Aromatic poly(1,3,4‐oxadiazole)s and poly(amide‐1,3,4‐oxadiazole)s containing ether sulfone linkages

Polyhydrazides and poly(amide‐hydrazide)s were prepared from two ether‐sulfone‐dicarboxylic acids, 4,4′‐[sulfonylbis(1,4‐phenylene)dioxy]dibenzoic acid and 4,4′‐[sulfonylbis(2,6‐dimethyl‐1,4‐phenylene)dioxy]dibenzoic acid, or their diacyl chlorides with terephthalic dihydrazide, isophthalic dihydrazide, and p‐aminobenzhydrazide via a phosphorylation reaction or a low‐temperature solution polycondensation. All the hydrazide polymers were found to be amorphous according to X‐ray diffraction analysis. They were readily soluble in polar organic solvents such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylacetamide and could afford colorless, flexible, and tough films with good mechanical strengths via solvent casting. These hydrazide polymers exhibited glass‐transition temperatures of 149–207 °C and could be thermally cyclodehydrated into the corresponding oxadiazole polymers in the solid state at elevated temperatures. Although the oxadiazole polymers showed a significantly decreased solubility with respect to their hydrazide prepolymers, some oxadiazole polymers were still organosoluble. The thermally converted oxadiazole polymers had glass‐transition temperatures of 217–255 °C and softening temperatures of 215–268 °C and did not show significant weight loss before 400 °C in nitrogen or air. For a comparative study, related sulfonyl polymers without the ether groups were also synthesized from 4,4′‐sulfonyldibenzoic acid and the hydrazide monomers by the same synthetic routes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2271–2286, 2001     

Synthesis and optical and electrochemical properties of novel polyethers containing isolated distyrylbenzene derivatives and side‐aromatic 1,3,4‐oxadiazole chromophores

New polyethers ( P2 , P4 ) with isolated emitting distyrylbenzene derivatives and pendant aromatic 1,3,4‐oxadiazole chromophores have been prepared by the Horner–Wadsworth–Emmons olefination reaction. Polyethers P1 and P3 without oxadiazole groups have also been synthesized for comparison. The reduced viscosities were about 0.20–0.33 dL/g, and the solubility in organic solvents increased with a number of side methoxy or ethoxy substituents in the distyrylbenzene section. Absorption spectra showed two peaks at 371–388 and 304 nm that corresponded to the π‐π* transition of the conjugated distyrylbenzene derivatives and aromatic oxadiazoles, respectively. The band gaps were at 2.76–2.85 eV, which were calculated from onset absorption in the film state. The photoluminescence (PL) maxima were at 459–469 nm, indicating that they are blue‐emitting materials, and the relative PL quantum efficiencies were 0.62–0.77 and 0.23–0.40 in solution and the film state, respectively. Cyclic voltammetric investigations demonstrated that oxadiazole moieties decrease the barrier of electron injection but also retard hole injection. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2571–2580, 2001     

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.     

“One‐pot” synthesis of aromatic poly(1,3,4‐oxadiazole)s in novel solvents—ionic liquids

The new convenient method for the synthesis of high molecular weight aromatic poly(1,3,4‐oxadiazole)s (PODs) has been proposed. These polymers were prepared by “one‐pot” procedure from dicarboxylic acid and hydrazine's salt (sulfate, phosphate) or dicarboxylic acid dihydrazides. The mixture of ionic liquid and triphenyl phosphite was used both as a solvent and condensing agent. The polycyclization occurred at a sufficiently low temperature of 210 °C for 2–5 h and resulted in obtaining film‐forming PODs having inherent viscosities up to 0.9 dL/g and good thermal stability. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 380–394, 2006     

Green synthesis of new thiouracilodepsipeptides in ionic liquid: One‐pot four‐component reaction of isocyanides

Thiouracil‐containing depsipeptides were produced via one‐pot four‐component condensation/Passerini tandem reaction of thiouracil, 2‐chloroacetic acid derivatives, ketones, and isocyanides in ionic liquid as green reaction media in high yields.     

