Preparation of a new 1,2,3-trithiolane, trans-9,10,11-trithiabicyclo[6.3.0]undecane, and its oxidation reactions

Article abstract of DOI:10.1016/j.tet.2006.03.044

The reaction of trans-cyclooctene with S₈O yielded a novel bicyclic 1,2,3-trithiolane and trans-9,10,11-trithiabicyclo[6.3.0]undecane (7). Oxidation of the trithiolane with dimethyldioxirane yielded three monoxides, which are assigned to two isomeric 9-oxides, rel-(1R,8R,9S)-9-oxide (15) and rel-(1R,8R,9R)-9-oxide (16), and 10-oxide (17). Further oxidation of rel-(1R,8R,9S)-9-oxide (15) provided rel-(1R,8R,9S,11S)-9,11-dioxide (18) and rel-(1R,8R,9R,11S)-9,11-dioxide (19), while that of rel-(1R,8R,9R)-9-oxide (16) gave rel-(1R,8R,9R,11S)-9,11-dioxide (19) and rel-(1R,8R,9R,11R)-9,11-dioxide (20). The structures of 18 and 19 were determined by X-ray crystallography. The structures of other oxides were elucidated by the spectroscopic data and results of further chemical transformations. Two isomers, 15 and 16, isomerized to one another. A 9,11-dioxide 20 isomerized to 19, which is in equilibrium with 18, where 18 is thermodynamically the most stable isomer.

Full text of DOI:10.1016/j.tet.2006.03.044

Tetrahedron 62 (2006) 5441–5447
Preparation of a new 1,2,3-trithiolane,
trans-9,10,11-trithiabicyclo[6.3.0]undecane,
and its oxidation reactions
*
Akihiko Ishii, Manami Suzuki and Remi Yamashita
Department of Chemistry, Faculty of Science, Saitama University, Sakura-ku, Saitama,
Saitama 338-8570, Japan
Received 8 March 2006; revised 15 March 2006; accepted 16 March 2006
Available online 25 April 2006
Abstract—The reaction of trans-cyclooctene with S8O yielded a novel bicyclic 1,2,3-trithiolane and trans-9,10,11-trithiabicyclo[6.3.0]-
undecane (7). Oxidation of the trithiolane with dimethyldioxirane yielded three monoxides, which are assigned to two isomeric 9-oxides,
rel-(1R,8R,9S)-9-oxide (15) and rel-(1R,8R,9R)-9-oxide (16), and 10-oxide (17). Further oxidation of rel-(1R,8R,9S)-9-oxide (15)
provided rel-(1R,8R,9S,11S)-9,11-dioxide (18) and rel-(1R,8R,9R,11S)-9,11-dioxide (19), while that of rel-(1R,8R,9R)-9-oxide (16) gave
rel-(1R,8R,9R,11S)-9,11-dioxide (19) and rel-(1R,8R,9R,11R)-9,11-dioxide (20). The structures of 18 and 19 were determined by X-ray
crystallography. The structures of other oxides were elucidated by the spectroscopic data and results of further chemical transformations.
Two isomers, 15 and 16, isomerized to one another. A 9,11-dioxide 20 isomerized to 19, which is in equilibrium with 18, where 18 is
thermodynamically the most stable isomer.
Ó 2006 Elsevier Ltd. All rights reserved.
S
O
1. Introduction
S
Ph
Ph
O
S
S
S
1,2,3-Trithiolane 1 is the trithio analog of molozonide, and
several derivatives, including their oxides, have been re-
ported so far.1,2 Most of the derivatives were prepared by
reaction of alkenes with sulfur allotropes under vigorous3–12
or mild13–15 conditions, and a few were obtained by dimer-
ization of a thioketone S-oxide,16 by reaction of 1,2-dithiols
and their equivalents with sulfurating reagents,17–19 or by re-
duction of a pentathiane followed by air oxidation.20 On the
other hand, oxidations of acyclic and cyclic di-,21 tri-,22
tetra-,23 and higher polysulfanes24,25 have attracted con-
siderable attention from the viewpoints of regiochemistry,
stereochemistry, stability, and reactivities of the oxides
formed. We have been studying the synthesis and oxidation
of cyclic di-, tetra-, and pentasulfanes.24,25 trans-Cyclo-
octene (2) has high reactivity toward sulfurating reagents.
