Step 2: Synthesis of 5-bromo-6-methoxy-1H-indazole (compound A33). 5-Bromo-2-fluoro-4-methoxybenzaldehyde (9 g, 38.6 mmol), o-hydroxylamine hydrochloride (3.23 g, 38.6 mmol) and potassium carbonate (5.87 g, 42.5 mmol) were dissolved in 1,2-dimethoxyethane (90 mL). The reaction mixture was stirred at 100 °C for 1 hour. After completion of the reaction, it was cooled to room temperature, the solids were removed by filtration and the filtrate was concentrated under reduced pressure. To the concentrate was added dimethylacetamide (90 mL) and hydrazine monohydrate (18 mL), and the mixture was stirred at 150 °C overnight. At the end of the reaction, it was cooled to room temperature, water was added to the reaction mixture and the aqueous layer was extracted with ethyl acetate. The organic layers were combined, washed sequentially with water and saturated aqueous sodium chloride and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure to give a yellow paste compound A33 (8.26 g, yield: 94%).ESI-MS m/z: 227,229 [M + H]+; 1H-NMR (300 MHz, CDCl3) δ (ppm): 3.96 (s, 3H), 6.92 (s, 1H), 7.94 (d, J=1.1 Hz, 2H).
