249 research outputs found
Synthesis of Water-soluble Triazole Ligands and Application of Their Metal Complexes in Biphasic Hydrogenations of C=C and C=O
No full textAbstract:
Homogenous catalysis is a powerful tool for organic synthesis but its success in industrial application is limited because of difficult catalyst separation and reuse. To overcome these issues, the use of biphasic catalysis is at present of great interest because the catalyst is confined in one of the two-phases and the product in the other phase allowing for a prompt recovery of the product and an easy recycle of the catalyst. In particular, the development of water soluble catalysts for aqueous/organic biphasic reactions is increasingly attractive [1]. Our research group has been involved in the synthesis of triazolyl ligands by taking advantage of the copper-catalyzed azide-alkyne [3+2] cyclization [2]. Recently, we have synthesized a small library of N-N or N-S ligands which have been employed in Suzuki-Miyaura reactions [3,4]. In this work, we wish to present our studies on biphasic (water/toluene) catalytic hydrogenation of C=O and C=C (Schemes 3 & 4) double bonds using a water soluble triazole ligand in combination with Ruthenium and Iridium.
[1] (a) Cornils B.; Herrmann W. A.; Horvath I. T.; Leitner W.; Mecking S.; Olivier-Bourbigou H.; Vogt (Eds.) D. Multiphase Homogeneous Catalysis, Wiley-VCH, Weinheim, 2005. (b) Joo F. Aqueous Organometallic Catalysis, Kluwer Acad. Publ. Dordrecht, 2001. [2] V. V. Rostovtsev, L.G. Green, V.V. Fokin, K.B. Sharpless, Angew. Chem., Int. Ed. 2002, 41, 2596. [3] Amadio E.; Scrivanti A.; Chessa G.; Matteoli U.; Beghetto V.; Bertoldini M.; Rancan M.; Venzo A.; Bertani R. J. Org. Chem. 2012, 716, 193. [4] Amadio E.; Bertoldini M.; Scrivanti A.; Chessa G.; Beghetto V.; Matteoli U.; Bertani R.; Dolmella A. Inorg. Chim. Acta 2011, 370, 388
Design and Aerodynamic Optimization of a Thin-Haul Aircraft with Distributed Electric Propulsion: ZETHA
No full textSanità pubblica veterinaria e malattie infettive del cavallo ai sensi del REG. (UE) N. 2016/429=Veterinary public health and infectious horse diseases in (EU) regulation Nr. 2016/429
No full textGli Autori presentano il nuovo Regolamento n.429/2016 in materia di Sanità Animale, in particolare nel campo ippiatrico, con la finalità di evidenziare delle idonee linee guida per il veterinario dipendente del SSN in merito alle malattie infettive trasmissibili degli equidi soggette ad obbligo di denuncia. Il lavoro si articola in macro-capitoli, passando attraverso la descrizione dettagliata del nuovo Animal Health Law, le malattie emergenti ed il concetto di notifica di malattia. Si vuole fornire in tal modo un supporto al medico veterinario, aumentandone il livello di conoscenza riguardo l’applicazione e la conformità del nuovo Regolamento.The Authors present the new EU Regulation n. 429/2016 on Animal Health in the hippiatric field, with the aim of highlighting the appropriate guidelines for the SSN veterinarian on communicable infectious diseases of equidae subjected to reporting obligations. The work is articulated in macro-chapters, including the detailed description of the new Animal Health Law, emerging diseases and the concept of disease notification. In this way, we want to provide support to the Official veterinarian, and to increase the level of knowledge of the application the new regulation and the compliance with it
Involvement of FIS on the H-NS mediated regulation of virF gene of Shigella and Escherichia coli EIEC
No full text4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride-assisted amide crosslinking of carboxymethyl cellulose for high-performing films
No full textThis study reports the first example of crosslinking of carboxymethyl cellulose (CMC) and aliphatic diamines (CMCA) using a condensation agent, (4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride (DMTMM)), to prepare highly functional films for food packaging application. The novelty of this work lies in the combination of diamine crosslinking and DMTMM activation to produce films with enhanced barrier and mechanical properties. Products were analysed by mono-/bi-dimensional NMR to prove the amide linkage and by the modification degree (MoD) for diamine quantification. The physical-chemical characteristics of the CMCA films were further determined by DSC, TGA, SEM, and ATR-FTIR, and the moisture content (MC%), moisture uptake (MU%), water vapour permeability (WVP), oil absorption ratio (OAR), and tensile strength (TS) evidenced the key role of DMTMM in the formation of strong covalent bonds between the carboxylate groups of CMC and the diamine, influencing the properties of CMCA films. When a COONa/ethylenediamine/DMTMM molar ratio of 6/1/2 was employed, the best WVP (2.63 ± 0.24 × 10−10 g m−1 s−1 Pa−1), OAR (7.4 ± 0.5 × 10−2%), and transparency were obtained, along with an exceptionally high UVC barrier and one of the highest TS values ever reported for CMC films (75.90 ± 2.90 MPa). Results clearly highlight that the presence of the diamine hydrophobic alkyl chain plays a key role in improving the physical-mechanical characteristics of CMCA, making it superior to the best-performing CMC films reported in the literature and as a sustainable alternative for food packaging applications
Waste Cooking Oil as Eco-Friendly Rejuvenator for Reclaimed Asphalt Pavement
