- Synthesis of cyclic carbonate from carbon dioxide and epoxide using amino acid ionic liquid under 1atm pressure
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Herein, we report an effective synthesis of cyclic carbonates by cycloaddition of carbon dioxide to epoxide using a modified amino acid ionic liquid as catalyst under 1atm pressure. With triethylamine as co-catalyst, the catalytic activity of the l-proline based ionic liquid was greatly enhanced, and up to 97% isolated yield of cyclic carbonate was achieved at 90C under atmospheric pressure without organic solvent and metal component.
- Gong, Qing,Luo, Huadong,Cao, Jin,Shang, Yuhan,Zhang, Haibo,Wang, Wenjing,Zhou, Xiaohai
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- Synthesis of Cyclohexene Carbonate Catalyzed by Polymer-Supported Catalysts
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A series of polystyrene-divinylbenzene cross-linked resin (PS)-supported zinc chloride catalysts were prepared in this study. They can efficiently catalyze the solventless cycloaddition of cyclohexene oxide with carbon dioxide in the presence of tetrabutylammonium bromide (TBAB) as cocatalyst under relatively mild reaction conditions. The catalyst is composed of carrier, connecting arm, ligand, and active ingredient. The connecting arms of different lengths can significantly affect the catalytic activity. Among these catalysts, the one using diethylene glycol as connecting arm and 2-aminopyridine as ligand, named PS-DEG-2ap-ZnCl2, showed the optimal catalytic performance. The yield of cyclohexene carbonate was 95.18% calculated by gas chromatographic analysis under the optimal conditions (393 K, 5 MPa, 6 h). Moreover, the catalyst showed good stability and reusability. From the viewpoint of industrial application, the catalyst is attractive because of its excellent catalytic efficiency on the synthesis of cyclohexene carbonate. GRAPHICAL ABSTRACT.
- Cui, Ke,Liang, Zhengyong,Zhang, Jing,Zhang, Yadong
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- Diethylene Glycol/NaBr Catalyzed CO2 Insertion into Terminal Epoxides: From Batch to Continuous Flow
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CO2 insertion reactions on terminal epoxides (styrene oxide, 1,2-epoxyhexane and butyl glycidyl ether) were performed in a binary homogeneous mixture comprising NaBr as the nucleophilic catalyst and diethylene glycol (DEG) as both solvent and catalyst activator (cation coordinating agent). The reaction protocol was initially studied under batch conditions either in autoclaves and glass reactors: quantitative formation of the cyclic organic carbonate products (COCs) were achieved at T=100 °C and p0(CO2)=1–40 bar. The process was then transferred to continuous-flow (CF) mode. The effects of the reaction parameters (T, p(CO2), catalyst loading, and flow rates) were studied using microfluidic reactors of capacities variable from 7.85 ? 10?2 to 0.157 cm3. Albeit the CF reaction took place at T=220 °C and 120 bar, CF improved the productivity and allowed catalyst recycle through a semi-continuous extraction procedure. For the model case of 1,2-epoxyhexane, the (non-optimized) rate of formation of the corresponding carbonate, 4-butyl-1,3-dioxolan-2-one, was increased up to 27.6 mmol h?1 equiv.?1, a value 2.5 higher than in the batch mode. Moreover, the NaBr/DEG mixture was reusable without loss of performance for at least 4 subsequent CF-tests.
