UC Irvine

Chapter 1. This chapter provides a very brief introduction to the field of homogeneous gold(I) catalysis and discusses the context of the Blum group's previous studies in this area.

Chapter 2: Organogold compounds undergo stoichiometric cross-coupling reactions with aryl and vinyl bromides in high yield under mild, nickel-catalyzed conditions. The reaction tolerates both electron-rich and electron-poor organogold complexes, and vinyl bromides undergo cross-coupling with high stereoselectivity. This novel transformation links well-established nickel catalysis with more recent developments in organogold transformations.

Chapter 3: A vinyl aziridine activation strategy cocatalyzed by Pd(0) and a Au(I) Lewis acid was developed. This rearrangement installs a C-C and a C-N bond in one synthetic step to form pyrrolizidine and indolizidine products. Two proposed mechanistic roles for the gold cocatalyst were considered: (1) carbophilic gold catalysis or (2) azaphilic gold catalysis. Mechanistic studies support an azaphilic Lewis acid activation of the aziridine over a carbophilic Lewis acid activation of the alkene.

Chapter 4: A borylation reaction cocatalyzed by Au and Rh was proposed as a means of isolating catalytic organogold intermediates as the corresponding organoboron derivatives for use in subsequent functionalization steps. Products consistent with the proposed reactivity were obtained, but control experiments indicated no role for Rh in the reaction; organogold complexes were found to undergo facile thermal reactivity with electrophilic B without Rh. Electronic effects in the chemoselective borylation of heterocyclic organogold complexes were studied, suggesting design parameters used in the development of the Au-catalyzed borylation reactions discussed in Chapters 5 and 6.

Chapter 5: For nearly 70 years, the addition of boron-X sigma bonds to carbon-carbon multiple bonds has been employed in the preparation of organoboron reagents. However, the significantly higher strength of boron-oxygen bonds has thus far precluded their activation for addition, preventing a direct route to access a potentially valuable class of oxygen-containing organoboron reagents for divergent synthesis. Herein is discussed an alkoxyboration reaction, the addition of boron-oxygen sigma bonds to alkynes. Functionalized O-heterocyclic boronic acid derivatives are produced using this transformation, which is mild and exhibits broad functional group compatibility. Our results demonstrate activation of this boron-oxygen bond using a gold catalysis strategy that is fundamentally different from that used previously for other boron addition reactions.

Chapter 6: Four additional investigations stemming from the benzofuran-forming alkoxyboration reaction (Chapter 5) are described. Discussed are electronic effects in the B/Au transmetalation reaction, progress towards an intermolecular alkoxyboration reaction, and the expansion of the alkoxyboration concept to two additional substrate classes for intramolecular B-O sigma-bond activation reactivity.