Search results for "Catalysis"

Two New Acylated Tridesmosidic Saponins from Astragalus armatus

2010

Two new tridesmosidic glycosides of (3β,6α,16β,20R,24S)-20,24-epoxycycloartane-3,6,16,25-tetrol (=cycloastragenol), armatosides I and II (1 and 2, resp.), were isolated from the roots of Astragalus armatus (Fabaceae) as well as the known bidesmosidic glycosides of cycloastragenol, trigonoside II (3) and trojanoside H (4). Their structures were elucidated as (3β,6α,16β,20R,24S)-3-O-(2,3-di-O-acetyl-β-D-xylopyranosyl)-20,24-epoxy-25-O-β-D-glucopyranosyl-6-O-β-D-xylopyranosylcycloartane-3,6,16,25-tetrol (1), and (3β,6α,16β,20R,24S)-3-O-(2-O-acetyl-β-D-xylopyranosyl)-20,24-epoxy-25-O-β-D-glucopyranosyl-6-O-β-D-xylopyranosylcycloartane-3,6,16,25-tetrol (2). These structures were established by e…

ChemInform Abstract: Synthesis of a Naphtho-pyrido-Annulated Iodonium Salt and Pd-Catalyzed Transformation to 7H-Naphtho[1,8-bc][1,5]naphthyridine.

2014

Nitropyridylnaphthalene is the central intermediate for the synthesis of naphthonaphthyridine and benzo-δ-carboline. Whereas the Cadogan reaction gives the carboline, transformation of the nitro group to iodo followed by oxidation and cyclization results in an iodonium salt. A twofold Pd-catalyzed amination leads to the naphthyridine.

Synthesis of a Naphtho-pyrido-Annulated Iodonium Salt and Pd-Catalyzed Transformation to 7H-Naphtho[1,8-bc][1,5]naphthyridine

2013

Nitropyridylnaphthalene is the central intermediate for the synthesis of naphthonaphthyridine and benzo-δ-carboline. Whereas the Cadogan reaction gives the carboline, transformation of the nitro group to iodo followed by oxidation and cyclization results in an iodonium salt. A twofold Pd-catalyzed amination leads to the naphthyridine.

Bridge-Clamp Bis(tetrazine)s with [N] 8 π-Stacking Interactions and Azido- s -Aryl Tetrazines: Two Classes of Doubly Clickable Tetrazines

2020

Click chemistry at a tetrazine core is useful for bioorthogonal labeling and crosslinking. Introduced here are two new classes of doubly clickable s-aryl tetrazines synthesized by Cu-catalyzed cross-coupling. Homocoupling of o-brominated s-aryl tetrazines leads to bis(tetrazine)s structurally characterized by tetrazine cores arranged face-to-face. [N]8 π-stacking interactions are essential to the conformation. Upon inverse electron demand Diels-Alder (iEDDA) cycloaddition, the bis(tetrazine)s produce a unique staple structure. The o-azidation of s-aryl tetrazines introduces a second proximal intermolecular clickable function that leads to double click chemistry opportunities. The stepwise i…

CeO2−x nanorods with intrinsic urease-like activity

2018

The large-scale production and ecotoxicity of urea make its removal from wastewater a health and environmental challenge. Whereas the industrial removal of urea relies on hydrolysis at elevated temperatures and high pressure, nature solves the urea disposal problem with the enzyme urease under ambient conditions. We show that CeO2−x nanorods (NRs) act as the first and efficient green urease mimic that catalyzes the hydrolysis of urea under ambient conditions with an activity (kcat = 9.58 × 101 s−1) about one order of magnitude lower than that of the native jack bean urease. The surface properties of CeO2−x NRs were probed by varying the Ce4+/Ce3+ ratio through La doping. Although La substit…

Soluble Complexes of Cobalt Oxide Fragments Bring the Unique CO2 Photoreduction Activity of a Bulk Material into the Flexible Domain of Molecular Sci…

2021

The deposition of metal oxides is essential to the fabrication of numerous multicomponent solid-state devices and catalysts. However, the reproducible formation of homogeneous metal oxide films or of nanoparticle dispersions at solid interfaces remains an ongoing challenge. Here we report that molecular hexaniobate cluster anion complexes of structurally and electronically distinct fragments of cubic-spinel and monoclinic Co3O4 can serve as tractable yet well-defined functional analogues of bulk cobalt oxide. Notably, the energies of the highest-occupied and lowest-unoccupied molecular orbitals (HOMO and LUMO) of the molecular complexes, 1, closely match the valence- and conduction-band (VB…

UV photocatalytic oxidation of paint solvent compounds in air using an annular TiO2-supported reactor

2010

BACKGROUND: One of the most important industrial sources of volatile organic compounds (VOCs) is related to coating and painting applications. In this sense, photocatalytic oxidation can become an innovative and promising alternative for the remediation of air polluted by VOCs. In this study the UV photodegradation of m-xylene, toluene and n-butyl acetate, as representative compounds of paint solvents, was carried out in an annular reactor using a TiO2–glass wool supported catalyst. RESULTS The removal of each component and their mixture, simulating an industrial emission, was evaluated under different operational conditions. A maximum elimination capacity of 12, 18 and 80 mg C m−3 s−1 was …

Frontispiece: Hierarchy of Asymmetry at Work: Chain-Dependent Helix-to-Helix Interactions in Supramolecular Polymers

2018

Cover Feature: Towards Atomically Precise Supported Catalysts from Monolayer‐Protected Clusters: The Critical Role of the Support (Chem. Eur. J. 31/2…

2020

New insights for materials science characterisation using different complementary techniques combined with X-ray absorption Spectroscopy

2005

The combination of x-ray absorption spectroscopy (XAS) with UV-Vis and Raman spectroscopies or with Differential Scanning Calorimetry (DSC) has been recently carried out on the D44 beamline of DCI-LURE. The different set-ups used to perform such combinations are described and examples of combined investigations belonging to different field of materials science (coordination chemistry, sol-gel and catalysis) are presented.