Regioselective N‐Arylation of Some Pyrimidine and Purine Nucleobases

N‐Arylation of some pyrimidine and purine nucleobases in the presence of SiO₂ and Cs₂CO₃ under solvent‐free as well as in solution conditions is described. In these conditions, N1‐aryl pyrimidines and N9‐aryl purines have been obtained regioselectively in moderate to high yields with relatively short reaction times.     

Synthesis of Some Unusual (1,2,4‐Oxadiazole)‐Linked Hexenopyranosides and Mannopyranosides

A copper‐catalyzed reaction of propargyl 4,6‐di‐O‐acetyl‐2,3‐dideoxy‐α‐D‐erythro‐hex‐2‐enopyranoside with 3‐(4‐azidophenyl)‐1,2,4‐oxadiazoles gave the corresponding hexenopyranosides bearing an 1,2,4‐oxadiazole subunit in the aglyconic part of the molecule. The same reaction between ethyl 4‐azido‐2,3,4‐trideoxy‐α‐D‐erythro‐hex‐2‐enopyranoside and acetylenic 1,2,4‐oxadiazoles afforded the corresponding hexenopyranosides carrying a triazole and a 1,2,4‐oxadiazole ring at C‐4 of the carbohydrate. Combination of the two sequences gave hexenopyranosides displaying two 1,2,4‐oxadiazole subunits, each one being embedded in the C‐1 and C‐4 frameworks, of the carbohydrate moiety. A simple dihydroxylation reaction of these unsaturated carbohydrates yielded a series of mannopyranosides bearing one or two 1,2,4‐oxadiazole subunits at C‐1 or C‐4. These new compounds were evaluated for their cytotoxic activities against two cell strains: NCI‐H₂₉₂ (lung carcinoma) and Hep‐2 (larynx carcinoma), some of them presenting impressive cell growth inhibitions.     

Synthesis of Some N-Alkoxycarbonyl-N″-benzoyl-benzamidrazones（p-toluamidrazones） and 1,3,5-Trisubstituted 1,2,4-Triazole Derivatives from N-Benzoylimidates and their Antimicrobial and Anticancer Screening Studies

Some new N-alkoxycarbonyl-N″-benzoyl-benzamidrazones （p-toluamidrazones） 3a-3d, and 1,3,5-trisubstituted 1,2,4-triazole 4a-4h derivatives by starting from N-benzoylbenzimidates or N-benzoyl-p-toluimidates. The structures of compounds 3 and 4 were established on the basis of elemental analyses, IR, ^1H NMR, ^13C NMR and UV data. Antimicrobial experiments of the compounds performed by using agar-well diffusion and broth microdilution methods revealed that only compounds 3a-3d, 4a and 4b showed inhibitory effect only on Candida albicans ATCC 60193. However, compound 4b had also specific antibacterial activity against Staphylococcus aureus ATCC 25923. The other compounds showed neither antifungal nor antibacterial activities. Compounds 3a, 4a and 4b have been screened on three human tumor cell lines, breast cancer （MCF7）, non small cell lung cancer （NCI-H460）, and CNS cancer （SF-268） at the National Cancer Institute （NCI）, USA, which were found to exhibit low antiproliferative activity.     

Structures and Properties of 1,2,3-Triazoles and 1,2,4-Triazoles

1 INTRODUCTION In the energetic material field, extensive attention was paid to insensitive compounds possessing not only high energetic density but also good stability. Previous studies[1] have shown that some small mo- lecular compounds such as azoles are good candi- dates for excellent explosives. For example, explo- sives containing triazole rings have the advantages of less molecular weight, high nitrogen content and density, good thermal stability, low impact sensiti- vity and large …     

Viscosities of Some Tetraalkylammonium and Alkali-Metal Salts in N,N-Dimethylacetamide at 25°C

