Novel syntheses of symmetrical 2,5-diaryl-1,3,4-oxadiazoles and 1,4-phenylenebis-1,3,4-oxadiazoles

The reactions of trichloromethylarenes with excess hydrazine hydrate in ethanol gives symmetrical 2,5-diaryl-1,3,4-oxadiazoles in 68–96% yields. The reaction of 1,4-bis(trichloromethyl)benzene with acylhydrazines in an ethanol-pyridine mixture gives the corresponding substituted or unsubstituted 1,4-phenylenebis-1,3,4-oxadiazoles in 35–51% yields. The mass spectra of 2,5-diaryl-1,3,4-oxadiazoles and 1,4-phenylenebis-1,3,4-oxadiazoles were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2309–2316, November, 1998.     

Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from trichloromethylarenes and acylhydrazines

A preparative synthesis of 2,5-disubstituted 1,3,4-oxadiazoles by the reaction of trichloromethylarenes with hydrazides of carboxylic acids of the aliphatic, aromatic and heteroaromatic series in methanol or ethanol in the presence of pyridine was developed.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 686–692, May, 1994. Original article submitted April 8, 1994.     

Synthesis of 2,5-Dialkyl-1,3,4-oxadiazoles Bearing Carboxymethylamino Groups

A series of new symmetrical 2,5-dialkyl-1,3,4-oxadiazoles containing substituted alkyl groups at the terminal positions with substituents, such as bromine, isopropyloxycarbonylmethylamino, and carboxymethylamino, were successfully synthesized. The developed multistep method employed commercially available acid chlorides differing in alkyl chain length and terminal substituent, hydrazine hydrate, and phosphorus oxychloride. The intermediate bromine-containing 2,5-dialkyl-1,3,4-oxadiazoles were easily substituted with diisopropyl iminodiacetate, followed by hydrolysis in aqueous methanol solution giving the corresponding 1,3,4-oxadiazoles bearing carboxymethylamino substituents. The structure of all products was confirmed by conventional spectroscopic methods including ¹H NMR, ¹³C NMR, and HRMS.     

Synthesis and Reactions of Novel 2,5-Disubstituted 1,3,4-Thiadiazoles

The desired 1,3,4-thiadiazole compounds bearing different substituents were obtained by the cyclization of the corresponding thiosemicarbazide followed by the reaction with electrophilic reagents, such as aromatic aldehydes, isatin, phenyl isothiocyanate, and carbon disulfide. The newly synthesized 2,5-disubstituted 1,3,4-thiadiazoles were obtained in good yields and their structures were elucidated by spectral data and elemental analysis.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles containing benzothiazolylthiol grouping

A series of 2,5-substituted 1,3,4-oxadiazoles containing 2-benzothiazolylthiomethyl grouping has been synthesized by condensing derivatives of (2-benzothiazolylthio)acetic acid with imino ester hydrochlorides and hydrazides of carboxylic acids, by the cyclodehydration of N-acyl-N-(2-benzothiazolylthioacetyl)hydrazines under the action of POCl, and also by the reaction of 2-mercaptobenzothiazole with 2-chloromethyl-1,3,4-oxadiazoles in the presence of sodium methylate.I. M. Gubkin Russian State University for Petroleum and Gas, Moscow 117917. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 249–255, February, 2000.     

Microwave-Assisted Synthesis and Antifungal Activity of 2,5-Disubstituted-1,3,4-oxadiazoles Containing Azulene Moiety

Microwave-assisted as well as conventional synthesis of 2,5-disubstituted-1,3,4-oxadiazoles containing the azulene moiety was carried out, and their antifungal activity is also reported.     

Microwave assisted syntheses of 2,5-disubstituted 1,3,4-oxadiazoles

2,5-Disubstituted 1,3,4-oxadiazoles have been synthesized by oxidation of 1-aroyl-2-arylidene hydrazines with potassium permanganate on the surface of a solid mineral support as well as in mixtures of acetone and water under microwave irradiation.     

Synthesis of picryl-substituted 1,3,4-oxadiazoles

A convenient procedure was developed for the synthesis of picryl-substituted 1,3,4-oxadiazoles. The nucleophilic replacement of the nitro group in picroylacylhydrazines under the action of thiophenol was studied. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1583–1585, September, 2000.     

Reactions with Hydrazonoyl Halides 341: Synthesis of Some New 2,3-Dihydro-1,3,4-thiadiazoles

Hydrazonoyl halides 4a–h have been caused to react with each of alkyl carbodithioates (3, 13–17)a,b in the presence of triethylamine to give 2,3-dihydro-1,3,4-thiadiazoles in good yields. Structures of the new compounds were elucidated on the basis of elemental analyses, spectral data, and alternative methods of synthesis whenever possible.     

Syntheses and insecticidal activities of novel 2,5-disubstituted 1,3,4-oxadiazoles

Nine novel symmetrical and asymmetrical 2,5-disubstituted 1,3,4-oxadiazoles have been synthesized by a facile and mild method with high yield. Meantime, it was found that the fluorine was easy substituted by hydrazine in polyhalogen-substituted aroyl hydrazine. The preliminary bioassay tests show that two of the compounds (D5 and D6) exhibited a significant insecticidal activity (LC₅₀=116.02 and 70.93 mg l⁻¹) on armyworm, Leucania separata Walker. Using the Drug Discovery Workbench (DDW) (Cerius²), structure-activities relationship was studied.     

