J IRAN CHEM SOC
Table 3 Successive trials by using recoverable Pd(II)@AEA-
Fe3O4NP for the epoxidation of styrene
For investigation of the scope and limitations of the
method, the catalyst activity was evaluated for the oxida-
tion of various styrene derivatives. The reaction was per-
formed for styrene derivatives with electron-withdrawing
and electron-donating substitutes successfully in high
Potential Pd leaching into the reaction mixture was also
analyzed with FAAS analysis. For this purpose, samples
were taken through a syringe filter during the heterogene-
ous oxidation reaction of styrene, the solvent was evapo-
rated, and the residue was dissolved in HNO3. The analysis
of these samples with FAAS showed that the Pd concen-
tration in the reaction solution was less than the detection
limit.
Trial
Catalyst amount (g)
Yield (%)a
1
2
3
4
0.10
0.99
0.99
0.99
91
91
90
90
Styrene (1 mmol), DMA (4 mol%), H2O2 (3 mmol), H2O (5 mL),
100 °C, 2 h
a
Isolated yield
Recyclability of the Pd(II)@AEA-Fe3O4NP was exam-
ined in the oxidation reaction of styrene. After carrying out
the reaction, the catalyst was separated with a magnet as
a dark solid, washed with EtOH (2 × 5 mL) and reused.
Only minor decreases in the reaction yield were observed
after four repetitive cycles for the reaction (Table 3).
Table 1 Optimization of the reaction conditions for epoxidation of
styrene
Entry Catalyst amount Solvent Temp. (°C) Time (h) Yield (%)a
(Pd mol%)
The durability of catalyst was investigated with FTIR
which any changes were observed in FTIR after recycling
of the catalyst in every steps (see supporting information).
1
1
2
3
2
2
2
2
2
2
2
2
2
2
2
2
2
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
100
100
100
100
100
100
100
100
2
2
58
91
91
33
41
68
76
73
48
83
80
67
90
72
87
37
2
3
2
4b
5b
6b
7c
8d
9
2
4
Conclusions
12
2
In conclusion, we have demonstrated the Pd(II)@AEA-
Fe3O4NP-assisted epoxidation of styrene into styrene
oxide. High yield of styrene oxide was obtained selectively
in short reaction duration. H2O as a green solvent, H2O2 as
a green oxidant and development of an organic solvent-free
approach are other advantages of this report. Separation of
the catalyst with a magnet and recyclability of the catalyst
are characteristics of this reaction.
2
DMA 100
MeCN Ref.
EtOH Ref.
CH2Cl2 Ref.
MeOH Ref.
2
10
11
12
13
14
15
16
3
2
2
2
H2O
H2O
H2O
80
90
r.t.
4
2
Acknowledgments We gratefully acknowledge financial support
from the Research Council of Urmia University.
24
Reaction conditions: styrene (1 mmol), DMA (4 mol%), H2O2
(3 mmol), solvent (5 mL)
a
Isolated yield, b without DMA, c DMA (3 mol%), d H2O2 (2 mmol)
References
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Table 2 Epoxidation of styrene derivatives in the presence of
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Reaction conditions: olefine (1 mmol), DMA (4 mol%), H2O2
(3 mmol), H2O2 (5 mL), 100 °C, 2 h
a
Isolated yield
1 3