Synthesis and Antibacterial Evaluation of Novel 3,6-Disubstituted Coumarin Derivatives

Abstract

All the reagents and solvents were purchased from Aldrich/Merck and used without further purifications. Melting points were determined in open capillaries using Stuart SMP30 apparatus and are uncorrected. The progress of the reactions as well as purity of compounds was monitored by thin layer chromatography with F 254 silica-gel precoated sheets using hexane/ethyl acetate 8/2 as eluent; UV light and iodine vapours were used for detection. IR spectra were recorded on a Perkin-Elmer 100S spectrometer utilizing KBr pellets. 1 H NMR and 13 C NMR spectra were obtained at 400 MHz and 100 MHz respectively on Bruker using DMSO-d 6 as solvent and TMS as internal standard. Elemental analyses were performed on a Carlo-Erba model EA1108 analytical unit. Mass spectra were recorded on a Jeol JMSD-300 spectrometer. General procedure for the synthesis of ethyl-2-(3-acetyl-2-oxo-2H-chromen-6-yl)-4methylthiazole-5-carboxylate (3)A mixture of ethyl 2-(3-formyl-4-hydroxyphenyl)-4-methylthiazole-5-carboxylate (1) (0.1 mol) and ethylacetoacetate (2) (0.12 mol) were dissolved in ethanol and cooled at 0-5 0 C. Piperidine (1 mL) was added drop wise to this mixture while stirring. The reaction mixture left overnight, resulting in the formation of yellow colored solid. Purification by recrystallization from ethanol to afford analytically pure product. General procedure for the synthesis of 3,6-disubstituted coumarin derivatives (6a-l)A mixture of ethyl-2-(3-acetyl-2-oxo-2H-chromen-6-yl)-4-methylthiazole-5-carboxylate (3, 1 mmol), thiosemicarbazide (1 mmol) and various phenacyl bromides (5a-g) / 3-(2-bromoacetyl)-2H-chromen-2-ones (5h-k) / 2-(2-bromoacetyl)-3H-benzo[f]chromen-3-one (5l) (1 mmol) were dissolved in 10 mL of absolute ethanol in the presence of catalytic amount of acetic acid and heated at refluxing temperature for 2-4 hrs. Monitored the reaction by TLC and poured contents in an ice cold water, the solid obtained was filtered, dried and recrystallised in ethanol.

Synthesis of 7‐{[2‐(4‐ substituted phenyl)‐2‐oxoethyl] amino}‐4‐methyl‐2H‐1‐benzopyran‐2‐one derivatives and evaluation of their pharmacological activities

“…Recently, new benzopyrans and their uses have been developed thats way we studied their biological potentials as anti-diabetic, anti-inflammatory and in silico molecular docking application. [43] Ravibabu Velpula et al, synthesised disubstituted coumarin derivatives using phencyl bromides, [44] N V Purohith synthesised benzopyran derivatives using substituted phencyal bromides, [45] and Manjunath Ghate et.al., reported the reaction of 4-bromo methyl coumarin with 2, 4-dihydroxy acetophenones [46] The number of publications devoted to the study of benzopyrans increases each year. Significant advances have been made in their use in medicine.…”