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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Development and application of new chiral -amino alcohols in synthesis and catalysis : Use of 2-azanorboryl-3-methanols as common intermediates in synthesis and catalysis

Pinho, Pedro January 2001 (has links)
The development and application of unnatural amino alcohols,prepared via hetero-Diels-Alder reactions,in synthesis and catalysis is described.The studies are concerned with the [i]scope of the hetero-Diels-Alder reaction and preparation of important intermediates in the synthesis of antiviral agents,[ii ]application of amino alcohols in the ruthenium transfer hydrogenation of ketones,[iii ]use of similar precursors in the in situ generation of oxazaborolidines for reduction of ketones,and [iv] development and application of new chiral auxiliaries for dialkylzinc additions to activated imines, respectively. [i ]The use of chiral exo -2-azanorbornyl-3-carboxylates in the preparation of enantiopure cyclopentyl-amines is described.At the same time the scope of the hetero-Diels-Alder reaction,used in their preparation,is extended by manipulations of the dienophiles. [ii ]Application of 2-azanorbornyl-3-methanol as a very efficient ligand in the ruthenium-catalysed asymmetric transfer hydrogenation of aromatic ketones.This ligand (2 mol%)in combination with [RuCl2(p -cymene)]2 (0.25 mol%)gave rise to a very fast reaction (1.5 h)leading to the reduced products in excellent yields and enantioselectivities (up to 97%ee ). [iii ]Preparation of α-disubstituded 2-azanorbornyl-3-methanols,in situ generation of the corresponding oxazaborolidines,and use of the latter in reduction of aromatic ketones.Concentration, solvent,and temperature effects on the reaction outcome are described. [iv ]Development of two generations of chiral auxiliaries for the addition of dialkylzinc reagents to N - (diphenylphosphinoyl)imines.Studies using density functional computations allowed the rationalisation of the reaction mechanism and the development of a second generation of ligands that improved the previously reported results.Up to 98%ee could be obtained with these new ligands. Solvent effects on the outcome of the reaction and extension of the work to a larger variety of N - (diphenylphosphinoyl)imines are described.

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