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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.

A Series of hybrid 3-(5-mercapto-1,3,4-oxadiazol-2-yl)-2H-selenopyrano[2,3-b]quinolin-2-one derivatives (3a-f) were synthesized by the reaction of 2-oxo-2H-selenopyrano[2,3-b]quinoline-3-carbohydrazides (2a-f) with carbon disulphide and potassium hydroxide in the presence of ethanol as solvent. The intermediates 2-oxo-2H-selenopyrano[2,3-b]quinoline-3-carbohydrazides (2a-f) were obtained by the reaction of 2-oxo-2H-selenopyrano[2,3-b]quinoline-3-carboxylates (1a-f) with hydrazine hydrate in ethanol. These (1a-f) were synthesized from available literature method. All the newly synthesized derivatives have been characterized by IR, 1H NMR, 13C NMR spectral and elemental analysis.

The present work deals with synthesis and characterization of some of novel 2H-[1,4]oxaselenepino[5,6-b]quinolin-3(5H)-ones derivatives. A series of 2‑chloro-3-formylquinolines (2a-I) were synthesized from substituted acetanilides (1a-I) using available protocol method and a series of 2‑chloro-3-formylquinolines (2a-l) are converted into 3-formyl-2-selenoquinolines (3a-l) using NaHSe. The resulting 3-formyl-2-selenoquinolines (3a-l) on reduction with sodiumborohydride in methanol afforded a diversely functionalized primary alcoholic derivatives (4a-l). These (2-Hydroselenoquinolin-3-yl)methanols (4a-l) on reacts with chloroacetic acid in the presence of aqueous potassium hydroxide in ethanol gives 2-((3-(Hydroxymethyl)quinolin-2-yl)selanyl)aceticacids (5a-l) scaffolds. The title compounds (6a-l) were prepared by the cyclisation of (5a-l) scaffolds in the presence of P2O5 with dioxane as a solvent. The structures of all the newly synthesized compounds were elucidated on the basis of their elemental analysis, IR, 1H NMR,13C NMR and mass spectral data.

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.