2,083 research outputs found
Synthesis and characterization of novel ligands and application of their transition metal complexes as catalysts or anticancer agents
No full textIn this Thesis work, we report an innovative approach for the synthesis of 2-bromoacrylic acid and its ester derivatives that are the key intermediates in the synthesis of chiral aryloxypropionic acid an important class of herbicides. The synthesis of the bromo substitued acrylics was carried out via carbonylation of (trimethylsilyl)acetylene using as catalytic system Pd(OCOCH3)2 in combination with CH3SO3H and 2-(6-methyl)(diphenylphosphine)pyridine. When the reaction is carried out in methanol, methyl 2-(trimethylsilyl)acrylate was obtained in good yields with a branched/linear ratio 95/5. On the other hand, hydroxycarbonylation reactions give 2-(trimethylsilyl)acrylic acid with lower conversions and selectivities (ca. 53%, and 93/7 respectively). The effects of phosphine/palladium, acid/palladium, reaction time, temperature, and CO pressure on the substrate conversion and selectivity towards branched isomer have been investigated. Methyl 2,3-dibromo-2-(trimethylsilyl)propanoate is easily prepared by reaction of methyl 2-(trimethylsilyl)acrylate with bromine in dry dichloromethane. Then bromodesylilation of 2-(trimethylsilyl)acrylate in the presence of an excess of base gives 2-bromoacrylic acid in good yield (ca. 90%).
A series of triazole ligands were synthesized by the CuAAC reaction. They were employed as chelating ligands to prepare Ru(II), Pd(II), and Co(II) complexes. Ligands and metal complexes have been characterized by analytical data, ESI-MS and 1H and 13C NMR spectroscopy.
The water soluble sodium 2-(1-((pyridin-2-yl)methyl)-1H-1,2,3-triazol-4-yl)ethyl sulfate ligand
has been employed as ligand in biphasic water/organic solvent catalysis. A preformed ruthenium complex and an iridium system containing this water soluble pyridyl-triazolyl ligand were successfully employed in water/toluene biphasic catalytic hydrogenation of C=C and C=O double bonds. The hydrogenation of styrene, 2-cyclohexene-1-one, m-diisopropenylbenzene, and cinnamaldehyde has been investigated. The water soluble 2-(1-(2-(methylthio)ethyl)-1H-1,2,3-triazol-4-yl)ethanol ligand in combination with [RhCl(COD)]2 gives a system displaying good activity in olefin hydroformylation.
The above water soluble [RuCl(η6-p-cymene)(sulphated ligand)] complex has been tested in vitro against several human cancer cell lines (A375, A431, BxPC3, A549 and HCT-15.) derived from solid tumors by the MTT test. Preliminary results indicate that the ruthenium complex is less cytotoxic than cisplatin but has a potential as antimetastatic agent
The intriguing methoxycarbonylation of trimethylsilylacetylene in the presence of Drent's catalytic system
No full textThe alkoxycarbonylation of trimethylsilylacetylene has been studied in order to develop an atom economic sustainable synthesis of 2-(trimethylsilyl)acrylates, a family of valuable intermediates. Pd(OAc)2 in combination with CH3SO3H and diphenyl-(pyridin-2-yl)phosphine or diphenyl-(6-methyl-pyridin-2-yl)phosphine is an active catalyst for the reaction affording mixtures of the sought 2-(trimethylsilyl)acrylate and the isomeric 3-(trimethylsilyl)acrylate. The phosphine ligand has a dramatic effect on the reaction. When employing diphenyl-(pyridin-2-yl)phosphine, it is necessary to carry out the reaction at 80°C in order to observe a modest catalytic activity, and the product is an almost equimolecular mixture of the two isomeric esters. On the contrary, when employing diphenyl-(6-methyl-pyridin-2-yl)phosphine, the reaction proceeds under much milder conditions affording with high rate (turnover frequency [TOF] up to 1200 h−1) and selectivity (>95%) of the sought 2-(trimethylsilyl)acrylate. The reaction conditions have been optimized, and the effects of phosphine/palladium, acid/palladium, reaction time, temperature, and CO pressure have been investigated. © 2021 The Authors. Applied Organometallic Chemistry published by John Wiley & Sons Ltd
Synthesis, Characterization and Antibacterial Activity on Dinuclear Schiff-base Macrocyclic Metal Complexes
