2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 5-Bromoacenaphthylene

To 25.4 g (107.3 mmol) of 5-bromoacenaphthene and 500 mL of dehydrated benzene, 29.2 g (128.7 mmol) of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was added, and the mixture was stirred for 6 hours under heat refluxing. Furthermore, 6.0 g (26.4 mmol) of DDQ was added to the reaction mixture, and the mixture was stirred for 4 hours by heating. After allowing the resultant mixture to stand for cooling, a precipitate was filtered off and washed with chloroform. Filtrates were combined and washed with a 10% sodium hydroxide aqueous solution and water. After liquid separation, an organic phase was dried over anhydrous sodium sulfate, and the solvent was distilled off. The residue was dried under reduced pressure to obtain 13.0 g (yield: 51.6%) of 5-bromoacenaphthylene as a brown solid.