Toluene → 1-(1,3-Dioxolan-2-yl)-2-(1-hydroxy-2,3,4,5-tetramethyl-2-cyclopentenyl)benzene

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Under a nitrogen atmosphere, a solution of 2-(1,3-dioxolan-2-yl)-bromobenzene (34.36 g, 150.0 mmol) in diethyl ether (206 g) was cooled to −70° C. and a solution of n-butyllithium in n-hexane (1.56 M, 100.96 mL) was added dropwise thereto. After keeping the temperature for 1 hr, a solution of 2,3,4,5-tetramethylcyclopentenone (21.77 g, 157.5 mmol) in diethyl ether (137 g) was added dropwise to the mixture. After raising the temperature to 25° C., the mixture was stirred for 3 hrs. After quenching the reaction by addition of toluene and water, the aqueous layer was removed. The obtained organic layer was washed with saturated brine and then dried over sodium sulfate. The solvent was removed to give a crude product of 1-(1,3-dioxolan-2-yl)-2-(1-hydroxy-2,3,4,5-tetramethyl-2-cyclopentenyl)benzene. To the obtained crude product were added tetrahydrofuran (770 g), 3% aqueous hydrochloric acid solution (385.2 g) and acetone (77 g) and the mixture was stirred at 25° C. for 24 hrs. After the reaction, toluene was added the reaction mixture. The organic layer was washed with water and saturated brine and then dried over sodium sulfate, and the solvent was removed. The residue was purified by silica gel column chromatography to give 2-(2,3,4,5-tetramethylcyclopentadienyl)benzaldehyde (15.78 g, yield 46.5%).

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