Hydrochloric Acid → 5-Amino-4-[3-(1-ethoxyvinyl)benzoyl]-1-(4-fluorophenyl)pyrazole

Participants

Reaction Conditions

Reaction Steps

A mixture of 5-amino-4-(3-bromobenzoyl)-1-(4-fluorophenyl)pyrazole (3.5 g, 9.7 mmol) [prepared as described in Example 1 above], tributyl-(1-ethoxyvinyl)tin (4.3 ml, 12.36 mmol) and tetrakis(triphenylphosphine)palladium (1.0 g, 0.87 mmol) in dimethylformamide (25 ml) was heated at 95° C. under argon. After 16 h, the reaction mixture was cooled to room temperature and 10% aqueous hydrochloric acid (25 ml) was slowly added. After 30 min., the reaction mixture was diluted with ethyl acetate and filtered through Celite®. The organic layer was separated and washed with brine, dried over sodium sulfate and concentrated in vacuo. The residue was purified by flash chromatography (elution gradient: 10-60% ethyl acetate/hexane) to give 5-amino-4-[3-(1-ethoxyvinyl)benzoyl]-1-(4-fluorophenyl)pyrazole which was dissolved in tetrahydrofuran (50 ml). 1 N hydrochloric acid (20 ml) was added and the reaction mixture was stirred at room temperature for 16 h. The organic layer was separated, washed with brine, dried over sodium sulfate and concentrated in vacuo. The crude product was purified by flash chromatography (elution gradient: 20-50% ethyl acetate/hexane) and then was recrystallized from a mixture of ethyl acetate/hexane to give 5-amino-4-[3-acetylbenzoyl]-1-(4-fluorophenyl)pyrazole (2.0 g).

Provenance & Evidence