Lithium Hydroxide → 1H-indole-6-carboxylic acid

Temperature

80 °C

Lithium hydroxide (0.72 g, 17.2 mmol, 3 equiv.) in water (10 mL) was added to methyl indole-6-carboxylate (1 g, 5.7 mmol, 1 equiv.) in tetrahydrofuran (10 mL) and the mixture stirred at 80° C. for 16 hours. The solution was concentrated under vacuum then diluted with dichloromethane (10 mL) and the organic layer extracted with water (3×10 mL). The aqueous phase was acidified to pH<1 with concentrated HCl forming a precipitate. The precipitate was filtered and washed with 1 M aqueous HCl (3×10 mL) to afford 1H-indole-6-carboxylic acid as a white solid, 0.807 g (88% yield). LC @215 nm; Rt 1.02: 100%, m/z (ES+): 162 (M+H+.); δH (400 MHz; MeOD) 8.15 (1H, d), 7.72 (1H, m), 7.67 (1H, m), 7.45 (1H, m), 6.53 (1H, m).

1. concentrationThe solution was concentrated under vacuum
2. additionthen diluted with dichloromethane (10 mL)
3. extractionthe organic layer extracted with water (3×10 mL)
4. filtrationThe precipitate was filtered
5. washwashed with 1 M aqueous HCl (3×10 mL)

ORD record

ord-91c0da0e9c2d491c8e7edf55342a13c7

Source dataset

uspto-grants-2010_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07713996B2