Heptagon/Octagon-Fused Diporphyrins or Spiro-Pentagon-Bridged Dichlorin from p-Terphenylene-Bridged Diporphyrin.

Intramolecular fusion reactions of a p-terphenylene-bridged Ni II porphyrin dimer gave different products, depending upon reaction conditions. Oxidation with Fe(OTf) 3 provided syn- and anti-doubly heptagon-fused Ni II porphyrin dimers showing enlarged π-electronic networks, probably via a radical mechanism, while treatment with methanesulfonic acid provided a spiro-pentagon-bridged Ni II chlorin dimer via acid-catalyzed Friedel-Crafts type cyclization. Further, a doubly octagon-fused Ni II porphyrin dimer was synthesized via a sequence of double meso-formylation, reduction to corresponding diol, and BF 3 -catalyzed cyclization.