Banana-shaped 1,2,4-oxadiazoles

3,5-Disubstituted 1,2,4-oxadiazoles are a new type of liquid crystalline (LC) compounds with asymmetrical five-membered heterocycle as a central unit. They have a bent shape and are very convenient model-compounds for studying the dependence of the LC properties on the molecular design. We have also synthesized and investigated ‘banana-shaped’ 1,2,4-oxadiazoles using the ester groups as the linkage units. The new compounds exhibit spontaneous polarization in the smectic phase, even if there is no chiral group in the molecules. Preliminary experimental data suggest the presence of spontaneous polarization in the nematic phase as well. In order to study the structural properties of the LC phases, X-ray diffraction (XRD) measurements on powder samples have been carried out. Based on the XRD data, a model of the structural arrangement of the bent molecules in the smectic phase is provided, which accounts for the macroscopic spontaneous polarization as well as the ferroelectric switching behavior.     

Mass Spectra of 1,2,4-Oxadiazole-5-thiones and 1,2,4-Thiadiazole-5-ones

The mass spectra of 3,4-disubstituted-1,2,4-oxadiazole-5(4H)-thione and 3,4-disubstituted-1,2,4-thiadiazole-5(4H)-ones have been studied. The rearrangement of molecular ion of 1,2,4-oxadiazole-5-thiones to 1,2,4-thiadiazole-5-ones was proposed. Some major fragments observed in the spectra were interpreted and the fragmentation patterns involving McLafferty rearrangements were reported.     

Strategies for synthesis of 1,2,4-triazole-containing scaffolds using 3-amino-1,2,4-triazole

Molecular Diversity - 1,2,4-Triazole-containing scaffolds are unique heterocyclic compounds present in an array of pharmaceuticals and biologically important compounds used in the drug-discovery...     

Solid-supported syntheses of 3-thio-1,2,4-triazoles

Two solid-supported synthesis strategies for the preparation of 3-thio-1,2,4-triazoles are described. In the first, Rink amide resin is combined with Fmoc-protected ω-amino acids, acid hydrazides, and alkyl halides to provide diverse sets of starting materials from which numerous triazoles may be prepared. The second employs t-alkylcarbamateresin (Boc resin) which permits the use of additional pools of starting materials, including isothiocyanates and α- and ω-amino esters, resulting in triazoles with patterns of functional groups that are not possible from the initial route. The combination of multiple resins and resin attachment sites allows the preparation of a diverse library based upon the3-thio-1,2,4-triazole scaffold and avoids the pitfallof having a single linker functionality present at the same position in all library members. General synthetic procedures and representative products from each route are presented. A similarity analysis of representative sublibraries from each synthesis strategy concludes that variation of the solid-phase linker chemistry and attachment site can enhance molecular diversity of the combined triazole library. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spectrofluorimetric Determination Of Indium with 1,2,4-Trihydroxyanthraquinone

A new method for the spectrofluorimetric determination of indium by formation of a fluorescent 1:1 complex with 1,2,4-trihydroxyanthraquinone is proposed. The complex is formed in a mixed, 60:40 v/v acetone-water medium at pH 3.8 provided by an acetic acid-sodium acetate buffer. The calibration graph is linear between 10 and 600 ng/ml. The effect of potential interferents on the determination was assessed and the proposed method was applied to the determination of indium in synthetic samples.     

1,2,4-三唑-3-羧酸溶液的拉曼光谱研究

本文实验测量了1,2,4-三唑-3-羧酸根(TC^-阴离子)及其环去质子化衍生物(dp-TC^2-二价阴离子)在水溶液中的拉曼光谱,并采用MN15泛函和PCM溶剂模型计算了其几何结构、振动频率和拉曼强度. 基于计算光谱和氘化位移的测量,对dp-TC^2-的拉曼光谱做了清楚的光谱标识. 本文还系统研究了TC^-阴离子的各种质子互变异构体,发现2H互变异构体比其他互变异构体更稳定,并且TC^-溶液的实验拉曼光谱与单体2H互变异构体的计算光谱也基本一致. 与计算光谱相比,实验观测到的谱带分裂可能来自于TC^-的氢键结合二聚体的影响.     

Synthesis and crystal structure of new heterocycles containing 1,2,4-oxadiazole, 1,2,4-oxadiazolone (thione), hydantoin,and mercaptobenzimidazole units

A number of 1,2,4-oxadiazolone and mercapto nitro benzimidazole derivatives containing 1,2,4-oxadiazole and hydantoin moieties have been prepared, and their structures were identified by means of spectral/physical characteristics including X-ray diffraction data.     

3-苯基-6-(4-甲苯基)-1,2,4-三唑[4,3-b]-1,2,4-三嗪晶体结构及其光电性能

为了开发稠环化合物3-苯基-6-(4-甲苯基)-1,2,4-三唑[4,3-b]-1,2,4-三嗪的光电性能,本文利用Gaussian程序研究了该化合物的晶体结构,采用密度泛函理论B3LYP方法选取6-31G(d)基组对其性能进行了量子化学计算研究,得到了稳定的几何构型和键长、键角且数据与实验值相符.从电荷转移、前线轨道能量和电子发射光谱等性质探讨了6位苯环上含有不同取代基时化合物性能的变化,含不同取代基时化合物分子的发射波长介于512～521 nm之间,并对含不同取代基化合物的光电性能进行分析.不同取代基以诱导和共轭效应协同作用于化合物上,通过改变电荷转移数量来影响化合物光电性能.根据计算结果预见该类化合物可以用来做光电材料.     

