Scientia Iranica
Volume:22 Issue: 6, 2015

A facile and environmentally benign series of carbamates derived from coumarin were synthesizedThe synthesis of 7-hydroxy-4-methyl-2H-1-benzopyran-2-one(3)was carried out by gearing up resorcinol (1) and ethyl acetoacetate (2)in a strong acidic media. Carbamates, 7and8,were synthesized by reacting phenylchloroformate (4) with substituted aliphatic amines, 5 and6, under dynamic pH control in aqueous media in the presence of Na2CO3 solution. The molecules 37 and 8 werebrominated to 3a7a and8a. The molecules 99a10 and 11 were synthesized by further reaction of 3 and3a with the electrophilic carbamates, 77a and 8 in a polar aprotic solvent using LiH as an activator. Finally, the compound 12 was synthesized by the nitration of 10. Structures of all the compounds were determined by IR, 1HNMR, 13C-NMR and EI-MS spectroscopic techniques. The bioactivity results of all the synthesized compounds against four gram-negative and two gram-positive bacteria showed that the synthesized coumarin derivatives exhibited moderate to good %age inhibition activity.

A mild and sustainable three component passerini reaction, in biodegradable deep eutectic solvent based choline chloride:urea (1:2) is described. The reaction proceeds at room temperature involving substituted benzaldehyde, benzoic acid and cyclohexyl isocyanide, with short reaction time and good to excellent yields (65-90%) without tedious workup.

Sulfonic acid-functionalized pyridinium chloride ionic liquid {[Pyridine–SO3H]Cl} can effectively promote the one-pot multi-component condensation reaction between benzil, aldehydes, primary amines and ammonium acetate under solvent-free conditions at 100 ºC to give the desired 1,2,4,5-tetrasubstituted imidazoles, in high yields and short reaction times.

The main interaction between furan and zeolites leads to formation of a hydrogen bond between the O atom of furan and the OH groups of zeolites. The present work reports a theoretical study about the structural, vibrational, and topologic properties of charge distribution of the molecular complexes between furan and the series of acids sites of zeolites. The calculated structural parameters are the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (
E), hardness (), softness (S), absolute electronegativity (), electrophilicity index (!), and the fractions of electrons transferred (
N) from zeolites molecules to furan. We show that the H atom of the bridged OH group of zeolite clusters attacks the O atom of furan.

In this work, characterization of Brønsted acidic ionic liquid namely pyrazinium di(hydrogen sulfate){PyH2(HSO42} using 1H and 13C NMR, mass, thermogravimetry(TG) and derivative thermogravimetry(DTG) data is achieved. Afterward, it is used as a highly efficient, green and homogeneous catalyst to promote the following organic transformations under solvent-free conditions: (i) the synthesis of 14-aryl-14H-dibenzo[aj]xanthenesfrom2-naphthol and arylaldehydes, (ii) the preparation of 9-aryl-1,8-dioxo-octahydroxanthenes by the reaction of dimedone (5,5-dimethyl-1,3-cyclohexanedione)with arylaldehydes, (iii) the synthesis of 1-amidoalkyl/carbamatoalkyl-2-naphthols by the condensation of 2-naphthol with aromatic aldehydes and amide derivatives/alkyl carbamates.

A one-pot and simple method for the solvent-free synthesis of chalcones and dibenzylidene alkanones, catalyzed by heterogeneous and nanoporous MCM-41-SO3H catalyst is reported. The products were afforded in most cases with excellent yields.

In this study, graphite nanosheets were prepared by powdering expanded graphite with sonication in aqueous alcoholic solution. A facile process for the synthesis of expanded graphite filled polythiophene (PTh/EG) conducting composites was developed. The nanocomposites were fabricated via chemical polymerization of thiophene monomer in the presence of expanded graphite nanosheets in various proportions. Nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Scanning Tunneling Microscopy (STM), X-ray diffraction (XRD), cyclic voltammetry (CV) and electrical conductivity measurements.. SEM observations from cross-sections of EGwere performed to understand the microstructure occurrence during interpenetration.Electrical conductivity of PTh/EG was notably enhanced by the introduction of EG. The composite exhibited good electrical conductivity of 125 Scm-1 when the EG content was 0.5 wt %. CV is the most commonly used technique for evaluation of electrochemical properties of a film on the electrode surface.The composites also showed excellent electrochemical reversibility at the scan rate of 50 mVs-1 and maximum reversible electrochemical response was almost unchanged even up to 100 cycles. The stability of oxidation and reduction peaks of nanocomposites in cyclic voltammetry up to 100 cycles show that obtained nanocomposites are very appropriate to be used in rechargeable batteries.

Two new Schi base ligands, (E)-4-(3-ethoxy-2-hydroxybenzylideneamino) benzoic acid (L1) and (E)-4-(3-methoxy-2-hydroxy-benzylideneamino)benzoic acid (L2), were synthesized and characterized by elemental analyses, FT-IR, NMR spectroscopy and single-crystal X-ray di raction analysis. The compound, L1, was crystallized in the triclinic system, space group P - 1, with a = 4:9897(3) A, b = 6:9109(5) A, c = 20:7694(15) A, = 83:690(4), = 84:855(4), = 78:698(4), V = 696:35(8) A3, and Z = 2. The compound L2 was crystallized in the orthorhombic system, non-centerosymmetric space group, P212121, with a = 4:7824(4) A, b = 10:2031(11) A, c = 30:516(3) A, V = 1489:0(3) A3, and Z = 4. Both L1 and L2 display a trans-con guration about the C=N double bond. The Density Functional Theory (DFT) and the Time-Dependent Density Functional Theory (TD-DFT) were used to study the ground state properties (molecular orbitals), and interpret the absorption spectra of these ligands, respectively. Electronic Di erence Density Maps (EDDMs) were calculated from the TD-DFT study, indicating the change of electron density in the singlet excited states.

