SYNTHESIS, CHARACTERIZATION, AND ANTIMICROBIAL ACTIVITY OF ETHYL 4-[3- CHLOROQUINOXALIN-2-YL] AMINO] BENZOATE

A novel hybrid compound, Ethyl 4-[(3-chloroquinoxalin-2-yl)amino]benzoate (ECQAB), was designed and synthesized in two steps, followed by comprehensive characterization using various spectroscopic and analytical techniques. The synthesis process involved the condensation of ortho-phenylenediamine with ethyl pyruvate to produce 3-methylquinoxalin-2(1H)-one, which was then chlorinated using phosphorus oxychloride (POCl₃) before undergoing nucleophilic aromatic substitution with ethyl 4-aminobenzoate. The structure of the compound was definitively confirmed through infrared spectroscopy (IR), proton nuclear magnetic resonance (¹H NMR), carbon-13 NMR (¹³C NMR), and high-resolution mass spectrometry (HRMS). The newly synthesized ECQAB was assessed in vitro for its antimicrobial properties against four bacterial strains—Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa—as well as two fungal strains—Candida albicans and Aspergillus Niger—utilizing agar disc diffusion and micro-broth dilution methods. ECQAB exhibited significant broad-spectrum antimicrobial activity, with minimum inhibitory concentration (MIC) values ranging from 15.6 to 62.5 µg/mL, comparable to the reference standards ciprofloxacin and fluconazole. Notably, it showed impressive effectiveness against S. aureus (MIC = 15.6 µg/mL) and C. albicans (MIC = 31.25 µg/mL). These promising results indicate that the quinoxaline framework featuring a chloro substituent along with an amino benzoate group has considerable potential as a foundation for developing new antimicrobial agents.