123931-62-4Relevant articles and documents
Strongly Lewis Acidic Metal-Organic Frameworks for Continuous Flow Catalysis
Ji, Pengfei,Feng, Xuanyu,Oliveres, Pau,Li, Zhe,Murakami, Akiko,Wang, Cheng,Lin, Wenbin
supporting information, p. 14878 - 14888 (2019/10/02)
The synthesis of highly acidic metal-organic frameworks (MOFs) has attracted significant research interest in recent years. We report here the design of a strongly Lewis acidic MOF, ZrOTf-BTC, through two-step transformation of MOF-808 (Zr-BTC) secondary building units (SBUs). Zr-BTC was first treated with 1 M hydrochloric acid solution to afford ZrOH-BTC by replacing each bridging formate group with a pair of hydroxide and water groups. The resultant ZrOH-BTC was further treated with trimethylsilyl triflate (Me3SiOTf) to afford ZrOTf-BTC by taking advantage of the oxophilicity of the Me3Si group. Electron paramagnetic resonance spectra of Zr-bound superoxide and fluorescence spectra of Zr-bound N-methylacridone provided a quantitative measurement of Lewis acidity of ZrOTf-BTC with an energy splitting (?E) of 0.99 eV between the ?x? and ?y? orbitals, which is competitive to the homogeneous benchmark Sc(OTf)3. ZrOTf-BTC was shown to be a highly active solid Lewis acid catalyst for a broad range of important organic transformations under mild conditions, including Diels-Alder reaction, epoxide ring-opening reaction, Friedel-Crafts acylation, and alkene hydroalkoxylation reaction. The MOF catalyst outperformed Sc(OTf)3 in terms of both catalytic activity and catalyst lifetime. Moreover, we developed a ZrOTf-BTC?SiO2 composite as an efficient solid Lewis acid catalyst for continuous flow catalysis. The Zr centers in ZrOTf-BTC?SiO2 feature identical coordination environment to ZrOTf-BTC based on spectroscopic evidence. ZrOTf-BTC?SiO2 displayed exceptionally high turnover numbers (TONs) of 1700 for Diels-Alder reaction, 2700 for epoxide ring-opening reaction, and 326 for Friedel-Crafts acylation under flow conditions. We have thus created strongly Lewis acidic sites in MOFs via triflation and constructed the MOF?SiO2 composite for continuous flow catalysis of important organic transformations.
Investigation and mechanistic study into intramolecular hydroalkoxylation of unactivated alkenols catalyzed by cationic lanthanide complexes
Zhu, Xuehua,Li, Guoyao,Xu, Fan,Zhang, Yong,Xue, Mingqiang,Shen, Qi
, p. 1451 - 1458 (2017/02/19)
Cationic lanthanide complexes of the type [Ln(CH3CN)9]3+[(AlCl4)3]3–·CH3CN (Ln = Pr, Nd, Sm, Gd, Er, Yb, Y) served as effective catalysts for the intramolecular hydroalkoxylation/cyclization of unactivated alkenols to yield the cyclic ethers with Markovnikov regioselectivity under mild conditions. Novel cationic complexes, [AlCl(CH3CN)5]2+[(AlCl4)2]2–·CH3CN and [Nd(CH3CN)9]3+[(FeCl4)3]3–·CH3CN, were synthesized and evaluated for the intramolecular hydroalkoxylation/cyclization of unactivated alkenols for comparison. The active sequence of [Nd(CH3CN)9]3+[(FeCl4)3]3–·CH3CN 3CN)5]2+[(AlCl4)2]2–·CH3CN 3CN)9]3+[(AlCl4)3]3–·CH3CN observed indicated that both the cation and anion have great influence on the activity. Comparative study on the activity of AlCl3and its cationic complex [AlCl(CH3CN)5]2+[(AlCl4)2]2–·CH3CN revealed the formation of the cationic Al center enhanced the activity greatly. The1H NMR studies indicated the activation of hydroxyl and olefin by the cationic Ln3+center were involved in the reaction pathways.
Activation of sp3 and sp2 C-H bonds of oxygen containing heterocyclic molecules for alkylation and arylation reactions catalyzed by an iron complex
Gartia, Yashraj,Ramidi, Punnamchandar,Cheerla, Sreevishnu,Felton, Charlette M.,Jones, Darin E.,Das, Bhaskar C.,Ghosh, Anindya
, p. 253 - 259 (2014/07/07)
Activation of both sp3 and sp2 CH bonds is reported using an efficient iron(III) complex (1) of a ligand (N2,N6-bis(2,6- diisopropylphenyl)pyridine-2,6-dicarboxamide: L). The iron(III) complex showed catalytic activity of CC coupling reaction of oxygen containing heterocycles, e.g. tetrahydrofuran (THF), with various alkyl, allyl and aryl Grignard reagents under ambient reaction conditions. Complex 1 demonstrated excellent activity and reactions were completed within 30 min to 1 h. A high turnover frequency (TOF) of 1700 h-1 using a low catalyst loading of 0.02 mol% was obtained for the reaction. Interestingly, the catalyst was selective in activation of the CH bond adjacent to the oxygen in various oxygen containing heterocyclic molecules to yield 2-substitituted products.