No full textSchiff-bases and their dinuclear metal complexes have been extensively received special attention because of their wide range of applications including catalysts, medicine crystal engineering, anti-corrosion agent, and biological activities [1]. Dinuclear macrocyclic lead (II) complex, Pb2L1(SCN)4 was synthesized by template condensation of pyridine-2,6-dicarboxaldehyde and 1,2-bis (2-aminoethoxy) ethane in presence of Pb(SCN)2 as the metal source, here L1 is tetra-Schiff-base macrocycle. Transmetallation treatment of Pb2L1(SCN)4 with Co(PF6)2.6H2O produced the new complex, Co2L1(SCN)4 [2]. Reduction of lead (II) complex gave new reduced tetra-Schiff-base macrocyclic ligand, L2[3]. All the metal complexes and ligand were characterized by UV-Visible, FT-IR, 1H NMR spectroscopy. The antibacterial activities against some pathogenic gram positive and gram negative bacteria were studied by cylinder disk diffusion method. The complexes were found to inhibit the growth of bacteria
Biphase hydroformylation catalyzed by rhodium in combination with a water-soluble pyridyl- triazole ligand
No full text[RhCl(COD)]2 in combination with a water soluble sulphonated pyridyl-triazolyl N,N-bidentate ligand
efficiently catalyzes styrene and 1-hexene hydroformylation in water/organic solvent biphasic systems.
The catalyst displays a good activity affording mixtures of linear and branched aldehydes with complete
chemoselectivity. The aqueous catalytic phase may be recycled four times giving complete substrate
conversion by 18 h. Mercury-poisoning experiments and transmission electron microscopy indicate that,
after the first catalytic run, rhodium is present in the aqueous phase in nanoparticle form.[RhCl(COD)]2 in combination with a water soluble sulphonated pyridyl-triazolyl N,N-bidentate ligand efficiently catalyzes styrene and 1-hexene hydroformylation in water/organic solvent biphasic systems. The catalyst displays a good activity affording mixtures of linear and branched aldehydes with complete chemoselectivity. The aqueous catalytic phase may be recycled four times giving complete substrate conversion by 18h. Mercury-poisoning experiments and transmission electron microscopy indicate that, after the first catalytic run, rhodium is present in the aqueous phase in nanoparticle form
Congestion control in Mobile Ad-Hoc networks (MANETs)
No full textThis thesis report is submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Computer Science and Engineering, 2011.Cataloged from PDF version of thesis report.Includes bibliographical references (page 39).Md. Mahbubul AlamTanmoon Taz ShetuB. Computer Science and Engineerin
A water-soluble pyridyl-triazole ligand for aqueous phase palladium catalyzed Suzuki–Miyaura coupling
No full textAn Overview on Wood Waste Valorization as Biopolymers and Biocomposites: Definition, Classification, Production, Properties and Applications
No full textBio-based polymers, obtained from natural biomass, are nowadays considered good candidates for the replacement of traditional fossil-derived plastics. The need for substituting traditional synthetic plastics is mainly driven by many concerns about their detrimental effects on the environment and human health. The most innovative way to produce bioplastics involves the use of raw materials derived from wastes. Raw materials are of vital importance for human and animal health and due to their economic and environmental benefits. Among these, wood waste is gaining popularity as an innovative raw material for biopolymer manufacturing. On the other hand, the use of wastes as a source to produce biopolymers and biocomposites is still under development and the processing methods are currently being studied in order to reach a high reproducibility and thus increase the yield of production. This study therefore aimed to cover the current developments in the classification, manufacturing, performances and fields of application of bio-based polymers, especially focusing on wood waste sources. The work was carried out using both a descriptive and an analytical methodology: first, a description of the state of art as it exists at present was reported, then the available information was analyzed to make a critical evaluation of the results. A second way to employ wood scraps involves their use as bio-reinforcements for composites; therefore, the increase in the mechanical response obtained by the addition of wood waste in different bio-based matrices was explored in this work. Results showed an increase in Young’s modulus up to 9 GPa for wood-reinforced PLA and up to 6 GPa for wood-reinforced PHA
