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Catalytic study demonstrates enantiodivergent vinylogous aldol–cyclization in oxindole synthesis, indicating dienolate geometry governs stereochemical outcomes.
In this study, we reported a hydrogen-bond-donor-directed enantiodivergent vinylogous aldol–cyclization cascade reaction of 3-alkylidene oxindoles with isatins and o -quinones. Both enantiomers can be prepared by thiourea or squaramide cinchona alkaloid bifunctional organocatalysts with the same quinine scaffold. Kinetic study data provided the possible reaction mechanism for the vinylogous aldol–cyclization cascade reaction. The DFT calculation data showed the geometry of the generated dienolates from pronucleophiles dominated the observed switch of enantioselectivity.
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Tsou et al. (2022) studied this question.
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