Direct Asymmetric Aldol Reaction Catalyzed by C2-Symmetrical Chiral Primary Amine Organocatalysts
作者:Gong-Jian Zhu、Chao-Shan Da、Ya-Ning Jia、Xiao Ma、Lei Yi
DOI:10.2174/157017810790533904
日期:2010.1.1
C-2-symmetrical chiral primaryamines were synthesized from chiral BINOL and diamines. Then their catalytic activities in the asymmetricaldolreactions were evaluated, and the result indicated that 1c was the optimal organocatalyst. The reaction of a variety of aromatic aldehydes with aliphatic ketones, catalyzed by 20 mol % 1c in the addition of benzoic acid in carbon tetrachloride, afforded the aldol products
Synthesis and Characterization of Monosaccharide Derivatives and Application of Sugar-Based Prolinamides in Asymmetric Synthesis
作者:Jyoti Agarwal、Rama Krishna Peddinti
DOI:10.1002/ejoc.201200522
日期:2012.11
were converted into the corresponding prolinamide organocatalysts (i.e., 1a, 2a, 3a, and 3b) in high yields. The catalytic activity of these sugar-based prolinamide organocatalysts was demonstrated in asymmetric aldol reactions in various solvents and at different temperatures. The oraganocatalyst 3a was shown to be an efficient and powerful organocatalyst for the enantioselective aldol reaction of various
2,4-Dinitrophenol as an Effective Cocatalyst: Greatly Improving the Activities and Enantioselectivities of Primary Amine Organocatalysts for Asymmetric Aldol Reactions
Seven primary amine organocatalysts 1a−g were readily prepared from natural primary amino acids via two steps and then were used to catalyze the directasymmetricaldolreaction, but they showed very poor enantioselectivities and activities. As an effective cocatalyst, 2,4-dinitrophenol (DNP) dramatically elevated the activities and enantioselectivities of these very inefficient primary amine organocatalysts
regio- and diastereoselectivity and enantioselectivity under ambient temperature. Significantly, the reactions accommodate the synthetically important but challenging substrates, such as linear aliphaticketones, with high regioselectivity and unprecedented syn diastereoselectivity. These results are in sharp contrast with the secondary amine mediated similar reactions wherein anti diastereoselectivity
Unexpected Beneficial Effect of ortho-Substituents on the (S)-Proline-Catalyzed Asymmetric Aldol Reaction of Acetone with Aromatic Aldehydes
作者:Benjamin List、Alberto Martínez、Manuel van Gemmeren
DOI:10.1055/s-0033-1340920
日期:——
An intriguing effect of electronegative 2,6-substituents on the stereochemical outcome of (S) -proline-catalyzed aldol reactions between benzaldehyde derivatives and acetone is reported. Remarkably high enantioselectivities can be achieved with such substrates.