نتایج جستجو برای: brønsted acid
تعداد نتایج: 747867 فیلتر نتایج به سال:
Reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid-catalyzed conversion of xylose into furfural. A solvent of particular importance is γ-valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2-pro...
The direct conversion of methane and carbon dioxide to acetic acid is one of the most challenging research topics. Using the density functional theory (M06-L) the study reveals the catalytic activity of the Au(I)-ZSM-5 zeolite in this reaction. The Au(I)-ZSM-5 is represented by a 34T quantum cluster model. The activation of the C-H bond over the Au-ZSM-5 zeolite would readily take place via the...
From the synthetic point of view, organic synthesis via catalytic processes offers many benefits. Catalysis frequently obviates the excessive use of the activating reagents and associated tedious purification processes, thereby offering more environmentally benign synthetic processes. Furthermore, the specific activation mode of a catalyst allows for highly chemoselective transformations that a...
Direct catalytic addition of acetonitrile pronucleophiles to thiophosphinoylimines is described. Soft Lewis acid-hard Brønsted base cooperative catalysis is crucial to promote this elusive carbon-carbon bond-forming reaction in an enantioselective fashion.
We have discovered thiazepine moiety-controlled regioselective skeletal rearrangements of 7-oxanorbornadiene derivatives (2, 7 and 12) with high regioselectivity and/or diastereoselectivity in the presence of Brønsted acid.
Brønsted acidic ionic liquid triethylamine-bonded sulfonic acid {[Et3N-SO3H]Cl} efficiently catalyzes the one-pot multi-component condensation of 2-naphthol with arylaldehydes and dimedone (5,5-dimethylcyclohexane-1,3-dione) under solvent-free conditions to afford 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones in high yields and relatively short reaction times.
The design, synthesis, and development of a new class of modular, strongly basic, and tunable bifunctional Brønsted base/H-bond-donor organocatalysts are reported. These catalysts incorporate a triaryliminophosphorane as the Brønsted basic moiety and are readily synthesized via a last step Staudinger reaction of a chiral organoazide and a triarylphosphine. Their application to the first general...
The first highly diastereo- and enantioselective additions of a halogen and phosphoramidic acid to unactivated alkenes have been developed, catalyzed by a chiral Brønsted acid. A unique feature of these additions is the opportunity for stereocontrol at two noncontiguous chiral centers, carbon and phosphorus, leading to cyclic P-chiral phosphoramidates. In addition to their inherent value, the p...
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