1,720,975 research outputs found
Solvent-free direct esterification of acrylic acid with 2-ethylhexyl alcohol using simple Zn(II) catalysts
No full textDirect esterification of acrylic acid with 2-ethylhexyl alcohol was investigated using low toxic and cheap Zn(II) salts as catalysts. An initial screening using Zn(ClO4)2, ZnCl2, Zn(OAc)2 and ZnO disclosed that the most effective was the perchlorate, which was used for the subsequent refining of the study. In optimized conditions (0.5 % mol of polymerization inhibitor, 0.1 % mol of catalyst, 170 °C, 4 h) the product was obtained in 99 % yield. A kinetic model was proposed to quantify the contribution of each chemical reaction of the network, allowing a quantitative comparison of the effect of the inhibitors on the acrylic acid esterification side-reactions
Five-Coordinate Platinum(II) Compounds as Potential Anticancer Agents
No full textFive-coordinate platinum(II) complexes represent a minority compared to the well-known class of square-planar species. However, since the first appearances in the literature, their general properties have attracted much interest. In particular, their potential to act as anticancer agents has been considered, and several studies have demonstrated their effectiveness as pro-drugs. The review traces the progress of these investigations over time and the subsequent refinements in the structures. It also reports their synthesis, general properties, cytotoxic activity and ability to interact with biological macromolecules
1,3-Dioxolane compounds (DOXs) as biobased reaction media
No full textSolvents constitute around 80% of the total volume of chemicals used in fine-chemical processes and contribute significantly to their environmental impact and hazard profile. Thus, there is a strong driving force towards the replacement of traditional fossil-based solvents by alternatives that are more benign in terms of their origin, availability, convenience of synthesis, handling, biodegradability and environmental impact. In the class of polar aprotic solvents, the most successful “green” replacement is γ-valerolactone (GVL). Here, we propose the use of a structurally related compound, 5-methyl-1,3-dioxolane-4-one (LA-H,H), as a reaction medium. It is easily prepared from lactic acid and formaldehyde and satisfies the criteria for a green solvent. It is stable under neutral or basic conditions. Despite the presence of a ketal functionality, it even survives mildly acidic conditions. Evaluation of the Kamlet–Taft and Hansen solvent parameters shows that indeed LA-H,H and GVL are closely similar, suggesting that LA-H,H is an effective new green entry in the class of polar aprotic solvents. We have tested its performance in Pd-catalyzed Heck arylation of methyl acrylate and in the Menschutkin reaction of N-methylimidazole with 1-iodobutane. LA-H,H is also the parent of a whole family of potential solvents easily prepared from two green precursors: α-hydroxy carboxylic acids (lactic, mandelic, and α-hydroxyisobutyric acids) and aldehydes/ketones (formaldehyde, acetaldehyde, and acetone); five such variations were briefly examined. Interestingly, LA-H,H has the unusual property of forming a three-phase system when combined with water and hexane, which may allow technological variations that are not possible with the more normal one- and two-phase systems. As a curiosity, a rare four-phase system is achievable combining LA-H,H with octane, water and perfluorodecaline
Homogeneous Catalysis and Heterogeneous Recycling: A Simple Zn(II) Catalyst for Green Fatty Acid Esterification
No full textThis work describes the use of simple zinc(II) salts (ZnCl2, ZnCO3, Zn(OAc)2, ZnO, Zn(ClO4)2, Zn(TfO)2, and Zn(BF4)2) as effective catalysts for the esterification of fatty acids with long-chain alcohols and simple polyols through a homogeneous system that allows the gradual and selective removal of water. The results show that the catalytic activity depends on the nature of the counterion: the most effective are the salts with poorly coordinating anions (perchlorate and triflate) or containing basic Brønsted anions (oxide, acetate, and carbonate). However, only with the latter is it possible to fully recover the catalyst at the end of each run, which is easily filtered in the form of zinc carboxylate, given its insolubility in the ester produced. In this way, it is possible to recycle the catalyst numerous times, without any loss of activity. This beneficial prerogative couples the efficiency of the homogeneous catalysis with the advantage of the heterogeneous catalysis. The process is, therefore, truly sustainable, given its high efficiency, low energy consumption, ease of purification, and the absence of auxiliary substances and byproducts
