Bimacrocyclic concave N-heterocyclic carbenes (NHCs): Synthesis, structure and application in catalyses

Ole Winkelmann, Ulrich Lüning
2009 Supramolecular chemistry (Print)  
Imidazolinium moieties have been incorporated into bimacrocycles to generate precursors for concave N-heterocyclic carbenes (NHCs). Starting from 2-nitroresorcinol and alkenols, symmetric concave imidazolinium salts 1 were obtained. Bimacrocyclization was achieved via ring closing metathesis (RCM). In an analogous fashion, axially chiral concave imidazolinium salts 2 were obtained by using a naphthalene bridgehead devoid of local C 2symmetry. The concave NHCs derived from the symmetric
more » ... s 1 were used as nucleophilic catalysts for the synthesis of γ γ γ γ-butyrolactones and as ligands for transition metal catalysts. Copper complex 18 was used as catalyst for the cyclopropanation of styrene and indene with ethyl diazoacetate (EDA). Palladium complex 24 was used as catalyst for Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions.
doi:10.1080/10610270802468413 fatcat:ypihu3kd2jgfvecwlhi7x6k4r4