Synthesis and Antimicrobial Activity of Some New N‐substituted‐5‐arylidene‐thiazolidine‐2,4‐diones

A total of 17 new N‐substituted derivatives ( 2b , 2c , 2d , 2e , 2f , 2g , 2h , 2i , 2j , 2k and 3b , 3c , 3d , 3e , 3f , 3g , 3h ) of 5‐((2‐phenylthiazol‐4‐yl)methylene) thiazolidine‐2,4‐dione ( 2a ) and 5‐(2,6‐dichloro‐ benzylidene)thiazolidine‐2,4‐dione ( 3a ) were synthesized. The structural elucidation of the newly synthesized compounds was based on elemental analysis and spectroscopic data (MS, ¹H NMR, ¹³C NMR), and their antimicrobial activities were assessed in vitro against several strains of Gram‐positive and Gram‐negative bacteria and one fungal strain (Candida albicans) as growth inhibition diameter. Some of them showed modest to good antibacterial activity against Gram‐negative Escherichia coli and Salmonella typhimurium and Gram‐positive Staphylococcus aureus, Bacillus cereus, and Enterococcus fecalis bacterial strains, whereas almost all the compounds were inactive against Listeria monocytogenes. All of the synthesized compounds showed moderate to very good activity against C. albicans.     

A Facile and Efficient Synthesis of 2‐(5‐(4‐Substitutedphenyl)‐4, 5‐dihydro‐3‐phenylpyrazol‐1‐yl)‐6‐Substitutedbenzothiazoles and Their Biological Studies

A series of new 1‐substituted 3, 5‐diarylpyrazolines ( 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ) were synthesized in good yield by both conventional and microwave‐assisted synthesis from α, β‐ unsaturated ketones ( 6 , 7 , 8 , 9 ) in n‐butanol and benzothiazole hydrazines ( 2 , 3 , 4 , 5 ). All the new compounds were characterized by IR, NMR, and mass spectral data. The synthesized compounds ( 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ) were evaluated for antibacterial and anthelmintic activities. The compounds showed potent anthelmintic activity against earthworm species (Eudrilus eugeniae) and moderate antibacterial activity against bacterial strains such as Gram positive bacteria, Enterococcus faecalis, Staphylococcus aureus, and Bacillus subtilis, and Gram negative bacteria, Escherichia coli and Proteus mirabilis.     

Synthesis and Antimicrobial Evaluation of Some New 4,5′‐Bisthiazoles

Thiazole and bisthiazole derivatives represent a prevalent scaffold in the antimicrobial drug discovery. Therefore, we have decided to synthesize some new series of 4,5′‐bisthiazoles. A total of 17 compounds were synthesized, their structural elucidation being based on elemental analysis (C,H,N,S) and spectroscopic data (MS and ¹H NMR). Their in vitro antimicrobial activities were assessed against several Gram‐positive and Gram‐negative bacteria strains and also against one fungal strain (Candida albicans) using the difusimetric method. Some of the compounds showed modest to good antibacterial activity against Gram‐negative Escherichia coli and Salmonella typhimurium and Gram‐positive Staphylococcus aureus and Bacillus cereus bacterial strains. All of the synthesized compounds showed moderate to very good antifungal activity against C. albicans.     

Synthesis and Evaluation of Antimicrobial Activity of Some New Hetaryl‐Azoles Derivatives Obtained from 2‐Aryl‐4‐methylthiazol‐5‐carbohydrazides and Isonicotinic Acid Hydrazide

A series of new 1,3,4‐oxadiazole/thiadiazole and 1,2,4‐triazole derivatives have been synthesized starting from 2‐aryl‐4‐methylthiazol‐5‐carbohydrazides and isonicotinic acid hydrazide. All the newly synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR, and mass spectrometry. The synthesized compounds were screened for their antibacterial and antifungal activity, assessed as growth inhibition diameter. Some of them showed good antibacterial activity against gram positive Staphylococcus aureus, while the antibacterial activity against Listeria monocytogenes, Escherichia coli, and Salmonella typhymurium and antifungal activity against Candida albicans was modest. None of the tested compounds showed inhibitory activity against gram positive bacteria Enterococcus faecalis and Bacillus cereus and against gram negative bacteria Pseudomonas aeruginosa.     

