Asymmetric Construction of Remote Vicinal Quaternary and Tertiary Stereocenters via Direct Doubly Vinylogous Michael Addition
作者:Subhrajit Rout、Harshit Joshi、Vinod K. Singh
DOI:10.1021/acs.orglett.8b00493
日期:2018.4.20
An asymmetric direct doubly vinylogousMichaeladdition has been developed for the generation of sterically congested vicinal quaternary and tertiary stereocenters. This doubly vinylogousMichaeladdition of β,γ-unsaturated butenolides to 3-methyl-4-nitro-5-alkenyl isoxazoles, powered by a bifunctional squaramide, affords a broad range of densely functionalized enantioenriched γ,γ-disubstituted butenolides
1,3-Dipolar cycloaddition enabled isoxazole-fused spiropyrrolidine oxindoles syntheses from 3-methyl-4-nitro-5-alkenyl-isoxazoles and azomethine ylides
作者:Xiong-Wei Liu、Zhen Yao、Jun Yang、Zhi-Yong Chen、Xiong-Li Liu、Zhi Zhao、Yi Lu、Ying Zhou、Yu Cao
DOI:10.1016/j.tet.2016.01.029
日期:2016.3
A facile and efficient methodology was developed for the synthesis of isoxazole-fused spiropyrrolidine oxindoles 3–5 via a 1,3-dipolarcycloaddition reaction of 3-methyl-4-nitro-5-alkenyl-isoxazoles with azomethine ylides (thermally generated in situ from isatin derivatives and proline or thioproline or sarcosine). Products bearing adjacent quaternary-tertiary centers were smoothly obtained in high
Chiral Squaramide Catalyzed Enantioselective 1,6-Michael Addition of Pyrazolin-5-ones to Styrylisoxazole Derivatives
作者:Vivek Sharma、Jasneet Kaur、Swapandeep S. Chimni
DOI:10.1002/ejoc.201800589
日期:2018.7.13
The cinchonidine squaramide catalyzed enantioselective 1,6‐Michaeladdition reaction of 3‐methyl‐4‐nitro‐5‐alkenylisoxazoles and pyrazolin‐5‐ones has been developed. Under mild reaction conditions, heterocyclic products that contain both pyrazole and isoxazole moieties were produced in up to 91 % yield with enantiomeric ratios (er) up to 91:9.