Step b) Synthesis of 6-bromo-[1,2,4]triazolo[1,5-a]pyridin-2-amine
Ethyl {[(5-bromopyridin-2-yl)amino]thiocarbonyl}carbamate (12.3 g, 40.4 mmol), hydroxylamine hydrochloride (14.1 g, 202 mmol), and N,N-diisopropylethylamine (DIEA, 15.7 g, 122 mmol) were suspended in a solvent mixture of methanol (MeOH) and ethanol (EtOH) (1:1, v/v). 200 mL). The reaction mixture was stirred at room temperature for 2 h, then warmed up to 70 °C and continued the reaction for 3 h. The reaction was carried out under reduced pressure by distillation. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was dissolved in a solvent mixture of dioxane and water (1:1, v/v) and filtered to afford the target product 6-bromo-[1,2,4]triazolo[1,5-a]pyridin-2-amine as an off-white powder (42.6 g, 99% yield).
The product was analyzed by high performance liquid chromatography (HPLC) with a retention time (Rt) of 1.1 min (purity 99.8%). Liquid chromatography-mass spectrometry (LC/MS) analysis showed that the molecular ion peak [M+H]+ (ESI) was 215.3.
![ethyl {[(5-bromopyridin-2-yl)amino]carbonothioyl}-carbamate](/CAS/GIF/1010120-60-1.gif)
![6-Bromo-[1,2,4]triazolo[1,5-a]pyridin-2-ylamine](/CAS/GIF/947248-68-2.gif)