1745-81-9Relevant academic research and scientific papers
Degradation of lignin with aqueous ammonium-based ionic liquid solutions under milder conditions
Gupta, Bhupender S.,Lee, Ming-Jer,Tolesa, Leta Deressa
, p. 3357 - 3365 (2019)
This study investigates the performance of two aqueous ionic liquids (ILs), dimethylbutylammonium acetate ([DMBA][Ac]) and dimethylbutylammonium butanoate ([DMBA][B]), solutions for depolymerizing alkali lignin into valuable phenolic compounds. The favorable operation conditions, including reaction temperature and reaction time, are explored. The extent of depolymerization of the lignin is evaluated by analysis with gel permeation chromatography (GPC). The results show that the average molecular weights of the depolymerized lignin samples can be reduced by as high as 93.8% and 86.8% after treating with the aqueous [DMBA][Ac] and [DMBA][B], respectively. Moreover, the aromatic chemical species in the depolymerized solutions are identified by using gas chromatography?mass spectrophotometry (GC-MS). The confirmation of the chemical species is further made by using a series of spectroscopic techniques, such as FT-IR, and 1H NMR and 13C NMR spectroscopy. Promising results have been achieved for the depolymerization of the lignin into valuable chemicals by using the proposed green media, aqueous solutions of ionic liquids [DMBA][Ac] and [DMBA][B], under milder conditions.
The impact of Novel Process Windows on the Claisen rearrangement
Kobayashi, Hiroki,Driessen, Brian,Van Osch, Dannie J.G.P.,Talla, Ali,Ookawara, Shinichi,No?l, Timothy,Hessel, Volker
, p. 2885 - 2890 (2013)
The impact of Novel Process Windows on the Claisen rearrangement in microflow was investigated. Elevated temperatures (up to 300 °C) were crucial to achieve full conversion of allyl phenyl ether in the Claisen rearrangement. We observed that 1-butanol was the optimal reaction solvent for this transformation in flow. Solvent-free reaction conditions were feasible for the Claisen rearrangement and provided quantitative yields of the target product at 280 °C and 100 bar. Also elevated reaction pressures (up to 300 bar) were investigated in the Claisen rearrangement. We found that thermal expansion and pressure-related compression phenomena cannot be ignored at such harsh reaction conditions. These phenomena lead to large deviations of the desired residence time (as calculated from the nominal flow rate) and have a clear impact on the observed reaction trends. Finally, we also investigated the temperature effect on the Johnson-Claisen rearrangement of cinnamyl alcohol. Quantitative yields were obtained at 200 °C and at 100 bar.
A flow reactor with inline analytics: Design and implementation
Somerville, Kristina,Tilley, Michael,Li, Guanlong,Mallik, Debasis,Organ, Michael G.
, p. 1315 - 1320 (2014)
A continuous flow system complete with inline analytics is described. Sampling from a high pressure reactor and automated delivery mechanisms are detailed. The ability of the system to maintain critical process parameters (CPP) throughout a reaction process is demonstrated. Setup performance was evaluated using the Claisen rearrangement of allyl phenyl ether (1).
Water-Accelerated Tandem Claisen Rearrangement-Catalytic Asymmetric Carboalumination
Wipf, Peter,Ribe, Seth
, p. 1503 - 1505 (2001)
matrix presented The addition of stoichiometric quantities of water accelerates both the trimethylaluminum-mediated aromatic Claisen reaction and the chiral zirconocene-catalyzed asymmetric carboalumination of terminal alkenes. The two reactions occur in a tandem sequence resulting in the selective formation of two new C-C and one C-O bond after oxidative quench of the intermediate trialkylalane.
A continuous-flow microwave reactor for conducting high-temperature and high-pressure chemical reactions
Sauks, Jennifer M.,Mallik, Debasis,Lawryshyn, Yuri,Bender, Timothy,Organ, Michael
, p. 1310 - 1314 (2014)
A continuous-flow microwave reactor with a unique pressure control device is described. The reactor has been designed to withstand extremely high pressure without the involvement of a conventional backpressure-creating device that commonly results in carryover and cross-contamination problems. The reactor efficiency has been evaluated by product conversions using two model reactions, namely, the Claisen rearrangement and the synthesis of benzimidazole.
Vibrational Activation. 2.1 Acceleration of Bond-Making Reactions by Solvent Viscosity as a Model for Enzymic Catalysis. The Claisen Rearrangement and the Diels-Alder Reaction
Firestone, Raymond A.,Vitale, Mark A.
