Sc(OTf)3-Catalyzed [3+2]-Cycloaddition of Diazoacetoacetate Enones and N-Aryl Nitrones: Diastereoselective Synthesis of Functionalized Isoxazolidines with Three Contiguous Stereogenic Centers
作者:Xichen Xu、Yingjun Zhao、Di Wu
DOI:10.1055/s-0041-1737804
日期:2022.5
A catalytic [3+2]-cycloaddition using Sc(OTf)3 as a Lewis acid catalyst is developed. This catalytic 1,3-dipolar cycloaddition diastereoselectively transforms diazoacetoacetate enones and N-aryl nitrones into highly functionalized isoxazolidines bearing three contiguous chiral centers. The feasibility of the uncatalyzed 1,3-dipolar cycloaddition is postulated by DFT calculations and substantiated
Rh2(esp)2-Catalyzed Redox/Cycloaddition Cascade of Diazoacetoacetate Enones with N-Methyl Nitrones: Diastereoselective Synthesis of β-Lactams with Two Adjacent Chiral Centers
作者:Xichen Xu、Yingjun Zhao、Rujie Xu、Zhengqing Xu
DOI:10.1055/s-0040-1719883
日期:2022.5
employing Rh2(esp)2 as the catalyst, a reaction cascade operates by reducing an N-methyl nitrone to the corresponding N-methyl imine in the presence of a first molecule of the diazoacetoacetate enone. A second molecule of the diazoacetoacetate enone sensing a change in the reaction medium undergoes a Wolff rearrangement to afford a vinyl ketene. This vinyl ketene then reacts with the in situ generated