C2-Symmetric Cinchona Alkaloid Derivatives: Versatile Catalysts for the Enantioselective C-C Bond Forming Conjugate Addition of Nucleophiles to Simple α,β-Unsaturated Acyl Pyrazoles

A single C-2-symmetric squaramide catalyst system allows the facile addition of either malononitrile or benzyl nitroacetate to simple pyrazole-based Michael acceptors with excellent enantiocontrol and at lower catalyst loadings than previously possible. The latter reactions are not diastereoselective, however facile hydrogenolysis leads to decarboxylation and formation of the formal adduct from the addition of nitromethane (a very recalcitrant nucleophile in this chemistry) with excellent yield and enantiocontrol.