Synthesis and Anti‐cancer Activity of 1,3,4‐Thiadiazole and 1,3‐Thiazole Derivatives Having 1,3,4‐Oxadiazole Moiety

Reaction of 1,3,4‐oxadiazolyl‐phenylthiourea 3 with hydrazonoyl halides gave the corresponding 1,3,4‐oxadiazolylimino‐1,3,4‐thiadiazoles. Also, treatment of 3 with ethyl chloroacetate and α‐haloketones afforded the corresponding thiazolidinone and thiazole derivatives, respectively. The structures of the synthesized products were confirmed by spectral data. Ten compounds were evaluated for their anti‐cancer activity against the colon carcinoma cell line (HCT‐116). The results revealed that 1,3,4‐thiadiazole derivatives 13d and 19c (IC₅₀ = 0.73 and 0.86 µg/mL, respectively) have promising antitumor activity against colon carcinoma (HCT‐116), and most of the tested compounds showed moderate anti‐cancer activity.     

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.     

Synthesis,Reactions and Antimicrobial Activity of Some New Indolyl‐1,3,4‐Oxadiazole,Triazole and Pyrazole Derivatives

Indole‐3‐carboxylic acid hydrazide 3 was prepared and was treated with aromatic aldehydes in ethanol to give the corresponding hydrazone derivatives 4–7 in good yields. The indole carbohydrazide was incorporated into the 3‐indolyloxadiazoles 8–11 and 18 , 3‐indolyltriazoles 13–17 and 35 , 3‐indolylpyrazole derivatives 19–23 and carbamate derivatives 26–27 . Furthermore, interaction of the carboazide 24 with hydrazine hydrate in refluxing toluene afforded the corresponding semicarbazide derivative 30 . The thiadiazine derivative 34 was also prepared. Some of these compounds were screened in vitro for their antibacterial and antifungal activity.     

Synthesis,Nematicidal Activity,and 3D‐QSAR of Novel 1,3,4‐Oxadiazole/ Thiadiazole Thioether Derivatives

Forty one novel 1,3,4‐oxadiazole/thiadiazole thioether derivatives containing phenoxy moiety were designed and synthesized. Bioassay demonstrated that some of them showed remarkable activities against Tylenchulus semipenetrans in vitro and in vivo. Compounds 20 , 21 , 35 and 39 showed excellent lethal activities after treatment for 48 h in vitro, with LC₅₀ values of 13.4 ± 1.8, 11.7 ± 2.5, 13.7 ± 2.4 and 13.3 ± 1.1 mg·L^–1, respectively, which were obviously superior to fosthiazate (49.1 ± 2.8 mg·L^–1) and avermectin (26.6 ± 2.3 mg·L^–1). Compound 21 can effectively control the citrus nematode disease caused by T. semipenetrans at 200 mg·L^–1 in vivo with (68 ± 3)% inhibitory effect, which was even better than that of avermectin ((63 ± 2)%). The CoMFA and CoMSIA models of three‐dimensional quantitative structure‐activity relationships (3D‐QSARs) were established. The compound 33 was designed based on the 3D‐QSAR models with more vigorous nematicidal activities in vitro (LC₅₀ = 9.8 ± 1.4 mg·L^–1) and in vivo ((70 ± 5)%). These results demonstrated that compound 33 can be considered as a potential nematicide.     

Synthesis of New 1,3,4‐Oxadiazol,Thiadiazole, 1,2,4‐Triazole,and Arylidene Hydrazide Derivatives of 4‐Oxo‐1,4‐dihydroquinoline with Antimicrobial Evaluation

A series of substituted 1,3,4‐oxadiazole, 1,2,4‐triazole, and 1,3,4‐thiadiazole derivatives of the substituted 3‐carboethoxy‐1,4‐dihydro‐4‐oxoquinoline have been synthesized through the reaction of the key intermediate thiosemicarbazide derivatives with different reagents. N′‐Arylidene‐4‐oxo‐1,4‐dihydroquinoline‐3‐carbohydrazides were also synthesized through the condensation reaction of the corresponding hydrazides with the appropriate aldehydes. Antimicrobial activity of some of the synthesized compounds was evaluated.     

