Tri-tert-butylphosphine (304 mg, 1.50 mmol) in toluene (38 ml) was added under nitrogen to a deoxygenated mixture of carbazole (16.9 g, 0.100 mmol), 4,4′-dibromobiphenyl (15.7 g, 50.4 mmol), sodium tert-butoxide (30.9 g, 321 mmol) and palladium acetate (115 mg, 0.512 mmol) in toluene (50 ml) and the resulting mixture was heated at reflux under nitrogen for 10 days. The reaction mixture was cooled to room temperature and then diluted with more toluene (200 ml). The reaction mixture was filtered to remove the sodium salts. The filtrate was concentrated to dryness to give the crude product as a pale brown solid. The crude product was purified first by chromatography on silica using dichloromethane as the eluent followed by recrystallisation from toluene. The material was then sublimed at 280-281° C. at 10−6 mm Hg to give the product 4,4′-bis(carbazol-9-yl)biphenyl (1) (18.3 g, 75%), as an off-white solid with melting point 280-281° C. (lit. m.p. 281° C.).
