Complete 2,5‐Diastereocontrol in the Organocatalytic Enantioselective [3+2] Cycloaddition of Enals with Azomethine Ylides Derived from α‐Iminocyanoacetates: Asymmetric Synthesis of Pyrrolidines with Four Stereocentres

Abstract

AbstractRacemic α‐iminocyanoacetates have been used as azomethine ylide precursors in the catalytic enantioselective [3+2] cycloaddition with α,β‐unsaturated aldehydes catalyzed by (S)‐α,α‐diphenylprolinol leading to the fully stereocontrolled formation of pyrrolidine cycloadducts with four stereocentres, one of them being a quaternary one. The reaction proceeded with excellent yields, endo‐selectivities and enantioselectivities. Remarkably, complete 2,5‐diastereoselection has also been achieved under the optimized reaction conditions, which has been explained in terms of the participation of intramolecular H‐bonding interaction which contributes to stabilize one determined geometry for the in situ generated azomethine ylide.