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FULL PAPERS
Conclusions
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In conclusion, we have immobilized, for the first time,
triflic acid onto magnetic g-Fe2O3@SiO2 and applied
the immobilized catalyst (g-Fe2O3@SiO2-TfOH) in the
dihydroperoxidation of a wide variety of carbonyl
compounds. The corresponding gem-dihydroperoxides
were obtained in moderate to high yields with aque-
ous H2O2 (30%) as oxidant. Product separation and
catalyst recycling are easy and simple with the assis-
tance of an external magnet. The catalyst can be re-
covered and reused for seven times with little loss of
activity.
Experimental Section
Synthesis of Triflic Acid-Functionalized Silica-Coated
Magnetic Nanoparticles
To a suspension of g-Fe2O3@SiO2 (1 g) in Et2O (50 mL),
TfOH (0.30 mmol) was added. The mixture was irradiated
in the ultrasonic bath for 60 min at room temperature. The
Et2O was removed and the residue was heated at 708C
under reduced pressure for 24 h to afford g-Fe2O3@SiO2-
TfOH (0.30 mmolgÀ1, 10 mg=0.0030 mmol of TfOH).
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General Procedure for Synthesis of gem-
Dihydroperoxides
A mixture of carbonyl compound (1 mmol), 30% aqueous
H2O2 (4.0 mmol) and g-Fe2O3@SiO2-TfOH (0.1 mmol) in
MeCN (5 mL) was stirred at room temperature. The prog-
ress of reaction was monitored by TLC using N,N,N’,N’-tet-
ramethyl-p-phenylenediamine dihydrochloride as a chroma-
togenic reagent. After completion of the reaction, the cata-
lyst was separated with the aid of an external magnet. The
mixture was diluted with water (5 mL), extracted with ethyl
acetate. The combined organic layer was washed with brine,
dried (MgSO4) and the solvent was evaporated under
vacuum. The residue was purified by short column chroma-
tography on silica gel using ethyl acetate/petroleum ether as
solvent to provide the pure products.
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We gratefully acknowledge the National Natural Science
Foundation of China (20872025 and 21072042) and the
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Nature
Science
Foundation
of
Hebei
Province
(B2011205031) for the financial support.
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