Water → 7-Cyano-2-methoxy-1-naphthaldehyde

Under nitrogen atmosphere, 3.7 g of 2-cyano-7-methoxynaphthalene was dissolved in 40 ml of dichloro-methane, and 6.6 ml of titanium tetrachloride and 4.6 ml of dichloromethyl methyl ether were added dropwise into the resulting solution at 0° C. in this order. The resulting mixture was stirred at room temperature for 30 minutes and cooled to 0° C. again. Water was added to the resulting mixture to cease the reaction, and the resulting mixture was extracted with dichloromethane (100 ml×2). The organic layers were combined, washed with water, a saturated aqueous solution of sodium bicarbonate and brine successively, dried over anhydrous magnesium sulfate, and filtered. The filtrate was concentrated and the resulting crude crystal was washed with ether and dried to give 3.3 g of the title compound as colorless crystals.