- Rigo, Davide,Calmanti, Roberto,Perosa, Alvise,Selva, Maurizio,Fiorani, Giulia
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p. 2005 - 2016
(2021/02/27)
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- Direct oxidative carboxylation of terminal olefins to cyclic carbonates by tungstate assisted-tandem catalysis
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Tungstate catalysts are well established for olefin epoxidation reactions, while their catalytic activity for CO2 insertion in epoxides is a more recent discovery. This dual reactivity of tungstate prompted the present development of a catalytic tandem process for the direct conversion of olefins into the corresponding cyclic organic carbonates (COCs). Each of the two steps was studied in the presence of the ammonium tungstate ionic liquid catalyst-[N8,8,8,1]2[WO4]-obtained via a benign procedure starting from ammonium methylcarbonate ionic liquids. The catalytic epoxidation first step was optimised on 1-decene as model substrate, using H2O2 as benign oxidant, [N8,8,8,1]2[WO4] as catalyst and phosphoric acid as promoter affording quantitative conversion with 92% selectivity towards decene oxide. Unfortunately, the addition of CO2 from the start (auto-tandem catalysis) gave low yields of decene carbonate (10%). On the contrary, the addition of 1 atm CO2 and tetrabutyl ammonium iodide after completion of the epoxidation first step without any intermediate work-up (assisted-tandem catalysis) afforded a 94% yield in decene carbonate. The protocol could be scaled up to a 10 gram scale. The scope of the reaction was demonstrated for primary aliphatic olefins with different alkyl chain lengths (C6-C16), while cyclic and aromatic activated olefins such as cyclohexene and styrene suffered from the formation of undesired overoxidation products in the first step.
- Calmanti, Roberto,Perosa, Alvise,Selva, Maurizio
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p. 7609 - 7619
(2021/10/12)
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- Metalated-bipyridine-based porous hybrid polymers with POSS-derived Si-OH groups for synergistic catalytic CO2fixation
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Herein, we construct a new series of N-heterocyclic ligand bipyridine-based porous hybrid polymers (denoted Bpy-PHPs) from the Heck reaction of a rigid building unit octavinylsilsesquioxane (VPOSS) and 5,5′-dibromo-2,2′-bipyridine. Surprisingly, the typical sample Bpy-PHP-4 was found to be a metal-/halogen-free heterogeneous catalyst in the cycloaddition reaction of CO2 with a few epoxides under atmospheric pressure. After coordination with ZnBr2, the resultant ZnBr2@Bpy-PHP-4 afforded largely enhanced heterogeneous catalytic activities upon the conversion of carbon dioxide (CO2) and various epoxides into cyclic carbonates without using any co-catalysts under mild conditions. The moderate catalytic activities of Bpy-PHP-4 may be due to the presence of hydrogen bond donors (HBDs), i.e., polyhedral oligomeric silsesquioxane (POSS)-derived Si-OH groups and N active sites from Bpy linkers. In comparison, the high catalytic efficiency of ZnBr2@Bpy-PHP-4 should be attributed to the synergistic catalysis of Si-OH groups, N active atoms, and Bpy-coordinated ZnBr2. Moreover, the catalyst ZnBr2@Bpy-PHP-4 can be easily recovered and reused ten times without any significant loss of catalytic activities. This work affords an efficient metal-based porous hybrid polymer heterogeneous catalyst for the cycloaddition reaction of CO2 and epoxides under mild and co-catalyst-free conditions.
- Zhang, Yadong,Luo, Niu,Xu, Jingyu,Liu, Ke,Zhang, Shengqi,Xu, Qinglin,Huang, Rui,Long, Zhouyang,Tong, Minman,Chen, Guojian
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p. 11300 - 11309
(2020/09/02)
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- Methoxy Groups Increase Reactivity of Bifunctional Tetraarylphosphonium Salt Catalysts for Carbon Dioxide Fixation: A Mechanistic Study
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The development of carbon dioxide fixation under mild conditions is a central theme in organic synthesis. Despite the tremendous progress in the field of organocatalysis in the past two decades, the coupling reactions of epoxides with carbon dioxide that proceed at atmospheric pressure at temperatures of less than 100 °C have remained challenging. In our aspirational studies of tetraarylphosphonium salts (TAPS) catalysis, we report here the bifunctional TAPS-catalyzed synthesis of five-membered cyclic carbonates by chemical fixation using 1 atm of carbon dioxide at 60 °C. Intriguing substituent effects of TAPS were observed, in which electron-donating groups enhanced their reactivity. In addition, the mechanism was thoroughly investigated by undertaking both experimental and theoretical studies, suggesting that the electronic properties of TAPS affect carbon dioxide insertion into halohydrin intermediates. The results provided fruitful information to understand the origin of the TAPS behavior, which would contribute to the design of novel catalysts for carbon dioxide capture.
