Alkylidene Meldrum′s Acid as Acceptor‐Donor‐Acceptor with Azomethine Ylide for Organocatalytic Asymmetric (3+2) Cycloaddition/Annulation: Synthesis of Chromeno[4,3‐b]pyrrolidine

Abstract

AbstractA quinine‐derived thiourea‐catalyzed enantioselective double annulation strategy using alkylidene Meldrum′s acid as an acceptor‐donor‐acceptor with salicylaldehyde‐derived azomethine ylide is reported. The methodology is realized via a (3+2) cycloaddition/transesterification/decarboxylation sequence, giving chromeno[4,3‐b]pyrrolidines within 15–420 minutes at room temperature in 51–97% yields with 92–99% ee under 1–10 mol% catalyst loading. A plausible activation model is proposed for the excellent stereoinduction by H‐bond interaction between the catalyst and the Meldrum′s acid motif according to control experiments.