Catalytic asymmetric sulfimidation of 1,3-dithianes

Article abstract of DOI:10.1039/a802915f

A direct catalytic sulfimidation of 1,3-dithianes to the corresponding chiral monosulfimides with N-(p-tolylsulfonyl)imino(phenyl)iodinane (TsN=IPh) using a catalytic amount of copper(I) triflate (CuOTf) and a chiral 4,4′-disubstituted bis(oxazoline) as l

Full text of DOI:10.1039/a802915f

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Catalytic asymmetric sulfimidation of 1,3-dithianes
Yoshihiro Miyake, Hiroya Takada, Kouichi Ohe and Sakae Uemura*
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering,
Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
A direct catalytic sulfimidation of 1,3-dithianes to the corresponding chiral monosulfimides with
N-(p-tolylsulfonyl)imino(phenyl)iodinane (TsN᎐IPh) using a catalytic amount of copper(I) triflate
᎐
(
CuOTf) and a chiral 4,4Ј-disubstituted bis(oxazoline) as ligand has been developed. The reaction
affords the chiral monosulfimides in good yield and with moderate enantioselectivity (up to 40% ee).
a
Table 1 Asymmetric sulfimidation of 1,3-dithiane 5
Introduction
Organosulfur compounds have long been known to be useful
and important in organic synthesis. 1,3-Dithianes, the typical
thioacetals, have been extensively used as acyl anion equivalents
because they can be prepared easily by masking the carbonyl
Entry
T/ЊC
t/h
Ligand
Yield (%)
Ee (%)
1
2
3
4
5
6
r.t
r.t
r.t
0
0
0
0
0
0
20
20
20
—
4a
4b
4a
4a
4a
4a
4c
4d
4a
4a
4a
9
77
39
54
61
83
66
42
4
—
15
0
1
compounds with dithiols. Recently the groups of Page,
0.5
9
2
3
Aggarwal and Toru reported the synthesis of enantiomeri-
20
40
20
20
20
20
40
40
18
17
17
14
0
16
18
20
cally enriched 1,3-dithiane monoxides 1 or trans-dioxides 2 and
b
7
8
9
0
1
2
R
R
R
S
S
O
2
S
O
O
NTs
S
S
S
1
1
1
Ϫ20
Ϫ20
Ϫ20
61
76
79
1
3
a
b
the enantioselective carbon–carbon bond forming reactions
using these oxides as chiral auxiliaries as well as chiral acyl
anion equivalents. Aggarwal and co-workers have found that
compound 2 (R = H) undergoes selective addition to aromatic
aldehydes when the reactions are carried out under equilibrium
The concentration of 5 is 0.2 . The concentration of 5 is 0.1 .
sulfimidation of monosulfides, probably because of the form-
ation of a better copper() catalyst. The product also showed
optical activity; namely, asymmetric induction occurred
(Scheme 2). Typical results for the asymmetric sulfimidation of
4
control (using the Na anion of 2). On the other hand, the study
of sulfimides 3, the nitrogen analogues of sulfoxides, has hardly
5
been developed. We have recently reported a direct catalytic
TsN=IPh (1 equiv.)
sulfimidation of prochiral sulfides to chiral sulfimides with
CuOTf (5 mol%)
4 (6 mol%)
NTs
N-(p-tolylsulfonyl)imino(phenyl)iodinane (TsN᎐IPh) using a
᎐
S
S
S
NTs
+
catalytic amount of copper() triflate (CuOTf) and chiral
S
toluene
S
S
6
bis(oxazoline) ligand (Scheme 1). As a continuation of this
5
6
Scheme 2
TsN=IPh (1 equiv.)
CuOTf (5 mol%)
NTs
5
in toluene under a variety of conditions are shown in Table 1.
S
4a (6 mol%)
Bn
Nap
S *
Solvents such as dichloromethane, tetrahydrofuran (THF) and
diethyl ether were completely ineffective for this reaction. In
acetonitrile, the reaction proceeded, but no asymmetric induc-
tion occurred. As can be seen in Table 1, longer reaction times
improved the product yield, but the reaction time, the reaction
temperature and the substrate concentration did not show
much influence on the enantioselectivity of this reaction. Chiral
ligands such as diamine 4b (entry 3) and 4d (entry 9) were not
toluene
Bn
Nap
2
5 °C, 48 h
yield 75%, 71% ee
O
N
O
4
a :
N
Ph
Ph
effective at all for asymmetric induction. The Schiff base ligand
Scheme 1
7
4
e, effective for asymmetric aziridination, was completely
study, we describe herein the result of the application of this
asymmetric imidation method to 1,3-dithianes for the synthesis
of enantiomerically enriched sulfimides 3, which might be
usable as a new type of chiral auxiliary.
