Copper-catalyzed enantioselective difunctionalization of alkene reactions: Aminohalogenation and carboetherification
Bovino, Michael Thomas
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Heterocycles are an abundant class of compounds found throughout nature as well as the chemical industry. Due to their common occurrence in biologically active compounds as well as their use as ligands for asymmetric catalysis, nitrogen and oxygen heterocycles and the means for their synthesis are of particular interest. The research that follows has helped to further expand the utility of the copper(II)-catalyzed, enantioselective difunctionalizations of alkenes for the formation of saturated chiral nitrogen and oxygen heterocycles. In chapter one, a brief review of current aminohalogenation technology is given before a new copper(II)-catalyzed, enantioselective alkene aminohalogenation reaction is discussed. Both aryl and aliphatic gamma-alkenyl sulfonamides are reactive substrates, providing chiral vicinal haloamine products with good to excellent yields and enantiomeric excesses. This reaction represents a significant advancement in the area of aminohalogenation reactions as it occurs through a unique reaction mechanism that allows previously unexplored terminal alkenes to participate in an enantioselective process. In this reaction, a sulfonyl protected nitrogen and an iodide, bromide or chloride are added across an unactivated alkene with concomitant creation of an amine-bearing stereocenter. These chiral haloamines can be useful chiral synthetic building blocks for the construction of more complex synthetic targets. Chapter two will detail my contribution of a concise and scalable ligand synthesis for application to a multi-gram scale enantioselective copper-catalyzed aminooxygenation reaction. This reaction provides a scalable synthetic route to chiral 2-alkoxymethyl indolines. Lastly, in chapter three, the copper(II)-catalyzed, doubly intramolecular carboetherification reaction is first rendered enantioselective and then expanded to include an intra/intermolecular version. In this reaction, an alcohol and a carbon are added across an unactivated alkene with creation of an oxygen-bearing stereocenter. Several reactive alcohol substrates as well as alkene acceptors have been identified with yields and enantiomeric excesses ranging from good to excellent. The chiral tetrahydrofuran products formed can be useful synthetic building blocks for more complex targets.