Benzothiazines in Synthesis. Further Studies of the Intramolecular, Stereoselective Addition of Sulfonimidoyl Carbanions to α,β-Unsaturated Functional Groups

A variety of alkenes substituted by electron-withdrawing groups serve as competent electrophiles for the stereoselective, intramolecular nucleophilic addition of sulfonimidoyl carbanions to form benzothiazines. This reaction generally proceeds with complete stereoselectivity within the limits of our detection. In some cases, benzothiazine formation occurs in a single pot at relatively high temperatures during N-arylation of the simple sulfoximine used in this study. Yet, the process occurs with the same direction and extent of stereoselectivity as that seen when the Michael addition is performed at very low temperatures.