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Showing 1 to 20 of 59 for “"Brønsted Acid"”.
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Brønsted acid-catalyzed alkylation of tetrazoles with alcohols
… convenient alkylating reagents. While Lewis and Brønsted acid-catalyzed alkylations of tetrazoles using alcohols have been reported, their drawbacks include the necessity to use excess of strong Brønsted acid, narrow scope, long reaction time and poor functional group tolerance. Recently, we …
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Brønsted Acid Catalyzed Carbon-Carbon Bond Forming Reactions
… development of new methodology in the field of Brønsted acid catalysis enabling rapid synthesis of medicinally relevant compounds. It is foreseen that small molecule sulfonic acids evaluated in this research project will unveil new asymmetric carbon carbon bond forming reactions between …
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Mechanism-Guided Studies of Brønsted Acid and Base Organocatalysis
… in the presence and absence of chiral phosphoric acid catalysts. In order to gain mechanistic insight into the asymmetric Mannich reaction, a structurally homologous series of N-Boc imines and BINOL-derived phosphoric acid and thiophosphoric acid catalysts were synthesised. The degree of …
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Brønsted Acid-Catalyzed Reactions of Vinylboronic Acids and Benzhydryl Alcohols
… on harsh reaction conditions or the use of Lewis acid catalysts, which leads to low functional group tolerance. Herein, a methodology for the formation of 1,3,3-triphenylpropene derivatives through a Brønsted acid-catalyzed reaction of styrylboronic acids and benzhydryl alcohols is reported. The …
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Brønsted acid-catalyzed stereoselective allylation of exo-glycals with allyltrimethylsilane
… of exo-glycals using allyltrimethylsilane. This Brønsted acid-catalyzed transformation for the preparation of C,C-glycosides occurs readily in the presence of a tetrafluoroboric acid diethyl ether complex. In contrast to previously reported procedures, this reaction proceeds in a …
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Brønsted acid-catalyzed reaction of alkynyltrifluoroborates with acetals and ketals
… great importance in synthetic organic chemistry. Brønsted acid catalysis is a powerful synthetic tool to make many different compounds, however, the current carbon-based nucleophiles are the major limitation of acid-catalyzed reactions. In effort to expand repertoire of Brønsted acid compatible …
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Electrostatically Enhanced Phosphoric Acids and Their Applications in Brønsted Acid Catalysis
Different types of Brønsted acid catalysts are commonly used in a wide variety of organic transformations and are of continuing interest because there is a general need to carry out reactions in a faster and higher yielding manner with greater selectivities. Phosphoric acid derivatives, with their …
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Mechanism and application of Lewis and Brønsted acid effects in organotransition metal catalysis
… some combination of a transition metal, Lewis acid, and Brønsted acid. Chapter 1 reviews the literature regarding the cooperativity of transition metal and Lewis acid catalysis, and discusses four main areas in organic synthesis and the facilitation of these trnasformations by Lewis acids: (a) …
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Mechanistic Studies of pi-Activation Catalysis by Cationic Gold(I) and Brønsted-acid
… binding interaction and undergoes an acid-catalyzed rearrangement to yield a stable bicyclo[3.2.0]heptane product which can further isomerize in the presence of Ag+. In a further effort to understand the reactive species in catalytic cycloisomerizations, the first example of a gold …
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Direct Brønsted acid-catalyzed functionalization of benzhydryl alcohols and 2-ethoxytetrahydrofuran using potassium trifluoroborate salts
… expensive and sensitive transition metals. Lewis acid-catalyzed reactions involving organotrifluoroborates have emerged as an alternative to metal-catalyzed protocols. However, these methods rely on generating unstable boron dihalide species thereby resulting in low functional group tolerance. A …
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Borox catalysis : a new frontier in chiral Bronsted acid catalysis derived from chiral borate anions
… has been on the development of the new chiral Brønsted acid catalysts, large-scale synthesis, novel reaction methodologies and understanding their mechanisms by experimental/computational analysis. In due course of time, a pool of unprecedented chiral Brønsted acid catalysts known to be "BOROX" …
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Poisoning and Sulfation on Vanadia SCR Catalyst
… increase ammonia adsorption intensity on Brønsted acid sites. Activity measurements by MS showed K, Na, and Ca poison SCR catalysts, and sulfation and tungsten enhance SCR NOx reduction activity. Both the decrease and increase of catalyst activity arise from the decrease and increase of …
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Harnessing cheminformatics for catalyst design I. Investigation into a general, asymmetric synthesis of cinchona alkaloid analogs towards asymmetric phase transfer II. Development of an enantioselective brønsted acid catalyzed four-component Ugi reaction
… reaction. Second, (R)-BINOL derived phosphoric acids were studied in regards to the brønsted acid catalyzed Ugi reaction. In regards to Cinchona alkaloids, the concentration was first on methodology develop to rapidly synthesize diverse Cinchona-like analogs in a highly enantioenriched fashion. …
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Rational design and synthesis of zeolite acid catalysts for applications in biomass conversion
… these frameworks to create isolated Lewis and Brønsted acid sites. This thesis uses synthesis, characterization, and reactivity studies to develop novel zeolite acid catalysts for upgrading biomass platform molecules. The first section focuses on designing hierarchical Brønsted acid zeolites to …
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Lewis base catalyzed enantioselective sulfenoamination of alkenes
The concept of Lewis base activation of Lewis acid has been successfully applied to the enantioselective sulfenoamination of olefins. The unreactive, achiral Lewis acidic sulfenylating agent, N-arylthiophthalimide, is activated by the coordination of a chiral Lewis base, binaphthyl-derived …
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An Examination of γ-valerolactone Ring Opening and Decarboxylation in Multiphase System and Over Various Solid Acid Catalysts
… commercial potentials. Of interest here is the acid-catalyzed ring opening of GVL to form pentenoic acid (PEA) isomers and following decarboxylation to produce butenes. In this study, GVL ring opening, and decarboxylation are examined in both liquid and gas phases over various catalytic systems …
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An Examination Of Γ-valerolactone Ring Opening And Decarboxylation In Multiphase System And Over Various Solid Acid Catalysts
… commercial potentials. Of interest here is the acid-catalyzed ring opening of GVL to form pentenoic acid (PEA) isomers and following decarboxylation to produce butenes. In this study, GVL ring opening, and decarboxylation are examined in both liquid and gas phases over various catalytic systems …
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Thermochemical Interconnectivities of Active Sites on Metal Oxides and their Catalytic Consequences in C−O Formation and C−H Scission Chemistry
… coordinated protons on lattice O-atoms act as Brønsted acid sites (H+), the coordinatively unsaturated cationic metal centers function as Lewis acid sites (Mδ+−Oδ−), and the anionic lattice O-atoms serve as redox sites (O*). These active sites coexist and collectively catalyze both parallel and …
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Promotion of Heterogeneous Acid and Base Catalysts for Biomass Upgrading
… source for chemicals production. Homogeneous acids and bases have been shown to be active for a wide variety of chemical reactions useful in converting bio-based substrates to existing and novel chemicals; however, the costly separations associated with homogeneous catalysts have necessitated …
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