1412
LETTERS
SYNLETT
The s-syn conformation which would lead to the cis olefinic bond, like
in species 7, is sterically considerably more demanding than the s-anti.
Consequently, the formation of a cis olefinic species like 7 is not
preferred but rather that of the corresponding trans olefin. Therefore,
pathway B can be considered as highly unlikely.
are very grateful to Prof. Curci, Università di Bari, for supplying a
sample of TFDO and advising in the use of this oxidizing agent.
References and Notes:
(1) (a) Roberts, D. W.; Williams, D. L. Tetrahedron 1987, 43, 1027.
(b) Lee, A. W. H.; Chan, W. H.; Jiang, L. S.; Poon, K. W. J. Chem.
Soc., Chem. Commun., 1997, 611.
Support for the sulfene pathway was obtained from sulfene trapping
3a,13
14
experiments
in methanol.
In fact, treatment of 3a,b with
triethylamine in methanol gave methyl 3-hydroxy-alk-1-ene sulfonates
15
(2) (a) van Haard, P. M. M.; Thijs, L.; Zwanenburg, B. Tetrahedron
Lett., 1975, 803. (b) Thijs, L.; Smeets, F. L. M.; Cillissen, P. J. M.;
Harmsen, J.; Zwanenburg, B. Tetrahedron, 1988, 36, 2141.
8a,b in 60 and 51% yield, respectively (Scheme 4). The trans
geometry of this product 8 can be explained in a manner similar to that
given for the formation of γ-hydroxy-α,β-unsaturated esters from epoxy
16
17
ketenes. It is of interest to note that treatment of epoxy sulfonate 9
(3) (a) Opitz, G. Angew. Chem., 1967, 79, 162. (b) King, J. F. Acc.
Chem. Res., 1975, 8, 10. (c) King, J. F.; Rathore, R. The Chemistry
of the Sulphonic Acids, Esters and Their Derivatives, Ed. by Patai,
S; Rappoport, Z., John Wiley & Sons, Chichester, 1991, Ch. 17,
697. (d) Lenz, B. G.; Zwanenburg, B. In Houben Weyl, Methoden
in der Organische Chemie, Thieme Verlag: Stuttgard, 1985, Band
11/2, p 1326.
with triethylamine (Scheme 4) did not lead to any epoxide opening,
supporting the view that pathway B in scheme 3 is not likely to occur.
(4) Truce, W. E.; Norell, J. R. J. Am. Chem. Soc., 1963, 85, 3231.
(5) Nakayama, J.; Tanuma, M.; Honda, Y.; Hoshino, M. Tetrahedron
Lett., 1984, 25, 4553.
(6) Midura, W.; Zwanenburg, B. unpublished results
(7) Mello, M.; Fiorentino, M.; Fusco, C.; Curci, R. J. Am. Chem. Soc.,
1989, 111, 6749.
(8) Preparation of 3. General procedure: to a solution of 6 (1.5 mmol)
in dichloromethane (2 ml), 2.5 ml of a 0.9M solution of methyl
trifluoromethyl dioxirane was added at 0°C. After 6 h of stirring at
0°C, the dichloromethane and the trifluoroacetone were
Scheme 4
1
The sultones 1 were also prepared in an alternative manner (Scheme 5).
Treatment of sulfonyl chlorides 6 with bromodan (1,3-dibromo-5,5-
dimethylhydantoine) in ether/water 1:1 gave 4-bromo sultones 10a,b
in 65 and 60% yield, respectively. Subsequent dehydrobromination with
triethylamine gave alk-1-ene-1,3-sultones 1a,b in 85% yield.
evaporated. H NMR of the residue showed the complete
conversion of 6 into 3.
18
-1
1
(9) 3a: oil; IR (neat): 1370, 1165 (SO ) cm ; H NMR (200MHz,
2
CDCl ) δ 2.7-3.1 (2H, m, CH ), 3.47 (1H, m, CH), 3.83 (2H, d, J
3
2
-1
= 5.25 Hz, CH SO Cl). 3b: oil; IR (neat): 1350, 1175 (SO ) cm ;
H NMR (200MHz, CDCl ) δ: 1.40 (3H, d, J = 5.1 Hz, CH ), 3.02
2
2
2
1
3
3
(1H, dq, J = 5.1, J = 2.5 Hz, CH), 3.20 (1H, m, J = 2.5 Hz,
1
2
13
CHCH ), 3.75-3.91 (2H, m, CH SO Cl); C NMR (50MHz,
2
2
2
CDCl ) δ: 17.1 (CH ), 52.2 (CH), 54.6 (CH), 67.5 (CH ); m/z 135
3
3
2
+
+
(M -Cl), 71 (M -SO Cl).
2
(10) Preparation of 1. General procedure: to a solution of 3 (1 mmol) in
dry diethylether (10 ml), triethylamine (1.1 mmol) in dry
diethylether (6 ml) was added at -40°C. After 30 mins of stirring
Scheme 5
at -40°C and 2 h at room temperature, Et N·HCl was removed by
3
filtration and the solvent was evaporated. Purification of the crude
product by preparative TCL (eluent: light petroleum-ethyl acetate
1:1) gave 1.
In a preliminary study, the unsaturated sultone 1b was treated with
phenylthiol in THF in the presence of 0.1 equiv. of sodium methoxide,
19
to give the Michael adduct, 5-methyl-4-phenylsulfanyl sultone 11, as
-1
1
the major product (45%). Reaction of 1b with methanol in the presence
(11) 1b: oil; IR (CCl ) 3100, 3060, 2960, 2920, 1360, 1190 cm ; H
4
of a catalytic amount of base similarly gave 5-methyl-4-methoxy
NMR (200MHz, CDCl ) δ: 1.62 (3H, d, J = 6.7 Hz, CH ), 5.38
(1H, m, J = 6.7, J = J = 2.1 Hz, CHCH ), 6.76 (1H, dd, J = 6.6,
3
3
20
sultone 12 in 70% yield (Scheme 6).
1
2
3
3
1
J = 2.1 Hz, vinylic H), 6.88 (1H, dd, J = 6.6, J = 1.6 Hz, vinylic
2
1
2
13
H); C NMR (50MHz, CDCl ) δ: 20.40 (CH ), 81.90 (CH),
125.20 (CH), 141.50 (CH); m/z 135 (M +1), 119 (M -CH ).
3
3
+
+
3
(12) (a) King, J. F.; de Mayo, P.; McIntosh, C. L.; Piers, K.; Smith, D.
J. H. Can. J. Chem., 1970, 48, 3704. (b) Hellberger, J. H.; Muller,
G.; Ger. 1, 146, 870, 1963; Chem Abstr., 1963, 59, 11259d.
Scheme 6
(13) (a) Truce, W. E.; Campbell, R. W. J. Am. Chem. Soc., 1966, 88,
3599. (b) King, J. F.; Durst, T. J. Am. Chem. Soc., 1965, 87, 5684.
Acknowledgements: Financial support of this work by the Ministero
dell’Università e della Ricerca Scientifica e Tecnologica (MURST),
Italy, is gratefully acknowledged. G.K. and S.T.H.W. are grateful for the
support from the Erasmus programme ICP-96-NL-1007/13. The authors
(14) Cf. Dehydrochlorination of 2-substituted ethanesulfonyl chlorides,
which involves initial sulfene formation followed by a further
reaction during the sulfene trapping step. King, J. F.; Hillhouse, J.