Sodium Hydroxide → 1H-indole-2,5-dicarboxylic Acid

Participants

Reaction Conditions

Reaction Steps

A solution of 1H-indole-2,5-dicarboxylic acid 2-ethyl ester (20.0 g, 85.75 mmole) and NaOH (100 mmole) in a mixture of water/MeOH (1/1) (200 ml) was stirred at 50° C. for 4 h and then overnight at ambient temperature. The reaction mixture was evaporated in vacuo to dryness and the residue was dissolved in water (200 ml) and acidified with 1M HCl up to pH=3. The precipitates were collected on the filter and washed with water (3×50 ml) and dried over phosphorus pentoxide in dessicator to give indole-2,5-dicarboxylic acid 1 (10.38 g, 59%) of compound 1 as white crystals. MS: 203.7 (M−2H); 204.7 (M−H). 1H-NMR (DMSO-d6): δ 8.32 (m, 1H, H-4, indole); 7.80 (m, 1H, H-6, indole); 7.45 (d, 1H, H-7, indole); 7.22 (s, 1H, H-3, indole).

Provenance & Evidence