Synthesis
General procedure for the synthesis of 3,5-dibromo-4-chloropyridine from 3,5-dibromopyridin-4(1H)-one: to 3,5-dibromopyridin-4(1H)-one (0.25 g, 1.0 mmol) was added phosphorous trichloride (POCl3, 2 mL), and the reaction mixture was heated and refluxed for 2 hours at 100 °C. Upon completion of the reaction, the mixture was slowly poured into an ice-water mixture (25 g) and the pH was adjusted to alkaline with saturated sodium bicarbonate solution. Subsequently, the aqueous phase was extracted with dichloromethane (CH2Cl2, 2 x 20 mL), the organic phases were combined and washed with brine (25 mL). The organic layer was dried over anhydrous magnesium sulfate (MgSO4) and concentrated under reduced pressure to afford 3,5-dibromo-4-chloropyridine as a white solid (275 mg, 100% yield). The melting point of the product was 101-103 °C; mass spectrometry analysis showed m/z 272 (100%, [M+H]+).
References
[1] Patent: WO2010/41054, 2010, A1. Location in patent: Page/Page column 39
[2] Tetrahedron, 2010, vol. 66, # 13, p. 2398 - 2403
[3] Journal of Organic Chemistry, 2000, vol. 65, # 10, p. 3154 - 3159
[4] Patent: US2003/17942, 2003, A1
[5] Journal of the American Chemical Society, 2012, vol. 134, # 22, p. 9390 - 9399