Adam and his co-workers have reported that the reactions
of 2 with 3–5 gave the corresponding trans-episulfide 6 in
high yields.26–30 In relation to our study on S8O as an S2O
equivalent,31 we examined the reaction of 2 with S8O,32
and found the formation of a novel 1,2,3-trithiolane deriva-
tive 7 together with 6.
1
2
3
O
O
S
S
S
H
H
S
Et2N
Mo
S
S
S
n
S
NEt2
6: n = 1
7: n = 3
4
5
Concerning oxides of 1,2,3-trithiolanes, a limited number
of 1- and 2-oxides17,19,33,34 and 1,1-dioxides16,34 have
been reported. Ghosh and Bartlett reported on oxidation
of trithiolane 8 with MCPBA giving endo- and exo-1-
oxides and endo-2-oxide, and with ozone giving endo-
and exo-2-oxides.17 Oxidation of 9 with MCPBA yielded
endo- and exo-3-oxides.17 Satoh and Sato reported that
oxidation of 10 with MCPBA gave 1-oxide 11, while that
with NCS or NBS provided 1,1-dioxide 12 through 11.34
Further oxidation of 11 with MCPBA gave disulfinic acid
13, where intervention of 1,3-dioxide 14 was proposed.34
In this paper we report on the preparation of a novel
1,2,3-trithiolane 7 and its oxidation giving three monoxides
and three 1,3-dioxides together with isomerization between
them.
Keywords: Trithiolane; Cyclooctene; Octasulfur monoxide; Oxidation;
Isomerization.
* Corresponding author. Tel.: +81 48 858 3394; fax: +81 48 858 3700;
e-mail: ishiiaki@chem.saitama-u.ac.jp
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.03.044

5442
A. Ishii et al. / Tetrahedron 62 (2006) 5441–5447
Table 1. Yields of products in oxidation of trithiolane 7
S
-
-O2S
SO2
O
O
S
m
n
S
3
S
Entry
Oxidant (equiv)
Yields (%)
15
16
17
18
19
20
7
S
S
1
2
DMDa (1)
DMDa (2)
MCPBA (1)
16
0
20
33
0
53
15
0
7
8
0
0
9
R
1
2
3
21b 64b 10b 5b
R = H (8)
Ph (9)
13
10: m = n = 0
c
4
0
0
11: m = 1, n = 0
12: m = 2, n = 0
14: m = n = 1
a
Dimethyldioxirane.
1H NMR integral ratio.
b
c
A small amount of 19 was detected by 1H NMR.
2. Results and discussion
trans-Cyclooctene (2)35 was treated with S8O32 in CS2
at room temperature. After chromatographic purification,
we isolated trans-9,10,11-trithiabicyclo[6.3.0]undecane 7,
a 1,2,3-trithiolane, as a yellow oil in 33% yield together
with trans-episulfide 6 in 13% yield (Eq. 1).
H
S
S
S8O
+
6
S
2
CS2, r.t.
13 h
(1)
13%
H
7 33%
The 13C NMR spectrum of 7 showed four signals due to sp3
carbons at d 24.6 (CH2), 26.5 (CH2), 34.8 (CH2), and 63.5
(CH), and the 1H NMR spectrum exhibited two methine pro-
tons at d 3.78–3.84 as a multiplet. As we could not determine
the stereochemistry of 7, whether cis or trans, with these
NMR data, we examined derivation of 7 into its oxides to
make the structure unsymmetrical for observing the vicinal
coupling constant between the methine protons.
Figure 1. ORTEP drawing of rel-(1R,8R,9S,11S)-9,10,11-trithiabi-
cyclo[6.3.0]undecane 9,11-dioxide (18) (30% ellipsoidal probability).
˚
Selected bond lengths (A), bond angles (deg), and dihedral angles (deg):
S1–O1 1.482(2); S1–C1 1.833(3); S1–S2 2.1249(16); S2–S3 2.1259(14);
S3–O2 1.473(2); S3–C2 1.832(3); C1–C2 1.524(4); C1–S1–S2 93.58(10);
S1–S2–S3 101.13(5); C2–S3–S2 94.09(10); C2–C1–S1 108.0(2); C1–
C2–S3 107.29(18); H1–C1–C2–H2 ꢁ157(3); S3–C2–C1–S1 68.3(2); S1–
S2–S3–C2 14.07(9); C1–S1–S2–S3 14.74(10); O1–S1–C1–C2 62.7(2);
O2–S3–C2–C1 62.8(2).