Parallel synthesis of 1,2,4-triazole derivatives using microwave and continuous-flow techniques

Abstract  

An efficient and convenient solution-phase synthesis of a 1H-1,2,4-triazole library with potential agrochemical activity is reported employing microwave-assisted organic synthesis (MAOS) and continuous-flow microfluidic synthetic methods starting from commercially available 3,5-dibromo-1H-1,2,4-triazole (1). MAOS was used for the synthesis of 5-amino-3-bromo-1,2,4-triazole analogs 3 and for their 3-aryl derivatives 4 via Suzuki–Miyaura coupling with polymer-supported catalyst. A microfluidic hydrogenation reactor integrated into an automated parallel synthesis platform was built and utilized for the reductive dehalogenation reactions providing 5-aminotriazoles (5).     

Experimental Investigation and Modeling of the Cathodoluminescence of 1,2,4-Triazine Derivatives

We carried out experimental and theoretical investigations of the luminescence characteristics of 1,2,4-triazine derivatives and revealed the factors of a molecular structure that determine the cathodoluminescence wavelength. We obtained a satisfactory agreement between the experimental and calculated spectral characteristics. A number of reasons for the bathochromic and hypsochromic shifts of bands and also a change in the intensity of the pulsed cathodoluminescence were determined. Luminophor fragments of compounds have been revealed. We suggested variants of structural changes to increase the intensity and shift of the luminescence bands. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 586–590, September–October, 2005.     

A review on synthetic account of 1,2,4-oxadiazoles as anti-infective agents

Molecular Diversity - Most of the currently marketed drugs consist of heterocyclic scaffolds containing nitrogen and or oxygen as heteroatoms in their structures. Several research groups have...     

Nuclear Magnetic Resonance Spectra of 1,2,3- and 1,2,4- Tribromobenzenes

Abstract

The nmr spectra of trisubstituted benzenes such as 1,2,4-chloro⁽¹⁾ and 1,2,5-bromo⁽²⁾ compounds have been reported already. We will report here the results on 1,2,3- and 1,2,4-tribromobenzenes. The samples were synthesized and purified by zone melting- method at the Chiba Institute of Technology. They were dissolved in CCl⁴ with the concentrations of ca. 20 and 75 wt % for 1,2,3- and 1,2,4-compounds, respectively. The spectrometers used are the ones of the types of JNMC-6OH and 100H of Japan Electron Optics Company. The nmr paparameters of 1,2,3- halogenocompounds were obtained by the direct analysis of the spectra taking the system as the one of the AB² type. Those for 1,2,4-compounds were obtained with the use of the electronic computer HITAC-5020 at the University of Tokyo and with the program supplied by Bothner-By. Tetramethyl silane, TMS, was used as the internal standard and the results of the analysis of the spectra at 60 MHz are shown in Table 1. Those values for 1,2,3-trichloro benzene were compared with those obtained from the spectrum at 100 MHz and those in the literature.⁽¹⁾     

The HeI photoelectron spectra of methyl-substituted 1,2,4-pentatrienes (vinylallene)

The HeI photoelectron spectra of trans-1,2,4-hexatriene(1), 4-methyl-1,2,4-pentatriene(2), 3-methyl-1,2,4-pentatriene(3), 1,3,4-hexatriene(4) and 3,4-dimethyl-1,2,4-pentatriene(5) have been obtained and interpreted. LCBO and CNDO/S calculations indicate for the highest energy orbitals a π,π,π,σ sequence as in 1,2,4-pentatriene. The effect of methyl substitution on the three π orbitals is analyzed.     

1,5-二芳基-3-氯甲基硫代-1H-1,2,4-三唑的合成及其结构表征

1-芳酰基-3-苯氨基硫脲与二氯甲烷在无溶剂条件下反应合成了4种1,5-二芳基-3-氯甲基硫代-1H-1,2,4-三唑类化合物,产率为64%-74%.产物的结构通过红外光谱、核磁共振光谱和高分辨质谱进行了表征.     

Magnetic and Spectroscopic Studies of Metallic Halide Complexes with N-Methyl-1,2,4-Triazoles

Complexes of metal (II) halides with N-methyl-1,2,4-triazoles have been prepared, characterized, and studied by magnetism, and electronic and vibrational spectroscopies. The complex with 1:4 stoichiometry is monomeric; those of 1:1 or 1:2 stoichiometries are polymeric. It is seen from electronic studies that metal ions are trans-octahedrally coordinated and chromophores are MX₄N₂ or MX₂N₄. These structural results are in accordance with the magnitude of magnetic exchange between metallic ions. The effects of metal–ligand bond formation on the vibrational modes of the studied N-methyl-triazoles show the coordination mode of the ligand. In the low-frequency range, assignments of metal–nitrogen and metal-halide stretching vibrations confirm advanced structural proposals.     

Quadrupole hyperfine structure of the microwave spectrum of 1,2,4-triazole and N-deuterotriazole

We report the analysis of the hyperfine structure in the microwave spectrum of 1,2,4-Triazole. Principal quadrupole coupling constants at each of the three inequivalent ¹⁴N nuclei have been obtained.     

Synthesis of 3-aryl-1,2,4-benzotriazines via intramolecular cyclization of solid-supported o-hydrazidoanilines

An efficient solid-phase protocol for the rapid generation of libraries of biologically promising 1,2,4-benzotriazines, including amino acid-derived components, is described.