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This work focuses on developing and evaluating new chiral catalysts for asymmetric C-C and C-H bond-forming reactions. The first part introduces an ESI-MS screening method that determines a chiral catalyst's selectivity in palladium-catalyzed asymmetric allylic alkylation by testing its racemic form. This method proved valuable in evaluating new aryl-PHOX-type ligands, which are challenging to access in enantiopure form. The second part explores new PHOX-type ligands in iridium-catalyzed asymmetric hydrogenation of various unsaturated compounds, revealing low activities and selectivities, except for one ligand that showed promise in hydrogenating allylic alcohols and imines. Additionally, air- and moisture-stable secondary phosphine oxide (SPO) bidentate ligands were tested in palladium-catalyzed asymmetric allylic alkylation. While SPO, N-ligands were inactive, SPO, P ligands promoted the desired reaction selectively, albeit with low activity. A new organo-catalyst based on 2,3-dihydrobenzo[1,4]oxazine was developed for asymmetric transfer-hydrogenation of α,β-unsaturated aldehydes, achieving good activities and high enantioselectivities for β,β-diaryl acrylaldehydes. An ESI-MS mechanistic study on a tripeptide-catalyzed conjugate addition reaction revealed all intermediates of the enamine mechanism and identified the enamine's attack on nitroolefins as the selectivity-determining step. The final part aimed at asymmetric α-al
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Development and evaluation of chiral catalysts for asymetric C-C and C-H bond forming reactions, Christian Ebner
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- 2012
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