Asymmetric Synthesis of Bioxindole-Substituted Hexahydrofuro[2,3-b]furans via Hydroquinine Anthraquinone-1,4-diyl Diether-Catalyzed Domino Annulation of Acylidenoxindoles/Isatins, Acylidenoxindoles and Allenoates.

Hydroquinine anthraquinone-1,4-diyl diether [(DHQ)(2)AQN]-catalyzed unprecedented asymmetric domino annulation reactions of acylidenoxindoles/isatins, acylidenoxindoles and allenoates are disclosed in this communication, providing a facile access to hexahydrofuro[2,3-b]furans containing four contiguous chiral centers in good to excellent yields along with good to excellent ee values and moderate to good dr values. Based on theoretical investigations, a concerted [3+2] ring-closure process was proposed, in which steric hindrance and pi-pi stacking interaction between catalyst and substrate subtly co-control the diastereoselectivity of the reaction.