Highly enantioselective biomimetic intramolecular dehydration: kinetic resolution of β-hydroxy ketones catalyzed by β-turn tetrapeptides
摘要:
Racemic beta-hydroxy ketones were kinetically resoluted into the enantiopure isomers and (E)-alpha,beta-unsaturated ketones using catalytic asymmetric intramolecular dehydration for the first time. Synthetic tetrapeptides were used to imitate fatty acid dehydratases to efficiently discriminate racemic beta-hydroxy ketones, enantioselectively catalyze the intramolecular dehydration, and result in highly enantioenriched beta-hydroxy and (E)-alpha,beta-unsaturated ketones in the environmentally benign process. Mechanistically, the high discrimination of the racemic substrates and successive enantioselective dehydration are highly dependent on the cooperative catalysis of the NH2 and COOH groups of the peptide. (C) 2013 Elsevier Ltd. All rights reserved.
Chiral organoaluminum complex 1 efficiently catalyzed the asymmetric hetero-ene reaction of commercially available 2-methoxypropene (2) with aldehydes under mild conditions to give the corresponding β-hydroxymethyl ketones 3 in good to excellent chemical yields with high enantiomeric excesses. The asymmetriccatalysis of 1 was further applied to the carbonyl addition of methallylsilanes, where exclusive
Rational Combination of Two Privileged Chiral Backbones: Highly Efficient Organocatalysts for Asymmetric Direct Aldol Reactions between Aromatic Aldehydes and Acylic Ketones
A new class of organocatalysts has been designed by rational combination of proline with cinchona alkaloids. The chiral amine 3a, prepared from l-proline and cinchonidine, has been found to be an efficient catalyst for the directaldolreactions of acetone or 2-butanone with a wide range of aldehydes (up to 98% ee). The cinchonidine backbone is essential to the reaction efficiency and enantioselectivity
The Zn–proline complex is shown to catalyze the aldolreaction of acetone and a wide range of arenecarbaldehydes in aqueous media, accepting even deactivated arenecarbaldehydes such as methoxybenzaldehydes in good yields. Enantiomeric excesses of up to 56 % could be obtained with 5 mol-% of the catalyst at room temperature, and up to 66 %
Novel binaphthyl-based chiral bifunctional organocatalysts were designed, synthesized and successfully applied to the asymmetric List–Lerner–Barbas aldol reaction in the presence of water. These organocatalysts were found to be effective catalysts for the reactions of symmetrical, unsymmetrical and cyclic ketones with different aldehydes to give the corresponding aldol products with higher yields (up
Highly Efficient Direct Asymmetric Aldol Reactions Catalyzed by a Prolinethioamide Derivative in Aqueous Media
作者:Bing Wang、Xin-wang Liu、Ling-yan Liu、Wei-xing Chang、Jing Li
DOI:10.1002/ejoc.201001115
日期:2010.11
acids L-proline and L-valine, was studied for the directasymmetricaldolreaction of acetone with various aromatic aldehydes at 0 °C or room temperature. A loading of only 0.1―0.2 mol-% of derivative 1c was employed in this catalytic system, and excellent enantio-selectivities and yields (up to 98 % yield, >99 % ee) could be achieved in aqueous media.