Cope rearrangements degenerate

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 ... 

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... 

Another compound for which degenerate Cope rearrangements result in equivalence for all the carbons is hypostrophene W1). In the case of the compound barbaralane (108) (bullvalene in which one CH=CH has been replaced by a CH2) ... 

Consider the two examples of degenerate Cope rearrangement shown in Fig. 19. 

SCHEME 18. van der Waals volume of activation AV and volume of activation calculated for degenerate Cope rearrangement of 1,5-hexadiene... 

This is perhaps the area where there is the most optimism of attaining the elusive goal of neutral homoaromaticity. It has been suggested that semibullvalene [83], which undergoes degenerate Cope rearrangements through a homoaromatic transition state [83b] (2) with extremely low... 

Characteristics and energetics of the photo-induced electron-transfer degenerate Cope rearrangement of 2,5-diarylhexa-l,5-dienes have been reported in detail. Oxygentrapping experiments have established the two-step nature of the rearrangement of... 

When the dibromo dicyano derivative 368 was later prepared, it was found to exhibit a higher activation barrier to degenerate Cope rearrangement than the parent hydrocarbon... 

Doering and Roth, at the time of their first investigations of 86 in 1963, proposed that the structure 90, which they named bullvalene, should undergo degenerate Cope rearrangements that would make each of the ten CH groups equivalent.179 Equation 12.109 illustrates just a few of these transformations.180... 

H. Quast, M. Seefelder, Angew. Chem. Int. Ed. Engl. 38, 1064 (1999). The Equilibrium between Localized and Delocalized States of Thermochromic Semibullvalenes and Barbaralanes—Direct Observation of Transition States of Degenerate Cope Rearrangements. 

Figure 3. One of the three possible pathways in the degenerate Cope rearrangement of bullvalene.

J. S. McKennis, L. Brener, J. S. Ward, R. Pettit, The Degenerate Cope Rearrangements in Hypostrophene, A Novel CioHio Hydrocarbon. J. Am. Chem. Soc. 1971, 93, 4957M958. 

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