[C:1]([O:8][CH2:9][CH3:10])(=[O:7])[C:2]([O:4]CC)=O.[C:11]1([CH3:19])[CH:16]=[CH:15][CH:14]=[CH:13][C:12]=1[Mg]Cl.[Cl-].[NH4+].CCCCCC.C(OCC)(=O)C>C1COCC1>[CH3:19][C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][C:12]=1[C:2]([C:1]([O:8][CH2:9][CH3:10])=[O:7])=[O:4]
A solution of diethyl oxalate (30 g) in anhydrous THF (300 ml) was cooled to -30° C. A solution of o-tolyl magnesium chloride in THF (1 M, 140 ml) was added to the above solution at a temperature of the reaction solution of -20° C. After stirring at -30° C. for 30 minutes, the mixture was allowed to warm up to 0° C. and combined with an aqueous ammonium chloride solution. The mixture was concentrated under reduced pressure. The residue was treated with water and diethyl ether and phases were separated. The organic phase was washed with water, dried over anhydrous magnesium sulfate and concentrated to give a yellow oil. The oil was subjected to silica gel column chromatography (eluent: hexane/ethyl acetate=10/1) to give the desired ethyl 2-methylbenzoylformate (18 g, yield: 87%).
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