The general procedure for the synthesis of 4,5-diazafluoren-9-one from 1,10-phenanthroline was as follows: 1,10-phenanthroline (4.0 g, 22.2 mmol) and potassium hydroxide (KOH, 4.0 g, 71.3 mmol) were dissolved in water (250 mL), heated to boiling and maintained for 1 hour. Subsequently, a hot solution of potassium permanganate (KMnO4, 10.0 g, 63.3 mmol) dissolved in water (150 mL) was added slowly and dropwise over about 1 hour. The reaction mixture was continued to be boiled for 2 hours and then thermally filtered. After cooling the orange colored filtrate, it was extracted with chloroform. The organic extracts were combined and dried with anhydrous sodium sulfate (Na2SO4). After removal of solvent, the crude product was obtained. Further purification was carried out by silica gel column chromatography using acetone/petroleum ether (2:1, v/v) as eluent, resulting in pure 4,5-diazafluoren-9-one as a yellow solid (2 g, 50% yield).1H NMR (CDCl3) data were as follows: δ= 8.80 (d, 2H), 7.96 (d, 2H), 7.35 (d, 2H).
