Silica Sulfuric Acid/Sodium Dichromate Dihydrate as an Efficient Heterogeneous Method for the Oxidation of Alcohols Under Mild Conditions

A combination of silica sulfuric acid and sodium dichromate dihydrate in the presence of wet SiO 2 were used as an effective oxidizing agent for the oxidation of alcohols to their corresponding aldehyde or ketone derivatives in dichloromethane or toluene with excellent yields.     

One‐Pot Synthesis of 4‐(2,3‐Dihydro‐2‐hydroxy‐1,3‐dioxo‐1H‐inden‐2‐yl)‐Substituted 1‐Aryl‐1H‐pyrazole‐3‐carboxylates via a Tandem Three‐Component Reaction

The hitherto unreported, highly functionalized 1H‐pyrazole‐3‐carboxylates 3 have been synthesized in good yields via a one‐pot three‐component domino reaction of phenylhydrazines, dialkyl acetylenedicarboxylates, and ninhydrin under mild conditions for the first time. No co‐catalyst or activator is required for this multicomponent reaction, and the reaction is, from an experimental point of view, simple to perform (Scheme 1). The structures of compounds 3 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization/addition reaction is proposed (Scheme 2).     

On-column N-dearylation of 2-azetidinones by silica-supported ceric ammonium nitrate

A modified traditional preparative chromatographic column can be used to achieve quantitative N-dearylation of N-(alkoxyphenyl), N-(alkoxynaphthyl), and N-(alkoxybenzyl)-2-azetidinones under mild conditions. Starting materials are charged on top of the column and the pure N-unsubstituted 2-azetidinones leave the column minutes later without need for other purifications. The yields are good-to-excellent and the reaction condition is mild, easy, efficient, and cheap.     

Sequential spectrophotometric determination of trace amounts of periodate and iodate in water samples after micelle-mediated extraction

A cloud point extraction process using the nonionic surfactant Triton X-114 for extraction and preconcentration of periodate and iodate ions from aqueous solution was investigated. The method is based on the extraction of triiodide ion, the colored product of the reaction of periodate and iodate with iodide in acidic media. The triiodide was concentrated in surfactant rich phase and then determined spectrophotometrically at 358 nm. For the determination of periodate and iodate in mixture, two sets of conditions were established. In one set of conditions only periodate reacted with iodide but in the other set both ions reacted with iodide. The data were evaluated by the method of proportional equations. The optimal extraction and reaction conditions (e.g., surfactant and reagent concentrations and centrifuge time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration factor, and enhancement factors) were obtained. Under the optimized conditions, the methods allowed the determination of periodate and iodate at concentrations between 2.0 and 1000 and 4.0 and 400 ng/mL, respectively. The proposed method was successfully applied to the determination of periodate and iodate in water samples.     

Influence of population and radius of cavity bubbles on size of sodium chloride crystals in ultrasound ablation

Crystal size distribution as a function of power in ultrasound ablation is simulated by using a theoretical method based on population and radius of bubbles. In this method, population and radius of bubbles are related to ultrasound power and Debye temperature of crystals. The best power for production of crystals with uniform size is obtained from the theory. In addition, it is shown that the population of bubbles effects the radius of the productions and the radius of bubbles influences the population of products. Results from the theory are supported by experimental results.     

Synthesis of novel N-sulfonyl monocyclic beta-lactams as potential antibacterial agents

New cis monocyclic beta-lactams were synthesized by [2+2] Staudinger cycloaddition reactions of the imine (3,4-dimethoxybenzylidene)-(4-methoxyphenyl)-amine and ketenes derived from different acyl chlorides and Et3N. These monocyclic beta-lactams were then cleaved by ceric ammonium nitrate (CAN) to give NH-monocyclic beta-lactams, which in turn were converted to N-sulfonyl monocyclic beta-lactams by treatment with four different sulfonyl chlorides in the presence of Et3N and 4,4-dimethyl-aminopyridine (DMAP).     

Catalytic adsorptive stripping voltammetry determination of ultra trace amount of molybdenum using factorial design for optimization

A highly sensitive procedure is presented for the determination of ultra-trace concentration of molybdenum by catalytic adsorptive stripping voltammetry. The method is based on adsorptive accumulation of the molybdenum (Mo)-pyrocatechol violet (PCV) complex on to a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by chlorate. The influence of variables was completely studied by factorial design analysis. Optimum analytical conditions for the determination of molybdenum were established. Molybdenum can be determined in the range 1.0 × 10⁻³-100.0 ng ml⁻¹ with a limit of detection of 0.2 pg ml⁻¹. The influence of potential interfering ions on the determination of molybdenum was studied. The procedure was applied to the determination of molybdenum in mineral water and some analytical grade substances with satisfactory results.     

Simulation for business process re-engineering: case study of a database management system

This paper describes the use of discrete event simulation in the resource, throughput and content analysis and improvement of a business process in the Iranian Information and Documentation Centre (IRANDOC). The process was initially mapped using Data Flow Diagrams (DFD), and the objectives of the study for a range of users were captured using the Delphi method. The time taken for the tasks in the process were estimated by work study, and the simulation was developed in ServiceModel?. The simulation was valuable in understanding why the current systems were not performing satisfactorily and led to a number of proposals for improvement. This mixed use of hard (simulation) and soft (Delphi) methods proved a fruitful way to gain process improvements and could be employed in other organisations.     

Synthesis of a novel bifunctional oxyammonium-based ionic liquid: Application for the synthesis of pyrano[4,3-b]pyrans and tetrahydrobenzo[b]pyrans

In the present investigation, a novel bifunctional oxyammonium-based ionic liquid, namely, 2,2′-(ethane-1,2-diylbis[oxy])bis(ethan-1-aminium)-2,2,2-trifluoroacetate, was designed and synthesized. The structure of the titled ionic liquid was characterized using Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (¹HNMR), carbon nuclear magnetic resonance (¹³CNMR), fluorine nuclear magnetic resonance (¹⁹FNMR), homonuclear COSY nuclear magnetic resonance (NMR), thermogravimetry (TG), derivative thermogravimetry (DTG) analysis, X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The described ionic liquid demonstrated robust catalytic performance in the synthesis of pyrano[4,3-b]pyrans and tetrahydrobenzo[b]pyran derivatives. The ionic liquid presents a high potential of recycling and reusing capability in both types of model reactions.     

Brønsted Acidic Ionic Liquid–Catalyzed One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones and Thiones Under Solvent-Free Conditions

An efficient and convenient procedure for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones and thiones by condensation of ethylacetoacetate, aldehydes, and urea or thiourea in the presence of methylimidazolium hydrogensulfate is described. Aromatic and aliphatic aldehydes reacted easily to afford the corresponding 3,4-dihydropyrimidin-2(1H)-ones and thiones under solvent-free conditions. The use of nontoxic and inexpensive materials, straightforward and clean workup, short reaction times, and good yields are the advantages of this method.