[Omim][BF4], a green and recyclable ionic liquid medium for the one-pot chemoselective synthesis of benzoxazinones

An efficient procedure for the one-pot chemoselective synthesis of 2H-benzo[b][1,4]oxazin-3(4H)-one derivatives from their corresponding o-aminophenols is developed using DBU in the ionic liquid [omim][BF₄]. Upon completion of the reaction and separation of the product, the ionic liquid is recovered and successfully reused over nine recycles without any noticeable loss of performance.     

Electronic structure of sulfur terminated zigzag boron nitride nanotube: A computational study

Density functional theory (DFT) calculations have been performed to investigate the electronic and structural properties of sulfur (S) terminated models of zigzag boron nitride (BN) nanotube. Four models including pristine, boron (B) tip terminated by S, nitrogen (N) tip terminated by S, and both of B and N tips terminated by S have been considered for optimizations and chemical shielding (CS) parameters calculations. The results indicate that the B–N bond lengths do not detect any changes due to the S-termination but the band gaps and dipole moments detect notable changes especially for the model of the N-tip terminated by the S atoms. The CS parameters also indicate that the atoms of the models are divided into layers with similar parameters in each layer. In the model of the B-tip terminated by the S atoms, the CS parameters indicate strong chemical bonding of N- and S-layers; however, only some attractions between the B- and S-layers of the model of the N-tip terminated by the S atoms have been detected. In the model of B and N tips terminated by the S atoms, the most significant changes among the models are detected.     

Diastereoselective synthesis of spiro-functionalized tetraalkyl benzoisoquinopyrrolonaphthyridine-tetracarboxylates from isoquinoline, dialkyl acetylenedicarboxylates, and indane-1,3-dione

An effective route to spiro-functionalized fused polycyclic derivatives of isoquinoline is described via tandem reaction of isoquinoline, dialkyl acetylenedicarboxylates, and indane-1,3-dione.     

Radiosynthesis of [18F]-5-[2-(2-chlorophenoxy)phenyl]-1,3,4-oxadiazole-2-yl-4-fluorobenzoate: A labeled ligand for benzodiazepine receptors

5-[2-(2-Chlorophenoxy)phenyl]-1,3,4-oxadiazole-2-yl-4-fluorobenzoate 6a, the non-classic benzodiazepine ligand, has been shown to elicit a significant anticonvulsant activity against pentylenetetrazole-induced convulsion. In order to perform biological studies, we decided to prepare the [¹⁸F]-labeled compound. This compound was prepared in no-carrier-added (n.c.a) form from 5-[2-(2-chlorophenoxy)phenyl]-1,3,4-oxadiazole-2-yl-4-N,N,N-trimethylanilinium triflate 5 in one step at 125 °C in Kryptofix 2.2.2/[¹⁸F] and DMSO as the solvent followed by column chromatography. The synthesis took 20 minutes with an overall radiochemical yield of 70-75% (EOS) and a specific activity about 74 GBq/mmole and chemical-radiochemical purity more than 95%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Amplification of optical delay by use of matched linearly chirped fiber Bragg gratings

We describe the use of a matched linearly chirped fiber Bragg grating (FBG) pair as a key element in an adjustable optical delay line. This delay line has the unique property that the achievable optical group delay is orders of magnitude greater (factor of 10(2) in our experiment) than the actual physical displacement. We demonstrate operation of such an optical delay line over a delay range of 3.5 mm using a pair of matched 1300-nm chirped FBGs with a bandwidth of 20 nm each.     

Flow-injection determination of ascorbic acid and cysteine simultaneously with spectrofluorometric detection.

