Journal of the Iranian Chemical Society
Volume:6 Issue: 3, Sept 2009

The electrochemical oxidation of catechols was described and has shown that these compounds can be oxidized to related o-benzoquinones. The electrochemically generated o-benzoquinones are quite reactive and can be attacked by a variety of nucleophiles under various mechanistic disciplines such as CE, EC, EC'', ECE, ECEC, ECEC2, ECECE, ECECEC, ECECECE and trimerization, in which E represents an electron transfer at the electrode surface, and C represents a homogeneous chemical reaction. The mechanistic pathways and final products are depending on some parameters such as electron withdrawing or donating properties of nucleophile, electrolysis medium (solvent, acidity or pH) and nature of catechol.

α-β-Unsaturated carbonyl compounds on condensation with o-phenylenediamine in the presence of catalyst sulfamic acid under solvent free conditions, resulted in the formation of corresponding benzo-[b]-1,4-diazepines in excellent yields.

A novel and efficient procedure for the synthesis of 1,8-dioxo-octahydro-xanthenes through one-pot condensation of 5,5-dimethyl-1,3-cyclohexadione with aryl aldehydes in the presence of selectfluorTM [1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2,2,2]octane bis(tetrafluoroborate) as catalyst under solvent free conditions was applied. It demonstrated several advantages such as good yields of products, simple operation, convenient separation, and inexpensive catalyst.

Magnetic interaction was included in the simulation of the evolution of the electron wave-packet of the hydrogen molecular ion H2+ in femtosecond intense pulsed laser fields applied along the molecular axis. This evolution was followed by solving 2-D time-dependent Schrödinger equation at some fixed inter-nuclear separations. Magnetic interaction effects at non-relativistic intensities induced a phase shift in the time evolution of the electron wave-packet, and an excess z-component angular momentum as compared with the results obtained in the absence of magnetic interaction. Furthermore, the H2+ electron WP displacement showed a drift and wiggling in the propagation direction which was different from that observed under pure electric field of the laser pulse. The local fluxes at different points of the 2-D space borders and the time-dependent induced angular momentum are calculated and analyzed.

Compounds containing oxathiadiazolone nucleus bearing substituted coumarin ring were designed and synthesized while retaining the pharmacophores required for binding with p38 MAP kinase. A four-step synthetic scheme was employed for the synthesis of 7-methoxy-4-(3΄-substituted-2΄-oxo-1΄,2΄,3΄,5΄-oxathiadiazol-4΄-yl)-coumarin. The reactions were monitored by TLC and structures of the intermediates and the target compounds were ascertained by IR, NMR, Mass spectral data. The compounds were found to possess anti-inflammatory activity comparable to indomethacin. Superimposition studies of the target compounds with the lead p38 kinase inhibitors suggested that anti-inflammatory activity of the target compounds may be due to p38 MAP kinase inhibition. It was also suggested that methoxy group on coumarin nucleus may improve the binding profile with p38 MAP kinase.

A quick and efficient, one-pot synthesis of carbazates was accomplished in high yields by the reaction of various primary, secondary, and tertiary alkyl halides with a variety of substituted hydrazines using Amberlite IRA 400 basic resin/CO2 system. The reaction conditions were mild with simpler work-up procedures than the previously reported methods.

Sodium periodate efficiently catalyzed the three-component Biginelli reaction of an aldehyde, α β-keto ester or β-keto ketone, and urea or thiourea at room temperature under solvent-free conditions and afforded the corresponding 3,4-dihydropyrimidine-2-(1H)-ones in excellent yields.

A smooth conversion of substituted 1-(2-hydroxy phenyl)-3-phenyl-1,3-propane diones to flavones has been done using n-butyl-3-methyl-imidazolium tetrafluoroborate ionic liquid.

Highly efficient acetylation and benzoylation of alcohols, phenols, amines and thiols with acetic and benzoic anhydrides catalyzed by new and reusable zirconyl triflate, ZrO(OTf)2, is reported. The high catalytic activity of electron deficient ZrO(OTf)2 can be used for the acetylation and benzoylation of not only primary alcohols but also sterically-hindered secondary and tertiary alcohols with acetic and benzoic anhydrides. Acetylation of phenols with acetic and benzoic anhydrides was achieved to afford the desired acetates and benzoates efficiently. This catalyst also efficiently catalyzed the acetylation and benzoylation of amines and thiols whereby the corresponding amides and thioesters were obtained in good to excellent yields. This catalyst can be reused several times without loss of its activity.

