Potassium Carbonate → Indoline-2-carboxylic acid, (S)-

Participants

Reaction Conditions

Reaction Steps

A flask was charged successively with 9.76 g (40.0 mmol) (S)-2-bromophenylalanine, 5.80 g (42.0 mmol) K2CO3, 40 mg (0.4 mmol) CuCl and 40 g NMP. The reactor was flushed with argon and then kept under a slow stream of argon. The reaction mixture was stirred and heated until 80° C. and kept at this temperature. Samples were taken regularly and analyzed by HPLC. After 3.5 h full conversion of (S)-2-bromophenylalanine was found. The reaction mixture was cooled to 25° C. and then 40 mL H2O and 50 mL aqueous EtOAc were added. The pH of this mixture was adjusted to 3.3 with 3.5 g 37% aqueous HCl. The phases were separated. The H2O phase was extracted with 2×50 mL aqueous EtOAc. The combined organic layers were washed with 25 mL sat aqueous NaCl. Then the organic phase was concentrated. The residue was dissolved in 16 mL 5N HCl, followed by pH adjustment to 2.1 with 9.4 g 32% aqueous NaOH. The precipitated (S)-2,3-dihydro-1H-indole-2-carboxylic acid was isolated by filtration and washed with 2×10 mL H2O. 3.24 g (19.8 mmol) (S)-2,3-dihydro-1H-indole-2-carboxylic acid was found after drying. Yield 49.5%, ee>99%.

Provenance & Evidence