Hydrochloric Acid → (2R)-chloro-3-phenylpropionic acid

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

Thionyl chloride (43.8 g, 368.4 mmol) was added dropwise to a solution of 20.4 g (122.8 mmol) of (2S)-2-hydroxy-3-phenylpropionic acid (optical purity 100% ee (S)) in 200 ml of tetrahydrofuran, and the mixture was stirred at 35 to 40° C. for 2 hours. To that solution was added 1.8 g (24.6 mmol) of dimethylformamide, and the mixture was stirred at 42 to 44° C. for 6 hours. This reaction mixture was cooled and, while maintaining the temperature at 20° C., 70 ml of water was added dropwise and, after about an hour of stirring, the mixture was extracted with 200 ml of toluene. Water (70 ml) was added to the organic phase and, after pH adjustment to 9.0 with a 30% aqueous solution of sodium hydroxide, the organic phase was removed by phase separation. To the aqueous phase obtained was added 200 ml of toluene, the pH was adjusted to 1.0 with 35% aqueous hydrochloric acid, and the aqueous phase was removed by phase separation. The toluene was distilled off under reduced pressure from the thus-obtained toluene phase to give 21.1 g (114.3 mmol, yield 93%) of (2R)-2-chloro-3-phenylpropionic acid. The optical purity of the product as determined by the same method as in Example 12 was 99.8% ee (R) (rate of configurational inversion 99.8%).

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