Episulfonium salts

When the reaction was run in CH3CN, migration of the EtS group to the 2-position was observed. This is attributed to episulfonium salt formation, with the resultant addition of acetate at the anomeric position. ... 

Halogen atoms at position 3 in tetrahydrothiins are labilized toward nucleophiles by the sulfur atom, by the formation of a bicyclic episulfonium salt as observed in the chemistry... 

In thiepanes 89, 90, and 92, transannular attack at C3 or C4 could lead to a mixture of polyhydroxylated tetrahy-drothiopyrans or tetrahydrothiophenes. However, by the reaction of substrates 89 (or 90) and 92 with Me3SiI, 91 and 93 were obtained exclusively (free of any five-membered cyclic sulfides), respectively, through a seven- to six-membered ring-contraction reaction. In both cases, as predicted for an Sn2 transannular cyclization and due to the presence of a -symmetric axis (Scheme 11), only one diastereoisomer was obtained. Episulfonium salt was proposed to be formed by a stereo- and regiospecific process, followed by a ring contraction toward the more stable tetrahydrothiopyran derivative. 

The formation of episulfuranes from /J-halothioethers may be understood in terms of the slow equilibrium of / -halothioethers with the episulfonium salt (Scheme 63). The /J-halothioether ((178) or (179)) is regenerated by attack of the halide ion on carbon (kinetic control), whereas the attack on sulfur yields the episulfurane. The episulfurane ((176) or (177)) becomes the thermodynamic product ((180) or (181)) in the case of fluorothioethers, presumably because of the stability of the F—S bond (87TL4593). The stabilizing effect of the ring systems has also been invoked to explain the stability of sulfuranes. 

Episulfonium salts. The reagent reacts with alkenes in CH2CI2 at 0° or in SO2 at -60° to give thiiranium salts (2, episulfonium salts) in 85-90% yield. These products are stable for some time at -10. ... 

ENYNES Diacetatobis(triphenylphosphine)paIladium(II). Tetrakis(triphenylphosphine)-palladium(O). Tetramethylethylenediamine. 1 -TrimethyIsilylpropynylcopper. EPISULFONIUM SALTS Methyl(bismethylthio)sulfonium hexachloroantimonate. EPOXIDES Bromomethyllithium. Diphenyl selenide. Methaneselenol. 

Dialkyl(alkylthio)sulfonium salts add across carbon-carbon double and triple bonds in a trans-stereospecific manner (37). Episulfonium salts are conveniently prepared by treatment of olefins with methyl(bismethylthio)sulfonium... 

Acetylene-1 -thioethers Enesulfonium salts Episulfonium salts Thioenolethers Vinyl thioethers 15 Thioenols Thioketenes Thioynolethers Thioynols... 

---