Hydrochloric Acid → 2-Methyl-5-phenylbenzaldehyde

Under nitrogen atmosphere, 126 g (650 mmol) of 2-methyl-5-phenylbenzonitrile was dissolved in 700 ml of anhydrous toluene, and to the resulted solution was dropped 780 ml of a toluene solution of diisobutyl aluminum hydride (1.0 M solution; 780 mmol) at −10 to 0° C., and the mixture was stirred at room temperature overnight. To the reaction solution was dropped 25 ml of ethyl acetate, and this was poured into a mixture of 2.5 L of ice water and 270 ml of concentrated hydrochloric acid. After stirring at 70 to 75° C. for 1 hour, the mixture was cooled to room temperature, and separated. The organic layer was washed with water, saturated sodium bicarbonate solution, then, water, and concentrated to obtain 123 g of 2-methyl-5-phenylbenzaldehyde.