Direct and Solvent-Free Oxidative Cleavage of Double Bonds in High-Oleic Vegetable Oils
No full textAn unprecedented direct oxidation of high-oleic triglycerides to produce azelaic glycerides has been carried out by using a catalytic system based on H2WO4/H2O2. The results are highly competitive with those reported so far for simpler feedstock: at low catalyst loading the oxidation proceeds with satisfactory yields also starting from a real waste oil matrix without any prior purification
Emerging catalysis in biomass valorisation: simple Zn(II) catalysts for fatty acids esterification and transesterification
No full textThe growing concern about global warming and the consumption of fossil fuels has driven in recent decades the use of biomass as a renewable feedstock. In this context, vegetable oils, the corresponding fatty acids (FAs) and esters (FAEs) have primary importance: their esterification and transesterification lead to innovative products, that find application in several sectors, from biofuels to solvents, from surfactants to cosmetic ingredients and plasticizers. Lewis acid catalysis represents the most accredited methodology for developing processes of esterification and transesterification in line with sustainability requirements. The results available so far reveal the prevalent catalytic role of Zn(II) salts and coordination compounds, due to their beneficial eco-toxicological profile, combined with an appropriate acidity, finely tunable through selective functionalization. This review provides a picture of the state of the art in this important sector of biomass valorization
Solvent-free transesterification of methyl levulinate and esterification of levulinic acid catalyzed by a homogeneous iron(III) dimer complex
No full textLevulinic acid esters MeC(O)CH2CH2CO2R (LAE) are emerging bio-based chemicals used as solvents, additives and plasticizers. In this work a variety of levulinates (R= n-butyl, n-hexyl, n-octyl, 2-ethylhexyl, geranyl, 2-ethoxyethyl, benzyl, 2-octyl, cyclohexyl, menthyl) is obtained from the solvent-free transesterification of methyl levulinate (ML) and esterification of levulinic acid (LA), catalyzed by a dimeric complex of iron(III). The results are competitive with the few related reports of literature mainly based on heterogeneous catalysis. This first systematic study based on a homogeneous catalytic system therefore represents a significant extension within the field of biomass valorization
Hydrophilic ligands derived from glucose: synthesis, characterization and invitro cytotoxic activity on cancer cells of Pt(II) complexes
No full textAiming to contribute to the design of new antitumoral drugs, we synthesized new hydrophilic Pt(II) complexes
of general formula [PtCl2(N,N0)] containing nitrogen bidentate amine–imine and di-imine ligands
derived from glucose. Some chemical properties were discussed. The X-ray molecular structure of
[PtCl2(a-D-glucopyranoside-methyl-6-deoxy-6(2-(methylimino)methyl)pyridine) (D) was reported. [Pt
Cl2(b-D-glucopyranosylimine-N-(2-pyridinylmethyl))] (A), which is well-soluble both in organic solvents
and in water, was tested for cytotoxicity
A hydrophilic olefin Pt(0) complex containing a glucoconjugated 2-iminopyridine ligand: Synthesis, characterization, stereochemistry and biological activity
No full textThe synthesis of a novel water-soluble Pt(0) complex [Pt(1-gluAc)(dmf)] containing a glucoconjugated 2-iminopyridine ligand and dimethylfumarate is reported. Highly diastereoselectivity leads to the prevalent formation of only one of the possible diasteroisomers, which has been characterized by mono- and bi-dimensional NMR techniques. The anticancer activity of the complex was evaluated against two couples of cell lines, and the IC50 values reveal that it is more cytotoxic than cisplatin but no selective toward cancer cells
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