title: Subporphyrins: emerging contracted porphyrins with aromatic 14pi-electronic systems and bowl-shaped structures: rational and unexpected synthetic routes.
abstract: Subporphyrin is a ring-contracted porphyrin congener consisting of three pyrrolic subunits domed in a C3 symmetric bowl arrangement. Subporphyrin had long been elusive until the first synthesis of tribenzosubporphine in 2006. Shortly after, synthetic protocols of subpyriporphyrin, meso-aryl-substituted subporphyrins, and meso-aryl substituted subchlorins were developed. Subporphyrins display interesting properties including distinct aromaticity arising from 14pi-electronic conjugation, green fluorescence, and strong influences of meso-aryl substituents on the electronic network of the macrocycle. Besides the rational synthetic routes, an unexpected route to a specific subporphyrin from a [32]heptaphyrin(1.1.1.1.1.1.1) was discovered via a thermal extrusion reaction upon Cu(II)-B(III) cooperative metallation. In this Perspective, we review recent progress on subporphyrin chemistry and unprecedented ring-splitting reactions of medium size expanded porphyrins that are triggered upon metallation.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Inokuma
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Osuka
mesh_terms: D018360:Crystallography, X-Ray; D004581:Electronics; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D008958:Models, Molecular; D011166:Porphyrins / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D006841:Hydrocarbons, Aromatic; D011166:Porphyrins