M. Vafaeezadeh et al. / Catalysis Communications 26 (2012) 54–57
57
operationally simple procedure is among the benefits of the current
protocol. [BMIm] WO in combination with a heterogeneous acid cata-
2
4
lyst results in an alternative reaction media and catalyst precursor
which promotes the diffusion of both aqueous and organic reactants
across the pores of the catalyst in the absence of any organic solvents
and phase transfer catalysts. However, further developments of this
novel concept are in progress in our laboratories.
Acknowledgments
We gratefully acknowledge Prof. Dr. Mohammad Reza Saidi for
some laboratory supports.
Appendix A. Supplementary data
Scheme 1. Reaction pathway for oxidation of cyclohexene to adipic acid [5].
Supplementary data (picture of the catalyst 1, thermogravimetric
analysis, atomic absorption result of the catalyst 1, GC–MS analysis
of adipic acid 1H and CNMR spectra of the ionic liquid and adipic
acid) associated with this letter can be found in the online version.
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.catcom.2012.04.031.
13
Table 1
The data of the catalytic performance in direct oxidation of cyclohexene to adipic acid
at 75 °C.
Entry
Catalyst
Time (h)
Catalyst (g)
% Yielda
1
2
3
4
5
6
7
8
9
Catalyst 1
Catalyst 1
Catalyst 1
Catalyst 1
Catalyst 1
10
15
18
18
18
18
18
18
18
18
0.40
0.40
0.40
0.40
0.55
0.40
0.40
0.24
0.40
0.16
45
82
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b
87
80
c
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d
Catalyst 1
Catalyst 1
71
e
79
[
[
[
[
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Silica sulphamic acid
N. R.
N. R.f
N. R.
Silica@[BMIm]
2 4
WO
10
[BMIm] WO
2
4
a
Yields refer to pure isolated product of adipic acid and gave satisfactory 1HNMR
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and CNMR spectra.
b
The optimum reaction condition.
Molar ratio of H O /CyH=6.
2 2
The catalyst washed with ethanol and was used in the second run.
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c
d
e
f
[
[
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The [BMIm]
2
4
ionic liquid was supported onto the un-functionalized silica gel.
[
[
[
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were supported in the form of physisorption methods, such as
supported liquid phase (SLP), the maximum leaching of ionic liquids
was observed [28]. In the next stage, background catalytic reactions
were also explored. For the purpose of comparison, silica sulphamic
acid not charged with ionic liquid and silica gel alone loaded with
[
[
16] R. Neumann, M. Cohen, Angewandte Chemie International Edition 36 (1997)
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[
[
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[
(
BMIm]
Table 1, entries 8, 9). No adipic acid product was obtained in this re-
action condition. Notably, no adipic acid product was obtained by
using of homogeneous [BMIm] WO proving the crucial role of acidic
2 4
WO were examined under identical reaction conditions
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Catalysis A: Chemical 245 (2006) 69.
2
4
[
[
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[
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4
. Conclusion
In summary, we have developed a solvent and halide-free route to
oxidation of cyclohexene to adipic acid. Safe, relatively clean and