Premium
Selective Synthesis of New Tetracyclic Coumarin‐fused Pyrazolo[3,4‐ b ]pyridines and Pyrazolo[3,4‐ b ]pyridin‐6(7 H )‐ones
Author(s) -
Liu Meilin,
Yin Guodong,
Zhu Can,
Yao Chaochao
Publication year - 2016
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.2473
Subject(s) - chemistry , acetic acid , coumarin , acetonitrile , ethanol , bond cleavage , pyran , medicinal chemistry , stereochemistry , organic chemistry , catalysis
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 ( 4 ) and pyrazolo[3,4‐ b ]pyridines ( 5 ) were obtained in acetonitrile and dimethylsulfoxide medium, respectively. The reaction gave rise to 4,5‐dihydro‐1H‐pyrazolo[3,4‐ b ]pyridin‐6(7 H )‐ones ( 6 ) 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.