conditions. It was thought that the differences in reactivity
between sulfilimine 2 and sulfoxide 3 arose from the en-
hanced basicity of the nitrogen in 2 compared to the oxygen
in 3. Along the same lines, we speculated that elimination
of sulfilimines 4 would proceed under milder conditions than
those for elimination of sulfoxides 5 (Scheme 2). Several
4a from phenyl sulfides failed in spite of many trials, and
so we then planned to prepare N-H sulfilimines from phenyl
sulfides. Among some methods known for the preparation
of N-H sulfilimines from phenyl sulfides,16,17 the use of
O-mesitylenesulfonylhydroxylamine (MSH)18 was chosen as
this reagent seemed to allow N-H sulfilimines to be prepared
under mild conditions.17
Phenyl sulfide 6 was treated with MSH at 0 °C in
dichloromethane to generate S-aminosulfonium salt 7 (Scheme
3). Quantitative formation of 7 was confirmed by H NMR
Scheme 2. Comparison between Elimination of 4 and That of
1
5
Scheme 3. One-Pot Elimination of 6 to 9 Using MSH
examples of elimination of N-substituted sulfilimines,9
including N-ethoxycarbonyl-,10 N-tosyl-,11 N-carbamoyl-,12
N-acyl-,13 N-phenyl-,14 and N-H sulfilimines,15 have been
reported. However, sulfilimines that have an electron-
withdrawing group on the nitrogen atom (R3 of 4 ) electron-
withdrawing group) required elevated temperatures for
elimination. We therefore planned to establish a new method
for the efficient and mild elimination of sulfilimines that do
not have an electron-withdrawing group (R3 of 4 * electron-
withdrawing group). We describe here a one-pot elimination
of phenyl sulfides to alkenes via N-H sulfilimines that
proceeds at ambient temperature which is also applicable to
the synthesis of R,â-unsaturated carbonyl compounds.
First, we investigated elimination of sulfilimines bearing a
tert-butyl group on the nitrogen atom (R3 of 4 ) tert-butyl)
expecting mild elimination as observed in the intermediate
2. However, preparation of N-tert-butyl phenyl sulfilimines
analysis of a mixture of 6 and MSH in CDCl3.19 Then suitable
bases needed for the in situ generation of sulfilimine 8 from
7 were screened (Table 1). The use of DBU directly gave
Table 1. Effect of Bases on One-Pot Elimination of Phenyl
Sulfide 6 to Alkene 9a
entry
base (equiv)
yield (%)b
recovered 6 (%)b
1
2
3
4
5
6
i-Pr2NEt (2)
DBU (2)
t-BuOK (1.5)
K2CO3 (10)
K2CO3 (10) + MS4A
CsF (5)
0
0
16
8
6
10
6
42
78
80
80
83
a For reaction conditions, see Scheme 3. b Determined by 1H NMR
analysis.
(5) (a) Clive, D. L. J. Tetrahedron 1978, 34, 1049-1132. (b) Reich, H.
J. Acc. Chem. Res. 1979, 12, 22-30. (c) Paulmier, C. In Selenium Reagents
and Intermediates in Organic Synthesis; Pergamon Press: Oxford, 1986.
(6) Review: (a) Depuy, C. H.; King, R. W. Chem. ReV. 1960, 60, 431-
457. (b) Astles, P. C.; Mortlock, S. V.; Thomas, E. J. In ComprehensiVe
Organic Synthesis; Trost, B. M., Fleming, I., Heathcock, C. H., Eds.;
Pergamon Press: New York, 1991; Vol. 6, pp 1011-1039.
(7) Matsuo, J. J. Synth. Org. Chem. Jpn. 2004, 62, 574-583.
(8) (a) Mukaiyama, T.; Matsuo, J.; Kitagawa, H. Chem. Lett. 2000,
1250-1251. (b) Matsuo, J.; Aizawa, Y. Tetrahedron Lett. 2005, 46, 407-410.
(9) Gilchrist, T. L.; Moody, C. J. Chem. ReV. 1977, 77, 409-435.
(10) Whitfield, G. F.; Beilan, H. S.; Saika, D.; Swern, D. J. Org. Chem.
1974, 39, 2148-2152.
alkene 9 in 42% yield even at room temperature, while
diisopropylethylamine did not give 9 (entries 1 and 2). The
use of potassium tert-butoxide improved the yield of alkene
9 to 78% yield (entry 3). Inorganic bases such as potassium
carbonate and cesium fluoride were found to be effective,
and the presence of molecular sieves 4A did not affect the
efficiency of the elimination (entries 4-6). As described
(11) (a) Oae, S.; Tsujihara, K.; Furukawa, N. Tetrahedron Lett. 1970,
2663-2666. (b) Tsujihara, K.; Furukawa, N.; Oae, S. Tetrahedron 1971, 27,
4921-4930. (c) Tsujihara, K.; Harada, K.; Furukawa, N.; Oae, S. Tetrahed-
ron 1971, 27, 6101-6108. (d) Oae, S.; Harada, K.; Tsujihara, K.; Furukawa,
N. Bull. Chem. Soc. Jpn. 1973, 46, 3482-3486. (e) Furukawa, N.; Hatanaka,
T.; Harada, K.; Oae, S. Bull. Chem. Soc. Jpn. 1976, 49, 2337-2338.
(12) Oae, S.; Masuda, T.; Tsujihara, K.; Furukawa, N. Bull. Chem. Soc.
Jpn. 1972, 45, 3586-3590.
(16) Furukawa, N.; Omata, T.; Yoshimura, T.; Aida, T.; Oae, S.
Tetrahedron Lett. 1972, 1619-1622.
(17) Tamura, Y.; Sumoto, K.; Minamikawa, J.; Ikeda, M. Tetrahedron
Lett. 1972, 4137-4140.
(18) (a) Tamura, Y.; Minamikawa, J.; Sumoto, K.; Fujii, S.; Ikeda, M.
J. Org. Chem. 1973, 38, 1239-1241. (b) Johnson, C. R.; Kirchhoff, R. A.;
Corkins, H. G. J. Org. Chem. 1974, 39, 2458-2459.
(19) We observed that phenyl sulfide 6 hardly reacted with hydroxy-
lamine-O-sulfonic acid (HAS) even at room temperature, while Appel
reported that dimethylsulfide and diethylsulfide reacted with HAS to give
the corresponding S-aminosulfonium salts. See: Appel, R.; Buchiner, W.
Chem. Ber. 1962, 95, 849-854.
(13) (a) Papa, A. J. J. Org. Chem. 1970, 35, 2837-2840. (b) Kise, H.;
Whitfield, G. F.; Swern, D. J. Org. Chem. 1972, 37, 1125-1128.
(14) Gassman, P. G.; Gruetzmacher, G. D. J. Am. Chem. Soc. 1974, 96,
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(15) Appel, R.; Bu¨chner, W. Chem. Ber. 1962, 95, 855-866.
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