Bifunctional Porphyrin Catalysts for the Synthesis of Cyclic Carbonates from Epoxides and CO<sub>2</sub>: Structural Optimization and Mechanistic Study
ring closure formed the cyclic carbonate and regenerated the catalyst. Density functional theory calculations gave results consistent with the experimental results, revealing that the quaternary ammoniumcation underwent conformational changes that stabilized various anionic species generated during the catalytic cycle. The high activity of 1d and 1o was due to the cooperative action of the Mg(II) and
我们制备了双功能 Mg(II) 卟啉催化剂 1,用于从环氧化物和 CO2 无溶剂合成环状碳酸酯。分别具有 Br(-)、Cl(-) 和 I(-) 反阴离子的 1d、1h 和 1i 的活性按 1i < 1h < 1d 的顺序增加。带有四个具有不同烷基链长度的四烷基溴化铵基团的催化剂 1d 和 1j-m 表现出相当但略有不同的活性。基于优异的催化剂 1d,我们合成了具有 8 个四烷基溴化铵基团的 Mg(II) 卟啉 1o,显示出更高的催化活性(周转次数,138,000;周转频率,19,000 h(-1))。使用1d研究了催化机理。在 1-6 MPa 范围内的初始 CO2 压力下,产量几乎保持不变,表明 CO2 不参与该压力范围内的速率决定步骤。在超临界 CO2 中没有反应进行,可能是因为环氧化物(催化剂溶解在其中)溶解在超临界 CO2 中并被其稀释。用 (18)O 标记的 CO2 和 D 标记的环氧化物进行的实验表明,催化循环涉及
Development of Isostructural Porphyrin–Salen Chiral Metal–Organic Frameworks through Postsynthetic Metalation Based on Single-Crystal to Single-Crystal Transformation
2–7) have been synthesized through postsynthetic metalation (PSMet) of the parent ps-CMOF via single-crystal to single-crystaltransformation. Crystal structures of these ps-CMOF analogues revealed the same topological structure but varied metal entities compared to those of the parent framework. Note that the PSMet process involves three methods involving cation exchange at the nodes, cation exchange
Kinetic Resolution of Epoxides with CO
<sub>2</sub>
Catalyzed by a Chiral‐at‐Iridium Complex
作者:Jie Qin、Vladimir A. Larionov、Klaus Harms、Eric Meggers
DOI:10.1002/cssc.201802049
日期:2019.1.10
Chiral‐at‐metal bis‐cyclometalated iridium(III) complexes are introduced as a new class of chiral catalysts for the reaction of epoxides with CO2 to form cyclic carbonates under conditions of kineticresolution. Reactions are typically performed at room temperature in the presence of 1 mol % of iridium catalyst and 1.5 mol % of tetraethylammonium bromide as the nucleophilic cocatalyst to provide selectivity
Bifunctional Aluminum Catalyst for CO<sub>2</sub> Fixation: Regioselective Ring Opening of Three-Membered Heterocyclic Compounds
作者:Wei-Min Ren、Ye Liu、Xiao-Bing Lu
DOI:10.1021/jo501926p
日期:2014.10.17
Regioselective ring opening of three-membered heterocyclic compounds (epoxides or N-substituted aziridines) at various temperatures was observed in coupling reactions with CO2 by the use of an aluminum–salen catalyst in conjunction with intramolecular quaternary ammonium salts as cocatalysts, affording the corresponding five-membered cyclic products with complete configuration retention at the methine
Bimetallic scorpionate-based helical organoaluminum complexes for efficient carbon dioxide fixation into a variety of cyclic carbonates
作者:Marta Navarro、Luis F. Sánchez-Barba、Andrés Garcés、Juan Fernández-Baeza、Israel Fernández、Agustín Lara-Sánchez、Ana M. Rodríguez
DOI:10.1039/d0cy00593b
日期:——
preferential arrangement of the ancillary scorpionates in the bimetallic complexes and rationalized the proposed reaction mechanism. Bimetallic complexes were investigated as catalysts in combination with halides for the cycloaddition reaction of CO2 with a wide range of epoxides for cyclic carbonate formation. These studies led to the development of a sustainable, inexpensive, efficient and selective bicomponent
可以通过加热初步的双核加合物或通过直接加热2当量的配体配体来获得新的双金属螺旋铝配合物。的AlR 3。X射线衍射分析证实了配体中的高配位通用性和配合物中存在螺旋手性。DFT计算证实了双金属配合物中辅助蝎子的优先排列,并合理化了所提出的反应机理。研究了双金属配合物作为催化剂与卤化物结合用于CO 2的环加成反应与多种环氧化物形成环状碳酸酯。这些研究导致了可持续,廉价,高效和选择性的双组分系统的开发,该系统具有非常广泛的底物范围,包括内部的和具有挑战性的生物基三取代萜烯衍生的底物,在温和条件下可实现高反式环氧丙烷的转化率(79%转化温度为70°C,10 bar CO 2,1 mol%,66 h)