Hydrogen Peroxide → Methyl 3-hydroxyquinoline-8-carboxylate

To the mixture of 8-quinoline carboxylic acid (500 mg, 2.89 mmol) in THF (80 mL) was added CH2N2 in Et2O sol. [Prepared from nitrosomethylurea (1.65 g) and 50% KOH (5 mL)] at room temperature. The reaction mixture was stirred for 12 h and then concentrated to give the intermediate ester. 1H NMR (300 MHz, DMSO-d6) δ 3.92 (3H, s), 7.60-7.70 (2H, m), 7.93-7.96 (1H, m), 8.14-8.17 (1H, m), 8.44-8.48 (1H, m), 8.97-8.99 (1H, m). To a solution of the intermediate 8-Quinolinecarboxylic acid methyl ester (2.89 mmol) in AcOH (4 mL) was added 30% H2O2 (0.6 mL). The reaction mixture was heated at 85° C. for 7.5 h. The reaction mixture was treated with sat NaHCO3, and extracted six times with CHCl3. Organic layer was dried over anhydrous MgSO4, and concentrated. Crude residue was triturated with CHCl3/toluene to provide compound 97 (256 mg, 44%, in 2 steps). 1H NMR (300 MHz, DMSO-d6) δ 3.89 (3H, s), 7.52 (1H, d, J=6.9 Hz), 7.57 (1H, d, J=1.5 Hz), 7.66 (1H, dd, J=1.5, 6.9 Hz), 7.95 (1H, dd, J=1.5, 8.1 Hz), 8.63 (1H, d, J=2.7 Hz), 10.5 (1H, br s).