J. Thanusu

A convenient 'one-pot' synthesis and in vitro microbiological evaluation of novel 2,7-diaryl-(1,4)-diazepan-5-ones

A convenient method for the ‘one-pot’ synthesis of novel target molecule 2,7-diaryl-[1,4]-diazepan-5-ones from the respective 2,6-diaryl-piperidin-4-ones was catalyzed by NaHSO4.Al2O3 heterogeneous catalyst in dry media under microwave irradiation in solvent-free conditions. Moreover, the catalyst could be recovered and re-used up to 4 times after washing with ethyl acetate. They were evaluated for potential antibacterial activity against Staphylococcus aureus, β-Haemolytic streptococcus, Vibreo cholerae, Salmonella typhii, Escherichia coli, Klebsiella pneumonia, Pseudomonas and antifungal activity against Aspergillus flavus, Aspergillus fumigatus, Mucor, Candida albicans and Rhizopus. Structure-Activity Relationship (SAR) led to the conclusion that, of all the compounds 25–32 tested, compound 30 exerted strong in vitro antibacterial activity against S. aureus, S. typhii, and Pseudomonas and all the compounds 25–32 were less active against E. coli, whereas all the compounds 25–32 displayed potent in vitro antifungal activity against all the fungal strains used, except compound 30, which was more effectual against Mucor.

Synthesis and in vitro microbiological evaluation of an array of biolabile 2-morpholino-N-(4,6-diarylpyrimidin-2-yl)acetamides

Biolabile 2-morpholino-N-(4,6-diarylpyrimidin-2-yl)acetamides 34-42 have been synthesized and evaluated for their in vitro antibacterial and antifungal activities. The minimum inhibitory concentration tested for the same compounds against the same set of bacterial and fungal strains shows that the compounds 36 and 38 against beta-Heamolytic streptococcus and Klebsiella pneumonia, 40 against Escherichia coli and Pseudomonas, have excellent antibacterial activity. Compounds 36, 38 and 42 show inhibition against Aspergillus flavus, compound 41 against Microsporum gypsuem, 42 against Mucor, and compounds 39 and 40 against Rhizopus.

New environmentally-friendly solvent-free synthesis of imines using calcium oxide under microwave irradiation

Condensation of structurally diverse aldehydes including heterocyclic aldehydes, like furfural, with various amines in the presence of calcium oxide affording the corresponding imines in solvent-free conditions in good to excellent yields under microwave irradiation is described. A comparative study has been done under thermal conditions. The synergy between dry media and microwave irradiation in this reaction is evaluated by condensing less electrophilic aldehydes with poorly nucleophilic amines. The main advantages of this environmentally friendly protocol are the use of the non-toxic and inexpensive reagent calcium oxide and the considerable rate enhancement in comparison with a thermal reaction.

Design, ‘one-pot’ synthesis, characterization, antibacterial and antifungal activities of novel 6-aryl-1,2,4,5-tetrazinan-3-thiones in dry media

A novel ‘one-pot’ synthesis of 6-aryl-1,2,4,5-tetrazinan-3-thiones is carried out by the three-component coupling of thiourea, various structurally diverse aromatic aldehydes and ammonium acetate in the presence of reusable NaHSO4·SiO2 heterogeneous catalyst in dry media under microwave irradiation. FT-IR, 1H NMR, D2O Exchange, HOMOCOR, 13C NMR, MS and elemental analysis characterize all the synthesized compounds. In vitro antibacterial/fungal activities are carried out for all the synthesized eight new compounds. All the compounds are more active against bacterial strains namely Staphylococcus aureus, β-Heamolytic streptococcus, Vibreo cholerae, Salmonella typhii, Shigella felxneri, Klebsiella pneumonia and Pseudomonas except compounds 1 and 6, while compound 6 shows promising activity against Salmonella typhii. Moreover, of all the compounds tested, compounds 3 and 8 are more effectual against all the tested fungal strains.

