PyBidine‐Cu(OTf)2‐Catalyzed Asymmetric [3 + 2] Cycloaddition with Imino Esters: Harmony of Cu‐Lewis Acid and Imidazolidine‐NH Hydrogen Bonding in Concerto Catalysis.

A Cu-catalyzed [3 + 2] cycloaddition of exomethylene substituted indolinones (I) and (IV) with imino esters (II) and (V) is investigated in the presence of chiral pyridine-based chelating ligands such as (PDB) to yield spirocyclic compounds (III) and (V).