New scaffold organocatalysts of chiral 3,2′-pyrrolidinyl spirooxindoles promoted enantioselective aldol condensation between isatins and acetone

The evaluation of a new scaffold organocatalyst of chiral spiro (S)-1-benzylspiro[indoline-3,2′-pyrrolidin]-2-one in the enantioselective aldol condensation between isatins and acetone has been executed, and a series of chiral 3-hydroxy-3-(2-oxopropyl)-indolin-2-ones have been prepared in excellent yields (up to 97%) with good enantioselectivities (up to 82% ee). Compared with the generally used chiral prolinamide organocatalysts, the enantioselectivities of our catalysts are more possibly determined by steric control rather than amide NH hydrogen bonding which is generally beneficial for an enamine organocatalysis.