3,4-Dimethylbenzaldehyde → 1-(1,3-Dioxolan-2-yl)-3-(3,4-dimethylphenyl)propane

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Reaction Steps

[2-(1,3-Dioxolan-2-yl)ethyl]triphenylphosphonium bromide (99.2 g, 224 inmol) was suspended in tetrahydrofuran (200 mL) and a solution of potassium t-butoxide (25.1 g, 224 mmol) in tetrahydrofuran (200 mL) was added thereto under nitrogen atmosphere over 30 minutes, followed by stirring of the mixture under ice-cooling for 30 minutes. A solution of 3,4-dimethylbenzaldehyde (20.2 g, 151 mmol) in tetrahydrofuran (100 mL) was added thereto over 20 minutes and the mixture was stirred under ice-cooling for 20 minutes. A saturated aqueous ammonium chloride solution and ethyl acetate were added to the reaction mixture to separate it. The thus obtained organic phase was separated, washed with water and a saturated aqueous NaCl solution and dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure and the residue was purified by silica gel chromatography (hexane:ethyl acetate, 15:1-10:1) to obtain a crude product (29.9 g). 10% Palladium-carbon (3.01 g, 50% hydrous) was added to a solution of the obtained crude product (29.9 g) in methanol (300 mL) and the mixture was stirred at room temperature under hydrogen atmosphere for 2 hours. After the palladium-carbon in the reaction mixture was Celite-filtered, the filtrate was evaporated under reduced pressure. The residue was purified by silica gel chromatography (hexane:ethyl acetate, 10:1) to obtain [1-(1,3-dioxolan-2-yl)-3-(3,4-dimethylphenyl)propane (29.6 g, yield: 98%). Water (250 mL) -was added to a solution of the obtained [1-(1,3-dioxolan-2-yl)-3-(3,4-dimethylphenyl)]propane (29.6 g, 134.4 mmol) in tetrahydrofuran (250 mL) and OXONE™ (248 g, 403 mmol) was added thereto with stirring at room temperature over 20 minutes, followed by stirring of the mixture at room temperature for 18 hours. The insolubles were separated by filtration and a 1N aqueous sodium hydroxide solution was added thereto to bring the pH to 11. Ether was added thereto to separate it. A 1N aqueous hydrochloric acid solution was added to an aqueous phase to bring the pH to 2 and ethyl acetate was added thereto to separate it. The thus obtained organic phase was separated, washed with water and a saturated aqueous NaCl solution and dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure to obtain the title compound (26.1 g, yield: 98%).

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