Catalytic Asymmetric Conjugate Addition of NaHSO₃ to Chalcones

Significance

The first catalytic enantioselective 1,4-addition of the hydrogen sulfite ion to α,β-unsaturated ketones has been reported. Chalcones 2 were identified as suitable substrates for a highly enantioselective reaction catalyzed by cinchona-based thiourea catalyst 1a. The use of pseudo-enantiomeric catalyst 1b enabled the preparation of compounds ent-3 with comparable selectivity.