- Highly synergistic effect of ionic liquids and Zn-based catalysts for synthesis of cyclic carbonates from urea and diols
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The development of stable and efficient catalysts is an attractive topic for green chemistry reactions under mild reaction conditions. In order to improve solvent-free synthesis of cyclic carbonates from urea and diols, a binary catalyst systems of Zn-based and different ionic liquids (ILs) were developed and examined in this study. The yield of ethylene carbonate (EC) could reach to 92.2% in the presence of C16mimCl/ZnCl2 catalyst. Through exploring the structure-activity relationships of cation and anion, it was confirmed that a synergistic effect of cation and anion of catalyst had important influences on urea alcoholysis. Additionally, the controlling step of EC synthesis reaction involving the elimination of an ammonia molecule from intermediates had been revealed by in situ FT-IR. This could afford a guided insight for synthesizing cyclic carbonates with high yield. Furthermore, a possible mechanism for the catalytic process was proposed based on DFT and the experimental results via FT-IR, 1H-NMR and 13C NMR analysis, which revealed that not only a probable synergistic effects of cation-anion matters, but also C(2)-H of ILs and Zn2+ played a key role in accelerating the reaction of urea alcoholysis. This catalytic mechanism study is to provide a preliminary basis to develop novel catalysts for cyclic carbonates from urea and diols through a green synthetic pathway.
- Cheng, Weiguo,Deng, Lili,Dong, Li,He, Hongyan,Li, Zengxi,Qian, Wei,Shi, Zijie,Su, Qian,Sun, Wenzhong
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- Ethylene carbonate production by cyclocondensation of ethylene glycol and urea in the presence of metal oxides and metal acetylacetonates
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A promising method for the production of ethylene carbonate is the cyclocondensation of ethylene glycol and urea in the presence of a catalyst. In this study, the catalytic effect of oxides and acetylacetonates of various metals on the occurrence of this reaction has been examined. It has been shown that cobalt acetylacetonate is the most effective catalyst. The effect of reaction conditions (temperature, pressure, contact time, and catalyst concentration) on the main parameters of catalytic conversion has been studied.
- Lyadov,Kochubeev,Markova,Khadzhiev
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p. 852 - 856
(2017/01/28)
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- One-pot alkoxylation of phenols with urea and 1,2-glycols
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A one-pot epoxide-free alkoxylation process has been developed for phenolic compounds. The process involves heating phenols and urea in 1,2-glycols at 170-190 °C using Na2CO3/ZnO as co-catalysts under atmospheric conditions. During the course of this new alkoxylation reaction, a five-membered ring cyclic carbonate intermediate, ethylene carbonate (EC) or propylene carbonate (PPC), was produced in-transit as the key intermediate and was subsequently consumed by phenols to form alkoxylated ether alcohols as final products in excellent yields. For instance, phenol, bisphenol A (BPA), hydroquinone and resorcinol were converted into their respective mono-alkoxylated ether alcohols on each of their phenolic groups in 80-95% isolated yields. In propoxylation of phenols, this approach shows great product selectivity favoring production of high secondary alcohols over primary alcohols in isomeric ratios of nearing 95/5. Since ammonia (NH3) and carbon dioxide (CO2) evolving from the reaction can be re-combined in theory into urea for re-use, the overall net-alkoxylation by this approach can be regarded as a simple condensation reaction of phenols with 1,2-glycols giving off water as its by-product. This one-pot process is simple, safe and environmentally friendlier than the conventional alkoxylated processes based on ethylene oxide (EO) or propylene oxide (PO). Moreover, this process is particularly well-suited for making short chain-length alkoxyether alcohols of phenols.
- Lin, Hsing-Yo,Dai, Shenghong A.
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scheme or table
p. 167 - 173
(2011/04/19)
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- Quantitative solid-state reactions of amines with carbonyl compounds and isothiocyanates
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A series of solid-state reactions is reported of gaseous or solid amines with aldehydes to give imines, with solid anhydrides to give diamides (therefrom imides) or amidic carboxylic salts or imides, with solid imides to give diamides, with solid lactones or carbonates to give functionalized carbamic esters, with polycarbonates to give degradative aminolysis, and with solid isothiocyanates to give thioureas. Diamides give imides by solid-state thermolysis or acid catalysis. Various double, two-step, 3-cascade, and sequential reactions are reported in the solid state without melting. The yields are quantitative in 53 reported reaction examples and no workup (except for washings in four cases) is required in the 100% yield reactions. Three initially solid-state reactions but with liquid product were not quantitative. An upscaling to the kg scale shows promise of the technique for large scale applications. Supermicroscopic analyses with AFM elucidate the solid-state mechanism by virtue of far-reaching anisotropic molecular movements in three-step processes. Gas-solid aminolyses of polycarbonates are also studied with AFM. The implications to sustainable chemistry are discussed. (C) 2000 Elsevier Science Ltd.
- Kaupp, Gerd,Schmeyers, Jens,Boy, Juergen
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p. 6899 - 6911
(2007/10/03)
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- Steroids
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Steroids of the formula STR1 wherein R1 to R4, X and n have the significance given in the description, which lower the intestinal resorption of cholesterol and plasma cholesterol and a process of making same from corresponding steroids having an alcohol residue of the formula --O--X--OH in the 3-position.
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- Curable compositions comprising glycidil ethers of hydroxyalkyl carbamates
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Glycidyl ethers of hydroxyalkyl carbamates of the general formula I in which R is a C1-15aliphatic or cycloaliphatic linking group; R' is H or C1-3alkyl, at least one R' being hydrogen; m is 0, 1, 2 or 3; n is 1, 2, 3 or 4; and m + n is 2, 3 or 4,are prepared which are suitable for resinous binders for coatings and as crosslinking agents for carboxyl-functional resins such as acrylic resins.
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- Studies of the Cyclic Amidoacetal Carbamate Moiety of the Maytansinoids
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A synthesis of cyclic urethane amidoacetals of the type present in the maytansinoid ansa macrolides is reported both to serve as a synthetic model and to explore the chemistry of the hydroxylated intermediates of structures 5 and 6.These compounds are prepared by aldol cyclization of the open-chain amidoacetal aldehyde 4e.Compound 5 is the product of kinetic control, which rearranges to the stable isomeric end products 6 and 7, the latter of which possesses a five-membered urethane ring.The elucidation of structure, stereochemistry, and conformation of these substances is described.The removal of the secondary hydroxyl group of 5 to form 17a is accomplished in three steps.
- Gormley, Glenn,Chan, Y. Y.,Fried, Josef
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p. 1447 - 1454
(2007/10/02)
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