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991.
992.
M. Abdallah I. Zaafarany S.O. Al-Karanee A.A. Abd El-Fattah 《Arabian Journal of Chemistry》2012,5(2):225-234
The corrosion behavior of aluminum and three aluminum–silicon alloys in different concentrations of HCl solutions and its inhibition by antihypertensive drugs was studied using potentiostatic polarization measurements. As the acid concentration increases, the rate of corrosion increases. Aluminum is less susceptible to corrosion than any of Al–Si alloys. The inhibition efficiency of the drug compounds increases with their concentration up to a critical value. At higher additive concentrations the inhibition efficiency starts to decrease. The inhibitive action of these compounds is due to their formation of insoluble complex adsorbed on the metal surface. The adsorption follows Langmuir adsorption isotherms. It was found that the drugs compounds provide protection to Al and Al–Si alloys against pitting corrosion by shifting the pitting potential to more positive direction until critical drug concentrations (250 ppm). After this critical concentration the inhibition against to pitting corrosion starts to decrease. 相似文献
993.
Elizabeth C. Frye Dr. Cornelius J. O' Connor David G. Twigg Bryony Elbert Luca Laraia Dr. David G. Hulcoop Prof. Ashok R. Venkitaraman Dr. David R. Spring 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(28):8774-8779
The Hiyama cross‐coupling reaction is a powerful method for carbon–carbon bond formation. To date, the substrate scope of this reaction has predominantly been limited to sp2–sp2 coupling reactions. Herein, the palladium‐catalysed Hiyama type cross‐coupling of vinyldisiloxanes with benzylic and allylic bromides, chlorides, tosylates and mesylates is reported. A wide variety of functional groups were tolerated, and the synthetic utility of the methodology was exemplified through the efficient total synthesis of the cytotoxic natural product bussealin A. In addition, the antiproliferative ability of bussealin A was evaluated in two cancer‐cell lines. 相似文献
994.
Prakash T. Parvatkar Dr. Perunninakulath S. Parameswaran Prof. Dr. Santosh G. Tilve 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(18):5460-5489
Heterocyclic scaffolds represent the key structural subunits of many biologically active compounds. Over the last few years iodine‐mediated reactions have been extensively studied due to their low cost and eco‐friendliness. This Review covers advances in the field of iodine‐mediated synthesis of heterocyclic compounds since 2006, especially with an emphasis on mechanisms of ring formation. In this article, syntheses of different heterocycles are classified based on the manipulation of functional groups. 相似文献
995.
Dr. Shamil Nizamov Dr. Katrin I. Willig Dipl.‐Chem. Maksim V. Sednev Dr. Vladimir N. Belov Prof. Stefan W. Hell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(51):16339-16348
Photostable and bright fluorescent dyes with large Stokes shifts are widely used as markers in far‐field optical microscopy, but the variety of useful dyes is limited. The present study introduces new 3‐heteroaryl coumarins decorated with a primary phosphate group (OP(O)(OH)2) attached to C‐4 in 2,2,4‐trimethyl‐1,2‐dihydroquinoline fragment fused with the coumarin fluorophore. The general synthetic route is based on the Suzuki reaction of 3‐bromocoumarines with hetarylboronic acids followed by oxidation of the methyl group at the C?C bond with SeO2 (to an aldehyde), reduction with NaBH4 (to an alcohol), and conversion into a primary phosphate. The 4 position in the coumarin system may be unsubstituted or bear a methyl group. Phosphorylated coumarins were found to have high fluorescence quantum yields in the free state and after conjugation with proteins (in aqueous buffers). In super‐resolution light microscopy with stimulated emission depletion (STED), the new coumarin dyes provide an optical resolution of 40–60 nm with a low background signal. Due to their large Stokes shifts and high photostability, phosphorylated coumarins enable to combine multilabel imaging (using one detector and several excitation sources) with diffraction unlimited optical resolution. 相似文献
996.
997.
998.
Ali Sarafraz-Yazdi Amirhassan AmiriGholamhossein Rounaghi Hossein Eshtiagh-Hosseini 《Analytica chimica acta》2012
In this study, poly(ethylene glycol) (PEG) grafted multi-walled carbon nanotubes (PEG-g-MWCNTs) were synthesized by the covalent functionalization of MWCNTs with hydroxyl-terminated PEG chains. PEG-g-MWCNTs was used as a novel stationary phase to prepare the sol–gel solid-phase microextraction (SPME) fiber in combination with gas chromatography–flame ionization detector (GC–FID) for the determination of ibuprofen, naproxen and diclofenac in real water samples. 相似文献
999.
The paper presents a novel method for the flotation separation of Bi3+ using microcrystalline adsorption system prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of KI and dodecyl trimethyl ammonium bromide (DTMAB), various salts and acidity etc. on the flotation yield of Bi3+ have been investigated to select the optimum experimental conditions. The possible flotation separation mechanism of Bi3+ was discussed. The results showed that under the optimum conditions, dodecyl trimethyl ammonium bromide cation (DTMAB+ ) reacted with I? to produce themicrocrystalline matter (Ms‐M) of (DTMAB+·I?), the water‐insoluble ternary association complex of (DTMAB)3[BiI6] which produced by Bi3+ and I?, DTMAB+ was quantificationally adsorbed on the surface of Ms‐M of (DTMAB+·I?) and was floated above water phase, the liquid‐solid phases were formed with clear interface. In this condition, K+, Na+, Ca2+, Mg2+, Co2+, Ni2+, Mn2+, Zn2+, Fe2+ and Al3+ could not be floated. Therefore, Bi3+ was separated completely from the above metal ions. A new method for flotation separation and determination of bismuth using microcrystalline adsorption system was established. The proposed method has been successfully applied to the determination of Bi3+ in bismuthiferous drug samples, and the results agreed well with those obtained by pharmacopoeia method. The recoveries were 94.1%~106.8%, and the RSD was 1.5%~2.3%. 相似文献
1000.
A very efficient and mild procedure for preparation of silyl ethers from benzylic, allylic, propargilic alcohols, phenols, naphtoles and some of phenolic drugs with trimethylsilylchloride (TMSCl), triethylsilylchloride (TESCl) and t‐buthyldimethylsilyl chloride (TDSCl) ethers in the presence of Fe(HSO4)3/Et3N in room temperature in excellent yields is reported. This procedure also allows the excellent selectivity for silylation of alcohols and phenols. 相似文献