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New Journal of Chemistry
Page 5 of 7
DOI: 10.1039/C7NJ02062G
Journal Name
COMMUNICATION
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applications in other useful organic transformation using
Cu/Ag@SiO2 NP are in progress and we believe that the
present catalyst will find many more applications in near
future.
Acknowledgment
1
2
3
4
5
6
7
8
Recycle
(a) Reusability of Cu/Ag@SiO2 NPs for oxidative
We are pleased to acknowledge Department of Science and
Technology, New Delhi, Govt. of India (NO.SB/FT/CS-023/2012)
for the financial support. Special thanks to Prof. B. C. Ranu and
his group for their help in NMR studies.
Fig.
4
dehydrogenation of benzyl; (b) TEM image of eight times
reused catalyst.
Finally, a comparison study has been demonstrated in Table 4
to show the powerful oxidation ability of our present catalyst.
It is clearly seen that the present method is more suitable and
selective for the transformation of benzyl alcohol (BzOH) to
benzaldehyde.
Notes and references
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3. R. C. Larock, 2nd ed.; Wiley-VCH: New York, 1999; p 1234.
4. I. W. C. E. Arends, R. A. Sheldon, 2nd ed.; Wiley-VCH:
Weinheim, 2010; p 147.
Table 4 Comparative study of present vs. previously reported
methodologies for the oxidation of benzyl alcohols (BzOH)
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Entr Catalyst
y
Reaction
Yield
Substrate
scope
Conditions (%)
1
Cu/Ag@
SiO2 NPsa
Toluene;
TBHP; 120
oC; 4h
72-99 Benzoin
&
Commun., 2003, 4, 171.
BzOH (18)
8. A. Martin, U. Bentrup, A. Brückner, B. Lücke, Catal. Lett.,
1999, 59, 61.
2
3
4
Au/Pd@
TiO2 NPs38
Au/Pd@
Neat; O2; 71
90 oC; 6h
Only BzOH
9. D. V. Bavykin, A. A. Lapkin, S. T. Kolaczkowski, P. K.
Plucinski, Appl. Catal. A. 2005, 288, 175.
Neat; O2; 27
100 oC; 4h
Only BzOH
Only BzOH
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TiO2 NPs48
Au/Pd@
11. F. A. Luzzio, F. S. Guziec, Jr. Org. Prep. Proced. Int. 1988, 20
,
Micro-
34
533.
TiO2 NPs49
packed bed
reactor; O2;
12. R. J. K. Taylor, M. Reid, J. Foot, S. A. Raw, Acc. Chem. Res.,
2005, 38, 851.
140
oC;
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Lett., 1981, 22, 1605-1608.
7.5h
5
Au/Pd@
Neat; O2; 13
Only BzOH
MgO NPs50 90 oC; 4h
aPresent work
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,
Conclusions
663.
In conclusion, we have demonstrated synthesis of smart
Cu/Ag@SiO2 NPs under ultrasonic irradiation and
characterized by the powder XRD, FESEM, HRTEM studies. The
Cu/Ag@SiO2 NPs showed excellent activity and selectivity for
the oxidation benzoins to benzil derivatives and outstanding
selectivity for the oxidation of primary/secondary benzyl
alcohols to aldehydes/ketones respectively without further
oxidation to carboxylic acids. The reaction possibly proceeded
via Cu/Ag mediated degradation of tert-butylhydroperoxide to
molecular oxygen followed by the Ag-catalyzed generation of
active oxygen species from molecular oxygen. The Cu/Ag@SiO2
NPs were very robust and recovered easily from the reaction
mixture simply by filtration and reused for at least eight times
without significant loss of catalytic performance. The
19. B.-Z. Zhan, M. A. White, T.-K. Sham, J. A. Pincock, R. J.
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