Synthesis,Reactions, and Anticancer Activity of Some 1,3,4-Thiadiazole/Thiadiazine Derivatives of Carbazole

A novel method for the synthesis of 1,3,4-thiadiazole and 1,3,4-thiadiazine derivatives bearing a carbazole moiety is described. Carbazole was transformed into carbazole-9-thiocarbohydrazide in two steps. This compound was allowed to react with various electrophiles to yield 1,3,4-thiadiazole derivatives. The reaction with bifunctional electrophiles led to 1,3,4-thiadiazines. 2-(Carbazol-9-yl)-5,6-dihydro-4H-1,3,4-thiadiazin-5-one reacted with piperidine and formaldehyde to yield the 4-(piperidin-1-ylmethyl) derivative. The reaction with aromatic aldehydes led to the corresponding 6-arylidene derivatives, which were transformed into pyrimidino[4,5-e]-1,3,4-thiadiazines and pyrazolo[3,4-e]-1,3,4-thiadiazines by a reaction with guanidine, acetamidine, or phenylhydrazine, respectively. Structures of the products were confirmed by ¹H NMR, ¹³C NMR, IR, and mass spectrometric measurements. Selected examples of products were screened for anticancer activity.     

1H, 13C, 15N and 19F NMR study of acetylation products of heterocyclic thiosemicarbazones

Novel 2-acetylamino-4-acetyl-5-aryl(heteryl)-1,3,4-thiadiazolines, 2-acetylamino-5-aryl(heteryl)-1,3,4-thiadiazoles, and some of their salts were prepared and studied by multinuclear 1H, 13C, 15N, 19F and 2D NMR spectroscopy. The acetylation of thiosemicarbazones is accompanied by ring closure to form the corresponding 1,3,4-thiadiazolines and 1,3,4-thiadiazoles. 15N NMR spectroscopy is a unique method for the identification of thiadiazole pyridinium salts.     

Synthesis of arylethylene derivatives of 2, 5-diphenyl-1, 3, 4-oxadiazole

The synthesis of arylethylene derivatives of 2,5-diphenyl-1,3,4-oxadiazole by the Wittig reaction from 2-(p-bromomethylphenyl)-5-phenyl-1,3,4-oxadiazole and aromatic aldehydes is described. The compounds obtained fluoresce strongly on irradiation with UV light.     

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.     

Benzohydrazides,benzothiohydrazides, and benzamidrazones as sources of 1,3,4(2H)-oxadiazolenones, 1,3,4(2H)-thiadiazolenones,and 1,2,4(5H)-triazolenones

Benzohydrazides, benzothiohydrazides, and benzamidrazones have been converted to 1,3,4(2H)-oxadiazolenones, 1,3,4(2H)-thiadiazolenenones, and 1,2,4(5H)-triazolenones respectively by reaction with ethyl chloroformate, with ethyl thiolchloroformate, and with phenyl isocyanate. In some reactions, a carbamate or urea has been isolated as intermediate.     

Preparation of halomethyl-1,3,4-thiadiazoles. Conversion to 2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole,an important antimicrobial agent

A new route for the synthesis of 2-amino-5-(l-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazole ( 1 ) is described. This route was based upon the preparation of 2-amino-5-halomethyl-1,3,4-thiadiazoles by condensation of haloacetic acids with thiosemicarbazide. One of these intermediates, 2-acetamido-5-dichloromethyl-1,3,4-thiadiazole ( 4 ), was hydrolyzed to the corresponding 5-amino-2-carboxaldehyde 6 , which was trapped as its oxime 5 . 5-Acetamido-1,3,4-thiadiazole-2-carbonitrile ( 7 ), formed upon dehydration of 5 , was then converted into 2-amino-5-(2-imidazolyl)-1,3,4-thiadiazole ( 11 ) by a route based on the Pinner amidine synthesis. Methylation and nitration of the imidazole moiety then completed the preparation of 1.     

