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RSC Advances
Page 5 of 6
DOI: 10.1039/C5RA27680B
Journal Name
ARTICLE
Table 3. Comparison of different catalysts in the formation of N-
benzylformamide.
Conclusions
Entry
Catalyst
Condition
Time
(h)
30
36
16
16
36
10
Yield
(%)
93
83
81
86
94
92
Ref.
In conclusion we have demonstrated an environment friendly,
inexpensive and magnetically separable Fe(OH)3@Fe3O4
catalytic system for transamidation. This catalyst exhibited
high catalytic activity for transamidation of amines with
amides, urea, thiourea and phthalimide. By using this catalytic
system, all corresponding target products were obtained in
moderate to good yields. Due to its straightforward
preparation, facial separation from the reaction medium and
recyclability, the Fe(OH)3@Fe3O4 catalytic system described
18
19
1
2
3
4
5
6
Fe(NO3)3.9H2O
Chitosan
B(OH)3
H2NOH.HCl
L-Proline
Toluene/reflux
Neat/150 °C
H2O/100 °C
Toluene/reflux
Neat/150 °C
p-xylene/reflux
10a
9a
20
Fe(OH)3@Fe3O4
---
Experimental
here, represents
reported protocols.
a good compliment to the previously
All experiments were carried out under argon. All chemicals
and solvents were purchased from commercial suppliers and
used without further purification. FT-IR spectra were obtained
over the region 400−4000 cm−1 with a Nicolet IR100 FT-IR with
Acknowledgements
spectroscopic grade KBr. H NMR and 13C NMR spectra were
1
We acknowledge Tarbiat Modares University for partial
support of this work.
recorded on a Bruker Avance (DRX 400 MHz and DRX 500 MHz)
in pure deuterated CDCl3, and DMSO-d6 solvents with
tetramethylsilane (TMS) as internal standard.
Notes and references
Preparation of Fe(OH)3@Fe3O4 Catalyst. The synthesis of the
Fe(OH)3@Fe3O4 catalyst was conducted according to the
procedure previously reported.16 In a typical preparation
procedure, the mixture of FeCl3·6H2O (4.0 mmol) and
FeCl2·4H2O (2.0 mmol) salts in deionized water (40.0 mL) was
placed in a two-necked flask under vigorous stirring. An
ammonia solution (25% (w/w)) was added in dropwise manner
over 5 min to the stirring mixture to maintain the reaction pH
about 11. The resulting black dispersion was stirred vigorously
for 1h at room temperature and then was refluxed for 1h.
Fe3O4 nanoparticles were magnetically gathered and the
residue was repeatedly washed with water and ethanol.
Subsequently, as-prepared Fe3O4 nanoparticles and 15.0 mmol
of FeCl3·6H2O were ultrasonically dispersed into 10.0 mL of
ethanol. After totally dissolution and dispersion, the
nanoparticles were separated from the ethanol solution by
magnetic decantation and dried at 80 °C for 4h.
Fe(OH)3@Fe3O4 nanoparticles were obtained by dropwise
addition of aqueous ammonia (25% (w/w), 5 mL) to the dried
brown nanoparticles under vigorous stirring. Finally, the
products of Fe(OH)3@Fe3O4 were magnetically separated,
washed with water, and dried in an oven at 373 K overnight for
further usage.
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General Procedure for the synthesis of products 3a-y. To a
mixture of catalyst (30.0 mg, 2.6 mol%) and amine (1.0 mmol)
in p-xylene (1.0 mL) was added amide (1.0 mmol) under argon
atmosphere, and the mixture was refluxed for 10 h. After
completion, the reaction mixture was allowed to cool to room
temperature. It was then diluted with EtOAc and the catalyst
was separated from the reaction mixture by using an external
magnet and washed twice with EtOAc, all volatiles were
removed under vacuum, and the resulting residue was purified
by column chromatography on silica gel to afford the desired
product.
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