Dimethylformamide → 6-fluoro-1H-indazole-5-carbaldehyde

A solution of 5-bromo-6-fluoro-1H-indazole (3 g, 13.95 mmol) in THF (10 mL) was added to a suspension of NaH (3.38 g, 141 mmol) in THF (100 mL) over 10 min at 0° C. The RM was cooled to −70° C. then the s-Buli solution (1.4 M, 19 mL) was added slowly over 20 min. It was stirred at this temperature for 45 min. A solution of DMF (6.18 mL, 80 mmol) in THF (10 mL) was added over 15 min at −70° C. and the RM was then warmed up to rt over 1 h 30. The reaction was quenched with 100 mL of 1 N HCl. The RM was extracted twice with EtOAc. Then the organics were joined and washed with brine, dried over Na2SO4 and the solvent was removed. The residue was triturated for 1 h with Et2O. The precipitate formed was filtered off and identified as the desired aldehyde. The filtrate was left in the freezer over night and a second batch of the product was filtered off to afford the title compound as a light yellow solid (tR 0.7 min (conditions 2), MH+=165, 1H-NMR in DMSO-d6: 13.50 (s, 1H); 10.15 (s, 1H); 8.39 (d, 1H); 8.32 (s, 1H); 7.45 (d, 1H)).