Synthesis
2-Chloro-3-aminopyridine (0.0465 mol) was dissolved in tetrahydrofuran (45 mL) under nitrogen protection and cooled to -78 °C. A 2.0 M solution of lithium diisopropylammonium (LDA, 0.0513 mol) was added slowly and dropwise. The reaction mixture was slowly warmed to 0 °C and stirred at this temperature for 1 hour. Subsequently, the reaction mixture was cooled again to -78 °C and iodomethane (0.0582 mol) was added. The reaction mixture was slowly warmed to room temperature and stirring was continued for 16 hours. Upon completion of the reaction, the reaction was quenched by the addition of saturated ammonium chloride solution and the mixture was extracted with ethyl acetate. The organic layers were combined, dried with anhydrous sodium sulfate, filtered and the solvent was concentrated under reduced pressure. The residue was purified by silica gel short column chromatography (eluent: hexane/ethyl acetate, 80/20). The fraction containing the target product was collected and the solvent was concentrated under reduced pressure to give 5.91 g of 2-chloro-3-methylaminopyridine (intermediate compound 1) in 89% yield.
References
[1] Patent: WO2004/106298, 2004, A1. Location in patent: Page 19-20
[2] Synthesis, 1999, # 11, p. 1893 - 1902
[3] Advanced Functional Materials, 2018, vol. 28, # 44,
[4] Patent: US2004/19051, 2004, A1. Location in patent: Page 11
