6,8-dichloro-2,7-naphthyridin-1-ol

Synthesis

Step 4: To a sealed reaction tube was added 2,6-dichloro-4-[(1E)-2-(dimethylamino)vinyl]pyridine-3-carbonitrile (4.0 g, 16.6 mmol) and concentrated hydrochloric acid (20 mL). The reaction mixture was stirred at 45 °C for 18 hours. After completion of the reaction, it was cooled to room temperature and ice water was added to the reaction solution to form a yellow slurry. The precipitate was collected by filtration, washed sequentially with cold water, ether and ethyl acetate, and then dried under vacuum to afford 6,8-dichloro-2,7-naphthyridin-1(2H)-one as a pale yellow solid (80% yield). Mass spectrum (MS) m/z: 215.0 (M + 1). 1H NMR (300 MHz, DMSO-d6): δ 11.75 (s, 1H), 7.76 (s, 1H), 7.50 (t, J = 6.6 Hz, 1H), 6.52 (d, J = 6.6 Hz, 1H).

References

[1] Patent: WO2013/185353, 2013, A1. Location in patent: Page/Page column 21
[2] Patent: WO2014/165232, 2014, A1. Location in patent: Paragraph 0178; 0179
[3] Patent: US2015/119387, 2015, A1. Location in patent: Paragraph 0179; 0180
[4] Patent: JP2017/95498, 2017, A. Location in patent: Paragraph 0085; 0086
[5] Patent: CN104530042, 2017, B. Location in patent: Paragraph 0171; 0183; 0184; 0185