Bicyclo octadiene, Cope

It was pointed out earlier that a Cope rearrangement of 1,5-hexadiene gives 1,5-hexadiene. This is a degenerate Cope rearrangement (p. 1380). Another molecule that undergoes it is bicyclo[5.1.0]octadiene (105). At room temperature the NMR... 

Eine Moglichkeit der Synthese einfacher Vierringverbindungen aus Cyclooctatetraenderivaten beruht auf der thermischen Spaltung der Dienaddukte vom Typ (XVIII) nach Alder-Rickert. Bei Anwendung dieser Methode erhielten Cope und Mitarbeiter (57) aus dem Addukt von Cyclooctatrien-I.3.5 bzw. Bicyclo(4.2.0)octadien-2.4 und Acetylen-dicarbonsauredimethylester (XVIII X=H) in vorzuglicher Ausbeute... 

This equilibrium was first studied by Cope et a .54 in 1952. The Gibbs energy difference is small and the rate of interconversion slow at room temperature. Huisgen et al.55 examined the influence of variations of the ethane fragment on the position of the equilibrium. Attachment of a tricarbonyliron moiety apparently causes stabilization of the bicyclo[4.2.0]octadiene system,56 whereas with tricarbonylmolybdenum the monocyclic isomer is isolated as its metal complex.57... 

The next homolog in the cyclic series, 1,3,5-cyclooctatriene, also closes in a readily reversible transformation to bicyclo[4.2.0]octadiene (Equation 12.63). Cope and his collaborators reported this valence isomerization in 1952. They were able to separate the isomers, which revert to the equilibrium mixture of 85 percent 51 and 15 percent 52 on heating at 100°C for 1 hr.113 Huisgen has reported activation parameters of A Hi = 26.6 kcal mole-1, AS = — 1 cal... 

The formation of the bicyclo[3.2.1]octadienes in Table 1 in such high yields implies that the cyclopropanation step occurs with very high diasteroselectivity because only cis- divinylcyclopropanes are expected to undergo a Cope rearrangement under the mild reaction conditions. Such stereoselectivity is very unusual in the carbenoid... 

Ikeda, H., Takasaki, T., Takahashi, Y, Konno, A., Matsumoto, M., Hoshi, Y, Aoki, T., Suzuki, T, Goodman, J., and Miyashi, T, Photoinduced electron-transfer Cope rearrangements of 3,6-diaryl-2,6-octadienes and 2,5-diaryl-3,4-dimethyl-l,5-hexadienes stereospecificity and an unexpected formation of the bicyclo[2.2.0]hexane derivatives,/. Org. Chem., 64,1640, 1999. 

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