Synthesis and characterization of mono- and bicyclic heterocyclic derivatives containing 1,2,4-triazole, 1,3,4-thia-, and -oxadiazole rings

A series of new N- and S-substituted 1,3,4-oxadiazole derivatives were synthesized. 5-Pyridin-3-yl-3-[2-(5-thioxo-4,5-dihydro-l,3,4-thiadiazol-2-yl)ethyl]-1,3,4-oxadiazole-2(3H)-thione and 5-[(5-(pyridin-3-yl)-1,3,4-oxadiazol-2-ylthio)methyl]-N-phenyl-1,3,4-thiadiazol-2-amine were formed by cyclization of 3-(5-pyridin-3-yl-2-thioxo-1,3,4-oxadiazol-3(2H)-ylpropanimidohydrazide and 2-[(5-pyridin-3-yl-1,3,4-oxadiazol-2-yl)thio]thiosemicarbazide with CS₂ and H₂SO₄. On the other hand, a number of new bicyclic 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole derivatives were synthesized. 6-Pyridin-3-ylbis[1,2,4]‐triazolo[3,4-b:4′,3′-d][1,3,4]thiadiazole-3(2H)-thione was synthesized by reaction of 6-(hydrazino)-3-pyridine-3-yl[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole with CS₂/KOH/EtOH. The structures of the newly synthesized compounds were elucidated by the spectral and analytical data IR, Mass, and ¹H NMR spectra. Correspondence: Adel A.-H. Abdel-Rahman, Department of Chemistry, Faculty of Science, Menoufia University, Shebin El-Koam, Egypt; Wael A. El-Sayed, National Research Centre, Department of Photochemistry, Cairo, Egypt.     

Synthesis, characterization and antifungal evaluation of 5-substituted-4-amino-1,2,4-triazole-3-thioesters

A series of 5-substituted-4-amino-1,2,4-triazole-3-thioesters was synthesized by converting variously substituted organic acids successively into the corresponding esters, hydrazides, 5-substituted-1,3,4-oxadiazole-2-thiols, 5-substituted-1,2,4-triazole-2-thiols and 5-substituted-1,3,4-oxadiazole-2-thioesters. Finally the target compounds were obtained by refluxing 5-substituted-1,3,4-oxadiazole-2-thioesters in the presence of hydrazine hydrate and absolute alcohol. The structures of the synthesized compounds were established by physicochemical and spectroscopic methods. The synthesized compounds were evaluated for their in vitro antifungal activity. Some of the evaluated compounds possessed significant antifungal activity as compared to a terbinafine standard.     

Synthesis and Reactivity of Enaminones: Synthesis of Some 1,3,4‐Thiadiazole Linked to Pyrazole,Pyridine, Benzimidazolopyrimidine,Pyrazolopyrimidine, Pyrazolotriazine and Triazolotriazine Derivatives

1,3,4‐Thiadiazole‐enaminone ( 6 ) was synthesized via reaction of the benzamide ( 5 ) with DMF‐DMA. The simple thiadiazole‐enaminone ( 6 ) was used as a synthetic precursor for the synthesis of a wide variety of new heterocyclic compounds, including the 5‐substituted‐1,3,4‐thiadiazole derivatives ( 7 ), ( 8 ), ( 16 ), ( 17 ) and ( 18 ), which were obtained via reactions of ( 6 ) with nitrogen nucleophiles. Also, reactions of enaminone ( 6 ) with carbon nucleophiles afforded the respective 1,3,4‐thiadiazoles ( 10a , 10b ). Diazotization of the benzamide ( 20 ) with the heteroaromatic amine salts gave the hydrazone derivatives ( 21 ) and ( 22 ). Cyclization of the latter hydrazones yielded the corresponding pyrazolotriazine and 1,2,4‐triazolotriazine derivatives ( 23 ) and ( 24 ), respectively. All newly synthesized compounds were elucidated by considering the data of both elemental and spectral analysis.     

