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Synthesis of Electron‐Deficient Tetrahydro‐ and Dihydroimidazo[1,2‐ f ]phenanthridines by Microwave‐Mediated IMDAF Reactions
Author(s) -
Gulbrandsen Håkon Sætren,
Alfaro Jessica Lizeth Dominguez,
Read Matthew Lovell,
Gundersen LiseLotte
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201700180
Subject(s) - chemistry , benzylamine , phenanthridine , intramolecular force , moiety , aromatization , polar effect , furan , medicinal chemistry , microwave chemistry , photochemistry , stereochemistry , microwave irradiation , organic chemistry , catalysis
N ‐Substituted tetrahydroimidazo[1,2‐ f ]phenanthridines (TIPs) and dihydroimidazo[1,2‐ f ]phenanthridines (DIPs) have a variety of interesting properties, but structural variations of these compounds have, until now, included nitrogen substituents. Herein, TIPs and DIPs that have electron‐withdrawing groups on the phenanthridine moiety have been synthesized. A microwave‐mediated one‐pot intramolecular Diels–Alder reaction of furan (IMDAF) and subsequent aromatization were employed as the key steps. The electron‐deficient dihydrophenanthridines constructed by an IMDAF were oxidized in situ by 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ), and the salts generated were treated with benzylamine to give N ‐benzyl TIP compounds. These TIPs were remarkably stable towards air‐mediated oxidation relative to those TIPs that do not contain electron‐withdrawing substituents and were isolated in high yields. Electron‐deficient TIPs were easily oxidized to give the corresponding DIPs by treatment with N ‐bromosuccinimide.