Catalytic enantioselective formal hetero-Diels-Alder reactions of enones with isatins to give spirooxindole tetrahydropyranones.

Organocatalytic formal hetero-Diels-Alder reactions of enones with isatins, which gave highly enantiomerically enriched functionalized spirooxindole tetrahydropyranones via an enamine-based mechanism, were developed. The catalyst systems were identified by a screen of combinations of amines, acids, and additives. With the identified catalyst systems, various spirooxindole tetrahydropyranones were synthesized in high yields with high diastereo- and enantioselectivities (see scheme).