6
534
M. Collinet-Fressancourt et al. / Tetrahedron Letters 51 (2010) 6531–6534
the rate of 1
O production when DMSO is added to the reaction
2
medium. It actually shortens the time required for complete oxida-
tion of the substrate. The process is simple and kinetically im-
proved compared to peroxidations conducted in MeOH without
DMSO for which a careful controlled addition of H
2 2
O is required.
It is thus an interesting alternative to the more intricate micro-
1
0
emulsions for the dark singlet oxygenation of low molecular
weight hydrophobic substrates.
Acknowledgments
We are grateful to Université Lille1 for financial support.
Supplementary data
Figure 5. Peroxidation of
2 2
a-terpinene 0.25 M with H O 1 M (gray) and in the
2 4
presence of DMSO 0.25 M (black). Conditions: methanol, [Na MoO ] = 0.05 M,
T = 25 °C.
References and notes
3
H
.3. Oxidation of a-terpinene and b-citronellol with the system
1.
2.
3.
(a) Aubry, J.-M.; Cazin, B. Inorg. Chem. 1988, 27, 2013–2014; (b) Aubry, J. M. J.
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ꢀ
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This procedure was then applied to the peroxidation of
a
-ter-
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8731–8734.
1
pinene 1 and b-citronellol 2. Compound 1 reacts with O
2
accord-
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010, 14, 259–262.
2
provides a mixture of two hydroperoxides according to the ene
5.
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reaction. Results are reported in Table 2.
Addition of DMSO clearly boosts the rates of peroxidation of
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than 95% of b-citronellol is more than three-times shorter when
1
416; (e) Baciocchi, E.; Giacco, T. D.; Elisei, F.; Gerini, M. F.; Guerra, M.; Lapi, A.;
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0
.25 M DMSO is added (Fig. 4). In the case of
of 0.25 M DMSO accelerates the reaction rate by a factor 2.7
Fig. 5). In all cases, the reactions lead to the expected oxidation
products.
a-terpinene, addition
4
(
(
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7
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4
. Conclusion
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The intrinsic reactivity of peroxomolybdates, which may be a
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drawback because it can lead to side reactions, such as epoxida-
tion, is proved herein to be beneficial as it significantly accelerates
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Chantu, R.; Adam, W. J. Am. Chem. Soc. 2004, 126, 10692–10700.