C,N-二苯基硝酮1与N-芳基马来酰亚胺2的环加成反应提供了两个具有高选择性的非对映异构异恶唑烷。已经基于1 H NMR,1 H NMR COSY,13 C NMR和IR光谱确定了加合物的结构和空间构型。假定在1,3-偶极环加成过程中,马来酰亚胺和硝酮的芳环之间存在π-π堆积相互作用,以控制反应的外-内选择性。因此,外-内比率取决于C,N的C-苯环上存在的取代基的位置-二苯基硝酮。
Catalytic Diastereo- and Enantioselective Synthesis of 2-Imidazolinones
作者:Pablo Martínez-Pardo、Gonzalo Blay、Alba Escrivá-Palomo、Amparo Sanz-Marco、Carlos Vila、José R. Pedro
DOI:10.1021/acs.orglett.9b01244
日期:2019.6.7
Chiral cyclic ureas (2-imidazolinones) were prepared by the reaction of nitrones and isocyanoacetate esters using a multicatalytic system that combines a bifunctional Brønsted base–squaramide organocatalyst and Ag+ as a Lewis acid. The reaction could be achieved with a range of nitrones derived from aryl- and cycloalkylaldehydes with moderate diastereo- and good enantioselectivity. A plausible mechanism
Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of β‐Fluoroalkylated α,β‐Unsaturated 2‐Pyridylsulfones with Nitrones for Chiral Fluoroalkylated Isoxazolidines and γ‐Amino Alcohols
across various aromatic and aliphatic nitrones in the presence of a chiral NiII/bis(oxazoline) catalyst. The process was tuned by 4 Å molecular sieves, chiralbis(oxazoline) ligands, reaction solvents, and temperature. A wide array of optically pure fluoroalkylated isoxazolidines were obtained, thus facilitating the asymmetric synthesis of an enantioenriched α‐trifluoromethylated γ‐amino alcohol in gram‐scale
Rhodium(III)‐Catalyzed Asymmetric Access to Spirocycles through C−H Activation and Axial‐to‐Central Chirality Transfer
作者:Lingheng Kong、Xi Han、Song Liu、Yun Zou、Yu Lan、Xingwei Li
DOI:10.1002/anie.202000174
日期:2020.4.27
Axial-to-central chirality transfer is an important strategy to construct chiral centers, where the axiallychiral reagents are mostly limited to atropomerically stable ones. Reported herein is a RhIII -catalyzed enantioselective spiroannulative synthesis of nitrones. The coupling proceeds via C-Harylation to give an atropomerically metastable biaryl, followed by intramolecular dearomative trapping
A [4+1] Cyclative Capture Approach to 3
<i>H</i>
‐Indole‐
<i>N</i>
‐oxides at Room Temperature by Rhodium(III)‐Catalyzed CH Activation
作者:Yaxi Yang、Xuan Wang、Yuanchao Li、Bing Zhou
DOI:10.1002/anie.201508702
日期:2015.12.14
The rhodium(III)‐catalyzed [3+2] CH cyclization of aniline derivatives and internal alkynes represents a useful contribution to straightforward synthesis of indoles. However, there is no report on the more challenging synthesis of pharmaceutically important N‐hydroxyindoles and 3H‐indole‐N‐oxides. Reported herein is the first rhodium(III)‐catalyzed [4+1] CH oxidative cyclization of nitrones with
Nickel(II)-Catalyzed Enantioselective 1,3-Dipolar Cycloaddition of Nitrones with α,β-Unsaturated Acylcarboxylates
作者:Lei Xie、Xuan Yu、Jiaqi Li、Zhenhua Zhang、Zhaohai Qin、Bin Fu
DOI:10.1002/ejoc.201601540
日期:2017.1.18
The highly enantioselective 1,3-dipolarcycloaddition of nitrones with α,β-unsaturated acylcarboxylates was realized for the first time by using a chiral bis(indano-oxazoline)-based Ni complex. The reaction proceeded smoothly under mild conditions and provided isoxazolidines with three contiguous stereocenters in high yields with excellent diastereoselectivities (>20:1 dr) and enantioselectivities
通过使用基于手性双(茚并恶唑啉)的 Ni 配合物,首次实现了硝酮与 α,β-不饱和酰基羧酸酯的高度对映选择性 1,3-偶极环加成反应。该反应在温和条件下顺利进行,并以高产率提供具有三个连续立体中心的异恶唑烷,具有优异的非对映选择性(> 20:1 dr)和对映选择性(高达 99% ee)。反应放大到克级,产物很容易转化为γ-氨基醇和其他潜在的生物活性化合物。