2-Phenyl-5-(trichloromethyl)-1,3,4-oxadiazoles,A new class of antimalarial substances

An investigation of hybrids of 2,5-dimethyl-1,3,4-oxadiazole (I) and α,α,α,α',α',α'-hexachloro-p-xylene (Hetol®) (II) as potential antimalarial agents led to the synthesis of representative 2-phenyI-5-(trichloromethyl)-1,3,4-oxadiazoles (VIa-f, VIII-X) and related trichloromethyl 1,2,4-oxadiazole, 1,3,4-oxadiazoles, and 1,3,4-thiadiazole (VII, XIII-XV). Treatment of the appropriately substituted benzoic: acid hydrazides (IVa-f) with trichloroacetic anhydride afforded the intermediate 1-benzoyl-2-(triehloroacetyl)hydrazines (Va-f) which were cyclized to the desired 5-(chlorophenyl, tolyl, or α,α,α-trifluorotolyl)-2-(trichloromethyl)-1,3,4-oxadiazoles (VIa-f) (44–66%) in situ utilizing phosphorous oxychloride. Chlorination of the 5-tolyl-2-(trichloromethyl)-1,3,4-oxadiazoles (VId-f) afforded 2-(trichloromethyl)-5-(α,α,α-trichloro-m- and p-tolyl)-1,3,4-oxadiazole (VIII and IX) and 2-(α,α,α,α',α',α'-hexachloro-3,5-xylyl)-5-(trichloromethyl)-1,3,4-oxadiazole (X) in 23–56% yield. Each of the 2-phenyl-5-(trichloromethyl)-1,3,4-oxadiazoles (VIa-f, VIII-X) was active against Plasmodium berghei in mice when administered in single 160 or 640 mg./kg. subcutaneous doses or given orally by drug-diet for 6 days at doses of 29–336 mg./kg./day. The 2-(trichloromethyl)-5-(α,α,α-trichlorotolyl)-1,3,4-oxadiazoles (VIII-X) were the most active compounds prepared and exhibited activity against P. berghei comparable with Hetol®. Structure-activity relationships are discussed.     

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 of 1,3,4-thiadiazines,bis-1,3,4-thiadiazoles, [1,2,4]triazino[3,4-b][1,3,4]thiadiazine,thiazolines from carbonothioic dihydrazide

A novel and efficient synthesis of 1,3,4-thiadiazines, bis-1,3,4-thiadiazoles, [1,2,4]triazino[3,4-b][1,3,4]thiadiazine, and thiazolines is reported from the reaction of α-haloketo hydrazonoyl halides with carbonothioic dihydrazide or its analogues. The structures were elucidated on the basis of their elemental analysis, spectral data and an alternative synthetic route.     

Reactions of Aroylhydrazones,IV: Synthesis of Nitrogen Heterocycles from Opianic Acid Hydrazones

Opianic acid reacts with various hydrazines to yield either hydrazone ( 3, 6 ) or phthalazinone ( 4 ) derivatives depending upon the electronic properties of the substituent attached to the hydrazine molecule. Oxidative cyclization of opianic acid aroylhydrazones with iodine and yellow mercuric oxide gave the 1,3,4-oxadiazole derivatives 21 . The aroylhydrazones were also condensatively cyclized by heating with acetic anhydride to give the 1,3,4-oxadiazoline derivatives 24 . Structures assigned to the prepared compounds were corroborated by studying their chemical as well as their spectral characteristics.     

Uracyl derivatives functionalized with N-, S-, O-heterocycles

Reactions of 1,3-bis(bromopentyl)-5(6)-substituted uracyls with a series of five-membered heterocycles containing in the ring N, S, or O atoms and a mercapto group as a substituent at the carbon atom of the ring afforded uracyl derivatives of acyclic and macrocyclic structure with 2-thiobenzoxazole, 2-thio-5-methyl-1,3,4-thiadiazole, 2-thiobenzimidazole, and 2,5-dithio-1,3,4-thiadiazole fragments. N atoms of benzoxazole and imidazole fragments of compounds obtained undergo alkylation and quaternization with alkyl iodides and alkyl tosylates.     

The 1,3,4-oxadiazole moiety,a protective synthon for indirect radioiodination

2-(4-Hydroxyphenyl)-1,3,4-oxadiazole can readily be iodinated/radioiodinated to 2-(3,5-diiodo-4-hydroxy-phenyl)-1,3,4-oxadiazole which in a one-step hydrolysis-condensation serves as an indirect prosthetic moiety for iodination of carbonyl compounds.     

