Br[C:2]1[N:7]2[N:8]=[C:9](N)[N:10]=[C:6]2[CH:5]=[CH:4][CH:3]=1.N([O-])=O.[Na+].[BrH:16]>O.[Cu]Br>[Br:16][C:9]1[N:10]=[C:6]2[CH:5]=[CH:4][CH:3]=[CH:2][N:7]2[N:8]=1
2-Bromo-[1,2,4]triazolo[1,5-a]pyridine. A suspension of [1,2,4]triazolo[1,5-a]pyridin-2-amine (0.500 g, 3.73 mmol, obtained from pyridin-2-amine following an analogous procedure as the one described for 5-bromo-[1,2,4]triazolo[1,5-a]pyridin-2-amine) in 48% HBr (5 mL) was cooled to 0° C. and slowly treated with a solution of sodium nitrite (0.386 g, 5.59 mmol) in water (2 mL) resulting in a dark brown suspension with brown gas evolution. The mixture was stirred for 1 h. A dark purple solution of copper(I) bromide (0.642 g, 4.47 mmol) in 48% HBr (2 mL) was added and the reaction mixture was stirred overnight at room temperature. The purple suspension was poured into water (15 mL) and the resulting yellow-orange suspension was collected and dried to give an orange solid which was further purified by column chromatography (eluting with 100% dicholomethane) to afford 2-bromo-[1,2,4]triazolo[1,5-a]pyridine (0.455 g, 61% yield). 1H NMR (400 MHz, DMSO-d6) δ (ppm) 8.96 (dt, 1H), 7.81-7.91 (m, 1H), 7.68-7.79 (m, 1H), 7.27 (td, J=1.37, 6.93 Hz, 1H); MS (ESI) m/z 197.9 [M]+and 200.1 [M+2]+.
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