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Iridium-Catalyzed Enantioselective C(sp3)-H Amidation Controlled by Attractive Noncovalent Interactions.

08:00 EDT 12th April 2019 | BioPortfolio

Summary of "Iridium-Catalyzed Enantioselective C(sp3)-H Amidation Controlled by Attractive Noncovalent Interactions."

While remarkable progress has been made over the past decade, new design strategies for chiral catalysts in enantioselective C(sp3)-H functionalization reactions are still highly desirable. In particular, the ability to use attractive non-covalent interactions for rate acceleration and enantiocontrol would significantly expand the current arsenal for asymmetric metal catalysis. Herein, we report the development of a highly enantioselective Ir(III)-catalyzed intramolecular C(sp3)-H amidation reaction of dioxazolone substrates for synthesis of optically enriched γ-lactams using a newly designed γ-amino acid-based chiral ligand. This Ir-catalyzed reaction proceeds with excellent efficiency and with outstanding enantioselectivity for both activated and unactivated alkyl C(sp3)-H bonds under very mild conditions. It offers the first general route for asymmetric synthesis of γ-alkyl γ-lactams. Water was found to be a unique co-solvent to achieve excellent enantioselectivity for γ-aryl lactam production. Mechanistic studies revealed that the ligands form a well-defined groove-type chiral pocket around the Ir center. The hydrophobic effect of this pocket allows facile stereo-controlled binding of substrates in polar or aqueous media. In-stead of capitalizing on steric repulsions as in the conventional approaches, this new Ir catalyst operates through an unprecedented enantiocontrol mechanism for intramolecular nitrenoid C-H insertion featuring multiple attractive non-covalent interactions.

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This article was published in the following journal.

Name: Journal of the American Chemical Society
ISSN: 1520-5126
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