Triethylamine → Methyl [(5-chloropyridin-2-yl)amino](oxo)acetate

2-Amino-5-chloropyridine (1.16 g) and triethylamine (1.51 mL) were dissolved in methylene chloride (26 mL), and ethyl chlorooxoacetate (1.10 mL) was added thereto under ice cooling, followed by stirring at room temperature for 14 hours. Saturated aqueous sodium hydrogencarbonate was added to the reaction mixture to partition the mixture, and the organic layer was dried over sodium sulfate anhydrate. The solvent was distilled away under reduced pressure, and the residue was purified by silica gel column chromatography (hexane:ethyl acetate=3:1). The resultant pale-yellow solid was dissolved in methanol (20 mL), and the solution was stirred at 50° C. for 11 hours. The reaction mixture was concentrated under reduced pressure. The precipitated crystals were collected by filtration, and were dried, to thereby give the title compound (0.43 g).