Title:
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Synthesis and applications of new chiral auxiliaries
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The work described in this thesis has been concerned with the synthesis of a number of different chiral oxazolidinones. These were all prepared from cheap chiral pool starting materials, in particular carbohydrates and terpene-alcohols. The synthetic route employed utilised the well known but little used stereospecific nitrene insertion process. A selection of these newly synthesised chiral oxazolidinones were evaluated as chiral auxiliaries by employing them in a range of asymmetric transformations. The reactions studied include Lewis acid catalysed Diels-Alder reactions, lithium enolate mediated aldol reactions, a 1,4-cojugate addition reaction, a nitrile oxide cycloaddition reaction, and an α-bromination reaction. Other applications investigated were the resolution of racemic acid halides and of an amine. The chiral oxazolidinone auxiliaries developed from carbohydrates (in particular those developed from α-D-galactose) were found to give very high levels of asymmetric induction; whereas the auxiliary developed from a terpene alcohol ((-)-3-Pinanol) was found to give very poor stereoselectivities. In addition to the above experiments, an oxazolidinone derived from endo-borneol was thiated, using commercially available Lawessons reagent, to give the corresponding oxazolidinthione. This product was found to possess an extremely intense U.V. absorption band.
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