D. Ashok

Microwave-assisted synthesis of novel 1,2,3-triazole derivatives and their antimicrobial activity

An environmentally benign and economic synthesis of 1-[7-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-aryl-2-propen-1-ones and 1-[5-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-aryl-propen-1-ones is described. The procedure takes place by the 1,3-dipolar cycloaddition (‘‘click-reaction’’) between azides and alkynes catalysed by copper (I) salts. The simplicity of this reaction and the ease of formation and purification of the resulting products have opened new opportunities in generating vast arrays of compounds with biological potential. The structures of the synthesized compounds have been established on the basis of physical and spectral data. All the synthesized compounds were tested in vitro for their antibacterial and antifungal activities. Compounds 8a (R1=H, R2=H, R3=H), 8b (R1=H, R2=CH3, R3=H), 8d (R1=OCH3, R2=OCH3, R3=H), 8e (R1=OCH3, R2=OCH3, R3=OCH3), 13a (R1=H, R2=H, R3=H), 13d (R1=OCH3, R2=OCH3, R3=H) and 13e (R1=OCH3, R2=OCH3, R3=OCH3) showed significant antimicrobial properties.

Microwave-assisted synthesis of 2-(4,5-dihydro-5-(tetrazolo[1,5-a]quinoline-4-yl)-1H-pyrazol-3-yl)-substituted phenols

Abstract A series of pyrazolines 4a–h has been synthesized by Michael addition of chalcones 3a–h with hydrazine hydrate in the presence of sodium acetate under conventional heating or microwave irradiation. Structures of the newly synthesized pyrazolines 4a–h have been established on the basis of IR, 1H, 13C NMR and mass spectral data.

Microwave-assisted synthesis of substituted 4-chloro-8-methyl-2-phenyl-1,5-dioxa-2H-phenanthren-6-ones and their antimicrobial activity

Chromene and coumarin scaffolds are known for their potential antimicrobial activity. Herein, we have synthesized hybrid compounds containing both, substituted 4-chloro-8-methyl-2-phenyl-1,5-dioxa-2H-phenanthren-6-ones, 3a–o have been synthesized from substituted (E)-1-(7-Hydroxy-4-methyl-8-coumarinyl)-3-phenyl-2-propen-1-ones, 2a–o in good yield using the microwave-assisted Vilsmeier–Haack reaction. All the synthesized compounds were tested in vitro for their antimicrobial activity. The compounds 3e, 3f and 3g were found to be potent against tested fungal and bacterial strains.

Facile ionic liquid-mediated, microwave assisted green synthesis, and antioxidant studies of novel indolin-2-one annulated spirochromanone conjugates

A convenient and efficient synthetic protocol of ionic liquid, 1-n-butyl-3-methylimidazolium tetrachloroferrate, [bmim]Cl·FeCl3 mediated synthesis of novel indolin-2-one annulated spirochromanone conjugates was described. These spirochromanone conjugates were efficiently synthesized by Kabbe condensation of substituted 3-[2-(5-acetyl-2,4-dihydroxyhenyl)-2-oxoethylidene]indolin-2-ones with various cycloalkanones catalyzed by pyrrolidine in ionic liquid [bmim]Cl·FeCl3 under microwave irradiation. This approach offers the advantages of short reaction time, mild reaction conditions, high yields, convenient operation, and reuse of ionic liquid. The synthesized compounds were evaluated for their antioxidant activity. Among the compounds synthesized, IVb and IVd exhibited the highest antioxidant activity. The IC50 values for compounds IVb and IVd were found to be 1.25 and 1.74 μM, respectively, comparable to that of ascorbic acid (IC50 8.64 μM), a standard antioxidant agent.

Microwave-assisted synthesis of 10-aryl-4-methyl-2-oxo-8-phenyl-2,8-dihydropyrano[2,3-f]chromene-9-carbaldehydes by Suzuki coupling and their antimicrobial activity

A series of new pyranochromenes has been synthesized by conventional and microwave irradiation methods from 10-chloro-4-methyl-2-oxo-8-phenyl-2,8-dihydropyrano[2,3-f]chromene-9-carbaldehyde using the Suzuki coupling. All the synthesized compounds were characterized by standard spectroscopic methods and elemental analysis and screened for their antibacterial and antifungal activities.

