Asymmetric Catalysis, CIII [1]: Enantioselective Michael Addition of 1,3-Dicarbonyl Compounds to Conjugated Nitroalkenes

Abstract

Optically active Michael adducts were synthesized by addition of 1,3-dicarbonyl compounds to conjugated nitroalkenes. Good chemical yields were obtained for nitroalkenes stabilized by an aromatic substituent without any further substituents at the double bond. Acetylacetone and methyl-2,3-dihydro-1-oxo-1H-indene-2-carboxylate were used as Michael donors and four cinchona alkaloids as chiral base catalysts. Enantiomeric excess determinations were performed by 1H NMR spectroscopy in the presence of the Pirkle alcohol and by HPLC on chiral stationary phases. A correlation between the relative configuration of the prevailing isomer of the Michael adduct and the catalysts was established.