- Toda, Yasunori,Komiyama, Yutaka,Esaki, Hiroyoshi,Fukushima, Kazuaki,Suga, Hiroyuki
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supporting information
p. 15578 - 15589
(2019/11/21)
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- Selective Conversion of CO 2 and Switchable Alcohols into Linear or Cyclic Carbonates via Versatile Zinc Catalysis
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It is promising and challenging to achieve the effective construction of carbonates using CO 2 and a non-noble metal catalyst. Herein, selective catalytic conversion of CO 2 and switchable alcohol candidates to produce linear or cyclic carbonates and α-hydroxy ketones via effective zinc catalyst was developed. A series of primary alcohols and cyclohexanol, 1,2-diols, and water can serve as nucleophiles to give alkyl or aryl 2-substituted-3-oxobutan-2-yl carbonates, substituted 1,3-dioxolan-2-ones, 3-substituted 3-hydroxybutan-2-ones, respectively with excellent selectivity and high yields.
- Song, Qing-Wen,Zhao, Qing-Ning,Li, Jing-Yuan,Zhang, Kan,Liu, Ping
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p. 739 - 746
(2019/01/23)
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- Method for chemically fixing carbon dioxide to synthesize cyclic carbonate under normal temperature and normal pressure condition of eutectic ionic liquid (by machine translation)
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The method uses carbon dioxide and different substituent epoxy compounds as raw materials, adopts quaternary phosphonium bromide salt, aminophenol according to molar ratio ?timetime?: 3, the reaction pressure of 5%~10% and the reaction temperature of 12~24 unitunitz ?, and the 1:2~1 reaction time ranges hours to synthesize the corresponding cyclic carbonate . the method comprises the following steps: preparing a catalyst, and synthesizing 0.1 mpa the cyclic carbonate by 25 °C using the novel eutectic ionic liquid in a molar ratio of carbon dioxide and different substituted base epoxy compounds. The novel eutectic ionic liquid is simple and efficient in preparation, cheap and accessible in raw materials, excellent in catalytic performance, and capable of realizing high-selectivity synthesis of cyclic carbonate under normal temperature, normal pressure and the like. , The invention avoids the use, the catalyst and the product of the toxic transition metal, the volatile organic solvent and the cocatalyst, and belongs to an environment-friendly catalyst. (by machine translation)
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Paragraph 0030; 0039; 0041
(2019/07/16)
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- Post-modified porphyrin imine gels with improved chemical stability and efficient heterogeneous activity in CO2 transformation
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Efficient heterogeneous gel catalysts have been developed based on dynamic covalent chemistry and post-modification methods for the chemical fixation of CO2. Various porphyrin-based imine gels are synthesized and subsequent reduction of imine bonds and metallation with various metal centers yields gel catalysts. The gels are characterized by a number of techniques including SEM, TEM, EDX, FT-IR, CP/MAS 13C NMR, and XPS. The resulting gels not only have network structures including micro-, meso- and macropores, but also show improved chemical stability and strong interactions between CO2 and pore channels. The gel catalysts show good catalytic activity towards the cycloaddition of epoxides with CO2 to cyclic carbonates using wet gels. Post-modified gel catalysts with a Zn(ii) center (ZnTAPP-Go-r) show a high product yield and high stability with recyclability over 5 cycles.
