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2,2-Bipyridinyl-5-carboxylic acid (3).11 Potassium permanganate (12.3 g, 78 mmol) was added in 7 portions at 1 h intervals to a solution of 2 (3.4 g, 20 mmol) in water (200 mL). The mixture was heated at 70 C for 3 h and then at 90 C for 4 h more. The brown mixture was then ¬èltered while hot through celite and washed with hot water (2  25 mL). The ¬èltrate was concentrated to approximately 10 mL under reduced pressure, and then 1 M HCl was added slowly until a pH of 4 was obtained. The residue was then ¬èltered and dried to obtain pure 3 (1.2 g, 30%) as a white solid. 1H NMR (400 MHz, DMSO) d 9.19 (s, 1H), 8.76 (d, J ¼ 4.3 Hz, 1H), 8.42¨C8.54 (m, 3H), 8.01 (t, J ¼ 7.1 Hz, 1H), 7.52¨C7.55 (m, 1H); 13C NMR (101 MHz, DMSO) d 166.6,
158.8, 154.7, 150.6, 150.0, 138.7, 137.9, 127.0, 125.4, 121.7, 120.7. ·µ»ØСľ³æ²é¿´¸ü¶à