With 9,9-dimethylfluorene-2,7-diboronic acid and 2,7-diiodo-9,9-dimethyl fluorene, which are synthesized according to synthesis example 1, a Suzuki reaction is carried out. Under a nitrogen atmosphere, tetrakis(triphenylphosphine)palladium(0) (1.0 mmol) is dissolved in THF (50 ml), followed by adding thereto 2,7-diiodo-9,9-dimethyl fluorene (50 mmol), a solution of 2M Na2CO3 (50 ml) and 9,9-dimethylfluorene-2,7-diboronic acid (25 mmol)/THF (100 ml) in this order. Thereafter, after refluxing for 7 hr, a reaction is brought to an end. The solution is cooled to room temperature, followed by substituting with toluene and adding substantially 30 ml of 1N HCl, further followed by washing a toluene phase with water until neutrality is obtained. After drying with sodium sulfate, followed by filtering and distilling the solvent away, and thereby a crude product is obtained. After washing with substantially 100 ml of methanol, a colorless crystal is obtained. Furthermore, by passing through a short column from hexane/ethyl acetate to remove original components, finally followed by recrystallizing, and thereby fluorene trimer (20 mmol) is obtained.
