Transition-metal-free,atom-economical cascade synthesis of novel 2-sulfonated-benzo[f][1,7]naphthyridines and their cytotoxic activities

An efficient, transition-metal-free cascade synthetic method has been developed for new 2-aryl/heteroaryl sulfonated benzo[f][1,7]naphthyridines. It is tert-butyl hydroperoxide (TBHP) mediated highly regioselective sulfonylation?cyclization?aromatization process between N-(3-aryl/heteroarylprop-2-yn-1-yl)quinolin-3-amines and aryl/heteroaryl sulfonylhydrazides. This synthetic protocol offers one-step strategy for CS and CC bond formations with a broad range of functional group tolerance. It is a simple, mild, and atom-economical route for the synthesis of various valuable functionalized 1, 2-aryl/heteroaryl sulfonated benzo[f][1,7]naphthyridines in moderate yields. Since the core motif of 2-sulfonated benzo[f][1,7]naphthyridines are biologically and pharmaceutically important (TLR activity 7, 8 modulators). Additionally, the synthesized derivatives were evaluated for their in vitro cytotoxic activities against six human cancer cell lines including lung (NCIH23), colon (HCT15), gastric (NUCG-3), renal (ACHN), prostate (PC-3), and breast (MDA-MB-231) cell lines. These compounds displayed significant cytotoxic activities against all tested human cancer cell lines.     

Catalyst-free and atom-economic synthesis of substituted 1-acetyl and 1-hydroxyl carbazoles

The first-ever Diels-Alder reactions of 3-alkenyl indoles with a conjugated alkynyl ketone are reported. These reactions proceed in an atom-economic manner without a catalyst and give various substituted 1-acetyl carbazoles in moderate to excellent yields. These products can be converted to 1-hydroxyl carbazoles in high yields under mild reaction conditions.     

Visible light-promoted metal-free aerobic oxyphosphorylation of olefins: A facile approach to β-ketophosphine oxides

A metal-free direct aerobic oxyphosphorylation of alkenes with H-phosphine oxides has been developed utilizing visible light photoredox catalysis. A variety of β-ketophosphine oxides have been obtained in good yields from simple olefins under air with inexpensive rhodamine B as the non-metallic photocatalyst. This method provides a mild, green, and practical synthetic approach to valuable β-ketophosphine oxides.     

Kinetic determination of ascorbic acid by the BZ oscillating chemical system

A new analytical method for the determination of ascorbic acid by the perturbation caused by different amounts of ascorbic acid on the BZ oscillating chemical system involving the Ce(IV)-catalyzed reaction between potassium bromate and malonic acid in a acidic medium is proposed. The method relies on the linear relationship between the change in the oscillation amplitude of the chemical system and the concentration of ascorbic acid, which is in this work exposed for the first time. The calibration curve is linearly proportional to the concentration of ascorbic acid over the range 3.5x10(-6)-4.7x10(-4) M, with the regression coefficient is 0.9975. Two different methodologies were used to address the determination. Some aspects of the potential mechanism of action of ascorbic acid on the BZ oscillating chemical system are discussed in detail.     

Density functional theory studies on the dissociation energies of metallic salts: relationship between lattice and dissociation energies

The formation and physicochemical properties of polymer electrolytes strongly depend on the lattice energy of metal salts. An indirect but efficient way to estimate the lattice energy through the relationship between the heterolytic bond dissociation and lattice energies is proposed in this work. The heterolytic bond dissociation energies for alkali metal compounds were calculated theoretically using the Density Functional Theory (DFT) of B3LYP level with 6‐311+G(d,p) and 6‐311+G(2df,p) basis sets. For transition metal compounds, the same method was employed except for using the effective core potential (ECP) of LANL2DZ and SDD on transition metals for 6‐311+G(d,p) and 6‐311+G(2df,p) calculations, respectively. The dissociation energies calculated by 6‐311+G(2df,p) basis set combined with SDD basis set were better correlated with the experimental values with average error of ca. ±1.0% than those by 6‐311+G* combined with the LANL2DZ basis set. The relationship between dissociation and lattice energies was found to be fairly linear (r>0.98). Thus, this method can be used to estimate the lattice energy of an unknown ionic compound with reasonably high accuracy. We also found that the dissociation energies of transition metal salts were relatively larger than those of alkaline metal salts for comparable ionic radii. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 827–834, 2001     

