Synthesis and catalytic activity of carbon supported copper nanoparticles for the synthesis of aryl nitriles and 1,2,3-triazoles

Article abstract of DOI:10.1039/c4ra09935d

Various substituted aryl nitrile and 1,2,3-triazole derivatives were prepared by using carbon supported copper nanoparticles (C/Cu NPs) as a heterogeneous catalyst under ligand-free conditions, which provided good to excellent yields. The nanocatalyst can be recycled and reused several times without significant loss of catalytic activity.

Full text of DOI:10.1039/c4ra09935d

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Page 1 of 17
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Synthesis and catalytic activity of carbon supported copper nanoparticles for
the synthesis of aryl nitriles and 1,2,3-triazoles
Mahmoud Nasrollahzadeh,* Babak Jaleh, Parisa Fakhri, Ali Zahraei and Esmaeil Ghadery

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Synthesis and catalytic activity of carbon supported copper nanoparticles
for the synthesis of aryl nitriles and 1,2,3-triazoles
Mahmoud Nasrollahzadeh,*,a Babak Jaleh,b Parisa Fakhri,b Ali Zahraeic and Esmaeil Ghaderyd
aDepartment of Chemistry, Faculty of Science, University of Qom, Qom 3716146611, Iran
bPhysics Department, Bu-Ali Sina University, Hamedan, Iran
cYoung Researchers and Elite Club, Qom Branch, Islamic Azad University, Qom, Iran
dFaculty of Chemistry, Bu-Ali Sina University, Hamedan, Iran
Various substituted aryl nitrile and 1,2,3ꢀtriazole derivatives were prepared by using carbon supported copper
nanoparticles (C/Cu NPs) as a heterogeneous catalyst under ligandꢀfree conditions, which provided good to
excellent yields. The nanocatalyst can be recycled and reused several times without significant loss of its
catalytic activity.
Introduction
Nitriles have been used widely in synthetic organic chemistry and in industry for the manufacture of various
pharmaceutical compounds, herbicides, agrochemicals and dyes.1 They are also versatile intermediates in
synthetic organic chemistry, since they can be easily transformed into various classes of compounds such as
nitrogenꢀcontaining heterocycles, aldehydes, carboxylic acids and acid derivatives.2
The classical approaches to nitriles are based on the reaction of aryl halides with stoichiometric amounts of
CuCN,3 Sandmeyer reaction via the diazotization of anilines4 or the transition metalꢀcatalyzed cyanation of aryl
halides using KCN, NaCN, Me3SiCN and Zn(CN)2 as cyanating agents.5 However, there are several factors in
some of these methods which limited their applications. In many of these cases, the applicable reagents are
toxic, hazardous, sensitive to moisture, expensive or out of accessible and cannot be stored. Among cyanation
agents in the synthesis of nitriles, CuCN and Zn(CN)2 lead to heavy metal waste. Also, most of the other
methods for the synthesis of nitriles have disadvantages such as long reaction times, formation of side products,
use of expensive catalyst, severalꢀstep methods and low yields. Therefore, it is desirable to develop a more
efficient and convenient method for the synthesis of aryl nitriles without the application of expensive, moisture
sensitive and toxic reagents.
Among cyanation agents in the synthesis of nitriles, K4Fe(CN)6 is commercially available on ton scale and
cheaper than KCN and NaCN and even used in food industry for metal precipitation. Also, it is a nonexplosive,
nonꢀflammable, nonexpensive and nonꢀtoxic cyanide source and can be easily stored and is neither moisture
sensitive and nor very volatile.6 Several syntheses of aryl nitriles have been reported using K4Fe(CN)6 in the
presence of palladium or copper homogeneous catalysts,7,8 while less expensive copper heterogeneous catalysts
have less received attention. The problem with homogeneous catalysis is the difficulty to separate the catalyst
*Corresponding author. Tel.: +98 25 32103595; Fax: +98 25 32850953.
E-mail address: mahmoudnasr81@gmail.com (M. Nasrollahzadeh).