Synthesis and study of the properties of tetrazoles,azides, triazenes,and azo compounds of the thiadiazole series

Azo compounds and bistriazenes were obtained by diazo coupling of diazotized 5-amino-2-R-1,3,4-thiadiazoles; tetrazolo[4,5-b]-1,3,4-thiadiazoles, to which azido-tetrazole tautomerism is peculiar, were obtained by replacement of the diazo group by an azido group. The structures of the products were confirmed by their IR and UV spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 933–936, July, 1980.     

Synthesis of some polyureas based on diamino derivatives of bis-1, 3, 4-oxadiazole

Ortho-, meta, and para-nitrobenzoyl derivatives of the dihydrazides of succinic, glutaric, adipic, and azelaic acids are prepared, from which are obtained nitro and amlno derivatives of bis-1,3,4- diazole. Various conditions for synthesizing these compounds are investigated. A series of polyureas is obtained by reacting diamino derivatives of bis-1,3,4-oxadiaole with diisocyanates, and some of their properties are investigated.     

3,6-二取代苯基-二-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑衍生物的合成

以2,5-二巯基-1,3,4-噻二唑为原料, 与水合肼缩合, 生成2,5-二肼基-1,3,4-噻二唑. 2,5-二肼基-1,3,4-噻二唑与苯甲酰氯反应生成2,5-二酰肼基-1,3,4-噻二唑, 以POCl₃为环合剂环合酰肼基-1,3,4-噻二唑, 合成3,6-二取代苯基- 二-1,2,4-三唑并[3,4-b]-1,3,4-噻二唑衍生物, 合成的新化合物的结构通过元素分析、红外光谱、核磁共振氢谱和质谱予以证实, 并提出了环化反应机理.     

Synthesis,Characterization, and Screening for Analgesic and Anti‐Inflammatory Activities of Schiff Bases of 1,3,4‐Oxadiazoles Linked With Quinazolin‐4‐One

Sixteen Schiff bases of quinazolin‐4‐one‐linked 1,3,4‐oxadiazoles were synthesized by reaction with different aromatic aldehydes. Purity of newly synthesized derivatives was confirmed through thin‐layer chromatography, combustion analysis, and melting point. The structure of the derivatives was confirmed by determining infrared spectroscopy, nuclear magnetic resonance, and mass spectroscopy. All the synthesized derivatives were evaluated for their analgesic and anti‐inflammatory activities in mice and rats, respectively. In animal studies, the derivative (E )‐3‐(5‐(4‐(4‐methoxybenzylideneamino)phenyl)‐1,3,4‐oxadiazol‐2‐yl)‐2‐phenylquinazolin‐4(3H )‐one showed more potent analgesic activity and the derivative (Z )‐3‐(5‐(2‐(2‐hydroxybenzylideneamino)phenyl)‐1,3,4‐oxadiazol‐2‐yl)‐2‐phenylquinazolin‐4(3H )‐one showed more potent anti‐inflammatory activity as compared with other derivatives. The results of the present study indicate that reactions of 3‐(5‐(4‐aminophenyl)‐1,3,4‐oxadiazol‐2‐yl)‐2‐phenylquinazolin‐4(3H )‐one and 3‐(5‐(2‐aminophenyl)‐1,3,4‐oxadiazol‐2‐yl)‐2‐phenylquinazolin‐4(3H )‐one with different aromatic aldehydes produce Schiff bases of quinazolin‐4‐one‐linked 1,3,4‐oxadiazoles with potent analgesic and anti‐inflammatory activities.     

Propylene oxide assisted one-pot,tandem synthesis of substituted-1,3,4-oxadiazole-2(3H)-ones in water

It has been developed for the synthesis of substituted-1,3,4-oxadiazole-2(3H)-one derivatives via a novel one-pot, tandem procedure assisted by propylene oxide. The 5-substitued-1,3,4-oxadiazole-2(3H)-ones and 3,5-disubstitued-1,3,4-oxadiazole-2(3H)-ones were, respectively, obtained from three-component reaction of acylhydrazines, carbon disulfide, and propylene oxide, and four-component reaction of acylhydarazines, carbon disulfide, propylene oxide, and organic halides. The reactions were carried out using water as solvent in the presence of potassium phosphate to afford the expected products in good to excellent yields.