二氧化硫脲:一锅合成吡喃并[4,3-b] 吡喃类化合物的高效可重复使用有机催化剂（英文）简

A series of pyrano[4,3-b]pyran derivatives have been synthesized in excellent yields by the reaction of aromatic aldehydes with malononitrile or cyanoacetate and 4-hydroxy-6-methylpyran-2-one in water at 80℃, with the transformation being catalyzed by an aqueous solution of thiourea dioxide (TUD). Upon completion of the reaction, the product was isolated by filtration or extraction and the remaining aqueous TUD solution could be reused several times without any discernible impact on its catalytic activity. This procedure offers several advantages over existing procedures, including high yields, operational simplicity, the use of a non-toxic catalyst and solvent, short reaction time and minimum pollution of the environment, making it a useful and attractive process for the preparation of pyrano[4,3-b]pyran derivatives.     

Preparation and characterization of a suite of ephedra-containing standard reference materials

The National Institute of Standards and Technology, the U.S. Food and Drug Administration, Center for Drug Evaluation and Research and Center for Food Safety and Applied Nutrition, and the National Institutes of Health, Office of Dietary Supplements, are collaborating to produce a series of Standard Reference Materials (SRMs) for dietary supplements. A suite of ephedra materials is the first in the series, and this paper describes the acquisition, preparation, and value assignment of these materials: SRMs 3240 Ephedra sinica Stapf Aerial Parts, 3241 E. sinica Stapf Native Extract, 3242 E. sinica Stapf Commercial Extract, 3243 Ephedra-Containing Solid Oral Dosage Form, and 3244 Ephedra-Containing Protein Powder. Values are assigned for ephedrine alkaloids and toxic elements in all 5 materials. Values are assigned for other analytes (e.g., caffeine, nutrient elements, proximates, etc.) in some of the materials, as appropriate. Materials in this suite of SRMs are intended for use as primary control materials when values are assigned to in-house (secondary) control materials and for validation of analytical methods for the measurement of alkaloids, toxic elements, and, in the case of SRM 3244, nutrients in similar materials.     

Polycatenar oligophenylene liquid crystals

We report the synthesis of oligophenylene polycatenar liquid crystals incorporating 1,4‐disubstituted phenyl rings joined by a direct carbon carbon bond and some pyrimidine analogues. The nature of the linkages does appear to affect the mesomorphism significantly. The ratio of the aromatic core to the aliphatic chains is varied systematically by changing the number of 1,4‐disubstituted phenyl rings and the length of the aliphatic chains. This strongly influences the transition temperatures of the mesophases. Some of the compounds are columnar over an extended temperature range of more than 200°C with melting points below room temperature. We suggest that a combination of the poor overlap of the conjugated electron system of the molecular cores making up the columnar structure and the high concentration of aliphatic chains leads to a low charge‐carrier mobility.     

Diffusive transport of Cu(II) ions through thin ion imprinted polymeric membranes

A novel ion imprinted polymeric membrane (IIPM) for copper (Cu) ions transport was prepared by a ion imprinting technique via cross-linking of blended chitosan (CS)/polyvinyl alcohol (PVA) using glutaraldehyde (GA) as the cross-linker and Cu ions as the template. The obtained IIPM was characterised and evaluated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and permeation studies. Cavities of IIPM containing recognition sites for Cu ions were formed in the compact structure of the CS/PVA membrane which was prepared via the solution casting method. Under the optimum conditions, transport factor of the IIPM reached 2 when the permeation time was 18 h. Selective permeation of Cu ions versus nickel ions through the imprinted membrane was confirmed and a selectivity factor of 1.71 was obtained.     

Synthesis, crystal structure and DFT analysis of a new trinuclear complex of copper

The new trinuclear complex [Cu₂(μ-L)₂CuCl₂] has been synthesized and characterized by elemental analysis, IR, UV-Vis and X-ray spectroscopy, where L is a dianionic tetradentate Schiff base ligand with N₂O₂ donor atoms. The molecular structure of [Cu₂(μ-L)₂CuCl₂] was determined by X-ray crystallography. In the complex, the most remarkable aspect of the trinuclear complex is that it adopts a bent structure for the three copper atoms, with a Cu1Cu3Cu2 intramolecular angle of approximately 90.62(2)°. All three copper atoms are five coordinate, with a slightly distorted square pyramidal geometry. In the two terminals moieties, the basal plane of the square pyramidal is formed by two oxygen atoms and two nitrogen atoms of the Schiff base ligand, and the apical position at the Cu atom is occupied by the bridging Cl1 anion. The Cu1Cl1Cu2 angle is 110.51(5)°. The central copper atom also has a five-coordinate, slightly distorted square pyramidal geometry, with four phenolato oxygens belonging to the Schiff base ligands from Cu(salpn) units describing the square planar base and the Cl anions being apical. The optimized structure of the complex has been studied using the B3LYP/6-31G(d)/LanL2TZf level of theory. The calculation shows that all the copper atoms are five coordinate with distorted square pyramidal structures, which is consistent with experimental data.     

Silica-supported perchloric acid (HClO4–SiO2): a mild, reusable and highly efficient heterogeneous catalyst for multicomponent synthesis of 1,4-dihydropyridines via unsymmetrical Hantzsch reaction

Facile synthesis of some 1,4-dihydropyridine derivatives via Hantzsch reaction of 5,5-dimethyl-1,3-cyclohexanedione (dimedone), 1,3-diphenyl-2-propen-1-one derivatives and ammonium acetate under solvent-free condition in the presence of silica-supported perchloric acid (HClO₄–SiO₂) is described. The catalyst is easily prepared, stable, reusable and efficient under the reaction conditions.     

Nonergodic Quadratic Stochastic Operators

Mathematical Notes -     

An excellent copper selective chemosensor based on calix[4]arene framework

The article depicts a detailed study regarding copper selective chemosensing and complexation nature of 5,11,17,23-tetrakis[(N,N-diphenylamino)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (PAC4). Its photophysical characteristics in various solvents of different polarities along with the influence of acid and base on its spectral properties in these solvents are also discussed. The complexation affinity of PAC4 with regard to its latent applications as Cu(II) selective colorimetric and fluorescent sensor among the selected series of various cations such as Li(I), Na(I), K(I), Rb(I), Ba(II), Sr(II), Al(III), Fe(III), Cd(II), Co(II), Hg(II), Mn(II), Ni(II), Pb(II) and Zn(II) was examined by UV–visible and fluorescence emission spectroscopy in dichloromethane:acetonitrile (DCM:MeCN) solvent system. In addition, the process of complexation has been investigated through Job's plot and it has been observed that the complex between PAC4 and Cu(II) is formed in 1:1 stoichiometric ratio. The complex formation between PAC4 and Cu(II) has also been confirmed by FT-IR spectroscopy and thermal gravimetric analysis (TGA).     

Pseudo four-component and regioselective synthesis of 4-amino-3,5-dicyano-6-arylphthalates using triethylamine catalyst

An efficient triethylamine-catalyzed synthesis of 4-amino-3,5-dicyano-6-arylphthalates is described.A one-pot,simple pseudo four-component reaction between arylaldehydes,dialkyl acetylenedicarboxylates, and twice as much malononitrile gave 4-amino-3,5-dicyano-6-arylphthalates in good to excellent yields.     

Real-time chirp diagnostic for ultrashort laser pulses

Using a real-time Fourier-transform algorithm, we present a simple technique for measuring the chirp of femtosecond laser pulses. We demonstrate significantly enhanced sensitivity compared with standard autocorrelation measurements.