Trithiolane 7 was treated with an acetone solution of di-
methyldioxirane (DMD)37,38 (1 equiv) in dichloromethane
at 0 ꢀC to give two 9-oxides 15 (16%) and 16 (33%), 10-oxide
17 (15%), and two 9,10-dioxides 18 (8%) with recovery of
7 (9%) (Eq. 2; Table 1, entry 1). When 2 equiv of DMD
were used, 9,10-dioxides 18, 19, and 20 were formed in the
ratio of 21:64:10 with the recovery of 7 (based on 1H NMR
integral ratio) (entry 2). Oxidation of 7 with MCPBA
(1 equiv) provided a similar set of products. Except 20, all
the oxides were isolated.
O
H
H
S
S
S
S
[O]
+
S
O
7
S
CH2Cl2
0 °C
H
H
17
15, 16
(2)
O
H
S
+
S
S
H
O
18, 19, 20
Figure 2. ORTEP drawing of rel-(1R,8R,9R,11S)-9,10,11-trithiabi-
cyclo[6.3.0]undecane 9,11-dioxide (19) (30% ellipsoidal probability).
˚
Selected bond lengths (A), bond angles (deg), and dihedral angles (deg):
2.1. Structure determination of the oxides of 7
S1–O1 1.487(5); S1–C1 1.837(5); S1–S2 2.110(2); S2–S3 2.118(2); S3–
O2 1.487(5); S3–C2 1.846(6); C1–C2 1.520(7); C1–S1–S2 92.49(19);
S1–S2–S3 99.57(8); C2–S3–S2 96.12(18); C2–C1–S1 108.3(4); C1–C2–
S3 114.8(4); H1–C1–C2–H2 ꢁ172.9(7); S3–C2–C1–S1 ꢁ51.0(3); S1–
S2–S3–C2 15.4(2); C1–S1–S2–S3 ꢁ37.1(2); O1–S1–C1–C2 ꢁ58.8(4);
O2–S3–C2–C1 129.9(4).
While monoxides 15–17 were oily materials, we could
obtain single crystals of dioxides 18 and 19 suitable for
X-ray crystallography. The ORTEP drawings of 18 and
19 are depicted in Figures 1 and 2, respectively. The

A. Ishii et al. / Tetrahedron 62 (2006) 5441–5447
5443
conjunction of the two rings in 18 and 19 was trans, and their
relative stereochemistries including the configuration of the
S]O groups were determined to be rel-(1R,8R,9S,11S)-
9,11-dioxide and rel-(1R,8R,9R,11S)-9,11-dioxide, respec-
tively. Of necessity, the stereochemistry of 7 was determined
to be trans, showing that the stereochemistry of the starting
trans-alkene was retained.
in the NMR time scale, and the structure was assigned to
be rel-(1R,8R,9R,11R)-9,11-dioxide 20.
DMD
(1 equiv)
15
18
+
19
(3)
(4)
43%
47%
DMD
O
(1 equiv)
O
H
H
16
18
+
19
+
20
S*
S*
S
S
S
S
R*
R*
R*
R*
2%
35%
54%
S
S*
S
R*
H
H
O
O
O
H
19
18
R*
S
S
R*
R*
S
R*
In the crystal, the trithiolane ring of 18 took a half-chair con-
formation, and the eight-membered ring took a boat–chair
conformation, which is one of the most stable family of con-
formations of cyclooctane.39 Each of the two oxygen atoms
in 18 possessed the axial position and was trans to the vicinal
hydrogen atom [O(1)–S(1)–C(1)–H(1) 178(2)ꢀ, O(2)–S(3)–
C(2)–H(2) 177(2)ꢀ]. The 13C NMR spectrum, measured at
room temperature, showed only four signals due to sp3
carbons, indicating that 18 has a symmetric structure in the
H
O
20
Three possible stereoisomers of 9,11-dioxides (18–20) were
thus obtained and their structures were clearly determined.
Based on the results of Eqs. 3 and 4, the structures of mon-
oxides 15 and 16 are assigned to be rel-(1R,8R,9S)-9-oxide
and rel-(1R,8R,9R)-9-oxide, respectively. As summarized
in Scheme 1, oxidation of trithiolane 7 and 9-oxides 15
and 16 proceeded without stereoselectivity to give two
possible stereoisomers, 15 and 16, 18 and 19, and 19 and
20, respectively. Table 2 summarizes NMR data of the
methine protons and carbons of 7 and its oxides, 15–20.
