Organocatalytic Asymmetric Transferhydrogenation of β-Nitroacrylates: Accessing β2-Amino Acids
摘要:
We describe a highly efficient and enantioselective Hantzsch ester mediated conjugate reduction of beta-nitroacrylates that is catalyzed by a Jacobsen thiourea catalyst as a key step in a new route to optically active beta2-amino acids.
First Iridium-Catalyzed Highly Enantioselective Hydrogenation of β-Nitroacrylates
摘要:
The first highly chemo- and enantioselective hydrogenation of beta-nitroacrylates was accomplished with an iridium catalyst (Ir-4) with yields and enantioselectivities of up to 96% and 98% ee, respectively. The resulting alpha chiral beta-nitro propionates are attractive building blocks for the synthesis of chiral beta(2)-amino acids, which are the core scaffolds of bioactive natural products, pharmaceuticals, and beta-peptides.
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
Synthesis of Quaternary-Carbon-Containing β<sup>2,2</sup>-Amino Acids by the Rh<sup>I</sup>-Catalyzed Enantioselective Arylation of α-Substituted β-Nitroacrylates
An enantioselective RhI‐catalyzed conjugate addition reaction of α‐substituted β‐nitroacrylates with various arylboronic acids by using chiral RhI diene catalysts is described for the first time. The addition reaction proceeds under mild conditions in a range of common organic solvents and additives, and it affords the corresponding quaternary‐carbon‐containing α,α‐disubstituted β‐nitropropionate products
A General Catalytic Enantioselective Transfer Hydrogenation Reaction of β,β-Disubstituted Nitroalkenes Promoted by a Simple Organocatalyst
作者:Luca Bernardi、Mariafrancesca Fochi
DOI:10.3390/molecules21081000
日期:——
encompassing various nitroalkene classes; (ii) Hantzsch esters as convenient (on a preparative scale) hydrogen surrogates; (iii) a simple and commercially available thiourea as catalyst; (iv) user-friendly procedures. Overall, the proposed protocol gives a practical dimension to the catalyticenantioselective reduction of β,β-disubstituted nitroalkenes, offering a useful and general platform for the preparation
Asymmetric conjugate addition of arylboronic acids to 2-nitroacrylamide in the presence of cationic palladium-Chiraphos complex proceeds with high yield and enantioselectivity (73-89% ee) using as low as 0.05-0.25 mol % of the catalyst. The adducts can be smoothly transformed into the corresponding beta(2)-homophenylglycines in two simple steps. (C) 2013 Elsevier Ltd. All rights reserved.
First Iridium-Catalyzed Highly Enantioselective Hydrogenation of β-Nitroacrylates
The first highly chemo- and enantioselective hydrogenation of beta-nitroacrylates was accomplished with an iridium catalyst (Ir-4) with yields and enantioselectivities of up to 96% and 98% ee, respectively. The resulting alpha chiral beta-nitro propionates are attractive building blocks for the synthesis of chiral beta(2)-amino acids, which are the core scaffolds of bioactive natural products, pharmaceuticals, and beta-peptides.