Rational Synthesis of Antiaromatic 5,15-Dioxaporphyrin and Oxidation into β,β-Linked Dimers

Akihide Nishiyama; Masaya Fukuda; Shigeki Mori; Ko Furukawa; Heike Fliegl; Hiroyuki Furuta; Soji Shimizu

doi:10.1002/anie.201804648

Rational Synthesis of Antiaromatic 5,15-Dioxaporphyrin and Oxidation into β,β-Linked Dimers

Angew Chem Int Ed Engl. 2018 Jul 26;57(31):9728-9733. doi: 10.1002/anie.201804648. Epub 2018 Jul 13.

Authors

Akihide Nishiyama¹, Masaya Fukuda¹, Shigeki Mori², Ko Furukawa³, Heike Fliegl⁴, Hiroyuki Furuta^{1

5}, Soji Shimizu^{1

5}

Affiliations

¹ Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka, 819-0395, Japan.
² Advanced Research Support Center (ADRES), Ehime University, Matsuyama, 790-8577, Japan.
³ Center for Instrumental Analysis, Institute for Research Promotion, Niigata University, Niigata, 950-2181, Japan.
⁴ Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, 0315, Oslo, Norway.
⁵ Center for Molecular Systems (CMS), Kyushu University, Fukuoka, 819-0395, Japan.

PMID: 29901249
DOI: 10.1002/anie.201804648

Abstract

5,15-Dioxaporphyrin was synthesized for the first time by a nucleophilic aromatic substitution reaction of a nickel bis(α,α'-dibromodipyrrin) complex with benzaldoxime, followed by an intramolecular annulation of the α-hydroxy-substituted intermediate. This unprecedented molecule is a 20π-electron antiaromatic system, in terms of Hückel's rule of aromaticity, because lone pair electrons of oxygen atoms are incorporated into the 18π-electron conjugated system of the porphyrin. A theoretical analysis based on the gauge-including magnetically induced current method confirmed its antiaromaticity and a dominant inner ring pathway for the ring current. The unique reactivity of 5,15-dioxaporphyrin forming a β,β-linked dimer upon oxidation was also revealed.

Keywords: aromaticity; dimers; heterocycles; porphyrinoids; redox chemistry.