33 research outputs found

    Recent Advances in Asymmetric Organocatalyzed Conjugate Additions to Nitroalkenes

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    The asymmetric conjugate addition of carbon and heteroatom nucleophiles to nitroalkenes is a very interesting tool for the construction of highly functionalized synthetic building blocks. Thanks to the rapid development of asymmetric organocatalysis, significant progress has been made during the last years in achieving efficiently this process, concerning chiral organocatalysts, substrates and reaction conditions. This review surveys the advances in asymmetric organocatalytic conjugate addition reactions to α,β-unsaturated nitroalkenes developed between 2013 and early 2017.We thank the financial support from the Spanish Ministerio de Economía, Industria y Competitividad (CTQ2015-66624-P) and the University of Alicante (UAUSTI16-03, AUSTI16-10, VIGROB-173, VIGROB-285)

    Organocatalysis and beyond: Activating reactions with two catalytic species

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    Since the beginning of the millennium, organocatalysis has been gaining a predominant role in asymmetric synthesis and it is, nowadays, a foundation of catalysis. Synergistic catalysis, combining two or more different catalytic cycles acting in concert, exploits the vast knowledge acquired in organocatalysis and other fields to perform reactions that would be otherwise impossible. Merging organocatalysis with photo-, metallo- and organocatalysis itself, researchers have ingeniously devised a range of activations. This feature review, focusing on selected synergistic catalytic approaches, aims to provide a flavor of the creativity and innovation in the area, showing ground-breaking examples of organocatalysts, such as proline derivatives, hydrogen bond-mediated, Cinchona alkaloids or phosphoric acids catalysts, which work cooperatively with different catalytic partners

    Direct Enantioselective Michael Reactions of Ketones and Aldehydes with Nitroalkenes under Brønsted Base/H-Bonding Catalysis

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    467 p.promover la a-funcionalización directa y enantioselectiva de cetonas y aldehídos con ciertascaracterísticas estructurales. Específicamente, en esta Tesis Doctoral se ha estudiado la reacción deMichael enantioselectiva de cetonas y aldehídos con nitroolefinas promovida por bases de Brønstedbifuncionales, lo que conduce a los correspondientes aductos con muy buen estereocontrol. En estasreacciones se han empleado a-hidroxicetonas saturadas e insaturadas, bencil alquinil cetonas yarilacetaldehídos como dadores de Michael eficientes.La posterior elaboración de los correspondientes aductos ha proporcionado a) mediante escisiónoxidativa de la función aciloínica en el caso de las a-hidroxicetonas, ácidos carboxílicos y aldehídos a-funcionalizados enantiopuros, b) mediante reducción de las bencil alquinil cetonas a-funcionalizadas,cetonas dialquílicas no simétricas a-sustituidas enantiopuras, c) mediante ciclación ipso intramolecularde los correspondientes aductos de las bencil alquinil cetonas, espirociclos y estructuras molecularestricíclicas.Para el estudio de la citada reacción con aldehídos una nueva familia de catalizadores de basesde Brønsted que contienen un amino ácido y el grupo escuaramida ha sido sintetizada para obtener loscorrespondientes aductos con elevada estereoselectividad.Finalmente, durante una breve estancia en la Unviersidad de Toronto en los Lash MillerChemical Laboratories, bajo la supervisión del Prof. Robert Batey, se ha llevado a cabo el estudio y lavalidación de una metodología para la síntesis de 5-aminotetrazoles 1-sustituidos obteniéndose conbuenos rendimientos

    Direct Enantioselective Michael Reactions of Ketones and Aldehydes with Nitroalkenes under Brønsted Base/H-Bonding Catalysis

