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![Plausible mechanism for cycloadition of CO2 and epoxide catalyzed by Cn (mim) (mim) Br2 and ZnBr2 (n = 3, 4, 6) [20]](publication/317771119/figure/fig3/AS:941520542781441@1601487398039/Plausible-mechanism-for-cycloadition-of-CO2-and-epoxide-catalyzed-by-Cn-mim-mim-Br2.gif)
Plausible mechanism for cycloadition of CO2 and epoxide catalyzed by Cn (mim) (mim) Br2 and ZnBr2 (n = 3, 4, 6) [20]
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Cyclic carbonate synthesis is an attractive route to utilize CO2 and reduce green house gas. Numbers of studies have been reported on catalytic synthesis of cyclic carbonate, however, very few studies reported on kinetic analysis of cycloaddition reaction. Present study reports a kinetic analysis for coupling reaction of epichlorohydrin (ECH) and c...
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The activation of abundant molecules such as hydrocarbons and atmospheric nitrogen (N2) remains a challenge because these molecules are often inert. The formation of carbon–nitrogen bonds from N2 typically has required reactive organic precursors that are incompatible with the reducing conditions that promote N2 reactivity¹, which has prevented cat...
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... The reaction rate can be estimated by using equations (S1-S3), which shows that the CO 2 cycloaddition reaction follows first-order kinetics with a rate constant of 0.063 h − 1 (Fig. 3e) [40,41]. It is noted that PZn-3 exhibits a comparable rate constant than kinds of typical catalysts (even homogeneous ones) under much lower reaction pressure and temperature (Table S4) [42][43][44][45][46], revealing its superior catalytic activity. ...
Lewis pair catalyst is considered to be a cutting-edge tool for the low-energy activation and subsequent conversion of CO2, which, yet suffers from complex preparation and unclear design strategy. This work proposes a one-step strategy for precisely constructing Lewis pair heterogeneous catalysts through the coordination of amino-functionalized poly(ionic liquid) (PIL) and metal cations for atmospheric CO2 conversion to cyclic carbonates. Self-tunability in the strength and ratio of Lewis acidic/basic sites is imparted by the facile regulation of the type/content of metal ions (Zn²⁺/Co²⁺/Cu²⁺), which is crucial for promoting acid/base cooperation in CO2 cycloaddition. The synergy of M²⁺, Br⁻ and C-2 proton on imidazolium ring with an optimum acid/base molar ratio of ca. 1.47 has been proved to activate CO2 and epoxides synchronously, inducing a promising catalytic activity with high yield (∼95 %) and selectivity (>99 %) of cyclic carbonates under atmospheric pressure and low temperature (≤75 °C) without cocatalyst.
... The mechanistic role of TBIL to promote the synthesis of 301 have been supported using DFT studies. Following the similar line of approach for the synthesis of 4-chloromethyl-1,3-dioxolan-2-one (683), Jaiswal and Varma have reported cycloaddition of epichlorohydrin (682) and carbon dioxide (486) at 50-110°C without solvent through the catalytic assistance of dicationic ILs, 1,3-bis(3methylimidazolium-1-yl)hexane dibromide [C 6 (mim)(mim)Br 2 ] and zinc bromide as co-catalysts (Scheme 256) [361]. Further, they have claimed the industrial applicability of the present catalytic system for the synthesis of cyclic carbonates. ...
Heterocycles constitute the integral part of the most of United States food and drug administration (USFDA) approved drugs. Over the past decade, ionic liquids have emerged as a clean, efficient and environmentally benign alternative to the hazardous volatile organic solvents in addition to numerous other remarkable applications owing to their renewability, biodegradability, abundance and inexpensive nature. These properties could be finely tuned based on the demand of several applications in chemical transformations through alteration of their compositional counterparts such as; anions and cations. The current work emphasizes the significant insights into the undisputable applications of these ionic liquids such as catalyst, solvent, co-solvent, ligand in homo and heterogeneous reactions and their use as support in several synthetic transformations. Significant efforts have been made to provide critical inputs on the mechanistic insights such as hydrogen bond formation, amphiphilic electrophile-nucleophile dual activation, bifunctional catalysis, phase-transfer catalysis, and organocatalysis for ionic liquid catalyzed organic transformation. Additionally, the present comprehensive and critical review shall help the reader to select the suitable ILs for synthesizing of desired heterocycles. The present review shall focus on recent advancements and applications of ionic liquids as solvent and catalysts in the synthesis of heterocycles reported from 2013 to 2020.
Novel binding motifs suitable for the construction of multitopic guest-based molecular devices (e.g., switches, sensors, data storage, and catalysts) are needed in supramolecular chemistry. No rigid, aliphatic binding motif that allows for axial disubstitution has been described for cucurbit[6]uril (CB6) so far. We prepared three model guests combining spiro[3.3]heptane and bicyclo[1.1.1]pentane centerpieces with imidazolium and ammonium termini. We described their binding properties toward CB6/7 and α-/β-CD using NMR, titration calorimetry, mass spectrometry, and single-crystal X-ray diffraction. We found that a bisimidazolio spiro[3.3]heptane guest forms inclusion complexes with CB6, CB7, and β-CD with respective association constants of 4.0 × 10⁴, 1.2 × 10¹², and 1.4 × 10². Due to less hindering terminal groups, the diammonio analogue forms more stable complexes with CB6 (K = 1.4 × 10⁶) and CB7 (K = 3.8 × 10¹²). The bisimidazolio bicyclo[1.1.1]pentane guest forms a highly stable complex only with CB7 with a K value of 1.1 × 10¹¹. The high selectivity of the new binding motifs implies promising potential in the construction of multitopic supramolecular components.
