Catalytic Enantioselective Addition of Cyclic β-Keto Esters with Activated Olefins and N-Boc Imines Using Chiral C2-Symmetric Cationic Pd2+ N-Heterocyclic Carbene (NHC) Diaqua Complexes

The asymmetric addition of cyclic beta-keto esters to activated olefins and N-Boc imines was realized by using chiral cationic C-2-symmetric N-heterocyclic carbene (NHC) Pd2+ diaqua complexes 1a,b as the catalysts, producing the corresponding adducts in moderate to high yields (up to 95%) and with good to high entail ioselectivities (up to 96% ee). Nevertheless, the most significant observation is that when the (R)-NHC Pd2+ complex was used in these reactions, different absolute configurations were observed in comparison to those obtained with catalysts obtained from (R)-phosphane ligands.