol (2 Â 5 mL). The recovered catalyst
was washed with acetone, dried and stored for another consecutive reaction run. The filtrates were evaporated to dryness,
and then the solid residue was recrystallized in ethanol/water (1:3, v/v) to give pure product crystals.
Acknowledgment
We are thankful to the Khatam Al-Anbia, University of Technology, for the partial support of this work.
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