Synthesis of a water‐soluble thio‐triazole ligand for biphase rhodium catalyzed hydroformylation of styrene
No full textAn environmentally safe water-soluble new ligand (2-(1-(2-(methylthio)ethyl)-1H-1,2,3-triazol-4-yl)ethanol) (ligand 1) has
been synthesized by the click reaction between (2-azidoethyl)(methyl)sulfane and 3-butyn-1-ol. The structure of the novel
ligand was confirmed by NMR spectroscopy. In situ combination of ligand 1 with [Rh(COD)Cl]2 and [Rh (CO)2(acac)] (Rh:
ligand = 1: 4) successfully employed for the biphasic catalytic hydroformylation of styrene. The formation of branched
2-phenylpropanol was confirmed by gas chromatogphic analysis. The recycled catalytic aqueous phase can be used
three runs with remarkable catalytic efficiency
Microwave-Assisted Extraction of Cellulose from Waste Olive Wood Powder Using Deep Eutectic Solvents
No full textMicrowave-assisted extraction (MAE) is a very effective and sustainable method for extracting cellulose
from lignocellulosic materials due to the substantial reduction in the process time and amounts of
solvents required for each process. Deep eutectic solvents (DES) are used for cellulose extraction due to
their environmental friendliness and high extraction yields. This work explores the possibility to use
microwave-synthesized DES to extract cellulose from olive wood powder (OWP) waste. The conventional
process (CP) requires the use of high amounts of chemicals and long times for quantitative extractions.
Three techniques for the cellulose extraction were compared: a standard procedure by Technical
Association of the Pulp and Paper Industry (TAPPI), CP, and MAE utilizing DES to evaluate the
effectiveness of these techniques. Results showed that the TAPPI method yielded 55.0 wt% cellulose,
whereas the CP method yielded 50.6 wt% cellulose. The optimum conditions for MAE using choline
chloride-lactic acid (ChCl:LA, 1:4) and choline chloride-citric acid (ChCl:CA:H2O, 1:1:6) were found to be
20-min irradiation time at 130 oC to obtain cellulose yields of 47.8 wt% and 45.6 wt%, respectively,
showing that both DES were effective for cellulose extraction from OWP. The comparison between all
procedures showed that MAE required shorter times and smaller quantities of chemicals, making it an
eco-friendlier option. The extracted cellulose was characterized by thermogravimetric analysis (TGA),
Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning electron
microscopy (SEM). Results suggested that MAE with DES is a promising approach, with prospective
applications in the packaging, textiles, and paper industries
The alkoxycarbonylation of protected propargyl alcohols
No full textPalladium-catalyzed alkoxycarbonylation of the C≡C triple bond of propargyl alcohol is a sustainable synthetic
approach to 2-(hydroxymethyl)acrylates, a family of valuable intermediates. The developed synthetic protocol
includes protection of the alcoholic function of the alkyne before its carbonylation in the presence of Drent’s
catalytic system. Protection step effectively extends the catalyst life hence enhancing the practical applicability
of the reaction. The effectiveness of some different protecting groups (benzyl, acetyl and trimethylsilyl) has been
assessed and the influence of the reaction parameters investigated.Palladium-catalyzed alkoxycarbonylation of the C≡C triple bond of propargyl alcohol is a sustainable synthetic approach to 2-(hydroxymethyl)acrylates, a family of valuable intermediates. The developed synthetic protocol includes protection of the alcoholic function of the alkyne before its carbonylation in the presence of Drent's catalytic system. Protection step effectively extends the catalyst life hence enhancing the practical applicability of the reaction. The effectiveness of some different protecting groups (benzyl, acetyl and trimethylsilyl) has been assessed and the influence of the reaction parameters investigated
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