General procedure for the synthesis of 9-fluorenone-2-carboxylic acid from the compound (CAS: 3096-44-4): potassium hydroxide (1.6 g, 29.4 mmol) was added to a mixture of methanol (7 mL) and water (7 mL) containing compound 12 (200 mg, 0.98 mmol), and the reaction mixture was stirred for 6 hours at 110 °C. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently concentrated under reduced pressure. The pH was adjusted to 3 with 1 N hydrochloric acid and the mixture was extracted with ethyl acetate (30 mL x 3). The organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated to afford the target product 9-fluorenone-2-carboxylic acid (200 mg, 91% yield) as a yellow solid.1H NMR (400 MHz, DMSO-d6) δ 13.30 (s, 1H), 8.19 (d, J = 7.6 Hz, 1H), 8.03 (s, 1H), 7.97-9.89 ( m, 2H), 7.72-7.64 (m, 2H), 7.50-7.44 (m, 1H).
