Highly Active and Robust Metalloporphyrin Catalysts for the Synthesis of Cyclic Carbonates from a Broad Range of Epoxides and Carbon Dioxide

Bifunctional metalloporphyrins with quaternary ammonium bromides (nucleophiles) at the meta, para, or ortho positions of meso‐phenyl groups were synthesized as catalysts for the formation of cyclic carbonates from epoxides and carbon dioxide under solvent‐free conditions. The meta‐substituted catalysts exhibited high catalytic performance, whereas the para‐ and ortho‐substituted catalysts showed moderate and low activity, respectively. DFT calculations revealed the origin of the advantage of the meta‐substituted catalyst, which could use the flexible quaternary ammonium cation at the meta position to stabilize various anionic species generated during catalysis. A zinc(II) porphyrin with eight nucleophiles at the meta positions showed very high catalytic activity (turnover number (TON)=240 000 at 120 °C, turnover frequency (TOF)=31 500 h^?1 at 170 °C) at an initial CO₂ pressure of 1.7 MPa; catalyzed the reaction even at atmospheric CO₂ pressure (balloon) at ambient temperature (20 °C); and was applicable to a broad range of substrates, including terminal and internal epoxides.     

二氧化碳与环氧化合物合成环状碳酸酯的研究进展

二氧化碳作为温室气体和储量大、无毒且可循环利用的碳资源,其化学利用受到了人们的广泛关注. 二氧化碳与环氧化合物通过环加成反应制备环状碳酸酯是二氧化碳化学法利用最为有效的途径之一. 本文综述了近年来该反应的研究进展,讨论了催化剂作用下的反应机理.     

Development of a Halide‐Free Aluminium‐Based Catalyst for the Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide

Kinetic studies of the synthesis of glycerol carbonate from glycidol and carbon dioxide have been carried out. These showed that under suitable reaction conditions, bimetallic aluminium(salen) complex 4 is able to catalyse the conversion of epoxides into the corresponding cyclic carbonates without the need for a co‐catalyst.     

Deep Eutectic Solvents as Catalysts for Cyclic Carbonates Synthesis from CO2 and Epoxides

In recent years, the chemical industry has put emphasis on designing or modifying chemical processes that would increasingly meet the requirements of the adopted proecological sustainable development strategy and the principles of green chemistry. The development of cyclic carbonate synthesis from CO₂ and epoxides undoubtedly follows this trend. First, it represents a significant improvement over the older glycol phosgenation method. Second, it uses renewable and naturally abundant carbon dioxide as a raw material. Third, the process is most often solvent-free. However, due to the low reactivity of carbon dioxide, the process of synthesising cyclic carbonates requires the use of a catalyst. The efforts of researchers are mainly focused on the search for new, effective catalysts that will enable this reaction to be carried out under mild conditions with high efficiency and selectivity. Recently, deep eutectic solvents (DES) have become the subject of interest as potential effective, cheap, and biodegradable catalysts for this process. The work presents an up-to-date overview of the method of cyclic carbonate synthesis from CO₂ and epoxides with the use of DES as catalysts.     

Zinc Imine Polyhedral Oligomeric Silsesquioxane as a Quattro-Site Catalyst for the Synthesis of Cyclic Carbonates from Epoxides and Low-Pressure CO2

In the present research, the synthesis, spectroscopic characterization, and structural investigations of a unique Zn^II complex of imine-functionalized polyhedral oligomeric silsesquioxane (POSS) is designed, and hereby described, as a catalyst for the synthesis of cyclic carbonates from epoxides and CO₂. The uncommon features of the designed catalytic system is the elimination of the need for a high pressure of CO₂ and the significant shortening of reaction times commonly associated with such difficult transformations like that of styrene oxide to styrene carbonate. Our studies have shown that imine-POSS is able to chelate metal ions like Zn^II to form a unique coordination complex. The silsesquioxane core and the hindrance of the side arms (their steric effect) influence the construction process of the homoleptic Zn₄@POSS-1 complex. The compound was characterized in solution by NMR (¹H, ¹³C, ²⁹Si), ESI-MS, UV/Vis spectroscopy and in the solid state by thermogravimetric/differential thermal analysis (TG-DTA), elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), cross-polarization magic angle spinning (CP MAS) NMR (¹³C, ²⁹Si) spectroscopy, and X-ray crystallography.     

