[CH3:1][O-:2].[Na+].Cl[CH2:5][C:6](=[O:12])[CH2:7][C:8]([O:10][CH3:11])=[O:9].O.Cl>C(#N)C.C(O)(=O)C>[CH3:1][O:2][CH2:5][C:6](=[O:12])[CH2:7][C:8]([O:10][CH3:11])=[O:9]113.4 g (2.1 mmol) of sodium methylate are suspended in 150 ml of acetonitrile. 150.5 g (1 mol) of methyl 4-chloroacetoacetate are thereupon allowed to flow in within 5 minutes. The temperature rises, but it is held at 68°-70° C. by cooling. The mixture is subsequently stirred at 70° C. for a further 25 minutes. The reaction mixture is poured into a solution of 350 ml of distilled water and 9 g of acetic acid and held at a pH value of 6-7 by the addition of a total of 83 ml of 32% hydrochloric acid. The organic layer is separated in a separating funnel and the aqueous layer is extracted 3 times with 200 ml of acetonitrile each time. The combined organic phases are dried over magnesium sulphate and concentrated on a rotary evaporator. The crude product distils at 55°-57° C./0.6 mbar. There are obtained 132.34 g (90.6 %) of methyl 4-methoxy-acetoacetate.
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