, p. 2160 - 2164 (1981)
The vibrational activation theory holds that enzymes catalyze reactions in part by simply immobilizing the reactants.Typical bond-making reactions should then go faster at high viscosities.This prediction has now been verified for two different reactions.At 138 deg C the Claisen rearrangement of phenyl allyl ether goes at relative rates of 1.00, 0.98, 1.13, and 1.36 in n-octane, isooctane, n-octacosane, and Nujol, whose relative viscosities at 100 deg C are 1.00, 0.94, 4.92, and 11.8, respectively.The relationship is linear with slope 0.041.Addition of polyethylene to the Nujol raises the relative viscosity to 48.5 and the relative rate to 1.70.The intramolecular Diels-Alder cyclization of N-propargyl-9-anthroamide at 100 deg C goes at relative rates 1.00, 1.16, 1.25, and 1.38 in mono-, di-, tri- and tetraglyme, whose relative viscosities at 100 deg C are 1.00, 1.28, 1.54, and 1.99, respectively.The relationship is again linear, with slope 0.37.In addition, the following examples from the literature are analyzed in terms of viscosity-induced accelerations: the dimerization of cyclopentadiene, pressure-accelerated reactions where /-ΔV(excit.)/ > /-ΔV/ and liquid/gas rate ratios are > 1.A test of the theory that the liquid/gas phenomenon stems from hyperpolarizability of the transition state was made by measuring Claisen relative rates in five solvents of widely varying refractive indices.No relationship between rate and solvent polarizability was found.
Highly-selective and high-speed Claisen rearrangement induced with subcritical water microreaction in the absence of catalyst
Sato, Masahiro,Otabe, Nobuhiro,Tuji, Tomoya,Matsushima, Keiichiro,Kawanami, Hajime,Chatterjee, Maya,Yokoyama, Toshiro,Ikushima, Yutaka,Suzuki, Toshishige Maro
, p. 763 - 766 (2009)
Highly-selective, high-speed aromatic and aliphatic Claisen rearrangement was shown to give the corresponding product in an excellent yield induced by subcritical water microreaction in the absence of catalyst.
The ene reaction between maleimides and allyl-substituted aromatics
Cunningham, Ian D.,Brownhill, Andrew,Hamerton, Ian,Howlin, Brendan J.
, p. 13473 - 13494 (1997)
The products from the 'ene' reaction between allyl-substituted aromatics and maleic anhydride, maleimide, N-phenylmaleimide and N-(4-phenoxyphenyl)maleimide have been isolated and characterised, and a semi-quantitative assessment of ene and enophile reactivities has been made. The reaction between N-phenylmaleimide and allylaromatics bearing a 1,3,5-triazine substituent has been investigated as a model for a proposed cyanate ester-bis-maleimide-allyl cyanate ester ter-polymerisation.
Heteropoly acid encapsulated SBA-15/TiO2 nanocomposites and their unusual performance in acid-catalysed organic transformations
Sawant, Dhanashri P.,Justus, Josena,Balasubramanian, Veerappan V.,Ariga, Katsuhiko,Srinivasu, Pavuluri,Velmathi, Sivan,Halligudi, Shivappa B.,Vinu, Ajayan
, p. 3200 - 3212 (2008)
The preparation of SBA-15/ TiO2 nanocomposites with different loadings of Keggin-type 12-tungstophosphoric acid (TPA) nanocrystals in their mesochannels through a simple and effective vacuum impregnation method is reported for the first time. The catalysts have been characterised by various sophisticated techniques, including XRD, HRSEM, and TEM. It has been found that the acidity and the textural parameters of the nanocomposites can be controlled by simply changing the loadings of TPA and TiO2 or the calcination temperature. TPA and TiO2 loadings of 15 and 22.4 wt%, respectively, and a calcination temperature of 1123 K have proved to be optimal for obtaining mesoporous nanocomposite materials with the highest acidity. Moreover, the activities of these catalysts in promoting hydroamination as well as Mannich and Claisen rearrangement reactions have been extensively investigated. The results show that the amount of TPA has a great influence on the activity of the nanocomposites in all of the reactions studied. The effects of other reaction parameters, such as temperature and reaction time, on the conversion and product selectivity have also been studied in detail. A kinetic analysis of the formation of the products under various reaction conditions is presented. It has been found that the activity of the nanocomposite composed of 15wt% TPA deposited on 22.4 wt of TiO2 on SBA-15 in promoting the studied reaction is remarkably higher than the catalytic activities shown by pure TPA, TiO2-loaded SBA-15, or TPA-loaded SBA-15. The results obtained have indicated that the acidity and the structural control of the nanocomposite materials are highly critical for obtaining excellent catalytic activity, and the presented highly acidic nanocomposites are considered to show great potential for use as catalysts in promoting many acid-catalysed organic transformations.
Photochemical electron transfer across a liquid/liquid interface: Methylene Blue-sensitized decarboxylation of substituted carboxylic acids
Das, Suresh,Thanulingam,Rajesh,George
, p. 1337 - 1340 (1995)
Methylene Blue photocatalyzed electron transfer reactions of some substituted carboxylic acids across the water/benzene interface lead to efficient decarboxylation of these acids and the utility of this procedure has been demonstrated by the synthesis of some dihydrobenzopyran and dihydrobenzofuran derivatives.