Microwave Assisted Green Synthesis of Pyrazole, 1, 2, 3‐ Triazole Based Novel Benzohydrazones and Their Antibacterial Activities

A series of novel pyrazole, triazole based benzohydrazones ( 7a‐l ) were synthesized via conventional and microwave methods in the presence of acetic acid catalyst. Microwave method provided green and economical approach towards the synthesis of novel Schiff bases ( 7a‐l ). Some intermediates and all the final compounds were characterized by NMR, mass, and elemental analysis. The compounds were screened for their in vitro antibacterial activity against Gram‐negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and Gram‐positive bacteria (Staphylococcus aureus and Bacillus cereus). Compounds 7e and 7g showed good antibacterial activity.     

Synthesis and Evaluation of Novel 5‐cyclohexyl‐2‐(4″‐substitutedphenyl)‐3‐(2″‐substitutedphenyl)4H‐2,3,3a,5,6,6a‐hexahydropyrrolo[3,4‐d]isoxazole‐4,6‐dione Derivatives for Their In Vitro Antioxidant and Antibacterial Activities

1,3‐Dipolar cycloaddition reactions of N‐cyclohexyl maleimide ( 1 ) with azomethine N‐oxide ( 2 ) have afforded novel isoxazolidine ( 3 ) in excellent yield. Their structures have been characterized from their IR, ¹H‐NMR, ¹³C‐NMR, ¹H,¹H‐COSY, MS(ESI), and elemental analysis techniques. In vitro antibacterial activity of the synthesized compounds were investigated against a representative panel of pathogenic strains specifically two Gram‐positive bacteria (Staphylococcus aureus and Streptococcus pyogenes ) and two Gram‐negative bacteria (Pseudomonas aeruginosa and Escherichia coli ) using agar‐well diffusion assay. Some of the compounds ( 3a , 3k , 3n , and 3o ) exhibited promising antibacterial activities. All the synthesized compounds have also been screened for their antioxidant activities and were found to be significantly active.     

Zeolite‐Supported One‐Pot Synthesis of Bis‐azetidinones under Microwave Irradiation

In an attempt to synthesize antibacterial agents effective against gram‐positive and gram‐negative bacteria, the efficient synthesis of novel bis‐azetidinones ( 3a–j ) has been established. Thus, cycloaddition reaction of substituted bis‐imines with chloroacetylchloride under microwave irradiation in the presence of zeolite yielded bis‐azetidinones ( 3a–j ). Structures of the synthesized compounds have been elucidated on the basis of their elemental analysis and spectral data (IR, ¹H‐NMR, ¹³C‐NMR, and mass spectra). The synthesized bis‐azetidinones were screened for their antibacterial activity against five microorganisms: Bacillus subtilis, Proteus vulgaris, Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli. They were found to exhibit good to moderate antibacterial activity.     

Novel 7‐Nitro‐1‐(Piperidin‐4‐yl)‐4,5‐Dihydro‐[1,2,4] Triazolo[4,3‐a]Quinoline‐Sulphonamide Derivatives as Antimicrobial Agents: Design,Synthesis, and Bio‐Activity

In attempt to search for more potent antimicrobial agents, a series of 7‐nitro‐1‐(piperidin‐4‐yl)‐4,5‐dihydro‐[1,2,4]triazolo[4,3‐a]quinoline‐derived sulphonamides were synthesized. Their structures were established by elemental analyses, IR, and NMR (¹H and ¹³C) spectral data. The antibacterial activity of the obtained compounds was investigated against different Gram‐negative (Escherichia coli and Pseudomonas aeruginosa) and Gram‐positive (Bacillus subtilis and Staphylococcus aureus) bacteria and antifungal activity against two fungal strains (Aspergillus niger and Aspergillus clavatus) using disk diffusion method at various concentrations (20, 40, 60, and 80 μg/mL). The study reveals that most of the title compounds showed significant antibacterial and fungal activity when compared with their respective standards streptomycin and griseofulvin.     

