Elucidation of the stereochemistry of thiirane formation from a 1λ4,2-dithietane bearing two chiral carbon centers

Article abstract of DOI:10.1002/hc.20630

A tetracoordinated sulfurane bearing a 1λ⁴,2-dithietane moiety, whose 3- and 4-positions were chiral carbon centers, was synthesized. Its thermolysis gave the corresponding thiirane as a single diastereomer, whose configuration and stereochemis

Full text of DOI:10.1002/hc.20630

Heteroatom Chemistry
Volume 21, Number 6, 2010
Elucidation of the Stereochemistry of Thiirane
4
Formation from a 1λ ,2-Dithietane Bearing
Two Chiral Carbon Centers
Shinpei Kusaka, Naokazu Kano, and Takayuki Kawashima
Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-0033, Japan
Received 24 April 2010; revised 28 June 2010
nated sulfurane bearing the Martin ligand [3] and a
ABSTRACT: A tetracoordinated sulfurane bearing
four-membered ring, gave the oxirane with retention
a 1λ4,2-dithietane moiety, whose 3- and 4-positions
of the relative configuration, suggesting the ligand-
were chiral carbon centers, was synthesized. Its ther-
coupling mechanism [2]. In contrast, the oxirane
molysis gave the corresponding thiirane as a single
with inversion of configuration was obtained upon
diastereomer, whose configuration and stereochem-
heating in the presence of lithium bromide, which in-
ꢀ
C
istry were determined.
2010 Wiley Periodicals, Inc.
duced a heterolytic cleavage of the S(IV) O bond [2].
We also reported the synthesis of the sulfur-
substituted sulfurane 1 bearing a 1λ4,2-dithietane
moiety, whose thermolysis gave the correspond-
ing cyclic sulfenate and triphenylthiirane [4]
(Scheme 1).
Heteroatom Chem 21:412–417, 2010; View this article on-
line at wileyonlinelibrary.com. DOI 10.1002/hc.20630
INTRODUCTION
This reaction seems to proceed via the ligand-
coupling mechanism. However, this is not certain
because the product is the same as that from the
other reaction mechanism. In addition, it might pro-
ceed via the latter reaction mechanism considering
the polarized apical bonds.
The reaction mechanism can be determined by
ascertaining whether the relative configuration of
the resulting thiirane is retained or inverted. To dis-
tinguish between the two mechanisms, it is neces-
sary to introduce another chiral center to the 3-
position. In this paper, we wish to report the synthe-
sis and thermolysis of 1λ4,2-dithietane bearing chiral
carbon centers at both the 3- and 4-positions.
Tetracoordinated sulfuranes are usually thermally
unstable and easily reduced to divalent sulfur com-
pounds with the loss of two ligands. In general,
two mechanisms are considered for such a reac-
tion. One is a concerted reductive elimination of two
ligands, which is called a ligand coupling. The other
is ligand dissociation to form a sulfonium salt fol-
lowed by a nucleophilic attack on another ligand by
the dissociated ligand. Although the ligand-coupling
mechanism is common in the chemistry of hyper-
valent organosulfur compounds [1], some reactions
have been reported to proceed via the latter reac-
tion mechanism [2]. We reported previously that the
thermolysis of a 1,2λ6-oxathietane, a pentacoordi-
RESULTS AND DISCUSSION
Correspondence to: Naokazu Kano; e-mail: kano@chem.s.u
-tokyo.ac.jp. Takayuki Kawashima; e-mail: takayuki@chem.s.u
-tokyo.ac.jp.
A tetracoordinated 1λ4,2-dithietane bearing the Mar-
tin ligand and two chiral carbon centers at the 3-
and 4-positions was synthesized from benzyl sulfide
4, according to the method reported previously [4],
Contract grant sponsor: Global COE program from the Japan
Society for the Promotion of Science.
c
ꢀ
2010 Wiley Periodicals, Inc.
412

Elucidation of the Stereochemistry of Thiirane Formation from a 1λ4,2-Dithietane Bearing Two Chiral Carbon Centers 413
SCHEME 1 Thermolysis of 1λ4,2-dithietane 1.
and obtained as a mixture of two diastereomers, 9a
and 9b (Scheme 2).
