2,2-dimethyl-1,2,3,4,4a,4b,8a,9-octahydro-1,3-methanophenanthrene-5,8-dione

4,4-difluorocyclohexa-2,5-dien-1-one

9,10-dioxoanthracene-2,7-dicarboxylic acid

4-hydroxycyclohexa-2,5-dien-1-one

9,9'-Bixanthene