Bifunctional chiral organocatalysts comprising thiourea and tertiaryamine groups were synthesized. They act as efficientcatalysts for asymmetric Michaeladdition of arylthiols to alpha,beta-unsaturated carbonyl compounds. Enantioselectivity up to 85% has been achieved. Asymmetric alpha-protonation reaction (up to 60% ee) can be obtained in the presence of the bifunctionalcatalyst.
Addition of aromatic thiols to conjugated cycloalkenones, catalyzed by chiral .beta.-hydroxy amines. A mechanistic study of homogeneous catalytic asymmetric synthesis