The installation of an imidazolium tag via acetate connection to the C-4 of cis-4-hydroxy-L-proline provides a highlyefficient catalyst for the directasymmetricaldolreaction, that works in a remarkably low catalyst loading (0.1 mol%) affording TONs up to 930 in the case of electron-poor aromatic aldehydes with ee up to >99%.
Proline-Histidine Dipeptide: A Suitable Template for Generating Ion-Tagged Organocatalysts for the Asymmetric Aldol Reaction
作者:Heena Inani、Avtar Singh、Sergei G. Zlotin、Srinivasan Easwar、Meeta Bhati、Kiran Kumari、Alexander S. Kucherenko
DOI:10.1055/a-1477-4871
日期:2021.8
Proline-histidine dipeptide laid the foundation for the construction of three new ion-tagged organocatalysts, utilising the imidazole moiety of histidine for generating the quaternary species. A brief comparative investigation of the catalysts in the enamine-mediated direct asymmetric aldol reaction brought out their contrasting features, particularly under aqueous conditions. The best among them was
Probing the Synergistic Catalytic Model: A Rationally Designed Urea-Tagged Proline Catalyst for the Direct Asymmetric Aldol Reaction
作者:Meeta Bhati、Kiran Kumari、Srinivasan Easwar
DOI:10.1021/acs.joc.8b00962
日期:2018.8.3
functional groups in the transition state of the enamine route to the asymmetric aldol reaction. The catalyst proved to be an excellent performer, delivering aldols in high yields and with excellent enantio- and diastereoselectivities using just 2 mol % loading in the presence of water; it also exhibited good levels of recyclability underaqueousconditions. The favorable results reveal the interesting
Exploring “Through-Bond” Proximity between the Ion Tag and Reaction Site of an Imidazolium-Proline Catalyst for the Direct Asymmetric Aldol Reaction
作者:Meeta Bhati、Shruti Upadhyay、Srinivasan Easwar
DOI:10.1002/ejoc.201700021
日期:2017.4.3
on the effect of through-bond proximity of the ion-tag to the reaction site in an enamine mediated direct asymmetric aldolreaction. The new catalyst, having a reduced bond-spacer between the imidazolium tag and the amino acid moiety as compared to conceptually similar predecessors, proved to be an excellent performer in aldolreactions carried out in the presence of water under solvent-free conditions
Chiral 1,2-diaminocyclohexane as organocatalyst for enantioselective aldol reaction
作者:Yi Liu、Junfeng Wang、Qi Sun、Runtao Li
DOI:10.1016/j.tetlet.2011.04.116
日期:2011.7
catalyze the asymmetric aldolreaction in MeOH–H2O. Cyclic ketones as aldol substrates gave the anti-β-hydroxyketone products with moderate to good yields, diastereoselectivity and enantioselectivity (up to 78% yield, >20:1 anti/syn, 94% ee). Hydroxyacetone as aldol substrate afforded the syn-α, β-dihydroxyketones as major products in up to 85% yield with good enantioselectivity (up to >20:1 syn/anti
一个简单的和可商购的手性1,2-二氨基环己烷作为催化剂,己二酸作为助催化剂能有效地催化在MeOH-H不对称醛醇缩合反应2 O.环酮类如醇醛底物,得到反-β-羟基酮产品具有中度至良好的收率,非对映选择性和对映选择性(高达78%的收率,抗/顺式> 20:1,94%ee)。羟丙酮作为醇醛底物以主要产物顺-α,β-二羟基酮的形式提供了高达85%的收率和良好的对映选择性(高达> 20:1 syn / anti,93%ee)。