A mixture of 38.5 g of the 1-(4-diphenylaminophenyl)-2-(4-methoxyphenyl)ethane prepared in Synthesis Example 1-2, 200 ml of sulfolane, and 45 g of sodium iodide was stirred in a four-neck flask at 120° C. to obtain a solution. The thus obtained solution was cooled to 60° C., and 2 ml of distilled water was added to the solution. 32.6 g of trimethylchlorosilane was then added dropwise to the above solution over a period of 30 minutes. Thus, the reaction was carried out at 60° to 70° C. for three hours. The thus obtained reaction mixture was poured into 500 ml of water, whereby a brown tar was obtained. The thus obtained tar was washed with 200 ml of water several times, and dissolved in 300 ml of toluene, whereby a brown toluene solution was obtained. The thus obtained toluene solution was washed twice with 100 ml of a saturated aqueous solution of sodium sulfite, whereby a transparent toluene solution of light yellow in color was obtained. After the thus obtained transparent toluene solution was dried over anhydrous magnesium sulfate, a solvent was distilled away. The thus obtained product was subjected to chromatography using a silica gel and toluene, whereby 31.4 g of 1-(4-diphenylaminophenyl)-2-(4-hydroxyphenyl)ethane was obtained as an oily material.
