نتایج جستجو برای: lewis acid

تعداد نتایج: 761908  

Journal: :Journal of the American Chemical Society 2013
Vinit Choudhary Samir H Mushrif Christopher Ho Andrzej Anderko Vladimiros Nikolakis Nebojsa S Marinkovic Anatoly I Frenkel Stanley I Sandler Dionisios G Vlachos

5-(Hydroxymethyl)furfural (HMF) and levulinic acid production from glucose in a cascade of reactions using a Lewis acid (CrCl3) catalyst together with a Brønsted acid (HCl) catalyst in aqueous media is investigated. It is shown that CrCl3 is an active Lewis acid catalyst in glucose isomerization to fructose, and the combined Lewis and Brønsted acid catalysts perform the isomerization and dehydr...

Journal: :Dalton transactions 2008
Karl-Christian Schwan Ariane Adolf Christine Thoms Manfred Zabel Alexey Y Timoshkin Manfred Scheer

The halogenation of Lewis-acid/base-stabilised phosphanylboranes () and arsanylboranes () with CX4 (X=Cl, Br) leads selectively to the substitution of both protons at the pentel atom and the new compounds [(CO)5W(X2PBH2.NMe3)] (:X=Cl, :X=Br) and [(CO)5W(X2AsBH2.NMe3)] (:X=Cl, :X=Br), respectively, are obtained. The new products were comprehensively characterised by spectroscopic methods and by ...

Journal: :Chemical Science 2021

An original multi-cooperative catalytic approach was developed by combining metal–ligand cooperation and Lewis acid activation.

2016
Mark E. Davis

Microporous and mesoporous zincosilicates (e.g., CIT-6, VPI-8, Zn-MFI, and Zn-MCM-41) synthesized in the presence of alkali cations contain two broad types of Zn sites: one that is a dication analog of the monocation ion-exchangeable Al-site in aluminosilicates, while the other resembles isolated Zn sites on amorphous silica. The ratio of these sites varies, depending on the synthesis condition...

Journal: :Beilstein Journal of Organic Chemistry 2013

Journal: :Chemistry – A European Journal 2020

Journal: :Chemical communications 2014
Masahiro Sai Matsujiro Akakura Hisashi Yamamoto

In the silyl Lewis acid-promoted Mukaiyama aldol reaction, the steric and electronic properties of the silyl group on the silyl Lewis acid influence the reaction mechanism and product distribution. When super silyl triflates such as (TMS)3SiOTf and (TES)3SiOTf are used as Lewis acids, the silyl group of the silyl enol ether chemoselectively transfers to the product. The mechanistic details have...

2016

Chiral supramolecular boron Lewis acid catalysts were developed with the use of chiral 3-phosphoryl-BINOLs, 2-cyanophenylboronic acids, and tris(pentafluorophenyl)borane based on CN···B and PO···B coordination bonds. In particular, coordinated tris(pentafluorophenyl)boranes can increase the Lewis acidity of the active center based on the Lewis acidassisted Lewis acid catalyst system. A possible...

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