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81.
A number of [2, 1-b] fused phosphono substituted-thioxo-pyrans 7,10,13 and 18 have been regioselectively synthesised from the reaction of the corresponding α-methylene carbonyl compound with phosphenato-substituted 1,3-dithietane 1. Conversely, 2-thiohydantoin 14 reacts with 1 to afford the respective 4-substituted derivative 15. 相似文献
82.
《合成通讯》2013,43(10):1615-1624
ABSTRACT Sitaxsentan sodium (1, TBC11251Na) is an ETA selective endothelin antagonist under clinical development for pulmonary arterial hypertension and congestive heart failure. Second generation compounds, as exemplified by TBC2576 (2) are currently under development in our laboratories. To rapidly access analogs of 1 and 2, a route was developed for the selective alkylation or acylation of the corresponding di- or trianions derived from these two highly functionalized compounds. We report here on this straightforward, yet effective, procedure consisting of treating the di- or trianions with an excess amount of electrophiles, followed by a rapid quench. In this manner, selective alkylation or acylation of 1 and 2 was achieved with satisfactory yields. 相似文献
83.
Hou-Jen Tsai Shyi-Chen Wu 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):191-204
Abstract Treatment of ethyl oxalyl chloride or methyl oxalyl chloride with lithium diisopropyl(carboethoxyfluoromethyl)phosphonate[(i-PrO)2P(O)CFCO2Et]?Li+ 2 followed by in siru nucle-ophilic addition with methylmagnesium iodide or vinyl magnesium bromide affords with exclusive E-stereoselectivity formation of diethyl-2-fluoro-3-methyl fumarate (CH3)(C02Et)C[dbnd]CFCO2Et 4 or 75% of the E-isomer of a-fluoro-P-vinyl-a,P-unsaturated diester (E,Z)-(CH2[dbnd]CH)(CO2C2H5)C[dbnd]CFCO2Et 5, respectively. However, direct reaction of ethyl pyruvate with 2 gives the fluoro-olefin (CH3)(CO2Et)C[dbnd]CFCO2Et 4 with 79% E-stere-oselectivity. The E/Zratio of (CH2[dbnd]CH)(CO2Et)C[dbnd]CFCO2Et 5 depends on the HMFT or DMPU cosolvents present in the reaction mixture. 相似文献
84.
85.
Jeffrey J. Sweterlitsch Perminus Mungara Roger W. Jones Jay-lin Jane 《International Journal of Polymer Analysis and Characterization》2013,18(6):464-468
Soy protein–based polymers offer promising performance properties, but their characteristics are sensitively dependent on production conditions, so on-line monitoring could help provide the needed control during production. Mid-infrared spectroscopy combined with partial least squares offer the needed analysis, but the opacity of many materials in the mid-infrared range limits its conventional application. Transient infrared spectroscopy is a method of acquiring mid-infrared spectra from moving streams in real time that avoids the opacity problem. We apply transient infrared spectroscopy to a polymer of soy protein and polyisoprene-graft-maleic anhydride–modified natural rubber during its compounding extrusion to measure tensile strength and Young's modulus. 相似文献
86.
《Green Chemistry Letters and Reviews》2013,6(1):91-95
Abstract Morpholinium bisulfate [morH][HSO4] found to be highly inexpensive, efficient, and reusable catalyst to promote the acylation of phenols, thiols, alcohols, and amines in presence of acetic anhydride under solvent-free condition with excellent yields by stirring at room temperature. Present methodology deals with remarkable features of mild reaction condition, high yielding, shorter reaction time, easy workup, and more importantly, environmentally benign. 相似文献
87.
《Green Chemistry Letters and Reviews》2013,6(4):335-339
Abstract Hydrotalcite containing magnesium and aluminium (Mg–Al HT) with a molar ratio of Mg(II)/Al(III) = 2.5 has been prepared by a co-precipitation method using the effluent of a Friedel–Crafts acylation reaction. The HT was calcined at 500°C and reconstructed with deionized water. The synthesized HT was characterized by XRD and FT-IR spectroscopy and was successfully used as a catalyst in the Knoevenagel reaction of aldehydes and active methylene compounds. The catalyst was found to be reusable. 相似文献
88.
A previously developed method based on continuous on-line leaching with artificial gastro-intestinal fluids was used to determine the bio-accessible fraction of As, Cu, Fe, V and Zn in brown and white rice from California by inductively coupled mass spectrometry (ICP-MS). Saliva generally accounted for the largest percentage of total element leached in comparison to gastric and intestinal juices. Arsenic speciation analysis was performed on the saliva and gastric juice leachates using ion exchange chromatography coupled to ICP-MS. The four most toxic species of As (As(III), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA) and As(V)), as well as Cl− in the gastric juice leachate, were successfully separated within 5.5 min using a simple nitric acid gradient. While cooking rice had relatively little effect on total bio-accessibility, a change in species from As(V) and DMA to As(III) was observed for both types of rice. On the other hand, washing the rice with doubly deionized water prior to cooking removed a large percentage of the total bio-accessible fraction of As, Cu, Fe, V and Zn. 相似文献
89.
In general, the reduction of disulfide bonds with tris(2-carboxyethyl)phosphine (TCEP) is performed using off-line operation, which is not only time-consuming but also vulnerable to the spontaneous re-oxidation of thiols during sample preparation and subsequent analysis procedures. To the best of our knowledge, there has been not any case on the on-line reduction for biological disulfides coupled with high performance liquid chromatography (HPLC). In this study, these obstacles are overcome by packing Zn(II)-TCEP complexes into a home-made column. The as-synthesized Zn(II)-TCEP complexes enable efficient reduction of disulfide bonds at pH 3.0. This acidic pH value was compatible with that of the mobile phase for HPLC separation of thiols and disulfides. Therefore, using fluorosurfactant-prepared triangular gold nanoparticles as HPLC postcolumn specific chemiluminescence (CL) reagents for thiols, the feasibility of the established on-line reduction column has been confirmed for the direct identification of both thiols and disulfides by incorporating this reduction column into a single chromatographic separation. Detection limits for these analytes range from 8.3 to 25.4 nM and the linear range in a log–log plot can comprise three orders of magnitude. Finally, the utility of this automated on-line reduction of disulfides-HPLC-CL system has been demonstrated for the reliable determination of thiols and disulfides in human urine and plasma samples. 相似文献
90.
This work presents an automatic system, based on an electronic tongue, for resolution of mixtures of three pesticides. Inhibition detections were performed during the steady state of biosensors response. Three biosensors were built using two enzymes, electric eel (EE), genetically-modified Drosophila melanogaster (B131), and electric eel co-immobilized with drosophila melanogaster (BH). Calibrations curves for paraoxon, dichorlvos, and carbofuran were performed in the ranges 0.4–50.4 µM, 0.01–1.01 µM, 0.01–0.41 µM with LOD of 3.91 × 10?8, 6.30 × 10?11, and 5.84 × 10?10, respectively. An artificial neural network (ANN) was used to model the combined response of three pesticides. A set of 19 mixtures were prepared in order to train the artificial neural network, the modeling was validated with a set of 6 spiked samples of river water. The error and recovery yields were found in consistent with expected values. 相似文献