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.

[1] Chemical Science, 2014, vol. 5, # 4, p. 1506 - 1512
[2] Patent: EP2419391, 2014, B1. Location in patent: Paragraph 0134; 0135
[3] European Journal of Organic Chemistry, 1999, # 5, p. 1191 - 1200
[4] European Journal of Organic Chemistry, 2015, vol. 2015, # 5, p. 1033 - 1039
[5] Patent: EP1623968, 2006, A1. Location in patent: Page/Page column 36