ipso-Substitution Reaction of Nitro Group with Hydrogen in 5-Nitropyridines

As a result of the oxidative aromatization of 5-nitro-1,4-dihydropyridines with hydrogen peroxide in a dioxane solution, previously unreported in the literature on the 5-(3-)nitropyridines derivatives radical ipso-substitution reaction of the nitro group with hydrogen was discovered. Upon careful examination of the nitro group ipso-substitution reaction, the formation of several by-products such as oxadiaziridine N-oxide, diazene and benzamide, associated with the oxidative-reductive combination of two molecules of 5-nitropyridine and its oxidative destruction, was observed. A possible mechanism for the radical ipso-substitution reaction of the nitro group with hydrogen has been proposed. It was found that the presence of an alkyl or aryl substituent at the 4-position of 5-nitropyridine derivatives does not lead to the ipso-substitution of nitro group with hydrogen. Molecular docking of several by-products’ structures to the presumed antimicrobial activity revealed higher binding affinity values (kcal/mol) with selected protein receptors ranging from –7.7 to –11.7 kcal/mol compared to the antibiotic ciprofloxacin, making them promising candidates for further investigation of potential antimicrobial activity.