The viscosities of solutions of tetrapropylammonium bromide (Pr₄NBr), tetrabutylammonium bromide (Bu₄NBr), tetrapentylammonium bromide (Pen₄NBr), tetrahexylammonium bromide (Hex₄NBr), tetraheptylammonium bromide (Hep₄NBr), tetraoctylammonium bromide (Oct₄NBr), tetrabutylammonium tetraphenylborate (Bu₄NBPh₄), sodium tetraphenylborate (NaBPh₄), and potassium tetraphenylborate (KBPh₄) in N,N-dimethylacetamide are reported at 25^°C. The viscosity data havebeen analyzed by the Jones-Dole equation for associated electrolytes to evaluate the viscosity B coefficients of the electrolytes. These data have also been analyzed by the transition-state theory to obtain the contribution of the solutes to the free energy of activation for viscous flow of the solution. The ionic contribution to the viscosity B coefficient and the free energy of activation for viscous flow have been estimated using of the reference electrolyte Bu₄NBPh₄. The bromide, tetraphenylborate, and tetraalkylammonium ions are found to be weakly solvated in N,N-dimethylacetamide, whereas significant solvation has been detected for sodium and potassium ions. The viscosity of the solvent is greatly modified by the presence of all the ions investigated here with the exception of the bromide ion.     

Synthesis and Study of Complexes of Some Trivalent Lanthanides and Americium with N,N-Dimethylacetamide and PW12O403–Anions

The synthesis of crystalline complexes of trivalent lanthanides and americium with N,N-dimethylacetamide (DMAA) and PW₁₂O₄₀ ^3–anions was described. Their IR and electronic absorption spectra were studied. The structure of the neodymium complex [Nd(DMAA)₆PW₁₂O₄₀] was determined using X-ray diffraction analysis. The thermal behavior of the lanthanide complexes was studied. In the 300–400°C temperature interval, even in air, intramolecular partial reduction of the anion occurs to form products which can be characterized as tungsten bronzes.     

Complexation Studies of N,N′-ethylenedi-L-cysteine with Some Metal Ions

As part of a search for environmentally friendly metal chelating ligands, the stability constants of N, N′-ethylenedi-L-cysteine (EC) complexes with Ca(II), Cu(II), Mg(II) and Mn(II) were determined by potentiometry with a glass electrode in aqueous solutions containing 0.1 mol⋅L⁻¹ KCl at 25 °C. Final models are proposed. For the Ca(II)–EC system, the overall stability constants are log ₁₀ β _CaHL=14.53±0.03, log ₁₀ β _CaL=4.79±0.01 and log ₁₀ β _CaL2=8.38±0.04. For the M(II)–EC systems, where M=Cu(II) or Mg(II), the overall stability constants are log₁₀ β _CuHL=31.19±0.02 and log ₁₀ β _CuL=27.02±0.06 for Cu(II), and are log ₁₀ β _MgHL=14.84±0.02 and log ₁₀ β _MgL=6.164±0.008 for Mg(II). For the Mn(II)–EC system, the overall stability constant is log ₁₀ β _MnL=10.12±0.01. Metal–chelate speciations simulations showed that EC is an efficient chelating agent for Cd(II), Co(II), Cu(II), Ni(II), Pb(II) and Zn(II) for pH≥7.     

Synthesis and Characterizations of Some New Diacylhydrazones

Acylhydrazine and hydrazine are highly reactive chemicals that have a wide spectrum of uses such as in the chemical and pharmaceutical industries and as a fuel and propellant in aircraft, rockets and satellites. And they can react with microelement in the organism, so they were reported to possess different biological and pharmacological activities, such as antiphthistic, antitumour and so on. But, acylhydrazine and hydrazine have free group of NH2, so they usually have some toxicity to the organism. Hydrazones were investigated in view of the possibility of their being less toxic than the parent hydrazides, because of the blocking of the free NH2 group. In order to reduce the toxicity to the organism, people have been interested in the hydrazones compounds in recent years. In this work, 2,6-dimethylpyridine-3,5-diacylhydrazones were synthesized.     

Synthesis and Chelating Properties of Polystyrene Supported Schiff Base (N,N′-disalicylidenepropylenetriamine) Resin Toward Some Divalent Metal Ions

A new polystyrene-supported Schiff base resin, N,N-bis(salicylidenepropylenetriamine)- aminomethyl polystyrene, has been synthesized through a reaction between the commercially available 4-chloromethyl polystyrene polymer and the Schiff base, N,N′-disalicylidenepropylenetriamine. The chelation behavior of this resin toward the divalent metal ions Cu^{2 +}, Ni^{2 +}, Zn^{2 +}, and Pb^{2 +} in aqueous solutions was investigated. Batch equilibration experiments were carried out as a function of contact time, pH, amount of metal-ion, polymer mass, and temperature. The amount of metal-ion uptake of the polymers was determined by using atomic absorption spectrometry (AAS). Results of the study revealed that the resin exhibited higher capacities and a more pronounced adsorption toward Cu^{2 +} and that the metal-ion uptake follows the order: Cu^{2 +} > Zn ^{2 +} > Ni^{2 +} > Pb²⁺. The adsorption and binding capacity of the resin toward the various metal ions investigated are discussed.     