No full textOver 50 MioT of Waste Cooking Oil (WCO) was collected worldwide in 2020 from domestic and industrial activities, constituting a potential hazard for both water and land environments, and requiring appropriate disposal management strategies. In line with the principles of circular economy and eco-design, in this paper an innovative methodology for the valorisation of WCO as a rejuvenating agent for bitumen 50/70 coming from Reclaimed Asphalt Pavement (RAP) is reported. In particular, WCO or hydrolysed WCO (HWCO) was modified by transesterification or amidation reactions to achieve various WCO esters and amides. All samples were characterised by nuclear magnetic resonance, melting, and boiling point. Since rejuvenating agents for RAP Cold Mix Asphalt require a melting point <= 0 degrees C, only WCO esters could further be tested. Efficiency of WCO esters was assessed by means of the Asphaltenes Dispersant Test and the Heithaus Parameter. In particular, bitumen blends containing 25 wt% of WCO modified with 2-phenylethyl alcohol, showed high dispersing capacity in n-heptane even after a week, compared to bitumen alone (1 h). Additionally, the Heithaus Parameter of this bitumen blend was almost three times higher than bitumen alone, further demonstrating beneficial effects deriving from the use of WCO esters as rejuvenating agents
Mechanism of the alkoxycarbonylation of alkynes in the presence of the Pd(OAc)2/PPh2Py/CH3SO3H catalytic system
No full textThe mechanism of the carbonylation of alkynes promoted by the Pd(OAc)2/2-pyridyldiphenylphosphine/methanesulfonic acid catalytic system has been studied. The carbonylation of 2-butyne in the presence of methanol affords stereospecifically the methyl ester of (E)-2-methyl-2-butenoic acid, indicating that the addition of H and COOCH3 moieties proceeds with cis stereochemistry. Experiments carried out using 1-alkynes and CH3OD reveal that the catalyst also promotes the exchange of the terminal hydrogen of the alkyne with the deuterium of the alcohol. 1H NMR experiments show that upon addition of phenylacetylene to a CD2Cl2 solution containing the catalyst and CH3OH a palladium complex having a 2-styryl group bound to the metal center, Pd-C(C6H5)=CH2, is formed. This species can be invoked as an intermediate to account for both the H/D exchange and the carbonylation reaction. Carbonylation of 2-butyne in the presence of a 1/1 mixture of CH3OH and CH3OD indicates that a fairly large isotope effect (kH/kD = 6.4) is operative. All these results suggest that the carbonylation of alkynes proceeds via the protonation of a Pd(0)-alkyne species to give a Pd-vinyl complex, followed by CO insertion and alcoholysis
Carbonylation of terminal alkynes catalysed by Pd complexes in combination with tri(2-furyl)phosphine and methanesulfonic acid
No full textPd(OAc)2 in combination with tri(2-furyl)phosphine and methanesulfonic acid is an efficient catalyst for the alkoxycarbonylation of 1-alkynes. Fairly good reaction rates are obtained under mild conditions (50-80°C and P(CO) = 20 bar) with high regioselectivity (ca. 95%) towards the formation of 2-substituted acrylic ester
New insights into the alkoxycarbonylation of propargyl alcohol
No full textThe challenging carbonylation of propargyl alcohol is effectively catalyzed by Pd(OAc)2 in combination with diphenyl-(6-methyl-pyridin-2-yl)phosphine and methanesulfonic acid. In dichloroethane at 20–50 ◦C, the reaction affords with almost complete regioselectivity alkyl 2-(hydroxymethyl)acrylates. Turnover frequency numbers (TOF) of up to 450 h−1 can be achieved working at 50 ◦C, while a maximum turnover number (TON) of about 730 is obtained at 30 ◦C. The catalyst longevity is limited because the carbonylation product reacts with the phosphorus atom of the ligand to give a quaternary phosphonium
salt. This reaction leads to deactivation of the catalyst and eventually to palladium black formation
Chitosan as a Bio-Based Ligand for the Production of Hydrogenation Catalysts
No full textBio-based polymers are attracting increasing interest as alternatives to harmful and environmentally concerning non-biodegradable fossil-based products. In particular, bio-based polymers may be employed as ligands for the preparation of metal nanoparticles (M(0)NPs). In this study, chitosan (CS) was used for the stabilization of Ru(0) and Rh(0) metal nanoparticles (MNPs), prepared by simply mixing RhCl3 × 3H2O or RuCl3 with an aqueous solution of CS, followed by NaBH4 reduction. The formation of M(0)NPs-CS was confirmed by Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Analysis (EDX), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). Their size was estimated to be below 40 nm for Rh(0)-CS and 10nm for Ru(0)-CS by SEM analysis. M(0)NPs-CS were employed for the hydrogenation of (E)-cinnamic aldehyde and levulinic acid. Easy recovery by liquid-liquid extraction made it possible to separate the catalyst from the reaction products. Recycling experiments demonstrated that M(0)NPs-CS were highly efficient up to four times in the best hydrogenation conditions. The data found in this study show that CS is an excellent ligand for the stabilization of Rh(0) and Ru(0) nanoparticles, allowing the production of some of the most efficient, selective and recyclable hydrogenation catalysts known in the literature
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