Synthesis and biological evaluation of new 4‐(4‐(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)phenyl)‐2‐phenylthiazole derivatives

A novel series of 4‐(4‐(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)phenyl)‐2‐substitutedthiazole derivatives ( 8a‐l) have been synthesized by [3 + 2] cycloaddition reaction of 4‐(4‐ethynylphenyl)‐2‐substitutedthiazole with substituted benzyl azide in aqueous DMF. Starting compounds 4‐(4‐ethynylphenyl)‐2‐substitutedthiazole ( 6a‐d ) were synthesized by reaction of 4‐(2‐substitutedthiazol‐4‐yl)benzaldehyde with Ohira‐Bestmann reagent in methanol. The structures of these novel triazole‐thiazole clubbed derivatives were confirmed by the spectral analysis. The title compounds ( 8a‐l ) were tested for antimycobacterial activity against Mycobacterium tuberculosis H37Ra active and dormant (MTB, ATCC 25177) and antimicrobial activity against standard Gram‐positive bacteria, Staphylococcus aureus (NCIM 2602) and Bacillus subtilis (NCIM 2162), and Gram‐negative bacteria, Escherichia coli (NCIM 2576) and Pseudomonas flurescence (NCIM 2059). Compounds 8a , 8b , 8c , and 8h reported good activity against B subtilis, compounds 8a , 8b , and 8c showed good activity against S aureus, and compound 8b showed good activity against dormant M tuberculosis H37Rv strain. Compounds 8b and 8c found more potent against Gram positive and dormant M tuberculosis H37Rv strains. These novel triazole‐thiazole clubbed analogues found to be a capable leads for further optimization and development.     

Synthesis and antimicrobial activity of some 7‐aryl‐5,6‐dihydro‐14‐aza[1]benzopyrano[3,4‐b]phenanthren‐8H‐ones

The title compounds, 7‐aryl‐5,6‐dihydro‐14‐aza[1]benzopyrano[3,4‐b]phenanthren‐8H‐ones 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l have been synthesized by reacting various 4‐hydroxy coumarins 1a , 1b , 1c with 2‐arylidene‐1‐tetralones 2a , 2b , 2c , 2d in the presence of ammonium acetate and acetic acid under Krohnke's reaction condition. The structures of all the synthesized compounds were supported by analytical, IR, ¹H‐NMR, and ¹³C‐NMR data. All the synthesized compounds 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l have been screened for their antibacterial activities against Escherichia coli (Gram ?ve bacteria), Bacillus subtilis (Gram +ve bacteria), and antifungal activity against Candida albicans (Fungi). J. Heterocyclic Chem., (2011).     

Microwave‐assisted Synthesis of Hybrid Heterocyclics as Biological Potent Molecules

A series of novel 5‐((1H‐benzo[d]imidazol‐2‐yl)methyl)‐2‐((3aR,5S,6S,6aR)‐2,2‐dimethyl‐6‐((1‐phenyl‐1H‐1,2,3‐triazol‐4‐yl)methoxy)tetrahydrofuro[2,3‐d][1,3]dioxol‐5‐yl)‐3‐phenylthiazolidin‐4‐ones 9a–n has been synthesized from triazole‐linked thiazolidinone derivatives 8a–g with o‐phenylenediamine and characterized by IR, NMR, MS, and elemental analyses. Further, these compounds were screened for their antibacterial activity against Gram‐positive bacteria, namely, Bacillus subtilis (ATCC 6633), Staphylococcus aureus (ATCC 6538p), and Micrococcus luteus (IFC 12708), and Gram‐negative bacteria, namely, Proteus vulgaris (ATCC 3851), Salmonella typhimurium (ATCC 14028), and Escherichia coli (ATCC 25922). Among the screened compounds, compounds 9b , 9d , 9h , and 9i are highly active against almost all selected bacterial strains; the remaining compounds showed moderate to good activity and emerged as potential molecules for further development.     

Synthesis and antimicrobial evaluation of some new bicyclopyrazolone‐based thiopyran ring systems

A series of bicyclopyrazolones were synthesized from the condensation reaction of methyl 4‐oxotetrahydro‐2H‐thiopyran‐3‐carboxylate with hydrazine derivatives in ethanol. All synthesized products were characterized by FT‐IR, ¹H, and ¹³C NMR spectral data, elemental analyses, and mass spectrometry. The antibacterial and antifungal activities of these compounds were evaluated against Staphylococcus aureus and Bacillus subtilis as Gram‐positive bacteria, Escherichia coli and Pseudomonas aeruginosa as Gram‐negative bacteria, and the fungus Candida albicans. The results revealed that bicyclopyrazolones including an aryl or aryl sulfonyl group in the N‐2 position of the pyrazolone moiety are the most effective against all the microorganisms studied in this work.     

