General procedure for the synthesis of 5-bromo-3-methyl-1H-pyrazolo[3,4-c]pyridine from 1-(2-bromo-5-fluoro-4-pyridinyl)ethanone: 50 mL of anhydrous ethylene glycol was added to dissolve 1-(2-bromo-5-fluoro-4-pyridinyl)ethanone (8.2 g, 37.6 mmol) in a 150 mL pressure flask. Subsequently, anhydrous hydrazine (1.24 mL, 39.5 mmol) was added slowly dropwise via syringe. The light yellow mixture obtained by stirring was sealed and the reaction was heated at 165°C. After 3.5 h, the orange-brown reaction mixture was removed from the heat source and cooled to room temperature. The reaction mixture was poured into a stirred mixture of 300 g of ice water (1:1), at which point a solid precipitated. After continued stirring for 10 minutes, the heterogeneous mixture was vacuum filtered. The collected solid was dried under vacuum to give a high purity off-white solid product (7.9 g, 99% yield), which could be used in subsequent reactions without further purification. Product characterization data: 1H NMR (CD3OD-d4) δ 8.73 (s, 1H), 7.98 (s, 1H), 2.59 (s, 3H); LC/MS (MH+) = 211.5, 213.7; retention time (RT) = 1.33 min.
![5-Bromo-3-methyl-1H-pyrazolo[3,4-c]pyridine](/CAS/GIF/929617-30-1.gif)