ineffective for this asymmetric sulfimidation. From these results
the optimum conditions for asymmetric sulfimidation were
judged to be the use of CuOTf and chiral bis(oxazoline) ligand
4a in toluene (0.2 ) at 0 ЊC for 20 h. Even under the best
conditions employed, the enantioselectivity was at most 20% ee.
There are four sites on the sulfur atoms of the 1,3-dithiane
able to attack the nitrogen of the nitrene complex; namely,
equatorial and axial lone pairs of each sulfur atom. One of our
proposed models for the orientation of the reagents (5, 4a,
Results and discussion
First, sulfimidation of 1,3-dithiane 5 with TsN᎐IPh was exam-
᎐
ined in toluene in the presence of CuOTf as catalyst. The
expected monosulfimidation product 6 was produced, but in
low yield. However, when a chiral ligand 4 was added, the
product yield was much increased, as has been observed in the
CuOTf and TsN᎐IPh) prior to imidation is shown in Fig. 1. The
᎐
enantioselectivity depends on which of the two sulfur atoms
attacks the nitrene moiety in the copper complex. Since the
J. Chem. Soc., Perkin Trans. 1, 1998
2373

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Table 2 Asymmetric sulfimidation of 2-substituted 1,3-dithianes 7
S
S
Diastereo-
mers of 8
Me
Ph
trans-8
O
O
S
NTs
Yield
Product (%)
S
a
N
Me
Cu
N
Entry Substrate
trans:cis
Ee (%)
Ph
b
1
2
3
7a R = Me
8a
8b
8c
70
57
68
94:6
100:0
100:0
40
36
32
NTs
b
7b R = Bn
b
Fig. 1 A model for the orientation of reagents
7c R = CH C H -
CH -o
2
6
4
3
c
4
5
7d R = SiMe Ph
8d
8e
35
39
100:0
100:0
5
9
2
S
c
NTs
7e R = SiMe3
S
a
1
b
Determined by H NMR analysis. Determined by HPLC using suit-
E
c
1
able chiral columns. Determined by H NMR analysis in the presence
of Eu(hfc)3.
NTs
S
S
S
S
S
S
1
.5%
TsN
NTs
13.6%
H
H
A
E′
H
N
SO2
Bn
Me
Fig. 2 Flip of the 1,3-dithiane monosulfimide
S
H
S
H
NMe2
Fig. 3 NOE spectrum of 2-benzyl-1,3-dithiane monosulfimide
O
O
O
O
N
N
N
N
TsN=IPh (1 equiv.)
CuOTf (5 mol%)
NMe2
Ph
Ph
But
But
NTs
4
a (6 mol%)
S
R
S
R
NTs
S
R
R
4
a
4b
4c
+
+
S
toluene
0
S
S
°C, 20 h
7
(S)-trans-8
(R)-trans-8
CN
O
O
+
S
R
S
N
N
S
S
NTs
N
N
NTs
H
Ph
Ph
(
R)-cis-8
(S)-cis-8
Scheme 3
sulfimide 8a comprises two diastereoisomers (trans:cis = 94:6)
entry 1), while the imidation of 7b–e resulted in exclusive
4d
4e
(
formation of the equatorial imidation products 8b–e (entries 2–
5). 2-Substituted 1,3-dithianes gave higher ees (up to 40% ee)
than 1,3-dithiane 5 as we expected (Table 2; entries 1, 2 and 3),
but the introduction of much bulkier substituents was not fruit-
ful (Table 2; entries 4 and 5). When 2-trimethylsilyl-2-methyl-
1,3-dithiane 7f and (1R,2R)-2-(1,3-dithian-2-yl)-2-methoxy-
1,7,7-trimethylbicyclo[2.2.1]heptane 7g (1,3-dithian-2-yl--
absolute configuration of the major enantiomer of the product
sulfimide is not yet known, it is not yet clear which sulfur atom
approaches the nitrene moiety. Here, we assume that the front
sulfur atom plays this role in Fig. 1 and, thus, there are two
attacking lone pairs, equatorial and axial. The products then
should be an equatorial (E) and an axial (A) isomer, respect-
5
ively. In the axial isomer A, a flip of the six-membered ring
gives the more stable equatorial isomer EЈ (Fig. 2). The isomer
EЈ is an enantiomer of the equatorial isomer E (Fig. 2) and
its formation may lower the enantioselectivity. The conform-
ational preference of the equatorial isomer 6 has already been
Me
S
S
SiMe3
S
S
MeO
5a,b
rationalized by NMR spectroscopy
and X-ray crystal-
5c
lography. From this hypothesis, we envisaged the use of suit-
ably substituted 1,3-dithianes as starting materials in order to
avoid the ring flip of the product monosulfimides. In these
cases a higher enantioselectivity might be expected. The asym-
metric sulfimidation of a variety of substituted 1,3-dithianes
was investigated next.
