A series of phenyl-substituted 1,4-dihydro-1,4-epoxynaphthalenes was prepared relying on Diels-Alder reactions of 1,3-diphenylisobenzofuran with various dienophiles. These products were to be epoxidized to provide substrates for an epoxide rearrangement study. Reaction of diphenylacetylene as the dienophile provided a stable cycloadduct in 85% yield. Upon expoxidation of the cycloadduct with mCPBA in methylene chloride the presumed epoxide was not isolated. Reaction conditions allowed for the putative epoxide to rearrange, via a Grob fragmentation pathway, affording a substituted 1(H)-isochromene, identified via GC-MS and C-13 NMR, in 81% yield. Phase transfer conditions allowed for the epoxide to be isolated. This product could then be rearranged, although slowly, upon treatment with lithium perchlorate in refluxing toluene. With the other dienophiles studied, the Diels-Alder cycloadducts were unstable and underwent aromatizing ring opening rearrangements.