Frontier-Controlled Pericyclic Reactions of a Powerful Electron-Attracting Fused-Ring Cyclopentadienone

Article abstract of DOI:10.1021/jo00140a028

2-Oxo-1,3-bis(ethoxycarbonyl)-2H-cyclopentaacenaphthylene (1a) reacts readily with dienophile to give <4 + 2> ? cycloadducts that lose carbon monoxide spontaneously to afford tetrasubstituted 1,3-cyclohexadiene derivatives.The cycloadducts with conjugated cyclic olefins undergo facile Cope rearrangement.Adducts with nonconjugated olefins are transformed into intramolecular double Diels-Alder adducts on heating.A proposed pathway for the pericyclic reaction of 1a with cycloheptatriene is supported by an X-ray crystallographic study of the structure of the syn-endo <2 + 4> ? cycloadduct.The cycloaddition reactions of 1a are discussed in terms of frontier molecular orbital (FMO) theory.Molecular mechanics calculations indicate that strain release in the norbornen-7-one system fused to the acenaphthylene ring is important in the decarbonylation reaction and the Cope rearrangement of the primary Diels-Alder adducts of 1a.