7g
7f
camphor) were used as substrates, the imidation itself did not
proceed. Next, we treated the 5-position substituted 1,3-
dithianes (9). The result was slightly complicated. As shown in
Scheme 4, the diastereoselectivity was higher in the case of 9b
(R = Bu ) than in that of 9a (R = Me), but there was not much
difference in the enantioselectivty of the major diastereoisomer,
t
The imidation of 2-substituted 1,3-dithiane derivatives 7 gave
the corresponding sulfimides 8 (Scheme 3). Theoretically, the
products should consist of four diastereoisomers because they
have two chiral centers, but the diastereoselectivity was very
high in this reaction, as shown in Table 2. Here, the ratio of
diastereoisomers was determined by integration of the methine
protons at the 2-position of 2-methyl-1,3-dithiane 1-tosylimide
the cis isomer. The ratio of the two isomers was determined
from the H NMR spectrum of the crude product, in which
1
the methyl protons at the 5-position of monosulfimide 10a
appeared at δ 1.13 and 1.31, respectively. Likewise, the
diastereoisomeric ratio was determined by integration of the
tert-butyl protons at the 5-position of the monosulfimide 10b,
which appeared at δ 0.93 and 0.96, each as a singlet, respect-
ively. In the case of cis-4,6-dimethyl-1,3-dithiane 11, the imid-
ation proceeded to give the corresponding chiral sulfimide with
8
a which appeared at δ 3.98 and 4.12, as a quartet, respect-
ively. The NOE spectrum (see Fig. 3) showed that the major
diastereoisomer is the trans isomer (all the substituents of these
products are present in equatorial positions). The mono-
2
374
J. Chem. Soc., Perkin Trans. 1, 1998

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TsN=IPh (1 equiv.)
CuOTf (5 mol%)
4a (6 mol%)
Disubstituted bis(oxazoline)s (4a, 4c, 4d) and Eu(hfc) were
3
–
NTs
purchased from Aldrich Chemical Co. 1,3-Dithiane 5, 2-methyl-
1,3-dithiane 7a and 2-trimethylsilyl-1,3-dithiane 7e were com-
mercial products. Other substituted 1,3-dithiane derivatives
–
R
S
R
R
S
R
R
S
NTs +
S
S
S
toluene
0 °C, 20 h
9
(
S)-cis-10
(R)-cis-10
9
9
10
10
11
(
7b, 7d, 9a, 9b, 11 ) were prepared by the reported
9
a R = Me
methods and typical procedures are shown below. N-(p-
t
9b R = Bu
Tolylsulfonyl)imino(phenyl)iodinane (TsN᎐IPh) was prepared
᎐
+
S
S
+
S
S
NTs
by the reported procedure from (diacetoxyiodo)benzene and
6b,12
NTs
R)-trans-10
toluene-p-sulfonamide.
Dichloromethane was distilled from
(
(S)-trans-10
CaH and acetonitrile and toluene were distilled from P O just
2
2
5
before use.
1
0a: yield 71%
cis : trans = 87:13, 30% ee
Typical procedure for preparation of 2-substituted 1,3-dithiane
derivatives
1
0b: yield 63%
9
cis : trans = 96:4, 31% ee
To a solution of 1,3-dithiane (1.80 g, 18 mmol) in THF (50 ml)
was added BuLi (1.6  hexane solution; 11 ml, 18 mmol) under
nitrogen at Ϫ20 ЊC. After the mixture had been stirred for 0.5 h,
it was treated with organic halide at room temperature for 18 h.
Scheme 4
TsN=IPh(1 equiv.)
