Strained Aromatic Systems. Synthesis of Cyclopropabenzocyclobutenes, Cyclopropanaphthocyclobutenes, and Related Compounds

Article abstract of DOI:10.1021/jo01309a024

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 cyclopropacyclobutanaphthalene (45) by Diels-Alder addition to diethyl cyclobutene-1,2-dicarboxylate, oxidation, and treatment with KO-t-Bu.Attempts to convert 9 into cyclopropaanthracene were unsuccessful.The corresponding diene 15 could not be converted into cyclopropa<3,4>cyclobutabenzene (4), but this compound was prepared by treatment of 27, obtained from chlorocarbene addition to bicyclo<4.2.0>octa -2,4-diene, with KO-t-Bu.Unsuccessful attempts to prepare substituted derivatives of 3, 4, and cyclopropaanthracene as well as cyclopropacyclobutanaphthalene and dicyclopropanaphthalene are described.The chemical and physical properties of 3, 4, and 45 and the chemistry of the dienes 9, 15, and 36 are outlined, and some conclusions are drawn regarding the scope of the Billups reaction.