Tài liệu miễn phí Hoá học
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Synthetic access to some new benzothiazole-based 1,3,4-thiadiazole and 1,3-thiazole derivatives
1-(Benzothiazol-2-yl)-3-phenylthiourea 2 was prepared and treated with hydrazonoyl chlorides 3a–e to yield the corresponding 5-(benzothiazol-2-ylimino)-1,3,4-thiadiazole derivatives 6a–e, respectively. Reaction of the thiourea derivative 2 with ethyl 2-chloro-3-oxobutanoate 9 afforded the corresponding 2-(benzothiazol-2-ylimino)thiazole5-carboxylate derivative 11. The newly synthesized heterocyclic derivatives were confirmed from their elemental and spectral analyses.
4/5/2023 5:34:16 AM +00:00
Immobilization of laccase onto a porous nanocomposite: application for textile dye degradation
Decolorization of Reactive Red 3 from aqueous solution by laccase immobilized on the nanocomposite was studied in different conditions (pH, temperature, dye concentration, and reaction time) to investigate the decolorization activity with repeated use and storage. The results indicated that more than 77% of the activity of laccase immobilized systems was retained at the end of 10 cycles. The final decolorization capacity of the immobilized laccase was significantly higher (65%) than that of free laccase (33%) in the chosen optimized conditions (pH 5, 20 ◦ C, 0.05 mg/mL laccase concentration, and 90 min).
4/5/2023 5:34:06 AM +00:00
Synthesis of novel chiral bisoxazoline ligands with a norbornadiene backbone: use in the copper-catalyzed enantioselective Henry reaction
Novel chiral bisoxazoline ligands based on norbornadiene were synthesized and used for the asymmetric Henry reaction. Various aromatic aldehydes were converted into chiral β -nitro alcohols with high yields and moderate to acceptable enantioselectivities under the optimized reaction conditions. The short and efficient synthesis of bisoxazoline ligands, the flexibility in ligand design, coordination to a large number of transition metals, and excellent enantioselectivity in many reactions make these ligands indispensable in asymmetric catalysis.
4/5/2023 5:33:59 AM +00:00
Wittig–Horner reagents: powerful tools in the synthesis of 5-and 6-heterocyclic compounds; shedding light on their application in pharmaceutical chemistry
This paper reviews literature over 25 years’ activity on phosphoryl carbanion reagents and shows that these compounds are powerful tools in organic chemistry. The main target of this review is to outline some of the reactive peculiarities that make this class of compounds powerful tools in the synthesis of 5- and 6-heterocyclic compounds and/or substituted heterocycle phosphor esters. The importance of these latter compounds in pharmacology is also discussed.
4/5/2023 5:33:51 AM +00:00
Synthetic approaches towards the synthesis of beta-blockers (betaxolol, metoprolol, sotalol, and timolol)
Numerous efficient synthetic methodologies have been elaborated for the synthesis of β -blockers since the introduction of propranolol (a beta-blocker) in 1968. In this review, focus is placed on the more concise asymmetric and bioenzymatic synthetic approaches attempted towards the synthesis of beta-blockers (betaxolol, metoprolol, sotalol, and timolol).
4/5/2023 5:33:42 AM +00:00
A convenient route for the synthesis of new thiadiazoles
The present work describes the preparation of new thiadiazoles through a simple intramolecular reaction of mono- and bis-hydrazonoyl halides with methyl hydrogen phenyl carbonimidodithioate or methyl-2-arylidene hydrazinecarbodithioate. The synthetic method involves nucleophilic substitution followed by intramolecular cyclization reactions mediated by evolution of methanethiol. The structures of the title compounds were elucidated by elemental analyses, and FTIR, MS and NMR spectra.
