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
Merrifield Resin Supported Dipeptides: Efficient and Recyclable Organocatalysts for Asymmetric Aldol Reactions under Neat Reaction Conditions
作者:Lei Wang、Jincan Yan
DOI:10.1055/s-2008-1067104
日期:——
A number of Merrifield resin supported dipeptide and tripeptidecatalysts have been developed of which Pro-Ala-O-P, catalyst A, was found to be an efficientcatalyst for asymmetric direct aldol reactions. Aldehydes and ketones underwent smooth aldol reaction in the presence of a catalytic amount of A at room temperature under neat reaction conditions and generated the corresponding products with excellent
已经开发了许多 Merrifield 树脂负载的二肽和三肽催化剂,其中 Pro-Ala-OP 催化剂 A 被发现是不对称直接羟醛反应的有效催化剂。醛和酮在催化量的 A 存在下在室温下在纯反应条件下进行平稳的醛醇反应,并产生具有优异分离收率 (≤98%)、良好的非对映选择性 (dr ≤ 90:10) 和对映选择性 ( ≤95% ee)。此外,催化剂A可以使用七次而不会损失其催化活性。
d-Fructose-derived β-amino alcohol catalyzed direct asymmetric aldol reaction in the presence of p-nitrophenol
D-Fructose derived β-amino alcohols 2 and 3 were used as organocatalysts for direct asymmetric aldol reaction of various aromatic aldehydes with three kinds of cyclic ketones in the presence of different additives as a co-catalyst. The results showed that the combinations of β-amino alcohol 2 and p-nitrophenol built up a novel catalytic system. Loading of 20 mol% 2 and 15 mol% p-nitrophenol gave excellent yields (up to 98% with respect to aldehyde) of aldol reaction products with good enantioselectivity (up to 87% ee). Accordingly, a mechanism for the reaction was proposed by 1H NMR spectrum in this paper. Furthermore, the catalysts can be reused and have the significant catalyst recovery (77â84%).