Conformational enantiodiscrimination for asymmetric construction of atropisomers.

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 Ligand-Enabled Copper-Catalyzed Asymmetric Oxidative Coupling of 2-Naphthols for the Synthesis of 6,6'-Disubstituted BINOLs.

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 2-naphthols, affording 6,6'-disubstituted BINOLs in up to 89% yield with good enantioselectivities (up to 96:4 e.r.).