- Liao, Peisen,Cai, Guangmei,Shi, Jianying,Zhang, Jianyong
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p. 10017 - 10024
(2019/07/04)
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- Straightforward synthesis of MTW-type magnesium silicalite for CO2 fixation with epoxides under mild conditions
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Aluminum-free magnesium silicalite with MTW topology (Mg-Si-ZSM-12) was fabricated via a straightforward hydrothermal synthesis route involving an initial acid co-hydrolysis step. Mg incorporation endowed superior basic properties to the MTW framework, as illustrated by CO2 sorption and temperature programmed desorption plus the activity in a typical basic reaction, Knoevenagel condensation. Mg-Si-ZSM-12 catalyzed the coupling of atmospheric CO2 with epoxides and led to the efficient production of cyclic carbonates with high yield and selectivity at relatively low temperature (down to 60 °C). The present strategy afforded a zeolitic solid base with regular 12-membered ring microporous channels that has potential application in CO2 fixation.
- Wen, Haimeng,Xie, Jingyan,Zhou, Yang,Zhou, Yu,Wang, Jun
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p. 5725 - 5735
(2019/10/23)
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- Tetraarylphosphonium Salt-Catalyzed Synthesis of Oxazolidinones from Isocyanates and Epoxides
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Preparation of a range of oxazolidinones, including enantioenriched N-aryl-substituted oxazolidinones, in which tetraarylphosphonium salts (TAPS) catalyze the [3 + 2] coupling reaction of isocyanates and epoxides effectively, is described. The key finding is a Br?nsted acid/halide ion bifunctional catalyst that can accelerate epoxide ring opening with high regioselectivity. Mechanistic studies disclosed that the ylide generated from TAPS, along with the formation of halohydrins, plays a crucial role in the reaction with isocyanates.
- Toda, Yasunori,Gomyou, Shuto,Tanaka, Shoya,Komiyama, Yutaka,Kikuchi, Ayaka,Suga, Hiroyuki
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supporting information
p. 5786 - 5789
(2017/11/10)
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- Imidazolium bromide ionic liquid containing amine groups and preparation method and application of ionic liquid
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The invention relates to imidazolium bromide ionic liquid containing amine groups and a preparation method and application of the ionic liquid. The structural formula of the imidazolium bromide ionic liquid containing amine groups is shown as the formula (I). Under protection of nitrogen, 3-bromopropylamine hydrobromide or 2-bromoethylamine hydrobromide and imidazole are dissolved in anhydrous ethanol after being mixed, reflux reaction is conducted for 20-25 h at 85-95 DEG C, ethanol is removed through vacuum distillation, an organic solvent is added, stirring and filtering are conducted, the organic solvent is removed from filter liquid through vacuum distillation, a KOH aqueous solution is added after vacuum drying so that the pH of the solution can be 8-9, filtering is conducted, solid is added into anhydrous ethanol and stirred, filtering is conducted again, filter liquid is dried in a vacuum mode, and the target product is obtained. In the process that catalytic epoxidation compound is used for synthesizing cyclic carbonate, the ionic liquid has the advantages that the yield is high, activity is high, no catalysts or solvents are needed, reaction conditions are mild, stability is high, and recycling is conducted many times. Please see the formula (I) in the description.
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Paragraph 0065; 0066; 0067; 0068; 0069
(2017/01/12)
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- CYCLIC CARBONATE PRODUCTION METHOD
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PROBLEM TO BE SOLVED: To provide a production method for obtaining a cyclic carbonate with a relatively high yield without utilizing high-pressure carbon dioxide and without utilizing any metal catalyst. SOLUTION: A cyclic carbonate production method comprises reacting an epoxy compound represented by the formula (1) with carbon dioxide in the presence of a compound represented by PhCH2-X (Ph is a phenyl group; and X is a halogen atom), a homopolymer of chloromethylstyrene, a copolymer of chloromethylstyrene and styrene, or a chloromethylated polystyrene, so as to obtain a cyclic carbonate represented by the formula (2). (R is a substituted/unsubstituted C6-20 aryl group, a substituted/unsubstituted C1-20 alkyl group, or a substituted/unsubstituted C2-20 alkylene group.) COPYRIGHT: (C)2016,JPOandINPIT
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Paragraph 0032; 0033; 0034
(2017/01/09)
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- A process for the preparation of cyclic carbonic ester
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The invention discloses a preparation method of cyclic carbonate. The method is characterized in that olefin and CO2 are adopted as raw materials, a metal Salen compound is used as a catalyst, pyridine n-oxide is used as an assistant catalyst, an oxidant and an organic solvent of a given amount are added, epoxidation reaction and cycloaddition reaction are respectively carried out in a same reaction kettle, and the cyclic carbonate can be directly and high selectively acquired in a one-step method. The preparation method has characteristics of simplicity in operation, moderate reaction condition, good catalytic effect, cheap raw material, available raw materials, and the like.