The kinetics of the oxidation of neutral red by bromate was investigated in the presence of cationic surfactant (N-dodecylpyridinium chloride) and strongly acidic media over the temperature range 22-35 °C. The kinetic studies were carried out as a function of different variables like concentration and temperature. The described reaction rate is greatly catalyzed by the presence of trace amount of Fe(II) ions and followed by pseudo-third-order kinetics with respect to dye concentration. A possible mechanism for the catalyzed reaction is offered which is found to be coincidentally congruent with experimental findings. The derived rate equation is in good agreement with the experimental observations. Thermodynamic parameters were also evaluated.

Efficient and regioselective conversion of epoxides to 1,2-azidoalcohols has been carried out by treatment of sodium azide using polyethylene glycol as the reaction medium. The reaction afforded the corresponding products with high regioselectivity under mild reaction conditions.

A novel and simple method for rapid conversion of thioamides to the corresponding 1,2,4-thiadiazole derivatives was developed. It was shown that, thioamides undergo clean and efficient oxidation and cyclization in their conversion to 1,2,4-thiadiazoles using N-benzyl-DABCO-tribromide in wet solid-solid conditions.

Two novel Platinum(II) and Palladium(II) complexes of 2,2''-bipyridine (bpy) with ethyldithiocarbamate (Et-dtc) were synthesized. These complexes were characterized by spectroscopic methods such as ultraviolet-visible, infrared and 1H NMR as well as conductivity measurements and chemical analysis. In these complexes, the dithiocarbamate ligand coordinates with Pt(II) or Pd(II) center as bidentate with two sulfur atoms. These water soluble complexes were tested for their in vitro anti-tumor activity against chronic myelogenous leukemia cell line, K562. They show Cc50 values lower than those of cisplatin. The mode of binding of the complexes to calf thymus DNA, were investigated by circular dichroism, ultraviolet difference and fluorescence spectroscopy. These complexes can denature DNA at very low concentrations (~100 µM). Both complexes exhibit cooperative binding and presumably intercalate into DNA. Remarkably, most of the experimental results indicate that the tendency of the Pd(II) complex to interact with DNA and its anti-tumor activity against K562 is more than that of its Pt(II) analog.

In this research, the efficiency of ZnO and TiO2 was compared by photocatalytic degradation of Congo red azo dye. The effects of some parameters such as pH, dye concentration and irradiation time on the degradation rate of dye solution were also examined. In addition, the aggregation feature of Congo red was studied by using UV-Vis spectroscopy techniques. The recovery of the ZnO catalyst was also investigated.

In this paper, photocatalytic degradation of commercial textile azo dyes catalyzed by titanium dioxide and modified titanium dioxide with Ag metal (1% w/w) in aqueous solution under irradiation with a 400 W high-pressure mercury lamp is reported. The effect of various parameters such as irradiation time of UV light, amount of photocatalyst, flow rate of oxygen, pH and temperature for the Ag-TiO2 photocatalyst were investigated. Kinetic investigations of photodegradation indicated that reactions obey improved Langmuir-Hinshelwood model and pseudo-first-order law. The rate constant studies of photocatalytic degradation reactions for Ag-TiO2 and TiO2 photocatalysts indicated that in all cases the rate constant of the reaction for Ag-TiO2 was higher than that of TiO2.

The Michael addition of indoles to α,β-unsaturated electron deficient compounds was catalyzed efficiently at room temperature in acidic micellar solution of sodium dodecyl sulfate (SDS). The substitution on the indole nucleus occurred exclusively at the 3-position in good to excellent yields, and no N-alkylation products were observed.

A sensitive and simple method for determination of iron species after separation/preconcentration by cloud point extraction (CPE) has been developed. When the temperature is higher than the cloud point extraction temperature (60 °C), the complexes of iron(II) and iron(III) species with ferron enter the surfactant-rich phase. Total amount of iron in the surfactant-rich phase was analyzed by FI-AAS, whereas, Fe(II) concentration was determined by a spectrophotometric method using mathematical equation to overcome the interference of Fe(III), when they are both present in the same solution. In this way the time-consuming and labor-intensive steps of preoxidation of Fe(II) or reduction of Fe(III) were eliminated. The parameters affecting could point extraction, such as concentrations of ferron and Triton X-114, pH, and equilibrium temperature were systematically investigated. Under the optimum conditions, the calibration curves were linear over the range of 10-250 and 5-150 µg l-1 for 20 and 40 ml preconcentration volume, respectively. The detection limit was 1.7 µg l-1, and relative standard deviation (RSD) was 2.1% for 20 ml preconcentration volume. The method was applied to the determination of iron species in water samples and total iron in milk. The accuracy was determined by recovery experiment, independent analysis by furnace atomic absorption spectrometry and analysis of certified reference water.

