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

Temperature

80 °C

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%.

1. customThe reactor was flushed with argon
2. temperatureThe reaction mixture was cooled to 25° C.
3. addition40 mL H2O and 50 mL aqueous EtOAc were added
4. customThe phases were separated
5. extractionThe H2O phase was extracted with 2×50 mL aqueous EtOAc
6. washThe combined organic layers were washed with 25 mL
7. concentrationThen the organic phase was concentrated
8. dissolutionThe residue was dissolved in 16 mL 5N HCl

ORD record

ord-f0e50b94f7bc4b6aa07aedb620fb705c

Source dataset

uspto-grants-2010_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07732621B2