The diene 9, prepared in four steps from diethyl cyclohex-4-ene-1, 2-dicarboxylate, was converted into cyclopropa [4, 5] benzocyclobutene (3) by photoirradiation to the cyclobutene 20 followed by treatment with KO-t-Bu and into cyclopropa [e] cyclobuta [blnaphthalene (45) by Diels-Alder addition to diethyl cyclobutene-1, 2-dicarboxylate, oxidation, and treatment with KO-t-Bu. Attempts to convert 9 into cyclopropa [b] anthracene were unsuccessful. The ...