Mechanistic Study on Ring‐Contracting Skeletal Rearrangement from Porphycene to Isocorrole by Experimental and Theoretical Methods

• Published in: European journal of organic chemistry 2020-03, Vol.2020 (12), p.1811-1816
• Main Authors: Koide, Taro, Maeda, Takafumi, Abe, Tsukasa, Shiota, Yoshihito, Yano, Yoshio, Ono, Toshikazu, Yoshizawa, Kazunari, Hisaeda, Yoshio
• Format: Article
• Language: English
• Subjects: Contraction; Electrochemical analysis; Isocorroles; Porphycenes; Reaction mechanisms; Ring contraction; Skeletal rearrangement
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201901659

In this study, the ring contracting skeletal rearrangement reaction in one‐pot under basic conditions from octaethylporphycene to two types of isocorroles, i.e., the meso‐formyl and meso‐free forms, was confirmed and the reaction mechanism was proposed by the comparative analyses of the experimental and theoretical studies. The electron accepting nature of the porphycene and imine‐amine conversion of pyrrole rings make it possible to react with hydroxide ions and the following reaction to afford isocorroles. Based on this reaction, the valence of the compound as a ligand as well as the photochemical and electrochemical properties were dramatically changed. The ring‐contracting aromatic to aromatic skeletal rearrangement reaction from β‐octaethylporphycene to two‐types of isocorroles in one pot under basic conditions was confirmed. The electrochemical and photochemical properties were dramatically changed by the ring contraction. The mechanism of this unique reaction was proposed on the basis of the results of experimental and theoretical studies.