Synthesis of dibromo-triazoles and their amination with hydroxylamine-O-sulphonic acid

N-heterocyclic compounds have a wide range of applications in medicinal chemistry, bioconjugation and materials chemistry due to their high biological activity, low toxicity and high systemic nature. Dibromo-triazoles and their amino derivatives are important functional materials. 3,5-Dibromo-4H-1,2,4-triazole (1, yield 74%) can be easily synthesised from 1H-1,2,4-triazole (2) using bromine, N-bromosuccinimide or other brominating agents in a high yield. The 3,5-dibromo-4-amino-1,2,4-triazole and 3,5-dibromo-1-amino-1,2,4-triazole (3, yield 21%) can be prepared by reacting compound 1 with hydroxylamine-O-sulphonic acid in weakly alkaline aqueous solutions at reflux temperature. Pure compound 3, a colourless solid, was finally obtained after a column chromatography. 4,5-dibromo-1-amino-1,2,3-triazole and 4,5-dibromo-2-amino-1,2,3-triazole (4, yield 30%) can also be prepared with 1H-1,2,3-triazole (5) as the starting reactant and 4,5-dibromo-1H-1,2,3-triazole (6, yield 78%) as the intermediate. The structures of the compounds above were confirmed using ¹H-NMR, ¹³C-NMR, infrared (IR), LC-MS, XRD and elementary analysis. According to the characterisation results, these compounds have two isomers.