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Catalytic Asymmetric Hydrogenation and Hydroboration Reactions
The catalytic asymmetric hydrogenation (CAH) reaction is a preeminent tool for the generation of stereocenters. A large number of metal-ligand combinations have been developed to address specific challenges but limitations, especially with tetrasubstituted olefins, remain. The first portion of this dissertation focuses on the oxime-directed catalytic asymmetric hydrogenations of allylic oximes. The observation of an unexpected interaction in the catalytic cycle led to a series of new catalyst systems that efficiently reduce di-, tri- and tetrasubstituted olefins in less than one hour at one atm hydrogen pressure. Mechanistic probing provided evidence to support a new mechanism for which the activator-promoted asymmetric hydrogenations of oximes are thought to occur. The catalytic asymmetric hydroboration reaction is a cornerstone in asymmetric catalysis due to the wide variety of stereospecific transformations capable of the carbon–boron bond. A variety of regiodivergent, chiral boronates were prepared using the developed methodology included herein. Stereospecific conversion of these chiral products into boronic acids, borocycles, tertiary alcohols, and all-carbon quaternary compounds was illustrated. The new catalyst systems developed in the previous section were demonstrated to be efficient hydroboration catalysts as well.
Bochat, Andrew Jerome, "Catalytic Asymmetric Hydrogenation and Hydroboration Reactions" (2020). ETD collection for University of Nebraska - Lincoln. AAI28031664.