a) Preparation of 6-chloro-N-methylnicotinamide: 6-chloro-3-pyridinecarbonyl chloride (5.65 g, 32.1 mmol) was dissolved in tetrahydrofuran (64 mL), and triethylamine (5.59 mL, 40.1 mmol) and tetrahydrofuran solution of methylamine (20.1 mL, 40.1 mmol) were added sequentially, and the reaction was carried out under the condition of ice bath. After addition, the ice bath was withdrawn and the reaction was stirred at room temperature for 3.5 hours. After completion of the reaction, the reaction solution was concentrated under reduced pressure and the resulting residue was purified by recrystallization (ethyl acetate/hexane) to afford 6-chloro-N-methyl-nicotinamide (5.06 g, 92% yield) as light brown crystals.1H-NMR (CDCl3) δ: 3.05 (3H, d, J = 4.6 Hz), 6.14 (1H, brs), 7.42 (1H, d, J = 8.3 Hz), 8.09 (1H, dd, J = 2.4, 8.3 Hz), 8.72 (1H, d, J = 2.4 Hz).
