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 NAH hydrogen bonding which is generally beneficial for an enamine organocatalysis. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

The evaluation of a new scaffold organocatalyst shows excellent yields and good enantioselectivities in the enantioselective aldol condensation. The steric control plays a more important role in determining the enantioselectivity compared to amide NAH hydrogen bonding.