Bicyclo octadiene, Cope rearrangement

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... 

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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