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Showing 1 to 20 of 94 for “"Brønsted"”.
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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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Asymmetric Catalysis with Brønsted Acids: Experiments and Calculations
… on enantioselective catalysis using BINOL-based Brønsted acids. The initial part of this work comprises the development of chiral phosphoric acids and N-triflylphosphoramides having alternative groups at the 3,3’- positions, different from the widely common aryl scaffolds. These motifs include …
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Charge-Enhanced Brønsted Acids: Catalyst Designs and Analytical Methods
… As a result, charged hydrogen bond donors and Brønsted acids have been synthesized and are more effective catalysts in nonpolar media compared to their neutral analogues. In this dissertation, this charge enhanced effect is examined through a structure-reactivity relationship and new …
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Mechanism-Guided Studies of Brønsted Acid and Base Organocatalysis
… a class of highly successful nucleophilic/Brønsted base organocatalysts. As these carbenes are generated in situ from azolium ions during organocatalytic reactions, knowledge of the acidity of the parent ion is much sought after. This thesis describes the determination of aqueous pKa values …
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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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Brønsted Acid-Catalyzed Reactions of Vinylboronic Acids and Benzhydryl Alcohols
… of 1,3,3-triphenylpropene derivatives through a Brønsted acid-catalyzed reaction of styrylboronic acids and benzhydryl alcohols is reported. The use of tetrafluoroboric acid diethyl ether complex (HBF4·OEt2) in substoichiometric amounts is desirable as it allows for the introduction of the …
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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
… 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) C-C bond …
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Mechanistic Studies of pi-Activation Catalysis by Cationic Gold(I) and Brønsted-acid
… hydrofunctionalization and similar Brønsted acid-catalyzed additions, the kinetics and stereochemistry of intramolucar acid-catalyzed hydrofunctionalizion were studied. In all cases, the transformations were > 95 % selective for <italic>anti</italic>-addition and displayed rate laws …
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Direct Brønsted acid-catalyzed functionalization of benzhydryl alcohols and 2-ethoxytetrahydrofuran using potassium trifluoroborate salts
… resulting in low functional group tolerance. A Brønsted acid-catalyzed carbon-carbon bond forming methodology involving alkenyl- and alkynyltrifluoroborates and in situ generated carbocations has been developed. In the presence of HBF4, we have shown that organotrifluoroborates react with …
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Síntesis de indoles y carbazoles funcionalizados: catálisis con complejos de Au(III) y ácidos de Brønsted
… en Síntesis Orgánica utilizando ácidos de Brønsted y complejos de oro(III) como catalizadores. El hilo conductor es el núcleo indólico, cuya funcionalización selectiva continúa siendo un objetivo relevante en Química Orgánica. Bajo catálisis con ácidos de Brønsted hemos desarrollado una …
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3-Propargilindoles y 3-Alenilmetilindoles: síntesis y reacciones catalizadas por ácidos de Brønsted y complejos de oro
… dos sistemas catalíticos diferentes, ácidos de Brønsted y complejos de oro. De esta forma, partiendo de 3-propargilindoles se han puesto a punto distintas metodologías para la obtención de indolilderivados de alta complejidad mediante reacciones en cascada iniciadas por una migración 1,2 del …
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Síntesis de compuestos orgánicos de azufre mediante el empleo de catalizadores metálicos, reactivos electrófilos y ácidos de brønsted
… catalizados por metales de transición, ácidos de Brønsted y reactivos electrófilos. 4 En primer lugar, se estudia la reacción de acoplamiento cruzado de tioles con haluros de alquenilo y pseudo-haluros catalizada por complejos de paladio, mediante una nueva estrategia de acoplamiento cruzado C‒S. …
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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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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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