[Synthesis]
1-Benzyl-4-hydroxy-1,8-naphthyridin-2(1H)-one (2.52 g, 10 mmol) was used as a raw material, which was dissolved in phosphoryl chloride (100 mL) and heated to reflux for 2 hours. After the reaction was completed, it was cooled to room temperature and the reaction mixture was slowly added dropwise to crushed ice while stirring. The reaction solution was neutralized with sodium hydroxide solution and subsequently extracted with ethyl acetate. The organic phase was separated, washed with saturated brine and dried over anhydrous sodium sulfate. After concentration under reduced pressure to remove the solvent, purification by column chromatography afforded 1-benzyl-4-chloro-1,8-naphthyridin-2(1H)-one (1.26 g, 47% yield) and 2,4-dichloro-1,8-diazanaphthalene (556 mg, 28% yield).
1-Benzyl-4-chloro-1,8-naphthyridin-2(1H)-one: 1H NMR (500 MHz, CDCl3) δ 8.64 (d, J = 3.0 Hz, 1H), 8.22 (d, J = 7.0 Hz, 1H), 7.49 (d, J = 7.0 Hz, 2H), 7.21-7.28 (m, 4H), 6.94 (s, 1H), 5.73 (s, 2H); 13C NMR (125 MHz, CDCl3) δ 161.62, 151.31, 149.38, 143.20, 137.49, 134.57, 128.92, 128.55, 127.58, 122.40, 118.80, 115.00, 44.56; LCMS (EI) m/z 270.9 (M+), 273.0.
2,4-Dichloro-1,8-diazanaphthalene: 1H NMR (500 MHz, CDCl3) δ 9.10 (d, J = 3.0 Hz, 1H), 8.51 (d, J = 8.5 Hz, 1H), 7.57 (dd, J = 8.5, 3.0 Hz, 1H), 7.54 (s, 1H); 13C NMR (125 MHz, CDCl3) δ 155.63, 155.39, 153.62, 144.70, 133.97, 123.38, 123.36, 120.69; LCMS (EI) m/z 198.9 (M+), 200.7, 203.0. |