64-18-6

1019918-39-8

832735-60-1

General procedure for the synthesis of 7-bromo[1,2,4]triazolo[4,3-a]pyridine from formic acid and 4-bromo-2-hydrazinopyridine: 4-bromo-2-hydrazinopyridine (Compound 41.1, 1.0 equiv) was suspended in formic acid (3 mL). The reaction mixture was heated and stirred at 100 °C for 1 hour. After completion of the reaction, the mixture was cooled to room temperature. The VOCs were evaporated under reduced pressure and water (50 mL) was added to the residue. The precipitated solid was collected by filtration, washed with water and dried under reduced pressure at 50 °C to afford 7-bromo[1,2,4]triazolo[4,3-a]pyridine (Compound 41.2, 1.68 g, 90% yield) as an off-white solid. Mass spectrum (electrospray positive ion mode) m/z: 198, 200 [M+H]+.