Into a four-neck flask were weighed 28.81 g (44.9 mmol) of the bis(3,5-di-t-butyl-4-methoxyphenyl)(2-bromophenyl)phosphine oxide (6). The atmosphere of the reaction vessel which was fitted with a thermometer, a condenser tube, and a dropping funnel with a pressure-equalizing tube was completely replaced with nitrogen. Thereto were added 300 mL of toluene, 29.92 g (247.0 mmol) of N,N′-dimethylaniline, and 30.41 g (224.5 mmol) of trichlorosilane, followed by 15 hours of heating at reflux. After the completion of the reaction, the reaction mixture was poured into 180 mL of 25% sodium hydroxide aqueous solution at 0° C. to 10° C. After 30 minutes of stirring at room temperature, the layers were separated from each other. The water layer was extracted with toluene (100 mL). The combined organic layer was washed with 1N hydrochloric acid aqueous solution, water and brine and dried over anhydrous magnesium sulfate. Toluene was removed by evaporation and the residue was recrystallized from toluene-methanol to obtain the title compound (24.30 g, a white solid).
