Facile domino access to chiral mono-, bi-, and tricyclic 2,3-dihydrofurans

The asymmetric domino Michael-S(N)2 reaction of various 1,3-dicarbonyl compounds to α-bromonitroalkenes is described for the first time, employing readily available cinchona-derived bifunctional thioureas as organocatalysts. The novel transformations were highly regio-, chemo-, diastereo-, and enantioselective, which simultaneously gave the chiral tricyclic 2,3-dihydrofurans, bicyclic 2,3-dihydrofurans, and tetrasubstituted 2,3-dihydrofurans with two vicinal chiral carbon centers.     

Total Synthesis of Plakortone B

Plakortone B is a naturally occurring bicyclic[3.3.0]furanolactone compound with attractive bioactivities. Although the relative configuration of plakortone B’s central core had been established by NMR spectroscopic methods, the absolute configuration of its four stereocenters remained unknown. In the present paper, all four possible isomers of plakortone B were synthesized and one of these molecules was found to be identical with the natural plakortone B on the basis of ¹H, ¹³C NMR spectra and specific rotation comparisons. Thus, the absolute configuration of the natural plakortone B was determined to be (3S,4S,6R,10R).     

Design,synthesis, and characterization of a combined main-chain/side-chain liquid-crystalline polymer based on ethyl cellulose

A novel combined main-chain/side-chain liquid-crystalline polymer based on an ethyl cellulose main chain containing azobenzene mesogens (AzoEC) was successfully synthesized. Molecular characterization of the resulting polymers with different degrees of substitution (DS) was performed with proton nuclear magnetic resonance (¹H NMR), Fourier-transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). Thermal stability was investigated by thermogravimetric analysis (TGA). The phase transitions and liquid-crystalline behavior of these polymers were investigated by differential-scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The results indicate that DS has substantial effect on the liquid-crystalline behavior of these polymers. AzoEC with low DS only shows the cholesteric phase similar to ethyl cellulose (EC). However, when DS increases to a specific value, AzoEC begins to show fascinating supramolecular structures. The supramolecular structure of AzoEC with maximum DS consisted of a large-scale ordered lamellar structure formed by EC main chains and a small-scale ordered structure formed by azobenzene mesogens.     

Cyano and Isocyano-substituted Tetraphenylethylene with AIE Behavior and Mechanoresponsive Behavior

Dual-functional materials with AIE behavior and mech-anoresponsive behavior have attracted considerable attention due to their promising applications in mechano...     

Rigidochromism by imide functionalisation of an aminomaleimide fluorophore

Fluorescent dyes that exhibit high solid state quantum yields and sensitivity to the mechanical properties of their local environment are useful for a wide variety of applications, but are limited in chemical diversity. We report a trityl-functionalised maleimide that displays rigidochromic behaviour, becoming highly fluorescent when immobilised in a solid matrix, while displaying negligible fluorescence in solution. Furthermore, the dye''s quantum yield is shown to be sensitive to the nature of the surrounding matrix. Computational studies reveal that this behaviour arises from the precise tuning of inter- and intramolecular noncovalent interactions. This work expands the diversity of molecules exhibiting solid state environment sensitivity, and provides important fundamental insights into their design.

In this study, by systematic tuning of imide substituent a maleimides dye with sensitivity to its solid-state environment was investigated.     

通过控制陷阱分布实现高灵敏度窄带近红外响应有机光探测器

近红外(NIR)窄带光电探测在机器视觉、医学检测、智能通信等领域具有重要应用.本文提出了一种基于激子解离窄化机制的改进型层级器件结构,以实现响应峰值为940 nm的近红外窄带有机光电探测器(OPD).系统研究表明,通过调节器件内部的陷阱态密度分布,可以有效地提高窄带探测器的外量子效率(EQE)峰值.最终,基于双激子耗散...     