Electrical Conductance of Some Symmetrical Tetraalkylammonium and Alkali Salts in N,N-Dimethylacetamide at 25°C

Precise measurements of electrical conductances of solutions of tetraethylammonium bromide, tetrapropylammonium bromide, tetrapentylammonium bromide, tetrahexylammonium bromide, tetraheptylammonium bromide, tetraocytylammonium bromide, sodium tetraphenylborate, and potassium tetraphenylborate in N,N-dimethylacetamide at 25^°C are reported for the concentration range 0.005-0.015 mol-dm^–3. The conductance data have been analyzed by the 1978 Fuoss conductance-concentration equation in terms of the limiting molar conductance, the association constant, and the association diameter. The limiting ionic conductances have been estimated from the appropriate division of the limiting molar conductivity value of the reference electrolyte Bu₄NBPh₄. Slight ionic association was found for all these salts in this solvent medium. Tetraalkylammonium ions are found to be unsolvated in N,N-dimethylacetamide, whereas significant solvation has been noticed for sodium and potassium ions.     

Syntheses and Structure-Odor Relationship of Some γ-Lactones

A lot of norbornene derivatives and lactones are widely used as fragrant components in food or cosmetics. We expected that a series of new compounds with better odor character could be obtained when these two skeleton structures were combined. Thus, a series of endoand exo-5,5-disubstituted-3-oxo-4-oxatricyclo[5,2,1,0~(2,6)]dec-8-enes(Ⅰ) were synthesized.     

Syntheses and Crystal Structures of Some Aryloxy and Alkoxy Substituted Phthalonitriles

Phthalonitriles substituted with aryloxy and alkoxy groups have been synthesized and characterized by elemental analyses, IR, mass spectra and 1H NMR spectroscopy. And four of such crystal structures have also been determined. In the crystal structures, the major inter- molecular interactions between the neighboring molecules are the hydrogen bonds as C≡N···H and C-O···H that lead to similar networks in the crystal structures.     

Rapid Access of Some Chloro‐substituted Isocoumarins and Biological Activity Toward Some Pathogenic Systems

Sulphuric acid–catalyzed chloralhydrate condensation with different m‐substituted benzoic acids formed trichlorophthalides 1, from which Zn+AcOH reduction afforded various dichloro derivatives 2. These derivatives 2 on treatment with alkaline Hg(OAc)₂+I₂ furnished different substituted isocoumarins 4.     

Structures and stability of N9, N9 − and N9 + clusters

 Ab initio molecular orbital calculations for N₉, N⁻ ₉ and N⁺ ₉ isomers were carried out at the HF/ 6-31G*, B3PW91/6-31G*, B3LYP/6-31G* and MP2/ 6-31G* levels of theory. Stable equilibrium geometric structures were determined by harmonic vibrational frequency analyses at the HF/6-31G*, B3PW91/6-31G* and B3LYP/6-31G* levels of theory. The most stable free-radical N₉ cluster is structure 1 with C _{2 v} symmetry and that of anion N⁻ ₉ is structure 3 with C _s symmetry. Only one stable structure of the N⁺ ₉ cation with C _{2 v} symmetry was predicted. Their potential application as high-energy-density materials has been examined. Received: 15 June 1999 / Accepted: 11 October 1999 / Published online: 14 March 2000     

N,N′-Diacylated imidazolidines and hexahydropyrimidines

A method for the preparation ofN-monoacyl imidazolidines and hexahydropyrimidines (as hydrochlorides) by interaction of monoacylated derivatives of ethylenediamine and trimethylenediamine with chloromethyl methyl ether was developed. Also a method for the preparation ofN,N-diacylimidazolidines and hexahydropyrimidines either by acylation of their monoacyl derivatives or by reaction of the correspondingN,N-diacyl alkylenediamine derivatives with dimethoxymethane, diacetoxymethane, 1,3,5-trioxane or chloromethyl methyl ether was designed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1452–1456, August, 1994.     

