Organocatalytic Enantio- and Diastereoselective Synthesis of Dispirooxindole Derivatives with Adjacent Spirocyclic Centers via [4 + 2] Cycloadditions

The highly diastereo- and enantioselective organocatalytic synthesis of six-membered ring dispirocyclohexane oxindole derivatives with adjacent spirocyclic centers via [4 + 2] cycloadditions is described. The combination of a cinchonidine-derived primary amine catalyst with p-methylbenzoic acid as a cocatalyst allows access to a broad range of dispirocyclohexane oxindoles. The influence of substituents on the reaction outcome was thoroughly evaluated, including those at the N-position of the oxindole and those at the terminal carbon of the C═C double bond.