Synthesis of isolable thiirane 1-imides and their stereospecific ring-enlargement to 1,2-thiazetidines

Article abstract of DOI:10.1246/cl.2008.658

The isolation of thiirane 1-imides was achieved via imination of anti- and syn-9,9′-bibenzonorbornenylidene sulfides by Chloramine T at room temperature, followed by crystallization of the reaction mixture at -18°C. Allowing CD₂Cl₂ s

Full text of DOI:10.1246/cl.2008.658

658
Chemistry Letters Vol.37, No.6 (2008)
Synthesis of Isolable Thiirane 1-Imides and Their Stereospecific Ring-enlargement
to 1,2-Thiazetidines
Yoshiaki Sugihara,ꢀ Yui Aoyama, Haruki Okada, and Juzo Nakayamaꢀ
Department of Chemistry, Graduate School of Science and Engineering, Saitama University,
Sakura-ku, Saitama 338-8570
(Received April 14, 2008; CL-080385; E-mail: ysugi@chem.saitama-u.ac.jp)
The isolation of thiirane 1-imides was achieved via imina-
The imination of 2,20-biadamantylidene sulfide 1c9 in
CH3CN–CHCl3 (1:3) at ꢁ18 ꢂC for 3.5 h gave 2c and 4c in 90
and 10% yields, respectively (Scheme 2). As the proportion of
CH3CN in the solvent was smaller, the yield of 2c increased
slightly but the reaction time was prolonged. trans-Stilbene
sulfide 1d, which carries two less hindered phenyl groups, react-
ed with Chloramine T at ꢁ18 ꢂC to give trans-stilbene 4d in 95%
yield stereoselectively, whereas cis-stilbene sulfide 1e to form
cis-stilbene 4e in 60% yield together with 4d in 28% yield. Steric
crowdness around the thiirane imide moiety probably stabilizes
2a–2c kinetically.
tion of anti- and syn-9,90-bibenzonorbornenylidene sulfides by
Chloramine T at room temperature, followed by crystallization
of the reaction mixture at ꢁ18 ꢂC. Allowing CD2Cl2 solutions
of the thiirane 1-imides stand at room temperature or heating
their crystals to around 120 ꢂC led to the formation of the corre-
sponding 1,2-thiazetidines with retention of the configuration
of the thiirane 1-imides.
In our continuing interest in the chemistry of anti- and syn-
9,90-bibenzonorbornenylidenes and their derivatives,1 we report-
ed that methylsulfonium salts of anti- and syn-9,90-bibenzonor-
bornenylidene sulfides were synthesized by reactions of anti-
sulfide 1a and syn-sulfide 1b with Me3OBF4 at low temperature
and isomerized each other in CDCl3 above room temperature.2
In this connection, we have been greatly interested in chemistry
of S-aminothiiranium salts and thiirane 1-imides. While a large
number of studies of the chemistry of thiirane 1-oxides has been
reported,3 only a few reports have dealt with thiirane 1-imides
as a reaction intermediate.4,5 We report here the synthesis of
the first isolable thiirane 1-imides by imination of thiiranes
and their stereospecific ring-enlargement to 1,2-thiazetidines.
Chloramine T was used successfully as an imination agent
for the synthesis of thiirane 1-imides (Scheme 1).6 Thus, the
imination of 1a in CH3CN–CH2Cl2 (1:3) at room temperature
followed by crystallization of the reaction mixture from
CH2Cl2–hexane at ꢁ18 ꢂC gave anti-thiirane 1-imide 2a as
colorless crystals in 85% yield. The resulting filtrate was purified
by silica-gel column chromatography to afford anti-1,2-thiazeti-
dine 3a, the second isolable 1,2-thiazetidine,7 and 4a in 6 and 2%
yields, respectively. The same procedure for 1b gave 2b, 3b, and
5b in 82, 6, and 4% yields, respectively. The reaction mixture
of 1a was crystallized at room temperature to give 3a in 62%
yield; no trace amount of 2a was observed. On the other hand,
the imination of 1a with PhI=NTs in the presence of CuI catalyst
did not provide 2a.8
The thiirane 1-imides, 2a and 2b, are thermally more labile
than the corresponding thiirane 1-oxides, 5a and 5b. Thus, 2a
and 2b were heated neat above 120 ꢂC to provide 3a and 3b, re-
spectively, in which the stereochemistry of the thiirane 1-imide
was retained (Scheme 3), while 5a and 5b melt without decom-
position at 224–226 and 211–212 ꢂC, respectively. Even letting
CD2Cl2 solutions of 2a and 2b stand at room temperature also
led to the stereospecific formation of 3a and 3b, respectively.
The probable mechanism of the formation of 3a is as
follows. The C–S bond that faces the ethylene bridge of 2a is
NTs
S
S
Chloramine T
solvent, time
–18 °C
+
1c
2c
4c
CH3CN–CHCl3 (1:3), 3.5 h 90%
10%
7%
5%
CH3CN–CHCl3 (1:30), 5 h
CHCl3, 2 days
93%
95%
Scheme 2.
NTs
S
Ts
S
NTs
N
+
1a
+
+
1b
+
4a
2a
3a
6a
neat, 120–125 °C, 1 h
CD2Cl2, r.t., 1 day
74%
55%
9%
21%
7%
3%
7%
24%
NTs
NTs
S
Ts
N
S
NTs
S
S
NTs
S
Chloramine T
CH3CN–
CH2Cl2
+
+
+
1b
+
+
(1:3), r.t.,
1 h
2b
3b
4b
22%
6b
1a
3a
2a
4a
2%
6%
85%
neat, 120 °C, 5 h
CD2Cl2, r.t., 1 day
60%
quant.
15%
3%
NTs
S
O
S
S
NTs
S
–
N
S
–
N
O
S
Ts
Ts
Ts
N
Chloramine T
CH3CN–
CH2Cl2
+
+
S
S
+
+
(1:3), r.t.,
30 min
1b
2b
82%
3b
6%
5b
4%
5a
7
8
9
Scheme 1.
Scheme 3.
Copyright Ó 2008 The Chemical Society of Japan

