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Substituted quinolinones. 31. Some new pyrano[3,2‐ c ]quinoline‐3‐carboxamides and their antioxidant activity
Author(s) -
Othman Elham S.,
Hassan Heba,
Abass Mohamed
Publication year - 2019
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.3721
Subject(s) - chemistry , quinoline , hydrazine (antidepressant) , malononitrile , malonic acid , dimethylformamide , organic chemistry , antioxidant , derivative (finance) , carboxamide , ethyl ester , dimer , condensation , carboxylic acid , medicinal chemistry , solvent , catalysis , physics , chromatography , financial economics , economics , thermodynamics
1‐Ethyl‐4‐hydroxy‐2‐oxo‐1,2‐dihydroquinoline‐3‐carbaldehyde ( 1 ) was annulated using malonic acid and/or its ethyl ester to furnish pyrano[3,2‐ c ]quinoline‐3‐carboxylic acid 2 and its ester 3 . Interconversions between acid 2 and ester 3 were successfully carried out. The anticipated pyrano[3,2‐ c ]quinoline‐3‐carboxamides 5–12 were conveniently attained via condensation of ester 3 with the proper amine. Surprisingly, treatment of ester 3 with dimethylformamide (DMF) in acidic media led to the carboxamide 5 . All attempts to convert ester 3 to its corresponding acid hydrazides by interaction with the proper hydrazine derivative led to formation of pyrazolidinediones 15 and 17 . Ester 3 underwent cyclo‐condensation with malononitrile dimer affording pyrido[3′,4′:5,6]pyrano[3,2‐ c ]quinoline derivative 18 . The new compounds revealed significant antioxidant effect, which suggests that most of them are possible potent antioxidant agents.