986 resultados para Cycloaddition dipolaire-[3 2]
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Brown sediment with clasts ranging from small to large in size. The clast shape ranges from angular to sub-rounded. Rotation structures are the most commonly seen micro-structure in this sample. Necking structures, comet structures, grain crushing and lineations can also be seen in minor amounts throughout the sample.
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Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal
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Rapport d'analyse d'intervention présenté à la Faculté des arts et sciences en vue de l'obtention du grade de Maîtrise ès sciences (M. Sc.) en psychoéducation.
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Burgess reagent first prepared by E. M. Burgess in 1968, is a mild and selective dehydrating agent for secondary and tertiary alcohols and due to the amphipolar nature it is gainfully employed in a number of creative synthetic ventures. A close examination of the structure of Burgess reagent reveals that it can act as a 1,2-dipole. To the best of our knowledge, no attempts have been made to tap full synthetic potential of the amphipolar nature of this reagent and no reports on 1,3-dipolar addition to a σ-bond in acyclic systems are available in literature. In this context, we propose to unravel novel applications of Burgess reagent based on its amphipolar nature. Rich and multifaceted chemistry of nitrones form the basis of many successful chemical transformations used in attractive synthetic strategies. For the last 50 years special attention has been given to nitrones due to their successful application as building blocks in the synthesis of various natural and biologically active compounds. Our interest in nitrones stems out of its unique character: i.e. it is a 1,3-dipole exhibiting distinct nucleophilic activity. We reasoned that 1,3-dipole possessing significant nucleophilicity should react with amphipolar Burgess reagent with elimination of triethylamine to give the corresponding five-membered ring product by formal dipolar addition to a σ bond. To test this hypothesis we studied the reaction of nitrones with Burgess reagent. This thesis reveals our attempts to explore the [3+2] annulation reaction of nitrones with Burgess reagent which was found to be followed by a rearrangementinvolving C-to-N aryl migration, ultimately resulting in diarylamines and carbamates. We have also examined the reaction of cyanuric chloride with nitrones in DMF with a view to exploit the nucleophilicty of nitrones and to unravel the migratory aptitude, if any, observed in this reaction
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ABSTRACT In the first two seminars we looked at the evolution of Ontologies from the current OWL level towards more powerful/expressive models and the corresponding hierarchy of Logics that underpin every stage of this evolution. We examined this in the more general context of the general evolution of the Web as a mathematical (directed and weighed) graph and the archetypical “living network” In the third seminar we will analyze further some of the startling properties that the Web has as a graph/network and which it shares with an array of “real-life” networks as well as some key elements of the mathematics (probability, statistics and graph theory) that underpin all this. No mathematical prerequisites are assumed or required. We will outline some directions that current (2005-now) research is taking and conclude with some illustrations/examples from ongoing research and applications that show great promise.
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Resumen basado en el de la publicación
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Trabajo presentado a: 'I premios internacionales redELE para la creación de unidades didácticas del español como lengua extranjera', Orden ECI-3268-2005 de 10 de octubre. Incluye anexo con resumen de las autoras y bibliografía (2 p.). Resumen basado en el de la publicación
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Premios Nacionales de Innovación Educativa CIDE 2001