Chemistry Letters Vol.37, No.6 (2008)
659
S1–C1–C2–N dihedral angle of 14.7(1)ꢂ, and the N1 atom is
pyramidal. The molecule of 3a has no symmetry elements in
NTs
S
S
˚
the crystals. The C2–N bond [1.5416(8) A] is much longer
+
TsNH2
+
heat
16
˚
than the common C–N bond (1.47 A). Other bond lengths in
the 1,2-thiazetidine ring are almost same as the common C–C
2c
4c
69%
45%
1c
29%
51%
neat, 145 °C, 1.5 h
CDCl3, 55 °C, 5 h
77%
98%
16
16
17
˚
˚
˚
(1.53 A), C–S (1.82 A), and S–N (1.76 A) bond lengths.
The 13C NMR spectra of 3a and 3b in CDCl3 at 25 ꢂC appear
that they both have seven-sp3 and ten-sp2 carbon peaks in which
the ring carbon signals appear at ꢀ 84.5 and 94.2 for 3a and ꢀ
83.3 and 96.3 for 3b, respectively. The 1,2-thiazetidines are
symmetric under the conditions, so that both inversion of
the pyramidal nitrogen atom and puckering of the nonplanar
1,2-thiazetidine ring take place.
O
S
S
NTs
NTs
S
NTs
S
H
H
5c
10
11
3c
Scheme 4.
cleaved to form intermediate 7 or 8. The neighboring group par-
ticipation of the benzene ring both assists to open the thiirane
ring and stabilizes the intermediate. Recombination of the cation
and anion centers in 7 or the two radical centers in 9 that is
formed from 8 gives 3a. This process is more rapid than rotation
about the central C–C bond of 7 or 9.
The thiirane 1-imide 2c decomposed on heating both neat at
145 ꢂC and in CDCl3 at 55 ꢂC to form 1c, 4c, and TsNH2
(Scheme 4). The thermal decomposition would proceed as fol-
lows. Initially, 4c and TsN=S4,10 are formed similar to the ther-
molysis of 5c in refluxing toluene forming 4c and intermediary
S=O.11 Water as an impurity or the resulting TsN=S attacks
the nitrogen atom on 2c to afford 1c and TsN=S=X (X =
NTs or O). Finally the remaining TsN=S and TsN=S=X
were hydrolyzed to form TsNH2 together with SO12 and SO2,
respectively. Steric repulsion between the substituents in the
transition state of the reaction of 2c to 3c is probably much more
serious than those from 2a and 2b.
The 13C NMR spectra of 2 in CDCl3 at ꢁ20 ꢂC show eleven-
sp3 and fifteen-sp2 carbon peaks for 2a,13 six-sp3 and ten-sp2
carbon peaks for 2b, and eleven-sp3 and four-sp2 carbon peaks
for 2c. Thus, 2a is not symmetric, and 2b and 2c have Cs sym-
metry in which the plane bisects the plane of the thiirane ring
vertically through the S–N bond. Inversion of the pyramidal
sulfur atom was not observed under these conditions. The ring
carbon signals of the thiirane 1-imides (2a: ꢀ 82.8, 83.7, 2b: ꢀ
79.9, 2c: ꢀ 77.3) appear at lower fields than do those of the cor-
responding thiiranes (1a: ꢀ 74.7, 75.2, 1b: ꢀ 72.3, 1c:11b ꢀ 71.7)
and thiirane 1-oxides (5a: ꢀ 80.6, 81.7, 5b: ꢀ 78.5, 5c:11b ꢀ 72.9).
Thus, the C–S bond electrons in the thiirane ring would be
withdrawn more strongly by the N-tosylsulfilimine parts in 2