CuOTf (5 mol%)
4
a (6 mol%)
The reaction mixture was diluted with aqueous NH Cl and
then extracted with diethyl ether (3 × 30 ml). The combined
S
S
4
NTs
S
S
toluene
0
°C, 20 h
organic layers were dried (MgSO ) and evaporated to give the
4
1
1
12
yield 59%, 33% ee
crude product. Purification by silica gel column chromato-
graphy gave the corresponding 2-substituted 1,3-dithiane.
2
-o-Tolylmethyl-1,3-dithiane (7c). Colorless oil, 55% yield;
eluent: n-hexane–diethyl ether = 20:1; δH 1.84–1.93 (m, 1H),
.07–2.34 (m, 1H), 2.36 (s, 3H), 2.77–2.84 (m, 4H), 3.03 (d,
J 7.4, 2H), 4.25 (t, J 7.4, 2H), 7.12–7.21 (m, 5H); δ 19.6, 25.8,
Scheme 5
2
a similar enantioselectivity to that described above (Scheme 5).
These results showed that the position, number and bulkiness of
the substituents did not much affect the enantioselectivity of
the product sulfimides.
Similar imidation was also attempted by switching from the
six-membered ring thioacetals to five- and seven-membered
C
3
0.7, 38.9, 47.9, 125.7, 127.1, 130.1, 130.4, 135.7, 136.4.
Typical procedure for preparation of 5-substituted 1,3-dithiane
10,11
and 4,6-dimethyl-1,3-dithiane derivatives
The 5-substituted and 4,6-disubstituted dithiols were prepared
from the corresponding diols. The solution of thiol (15 mmol)
and dimethoxymethane (17 mmol) in 25 ml of chloroform was
added slowly to a solution of 47% boron trifluoride–diethyl
ether complex (2 ml) and acetic acid (4 ml) in 5 ml of chloro-
form under reflux with stirring. After the addition, the reaction
mixture was stirred for a further 3 h. The solution was washed
twice with water, twice with aqueous KOH and twice again with
water. Purification by distillation or recrystallization gave the
corresponding 1,3-dithiane.
analogues such as 1,3-dithiolane 13 and 1,3-dithiepane 15
Scheme 6). Compound 13 gave the expected sulfimide 14 in
8
(
TsN=IPh (1 equiv.)
CuOTf (5 mol%)
NTs
4a (6 mol%)
S
S
S
S
toluene
0
°C, 20 h
13
14
yield 14%, 11% ee
General procedure for asymmetric sulfimidation of 1,3-dithiane
derivatives
To a solution of CuOTf (2.60 mg, 0.010 mmol) and 4,4Ј-
disubstituted bis(oxazoline) 4a (4.11 mg, 0.012 mmol) in 1.0
NTs
S
S
S
S
ml of toluene were added first TsN᎐IPh (75.0 mg, 0.200 mmol)
᎐
1
5
16
and then the 1,3-dithiane derivative (0.20 mmol). The result-
ing mixture was stirred under nitrogen at 0 ЊC for 20 h, and
then treated with saturated aqueous NaCl and extracted with
dichloromethane. The extract was dried (anhydrous MgSO4)
and evaporation of the solvent left a pale yellow oil. Purifi-
cation by silica gel column chromatography gave the corres-
ponding optically active sulfimide in a pure form as a colorless
oil which sometimes solidifies. The diastereomeric ratios (8a,
Scheme 6
1
4% yield with 11% ee, while compound 15 did not react at all
with TsN᎐IPh.
᎐
Experimental
1
General
10a, 10b) were determined by H NMR analysis (270 MHz).
1
13
H and C NMR spectra were measured on JEOL EX-400
and JNM-GSX270 spectrometers for solutions in CDCl3
Enantiomeric excesses were determined by HPLC using a
1
suitable chiral column or H NMR analysis (270 MHz) in the
with Me Si as an internal standard; J values are given in Hz.
presence of Eu(hfc) as shown below.
4
3
The following abbreviations are used: s: singlet, d: doublet,
t: triplet, q: quartet, m: multiplet. IR spectra were recorded
with a Nicolet Impact 400D FT-IR spectrometer. High-
resolution mass spectra (HRMS) were obtained with a JEOL
JMS-SX102A spectrometer. Melting points are uncorrected.
