Catalyticasymmetric vinylogous Mukaiyama reactions on ketones, leading to the formation of alpha,beta-unsaturated lactones with tertiary alcohols, have been described (11 examples, up to 93% ee). This methodology has been applied in a formal enantioselective synthesis of taurospongin A (12 steps, 6% overall yield).
Lewis Acid Catalyzed Diastereoselective Vinylogous Mannich Reaction Induced by O-Pivaloylated d-Galactosylamine as the Chiral Auxiliary: Stereoselective Synthesis of 6-Arylpiperidin-2-ones
derivatives, in the form of (S)-δ-amino-δ-arylpent-2-enoic ester, has been achieved in high yield via a vinylogous Mannich reaction, utilizing poly-O-pivaloylated d-galacosylamine as the chiral auxiliary. (S)-6-p-Tolylpiperidine-2-one can be stereoselectively synthesized from (S)-δ-amino-δ-arylpent-2-enoic ester by sequential hydrogenation of the double bond, cyclic lactam formation, and removal of
A tunable and highly regio- and diastereoselective addition of acyclic silyl dienolates 2 to several alpha-fluoroalkyl sulfinylimines 1 was developed. By appropriate choice of the Lewis acid catalyst, two new chiral alpha-fluoroalkyl amines 3 and 4 were obtained in good yields and excellent diastereoselectivities (up to >99 : 1 dr), respectively.
OMe) and a substituted enolate chain between SiMe3 and various CuI complexes was examined. Reaction mechanisms pass through a cyclic transition state in which the reaction coordinate is associated with rotation of the SiMe3 moiety. The dependence of the thermodynamic and kinetic features on the nature of the active and ancillary ligands was examined. Formation of copper enolate is shown to be favored