1
NMR time scale in solution. In the H NMR spectrum,
H(1) and H(2) appeared at d 4.23–4.25 as a multiplet.
In the case of dioxide 19, the trithiolane and the cyclooctane
rings took conformations similar to those of 18. One of the
two oxygen atoms [O(1)] possessed the axial position and
the other [O(2)] possessed the equatorial one in the crystal,
where the former is trans to the vicinal hydrogen [O(1)–
S(1)–C(1)–H(1) 179.0(5)ꢀ] and the latter was cis to the
vicinal hydrogen [O(2)–S(3)–C(2)–H(2) 9.9(4)ꢀ]. In the 1H
NMR spectrum, two methine protons resonated at d 3.57
and 4.82 with the vicinal coupling constant of 12.0 Hz, indi-
cating that the hydrogen atoms take a trans conformation
also in solution.
O
O
H
H
S*
R*
S
S
S
R*
R*
S
S
R*
R*
S
H
15
H
16
18
19
20
[O]
[O]
15
16
[O]
7
The structure of 10-oxide 17 was elucidated as follows. In
the 13C NMR spectrum, all carbons were nonequivalent
with each other and in the 1H NMR spectrum the vicinal cou-
pling constant between the methine protons (d 4.19 and 4.60)
was 11.3 Hz. Unlike the cases of 15 and 16 as discussed be-
low, oxidation of 17 with DMD gave a mixture of unidenti-
fied compounds and not dioxides 18 or 19, which indicates
that 17 is not a 9-oxide but a 10-oxide of 7.
Scheme 1.
Table 2. NMR data of methine protons and methine carbons of 7 and 15–20
Methine protons (d)
Methine carbons (d)
7
3.78–3.84 (m)
63.5
15
16
17
18
19
20
3.39–3.44 (m), 3.92–3.98 (m)
3.48–3.54 (m), 3.64–3.69 (m)
4.19 (ddd), 4.60 (ddd) (Jvic¼11.3 Hz)
4.23–4.25 (m)
57.2, 79.9
60.2, 86.6
60.8, 70.2
73.4
73.9, 81.2
75.8
1H and 13C NMR spectroscopies of 15 and 16 showed that all
of their protons and carbons were nonequivalent. Oxidation
reactions of 15 and 16 were investigated to obtain further in-
formation on regio- and stereochemistries of their S]O
groups. When 15 was oxidized with DMD at 0 ꢀC, dioxides
18 (43%) and 19 (47%) were formed (Eq. 3). On the other
hand, oxidation of 16 yielded another dioxide 20 (54%)
and 19 (35%) together with a small amount of 18 (2%)
(Eq. 4). The formation of a small amount of 18 seems to
be due to isomerization of 19 as described later. The 13C
NMR spectrum of the mixture of 19 and 20 (with a small
amount of 18), measured at ꢁ20 ꢀC, showed only four sp3
carbon signals due to 20 at d 23.3, 25.5, 27.9, and 75.8.
The methine protons of 20 were observed at d 3.72–3.80
as a multiplet. Thus, dioxide 20 has a symmetric structure
3.57 (ddd), 4.82 (ddd) (Jvic¼12.0 Hz)
3.72–3.80 (m)
2.2. Isomerization
We observed mutual isomerization between monoxides 15
and 16. When a solution of 15 in CDCl3 was warmed at
55 ꢀC, 16 appeared gradually and the ratio of 15 and 16
reached 30:70 after 24 h (Eq. 5). Similarly, a solution of
pure 16 became a 29:71 mixture of 15 and 16 under same
conditions (Eq. 6). Ghosh and Bartlett reported that mutual

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A. Ishii et al. / Tetrahedron 62 (2006) 5441–5447
2.3. Desulfuration of 7
S
O2
O
O
S
O
S
S
S
O
S
- O2
Desulfuration of 7 was examined in expectation of the for-
mation of the corresponding 1,2-dithietane.42,43 Trithiolane
7 was treated with triphenylphosphine (1 equiv) in CDCl3
at room temperature to give cis-episulfide 2326 (22%) with
recovery of 7 (75%) (Eq. 7). Compound 23 would be formed
by an intramolecular SN2 reaction as shown in Scheme 4.
21
- O2
O2
S
S
S
O
22
H
PPh3
(1 equiv)
Scheme 2.
+
S
7
7
CDCl3, r.t.
