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Carboranes as Aryl Mimetics in Catalysis: A Highly Active Zwitterionic NHC‐Precatalyst
Author(s) -
Selg Christoph,
Neumann Wilma,
Lönnecke Peter,
HeyHawkins Evamarie,
Zeitler Kirsten
Publication year - 2017
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.201700209
Subject(s) - carbene , aryl , substituent , catalysis , steric effects , chemistry , combinatorial chemistry , delocalized electron , organocatalysis , chirality (physics) , carborane , organic chemistry , enantioselective synthesis , alkyl , chiral symmetry breaking , physics , quantum mechanics , quark , nambu–jona lasinio model
Modern catalysis takes advantage of aryl‐based interactions to tune and control reactions. In the design of N ‐heterocyclic‐carbene catalysts, both the electronic and steric nature of the nitrogen substituents play a crucial role. Although hydrocarbon‐based systems and especially aryl residues have contributed considerably to overcome multifaceted catalytic challenges, the unique properties of carborane moieties, including delocalized charge, potential planar chirality, and well‐known thermodynamic stability, offer unprecedented opportunities to develop new catalysts while being employed as aryl mimetics. We report a straightforward synthetic route to a novel zwitterionic triazolium‐based N ‐heterocyclic carbene (NHC) precatalyst bearing a 7,8‐dicarba‐ nido ‐undecaboranyl substituent. The catalyst's excellent activity and its broad applicability are demonstrated in a wide range of organocatalytic transformations. Comparison of the performance with known N ‐aryl NHC catalysts offers preliminary insights into the stereoelectronic nature of this nido ‐carboranyl substituent.