1-Butanol → 5-bromo-4-fluoro-2,3-dimethyl-2H-indazole

Participants

Reaction Steps

To a solution of 1-(3-bromo-2,6-difluorophenyl)ethanone (4.25 g) in n-butanol (50 ml) was added hydrazine monohydrate (1.06 ml) at room temperature, and the mixture was heated under reflux for 20 hr. The reaction mixture was cooled, and added to water, and the mixture was extracted with ethyl acetate. The obtained organic layer was washed with saturated aqueous sodium hydrogen carbonate solution and saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane/ethyl acetate). The residue was dissolved in ethyl acetate (50 ml), trimethyloxonium tetrafluoroborate (4.01 g) was added at room temperature, and the mixture was stirred at the same temperature for 3 hr. The reaction mixture was added dropwise to water, and the mixture was extracted with ethyl acetate. The organic layer was washed with water and saturated brine, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (hexane/ethyl acetate) to give the title compound (224 mg).

Provenance & Evidence