Readily available hydrogen bond catalysts for the asymmetric transfer hydrogenation of nitroolefins
作者:Jakob F. Schneider、Markus B. Lauber、Vanessa Muhr、Domenic Kratzer、Jan Paradies
DOI:10.1039/c1ob05059a
日期:——
focuses on readily accessible thiourea hydrogen bond catalysts derived from amino acids, whose steric and electronic features are modulated by their degree of substitution at the carbinol carbon center. These catalysts were applied in the asymmetric transfer hydrogenation of nitroolefins furnishing the chiral products in up to 99% yield and 86% enantiomeric excess. The proposed catalyst's mode of action
Influence of the Double-Bond Geometry of the Michael Acceptor on Copper-Catalyzed Asymmetric Conjugate Addition
作者:Magali Vuagnoux-d'Augustin、Alexandre Alexakis
DOI:10.1002/ejoc.200700424
日期:2007.12
aspects, a study of the influence of the (E)/(Z) double-bond geometry of the Michael acceptor on the enantioselectivity of copper-catalyzedasymmetricconjugateaddition reactions has been realized. In spite of numerous articles concerning copper-catalyzedasymmetricconjugateaddition reactions, the major factors of such a reaction are quite difficult to elucidate. Although our experiments have not allowed
Four NAD(P)H-dependent non-flavin ene reductases have been investigated for their ability to reduce activatedC=Cbonds in an asymmetric fashion by using 20 structurally diverse substrates. In comparison with flavin-dependent OldYellowEnzyme homologues, a higher degree of electronic activation was required, because the best activities were obtained with enals and nitroalkenes rather than enones and
Efficient Cu-Catalyzed Asymmetric Conjugate Additions of Alkylzinc Reagents to Aromatic and Aliphatic Acyclic Nitroalkenes
作者:Dawn M. Mampreian、Amir H. Hoveyda
DOI:10.1021/ol0488338
日期:2004.8.1
Cu-catalyzed method for asymmetric conjugate addition (ACA) of alkylzinc reagents to acyclic disubstituted nitroalkenes is presented. Reactions are typically effected at ambient temperature in the presence of 2 mol % chiral dipeptide phosphine and 1 mol % (CuOTf)(2).C(6)H(6). Nitroalkenes bearing aromatic as well as aliphatic substituents readily undergo asymmetricadditions. [reaction: see text]
A modularsugar-based phosphoroamidite L1–L5a–g and phosphite L6–L9a–g ligandlibrary was tested in the asymmetric Cu-catalyzed 1,4-conjugate addition reactions of β-substituted (cyclic and linear) and β,β′-disubstituted (cyclic) enones. The selectivity depended strongly on the configuration of carbon atom C-3, the size of the sugar backbone ring, the flexibility of the ligand backbone, the substituents