[C:1]([O:7][CH3:8])(=[O:6])[CH2:2][C:3]([CH3:5])=[O:4].[OH-].[Ca+2].[OH-].[Cl:12][CH2:13][CH2:14]CC(Cl)=O.CO.Cl>C1(C)C=CC=CC=1>[CH3:8][O:7][C:1](=[O:6])[CH2:2][C:3](=[O:4])[CH2:5][CH2:14][CH2:13][Cl:12]
In an atmosphere of nitrogen, methyl acetoacetate (480 g, 4.14 mol), calcium hydroxide (80.0 g, 1.08 mol) and toluene (4822 ml) were added to a 10 liter capacity flask, and dehydration/draining was carried out under toluene reflux. After 1 hour, by cooling to 60° C., 4-chlorobutanoic acid chloride (254 g, 1.8 mol) was added dropwise thereto, followed by stirring at 60° C. Further 1 hour thereafter, methanol (1325 g, 41.4 mol) was added thereto, followed by stirring for 6 hours under methanol reflux. After completion of the reaction, the reaction was stopped with 432 ml (2.16 mol) of 5 N hydrochloric acid, and then the organic layer was separated and the organic layer was washed with 5% sodium carbonate aqueous solution and water. After evaporation of the solvent under a reduced pressure using an evaporator, the residue was distilled under a reduced pressure (75 to 85° C./0.1 ton) to obtain crude 6-chloro-3-oxo-hexanoic acid methyl ester (1); 214.9 g (GC purity; δ 0.3%).
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