A simple and sensitive spectrofluorometric method was developed for the simultaneous determination of ascorbic acid and cysteine by a flow-injection system. This method is based on the reduction of Tl(III) with ascorbic acid or cysteine in acidic media, producing fluorescence reagent, TlCl3(2-) (lambdaex = 227 nm, lambdaem = 419 nm). The injected sample solution was divided into two separate streams. The first stream was treated with Tl(III) at pH 3.0 and then passed through a 270 cm reaction coil to the flow cell of the spectrofluorometer, where the fluorescence intensity was measured. This signal is related to ascorbic acid and cysteine concentration. The second part of the injected sample solution was treated with Tl(III) in HCl solution and then passed through a 50 cm reaction coil to the flow cell and the fluorescence intensity was measured. This signal is related only to cysteine. Thus, the ascorbic acid content was determined directly by the difference according to the calibration curve. Ascorbic acid and cysteine can be determined in the range of 1 x 10(-6) to 5.0 x 10(-5) M, at a rate of 16 samples per hour. The limits of detection (S/N = 3) were 8 x 10(-7) M for ascorbic acid and 7 x 10(-7) M for cysteine. The influence of potential interfering substances was studied. The proposed method was successfully applied to the simultaneous determination of both analytes in real samples.     

Investigation the chemical reactivity of positions N‐3, C‐5 and C6‐methyl group in biginelli type compounds and synthesis of new dihydropyrimidine derivatives

The compounds 5‐ethoxycarbonyl‐1,6‐dimethyl‐4‐(3‐nitrophenyl)‐3,4‐dihydropyrimidin‐2(lH)‐one (5) and 5‐ethoxycarbonyl‐1‐phenyl‐6‐methyl‐4‐(3‐nitrophenyl)‐3,4‐dihydropyrimidin‐2(lH)‐one (1) were prepared by the Biginelli condensation method and they converted to eight N‐3 substituted dihydropyrimidines using NaH and various electrophiles (ClCO₂Et, TsCl, Ac₂O, AcCl and PhCOCl). Compound (1) was mono‐brominated at the C₆‐methyl group using bromine solution. Reaction of the bromo derivative with amino nucleophiles such as methyl amine and cyclohexyl amine produced two pyrrolo‐pyrimidine derivatives. All the compounds except 5‐ethoxycarbonyl‐1‐phenyl‐6‐methyl‐4‐(3‐nitrophenyl)‐3,4‐dihydropyrimidin‐2(l_H)‐one ( 4 ) were purified by recrystallization methods. The structure of all the new compounds was confirmed using FT‐ir,¹H nmr, ¹³C nmr spectral and elemental analyses methods.     

Development of PVC/Silica Hybrids Using PVC Plastisols

A novel method for producing a plasticised PVC with increased porosity has been developed, by the use of an organic-inorganic hybrid. Silica was produced in situ from tetraethoxysilane via a hydrolytic sol-gel processing route. Tetrahydrofuran was used as co-solvent, and γ-glycidyloxypropyl-trimethoxysilane as coupling agent. The films produced were transparent, with moderate mechanical properties. A film containing 20% silica showed a 45% increase in water vapour permeability.     

Fluidized Bed Polyethylene Reactor Modeling in Condensed Mode Operation

Summary: Modeling of fluidized bed reactor for polyethylene production in the condensed mode operation is proposed in this paper. A two-phase model including the emulsion and bubble phases with the constant bubble size is employed to describe hydrodynamic behavior of the reactor. The kinetics of Ziegler-Natta polymerization is also modeled with a two active site model. The phase behavior and solubility of low molecular weight components in polyethylene are estimated with the Sanchez-Lacombe equation of state. The validation of the model is carried out with industrial data for an ethylene and 1-butene copolymerization with the isopentane as a condensable component. The simulation results are in good agreement with industrial data. The model is also used to study quantitatively the effect of the inlet stream temperature to the reactor and isopentane concentration in the reactor on the production rate. For instance, in a typical process, when the inlet stream temperature changes 10 °C, the production rate will alter about 40%. Furthermore, the change of the isopentane concentration around 1 mole percentage leads to a variation of production rate about 14%.