Chiral N‐Heterocyclic Carbene Ligands Bearing a Pyridine Moiety for the Copper‐Catalyzed Alkylation of N‐Sulfonylimines with Dialkylzinc Reagents |
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| Authors: | Dr Takahiro Soeta Tomohiro Ishizaka Yuta Tabatake Prof?Dr Yutaka Ukaji |
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| Affiliation: | Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920‐1192 (Japan), Fax: (+81)?76‐264‐5742 |
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| Abstract: | 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. |
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| Keywords: | asymmetric alkylation copper catalysis enantioselectivity N‐heterocyclic carbenes N‐sulfonylimines |
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