In the present study, we report the design and eco‐benign synthesis of new class of carbazolyl‐1,4‐dihydropyridine (1,4‐CDHP) and carbazolyl‐1,8‐dioxodecahydroacridine (CAD) derivatives via a three‐component coupling reaction of substituted carbazole aldehydes, ethyl acetoacetate/dimedone, and ammonium acetate under solvent‐free conditions at 112°C to 115°C. We also report an efficient one‐pot synthesis of new class of carbazolyl polyhydroquinoline (CPQ) derivatives via a four‐component coupling reaction of substituted ethyl acetoacetate, dimedone, ammonium acetate, and carbazole aldehydes in acetonitrile/water medium (3:1) at 73°C to 75°C in moderate yields. All the products were thoroughly characterized by 1H NMR, 13C NMR, Fourier transform infrared (FTIR), mass spectral, and CHN analysis. The synthesized heterocyclic compounds were evaluated for their in vitro antibacterial activity against pathogenic strains of both Gram‐negative and Gram‐positive bacteria. Minimum inhibitory concentration (MIC) of the active compounds was evaluated by macrodilution method. The CPQ derivative (8a) displayed superior antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi with the MIC values of 16.0 to 32.0 μg/mL in comparison with the reference drug. The mechanism of antibacterial action of the CPQ derivatives was investigated via scanning electron microscope (SEM) studies. The molecular docking studies indicate that the CPQ derivative (8a) binds to the cell wall protein of E coli and P aeruginosa by formation of hydrogen bonds with amino acid residues (TYR328 and GLU249) of the bacterial cell wall protein. The 1,4‐CDHP, CAD, and CPQ derivatives were either noncytotoxic or exhibited minimal cytotoxicity towards human mononuclear cells from peripheral blood. All the products were evaluated for Lipinski rule of five (RO5) and were found to have good oral bioavailability.

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In the present study, we report a recyclable, nanocrystalline CdS thin film mediated efficient one‐pot, three component synthesis of Hantzsch 1, 4 Dihydropyridine in good yields. The catalyst is also effective for the efficient synthesis of Polyhydroquinoline and 1, 8‐dioxodecahydroacridine derivatives in good to excellent yields. The CdS thin film catalyst was prepared by chemical bath deposition (CBD) technique. The cadmium sulphide thin film was characterized by powder XRD and FT‐IR studies. The average crystallite size (D) was calculated from powder XRD by using Scherrer formula and SEM analysis. The elemental composition of the CdS thin film was established by EDS analysis. The effect of temperature, substituent's, catalyst loading and mole ratio on the reaction was also studied. All the products were thoroughly characterized by 1H‐NMR, 13C‐NMR, FT‐IR, Mass spectral and CHN analysis. A plausible mechanism for the CdS thin film catalyzed synthesis of 1, 4 DHP's is proposed. The heterogeneous catalyst could be easily recovered from the reaction mixture and successively reused at least five times without loss of activity.

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