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The cyclooxygenase-2 (COX-2) enzyme is an important target for drug discovery and development of novel anti-inflammatory agents. Selective COX-2 inhibitors have the advantage of reduced side-effects, which result from COX-1 inhibition that is usually observed with nonselective COX inhibitors. In this study, the design and synthesis of a new series of 7-methoxy indolizines as bioisostere indomethacin analogues (5a–e) were carried out and evaluated for COX-2 enzyme inhibition. All the compounds showed activity in micromolar ranges, and the compound diethyl 3-(4-cyanobenzoyl)-7-methoxyindolizine-1,2-dicarboxylate (5a) emerged as a promising COX-2 inhibitor with an IC50 of 5.84 µM, as compared to indomethacin (IC50 = 6.84 µM). The molecular modeling study of indolizines indicated that hydrophobic interactions were the major contribution to COX-2 inhibition. The title compound diethyl 3-(4-bromobenzoyl)-7-methoxyindolizine-1,2-dicarboxylate (5c) was subjected for single-crystal X-ray studies, Hirshfeld surface analysis, and energy framework calculations. The X-ray diffraction analysis showed that the molecule (5c) crystallizes in the monoclinic crystal system with space group P 21/n with a = 12.0497(6)Å, b = 17.8324(10)Å, c = 19.6052(11)Å, α = 90.000°, β = 100.372(1)°, γ = 90.000°, and V = 4143.8(4)Å3. In addition, with the help of Crystal Explorer software program using the B3LYP/6-31G(d, p) basis set, the theoretical calculation of the interaction and graphical representation of energy value was measured in the form of the energy framework in terms of coulombic, dispersion, and total energy.

Synthesis and antimicrobial activities of novel S-5-(2-oxo-2H-selenopyrano [2,3-b]quinolin-3-yl)-1,3,4-oxadiazol-2-yl-2-cyanoethanethioates derivatives was undertaken employing a convenient and easily accessible procedure. A Series of S-5-(2-oxo-2H-selenopyrano[2,3-b]quinolin-3-yl)-1,3,4-oxadiazol-2-yl 2-cyanoethanethioates are synthesized by a simple and efficient one-pot reaction of substituted 3-(5-mercapto-1,3,4-oxadiazol-2-yl)-2H-selenopyrano[2,3-b]quinolin-2-ones with 2-cyanoacetyl chloride and potassium carbonate in the presence dimethyl formamide as a solvent. This reaction sequence involves a nucleophilic substitution of -S-H of 1,2,3-oxadiazole with 2-cyanoacetyl chloride. The structures of all the synthesized products were confirmed with their elemental analysis, IR,1H NMR and mass spectral analysis. All the newly synthesized compounds (2a-f) were screened for in vitro antimicrobial activities (Minimum Inhibitory Concentration (MIC) of three (Staphylococcus aureus, Micrococcus roseus) and (Escherichia coli) by disk diffusion method using ampicillin as positive and Dimethylformamide (DMF) as negative control. The tested, compounds 2d and 2e were highly active against S. aureus-ATCC 25953 and M. roseus-NCTC 07523 (gram positive) and moderately active against E. coli-ATCC 25922 (gram negative), compound 2c was slightly active against M. roseus and E. coli. Compound 2e was slightly active against S. aureus and M. roseus and compounds 2a and 2b were slightly active against M. roseus.

The present study involves the synthesis of substituted novel ethyl 2-oxo-2H-selenopyrano[2,3-b]quinoline-3-carboxylates (4a-f) by the reaction of 3-formyl-2-selenoquinolines (3a-f) with diethyl malanoate in the presence of piperidine. 3-Formyl-2-selenoquinolines (3a-f) were prepared by the action of NaHSe on substituted 2-chloroquinoline-3-carbaldehydes (2a-f). A series of 2-chloroquinoline-3-carbaldehydes (2a-f) were synthesized from substituted acetanilides (1a-f) using available protocol method. The structures of all the newly synthesized compounds were characterized by their elemental analysis, IR, 1H NMR, 13C-NMR and mass spectral data. All the newly synthesized compounds (4a-f) were evaluated for antimicrobial activities. Among the compounds tested, 4d and 4e were highly active against S. aureus and M. roseus.

In the present study, we have worked out a convenient route for the synthesis of new series of novel 3-acetyl-2H-selenopyrano[2,3-b]quinolin-2-ones (4a-f) by the cyclization of 3-formyl-2-selenoquinolines (3a-f) using ethyl acetoacetate in the presence of catalytic amount of piperidine in acetonitrile as a solvent. The structures of all the synthesized products were confirmed with their elemental analysis, IR, 1H NMR, 13C NMR and mass spectral analysis. All the newly synthesized compounds (4a-f) were screened for in vitro antibacterial activities of three (Staphylococcus aureus, Micrococcus roseus) and (Escherichia coli) by disk diffusion method using ampicillin as positive and Dimethylformamide (DMF) as negative control. The tested, compounds 4d and 4e were highly active against S. aureus and M. roseus (gram positive) and moderately active against E. coli (gram negative), compound 4c was slightly active against M. roseus and E. coli. Compound 4e was slightly active against S. aureus and M. roseus and compounds 4a and 4b were slightly active against M. roseus.