1

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from the reaction mixture and the impossibility to reuse it in consecutive reactions. Thus, the use of ligandꢀfree
heterogeneous copper catalysts is often desirable from the perspective of process development due to their easy
handling, simple recovery, and recycling.
Since catalysis takes place on metal surface, nanoparticles (NPs) are much more reactive than the particulate
metal counterpart due to their small sizes and large surface areas. So, heterogeneous catalysts are more and more
used in the form of nanoparticles. Recently, considerable afford has also been devoted to the application of
Cu(0)/Cuꢀoxideꢀnanoparticles as substitutes of bulk Cu metal in the title reaction in order to reduce the catalyst
loading, reaction time and also to minimize the undesired products.9 Immobilization of catalysts on solid
supports is one of the best methods to improve the efficiency and recovery of catalysts; many solid supported
catalysts have been successfully utilized for catalytic applications.10ꢀ18 Most commonly used solid supports
involve TiO2,10 zeolites,11,12 magneticꢀmaterials,13,14 graphene,15 insoluble polymers16,17 and gums.18 To prevent
the agglomeration of metal nanoparticles (MNPs) and the overꢀstoichiometric use of Cu reagents, several
inorganic materials such as alumina and silica have been used as a support for MNPs.19 It has been shown that
embedding copper nanoparticles in supports such as silica improves both the catalytic stability and activity.
Recently carbon (C) structures are widely studied as supports of depositing metal nanoparticles as
heterogeneous catalysts due to their extraordinary structure, good electronic conductivity, and improved
accessibility of reactants to the active sites.20 On the other hand, C structures display high surface area, tuneable
porosity, extraordinary stability in acid and basic media as well as at high pressures and temperatures.21
Transition MNPs supported on Cꢀcatalyzed reactions provide the advantages of high atom efficiency, simplified
isolation of product, and easy recovery and recyclability of the catalyst.22 Moreover, the decoration of transition
MNPs onto the C support has shown a more versatility in carrying out the highly selective catalytic processes.23
These outstanding catalytic activities of Cꢀsupported MNPs are mainly due to the effective dispersion in various
solvents, very less aggregation of MNPs and larger surface area of the nanocatalyst.24
In continuation of our efforts to develop environmentally friendly synthetic methodologies,25 we report the
synthesis of carbon supported copper nanoparticles (C/Cu NPs) in a single step by using the spark method and
their application for oneꢀpot synthesis of 1,2,3ꢀtriazoles and aryl nitriles under ligandꢀfree conditions (Scheme
1). This heterogeneous catalyst system exhibits an excellent catalytic performance for these transformations and
can be repeatedly used and subsequently recovered after the reaction.
Results and discussion
Characterization of catalyst
2

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The stable C/Cu NPs obtained were fully characterized by BET, FTꢀIR, SEM, EDS, Raman and XRD and their
behavior as catalyst was tested for the synthesis of 1,2,3ꢀtriazoles and aryl nitriles under ligandꢀfree conditions.
The morphology of the C and C/Cu NPs are shown in the SEM image displayed Figure 1a and b. Figure 1a
shows that the obtained carbon powder has a porous structure and nonuniform morphology, comprising
differently shaped structures. Figure 1b indicated that produced copper nanoparticles were homogeneously
supported on the carbon particles, also morphology of carbon structures altered. EDS analysis (Figure 1c)
evidently shows the presence of copper and carbon in the sample. Also atomic and weight ratio are listed.
(a)
(b)
(c)
Figure 1. a) SEM image of carbon, b) SEM image of C/Cu NPs and c) EDS analysis of C/Cu NPs.
Figure 2a and b shows Xꢀray diffraction of C and C/Cu NPs respectively. In Figure 2a, the diffraction peaks
at 26.4° and 43.5° can be attributed to the graphite structures (002) and (100). The broad band near (002) peak is
also observed, implying presence of amorphous carbon in the sample.26 By combining SEM and XRD results, it
can be therefore inferred that this sample is contained of a highly disordered materials in the form of amorphous
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carbon that accompanied with a mount of crystalline structures in graphite form. Therefore, the crystallites in
the C samples have intermediate structures between graphite and amorphous state.
