An intimate mixture of 35 g. (0.094 mole) of tetraphenylcyclopentadienone (p. 806) and 9.3 g. (0.095 mole) of maleic anhydride is placed in a 200-ml. round-bottomed flask (Note 1), and to it is added 25 ml. of bromobenzene. After the mixture has been refluxed gently for 3.5 hours (Note 2), it is cooled (Note 3), a solution of 7 ml. of bromine in 10 ml. of bromobenzene is added through the condenser, and the flask is shaken until the reagents are thoroughly mixed. After the first exothermic reaction has subsided, the mixture is refluxed gently for 3 hours (Note 4). The flask is then immersed in a cooling bath and the temperature of the mixture is held at 0–10° for 2–3 hours. The mixture is filtered with suction, and the crystalline product is washed three times with 10-ml. portions of petroleum ether (b.p. 60–68°). After the product has been dried in the air, it weighs 37–38 g. (87–89%) and melts at 289–290°. It is light brown, but when pulverized it is almost colorless. The filtrate, when diluted with an equal volume of petroleum ether and cooled to 0–10°, yields an additional 2–3 g. of a less pure product which melts at 285–288°. The impure material may be purified by recrystallization from benzene, using 8–9 ml. of benzene per gram of solid (Note 5).