Synthesis and Antimicrobial Screening of Some Novel 2‐(5‐(4‐(1H‐Benzo[d][1,2,3]triazol‐1‐yl)phenyl)‐4,5‐dihydro‐1H‐pyrazol‐3‐yl)phenols Incorporated by Triazole Moiety

A novel series of 2‐(5‐(4‐(1H‐benzo[d][1,2,3]triazol‐1‐yl)phenyl)‐4,5‐dihydro‐1H‐pyrazol‐3‐yl)phenols derivative has been synthesized from (E)‐3‐(4‐(1H‐benzo[d][1,2,3]triazol‐1‐yl)phenyl)‐1‐(2‐hydroxyphenyl)prop‐2‐en‐1‐ones in ethanol and hydrazine hydrate under reflux condition. The synthesized compounds were screened for antibacterial activity against Gram‐positive bacteria viz Staphylococcus aureus and Bacillus subtilis and Gram‐negative bacteria viz Escherichia coli and Salmonella typhi, respectively. Some of the tested compounds showed significant antimicrobial activity. IR, ¹H NMR, mass spectral data, and elemental analysis elucidated the structures of all the newly synthesized compounds.     

Organoiodine(III) Mediated Synthesis of Novel Symmetrical Bis([1,2,4]triazolo)[3,4‐a:4′,3′‐c]phthalazines as Antibacterial and Antifungal Agents

A series of new symmetrical 3,6‐bis(aryl)bis([1,2,4]triazolo)[3,4‐a:4′,3′‐c]phthalazines 9a‐l has been conveniently synthesized by oxidative cyclization of 1,4‐bis(substituted benzalhydrazino)phthalazines 8a‐l promoted by iodobenzene diacetate under mild conditions (12 examples, up to 93% yield). All the 12 compounds were tested in vitro for their antibacterial activity against two Gram‐positive bacteria, namely, Staphylococcus aureus, Bacillus subtilis and two Gram‐negative bacteria, namely, Escherichia coli and Pseudomonas aeruginosa. All the synthesized compounds were also tested for their antifungal action against two fungi, Aspergillus niger and Aspergillus flavus.     

Synthesis,Antimicrobial, and Antioxidant Screening of Aryl Acetic Acid Incorporated 1,2,4‐Triazolo‐1,3,4‐Thiadiazole Derivatives

Some novel [1,2,4]triazolo[3,4‐b][1,3,4]thiadiazole derivatives were synthesized from aryl acetic acids. All the synthesized derivatives were selected for the screening of antibacterial potential against Gram‐positive bacteria [Staphylococcus aureus (MTCC 3160) and Micrococcus luteus (MTCC 1538)] and Gram‐negative bacteria [Escherichia coli (MTCC 1652) and Pseudomonas aeruginosa (MTCC 424)] and antifungal potential against Aspergillus niger (MTCC 8652) and Candida albicans (MTCC 227), and free radical scavenging activity through 2,2‐diphenyl‐2‐picrylhydrazyl hydrate method. The compounds TH‐4 , TH‐13 , and TH‐19 were found to be more potent antimicrobial agents compared to standard drugs. The compounds TH‐3 , TH‐9 , and TH‐18 also showed significant antimicrobial activity. The compound TH‐13 showed antioxidant activity with IC₅₀ value better than the standard compound. The structures of all the synthesized compounds were confirmed by Fourier transform infrared, ¹H‐NMR, liquid chromatography–mass spectrometry, and CHN analyzer.     

Derivational,Structural, and Biological Studies of Some New Pyrazolyl,Isoxazolyl, Pyrimidinyl,Pyridazinyl, and Pyridopyridazinyl from 4‐Substituted Antipyrine

(1,5‐Dimethyl‐3‐oxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazol‐4‐yl)carbono‐hydrazonoyl dicyanide was used as a key intermediate for the synthesis of novel pyrazole, isoxazole, pyrimidine, and pyridazine derivatives. The newly synthesized compounds were characterized by elemental analyses and spectral data (IR, ¹H‐NMR, ¹³C‐NMR, and mass spectra). The compounds were tested for their in vitro antibacterial activity against Gram‐positive bacteria as (Staphylococcus aureus and Bacillus subtilis ) and Gram‐negative bacteria (Pseudomonas aeruginosa and Escherichia coli ). The investigated compounds were tested against two strains of fungi Botrytis fabae and Fusarium oxysporum using diffusion agar technique. The biological results showed clearly that most of the synthesized compounds revealed mild to moderate activity against the used microorganisms.     

