3
78 Li et al.
in situ through the reaction of metallic samarium
with indium(III) chloride in the first step, and then
sodium alkyl thiosulfate forms an alkyl sulfur free
radical (reduction process) with low valent indium
under the reaction conditions followed by the cleav-
age of sulfur–sulfur bond in substrate. It may be as-
sumed that this reduction is also going through a
single-electron-transfer (SET) process like another
reduction by using indium metal in aqueous media
Di(n-decyl)disulfide. Oil [16]; IR (film) ꢀmax:
1
2978, 2957, 2868, 1472, 1388, 723; H NMR (CDCl )
3
δ: 0.85 (t, J = 7.1 Hz, 6H), 1.18–1.71 (m, 32H), 2.64
(t, J = 7.1 Hz, 4H).
Di(n-octyl)disulfide. Oil [16]; IR (film) ꢀmax
:
1
2
975, 2960, 2880, 1460, 1380, 720; H NMR (CDCl )
3
δ: 0.88 (t, J = 7.0 Hz, 6H), 1.23–1.74 (m, 24H), 2.62
(
t, J = 7.0 Hz, 4H).
[14]. The generated alkyl sulfur radical reacts with
Di(n-heptyl)disulfide. Oil [16]; IR (film) ꢀmax
:
another alkyl sulfur radical (homo-coupling process)
to afford symmetrical disulfide [15].
1
2
972, 2966, 2885, 1469, 1383, 721; H NMR (CDCl
3
)
δ: 0.89 (t, J = 7.1 Hz, 6H), 1.23–1.72 (m, 20H), 2.65
(
t, J = 7.1 Hz, 4H).
EXPERIMENTAL
Di(n-hexyl)disulfide. Oil [16]; IR (film) ꢀmax
:
All melting points were recorded on a WRS-1A melt-
1
2
977, 2961, 2878, 1466, 1386, 724; H NMR (CDCl
3
)
1
ing point apparatus and are uncorrected. All H NMR
δ: 0.90 (t, J = 7.2 Hz, 6H), 1.24–1.70 (m, 16H), 2.58
spectra were recorded on a 60 MHz JEOL MY 60 FT-
NMR or a 300 MHz Bruker AZ 300 spectrometer.
Chemical shifts are given as δ value with reference
to tetramethylsilane (TMS) as internal standard. IR
spectra were obtained by using a Nicolet NEXUS 470
spectrophotometer. The reagents were received from
commercial supply without purification prior to use.
Products were purified by flash column chromatog-
raphy.
(
t, J = 7.1 Hz, 4H).
Di(n-butyl)disulfide. Oil [17]; IR (film) ꢀmax:
1
2975, 2956, 2871, 1469, 1380, 720; H NMR (CDCl )
3
δ: 0.89 (t, J = 7.1 Hz, 6H), 1.35–1.59 (m, 8H), 2.55 (t,
J = 7.2 Hz, 4H).
◦
◦
Dibenzyldisulfide. mp 70 C (Lit. [16] 71 C); IR
(
1
1
KBr) ꢀmax: 3080, 3040, 2980, 2940, 2870, 1610, 1590,
1
500; H NMR (CDCl
0H).
3
) δ: 3.52 (s, 4H), 6.87–7.33 (m,
General Procedure for the Preparation
of Disulfides
◦
Di(p-chlorobenzyl)disulfide. mp 59 C (Lit. [14]
◦
5
1
6
8 C); IR (KBr) ꢀmax: 3076, 3033, 2987, 2936, 2874,
Under an inert atmosphere of nitrogen, indium(III)
chloride (0.1 mmol), metallic samarium powder
1
606, 1594, 1500; H NMR (CDCl
3
) δ: 3.51 (s, 4H),
.92–7.31 (q, 8H).
(
1 mmol), and sodium alkyl thiosulfate (1 mmol)
were placed in a round-bottomed flask, and THF-
O (V/V, 1/2, 5 ml) was added in one portion.
The mixture was stirred at room temperature for
h. After quenching with dilute hydrochloric acid
◦
Di(p-methylbenzyl)disulfide. mp 50–52 C (Lit.
H
2
◦
[
2
2
18] 48.5–50 C); IR (KBr) ꢀmax: 3075, 3028, 2979,
1
932, 2872, 1605, 1591, 1498; H NMR (CDCl ) δ:
3
4
.35 (s, 6H), 3.56 (s, 4H), 6.92–7.02 (q, 8H).
(
(
0.2 mol/l, 3 ml), the product was extracted with ether
2 × 20 ml). After the organic layer was dried over
CONCLUSION
In summary, we have found that indium(III) chloride
10% mol) and metallic samarium powder is a useful
reductive system for the reduction of sodium alkyl
thiosulfates to disulfides in aqueous media. The re-
markable advantages of this reaction are mild, neu-
tral, and environmental-friendly reaction condition,
simple operation, and good yields.
anhydrous sodium sulfate, the solvent was evapo-
rated under reduced pressure. The residue was pu-
rified by flash chromatography on silica gel using
hexane–ethyl acetate as eluting agent to give the pure
product.
(
◦
Di(n-hexadecyl)disulfide. mp 50–51 C (Lit. [16]
◦
5
7
1
0 C); IR (KBr) ꢀmax: 2975, 2950, 2870, 1480, 1380,
1
25; H NMR (CDCl
3
) δ: 0.86 (t, J = 7.1 Hz, 6H),
.24–1.74 (m, 56H), 2.64 (t, J = 7.0 Hz, 4H).
REFERENCES
◦
◦
[1] (a) Ogawa, A.; Nishiyama, T.; Kambe, N.; Murai, S.;
Sonoda, N. Tetrahedron Lett 1987, 28, 3271–3274; (b)
Antebi, S.; Alper, H. Tetrahedron Lett 1985, 26, 2609–
Di(n-dodecyl)disulfide. mp 30 C (Lit. [16] 30 C);
1
IR (KBr) ꢀmax: 2980, 2960, 2880, 1470, 1385, 720; H
NMR (CDCl
) δ: 0.86 (t, J = 7.2 Hz, 6H), 1.21–1.76
m, 40H), 2.61 (t, J = 7.0 Hz, 4H).
3
2612; (c) Fontana, S. A.; Davis, C. R.; He, Y. B.; Burton,
D. J. Tetrahedron 1996, 52, 37–44.
(