A Simple and One‐Pot Synthesis of β‐Sultams by Using the Vilsmeier Reagent

Mild and efficient one‐pot synthesis of β‐sultams with the Vilsmeier reagent proceeded in good to excellent yield. [2 + 2] Cycloaddition of imines with sulfenes (prepared in situ) afforded the corresponding cis‐β‐sultams. Optimization of solvents, molar ratio of reagents,and temperature was performed. Toxic and corrosive compounds have been avoided in this novel method.     

Straightforward Approach Toward Dihydrothiazoles via Intramolecular Bromocyclization

An intramolecular bromonium ion–assisted cyclization with sulfur as an internal nucleophile is described. Starting from benzoyl chlorides, this method provides an easy procedure for the synthesis of dihydrothiazole derivatives in moderate to good yields.     

Validated Simultaneous Gradient Ultra-Performance Liquid Chromatographic Quantification of Some Proton Pump Inhibitor Drug Residues in Saudi Pharmaceutical Industrial Wastewater

Monitoring and quantification of active pharmaceutical ingredients (APIs) in the environment constitute important and challenging tasks, as they are directly associated with human health. Three commonly used proton pump inhibitors (PPIs), namely, omeprazole sodium (OMP), pantoprazole sodium (PNT), and lansoprazole sodium (LNZ) are well separated and quantified using ultra-performance liquid chromatography (UPLC) in pharmaceutical industrial wastewater. The separation of the studied drugs was performed on a stationary phase with a Waters^TM column (100 × 2.1 mm, 1.7 µm). The mobile phase was composed of methanol:0.05 M potassium dihydrogen phosphate buffer (adjusted to pH 7.5 using NaOH) (50:50, v/v). The elution process was done in gradient mode by changing the relative proportions of the mobile phase components with time to get an optimum separation pattern. The flow rate of the developing system was adjusted to 0.8 mL/minute. Detection of the separated drugs was performed at 230 nm. The studied drugs were quantified in the concentration range of 10–200 ng/mL for all drugs. The cited method was fully validated according to the international conference on harmonization (ICH-Q2B) guidelines, then it was applied successfully for quantification of the studied PPIs in real wastewater samples after their solid phase extraction (SPE).     

The Vilsmeier reagent: a useful and versatile reagent for the synthesis of 2-azetidinones

(Chloromethylene)dimethylammonium chloride (Vilsmeier reagent), prepared easily from N,N-dimethylformamide and oxalyl chloride or thionyl chloride, works as a versatile acid activator reagent for the direct [2+2] ketene-imine cycloaddition of substituted acetic acid and imines in one-pot synthesis under mild conditions. Monocyclic, spirocyclic and 3-electron-withdrawing group β-lactams were synthesized by this method and optimization of conditions were performed.     

The effect of La-substitution on magnetic properties of nanosized Sr1−xLaxTi0.05Zn0.2(Fe)11.75−δ(Fe)δO19 powders

A series of La-substituted M-type Sr hexaferrite powders Sr_1−xLa_xTi_0.05Zn_0.2Fe³⁺_11.75O₁₉, wherein x ranges from 0.1 to 0.5 with a step of 0.1, have been prepared by the conventional ceramic method and were then milled in a high energy mill to prepare nanosized powders. XRD investigation of the calcined and the milled powders shows that single phase hexaferrite structure has been formed after calcining and has not changed after milling. The lattice parameters and the mean crystallite sizes of the samples have been determined from the XRD data and Scherrer's formula. The results show that the lattice parameters (“а” and “c”) decrease with increase in La-substitution and the mean crystallite size of the milled powders is about 17 nm. Coercivities and magnetizations of the samples in a magnetic field of 16 kOe have been determined from the room temperature hysteresis loops. It was found that both parameters increase with La substitutions up to 0.3 and then decrease for higher substitutions. These variations were attributed to the enhancement of hyperfine field and spin-canting magnetic structure when La content increases. In addition, the magnetizations were smaller for the nanosized samples in comparison with those of bulk ones, which were discussed according to the core-shell model. Also the results show that annealing of the nanosized samples up to 500 °C can enhance coercivity and magnetization of the samples, which is discussed based on crystallite size growth.     

Nondestructive room-temperature adsorption of 2,4,6-tri(2'-thienyl)-1,3,5-triazine on a Si-B interface: high-resolution STM imaging and molecular modeling

Organic nanostructures on semiconductors are currently investigated but the surfaces are known to interact strongly with molecules. To reduce the molecule-surface interaction, we used the Si(111)-B square root 3 x square root 3R30 degrees . Deposition of isolated 2,4,6-tri(2'-thienyl)-1,3,5-triazine, was achieved at room temperature without modification of their pi skeleton. This fascinating arrangement, observed by STM, has been validated by full density functional theory computations onto the entire system. The theoretical results give a clear explanation for the specific adsorption sites of molecules on the substrate.     

Adsorption of an organic zwitterion on a Si(1 1 1)-7 × 7 surface at room temperature

The couple sulfonato/Si(1 1 1)-7 × 7 leads to remarkable 2D chiral molecular assembly with a stability improved at room temperature. The voltage-dependency of the STM images has been experimentally investigated and the correlation between STM images and PDOS has been studied. The proposed empirical model of the adsorption of molecules on Si(1 1 1)-7 × 7 has been justified by the experimental and theoretical data.     

Game of cops and robbers in oriented quotients of the integer grid

The integer grid $\mathbb{Z}\square \mathbb{Z}$ has four typical orientations of its edges which make it a vertex-transitive digraph. In this paper we analyze the game of Cops and Robbers on arbitrary finite quotients of these directed grids.     

A note on k-cop-win graphs

The game of Cops and Robbers is a very well known game played on graphs. In this paper we will show that minimum order of a graph that needs $k$ cops to guarantee the robber’s capture is increasing in $k$.