[CH2:1]([O:3][C:4]([C:6]1[CH:7]=[N:8][C:9]2[C:14]([C:15]=1Cl)=[N:13][C:12]([O:17][CH3:18])=[CH:11][CH:10]=2)=[O:5])[CH3:2].C(N(CC)CC)C.C(OCC)(=O)C>[Pd].C(O)C>[CH2:1]([O:3][C:4]([C:6]1[CH:7]=[N:8][C:9]2[C:14]([CH:15]=1)=[N:13][C:12]([O:17][CH3:18])=[CH:11][CH:10]=2)=[O:5])[CH3:2]A mixture of 4-chloro-6-methoxy-[1,5]naphthyridine-3-carboxylic acid ethyl ester (75 g, 241.86 mmol, 1.0 eq), triethylamine (75 mL, 538.08 mmol, 2.22 eq), and 10% palladium on activated carbon (8.2 g) in ethanol (1350 mL) is stirred under hydrogen flow at room temperature for 6 hours. The catalyst is then removed by filtration and the solution is evaporated to dryness to give a yellow solid as crude product, which is purified by column chromatography (silica gel, eluent: petroleum ether:ethyl acetate, 5:1, v/v) to afford 6-methoxy-[1,5]naphthyridine-3-carboxylic acid ethyl ester as a light yellow powder (46.2 g, 77% yield).
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