ChemComm
Communication
a
Table 2 Heterogeneous reduction of substituted nitrobenzene with hydrazine
phenylboronic acid (Table S3, ESI†), there was a small decrease in
the activity after each recycling of the catalyst. The viscosity of DMF
used as solvent in Suzuki coupling is lower than EtOH. Therefore,
b
Entry
Aryl halides
Product
Yield (%) the small decline of catalytic activity seems to result from incom-
plete magnetic separation of the catalyst during the consecutive
1
2
3
4
5
99
recycling. The ICP-AES analysis showed that 2.1% of Pd species
remained in the reaction solution. The magnetically recyclable
hollow nanocomposite catalyst can be readily synthesized on a large
scale using a simple process. For example, when larger amounts of
99
98
starting materials (ꢂ5) were used, B2.3 g of the nanocomposite
99
94
catalyst could be obtained by one batch synthesis (Fig. S14, ESI†).
In conclusion, we have described a highly active magnetically
recyclable hollow nanocomposite catalyst prepared by a simple,
economical, and scalable synthetic process. The designed nanocom-
posite with a high surface area accommodates large amounts of
small catalyst NPs providing high catalytic activity. Variable catalyst
6
7
95
91
a
Reaction conditions: 0.5 substituted nitrobenzene, hydrazine (2 equiv.), NPs such as Pd, Pt, and Rh can be loaded on the nanocomposite for
Rh catalyst (1 mol%), EtOH, 80 1C, 2.5 h. The yields were determined by
b
different catalytic reactions. The efficiency of the nanocomposite was
verified in reduction of nitroarenes and Suzuki reactions providing
GC-MS using an internal standard.
excellent yields. The magnetic properties of the nanocomposite can
be readily utilized for the easy recovery and recycling of the catalyst.
The catalysts could be reused for five consecutive cycles in reduction
of nitrobenzene and Suzuki coupling of bromobenzene.
Table 3 Magnetic separation and recycling of the catalyst in heterogeneous
a
reduction of nitrobenzene with hydrazine
We acknowledge financial support from the Research Center
5th Program of Institute for Basic Science (IBS) in Korea.
Cycle
1st
99
2nd
99
3rd
97
4th
95
b
Yield of product
96
Notes and references
a
Reaction conditions: 0.5 nitrobenzene, hydrazine (2 equiv.), Rh
b
catalyst (1 mol%), EtOH, 80 1C, 2.5 h. The yields were determined
by GC-MS using an internal standard.
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2
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11
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TEM images of this catalyst show that Rh NPs are uniform with an
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using a magnet, and reused in the next reaction.
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When we examined the magnetic separation and durability of
the Pd catalyst in the Suzuki coupling of bromobenzene with
This journal is c The Royal Society of Chemistry 2013
Chem. Commun.