31872-64-7

General procedure for the synthesis of 3-chloro-4-hydroxy-5-nitropyridine from 4-hydroxy-3-nitropyridine: 3-nitropyridin-4-ol (8-a, 20 g, 142.76 mmol, 1 eq.) was dissolved in 50% aqueous acetic acid (250 mL) and reacted with the passage of chlorine gas for 20 h at room temperature. After completion of the reaction, the precipitate was collected by filtration and washed with distilled water. Intermediate 9-b (24 g, 97% yield) was finally obtained.

[1] Patent: WO2013/186332, 2013, A1. Location in patent: Page/Page column 51
[2] Patent: WO2013/186335, 2013, A1. Location in patent: Page/Page column 76
[3] Journal of Medicinal Chemistry, 2006, vol. 49, # 17, p. 5352 - 5362
[4] Patent: WO2009/108551, 2009, A2. Location in patent: Page/Page column 65-66