Cobb, Alexander John Andre; (2001) Chiral diamines in asymmetric synthesis. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The synthesis of a range of novel enantiomerically pure vicinal 1,2-diamines is described as has their subsequent use as asymmetric catalysts. Most of the amines are of a C2 symmetric nature and are derivatives of (1R, 2R)-(-)-1,2-diaminocyclohexane, although several disymmetric ligands have been prepared. The preparation of these ligand systems is described including the synthesis of those with just the two stereogenic centres of the diaminocyclohexane as well as those with additional stereogenicity. The addition of a secondary chiral centre gives rise to the possibility of having several diastereomers which have all been synthesised where relevant. Furthermore, most of these ligands have been prepared as both secondary and tertiary amines. The amine ligands have been tested on a variety of reactions such as the asymmetric addition of diethylzinc to benzaldehyde, the asymmetric 1,4-conjugate Michael addition and to a lesser extent the asymmetric lithium mediated deprotonation and asymmetric epoxidations. The effects of varying from secondary to tertiary amines, and from having two stereogenic centres to having four has been recorded for the first two mentioned processes. From these results, catalytic models have been proposed to explain the enantioselectivity of the systems. A large majority of the intermediates required for the synthesis of the amines have also been tested to varying success and this is also described. Finally, full experimental data has been given as well as a full list of references.

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