4/5/2023 5:33:36 AM +00:00
Purification and characterization of mitochondrial thioredoxin reductase enzyme from rainbow trout (Oncorhynchus mykiss) liver and investigation of the in vitro effects of some metal ions on the enzyme
Thioredoxin reductase (E.C 1.6.4.5.; TrxR) is an enzyme belonging to the flavoprotein family of pyridine nucleotide-disulfide oxidoreductases. In this study, mitochondrial TrxR enzyme was purified from rainbow trout mitochondria. Thanks to the 2 consecutive procedures (preparation of homogenate and 2’,5’-ADP Sepharose 4B affinity chromatography), the enzyme, having the specific activity of 11.9 EU mg protein-1, was purified with a yield of 2.38% and 672-fold. The purity of the enzyme was monitored and the molecular weight of its subunits was calculated as 70 kDa by SDS-PAGE. The native molecular mass of the enzyme was found to be approximately 151 kDa by gel filtration chromatography.
4/5/2023 5:33:29 AM +00:00
Liquid state 15N NMR studies of 15N isotope labeled phthalocyanines
15N labeled soluble metallo- and metal-free phthalocyanines are described for the first time. The complexes were synthesized starting from phthalic anhydride derivatives using 98% 15N enriched urea. The effects of the substitution pattern, aggregation, and coordinated metal on 15 N chemical shifts in liquid state NMR were studied.
4/5/2023 5:33:23 AM +00:00
Adsorptive features of polyacrylamide–aluminosilicate composites for methylene blue
Polyacrylamide–montmorillonite (PAAm-Mt) and polyacrylamide–clinoptilolite (PAAm-Z) composites were prepared by cross-linked polymerization of acrylamide in dispersions of Mt and Z. The composites were characterized by FT-IR, SEM, XRD, CEC, and PZC analysis. The adsorptive features of PAAm-Mt and PAAm-Z for methylene blue (MB) were investigated by their relevance to initial dye concentration, temperature, contact time, PZC, and pH.
4/5/2023 5:33:15 AM +00:00
Systematic optimization of chemical deposition conditions for synthesis of vanadium(V) oxide xerogels
We performed the optimization of conditions in chemical bath deposition using the design of experimental methodology. Factorial design (23) was used for finding the optimal conditions of preparing vanadium(V) oxide xerogel thin films with better electrochromic properties suitable for electrochemical applications. The thin films were prepared by acidification of NH4 VO3 aqueous solution with chemical bath deposition.
4/5/2023 5:33:08 AM +00:00
Voltammetric determination of famotidine on a disposable pencil graphite electrode
The present paper describes the use of a disposable pencil graphite electrode (PGE) for the voltammetric determination of famotidine. Cyclic voltammetric studies using different supporting electrolytes emphasized an irreversible oxidation of famotidine on the PGE. The electrode process is diffusion-controlled and pH-dependent. Differential pulse voltammetry (DPV) in phosphate buffer solution of pH 6.81 was employed for famotidine’s quantitative determination.
4/5/2023 5:33:02 AM +00:00
Durability of carbon/conducting polymer composite supported Pt catalysts prepared by supercritical carbon dioxide deposition
The prepared materials were characterized by using BET, TGA, XRD, and TEM techniques. Cyclic voltammetry was used in order to determine the electrocatalytic activity of the prepared catalyst for hydrogen oxidation and oxygen reduction reactions that occur in proton exchange membrane fuel cells (PEMFCs). The Pt loading obtained over the composite material was around 10%. TEM results showed highly dispersed and small nanoparticles over the composite material by using scCO2 deposition. Pt dissolution/agglomeration and carbon corrosion tests were applied to the composite supported Pt catalyst in order to determine its durability.
4/5/2023 5:32:55 AM +00:00
Square wave voltammetric determination of valproic acid in pharmaceutical Preparations
The electrochemical behavior of valproic acid (VAL) was investigated using square wave voltammetry, cyclic voltammetry, and sampled direct current polarography and a new square wave voltammetric method was developed for determination of VAL in pharmaceutical preparations. Recovery studies for the accuracy of the method were performed by adding known amounts of VAL and it was found to be 109.67 ± 4.85%. The proposed method was successfully applied to pharmaceutical products on the market.
