218-01-9

131222-99-6

First, 15.16 g (66.4 mmol) of 2-benzophenanthrene (compound a-1) and 350 mL of carbon tetrachloride were added to a 500 mL three-necked flask. While stirring the mixture at room temperature, 21 g (131 mmol) of bromine was slowly added dropwise over 100 min. Subsequently, the temperature of the reaction solution was raised and heated to reflux for 3 hours. Upon completion of the reaction, the reaction solution was cooled to room temperature and the precipitated crystals were collected by filtration. The resulting crystals were recrystallized using toluene as a solvent. Ultimately, 19.5 g of 6,12-dibromotropic acid (compound a-2, white crystals) was obtained in 76.1% yield.