Porphyrins are generally synthesized by the acid-catalyzed condensation of pyrroles with aldehyde derivatives, followed by oxidative aromatization, a method originally developed by Rothemund and co-workers. Since this synthetic strategy was reported, porphyrin derivatives have played a central role in a wide range of functional materials. We have developed a novel synthetic approach to ABCD-porphyrins by employing platinum as a template, which promotes a cascade sequence involving coordination, cyclization, and dehydrative aromatization.[1] In this method, refluxing the mixture of corresponding mono-dipyrrinatoPt(II)Cl(COE) (COE=cyclooctene) and bisformyldipyrine under nitrogen atmosphere affords ABCD-porphyrin platinum complexes in good yields. Further studies on functional molecules based on this synthetic methodology will be reported in due course.

[1] Chem. Eur. J. 2023, 29, e202301717.

　By appropriately controlling the reaction temperature in the above-mentioned template synthesis, oxidative aromatization can be favored over dehydrative aromatization, leading to the formation of AB-dihydroxyporphyrins. We recently discovered that this intermediate can be conveniently converted into AB-porphyrin quinones by treatment with MnO₂, a mild oxidant.[2] We regard this compound as an important synthon of porphyrinoids and are planning to transform it into functional large molecular architectures.

[2] Asian. J. Org. Chem. 2024, e202400375.

Chiral porphyrins have provided important academic insights in the fields of photofunctional materials and catalysis. Platinum porphyrins are particularly attractive materials owing to their excellent light-harvesting ability through the Soret band, efficient intersystem crossing to the triplet state, and room-temperature phosphorescence properties. However, due to their rigid planarity and the Lewis basicity of the Pt center, chiral induction has been challenging.

In the above-mentioned platinum-templated synthesis, the readily accessible ABCD-hydroxyporphyrin can be converted into a triflate derivative, which is amenable to Pd-catalyzed functional group transformations. This ABCD-porphyrin-OTf serves as a versatile precursor to intrinsically chiral porphyrins. In this work, we successfully synthesized optically active ABCD-porphyrins with intrinsic chirality (without external chiral sources) via Suzuki–Miyaura cross-coupling reactions.[3]

The obtained compounds exhibited remarkably bright circularly polarized phosphorescence (Bcpp > 10^1 M⁻¹ cm⁻¹, the second-brightest ever reported), arising from the combined effects of the porphyrin Soret band, room-temperature phosphorescence properties, and effective chiral induction.　

[3] Chem. Commun. 2025, 61, 957-960.