An attempt was made to investigate the potential of two widely used commercial nano and micro TiO2 photocatalysts in degradation and mineralization of a typical azo dye “direct blue 71” in water. A special circulating up-flow reactor with an UV-C-150 W lamp was employed and the influence of the operational parameters was investigated. The results showed that both the photolysis and photocatalysis cause decomposition simultaneously. Despite a half concentration, the nano TiO2 particles provide a nearly twice efficiency, and for the vital case of mineralization 98% reduction in COD after 120 min irradiation. The influence of turbidity of catalyst particles was determined with a novel method and was taken into account in kinetic studies. It was found that the bulk degradation by the OH radicals has a major role in the photocatalysis process.

Cobalt sulfide nanoparticles were introduced into the medium-pore zeolite ZSM-5 (Zeolite Scony Mobil Five) by ion exchange in aqueous suspension and also by the addition of cobalt sulfate to the synthesis gel in hydrothermal zeolite synthesis. The latter method was systematically studied in the presence of tetraethylammonium ions as organic agents. The materials were characterized by chemical analysis, x-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), energy dispersion x-ray (EDX), IR, BET and diffuse reflectance spectroscopy (DRS). SEM picture and BET were used to discriminate between CoS nanoparticles in the zeolite pores and on the outer crystal surface. Their crystalline structure and morphology were studied by XRD and scanning electron microscopy. The results showed that in hydrothermal method zeolite acts as a template. CoS nanoparticles with an approximate size of 22 nm grow on the surface of zeolite. In ion exchange method, however, the majority of CoS nanoparticles are about 6 nm in diameter, located on the surface of the MFI (type materials ZSM-5) structure. Exciton absorption peaks at higher energy than the fundamental absorption edge of bulk CoS indicate quantum confinement effect in nanoparticles as a consequence of their small size. The absorption spectra show that the optical band gap for CoS nanoparticles produced by hydrothermal and ion exchange methods is 3.68 and 4.1 eV, respectively.

Novel metal organic frameworks including {(pipzH2)[Mn(py-2,3-dc)2]·7.75H2O}n, 1, {(pipzH2)[Zn(py-2,3-dc)2]·4H2O}n, 2, [Cd(py-2,3-dc)(H2O)3]n, 3 and {(pipzH2)[Hg4Cl10]}n, 4, in which pipz is piperazine and py-2,3-dcH2 is pyridine-2,3-dicarboxylic acid were synthesized applying a proton transfer ion pair i.e.(pipzH2)(py-2,3-dcH)2 and corresponding metallic salts and studied by IR, 1H NMR, 13C NMR spectroscopy and single crystal X-ray diffractometry. The space group of compounds 1 and 4 are P21/c and C2/c of monoclinic system, respectively. The crystal dimensions are a = 20.108(2) Å, b = 19.910(2) Å, c = 12.997(1) Å, β = 94.354(2)š for 1 and a = 15.940(1) Å, b = 11.2690(9) Å, c = 11.1307(9) Å, β = 90.685(2)š for 4. The crystal structures of 2 and 3 have been reported previously. However, their solution studies are discussed here. The compounds had all polymeric structures. Although ZnII, CdII and HgII were elements of the same group, their behavior against the ion pair was essentially different. Various supramolecular interactions mainly hydrogen bonds of the type O-H···O, N-H···O, C-H···O, N-H···Cl and C-H···Cl were observed in the structures. There was an unusual and huge water cluster in the structure of compound 1. The solution states of compounds 1-4 were studied and reported. The protonation constants of pipz and py-2,3-dc, the py-2,3-dc/pipz proton transfer equilibrium constants and stoichiometry and stability of the system with Mn2+, Zn2+, Cd2+ and Hg2+ ions in aqueous solution were investigated by potentiometric pH titrations.

Various ethyl 3,4-dihydropyrimidin-2(1H)-one-5-carboxylates were oxidized to their corresponding ethyl pyrimidin-2(1H)-one-5-carboxylates by potassium peroxydisulfate in refluxing aqueous acetonitrile. The products were obtained in good to excellent yields. The effect of the nature of 4-substituent and also the nature of solvent play an important role on the rate of oxidation.