Facile synthesis of multi‐functional 1,3,4‐thiadiazine derivatives bearing phthalazine,pyridazine, and pyrido‐pyridazine moieties

A series of novel, multifunctional 1,3,4‐thiadiazine derivatives bearing phthalazines, pyridazines and pyrido‐pyridazines ( 9–13 ) have been synthesized via the multicomponent reaction of (3‐(2‐bromo‐2‐[2‐chloropyrimidin‐4‐yl]acetyl)‐2‐chlorophenyl)‐2,6‐dichloro benzene‐sulfonamide with thiocarbohydrazide and various anhydrides. The reactions were performed by refluxing the components in mixed ethanol/acetic acid to afford the corresponding products in good to excellent yields. All the synthesized compounds were characterized by analytical and spectral studies. The developed method features short reaction time, simple work‐up without chromatographic separation, and a broad range of substrate applicability.     

The Reaction of (N‐Isocyanimino)triphenylphosphorane with Biacetyl in the Presence of Aromatic Carboxylic Acids: Efficient One‐Pot Three‐Component Reaction for the Synthesis of 3‐(5‐Aryl‐1,3,4‐oxadiazol‐2‐yl)‐3‐hydroxybutan‐2‐one Derivatives

Reactions of biacetyl (=butane‐2,3‐dione) with (N‐isocyanimino)triphenylphosphorane in the presence of aromatic carboxylic acids proceed smoothly at room temperature and under neutral conditions to afford 3‐(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)‐3‐hydroxybutan‐2‐one derivatives in high yields.     

Synthesis and Antifungal Screening of 2‐(2‐Aryl‐4‐methyl‐thiazol‐5‐yl)‐5‐((2‐aryl/benzylthiazol‐4‐yl)methyl)‐1,3,4‐oxadiazole Derivatives

A new series of synthesis and biological screening of 2‐(2‐aryl‐4‐methyl‐thiazol‐5‐yl)‐5‐((2‐aryl/benzylthiazol‐4‐yl)methyl)‐1,3,4‐oxadiazole derivatives 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i was achieved by condensation of 2‐(2‐aryl/benzylthiazol‐4‐yl)acetohydrazide 2a , 2b , 2c with 4‐methyl‐2‐arylthiazole‐5‐carbaldehyde 3a , 3b , 3c followed by oxidative cyclization of N'‐((4‐methyl‐2‐arylthiazol‐5‐yl)methylene)‐2‐(2‐aryl/benzylthiazol‐4‐yl)acetohydrazide 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i using iodobenzene diacetate as oxidizing agent. All the synthesized compounds were screened for their in vitro antifungal activity against Candida albicans, Candida tropicalis, Aspergillus niger, and Aspergillus flavus. Some of the synthesized compounds showed good antifungal activity.     

Synthesis,liquid crystalline properties and fluorescence of polycatenar 1,3,4‐oxadiazole derivatives

A series of hexacatenar liquid crystals containing the 1,3,4‐oxadiazole group as rigid core, i.e. 1,4‐bis[(3,4,5‐trialkoxyphenyl)‐1,3,4‐oxadiazolyl]‐ benzene (P‐P‐oxd‐n), were designed and synthesised. Based on a detailed study of their thermotropic phase behaviour and mesophase structures, it was revealed that columnar phases are generated in these materials. Furthermore, combination of experimental and calculated results enabled a proposal for the molecular packing in the mesophase. The photoluminescent properties of these materials were examined using P‐P‐oxd‐8 as an example. A strong blue light emission (λ_max = 456 nm) was observed in P‐P‐oxd‐8 and a higher quantum yield was obtained in dilute chloroform solution.     

