Synthesis, reactions, and antimicrobial evaluations of new benzo[e][1,3]thiazine derivatives

4H‐Spiro[benzo[d][1,3]oxathiine‐2,1′‐cyclohexan]‐4‐one undergoes aminolysis with certain aromatic amines to give the respective 4‐benzenesulfonamide, Ethyl benzoate, and 4‐acetylphenyl of 4‐oxospirobenzo[e][1,3]thiazine derivatives. The Schiff bases prepared by reacting Ethyl benzoate derivative 2a with aldehydes, undergoes cyclocondensation with thioglycolic acid yielding p‐methoxyphenyl and 2‐(thiophen‐2‐yl) thiazolidinone derivatives. Treatment of the benzoate derivative with hydrazine hydrate afforded the corresponding benzohydrazide derivative which upon reaction with phenyl isocyanate and phenyl isothiocyanate afforded the urea and thiourea derivatives. New pyrimidine, pyridone, and imino pyridine derivatives of 4‐oxospirobenzo[e][1,3]thiazine were also successfully prepared by reacting 2b or 2c with the appropriate organic reagents. Structural elucidations for the new products were based upon compatible microanalytical and spectroscopic measurements. Besides, their biological screening indicated that they possess potent antimicrobial activity in comparison with reference drugs.