Synthesis of 9-substituted xanthenes by the condensation of arynes with ortho-hydroxychalcones
摘要:
The reaction of o-(trimethylsilyl)aryl triflates, CsF, and o-hydroxychalcones affords a general and efficient way to prepare biologically interesting 9-substituted xanthenes. This chemistry presumably proceeds by the tandem intermolecular nucleophilic attack of the phenoxide of the chalcone on the aryne and subsequent intramolecular Michael addition. The introduction of an external base, Cs2CO3, has proven beneficial in this reaction. (c) 2012 Elsevier Ltd. All rights reserved.
A combination of polarity reversal, Diels–Alder cycloaddition and skeletal remodeling to access pyridine-fused nitrones
作者:Huabin Han、Chaoyang Li、Xinyue Niu、Yuxia Wang、Wenjing Zhang、Qilin Wang
DOI:10.1039/d2cc00155a
日期:——
An unprecedented cascade strategy consisting of polarity reversal, normal electron-demand Diels–Alder cycloaddition and skeletal remodeling was developed to construct novel pyridine-fused nitrones in up to 82% yield. The key to the success was the umpolung process, which transformed the electron-deficient 3-nitropyridinium ring into a reactive, π-extended cyclic nitroalkene, serving as a rarely reported