32.14 g (0.1 mol) of the above prepared 5-(N,N-diphenylamino)acenaphthene was dissolved in 300 ml of N,N-dimethylformamide, and 22.73 g (0.15 mol) of phosphorus oxychloride was dropwise added thereto at room temperature for 30 minutes. After raising the temperature to 50° C., the reaction mixture was stirred for 14 hours. The reaction was determined to be finished when disappearance of 5-(N,N-diphenylamino)acenaphthene was identified. The reaction product was poured into an aqueous solution having 45 g (1.05 mol) of 93% sodium hydroxide dissolved in 1000 ml of water. The resultant mixture was cooled to precipitate a crystal, and the crystal was filtrated, washed with water and dried to obtain 30.27 g (yield: 86.6%, melting point: 138.0°-141.0° C.) of 5-[N-(4-formylphenyl)-N-phenylamino]acenaphthene.