Some Reactions of Vinyl Isocyanate and Its Copolymers∗

Linear, soluble copolymers of vinyl isocyanate with styrene and methyl methacrylate were obtained when the comonomer:vinyl isocyanate ratio in the copolymer was greater than 9:1. When the comonomer to isocyanate ratio was less than 2:1, the copolymers were insoluble. Infrared evidence indicated that spontaneous cross-linking through the isocyanate function occurred by a mechanism similar to the known reaction by which isocyanates undergo dimerization and trimerization. The soluble copolymers retained the reactive isocyanate moeity as was shown by their reactivity with n-butylamine and ethanol to produce, respectively, the corresponding polyurea and polycarbamate, and with ethylenediamine and water to produce cross-linked polymers. The intrinsic viscosity [η] for the 9:1 methyl methacrylate: vinyl isocyanate copolymer was 0.22 dl/g while that for the corresponding ethyl carbamate was 0.24 dl/g.     

Tandem A N—A N reactions in the synthesis of 1H-pyrrolo[3,2-e]-1,2,4-triazines and products of their oxidative transformations

The reactions of 3-aryl-1,2,4-triazines with -aminovinyl ketones or ethyl -aminocrotonates in acetic anhydride at room temperature afforded cyclic products of the tandem nucleophilic addition, viz., 3a,4,7,7a-tetrahydro-1H-pyrrolo[3,2-e]-1,2,4-triazines, in good yields. Under oxidative conditions, the latter compounds underwent the pyrrole-ring opening under the action of potassium permanganate to form the corresponding triazinones and were transformed into thriazolyl-substituted pyridines under the action of selenious acid.     

A Convenient Synthesis for Some New Pyrido[4′,3′:4,5]thieno[2,3-d]pyrimidines and Related Fused 1,2,4-Triazolo and 1,3,4-Thiadiazolo-derivatives

Diethyl 2-isothiocyanato-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3,6 dicarboxylate 1 is a convenient and useful starting matrial for the constructions of heterocyclic systems. It was utilized to synthesize derivatives of the novel heterocyclic systems pyrido[4',3':4,5]thieno[2,3-d]pyrimidine 4 , 10 , pyrido[4',3':4,5]thieno[2,3-d]-[1,2,4]triazolo[1,5-a]pyrimidine 7 , 11a-e and pyrido[4',3':4,5]thieno[2,3-d][1,3,4]thiadiazolo[3,2-a]pyrimidine 12-14 .     

The Effect of Temperature on the Equivalent Conductivities and Ion-Association Constants of Some Tris-(ethylenediamine)chromium(III) Complexes in N,N-dimethylformamide and N,N-dimethylacetamide

The equivalent conductivities of tris-(ethylenediamine)chromium complexes, [Cr(en)₃]X₃ (where X⁻= Cl⁻, Br⁻, I⁻; en = ethylenediamine) were measured as functions of temperature (278.15 to 328.15 K) and concentration [(1.948 ×10⁻⁴ to 10.728 ×10⁻⁴ mol⋅dm⁻³) and (2.282 ×10⁻⁴ to 11.246 ×10⁻⁴ mol⋅dm⁻³)] in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAC), respectively. Equivalent conductivity values for [Cr(en)₃]X₃ in DMF were found to be higher than those in DMAC. The conductivity data were analyzed with the Robinson-Stokes equations. For [Cr(en)₃]X₃, the limiting equivalent ionic conductivities of [Cr(en)₃]³⁺ and the ion-association constants (K _A) of the ion-pair between [Cr(en)₃]³⁺ and the monovalent halide anions were determined in DMF and DMAC. The values of K _A for three complex salts in DMF were higher than those in DMAC. This can be ascribed to an increase of the ion-association constants with a decrease of the relative permittivity of the solvents. The values of K _A at 298.15 K decreased in the order Cl⁻> Br⁻> I⁻ in DMF and Cl⁻> I⁻> Br⁻ in DMAC. The K _A values for [Cr(en)₃]Cl₃ increased with increasing temperature in both DMF and DMAC. For [Cr(en)₃]X₃(X⁻= Br⁻, I⁻) in both solvents, this indicates increasing disorder occurs with increasing temperature. Thermodynamic parameters (standard Gibbs energy, enthalpy and entropy changes) were determined from the temperature dependence of K _A in DMF and DMAC. These parameters were inter-compared in their dependences on temperature and solvent.