Enantioselective Organocatalytic Addition of 1,3-Dicarbonyl Compounds to β-Arylvinyl Triflones

Abstract

The sulfonyl group is able to polarize adjacent C=C bonds, but strength of the effect considerably varies with sulfonyl substituents (SO₂X). In this report, we present asymmetric organocatalyzed conjugate addition of 1,3-dicarbonyl compounds to β-arylvinyl triflones (ArCH=CHSO₂CF₃). The reaction runs under mild conditions with 5 mol % of tertiary amino-thiourea to afford Michael-type adducts in high yields and enantioselectivities. Comparative experiments reveal that electron-withdrawing properties increase in the series SO₂F ≪ SO₂CF₃ < SO₂C₄F₉, with the latter approaching strength of the nitro group.