Selective Synthesis of New Tetracyclic Coumarin-fused Pyrazolo[3,4-b]pyridines and Pyrazolo[3,4-b]pyridin-6(7H)-ones

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• 作者：Meilin Liu ; Guodong Yin ; Can Zhu and Chaochao Yao
• 刊名：Journal of Heterocyclic Chemistry
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：53
• 期：5
• 页码：1617-1625
• 全文大小：1240K
• ISSN：1943-5193

文摘

A three-component reaction for the synthesis of new coumarin-fused tetracyclic system from 4-hydroxycoumarin, aldehydes, and 5-aminopyrazoles/5-aminoisoxazole is described. In the presence of acetic acid, 4,7-dihydro-1H-pyrazolo[3,4-b]pyridines () and pyrazolo[3,4-b]pyridines () were obtained in acetonitrile and dimethylsulfoxide medium, respectively. The reaction gave rise to 4,5-dihydro-1H-pyrazolo[3,4-b]pyridin-6(7H)-ones () in acetic acid–ethanol combination system, which involved the C–O bond cleavage. 4-Hydroxy-6-methyl-2H-pyran-2-one and acenaphthylene-1,2-dione were also examined, affording the corresponding C–O bond cleavage products. Mechanism indicates that the reaction is reversible in acetic acid–ethanol combination system.