| One of the major fields of modern organic chemistry is research into the synthesis of enantiomerically pure carbogens. This area of research is driven mostly by the relationship between biological activity and chirality in drug-receptor interactions and its importance has been recognized with the 2001 Nobel Prize for Chemistry being awarded to three practitioners in this field. In many cases, economical routes to enantiomerically pure substances are available using enantioselective catalysts. The basis for most of these catalytic enantioselective reactions involves formation of a chiral metallocyclic Lewis acid from a chiral catalyst precursor and a suitable organometallic species. Chirality transfer is accomplished through coordination of a prochiral Lewis basic reactant, eg., aldehyde, ketone, alkene, etc., with the chiral Lewis acid metallocycle. Such coordination locks the reactant into a chiral environment where steric and/or electronic effects will perjudice approach of an incoming reactant (typically a nucleophilic species) to make formation of one enantiomer more favorable than the other. Careful study of proposed transition states and structures of successful catalyst systems led to the conclusion that inclusion of the tricarbonyl (η6 arene) chromium (0) group in certain catalyst structures would have a pronounced beneficial effect on enantioselectivity.; This dissertation outlines the design, attempted preparation, preparation, and application of new classes of enantioselective catalysts as well a cost effective chiral auxiliary. Specifically, the stereodirective and electronic properties of chiral arene chromium carbonyl complexes have been exploited. The attempted synthesis of a family of oxazoline arene chromium carbonyl ligands containing phosphine functionality ortho to the oxazoline is described. In the process of attempting this synthesis an oxazoline arene chromium carbonyl ligand containing thiophene functionality was produced and used as a bidentate ligand in nickel catalyzed Diels-Alder cycloaddition, palladium catalyzed allylic acetate substitution, and rhodium catalyzed hydrosilylation reactions. A new family of bidentate planar chiral heterocyclic phosphine ligands was also produced. A new family of bidentate catalysts containing phosphine and benzylic thiophene functionality was prepared and used in both palladium, catalyzed allylic acetate substitution and palladium catalyzed hydrosilylation reactions, giving good product enantioexcess. A series of isomannide derivatives were prepared and evaluated as templates for asymmetric Diels-Alder cycloaddition, conjugate addition, cyclopropanation, and enolate reactions. Finally, a new method for catalyst screening has been developed which utilizes direct-injection LCNMR along with automated sampling. Determination and fabrication of system components was accomplished, and an automated procedure for analysis has been established. |
