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For leading references on heterogeneous palladium catalyst for aerobic
oxidation of alcohols see: (a) K. Moroi, K. Yamaguchi, T. Hara, T.
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5
6
7
Fig. 3 TEM image of Pd@PMO-IL after five time uses, the arrows show
a number of the Pd-nanoparticles in the mesochannels.
8
1
2
1572–11573; (b) Y. Uozumi and R. Nakao, Angew. Chem., Int. Ed.,
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Scheme 4 A possible model for the aerobic oxidation of alcohols using
Pd@PMO-IL.
4
779; (h) K. Hara, S. Tayama, H. Kano, T. Masuda, S. Takakusagi, T.
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In conclusion, we have demonstrated, for the first time, the
significant efficiency of ionic liquid based PMO material in the
production and stabilization of active palladium species in the
aerobic oxidation of alcohols. The results showed that several
types of primary and secondary aromatic, hetreoaromatic, allylic
and aliphatic alcohols could be oxidized to their correspond-
ing carbonyl compounds in the presence of a low loading of
Pd@PMO-IL catalyst at short reaction times. Moreover, the
catalyst could be easily recovered and reused to give quantitative
yield of carbonyl adducts even after 10 recycling runs. The
hot filtration test, atomic spectroscopy and the results of the
effect of poisons were in good agreement with the recovery
study and confirmed that the Pd@PMO-IL catalyst operated
through a heterogeneous pathway. Furthermore, the nitrogen-
sorption experiment and TEM analysis of the recovered catalyst
also proved the high efficiency of the PMO-IL nanostructure
in the successful immobilization of stable and well distributed
active Pd-nanoparticles. This superior effectiveness of Pd@PMO-
IL nanocatalyst may be attributed to isolated ionic liquid units
incorporated in the mesochannels which could control the reaction
mechanism through preventing the formation of agglomerated Pd-
nanoparticles as well as stabilization of active catalytic palladium
species (as shown by TEM image). It is also important to note that
studies on some more practical applications of the Pd@PMO-IL
catalyst in other organic transformations are currently underway
in our laboratories.
2
93–298.
9
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65; (e) H. Miyamura, R. Matsubara, Y. Miyazaki and S. Kobayashi,
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1
0 For more recent leading references on heterogeneous Ru catalyst for
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