Hydrogen Peroxide → (S)-alpha-Methyl-3,5-bis(trifluoromethyl)benzeneacetic Acid

Participants

Reaction Conditions

Reaction Steps

Aqueous hydrogen peroxide (30%, 14 mL) then lithium hydroxide monohydrate (944 mg, 22.4 mmol) were added to a stirred, degassed, cooled (0° C.) solution of (4S)-3-{(2S)-1-oxo-2-[3,5-bis(trifluoromethyl)phenyl]propyl}-4-(phenylmethyl)-2-oxazolidinone (Description 38, 5.0 g, 11.2 mmol) in tetrahydrofuran/water (4:1, 50 mL) and the mixture was stirred at 0° C. for 2.5 hours. Aqueous sodium bisulfite (10%) was added slowly, maintaining the internal temperature below 5° C., until the mixture was acidic. The mixture was extracted with ethyl acetate, the combined organic fractions were dried (MgSO4) and the solvent was evaporated under reduced pressure. The residue was triturated with isohexane and filtered, washing with isohexane. The solvent was evaporated under reduced pressure and the residue was dissolved in ethyl acetate (10 mL/g) and heated to reflux. Dicyclohexylamine (2.45 mL, 12.3 mmol) was added and the mixture was cooled. The solid was collected, suspended in ethyl acetate and washed with aqueous citric acid (10%). The organic layer was washed with water, dried (MgSO4) and the solvent was evaporated under reduced pressure to give the title compound as a colorless solid (1.7 g, 53%). 1H NMR (400 MHz, CDCl3) δ 7.81 (1H, s), 7.78 (2H, s), 3.90 (1H, q, J 7.2 Hz), and 1.60 (3H, d, J 7.2 Hz). e.e. (determined by 500 MHz, 1H NMR of a mixture of 140 mmol of acid and 70 mmol of (1R,2R)-1,2-diphenyl-1,2-ethanediamine, at 284K in CDCl3)>99%.

Provenance & Evidence