In this study, novel benzamide derivatives were synthesized from the ring opening of benzoxazin-4-one in conduction with primary aromatic amines in relatively short reaction durations (1-5) minutes. In just a few minutes, sulphuric acid was utilized to cyclodehydration of benzamide derivatives into quinazolinones intramolecularly. FT-IR, 1H-NMR, 13C-NMR, and DEPT -135- 13C-NMR were used to characterize the structure of newly synthesized compounds, and single crystal X-Ray was used to confirm the structure of compound 3a. The synthesized compounds were shown to have potent antibacterial activity against microorganisms, and a molecular docking analysis revealed a favorable binding contact with the target bacterial DNA gyrase (PDB ID: 1KZN) of S. aureus. Furthermore, in silico ADMET calculations were performed for all synthesized compounds that showed promise when compared to conventional ciprofloxacin.