ZnCl2 catalyzed efficient synthesis of 1,3,4-oxadiazole and 1,3,4-thiadiazole

New methods for the synthesis of 1,3,4-oxadiazole and 1,3,4-thiadiazole have been described. No cyclizations took place in the absence of ZnCl₂. 1,3,4-Thiadiazoles are formed in the presence of ZnCl₂ alone, whereas oxadiazoles are produced when a base such as Et₃N or KOH was used along with ZnCl₂. % Yields are optimized.     

Neue acetonylsubstituierte Azole II. 3-Acetonyl-1,2,4-oxadiazole, 2-Acetonyl-1,3,4-oxadiazole und 5-Acetonyl-1,2,4-thiadiazole

3-Acetonyl-1,2,4-oxadiazoles and 2-acetonyl-1,3,4-oxadiazoles are accessible starting with the ketal of acetoacetamide oxime and the ketal of acetoacetic acid hydrazide, respectively. 5-Acetonyl-1,2,4-thiadiazoles are obtained from 5-chloro-1,2,4-thiadiazoles andtert.-butyl acetoacetate. These Acetonyl-azoles are starting materials for three series of azolylvinyl phosphates and phosphonates.

Herrn Prof. Dr.Klaus Weissermel zu seinem 60. Geburtstag.     

Synthesis,characterization and comparative study of mesomorphic properties of some new compounds containing both 1,2,4- and 1,3,4-oxadiazole moieties linked in the same molecule

One new homologous series of compounds containing 1,2,4- and 1,3,4-oxadiazole rings in the same molecule was synthesized. 3-(4-Butoxyphenyl)-5-{4-[5-(4-alkoxyphenyl)-1,3,4-oxadiazol-2-yl]phenyl}-1,2,4-oxadiazole (VII)_1–8 were synthesized by several procedures. This series has been characterized by FT-IR and ¹H NMR spectroscopy. Their liquid crystalline properties were studied by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). This series did not show any liquid crystalline behaviors and only crystal to isotropic liquid transition was observed.     

Solid-phase parallel synthesis of 1,3,4-oxadiazole based peptidomimetic library as a potential modulator of protein-protein interactions

Design and solid phase synthesis of the 1,3,4-oxadiazole based peptidomimetic library is presented. Library synthesis starts from the coupling of the thiosemicarbazide resin with Fmoc-protected amino acid following desulfurative cyclization to 1,3,4-oxadiazoles. Following substitution of the secondary amine with the 3-nitrobenzoyl functional group and its further reduction were performed. Thus, the functionalization with amino acids could be performed on both sides of the core skeleton. After diversification and cleavage from the resin using TFA: DCM cleavage cocktail, an enantiopure library of compounds was obtained. Further evaluation of physicochemical properties was performed.     

Integration of naturally bioactive thiazolium and 1,3,4-oxadiazole fragments in a single molecular architecture as prospective antimicrobial surrogates

Plant microbial diseases caused global production constraints have become one of the most challenging events, thus urgently needing to be addressed nowadays. To efficiently promote the discovery of promising antimicrobial surrogates, a type of 1,3,4-oxadiazole thioethers owning naturally bioactive thiazolium patterns was designed and fabricated. Antibacterial screening results revealed that title compounds could significantly inhibit the growth of pathogens Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, and Xanthomonas axonopodis pv. citri. And the related antibacterial efficacy was elevated by approximately 386-, 16-, and 24-folds comparing those of mainly used commercial agents bismerthiazol and thiodiazole copper. In vivo experiment suggested that A₉ could manage rice bacterial blight with the corresponding curative and protection efficiencies of 48.01% and 50.55% at 200 μg/mL. Moreover, SEM patterns and fluorescence spectra were performed to explore the possible antibacterial mechanism. Preliminary antifungal bioassays revealed that these molecules paraded broad-spectrum inhibition effects against three tested fungal strains. Considering the simple molecular skeleton and significant biological actions, title compounds can be further explored as potential antimicrobial surrogates for managing plant bacterial and fungal diseases.     