100
(a)
90
80
70
60
50
40
30
20
10
0
10
15
20
25
30
35
40
45
50
2 Theta (degree)
3000
2500
2000
1500
1000
500
(b)
Cu
Cu
Cu
0
10
20
30
40
50
60
70
80
2 Theta (degree)
Figure 2. XRD pattern of a) C and b) C/Cu NPs.
In Figure 2b, three diffraction peaks at 2θ values of 43.4°, 50.5° and 74.1° corresponding to (111), (200) and
(220) planes of copper were observed that can be indexed to standard XRD data for copper (JCPDS 04ꢀ0836).
The corresponding dꢀspacing values of these peaks were calculated and were listed in Table 1. It is obvious that
the positions of diffraction peaks and dꢀspacing values matched well with standard copper. The XRD study
confirms that the resultant particles are fcc copper nanopowder. Also, in the XRD pattern of C/Cu NPs, copper
nanoparticle diffraction peaks are so intense that those peaks related to carbon structures are not observable.
Moreover, no diffraction peaks were observed for copper oxide indicating the formation of pure copper
nanoparticles. EDS result (Figure 1c) was proved this result.
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Table1.
Experimental and standard 2θ and dꢀvalue of copper.
Experimental data
JCPDS (04ꢀ0836)
2θ (°) dꢀspacing (Å)
hkl
2θ (°)
43.4
dꢀspacing (Å)
2.087
43.3
50.4
74.1
2.088
1.808
1.278
111
200
220
50.5
74.1
1.805
1.278
Figure 3 presents the IR spectrum of the C and C/Cu NPs and the three major absorption modes are detected:
3450 cmꢀ1 assigned to the OꢀH groups, 1585 cmꢀ1 attributed to the C=C band and 1250 cmꢀ1 from CꢀO.27
C-Cu
C
C=C C-OH
C-O
O-H
3900
3400
2900
2400
1900
1400
900
400
Wavenumber(cm-1)
Figure 3. FTꢀIR spectra of C and C/Cu NPs.
Raman spectroscopy is known as a powerful technique in characterization of carbon carbonaceous materials.
The structural features of C/Cu NPs have also been identified using Raman spectroscopy displayed in Figure 4.
Two characteristic bands were observed in the Raman spectrum. The peak at about 1570 cmꢀ1 (G band) is
corresponded to an E2g mode of graphite,28 while another peak at about 1274 cmꢀ1 (D band) is related to the
defects and disorder.29
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1200
1000
800
600
400
200
0
D band
G band
500
1000
1500
2000
2500
wavenumber(cm-1)
Figure 4. Raman spectra of C/Cu NPs.
N2 adsorptionꢀdesorption isotherms of C and C/Cu NPs was shown in Figure 5a and b. The BET surface area
of C and Cu/C are 86.52 m2/g and 45.56 m2/g respectively.
The pore size distributions plots, obtained from DFT method, are also shown in inner charts in Figure 5a and
b. Main pore size is 8.6 nm for C and 12.64 nm for C/Cu NPs sample.
140
0.04
(a)
120
0.02
100
0
80
60
40
20
0
0
5
10
15
Pore diameter(nm)
0
0.2
0.4
0.6
0.8
1
Relative Pressure(P/P0)
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100
90
80
70
60
50
40
30
20
10
0
0.03
0.02
0.01
0
(b)
0
5
10
15
Pore diameter(nm)
0
0.2
0.4
0.6
0.8
1
Relative Pressure(P/P0)
Figure 5. The N2 adsorptionꢀdesorption isotherm and DFT pore size distribution plot of a) C and b) C/Cu NPs.