Analytical thin layer chromatographies (TLC) were performed
with silica gel 60 Merck F-254 plates. Column chromatography
N-(1,3-Dithian-1-ylidene)toluene-p-sulfonamide (6). White
solid, mp 159–161 ЊC, 61% yield; 18% ee by Daicel chiralcel OD
(25% propan-2-ol–hexane); eluent: dichloromethane; νmax-
Ϫ1
(KBr)/cm 1137 (SO ), 1397 (SO ); δ 2.26–2.69 (m, 7H), 3.09
2
2
H
(ddd, 1H), 3.28–3.41 (m, 1H), 4.00 (d, J 12.6, 1H), 4.05 (br d, J
12.6, 1H), 7.25 (d, J 8.1, 2H), 7.79 (d, J 8.1, 2H); δ 21.4, 27.7,
C
28.1, 48.4, 48.8, 126.1, 129.3, 141.3, 141.9; Anal. Calc. for
C H NO S : C, 45.65; H, 5.22; N, 4.84. Found: C, 45.41; H,
on SiO was performed with Wakogel C-300. HPLC analyses
2
11 15
2 3
were performed on an HLC-803A instrument (Tosoh) with a
UV-8011 detector at 40 ЊC. Elemental analyses were performed
at the Microanalytical Center of Kyoto University. 4,4Ј-
5.14; N, 4.74%.
N-(2-Methyl-1,3-dithian-1-ylidene)toluene-p-sulfonamide
(trans-8a). White solid, mp 172–173 ЊC (lit., 171–172 ЊC), 70%
13
J. Chem. Soc., Perkin Trans. 1, 1998
2375

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yield; 40% ee by Diacel chiralpak AS (25% propan-2-ol–
N-(5-tert-Butyl-1,3-dithian-1-ylidene)toluene-p-sulfonamide1
Ϫ1
hexane); eluent: dichloromethane; νmax(KBr)/cm 1165 (SO ),
(cis-10b). White solid, mp 116–118 ЊC, 71% yield; 31% ee by H
2
2
1
1
1
1
2
311 (SO ); δ 1.46 (d, J 6.9, 3H), 2.23–2.53 (m, 5H), 2.61 (dt, J
NMR analysis in the presence of Eu(hfc) ; eluent: dichloro-
2
H
3
2
2
Ϫ1
2.2, 1H), 2.81 (ddd, J 12.2, J 14.2 and 2.4, 1H) 3.10 (ddd, J
methane; νmax(KBr)/cm 1141 (SO ), 1391 (SO ); δ 0.93 (s,
2
2
H
2
2.7, J 13.4 and 2.9, 1H), 3.32 (dt, J 12.7, 1H), 3.99 (q, J 6.9,
H), 7.24 (d, J 8.1, 2H), 7.79 (d, J 8.1, 2H); δ 15.7, 21.1, 29.3,
9.7, 50.6, 59.0, 126.2, 129.2, 141.5, 141.7; Anal. Calc. for
9H), 2.02 (dddd, J 12.9, 10.9, 2.7 and 2.2, 1H), 2.40–2.49 (m,
2 2
3H), 2.67 (dd, J 13.6, 1H), 2.85 (dd, J 12.9 and 12.6, 1H), 3.37
C
2
(dd, J 12.9, J 2.2, 1H), 3.83 (d, J 12.6, 1H), 4.01 (br d, J 12.6,
C H NO S : C, 47.50; H, 5.65; N, 4.62. Found: C, 47.32; H,
1H), 7.25 (d, J 7.8, 2H), 7.80 (d, J 7.8, 2H); δ 21.4, 26.9, 29.5,
12
17
2
3
C
5
.59; N, 4.58%.
N-(2-Benzyl-1,3-dithian-1-ylidene)toluene-p-sulfonamide
34.6, 48.2, 50.7, 51.1, 126.2, 129.3, 141.4, 141.9; Anal. Calc. for
C H NO S : C, 52.14; H, 6.71; N, 4.05. Found: C, 51.86; H,
6.44; N, 4.04%.
