General procedure for the synthesis of 1-chloro-2,7-naphthyridine from 2,7-naphthyridin-1(2H)-one hydrochloride: intermediate 2 (5.2 g, 28 mmol) was reacted with phosphorus trichloride (75 ml) for 24 h at 110°C with stirring. After completion of the reaction, the volatiles were removed by distillation under reduced pressure to give a dark colored oily substance. The oily substance was slowly poured into a mixture of saturated aqueous sodium bicarbonate (100 ml, containing 20 g of solid sodium bicarbonate) and ethyl acetate (100 ml) in a pre-cooled ice bath. After separation of the aqueous layer, the aqueous layer was re-extracted with ethyl acetate (2 x 75 ml). All organic phases were combined, washed with brine (15 ml), dried over anhydrous sodium sulfate and concentrated under reduced pressure to give 1-chloro-2,7-naphthyridine as a yellow solid (4.0 g, 85% yield).1H NMR (CDCl3) δ: 9.45 (1H, s), 8.81 (1H, d, J = 5.7 Hz), 8.47 (1H, d, J = 5.7 Hz), 7.66 (1H, d, J = 5.7 Hz), 7.60 (1H, d, J = 5.7 Hz); m/z (ES+, 70V) 165 and 167 (MH+).
![2H-[2,7]Naphthyridin-1-one hydrochloride](/CAS/20180629/GIF/369648-60-2.gif)
