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Highly Enantioselective Catalytic Allylboration of Ketiminoesters: Practical and Scalable Synthesis of α-Fully-Substituted Amino Esters

preprint
submitted on 23.07.2019 and posted on 24.07.2019 by Urmibhusan Bhakta, Padmanabha V. Kattamuri, Juha H. Siitonen, Lawrence B. Alemany, Laszlo Kurti
We report the first catalytic enantioselective allylboration of α-ketiminoesters to afford chiral α-allyl-α-aryl and α-allyl-α-trifluoromethyl amino esters in excellent isolated yields and with high optical purity. This operationally simple allylation proceeds under ambient conditions with indium(I)-iodide/BOX-type ligand (5–10 mol%) and can be performed on a gram scale. A proposed qualitative model for the high stereoselectivity indicates that the origin of selectivity is likely due to attractive interactions between the substrate and the BOX ligand. Using a different BOX-type ligand reverses the reaction’s absolute sense of enantioselectivity. The allylated products are easily converted to enantiomerically enriched α-substituted proline derivatives.

Funding

National Institutes of Health (R01 GM-114609-04)

National Science Foundation (CAREER:SusChEM CHE-1546097)

Robert A. Welch Foundation (grant C-1764)

History

Email Address of Submitting Author

kurti.laszlo@rice.edu

Institution

Rice University

Country

United States of America

ORCID For Submitting Author

0000-0002-3412-5894

Declaration of Conflict of Interest

No conflict of interest.

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