General procedure for the synthesis of 6-chlorophenanthridine from 6(5H)-phenanthridone: Phosphoryl chloride (15 mL) and dimethylaniline (0.63 mL) were sequentially added to a reaction flask containing phenanthridine (2.0 g), followed by heating and refluxing for 3 hours. Upon completion of the reaction, the reaction solution was slowly poured into water and the solid product was precipitated. The solid was extracted with chloroform and the combined organic phases were dried over anhydrous sodium sulfate. The desiccant was removed by filtration and the filtrate was concentrated to dryness under reduced pressure. The resulting crude product was purified by column chromatography (eluent: chloroform) to afford the target compound 6-chlorophenanthridine (2.1 g, yield: 96%).1H NMR (300 MHz, CDCl3, TMS, room temperature): δ 8.63-8.60 (1H, d), 8.55-8.52 (1H, d), 8.50-8.48 (1H, d), 8.11-8.09 (1H, d). 8.09 (1H, d), 7.94-7.92 (1H, t), 7.79-7.66 (3H, m).