Synthesis of Certain New Thiazole and 1,3,4‐Thiadiazole Derivatives via the Utility of 3‐Acetylindole

2‐(2‐(1‐(1H‐Indol‐3‐yl)ethylidene)‐hydrazinyl)‐4‐substituted 5‐(aryldiazenyl)thiazoles and 5‐((1‐(1H‐indol‐3‐yl)ethylidene)hydrazono)‐2‐substituted‐4‐phenyl‐4,5‐dihydro‐1,3,4‐thiadiazoles were synthesized via reaction of hydrazonoyl halides and 2‐(1‐(1H‐indol‐3‐yl)ethylidene)hydrazine‐1‐carbothioamide and alkyl 2‐(1‐(1H‐indol‐3‐yl)ethylidene)hydrazine‐1‐carbodithioate in ethanolic triethylamine. Structures of the newly synthesis were elucidated on the basis of elemental analysis, spectral data, and alternative synthetic route whenever possible.     

Synthesis of Extended 1,3,4‐Oxadiazole and 1,3,4‐Thiadiazole Derivatives in the Suzuki Cross‐coupling Reactions

New derivatives of 1,3,4‐oxadiazole and 1,3,4‐thiadiazole were synthesized by a palladium catalyzed Suzuki cross‐coupling reaction under the conditions of the phase transfer catalysis. The structure of the products, the absorption and emission spectra were also studied.     

Synthesis and Antimicrobial Activity of New 2,5‐Disubstituted 1,3,4‐Oxadiazoles and 1,2,4‐Triazoles and Their Sugar Derivatives

A series of new 2,5‐disubstituted‐1,3,4‐oxadiazole and 1,2,4‐triazole derivatives were synthesized by heterocyclization of acid hydrazide 1 and thiosemicarbazide derivative 2 . Furthermore, the acyclic C‐nucleoside analogs were prepared by cyclization of their corresponding sugar hydrazones by reaction with acetic anhydride. The antimicrobial activity of the prepared compounds was evaluated and some of the synthesized compounds revealed good activities against fungi.     

Synthesis and Antimicrobial Activity of Polyfunctionally Substituted Heterocyclic Compounds Derived from 5‐Cinnamoylamino‐2‐Cyanomethyl‐1,3,4‐Thiadiazole

Cinnamoyl isothiocyanate 1 was reacted with 2‐cyanoethanoic acid hydrazide 2 to afford 1‐cyanoacetyl‐4‐substituted thiosemicarbazide 3, which on treatment with a mixture of glacial acetic acid and acetic anhydride gave the desired 5‐cinnamoylamino‐2‐cyanomethyl‐1,3,4‐thiadiazole 4 . Compound 4 was subjected to react with aromatic aldehydes, phenylisothiocyanate, carbon disulphide, and arylidene malononitrile to give coumarin 5 , thiazolidines 8 , 9, and 1,3,4‐thiadiazolo[3,2‐a]pyridine 13 derivatives. The structures of all synthesized compounds were ascertained by spectral and analytical data. Antimicrobial activity of some of prepared compounds was investigated, and compounds 7, 8 were found to exhibit the highest strength.     

Synthesis and Antimicrobial Activity of New Derivatives of 1,3,4‐Thiadiazoles and 1,2,4‐Triazoles with 5‐Nitroindazole as Support

The synthesis of new derivatives of 1,3,4‐thiadiazoles and 1,2,4‐triazoles was achieved using the 1,4‐disubstituted thiosemicarbazides as intermediaries.     

Synthesis and Characterization of Some New Heteroaromatic Compounds Having Chirality Adjacent to a 1,3,4‐Thiadiazole Moiety and Their Antimicrobial Activities

Through a cyclization reaction of 2‐phenylbutyric acid with N‐ phenylthiosemicarbazide and POCl₃, novel 1,3,4‐thiadiazole derivatives were synthesized. Their structures were confirmed using IR, ¹H NMR, and ¹³C NMR spectroscopies and elemental analysis. The antibacterial activities of the obtained 1,3,4‐thiadiazole derivatives were tested against Gram‐negative bacteria (Salmonella enteritidis , Salmonella typhimurium , Enterobacter aerogenes , Salmonella infantis , Salmonella kentucky , and Escherichia coli ) and Gram‐positive bacteria (Staphylococcus aureus , Bacillus subtilis , and Enterococcus durans ) using a disk diffusion method. Moreover, an antifungal activity experiment was performed against Candida albicans using the disk diffusion method. It was observed that the synthesized 1,3,4‐thiadiazole derivatives exhibited effective antimicrobial activity against S. aureus , E. coli , and C. albicans . Based on these results, the 1,3,4‐thiadiazole derivatives can be considered as a source of bioactive agents for pharmacological and medicinal applications.     