4/5/2023 5:32:47 AM +00:00
Comparative study for the separation, preconcentration, and determination of copper and cadmium in real samples by using two different ligands
The metal complexes are retained on resin at pH 6.0 and eluted with 1.0 mol L −1 HCl in acetone in both methods. After the optimum conditions were determined, the methods were applied to seawater, stream water, rice, lentil, tea, tobacco, bulgur, chickpea, wheat, red pepper, black pepper, peppermint, and dried eggplant samples in order to determine the levels of copper and cadmium.
4/5/2023 5:32:40 AM +00:00
Synthesis and structural properties of N -3,4-(dichlorophenyl)-3-oxo-3- phenyl-2-(phenylcarbonyl)propanamide and its Cu(II) complex
The compounds were characterized by analytical and spectral methods. In addition, X-ray diffraction was performed to characterize and obtain detailed information about the structure of 3. The fully optimized geometries of compounds 3 and 4 were calculated at different basis sets by using the Gaussian09 (G09) software to investigate their 3D geometries and electronic structures. Comparisons between the calculated and experimental data including molecular structures, fundamental vibrational modes, and electronic properties were made. The comparisons showed that the theoretical data were compatible with the corresponding experimental values of compounds 3 and 4.
4/5/2023 5:32:26 AM +00:00
Synthesis and evaluation of a novel N–P-containing oil-based fire-retardant plasticizer for poly(vinyl chloride)
A novel N–P-containing soybean-oil-based fire-retardant plasticizer was synthesized using soybean oil methyl ester, 9,10-dihydro-9-oxa-phosphaphenanthrene-10-oxide (DOPO), and tris(2-hydroxyethyl) isocyanurate (THEIC). The structure was verified by Fourier transform infrared (FTIR) spectrometry and nuclear magnetic resonance (NMR) spectroscopy. The blends were characterized by thermogravimetric analysis (TGA), FTIR spectrometry, scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA).
4/5/2023 5:32:11 AM +00:00
Density functional study of the structure and water adsorption activity of an Al30O30 star-shaped alumina nanocage
Molecular and electronic structures of a novel Al30O30 star-shaped alumina nanocage (SANC) were studied using the recently developed CAM-B3LYP density functional method. Comparison of the stretching vibrational modes of this compound with the corresponding modes related to an Al20O30 perfect cage and Al50O75 tubular alumina nanomaterials showed a shift to lower frequencies, while the bending modes moved to higher frequencies. The highest occupied molecular orbital (HOMO) of the SANC had 65% nonbonding character, whereas the lowest unoccupied molecular orbital (LUMO) was 72% antibonding.
4/5/2023 5:31:56 AM +00:00
Synthesis and photochromism of new asymmetrical diarylethenes with a variable heteroaryl ring and a quinoline unit
Three new asymmetrical photochromic diarylethenes containing a variable heteroaryl ring and a quinoline unit were synthesized and their structures were determined by single-crystal X-ray diffraction analysis. Their properties, including photochromism, acidichromism, and fluorescence, were investigated systematically. For these diarylethenes, the one with an indole moiety had the largest absorption maximum, cyclization quantum yield, photoconversion ratio, emission peak, and fluorescent modulation efficiency.
4/5/2023 5:31:46 AM +00:00
Characterization and photocatalytic properties of TiO2/chitosan nanocomposites synthesized by hydrothermal process
Complete photodegradation of MG was successfully achieved with the aid of the nanocomposites. The optimum photocatalytic degradation conditions, irradiation time, irradiation power, and amount of catalyst were studied. Photocatalytic activity of the synthesized nanocomposites in terms of degradation of MG was compared with that of undoped TiO2 (synthesized by our team) and chitosan under normal conditions. It was concluded that the synthesized nanocomposites had better photocatalytic activity. The best result (100% degradation) was obtained with amount of nTC of 0.25 g and irradiation time of 120 min.
4/5/2023 5:31:38 AM +00:00
Synthetic protocols on 6H-benzo[c]chromen-6-ones: a review
6H-Benzo[c]chromen-6-ones serve as core structures of secondary metabolites and are of considerable pharmacological importance. Natural sources produce limited quantities, hence the need for synthetic procedures for 6H-benzo[c]chromen-6-ones, which are herein reviewed. The literature describes protocols such as the Suzuki coupling reactions for the synthesis of biaryl, which then undergoes lactonization, reactions of 3-formylcoumarin (chromenones) with 1,3-bis(silylenol ethers), radical mediated cyclization of arylbenzoates, metal or base catalyzed cyclization of phenyl2-halobenzoates and 2-halobenzyloxyphenols, and benzoic acid coupling with benzoquinone using electrophilic metalbased catalyst.
