Multifunctional Catalysts in the Asymmetric Mannich Reaction of Malononitrile with <i>N</i>-Phosphinoylimines: Coactivation by Halogen Bonding versus Hydrogen Bonding
enantioselective Mannich reaction between malononitrile and diphenylphosphinoyl-protected aldimine affording products in high yields (up to 98%) and moderate to high enantiomeric purities (ee up to 89%). Typically, noncovalent catalysts rely on several weak interactions to activate the substrate, with one or two of these giving the most notable contribution to activation. In this instance, instead of the
Direct catalytic asymmetric Mannich-type reactions of isomerizable aliphatic imines: chemoselective enolate formation from a hydroxyketone by a Zn-catalyst
A direct catalyticasymmetric Mannich-type reaction of isomerizable aliphaticimines is described. A Et2Zn/(S,S)-linked-BINOL complex was suitable for chemoselective enolate formation from a hydroxyketone in the presence of isomerizable aliphatic N-diphenylphosphinoyl imines. The reaction proceeds smoothly and β-alkyl-β-amino-α-hydroxyketones were obtained in good yield and high enantioselectivity