The catalyzed reaction of (RS)-1-phenylethanol and S-ethyl thio octanoate by lipase B from Candida Antarctica is studied, using density functional theory. Quantum mechanics cluster approach is used to model the enzyme’s active site. The results show that the catalytic triad amino acids of the enzyme do not abstract the alcoholic proton of 1-phenylethanol before a nucleophilic attack from the alcohol to the ester. A two-step mechanism is proposed for the reaction of theR-enantiomer of the alcohol with the ester. However, the results show no path for theS-enantiomer. We showed that the enantioselectivity of the enzyme is due to the different hydrogen-bonding patterns of the two enantiomers of the alcohol in the enzyme’s active site. The OH group of theR-enantiomer is directed toward Ser-105. While, the OH group of theS-enantiomer is far from Ser-105 and is directed toward Thr-40.

SBA-Pr-SO3H was used as green and recyclable catalyst for the synthesis of dihydropyrdo[2,3-d]pyrimidine derivatives by three component one-pot reaction between 6-amino-1,3-dimethyl uracil, aromatic aldehydes and 1,3-dicarbonyl compounds under reflux conditions. Some of synthesized dihydropyrido[2,3-d]pyrimidines were showed antimicrobial activities against some fungi and gram positive and negative bacteria.

The mono nitration of phenols and naphthols has been reported in high yields and short reaction times using the task specific ionic liquid based on nitrate ion, 1,4-bis(4-sulfobuthyl)-1,4-diazabicyclo[2.2.2]octane di nitrate, as reagent without acid co-catalyst at mild condition. The reagent could be recovered and reused several times without significant lose of reactivity.

A green approach for efficient and rapid synthesis of biologically active substituted 3,4-dihydropyrimidin-2(1H)-one(thione) derivatives using nano SbCl5.SiO2as a heterogeneous catalyst under solvent-free conditions is reported. The catalyst was characterized by FT-IR, XRD, SEM, TEM and TG-DTG analysis. Compared to the classical reactions, this method consistently has advantages of excellent yields, simple operation, short reaction time, and the avoidance of the use of organic solvents and eco-friendly protocol.

In this study, LaxSr1-xFeO3 (x = 0, 0.8) perovskite-type catalysts were prepared by gel combustion method and then 1.0 wt% palladium was loaded on them by a dry impregnation. The catalysts were characterized by XRD, SEM, H2-TPR, O2-TPD, NO-TPD and BET surface area techniques.H2-TPR profiles of the Pd/perovskite catalyst shows the reduction of Pd at around 140˚C which facilitates the reduction of NO in the H2-SCR. TPD results reveal that the substitution of Sr in the perovskites structure remarkably decreases the oxygen mobility and increases the NO adsorption. The H2-SCR of NO on the catalysts was performed in a temperature-programmed reaction apparatus in the presence of oxygen.The effect of carbon monoxide in the feed on H2-SCR was also investigated. The PLSFOcatalyst (1.0 wt% Pd/La0.8Sr0.2FeO3 shows the highest NO conversion and N2 selectivity at a moderate temperature of 190oC.

Due to the codon usage and high G+C contentof thetrans-4-proline-L-hydroxylase gene from the Dactylosporangium sp.strain RH1, the whole gene was optimized and cloned into several vectors for expression. In biotransformations with resting cells, the activity of the enzyme was investigated. The in-house modified plasmid pet-M-3C was found to yield the highest enzymatic activity. Additionally, after the primary fragment screening, the conversion efficiency of fragment 1-257 aa was enhanced from 76.60% to 88.97% compared with the full-length proline 4-hydroxylase within 60 h; we also found that truncation of the gene improved the solubility of the encoded protein.After optimizing the various induction conditions with respect to the enzymatic activity of the engineered strain, including the concentration of the inducer IPTG, the cell density before the inducer was added, the induction temperature and the induction time, the conversion efficiency was more than 97%within 48 h.

The aim of this paper is optimal operation of a divided-wall column (DWC) based on self-optimizing control (SOC). By now, the proposed SOC methods have been based on linearization of the process. The novelty of this paper is to overcome this shortcoming of the local optimality of SOC. Theoretically, changes in optimal sensitivity matrix from nominal design, due to changes in operating condition, make SOC deviate from steady state optimality. These deviations from optimal operation, in already available SOC structures, have to be counteracted by optimization layer in the control structure hierarchy which involves solving a large nonlinear optimization problem online. The proposed method in this paper solves this problem with modeling optimal sensitivity matrix with Takagi-Sugeno fuzzy inference. This fuzzy inference system is tuned offline. The proposed method is dynamically validated and compared with conventional SOC. The results showed that conventional SOC had high value of loss and deviated from optimal operation. However, in the same operating condition, the proposed method with the aid of Takagi-Sugeno fuzzy inference system, which involves online calculation of weighted average of some linear function, imposed small loss, made DWC track optimal trajectory and removed the need for online solving large nonlinear optimization problem.

Here, a series of immiscible displacement processes have been performed on fractured porous medium developed on glass micro-models in order to investigate the role of fracture characteristics on oil displacement efficiency during immiscible displacement process. Oil recoveries were determined from image analysis of continuously recorded pictures during different flooding schemes. A clear bypassing of displacing fluid which results in premature breakthrough of injected fluid due to the fracture has been observed. Moreover, the results showed a decrease of oil recovery when fracture''s length increased. In contrast, an increase of fracture orientation from flow direction increased oil recovery. Results of this work may be useful for through understanding of immiscible displacement process as well optimal field development plans.