A single diastereomer of β-(acetylthio)alkyl sul-
fide 6b was successfully separated by repeated re-
crystallization of the diastereomer mixture from
pentane and methanol, and its configuration was de-
termined by X-ray crystallographic analysis (Fig. 1;
Table 1). The configuration of the α- and β-positions
of the alkyl group of 6b was (S,R) or (R,S), both of
which existed in the unit cell of a single crystal as
two independent molecules.
FIGURE 1 ORTEP drawing of 6b (thermal ellipsoid plot with
1λ4,2-Dithietane 9b was synthesized from 6b as
a single diastereomer by the same method as that
shown in Scheme 2. In the synthetic scheme from
6–9, the relative stereochemistry of all the reactions
must be retained, and thus the configuration of 9b
must be identical to that of 6b.
50% probability)
butyl)thiobenzophenone and phenyldiazomethane
[5].
Because it was difficult to determine the con-
figuration of 10a spectroscopically, we determined
the configuration as follows: To begin, a thiirane
was stereospecifically converted to the correspond-
ing olefin. Next, the geometry of the olefin was
determined. That is, thiirane 10a was converted
to olefin 11a in good yield by reaction with tri-
irondodecacarbonyl (Scheme 3), which is known
to proceed with retention of configuration [6]. The
geometry of the olefin was determined to be the
E-configuration by comparison of its 1H and 13C
NMR spectra with that of an authentic sample
of (E)-1-(4-(tert-butyl)phenyl)-1,2-diphenylethylene
Although sufficient amounts of
a
single
diastereomer of 9b could not be prepared, the
other diastereomer, 1λ4,2-dithietane 9a, was suc-
cessfully separated by repeated recrystallization of
a diastereomeric mixture from carbon tetrachlo-
ride and hexane. Thiirane 10a was obtained and
isolated with 94% yield in the thermolysis of 9a in
toluene (Scheme 3). Formation of thiirane 10a was
1
confirmed by comparison of its H NMR spectrum
with that of one of the two diastereomers, which
were synthesized as authentic samples from 4-(tert-
SCHEME 2 Synthetic pathway for 1λ4,2-dithietane 9.
Heteroatom Chemistry DOI 10.1002/hc

414 Kusaka, Kano, and Kawashima
TABLE 1 Crystal Data and Refinement Details for 6b
Empirical formula
Formula weight
Crystal system
Space group
C41H46F6O2S2Si
776.99
Triclinic
P-1
Unit cell dimensions
˚
a (A)
12.661(4)
12.899(4)
˚
b (A)
˚
c (A)
26.178(7)
71.504(14)
74.200(15)
78.597(16)
3872(2)
4
α (◦)
β (◦)
γ (◦)
SCHEME 4 Alternative synthesis of 11a.
3
˚
V (A )
Z
EXPERIMENTAL
Dc (mg m−3
)
1.333
Absorption coefficient (mm−1) 0.232
All reactions were performed under argon atmo-
sphere unless otherwise noted. Solvents were dried
by standard methods and freshly distilled prior to
use. Preparative gel permeation liquid chromatog-
raphy (GPC) was performed by LC-908-C60 with
JAIGEL 1H and 2H columns (Japan Analytical In-
dustry) with chloroform as solvent. Silica-gel wet
column chromatography was performed by Wako-
gel C-200. The melting point was determined on a
Yanaco micromelting point apparatus and was un-
F (0 0 0)
1632
Crystal size (mm)
0.30 × 0.10 × 0.10
θ range (◦)
3.08–25.00
Reflections collected
Independent reflections
Data/restraint/parameter
Goodness-of-fit on F2
Final R indices [I > 2σ(I )]
R indices (all data)
25449
13307
13307/0/955
0.983
R1 = 0.0647, wR2 = 0.1238
R1 = 0.1628, wR2 = 0.1788
1
corrected. H (400 MHz) and 19F (376 MHz) NMR
11a, which was synthesized alternatively by Suzuki
coupling using (E)-diphenylbromoethylene and
4-(tert-butyl)phenylboronic acid (Scheme 4) [7].
