Crystal and molecular structure of 2,5-bis(fluorodinitromethyl)-1,3,4-oxadiazole

An X-ray structural study of 2,5-bis(fluorodinitromethyl)-1,3,4-oxadiazole (1), one of the representatives of azoles with strong electron-withdrawing substituents, has been carried out. It has been found that in the orthorhombic modification of1 the conformations of the fluorodinitromethyl groups are different. Intermolecular contacts in the crystal are realized through the heterocycles arranged at large angles to each other. The presence of strong electron-withdrawing substituents results in shortening of the C-O bonds and in a certain increase in the OCN angle in the 1,3,4-oxadiazole ring.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 639–641, April, 1994.     

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.     

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.     

2,5-双取代-1,3,4-噁二唑类化合物的合成与表征

以3-( 4-氟苯基) -1H-吡唑-5-甲酸乙酯为原料,与H2NNH2?H2O发生肼解生成3-( 4-氟苯基) -1H-吡唑-5-甲酰肼,再与CS2环化生成2-巯基噁二唑中间体,最后在巯基上进行烷基化反应合成了一系列新型的2-硫醚-5-吡唑基-1,3,4-噁二唑类化合物,并利用IR、1H NMR、HRMS等波谱技术对目标化合物结构进行了表征。该合成方法具有原料易得,后处理简便,收率较高的优点。     

Synthesis of substituted 1,3,4-oxadiazole derivatives

Monosubstituted oxadiazoles were synthesized by the reaction of hydrazides with triethyl orthoformate. Their reactions with benzoyl chloride gave benzoylcarbohydrazides, which under the action of thionyl chloride were cyclized to the respective 2,5-disubstituted oxadiazoles. 1-Aryl-4-(5-thioxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)-pyrrolidin-2-ones were synthesized from acid hydrazides using carbon disulfide under basic conditions. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 269-272, February, 2009.     

2,5-bis(trifluoromethyl)-1,3,4-oxadiazole in cycloaddition reactions

The cycloaddition of 2,5-bis(trifluoromethyl)-1,3,4-oxadiazole to dienophiles with cyclic and acyclic structures takes place according to a two-step mechanism with the extrusion of nitrogen and results in the formation of derivatives of 7-oxabicyclo [2.2.1]heptanes. A significant influence of the donor properties of the dienophiles, as well as of the spatial factors, on the realization of these processes has been discovered. However, solvation efects do not have a significant effect on the formation of the cycloadducts. The regio- and stereoselectivity of the cyclo-addition reactions has been noted.For a preliminary report, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 95–100, January, 1990.     

Novel 2,5-disubstituted-1,3,4-oxadiazole derivatives induce apoptosis in HepG2 cells through p53 mediated intrinsic pathway

A series of novel 1,3,4-oxadiazole derivatives (OSD, OCOD, ONOD, OPD, COD, PMOD, and PCOD) were synthesized and characterized. Their structures were confirmed on the basis of IR, NMR and mass spectroscopy and molecular weights were found in the range 300–325 g/mol. Cancerous cell lines (MCF-7, HepG2) and non-cancerous cell lines (Chang liver cells) were treated with these compounds for 48 h, which caused dose dependent decrease in the cell viability. From the seven derivatives, OSD was found to be most potent with IC₅₀ value close to 50 μM on all tested cell lines. Hence, this compound was selected for mechanistic study on HepG2 cell lines. Fluorescent cell staining and DNA fragmentation study of 50 μM OSD on HepG2 cells, showed events marked by apoptosis such as nuclear fragmentation, cytoplasm shrinkage and DNA damage. Further, the cells with same treatment were quantified for apoptosis using annexin V-PI flow cytometric technique. The percentage of apoptotic cells was significantly higher (p < 0.05) after OSD treatment compared to control cells. OSD induced a significant increase (p < 0.05) in the expression of the tumor suppressor p53 in HepG2 cells. The constitutive expression of anti-apoptotic protein Bcl-2 significantly decreased (p < 0.05) after treatment, while the expression of proapoptotic protein Bax significantly increased (p < 0.05). The change in Bax to Bcl-2 ratio suggested involvement of Bcl-2 family in induction of apoptosis. Furthermore, the levels of caspase-9 and caspase-3 were significantly (p < 0.05) up regulated in HepG2 cells after OSD treatment. The data suggest that 1,3,4-oxadiazole derivatives induce apoptosis mediated by intrinsic pathway of apoptosis. The findings strengthen the potential of the 1,3,4-oxadiazole scaffold OSD, as an agent with chemotherapeutic and cytostatic activity in human hepatocellular carcinoma in vitro.     

Synthesis,characterisation and mesomorphic behaviours of non-symmetrically substituted 1,2,4- and 1,3,4-oxadiazole derivatives

Two series of non-symmetrically substituted bent-core mesogens derived from the central 3,5 and 2,5 cores of the 1,2,4- and 1,3,4-oxadiazole derivatives, respectively, containing ether and ester linkage have been synthesised by several straightforward synthetic procedures, and their mesomorphic behaviour was studied by optical polarising microscopy (OPM) and differential scanning calorimetry (DSC). The last five homologues of the 1,2,4-oxadiazole series exhibit a monotropic nematic phase on cooling, while the 1,3,4-oxadiazole derivatives do not show any liquid crystalline properties but rather a crystal to isotropic transition is observed by OPM. We show that the bent angles of the 1,2,4- and 1,3,4-oxadiazole rings are crucial in observing the liquid crystal (LC) phases formed, and also that the length of the alkyl substituent is observed to have a significant effect on the nature of the LC phases.     