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Paragraph 0028; 0029
(2018/02/04)
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- Iron-Catalyzed Synthesis of Five-Membered Cyclic Carbonates from Vicinal Diols: Urea as Sustainable Carbonylation Agent
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A new iron-catalyzed synthesis of cyclic carbonates from the corresponding vicinal diols and urea is described. This straightforward transformation allows for the preparation of a variety of five-membered carbonates by employing an inexpensive and environmentally benign iron salt as the catalyst. The use of readily available feedstocks such as urea and polyols makes this a sustainable process. As ammonia is formed as the only stoichiometric byproduct, this process can also be characterized by its high atom economy.
- Pe?a-López, Miguel,Neumann, Helfried,Beller, Matthias
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supporting information
p. 3721 - 3727
(2016/08/16)
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- Immobilization of 1,5,7-triazabicyclo[4.4.0]dec-5-ene on magnetic γ-Fe2O3 nanoparticles: A highly recyclable and efficient nanocatalyst for the synthesis of organic carbonates
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1,5,7-Triazabicyclo[4.4.0]dec-5-ene was immobilized on magnetic γ-Fe2O3 nanoparticles as a magnetic nanocatalyst. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient and selective synthesis of organic carbonates by the direct condensation of alcohols and diethyl carbonate. The catalyst is quantitatively recovered by an external magnet and can be reused for six cycles with almost consistent activity. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene was immobilized on magnetic γ-Fe2O3 nanoparticles as a magnetic nanocatalyst. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient and selective synthesis of organic carbonates by the direct condensation of alcohols and diethyl carbonate. Copyright
- Wu, Liqiang,Tian, Shuanbao
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p. 2080 - 2087
(2014/05/06)
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- One-pot synthesis of cyclic carbonates from aldehydes, sulfur ylide, and CO2
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Treatment of aldehydes with sulfur ylide (CH2=SOMe2 or CH2=SMe2), in the presence of CO2 (1 atm) bubbled sequentially under mild conditions, produces cyclic carbonates in preparative yields. Sodium iodide formed in situ promotes the reaction between epoxide as intermediate and CO2 at ambient conditions, thus constituting a powerful metal-free synthesis of organic cyclic carbonates directly from aldehydes. Georg Thieme Verlag Stuttgart · New York.
- Aher, Ravindra D.,Kumar, B. Senthil,Sudalai, Arumugam
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- Biocompatible and recyclable amino acid binary catalyst for efficient chemical fixation of CO2
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In this work, the cycloaddition reactions of CO2 with various epoxides to form five-membered cyclic carbonates catalyzed by an efficient amino acid based biocompatible catalyst were investigated. It was found that the activity of amino acid could be obviously enhanced in the presence of alkali metal salts, and the l-tryptophan catalytic system was the most efficient among the catalysts employed. Based on the result, a possible mechanism for the synergetic effect of catalyst was proposed. The process reported here represents a simple, ecologically safer, cost-effective route to cyclic carbonates with high product quality, as well as easy catalyst recycling.