Therefore, it was shown that the relative stereochem-
istry was retained in the formation of thiirane 10a
from 1λ4,2-dithietane 9a, indicating that the thiirane
formation proceeded via the ligand-coupling mech-
anism.
spectra were recorded on a JEOL JNM-AL400 spec-
trometer using tetramethylsilane as an internal stan-
dard and trifluoroacetic acid as an external stan-
dard, respectively.13C (126 MHz) NMR spectra were
recorded on a Bruker-DRX500 spectrometer using
residual chloroform as an internal standard. High-
resolution mass spectral data were recorded on a
JEOL JMS-700MS station mass spectrometer. X-ray
crystallographic analysis was performed by Rigaku
MERCURY CCD spectrometer. Elemental analysis
was carried out at the Microanalytical Laboratory of
Department of Chemistry, Faculty of Science, The
University of Tokyo.
In conclusion, we achieved the synthesis of 1λ4,2-
dithietane 9, whose relative stereochemistry was re-
tained in its thermolysis. This result indicates that
the reaction mechanism for the thermolysis of 9 is
ligand coupling. It is interesting that the sulfuranes
featuring the four-membered structure showed the
same reactivity, ligand coupling, despite a change in
the contained heteroatom, even though the hyperva-
lent S(IV)–S(II) bond is very labile [8].
Synthesis of β-Alkoxyalkyl Sulfide 5
Lithium diisopropylamide (LDA) was prepared
from diisopropylamine (3.0 mL, 20 mmol) and
n-butyllithium (1.57 M in hexane, 15 mL, 24 mmol)
in THF (10 mL) at −78◦C, which was added drop-
wise to a THF solution (30 mL) of benzyl sulfide
4 [3] (10.0 g, 20.8 mmol) at −78◦C, and it was
stirred for 10 min. A THF solution (10 mL) of 4-
(tert-butyl)benzophenone [9] (5.2 g, 22 mmol) was
added to the reaction mixture and further stirred
for 30 min. After quenching with aqueous ammo-
nium chloride, the solution was warmed to room
temperature, extracted with chloroform, and dried
over anhydrous magnesium sulfate. After removal of
the solvent under reduced pressure, separation of the
SCHEME 3 Thermolysis of 9a and desulfurization of 10a.
Heteroatom Chemistry DOI 10.1002/hc

Elucidation of the Stereochemistry of Thiirane Formation from a 1λ4,2-Dithietane Bearing Two Chiral Carbon Centers 415
crude material with silica-gel column chromatogra-
6. White solid: mp 143.0–144.5◦C (decomp);
Anal. Calcd for C41H46F6O2S2Si: C, 63.38; H, 5.97.
Found; C, 63.30; H, 6.06%.
6a. H NMR (400 MHz, CDCl3) δ: 0.05 (s, 3H),
0.09 (s, 3H), 0.83 (s, 9H), 1.28 (s, 9H), 2.14 (s, 3H),
phy (hexane:chloroform = 3:1) gave a 10:9 diastereo-
mer mixture of 5a and 5b (11.8 g, 79%).
5. mp. 136.5–138.5◦C; Anal. Calcd for
C39H44F6O2SSi: C, 65.16; H, 6.17. Found; C,
65.21; H, 6.43%.
1
6.24 (s, 1H), 6.86–7.40 (m, 16H), 7.55 (d, J = 8.6 Hz,
1
1
5a. H NMR (400 MHz, CDCl3) δ: 0.14 (s, 3H),
2H); 13C{ H} NMR (126 MHz, CDCl3) δ: −2.47 (s),
0.18 (s, 3H), 0.75 (s, 9H), 1.30 (s, 9H), 3.08 (s, 1H),
−2.36 (s), 19.39 (s), 26.22 (s), 31.09 (s), 31.23 (s),
2
5.37 (s, 1H), 6.88–7.46 (m, 16H), 7.55 (d, J = 8.6
34.34 (s), 56.79 (s), 69.00 (s), 83.00 (sept, JCF
=
1
1
Hz, 2H);13C{ H} NMR (126 MHz, CDCl3) δ: −2.09
30.3 Hz), 122.70 (q, JCF = 291.0 Hz), 122.76 (q,
1 JCF = 290.4 Hz), 123.45 (s), 123.76 (s), 126.76 (s),
126.91 (s), 127.34 (s), 127.76 (s), 128.42 (s), 129.07
(br s), 129.60 (s), 130.07 (s), 130.34 (s), 130.90 (s),
131.37 (s), 138.78 (s), 138.92 (s), 139.11 (s), 149.36
(s), 194.26 (s). Two peaks of quaternary carbons
overlapped at δ 138.92; 19F NMR (376 MHz, CDCl3)
δ: −70.92 (br q, 4 JFF = 9.8 Hz, 3F), −70.60 (br s, 3F).
