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
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
a Cu(II) salt and TBAT yielding the corresponding copper dienolate is addressed. A combined NMR and cyclic voltammetry analysis first highlight the role of TBAT in the Cu(II) to Cu(I) reduction and the structure of the precatalytic species. From these first results a second set of NMR and theoretical studies enable the determination of the structure and the mechanism of formation of the copper dienolate
讨论了甲硅烷基二烯酸酯,Cu(II)盐和TBAT的反应产生相应的二烯丙基铜的反应。NMR和循环伏安分析相结合,首先突出了TBAT在Cu(II)还原为Cu(I)和预催化物质结构中的作用。从这些第一结果中,第二组NMR和理论研究使得能够确定二烯酸铜铜催化物质的结构和形成机理。最后,我们表明,铜催化剂通过二烯醇铜中间体促进了甲硅烷基二烯醇盐前体的E / Z s-顺式/ s-反式平衡。所有这些结果揭示了催化的和不对称的乙烯基Mukaiyama反应的某些特性。