Synthesis and Biological Activities of Novel 1,4-Bridged Bis-1,2,4-Triazoles,Bis-1,3,4-Thiadiazoles and Bis-1,3,4-Oxadiazoles

Abstract

The terephthalic acid hydrazide(1) reacted with phenyl/benzyl isothiocyanate2a,bto yield the corresponding bis-thiosemicarbazides4a,b,viaacid hydrolysis of the intermediate 3whereas cyclization of4gave the bis-1,2,4-triazoles 5,6and bis-1,3,4-thiadiazoles7,8. Similarly, compound 1reacted with phenyl isocyanate9to give the bis-semicarbazide10, which was cyclized to the bis-oxadiazole 11and/or bis-1,2,4-triazole12in POCl_ti3and NaOH respectively.     

One-pot synthesis, antibacterial and antifungal activities of novel 2,5-disubstituted-1,3,4-oxadiazoles

A series of novel 2,5-disubstituted-1,3,4-oxadiazoles have been synthesized from long-chain alkanoic and alkenoic acids. The structures of these compounds have been elucidated by elemental and spectral （IR, ^1H NMR, ^13C NMR, MS） analysis. Furthermore, compounds were screened for in vitro antibacterial activity against the representative panel of two Gram-positive and two Gram- negative bacteria. All the synthesized compounds were also tested for their inhibitory action against five strains of fungus. The various compounds show potent inhibitory action against test organisms. 2007 Abdul Rauf. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.     

Effects of symmetrically 2,5-disubstituted 1,3,4-oxadiazoles on the temperature range of liquid crystalline blue phases: a systematic study

Four series of symmetrically 2,5-disubstituted 1,3,4-oxadiazoles with different lateral substituents and terminal alkoxy chain length were synthesised and characterised. Then, all these bent-shaped compounds were separately doped into the blue phase (BP) liquid crystal host and their effects on the BP range of the host were investigated, which shows that the BP ranges varied greatly with the difference in the structure of 2,5-disubstituted 1,3,4-oxadiazoles and their doped concentration. Moreover, in order to explore the influence of the inherent molecular geometry and properties of the bent-shaped molecules on the stability of BPs, the molecular structures of all the compounds were studied by using the theory of density functional theory, and the optimised structural parameters of the molecules were calculated at the B3LYP/6–31G* level.     

Synthesis of 5-amino-1,3,4-thiadiazoles containing dithiocarbamate groups

Synthesis of alkyl ((5-[alkylamino]-1,3,4-thiadiazol-2-yl)methyl)carbamodithioates via the reaction of glycine-based dithiocarbamates with thiosemicarbazides in the presence of POCl₃ in ethanol is disclosed. The main advantages of this method including the use of ethanol as solvent, no need to column chromatography for purification and high to excellent yields of products are noteworthy.     

A novel series of 2,5-disubstituted 1,3,4-thiadiazoles as potential anticonvulsant agent

<正>In pursuit for better antiepileptic drug and the importance of semicarbazones and 2,5-disubstituted 1,3,4-thiadiazoles as anticonvulsant pharmacophore,a series of novel N-({5-[(6-methyl-1-benzofuran-3-y1)methyl]-1,3,4-thiadiazol-2-yl}carbamothioyl) -2/3/4-substitutedbenzamide were designed,synthesized and evaluated for their anticonvulsant activity.The findings of the present studies confirmed that the pharmacophore model with four binding sites is crucial for anticonvulsant activity. Structure-activity relationships among synthesized compounds were also established.     

Synthesis of branched polynuclear 1,3,4-oxadiazoles

The reaction of 5-substituted mono-and polytetrazoles with heterocyclic acid chlorides and trifluoroacetic acid anhydride gave branched polynuclear 1,3,4-oxadiazole systems. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1432–1437, September, 2008.     

Convenient preparation of unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles promoted by Dess-Martin reagent

2,5-Disubstituted 1,3,4-oxadiazoles have been conveniently prepared by oxidative cyclization of N-acyl-N′-aryliden-hydrazines promoted by an excess of Dess-Martin periodinane under mild conditions (23 examples, up to 92% isolated yields).     

The Behavior of Dimethylamino-substituted 2,5-Diaryloxazoles and 2,5-Diaryl-1,3,4-oxadiazoles Under Vilsmeier-Haack Conditions

It has been shown that dimethylamino-substituted 2,5-diaryloxazoles and 2,5-diaryl-1,3,4-oxadiazoles undergo heterocyclization under Vilsmeier-Haack conditions with the participation of the dimethylamino group to form quinazolinium salts. The oxazole ring can also be formylated at the free 4 position. In alkaline medium the quinazolinium ring is readily hydrolyzed with desalkylation.     

Polyethylene glycol (PEG) mediated green synthesis of 2,5-disubstituted 1,3,4-oxadiazoles catalyzed by ceric ammonium nitrate (CAN)

Abstract

Ceric ammonium nitrate in polyethylene glycol has been used as a sustainable, non-volatile, and ecofriendly catalytic medium for the green synthesis of 2,5-disubstituted 1,3,4-oxadiazoles. This protocol is effective toward various substrates having different functionalities. The easy recyclability of the reaction medium makes the reaction economically and potentially viable for commercial applications.