6b.1H NMR (400 MHz, CDCl3) δ: 0.03 (s, 3H),
0.08 (s, 3H), 0.82 (s, 9H), 1.33 (s, 9H), 2.11 (s, 3H),
6.16 (s, 1H), 6.86–7.40 (m, 16H), 7.59 (d, J = 8.6 Hz,
(s), −1.49 (s), 14.12 (s), 19.49 (s), 26.16 (s), 31.31
2
(s), 61.88 (s), 80.69 (s), 83.10 (sept, JCF = 29.6 Hz),
1
1
122.79 (q, JCF = 291.0 Hz), 122.95 (q, JCF = 291.2
Hz), 123.72 (s), 125.03 (s), 125.80 (s), 126.24 (s),
126.80 (s), 127.24 (s), 127.30 (s), 127.48 (s), 128.30
(br s), 128.92 (s), 129.45 (s), 129.94 (s), 130.46 (s),
137.01 (s), 137.59 (s), 141.83 (s), 144.57 (s), 149.93
4
(s); 19F NMR (376 MHz, CDCl3) δ: −72.29 (q, JFF
=
8.6 Hz, 3F), −71.37 (q, 4 JFF = 8.6 Hz, 3F).
5b.1H NMR (400 MHz, CDCl3) δ: 0.10 (s, 3H),
0.17 (s, 3H), 0.79 (s, 9H), 1.20 (s, 9H), 3.09 (s, 1H),
5.24 (s, 1H), 6.88–7.46 (m), 7.59 (d, J = 7.8 Hz, 2H);
1
2H);13C{ H} NMR (126 MHz, CDCl3) δ: −2.36 (s),
−2.29 (s), 19.43 (s), 26.29 (s), 31.18 (s), 31.28 (s),
13C{ H} NMR (126 MHz, CDCl3) δ: −2.13 (s), −1.63
34.49 (s), 56.64 (s), 68.68 (s), 83.27 (sept, JCF
=
1
2
1
(s), 19.49 (s), 22.65 (s), 26.19 (s), 31.23 (s), 62.43 (s),
30.3 Hz), 122.70 (q, JCF = 291.0 Hz), 122.80 (q,
1 JCF = 291.0 Hz), 123.77 (s), 123.97 (s), 126.41 (s),
126.62 (s), 126.84 (s), 127.39 (s), 128.15 (s), 129.05
(br s), 130.20 (s), 130.78 (s), 130.48 (s), 130.66 (s),
131.41 (s), 135.74 (s), 139.27 (s), 139.48 (s), 142.68
(s), 150.76 (s), 194.53 (s);19F NMR (376 MHz, CDCl3)
δ: −70.48 (br s, 3F), −71.11 (q, 4 JFF = 9.6 Hz, 3F).
2
80.98 (s), 83.62 (sept, JCF = 29.6 Hz), 123.69 (s),
124.42 (s), 125.57 (s), 126.42 (s), 126.86 (s), 126.93
(s), 127.13 (s), 127.98 (s), 128.40 (br s), 128.74 (s),
129.16 (s), 129.71 (s), 130.35 (s), 137.42 (s), 138.18
(s), 141.44 (s), 144.78 (s), 149.49 (s). Peaks of CF3
could not be assigned due to overlapping of the peaks
of 5a; 19F NMR (376 MHz, CDCl3) δ: −71.94 (m, 3F),
−71.82 (m, 3F).
Deprotection of the TBDMS Group of 7
To a THF solution (10 mL) of 6 (1.00 g, 1.28 mmol),
tetrabutylammonium fluoride (1 M in THF, 1.30
mL, 1.30 mmol) was added and the solution was
stirred at 0◦C for 15 min. The reaction mixture was
quenched with aqueous ammonium chloride, ex-
tracted with chloroform, and dried over anhydrous
magnesium sulfate. After removal of the solvent un-
der reduced pressure, separation by silica-gel col-
umn chromatography (chloroform) gave 7 (0.85 g,
100%) as a diastereomer mixture.
