2603-10-3Relevant academic research and scientific papers
Self-assembly of ionic liquids and metal complexes in super-cages of NaY: Integration of free catalysts and solvent molecules into confined catalytic sites
Ma, Yubo,He, Yude,Zhang, Qinghua,Shi, Feng,Ma, Xiangyuan,Lu, Liujin,Deng, Youquan
, p. 933 - 937 (2010)
The integration of a free metal complex, Pd(phen)2+, and a room temperature ionic liquid (IL) solvent molecule, 1-decyl-3-methyl imidazolium bromide, into a complete catalytically active site and confined in a NaY zeolite super-cage with an appropriate spatial arrangement was investigated. This integration was achieved through a molecular self-assembly method. A preliminary test of this catalyst system for the carbonylation of aniline to methyl phenyl carbamate indicated that far higher catalytic activity could be achieved (TOF increased from 3 000 to 23 000 h-1) with far lower amounts of the IL solvent and the Pd complex in comparison with a simple mixture of Pd(phen)Cl2/IL/NaY as the catalyst. This new system can also be applied to other areas of catalysis.
-, -, and bimetallic clusters as catalysts for carbonylation of nitrobenzene to methyl phenylcarbamate
Ragaini, Fabio,Cenini, Sergio,Fumagalli, Alessandro,Crotti, Corrado
, p. 401 - 408 (1992)
Bimetallic clusters of the general formula 2 (M = Fe, Ru, or Os; PPN- = (PPh3)2N+) are active catlysts in the presence of methanol for the carbonylation of nitrobenzene to methyl phenylcarbamate.The clusters are active even without co-catalyst, but the addition of bipy (2,2'-bipyridine) greatly enhances both rates and selectivities.In the absence of methanol the conversion was much lower, with a low selectivity in phenyl isocyanate.Interchanging Fe, Ru, and Os has a negligible effect on the activity and a moderate effect on the selectivity, with ruthenium being best.However, the monometallic rhodium cluster - proved to be both more active and selective, and the monomer - was found to be even better.This last catalytic system has been optimized with respect to temperature, CO pressure and the bipy/Rh ratio.The influence of solvent was also examined.
Oxidative carbonylation of aniline with a mesoporous silica gel immobilised Se-functionalised ionic liquid catalyst
Ma, Yubo,Shi, Feng,Deng, Youquan
, p. 344 - 347 (2010)
A series of BMImBF4-templated mesoporous silica gel immobilised Se-functionalised ionic liquids have been prepared. The catalysts were characterised by BET, FTIR and ICP-AES, and the results showed that the content of Se increased from 2.7 to 4.76 wt% with pore volume increasing from 0.83 to 1.26 cm3 g-1. Preliminary tests of this catalyst system on the carbonylation of aniline to afford methyl phenyl carbamate (MPC) indicated that good catalytic activity (higher than 74% aniline conversion with 99% MPC selectivity) could be achieved with higher than 150 mol h-1 mol -1 turnover frequency (TOF). TOF and aniline conversion slightly increased with increasing the content of Se from 2.7 to 3.0 wt%, then decreased when the content of Se increased to more than 3.0 wt%, this suggested that 2.7 to 3.0 wt% Se content should be appropriate for MPC synthesis. The appropriate Se content could be obtaineded by adjusting the range of pore volume of mesoporous silica gel from 0.83 to 0.85 cm3 g-1. In addition, the recycling test indicated that there was almost no deactivation of the catalyst when it was reused four times.
The Induction Period and Novel Active Species in Zn(OAc)2 Catalyzed Synthesis of Aromatic Carbamates
Li, Fang,Wang, Xi,Li, Hongqin,Wang, Shufang,Xue, Wei,Wang, Yanji
, p. 1478 - 1484 (2017)
Abstract: Zn(OAc)2 is known to exhibit excellent catalytic activity for aromatic carbamate synthesis by the reaction of aromatic amine and dimethyl carbonate (DMC). It is determined that an induction period exists during the synthesis of dimethyl-4,4′-methylenediphenyl dicarbamate (MDC) and methyl N-phenyl carbamate (MPC), although this period is more evident in the case of MDC. Zn(OAc)2 is able to catalyze the reaction of amine and DMC, but also react with DMC to form Zn4O(OAc)6, which also shows excellent catalytic activity for carbamate synthesis. As for MDC synthesis, Zn4O(OAc)6 plays the important role. However, Zn(OAc)2 plays the leading role in MPC synthesis. The deactivation of Zn4O(OAc)6 was also investigated. Zn4O(OAc)6 was initially transformed into Zn5(OH)8(OAc)2·2H2O (LHZA) and then into ZnO. Graphical Abstract: [Figure not available: see fulltext.].