Polyamides with pendant 1,3,4-oxadiazole and pyridine moieties

A novel aromatic diamine,2-（5-（3,5-diaminophenyl）-l,3,4-oxadiazole-2-yl）pyridine（POBD）,containing a pyridine ring and a 1,3,4-oxadiazole moiety,was synthesized.It was used in a polycondensation with various aromatic and aliphatic diacid chlorides to generate a series of new aromatic polyamides with pendant 1,3,4-oxadiazole groups.The prepared polyamides were characterized by IR,elemental analysis and through the synthesis of model compounds.Thermophysical properties of the synthesized polyamides have been studied by DSC,TGA and inherent viscosity measurements. Relatively high inherent viscosity values（0.76-1.62 dL/g,in 0.125%H₂SO₄ at 25℃） were observed for these compounds. Number average molecular weight（M_n） of the polymers was measured by vapor phase osmometry（VPO）.The introduction of bulky side chains in the structure of aromatic polyamides led to increased solubility of these polymers in common polar and aprotic solvents,such as DMF,DMSO,NMP and DMAc,which allowed thin films to be cast from polymer solutions. The highest molecular weight（M_n = 51190） was observed for polymer（DC）,which was prepared from pyridine-2,6-dichlorocarbonyl.     

Synthesis and pharmacological evaluation of 9(10H)-acridone bearing 1,3,4-oxadiazole derivatives as antimicrobial agents

In the present study a new acridone derivatives were synthesized. The newly synthesized compounds were characterized by IR, NMR and C, H, N, S analyses. All newly synthesized compounds were screened for their antibacterial (Staphylococcus aureus, Streptococcus viridans and Escherichia coil) and antifungal (Gibberela, Cercospora arachidicola, Physolospora piricola and Fusarium oxysporum) studies. The results revealed that all synthesized compounds have a significant biological activity against the tested microorganisms.     

Design,synthesis, and fungicidal activity of novel 1,3,4-oxadiazole derivatives

Employing the intermediate derivatization method (IDM), a series of 1,3,4-oxadiazole derivatives containing arylpyrazoloxyl moiety were designed and synthesized. In vitro bioassays showed that these compounds have moderate to significant fungicidal activity against rice sheath blight and sorghum anthracnose. Furthermore, compound 20 is a promising fungicide for further development.     

Columnar mesophases and phase behaviors of novel polycatenar mesogens containing bi-1,3,4-oxadiazole

A new series of liquid-crystalline bi-1,3,4-oxadiazole derivatives (2,2′-bis(3,4,5-trialkoxyphenyl)-bi-1,3,4-oxadiazole, BOXD-Tn, n=3, 4, 5, 6, 7, 8, 10, 14) were designed and synthesized. They have been confirmed to give rise to columnar mesophases. The columnar mesophases for BOXD-Tn (n=5, 6, 7, 8, 10) could be supercooled to −20 °C on the cooling runs. A room temperature Col_ho phase was obtained for BOXD-T14. All BOXD-Tn exhibit good fluorescence properties either in cyclohexane or in solid state.     

Application of newly synthesized bisazo dichloro-s-triazinyl reactive dyes bearing 1,3,4-oxadiazole molecule

Novel bisazo dichloro-s-triazinyl (DCT) reactive dyes (5a–h) containing 1,3,4-oxadiazole molecule as a tetrazo component were synthesized and applied on silk, wool and cotton fibers by exhaust dyeing method. The structures of these dyes were confirmed by UV–vis, FT-IR, ¹H and ¹³C NMR and elemental analyses. The exhaustion, fixation and fastness properties of the dyed fabric were assessed and the results demonstrated that these dyes showed moderate to very good light and good to excellent washing and rubbing fastness properties. The colorimetric data (L¹, a¹, b¹, C¹, H¹, K/S) of these dyes have also been studied in detail.     

对称双-1,3,4-噁二唑化合物的合成及性质

首先以苯氧乙酰肼和二酰氯为原料反应得到对称双酰肼化合物,再以POCl3合环得到系列对称双-1,3,4-噁二唑化合物。考察了该系列化合物的紫外-可见吸收光谱,其中,间苯双-1,3,4-噁二唑化合物在250nm附近有明显的最大吸收峰,对苯双-1,3,4-噁二唑化合物的最大吸收峰则红移至290nm附近;而脂肪族双-1,3,4-噁二唑化合物没有明显的最大吸收峰,说明没有大的共轭体系,与结构相符合。所有化合物的结构均经元素分析、IR、1H NMR和MS确证。     