Synthesis of β-(Acetylthio)alkyl Sulfide 6
To a THF solution (30 mg) of 5 (6.7 g, 9.3 mmol),
n-butyllithium (1.57 M in hexane, 6.1 mL, 9.6 mmol)
and chlorodiphenylphosphine (1.7 mL, 9.3 mmol)
were added dropwise at −78 ◦C, and the solu-
tion was stirred for 14 h with gradual warming
to room temperature. Solvent was removed un-
der reduced pressure, and the residue was dis-
solved in dichloromethane (30 mL), treated with 2,6-
dimethyl-1,4-benzoquinone (1.27 g, 9.3 mmol), and
stirred for 10 h. Thioacetic acid (1.7 mL, 18 mmol)
was added to the solution at 0◦C, and the solution
was stirred for 2 days at room temperature. The re-
action mixture was quenched with aqueous sodium
hydrocarboxylate, extracted with chloroform, and
dried over anhydrous magnesium sulfate. After re-
moval of the solvent under reduced pressure, sep-
aration by silica-gel column chromatography (hex-
ane:chloroform = 2:1) and then by GPC gave a 10:9
diastereomer mixture of 6a and 6b (1.85 g, 26%).
7. White solid: mp 157.0–159.0◦C (decomp);
Anal. Calcd for C35H32F6O2S2: C, 63.43; H, 4.87.
Found; C, 63.27; H, 5.07%.
1
7a. H NMR (400 MHz, CDCl3) δ: 1.35 (s, 9H),
2.10 (s, 3H), 6.16 (s, 1H), 6.73 (d, J = 7.4 Hz,
1
2H), 7.02–7.61 (m, 16H), 7.74 (s, 1H).13C{ H} NMR
(126 MHz, CDCl3) δ: 31.26 (s), 34.55 (s), 61.64 (s),
68.19 (s), 124.18 (s), 127.17 (s), 127.30 (s), 127.53
(s), 127.96 (s), 128.16 (s), 128.80 (s), 129.07 (br s),
129.88 (s), 130.37 (s), 131.03 (s), 133.64 (s), 135.07
(s), 136.33 (s), 137.66 (s), 141.61 (s), 151.38 (s),
193.76 (s). The C(CF3)2 and CF3 peaks could not be
Heteroatom Chemistry DOI 10.1002/hc

416 Kusaka, Kano, and Kawashima
Synthesis of 1λ4,2-Dithietane 9
assigned due to overlapping with the peaks of 7b.
Two peaks at δ 130.37 were overlapped. 19F NMR
4
To a carbon tetrachloride solution (20 mL) of 8 (0.55
g, 0.89 mmol), a carbon tetrachloride suspension
(10 mL) of NBS (0.16 g, 0.90 mmol) and then tri-
ethylamine (0.13 mL, 0.93 mmol) were sequentially
(376 MHz, CDCl3) δ: −76.51 (q, JFF = 8.6 Hz, 3F),
−76.24 (q, 4 JFF = 8.6 Hz,3F).
1
7b. H NMR (400 MHz, CDCl3) δ: 1.33 (s, 9H),
2.12 (s, 3H), 6.21 (s, 1H), 6.72 (d, J = 7.4 Hz,
◦
added at 0 C. The reaction mixture was stirred for
2H), 7.02–7.38 (m, 13H), 7.45 (d, J = 8.5 Hz, 2H),
1
7.54 (d, J = 7.3 Hz, 1H), 7.67 (s, 1H). 13C{ H}
5 min and filtered through Celite. Recrystallization
from carbon tetrachloride and hexane gave 9 (0.25
g, 45%) as a diastereomer mixture.
NMR (126 MHz, CDCl3) δ: 31.16 (s), 31.20 (s),
2
34.47 (s), 61.53 (s), 68.21(s), 80.53 (sept, JCF
=
9. mp. 88.8–89.8◦C (decomp); HRMS (FAB+, ma-
trix = PEG600 and m-nitrobenzyl alcohol) m/z calcd
for C33H29 F6OS2[M + H+] 619.1564, found: 619.1566.
