Example 21.1: Preparation of methyl 3-hydroxy-4-oxo-4,6-dihydro-pyrimido[1,2-b]indazole-2-carboxylate
Step 1: 2-Fluorobenzonitrile (605 mg, 5 mmol) was mixed with 85% hydrazine hydrate (352 mg, 6 mmol) in 1-butanol (3 mL). The reaction mixture was heated to reflux and stirred for 5 hours. After completion of the reaction, it was cooled to room temperature and the precipitate was collected by filtration. The filter cake was washed with dichloromethane and subsequently dried under vacuum to give 3-aminoindazole (293 mg, 44% yield).
1H NMR (300 MHz, D6-DMSO): δ 5.26-6.36 (brs, 2H), 6.84-6.93 (m, 1H), 7.18-7.24 (m, 2H), 7.67 (dt, J = 8.1, 0.9 Hz, 1H), 11.33 (s, 1H).
