A silver‐catalyzed highly enantioselective 1,3‐dipolar cycloaddition reaction of α‐silylimines with pyrone‐based trisubstituted olefins was developed affording bi‐ and tricyclic α‐quaternary‐carbon‐rich pyrano‐pyrrolidines in excellent yields. The tricyclic benzopyrone adducts thus obtained were efficiently transformed into highly complex tetracyclic scaffolds supporting four consecutive stereogenic
Condition-controlled selective synthesis of coumarins and flavones from 3-(2-hydroxyphenyl)propiolates and iodine
作者:Shuying Cai、Yang Shen、Ping Lu、Yanguang Wang
DOI:10.1016/j.tetlet.2011.05.150
日期:2011.8
2H-Chromen-2-ones (coumarins) and 4H-chromen-4-ones (flavones) were selectively prepared via the reaction of 3-(2-hydroxyphenyl)propiolates with iodine in toluene and N,N-dimethylformide, respectively. (C) 2011 Elsevier Ltd. All rights reserved.