Synthesis, spectral analysis and in vitro microbiological evaluation of 3-(3-alkyl-2,6-diarylpiperin-4-ylidene)-2-thioxoimidazolidin-4-ones as a new class of antibacterial and antifungal agents

In the present work, a new series of bis hybrid heterocycle comprising both piperidine and thiohydantoin nuclei together namely 3-(3-alkyl-2,6-diarylpiperin-4-ylidene)-2-thioxoimidazolidin-4-ones 46-60 was synthesized by the treatment of the respective thiosemicarbazones 31-45 with chloroethyl acetate and anhydrous sodium acetate in refluxing ethanol for 4h and were characterized by melting point, elemental analysis, MS, FT-IR, one-dimensional NMR ((1)H, D(2)O exchanged (1)H and (13)C), two dimensional HOMOCOSY and NOESY spectroscopic data. In addition, the title compounds were screened for their antimicrobial activities against a spectrum of clinically isolated microbial organisms. Compounds 47-50, 52-55 and 57-60 with fluoro, chloro, methoxy or methyl functions at the para position of phenyl rings attached to C-2 and C-6 carbons of piperidine moiety along with and without methyl substituent at position C-3 of the piperidine ring exerted potent biological activities against Staphylococcus aureus, beta-Hemolytic streptococcus, Vibrio cholerae, Escherichia coli, Pseudomonas aeruginosa, Aspergillus flavus, Candida albicans, Candida 6 and Candida 51 at a minimum inhibitory concentration.

Silica gel supported sodium hydrogen sulfate as an efficient and reusable heterogeneous catalyst for the synthesis of imines in solvent-free conditions under microwave irradiation

This synthesis of imines has been carried out efficiently by the condensation of carbonyl compounds with amines in the presence of silica gel supported sodium hydrogen sulfate (NaHSO4.SiO2) as a heterogeneous catalyst under microwave irradiation in solvent-free conditions. NaHSO4.SiO2 can be recovered and re-used up to ten times by simple washing with diethyl ether after each use and activated in an oven at 120 °C for 1 h, thus rendering the process more economical.

Three component one-pot synthesis of novel pyrimidino thiazolidin-4-ones catalyzed by activated fly ash

Abstract 2-Phenyl-3-(4,6-diarylpyrimidin-2-yl) thiazolidin-4-ones, 12–22, were synthesized with good yields in a short reaction time by the “one-pot” multicomponent reaction of the appropriate 2-amino-4,6-diarylpyrimidines, benzaldehyde, and thioglycolic acid under microwave irradiation in the presence of activated fly ash catalyst. The characterization of these compounds was confirmed by melting point, elemental analysis, MS, FT-IR, and one-dimensional NMR (1H and 13C) spectroscopic data.

Synthesis, antibacterial, and antifungal activities of biolabile (E)-1-(4-morpholinophenyl)-3-aryl-prop-2-en-1-ones

A collection of biolabile (E)-1-(4-morpholinophenyl)-3-aryl-prop-2-en-1-ones 8–13 are synthesized, characterized by melting point, elemental analysis, mass spectroscopy (MS), Fourier-transform infrared (FT-IR), and 1H and 13C nuclear magnetic resonance (NMR) spectroscopic data and evaluated for their in vitro antibacterial and antifungal activities. Compounds 8–13 exerted a wide range of antibacterial activities against all tested Gram-positive and Gram-negative bacterial strains. All the compounds 8–13 were more active against Pseudomonas. Of the synthesized compounds, compounds 9 and 11 exhibited a wide range of antibacterial activities against Staphylococcus aureus, β-Heamolytic streptococcus, Escherichia coli, Klebsiella pneumonia, and Pseudomonas. Compounds 10, 12, and 13 exerted strong antifungal activities against all tested fungal strains, namely Aspergillus flavus, Mucor, Rhizopus, and Microsporum gypsuem.Graphical Abstract

Design, synthesis, characterization, antibacterial and antifungal activities of a novel class of 5,7-diaryl-4,4-dimethyl-4,5,6,7-tetrahydropyridino[3,4-d]-1,2,3-selenadiazoles

Compound 26 is more potent against Escherichia coli. and 24 is more active against Staphylococcus aureus, β-Heamolytic streptococcus, Vibreo cholerae, Salmonella typhii, and Shigella flexneri than the standard drug ciprofloxacin. Moreover, of all the compounds tested, 26 is more effective against Aspergillus flavus and Mucor, than the standard drug fluconazole.

Synthesis, spectral analysis, antibacterial and antifungal activities of some 4,6-diaryl-4,5-dihydro-3-hydroxy-2[H]-indazole—a novel fused indazole derivative

A novel class of 4,6-diaryl-4,5-dihydro-3-hydroxy-2[H]-indazoles 25-32 were synthesized and evaluated for their in vitro antibacterial and antifungal activities. Four Compounds, which all possessed electron withdrawing functional groups (–Cl, –NO2, –Br) 27, 28, 30 and 32 were more potent against the tested bacterial/fungal strains than the standard bacterial and fungal drugs ciprofloxacin and fluconazole respectively.