A novel mono-quaternary phosphorus salt functionalized fiber (PANQPSF) was developed as the multifunctional material to simultaneously realize selective removal of sodium dodecyl benzene sulfonate (SDBS) from water and green conversion of CO2. Compared with other adsorption materials and functionalized fibers, PANQPSF exhibits the eminent adsorption performance for SDBS due to its high polarization and hydrophobicity, and the adsorption capacity can reach 5.1 mol mol⁻¹, equivalenting to 1066 mg g⁻¹. And the synergistic adsorption mechanism of electrostatic interaction and lipophilic interaction between PANQPSF and SDBS is proposed. Furthermore, the PANQPSF still keeps excellent adsorption capacity even after 10 cycles. More satisfactorily, PANQPSF is used to catalyze the cycloaddition reaction of CO2 and epoxy compounds. The catalytic mechanism based on the nucleophilicity of Br⁻ and the stabilizing effect of electrostatic interaction is promoted. In summary, the adsorption and catalytic performance prove that PANQPSF is an outstanding material with multi-dimensional applications.
Catalytic fixation of greenhouse gas CO2 into value-added chemicals under mild conditions was deemed as an effective pathway for carbon emissions mitigation, though facing big challenges. Herein, a novel hydroxyl-ionic liquid functionalized metalloporphyrin (ZnTpyp-IL) catalyst bearing hydrogen bond donor (HBD), Lewis acidic and nucleophilic sites was fabricated and invested in the CO2 cycloaddition without additive or solvent. The integration of ionic liquid endowed the framework with strong surface affinity to enrich CO2 molecules, while the cooperative interplay of multiple active sites further promoted the high-selective conversion of epichlorohydrin (ECH). Under optimal conditions (100 °C, 1 MPa, 4 h), the yield of corresponding chloropropene carbonate (CPC) reached 97.1 % (turnover frequency (TOF) = 52.4 h⁻¹), far superior to that of bare Tpyp (17.4 %). The preliminary kinetic studies revealed the lower activation energy (59.54 kJ/mol) needed to be overcome in the ring-opening process over ZnTpyp-IL. Moreover, a plausible dual-activation mechanism of hydrogen bonds and Zn centers for epoxides was proposed based on the density functional theory calculation (DFT) to explain the acceleration of rate-determining step. Coupled with the satisfactory reusability and substrate expansibility, the developed ZnTpyp-IL demonstrated its great potential as robust heterogeneous catalyst in the efficient utilization of C1 resource.
Considered as an important C1 source on earth, carbon dioxide (CO2) utilization and fixation has aroused great attention. Synthesis of cyclic carbonate are one of the most widely industrialized routes. Ionic liquids have been studied for highly efficient cyclic carbonate production due to their distinguished characteristics. In this work, highly efficient synthesis of propylene carbonate catalyzed by [bmim]Br was achieved via a continuous-flow microreaction system. Based on that, influence factors and kinetics parameters for propylene carbonate synthesis were obtained. And the flow patterns were investigated via transparent tube, which were proved to be slug flow. The activation energy for [bmim]Br in this microreaction system was 57.4 kJ/mol with the temperature range from 110 to 140 ℃, and the reaction was found to follow first-order on PO and CO2 concentrations, and first-order on [bmim]Br concentration. Verification of the kinetic models was also studied and proved a less than 12 % error range.
N,N'-Phenylenebis(5-tert-butylsalicylideneimine) is shown to be an effective single-component catalyst for the metal and halide free synthesis of cyclic carbonates from epoxides and carbon dioxide. Using this bis-phenolic catalyst, a series of eight epoxides has been converted into the corresponding cyclic carbonates. Many closely related catalyst structures were found to be catalytically inactive and the structural features necessary for catalytic activity have been delineated. Unusually, reactions could be carried out under solvent free conditions, or in the green solvents 2-MeTHF and propylene carbonate. Stereochemical studies showed that carbon dioxide insertion occurs exclusively at the terminal end of the epoxide and does so with loss of stereochemical purity if a 1-deutero-2-alkyl epoxide is used as substrate. On the basis of this evidence, an unprecedented, dual activation mechanism is proposed in which one phenol acts as a Brønsted acid to activate the epoxide, whilst the other reacts with carbon dioxide to form a carbonic half-ester intermediate which then ring-opens the activated epoxide. Two pathways are subsequently available for cyclization to a cyclic carbonate which have opposite stereochemical consequences. The experimental results suggest that ring-opening of the epoxide by the carbonic half-ester is the rate determining step of the catalytic cycle.
