A STUDY OF SYNTHESIS AND SOME REACTIONS OF 3-PHENYL-1,4-BENZOTHIAZINES

Condensation of o‐aminothiophenol with 2‐bromoacetophenone yields 3‐phenyI‐1,4‐benzo‐thiazine hydrobromide, which upon treatment with alkali gave a mixture of 3‐phenyl‐2H‐1,4‐benzothiazine (VIIa) and 3‐phenyl‐4H‐1,4‐benzothiazine (VIIb). Catalytic hydrogenation led to rearrangement of the benzothiazine (VIIa) to 2‐phenyl‐2‐methyl‐2,3‐dihydrobenzothiazole (X), while reduction with lithium aluminium hydride resulted in 3‐phenyl‐2,3‐dihydro‐4H‐1,4‐benzothiazine (XVI). The latter was transferred to 3‐phenyl‐4‐aminoalkyl‐2,3‐dihydro‐4H‐1,4‐benzothiazines (XVII and XVIII). Copyright © 1969 Journal of Heterocyclic Chemistry