Ultrasound- and microwave-assisted synthesis of (E)-1-aryl-3-[2-(piperidin-1-yl)quinolin-3-yl]prop-2-en-1-ones and (E)-1-aryl-3-[2-(pyrrolidin-1-yl)quinolin-3-yl]prop-2-en-1-ones, and their antimicrobial activity

Series of new (E)-1-aryl-3-[2-(piperidin-1-yl)quinolin-3-yl]prop-2-en-1-ones and (E)-1-aryl-3-[2-(pyrrolidin-1-yl)quinolin-3-yl]prop-2-en-1-ones have been efficiently prepared via the Claisen-Schmidt condensation of 2-(piperidin-1-yl)quinoline-3-carbaldehyde and 2-(pyrrolidin-1-yl)quinoline-3-carbaldehyde, respectively, with aryl methyl ketones under conditions of ultrasound and microwave irradiation. Structures of the products have been confirmed by IR, 1H NMR, 13C NMR, and mass spectroscopy, as well as by elemental analysis. Evaluation of the in vitro antibacterial activity against bacterial (Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli) and fungal (Aspergillus niger and Candida metapsilosis) strains has revealed good antimicrobial activity of some of the tested compounds.

Microwave-assisted synthesis and biological evaluation of carbazole-based chalcones, aurones and flavones

A new class of chalcones, aurones and flavones derived from carbazole is designed as potential antimicrobial and antioxidant agents. Synthesis of (Z)-2-((9-ethyl-9H-carbazol-3-yl)methylene)benzofuran-3(2H)-ones and 2-(9-ethyl-9H-carbazol-3-yl)-4H-chromen-4-ones was carried out by the oxidation of (E)-3-(9-ethyl-9H-carbazol-3-yl)-1-(2-hydroxyphenyl)prop-2-en-1-ones under microwave irradiation and conventional heating. All the newly synthesized compounds were characterized on the basis of IR, 1H NMR, 13C NMR, mass and analytical data. All the synthesized compounds were evaluated for their antibacterial, antifungal and antioxidant activities. Synthesized compounds were screened in vitro for antibacterial activity against two gram-positive bacterial strains like Staphylococcus aureus and Bacillus subtilis and two gram-negative bacterial strains like Escherichia coli and Klebsiella pneumonia and antifungal activity by inhibitory action against three fungal strains like Fusarium oxysporum, Aspergillus niger and Aspergillus flavus. The synthesized compounds were also evaluated for their DPPH radical scavenging activity. All the newly synthesized compounds have shown good antibacterial, antifungal and antioxidant activities.

Synthesis of novel 2,4,6-trisubstituted pyrimidine derivatives and their in vitro antimicrobial activity

A series of novel pyrimidines (6a–6i) has been synthesized from corresponding chalcones and isonicotinimidamide.HCl in the presence of potassium carbonate involving Michael addition followed by cycloaddition. All newly synthesised chalcones and pyrimidines were screened for in vitro antimicrobial activity against various Gram positive, Gram negative bacterial and fungal strains. Most of compounds displayed high antimicrobial activity compared to standard drugs Penicillin, Streptomycin and Ampothericin-B.

Microwave assisted synthesis, biological evaluation, and molecular docking of novel chroman scaffolds incorporating spirochromanone framework

A series of novel chroman scaffold incorporate spirochromanone derivatives were synthesized from 2-hydroxyacetophenone and cyclic alkanones under microwave irradiation in good yields. Newly synthesized compounds were characterized by analytical and spectral (IR, proton nuclear magnetic resonance, 13C nuclear magnetic resonance, and mass spectrometry) methods. The synthesized compounds were evaluated for their antioxidant and anti-inflammatory activities and were compared with standard drugs. Among all the synthesized compounds 3d (6.09), 3g (5.32), 3h (2.03), 4a (1.17), 4b (0.50), 4c (6.59), 4d (7.86), 4e (6.85), 4f (4.82), and 4g (6.59) were exhibited higher antioxidant activity comparable to that of ascorbic acid (IC50 8.64 µM). The compounds 3a, 3b, 3c, 4c, and 4d were found to have good anti-inflammatory activity. The binding mode of the titled compounds has been proposed based on the molecular docking studies.

Solvent-free microwave assisted synthesis of (E)-1-{3-[2-(9-Ethyl-9H-carbazol-3-yl)vinyl]benzofuran-2-yl}-2,2-dimethylpropan-1-ones and their antimicrobial activity

We report the solvent-free synthesis of (E)-1-{3-[2-(9-Ethyl-9H-carbazol-3-yl)vinyl]benzofuran-2-yl}-2,2-dimethylpropan-1-ones starting with 9-Ethyl-9H-carbazole-3-carbaldehyde under conventional and microwave irradiation methods. All products were characterised by IR, 1H NMR, 13C NMR, mass spectrometry, and elemental analysis. The compounds were tested in vitro for their antimicrobial activity.