[Cl-].[CH3:2][O:3]C[P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1.C(NC(C)C)(C)C.C([Li])CCC.[CH2:36]([O:40][C:41]1[CH:48]=[CH:47][CH:46]=[CH:45][C:42]=1[CH:43]=O)[CH:37]([CH3:39])[CH3:38].S(=O)(=O)(O)O>O1CCCC1.CCCCCC.O.C(OCC)(=O)C.O1CCOCC1>[CH2:36]([O:40][C:41]1[CH:48]=[CH:47][CH:46]=[CH:45][C:42]=1[CH2:43][CH:2]=[O:3])[CH:37]([CH3:39])[CH3:38]In 200 ml of tetrahydrofuran are suspended 144 g of (methoxymethyl)triphenylphosphonium chloride and 43 g of diisopropylamine, to which is dropwise added 253 ml of a 1.6 mol/L solution of n-butyllithium in hexane at −50° C. over a period of one hour. The mixture thus obtained is stirred at ambient temperature for one hour. Then, a solution of 25 g of 2-isobutoxy-benzaldehyde in 100 ml of tetrahydrofuran is dropwise added to the reaction mixture obtained above at −50° C. over a period of one hour, and the mixture thus obtained is stirred at ambient temperature for one hour. The reaction mixture is added to a mixture of ethyl acetate and water, and the organic layer is separated. The organic layer is washed with water and saturated aqueous solution of sodium chloride successively and dried over anhydrous magnesium sulfate, and then the solvent is distilled off under reduced pressure. The residue obtained above is mixed with 260 ml of 5% aqueous solution of sulfuric acid and 100 ml of dioxane, heated under reflux for 2 hours, cooled to ambient temperature and diluted with 500 ml of water. Ethyl acetate is added to the reaction mixture and the organic layer is separated. The organic layer is washed with water and saturated aqueous solution of sodium chloride successively and dried over anhydrous magnesium sulfate, and then the solvent is distilled off under reduced pressure. The residue thus obtained is purified by silica gel column chromatography (eluent; hexane:ethyl acetate=95:5) to obtain 17.5 g of 2-(2-isobutoxyphenyl)ethanal as a colorless oily product.
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