Date on Master's Thesis/Doctoral Dissertation
8-2014
Document Type
Doctoral Dissertation
Degree Name
Ph. D.
Department
Chemistry
Committee Chair
Hammond, Gerald B.
Committee Co-Chair (if applicable)
Burns, Christopher T.
Committee Member
Burns, Christopher T.
Committee Member
Baldwin, Richard P.
Committee Member
Zamborini, Francis P.
Committee Member
Gutierrez, Humberto R.
Subject
Catalysts; Gold
Abstract
The focus of my dissertation work was to study the basic mechanistic insights of gold-catalyzed reactions. Although the various mechanistic pathways of gold catalysis are better understood nowadays, numerous questions still remain unanswered concerning the nature of deactivation of the catalyst's active species, high resistance towards protodeauration, and how we can solve these problems to improve the efficiency of gold catalysis. To address these challenges in gold catalysis we conducted first a detailed experimental study to understand the mechanism of deactivation of gold active species. Based on the combination of experimental data, we proposed that gold disproportionation is preferred as compared to reduction of the active gold catalyst. To address the high resistance toward protodeauration, we explored a new strategy to enhance the efficacy of gold-catalyzed reactions through hydrogen-bonding assisted protodeauration using additives chosen for their pKBHX (hydrogen-bond basicity). To address the threshold phenomenon, we observed that high gold affinity impurities (halides, bases) in solvents, starting materials, filtration or drying agents could affect the reactivity of the gold catalyst adversely, which, in turn, may significantly reduce the TON of cationic gold. Use of a suitable acid activator (e.g. HOTf, In(OTf)3) reactivates the gold catalyst and makes the reaction proceed smoothly at low gold catalyst loading. To explore the reactivity of Au catalysts towards oxygen-atom transfer reactions, we investigated the gold-catalyzed addition of O-nucleophiles to alkynes and found that this reaction can produce synthetically important vinyl ether products in excellent yields and regioselectivities at room temperature. At higher temperature, 3,3-sigmatropic rearrangement of vinyl ether products gives access to highly functionalized benzotriazoles.
Recommended Citation
Kumar, Manish, "Mechanistic insights and functionalization of alkynes in homogeneous gold catalysis." (2014). Electronic Theses and Dissertations. Paper 781.
https://doi.org/10.18297/etd/781
