[22]Pentaphyrins(2.0.1.1.0) Displaying N‐Fusion, Pyrrole‐Rearrangement, and Dimerization Reactions Upon Oxidation and Metalation

Exploration of expanded porphyrins with unprecedented reactivities has remained important. Here [22]pentaphyrins(2.0.1.1.0) were synthesized as a constitutional isomer of sapphyrin by acid‐catalyzed cyclization of 1,14‐dibromo‐5,10‐diaryltripyrrin with 1,2‐di(pyrro‐2‐ly)ethenes. These pentaphyrins display roughly planar structures and varying aromaticities depending upon the vinylene structures. The 19,20‐ditolyl pentaphyrin gave an N‐fused product and an unprecedented pyrrole‐rearranged product, depending upon the oxidation conditions. Remarkably, upon the metalation with CuCl, the N‐fused product and the pyrrole‐rearranged product afforded an inner β ‐ β coupled face‐to‐face Cu II complex dimer and an outer β ‐ β coupled lateral Cu II complex dimer, respectively, in fairly good yields. Further, [22]pentaphyrin(2.0.1.1.0) fused with a Ni II porphyrin was effectively dimerized upon oxidation with MnO 2 to give a 16–16’ directly linked dl ‐dimer.