Bioactive Dioxo-Phosphobetaines derived from the reaction of Dichlorodinitrobenzofuroxane with various phosphines

The reactions of tertiary mono- and di-phosphines-specifically methyldiphenylphosphine, 1,2-bis(diphenylphosphino)ethane, and 1,3-bis(diphenylphosphino)propane-with the super-electrophilic heterocycle 5,7-dichloro-4,6-dinitrobenzofuroxane were investigated. These reactions proceeded via nucleophilic aromatic substitution of chlorine atoms and nitro groups on the benzene ring. The products of the reactions (phosphobetaine) were either monomeric or polymeric, depending on whether mono- or di-phosphines were used as reactants. The resulting compounds were characterised using elemental analysis, ¹H-, ¹³C-, and ³¹P NMR spectroscopy, and IR spectroscopy. The reaction mechanism was further elucidated by detecting the formation of NO radicals using EPR spectroscopy. Quantum mechanical calculations provided insights into the energetics, as well as the electrostatic, electronic, topological, and vibrational properties associated with the isomerisation equilibrium of the dioxo-phosphobetaine derivative of benzofuroxan obtained from the reaction with P(CH₃)Ph₂. Additionally, the synthesised compounds exhibited antibacterial activity against Gram-positive bacteria, including Bacillus cereus, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans. These findings suggest that the synthesised dioxo-phosphobetaines could serve as promising candidates for drugs or prodrugs in the treatment of bacterial infections.