4/5/2023 5:31:31 AM +00:00
The synthesis, characterization, and catalytic properties of (κ2 − C,N)-palladacycles with N-heterocyclic carbene-based ancillary ligands
Novel five-membered (κ2−C,N) -palladacyclic complexes were prepared from the reaction of the corresponding acetate-bridged palladacycle dimer with N-heterocyclic carbene (NHC) ligands in high yields. Palladacyclic complexes (3) were fully characterized by elemental analysis and 1H and 13C NMR spectroscopy. Palladacyclic complexes were tested as catalyst for the C–C bond forming reaction. These complexes were found to be efficient catalysts for the Suzuki–Miyaura reaction of aryl bromides.
4/5/2023 5:31:25 AM +00:00
Resorcinarene-mono-benzimidazolium salts as NHC ligands for Suzuki–Miyaura cross-couplings catalysts
Two mono-benzimidazolium salts of resorcinarene have been prepared and used as ligands in Suzuki–Miyaura cross-coupling reactions. They have been fully characterized by 1H and 13C NMR, MALDI, and FT-IR spectroscopic methods, and their structures were confirmed by X-ray diffraction analysis. These two new resorcinarene-based monobenzimidazolium salts showed good catalytic activity for coupling reactions in DMF. The highest conversion was achieved for arylation of 4-bromotoluene using the resorcinarenyl mono-dimethylbenzimidazolium salt.
4/5/2023 5:31:19 AM +00:00
Substituted 2-(2’-pyridyl)benzimidazole palladium(II) complexes as an efficient catalytic system for Suzuki–Miyaura cross-coupling reactions
The incorporation of N -coordinated benzimidazole complexes of palladium gave high catalytic activity in the Suzuki–Miyaura coupling of aryl halides substrates. After determining the best active catalyst as 5A1, bearing the mesityl substituent on the benzimidazole ring with the Pd(II) ion, optimization studies were carried out via changing the substrate, base, time, atmosphere, and the effect of water. The DMF:H2O (4/1) and Cs2CO3 as base were found to be critical for the efficiency of the reaction yield (100%).
4/5/2023 5:31:12 AM +00:00
New Pd(II) and Pt(II)-diaminophosphine complexes bearing cyclohexyl or isopropyl moiety: use of Pd(II) complexes as precatalyst in Mizoroki–Heck and Suzuki–Miyaura cross-coupling reactions
Two new diaminophosphine ligands, N ,N ’-bis(dicyclohexylphosphino)-2-(aminomethyl)aniline (1) and N ,N ’-bis(diisopropylphosphino)-2-(aminomethyl)aniline (2) were synthesized by the reaction of 2-(aminomethyl)aniline with two equivalents of Cy2PCl or (iPr)2PCl, respectively. Organophosphorus ligands have been extensively used in organometallic and inorganic chemistry, 1 and are mainly important in homogeneous catalysis. 2 In particular, diaminophosphines in which the two phosphorus atoms are connected to a carbon chain and have the same substituents on each phosphorus atom, such as bis(diphenylphosphino)ethane (dppe) and bis(diphenylphosphino)methane (dppm) have been widely studied.
4/5/2023 5:31:06 AM +00:00
Synthesis, characterization, and microwave-assisted catalytic activity in Heck, Suzuki, Sonogashira, and Buchwald–Hartwig cross-coupling reactions of novel benzimidazole salts bearing N-phthalimidoethyl and benzyl moieties
The novel benzimidazole salts (1–5), Pd(OAc)2, Cs2CO3, PEG, and Cu nanoparticles catalyzed, in high yield, the Sonogashira coupling reaction promoted by microwave irradiation in 10 min. The same benzimidazole salts (1–5), Pd(OAc)2, Cs2CO3, and TBAB catalyzed, in moderate or low yield, the Buchwald–Hartwig reaction assisted by microwave irradiation in 60 min. The efficiency of the catalyst system in these four reactions was discussed as well as the electron-releasing and withdrawing substituent effects on the benzimidazole ligands.