Evaluation of the catalytic activity of C/Cu NPs through the cyanation of aryl iodides
Usually the ligands play an important role for a successful copperꢀcatalyzed cyanation of aryl halides. For
optimization of the reaction conditions, we chose the reaction of phenyl iodide with K4Fe(CN)6 in the presence
of C/Cu NPs as the model reaction, and the effects of the base and solvents were examined. Various ligands
such as phosphine and nonphosphine for palladium catalyzed coupling reactions are described in the literature.
Most of these ligands are air and moisture sensitive, difficult to prepare, and expensive. Thus, catalysis under
ligandꢀfree conditions is an area of high importance. In this work, the prepared C/Cu NPs were used as
heterogeneous catalyst in the ligandꢀfree cyanation reaction. First, several solvents were screened for the
reaction. According to data given in Table 2, DMF was the most efficient solvent for this reaction (Table 2,
entry 5). After choosing DMF as the solvent, we examined several bases. Our experiments showed that the base
was necessary for the cyanation reaction (Table 2, entry 12). Among the selected bases, K2CO3 acted as the
most effective one (Table 2, entry 5). A decrease in the catalyst loading from 0.5 to 0.3 mol% afforded the
product in lower yield (Table 2, entry 13). No significant improvement on the yield was observed using higher
amounts of the catalyst (Table 2, entry 14) and 0.5 mol% of the catalyst was found to be optimum. We then used
the optimal reaction conditions (aryl halide (1.0 mmol), K4Fe(CN)6 (0.66 mmol), K2CO3 (1.0 mmol) and DMF
as solvent) for cyanation of different aryl halides at 120 °C. No surfactant or ligand was required.
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Table 2.
Ligandꢀfree cyanation reaction of K4Fe(CN)6 with phenyl iodide in the presence of different solvents and bases.a
Entry C/Cu NPs (mol%) Base
Solvent
Toluene
CH3CN
MeOH
NMP
Temperature ( ºC)
Time (h)
20
Yield b (%)
1
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.3
0.8
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Cs2CO3
Et3N
Reflux
Reflux
Reflux
120
0
2
20
0
3
20
0
4
12
87
96
94
25
45
51
83
63
0
5
DMF
120
12
6
DMF
120
12
7
DMF
120
12
8
NaF
DMF
120
12
9
KF
DMF
120
12
10
11
12
13
14
KOAc
Na2CO3
ꢀ
DMF
120
12
DMF
120
12
DMF
120
20
K2CO3
DMF
120
12
77
K2CO3
DMF
120
12
96
a Reaction conditions: phenyl iodide (1.0 mmol), K4Fe(CN)6 (0.66 mmol), base (1.0 mmol), solvent (5.0 mL).
b Yields after workꢀup.
Having optimized the conditions, we explored the general applicability of C/Cu NPs as a catalyst for ligandꢀ
free reaction of K4Fe(CN)6 with aryl iodides containing electronꢀwithdrawing or donating substituents. As
indicated in Table 3, it is evident that our method is reasonably general and can be applied to several types of
aryl iodides. The reactions were able to tolerate a wide range of functional groups. In all cases the reaction gave
the corresponding products in good to excellent yields. In addition, the reactions appeared to be insensitive to
the steric hindrance around the reaction site (Table 3, entry 4). As an example for electronꢀpoor nitrogen
heterocycles, 4ꢀiodopyridine and 3ꢀiodopyridine were cyanated in good yield (Table 3, entries 9 and 10).
Compared with the other literature works on the cyanation of aryl halides,4ꢀ8 the notable features of our
method are:
•
•
•
•
•
•
•
•
Elimination of toxic reagents and palladium or copper homogeneous catalysts;
Toxic and expensive ligands are not needed;
The yields of the products are high;
Ease of handling and cost efficiency of the catalyst;
The catalyst can be easily recovered and reused;
Toxic, hazardous, sensitive to moisture and expensive cyanide sources are avoided;
The use of K4Fe(CN)6 as a nonexplosive, nonꢀflammable, nonexpensive and nonꢀtoxic cyanide source;
The methodology is applicable to both the small and large scale.
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Table 3.