Synthesis and characterization of novel conjugated copolymers containing 3,4-dialkoxythiophene and 1,3,4-oxadiazole units

In this report we describe the synthesis, optical and electrochemical properties of new conjugated copolymers (P1-P4) based on 3,4-dialkoxythiophene and 1,3,4-oxadiazole units. The copolymers are prepared using the precursor polyhydrazide route. The chemical structures of the copolymers are confirmed using FTIR, NMR spectroscopy and CHNS analysis. The polymers exhibit good thermal stability with the onset decomposition temperature in nitrogen at around 300 °C. The optical and charge-transporting properties of the copolymers are investigated by UV-visible absorption spectroscopy, fluorescence emission spectroscopy and cyclic voltammetry. The polymers depicted blue/green fluorescence under the irradiation of UV light. Cyclic voltammetry studies reveal that these copolymers have low-lying LUMO energy levels ranging from −3.28 to −3.32 eV and high-lying HOMO energy levels ranging from −5.26 to −5.62 eV, which indicated that they may be promising candidates for the fabrication of polymer light-emitting diodes. In addition, the copolymers showed good third-order non-linear optical properties.     

Coordination-driven synthesis of Ag(I) compounds based on a double emission ligand consisting of 1,3,4-oxadiazole and cyclotriphosphazene units

A new ligand (L) which consists of cyclotriphosphazene and 1,3,4-oxadiazole units is reported. Two new Ag(I) coordination compounds {[Ag(L)SO₃CF₃] _n (1) and Ag₂L₂(NO₃)₂ (2)} based on L and Ag(I) salts are obtained. Compound 1 features a 1-D chain, in which the ligand L adopts a divergent trans-conformation, whereas 2 is a discrete binuclear Ag(I) molecule in which L adopts convergent cis-conformation. Compounds 1 and 2 are fully characterized by ¹H-NMR, Infrared, elemental analysis, X-ray powder, and single-crystal diffraction. Luminescent properties of 1 and 2 are investigated.     

Structures of substituted di-aryl-1,3,4-oxadiazole derivatives: 2,5-bis(pyridyl)- and 2,5-bis(aminophenyl)-substitution

Crystal structures of four different di-aryl-1,3,4-oxadiazole compounds (aryl = 2-pyridyl-, 3-pyridyl-, 2-aminophenyl-, 3-aminophenyl-) are determined. Crystallization of di(2-pyridyl)-1,3,4-oxadiazole yielded monoclinic and triclinic polymorphs. The structures are characterized by the occurrence of π–π interactions. Additionally, in case of the aminophenyl compounds intra- as well as intermolecular hydrogen bonds are found that influence the packing motif as well. Since these molecules are often used as ligands in metal–organic complexes similarities and differences of the molecular conformation between the molecules in the pure crystals and that of the ligands in the complexes are discussed.     

Preparation and properties of high performance bismaleimide resins based on 1,3,4-oxadiazole-containing monomers

In research towards high performance polymeric materials, two novel series of bismaleimide (BMI) resins based on 1,3,4-oxadiazole-containing monomers have been designed and prepared by the copolymeriziation reaction of 5-tert-butyl-1,3-bis[5-(4-maleimidophenyl)-1,3,4-oxadiazole-2-yl]benzene (Buoxd) or 4,4′-bis[5-(4-maleimidophenyl)-1,3,4-oxadiazole-2-yl]diphenyldimethylsilane (Sioxd) and 4,4′-bismaleimidodiphenylmethane (BMDM) in different feed ratios. The structures, thermal and dynamic mechanical properties of all the resulting BMI resins were carefully characterized by a combination of methods such as IR, DSC, TGA and DMA. Investigation of the copolymerization process has shown that with an increase of the weight ratio of Buoxd or Sioxd, melting transition temperature (T_m) of BMI monomer mixtures decreased and the exothermic polymerization temperature (T_p) increased. For all BMI monomer mixtures, a rapid polymerization process was observed in the early stage, as shown by the IR investigations. No glass transition was observed for the resulting BMI resins in the temperature range from 50 °C to 350 °C, indicating the formation of highly cross-linking networks. The initial thermal decomposition temperatures (T_d) of the BMI resins were in the range of 477-493 °C in nitrogen and 442-463 °C in the air. Dynamic mechanical analysis (DMA) of the composites made of the BMI resins and glass cloth showed high bending modulus not only at room temperature (E′, 1.9-5.3 GPa) but also at high temperature, e.g., 400 °C (E′, 1.7-4.4 GPa).     

