K. Ashok

Benzo[h]thiazolo[2,3-b]quinazolines by an efficient p-toluenesulfonic acid-catalyzed one-pot two-step tandem reaction

A highly efficient method has been developed for synthesis of 7,9-disubstituted-6,7-dihydro-5H-benzo[h]thiazolo[2,3-b]quinazolines via multicomponent one-pot two-step tandem reaction involving 1-tetralone, arylaldehydes, thiourea, and 4-chlorophenacyl bromide/(3-bromoacetyl)coumarin utilizing p-toluenesulfonic acid as catalyst in glacial acetic acid under reflux conditions. Analytically pure products are formed with excellent yield and short reaction time. All the synthesized compounds were confirmed by their spectral and elemental analyses.Graphical abstract

Eco-friendly synthesis of 1,8-naphthyridine 5-aryl-1,3,4-oxadiazole derivatives under solvent-free solid-state conditions and their antimicrobial activity

A simple and highly efficient green synthetic procedure has been described for the construction of 2-(2-(3-nitrophenyl)-1,8-naphthyridin-3-yl)-5-aryl-1,3,4-oxadiazole derivatives by grinding method involving hydrazine hydrate, arylaldehyde and oxidative cyclization with FeCl3·6H2O in solvent-free solid-state conditions afforded the corresponding compounds (6a–h) with excellent yields in short reaction times. All the synthesized products were evaluated for their antibacterial and fungal activities. Some of the products demonstrate moderate antibacterial activity and good antifungal activity. In particularly compounds 6c and 6g showed high antibacterial and antifungal activities. Moreover, our in silico studies have proved that strong binding affinity and more H-bonds interaction.Graphical Abstract

Microwave assisted aqueous phase synthesis of benzothiazoles and benzimidazoles in the presence of Ag 2 O

A simple and high yielding method for synthesized benzothiazoles and benzimidazole in water under micro wave irradiation by the reaction of 2-amino thiophenol and o-phenylenediamine with various aromatic aldehydes in the presence of Ag2O. Ag2O can be recovered and reused without significant loss of activity.

Polyhydroquinolines: 1-sulfopyridinium chloride catalyzed an efficient one-pot multicomponent synthesis via Hantzsch condensation under solvent-free conditions

Abstract A simple and highly efficient method has been developed for the construction of polyhydroquinoline derivatives via one-pot, four-component Hantzsch condensation of various aldehydes, dimedone, ethyl acetoacetate, and ammonium acetate in the presence of an ionic liquid, 1-sulpopyridinium chloride, as a catalyst under solvent-free conditions. This methodology has an advantage of high yields, short reaction times, a clean reaction profile, and reusability of the catalyst.Graphical Abstract

An Efficient Microwave-Assisted Synthesis of Novel 2-{4-[(3-Aryl-1,8-naphthyridin-2-yl)amino]phenyl}-1H-benzo[de]isoquinoline-1,3(2H)-diones and Their Antimicrobial Activity

The Buchwald–Hartwig amination reaction between 2-chloro-3-aryl-1,8-naphthyridines and 2-(4-aminophenyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione in the presence of the catalytic system Pd(PPh3)4 and the base KO-t-Bu in toluene was studied. The reaction was initiated by microwave irradiation. Highly efficient synthesis has been developed for 2-{4-[(3-aryl-1,8-naphthyridin-2-yl)amino]phenyl}-1H-benzo[de]isoquinoline-1,3(2H)-diones. Structures of the synthesized compounds were evaluated by IR, 1H and 13C NMR spectroscopy. All products were tested for antimicrobial activity against Escheria coli, Bacillus subtilis, Klebsiella pneumoniae, and Staphylococcus aureus.

