Synthesis of Allyl- and Propenyl-Substituted 1,3-Benzoxazines and Their Antimicrobial Activity

New 1,3-benzoxazine derivatives were obtained via Mannich reactions of 2-allyl- and 2-propenylphenol, formaldehyde, and primary amines (benzylamine and 4-bromoaniline) and then converted into the corresponding quaternary ammonium salts through interaction with HBr. The structures of the synthesized compounds were confirmed by PMR, C-13 NMR, and IR spectroscopy. The antimicrobial activity of the synthesized compounds against Staphylococcus aureus, Escherichia coli, Candida albicans, Shigella flexneri, Salmonella enterica, and Aspergillus niger was studied at concentrations of 20, 30, and 50 mg/L. The quaternary salts, especially the compound with an N-benzyl fragment in its structure that manifested bactericidal and fungicidal activity, exhibited the best antimicrobial properties. The synthesized benzoxazinium salts are proposed for further research as bactericidal and fungicidal substances.