4/5/2023 5:30:55 AM +00:00
Synthesis of new thiol-derivatized aminophosphines and their catalytic activities in C–C coupling reactions
A series of new aminophosphines [Ph 2PHN-C6 H4 -R, where R = o-SH (4a), m-SH (4b) or p-SH (4c)] were readily synthesized from cheap starting materials by the phosphorylation reaction of o, m, and p-aminothiophenols with Ph2PCl in the presence of triethyl amine. The new compounds were characterized by NMR and IR spectroscopy and microanalysis. In addition, aminophosphine ligands–palladium systems were investigated as precatalysts in C–C coupling reactions. Compounds 4b and 4c were proved to be excellent catalysts for Suzuki and Heck cross-coupling reactions.
4/5/2023 5:30:48 AM +00:00
Monodisperse palladium nanoparticles supported on chemically derived graphene: highly active and reusable nanocatalysts for Suzuki–Miyaura cross-coupling reactions
Addressed herein is the catalysis of monodisperse palladium nanoparticles (NPs) supported on chemically derived graphene (CDG) for the Suzuki–Miyaura cross-coupling of phenylboronic acid and various aryl halides. Monodisperse Pd NPs were synthesized by the solution phase reduction of palladium(II) acetylacetonate with morpholine borane complex in oleylamine and deposited on CDG via the liquid phase self-assembly method. Colloidal Pd NPs and CDG-Pd catalyst were characterized by TEM, XRD, SEM, and ICP-MS analyses.
4/5/2023 5:30:40 AM +00:00
Efficient C–C cross-coupling reactions by (isatin)-Schiff base functionalized magnetic nanoparticle-supported Cu(II) acetate as a magnetically recoverable catalyst
Copper catalysts were simply fabricated through surface modification of superparamagnetic iron nanoparticles with indoline-2,3-dione(isatin)-Schiff-base and interaction with Cu from low-cost commercially available starting materials. Catalysts were characterized using atomic absorption spectrophotometry, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, vibrating sample magnetometry, UV/Vis spectroscopy, scanning electron microscopy, and transmission electron microscopy.
4/5/2023 5:30:30 AM +00:00
Reactivity of the 2-aryl-6,8-dibromo-2,3-dihydroquinolin-4(1H)-ones in a palladium catalyzed Sonogashira cross-coupling reaction
Pd/C-PPh3–CuI catalyzed Sonogashira cross-coupling of the 2-aryl-6,8-dibromo-2,3-dihydroquinolin-4(1H)-ones with phenyl acetylene or 3-butyn-1-ol afforded the corresponding 8-alkynylated quinolin-4(1H)-one derivatives, exclusively. Double carbo-substitution to afford the 6,8-dialkynyl derivatives was observed when PdCl2(PPh3)2 was used as Pd(0) source. The monoalkynylated derivatives were, in turn, subjected to PdCl2 in acetonitrile under reflux to afford either the corresponding 2,4-diaryl-8-bromopyrrolo[3,2,1-ij]quinolinones or the 8-(4-hydroxybutanoyl)-substituted quinolinone derivatives, exclusively.
4/5/2023 5:30:22 AM +00:00
Palladium-catalyzed ligand-free and efficient Suzuki–Miyaura reaction of N -methyliminodiacetic acid boronates in water
A green and efficient protocol has been developed for the Pd(OAc)2-catalyzed ligand-free Suzuki–Miyaura reaction of N-methyliminodiacetic acid (MIDA) boronates in water. In the presence of Pd(OAc)2 as a catalyst and (i-Pr)2NH as a base, the cross-coupling reactions of aryl bromides with aryl MIDA boronates proceeded smoothly in water without any surfactant, and various functional groups were tolerated under the optimized conditions.
4/5/2023 5:30:15 AM +00:00