Microwave Promoted Epoxidation of α,β-Unsaturated Ketones in Aqueous Sodium Perborate

Article abstract of DOI:10.1039/a803846e

A series of α,β-unsaturated ketones has been treated with sodium perborate in water and 1,4-dioxane under microwave irradiation to produce α,β-epoxyketones in good yields.

Full text of DOI:10.1039/a803846e

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6
68 J. CHEM. RESEARCH (S), 1998
J. Chem. Research (S),
Microwave Promoted Epoxidation of a,b-Unsaturated
Ketones in Aqueous Sodium Perborate$
Ali Sharifi,* Mohammad Bolourtchian and Farshid Mohsenzadeh
1998, 668±669$
Chemistry & Chemical Engineering Research Center of Iran, P.O. Box 14335-186, Tehran, Iran
A series of ꢀ,ꢁ-unsaturated ketones has been treated with sodium perborate in water and 1,4-dioxane under microwave
irradiation to produce ꢀ,ꢁ-epoxyketones in good yields.
Recently, there has been growing interest in applying micro-
1
wave dielectric heating to accelerate organic reactions.
Oxidation reactions are less considered under microwave
irradiation due to unsafe and uncontrollable experimental
2
conditions. Sodium perborate is a very cheap and widely
used industrial chemical which is utilized as an oxidizing
Scheme 1
3
agent in organic chemistry: oxidation of anilines, sul®des,
6
these reactions, in both biphasic solvent mixtures and
ketones, hydroquinones, aromatic aldehydes, iodoarenes,
aromatic nitriles, azines, sulfur heterocycles, benzylic alco-
hols, a-hydroxycarboxylic acids, 1,2-diketones, a-hydroxy-
ketones, 1,2-diols, unsaturated compounds and oximes
7
monophasic aqueous solutions at di€erent temperatures to
enhance the rate and the yield of products. In this paper, we
report epoxidation of a,b-unsaturated ketones by sodium
perborate in water and a cosolvent (1,4-dioxane) under
microwave irradiation for 2±3 min to produce the corre-
sponding epoxides in good yields (Scheme 1, Table 1).
As seen in Table 1, the isolated yield under micro-
wave conditions is higher than in thermal reactions. Regio-
4
under di€erent conditions have been reported.
a,b-Unsaturated ketones react with sodium perborate
in water and a cosolvent to produce the corresponding
5
epoxides over a long period of time. Tetrahexylammonium
hydrogensulfate is used as a phase transfer catalyst for
Table 1 Epoxidation of a,b-unsaturated ketones with sodium perborate under microwave irradiation
a
b
Sodium perborate/substrate
(mole ratio)
Irradiation
time/min
Microwave yield
(%)
Thermal yield
(%)
Entry
1
Substrate
Product
c
92 (85)
d
c
88 (55)
d
3
3
2
2
2
3
100(73)
67(38)
78(60)
3
3
4
2
3
2
51(43)
79(68)
84(75)
4
5
3
3
88(82)
91(56)
3
3
2
3
83(79)
86(80)
100(26)
6
3
2
100(93)
±
a
1
All products were characterized by IR, H NMR and their spectroscopic data were similar to those reported. From ref. 5. The time of
b
c
thermal reactions were 5±26 h. GC yield. Isolated yield.
d
*
To receive any correspondence (e-mail: ccerci@neda.net)
speci®city is observed for entry 4; the spectral data are
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).
5
identical to those of the known compound. Other co-
solvents such as THF, DMSO, DMF were examined along

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J. CHEM. RESEARCH (S), 1998 669
with water. We observed a lower yield with those solvents
than with 1,4-dioxane, under the same conditions. The opti-
mum amount of sodium perborate is found to be 3 molar
equivalents with respect to the substrate. Irradiation was
carried out 3 or 4 times (each time for 15±20 s with 5 min
intervals), in order to avoid increase of pressure in the
closed Te¯on vessel.
Received, 21st May 1998; Accepted, 14th July 1998
Paper E/8/03846E
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5
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5
±7
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Experimental
1
IR spectra were obtained on a Perkin-Elmer 833 spectrometer, H
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internal standard. Microwave induced reactions were carried out in
a Moulinex MICRO-CHEF, 900 W at 2450 MHz.
General Procedure for Epoxidation of ꢀ,ꢁ-Unsaturated Ketones.Ð
A mixture of ketone (3 mmol) and sodium perborate (9 mmol) in
water (9 mL) and 1,4-dioxane (6 mL) in a closed Te¯on vessel
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3 4
using Me Si as
(
3
volume 250 mL) was irradiated for 2 min (four times, each time
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and dried over magnesium sulfate. After ®ltration the solvent was
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