Quinidine Thiourea‐Catalyzed Aldol Reaction of Unactivated Ketones: Highly Enantioselective Synthesis of 3‐Alkyl‐3‐hydroxyindolin‐2‐ones

Abstract

New catalysis mechanism! The asymmetric aldol reaction of unactivated ketones and activated carbonyl compounds is realized with a quinidine-derived thiourea catalyst (see scheme), and involves an enolate mechanism instead of the widely used enamine mechanism. With isatins as the substrate, the reaction can be applied to the enantioselective synthesis of biologically active 3-hydroxyindolin-2-ones.