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New Lipophilic 2‐Amino‐ N , N′ ‐dialkyl‐4,5‐dimethylimidazolium Cations: Synthesis, Structure, Properties, and Outstanding Thermal Stability in Alkaline Media
Author(s) -
Kunetskiy Roman A.,
Císařová Ivana,
Šaman David,
Lyapkalo Ilya M.
Publication year - 2009
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.200901203
Subject(s) - steric effects , chemistry , delocalized electron , homogeneous , thermal stability , alkyl , alkali metal , aqueous solution , medicinal chemistry , base (topology) , stereochemistry , organic chemistry , mathematical analysis , physics , mathematics , thermodynamics
A series of new N , N′ ‐dialkyl‐4,5‐dimethylimidazolium cations possessing electron‐rich 2‐imidazolylidene‐ or phosphoranylidene‐amino substituents has been efficiently synthesized from common precursors, N , N′ ‐dialkyl‐4,5‐dimethylimidazol‐2‐ylidenes. The new lipophilic salts obtained have been found to be highly stable towards strong alkali under both biphasic and homogeneous conditions. Their exceptional aqueous base resistance, which has hitherto only been seen with peralkylated polyaminophosphazenium cations, may be attributed to three factors: aromatic stabilization, efficient resonance charge delocalization, and steric protection of the exocyclic nitrogen linkage due to bulky lipophilic N ‐alkyl substituents.