- Yang, Zifeng,Sun, Jian,Cheng, Weiguo,Wang, Jinquan,Li, Qian,Zhang, Suojiang
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- Immobilization of 1,5,7-triazabicyclo[4.4.0]dec-5-ene on magnetic γ-Fe2O3 nanoparticles: A highly recyclable and efficient nanocatalyst for the synthesis of organic carbonates
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1,5,7-Triazabicyclo[4.4.0]dec-5-ene was immobilized on magnetic γ-Fe2O3 nanoparticles as a magnetic nanocatalyst. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient and selective synthesis of organic carbonates by the direct condensation of alcohols and diethyl carbonate. The catalyst is quantitatively recovered by an external magnet and can be reused for six cycles with almost consistent activity. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene was immobilized on magnetic γ-Fe2O3 nanoparticles as a magnetic nanocatalyst. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient and selective synthesis of organic carbonates by the direct condensation of alcohols and diethyl carbonate.
- Wu, Liqiang,Tian, Shuanbao
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p. 2080 - 2087
(2015/04/27)
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- Influence of temperature and pressure on cyclic carbonate synthesis catalyzed by bimetallic aluminum complexes and application to overall syn -bis-hydroxylation of alkenes
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The effect of moderate temperatures (22-100 °C) and pressures (1-10 bar) on the synthesis of cyclic carbonates from epoxides and carbon dioxide catalyzed by a combination of bimetallic aluminum complexes and tetrabutylammonium bromide is investigated. The combined bimetallic complex and tetrabutylammonium bromide catalyst system is shown to be an order of magnitude more active than the use of tetrabutylammonium bromide alone at all temperatures and pressures studied. At the higher temperatures and pressures used, disubstituted epoxides become substrates for the reaction and it is shown that reactions proceed with retention of the epoxide stereochemistry. This allowed a route for the overall syn-bis-hydroxylation of alkenes to be developed without the use of hazardous metal based reagents. At higher pressures it is also possible to use compressed air as the carbon dioxide source.
- Beattie, Christopher,North, Michael,Villuendas, Pedro,Young, Carl
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p. 419 - 426
(2013/03/13)
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- METHODS AND SYSTEMS FOR THE FORMATION OF CYCLIC CARBONATES
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Described herein are inventive methods for synthesis of cyclic carbonates from C02 and epoxide. In some embodiments, the methods are carried out in the presence of a catalyst comprising an electrophilic halogen. In some embodiments, the methods are carried out in a flow reactor.
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Page/Page column 30; 32
(2013/12/03)
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- Quaternary ammonium ionic liquids as Bi-functional catalysts for one-step synthesis of dimethyl carbonate from ethylene oxide, carbon dioxide and methanol
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One kind of novel ionic liquids (ILs) with a tertiary amino moiety and a quaternary ammonium group were synthesized and identified by FT-IR, 1H and 13C NMR. The elemental chemical state and basicity of ILs were determined by XPS and Hammett indicator method, respectively. Then the catalytic performance of these bi-functional catalysts was investigated in one-step synthesis of dimethyl carbonate (DMC) from ethylene oxide (EO), carbon dioxide and methanol. The best catalytic performance with 99% EO conversion and a maximum of 74% DMC selectivity was obtained using [N111,6N11]I as catalyst under optimized reaction conditions. And the catalyst could be reused for several times. Normally, stronger basicity could be obtained by altering the anions with different nucleophilicity in ILs and a better catalytic activity could be achieved correspondingly. A mechanism that both the ring opening of epoxide through nucleophilic attacks and the transesterification play an important role in the reaction was proposed based on experimental results.
- Li, Jian,Wang, Liguo,Shi, Feng,Liu, Shimin,He, Yude,Lu, Liujin,Ma, Xiangyuan,Deng, Youquan
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experimental part
p. 339 - 346
(2011/12/22)
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- Aerobic oxidative carboxylation of olefins with metalloporphyrin catalysts
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Dioxo(tetraphenylporphyrinato)ruthenium(vi) and quaternary onium salt were successfully developed as catalysts to initiate a three component reaction of olefin, O2, and CO2 at ambient temperature under low pressure. The reaction can be carried out under solvent-free or solvent conditions. Styrene carbonate was obtained in 76% yield with 100% selectivity using 4 mol% of catalyst under optimized conditions.