无机氧化物载体对催化CO_2与环氧化合物合成环状碳酸酯的促进作用(英文)

以一系列无机氧化物与四丁基溴化铵为双组分催化剂体系,考察了其催化CO2和环氧化合物合成环状碳酸酯的反应性能.结果表明,在四丁基溴化铵与这些本身并没有催化活性的无机氧化物共同作用下,反应活性明显提高,表现出很强的协同催化作用.另外,通过对SiO2的表面硅烷基化,考察了其表面羟基数量对反应活性的影响,发现当SiO2的表面经过硅烷基化以后,反应活性大幅度降低,表明无机氧化物表面羟基对CO2环加成反应活性有非常显著的促进作用.     

Synthesis of Cyclic Carbonates Catalysed by Aluminium Heteroscorpionate Complexes

New aluminium scorpionate based complexes have been prepared and used for the synthesis of cyclic carbonates from epoxides and carbon dioxide. Bimetallic aluminium(heteroscorpionate) complexes 9 – 14 were synthesised in very high yields. The single‐crystal X‐ray structures of 12 and 13 confirm an asymmetric κ²‐NO‐μ‐O arrangement in a dinuclear molecular disposition. These bimetallic aluminium complexes were investigated as catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide in the presence of ammonium salts. Under the optimal reaction conditions, complex 9 in combination with tetrabutylammonium bromide acts as a very efficient catalyst system for the conversion of both monosubstituted and internal epoxides into the corresponding cyclic carbonates showing broad substrate scope. Complex 9 and tetrabutylammonium bromide is the second most efficient aluminium‐based catalyst system for the reaction of internal epoxides with carbon dioxide. A kinetic study has been carried out and showed that the reactions were first order in complex 9 and tetrabutylammonium bromide concentrations. Based on the kinetic study, a catalytic cycle is proposed.     

Mechanism of Cyclic Carbonate Synthesis from Epoxides and CO2

Three interconnected catalytic cycles account for the title reaction catalyzed by a bimetallic aluminum(salen) complex and Bu₄NBr. In the first, Bu₄NBr acts as a nucleophile to activate the epoxide. In the second, Bu₃N generated in situ serves to activate CO₂. In the third, the aluminum(salen) complex brings the two activated species together so that the key bonds can be formed intramolecularly.

     

Green Catalytic Process for Cyclic Carbonate Synthesis from Carbon Dioxide under Mild Conditions

As a renewable and abundant C₁ resource possessing multiple attractive characteristics, such as low cost, nontoxicity, non‐flammability, and easy accessibility, CO₂ conversion into value‐added chemicals and fuels can contribute to green chemistry and sustainable development. Since CO₂ is a thermodynamically inert molecule, the activation of CO₂ is pivotal for its effective conversion. In this regard, the formation of a transition‐metal CO₂ complex through direct coordination is one of the most powerful ways to induce the inert CO₂ molecule to undergo chemical reactions. To date, numerous processes have been developed for efficient synthesis of cyclic carbonates from CO₂. On the basis of mechanistic understanding, we have developed efficient metal catalysts and green processes, including heterogeneous catalysis, and metal‐free systems, such as ionic liquids, for cyclic carbonate synthesis. The big challenge is to develop catalysts that promote the reaction under low pressure (preferably at 1 bar). In this context, bifunctional catalysis is capable of synergistic activation of both the substrate and CO₂ molecule, and thus, could render CO₂ conversion smoothly under mild conditions. Alternatively, converting CO₂ derivatives, that is, the captured CO₂ as an activated species, would more easily take place at low pressure in comparison with gaseous CO₂. The aim of this Personal Account is to summarize versatile catalytic processes for cyclic carbonate synthesis from CO₂, including epoxide/CO₂ coupling reaction, carboxylation of 1,2‐diol with CO₂, oxidative cyclization of olefins with CO₂, condensation of vicinal halohydrin with CO₂, carboxylative cyclization of propargyl alcohols with CO₂, and conversion of the CO₂ derivatives.

