In this study, a series of new bispyrazolines 8(a–f) have been prepared from the cyclization reactions of bischalcones 7(a–f) with phenyl hydrazine by refluxing under the alkaline alcoholic (KOH/EtOH) conditions. The O‐alkylation reactions of hydroxyl substituted chalcone 6 with different 1,ω‐dibromoalkanes in the presence of anhydrous potassium carbonate, tetrabutylammonium iodide, and dry acetone afforded the symmetrical new bischalcones 7(a–f) in good yields. Chalcone 6 was realized by using the Claisen–Schmidt reaction of m‐hydroxyacetophenone with bipheny‐4‐carboxaldehyde. The various spectroscopic parameters such as IR, 1H‐NMR, 13C‐NMR, and ESI‐MS have been thoroughly used for the structural interpretations of the newly prepared products. The in vitro antibacterial and antifungal activities of these compounds have been examined with the help of serial tube dilution method, and many of the tested products were found to be revealing the promising antimicrobial properties, which were evident from their minimum inhibitory concentration values. The molecular docking simulations of the synthesized substances have also been achieved to observe the structural association into the active site of the Escherichia coli FabH (PdB: 3IL9). Docking results of these compounds suggested that bispyrazoline 8b demonstrated the lowest binding energy that describes its higher stability into the pocket of E. coli. The excellent inhibitory activity of this bisheterocycle against E. coli FabH may be ascribed on the basis of hydrophobic and van der Waals interactions.

In the present study, the four series of N‐acetyl/N‐carbothioamide/N‐carboxamide/N‐phenyl‐based new bispyrazolines have been synthesized. These symmetrical bisheterocyclic products were prepared efficiently from the ring‐closure reactions of new bischalcones 2a‐d with appropriate cyclizing agents (hydrazine hydrate, thiosemicarbazide, semicarbazide, and phenyl hydrazine) under the alkaline ethanolic conditions. The compounds 2a‐d were obtained by treating hydroxyl‐substituted chalcone 1 with various dihalogenated reagents (α,α′‐dibromo‐o/m/p‐xylene and 4,4′‐bischloromethyl‐diphenyl) in anhydrous K2CO3/dry acetone/Bu4N+I− medium. The structures of all the newly synthesized products have been authenticated with the help of their IR, 1H‐NMR, 13C‐NMR, and ESI‐MS spectral data and their purity was corroborated with the help of elemental analysis and thin‐layer chromatography results. The in vitro antimicrobial screening of the newly synthesized intermediates and final bisheterocycles has also been performed by using the serial tube dilution technique against the selected number of microorganisms. The final bisheterocycles revealed better antibacterial and antifungal potencies as compared to their corresponding bischalcones. Among the symmetrical bisheterocyclic products, N‐acetyl and N‐carbothioamide‐substituted bispyrazolines were found to exhibit potential antimicrobial properties than the other products.

No abstract

The present research work describes the productive synthesis of novel bisbenzopyronopyran derivatives 4(a‐h) and 5(a‐h) via the photocyclization reactions of bischromones 3(a‐h) under the inert conditions. The latter compounds have been realized efficiently through the O‐alkylation reactions of the 3‐hydroxychromone 2 with suitable dihalogenated aliphatic/aromatic/heteroaromatic reagents in the presence of dry acetone/anhydrous K2CO3/Bu4N+I− (PTC). The cyclization reaction of chalcone 1 under the Algar‐Flynn‐Oyamada reaction conditions (KOH/H2O2) could results in the formation of compound 2 in the good yield. The structural scaffolds of the newly prepared bischromones and resultant bisbenzopyronopyrans have been certified from the meticulous analysis of their various spectroscopic parameters such as UV‐Vis, IR, 1H/13C‐NMR, and ESI‐MS. It was found that o/m/p‐xylene and pyridine‐linked final symmetrical bistetracycles exhibited higher antimicrobial potencies as compared to alkyl chain‐linked cyclized products. The bischromones 3(a‐h) could be able to endow modest level of antimicrobial behavior.

In this study, a series of new symmetrical N-carbothioamide substituted bispyrazolines (2a-f) had been systematically synthesized by using ring closure reactions of bischalcones (1a-f) with thiosemicarbazide under the alkaline-alcoholic conditions. The structures of bisheterocyclic products have been fully characterized on the basis of their IR, 1H & 13C NMR and ESI-MS spectral strategies. All the prepared compounds were also evaluated for their in vitro antimicrobial assay with the help of serial tube dilution procedure against the selected numbers of microbes (seven bacterial and five fungal strains). The most of the synthesized bisheterocycles exhibited noticeable antimicrobial potencies against the tested strains