Convenient Synthesis and Biological Activity of Mono and Diacyl 2,5‐Dimercapto‐1,3,4‐thiadiazole Derivatives

New derivatives of 2,5‐dimercapto‐1,3,4‐thiadiazole substituted both at one or two exocyclic sulfur atoms with a series of aroyl or ethoxycarbonyl groups were synthesized in reactions of 2,5‐dimercapto‐1,3,4‐thiadiazole salts with appropriate acid chlorides or ethyl chloroformate in mild conditions. The products were characterized by spectroscopy (¹H NMR, ¹³C NMR, IR, and HRMS). Some from the synthesized compounds were screened in vitro and in vivo for antibacterial and antifungal activities against a panel of reference strains of microorganisms. The study revealed that ethyl S‐(5‐mercapto‐1,3,4‐thiadiazol‐2‐yl) carbonothioate seems to be the most active and versatile compound against Gram‐positive bacteria, Gram‐negative bacteria, and plant pathogenic fungi.     

Synthesis and Antimicrobial Evaluation of Novel Polyfused Heterocycles‐Based Quinolone

Syntheses of some new heterocyclic compounds incorporating quinolone moieties were achieved via reaction of 4‐hydroxy‐7‐methoxyquinolin‐2(1H)‐one ( 1 ) or 3‐bromo‐4‐hydroxy‐7‐methoxyquinolin‐2(1H)‐one ( 2 ) with binucleophilic reagents. The newly synthesized compounds were characterized by elemental analyses and spectral data (IR, ¹H‐NMR and mass spectra). The newly synthesized compounds were screened for their antibacterial activity against Gram‐positive bacteria (Bacillus thuringiensis) and Gram‐negative bacteria (Escherichia coli). The results showed clearly that compounds 1 and 3 are the more potent antibacterial agents against E. coli, compounds 4 , 5 , 6 and 8 , 9 , 10 , 11 , 12 , 13 exhibited moderate activities against E. coli strain, and compounds 7 and 11 exhibited weak activities compared with Gentamicin as a well known standard drug.     

Synthesis and In Vitro Antibacterial Activity of Novel Steroidal (6R)‐Spiro‐1,3,4‐thiadiazoline Derivatives

Novel steroidal (6R)‐spiro‐1,3,4‐thiadiazoline derivatives were synthesized by the cyclization of steroidal thiosemicarbazones with acetic anhydride, screened in vitro against antibacterial activity using disc‐diffusion method and the minimum inhibitory concentration. The results showed that steroidal thiadiazoline derivatives exhibited better antibacterial activity than the steroidal thiosemicarbazone derivatives. Chloro and acetoxy substituents on the 3β‐position of the steroidal thiadiazoline ring increased the antibacterial activity. Among all the compounds, compound 7 and 8 were found better inhibitors of both types of bacteria (Gram‐positive and Gram‐negative) as compared to the respective drug amoxicillin. All the synthesized compounds were well characterized by spectroscopic methods such as IR, ¹H‐NMR, ¹³C‐NMR mass, and elemental analysis and their stereochemistry was also discussed.     

Synthesis and Biological Evaluation of Novel Bis[1,2,4]triazolo[3,4‐b] [1,3,4]oxadiazoles

A series of novel 6‐2‐methoxy‐5‐[4‐methoxy‐3‐(3‐aryl[1,2,4]triazolo[3,4‐b][1,3,4]oxadiazol‐6‐yl)benzyl]phenyl‐3‐aryl[1,2,4]triazolo[3,4‐b][1,3,4]oxadiazoles 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i , 7j has been synthesized and characterized via IR, ¹H NMR, ¹³C NMR, MS, and elemental analyses. Compounds 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i , 7j were also screened for their antibacterial activity against Gram‐positive bacteria viz. Bacillus subtilis (MTCC 441), Bacillus sphaericus (MTCC 11), and Staphylococcus aureus (MTCC 96), and Gram‐negative bacteria viz. Pseudomonas aeruginosa (MTCC 741), Klobsinella aerogenes (MTCC 39), and Chromobacterium violaceum (MTCC 2656). The antibacterial screening reveal that the presence of 2,4‐difluorophenyl ( 7e ) or 4‐nitrophenyl ( 7f ) of 2‐pyrazyl ( 7i ), or 2‐furyl ( 7j ) on the triazole moiety exhibited potent inhibitory activity comparable with the standard drug streptomycin, at the tested concentrations, and emerged as potential molecules for further development.