15
23
2 3
13
(
trans-8b). White solid, mp 161–163 ЊC (lit., 164 ЊC), 57%
yield; 36% ee by Daicel chiralcel OJ (25% propan-2-ol–hexane);
N-(4,6-Dimethyl-1,3-dithian-1-ylidene)toluene-p-sulfonamide
(11). White solid, mp 147–149 ЊC, 59% yield; 33% ee by Daicel
chiralpak AS (25% propan-2-ol–hexane); eluent: dichloro-
Ϫ1
eluent: dichloromethane; νmax(KBr)/cm 1152 (SO ), 1375
2
2
(
(
(
(
SO ); δ 2.25–2.70 (m, 7H), 2.74 (dd, J 14.3, J 10.3, 1H), 3.15
ddd, J 13.2, J 13.4 and 2.9, 1H), 3.39 (dt, J 13.2, 1H), 3.56
dd, J 14.3, J 3.3, 1H), 4.19 (dd, J 10.3 and 3.3, 1H), 7.14–7.30
2
H
2
2
Ϫ1
methane; νmax(KBr)/cm 1139 (SO ), 1393 (SO ); δ 1.24 (d,
2
2
H
2
J 6.9, 6H), 1.87–2.02 (m, 1H), 2.39 (s, 3H), 2.35–2.40 (m, 1H),
2.99–3.19 (m, 2H), 4.02 (s, 2H), 7.24 (d, J 8.2, 2H), 7.79 (d,
J 8.2, 2H); δC 17.1, 20.0, 21.4, 38.3, 45.3, 49.0, 56.6, 126.2,
129.2, 141.2, 141.8; Anal. Calc. for C H NO S : C, 49.2; H,
m, 7H), 7.84 (d, 2H); δ 21.4, 29.3, 29.7, 34.8, 51.1, 65.5, 126.2,
C
1
27.5, 128.5, 129.6, 134.5, 141.5, 141.9; Anal. Calc. for
C H NO S : C, 56.96; H, 5.58; N, 3.69. Found: C, 56.75; H,
18
21
2
3
13 19
2 3
5
.51; N, 3.71%.
6.03; N, 4.41. Found: C, 49.20; H, 5.98; N, 4.32%.
N-(2-o-Tolylmethyl-1,3-dithian-1-ylidene)toluene-p-sulfon-
amide (trans-8c). White solid, mp 111–113 ЊC, 68% yield; 32%
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1
3
1
H), 7.03–7.28 (m, 6H), 7.75 (d, 2H); δ 19.6, 21.4, 29.3, 29.7,
C
2.1, 51.1, 64.7, 125.9, 126.2, 127.6, 129.3, 130.4, 130.7, 132.9,
ϩ
36.8, 141.4, 141.9; m/z EIMS 393 (M ); HRMS: Calc. for
C H NO S : 393.0891. Found: 393.0892.
2 V. K. Aggarwal, G. Evans, E. Moya and J. Dowden, J. Org. Chem.,
19
23
2 3
1
992, 57, 6390.
N-(2-Trimethylsilyl-1,3-dithian-1-ylidene)toluene-p-sulfon-
1
3 (a) Y. Watanabe, Y. Ono, S. Hayashi, Y. Ueno and T. Toru, J. Chem.
Soc., Perkin Trans. 1, 1996, 1879; (b) Y. Watanabe, Y. Ono, Y. Ueno
and T. Toru, J. Chem. Soc., Perkin Trans. 1, 1998, 1087.
amide (trans-8d). Colorless oil, 32% yield; 9% ee by H NMR
analysis in the presence of Eu(hfc) ; eluent: dichloromethane;
3
Ϫ1
νmax(Nujol)/cm 1160 (SO ), 1329 (SO ); δ 0.19 (s, 9H), 2.29–
.66 (m, 7H), 2.96 (ddd, J 12.4, J 8.7 and 2.0, 1H), 3.28 (dt, J
2.4 and 2.3, 1H), 3.71 (s, 1H), 7.23 (d, J 8.1, 2H), 7.79 (d, J 8.1,
H); δ Ϫ2.1, 21.4, 29.1, 49.7, 52.6, 108.7, 126.2, 129.2, 129.4,
2
2
H
4 (a) V. K. Aggarwal, R. Franklin, J. Maddock, G. R. Evans,
A. Thomas, M. F. Mahon, K. C. Molloy and M. J. Rice, J. Org.
Chem., 1995, 60, 2174; (b) V. K. Aggarwal, A. Thomas and
S. Schade, Tetrahedron, 1997, 53, 16 213.
2
2
2
1
2
1
C
ϩ
5 (a) P. K. Claus and F. W. Vierhapper, J. Chem. Soc., Chem. Commun.,
29.7, 141.6, 142.0; m/z EIMS 361 (M ); HRMS: Calc. for
1
976, 1002; (b) R. B. Greenwald, D. H. Evans and J. R. DeMember,
C H NO S Si: 361.0660. Found: 361.0657; Anal. Calc. for
14
23
2 3
Tetrahedron Lett., 1975, 3885; (c) W. Errington, T. J. Sparey and
P. C. Taylor, J. Chem. Soc., Perkin Trans. 2, 1994, 1439; (d) G. Smith,
T. J. Sparey and P. C. Taylor, J. Chem. Soc., Perkin Trans. 1, 1996,
313.
