UC Berkeley

The following dissertation discusses the development of iridium catalysts for theundirected borylation of alkyl C–H bonds and includes in-depth studies on the mechanism of these transformations. Chapter 1 contains a comprehensive review of applications of the borylation of C–H bonds catalyzed by transition metals to the synthesis of complex molecules. This review is subdivided into sections highlighting the state-of-the-art of methodology of the undirected and directed borylation of aryl and alkyl C–H bonds, and focuses on the utility of these reactions for the syntheses of drug precursors, complex bioactive molecules, and optoelectronic materials. Additionally, the review contains a generalized overview of mechanisms by which these reactions occur. Finally, this review provides the author’s opinion on future directions for research on the borylation of alkyl C–H bonds. Chapter 2 describes the development of iridium-catalyzed borylation of the bridgehead, tertiary C–H bonds of bicyclopentanes and bicyclohexanes. Contained is an examination of the scope of the borylation of bicyclopentanes, bicyclohexanes, oxabicyclohexanes, and azabicyclohexanes. Also included are experimental and computational studies that reveal the mechanism of this reaction. Chapter 3 discusses the development of catalysts that enable the borylation of alkyl C– H bonds to occur at mild temperatures (65 ºC). Key to this development was the discovery that catalysts formed from 2-aminophenanthrolines and iridium undergo rapid activation and catalyze the borylation of alkyl C–H bonds at reduced temperatures, maintaining activity even at room temperature. Also included are experimental studies that provide initial information on the identity of the active catalyst species. Chapter 4 describes the mechanistic study of the origin of improved activation and reaction rates of the borylation of alkyl C–H bonds catalyzed by 2-aminophenanthroline complexes. Experimental studies enabled by a sterically protected aminophenanthroline demonstrate that the N-boryl iridium trisboryl complex is the resting state and that the corresponding N-boryl iridium bisboryl hydride complex is inactive for the borylation reaction.