5 h
(8)
75%
H
isomerization between 21 and 22 (2-oxides of 8) took place
not under argon but under O2, and they proposed the adduct
of 21 with 3O2 as the intermediate (Scheme 2).17 In contrast,
the isomerization between 15 and 16 was not influenced by
the presence or the absence of air. When 1,1-diphenyl-2-
picryl hydrazyl (DPPH) was added to a solution of 15 or
16, the isomerization was accelerated and the equilibrium
was attained in 19 h. This acceleration by a radical scaven-
ger was in quite contrast to our previous observations of
remarkable retardation by DPPH in the epimerization of
dithiirane 1-oxides (Eq. 7), where we proposed that a radical
contaminant (Xꢂ) caused the epimerization.40,41 In the
present case, DPPH itself might act as a radical catalyst.
23 22%
H
H
H
H
S-
S
S
S
+
S
23
S
PPh3
:PPh3
- -SSP+Ph3
Scheme 4.
3. Conclusion
The reaction of trans-cyclooctene with S8O at room temper-
ature yielded trans-9,10,11-trithiabicyclo[6.3.0]undecane
(7), a new 1,2,3-trithiolane, stereospecifically, together with
the corresponding trans-episulfide. In this reaction S8O
behavedlikeelemental sulfur activatedundervigorouscondi-
tions and worked towards trans-cyclooctene as an Sn-transfer
reagent under mild conditions, which should be contrasted
with S8O acting as an S2O-transfer reagent towards diazo-
methanes,31 1,3-butadienes,31 and cycloheptatriene.44 Oxi-
dation of 7 with DMD provided two 9-oxides (15 and 16),
one 10-oxide (17), and three 9,11-dioxides (18, 19, and 20).
The 9,11-dioxides are the first example of stable 1,2,3-tri-
thiolane 1,3-dioxides. Configuration of the sulfinyl groups
in 15, 16, 19, and 20 was relatively unstable and we observed
mutual isomerization between 15 and 16 and stepwise iso-
merization of 20 to 18 through 19.
15
15 + 16
30 : 70
CDCl3, 55 °C
(5)
(6)
24 h
15 + 16
29 : 71
16
CDCl3, 55 °C
24 h
R1
S
R1
R2
X
S
O
(7)
S
S
R2
X
O
9,11-Dioxides 19 and 20 isomerized to 18. When a solution
of a mixture of 18 (2%), 19 (35%), and 20 (54%) in CDCl3,
obtained in Eq. 4, was stood at room temperature for one day,
20 disappeared completely and the amounts of 18 (24%) and
19 (59%) increased. After four days, 18 became the major
component (69%) and 19 became the minor one (16%).
These observations indicate that the isomerization of 20 to
18 takes place stepwise through 19 and that isomerization
of 20 to 19 is faster than that of 19 to 18 (Scheme 3). The
thermodynamic instability of 19 and 20 compared with 18
would be due to the repulsion between the oxygen atom(s)
with the vicinal hydrogen atom.
4. Experimental
4.1. General
The melting points were determined on a Mel-Temp capil-
lary tube apparatus and are uncorrected. H and 13C NMR
1
spectra were determined on Bruker AM400 or DRX400
(400 and 100.7 MHz, respectively) spectrometers using
CDCl3 as the solvent at 25 ꢀC, unless otherwise noted. IR
spectra were taken on a Perkin–Elmer System 2000 FT-IR
spectrometer. Mass spectra were determined on a JEOL
JMS-700AM spectrometer operating at 70 eV in the EI
mode. Elemental analysis was performed by the Chemical
Analysis Center of Saitama University. Column chromato-
graphy was performed with silica gel (70–230 mesh), and
high-pressure liquid chromatography (HPLC) with a packed
SiO2 column (INERTSIL PREP-SIL: 10 or 20 mm i.d., GL
Science Inc.); the eluent is shown in parentheses. trans-
Cyclooctene was prepared by photoisomerization of com-
mercially available cis-cyclooctene.35,36 S8O was prepared
O
O
O
H
H
H
H
H
H
S
S
S
slow
fast
S
S
S
S
S
S
O
O
O
20
19
18
Scheme 3. Isomerization of 20 to 18 through 19.

