Br[C:2]1[CH:3]=[C:4]([O:11][CH3:12])[CH:5]=[C:6]2[C:10]=1[NH:9][N:8]=[CH:7]2.[H-].[Na+].C([Li])(C)(C)C.CN(C)[CH:22]=[O:23]>O1CCCC1>[CH3:12][O:11][C:4]1[CH:5]=[C:6]2[C:10](=[C:2]([CH:22]=[O:23])[CH:3]=1)[NH:9][N:8]=[CH:7]2
To a solution of 7-bromo-5-methoxy-1H-indazole (1.32 g, 5.81 mmol) in tetrahydrofuran (27 mL) at 0° C. was added sodium hydride (0.465 g, 11.62 mmol). The ice bath was removed and stirring continued for 20 min. The solution was cooled to −78° C. and treated with tert-butyllithium (1.7 M in pentane, 6.84 mL, 11.63 mmol) dropwise. The reaction was stirred at −78° C. for 10 min, allowed to warm gradually in the dewar to −50° C., recooled to −78° C., and then treated with dimethylformamide (1.8 mL, 23.25 mmol). After 15 min, the ice bath was removed and stirring continued for 1 h. The reaction was poured onto ice/1 M hydrochloric acid (20 mL). The mixture was extracted with ethyl acetate (2×). The organics were washed with water, then brine, dried over magnesium sulfate, and concentrated to give 1.1 g of 5-methoxy-1H-indazole-7-carbaldehyde (100%) as a tan solid. 1H-NMR (CDCl3, 300 MHz) δ 10.08 (s, 1H), 8.04 (s, 1H), 7.52 (s, 1H), 7.44 (m, 1H), 3.90 (s, 3H); Mass spec.: 177.09 (MH)+.
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