S. Rup et al. / Tetrahedron Letters 51 (2010) 3123–3126
3125
Table 3
the experiment. This suggests a hydrolysis of methyl benzoate in
water under ultrasonic irradiation too.
Olefin oxidation with 2% RuCl3/4.1 equiv NaIO4—2% AliquatÒ 336—H2O—US
Entry Reactant
Product
Reaction time Yielda
(min)
(%)
3. Conclusion
1
2
3
4
5
6
7
8
9
1-Decene
E5-Decene
Pelargonic acid
Valeric acid
30
15
15
20
15
30
35
30
45
480
76
74
74
81
65
93
75
96
85
62b
98b
In summary, we have reported the first results of the efficient
oxidative cleavage of olefins, in water, with the catalytic system
2% RuCl3/4.1 equiv NaIO4 whereas this oxidation reaction had been
described in biphasic water/organic solvent(s). Of course, all the
oxidation product yields are not up to the level of those obtained
in biphasic water/organic solvent(s),1,7,12,16 but our results demon-
strate that RuCl3/NaIO4 catalyst can be used in water for environ-
mentally benign reactions. The new reaction condition is due to
the concomitant use of 2% AliquatÒ 336 and 20 kHz ultrasonic
irradiation. The application of this condition for other organic com-
pounds (especially those soluble in water) and the reasons behind
the synergy between AliquatÒ 336 and US are currently under
investigation.
1-Methylcyclohexene 6-Oxoheptanoic acid
Cyclohexene
Cycloheptene
Cyclooctene
Adipic acid
Pimelic acid
Suberic acid
Norcamphoric acid
Azelaic acid
Sebacic acid
Azelaic acid
Norbornene
9-Decenoic acid
10-Undecenoic acid
Oleic acid
10
Pelargonic acid
a
Isolated yields.
b
The separation and purification of mono- and diacids are described in Ref. 16.
Table 4
Oxidation of other functions with 2% RuCl3/x equiv NaIO4—2% AliquatÒ 336—H2O—US
Entry Reactant
Product
Equiv
NaIO4
Reaction
time (min)
Yielda
(%)
Acknowledgements
1
2
3
4
1-Nonanol
2-Nonanol
Dibenzylsulfide Dibenzylsulfone
THF
Pelargonic acid
2-Nonanone
2
2
1
4.1
30
15
60
60
58
89
80
6b
We are grateful to ADEME (French Environment and Energy
Management Agency) and the Regional council of Lorraine for
financial support. We thank Mr P. Amard for helpful suggestions
about language English grammar and style.
c
-
Butyrolactone
a
Isolated yields.
Analytical GC proportions of crude product: 94% THF, 6%
References and notes
b
c
-butyrolactone.
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pelargonic acids was attributed to the extraction of the acids by
AcOEt and purification.22
Other organic functions were oxidized by RuCl3/NaIO4 catalytic
system (Table 4) with the theoretical amount of NaIO4 necessary to
oxidize the reactant. Reactions with alcohols (entries 1 and 2) were
performed with 2 equiv NaIO4 and led to an 89% 2-nonanone yield
for 2-nonanol. Concerning 1-nonanol, the low yield (58%) was ex-
plained by a side reaction between pelargonic acid and 1-nonanol
to produce nonyl pelargonate. Dibenzyl sulfide was also oxidized
in 60 min with 1 equiv NaIO4 into dibenzyl sulfone (entry 3). But
the oxidation of THF to c-butyrolactone was not efficient in spite
of the 4.1 equiv NaIO4 used (entry 4). The oxidation of benzylmeth-
ylether was performed with 2 equiv NaIO4 and the proportion of
final products was monitored by GC/MS (Fig. 3). In contrast to
biphasic aqueous/organic solvent mixtures,7,23 which led only to
methyl benzoate, we have mainly noted the formation of benzoic
acid. The presence of benzaldehyde suggests the hydrolysis of ben-
zylmethylether into benzyl alcohol, itself oxidized to benzaldehyde
and then to benzoic acid. This reaction is in competition with the
formation of methyl benzoate whose amount decreased during
100
80
60
40
20
0
16. Rup, S.; Zimmermann, F.; Meux, E.; Schneider, M.; Sindt, M.; Oget, N. Ultrason.
Sonochem. 2009, 16, 266–272.
17. The percent of water contained in RuCl3ÁxH2O was determined by
ThermoGravimetric Analysis. The TGA showed at 150 °C a weight loss of
water corresponding to 20.8% w/w and to RuCl3Á2.9H2O. So, the oxidation of
olefin by 5 mg RuCl3Á2.9H2O is in accordance with the ratio Ru/olefin 1:51
(2% mol).
18. Mills, A.; Holland, C. Ultrason. Sonochem. 1995, 2, S33–S38.
19. Typical procedure of 1-decene oxidation: ultrasonic irradiation was performed
with
a 130 W, 20 kHz ultrasonic processor (Model W75185) from Fisher
0
1
2
3
4
5
Scientific Bioblock: 3 mm diameter titanium probe (sonotrode W72435), the
ultrasonic amplitude was set at 40% and the tip of the probe was always placed
in the same position: 0.5 cm from the bottom of the flask. A 50 mL three-neck
round-bottomed flask was charged with 2 mol % RuCl3Á2.9H2O (5 mg),19
periodate (4.1 equiv NaIO4, 877 mg) and 7 mL of water, then AliquatÒ 336
(2 mol %, 8 mg) and 1-decene (1 mmol, 140 mg) were added. The reaction
Reaction time (h)
Benzaldehyde
Benzylmethylether Methyl benzoate
Benzoic acid
Figure 3. Benzylmethylether oxidation with 2% RuCl3/2 equiv NaIO4—2% AliquatÒ
336—H2O—US monitored by GC/MS.