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.
Tandem Catalysis by Lipase in a Vinyl Acetate-Mediated Cross-Aldol Reaction
作者:Manjeet Kumar、Bhahwal A. Shah、Subhash C. Taneja
DOI:10.1002/adsc.201000980
日期:2011.5
The lipase Novozym435 (0.6% w/w) was used in tandem with organocatalysts in a first vinyl/isopropenyl acetate‐mediated aldol reaction. The reaction was facilitated through the lipase‐catalyzed in situ generation of acetaldehyde/acetone. The important features of the present methodology include the mild and facile reaction conditions, regenerability of the lipase, comparatively high yields and minimal
A series of functionalized ionicliquids (FILs) incorporated with chiral-pyrrolidine unit have been synthesized and tested as reusable organocatalysts for direct aldolreactions. FIL 1b in combination with acetic acid and water as additives could effectively catalyze direct aldolreactions of various ketone donors in high yields and the FIL catalyst was easily recycled and reused for six times with
A Highly Efficient Organocatalyst for Direct Aldol Reactions of Ketones with Aldedydes
作者:Zhuo Tang、Zhi-Hua Yang、Xiao-Hua Chen、Lin-Feng Cun、Ai-Qiao Mi、Yao-Zhong Jiang、Liu-Zhu Gong
DOI:10.1021/ja0510156
日期:2005.6.1
prepared and evaluated for catalyzing the directAldolreaction of 4-nitrobenzaldehyde with acetone. Catalysts with strong electron-withdrawing groups are found to exhibit higher catalytic activity and enantioselectivity than their analogues with electron-donating groups. The presence of 2 mol % catalyst 4g significantly catalyzes the directAldolreactions of a wide range of aldehydes with acetone
Zr(OtBu)4-catalysed synthesis of acetone aldol adducts and domino aldol-Tishchenko reactions with diacetone alcohol as enol equivalent
作者:Christoph Schneider、Markus Hansch
DOI:10.1039/b102941j
日期:——
Zr(OtBu)4 was found to be a potent catalyst for the synthesis of acetone aldol adducts with diacetone alcohol as enol equivalent and for domino aldol-Tishchenko reaction giving rise to 1,3-anti-diol monoesters with excellent diastereoselectivity.
Fluorogenic aromatic aldehydes bearing arylethynyl groups were developed. They were used for monitoring the reaction progress of organocatalytic aldol reactions in DMSO through an increase in the fluorescence intensity based on the formation of the florescent aldol product. The ratios of the fluorescence intensities of the aldols to the aldehydes were more than 300. These results suggest that the fluorescence assay system using the aldehyde is useful for the rapid identification of superior aldol catalysts and reaction conditions. (c) 2014 Elsevier Ltd. All rights reserved.