Synthesis and Antimicrobial Activity of 2-Aryl-4H-3,1-benzoxazin-4-ones

Twenty derivatives of 2-aryl-4H-3,1-benzoxazin-4-one synthesized and their potential therapeutically significance tested against two strains of Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) and four strains of Gram negative bacteria (Shigella flexnari, Escherichia coli, Salmonella typhi and Pseudomonas aeruginsoa) by agar well diffusion method.The 2-(3-nitrophenyl)-4H-3,1benzoxazin-4-one (3f) recorded significant antibacterial activity against Bacillus subtilis whereas 2-(4-bromophenyl)-4H-3,1-benzoxazin-one (3o) exhibited weak antibacterial activity against Staphylococcus aureus.Further 2-(2-methylphenyl)-4H-3,1-benzoxazin-4-one (3b) showed significant activity against Shigella Flexnari, Escherichia coli, Pseudomonas aeruginsoa and Salmonella typhi.The antibacterial activity of synthesized derivatives of 2-aryl-4H-3,1-benzoxazin-4-one was compared to reference standard antibiotics amoxycillin, streptomycin, kanamycin and ciprofloxacin.The present study revealed that 2-aryl-4H-3,1-benzoxazin-4-ones possess good bactericidal activity against a panel of bacteria causing common bacterial diseases and therefore opens the possibility of finding latest clinically useful antibacterial compounds.The synthesized compounds were characterized by 1 H NMR, EI, FT-IR and elemental analysis. Key Words: 2-Aryl-4H-3,1-benzoxazin-4-ones, Synthesis, Antimicrobial activity, Agar well diffusion method.biological applications they can be used as starting materials for synthesis of 1,3,4-oxadiazoline-5-thione 12 , quinazolinone derivatives 13 and triazoles 14 .Like other heterocyclic compounds, benzoxazinones are used directly or indirectly in many industrial, academic research and clinical applications.We already explored many classes of compounds for their potential use in medicinal chemistry as well as their new synthetic methodology developments 15 .Therefore, capable therapeutic prospective of this class of compounds encouraged us to synthesize and biologically screen a series of structural variants of 2-aryl-4H-3,1-benzoxazin-4-one against various strains of Gram positive and Gram negative bacteria.EXPERIMENTAL IR spectra (KBr discs or MeOH) were recorded on a Bruker FT-IR IFS48 spectrophotometer.EI mass spectra data were recorded with various MAT 711 (70 eV) spectrophotometers and data are tabulated as m/z. 1 H NMR spectra were recorded in CDCl3 using Bruker AC400 (300 MHz and 400 MHz) spectrophotometer, respectively.Melting points were determined on a Büchi 434 melting point apparatus and were uncorrected.The progress of all reactions was monitored by