Synthesis and Reactivity of Enantiomerically Enriched Thiiranium Ions

Enantiomerically enriched thiiranium ion 5 has been prepared by silver‐assisted ionization of chloro sulfide 4 at ?20 °C. This thiiranium ion is configurationally stable in solution up to room temperature as demonstrated by the stereospecific capture of the ion by various oxygen‐ and nitrogen‐based nucleophiles. Both isolated olefins and weak Lewis bases can promote the racemization of 5 but these processes can also be suppressed at low temperature. Capture of 5 by methanol is faster than the racemization processes.