Synthesis
GENERAL STEPS: A THF solution (28.4 mL, 56.8 mmol) of 2M lithium diisopropylammonium (LDA) was slowly added to a tetrahydrofuran (THF, 70 mL) solution of 2,4-dichloropyridine (7 g, 47.3 mmol) at -78 °C, maintaining the temperature at -78 °C and stirring for 30 min. Upon completion of the reaction, the reaction mixture was quenched with excess dry ice, followed by warming to room temperature and continued stirring for 30 min. After neutralizing the reaction mixture with 1.5 N hydrochloric acid (HCl), it was diluted with ethyl acetate (100 mL) and washed sequentially with saturated brine (2 x 50 mL) and deionized water (100 mL). The organic layer was separated, dried over anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure to afford 2,4-dichloronicotinic acid (4.5 g, 23.44 mmol, 50% yield) as a brown solid. The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 8.47 (d, 1H), 7.74 (d, 1H).
References
[1] Patent: WO2016/149393, 2016, A1. Location in patent: Paragraph 0426
[2] Patent: US2011/77267, 2011, A1. Location in patent: Page/Page column 27
[3] European Journal of Organic Chemistry, 2001, # 7, p. 1371 - 1376
[4] Bioorganic and Medicinal Chemistry Letters, 2008, vol. 18, # 1, p. 386 - 390
[5] Patent: WO2015/116060, 2015, A1. Location in patent: Page/Page column 92
