THIIRANIUM AND THIIRENIUM IONS CHEMISTRY AND STEREOCHEMISTRY

The role of thiiranium and thiirenium ions in the electrophilic additi ons to alkenes and alkynes and the corresponding inverse reactions, ar e revisited also in the light of the recently reported rearrangements on some of these cations. The occurrence of S(N)2-Vin mechanism is dis cussed on the basis of the available experimental evidence and of quan to mechanical computation. Preliminary results on the reactivity of so me stable thiiranium ions as a function of substitution pattern and on the enantioselective bifunctionalization of alkene via an optically a ctive thiiranium ion are also reported.