38259-00-6Relevant articles and documents
Immobilization of a soluble metal complex in an organic network. Remarkable catalytic performance of a porous dialkoxyzirconium polyphenoxide as a functional organic zeolite analogue
Sawaki, Tomoya,Aoyama, Yasuhiro
, p. 4793 - 4798 (1999)
Treatment of anthracenebisresorcinol 1 (a tetraphenol) with Zr(O(t)Bu)4 in THF results in polycondensation to give an O-Zr-O network and affords a poly(dialkoxyzirconium phenoxide), 14- · 2[Zr(O(t)Bu)2] (Zr host), in quantitative yield as an insoluble, amorphous, microporous powder with a particle size of ~0.7 μm, a pore size of ~0.7 nm, and a specific surface area of ~200 m2/g. The powder exhibits reversible Langmuir-type adsorption/desorption of N2 at 77 K and hexane at 298 K. Adsorption and coadsorption of ethyl acetate, benzene, and other polar and apolar guests also occurs readily at 298 K. The Zr host catalyzes the Diels-Alder reaction of acrolein with 1,3-cyclohexadiene in a remarkable manner. As a solid metal- organic catalyst, it has a formula-based turnover rate constant of 40 h-1, which far exceeds those of its components, i.e., the soluble Lewis acid Zr(O(t)Bu)4 (0.1 h-1) and the hydrogen-bonded insoluble organic network 1 (0.3 h-1). The solid catalyst can be easily separated from the organic product, which is not contaminated with Zr or the reactants. The recovered catalyst can be used repeatedly without deactivation. The reaction can also be conducted in a flow system with the insoluble Zr host catalyst and a reactant mixture as a mobile phase. The remarkable catalytic performance of the Zr host and its easy preparation suggest that insoluble microporous metal-organic solid catalysts are workup-free and waste-free as well as resource- and energy-saving.
Carbon's Three-Center, Four-Electron Tetrel Bond, Treated Experimentally
Karim, Alavi,Schulz, Nils,Andersson, Hanna,Nekoueishahraki, Bijan,Carlsson, Anna-Carin C.,Sarabi, Daniel,Valkonen, Arto,Rissanen, Kari,Gr?fenstein, Jürgen,Keller, Sandro,Erdélyi, Máté
, p. 17571 - 17579 (2019/01/04)
Tetrel bonding is the noncovalent interaction of group IV elements with electron donors. It is a weak, directional interaction that resembles hydrogen and halogen bonding yet remains barely explored. Herein, we present an experimental investigation of the
Carbocations as lewis acid catalysts in diels-alder and Michael addition reactions
Bah, Juho,Franzen, Johan
, p. 1066 - 1072 (2014/02/14)
In general, Lewis acid catalysts are metal-based compounds that owe their reactivity to a low-lying empty orbital. However, one potential Lewis acid that has received negligible attention as a catalyst is the carbocation. We have demonstrated the potential of the carbocation as a highly powerful Lewis acid catalyst for organic reactions. The stable and easily available triphenylmethyl (trityl) cation was found to be a highly efficient catalyst for the Diels-Alder reaction for a range of substrates. Catalyst loadings as low as 500 ppm, excellent yields, and good endo/exo selectivities were achieved. Furthermore, by changing the electronic properties of the substituents on the tritylium ion, the Lewis acidity of the catalyst could be tuned to control the outcome of the reaction. The ability of this carbocation as a Lewis acid catalyst was also further extended to the Michael reaction. Copyright
