Cinchona Alkaloid Derived Primary Amine Catalyzed Intramolecular Desymmetrizing Aldolization Reaction of Diacetonyloxindoles

An asymmetric intramolecular desymmetrizing aldolization reaction was developed that uses 3,3'-diacetonyl-modified oxindole derivatives as substrates. The reaction is catalyzed by a cinchona alkaloid quinine derived primary amine in combination with an organic Bronsted acid. All reactions proceeded smoothly to afford the corresponding spiro[ cyclohexenone-oxindole] derivatives in high yields with excellent enantioselectivities. Because the amine salt catalyst quickly dehydrates the aldol products, no a-hydroxy ketone product was generated in this transformation.