To a solution of methyl 3,5-diiodobenzoate (3.0 g, 7.73 mmol), carbazole (3.0 g, 17.94 mmol), Cu (6.4 g, 100.71 mmol) and 18-crown-6 (65 mg, 0.25 mmol) in 1,2-dichlorobenzene (30.0 ml) was added potassium carbonate (12.6 g, 91.17 mmol) under nitrogen and stirring. The reaction was carried out at 180° C. for 10.5 hours. After cooling, the reaction mixture was filtrated. Then, the solid residues were carefully washed with THF. The THF and 1,2-dichlorobenzene were evaporated from the combined filtration solution. The product was purified by silica gel column chromatography using toluene as eluent. The final pure white product was obtained in 2.6 g (71.7%) by recrystallization from acetone/methanol.
