Rational design, enantioselective synthesis and catalytic applications of axially chiral EBINOLs

Axially chiral 1,1′-binaphthols (BINOLs) and 1,1′-spirobiindanes (SPINOLs) have achieved great success in the field of asymmetric catalysis. Although several modifications of these skeletons have been reported, new useful scaffolds are in high demand for asymmetric catalysis. Here, on the basis of our ongoing research on atropisomeric alkenes, we have rationally designed a versatile disubstituted 1,1′-(ethene-1,1-diyl)binaphthol (EBINOL) scaffold, which would be a fine complement to 1,1′-binaphthyl and 1,1′-spirobiindane skeletons for asymmetric catalysis. To construct this axially chiral motif asymmetrically, a chiral phosphoric acid-catalysed asymmetric hydroarylation of alkynes has been developed. This approach features an efficient and convergent route to the synthesis of EBINOLs with high functional group tolerance, complete E/Z-selectivity, and excellent enantioselectivities. Density function theory calculations reveal the mechanism and provide insights into the origins of the stereoselectivity and E/Z-selectivity of this chiral Bronsted acid-catalysed alkyne activation method. The potent application of this structural scaffold is demonstrated by a series of asymmetric reactions catalysed by EBINOL derivatives. Axially chiral compounds have proven to be privileged catalysts/ligands for asymmetric catalysis, with BINOL, SPNIOL and their derivatives being particularly successful. Here the authors report a family of axially chiral alkenes, and demonstrate their use in asymmetric catalysis.