1H-Pyrrolo[2,3-b]pyridine-5-carboxylic acid

754214-41-0

754214-42-1

The general procedure for the synthesis of 7-azaindole-5-carboxylic acid from the compound (CAS: 754214-41-0) was as follows: the crude acid 10 was dissolved in dichloromethane (5 mL), and DDQ was added in batches until TLC analysis showed complete consumption of the starting material. The reaction mixture was concentrated to give a solid residue containing azaindole 11. The residue was dissolved in 5% HCl in methanol solution (5 mL) and stirred for 1.5 hours at room temperature. After completion of the reaction, the mixture was concentrated and diluted with chloroform and saturated saline. The mixture was alkalized to pH 11 with 50% NaOH solution and the organic layer was discarded. The aqueous layer was neutralized with 6 M HCl and extracted with ethyl acetate (4 times). The organic extracts were combined, dried with magnesium sulfate, filtered and concentrated. The residue was purified by preparative thin layer chromatography (PTLC) using dichloromethane: methanol = 9:1 as eluent to give 7-azaindole-5-carboxylic acid 12 (3.19 mg, 3% overall yield in three steps). The product was characterized by 1H NMR (400 MHz, CD3OD): δ 6.58 (d, J = 3.5 Hz, 1H), 7.42 (d, J = 3.5 Hz, 1H), 8.58 (d, J = 2.0 Hz, 1H), 8.85 (d, J = 1.7 Hz, 1H).