Ethyl quinazoline-6-carboxylate (79 mg, 0.391 mmol) was dissolved in ethanol (4 mL), 1 N aqueous sodium hydroxide (4 mL) was added, and the reaction was stirred for 1 h at room temperature. Upon completion of the reaction, the pH of the reaction mixture was adjusted to 4 with 1 N hydrochloric acid, followed by vacuum evaporation to remove the solvent. Ethanol was added to the residue and the organic layer was concentrated. The residue was dissolved in ethyl acetate-tetrahydrofuran mixed solvent and dried with anhydrous magnesium sulfate followed by vacuum evaporation to give quinazoline-6-carboxylic acid (15 mg, 0.086 mmol, 22% yield). The resulting product was directly used in the subsequent reaction without further purification.1H-NMR (DMSO-d6) δ (ppm): 8.09 (1H, d, J = 8.8 Hz), 8.44 (1H, dd, J = 2.0, 8.8 Hz), 8.83 (1H, d, J = 2.0 Hz), 9.39 (1H, s), 9.79 (1H, s).