Synthesis of Some Pyrazole,Thiazole, Pyridine,and 1,3,4‐Thiadiazole Derivatives Incorporating 2‐Thiazolyl Moiety

Reaction of N‐(5‐acetyl‐4‐methylthiazol‐2‐yl)‐2‐cyanoacetamide 2 with hydrazonoyl chlorides ( 3a,b ) yielded the corresponding aminopyrazole derivatives ( 5a,b ), respectively. Reaction of 2 with α,β‐benzylidenemalononitrile derivatives 8a,b and 13a,b afforded the corresponding pyridine derivatives 12a,b and 17a,b , respectively. Treatment of 2 with phenylisothiocyanate in dimethylformamide/KOH followed by the addition of ethyl chloroacetate and the appropriate hydrazonoyl chlorides 3a,b and 27 gave the corresponding 1,3‐thiazole 21 and 1,2,4‐thiadiazole derivatives 24a,b and 30 , respectively. The newly synthesized compounds were confirmed from their elemental analyses and spectral data.     

Synthesis and Herbicidal Activity of Acylpyrazole Derivatives Containing 1,2,3‐Thiadiazole Moiety

A series of novel acylpyrazole derivatives containing 1,2,3‐thiadiazole ring 3a – 3m were synthesized by the condensations of 1‐phenyl‐3‐methyl‐4‐(substituted benzal or 4‐methyl‐1,2,3‐thiadiazole‐5‐carbonyl)‐5‐hydroxypyrazole 2 with 4‐methyl‐1,2,3‐thiadiazole‐5‐carbonyl chloride or substituted benzoyl chloride. Their structures were confirmed by IR, ¹H‐NMR, mass spectroscopy, and elemental analyses. The results of preliminary bioassays showed that some of the title compounds 3 exhibited moderate to good herbicidal activities against dicotyledonous plants (Brassica campestris L.) at the concentration of 100 mg/L. For example, compounds 3e , 3f , 3g , and 3k possessed 74.6%, 72.2%, 70.3%, and 84.5% inhibition against B. campestris L., respectively, whereas commercially available herbicide Sulcotrione showed only 35.0% inhibition at the same concentration. Moreover, these compounds displayed higher herbicidal activity against B. campestris L. than Echinochloa crus‐galli. However, these compounds showed weak activities at the concentration of 10 mg/L.     

Synthesis and Antibacterial Activity of Some New 2,5‐Disubstituted‐1,3,4‐oxadiazole Derivatives

Synthesis of some new oxadiazole derivatives starting from 1,2,3-benzo[d]triazole-1-acetic hydrazide (1) is described. The target compounds 2-(N-substituted-aminocarbonylmethylthio)-5-(1,2,3-benzo[d]triazol-1-ylmethyl)- 1,3,4-oxadiazole (4a—4i) and 2-[2-(N-substituted-aminocarbonyl)ethylthio]-5-(1,2,3-benzo[d]triazol-1-ylmethyl)- 1,3,4-oxadiazole (5a—5i) were obtained in good yields via cyclisation of 1 and subjected to antibacterial activity test against pathogenic bacteria. The halogen containing mono- and di-substituted derivatives showed excellent antibacterial activity compared to other analogues.     

Synthesis and Evaluation of 1,3,4‐Thiadiazole Derivatives Containing Cyclopentylpropionamide as Potential Antibacterial Agent

This study aimed to identify new strategies for the control of these plant bacterial diseases by combining a pharmacophoric group of different bioactive compounds. A series of 3‐cyclopentylpropionamide containing 1,3,4‐thiadiazole derivatives was synthesized and characterized via ¹H‐NMR, ¹³C‐NMR, and HRMS. Bioassay results indicated that compounds 7a , 7d , 7j , 7m , 7n , and 7s had excellent antibacterial activity compared with the positive control. Among them, compound 7a exhibited remarkable inhibitory effect against Xoo with an EC₅₀ of 21.41 μg/mL, which surpassed that of thiodiazole copper (67.71 μg/mL) and bismerthiazol (69.05 μg/mL). Greenhouse condition tests further revealed that 7a had approximately equal curative activity and better protection activity (41.58%) against bacterial leaf blight of rice than that of thiodiazole copper and bismerthiazol (46.86 and 42.25%, respectively). Structure–activity relationship analysis exhibited that sulfone fragment favored inhibition. Overall, this study suggested that derivatives containing 1,3,4‐thiadiazole 3‐cyclopentylpropanamide can be used as new lead compounds for bactericide studies.     

