Rearrangements of Internally‐bridged Octaphyrin(1.1.1.1.1.1.1.1)s to Porphyrin Dimers

Internally‐bridged octaphyrin(1.1.1.1.1.1.1.1) underwent a rearrangement to meso‐meso linked porphyrin dimer as a new metamorphosis. Extensive examination suggests that hydride‐addition is a key step for the rearrangements to afford thermodynamically more stable porphyrin framework. Further, β‐tetrabromo[36]octaphyrin was transformed to meso‐meso, β‐β, β‐β triply linked porphyrin dimer via a similar mechanism combined with Pd‐mediated reductive homocoupling. Internally‐bridged octaphyrin underwent skeletal rearrangement to meso‐meso linked porphyrin dimer upon ZnII metalation. This reaction was indeed triggered by hydride‐addition reaction to lead to thermodynamically more stable porphyrin framework. Furthermore, β‐tetrabromo[36]octaphyrin rearranged to meso‐meso, β‐β, β‐β triply linked porphyrin dimer via a similar mechanism combined with Pd‐mediated reductive coupling.