Formic Acid → (R)-2-Hydroxy-4-phenylbutyric acid

Participants

Reaction Steps

Into 1 ml of methanol were dissolved 7 mg (0.01 mmol) of [RuCl2(p-cymene)]2 and 8 mg (0.02 mmol) of (R,R)-TsDPEN to prepare a solution, and to the solution was dropwise added 2 mg (0.02 mmol) of triethylamine, followed by stirring for 0.5 hour at room temperature. To the reaction solution were dropwise added a solution prepared by dissolving 396 mg (2.2 mmol) of 2-oxo-4-phenylbutanoic acid into 4 ml of methanol, and 1.2 ml (8.9 mmol) of triethylamine was furthermore dropwise added thereto. The bath was heated up to a temperature of 40° C., and then 0.25 ml (6.7 mmol) of formic acid was dropwise added over 1 hour, followed by stirring for 2 hours at a bath temperature of 40° C. Upon completion of the reaction, the solvent was distilled off under reduced pressure. Thereto was added 2 ml of water, and then concentrated hydrochloric acid was gradually dropwise added under ice cooling; thus, pH of the solution was adjusted to 2. Extraction was performed twice with 20 ml of ethyl acetate, and then the organic phase was washed with 2 ml of a saturated aqueous solution of sodium chloride, followed by concentration under reduced pressure. As a result, 509 mg (yield 99%, 85% ee) of (2R)-hydroxy-4-phenylbutanoic acid was obtained. 1H-NMR (400 MHz, DMSO-d6): δ 7.28-7.14 (5H, m), 3.91-3.88 (1H, m), 2.66-2.62 (2H, m), 1.91-1.77 (2H, m).

Provenance & Evidence