A. Ishii et al. / Tetrahedron 62 (2006) 5441–5447
5445
by oxidation of S8 with trifluoroperacetic acid.32 An acetone
solution of dimethyldioxirane (DMD) was prepared by
oxidation of acetone with OxoneÒ (Sigma–Aldrich).37,38
4%) in this order. The mixture of 15 and 16 was separated
with HPLC (hexane/ether 2/1) to give 9-oxide 15 (9.4 mg,
20%) and 7-oxide 16 (24.9 mg, 53%).
4.2. Reaction of trans-cyclooctene with S8O
4.3.4. rel-(1R,8R,9S)-9,10,11-Trithiabicyclo[6.3.0]unde-
cane 9-oxide (15). Colorless oil. 1H NMR d 1.55–1.88 (m,
9H), 1.91–2.00 (m, 1H), 2.16–2.26 (m, 2H), 3.39–3.44 (m,
1H), 3.92–3.98 (m, 1H); 13C NMR d 23.9 (CH2), 24.7
(CH2), 26.2 (CH2), 26.4 (CH2), 27.5 (CH2), 34.9 (CH2),
57.2 (CH), 79.9 (CH); IR (neat) 1094 cmꢁ1 (S]O); MS
m/z 222 (M+). HRMS: calcd for C8H14OS3: M, 222.0207.
Found: M+, 222.0201.
trans-Cyclooctene (305 mg, 2.77 mmol) was added to a
solution of S8O (4.10 g, 15 mmol) in CS2 (70 mL) under
argon. The mixture was stirred for 13 h at room temperature.
After evaporation of the solvent under reduced pressure,
the residue was subjected to column chromatography
(hexane/dichloromethane 4/1) to remove elemental sulfur
and then subjected to HPLC (hexane/dichloromethane 4/1)
to give trans-9,10,11-trithiabicyclo[6.3.0]undecane (7)
(188 mg, 33%) and trans-episulfide 6 (52 mg, 13%) in this
order. Trithiolane 7 was purified by bulb-to-bulb distillation
(1.2 mmHg, 115 ꢀC).
4.3.5. rel-(1R,8R,9R)-9,10,11-Trithiabicyclo[6.3.0]unde-
cane 9-oxide (16). Colorless oil. 1H NMR d 1.38–1.47 (m,
1H), 1.50–1.88 (m, 9H), 2.22–2.37 (m, 2H), 3.48–3.54 (m,
1H), 3.64–3.69 (m, 1H); 13C NMR d 22.6 (CH2), 24.7
(CH2), 25.9 (CH2), 26.5 (CH2), 29.4 (CH2), 33.5 (CH2),
60.2 (CH), 86.6 (CH); IR (neat) 1088 cmꢁ1 (S]O); MS
m/z 222 (M+). HRMS: calcd for C8H14OS3: M, 222.0207.
Found: M+, 222.0209.
4.2.1. trans-9,10,11-Trithiabicyclo[6.3.0]undecane (7).
1
Yellow oil. H NMR d 1.54–1.84 (m, 10H), 2.14–2.22 (m,
2H), 3.78–3.84 (m, 2H); 13C NMR d 24.6 (CH2), 26.5
(CH2), 34.8 (CH2), 63.5 (CH); MS m/z 206 (M+). HRMS:
calcd for C8H14S3: M, 206.0258. Found: M+, 206.0258.
Anal. Calcd for C8H14S3: C, 46.55; H, 6.84. Found: C,
46.70; H, 6.86.
4.3.6. 9,10,11-Trithiabicyclo[6.3.0]undecane 10-oxide
(17). Colorless oil. H NMR d 1.53–1.74 (m, 5H), 1.79–
1
1.90 (m, 3H), 1.98–2.15 (m, 2H), 2.22–2.37 (m, 2H), 4.19
(ddd, J¼11.3, 8.1, 3.5 Hz, 1H), 4.60 (ddd, J¼11.3, 8.6,
3.0 Hz, 1H); 13C NMR d 24.3 (CH2), 25.2 (CH2), 25.3 (CH2),
26.4 (CH2), 26.5 (CH2), 27.6 (CH2), 60.8 (CH), 70.2 (CH); IR
(neat) 1107 cmꢁ1 (S]O); MS m/z 222 (M+). HRMS: calcd
for C8H14OS3: M, 222.0201. Found: M+, 222.0200.
