T. D. Phan et al. / Tetrahedron Letters 46 (2005) 397–400
399
a
Table 2. Results for oxygenation of methyl phenyl sulfide (MPS) and ethyl phenyl sulfide (EPS) catalyzed by 1
b
Entry
Substrate
Imidazole present
H
O
2 2
(equiv)
Reaction time (h)
Sulfide
Sulfoxide
Sulfone
Others
1
2
3
4
5
6
7
8
9
MPS
MPS
MPS
MPS
MPS
MPS
EPS
EPS
EPS
EPS
EPS
EPS
EPS
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
Yes
No
1
1
2
2
2
2
1
1
2
2
2
2
2
2.5
0.8
1.5
0.5
7.5
2.5
8
0
0
0
0
0
0
0
0
0
0
0
0
0
100
100
91
100
0
0
0
0
0
9
0
0
0
100
100
0
0
0
0
62
59
16
17
9
38
41
77
69
46
0
3
0
1
7
1
1
1
1
0
1
2
3
1
14
45
100
100
8
8
24
0
0
0
a
Reaction conditions similar to those in Table 1. Results depicted are an average of two runs.
b
2
Disulfides (PhSSPh) and their respective oxidation products [PhS(O)SPh or PhS(O)S(O)Ph and PhS(O) SPh].
a
Table 3. Results for oxygenation of 2-chloro-ethylphenyl sulfide (CEPS) catalyzed by 1
Entry Imidazole present
H
2
O
2
(equiv) Reaction Sulfide Sulfoxide 2-Chloro-ethylphenyl sulfone Phenyl vinyl sulfone Others
time (h)
b
1
2
3
4
5
6
No
Yes
No
Yes
No
Yes
1
1
2
2
2
2
6
2
0
0
0
0
0
0
67
73
0
0
0
0
0
33
27
b
c
6
82
72
75
70
13
27
25
30
5
1
0
0
c
3
0
24
24
0
0
a
b
c
Reaction conditions similar to those in Table 1. Results depicted are an average of two runs.
Disulfides (PhSSPh) and its respective oxidation products [PhS(O)SPh].
2
PhS(O)S(O)Ph or PhS(O) SPh.
cant in the decontamination of mustard gas since its sul-
2
Acknowledgements
1
fone is also highly toxic. Final products of oxygena-
tion of CEPS with 2 equiv of H O were identified as
Financial support from both the US Army Research
Office (DAAD 190110708) and the University of Miami
via the Provost Office is gratefully acknowledged.
2
2
phenyl vinyl sulfone (25–30%) and 2-chloro-ethylphenyl
sulfone (70–75%) (entries 4 and 5). Similar product dis-
tribution was observed in both the presence and absence
of imidazole, although a longer reaction time is required
for quantitative conversion for the latter. Allowing the
reaction to continue for several hours does not affect
the established product distribution (entries 4 and 6).
Previous studies of CEPS oxygenation catalyzed by var-
ious metal-based catalysts also found either phenyl vinyl
References and notes
1. Mikolajaczyk, M.; Drabowicz, J.; Kielbasinski, P. Chiral
Sulfur Reagents: Applications in Symmetric and Stereo-
selective Synthesis; CRC: Boca Raton, 1997.
2. Metzner, P.; Thuillier, A. Sulfur Reagents in Organic
Synthesis; Academic: London, 1994.
. Kagan, H. B. In Catalytic Asymmetric Synthesis, 2nd ed.;
Ojima, I., Ed.; Wiley-VCH: New York, 2000.
. Fernandez, I.; Khair, N. Chem. Rev. 2003, 103,
3
. Noyori, R.; Aoki, M.; Sato, K. Chem. Commun. 2003,
1
1
22
sulfone or 2-chloro-ethylphenyl sulfone as the final
product, but not a combination of these products. The
rate of sulfide oxygenation is much faster in comparison
with the rate of sulfoxide oxygenation for each
substrate.
3
4
5
651.
In summary, (Bu N) [c-SiW O (H O) ] (1) is remark-
1977.
6. Lane, B. S.; Burgess, K. Chem. Rev. 2003, 103,
4
4
10 34
2
2
ably efficient with its utilization of hydrogen peroxide in
the oxygenation of organic sulfides. The addition of
carboxylates, phosphate, or most notably imidazole,
enhances the rate of organic sulfide oxygenation. Prod-
uct distribution of phenyl vinyl sulfone and 2-chloro-
ethylphenyl sulfone was not significantly altered by the
addition of imidazole. Results reported herein reveal a
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4
1, 1925.
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002, 43, 3459.
1
00% utilization of H O by catalyst 1, enabling syn-
2 2
thetic control of organic sulfide oxygenation to form
either sulfoxide or sulfones with 1 or 2 equiv of H O ,
respectively.
2
2
2
11. Barker, J. E.; Ren, T. Tetrahedron Lett. 2004, 45,
4681.