- Synthesis of Carbonate Esters by Carboxymethylation Using NaAlO2 as a Highly Active Heterogeneous Catalyst
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Sodium aluminate is presented as a highly active heterogeneous catalyst that is able to convert a range of alcohols into the corresponding unsymmetrical carbonate esters by reaction with dimethyl carbonate. Preparing NaAlO2 via spray drying boosts the basic properties and the activity of the catalyst.
- Ramesh, Sreerangappa,Indukuri, Kiran,Riant, Olivier,Debecker, Damien P.
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p. 1846 - 1851
(2019/01/04)
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- Highly efficient Tsuji-Trost allylation in water catalyzed by Pd-nanoparticles
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Palladium nanoparticles stabilized by poly(vinylpyrrolidone) catalyze Tsuji-Trost allylations in water with very high turnover numbers. The di-allylation of methylene active compounds and the allylation of bio-based phenols was performed in high yield. The allylation of lignin showed a high selectivity towards the phenolic OH groups.
- Llevot,Monney,Sehlinger,Behrens,Meier
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supporting information
p. 5175 - 5178
(2017/07/12)
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- Rate and product studies on the solvolyses of allyl chloroformate
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The solvolysis rate constants of allyl chloroformate (CH 2=CHCH2OCOCl, 3) in 30 different solvents are well correlated with the extended Grunwald-Winstein equation, using the NT solvent nucleophilicity scale and YCl solvent ionizing scale, with the sensitivity values of 0.93 ± 0.05 and 0.41 ± 0.02 for l and m, respectively. These l and m values can be considered to support a S N2 reaction pathway. The activation enthalpies (ΔH≠) were 12.5 to 13.4 kcal·mol-1 and the activation entropies (ΔS≠) were -34.4 to -37.3 cal·mol-1·K -1, which is also consistent with the proposed bimolecular reaction mechanism. The solvent kinetic isotope effect (SKIE, kMeOH/k MeOD) of 2.16 was also in accord with the SN2 mechanism. The values of product selectivity (S) for the solvolyses of 3 in alcohol/water mixtures was 1.3 to 3.9, which is also consistent with the proposed bimolecular reaction mechanism.
- Koh, Han Joong,Kang, Suk Jin
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p. 4117 - 4121
(2013/08/23)
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- AROMATIC DICYANATE COMPOUNDS WITH HIGH ALIPHATIC CARBON CONTENT
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Aromatic dicyanate compounds which comprise aliphatic moieties having at least about six carbon atoms and resins and thermoset products based on these compounds.
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Page/Page column 25-26
(2009/10/22)
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- ETHYLENICALLY UNSATURATED MONOMERS COMPRISING ALIPHATIC AND AROMATIC MOIETIES
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Polymerizable monomers comprising at least one 1- or 2-propylene moiety and further comprising both aromatic moieties and additional aliphatic moieties and polymerizable mixtures, resins and thermoset products based on these monomers.
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Page/Page column 35-38
(2009/10/22)
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- Mechanism of formation of organic carbonates from aliphatic alcohols and carbon dioxide under mild conditions promoted by carbodiimides. DFT calculation and experimental study
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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(ORO=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 CO 2, 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.
- Aresta, Michele,Dibenedetto, Angela,Fracchiolla, Elisabetta,Giannoccaro, Potenzo,Pastore, Carlo,Papai, Imre,Schubert, Gabor
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p. 6177 - 6186
(2007/10/03)
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- Reactions of allyloxy(methoxy)carbene in solution. Carbene rearrangement and Claisen rearrangement of the carbene dimer
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Allyloxy(methoxy)carbene, with and without deuterium in the α-position of the allyloxy group, was generated in benzene at 50 and at 110°C. At the higher temperature, the carbene fragmented to allyl and methoxycarbonyl radicals that subsequently coupled. At the lower temperature, most of the carbene dimerised. The structure of the major product and the distribution of deuterium indicated that the dimer underwent Claisen rearrangement at 50°C to methyl 2-allyloxy-2-methoxy-4-pentenoate. Facile rearrangement of the dimer was supported by the results of a computation which placed the barrier at about 18 kcal mol-1.
- Plazuk, Damian,Warkentin, John,Werstiuk, Nick Henry
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p. 5788 - 5796
(2007/10/03)
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- THE NITROGENATED ALLYLIC SYSTEM AS AN INTRAMOLECULAR NUCLEOPHILE: A NEW ROUTE TO PYRAZOLES
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A new route to pyrazoles via the cyclization of N-allyl-N-nitrosoamides is described.
- Momose, Takefumi,Toyooka, Naoki,Ikuta, Takashi,Yanagino, Hironobu
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p. 789 - 793
(2007/10/02)
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- Preparation of alkyl carbonates
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Carbonate compounds are prepared by equilibrium interchange of carbonate functionality between lower alkyl carbonates especially dimethyl carbonate and alkyl halides such as allyl chloride at about 50° C. to about 250° C. in the presence of an initiator such as homogeneous or heterogeneous amines, phosphines, and ammonium or phosphonium quaternary salts.
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