1
29.6 Hz), 122.60 (q, JCF = 287.9 Hz), 122.80 (q,
1 JCF = 286.6 Hz), 124.18 (s), 127.25 (s), 127.30 (s),
127.95 (s), 128.10 (s), 128.26 (s), 128.63 (s), 129.10
(br s), 129.85 (s), 130.01 (s), 130.72 (s), 130.92 (s),
134.00 (s), 135.92 (s), 137.71 (s), 138.30 (s), 138.40
(s), 150.35 (s), 193.75 (s). 19F NMR (376 MHz, CDCl3)
1
9a. H NMR (400 MHz, CDCl3) δ: 1.22 (s, 9H),
6.80 (s, 1H), 7.0–7.7 (m, 17H), 8.31 (d, J = 8.0
1
Hz, 1H).13C{ H} NMR (126 MHz, CDCl3) δ: 31.15
1
4
4
(s), 34.22 (s), 60.09 (s), 95.32 (s), 122.86 (q, JCF
=
δ: −76.56 (q, JFF = 8.7 Hz, 3F), −76.10 (q, JFF
=
1
289.0 Hz), 122.91 (q, JCF = 289.1 Hz), 124.43 (s),
126.39 (s), 126.44 (s), 126.79 (s), 127.67 (s), 128.00
(s), 128.55 (s), 128.96 (s), 130.46 (s), 130.58 (s),
132.18 (s), 132.58 (s), 132.75 (s), 134.50 (s), 134.93
(s), 140.01 (s), 148.07 (s), 149.68 (s). The peak of
C(CF3)2 could not be observed due to low intensity
8.7 Hz, 3F).
Synthesis of β-Mercaptoalkyl Sulfide 8
To a methanol solution (50 mL) of 7 (0.85 g,
1.3 mmol), 12 M HCl (15 mL) was added and the
solution was stirred at 95◦C for 5 h. After removal of
the solvent under reduced pressure, purification by
GPC gave 8 (0.55 g, 69%) as a diastereomer mixture.
8. mp. 125.4–126.5◦C; MS (FAB+, matrix =
m-nitrobenzyl alcohol) m/z 587 [M – SH].
of the peak. 19F NMR (376 MHz) δ −78.50 (q, 4 JFF
=
8.7 Hz, 3F), −76.54 (q, 4 JFF = 8.7 Hz, 3F).
1
9b. H NMR (400 MHz, CDCl3) δ: 1.17 (s, 9H),
6.85 (s, 1H), 7.0–7.7 (m, 17H), 8.39 (d, J = 8.0 Hz,
1
1H).13C{ H} NMR (126 MHz, CDCl3) δ: 31.17 (s),
34.24 (s), 59.07 (s), 94.72 (s), 124.83 (s), 127.57
(s), 128.44 (s), 129.22 (s), 130.13 (s), 132.27 (s),
132.47 (s), 134.11 (s), 134.99 (s), 143.49 (s), 144.76
(s), 149.15 (s). Other peaks could not be assigned
due to overlapping with the peaks of 1a.19F NMR
1
8a. H NMR (400 MHz, CDCl3) δ: 1.28 (s, 9H),
2.73 (s, 1H), 5.42 (s, 1H), 6.86 (d, J = 7.8 Hz, 2H),
1
6.98–7.62 (m, 16H), 7.77 (s, 1H). 13C{ H} NMR (126
MHz, CDCl3) δ: 31.17 (s), 34.39 (s), 62.76 (s), 67.68
4
(376 MHz) δ −78.54 (q, JFF = 8.7 Hz, 3F), −76.77
2
1
(s), 80.56 (sept, JCF = 29.6 Hz), 122.63 (q, JCF
=
(q, 4 JFF = 8.7 Hz, 3F).
1
288.2 Hz), 122.82 (q, JCF = 287.5 Hz), 125.06 (s),
127.41 (s), 127.63 (s), 127.83 (s), 127.93 (s), 128.17
(s), 128.90 (s), 129.17 (s), 130.29 (s), 129.89 (s),
131.17 (s), 133.96 (s), 136.37 (s), 137.03 (s), 140.98
(s), 141.67 (s), 150.41 (s). One aromatic carbon peak
could not be assigned due to overlapping. 19F NMR
Thermolysis of 1λ4,2-Dithietane 9a
A CDCl3 solution (0.5 mL) of 9a (4 mg, 6.5 μmol)
with a few amounts of mesitylene as an internal stan-
dard in an NMR tube was degassed by freeze–pump–
thaw cycle for five times and then sealed. The NMR
tube was heated at 55◦C for 110 min. NMR measure-
ments were conducted after cooling down to room
temperature. Cyclic sulfenic ester 2 and 10a was ob-
served at 91% and 88% yields, respectively. The yield
for 2 was calculated from an integral ratio of the
peak of 2 with those of all measurable peaks in 19F
NMR, and the yield of 10a was calculated from com-
parison of the peak integration of 10a with that of
an aromatic peak of mesitylene.