Cyanation reaction of different aryl iodides with K4Fe(CN)6 in the presence of C/Cu NPs.a
Entry
1
Aryl iodide
Product
Yield b (%)
96 (93)c
2
3
4
94
93
90
MeO
CN
5
92
6
7
92
94
8
9
93
90
90
N
I
10
a
Reaction conditions: Aryl iodide (1.0 mmol), K4Fe(CN)6 (0.66 mmol), C/Cu NPs (0.5 mol%), K2CO3 (1.0
mmol), DMF (5.0 mL), 120 °C.
b Yields after workꢀup.
C Yields after the 5th cycle.
Evaluation of the catalytic activity of C/Cu NPs through the 1,3-diploar cycloaddition reactions between
sodium azide, terminal alkyne and organic halides
1,2,3ꢀTriazoles have a wide range of applications in the synthesis of pharmaceuticals.30 Most common method
for the preparation of 1,2,3ꢀtriazoles is the 1,3ꢀdipolar cycloaddition reactions between substituted alkynes and
azide derivatives.30 Recently, three component coupling reactions were reported for the preparation of triazoles
using catalysts such as microwave assisted Cu(0)ꢀCu(II), Cu(II)ꢀsodium ascorbateꢀlꢀproline, monometallic
palladium and bimetallic Pd(0)ꢀCu(I).30
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One of the main limitations of the copper catalyzed 1,3ꢀdipolar cycloaddition is the presence of a significant
amount of toxic, coloured, and expensive copper complexes in the end products. One strategy to circumvent the
problems related with copper contamination, which became quite popular during the last 5 years, is to
immobilize the catalyst on a heterogeneous support. In this way, it is economically and environmentally more
interesting to use the coupling reaction on a large scale since the heterogeneous supports can both facilitate the
isolation and the recycling of the catalytic system. Furthermore, supported catalysis possibly also provides a
way to improve the reaction rate. The efficiency and stability of C/Cu NPs prompted us to use the catalyst for
the commercially important 1,3ꢀdipolar cycloaddition.
For optimization of the reaction conditions, we chose the reaction of sodium azide with phenylacetylene and
benzyl bromide in the presence of C/Cu NPs at 70 °C in H2O as the model reaction. In the absence of catalyst,
the reactions did not proceed after a long reaction time. The best result was obtained with sodium azide (1.0
mmol), phenylacetylene (1.0 mmol), benzyl bromide (1.0 mmol), catalyst (0.5 mol%) and H2O (2.0 mL) which
gave the product in a good yield (97%).
Further we have tested the catalytic activity of C/Cu NPs for 1,3ꢀdipolar cycloaddition reactions with variety
of substrates and the results are summarized in Table 4. All the substrates produce the expected triazoles with
very good to excellent yields. The substituents (electronꢀwithdrawing, electronꢀreleasing and heterocycle) do not
have any peculiar effect, as most of the reactions were completed within 4ꢀ7 h. The catalyst was not effective for
iodobenzene (Table 4, entry 10).
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Table 4.
Synthesis of triazoles using C/Cu NPs.a
Entry
1
Halide derivative
Terminal alkyne
Product
Time (h) Yield b (%)
97, 94c
Ph
Ph
4
N
N
N
N
Ph
Ph
2
6
98
N
N
3
4
5
6
6
7
7
7
91
78
80
80
7
8
6
90
0
No reaction
10
a Reaction conditions: Organic halide (1.0 mmol), terminal alkyne (1.0 mmol), NaN3 (1.0 mmol), C/Cu NPs (0.5
mol%), H2O (2.0 mL), 70 °C.
b Yields after workꢀup.
c Yields after the fifth cycle.
The following items are observed in most of the procedures in the literature for the preparation of
triazoles31:
•
•
The use of toxic organic solvents;
Relatively low yields;
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•
•
•
•
•
•
The difficulties in preparation of the catalyst and availability of reagents;
The use of harsh reaction conditions (high temperature, hazards, ….);
Tedious workꢀup;
The overꢀstoichiometric use of Cu reagents;
The use of expensive ligands and homogeneous catalysts; and
The difficulties to recover and reuse for successive reaction cycles and the possibility of metal
contamination with the end product.
