1. Primary crystallization: 30 g of 1-(2,6-dichloro-3-fluorophenyl)ethanol was dissolved in 105 mL of petroleum ether and heated and stirred under argon protection for 40 minutes until complete dissolution. (R)-1-(2,6-dichloro-3-fluorophenyl)ethanol crystal seed was added, and the crystal seed was observed to become smaller after 45 min; the crystal seed completely disappeared after 1 h; a white solid precipitate precipitated after 3.5 h (precipitated to the bottom); the reaction was stopped after 10 h, and no further separation was required. Filtration and drying gave 22 g of product in 73.3% yield. The enantiomeric excess (ee) was 62.5% as detected by chiral chromatography.
2. Secondary crystallization: 30 g of the primary crystallization product was dissolved in 105 mL of petroleum ether and heated and stirred under argon protection for 45 min until complete dissolution. Add (R)-1-(2,6-dichloro-3-fluorophenyl)ethanol crystalline seed, after 45 minutes, the crystalline seed was observed to become smaller; after 1 hour, the crystalline seed completely disappeared; after 3.5 hours, a white solid precipitate precipitated (precipitated to the bottom); after 10 hours, the reaction was stopped, and there was no need for further separation. Filtration and drying gave 22 g of product in 73.3% yield. The enantiomeric excess (ee) was 95.0% by chiral chromatography.
3. Tertiary crystallization: 30 g of the secondary crystallization product was dissolved in 105 mL of petroleum ether and heated and stirred under argon protection for 40 min until complete dissolution. 45 min later, (R)-1-(2,6-dichloro-3-fluorophenyl)ethanol crystals were added; the crystals disappeared completely after 1 h; a white solid precipitate precipitated (to the bottom of the precipitate) after 3.5 h; the reaction was stopped after 10 h, and there was no need for further separation. The reaction was stopped after 10 hours without further separation. The reaction was stopped after 10 hours without further separation. 23 g of the product was obtained by filtration and drying, with a yield of 76.7%. The enantiomeric excess (ee) was 99.6% by chiral chromatography.