6 (a) H. Takada, Y. Nishibayashi, K. Ohe and S. Uemura, Chem.
Commun., 1996, 931; (b) H. Takada, Y. Nishibayashi, K. Ohe,
S. Uemura, C. P. Baird, T. J. Sparey and P. C. Taylor, J. Org. Chem.,
C H NO S Si: C, 46.50; H, 6.41; N, 3.87. Found: C, 45.97; H,
14
23
2 3
6
.45; N, 3.64%.
N-(2-Dimethylphenylsilyl-1,3-dithian-1-ylidene)toluene-p-
sulfonamide (trans-8e). Colorless oil, 35% yield; 5% ee by H
1
NMR analysis in the presence of Eu(hfc) ; eluent: dichloro-
3
Ϫ1
methane; νmax(Nujol)/cm 1139 (SO ), 1300 (SO ); δ 0.51 (s,
2
2
H
1
997, 62, 6512.
9
3
H), 0.58 (s, 3H), 2.21–2.61 (m, 7H), 2.91–3.02 (m, 1H), 3.23–
7
Z Li, R. W. Quan and E. N. Jacobsen, J. Am. Chem. Soc., 1995, 117,
.31 (m, 1H), 7.22–7.49 (m, 7H), 7.80 (d, J 8.3, 2H); δ Ϫ4.5,
5889.
C
Ϫ2.4, 21.4, 28.7, 29.4, 49.5, 52.6, 126.3, 128.0, 129.3, 130.3,
8 Attempts for sulfimidation of bis(phenylthio)methane, an acyclic
dithioacetal, under the present conditions resulted in the formation
of small amounts of seven unidentified products.
1
33.0, 134.4, 141.6, 142.1; Anal. Calc. for C H NO S Si: C,
19 25 2 3
5
3.86; H, 5.95; N, 3.31. Found: C, 53.93; H, 5.78; N, 3.27%.
9
(a) D. Seebach, Synthesis, 1969, 1, 17; (b) B. F. Bonini, M. Comes-
Franchini, M. Fochi, G. Mazzanti and A. Ricci, Tetrahedron, 1996,
N-(5-Methyl-1,3-dithian-1-ylidene)toluene-p-sulfonamide (cis-
0a). White solid, mp 186–188 ЊC, 71% yield; 30% ee by H
1
1
5
2, 4803.
NMR analysis in the presence of Eu(hfc) ; eluent: dichloro-
10 E. L. Eliel and R. O. Hutchins, J. Am. Chem. Soc., 1969, 91, 2703.
11 E. Juaristi, G. Cuevas and A. Vela, J. Am. Chem. Soc., 1994, 116,
5796.
3
Ϫ1
methane; νmax(KBr)/cm 1196 (SO ), 1368 (SO ); δ 1.12 (d,
J 6.4, 3H), 2.40–2.54 (m, 5H), 2.83 (dd, J 12.5 and 11.5, 1H),
.24 (br dd, J 11.5, 1H), 3.85 (d, J 12.7, 1H), 4.06 (br d, J
2.7, 1H), 7.25 (d, J 8.6, 2H), 7.79 (d, J 8.6, 2H); δ 21.4, 21.9,
4.7, 36.1, 48.1, 54.9, 126.2, 129.4, 141.4, 141.9; m/z EIMS 303
M ); HRMS: Calc. for C H NO S : 303.0421. Found:
2
2
H
2
2
2
2
12 Y. Yamada, T. Yamamoto and M. Okawara, Chem. Lett., 1975, 361.
3 H. Yoshida, T. Ogata and S. Inokawa, Synthesis, 1976, 552.
3
1
3
1
C
ϩ
(
Paper 8/02915F
12
17
2 3
3
4
03.0410; Anal. Calc. for C H NO S : C, 47.50; H, 5.65; N,
.62. Found: C, 46.46; H, 5.50; N, 4.22%.
Received, 20th April 1998
Accepted, 4th June 1998
12
17
2 3
2
376
J. Chem. Soc., Perkin Trans. 1, 1998