Molecular conformations induced by the rotation about single bonds play a crucial role in chemical transformations. Revealing the relationship between the conformations of chiral catalysts and the enantiodiscrimination is a formidable challenge due to the great difficulty in isolating the conformers. Herein, we report a chiral catalytic system composed of an achiral catalytically active unit and an axially chiral 1,1′-bi-2-naphthol (BINOL) unit which are connected via a C–O single bond. The two conformers of the catalyst induced by the rotation about the C–O bond, are determined via single-crystal X-ray diffraction and found to respectively lead to the formation of highly important axially chiral 1,1′-binaphthyl-2,2′-diamine (BINAM) and 2-amino-2′-hydroxy-1,1′-binaphthyl (NOBIN) derivatives in high yields (up to 98%), with excellent enantioselectivities (up to 98:2 e.r.) and opposite absolute configurations. The results highlight the importance of conformational dynamics of chiral catalysts in asymmetric catalysis.
Novel axially chiral ligands have been designed and synthesized by merging the chelating picolinic acid with substituted BINOLs. The in-situ-prepared copper catalysts from the ligands and CuI enable the asymmetric oxidative coupling of 2naphthols, affording 6,6′-disubstituted BINOLs in up to 89% yield with good enantioselectivities (up to 96:4 e.r.).
An axially chiral N,N-ligand developed from a [1,1′binaphthalene]-2,2′-diol (BINOL)-based skeleton and phenanthroline is found to be capable of promoting Pd-catalyzed asymmetric allylic amination and alkylation of allyl acetates. The reaction is compatible with cyclic and acyclic secondary amines, primary aliphatic amines, malononitrile, and dialkyl malonates, affording the corresponding chiral products in up to 99% yield and with up to >99% enantiomeric excess.
* sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.orglett.3c01972.Detailed experimental procedures, characterization data, and copies of nuclear magnetic resonance (NMR) and HPLC spectra (PDF)■ AUTHOR INFORMATION
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