Synthesis,optical properties,and electroluminescence of conjugated poly(p‐phenylenevinylene) derivatives containing 1,3,4‐oxadiazole and pyridine rings in the main chain

Three new poly(p‐phenylenevinylene) derivatives—PO, POD, and POP—with oxadiazole and pyridine rings along the main chain were synthesized via Heck coupling. The polymers were amorphous and dissolved readily in common organic solvents. They showed relatively low glass‐transition temperatures (up to 42 °C) and satisfactory thermal stability. Solutions of the polymers emitted blue‐greenish light with photoluminescence (PL) emission maxima around 460 nm and PL quantum yields of 0.28–0.49. Thin films of the polymers displayed PL emission maxima at 461–521 nm, and their tendency to form aggregates was significantly influenced by the chemical structure. Light‐emitting diodes with polymers PO and POP, with an indium tin oxide/poly(ethylenedioxythiophene) (PEDOT)/polymer/Ca configuration, emitted yellow and green light, respectively, and this could be attributed to excimer emission. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3212–3223, 2004     

Synthesis and characterization of poly(fluorene)‐based copolymers containing various 1,3,4‐oxadiazole pendants

A series of soluble alternating poly(fluorene)‐based copolymers containing electron‐transporting 1,3,4‐oxadiazole (OXD) and hole‐transporting carbazole pendants attached to the C‐9 position of fluorene units by long alkyl spacers were synthesized. These copolymers possess mesogenic and nonmesogenic pendants attached to a rigid mesogenic poly(fluorene) (PF) backbone. All these polymers exhibit glass‐forming liquid crystalline properties, including the nematic and smectic A (SmA) phases, and reveal much wider mesophasic temperature ranges than that of PF. The thermal properties and mesomorphism of these conjugated polymers are mainly affected by the nature of these pendants, and thus the mesophasic temperature ranges and glass‐forming properties are greatly enhanced by introducing the OXD pendants. In addition, the tendencies of crystallization and aggregation of PF are also suppressed by introducing the OXD pendants. A single layer device with P4 as an emitter shows a turn‐on voltage of 5 V and a bright luminescence of 2694 cd/m² at 11 V with a power efficiency of 1.28 cd/A at 100 mA/cm². © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2700–2711, 2005     

Efficient four‐component synthesis of spiroindole derivatives catalysed by a versatile and reusable nano‐paramagnetic catalyst

A simple, efficient and environmentally benign route was developed for the preparation of spiro(indoline‐3,4‐pyrano[2,3‐c ]pyrazole) derivatives with good yields from condensation of isatins, malononitrile (or ethyl cyanoacetate), hydrazine hydrate and ethyl acetoacetate catalysed by PFu@Fe₃O₄ nanocomposite. The use of easily available catalyst, shorter reaction times, better yields, simplicity of reaction, heterogeneous system and easy work‐up are the advantages of the method presented. Characterization of the catalyst was performed using Fourier transform infrared spectroscopy, X‐ray diffraction and transmission electron microscopy.     

Preparation of Poly(1,3,4‐oxadiazole‐2,5‐diyl‐1,2‐vinylene) via Anionic Mechanism

2,5‐Bis(chloromethyl)‐1,3,4‐oxadiazole was synthesized and dehydrohalogenation of this model compound was investigated under various base conditions. The formation of an intermediate with quinodimethane‐type structure is suggested for reaction in EtONa/EtOH. Polymerization of this intermediate proceeds via an anionic mechanism to form poly(1,3,4‐oxadiazole‐2,5‐diyl‐1,2‐vinylene). Polymerization at a toluene/water interface results in shorter polymerization times, milder conditions, higher molecular weights, higher yields and fewer defects in the polymer as compared to the corresponding polycondensation route.

     

Novel polyimides obtained from a new aromatic diamine (BAPO) containing pyridine and 1,3,4‐oxadiazole moieties for removal of Co(II) and Ni(II) ions

Novel, thermally stable polyimides (PIs) containing a 1,3,4‐oxadiazole and pyridine moieties based on a new aromatic diamine 2,5‐bis‐(aminopyridine‐2‐yl)‐1,3,4‐oxadiazole, BAPO, were synthesized. The prepared polymers were soluble in dimethysulfoxide (DMSO) and concentrated sulfuric acid at room temperature as well as in polar and aprotic solvents, such as, N‐methylpyrrolidone (NMP) and N,N‐dimethylacetamide (DMAc) at elevated temperature. Thermal behaviors of the PIs were studied by thermogravimetric analysis/dynamic thermal analysis (TGA‐DTA) and differential scanning calorimetry (DSC). The inherent viscosities of the PI solutions were in the range of 0.38–0.61 dl/g (in DMSO with a concentration of 0.125 g/dl at 25 ± 0.5°C). The removal of Co(II) and Ni(II) ions from aqueous solutions was performed using polymer 6, which was obtained from BAPO and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA). The maximum adsorption capacity was observed for Co(II) ion at pH = 7.0 (110.4 mg g^?1, 1.87 mmol g^?1). Copyright © 2015 John Wiley & Sons, Ltd.     

