Step 1: An aqueous solution (50 mL) of lithium hydroxide monohydrate (5.42 g, 141 mmol, 3.0 equiv) was slowly added to a tetrahydrofuran solution (200 mL) of methyl 7-quinolinecarboxylate (8.8 g, 47 mmol). The reaction mixture was stirred at room temperature for 16 hours. Upon completion of the reaction, the tetrahydrofuran was removed by distillation under reduced pressure. To the remaining aqueous phase, 1N aqueous hydrochloric acid solution (141 mL) was slowly added and the pH was adjusted to 7, at which time a white precipitate was produced. The precipitate was collected by filtration and washed sequentially with water and heptane. The resulting solid was dried in a vacuum oven at 50 °C to give 7-quinolinecarboxylic acid (8.4 g, 100% yield) as a white solid. Liquid chromatography analysis (detection wavelength 215 nm): retention time 0.66 min, purity 100%. Mass spectrum (electrospray positive ion mode): m/z 174 ([M+H]+). 1H NMR (400 MHz, d6-DMSO): δ 9.02 (1H, dd), 8.58 (1H, s), 8.48 (1H, d), 8.09 (2H, m), 7.66 (1H, dd).
