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- W1681335095 abstract "This thesis describes the coordination chemistry and catalytic applications of the 1,1,1-tris(oxazolinyl)ethane (“trisox”) family of ligands. The studies described herein are primarily concerned with the effect of the threefold rotational symmetry of the ligands, as well as the role of the third oxazoline arm in catalytic reactions in which there are intermediates that possess a bidentate coordination of the trisox ligand. The syntheses of highly symmetrical chiral 1,1,1-tris(oxazolinyl)ethane ligands bearing phenyl, benzyl or indanyl substituents, and of mixed bis- and trisoxazolines is described. The isomerisation of the 2-bromooxazolines was observed, in which the thermally induced rearrangement generates the corresponding α-bromo-isocyanate derivatives. Reaction of the latter with phenylethylamine led selectively to the N-cyclised aziridines or to the O-cyclised 2-aminooxazolines, depending on the reaction conditions. The coordination chemistry of the trisoxazoline ligands with palladium is then described. Palladium(II) chloride and allyl complexes and a number of palladium(0) complexes were successfully synthesised. The dynamic behaviour of these complexes in solution was studied and activation parameters were determined for the exchange of the oxazoline moieties. The systematic comparison of the catalytic efficiency of trisox- and bisox-palladium systems in allylic substitution is described. It was demonstrated that the trisoxazoline-based complexes are superior catalysts in direct comparison to the corresponding bisoxazoline-based catalysts. The study showed that the additional donor function appears to play a role in the product/substrate exchange step as well as in the initial generation of the active catalyst. Finally, the exploitation of the dynamic coordination of the trisoxazolines to copper(II) in two copper-catalysed asymmetric reactions is described. It has been shown that C3-symmetric trisoxazolines form highly efficient enantioselective copper(II) Lewis acid catalysts, in which their success is based on the concept of a stereoelectronic hemilability of the divalent copper. In a direct comparison with the analogous bisoxazoline systems, the trisox/copper catalysts have proven to be more efficient in an enantioselective Mannich reaction as well as an enantioselective a-amination of prochiral b-ketoesters in presence of low catalyst loadings. To conclude the implications of the use of chiral tridentate podands in stereoselective catalysis compared to the more established bidentate chelates have been highlighted." @default.
- W1681335095 created "2016-06-24" @default.
- W1681335095 creator A5035836734 @default.
- W1681335095 date "2007-01-01" @default.
- W1681335095 modified "2023-09-24" @default.
- W1681335095 title "Trisoxazolines: Synthesis and Application in Enantioselective Palladium- and Copper-catalysed Reactions" @default.
- W1681335095 doi "https://doi.org/10.11588/heidok.00007945" @default.
- W1681335095 hasPublicationYear "2007" @default.
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