Synthesis,characterization and anticancer evaluation of 2-(naphthalen-1-ylmethyl/naphthalen-2-yloxymethyl)-1-[5-(substituted phenyl)-[1,3,4]oxadiazol-2-ylmethyl]-1H-benzimidazole

In the present study o-phenylenediamine and naphtene-1-acetic acid/2-naphthoxyacetic acid were used as a starting material through a series of steps and 2-(naphthalen-1-ylmethyl/Naphthalen-2-yloxymethyl)-1H-benzimidazol-1-yl]acetohydrazide 5a, 5b were obtained. In the first series 1,3,4-oxadiazole derivatives have been synthesized from Schiff base of the corresponding hydrazide i.e. 2-[2-(naphthalen-1-ylmethyl)-1H-benzimidazol-1-yl]acetohydrazide 5a by using Chloramin-T. In the second series 1,3,4-oxadiazole has been synthesized from 2-{2-[(naphthalen-2-yloxy)methyl]-1Hbenzimidazol-1-yl}acetohydrazide 5b by using phosphorous oxychloride and aromatic acid. These compounds were evaluated by IR, NMR, Mass spectrometry, elemental analysis and finally in vitro anticancer evaluation was carried out by NCI 60 Cell screen at a single high dose (10–5 M) on various panel/cell lines. One compound 7c was found to be the most active on breast cancer cell line and compounds 4b and 7d were moderately active.     

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.     

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.     

Non-linear boomerang-shaped liquid crystals derived from 2,5-bis(p-hydroxyphenyl)-1,3,4-oxadiazole

Boomerang-shaped liquid crystals based on 2,5-bis(p-hydroxyphenyl)-1,3,4-oxadiazole (ODBP) having a ~ 134° bend in the mesogenic cores were synthesized and their properties investigated by optical microscopy and differential scanning calorimetry. Substituting the nonlinear ODBP mesogenic core with p-dodecyloxyphenyl tails resulted in a non-linear mesogen that exhibited five distinct mesophases and a clearing temperature of 204°C. The highest temperature phase appears to be nematic followed by a smectic C phase. The latter phase in freely suspended films does not appear to exhibit polar order. The highest temperature phase of 4,4'(1,3,4-Oxadiazole-2,5-diyl) di-p-heptylbenzoate shows a schlieren texture with a 2-brush pattern exclusively.     

Non-linear boomerang-shaped liquid crystals derived from 2,5-bis(p-hydroxyphenyl)-1,3,4-oxadiazole

Boomerang-shaped liquid crystals based on 2,5-bis(p-hydroxyphenyl)-1,3,4-oxadiazole (ODBP) having a ~ 134° bend in the mesogenic cores were synthesized and their properties investigated by optical microscopy and differential scanning calorimetry. Substituting the nonlinear ODBP mesogenic core with p-dodecyloxyphenyl tails resulted in a non-linear mesogen that exhibited five distinct mesophases and a clearing temperature of 204°C. The highest temperature phase appears to be nematic followed by a smectic C phase. The latter phase in freely suspended films does not appear to exhibit polar order. The highest temperature phase of 4,4'(1,3,4-Oxadiazole-2,5-diyl) di-p-heptylbenzoate shows a schlieren texture with a 2-brush pattern exclusively.     

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.     

Synthesis and bioactivities of novel 2-(thioether/sulfone)-5-pyrazolyl-1,3,4-oxadiazole derivatives

By introducing the pyrazole moiety into the 5-position of 1,3,4-oxadiazole,a series of novel 2-(thioether/sulfone)-5-pyrazolyl-l,3,4-oxadiazole derivatives were synthesized.Preliminary bioassays suggested that target compounds exhibited appreciable activity against pathogenic bacteria Xanthomonas oryzae pv.oryzae(Xoo) and five phytopathogenic fungi in vitro.Among them,the half-maximal effective concentration(EC_(50)) values of 6c,7a,7b and 7c against Xoo were within 16.6 μg/mL and 65.7 μg/mL,which were better than those of commercial agricultural antibacterial bismerthiazol(92.6 μg/mL) and thiodiazole copper(121.8 μg/mL).While compounds 7a,7b,and 7c exerted comprehensive antifungal activity toward five plant fungi,which were comparable with that of hymexazol.The results demonstrated that this kind of compounds can be further studied and developed as promising antifungal and antibacterial agents.     

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.     

2-[1-(1,2,4-三唑)甲基]-3-乙酰基-2,5-二取代芳基-1,3,4-噁二唑啉类化合物的合成

在冰醋酸存在下, 4-取代苯乙酮和溴素容易进行溴代反应, 得到α-溴-4-取代苯乙酮; 将其和1,2,4-三唑在丙酮中反应, 得到α-(1,2,4-三唑-1-基)-4-取代苯乙酮2; 在冰醋酸催化下, 2和4-取代苯甲酰肼1进行缩合, 得到相应酰腙衍生物3; 化合物3在乙酸酐的作用下环化生成一系列2-[1-(1,2,4-三唑)甲基]-3-乙酰基-2,5-二取代芳基-1,3,4-噁二唑啉4. 化合物4的结构经IR, 1H NMR, MS, 元素分析和单晶衍射确证.     

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.     

Spectroscopic,thermal and structural studies of a new mercury(II) one-dimensional coordination polymer, [Hg(3-bpo)2(SCN)2], 3-bpo = 2,5- bis (3-pyridyl)-1,3,4-oxadiazole

A new mercury(II)-organic polymeric complex generated from 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) as an angular dipyridyl derivative ligand, [Hg(3-bpo)₂(SCN)₂], was prepared from reactions of ligand 3-bpo with mercury(II) thiocyanate. The compound was characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR-spectroscopy and structurally determined by X-ray single crystal diffraction. The thermal stability of [Hg(3-bpo)₂(SCN)₂] was studied by thermal gravimetric (TG) and differential thermal analyses (DTA).