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
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]
Building the buildingblocks: A highly enantioselective hydrogenation of β‐aryl‐β‐alkyl disubstituted nitroalkenes 1 has been developed. This method results in enantiomericallypure nitroalkanes 2, which are versatile precursors for chemical synthesis.
Highly Enantioselective Reduction of β,β-Disubstituted Aromatic Nitroalkenes Catalyzed by <i>Clostridium sporogenes</i>
作者:Anna Fryszkowska、Karl Fisher、John M. Gardiner、Gill M. Stephens
DOI:10.1021/jo800124v
日期:2008.6.1
This is the first report of the use of Clostridium sporogenes extracts for enantioselective reduction of C═C double bonds of β,β-disubstituted (1) and α,β-disubstituted nitroalkenes (3). Crude enzyme preparations reduced aryl derivatives 1a−e and 1h, in 35−86% yield with ≥97% ee. Reduction of (E)- and (Z)-isomers of 1c gave the same enantiomer of 2c (≥99% ee). In contrast, α,β-disubstituted nitroalkene
mild and chemodivergent transformation involving nitroalkanes has been developed. Under optimized reaction conditions, in the presence of trichlorosilane and a tertiary amine, aliphatic nitroalkanes were selectively converted into amines or nitriles. Furthermore, when chiral β-substituted nitrocompounds were reacted, the stereochemical integrity of the stereocenter was maintained and α-functionalized