Bicyclopropenyls, structure

As an example of a more complex structure, the bicyclopropenyl derivative 11 was formed in good yield. Finally, 8-chlorobicyclo[5.1.0]octa-2,4-diene reacted with potassium tert-butoxide to give cyclooctatetraene from the e.TO-monochloride. ... 

In 1980, Sauer et al. synthesized 3,7-dicyanosemibullvalene 4-4 (Scheme 4.4). Cycloaddition of 1,2,4,5-tetrazines with 3,3 -bicyclopropenyl in a cycloaddition-cycloelimination sequence followed by hydrolysis, amination, and dehydration gave 3,7-dicyanosemibullvalene 4-4. The author also determined the activation barrier of Cope arrangement of 4-4 at -158 °C as 5.7 kcal/mol, slightly higher than the value 5.4 kcal/mol of unsubstituted SBV at the same temperature. This result indicates that electro-deficient cyano group at 3,7-position has little effect on the stabilization of delocalized structure [32]. 

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