Thiiranium and Thiirenium Ions

Protonated 2-methylthiiran exists as cis- and trans-isomers in FSOaH-ShF at — 78 °C according to n.m.r. data. Data pertinent to the relative rates of nucleophilic attack at carbon and sulphur in thiiranium ions were provided by an investigation concerned primarily with the exchange of 4-chloro-benzenesulphenyl chloride between cyclic chloroalkyl 4-chlorophenyl 

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Thiiranium and thiirenium ions as reaction intermediates and building blocks in organic synthesis 97G177. 

The same team studied also Art-butyl-substituted thiiranium and thiirenium ions in reactions with disulfides, which led to the formation of thietanium and thietium ions, respectively. However, this paper only reported upon the kinetics of this... 

G. H. Schmid Thiiranium and Thiirenium Ions, in Topics in Sulfur Chemistry, Vol. 3, 101, Thieme-Verlag, Stuttgart 1977... 

Thiiranium and thiirenium ions undergo (Scheme 76) <1997T15717>. 

The terms thiiranium and thiirenium ions ((150) and (151)) have been used to designate the positively charged three-membered sulfur-containing ring irrespective of the location of the coun-... 

Many investigations have been performed on the addition of sulphenyl halides, particularly chlorides, to alkenes and alkynes. Thiiranium and thiirenium ions, respectively, would be intermediates. The generality of these ions as intermediates in the addition to alkenes has been questioned in a critical review article. Modena and coworkers listed relative reactivities in the addition of 4-chlorobenzenesulphenyl chloride to alkenes and alkynes. Alkynes appear to be less reactive than alkenes, but the ratio very much depends upon structure. The highest ratio was observed for the parent pair ethene ethyne, namely 2.82 X 10 ... 

Cyclofunctionalization of Alkenes and Alkynes. The nucleophilic ring opening of thiiranium and thiirenium ions has been exploited for the synthesis of functionalized heterocycles using MesSsSbClg and suitably substituted alkenes and alkynes (eqs... 

Among alkenes and alkynes reacting successfully are ethene, pro-pene, 2-butene, cycloalkenes, acetylene, propyne, diphenylacety-lene. The products are written in eq. 24 and 25 as trans adducts but we have not yet studied the stereochemistry of addition. Whether or not thiiranium and thiirenium ion radical intermediates are involved is an interesting conjecture yet to be explored. 

Modena and et al. concluded, on the basis of experimental evidence, that nucleophilic substitution at thiiranium and thiirenium sulfur is sensitive to substituents, and that dialkyl disulfides approach the sulfur in a perpendicular sense, not in the collinear sense shown as the a -direction in 219 see also Section 1.05.8.3 <1999JA3944, 2000CEJ589>. Their rationale for the apparent difference between experimental and theoretical substitution mechanisms focused on bicentric versus monocentric nucleophiles. The former attack thiiranium ions in the 3c-direction and the latter in the y-direction. Radom s group disagrees on the basis of theory <1998JA7063, 2000CEJ590>. 

The Chemistry of Thiiranium Ions. - The chemistry of episulphonium ions and the reactions of alkenes with sulphenyl derivatives have been reviewed Stable thiiranium and thiirenium chlorides have been generated in S02. Kinetic studies for the quantitative generation of (329 R =R = Bu, X = Cl) from the ionization of (328) and the equilibrium between (330) and (331) in SO2 were followed, using n.m.r. spectrometry. Compounds (329 R = Bu, X = SbCls or BF4) have been isolated as stable salts at room temperature... 

Reactivity of Substituents at Sulfur - Thiiranium Ions, Thiirenium Ions, and Episulfuranes... 

REACTIVITY OF SUBSTITUENTS ATTACHED TO RING HETEROATOMS— THIIRANIUM IONS, THIIRENIUM IONS, AND EPISULFURANES... 

Molecular Orbital (M.O.) studies of reaction intermediates have been reported for the rearrangement of l-propenethiol, for the addition of sulphenyl halides to ethylene (sulphurane rather than thiiranium salt as intermediate), and for similar additions to alkynes (thiirenium ions or /ff-alkylthiovinyl cations, depending upon the substituents). Electronic effects of substituents on energy levels of orbitals of... 

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