Development and applications of copper(I) hydride catalysis in asymmetric reactions and heterocycle synthesis

• Main Author: Zhou, Yujing,Ph. D.Massachusetts Institute of Technology.
• Other Authors: Stephen L. Buchwald.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2021
• Subjects: Chemistry.
• Online Access: https://hdl.handle.net/1721.1/130831

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, February, 2021 === Cataloged from the official PDF of thesis. "February 2021." === Includes bibliographical references. === Chapter 2. Enantioselective CuH-Catalyzed Hydroacylation Employing Unsaturated Carboxylic Acids as Aldehyde Surrogates The direct asymmetric copper hydride (CuH)-catalyzed coupling of [alpha],[beta]-unsaturated carboxylic acids to aryl alkenes is developed to access chiral [alpha]-aryl dialkyl ketones. A variety of substrate substitution patterns, sensitive functional groups and heterocycles are tolerated in this reaction, which significantly expands the range of accessible products compared to existing hydroacylation methodology. Although mechanistic studies are ongoing, we propose that CuH-catalyzed silylation of unsaturated acids occurs to access a uniquely effective acyl electrophilic coupling partner. Chapter 3. CuH-Catalyzed Asymmetric Reduction of [alpha],[beta]-Unsaturated Carboxylic Acids to [beta]-Chiral Aldehydes The copper hydride (CuH)-catalyzed enantioselective reduction of [alpha],[beta]-unsaturated carboxylic acids to saturated aldehydes is reported. === This protocol provides a new method to access a variety of [beta]-chiral aldehydes in good yields, with high levels of enantioselectivity and broad functional group tolerance. A reaction pathway involving a ketene intermediate is proposed based on preliminary mechanistic studies and density functional theory calculations. Chapter 4. CuH-Catalyzed Asymmetric Reductive Amidation of [alpha],[beta]-Unsaturated Carboxylic Acids The direct enantioselective copper hydride (CuH)-catalyzed synthesis of [beta]-chiral amides from [alpha],[beta]-unsaturated carboxylic acids and secondary amines under mild reaction conditions is reported. The method utilizes readily accessible carboxylic acids, and tolerates a variety of functional groups at [beta]-position including several heteroarenes. A subsequent iridium-catalyzed reduction to [gamma]-chiral amines can be performed in the same flask without purification of the intermediate amides. Chapter 5. === CuH-Catalyzed Asymmetric Hydroamidation of Vinylarenes A CuH-catalyzed enantioselective hydroamidation reaction of vinylarenes has been developed using readily accessible 1,4,2-dioxazol-5-ones as electrophilic amidating reagents. This method provides a straightforward and efficient approach to synthesize chiral amides in good yields with high levels of enantiopurity under mild conditions. Moreover, this transformation tolerates substrates bearing a broad range of functional groups. Chapter 6. Enantioselective Allylation Using Allene, a Petroleum Cracking Byproduct Allene (C₃H₄) gas is produced and separated on million-metric-ton scale per year during petroleum refining but is rarely employed in organic synthesis. Meanwhile, the addition of an allyl group (C₃H₅) to ketones is among the most common and prototypical reactions in synthetic chemistry. === Herein, we report that the combination of allene gas with inexpensive and environmentally benign hydrosilanes, such as PMHS, can serve as a replacement for stoichiometric quantities of allylmetal reagents, which are required in most enantioselective ketone allylation reactions. This process is catalyzed by copper catalyst and commercially available ligands, operates without specialized equipment or pressurization, and tolerates a broad range of functional groups. Furthermore, the exceptional chemoselectivity of this catalyst system enables industrially relevant C3 hydrocarbon mixtures of allene with methylacetylene and propylene to be applied directly. Based on our strategy, we anticipate the rapid development of methods that leverage this unexploited feedstock as an allyl anion surrogate. Chapter 7. === Synthesis of Pyrroles through the CuH-Catalyzed Coupling of Enynes and Nitriles Herein, we describe an efficient method to prepare polysubstituted pyrroles via a copper-hydride (CuH)- catalyzed enyne-nitrile coupling reaction. This protocol accommodates both aromatic and aliphatic substituents and a broad range of functional groups, providing a variety of N-H pyrroles in good yields and with high regioselectivity. We propose that the Cu-based catalyst promotes both the initial reductive coupling and subsequent cyclization steps. Density functional theory (DFT) calculations were performed to help elucidate the reaction mechanism. === by Yujing Zhou. === Ph. D. === Ph.D. Massachusetts Institute of Technology, Department of Chemistry