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Concave Imidazolinium Salts as Precursors to Concave N‐Heterocyclic Carbenes
Author(s) -
Winkelmann Ole,
Näther Christian,
Lüning Ulrich
Publication year - 2007
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.200600843
Subject(s) - chemistry , deprotonation , adduct , metathesis , medicinal chemistry , alkene , ring (chemistry) , triethyl orthoformate , ion , polymer chemistry , organic chemistry , catalysis , polymerization , polymer
Concave bimacrocyclic imidazolinium ions 8 have been synthesized as precursors for N‐heterocyclic carbenes 9 (NHC) in 13 to 29 % overall yields based on 2‐nitroresorcinol ( 1 ). As bridgeheads, 2,6‐bis(ω‐alkenyloxy)anilines 3 have been synthesized from 1 . Reaction of 3 with oxalyl chloride, reduction to respective diamines 5 , and ring closure with triethyl orthoformate gave N , N ‐diaryl‐substituted imidazolinium ions 6 . The terminal vinyl groups were connected by ring‐closing metathesis to give bimacrocyclic imidazolinium ions 7 , whose alkene functions were hydrogenated to give saturated bimacrocyles 8 . The structure of 8a was elucidated by X‐ray analysis. The respective NHC 9 was generated by deprotonation with potassium tert ‐butoxide, and 9 was scavenged with CS 2 to give adduct 10 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)