Chiral rare earth organophosphates as homogeneous Lewis acid catalysts for the highly enantioselective hetero-Diels–Alder reactions
摘要:
Various trivalent rare earth-chiral phosphate complexes [(R)-l-RE, (R)-3-RE, and (R)-4-Ce] were prepared and evaluated as a Lewis acid catalyst for the asymmetric hetero-Diels-Alder reaction of aldehydes with the Danishefsky's diene. Some of them effectively promoted the reaction at room temperature in the presence or absence of achiral additives under homogeneous conditions to afford the corresponding cycloadducts with high ee's (up to 99% ee). During these reactions, remarkably high asymmetric amplifications (positive nonlinear effects) were observed as the first example in the metal ion-chiral ligand 1:3 catalytic system. A scandium catalyst bearing the H-8-BNP ligand, (R)-3-Sc, could be recovered after the reaction and successfully reused for the next round of reactions. In addition, the hetero-Diels-Alder reaction of alpha-keto esters was effectively catalyzed by the ytterbium complex, (R)-l-Yb, without any additives thus producing the asymmetric quaternary carbon in excellent enantioselectivities (up to > 99% ee). (C) 2003 Elsevier Ltd. All rights reserved.
Asymmetric Ring-Opening of Donor–Acceptor Cyclopropanes with Primary Arylamines Catalyzed by a Chiral Heterobimetallic Catalyst
作者:Weiwei Luo、Zhicheng Sun、E. H. Nisala Fernando、Vladimir N. Nesterov、Thomas R. Cundari、Hong Wang
DOI:10.1021/acscatal.9b02523
日期:2019.9.6
asymmetric ring-opening reaction of donor–acceptor cyclopropanes with primary arylamines was developed. The reaction was achieved through the utilization of a chiral heterobimetallic catalyst, delivering a variety of chiral γ-amino acid derivatives in up to 93% yield and 99% ee. Stereochemical experiments suggest a dominant role for kinetic resolution in this asymmetric process, which is supported by
开发了供体-受体环丙烷与伯芳基胺的有效催化不对称开环反应。该反应是通过利用手性杂双金属催化剂实现的,以高达93%的收率和99%的ee提供了各种手性的γ-氨基酸衍生物。立体化学实验表明,在该不对称过程中动力学拆分起着主导作用,这一点得到了对反应坐标的计算研究的支持。在这项工作中介绍了通过配体交换/重金属化过程形成的一类手性双金属路易斯酸催化剂。X射线晶体学证实了双金属催化剂的对称结构,即Yb(OTf)3 -Yb [ P ] 3。