Unmodified Primary Amine Organocatalysts for Asymmetric Michael Reactions in Aqueous Media
The organocatalytic asymmetric Michael addition of aldehydes to a nitro olefin in aqueous organic solvents catalysed by a broad range of simple primary amines and amino alcohols is reported. In particular, the use of (S,S)-diphenylethylenediamine, which is the chiral backbone of various organocatalysts, gave addition products in good yields and with good to high enantioselectivities (45–96 % ee). Remarkably high enantioselectivities were observed for the demanding conjugate addition of α,α-disubstituted aldehydes to nitrostyrene (96–98 % ee) in aqueous organic solvent mixtures.