     

Isocyanate‐ and Phosgene‐Free Routes to Polyfunctional Cyclic Carbonates and Green Polyurethanes by Fixation of Carbon Dioxide

The catalytic chemical fixation of carbon dioxide by carbonation of oxiranes, oxetanes, and polyols represents a very versatile green chemistry route to environmentally benign di‐ and polyfunctional cyclic carbonates as intermediates for the formation of non‐isocyanate poly­urethane (NIPU). Two synthetic pathways lead to NIPU thermoplastics and thermosets: i) polycondensation of diacarbamates or acyclic dicarbonates with diols or diamines, respectively, and ii) polyaddition by ring‐opening polymerization of di‐ and polyfunctional cyclic carbonates with di‐ and polyamines. The absence of hazardous and highly moisture‐sensitive isocyanates as intermediates eliminates the need for special safety precautions, drying and handling procedures. Incorporated into polymer backbones and side chains, carbonate groups enable facile tailoring of a great variety of urethane‐functional polymers. As compared with conventional polyurethanes, ring‐opening polymerization of polyfunctional cyclic carbonates affords polyhydroxyurethanes with unconventional architectures including NIPUs containing carbohydrate segments. NIPU/epoxy hybrid coatings can be applied on wet surfaces and exhibit improved adhesion, thermal stability and wear resistance. Combining chemical with biological carbon dioxide fixation affords 100% bio‐based NIPUs derived from plant oils, terpenes, carbohydrates, and bio polyols. Biocompatible and biodegradable NIPU as well as NIPU biocomposites hold great promise for biomedical applications.

     

有序介孔碳CMK-3负载离子液体催化CO2与环氧化物合成环状碳酸酯

采用有序介孔碳CMK-3为载体负载咪唑类离子液体制得CMK-3-IL催化剂,用X射线衍射(XRD)、透射电子显微镜(TEM)、N2吸附、热重分析和元素分析等手段表征了催化剂样品,并考察了CMK-3-IL催化剂催化CO2与环氧丙烷合成碳酸丙烯酯的反应性能。结果表明,离子液体被成功的负载到CMK-3载体上,CMK-3负载离子液体后孔道结构没有被破坏,但孔体积、孔径和比表面积均有所下降。催化实验表明,在120℃、2 MPa的条件下反应6 h,环氧丙烷转化率达到64%,碳酸丙烯酯选择性高达99%。     

Highly Active Aluminium Catalysts for the Formation of Organic Carbonates from CO2 and Oxiranes

Al^III complexes of amino‐tris(phenolate) ligand scaffolds have been prepared to attain highly Lewis acidic catalysts. Combination of the aforementioned systems with ammonium halides provides highly active catalysts for the synthesis of organic carbonates through addition of carbon dioxide to oxiranes with initial turnover frequencies among the highest reported to date within the context of cyclic carbonate formation. Density functional theory (DFT) studies combined with kinetic data provides a rational for the relative high activity found for these Al^III complexes, and the data are consistent with a monometallic mechanism. The activity and versatility of these Al^III complexes has also been evaluated against some state‐of‐the‐art catalysts and the combined results compare favorably in terms of catalyst construction, stability, activity, and applicability.     

双功能金属卟啉催化环氧化合物与 CO2 偶联反应合成环碳酸酯

 合成了新颖的双功能水溶性金属卟啉 催化剂 M(TTMAPP)I4(X) (M = Co, Fe, Mn 和 Cr; X = OAc, CF3COO, CCl3COO, OTs, Cl, Br 和 I), 研究了它们催化 CO2 与末端环氧化合物合成环碳酸酯的偶联反应. 分别考察了反应温度、不同金属的 Lewis 酸中心、抗衡离子和催化剂重复使用次数对反应性能的影响. 当以 Co(III)(TTMAPP)I4(OAc) 为催化剂, 底物与催化剂摩尔比为 1 000, 温度为 353 K, CO2 压力为 667 kPa 和无溶剂条件下, 反应 5 h 时丙烯环碳酸酯收率为 95.4%. 在 298 K, 底物与催化剂之比为 2 000 时, 加入 1 ml 甲醇, 反应 24 h 丙烯环碳酸酯收率为 19.4%. 催化剂可以用乙醚回收, 循环使用 5 次后催化剂活性没有明显降低.     