Synthesis and Antimicrobial Activity of New Substituted 5‐(Pyridine‐3‐yl)‐1,3,4‐Thiadiazoles and Their Sugar Derivatives

New substituted 5‐(pyridine‐3‐yl)‐1,3,4‐thiadiazoles, their sugar hydrazones and acyclic C‐nucleoside analogs as well as the corresponding thioglycoside derivatives were synthesized. The synthesized compounds were tested for their antimicrobial activity against Escherichia coli, Bacillus subtilis, Staph aureus, Aspergillus niger, and Candida albicans The obtained results indicated that most of tested compounds exhibited moderate to high antimicrobial activity while few compounds were found to exhibit little or no activity against the tested microorganisms.     

Synthesis and Herbicidal Activity of 2‐Aroxy‐propanamides Containing Pyrimidine and 1,3,4‐Thiadiazole Rings

A series of novel N‐{5‐[2‐(4,6‐dimethoxy‐pyrimidin‐2‐yloxy)‐phenyl]‐[1,3,4]thiadiazol‐2‐yl}2‐aroxy‐propanamides were designed and synthesized by the multistep reactions. 2‐(4,6‐Dimethoxy‐pyrimidin‐2‐yloxy)‐benzaldehyde ( 1 ) reacted with aminothiourea to yield 2 , which undergoes ring closure to give 5‐[2‐(4,6‐dimethoxy‐pyrimidin‐2‐yloxy)‐phenyl]‐[1,3,4]thiadiazol‐2‐amine ( 3 ) in the presence of ferric chloride in refluxing ethanol. 3 reacted with 2‐aroxy‐propionyl chlorides to give the target compounds 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i in moderate to good yields. Their structures were confirmed by IR, ¹H‐NMR, EIMS, and elemental analyses. The preliminary bioassay indicated that some of them displayed moderate to good selective herbicidal activity against Brassica campestris L. at the concentration of 100 mg/L. However, these compounds did not possess inhibitory activity against Echinochloa crus‐galli at the tested concentrations.     

Synthesis and Antimicrobial Activity of Some Novel Thiazoles, 1,3,4‐Thiadiazines, 1,3,4‐Thiadiazoles Incorporating Coumarin Moiety

Starting from 3‐acetyl‐2H‐chromen‐2‐one and hydrazinecarbothiohydrazide, new functionalized thiazoles, 1,3,4‐thiadiazines, and 1,3,4‐thiadiazoles were prepared. The structures of the compounds prepared were confirmed by both elemental and spectral analyses as well as by alternate synthesis. The antimicrobial activities of the compounds prepared were screened, and the results showed that most of such compounds exhibit considerable activities.     

Synthesis,Characterization, and Antimicrobial Properties of New 1,3,4‐Thiadiazoles Derived from Azo Dyes

Some new 1,3,4‐thiadiazoles derived from azo dyes were synthesized. Two different synthesis methods were used for these compounds: Esters pertaining to the azo dyes were converted into 1,3,4‐thiadiazoles, or benzothiazole ester derivatives were converted to 1,3,4‐thiadiazoles followed by the synthesis of azo dye derivatives. The desired products were successfully obtained using the latter method. The molecular structures of these compounds were characterized using spectroscopic methods such as FTIR, ¹H NMR, ¹³C NMR, and elemental analysis. Furthermore, antimicrobial activity was studied for the synthesized compounds. Compound 3e exhibited antimicrobial activity against three different microorganisms. Compounds 3a , 3b , and 3d had activity against two different microorganisms, while compound 3c showed activity against only one microorganism.     

Synthesis and Antifungal Activity of Novel 1,2,4‐Triazole Derivatives Containing 1,2,3‐Thiadiazole Moiety

Starting from carbonic acid diethyl ester, a series of 1,2,4‐triazole derivatives containing 1,2,3‐thiadiazole were synthesized. Reactions were performed by microwave irradiation or ultrasonic irradiation as well as by conventional heating. The structure of title compounds was characterized by ¹H‐NMR, MS, and elemental analyses. The fungicidal activities of these compounds were tested in vivo. Most of title compounds exhibited good antifungal activity against Pseudoperonospora cubensis. Some of title compounds displayed moderate antifungal activities against Fusarium oxysporum, Pseudoperonospora cubensis, Sphaerotheca fuligenea, Corynespora cassiicola, and Xanthomonas axonopodis.