The X-Ray Crystal Structures of (anti)-1,4,5,8,9,12-Hexahydro-1,4:5,8:9,12-triepoxytriphenylene, (anti)-9,10-Dibromo-1,4,5,8-tetrahydro-1,4:5,8-diepoxyanthracene, and (anti)-1,4,5,8-tetrahydro-1,4:5,8-dimethanoanthracene. Effects of Strained Bicyclic Annelation on Benzene.