To 4'-chloro-N,N-diphenyl-[1,1'-biphenyl]-4-amine (17.7 g, 50 mmol) and aniline (7 g, 75 mmol) was added dry toluene (150 ml) in a 250 ml two-neck flask. Palladium acetate (0.56 g, 2.5 mmol), t-Bu3P (0.225 g, 2.5 mmol) and sodium tert-butoxide (9.8 g, 100 mmol) were then added and the reaction was carried out at 125 °C for 10 hours. Upon completion of the reaction, 50 mL of water was added to quench the reaction and then extracted with ethyl acetate (150 mL). The organic phase was dried over anhydrous sodium sulfate, filtered and concentrated. Purification by column chromatography (petroleum ether: dichloromethane = 1:2) afforded the yellow solid product N,N,N'-triphenylbenzidine (17.9 g, 43.4 mmol, 86.9% yield).
