Bicyclo octa-3,5-diene Cope rearrangement

The Cope rearrangement of hexa-l,5-diene does not allow for differentiation of starting material and product this is called a degenerate Cope rearrangement. Another example is the automerization of bicyclo[5,l,0]octa-2,5-diene 7 ... 

The Claiscn rearrangement of allyl vinyl ethers is usually an irreversible reaction due to the energetic benefit of forming aC-O double bond. However, in strained bicyclic systems the retro-Claisen rearrangement (3-oxa-Cope rearrangement) of y,<5-unsaturated aldehydes has been observed32. Sometimes equilibrium mixtures of vinyl ether and carbonyl compound were found. For example, the ratio of the valence tautomers, bicyclo[3.1.0]hex-2-ene-6-cWo-methanal to 2-oxabicyclo[3.2.l]octa-3,6-diene, is approximately 7 333. Nevertheless this reaction was used in the preparation of a key intermediate in a prostacyclin synthesis34. 

The Cope rearrangement of 6-endo-vinylbicyclo[3.1.0]hex-2-ene (114) to bicyclo[3.2.1]octa-2,6-diene (115)2 has been shown to take place with a half-life of approximately 1 d at 25 C ( , = 22.9 kcal... 

The key intennediate for the synthesis of ( )-sinulaiene (159), a structurally unusual marine natural product, was the bicyclic divinylcyclopropane (160). Successful Cope rearrangement of this substance would be expected to proceed via the endo isomer (161) to produce the bicyclo[3.2.1]octa-2,6-diene (162), possessing the correct stereochemistry at C-4 (exo-isopropyl group) and fimctionality (exo-vinyl group at C-8, enol ether associated with C-6 and C-7) that would allow the straightforward preparation of the tricyclic ring system of ( )-(159). 

Bicyclo[5.1.0]octa-2,5-diene (homotropilidene), 290, undergoes a degenerate Cope rearrangement to 290a. At room temperature the H-NMR spectrum of 290 consists of a... 

Baldwin, J. E., Kaplan, M. S. Mechanistic alternative for the thermal antara-antara Cope rearrangements of bicyclo[3.2.0]hepta-2,6-dienes and bicyclo[4.2.0]octa-2,7-dienes. J. Am. Chem. Soc. 1971,93, 3969-3977. 

The Cope rearrangement of bicyclo[5.1.0]octa-2,5-diene (3,4-homotropylidene) (5) leads to a product that is identical with the substrate however, six of eight carbon atoms have changed places. The rearrangement is degenerate . As a consequence NMR and C NMR spectra... 

DEGENERATE COPE REARRANGEMENTS OF 4,8-BRlDGED BICYCLO 5.1.0 octa-2,5-dienes... 

Cope rearrangements of 2,6-disubstituted bicyclo[5,l,0]octa-2,5-dienes have been studied to determine the extent of bond making and bond breaking at the transition state. The interpretation of the results was complicated by the enforced boat-transition state, but comparison with polycyclic systems supports the hypothesis that, unlike Cope rearrangements in acyclic dienes, bond cleavage is at least synchronous with bond formation. ... 

W. von E. Doering and W. R. Roth, A rapidly reversible degenerate Cope rearrangement Bicyclo[5.1.0]octa-2,5-diene, Tetrahedron 19 (1963) 715-737. 

The conversion of (298) into (300) upon gas-phase thermolysis occurs by a Cope rearrangement and not by a [1,3] carbon shift or a bisallyl radical mechanism. Thus, similar treatment of (299) affords only (301). Rearrangement of 3-oxobicyclo-[3,2,l]oct-6-ene to 3-oxobicyclo[3,3,0]oct-6-ene occurs only at much higher temperature and presumably by way of a non-concerted mechanism. The nickel-catalysed reaction of norbornene with butadiene affords the 1 2 cxo-adduct (302) which upon thermolysis is converted into the valence isomer (303). Concerted and non-concerted Claisen-type rearrangements have been observed in the A, -phosphorin series. Tricyclo[7,3,0,0 ]dodeca-2,5,7,10-tetraene (304), which is available in six steps starting from bicyclo[3,3,0]octa-3,7-dien-2,6-dione, appears to be an essentially static structure (as assessed by n.m.r. spectroscopy) up to 141 The slow... 

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