New Synthons of 3-Hydroxyquinoline Derivatives Through SEAr

A new series of 3-hydroxyquinoline derivatives 2a-c has been synthesized by decarboxylation of corresponding quinoline-4-carboxylic acid derivatives 1a-c. These 3-hydroxyquinolines have been subjected to a number of electrophilic aromatic substitution reactions (SEAr) at C4 to obtain the target structures; 3, 4, 7, 8 and 10 through: bromination, formylation, Mannich reaction, coupling with diazonium salt and acylation, respectively. In addition, formation of fused pyrano[2,3-c]quinolin-3-one 5 and chalcone 11 were done. Trials for formation of chalcone analogue 6 were failed indicating 100% of 3-hydroxy tautomer of 2a-c. All the obtained compounds can act as good chelators and contain at least 3 H-bond acceptor groups. All compounds were evaluated for antioxidant activity by ABTS assay.