Synthesis and reactions of 2-mercaptomethyl-1,3,4-oxadiazolin-5-one

Summary The title compound (4) was synthesized from thioglycolic acid hydrazide and ethyl chloroformate. The reactions of4 with aromatic amines, amino derivatives, hydrazine hydrate, hydroxylamine, and formamide were studied. Addition of compound4 to ,-unsaturated compounds,i.e. chalcones, maleic anhydride, quinones, and acrylonitrile, was investigated.

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Synthese und Reaktionen von 2-Mercaptomethyl-1,3,4-oxadiazolin-5-on

Zusammenfassung Die Titelverbindung (4) wurde aus Thioglycolsäurehydrazid und Chlorameisensäureethylester hergestellt. Die Reaktionen von4 mit aromatischen Aminen, Aminoderivaten, Hydrazinhydrat, Hydroxylamin und Formamid sowie die Addition von4 an ,-ungesättigte Verbindungen (Chalkone, Maleinsäureanhydrid, Chinone, Acetonitril) wurden untersucht.

     

Decorating nickel phthalocyanine periphery by aryl-1,3,4-oxadiazole pendants: synthesis,characterization, and conductivity studies

We have decorated nickel phthalocyanine (NiPc) periphery by four different aryl-[1,3,4]-oxadiazole pendants. Introduction of aryl-[1,3,4]-oxadiazole pendants into the NiPc core results in improved thermal stability, fine-tuning of the position of the Q-band with decrease in band gap, indicating effective electronic communication between the two different ring systems with NiPc core. The magnitude of DC electrical conductivity for aryl-[1,3,4]-oxadiazole-substituted NiPcs 3a–3d is found to be ～10⁵ times higher than the parent NiPc (1). The temperature-dependent DC conductivity studies reveal semiconducting nature of the newly synthesized NiPc compounds with significant decrease in thermal activation energy (ΔE) compared to parent NiPc.     

Propylphosphonic anhydride (T3P): an efficient reagent for the one-pot synthesis of 1,2,4-oxadiazoles, 1,3,4-oxadiazoles, and 1,3,4-thiadiazoles

Propylphosphonic anhydride (T3P^®) has been demonstrated to be an efficient and mild reagent for the one-pot synthesis of 1,2,4-oxadiazoles, 1,3,4-oxadiazoles, and 1,3,4-thiadiazoles from carboxylic acids.     

A mild and efficient one pot synthesis of 1,3,4-oxadiazoles from carboxylic acids and acyl hydrazides

A convenient one pot method for the synthesis of 2,5-disubstituted 1,3,4-oxadiazoles from acids and acyl hydrazides is reported. Acid activation with CDI, followed by coupling with the desired acylhydrazide and dehydration in the same pot with Ph₃P and CBr₄ affords the corresponding 1,3,4-oxadiazoles in good yield. The scope of the acid and acylhydrazide components is presented.     

Synthesis and in vitro antibacterial activity of new oxoethylthio-1,3,4-oxadiazole derivatives

In the present investigation, a series of 2(4-pyridyl)-5[(aryl/heteroarylamino)-1-oxoethyl]thio-1,3,4-oxadiazole were synthesized using isonicotinohydrazide and substituted aryl/heteroaryl amines using pyridine as solvent. Newly synthesized compounds were tested for their in vitro anti-tubercular activity against Mycobacterium tuberculosis H37Rv using the BACTEC 460 radiometric system. Among the synthesized compounds, compounds 2(4-pyridyl)-5((2-nitrophenylamino)-1-oxoethyl)thio-1,3,4-oxadiazole (5e), 2(4-pyridyl)-5((4-nitrophenylamino)-1-oxoethyl)thio-1,3,4-oxadiazole (5g) and 2(4-pyridyl)-5((2-pyrrolylamino)-1-oxoethyl)thio-1,3,4-oxadiazole (5k) produced highest efficacy and exhibited >90% inhibition at a concentration of 0.0077, 0.0052 and 0.0089 μM, respectively. All the new compounds were pharmacologically evaluated for their in vitro Antimicrobial activity.