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Nitration of Porphyrin Systems: A Toolbox of Synthetic Methods
Author(s) -
Mikus Agnieszka,
Łopuszyńska Beata
Publication year - 2021
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.202000985
Subject(s) - porphyrin , nitration , electrophile , chemistry , combinatorial chemistry , electrophilic substitution , aryl , nucleophile , electrophilic aromatic substitution , molecule , nitro , computational chemistry , photochemistry , organic chemistry , catalysis , alkyl
This review addresses nitration reactions of porphyrin derivatives. Simple porphyrins modifications afford valuable intermediates in this area of chemistry. They are useful materials for further transformations, as the NO 2 group introduced into parent porphyrin system increases its electrophilic character, thus allowing a broad spectrum of subsequent reactions, e. g . reduction of NO 2 to NH 2 , subsequent diazotisation, nucleophilic substitution of hydrogen (in ortho ‐position to NO 2 ), a variety of cyclizations, etc. Such reactions are often utilized in the first steps of the designed syntheses, leading to attractive and useful target porphyrin molecules. This approach ( via nitro‐derivatives) allows synthesizing numerous porphyrin‐like compounds of a high degree of complexity, and has thus become one of the methods choice. The substitution by NO 2 group can take place at all positions of the porphyrin systems: four meso ‐positions (5, 10, 15, 20) and eight positions β (2, 3, 7, 8, 12, 13, 17, 18). The third possibility includes the nitration in meso ‐aryl rings attached to positions 5, 10, 15, and 20. The latter derivatives ( meso ‐aryl substituted ones) are a large, well‐known group of synthetic porphyrins. The nitration reactions described herein follow three various mechanisms: (a) radical, (b) via π‐cation radicals and π‐dications, and (c) electrophilic. All the above cases are discussed in detail. According to our knowledge, this is the first such systematic account concerning these reactions.