1,4-Dihydro-1,4-methanonaphthalene-5,6-diol 4.9 g (45 mmol) of benzoquinone was dissolved in 100 mL DCM and cooled to 0 degrees C in an ice bath. 3.7 mL (3.0 g, 45 mmol) freshly cracked cyclopentadiene was dissolved in 20 mL DCM and added from a dropping funnel to the cooled reaction flask over 20 minutes while stirring vigorously. The reaction was stirred in the ice bath for 1 hr, then brought to room temperature and stirred for 1 hr. Solvent was removed in vacuo, and a solution of 5 g NaOH in 120 mL 50% ethanol was added, producing an instant color change to black. The mixture was stirred for 45 minutes, acidified with 5% HCl, and extracted with diethyl ether.