Direct catalytic asymmetric vinylogous Michael addition to construct an all-carbon quaternary center with 3-alkenyl-oxindoles

Abstract

The first highly enantioselective asymmetric vinylogous Michael addition of α,α-dicyanoalkenes with 3-alkenyl-oxindoles catalyzed by chiral-at-metal complexes to deliver 3,3′-disubstituted oxindole bearing an all-carbon quaternary stereocenter has been developed. In the presence of 1.0 mol% of chiral Rh(III) complex, corresponding adducts were obtained in 21–98% yields with 80–97% ee. Remarkably, this protocol exhibited excellent advantages in terms of enantioselectivity, given the fact that as low as 0.05 mol% of chiral Rh(III) complex could promote the title reaction on a gram scale to afford the desired product with excellent enantiomer excess values. In addition, the utility of this approach was verified by the formal synthesis of sulfur-containing heterocyclic compounds.