Hydrogen Bromide → 6-Bromo-1H-indazole

Participants

Reaction Conditions

Reaction Steps

Sodium nitrite (315 mg, 4.56 mmol) was added in 2 portions to an ice-cooled suspension of 6-aminoindazole (500 mg, 3.8 mmol) in water (0.4 mL) and hydrobromic acid (48%, 1.8 mL). The reaction mixture was stirred for 10 minutes longer than required for the brown gas to disappear. Copper powder (35 mg, 0.55 mmol) was then added and the mixture heated gently until nitrogen evolution began. The reaction mixture was then alternately heated and cooled to control the rate of reaction. When nitrogen evolution ceased, the reaction mixture was heated at 90° C. for 30 minutes, cooled to room temperature, neutralized with aqueous sodium hydroxide and the product extracted into ethyl acetate. The organic layer was washed sequentially with water and brine, dried over sodium sulfate and the solvent removed in vacuo. Flash chromatography on silica gel (20-40% ethyl acetate in hexane) yield the title product (119 mg, 16%).

Provenance & Evidence