A) 3-methyl-8-hydroxyquinoline (15.9 g, 0.10 mol) is dissolved in dichloromethane and slowly added dropwise to 70% nitric acid (126 g, 1.8 mol) at 80°C to 100°C over a period of 1 hour while stirring is maintained. The gases generated during the reaction are scrubbed and vented. The reaction mixture is then heated at 100°C to 105°C for 4 h. After cooling to 85°C, the reaction mixture is treated with 88% formic acid (85%-95% concentration) for 20 min and continued heating at 85°C to 95°C for 0.5 h. The reaction solution is cooled to 0.5°C. The reaction solution was cooled to 0°C, stirred for 1 hour and filtered. The resulting solid was washed with acetone and dried to give 10.6 g of 5-methyl-2,3-pyridinedicarboxylic acid (58.6% yield), which was analyzed by HPLC for 97.4% purity.
[1] Patent: US5371229, 1994, A
[2] Journal of the Chemical Society, 1956, p. 4433,4437
[3] Synthesis, 1989, # 11, p. 880 - 882