Alternatively, a toluene (5 mL) solution of 9a (25
mg, 40 mmol) was heated at 80◦C for 30 min, and
then the solvent was removed. Purification of the
residue by silica-gel column chromatography (hex-
ane:chloroform = 2:1) gave 10a (13 mg, 94%).
4
(376 MHz, CDCl3) δ: −76.61 (q, JFF = 8.7 Hz, 3F),
−76.08 (q, 4 JFF = 8.7 Hz,3F).
1
8b. H NMR (400 MHz, CDCl3) δ: 1.37 (s, 9H),
2.74 (s, 1H), 5.39 (s, 1H), 6.91 (d, J = 7.3 Hz, 2H),
1
6.98–7.62 (m, 16H), 7.82 (s, 1H). 13C{ H} NMR (126
MHz, CDCl3) δ: 31.26 (s), 34.50 (s), 62.99 (s), 67.82
2
1
(s), 80.59 (sept, JCF = 29.4 Hz), 122.65 (q, JCF
=
1
288.2 Hz), 122.84 (q, JCF = 287.7 Hz), 124.76 (s),
127.25 (s), 127.45 (s), 127.74 (s), 127.84 (s), 128.25
(s), 128.96 (s), 129.15 (s), 129.41 (s), 129.82 (s),
131.08 (s), 133.91 (s), 136.55 (s), 137.17 (s), 139.33
(s), 144.07 (s), 150.75 (s). One peak could not be
assigned due to overlapping. 19F NMR (376 MHz,
4
CDCl3) δ: −76.68 (q, JFF = 8.3 Hz, 3F), −75.67 (q,
4 JFF = 8.3 Hz,3F).
Heteroatom Chemistry DOI 10.1002/hc

Elucidation of the Stereochemistry of Thiirane Formation from a 1λ4,2-Dithietane Bearing Two Chiral Carbon Centers 417
3.8 mmol), potassium hydroxide (50 mg, 89 mmol),
triphenylphosphine (4.5 mg, 17 μmol), and PdCl2
(3.5 mg, 20 μmol), and the reaction mixture was
stirred at room temperature for 1 h. It was extracted
with ether, washed with aqueous potassium hydrox-
ide, and dried over anhydrous magnesium sulfate.
After removal of the solvent, purification by silica-
gel column chromatography (hexane) gave 11a (41
mg, 38%).
Alternative Synthesis of a Diastereomer Mixture
of Thiiranes 10a and 10b
A
toluene (20 mL) solution of 4-(tert-butyl)
benzophenone (1.32 g, 5.59 mmol) and the Lawes-
son’s reagent (1.50 g, 3.71 mmol) was stirred
at 85◦C for 4.5 h. After removal of the sol-
vent, purification by silica-gel column chromatog-
raphy (hexane:chloroform = 2:1) gave 4-(tert-butyl)
thiobenzophenone (1.37 g, <99%), which was used
without further purification.
1
11a. H NMR (400 MHz, CDCl3) δ: 1.34 (s, 9H),
1
6.97 (s, 1H), 6.99–7.38 (m, 14H).13C{ H} NMR (126
A
toluene (15 mL) solution of 4-(tert-
MHz, CDCl3) δ: 31.29 (s), 34.52 (s), 125.11 (s), 126.56
(s), 127.12 (s), 127.29 (s), 127.43 (s), 127.91 (s),
128.58 (s), 129.48 (s), 130.33 (s), 137.46 (s), 140.36
(s), 140.42 (s), 142.29 (s), 150.58 (s).
butyl)thiobenzophenone (1.02 g, 4.02 mmol)
was treated with a toluene (60 mL) solution of
phenyldiazomethane at 85◦C for 30 min, which was
prepared by reported procedure [10] from sodium
hydroxide (2.0 g, 50 mmol), benzyltrimethyl-
ammonium chloride (20 mg, 0.18 mmol), and
benzaldehyde tosylhydrazone (1.57 g, 5.75 mmol).
After removal of the solvent under reduced pressure,
purification from silica-gel column chromatography
(hexane:chloroform = 2:1) gave a 1:1 diastereomer
mixture of thiiranes 10a and 10b (1.18 g, 85%).
10. mp. 135.0–137.0◦C (decomp).
