Study 6.5 Organic synthesis a stepurane derivative

Case Study 6.5 Organic synthesis - a stepurane derivative 

In contrast, cyclic (less flexible) di-Jt-methane systems also rearrange from the triplet state. For example, triplet sensitization of bicyclo[2.2.2]octa-2,5,7-triene (barrelene, 78) provides semibullvalene (79) in 40% chemical yield, whereas direct irradiation produces 

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