Facile One Pot Multi-Component Solvent-Free Synthesis of 2,4,5-Trisubstituted Imidazoles Using “Green” and Expeditious Ionic Liquid Catalyst under Microwave Irradiation

Acetic acid functionalized poly(4-vinylpyridinium) bromide is a highly efficient and recyclable catalyst for the construction of 2,4,5-trisubstituted imidazole derivatives by a three-component condensation of benzyl with various aldehydes and ammonium acetate under solvent free conditions. The microwave initiated process leads to analytically pure compounds within 2–5 min. The advantages of this “green” methodology are cost-effectiveness, simple procedure, low energy consumption, no involvement of organic solvents, safe operation, clean reaction profile, high yields, and recyclability of the catalyst.

A novel and efficient synthesis of 3-iodo substituted 1,8-naphthyridines by electrophilic cyclization of 2-amino nicotinaldehyde and their antimicrobial activity

Synthesis of substituted 1,8-naphthyridines based on 2-aminonicotinaldehyde under mild conditions is studied. Out of three electrophilic iodine sources (I2, NIS, and ICl) studied, I2 was determined to act most efficiently in the process. High overall yields were achieved for aliphatic substitution at the reaction center. All compounds were evaluated for antibacterial activity (Staphylococus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella pneumonia) and anti-fungi activity (Aspergillus flavus and Fusarium oxysporum).

Novel synthesis of substituted N-(3-aryl-1,8-naphthyridin-2-yl) and N,N′-bis(3-aryl-1,8-naphthyridin-2-yl)benzene-1,4-diamines and 2-(4-((3-aryl-1,8-naphthyridin-2-yl)amino)phenyl)isoindoline-1,3-diones and their biological evaluation

ABSTRACT A straightforward and highly efficient series of new substituted 3-aryl-1,8-naphthyridine derivatives 3a–e, 4a–e, and 6a–e were synthesized. Condensation dissimilar quantities of 2-chloro-3-aryl-1,8-naphthyridine 1a–e with benzene-1,4-diamine 2 and sodium ethoxide refluxing in ethanol solvent yielded the compounds 3a–e and 4a–e. The 2-(4-((3-aryl-1,8-naphthyridin-2-yl)amino)phenyl)isoindoline-1,3-diones 6a–e were obtained by treatment of compounds 3a–e with phthalic anhydride 5 in refluxing N,N-dimethylformamide is described. All synthesized compounds evaluated for their antimicrobial activity. The structures of the compounds have been proven on the established of spectral (IR, 1H NMR, and 13C NMR) data and elemental analyses. The reaction will be characterized by good efficacy, easy workup, simple purification of the products, and availability of catalyst. GRAPHICAL ABSTRACT

A Simple “Green” Synthesis of Novel Bis(3-aryl-1,8-naphthyridin-2-yl)sulfanes and 2-(Methylthio)-3-aryl-1,8-naphthyridines under Microwave Irradiation and Conventional Conditions

An eco-friendly and highly efficient synthesis of substituted bis(3-aryl-1,8-naphthyridin-2-yl)-sulfanes and 2-(methylthio)-3-aryl-1,8-naphthyridines under microwave and conventional conditions. The products are obtained with high yields and purity within short reaction time. The synthesized derivatives are screened for anti-microbial activity against bacteria and fungi. Molecular docking of the synthesized compounds with DNA Gyrase is studied.

Simple and efficient method for aromatization of tetrahydro-β-carbolines by using K2S2O8 as a catalyst and its antimicrobial activity comparison with molecular docking studies

A novel and efficient aromatization of tetrahydro-β-carbolines under mild conditions using K2S2O8 as a catalyst was developed. The method is applicable for all kinds of C1 substituted systems. All synthesized compounds were screened for their in vitro antibacterial activity against Staphylococus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella pneumonia, as well as fungi, such as Aspergillus flavus and Fusarium oxysporum. Compounds 4b, 4g, 4i, and 4k demonstrated excellent in vitro antibacterial and antifungal activities than the standard drugs. The docking studies were carried out for most active compounds 4b, 4g, 4i, and 4k.