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    467 p.promover la a-funcionalización directa y enantioselectiva de cetonas y aldehídos con ciertascaracterísticas estructurales. Específicamente, en esta Tesis Doctoral se ha estudiado la reacción deMichael enantioselectiva de cetonas y aldehídos con nitroolefinas promovida por bases de Brønstedbifuncionales, lo que conduce a los correspondientes aductos con muy buen estereocontrol. En estasreacciones se han empleado a-hidroxicetonas saturadas e insaturadas, bencil alquinil cetonas yarilacetaldehídos como dadores de Michael eficientes.La posterior elaboración de los correspondientes aductos ha proporcionado a) mediante escisiónoxidativa de la función aciloínica en el caso de las a-hidroxicetonas, ácidos carboxílicos y aldehídos a-funcionalizados enantiopuros, b) mediante reducción de las bencil alquinil cetonas a-funcionalizadas,cetonas dialquílicas no simétricas a-sustituidas enantiopuras, c) mediante ciclación ipso intramolecularde los correspondientes aductos de las bencil alquinil cetonas, espirociclos y estructuras molecularestricíclicas.Para el estudio de la citada reacción con aldehídos una nueva familia de catalizadores de basesde Brønsted que contienen un amino ácido y el grupo escuaramida ha sido sintetizada para obtener loscorrespondientes aductos con elevada estereoselectividad.Finalmente, durante una breve estancia en la Unviersidad de Toronto en los Lash MillerChemical Laboratories, bajo la supervisión del Prof. Robert Batey, se ha llevado a cabo el estudio y lavalidación de una metodología para la síntesis de 5-aminotetrazoles 1-sustituidos obteniéndose conbuenos rendimientos

    Dimeric Cinchona alkaloids

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    Recent Advances in Organocatalysis

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    Organocatalysis has recently attracted enormous attention as green and sustainable catalysis. It was realized as a fundamental field providing wide families of catalysts for important organic transformations. It will certainly develop in the future. Given the diversity of accessible transformations, metal-catalyzed reactions have become major tools in organic synthesis that will undoubtedly continue to have an important impact in the future. Alternatively, over the last years, a metal-free approach such as organocatalysis has reached a level of faithfulness, allowing researchers to discover new catalytic systems based on engagement of new or early-prepared organic molecules as organocatalysts. Organocatalysis meets green chemistry principles, especially the reduction of toxicity and chemical accidents, the biodegradability, and the use of benign and friendlier reaction media and conditions

    Development of Enantioselective Organocatalysis by Bifunctional Indane Amine-Thiourea Catalyst

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    Ph.DDOCTOR OF PHILOSOPH

    Chiral organocatalysts mediated asymmetric oxyfunctionalization and tandem reaction

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    2013 - 2014Asymmetric organocatalysis is a new rapidly growing field whose huge potential is becoming more and more evident.This PhD project has been conceived and developed in the context of non-covalent organocatalysis. The aim of this work has been to design, plan and develop new organocatalytic methodologies for the synthesis of optically active, densely functionalized, organic molecules whose functional groups are susceptible to further manipulation. The target molecules represent important motifs present in many biologically active natural and non-natural substances. The catalysts used are small chiral organic molecules, in particular the attention has been focused on bifunctional organocatalysts. The main features of the catalysts are their non-toxicity, stability to air and moisture and the ability to work under mild conditions that make them convenient tools in organic chemistry. These promoters are able to synergistically activate both the electrophile and the nucleophile through multiple hydrogen-bonding interactions provided by their acid and basic groups with the reactive groups of the reagents. The best-performing chiral scaffold of the bifunctional organocatalysts, employed in the methodologies herein developed, has been selected screening the activity of previously reported promoters such as ureas, thioureas, squaramides, amino alcohols. However, the design and synthesis of new optically pure bifunctional organocatalysts, modifying the chiral backbone and by tuning their stereoelectronic features, has been one of the objectives of this doctoral project. The stereoselective construction of a quaternary stereocentre, especially when it is an all-carbon quaternary stereocentre, is one of the most difficult goals in organic synthesis due to the steric congestion imposed by the four attached substituents. In this project, the synthesis of challenging molecules, bearing quaternary stereocentres in their structure, has been accomplished... [edited by author]XIII n.s
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