Crystallographic data for 6b have been de-
posited with Cambridge Crystallographic Data
Center (CCDC) as supplementary crystallographic
number CCDC 773607. These data can be ob-
tained free of charge via www.ccdc.cam.ac.uk/conts/
retrieving.html (or from the Cambridge Crystal-
lographic Data Centre, 12, Union Road, Cam-
bridge CB2 1EZ, UK; fax: +44 1223 336033; or
deposit@ccdc.cam.ac.uk).
1
10a. H NMR (400 MHz, CDCl3) δ: 1.29 (s, 9H),
1
4.66 (s, 1H), 7.05–7.38 (m, 14H).13C{ H} NMR (126
MHz, CDCl3) δ: 31.26 (s), 34.44 (s), 50.92 (s), 60.31
(s), 125.26 (s), 126.97 (s), 127.24 (s), 127.33 (s),
127.40 (s), 127.67 (s), 129.04 (s), 131.01 (s), 135.76
(s), 138.37 (s), 141.67 (s), 150.14 (s).
ACKNOWLEDGMENTS
We thank Tosoh Finechem Corp., Shin-etsu Chemi-
cal Co., Ltd., and Central Glass Co., Ltd., for gifts of
alkyllithiums, silicon compounds, and fluorine com-
pounds, respectively.
10b. 1H NMR (400 MHz) δ: 1.21 (s, 9H), 4.62 (s,
1
1H), 7.00–7.48 (m, 14H); 13C{ H} NMR (126 MHz,
CDCl3) δ: 31.23 (s), 34.34 (s), 50.94 (s), 60.35 (s),
124.30 (s), 127.11 (s), 127.21 (s), 127.59 (s), 127.86
(s), 128.26 (s), 129.08 (s), 130.41 (s), 135.20 (s),
135.79 (s), 144.96 (s), 149.89 (s).
REFERENCES
[1] Ogawa, S.; Matsunaga, Y.; Sato, S.; Erata, T.; Fu-
rukawa, N. Tetrahedron Lett 1992, 33, 93–96, and
references therein.
[2] Kawashima, T.; Ohno, F.; Okazaki, R.; Ikeda, H.;
Inagaki, S. J Am Chem Soc 1996, 118, 12455–12456.
[3] Perozzi, E. F.; Martin, J. C. J Am Chem Soc 1979,
101, 1591–1593.
[4] Kano, N.; Itoh, Y.; Watanabe, Y.; Kusaka, S.;
Kawashima, T. Angew Chem, Int Ed 2008, 47, 9430–
9433.
[5] For an example of a thiirane formation by a reaction
of a diazomethane and a thioketone, see Katada, T.;
Eguchi, S.; Sasaki, T. J Chem Soc, Perkin Trans 1
1984, 11, 2641–2647.
Desulfurization of Thiirane 10a
Thiirane 10a (18 mg, 52 μmol) and triirondo-
decacarbonyl (10 mg, 20 μmol) were dissolved in
benzene (5 mL) and stirred at 70◦C for 5 h. After
removal of the solvent under reduced pressure,
purification by silica-gel column chromatography
(hexane) gave 11a (15 mg, 92%).
Alternative Synthesis of (E)-1-(4-(Tert-
butyl)phenyl)-1,2-diphenylethylene 11a
[6] Trost, B. M.; Ziman, S. D. J Org Chem 1973, 38, 932–
936.
[7] Nunes, C. M.; Steffens, D.; Monteiro, A. L. Synlett
2007, 103–106.
[8] Gombler, W. Z Anorg Allg Chem 1978, 439, 193–206.
[9] Butler, J. C.; Ferstandig, L. L.; Clark, R. D. J Am Chem
Soc 1953, 76, 1906–1908.
[10] Sivaguru, J.; Sunoj, R. B.; Wada, T.; Origane, Y.;
Inoue, Y.; Ramamurthy, V. J Org Chem 2004, 69,
6533–6547.
To a 1:1 methanol-THF (10 mL) solution of meso-
1,2-dibromo-1,2-diphenylethane (0.12 g, 3.5 mmol),
potassium carboxylate (0.10 g, 7.2 mmol) at room
temperature was added and the solution was stirred
for 14 h. The reaction mixture was filtered off,
treated with 4-(tert-butyl)phenylboronic acid (68 mg,
Heteroatom Chemistry DOI 10.1002/hc