Table 3 Oxidation of sulfides 1a–i to sulfoxides 2a–i with 30% hydrogen peroxide using the microreactor and batch systemsa
Run Substrate
Product By-product Time/s Isolated yield (%, microreactor)
Time/h Isolated yield (%, batch reactor)
1
2
3
1
2
3
1
2a
2b
2c
2d
2e
3a
3b
3c
3d
3e
2.12
2.12
2.12
2.12
2.12
0
97
0
3
0
82
15
2
12
0
87
97
93
97
0
0
0
0
100
2
0
0
0
0
66
58
92
82
16
20
0
3
4b
5
0
6
0
24
5
(syn : anti = 25 : 75)c
(syn : anti = 24 : 76)c
6
2f
3f
2.12
0
90
0
1
0
78
20
7
8
2g
2h
3g
3h
2.12
2.12
0
0
100
82
0
9
3
2
0
0
86
69
10
22
9
2i
3i
2.12
0
66
26
1
0
64
27
a
b
The reaction was started by introducing a CH3CN solution of 1 (0.5 M, 2.0 mmol) to 30% hydrogen peroxide (40.0 mmol). The temperature of
c
1
this reaction was 45 1C. The diastereomeric ratio was determined by H NMR analysis.
was quenched with saturated aqueous Na2S2O3 at 0 1C. The
mixture was extracted with EtOAc, and the extract washed
with brine, dried over Na2SO4, filtered and concentrated in
vacuo. The residue was purified by column chromatography
on silica gel using n-hexane/ethyl acetate as the eluent.
Microreactor reaction; general procedure. A solution of 1 (2.0
mmol) in CH3CN (4.0 ml) was injected by syringe pump into a
T-shaped micromixer at a flow rate of 10.0 ml minÀ1 for 24 s. At
the same time, a solution of 30% hydrogen peroxide (40 mmol,
4.0 ml) in a syringe was also injected into the micromixer by
another syringe pump at a flow rate of 10.0 ml minÀ1 for 24 s at
room temperature. The reaction mixture was then allowed to flow
at room temperature for an additional 2.12 s though a stainless
steel reactor tube (f = 1000 mm, l = 0.9 m). The reaction mixture
was quenched with a saturated aqueous Na2S2O3 solution at 0 1C.
The mixture was extracted with EtOAc, washed with brine, dried
over Na2SO4, filtered and concentrated in vacuo. The residue was
purified by column chromatography on silica gel using n-hexane/
ethyl acetate as the eluent.
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actor was made of stainless steel and the inner diameter was 1000 mm.
11. A GL Sciences pre-cleaned 316 stainless steel tubing (bright
used. The channel diameter was 1000 mm.
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12. A Harvard syringe pump, model 11E Econoflo, cat. no. 70-2205
ꢀc
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3042 | Chem. Commun., 2008, 3040–3042