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Site‐Selective N‐Methylation of 5,15‐Diazaporphyrins: Reactive Cationic Porphyrinoids that Provide Isoporphyrin Analogues
Author(s) -
Chia Wen Xi,
Nishijo Mayu,
Kang Seongsoo,
Oh Juwon,
Nishimura Tsubasa,
Omori Hiroto,
Longevial JeanFrançois,
Miyake Yoshihiro,
Kim Dongho,
Shinokubo Hiroshi
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201905402
Subject(s) - chemistry , homo/lumo , deprotonation , reactivity (psychology) , cationic polymerization , alkylation , trifluoromethanesulfonate , cyclopentadiene , methylation , medicinal chemistry , conjugated system , molecule , photochemistry , stereochemistry , organic chemistry , catalysis , medicine , ion , biochemistry , polymer , alternative medicine , pathology , gene
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.