[Mg].BrC(Br)C.[CH2:6]([C:8]1[CH:13]=[C:12]([CH3:14])[CH:11]=[C:10]([CH2:15][CH3:16])[C:9]=1Br)[CH3:7].[C:18](OCC)(=[O:24])[C:19]([O:21][CH2:22][CH3:23])=[O:20].Cl>O1CCCC1>[CH2:6]([C:8]1[CH:13]=[C:12]([CH3:14])[CH:11]=[C:10]([CH2:15][CH3:16])[C:9]=1[C:18](=[O:24])[C:19]([O:21][CH2:22][CH3:23])=[O:20])[CH3:7]To a 3 L volume four-necked flask, magnesium (cutting chip) (35.31 g) and tetrahydrofuran (anhydrous) (600 ml) were added under a nitrogen atmosphere at room temperature. Once starting to stir, the internal temperature was raised to about 30° C., dibromoethane (25.4 g) was added dropwise over 20 minutes to the mixture. After the resulting mixture was stirred for 30 minutes, the internal temperature was raised to about 50° C. To the mixture was added dropwise 2,6-diethyl-4-methylbromobenzene (10-a) (300.18 g) dissolved in tetrahydrofuran (150 ml) over 2 hours. The resulting mixture was stirred at 50° C. for 1 hour and cooled. To the mixture was added dropwise diethyl oxalate (192.5 g) at about 0° C. over 15 minutes. The resulting mixture was stirred at room temperature for 2 hours. Then, 3.5% by weight of hydrochloric acid (1000 ml) and concentrated hydrochloric acid (60 ml) were added with cooling. After the organic solvent was removed under reduced pressure, the aqueous layer was extracted with tert-butyl methyl ether. The organic layer was concentrated under reduced pressure to give 320.82 g of ethyl 2-(2,6-diethyl-4-methylphenyl)-2-oxoacetate (9-a).
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