- Bai, Dongsheng,Jing, Huanwang
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supporting information; scheme or table
p. 39 - 41
(2010/05/17)
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- Process for producing cyclic carbonates
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A mixture of catalysts composed of tetrabutylammonium iodide (TBAI) and zinc iodide (ZnI2) is used for producing cyclic carbonates, in particular variously substituted 2-oxo-1,3-dioxolanes, starting from an epoxy and carbon dioxide, under conditions of pressure and temperature approaching ambient values and in the absence of a solvent.
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Page/Page column 12-13
(2009/06/27)
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- PROCESS FOR THE PREPARATION OF ALKYLENE CARBONATES
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An aqueous process for preparing alkylene carbonates from alkenes and carbon dioxide is described herein. The process comprises the reaction of alkenes with a bromine source, a base and carbon dioxide. The aqueous process can be rendered catalytic by using an oxidant capable of in situ conversion of bromide into bromine.
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Page/Page column 9-10; 16-17
(2008/06/13)
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- Correlation between the basicity of solid bases and their catalytic activity towards the synthesis of unsymmetrical organic carbonates
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The correlation between the basic properties of solid catalysts and the reaction rate of the selective synthesis of unsymmetrical organic carbonates via direct condensation of diethylcarbonate (DEC) and alcohols was investigated. A detailed kinetic study of the transesterification of 1-phenylethanol and DEC was made with catalysts with different basic strengths. The solids included fluorinated hydrotalcite, MgLa mixed oxides, CsF (pure or supported on α- and γ-aluminas), KF (pure or supported on α- and γ-aluminas), anatase, rutile, and zirconia. Basic properties were determined by the adsorption of CO2, measured by gravimetry coupled with mass spectrometry and by calorimetry. Both techniques show a higher basicity for MgLa mixed oxides. The rate of the reaction was roughly proportional to the number of strongly basic sites present on the catalyst, except for CsF/α-Al 2O3, which showed higher activity for several different substrates in spite of a lower number and strength of basic sites. This is attributed to the high nucleophilicity of the alcoholate formed as an intermediate. The addition of water to the reaction medium induces two effects: inhibition of the reaction and the promotion of etherification of the substrate by ethanol as a side reaction. The catalysts can be reused several times with a small loss of activity.
- Veldurthy, Bhaskar,Clacens, Jean-Marc,Figueras, Francois
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p. 237 - 242
(2007/10/03)
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- New highly active and selective heterogeneous catalytic system for the synthesis of unsymmetrical organic carbonates: A green protocol
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A green, efficient, and selective synthesis of unsymmetrical organic carbonates is realised in the liquid phase by direct condensation of an alcohol and diethyl carbonate, in an ecocompatible route, in the presence of a recyclable heterogeneous solid-base CsF/α-Al2O3 catalyst. The catalyst displayed unprecedented activity after activation at 393 K for 4 h and produced quantitative yields with a greater rate compared with solid bases reported so far. The present process is a potential alternative to replace soluble bases in commercial synthesis. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Veldurthy, Bhaskar,Clacens, Jean-Marc,Figueras, Francois
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p. 1972 - 1976
(2007/10/03)
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- DIASTEREOSELECTIVE FORMATION OF CYCLIC CARBONATES BY CYCLIZATION OF ALKENYLOXYCARBONYLOXY RADICALS
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The alkenyloxycarbonyloxy radical (8) derived from trans-hex-2-en-1-ol via the N-hydroxypyridin-2-thione carbonate (4) undergoes fast (kc > 4.0 x 108 s-1 at 80 deg C) cyclization exclusively in the exo mode to give a cyclic radical (9) which is converted into products (6, 7) by diastereoselective SH2 reactions; radicals derived from homoallylic alcohols behave similarly.
- Beckwith, Athelstan L. J.,Davison, G. E.
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