Thermal rearrangement of 2,2-disubstituted benzothiazoline I-oxides (1) in aprotic solvent afforded the corresponding 1,4-benzothiazines (2) and (3). The thermal reaction performed in the presence of electron-deficient acetylenic compounds produced new tricyclic compounds (7) whose structures have been established by an X-Ray crystal structure determination.
Non-stereospecific ring expansions of benzothiazoline sulfoxides