Direct Asymmetric Organocatalytic Michael Reactions of α,α-Disubstituted Aldehydes with β-Nitrostyrenes for the Synthesis of Quaternary Carbon-Containing Products

Direct asymmetric catalytic Michael reactions have been performed using chiral-amine/acid bifunctional catalysts. Performed with 0.3 equiv of (S)-(+)-1-(2-pyrrolidinylmethyl)pyrrolidine and 0.3 equiv of trifluoroacetic acid as the catalyst, the reaction of α,α-dialkylaldehydes with (E)-β-nitrostyrene provided the α,α-dialkyl Michael products in up to 96% yield with up to 91% ee. With respect to enantioselectivity, l-proline was a poor catalyst of this class of Michael reactions.