Organocatalytic asymmetric sulfa-michael addition to α,β- unsaturated ketones

The highly enantioselective organocatalytic sulfa-Michael addition to α,β-unsaturated ketones has been accomplished using benzyl and tert-butyl mercaptans as the sulfur-centered nucleophiles. Optically active products are obtained in high yields and good to excellent stereocontrol (up to 96% ee) from a large variety of enones. Central to these studies has been the use of the catalytic primary amine salt A, derived from 9-amino-(9-deoxy)-epi- hydroquinine and D-N-Boc-phenylglycine, in which both the cation and the anion are chiral, that exhibits high reactivity and selectivity for iminium ion catalysis with enones. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.