Abstract
The sulfonyl group is able to polarize adjacent C=C bonds, but strength of the effect considerably varies with sulfonyl substituents (SO(2)X). In this report, we present asymmetric organocatalyzed conjugate addition of 1,3-dicarbonyl compounds to β-arylvinyl triflones (ArCH=CHSO(2)CF(3)). 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 SO(2)F ≪ SO(2)CF(3) < SO(2)C(4)F(9), with the latter approaching strength of the nitro group.