Determination and modeling of isobaric vapor-liquid equilibria for the methylcarbamate + Methyl-N-phenyl carbamate system at different pressures
Xu, Dehua,Li, Huiquan,Li, Zhibao
, p. 3110 - 3117 (2013)
The vapor pressures of methylcarbamate (MC) and methyl n-phenyl carbamate (MPC), at different temperatures ranging from (341.45 to 418.45) K, have been measured using the quasi-static ebulliometric method. The experimental data were fitted to the Antoine
The carbonylation reaction of nitrobenzene to methyl phenylcarbamate: Highly efficient promoters for the palladium-phenanthroline catalytic system based on phosphorus acids
Ragaini, Fabio,Cognolato, Carlo,Gasperini, Michela,Cenini, Sergio
, p. 2886 - 2889 (2003)
Phenomenal! The activity of the palladium-phenanthroline catalytic system for the carbonylation of nitrobenzene to methyl phenylcarbamate is greatly enhanced by the addition of phosphorus acids. Of those that were studied, the best promoter is the very cheap, easily separable, and nontoxic phosphoric acid.
Highly selective phosgene-free carbamoylation of aniline by dimethyl carbonate under continuous-flow conditions
Grego, Sandra,Aricoi, Fabio,Tundo, Pietro
, p. 679 - 683 (2013)
Over the last 20 years organic carbamates have found numerous applications in pesticides, fungicides, herbicides, dyes, pharmaceuticals, cosmetics, and as protecting groups and intermediates for polyurethane synthesis. Recently, in order to avoid phosgene-based synthesis of carbamates, many environmentally benign and alternative pathways have been investigated. However, few examples of carbamoylation of aniline in continuous-flow apparatus have been reported. In this work, we report a high-yielding, dimethyl carbonate (DMC)-mediated carbamoylation of aniline in a fixed-bed continuously fed reactor employing basic zinc carbonate as catalyst. Several variables of the system have been investigated (i.e. molar ratio of reagents, flow rate, and reaction temperature) to optimize the operating conditions of the system.
Alternative, easy and efficient preparation of poly[4-(diacetoxyiodo) styrene] from poly(4-iodostyrene) using sodium perborate as the oxidant
Hossain, Md. Delwar,Kitamura, Tsugio
, p. 1253 - 1256 (2006)
An operationally simple, efficient, and considerably improved preparative procedure of poly[4-(diacetoxyiodo)styrene] (PSDIB) is reported. This procedure is performed with acetic acid, 1,2-dichloroethane, commercially available sodium perborate tetrahydrate as an oxidant, and triflic acid as an additive, and gives PSDIB after a short reaction time. PSDIB is employed as an oxidiz-ing agent in organic synthesis and can be regenerated and reused in the same reaction. Georg Thieme Verlag Stuttgart.
Mechanistic study of the palladium - Phenanthroline catalyzed carbonylation of nitroarenes and amines: Palladium - Carbonyl intermediates and bifunctional effects
Ragaini, Fabio,Gasperini, Michela,Cenini, Sergio,Arnera, Lucia,Caselli, Alessandro,Macchi, Piero,Casati, Nicola
, p. 8064 - 8077 (2009)
Palladium - phenanthroline complexes catalyze both the nitroarene carbonylation reaction and the amine oxidative carbonylation reaction to give, depending on the conditions, carbamates and ureas. There is evidence that the key step in both processes is the amine carbonylation. Here, we show that when the reaction is run in methanol key intermediate compounds have the general formula [Pd(RPhen)(COOMe)2] (1) (RPhen = l,10-phenanthroline or one of its substituted derivatives). The kinetics of the reaction of 1 with toluidine in the presence of a carboxylic or phosphorus acid is firstorder with respect to complex, acid, and toluidine. A CO atmosphere is also required for the reaction to proceed. Acid dimerization was shown not to be influential under the concentration conditions examined, but reaction between the acid and toluidine is not negligible and a correction has to be applied. Diphenylphosphinic acid is more effective than any carboxylic acid in promoting this reaction, as also observed under catalytic conditions. A series of equilibria and an irreversible acid-assisted proton transfer explain the observed data. Formation of an adduct between complexes of the kind 1 and CO was spectroscopically observed when RPhen = 2,9-Me2Phen. Several analogous complexes were also spectroscopically characterized and the X-ray structure of [Pd(2,9Me2Phen)Cl2(CO)] was solved. This shows an asymmetric coordination of the nitrogen ligand. Kinetic measurements were also conducted under catalytic conditions. An Eyring plot shows that the effect of the acidic promoter is to decrease the ?S * value, whereas no positive effect is observed on ?H*. A temperature-dependent correction for the reaction between the acid and aniline and phenanthroline present under the reaction conditions has to be applied. Comparison of the results obtained under stoichiometric and catalytic conditions strongly supports the view that 1 is involved even in the latter and that the acid is acting as a bifunctional promoter.
Carbamate synthesis by solid-base catalyzed reaction of disubstituted ureas and carbonates
Gupte,Shivarkar,Chaudhari
, p. 2620 - 2621 (2001)
A simple and efficient methodology to prepare carbamates has been demonstrated for the first time from symmetrical ureas and organic carbonates in the presence of solid base catalysts.
