Dimethylformamide → 5-Fluoro-1H-indazole-7-carboxaldehyde

Participants

Reaction Conditions

Reaction Steps

To a solution of 7-bromo-5-fluoro-1H-indazole (1.66 g, 7.72 mmol) in tetrahydrofuran (35 mL) at 0° C. was added sodium hydride (0.618 g, 15.4 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, 9.08 mL, 15.4 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 (2.39 mL, 30.9 mmol). After 15 min, the ice bath was removed and stirring continued for 1 h. The reaction was poured onto ice/I M hydrochloric acid (26.5 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 1.42 g of 5-fluoro-1H-indazole-7-carbaldehyde (quant.) as a light yellow solid. LC/MS (HPLC method 3): tR=1.39 min, 165.17(MH)+.

Provenance & Evidence