Abstract Multistep thermal fragmentation of quadruply bicyclo [2.2. 2] octadiene-fused porphyrins giving tetrabenzoporphyrins was examined in detail. After the first extrusion of an ethylene molecule from the porphyrin derivative, the opposite bicyclo [2.2. 2] octadiene moiety preferentially underwent the second retro-Diels–Alder reaction to give an opp- dibenzoporphyrin derivative rather than an adj-dibenzoporphyrin derivative. These two ...
