نتایج جستجو برای: lewis acid

تعداد نتایج: 761908  

Journal: :Organic chemistry frontiers 2021

Piancatelli rearrangement on substituted non-symmetrical furan-2,5-dicarbinols has been developed using an effective combination of microwave activation and Lewis acid catalyst.

Journal: :Fuel 2022

Production of 5-hydroxymethylfurfural (HMF) from biomass-derived glucose has great potential for synthesis renewable fuels and chemicals. Selective conversion to requires a balance between Lewis Brønsted acids the cascade isomerization followed by fructose dehydration. A dual Brønsted-Lewis acid, phosphotungstic acid encapsulated MIL-101(Al)–NH2 metal–organic frameworks (MOFs) was developed cat...

TiCl2/nano-γ-Al2O3 as a new heterogeneous Lewis acid catalyst was synthesized and characterized by FE-SEM, XRD, FT-IR, EDS, XRF, BET and TGA. N-substituted pyrroles have been synthesized via Paal–Knorr reaction in the presence of TiCl2/nano-γ-Al2O3 at room temperature under solvent-free conditions.

Journal: :Journal of the American Chemical Society 2005
Jan Blid Olaf Panknin Peter Somfai

An asymmetric Lewis acid-mediated [2,3]-sigmatropic rearrangement of allylic amines has been developed, affording the corresponding homoallylic amines in good yield and excellent enantioselectivities. The rearrangement proceeds by complexation of the chiral Lewis acid to the amine followed by deprotonation and rearrangement.

Journal: :Organic & biomolecular chemistry 2012
Hideto Miyabe Ryuta Asada Yoshiji Takemoto

An efficient approach for achieving radical cyclizations by using hydroxamate ester as a coordination tether with Lewis acid was studied. The chiral Lewis acid-mediated cascade radical addition-cyclization-trapping reaction proceeded smoothly with good enantio- and diastereoselectivities, providing various chiral γ-lactams.

Journal: :Chemical communications 2014
Ikuo Nakanishi Tomonori Kawashima Kei Ohkubo Tsukasa Waki Yoshihiro Uto Tadashi Kamada Toshihiko Ozawa Ken-Ichiro Matsumoto Shunichi Fukuzumi

Electron-transfer disproportionation of a 2,2-diphenyl-1-picrylhydrazyl radical (DPPH˙) occurred in the presence of Sc(3+) acting as a strong Lewis acid in deaerated acetonitrile. In contrast, in the case of weaker Lewis acids than Sc(3+), such as Mg(2+) and Li(+), external protons from acetic acid were required for the disproportionation of DPPH˙ to occur.

Fatemeh Derakhshan-Panah Malihe Safaiee, Mohammad Ali Zolfigol, Mohammad Mokhlesi

Silica Vanadic Acid, SVA, (oxo-vanadium has been supported on silica) as a dual Lewis and Bronsted acid ability was prepared and efficiently catalyzed one-pot multi-component condensation of enolizable ketones or alkyl acetoacetates with aromatic aldehydes, acetonitrile and acetyl chloride. The described reaction was produced β-acetamido ketone or ester derivatives in high to excellent yields i...

2014
Elliot J Lawrence Thomas J Herrington Andrew E Ashley Gregory G Wildgoose

In order to use H2 as a clean source of electricity, prohibitively rare and expensive precious metal electrocatalysts, such as Pt, are often used to overcome the large oxidative voltage required to convert H2 into 2 H(+) and 2 e(-). Herein, we report a metal-free approach to catalyze the oxidation of H2 by combining the ability of frustrated Lewis pairs (FLPs) to heterolytically cleave H2 with ...

Journal: :Chemical communications 2007
Jin Hong Kim Ji Woong Lee Ueon Sang Shin Jin Yong Lee Sang-Gi Lee Choong Eui Song

In the presence of a soluble organic salt containing non-coordinating anion (e.g., [bmim][SbF(6)] or [NR(4)][SbF(6)]), the catalytic activity of Lewis acid (MX(n)) was dramatically enhanced due to the anion exchange between the Lewis acid and organic salt.

Journal: :Organic & biomolecular chemistry 2012
Ana G Neo Jesús Díaz Stefano Marcaccini Carlos F Marcos

We report a novel Lewis acid catalysed tandem reaction of isocyanides, chromone 3-carboxylic acid and nucleophiles. An experimentally very simple procedure, involving the use of microwave irradiation in the presence of a Lewis acid catalyst, affords a representative collection of chromone-2-carboxamides and chromone-2-carboxamido-3-esters in high yields, in just a few minutes. Such an unprecede...

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