Silica Microspheres for SPE and Determination of Fungicides in Water by LC

A new method has been developed for the determination of metalaxyl, myclobutanil, and tebuconazole in environmental water samples with preconcentration by cartridges packed with SiO₂ microspheres prior to LC. Several parameters such as the volume and composition of eluent, sample flow rate, sample pH, and sample volume were optimized. Under the optimal conditions, excellent detection limits (S/N = 3) and precision (RSD, n = 6) were 0.02 ng mL^?1, 1.3% for metalaxyl, 0.02 ng mL^?1, and 2.4% for myclobutanil and 0.08 ng mL^?1 and 4.3% for tebuconazole, respectively. The method was applied to the analysis of real-water samples, and satisfactory results were obtained. The average spiked recoveries were in the range of 86.3–97.5%. These results indicate that SiO₂ microspheres have great potential to be used as a novel solid phase extraction adsorbent that could have wide applications in the environmental field.     

Carboxymethylchitosan covalently modified capillary column for open tubular capillary electrochromatography of basic proteins and opium alkaloids

A novel open tubular (OT) column covalently modified with hydrophilic polysaccharide, carboxymethylchitosan (CMC) as stationary phase has been developed, and employed for the separations of basic proteins and opium alkaloids by capillary electrochromatography (CEC). With the procedures including the silanization of 3-aminopropyltrimethoxysilane (APTS) and the combination of glutaraldehyde with amino-silylated silica surface and CMC, CMC was covalently bonded on the capillary inner wall and exhibited a remarkable tolerance and chemical stability against 0.1 mol/L HCl, 0.1 mol/L NaOH or some organic solvents. By varying the pH values of running buffer, a cathodic or anodic EOF could be gained in CMC modified column. With anodic EOF mode (pH<4.3), favorable separations of basic proteins (trypsin, ribonuclease A, lysozyme and cytochrome C) were successfully achieved with high column efficiencies ranging from 97,000 to 182,000 plates/m, and the undesired adsorptions of basic proteins on the inter-wall of capillary could be avoided. Good repeatability was gained with RSD of the migration time less than 1.3% for run-to-run (n=5) and less than 3.2% for day-to-day (n=3), RSD of peak area was less than 5.6% for run-to-run (n=5) and less than 8.8% for day-to-day (n=3). With cathodic EOF mode (pH>4.3), four opium alkaloids were also baseline separated in phosphate buffer (50 mmol/L, pH 6.0) with column efficiencies ranging from 92,000 to 132,000 plates/m. CMC-bonded OT capillary column might be used as an alternative medium for the further analysis of basic proteins and alkaline analytes.     

Preconcentration sensitive determination of pyrethroid insecticides in environmental water samples with solid phase extraction with SiO2 microspheres cartridge prior to high performance liquid chromatography

Present study developed a new method for the sensitive determination of pyrethroid insecticides with solid phase extraction in combination with high performance liquid chromatography and UV detector. SiO₂ microspheres, a new SiO₂ based material, was investigated for the enrichment ability and applicability as the solid phase extraction sorbent. Four pyrethroid pesticides such as fenpropathrin, cyhalothrin, fenvalevate and biphenthrin were used as the target analytes. Parameters that maybe influence the extraction efficiency such as the eluent type and its volume, sample flow rate, sample pH, and the sample volume were optimized in detail, and the optimal conditions were as followed: sample volume, 100 mL; concentration of methanol, 30%; acetone volume, 5 mL; sample flow rate, 4.2 mL min⁻¹; sample pH, 7. The experimental results indicated that there was good linearity in the concentration range of 0.1–50 μg L⁻¹ except biphenthrin in the range of 0.05–25 μg L⁻¹. The detection limits for fenpropathrin, cyhalothrin, fenvalevate and biphenthrin were in the range of 0.02–0.08 μg L⁻¹. The intra-day and day to day precisions (RSDs, n = 6) were in the ranges of 2.6–4.4% and 5.3–7.2%, respectively. The method was validated with five real environmental water samples, and all these results proved that proposed method could be used as a good alternative for the routine analysis for such pollutants in environmental samples.     

Composition determination of binary polymer mixtures by size exclusion chromatography with light scattering detection

<正>Base on the principle of absolute quantification of size exclusion chromatography(SEC),a light scattering(LS) detector coupled with a concentration detector(refractive index detector) is utilized to determine the compositions of complicated binary mixtures.A theoretical analysis predicts that the response factors for both LS and RI detectors are linear functions with the composition of any specified polymer mixtures in the binary polymer mixtures.Two pairs of complicated binary mixtures were used to test the theory mentioned in the present paper,and the experimental results show an excellent accordance with the theory.