Ion-paired chiral ligands for asymmetric palladium catalysis

Abstract

Conventional chiral ligands rely on the use of a covalently constructed, single chiral molecule embedded with coordinative functional groups. Here, we report a new strategy for the design of a chiral ligand for asymmetric transition-metal catalysis; our approach is based on the development of an achiral cationic ammonium–phosphine hybrid ligand paired with a chiral binaphtholate anion. This ion-paired chiral ligand imparts a remarkable stereocontrolling ability to its palladium complex, which catalyses a highly enantioselective allylic alkylation of α-nitrocarboxylates. By exploiting the possible combinations of the achiral onium entities with suitable coordinative functionalities and readily available chiral acids, this approach should contribute to the development of a broad range of metal-catalysed, stereoselective chemical transformations. Rather than create a chiral catalyst by combining a chiral ligand with a metal, here an achiral phosphine ligand endowed with a cationic ammonium group is ion-paired with a chiral binaphtholate. A palladium catalyst based on this strategy is shown to be effective for highly enantioselective allylic alkylation of α-nitrocarboxylates.

Cite this article

Ohmatsu, K., Ito, M., Kunieda, T. et al. Ion-paired chiral ligands for asymmetric palladium catalysis. Nature Chem 4, 473–477 (2012). https://doi.org/10.1038/nchem.1311

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