than by the sulfoxide parts in 5. In the IR spectra, very strong
S–N stretching absorption appeared at 970 for 2a, 956 for 2b,
and 961 cmꢁ1 for 2c, respectively. These values are almost the
same as are 965 for 10 and 966 cmꢁ1 for 11.14 The ring size of
2 slightly affects the value of the S–N stretch absorption.
The molecular structure of 3a is shown in Figure 1.15
The 1,2-thiazetidine ring adopts a puckered structure with the
References and Notes
1
a) Y. Sugihara, K. Noda, J. Nakayama, Bull. Chem. Soc. Jpn.
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Nakayama, Tetrahedron Lett. 2000, 41, 8911. d) K. Noda, Y.
Sugihara, J. Nakayama, Heteroat. Chem. 2001, 12, 625.
Y. Sugihara, Y. Aoyama, J. Nakayama, Chem. Lett. 2001, 980.
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b) D. C. Dittmer, in Comprehensive Heterocyclic Chemistry,
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Vol. 7, Chap. 5.06. c) W. Ando, N. Choi, N. Tokitoh, in Compre-
hensive Heterocyclic Chemistry II, ed. by A. R. Katritzky,
C. W. Rees, E. F. V. Scriven, Pergamon, Oxford, 1996, Vol. 1,
Chap. 1.05.
2
3
4
P. Raynolds, S. Zonnebelt, S. Bakker, R. M. Kellogg, J. Am.
Chem. Soc. 1974, 96, 3146.
5
6
Y. Hata, M. Watanabe, J. Org. Chem. 1980, 45, 1691.
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1075. c) F. G. Mann, W. J. Pope, J. Chem. Soc., Trans. 1922,
121, 1052.
7
8
The first isolable 1,2-thiazetidine: T. Otani, J. Takayama, Y.
Sugihara, A. Ishii, J. Nakayama, J. Am. Chem. Soc. 2003, 125,
8255.
a) H. Takada, Y. Nishibayashi, K. Ohe, S. Uemura, C. P. Baird,
T. J. Sparey, P. C. Taylor, J. Org. Chem. 1997, 62, 6512. b) T.
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10 O. Meth-Cohn, G. Vuuren, J. Chem. Soc., Perkin Trans. 1 1986,
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Soc. 2007, 129, 7250.
13 One of the fifteen-sp2 carbon peaks is due to a degeneracy of two
carbon peaks.
14 K. Tsujihara, N. Furukawa, S. Oae, Bull. Chem. Soc. Jpn. 1970,
43, 2153.
ꢀ
15 Crystal data for 3a: triclinic, P1, a ¼ 10:576ð1Þ, b ¼ 10:843ð1Þ,
˚
c ¼ 11:779ð1Þ A,
ꢁ ¼ 68:253ð3Þ,
ꢂ ¼ 73:390ð2Þ,
ꢃ ¼
78:866ð4Þꢂ, V ¼ 1196:50ð10Þ A , Z ¼ 2, Dcalcd ¼ 1:348
3
˚
1.7573(5) Å
Ts
Mg mꢁ3, R ¼ 0:053, wR ¼ 0:070, S ¼ 1:166.
S1
S1
Ts
79.1(1)°
1.8235(6) Å
89.8(1)°
S1
C1 C2
N
N
N
16 E. L. Eliel, S. H. Wilen, Stereochemistry of Organic Compounds,
Wiley-Interscience, New York, 1994, p. 13.
92.8(1)°
1.5416(8) Å
94.8(1)°
14.7(1)°
17 S. Oae, N. Furukawa, Sulfilimines and Related Derivatives,
American Chemical Society, Washington, D. C., 1983, p. 53.
18 Supporting Information is available electronically on the CSJ-
Journal Web site, http://www.csj.jp/journals/chem-lett/.
C1
C2
1.5564(8) Å
Figure 1. Molecular structure of 3a.
Published on the web (Advance View) May 24, 2008; doi:10.1246/cl.2008.658