N. Mizuno et al.
known except for epoxide, were produced (conversion based on hy-
drogen peroxide, 84%; epoxide yield, 31%) and the present epoxi-
dation system is not suitable for the production of acid-sensitive ep-
oxides. These results are consistent with the expectation that H+
would play an important role in the present epoxidation, as men-
tioned later.
Mastrorilli, J. Org. Chem. 1978, 43, 422; d) R. W. Murray, M. Singh,
B. L. Williams, H. M. Moncrieff, J. Org. Chem. 1996, 61, 1830.
[25] The recovered catalyst was recyclable; no substantial changes were
observed for in-situ IR and UV/Vis spectra, in contrast with the
H3PW12O40/H2O2 system; no formation of other tungstate com-
pounds
of
[a-SiW12O40]4ꢀ
,
[W2O3(O2)4
C
,
and
[17] The p
buten-1-ol, and 3-methyl-2-butenyl acetate, calculated at the HF/6-
311G(d,p) level, decreased in the order 2-methyl-2-pentene
A
ACHTREUNG
peroxotungstate fragments such as [W2O3(O2)4
(ꢀ8.97 eV)>3-methyl-2-buten-1-ol (ꢀ9.25 eV)>3-methyl-2-butenyl
[PO4{WO(O2)2}4]3ꢀ
.
acetate (ꢀ9.71 eV). The electron-withdrawing substituents reduce
[26] a) C. Venturello, E. Alneri, M. Ricci, J. Org. Chem. 1983, 48, 3831;
b) Y. Ishii, K. Yamawaki, T. Ura, H. Yamada, T. Yoshida, M.
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J. Chem. Soc. Dalton Trans. 1989, 1203.
both the electron density of the C=Cdouble bond and the
p(C=C)
A
HOMO energy, resulting in a decrease in the reactivity of the olefin
with electrophilic oxidants. We carried out the competitive epoxida-
tion of 2-methyl-2-pentene, 3-methyl-2-buten-1-ol, and 3-methyl-2-
butenyl acetate to confirm the template effect of the present epoxi-
dation. The reactivity decreased in the order 3-methyl-2-buten-1-ol
(2.5)>2-methyl-2-pentene (1.0)>3-methyl-2-butenyl acetate (0.2).
This order is not consistent with that of the p(C=C) HOMO ener-
R
gies, showing that the template effect reflects the reactivity of these
olefins. The template effect was also observed for the epoxidation of
geraniol and geranyl acetate.
[28] The reaction of reactive triphenylphosphine (1 mmol) with II
(20 mmol) in acetonitrile gave triphenylphosphine oxide (43 mmol),
with two equivalents of active oxygen species with respect to II,
while the quantitative determination of the active oxygen species by
iodometric titration was unsuccessful due to the interference of the
[18] a) A. L. Villa, B. F. Sels, D. E. De Vos, P. A. Jacobs, J. Org. Chem.
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[19] During preparation of this manuscript, Ren and co-workers have re-
ported that thioanisole were oxygenated to the corresponding sulf-
oxides with hydrogen peroxide under stoichiometric conditions in
the presence of imidazole and I. T. D. Phan, M. A. Kinch, J. E.
Barker, T. Ren, Tetrahedron Lett. 2005, 46, 397.
tetra(n-butyl)ammonium ions.
G
[29] Our attempts to obtain crystallographic quality single crystals of [g-
SiW10O32(O2)2]4ꢀ in acetonitrile, acetone, N,N-dimethylformamide,
dimethyl sulfoxide, dichloromethane, and 1,2-dichloroethane togeth-
er with vapor diffusion of poor solvents such as diethyl ether, meth-
anol, n-hexane, n-pentane, and benzene using K+, [(CH3)4N]+,
[20] The negative 1 value (ꢀ1.09) for a Hammett plot (log
A
[(C2H5)4N]+, [(n-C3H7)4N]+, [(n-C4H9)4N]+, [(n-C4H9)3
[(n-C4H9)3
(CH3)N]+, [Ph(CH3)3N]+, [Ph4P]+, [K([18]crown-6)]+, [K-
(dibenzo[18]crown-6)]+, and [(iso-C3H7)2NH2]+ as counterions have
A
s, Figure S1) for the competitive oxidation of thioanisole and p-sub-
stituted thioanisoles also indicates that the nucleophilic sulfide at-
tacks the electrophilic oxygen on the active oxygen species. a) J.
Arias, C. R. Newlands, M. M. Abu-Omar, Inorg. Chem. 2001, 40,
2185; b) D. A. Bennett, H. Yao, D. E. Richardson, Inorg. Chem.
2001, 40, 2996; c) N. S. Venkataramanan, S. Premsingh, S. Rajagopal,
K. Pitchumani, J. Org. Chem. 2003, 68, 7460.
A
ACHTREUNG
AHCTREUNG
been unsuccessful so far. Attempts with the other cations and sol-
vents are in progress.
[30] The CSI-MS and in-situ IR spectra measured immediately after ad-
dition of hydrogen peroxide (20 equiv relative to I) were the same
as those of II. One 29Si NMR signal at d=ꢀ84.1 ppm was observed
at 10 min (150 scans) after addition of hydrogen peroxide and the
183W NMR spectrum of the solution was the same as that of II (5000
scans, 60 min). Therefore, we estimated that the formation of II was
completed within 10 min.
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103, 3924.
[32] It is very difficult to distinguish the bands of peroxo species from
those of the polyoxometalate based on the isotopic shifts because
the bands related to peroxo species are very weak and overlap with
the intense bands of the skeletal vibration of the polyoxometalate.
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[23] The XSO value of I was lower than or comparable to those reported
for stoichiometric reagents such as dimethyldioxirane (0.07)
(ref. [22a]), peracetic acid (0.16) (ref. [22b]), m-CPBA (0.13)
(ref. [22b]), and HMPT-MoO(O2)2 (0.16) (ref. [22c]), and for H2O2-
based catalytic oxidations such as H2O2/HClO4 (0.05) (ref. [22a]), Ti-
[34] D. D. Perrin, W. L. F. Armarego, Purification of Laboratory Chemi-
cals, 3rd ed., Pergamon, Oxford, 1988.
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b
(0.07) (ref. [22d]), Ti-MCM-41 (0.06) (ref. [22d]), Na2WO4/
C6H5PO3H2/[CH3(n-C8H17)3N]HSO4 (<0.01) (ref. [22e]), and
CH3ReO3 (0.45) (ref. [22f]).
A
ACHTREUNG
[24] a) W. Adam, A. Corma, H. Garcꢁa, O. Weichold, J. Catal. 2000, 196,
339; b) W. Adam, C. M. Mitchell, C. R. Saha-Mçller, Eur. J. Org.
Chem. 1999, 785; c) G. Bellucci, G. Berti, M. Ferreti, G. Igrosso, E.
Received: March 17, 2006
Revised: July 18, 2006
Published online: September 19, 2006
648
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Chem. Eur. J. 2007, 13, 639 – 648