Site-Selective N-Methylation of 5,15-Diazaporphyrins: Reactive Cationic Porphyrinoids that Provide Isoporphyrin Analogues |
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Authors: | Wen Xi Chia Mayu Nishijo Seongsoo Kang Dr. Juwon Oh Tsubasa Nishimura Dr. Hiroto Omori Dr. Jean-François Longevial Prof. Dr. Yoshihiro Miyake Prof. Dr. Dongho Kim Prof. Dr. Hiroshi Shinokubo |
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Affiliation: | 1. Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 Japan;2. Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul, 03722 South Korea |
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Abstract: | N-Alkylation significantly changes the electronic and optical properties, as well as the reactivity of nitrogen-containing π-conjugated molecules. In this study, it is found that treating 5,15-diazaporphyrins with methyl triflate selectively affords the corresponding N-methyl-5,15-diazaporphyrinium cations in good yield. N-Methylation substantially alters the electronic properties and reactivity of diazaporphyrins. The electron-accepting properties of the N-methyl-5,15-diazaporphyrinium cations are enhanced due to their lowered LUMO level. Stabilization of the LUMO energy enables regio- and stereoselective Diels–Alder reactions of the cationic diazaporphyrin with cyclopentadiene. N-Methylation also enhances the acidity of the inner NH protons, and thus, allows facile deprotonation to provide nitrogen-substituted isoporphyrin analogues with only one NH group in the central cavity. |
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Keywords: | aromaticity conjugation cycloaddition methylation porphyrinoids |
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