Generation, Characterization, and Reactions of Thionium Ions Based on the Indirect Cation Pool Method

Abstract PhCH=S+Ar (Ar = p-FC6H4) was generated and accumulated for the first time in organic solvents that are commonly used for organic synthesis such as dichloromethane by the indirect cation pool method. The thionium ion is stable at temperatures lower than −20 °C, and reacts with carbon nucleophiles at the carbon adjacent to sulfur. The thionium ion was successfully characterized by UV, NMR, and IR measurements. Electronic structure of the thionium ion, in particular its bond character, is discussed based on the spectroscopic measurements and DFT calculations.