To a solution of 2-bromo-4-(6,7-dimethoxyphthalazin-1(2H)-on-4-yl)pyridine (362 mg) in dimethylformamide (2 ml) is added sodium hydride (48 mg, 62.4% in oil,) with ice-cooling under nitrogen atmosphere, and the mixture is stirred at room temperature for 30 minutes. To the mixture is methyl bromoacetate (0.11 ml) under ice-cooling, and the mixture is stirred for 15 minutes. To the mixture is added water, and the mixture is extracted with ethyl acetate. The extract is washed, dried, and concentrated to give 2-bromo-4-(6,7-dimethoxy-2-methoxycarbonylmethylphthalazin-1(2H)-on-4-yl)pyridine (390 mg).
