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Chiral N‐Heterocyclic Carbene Ligands Bearing a Pyridine Moiety for the Copper‐Catalyzed Alkylation of N ‐Sulfonylimines with Dialkylzinc Reagents
Author(s) -
Soeta Takahiro,
Ishizaka Tomohiro,
Tabatake Yuta,
Ukaji Yutaka
Publication year - 2014
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.201404241
Subject(s) - chemistry , alkylation , carbene , reagent , pyridine , catalysis , moiety , organic chemistry , solvent , combinatorial chemistry , medicinal chemistry
Amino acid‐derived chiral imidazolium salts, each bearing a pyridine ring, were developed as N‐heterocyclic carbene ligands. The copper‐catalyzed asymmetric alkylation of various N ‐sulfonylimines with dialkylzinc reagents in the presence of these chiral imidazolium salts afforded the corresponding alkylated products with high enantioselectivity (up to 99 % ee ). The addition of HMPA to the reaction mixture as a co‐solvent is critical in terms of chemical yield and enantioselectivity. A wide range of N ‐sulfonylimines and dialkylzinc reagents were found to be applicable to this reaction.