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Paper
centrifuge, washed and dried for next runs. As shown in Fig. 5
the catalyst was reused 12 times and no signicant loss of
activity was observed.
In order to investigate catalyst leaching, reaction between
phenyl acetylene, benzyl bromide, NaN3 was chosen as model
reaction. The reaction was performed in optimized condition
and aer half of the reaction time (60 min) the catalyst was
separated from the solution by hot ltration using hot ethyl
acetate. The rest of reaction mixture (in the absence of catalyst)
was allowed to stir for another 60 min. As seen in Fig. 6 no
triazole was produced aer catalyst removal. Moreover, atomic
absorption analysis of triazole product shows no copper ion in
it. These results show that catalyst is truly heterogeneous and
catalyst leaching is negligible under reaction condition.
Fig. 5 Recycling experiment.
Conclusion
In conclusion, we have prepared a novel heterogeneous copper
loaded catalyst based on cross-linked poly(ionic liquid)s. The
resulted catalyst was proven to be an effective and robust cata-
lyst for preparation of 1,2,3-triazoles in a green way. The catalyst
was easily prepared in large scale amount with high loading
level of copper ion. The catalyst was recovered and reused
several times without signicant loss of activity. Because of high
activity of catalyst in ppm amount the present protocol and
catalyst can be used in large scale industrial applications.
References
Fig. 6 Leaching experiment.
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To investigate the effect of imidazole groups as ligand we
used the mixture of vinyl imidazole and copper sulfate in ratio
of 2 : 1 as a homogenous catalyst. The result showed that
imidazole groups increased the activity of copper by complex-
ation (entry 22). However, this catalyst is effective but it is a
homogenous catalyst and its separation from the solution is an
issue.
In continue, the scope of three-component reaction of alkyl
halide, sodium azide and alkyne catalyzed by P[imCu/IL][Cl]
was investigated on a number of assorted substrates in opti-
mized condition (Table 2). Various substrates with electron
withdrawing and electron donating groups reacted under opti-
mized condition and gave corresponding triazoles in satisfac-
tory yields. Compared to aryl substrates, reaction of alkyl
substrates were slightly slower, although the yields of products
were still excellent. These results show that P[imCu/IL][Cl] is a
powerful catalyst for the synthesis of a broad range of triazoles.
Along with the high activity of P[imCu/IL][Cl] in a low weight
percent, another useful advantage of the catalyst is its reus-
ability. At the end of a reaction, the catalyst was easily separated
from solution by simple ltration. The reusability of P[imCu/IL]-
[Cl] was investigated in three component reaction between
phenyl acetylene, benzyl bromide and sodium azide as model
reaction (Table 2, entry 1). In order to prevent catalyst mass
losing, at the end of each cycle the catalyst was separated by
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29616 | RSC Adv., 2015, 5, 29609–29617
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