نتایج جستجو برای: brønsted acid and lewis acid catalyst
تعداد نتایج: 16951353 فیلتر نتایج به سال:
Catalytic chemoselective reactions of innately less reactive functionalities over more are described. A cooperative catalyst comprising a soft Lewis acid/hard Brønsted base enabled activation hydroxyl group an amino group, allowing for nucleophilic addition to electron-deficient olefins. The reaction could be applicable variety alcohols, including pharmaceuticals, without requiring tedious prot...
Rapid atomic layer deposition (RALD) has been applied to prepare various nanolaminates with repeated multilayer structures. The possible reaction pathways for RALD of the Al2O3/SiO2 nanolaminate using trimethylaluminum (TMA) and tris(tert-butoxy)silanol (TBS) are investigated by using density functional theory (DFT) calculations. The introduction of a Lewis-acid catalyst, TMA, can result in the...
Biomimetic conditions for a synthetic glycosylation reaction, inspired by the highly conserved functionality of carbohydrate active enzymes, were explored. At the outset, we sought to generate proof of principle for this approach to developing catalytic systems for glycosylation. However, control reactions and subsequent kinetic studies showed that a stoichiometric, irreversible reaction of the...
A gallium-catalyzed C–H propargylation of electron-rich arenes using bromoallenes is described. The development this reaction was first hampered by a side hydroarylation process catalyzed adventitious protons, easily generated from the solvent (1,2-dichloroethane). This hidden Brønsted acid catalysis could be bypassed K2CO3 as an insoluble base. unexpected compatibility base with Lewis catalyst...
A set of Y-type zeolites with Si/Al atomic ratios between 7–45 were studied as catalysts in the aminocyclization reaction acrolein and ammonia to produce pyridine 3-picoline. The catalytic activity tests at 360 °C revealed that conversion increased order Z45 < ZY34 ZY7 ZY17, agreement increase total acidity per gram catalyst. In all cases, bases cracking products (acetaldehyde formaldehyde) ...
Framework-associated aluminum is demonstrated to facilitate a reversible switch between Lewis and Brønsted acidity in zeolites with the acid sites preferentially populating side-pockets case of mordenite.
In the presence of a Brønsted acid catalyst, both aldehydes and N-Boc-aminals were converted to enecarbamates and N-Boc-iminium salts as activated nucleophiles and electrophiles, respectively, giving unprecedented Mannich adducts. The asymmetric variant of the present Mannich reaction has also been demonstrated with a chiral phosphoric acid catalyst.
The purpose of this study is to identify the deactivation mechanism(s) that occurs during aromatization dilute ethylene at 500 °C on Zn/H-MFI catalyst. More than 15 catalysts, with a Zn/H+ molar ratio ranging from 0 (H-ZSM5) 1.8 (Zn/H-ZSM5), were prepared by wet impregnation. Deactivation does not result Zn sublimation, but coking. function and coke deposition can be modelled simple exponential...
Two regiodivergent approaches to intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and amides have been developed, controlled by the reagents employed. With the Brønsted base KOt-Bu and CBrCl3 as radical initiator, benzo[d]imidazo[2,1-b]thiazoles are synthesized via attack at the α-carbon and keto carbon of the β-ketoester moiety. In contrast, switching to the Lewis acid cat...
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