Self‐Assembly of Luminescent Lanthanide Mesocates as Efficient Catalysts for Transforming Carbon Dioxide into Cyclic Carbonates

Four dinuclear lanthanide mesocates were fabricated through a spontaneous self‐assembly method, and the formation of these complexes was well studied by their absorption and emission spectra. These stable complexes were also found to exhibit superior performance in catalyzing the coupling reaction between epoxides and CO₂ with excellent recyclability. Moreover, the catalysts could be prepared on large scale. Moreover, the Yb and Lu complexes featured emissions in the near‐infrared and visible regions, respectively, and their intensities and lifetimes could be used for identification purposes. Thus, this new approach can be used to construct promising lanthanide complexes as efficient catalysts and it identifies the possibility to better study a catalytic reaction with a luminescent catalyst.     

新型氮杂环卡宾锌配合物催化CO2和环氧化物高效合成环状碳酸酯

合成了一系列新型的芘标记含溴亲核阴离子的氮杂环卡宾前驱体化合物,与卤化锌配位后获得具有CO₂捕获能力以及路易斯酸碱位点的NHC-PDBI-ZnX₂(X=Cl、Br、I)催化剂,通过¹H NMR、¹³C NMR、XPS、FT-IR、¹³C CP-MAS NMR和ICP-AES表征技术对该类催化剂结构和化学性质进行了表征.氮杂卡宾锌配合物被证明是有效的单组分多功能催化剂,对环氧丙烷和CO₂的环加成反应显示出较高的催化活性和选择性.最佳活性的NHCPDBI-ZnI₂催化剂在120℃、3.0 MPa、2.0 h等较温和条件下,取得98%以上碳酸丙烯酯收率.该催化剂还具有优异的底物普适性和循环使用稳定性,归因于路易斯酸性Zn²⁺与NHC-PBDI主链形成的强共价键.此外,结合FTIR等表征推测了反应机理,其中NHC-PDBI-ZnX₂的卡宾位吸附活化CO₂以及路易斯酸碱位点开环的...     

Triethanolamine/KI: A Multifunctional Catalyst for CO2 Activation and Conversion with Epoxides into Cyclic Carbonates

A catalytic system of triethanolamine/potassium iodide (KI) was proved to be efficient for the chemical fixation of CO₂ with epoxide. It was found that triethanolamine with dual function could activate both CO₂ and epoxides. Effects of parameters such as catalyst molar ratio and amount, reaction time, pressure, and temperature were studied systematically. As a result, 99% propylene oxide conversion as well as 99% propylene carbonate selectivity could be obtained under the optimal reaction condition. Furthermore, the catalyst was found to be applicable to a variety of terminal epoxides, providing the corresponding cyclic carbonates in good yields and selectivity. Moreover, the catalyst could be reused five times without loss of activity. This work presents an example of a cheap and efficient catalyst for the chemical fixation of CO₂ to high-value chemicals, which could help to improve the catalytic efficiency and decrease cost of products for larger applications.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]     

Mg(OH)Cl/KI as a Highly Active Heterogeneous Catalyst for the Synthesis of Cyclic Carbonates from CO2 and Epoxides under Solvent‐Free Conditions

The combination of magnesium hydroxyl chloride [Mg(OH)Cl] with KI could efficiently catalyze the coupling reaction of carbon dioxide with epoxides to give the corresponding cyclic carbonates in good to excellent yields (75.0% –98.3%) and high selectivity (99.6%) in the absence of organic solvents. The heterogeneous catalyst Mg(OH)Cl/KI could be reused at least six times almost without loss of the catalytic activity. The influence of some key factors (such as molar ratio of Mg(OH)Cl to KI, temperature, reaction time and CO₂ pressure) on the reaction was also discussed.     

水合碱金属卤化物催化 CO2 与环氧化物合成环状碳酸酯

 在不添加任何助剂及溶剂的条件下, 考察了水合碱金属卤化物催化 CO2 与环氧丙烷合成碳酸丙烯酯的反应性能. 结果表明, 水合碱金属卤化物表现出远高于无水碱金属卤化物的催化活性, 其中, 以 NaI2H2O 的催化性能最好, 在 120 C, 1 MPa 的条件下反应 1.5 h, 碳酸丙烯酯收率达 97%. 此外, NaI2H2O 在 CO2 与其它环氧化物合成相应环状碳酸酯反应中也表现出较高的催化活性.