All above items are wasting money and time consuming, so our proposed method can be considered as a
green protocol which the reaction will take place in water under heterogeneous conditions. None of the above
mentioned disadvantages are observed in our method. The methodology is applicable to both the small and large
scale. On the other hand, one pot procedure for the synthesis of 1,2,3ꢀtriazoles through the reaction between inꢀ
situ generated azides from its corresponding organic halides is highly desirable and economical as this avoids
the isolation step of azides. Also, the catalyst is easy to prepare, very versatile and reusable at a low copper
loading.
Catalyst recyclability
The reusability of the catalyst is a very important theme, especially for commercial applications. Therefore, the
recovery and reusability studies of the catalyst were done by conducting the reaction of iodobenzene with
K4Fe(CN)6 (cyanation). Not much decrease in the activity of catalyst was observed even after 5 cycles (Table 3
and Figure 6). Thus, the catalyst is stable during the cyanation reaction. The reusability of the catalyst was also
studied for the 1,3ꢀdipolar cycloaddition reactions under the present reaction conditions (Table 4, entry 1).
I
Yield %
K4Fe(CN)6
+
First Run
96 %
95 %
95 %
First Recycle
Second Recycle
C/Cu NPs, DMF,
K2CO3, 120 °C
Third Recycle
Fourth Recycle
Fifth Recycle
94 %
94 %
93 %
CN
Figure 6. Reusability of C/Cu NPs for cyanation of phenyl iodide.
Heterogeneity test
We carried out a hot filtration test, when the cyanation reaction was half done, catalyst were removed at the
reaction temperature, and the reactants were allowed to undergo further reaction in the solution. We confirmed
that there was no further conversion of the reactants in the absence of the catalyst (monitored by thin layer
chromatography). This shows that the reaction was caused by the heterogeneous catalyst only. These results
further confirmed the high recyclability of the catalyst.
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The scale-up synthesis of aryl nitriles and 1,2,3-triazoles
Finally, the scaleꢀup synthesis of aryl nitriles and 1,2,3ꢀtriazoles were also investigated in the reaction of aniline
with formic acid. The amount of the halide derivative increased to 15.0 mmol and the reaction was took place
with the same procedure and same conditions which it was successful and the product obtained in high yield.
After completion of the reaction, the insoluble catalyst was separated from the reaction mixture and reused.
Conclusions
Copper NPs immobilized on carbon, C/Cu NPs catalyst, has been utilized for the synthesis of aryl nitriles and
1,2,3ꢀtriazoles. The catalyst can be recycled and reused many times without losing its activity. In addition to
easy recovery and reusability of the catalyst for a number of runs, simple operation, use of benign cyanating
agent, requirement of no ligand and additive, elimination of homogeneous catalysts, good yields of products and
tolerance for a wide variety of functionality make this procedure an attractive one for the synthesis of aryl
nitriles and 1,2,3ꢀtriazoles. This procedure can be exploited in the synthesis of various drug intermediates.
Further investigations using this catalyst system are underway.
Experimental section
All reagents were purchased from the Merck and Aldrich chemical companies and used without further
purification. Products were characterized by comparison of their physical and spectral data with authentic
1
samples. The NMR (Nuclear Magnetic Resonance) spectra were recorded in DMSO. H NMR spectra were
recorded on a Bruker Avance DRX 400 MHz instruments. The chemical shifts (δ) are reported in ppm relative
to the TMS as an internal standard and J values are given in Hz. 13C NMR spectra were recorded at 100 Hz. FTꢀ
IR (Fourier transform infrared) spectra were recorded on a PerkinꢀElmer 781 spectrophotometer. Melting points
were taken in open capillary tubes with a BUCHI 510 melting point apparatus and were uncorrected. TLC was
performed on silica gel polygram SIL G/UV 254 plates. Morphology of samples was investigated by scanning
electron microscopy (SEM) (Cam scan MV2300). The chemical composition of the prepared nanostructures was
measured by Energy Dispersive Xꢀray Spectroscopy (EDX) performed in SEM. Xꢀray powder diffraction
(XRD) measurements were performed with a Philips powder diffractometer type PW 1373 goniometer. The
BrunauerꢀEmmettꢀTeller (BET) specific surface areas (SBET) and the porosity of the samples were evaluated
on the basis of nitrogen adsorption isotherms measured at 77 K using a BELSORPꢀmax nitrogen adsorption
apparatus (Japan Inc.). Raman spectra were performed on a Senterra model of Bruker Company (Germany) and
the used Raman spectrometer was a 785 nm laser source.
