100 g of 3-phenoxybenzyl 2-(3-chloro-4-ethoxyphenyl)-2-methylpropyl ether and 25 g of 97% potassium hydroxide were added to 300 ml of 1,3-dimethyl-2-imidazolidinone (hereinafter referred to as DMI) and the mixture was stirred at 150° C. for 18 h. After cooling to room temperature, the mixture was poured into water and made acidic with a concentrated aqueous hydrochloric acid solution. After extraction with benzene, the benzene solution was washed with water and dried. Benzene was distilled off under reduced pressure and the obtained oily residue was purified according to a column chromatography (silica gel, developer: benzene) to obtain 45.6 g of 3-phenoxybenzyl 2-(3-chloro-4-hydroxyphenyl)-2-methylpropyl ether (m.p. 68° to 69° C.).
