Asymmetric cross aldol addition of isatins with α,β-unsaturated ketones catalyzed by a bifunctional Br?nsted acid-Br?nsted base organocatalyst
The asymmetric cross-aldol reaction of isatins with α,β- unsaturated ketones has been developed under catalysis by a Cinchona alkaloid-derivated bifunctional Br?nsted acid-Br?nsted base catalyst, affording the aldol adducts in moderate to good yields (18-98%) with moderate to good enantioselectivities (30-97%). The noncovalent organo-catalyzed asymmetric cross-aldol reaction displays a broad substrate scope and wide functional-group tolerability, albeit the electronic and steric properties of both reaction partners have considerable and regular effects on the reactivity and stereocontrol.