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1.
Aresta M Dibenedetto A Fracchiolla E Giannoccaro P Pastore C Pápai I Schubert G 《The Journal of organic chemistry》2005,70(16):6177-6186
Dicyclohexylcarbodiimide (CyN=C=NCy, DCC) promotes the facile formation of organic carbonates from aliphatic alcohols and carbon dioxide at temperatures as low as 310 K and moderate pressure of CO2 (from 0.1 MPa) with an acceptable rate. The conversion yield of DCC is quantitative, and the reaction has a very high selectivity toward carbonates at 330 K; increasing the temperature increases the conversion rate, but lowers the selectivity. A detailed study has allowed us to isolate or identify the intermediates formed in the reaction of an alcohol with DCC in the presence or absence of carbon dioxide. The first step is the addition of alcohol to the cumulene (a known reaction) with formation of an O-alkyl isourea [RHNC(OR')=NR] that may interact with a second alcohol molecule via H-bond (a reaction never described thus far). Such an adduct can be detected by NMR. In alcohol, in absence of CO2, it converts into a carbamate and a secondary amine, while in the presence of CO2, the dialkyl carbonate, (RO)2CO, is formed together with urea [CyHN-CO-NHCy]. The reaction has been tested with various aliphatic alcohols such as methanol, ethanol, and allyl alcohol. It results in being a convenient route to the synthesis of diallyl carbonate, in particular. O-Methyl-N,N'-dicyclohexyl isourea also reacts with phenol in the presence of CO2 to directly afford for the very first time a mixed aliphatic-aromatic carbonate, (MeO)(PhO)CO. A DFT study has allowed us to estimate the energy of each intermediate and the relevant kinetic barriers in the described reactions, providing reasonable mechanistic details. Calculated data match very well the experimental results. The driving force of the reaction is the conversion of carbodiimide into the relevant urea, which is some 35 kcal/mol downhill with respect to the parent compound. The best operative conditions have been defined for achieving a quantitative yield of carbonate from carbodiimide. The role of temperature, pressure, and catalysts (Lewis acids and bases) has been established. As the urea can be reconverted into DCC, the reaction described in this article may further be developed for application to the synthesis of organic carbonates under selective and mild conditions. 相似文献
2.
Aresta M Tommasi I Quaranta E Fragale C Mascetti J Tranquille M Galan F Fouassier M 《Inorganic chemistry》1996,35(14):4254-4260
Extended labeling experiments have shown that formation of rhodium peroxocarbonate from CO(2) and [RhCl(eta(2)-O(2))(P)(3)] (P is PEt(2)Ph or PEtPh(2)) proceeds through O-O bond cleavage and CO(2) insertion. O-transfer to ancillary phosphine ligand to give R(3)P=O selectively (>85%) involves the Rh-linked O atom of the peroxo group of RhCl(CO(4))(P)(3). 相似文献
3.
Lucia D'Accolti Cosimo Annese Antonella Aresta Caterina Fusco 《Journal of heterocyclic chemistry》2014,51(5):1482-1486
Epoxides are essential building blocks in organic chemistry. The epoxidation of unsubstituted cyclic dienes 2 , 3 , 4 and triene 5 using dimethyldioxirane ( 1a ) and its trifluoro analog 1b methyl(trifluoromethyl)dioxirane has been investigated. The excellent yields obtained (90–98%) are accompanied by outstandingly high diastereoselectivities (90–98%). Interpretation of results based upon the early idea that polar groups can direct the dioxirane attack by dipole–dipole interaction provides a likely rationale, along with a more generalized mechanistic view. 相似文献
4.
Calvano CD Aresta A Palmisano F Zambonin CG 《Analytical and bioanalytical chemistry》2007,389(7-8):2075-2084
Laser desorption ionization time-of-flight mass spectrometry (LDI–TOF MS) was used to characterize olive and sunflower oils
before and after thermally assisted oxidation in order to develop a rapid fingerprinting method for oil that contains unchanged
and oxidized components. No matrix was used to assist laser desorption, and simplified mass spectra were obtained in the mass
range of interest (m/z 500–1000), where triacyl- and diacylglycerol ions were observed. Sample preparation was reduced to dissolving oil in chloroform
saturated with NaCl. Sodiated triacylglycerols (TAGs), their epoxy/hydroxy and hydroperoxy derivatives, as well as TAGs with
shortened chain fatty acids (β-scission products) were clearly observed in the spectra. LDI–TOF MS rapidly provides semiquantitative information about the
oxidation level of edible oil, and thus represents a very useful quality control tool.
