Aniline → 4-Chloro-2-[1,2,3]triazolo[4,5-b]pyridin-1-yl-phenylamine

1-(5-Chloro-2-nitrophenyl)-1H-[1,2,3]triazolo[4,5-b]pyridine (10 g, 36.3 mmol) was dissolved in 200 mL concentrated HCl in a 1 L round-bottom flask fitted with a magnetic stir bar. Iron powder (4.2 g, 74.4 mmol) was added in portions to the rapidly stirring solution. The resultant thick yellow slurry was allowed to stir overnight until no visible metallic iron was observed in the reaction vessel. The following day, LCMS analysis indicated complete reduction to the aniline. The mixture was subsequently transferred to a 500 mL Buchner funnel, with the assistance of a small amount of concentrated HCl to rinse out the remaining slurry from the reaction vessel, and the insoluble material was collected by vacuum filtration. The filter cake was then stirred into a thick paste with water (15 mL) and the solids collected by vacuum filtration. The material was again stirred in 15 mL water and filtered, the mother liquors were discarded, and the solid material dried in vacuo. The resultant light brown solid was slurried in 50 mL of 1:1 (v/v) EtOAc:acetonitrile and heated to the boiling point with a heat gun. The mixture was allowed to cool to room temperature and the solids were collected by vacuum filtration. The solids were subsequently washed with a small amount of 1:1 EtOAc:acetonitrile and dried in vacuo to generate 7.5 g 4-chloro-2-[1,2,3]triazolo[4,5-b]pyridin-1-yl-phenylamine (light grey solid, 84% yield).