4.3. Oxidation of trithiolane 7
4.3.1. DMD (1 equiv). DMD (0.0753 M, 2.70 mL,
0.20 mmol) was added dropwise to a solution of 7 (42 mg,
0.20 mmol) in dichloromethane (2 mL) under argon at
0 ꢀC. The mixture was stirred for 2 h at 0 ꢀC. The mixture
was transferred to a round-bottom flask and the solvent
was removed under reduced pressure with the flask being
dipped in an ice-water bath. The residue was subjected to
column chromatography (dichloromethane) to give trithio-
lane 7 (4.0 mg, 9%), 10-oxide 17 (6.4 mg, 15%), a mixture
of 9-oxides 15 and 16, and 9,11-dioxide 18 (3.7 mg, 8%)
in this order. The mixture of 15 and 16 was separated with
HPLC (hexane/ether 2/1) to give 9-oxide 15 (6.8 mg, 16%)
and 9-oxide 16 (14.5 mg, 33%).
4.3.7. rel-(1R,8R,9S,11S)-9,10,11-Trithiabicyclo[6.3.0]-
undecane 9,11-dioxide (18). Colorless plates, mp 114–
1
116 ꢀC (dichloromethane/ethanol). H NMR d 1.50–1.60
(m, 2H), 1.65–1.82 (m, 4H), 2.03–2.08 (m, 2H), 2.26–2.35
(m, 2H), 2.57–2.65 (m, 2H), 4.23–4.25 (m, 2H); 13C NMR
d 24.6 (CH2), 25.2 (CH2), 26.1 (CH2), 73.4 (CH); IR
(KBr) 1066 cmꢁ1 (S]O); MS m/z 238 (M+). HRMS: calcd
for C8H14O2S3: M, 238.0156. Found: M+, 238.0140.
4.3.7.1. Crystallographic data for 18. C8H14O2S3,
Mw¼238.39, colorless plate, 0.34ꢃ0.24ꢃ0.08 mm3, mono-
˚
4.3.2. DMD (2 equiv). DMD (0.0753 M, 2.63 mL,
0.20 mmol) was added dropwise to a solution of 7
(20.4 mg, 0.10 mmol) in dichloromethane (1 mL) under
argon at ꢁ35 ꢀC. The mixture was stirred for 2 h at ꢁ35 ꢀC.
At this temperature the solvent was removed under reduced
clinic, P21/c, a¼7.3540(3), b¼16.4810(8), c¼9.5776(7) A,
b¼115.430(2) , V¼1048.34(10) A , rcalcd¼1.510 g cmꢁ3
,
3
ꢀ
˚
Z¼4, m (Mo Ka)¼0.672 cmꢁ1. Mac Science DIP3000 dif-
fractometer with a graphite-monochromated Mo Ka radia-
˚
tion (l¼0.71073 A). The data reduction was made by the
1
pressure. The H NMR spectrum of the mixture showed
maXus program system. Intensity data of 2045 unique
reflections were collected in the range of ꢁ9ꢄhꢄ9,
ꢁ20ꢄkꢄ20, and ꢁ11ꢄlꢄ12. Absorption corrections were
done by a multi-scan method (SORTAV45). The structure
was solved with a direct method (SIR9746) and refined
with full-matrix least-squares (SHELXL-9747) using all
independent reflections, where nonhydrogen atoms were
refined anisotropically and hydrogen atoms were refined
isotropically. R1¼0.0524 (Iꢅ2sI, 1858 reflections),
wR2¼0.1394 (for all), and GOF¼1.038, 175 parameters;
that the mixture consisted of 18, 19, 20, and 7 in the ratio
of 21:64:10:5. Compound 20 could not be isolated because
of its instability.
4.3.3. MCPBA (1 equiv). A solution of MCPBA (88.6%,
40.4 mg, 0.21 mmol) in dichloromethane (3 mL) was added
dropwise to a solution of 7 (43.8 mg, 0.21 mmol) in di-
chloromethane (2 mL) under argon at 0 ꢀC. The mixture
was stirred for 2 h at 0 ꢀC. To the mixture were added aque-
ous Na2SO3 and then aqueous NaHCO3. The mixture was
extracted with dichloromethane, and the organic layer was
washed with water, dried over anhydrous MgSO4, and evap-
orated to dryness. The residue was subjected to column chro-
matography (dichloromethane) to give 10-oxide 17 (3.3 mg,
7%), a mixture of 15 and 16, and 9,10-dioxide 18 (2.1 mg,
ꢁ3
˚
max/min residual electron density¼0.771/ꢁ0.604 eA
.