Dedicated to Professor Pier Giorgio Zambonin on the occasion of his 72nd birthday. 相似文献
5.
The need to reduce the accumulation of CO(2) into the atmosphere requires new technologies able to reduce the CO(2) emission. The utilization of CO(2) as a building block may represent an interesting approach to synthetic methodologies less intensive in carbon and energy. In this paper the general properties of carbon dioxide and its interaction with metal centres is first considered. The potential of carbon dioxide as a raw material in the synthesis of chemicals such as carboxylates, carbonates, carbamates is then discussed. The utilization of CO(2) as source of carbon for the synthesis of fuels or other C(1) molecules such as formic acid and methanol is also described and the conditions for its implementation are outlined. A comparison of chemical and biotechnological conversion routes of CO(2) is made and the barriers to their exploitation are highlighted. 相似文献
6.
The synthesis, characterization, and properties of the cationic hydride [HPd(dppe)(2)](+)CF(3)SO3(-).1/8THF, the missing member of the family [HM(dppe)(2)](+)X(-) (M = Ni, Pd, Pt), are described. The Pd hydride is not stable in solution and may react as either a proton or a hydride donor. DFT QM/MM calculations of the [HPd(dppe)(2)](+) moiety have allowed us to predict its structure and reactivity. 相似文献
7.
Nb(OR)(4)[OC(O)OR] (R = Me, Et, allyl) compounds have been synthesized by the reaction of dimeric alkoxo complexes [Nb(OR)(5)](2) with CO(2). The kinetics of the reaction has shown that the monomer in equilibrium with the dimer is the species that reacts with CO(2). The resulting compounds are monomeric with a eta(2)-O,O-bonded hemicarbonate group. The CO(2) uptake is reversible. The hemicarbonates react with the parent alcohol to afford the relevant organic carbonate (RO)(2)CO with a turnover number (TON) of >2. 相似文献
8.
The covalent complex Rh(diphos)(η-BPh4) (I) reacts with CO in polar solvents to afford the cationic dicarbonyl cis-[Rh(diphos)(CO)2](BPh4). I is an effective catalyst for methylacetylene oligomerization and allene polymerization. In the presence of CO2 and methylacetylene, I affords 4,6-dimethyl-2-pyrone. 相似文献
9.
This paper discusses the epochal change in the reputation of carbon dioxide, which is now considered as a raw material alternative to fossil C for the synthesis of chemicals, materials and fuels, as opposed to a waste material that must be confined underground. In particular, its use as renewable C is compared to biomass. In this paper, a specific point is discussed: is ethanol (or any fuel) produced via the catalytic conversion of atmospheric CO2 different from the relevant biomass-sourced product(s)? The answer to this question is very important because it ultimately determines whether or not fuels derived from atmospheric CO2 (either e-fuels or solar fuels) have the right to be subsidized in the same way that biofuels are. Conclusions are drawn demonstrating that ethanol derived from atmospheric CO2 deserves the same benefits as bio-ethanol, with the additional advantage that its synthesis can be less pollutant than its production via the fermentation of sugars. The same concept can be applied to any fuel derived from atmospheric CO2. 相似文献
10.
Cosima D. Calvano Cristina De Ceglie Antonella Aresta Laura A. Facchini Carlo G. Zambonin 《Analytical and bioanalytical chemistry》2013,405(5):1641-1649
In the dairy industry one of the most common frauds is mixing high-value milk (sheep’s and goats’) with milk of lower value (cows’). This illegal practice has commercial, ethical, and serious sanitary consequences because consumers can be exposed to hidden allergens contained in the undeclared cows’ milk. Here, we investigated the possibility of using matrix-assisted laser-desorption/ionization (MALDI)-time of flight (TOF) mass spectrometry (MS) as a rapid, sensitive, and accurate technique for detection of milk adulteration by analysis of phospholipid profiles. Lipid extracts of pure raw milk, commercial milk, and binary mixtures of cows’ and goats’ milk and cows’ and sheep’s milk (the concentrations of each milk varied from 0 % to 50 %) were analyzed with α-cyano-4-chlorocinnamic acid as matrix. The abundance ratio of the ions at m/z 703 and m/z 706 was found to be species-correlated and was used as marker of cows’ milk in sheep’s and goats’ milk. Furthermore, the procedure could potentially be applied to cheese samples, because peaks at m/z 703 and 706 were also found in several commercial cheese samples. This approach proved to be an efficient, rapid, and inexpensive method of detecting milk fraud. Figure
MALDI-TOF MS analysis of intact phospholipid in milk mixtures 相似文献