Hydrogen Bromide → (R)-1-bromo-1-[3,5-bis(trifluoromethyl)phenyl]ethane

Participants

Reaction Conditions

Reaction Steps

Under argon atmosphere, (S)-[3,5-bis(trifluoromethyl)phenyl]ethanol (1) (300 g, 1.16 mol, 96% ee) was added dropwise with phosphorous tribromide (157.3 g, 0.58 mol) at a temperature lower than 20° C. on a water bath, and the mixture was stirred at 19 to 22° C. for 30 minutes. The reaction mixture was cooled, and added dropwise with hydrogen bromide (30% solution in acetic acid, 228 mL, 1.16 mol) at a temperature lower than 0° C., and the mixture was stirred at 13 to 15° C. for 16 hours. The reaction mixture was poured into ice water, and the mixture was extracted with n-hexane (3 L×2). The organic layers were combined, successively washed with saturated aqueous sodium hydrogencarbonate (3 L), and saturated brine (3 L), dried over anhydrous magnesium sulfate, and then concentrated under reduced pressure (90 to 100 mmHg) to obtain 389.2 g of a crude product. The resulting crude product was purified by column chromatography (silica gel: 900 g, developing solvent: n-hexane) to obtain 349.8 g of (R)-1-bromo-1-[3,5-bis(trifluoromethyl)phenyl]ethane (2) as colorless oil (yield: 93.8%).

Provenance & Evidence