4.3.8. rel-(1R,8R,9R,11S)-9,10,11-Trithiabicyclo[6.3.0]-
undecane 9,11-dioxide (19). Colorless plates, mp 109–
1
111 ꢀC (dichloromethane/ethanol). H NMR d 1.51–1.80
(m, 5H), 1.81–1.87 (m, 2H), 1.93–2.02 (m, 1H), 2.09–2.19

5446
A. Ishii et al. / Tetrahedron 62 (2006) 5441–5447
(m, 1H), 2.30–2.39 (m, 1H), 2.41–2.48 (m, 1H), 2.49–2.58
(m, 1H), 3.57 (ddd, J¼12.1, 9.4, 2.5 Hz, 1H), 4.82 (ddd,
J¼12.0, 7.7, 3.9 Hz, 1H); 13C NMR d 23.9, 24.2, 24.9,
26.3, 26.5, 28.5, 73.9, 81.2; IR (KBr) 1083, 1059 cmꢁ1
(S]O); MS m/z 238 (M+). HRMS: calcd for C8H14O2S3:
M, 238.0156. Found: M+, 238.0146.
was warmed at 55 ꢀC for 24 h (during heating, indoor light
was not shaded in particular). The mixture consisted of
30% of 9-oxide 15 and 70% of 9-oxide 16 based on the 1H
NMR integral ratio.
4.6.2. Isomerization of 9-oxide 16. In an NMR tube, a solu-
tion of 9-oxide 16 (2.3 mg, 0.010 mmol) in CDCl3 (0.4 mL)
was warmed at 55 ꢀC for 24 h (during heating, indoor light
was not shaded in particular). The mixture consisted
of 29% of 9-oxide 15 and 71% of 9-oxide 16 based on the
1H NMR integral ratio.
4.3.8.1. Crystallographic data for 19. C8H14O2S3,
Mw¼238.39, colorless plate, 0.34ꢃ0.22ꢃ0.08 mm3, ortho-
˚
rhombic, Pbca, a¼13.285(3), b¼16.608(3), c¼9.411(2) A,
V¼2067.4(7) A , rcalcd¼1.525 g cmꢁ3, Z¼8, m(Cu Ka)¼
3
˚
6.259 cmꢁ1. Mac Science MXC3KHF diffractometer with
graphite-monochromated
Cu
Ka
radiation
(l¼
4.7. Reaction of trithiolane 7 with triphenylphosphine
ꢀ
ꢀ
˚
1.54178 A), q/2q scans method in the range 3 <2q<140
(0<h<16, 0<k<20, 0<l<11), 1938 independent reflections.
Absorption correction was done by the psi-scan method.48
The structure was solved with a direct method (SIR9746)
and refined with full-matrix least-squares (SHELXL-9747)
using all independent reflections, where nonhydrogen atoms
were refined anisotropically. Hydrogen atoms were placed
by calculation. R1¼0.0862 (I>2sI, 1907 reflections),
A solution of triphenylphosphine (26.2 mg, 0.10 mmol) in
CDCl3 (1.5 mL) was added dropwise to a solution of trithio-
lane 7 (21.6 mg, 0.10 mmol) in CDCl3 (1 mL) under argon at
room temperature. The mixture was stirred for 5 h at room
temperature. To 0.5 mL of the mixture, was added 10.6 mg
(0.029 mmol) of 1,2,3,4-tetraphenyl-1,3-cyclopentadiene
as the internal standard. The 1H NMR spectrum of the
mixture showed the formation of 0.022 mmol (22%) of
cis-episulfide 2327 together with 0.075 mmol (75%) of 7.
wR2¼0.2264 (for all), GOF¼1.146, 119 paramꢁet3ers; max/
˚
min residual electron density¼1.947/ꢁ0.709 eA
.
CCDC-299893 (18) and CCDC-299892 (19) contain the sup-
plementary crystallographic data. These data can be obtained
free of charge at www.ccdc.cam.ac.uk/conts/retrieving.
html or from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1EZ, UK [Fax: (internat.)
+44 1223 336 033; e-mail: deposit@ccdc.cam.ac.uk].
Acknowledgements
This work was supported by the Innovative Research Orga-
nization, Saitama University (A04-64 and A05-23).
4.3.9. rel-(1R,8R,9R,11R)-9,10,11-Trithiabicyclo[6.3.0]-
1
undecane 9,11-dioxide (20). H NMR (ꢁ20 ꢀC) d 3.72–
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