4-Hydroxy-3-(2′-pyridyl)coumarins (4) (R = 6-Cl, H, 6-NO2, 8-NO2) were prepared in moderate to good yields by the intramolecular nucleophilic aromatic substitution reaction of β-ketoesters (I) in refluxing xylenes; evidence for the reversible formation of benzo[c]quinolizinium III from I (X = 4-Cl), with eventual formation of 4 (R = 6-Cl), is also presented.
4-Hydroxy-3-(2'-pyridyl)coumarins (4) (R = 6-Cl, H, 6-
NO2, 8- ) 通过 β- 的分子内亲核芳族取代反应以中等至高产率制备回流二
甲苯中的
酮酯 (I);还提供了从 I (X = 4-Cl) 可逆地形成苯并 [c]
喹啉 III 并最终形成 4 (R = 6-Cl) 的证据。