4-Nitrobenzoic Acid → 1(S)-[2(S)-(2,5-Difluoro-phenyl)oxiranyl]-ethanol

Participants

Reaction Conditions

Reaction Steps

DEAD (870 mg; 2 mmol) and p-nitrobenzoic acid (337 mg; 2 mmol) were dissolved in dry THF (3 ml) and the solution was cooled to 0° C. Then 1(R)-[2(S)-(2,5-Difluoro-phenyl)-oxiranyl]-ethanol (100 mg; 0.5 mmol) and triphenylphosphine (524 mg; 2 mmol) is dissolved in dry THF (10 ml) were added dropwise at such a rate to maintain the temperature below 10° C. The mixture was then allowed to react to completion at 20° C. for 20 hours. Half of the solvent was removed under reduced pressure. The reaction mixture is diluted with diethyl ether (80 ml) and washed with an aqueous saturated ammonium chloride solution. The organic phase is dried over magnesium sulfate. The solids are filtered off and the solvent is removed under reduced pressure. The residue is dissolved in methanol (25 ml) and treated with potassium carbonate (450 mg). The reaction mixture is diluted with an aqueous saturated ammonium chloride solution (30 ml). The reaction mixture is extracted with ethyl acetate (2 times 20 ml). The combined organic phases are washed with water (2 times 30 ml) and with brine (2 times 30 ml). The organic phase is dried over magnesium sulfate. The solids are filtered off and the solvent is removed under reduced pressure. The crude residue is purified by chromatography (Petrole ether/ethyl acetate 20:1). 53 mg (yield: 53%) of desired 1(S)-[2(S)-(2,5-Difluoro-phenyl)-oxiranyl]-ethanol was obtained as a colorless oil. The HPLC purity is 76%.

Provenance & Evidence