Synthesis and antibacterial activity of novel coumarinyl azo-chalcones

Abstract

Coumarinyl azo-chalcone is one of the coumarin derivatives containing moiety of chalcone. This coumarinyl azo-chalcones were prepared by introduction of substituents (N(CH2CH3)2, OH, Br and OCH3) on coumarin ring. The coumarinyl azo-chalcones (122-126) were synthesised by Claisen-Schmidt condensation reaction of coumarin and benzaldehydes derivatives. The coumarin precursors have been prepared through Knoevenagel Condensation reaction yielded 3-acetyl-7-(diethylamino)coumarin (111), 3-acetyl-7-hydroxycoumarin (112), 3-acetyl-6-bromocoumarin (113) and 3-acetyl-7-methoxycoumarin (114). Meanwhile, benzaldehydes derivatives were prepared by coupling reaction of azo compound under cold condition, afforded 2-hydroxy-5-((4'-nitrophenyl)diazenyl)benzaldehyde (118), 2-hydroxy-5-((4'-chlorophenyl)diazenyl)benzaldehyde (119), and 2-hydroxy-5-((4'-methylphenyl)diazenyl)benzaldehyde (120). Five coumarinyl azo-chalcones were synthesised and identified as 3-((2E)-(3-(2'-hydroxy-5'-((4"-nitrophenyl)diazenyl)phenyl)acryloyl)-6-bromo-2H-chromen-2-one (122), 3-((2E)-(3-(2'-hydroxy-5'-((4"-chlorophenyl)diazenyl)phenyl)acryloyl)-6-bromo-2H-chrom-en-2-one (123), 3-((2E)-(3-(2'-hydroxy-5'-((4"-methylphenyl)diazenyl)-phenyl)acryloyl)-6-bromo-2H-chrom-en-2-one (124), 3-((2E)-(3-(2'-hydroxy-5'-((4"-chlorophenyl)diazenyl)phenyl)acryloyl)-7-methoxy-2H-chromen-2-one (125), and 3-((2E)-(3-(2'-hydroxy-5'-((4"-methylphenyl)diazenyl)phenyl)acryloyl)-7-methoxy-2H-chromen-2-one (126). The compounds obtained were characterized by infrared and nuclear magnetic resonance (1D and 2D NMR) spectroscopy. All coumarinyl azo-chalcones (122-126) were tested for the antibacterial activity against Gram-positive and Gram-negative bacteria. Coumarinyl azo-chalcone (124) showed moderate activity towards all Gram-positive and Gram-negative bacteria.