Synthesis
GENERAL STEPS: 2,4-Dichloronicotinic acid (500 mg, 2.60 mmol) was dissolved in acetonitrile (10 mL) and cooled to 0°C. Subsequently, DBU (0.981 mL, 6.51 mmol) and iodomethane (0.814 mL, 13.0 mmol) were sequentially added to the solution. The reaction mixture was stirred at room temperature for 14 hours. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was dissolved in ethyl acetate (10 mL), washed once with water (5 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: ethyl acetate-hexane) to afford methyl 2,4-dichloronicotinate (260 mg, 1.262 mmol, 49% yield) as a light yellow oil.LC/MS (ESI) m/z 206.1 [(M + H)+, calculated value of 205.97 for C7H6Cl2NO2]; LC/MS retention time ( Method D): tR = 0.85 min. 1H NMR (300 MHz, CD3OD) δ ppm 8.42 (d, J = 5.4 Hz, 1H), 7.59 (d, J = 5.4 Hz, 1H), 3.99 (s, 3H).
References
[1] Tetrahedron Letters, 2011, vol. 52, # 4, p. 523 - 525
[2] Patent: WO2015/116060, 2015, A1. Location in patent: Page/Page column 92
[3] Patent: JP2015/528018, 2015, A. Location in patent: Paragraph 0190
[4] Patent: WO2017/218960, 2017, A1. Location in patent: Paragraph 00607
