Hydrochloric Acid → (R)-methanesulfonic acid 1-[3,5-bis(trifluoromethyl)phenyl]ethyl ester

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Reaction Steps

With reference to Japanese Patent No. 3938651, a solution of (R)-1-[3,5-bis(trifluoromethyl)phenyl]ethanol (optical purity, >99.5% ee; 1.6 g; 6.20 mmol) in dichloromethane (20 mL) was added with methanesulfonyl chloride (0.58 mL, 7.44 mmol), triethylamine (1.30 mL, 9.3 mmol), and dimethylaminopyridine (76 mg, 0.62 mmol) with stirring under ice cooling, and the mixture was stirred at the same temperature for 30 minutes. The reaction mixture was added with 1 N hydrochloric acid and chloroform at the same temperature, and the organic layer was separated. The aqueous layer was extracted with chloroform (20 mL×3), and the organic layers were combined, washed with saturated brine, then dried over anhydrous sodium sulfate, and concentrated under reduced pressure to obtain (R)-methanesulfonic acid 1-[3,5-bis(trifluoromethyl)phenyl]ethyl ester (2.23 g) as colorless oil. Then, a solution of the resulting (R)-methanesulfonic acid 1-[3,5-bis(trifluoromethyl)phenyl]ethyl ester (2.23 g) in N,N-dimethylformamide (20 mL) was added with sodium bromide (1.26 g, 12.25 mmol), and the mixture was stirred at 50° C. for 1 hour. The reaction mixture was added with water (30 mL) at room temperature, and the mixture was extracted with hexane (30 mL×3). The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and then concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (hexane:ethyl acetate=10:1) to obtain 1.85 g of 1-bromo-1-[3,5-bis(trifluoromethyl)phenyl]ethane as colorless oil. On the basis of the specific rotation, it was confirmed that the resulting 1-bromo-1-[3,5-bis(trifluoromethyl)phenyl]ethane was obtained after racemization.

Provenance & Evidence