Theoretical analysis of vibrational spectra and scaling‐factor of 2‐aryl‐1,3,4‐oxadiazole derivatives

In this study, the direct molecular structure implementations for calculating vibrational spectra and scaling factors, and infrared intensities at both the Hartree–Fock (HF) and density functional (B3LYP) levels of theory with 6‐31G(d), 6‐311G(d), 6‐31++G(d,p), and 6‐311++G(d,p) basis sets are presented. Also, vibrational frequencies have been investigated as dependence on the choice of method and basis set. The parameters of molecular geometry and vibrational frequencies values of 2‐aryl‐1,3,4‐oxadiazoles 5a–g in the ground state have been calculated. Theoretical determination of vibrational frequencies is quite useful both in understanding the relationship between the molecular structures and scaling factor. The data of 2‐aryl‐1,3,4‐oxadiazoles 5a–g display significant electronic properties provide the basis for future design of efficient materials having the oxadiazole core and theoretical IR studies. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Synthesis and electroluminescent properties of a novel 1,3,4‐oxadiazole‐containing polymer

The new blue light polymer, poly(1′,4′‐phenylene‐1″,4″‐[2″‐(2″″‐ethylhexyloxy)]phenylene‐1‴,4‴‐phenylene‐2,5‐oxadiazolyl) (PPEPPO) was synthesized through the Suzuki reaction of diboronic acid, 2‐methoxy‐[5‐(2′‐ethylhexyl)oxy]‐1,4‐benzene diboronic acid (MEHBBA) and dibromide, 2,5‐bis(4′‐bromophenyl)‐1,3,4‐oxadiazole. This polymer was characterized with various spectroscopic methods. The solid PL spectrum of PPEPPO has a maximum peak at 444 nm corresponding to blue light. Blue LED has been fabricated using this polymer as the electroluminescent layer, ITO as the anode, and aluminum as cathode. This device emitted a blue light, with 40 V of turn‐on voltage. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3086–3091, 2000     

One‐Pot,Four‐Component Synthesis of Fully Substituted 1,3,4‐Oxadiazole Derivatives from (Isocyanoimino)triphenylphosphorane,a Primary Amine,an Aromatic Carboxylic Acid,and Chloroacetone

The 1 : 1 imine intermediate 7 generated by the addition of a primary amine 2 to chloroacetone ( 1 ) is trapped by (isocyanoimino)triphenylphosphorane ( 4 ) in the presence of an aromatic carboxylic acid 3 and leads to the formation of the corresponding iminophosphorane intermediate 9 (Scheme 2). The 1,3,4‐oxadiazole derivatives 5 are then formed via an intramolecular aza‐Wittig reaction of the iminophosphorane intermediate 9 . The reactions were completed under neutral conditions at room temperature. The fully substituted 1,3,4‐oxadiazole derivatives 5 were produced in high yields (Table).     

Characterization of 2‐aryl‐1,3,4‐oxadiazoles by 15N and 13C NMR spectroscopy

¹⁵N NMR chemical shifts of 2‐aryl‐1,3,4‐oxadiazoles were assigned on the basis of the ¹H–¹⁵N HMBC experiment. Chemical shifts of the nitrogen and carbon atoms in the oxadiazole ring correlate with the Hammett σ‐constants of substituents in the aryl ring (r² ≥ 0.966 for N atoms). ¹⁵N NMR data are a suitable and sensitive means for characterizing long‐range electronic substituent effects. Additionally, ¹³C NMR data for these compounds are presented. Copyright © 2003 John Wiley & Sons, Ltd.