Electrostatic Layer‐by‐Layer Assembly of Polycation and DNA Multilayer Films by Real‐time Surface Plasmon Resonance Technique

The assembly of alternating DNA and positively charged poly‐(dimethyldiallylammonium chloride) (PDDA) multilayer films by electrostatic layer‐by‐layer adsorption has been studied. Real time surface plasmon resonance (BIAcore) technique was used to characterize and monitor the formation of multilayer films in solution in real time continuously. The results indicate that the uniform multilayer can be obtained on the poly‐(ethylenimine) (PEI) coated substrate surface. The kinetics of the adsorption of DNA on PDDA surface was also studied by real‐time BIAcore technique, and the observed rate constant was calculated using a Langmuir model (k_obs = (1.28 ± 0.08) × 10^?2s^?1).     

Studies on epoxy resins cured by cationic latent thermal catalysts: The effect of the catalysts on the thermal,rheological, and mechanical properties

To investigate the effect of catalysts on the thermal, rheological, and mechanical properties of an epoxy system, a resin based on diglycidyl ether of bisphenol‐A (DGEBA) was cured by two cationic latent thermal catalysts, N‐benzylpyrazinium hexafluoroantimonate (BPH) and N‐benzylquinoxalinium hexafluoroantimonate (BQH). Differential scanning calorimetry was used for the thermal characterization of the epoxy systems. Near‐infrared spectroscopy was employed to examine the cure reaction between the DGEBA and the latent thermal catalysts used. The rheological properties of the blend systems were investigated under an isothermal condition with a rheometer. To characterize the mechanical properties of the systems, flexure, fracture toughness (K_IC), and impact tests were performed. The phase morphology was studied with scanning electron microscopy of the fractured surfaces of mechanical test samples. The conversion and cure activation energy of the DGEBA/BQH system were higher than those of the DGEBA/BPH system. The crosslinking activation energy showed a result similar to that obtained from the cure kinetics of the blend systems. The flexure strength, K_IC, and impact properties of the DGEBA/BQH system were also superior to those of the DGEBA/BPH system. This was a result of the substituted benzene group of the BQH catalyst, which increased the crosslink density and structural stability of the epoxy system studied. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 187–195, 2001     

Asymmetric membrane formation via immersion precipitation method. I. Kinetic effect

The kinetic effect of the phase inversion process on the membrane morphology is explored, with emphasis on the diffusion coefficient of the nonsolvent as a measure of the solvent/nonsolvent exchange rate. The diffusion coefficient is closely related to the nonsolvent tolerance of the polymer solution, which was estimated from a pseudo-ternary phase diagram of the following system: polymer: polysulfone; solvent system: a mixture of the solvent 1-methyl-2-pyrrolidinone and a solvent additive (formic acid, water or ethanol); and nonsolvent: ethanol. Regardless of the kind of solvent additive employed, when the diffusion coefficient of the nonsolvent is high for a given gelation medium, then the membrane consists of a smooth, defect-free surface and macrovoid-free cross section, and is highly permeable to oxygen. However, using a polymer solution with a low diffusion coefficient results in a membrane of a rather defective morphology. Therefore, it is concluded that the diffusion coefficient of the nonsolvent is a crucial parameter in controlling membrane morphology.     

顶空单液滴微萃取-气相色谱法测定水中苯系物

采用顶空单液滴微萃取样品处理方法分离富集水中苯系物,用气相色谱法进行测定.考察了不同萃取剂、萃取条件对检测结果的影响.苯、甲苯、对二甲苯的检出限分别为0.05,0.05,0.03 μg·L-1,三种苯同系物的相关系数分别为0.999 2,0.998 5和0.997 2,回收率分别为98.3%,101.9%和97.3%.     

Microfluidic differential resistive pulse sensors

This study demonstrates an on-chip resistive pulse-sensing scheme with a design of symmetric mirror channels, which significantly reduces the noise and achieves better signal-to-noise ratio. Polystyrene particles of different sizes have been detected with the developed sensing scheme and a record low volume ratio of the particle to the sensing channel, or 0.0004%, has been detected with particles of 520 nm in diameter in a sensing aperture of 50x16x20 microm3. This volume ratio is about ten times lower than the lowest volume ratio reported in the literature including that specified for commercial Coulter counters.