Synthesis and properties of a novel cyclic sulfilimine, 2‐methyl‐2,4,1‐benzodithiazin‐2‐ium‐1‐ide

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A novel cyclic sulfilimine, 2‐methyl‐2,4,1‐benzodithiazin‐2‐ium‐1‐ide (4) was synthesized by deprotonation of the corresponding azasulfonium salt (3) with base. The compound 4 was oxidized with potassium permanganate to afford the sulfoximine 5, exclusively. On refluxing in several solvents, compound 4 underwent a ring contraction to afford benzothiazole (8) via the 1,2‐imino shift. The reaction of 4 with a variety of electrophiles, such as dialkyl acetylenedicarboxylate, acylating agents, diphenylcyclopropenone, and phenyl isocyanate, afforded ringopened adducts. Synthetic approaches to cyclic disulfonium ylides are also described.