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

24 July 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

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.

Keywords

Catalytic asymmetric allylboration
Chiral homoallylic amine
Chiral homoallylic aminoester
Trifluoromethylated amino acid
Fully substituted stereocenter
Chiral pyrrolidine derivatives

Supplementary materials

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Supporting Information Urmi JACS SI July 23 2019 FINAL
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