The asymmetric induction afforded by a chiral sulfinyl group in a palladium/Brønsted-acid-catalyzed intramolecular allylic amination was investigated. Predictions of the diastereoselectivity for various substrates under assumed total thermodynamic control were obtained from density functional theory (DFT), and the correlation with experimental data demonstrates abrupt changes to kinetic control across the substrate scope. The resulting heterocyclic product was readily converted to valuable isoindoline-1-carboxylic acid esters by a two-step oxidation sequence, providing asymmetric access to a key unnatural α-amino acid scaffold.
This paper reports the kinetic resolution of racemic
secondary
alcohols (O-nucleophiles) via stereoselective intramolecular
allylic substitution. The reaction was enabled by synergistic palladium
and chiral phosphoric acid catalysis and produced chiral cis-1,3-disubstituted 1,3-dihydroisobenzofurans with a selective factor
of up to 60.9 and a diastereomeric ratio of up to 7.8:1. Asymmetric
synthesis of a compound with antihistaminic activity was demonstrated
as the application of this methodology.
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