Into a 100-mL three-neck flask were put 1.2 g (4.8 mmol) of 2-chlorodibenzo[f,h]quinoxaline, 2.1 g (4.7 mmol) of 3,5-bis(9H-carbazol-9-yl)phenylboronic acid, and the air in the flask was replaced with nitrogen. To this mixture were added 18 mL of toluene, 6.0 mL of ethanol, and 6.0 mL of an aqueous solution of potassium carbonate (2.0 mol/L). This mixture was stirred to be degassed while the pressure was reduced. To this mixture was added 0.11 g (0.096 mmol) of tetrakis(triphenylphosphine)palladium(0), and the mixture was stirred at 80° C. for six hours under a nitrogen stream, so that a solid was precipitated. The precipitated solid was collected by suction filtration. To the obtained solid was added about 100 mL of water, washed by ultrasonic wave irradiation, and subjected to suction filtration to obtain a solid. To the obtained solid was added about 100 mL of ethanol, washed by ultrasonic wave irradiation, and subjected to suction filtration to obtain a solid. The obtained solid was dissolved in about 1.5 L of hot toluene, and this solution was suction-filtered through Celite and Florisil. A solid obtained by concentration of the filtrate was washed with toluene, so that 2.8 g of a yellow solid, which was the object of the synthesis, was obtained in a yield of 94%. The synthesis scheme of Step 3 is shown in (a-3).