Preparation of amorphous Carbon from tar
Carbon (C) has been synthesized by pyrolysis of tar. The tar was put in a tubular furnace at room temperature. A
flow of N2 was continuously passed over the furnace and the temperature was raised until 800 °C at a rate of 15
°C minꢀ1. The sample remained at 800 °C by 2 h. Then sample cooled slowly until room temperature. The
resulting sample becomes black and will be referred to as C.
Preparation of C/Cu NPs
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CarbonꢀCopper (C/Cu) composite powder was prepared by arc discharge method.32 The schematic of the
experimental setup is shown in Figure 7. Ar as carrier gas with a low flow rate was passed through the vessel
containing carbon powder and directed carbon particles toward the discharge chamber. In this chamber, two Cu
rods (diameter: 1.5 cm and length: 1 cm) were used as electrodes. The position of the bottom electrode was
fixed, whereas the top electrode was adjustable. The electrode gap was set to 2ꢀ3 mm at the beginning of the
experiment and a high current (90 A) and a low voltage (20 V) was established between the electrodes. Then,
the electrode gap was decreased until electrical discharge occurred between the electrodes resulting in
evaporation of the electrode material and formation of Cu nanoparticles. Therefore, when carbon powder was
transmitted through the electrodes, Cu nanoparticles were supported on carbon powder particles. Then, final
products were collected in powder form on a surface filter element by a vacuum pump.
Figure 7. Schematic of the experimental setup.
General procedure for the synthesis of aryl nitriles
To a mixture of aryl iodide (1.0 mmol), K4Fe(CN)6 (0.66 mmol), K2CO3 (1.0 mmol), C/Cu NPs (0.5 mol% Cu)
and 5 mL of solvent (DMF) was placed in a Schlenk tube (25 mL), and the mixture was vigorously stirred under
for 15 h at 120 ºC (Table 1 and 2). Upon completion, the mixture was cooled to room temperature, and diluted
with ether and water. Organic layer was washed with brine, dried over MgSO4, filtered and evaporated under
reduced pressure using rotary evaporator to give the crude product. The residue was purified by recrystallization
1
using ethanol and water. The purity of the compounds was checked by H NMR and yields are based on aryl
iodide. All the products are known and the spectroscopic data (FTꢀIR and NMR) and melting points were
consistent with those reported in the literature.4,33
General procedure for the synthesis of 1,2,3-triazoles
In a typical procedure, C/Cu NPs (0.5 mol%) were added to a mixture of phenylacetylene (1.0 mmol), organic
halide (1.0 mmol) and NaN3 (1.0 mmol) in water (2.0 mL) and the mixture was stirred 70 ºC. After completion
of the reaction (as monitored by TLC), the catalyst and the solid reaction product were centrifuged and the
reaction product was extracted with EtOAc. Organic layer was washed with water, dried over MgSO4, filtered
and evaporated under reduced pressure using rotary evaporator to give the crude product. Column
chromatography was performed using silica gel with ethyl acetate and nꢀhexane (2:8) as eluent to get pure
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DOI: 10.1039/C4RA09935D
product. All the products are known compounds and the spectral data (FTꢀIR and NMR) and melting points
were identical to those reported in the literature.31
Acknowledgments
We gratefully acknowledge the Iranian Nano Council and Universities of Qom and BuꢀAli Sina for the support
of this work.
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