Enantioselectivity-Switchable Organocatalytic [4 + 2]-Annulation to Access the Spirooxindole–Norcamphor Scaffold

An organocatalyzed enantiodivergent synthesis of a multifunctionalized spirooxindole-norcamphor scaffold via a [4 + 2]-annulation between cyclicα, β-unsaturated ketone and methylene indolinones has been established. The presence of CaCl2 in DMF could reverse the enantioselectivity to facilely deliver the enantiomers of the corresponding spirooxindoles. Both enantiomers of the corresponding spirooxindoles were obtained in excellent yield and diastereo-/enantioselectivity by employing one single prolinosulfonamide catalyst.