[CH3:1][O:2][C:3]([C:5]1[CH:17]=[CH:16][CH:15]=[C:14]([C:18](=O)[CH3:19])[C:6]=1[O:7][CH:8]([CH3:13])C(OC)=O)=[O:4].Cl.O1CCOCC1>O>[CH3:13][C:8]1[O:7][C:6]2[C:5]([C:3]([O:2][CH3:1])=[O:4])=[CH:17][CH:16]=[CH:15][C:14]=2[C:18]=1[CH3:19]A mixture of 4.42 g of methyl 2-(2-methoxycarbonyl-6-acetylphenoxy)propionate, 20 ml of 6N hydrochloric acid and 20 ml of dioxane is refluxed for 10 minutes, and water is added to the reaction mixture. The aqueous mixture is extracted with ethyl acetate. The extract is washed with water, dried and evaporated to remove solvent. The residue is dissolved in 30 ml of tetrahydrofuran, and 5.55 ml of oxalyl chloride and a drop of dimethylformamide are added to the solution. The mixture is stirred for 1 hour. The reaction mixture is evaporated to remove solvent and the residue is dissolved in 100 ml of benzene. The solution is added dropwise to a refluxed solution of 6.66 ml of triethylamine in benzene and the mixture is refluxed for 5 hours. The reaction mixture is washed successively with 2% hydrochloric acid and water, dried and evaporated to remove solvent. The residue is purified by silica gel column chromatography (solvent; n-hexane:ethyl acetate=5:1) to give 1.48 g of methyl 2,3-dimethylbenzofuran-7-carboxylate.
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