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Asymmetric anhydride opening : optimization and applications

By Iuliana Luisa Atodiresei

Abstract

This PhD thesis describes the desymmetrization of easily accessible meso-anhydrides by cinchona alkaloid-mediated opening with benzyl alcohol. This procedure was found to be applicable to a variety of structurally different substrates and leads to the corresponding optically active hemiesters with enantioselectivities of up to 99%. A simple reaction protocol was developed which allows the synthesis of either enantiomer selectively, generally without need of additional purification of the resulting benzyl monoester by chromatography or recrystallization. The synthetic usefulness of the method was demonstrated by the preparation of optically active beta-amino acids through a reaction sequence involving a Curtius degradation as a key step. Their complete deprotection could be accomplished in a single step by simple hydrogenation enabling the isolation of rather sensitive products. As an extension of this work, a general strategy for the synthesis of optically active C2- and C1-symmetric bisoxazolines was developed. Accordingly, eight cyclopentane derivatives were prepared in good overall yields. The catalytic activity of the copper (II) and zinc (II) complexes derived from these eight ligands was tested in the asymmetric Diels-Alder reaction. In addition, the effect of temperature and counterion on the reaction selectivity was also investigated. The catalytic behavior of the copper (II) complexes has also been evaluated in the related hetero Diels-Alder reaction between 1,3-cyclohexadiene and ethyl glyoxalate. The HDA-adducts were always obtained with high diastereoselectivities and promising enantioselectivities. Enantioselective cyclopropanation of styrene was the reaction chosen to determine the efficiency of the [Cu(box)]-(OTf) systems. In this context, enantioselectivities of up to 83 and 87% ee were attained for the trans and cis cyclopropanated products, respectively

Topics: info:eu-repo/classification/ddc/540, Anhydride, Ringöffnungsreaktion, Asymmetrische Reaktion, Chemie, anhydride opening, cinchona alkaloids, beta-amino acids, bisoxazolines
Publisher: Publikationsserver der RWTH Aachen University
Year: 2005
OAI identifier: oai:publications.rwth-aachen.de:62107
Provided by: RWTH Publications
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