N-(2-bromo-4-nitrophenyl)-3-methoxy-4-oxo-3,4-dihydro-2H-benzo[e][1,2]thiazine-3-carboxamide-1,1-dioxide was synthesized in three step process with 86 % overall yield. The final structure of compound was evaluated by using spectroscoanalytical methods (1H-NMR and FT-IR). Suitable crystals were obtained by slow evaporation method, and the final structure was confirmed unequivocally by performing single crystal X-ray diffraction (XRD) studies. Geometric parameters were calculated at B3LYP/6-31G (d, p) method with the help of Gaussian 09 software to validate spectrosopic and single crystal X-ray results. The computed data corroborated nicely with the experimental results (spectroscopic and X-ray). Frontier molecular orbitals (FMOs) and reactivity indices revealed the reactivity of benzothiazine derivative. Molecular electrostatic potential (MEP) was measured to understand the electro or nucleophilic nature of compound. Mulliken and natural population charge analysis (NBO) was carried out to prove inter and intramolecular hydrogen bonding.

Muhammad Nadeem Arshad, Naveen Kosar, Adullah Muhammad Asiri, Khurshid Ayub Islam Ullah Khan and Tariq Mahmood